Protecting core networks with dual-homing: A study on enhanced network availability, resource efficiency, and energy-savings

NASA Astrophysics Data System (ADS)

Abeywickrama, Sandu; Furdek, Marija; Monti, Paolo; Wosinska, Lena; Wong, Elaine

2016-12-01

Core network survivability affects the reliability performance of telecommunication networks and remains one of the most important network design considerations. This paper critically examines the benefits arising from utilizing dual-homing in the optical access networks to provide resource-efficient protection against link and node failures in the optical core segment. Four novel, heuristic-based RWA algorithms that provide dedicated path protection in networks with dual-homing are proposed and studied. These algorithms protect against different failure scenarios (i.e. single link or node failures) and are implemented with different optimization objectives (i.e., minimization of wavelength usage and path length). Results obtained through simulations and comparison with baseline architectures indicate that exploiting dual-homed architecture in the access segment can bring significant improvements in terms of core network resource usage, connection availability, and power consumption.

Cross-layer shared protection strategy towards data plane in software defined optical networks

NASA Astrophysics Data System (ADS)

Xiong, Yu; Li, Zhiqiang; Zhou, Bin; Dong, Xiancun

2018-04-01

In order to ensure reliable data transmission on the data plane and minimize resource consumption, a novel protection strategy towards data plane is proposed in software defined optical networks (SDON). Firstly, we establish a SDON architecture with hierarchical structure of data plane, which divides the data plane into four layers for getting fine-grained bandwidth resource. Then, we design the cross-layer routing and resource allocation based on this network architecture. Through jointly considering the bandwidth resource on all the layers, the SDN controller could allocate bandwidth resource to working path and backup path in an economical manner. Next, we construct auxiliary graphs and transform the shared protection problem into the graph vertex coloring problem. Therefore, the resource consumption on backup paths can be reduced further. The simulation results demonstrate that the proposed protection strategy can achieve lower protection overhead and higher resource utilization ratio.

A Dynamic Resilience Approach for WDM Optical Networks

NASA Astrophysics Data System (ADS)

Garg, Amit Kumar

2017-12-01

Optical fibres have been developed as a transmission medium to carry traffic in order to provide various services in telecommunications platform. Failure of this fibre caused loss of data which can interrupt communication services. This paper has been focused only on survivable schemes in order to guarantee both protection and restoration in WDM optical networks. In this paper, a dynamic resilience approach has been proposed whose objective is to route the flows in a way which minimizes the total amount of bandwidth used for working and protection paths. In the proposed approach, path-based protection is utilized because it yields lower overhead and is also suitable for global optimization where, in case of a single link failure, all the flows utilizing the failed link are re-routed to a pre-computed set of paths. The simulation results demonstrate that proposed approach is much more efficient as it provides better quality of services (QoS) in terms of network resource utilization, blocking probability etc. as compared to conventional protection and restoration schemes. The proposed approach seems to offer an attractive combination of features, with both ring like speed and mesh-like efficiency.

Piezoelectric Diffraction-Based Optical Switches

NASA Technical Reports Server (NTRS)

Spremo, Stevan; Fuhr, Peter; Schipper, John

2003-01-01

Piezoelectric diffraction-based optoelectronic devices have been invented to satisfy requirements for switching signals quickly among alternative optical paths in optical communication networks. These devices are capable of operating with switching times as short as microseconds or even nanoseconds in some cases.

An improved least cost routing approach for WDM optical network without wavelength converters

NASA Astrophysics Data System (ADS)

Bonani, Luiz H.; Forghani-elahabad, Majid

2016-12-01

Routing and wavelength assignment (RWA) problem has been an attractive problem in optical networks, and consequently several algorithms have been proposed in the literature to solve this problem. The most known techniques for the dynamic routing subproblem are fixed routing, fixed-alternate routing, and adaptive routing methods. The first one leads to a high blocking probability (BP) and the last one includes a high computational complexity and requires immense backing from the control and management protocols. The second one suggests a trade-off between performance and complexity, and hence we consider it to improve in our work. In fact, considering the RWA problem in a wavelength routed optical network with no wavelength converter, an improved technique is proposed for the routing subproblem in order to decrease the BP of the network. Based on fixed-alternate approach, the first k shortest paths (SPs) between each node pair is determined. We then rearrange the SPs according to a newly defined cost for the links and paths. Upon arriving a connection request, the sorted paths are consecutively checked for an available wavelength according to the most-used technique. We implement our proposed algorithm and the least-hop fixed-alternate algorithm to show how the rearrangement of SPs contributes to a lower BP in the network. The numerical results demonstrate the efficiency of our proposed algorithm in comparison with the others, considering different number of available wavelengths.

A multi-ring optical packet and circuit integrated network with optical buffering.

PubMed

Furukawa, Hideaki; Shinada, Satoshi; Miyazawa, Takaya; Harai, Hiroaki; Kawasaki, Wataru; Saito, Tatsuhiko; Matsunaga, Koji; Toyozumi, Tatuya; Wada, Naoya

2012-12-17

We newly developed a 3 × 3 integrated optical packet and circuit switch-node. Optical buffers and burst-mode erbium-doped fiber amplifiers with the gain flatness are installed in the 3 × 3 switch-node. The optical buffer can prevent packet collisions and decrease packet loss. We constructed a multi-ring optical packet and circuit integrated network testbed connecting two single-ring networks and a client network by the 3 × 3 switch-node. For the first time, we demonstrated 244 km fiber transmission and 5-node hopping of multiplexed 14-wavelength 10 Gbps optical paths and 100 Gbps optical packets encapsulating 10 Gigabit Ethernet frames on the testbed. Error-free (frame error rate < 1 × 10(-4)) operation was achieved with optical packets of various packet lengths. In addition, successful avoidance of packet collisions by optical buffers was confirmed.

Performance evaluation of distributed wavelength assignment in WDM optical networks

NASA Astrophysics Data System (ADS)

Hashiguchi, Tomohiro; Wang, Xi; Morikawa, Hiroyuki; Aoyama, Tomonori

2004-04-01

In WDM wavelength routed networks, prior to a data transfer, a call setup procedure is required to reserve a wavelength path between the source-destination node pairs. A distributed approach to a connection setup can achieve a very high speed, while improving the reliability and reducing the implementation cost of the networks. However, along with many advantages, several major challenges have been posed by the distributed scheme in how the management and allocation of wavelength could be efficiently carried out. In this thesis, we apply a distributed wavelength assignment algorithm named priority based wavelength assignment (PWA) that was originally proposed for the use in burst switched optical networks to the problem of reserving wavelengths of path reservation protocols in the distributed control optical networks. Instead of assigning wavelengths randomly, this approach lets each node select the "safest" wavelengths based on the information of wavelength utilization history, thus unnecessary future contention is prevented. The simulation results presented in this paper show that the proposed protocol can enhance the performance of the system without introducing any apparent drawbacks.

Performance evaluation of a burst-mode EDFA in an optical packet and circuit integrated network.

PubMed

Shiraiwa, Masaki; Awaji, Yoshinari; Furukawa, Hideaki; Shinada, Satoshi; Puttnam, Benjamin J; Wada, Naoya

2013-12-30

We experimentally investigate the performance of burst-mode EDFA in an optical packet and circuit integrated system. In such networks, packets and light paths can be dynamically assigned to the same fibers, resulting in gain transients in EDFAs throughout the network that can limit network performance. Here, we compare the performance of a 'burst-mode' EDFA (BM-EDFA), employing transient suppression techniques and optical feedback, with conventional EDFAs, and those using automatic gain control and previous BM-EDFA implementations. We first measure gain transients and other impairments in a simplified set-up before making frame error-rate measurements in a network demonstration.

A new method for solving routing and wavelength assignment problems under inaccurate routing information in optical networks with conversion capability

NASA Astrophysics Data System (ADS)

Luo, Yanting; Zhang, Yongjun; Gu, Wanyi

2009-11-01

In large dynamic networks it is extremely difficult to maintain accurate routing information on all network nodes. The existing studies have illustrated the impact of imprecise state information on the performance of dynamic routing and wavelength assignment (RWA) algorithms. An algorithm called Bypass Based Optical Routing (BBOR) proposed by Xavier Masip-Bruin et al can reduce the effects of having inaccurate routing information in networks operating under the wavelength-continuity constraint. Then they extended the BBOR mechanism (for convenience it's called EBBOR mechanism below) to be applied to the networks with sparse and limited wavelength conversion. But it only considers the characteristic of wavelength conversion in the step of computing the bypass-paths so that its performance may decline with increasing the degree of wavelength translation (this concept will be explained in the section of introduction again). We will demonstrate the issue through theoretical analysis and introduce a novel algorithm which modifies both the lightpath selection and the bypass-paths computation in comparison to EBBOR algorithm. Simulations show that the Modified EBBOR (MEBBOR) algorithm improves the blocking performance significantly in optical networks with Conversion Capability.

Spectrum efficient distance-adaptive paths for fixed and fixed-alternate routing in elastic optical networks

NASA Astrophysics Data System (ADS)

Agrawal, Anuj; Bhatia, Vimal; Prakash, Shashi

2018-01-01

Efficient utilization of spectrum is a key concern in the soon to be deployed elastic optical networks (EONs). To perform routing in EONs, various fixed routing (FR), and fixed-alternate routing (FAR) schemes are ubiquitously used. FR, and FAR schemes calculate a fixed route, and a prioritized list of a number of alternate routes, respectively, between different pairs of origin o and target t nodes in the network. The route calculation performed using FR and FAR schemes is predominantly based on either the physical distance, known as k -shortest paths (KSP), or on the hop count (HC). For survivable optical networks, FAR usually calculates link-disjoint (LD) paths. These conventional routing schemes have been efficiently used for decades in communication networks. However, in this paper, it has been demonstrated that these commonly used routing schemes cannot utilize the network spectral resources optimally in the newly introduced EONs. Thus, we propose a new routing scheme for EON, namely, k -distance adaptive paths (KDAP) that efficiently utilizes the benefit of distance-adaptive modulation, and bit rate-adaptive superchannel capability inherited by EON to improve spectrum utilization. In the proposed KDAP, routes are found and prioritized on the basis of bit rate, distance, spectrum granularity, and the number of links used for a particular route. To evaluate the performance of KSP, HC, LD, and the proposed KDAP, simulations have been performed for three different sized networks, namely, 7-node test network (TEST7), NSFNET, and 24-node US backbone network (UBN24). We comprehensively assess the performance of various conventional, and the proposed routing schemes by solving both the RSA and the dual RSA problems under homogeneous and heterogeneous traffic requirements. Simulation results demonstrate that there is a variation amongst the performance of KSP, HC, and LD, depending on the o - t pair, and the network topology and its connectivity. However, the proposed KDAP always performs better for all the considered networks and traffic scenarios, as compared to the conventional routing schemes, namely, KSP, HC, and LD. The proposed KDAP achieves up to 60 % , and 10.46 % improvement in terms of spectrum utilization, and resource utilization ratio, respectively, over the conventional routing schemes.

Sub-0.1 μm optical track width measurement

NASA Astrophysics Data System (ADS)

Smith, Richard J.; See, Chung W.; Somekh, Mike G.; Yacoot, Andrew

2005-08-01

In this paper, we will describe a technique that combines a common path scanning optical interferometer with artificial neural networks (ANN), to perform track width measurements that are significantly beyond the capability of conventional optical systems. Artificial neural networks have been used for many different applications. In the present case, ANNs are trained using profiles of known samples obtained from the scanning interferometer. They are then applied to tracks that have not previously been exposed to the networks. This paper will discuss the impacts of various ANN configurations, and the processing of the input signal on the training of the network. The profiles of the samples, which are used as the inputs to the ANNs, are obtained with a common path scanning optical interferometer. It provides extremely repeatable measurements, with very high signal to noise ratio, both are essential for the working of the ANNs. The characteristics of the system will be described. A number of samples with line widths ranging from 60nm-3μm have been measured to test the system. The system can measure line widths down to 60nm with a standard deviation of 3nm using optical wavelength of 633nm and a system numerical aperture of 0.3. These results will be presented in detail along with a discussion of the potential of this technique.

Performance of multi-hop parallel free-space optical communication over gamma-gamma fading channel with pointing errors.

PubMed

Gao, Zhengguang; Liu, Hongzhan; Ma, Xiaoping; Lu, Wei

2016-11-10

Multi-hop parallel relaying is considered in a free-space optical (FSO) communication system deploying binary phase-shift keying (BPSK) modulation under the combined effects of a gamma-gamma (GG) distribution and misalignment fading. Based on the best path selection criterion, the cumulative distribution function (CDF) of this cooperative random variable is derived. Then the performance of this optical mesh network is analyzed in detail. A Monte Carlo simulation is also conducted to demonstrate the effectiveness of the results for the average bit error rate (ABER) and outage probability. The numerical result proves that it needs a smaller average transmitted optical power to achieve the same ABER and outage probability when using the multi-hop parallel network in FSO links. Furthermore, the system use of more number of hops and cooperative paths can improve the quality of the communication.

Traffic engineering and regenerator placement in GMPLS networks with restoration

NASA Astrophysics Data System (ADS)

Yetginer, Emre; Karasan, Ezhan

2002-07-01

In this paper we study regenerator placement and traffic engineering of restorable paths in Generalized Multipro-tocol Label Switching (GMPLS) networks. Regenerators are necessary in optical networks due to transmission impairments. We study a network architecture where there are regenerators at selected nodes and we propose two heuristic algorithms for the regenerator placement problem. Performances of these algorithms in terms of required number of regenerators and computational complexity are evaluated. In this network architecture with sparse regeneration, offline computation of working and restoration paths is studied with bandwidth reservation and path rerouting as the restoration scheme. We study two approaches for selecting working and restoration paths from a set of candidate paths and formulate each method as an Integer Linear Programming (ILP) prob-lem. Traffic uncertainty model is developed in order to compare these methods based on their robustness with respect to changing traffic patterns. Traffic engineering methods are compared based on number of additional demands due to traffic uncertainty that can be carried. Regenerator placement algorithms are also evaluated from a traffic engineering point of view.

MPNACK: an optical switching scheme enabling the buffer-less reliable transmission

NASA Astrophysics Data System (ADS)

Yu, Xiaoshan; Gu, Huaxi; Wang, Kun; Xu, Meng; Guo, Yantao

2016-01-01

Optical data center networks are becoming an increasingly promising solution to solve the bottlenecks faced by electrical networks, such as low transmission bandwidth, high wiring complexity, and unaffordable power consumption. However, the optical circuit switching (OCS) network is not flexible enough to carry the traffic burst while the optical packet switching (OPS) network cannot solve the packet contention in an efficient way. To this end, an improved switching strategy named OPS with multi-hop Negative Acknowledgement (MPNACK) is proposed. This scheme uses a feedback mechanism, rather than the buffering structure, to handle the optical packet contention. The collided packet is treated as a NACK packet and sent back to the source server. When the sender receives this NACK packet, it knows a collision happens in the transmission path and a retransmission procedure is triggered. Overall, the OPS-NACK scheme enables a reliable transmission in the buffer-less optical network. Furthermore, with this scheme, the expensive and energy-hungry elements, optical or electrical buffers, can be removed from the optical interconnects, thus a more scalable and cost-efficient network can be constructed for cloud computing data centers.

An optimization method of VON mapping for energy efficiency and routing in elastic optical networks

NASA Astrophysics Data System (ADS)

Liu, Huanlin; Xiong, Cuilian; Chen, Yong; Li, Changping; Chen, Derun

2018-03-01

To improve resources utilization efficiency, network virtualization in elastic optical networks has been developed by sharing the same physical network for difference users and applications. In the process of virtual nodes mapping, longer paths between physical nodes will consume more spectrum resources and energy. To address the problem, we propose a virtual optical network mapping algorithm called genetic multi-objective optimize virtual optical network mapping algorithm (GM-OVONM-AL), which jointly optimizes the energy consumption and spectrum resources consumption in the process of virtual optical network mapping. Firstly, a vector function is proposed to balance the energy consumption and spectrum resources by optimizing population classification and crowding distance sorting. Then, an adaptive crossover operator based on hierarchical comparison is proposed to improve search ability and convergence speed. In addition, the principle of the survival of the fittest is introduced to select better individual according to the relationship of domination rank. Compared with the spectrum consecutiveness-opaque virtual optical network mapping-algorithm and baseline-opaque virtual optical network mapping algorithm, simulation results show the proposed GM-OVONM-AL can achieve the lowest bandwidth blocking probability and save the energy consumption.

Optical track width measurements below 100 nm using artificial neural networks

NASA Astrophysics Data System (ADS)

Smith, R. J.; See, C. W.; Somekh, M. G.; Yacoot, A.; Choi, E.

2005-12-01

This paper discusses the feasibility of using artificial neural networks (ANNs), together with a high precision scanning optical profiler, to measure very fine track widths that are considerably below the conventional diffraction limit of a conventional optical microscope. The ANN is trained using optical profiles obtained from tracks of known widths, the network is then assessed by applying it to test profiles. The optical profiler is an ultra-stable common path scanning interferometer, which provides extremely precise surface measurements. Preliminary results, obtained with a 0.3 NA objective lens and a laser wavelength of 633 nm, show that the system is capable of measuring a 50 nm track width, with a standard deviation less than 4 nm.

Moving the boundary between wavelength resources in optical packet and circuit integrated ring network.

PubMed

Furukawa, Hideaki; Miyazawa, Takaya; Wada, Naoya; Harai, Hiroaki

2014-01-13

Optical packet and circuit integrated (OPCI) networks provide both optical packet switching (OPS) and optical circuit switching (OCS) links on the same physical infrastructure using a wavelength multiplexing technique in order to deal with best-effort services and quality-guaranteed services. To immediately respond to changes in user demand for OPS and OCS links, OPCI networks should dynamically adjust the amount of wavelength resources for each link. We propose a resource-adjustable hybrid optical packet/circuit switch and transponder. We also verify that distributed control of resource adjustments can be applied to the OPCI ring network testbed we developed. In cooperation with the resource adjustment mechanism and the hybrid switch and transponder, we demonstrate that automatically allocating a shared resource and moving the wavelength resource boundary between OPS and OCS links can be successfully executed, depending on the number of optical paths in use.

Characteristics of color optical shutter with dye-doped polymer network liquid crystal.

PubMed

Lee, G H; Hwang, K Y; Jang, J E; Jin, Y W; Lee, S Y; Jung, J E

2011-03-01

The optical properties and the theoretical prediction of color optical shutter with dye-doped polymer network liquid crystal (PNLC) were investigated. The view-angle dependence of reflectance according to the bias conditions showed distinctive characteristics, which could be explained from the effects of dye absorption and path length. It was also shown that the thickness dependence of reflectance was strongly influenced by the light-scattering coefficient. Our experimental results matched up well with the theoretical prediction based on the light scattering of liquid crystals in polymer network and the absorption of dichroic dye. This work indicates potential to improve the optical device using dye-doped liquid crystal-polymer composite.

An improved approximate network blocking probability model for all-optical WDM Networks with heterogeneous link capacities

NASA Astrophysics Data System (ADS)

Khan, Akhtar Nawaz

2017-11-01

Currently, analytical models are used to compute approximate blocking probabilities in opaque and all-optical WDM networks with the homogeneous link capacities. Existing analytical models can also be extended to opaque WDM networking with heterogeneous link capacities due to the wavelength conversion at each switch node. However, existing analytical models cannot be utilized for all-optical WDM networking with heterogeneous structure of link capacities due to the wavelength continuity constraint and unequal numbers of wavelength channels on different links. In this work, a mathematical model is extended for computing approximate network blocking probabilities in heterogeneous all-optical WDM networks in which the path blocking is dominated by the link along the path with fewer number of wavelength channels. A wavelength assignment scheme is also proposed for dynamic traffic, termed as last-fit-first wavelength assignment, in which a wavelength channel with maximum index is assigned first to a lightpath request. Due to heterogeneous structure of link capacities and the wavelength continuity constraint, the wavelength channels with maximum indexes are utilized for minimum hop routes. Similarly, the wavelength channels with minimum indexes are utilized for multi-hop routes between source and destination pairs. The proposed scheme has lower blocking probability values compared to the existing heuristic for wavelength assignments. Finally, numerical results are computed in different network scenarios which are approximately equal to values obtained from simulations. Since January 2016, he is serving as Head of Department and an Assistant Professor in the Department of Electrical Engineering at UET, Peshawar-Jalozai Campus, Pakistan. From May 2013 to June 2015, he served Department of Telecommunication Engineering as an Assistant Professor at UET, Peshawar-Mardan Campus, Pakistan. He also worked as an International Internship scholar in the Fukuda Laboratory, National Institute of Informatics, Tokyo, Japan on the topic large-scale simulation for internet topology analysis. His research interests include design and analysis of optical WDM networks, network algorithms, network routing, and network resource optimization problems.

Design of Control Plane Architecture Based on Cloud Platform and Experimental Network Demonstration for Multi-domain SDON

NASA Astrophysics Data System (ADS)

Li, Ming; Yin, Hongxi; Xing, Fangyuan; Wang, Jingchao; Wang, Honghuan

2016-02-01

With the features of network virtualization and resource programming, Software Defined Optical Network (SDON) is considered as the future development trend of optical network, provisioning a more flexible, efficient and open network function, supporting intraconnection and interconnection of data centers. Meanwhile cloud platform can provide powerful computing, storage and management capabilities. In this paper, with the coordination of SDON and cloud platform, a multi-domain SDON architecture based on cloud control plane has been proposed, which is composed of data centers with database (DB), path computation element (PCE), SDON controller and orchestrator. In addition, the structure of the multidomain SDON orchestrator and OpenFlow-enabled optical node are proposed to realize the combination of centralized and distributed effective management and control platform. Finally, the functional verification and demonstration are performed through our optical experiment network.

Improved Electro-Optical Switches

NASA Technical Reports Server (NTRS)

Nelson, Bruce N.; Cooper, Ronald F.

1994-01-01

Improved single-pole, double-throw electro-optical switches operate in switching times less than microsecond developed for applications as optical communication systems and networks of optical sensors. Contain no moving parts. In comparison with some prior electro-optical switches, these are simpler and operate with smaller optical losses. Beam of light switched from one output path to other by applying, to electro-optical crystal, voltage causing polarization of beam of light to change from vertical to horizontal.

A Fully Implemented 12 × 12 Data Vortex Optical Packet Switching Interconnection Network

NASA Astrophysics Data System (ADS)

Shacham, Assaf; Small, Benjamin A.; Liboiron-Ladouceur, Odile; Bergman, Keren

2005-10-01

A fully functional optical packet switching (OPS) interconnection network based on the data vortex architecture is presented. The photonic switching fabric uniquely capitalizes on the enormous bandwidth advantage of wavelength division multiplexing (WDM) wavelength parallelism while delivering minimal packet transit latency. Utilizing semiconductor optical amplifier (SOA)-based switching nodes and conventional fiber-optic technology, the 12-port system exhibits a capacity of nearly 1 Tb/s. Optical packets containing an eight-wavelength WDM payload with 10 Gb/s per wavelength are routed successfully to all 12 ports while maintaining a bit error rate (BER) of 10-12 or better. Median port-to-port latencies of 110 ns are achieved with a distributed deflection routing network that resolves packet contention on-the-fly without the use of optical buffers and maintains the entire payload path in the optical domain.

Six-port optical switch for cluster-mesh photonic network-on-chip

NASA Astrophysics Data System (ADS)

Jia, Hao; Zhou, Ting; Zhao, Yunchou; Xia, Yuhao; Dai, Jincheng; Zhang, Lei; Ding, Jianfeng; Fu, Xin; Yang, Lin

2018-05-01

Photonic network-on-chip for high-performance multi-core processors has attracted substantial interest in recent years as it offers a systematic method to meet the demand of large bandwidth, low latency and low power dissipation. In this paper we demonstrate a non-blocking six-port optical switch for cluster-mesh photonic network-on-chip. The architecture is constructed by substituting three optical switching units of typical Spanke-Benes network to optical waveguide crossings. Compared with Spanke-Benes network, the number of optical switching units is reduced by 20%, while the connectivity of routing path is maintained. By this way the footprint and power consumption can be reduced at the expense of sacrificing the network latency performance in some cases. The device is realized by 12 thermally tuned silicon Mach-Zehnder optical switching units. Its theoretical spectral responses are evaluated by establishing a numerical model. The experimental spectral responses are also characterized, which indicates that the optical signal-to-noise ratios of the optical switch are larger than 13.5 dB in the wavelength range from 1525 nm to 1565 nm. Data transmission experiment with the data rate of 32 Gbps is implemented for each optical link.

On optimal designs of transparent WDM networks with 1 + 1 protection leveraged by all-optical XOR network coding schemes

NASA Astrophysics Data System (ADS)

Dao, Thanh Hai

2018-01-01

Network coding techniques are seen as the new dimension to improve the network performances thanks to the capability of utilizing network resources more efficiently. Indeed, the application of network coding to the realm of failure recovery in optical networks has been marking a major departure from traditional protection schemes as it could potentially achieve both rapid recovery and capacity improvement, challenging the prevailing wisdom of trading capacity efficiency for speed recovery and vice versa. In this context, the maturing of all-optical XOR technologies appears as a good match to the necessity of a more efficient protection in transparent optical networks. In addressing this opportunity, we propose to use a practical all-optical XOR network coding to leverage the conventional 1 + 1 optical path protection in transparent WDM optical networks. The network coding-assisted protection solution combines protection flows of two demands sharing the same destination node in supportive conditions, paving the way for reducing the backup capacity. A novel mathematical model taking into account the operation of new protection scheme for optimal network designs is formulated as the integer linear programming. Numerical results based on extensive simulations on realistic topologies, COST239 and NSFNET networks, are presented to highlight the benefits of our proposal compared to the conventional approach in terms of wavelength resources efficiency and network throughput.

A growth path for deep space communications

NASA Technical Reports Server (NTRS)

Layland, J. W.; Smith, J. G.

1987-01-01

Increased Deep Space Network (DPN) receiving capability far beyond that now available for Voyager is achievable through a mix of increased antenna aperture and increased frequency of operation. In this note a sequence of options are considered: adding midsized antennas for arraying with the existing network at X-band; converting to Ka-band and adding array elements; augmenting the DSN with an orbiting Ka-band station; and augmenting the DSN with an optical receiving capability, either on the ground or in space. Costs of these options are compared as means of achieving significantly increased receiving capability. The envelope of lowest costs projects a possible path for moving from X-band to Ka-band and thence to optical frequencies, and potentially for moving from ground-based to space-based apertures. The move to Ka-band is clearly of value now, with development of optical communications technology a good investment for the future.

Enabling Optical Network Test Bed for 5G Tests

NASA Astrophysics Data System (ADS)

Giuntini, Marco; Grazioso, Paolo; Matera, Francesco; Valenti, Alessandro; Attanasio, Vincenzo; Di Bartolo, Silvia; Nastri, Emanuele

2017-03-01

In this work, we show some experimental approaches concerning optical network design dedicated to 5G infrastructures. In particular, we show some implementations of network slicing based on Carrier Ethernet forwarding, which will be very suitable in the context of 5G heterogeneous networks, especially looking at services for vertical enterprises. We also show how to adopt a central unit (orchestrator) to automatically manage such logical paths according to quality-of-service requirements, which can be monitored at the user location. We also illustrate how novel all-optical processes, such as the ones based on all-optical wavelength conversion, can be used for multicasting, enabling development of TV broadcasting based on 4G-5G terminals. These managing and forwarding techniques, operating on optical links, are tested in a wireless environment on Wi-Fi cells and emulating LTE and WiMAX systems by means of the NS-3 code.

Performance improvement of optical CDMA networks with stochastic artificial bee colony optimization technique

NASA Astrophysics Data System (ADS)

Panda, Satyasen

2018-05-01

This paper proposes a modified artificial bee colony optimization (ABC) algorithm based on levy flight swarm intelligence referred as artificial bee colony levy flight stochastic walk (ABC-LFSW) optimization for optical code division multiple access (OCDMA) network. The ABC-LFSW algorithm is used to solve asset assignment problem based on signal to noise ratio (SNR) optimization in OCDM networks with quality of service constraints. The proposed optimization using ABC-LFSW algorithm provides methods for minimizing various noises and interferences, regulating the transmitted power and optimizing the network design for improving the power efficiency of the optical code path (OCP) from source node to destination node. In this regard, an optical system model is proposed for improving the network performance with optimized input parameters. The detailed discussion and simulation results based on transmitted power allocation and power efficiency of OCPs are included. The experimental results prove the superiority of the proposed network in terms of power efficiency and spectral efficiency in comparison to networks without any power allocation approach.

Studies of free-space optical links through simulated boundary layer and long-path turbulence

NASA Astrophysics Data System (ADS)

Wasiczko, Linda; Smolyaninov, Igor I.; Milner, Stuart D.; Davis, Christopher C.

2004-02-01

There is recent interest from the US Department of Defense in free space optical communication networks involving aircraft flying at various altitudes. The optical links between these aircraft may be as long as 100km, and involve communication between network nodes that are moving at sub-sonic speeds. An unresolved issue for links of this kind between pairs of aircraft is the effect of boundary layer turbulence near each aircraft, as well as along the atmospheric path between them. The deployment of optical wireless links in several different scenarios will be described. These include links near to the ground for which the turbulence parameter Cn2 varies along the path between transmitter (TX) and receiver (RX), high altitude links between aircraft, and ground to aircraft links. The last two of these may involve boundary layer turbulence near the aircraft node where the turbulence is localized either at the TX or at the RX. Some of the theoretical approaches to examining these situations will be described, as well as an ongoing program of research to examine these situations experimentally. Ways to mitigate the effects of node motion, and scintillation at the RX will be discussed, including the use of non-imaging concentrators at the RX.

Principle and verification of novel optical virtual private networks over multiprotocol label switching/optical packet switching networks

NASA Astrophysics Data System (ADS)

Zhang, Chongfu; Wang, Zhengsuan; Jin, Wei; Qiu, Kun

2012-11-01

A novel realization method of the optical virtual private networks (OVPN) over multiprotocol label switching/optical packet switching (MPLS/OPS) networks is proposed. In this scheme, the introduction of MPLS control plane makes OVPN over OPS networks more reliable and easier; OVPN makes use of the concept of high reconfiguration of light-paths offered by MPLS, to set up secure tunnels of high bandwidth across intelligent OPS networks. Through resource management, the signal mechanism, connection control, and the architecture of the creation and maintenance of OVPN are efficiently realized. We also present an OVPN architecture with two traffic priorities, which is used to analyze the capacity, throughput, delay time of the proposed networks, and the packet loss rate performance of the OVPN over MPLS/OPS networks based on full mesh topology. The results validate the applicability of such reliable connectivity to high quality services in the OVPN over MPLS/OPS networks. Along with the results, the feasibility of the approach as the basis for the next generation networks is demonstrated and discussed.

Laser Communications Relay Demonstration (LCRD) Update and the Path Towards Optical Relay Operations

NASA Technical Reports Server (NTRS)

Israel, David J.; Edwards, Bernard L.; Staren, John W.

2017-01-01

This paper provides a concept for an evolution of NASA's optical communications near Earth relay architecture. NASA's Laser Communications Relay Demonstration (LCRD), a joint project between NASA's Goddard Space Flight Center (GSFC), the Jet Propulsion Laboratory - California Institute of Technology (JPL), and the Massachusetts Institute of Technology Lincoln Laboratory (MIT LL). LCRD will provide a minimum of two years of high data rate optical communications service experiments in geosynchronous orbit (GEO), following launch in 2019. This paper will provide an update of the LCRD mission status and planned capabilities and experiments, followed by a discussion of the path from LCRD to operational network capabilities.

Laser Communications Relay Demonstration (LCRD) Update and the Path Towards Optical Relay Operations

NASA Technical Reports Server (NTRS)

Israel, David J.; Edwards, Bernard L.; Staren, John W.

2017-01-01

This Presentation provides a concept for an evolution of NASAs optical communications near Earth relay architecture. NASA's Laser Communications Relay Demonstration (LCRD), a joint project between NASAs Goddard Space Flight Center (GSFC), the Jet Propulsion Laboratory - California Institute of Technology (JPL), and the Massachusetts Institute of Technology Lincoln Laboratory (MIT LL). LCRD will provide a minimum of two years of high data rate optical communications service experiments in geosynchronous orbit (GEO), following launch in 2019. This paper will provide an update of the LCRD mission status and planned capabilities and experiments, followed by a discussion of the path from LCRD to operational network capabilities.

Reconfigurable routing protocol for free space optical sensor networks.

PubMed

Xie, Rong; Yang, Won-Hyuk; Kim, Young-Chon

2012-01-01

Recently, free space optical sensor networks (FSOSNs), which are based on free space optics (FSO) instead of radio frequency (RF), have gained increasing visibility over traditional wireless sensor networks (WSNs) due to their advantages such as larger capacity, higher security, and lower cost. However, the performance of FSOSNs is restricted to the requirement of a direct line-of-sight (LOS) path between a sender and a receiver pair. Once a node dies of energy depletion, the network would probably suffer from a dramatic decrease of connectivity, resulting in a huge loss of data packets. Thus, this paper proposes a reconfigurable routing protocol (RRP) to overcome this problem by dynamically reconfiguring the network virtual topology. The RRP works in three phases: (1) virtual topology construction, (2) routing establishment, and (3) reconfigurable routing. When data transmission begins, the data packets are first routed through the shortest hop paths. Then a reconfiguration is initiated by the node whose residual energy falls below a threshold. Nodes affected by this dying node are classified into two types, namely maintenance nodes and adjustment nodes, and they are reconfigured according to the types. An energy model is designed to evaluate the performance of RRP through OPNET simulation. Our simulation results indicate that the RRP achieves better performance compared with the simple-link protocol and a direct reconfiguration scheme in terms of connectivity, network lifetime, packet delivery ratio and the number of living nodes.

Quantum routing of single optical photons with a superconducting flux qubit

NASA Astrophysics Data System (ADS)

Xia, Keyu; Jelezko, Fedor; Twamley, Jason

2018-05-01

Interconnecting optical photons with superconducting circuits is a challenging problem but essential for building long-range superconducting quantum networks. We propose a hybrid quantum interface between the microwave and optical domains where the propagation of a single-photon pulse along a nanowaveguide is controlled in a coherent way by tuning the electromagnetically induced transparency window with the quantum state of a flux qubit mediated by the spin in a nanodiamond. The qubit can route a single-photon pulse using the nanodiamond into a quantum superposition of paths without the aid of an optical cavity—simplifying the setup. By preparing the flux qubit in a superposition state our cavityless scheme creates a hybrid state-path entanglement between a flying single optical photon and a static superconducting qubit.

Long range laser traversing system

NASA Technical Reports Server (NTRS)

Caudill, L. O. (Inventor)

1974-01-01

The relative azimuth bearing between first and second spaced terrestrial points which may be obscured from each other by intervening terrain is measured by placing at one of the points a laser source for projecting a collimated beam upwardly in the vertical plane. The collimated laser beam is detected at the second point by positioning the optical axis of a receiving instrument for the laser beam in such a manner that the beam intercepts the optical axis. In response to the optical axis intercepting the beam, the beam is deflected into two different ray paths by a beam splitter having an apex located on the optical axis. The energy in the ray paths is detected by separate photoresponsive elements that drive logic networks for proving indications of: (1) the optical axis intercepting the beam; (2) the beam being on the left of the optical axis and (3) the beam being on the right side of the optical axis.

Optical neural network system for pose determination of spinning satellites

NASA Technical Reports Server (NTRS)

Lee, Andrew; Casasent, David

1990-01-01

An optical neural network architecture and algorithm based on a Hopfield optimization network are presented for multitarget tracking. This tracker utilizes a neuron for every possible target track, and a quadratic energy function of neural activities which is minimized using gradient descent neural evolution. The neural net tracker is demonstrated as part of a system for determining position and orientation (pose) of spinning satellites with respect to a robotic spacecraft. The input to the system is time sequence video from a single camera. Novelty detection and filtering are utilized to locate and segment novel regions from the input images. The neural net multitarget tracker determines the correspondences (or tracks) of the novel regions as a function of time, and hence the paths of object (satellite) parts. The path traced out by a given part or region is approximately elliptical in image space, and the position, shape and orientation of the ellipse are functions of the satellite geometry and its pose. Having a geometric model of the satellite, and the elliptical path of a part in image space, the three-dimensional pose of the satellite is determined. Digital simulation results using this algorithm are presented for various satellite poses and lighting conditions.

Optical implementation of (3, 3, 2) regular rectangular CC-Banyan optical network

NASA Astrophysics Data System (ADS)

Yang, Junbo; Su, Xianyu

2007-07-01

CC-Banyan network plays an important role in the optical interconnection network. Based on previous reports of (2, 2, 3) the CC-Banyan network, another rectangular-Banyan network, i.e. (3, 3, 2) rectangular CC-Banyan network, has been discussed. First, according to its construction principle, the topological graph and the routing rule of (3, 3, 2) rectangular CC-Banyan network have been proposed. Then, the optically experimental setup of (3, 3, 2) rectangular CC-Banyan network has been designed and achieved. Each stage of node switch consists of phase spatial light modulator (PSLM) and polarizing beam-splitter (PBS), and fiber has been used to perform connection between adjacent stages. PBS features that s-component (perpendicular to the incident plane) of the incident light beam is reflected, and p-component (parallel to the incident plane) passes through it. According to switching logic, under the control of external electrical signals, PSLM functions to control routing paths of the signal beams, i.e. the polarization of each optical signal is rotated or not rotated 90° by a programmable PSLM. Finally, the discussion and analysis show that the experimental setup designed here can realize many functions such as optical signal switch and permutation. It has advantages of large number of input/output-ports, compact in structure, and low energy loss. Hence, the experimental setup can be used in optical communication and optical information processing.

Cirrus cloud retrieval with MSG/SEVIRI using artificial neural networks

NASA Astrophysics Data System (ADS)

Strandgren, Johan; Bugliaro, Luca; Sehnke, Frank; Schröder, Leon

2017-09-01

Cirrus clouds play an important role in climate as they tend to warm the Earth-atmosphere system. Nevertheless their physical properties remain one of the largest sources of uncertainty in atmospheric research. To better understand the physical processes of cirrus clouds and their climate impact, enhanced satellite observations are necessary. In this paper we present a new algorithm, CiPS (Cirrus Properties from SEVIRI), that detects cirrus clouds and retrieves the corresponding cloud top height, ice optical thickness and ice water path using the SEVIRI imager aboard the geostationary Meteosat Second Generation satellites. CiPS utilises a set of artificial neural networks trained with SEVIRI thermal observations, CALIOP backscatter products, the ECMWF surface temperature and auxiliary data. CiPS detects 71 and 95 % of all cirrus clouds with an optical thickness of 0.1 and 1.0, respectively, that are retrieved by CALIOP. Among the cirrus-free pixels, CiPS classifies 96 % correctly. With respect to CALIOP, the cloud top height retrieved by CiPS has a mean absolute percentage error of 10 % or less for cirrus clouds with a top height greater than 8 km. For the ice optical thickness, CiPS has a mean absolute percentage error of 50 % or less for cirrus clouds with an optical thickness between 0.35 and 1.8 and of 100 % or less for cirrus clouds with an optical thickness down to 0.07 with respect to the optical thickness retrieved by CALIOP. The ice water path retrieved by CiPS shows a similar performance, with mean absolute percentage errors of 100 % or less for cirrus clouds with an ice water path down to 1.7 g m-2. Since the training reference data from CALIOP only include ice water path and optical thickness for comparably thin clouds, CiPS also retrieves an opacity flag, which tells us whether a retrieved cirrus is likely to be too thick for CiPS to accurately derive the ice water path and optical thickness. By retrieving CALIOP-like cirrus properties with the large spatial coverage and high temporal resolution of SEVIRI during both day and night, CiPS is a powerful tool for analysing the temporal evolution of cirrus clouds including their optical and physical properties. To demonstrate this, the life cycle of a thin cirrus cloud is analysed.

Recognition of the optical packet header for two channels utilizing the parallel reservoir computing based on a semiconductor ring laser

NASA Astrophysics Data System (ADS)

Bao, Xiurong; Zhao, Qingchun; Yin, Hongxi; Qin, Jie

2018-05-01

In this paper, an all-optical parallel reservoir computing (RC) system with two channels for the optical packet header recognition is proposed and simulated, which is based on a semiconductor ring laser (SRL) with the characteristic of bidirectional light paths. The parallel optical loops are built through the cross-feedback of the bidirectional light paths where every optical loop can independently recognize each injected optical packet header. Two input signals are mapped and recognized simultaneously by training all-optical parallel reservoir, which is attributed to the nonlinear states in the laser. The recognition of optical packet headers for two channels from 4 bits to 32 bits is implemented through the simulation optimizing system parameters and therefore, the optimal recognition error ratio is 0. Since this structure can combine with the wavelength division multiplexing (WDM) optical packet switching network, the wavelength of each channel of optical packet headers for recognition can be different, and a better recognition result can be obtained.

A proposal for an SDN-based SIEPON architecture

NASA Astrophysics Data System (ADS)

Khalili, Hamzeh; Sallent, Sebastià; Piney, José Ramón; Rincón, David

2017-11-01

Passive Optical Network (PON) elements such as Optical Line Terminal (OLT) and Optical Network Units (ONUs) are currently managed by inflexible legacy network management systems. Software-Defined Networking (SDN) is a new networking paradigm that improves the operation and management of networks. In this paper, we propose a novel architecture, based on the SDN concept, for Ethernet Passive Optical Networks (EPON) that includes the Service Interoperability standard (SIEPON). In our proposal, the OLT is partially virtualized and some of its functionalities are allocated to the core network management system, while the OLT itself is replaced by an OpenFlow (OF) switch. A new MultiPoint MAC Control (MPMC) sublayer extension based on the OpenFlow protocol is presented. This would allow the SDN controller to manage and enhance the resource utilization, flow monitoring, bandwidth assignment, quality-of-service (QoS) guarantees, and energy management of the optical network access, to name a few possibilities. The OpenFlow switch is extended with synchronous ports to retain the time-critical nature of the EPON network. OpenFlow messages are also extended with new functionalities to implement the concept of EPON Service Paths (ESPs). Our simulation-based results demonstrate the effectiveness of the new architecture, while retaining a similar (or improved) performance in terms of delay and throughput when compared to legacy PONs.

Analytical Study of different types Of network failure detection and possible remedies

NASA Astrophysics Data System (ADS)

Saxena, Shikha; Chandra, Somnath

2012-07-01

Faults in a network have various causes,such as the failure of one or more routers, fiber-cuts, failure of physical elements at the optical layer, or extraneous causes like power outages. These faults are usually detected as failures of a set of dependent logical entities and the links affected by the failed components. A reliable control plane plays a crucial role in creating high-level services in the next-generation transport network based on the Generalized Multiprotocol Label Switching (GMPLS) or Automatically Switched Optical Networks (ASON) model. In this paper, approaches to control-plane survivability, based on protection and restoration mechanisms, are examined. Procedures for the control plane state recovery are also discussed, including link and node failure recovery and the concepts of monitoring paths (MPs) and monitoring cycles (MCs) for unique localization of shared risk linked group (SRLG) failures in all-optical networks. An SRLG failure is a failure of multiple links due to a failure of a common resource. MCs (MPs) start and end at same (distinct) monitoring location(s). They are constructed such that any SRLG failure results in the failure of a unique combination of paths and cycles. We derive necessary and sufficient conditions on the set of MCs and MPs needed for localizing an SRLG failure in an arbitrary graph. Procedure of Protection and Restoration of the SRLG failure by backup re-provisioning algorithm have also been discussed.

Three-dimensional crossbar interconnection using planar-integrated free-space optics and digital mirror-device

NASA Astrophysics Data System (ADS)

Lohmann, U.; Jahns, J.; Limmer, S.; Fey, D.

2011-01-01

We consider the implementation of a dynamic crossbar interconnect using planar-integrated free-space optics (PIFSO) and a digital mirror-device™ (DMD). Because of the 3D nature of free-space optics, this approach is able to solve geometrical problems with crossings of the signal paths that occur in waveguide optical and electrical interconnection, especially for large number of connections. The DMD device allows one to route the signals dynamically. Due to the large number of individual mirror elements in the DMD, different optical path configurations are possible, thus offering the chance for optimizing the network configuration. The optimization is achieved by using an evolutionary algorithm for finding best values for a skewless parallel interconnection. Here, we present results and experimental examples for the use of the PIFSO/DMD-setup.

High speed all optical networks

NASA Technical Reports Server (NTRS)

Chlamtac, Imrich; Ganz, Aura

1990-01-01

An inherent problem of conventional point-to-point wide area network (WAN) architectures is that they cannot translate optical transmission bandwidth into comparable user available throughput due to the limiting electronic processing speed of the switching nodes. The first solution to wavelength division multiplexing (WDM) based WAN networks that overcomes this limitation is presented. The proposed Lightnet architecture takes into account the idiosyncrasies of WDM switching/transmission leading to an efficient and pragmatic solution. The Lightnet architecture trades the ample WDM bandwidth for a reduction in the number of processing stages and a simplification of each switching stage, leading to drastically increased effective network throughputs. The principle of the Lightnet architecture is the construction and use of virtual topology networks, embedded in the original network in the wavelength domain. For this construction Lightnets utilize the new concept of lightpaths which constitute the links of the virtual topology. Lightpaths are all-optical, multihop, paths in the network that allow data to be switched through intermediate nodes using high throughput passive optical switches. The use of the virtual topologies and the associated switching design introduce a number of new ideas, which are discussed in detail.

Cross layer optimization for cloud-based radio over optical fiber networks

NASA Astrophysics Data System (ADS)

Shao, Sujie; Guo, Shaoyong; Qiu, Xuesong; Yang, Hui; Meng, Luoming

2016-07-01

To adapt the 5G communication, the cloud radio access network is a paradigm introduced by operators which aggregates all base stations computational resources into a cloud BBU pool. The interaction between RRH and BBU or resource schedule among BBUs in cloud have become more frequent and complex with the development of system scale and user requirement. It can promote the networking demand among RRHs and BBUs, and force to form elastic optical fiber switching and networking. In such network, multiple stratum resources of radio, optical and BBU processing unit have interweaved with each other. In this paper, we propose a novel multiple stratum optimization (MSO) architecture for cloud-based radio over optical fiber networks (C-RoFN) with software defined networking. Additionally, a global evaluation strategy (GES) is introduced in the proposed architecture. MSO can enhance the responsiveness to end-to-end user demands and globally optimize radio frequency, optical spectrum and BBU processing resources effectively to maximize radio coverage. The feasibility and efficiency of the proposed architecture with GES strategy are experimentally verified on OpenFlow-enabled testbed in terms of resource occupation and path provisioning latency.

Introduction of a new opto-electrical phase-locked loop in CMOS technology: the PMD-PLL

NASA Astrophysics Data System (ADS)

Ringbeck, Thorsten; Schwarte, Rudolf; Buxbaum, Bernd

1999-12-01

The huge and increasing need of information in the industrial world demands an enormous potential of bandwidth in telecommunication systems. Optical communication provides all participants with the whole spectrum of digital services like videophone, cable TV, video conferencing and online services. Especially fast and low cost opto-electrical receivers are badly needed in order to expand fiber networks to every home (FTTH--fiber to the home or FTTD--fiber to the desk, respectively). This paper proposes a new receiver structure which is designed to receiver optical data which are encoded by code division multiple access techniques (CDMA). For data recovery in such CDMA networks phase locked loops (PLL) are needed, which synchronize the local oscillator with the incoming clock. In optical code division multiple access networks these PLLs could be realized either with an electrical PLL after opto-electrical converting or directly in the optical path with a pure optical PLL.

Experimental demonstration of multi-dimensional resources integration for service provisioning in cloud radio over fiber network

NASA Astrophysics Data System (ADS)

Yang, Hui; Zhang, Jie; Ji, Yuefeng; He, Yongqi; Lee, Young

2016-07-01

Cloud radio access network (C-RAN) becomes a promising scenario to accommodate high-performance services with ubiquitous user coverage and real-time cloud computing in 5G area. However, the radio network, optical network and processing unit cloud have been decoupled from each other, so that their resources are controlled independently. Traditional architecture cannot implement the resource optimization and scheduling for the high-level service guarantee due to the communication obstacle among them with the growing number of mobile internet users. In this paper, we report a study on multi-dimensional resources integration (MDRI) for service provisioning in cloud radio over fiber network (C-RoFN). A resources integrated provisioning (RIP) scheme using an auxiliary graph is introduced based on the proposed architecture. The MDRI can enhance the responsiveness to dynamic end-to-end user demands and globally optimize radio frequency, optical network and processing resources effectively to maximize radio coverage. The feasibility of the proposed architecture is experimentally verified on OpenFlow-based enhanced SDN testbed. The performance of RIP scheme under heavy traffic load scenario is also quantitatively evaluated to demonstrate the efficiency of the proposal based on MDRI architecture in terms of resource utilization, path blocking probability, network cost and path provisioning latency, compared with other provisioning schemes.

Experimental demonstration of multi-dimensional resources integration for service provisioning in cloud radio over fiber network.

PubMed

Yang, Hui; Zhang, Jie; Ji, Yuefeng; He, Yongqi; Lee, Young

2016-07-28

Cloud radio access network (C-RAN) becomes a promising scenario to accommodate high-performance services with ubiquitous user coverage and real-time cloud computing in 5G area. However, the radio network, optical network and processing unit cloud have been decoupled from each other, so that their resources are controlled independently. Traditional architecture cannot implement the resource optimization and scheduling for the high-level service guarantee due to the communication obstacle among them with the growing number of mobile internet users. In this paper, we report a study on multi-dimensional resources integration (MDRI) for service provisioning in cloud radio over fiber network (C-RoFN). A resources integrated provisioning (RIP) scheme using an auxiliary graph is introduced based on the proposed architecture. The MDRI can enhance the responsiveness to dynamic end-to-end user demands and globally optimize radio frequency, optical network and processing resources effectively to maximize radio coverage. The feasibility of the proposed architecture is experimentally verified on OpenFlow-based enhanced SDN testbed. The performance of RIP scheme under heavy traffic load scenario is also quantitatively evaluated to demonstrate the efficiency of the proposal based on MDRI architecture in terms of resource utilization, path blocking probability, network cost and path provisioning latency, compared with other provisioning schemes.

Experimental demonstration of multi-dimensional resources integration for service provisioning in cloud radio over fiber network

PubMed Central

Yang, Hui; Zhang, Jie; Ji, Yuefeng; He, Yongqi; Lee, Young

2016-01-01

Cloud radio access network (C-RAN) becomes a promising scenario to accommodate high-performance services with ubiquitous user coverage and real-time cloud computing in 5G area. However, the radio network, optical network and processing unit cloud have been decoupled from each other, so that their resources are controlled independently. Traditional architecture cannot implement the resource optimization and scheduling for the high-level service guarantee due to the communication obstacle among them with the growing number of mobile internet users. In this paper, we report a study on multi-dimensional resources integration (MDRI) for service provisioning in cloud radio over fiber network (C-RoFN). A resources integrated provisioning (RIP) scheme using an auxiliary graph is introduced based on the proposed architecture. The MDRI can enhance the responsiveness to dynamic end-to-end user demands and globally optimize radio frequency, optical network and processing resources effectively to maximize radio coverage. The feasibility of the proposed architecture is experimentally verified on OpenFlow-based enhanced SDN testbed. The performance of RIP scheme under heavy traffic load scenario is also quantitatively evaluated to demonstrate the efficiency of the proposal based on MDRI architecture in terms of resource utilization, path blocking probability, network cost and path provisioning latency, compared with other provisioning schemes. PMID:27465296

Real-time monitoring implementation in a remote-pumped WDM PON

NASA Astrophysics Data System (ADS)

Liaw, S.-K.; Hong, K.-L.; Shei, Y.-S.

2008-08-01

We report on an improved configuration to monitor a passive optical network with high quality in service. This proposed system comprises fiber-Bragg gratings, a 1 × 4 optical switch, and an optical time-domain reflectometry to diagnose the broken point in real time. It could simultaneously detect multioptical network units in a WDM PON. The remote-pump integrated residual pumping reused function is implemented. Broken points in different optical paths can be detected simultaneously even when the distances to the central office are identical. The bit-error rate testing is verified with a small power penalty, making it an ideal solution for the real-time monitoring in a WDM PON.

Performance evaluation of multi-stratum resources optimization with network functions virtualization for cloud-based radio over optical fiber networks.

PubMed

Yang, Hui; He, Yongqi; Zhang, Jie; Ji, Yuefeng; Bai, Wei; Lee, Young

2016-04-18

Cloud radio access network (C-RAN) has become a promising scenario to accommodate high-performance services with ubiquitous user coverage and real-time cloud computing using cloud BBUs. In our previous work, we implemented cross stratum optimization of optical network and application stratums resources that allows to accommodate the services in optical networks. In view of this, this study extends to consider the multiple dimensional resources optimization of radio, optical and BBU processing in 5G age. We propose a novel multi-stratum resources optimization (MSRO) architecture with network functions virtualization for cloud-based radio over optical fiber networks (C-RoFN) using software defined control. A global evaluation scheme (GES) for MSRO in C-RoFN is introduced based on the proposed architecture. The MSRO can enhance the responsiveness to dynamic end-to-end user demands and globally optimize radio frequency, optical and BBU resources effectively to maximize radio coverage. The efficiency and feasibility of the proposed architecture are experimentally demonstrated on OpenFlow-based enhanced SDN testbed. The performance of GES under heavy traffic load scenario is also quantitatively evaluated based on MSRO architecture in terms of resource occupation rate and path provisioning latency, compared with other provisioning scheme.

An Experiment of GMPLS-Based Dispersion Compensation Control over In-Field Fibers

NASA Astrophysics Data System (ADS)

Seno, Shoichiro; Horiuchi, Eiichi; Yoshida, Sota; Sugihara, Takashi; Onohara, Kiyoshi; Kamei, Misato; Baba, Yoshimasa; Kubo, Kazuo; Mizuochi, Takashi

As ROADMs (Reconfigurable Optical Add/Drop Multiplexers) are becoming widely used in metro/core networks, distributed control of wavelength paths by extended GMPLS (Generalized MultiProtocol Label Switching) protocols has attracted much attention. For the automatic establishment of an arbitrary wavelength path satisfying dynamic traffic demands over a ROADM or WXC (Wavelength Cross Connect)-based network, precise determination of chromatic dispersion over the path and optimized assignment of dispersion compensation capabilities at related nodes are essential. This paper reports an experiment over in-field fibers where GMPLS-based control was applied for the automatic discovery of chromatic dispersion, path computation, and wavelength path establishment with dynamic adjustment of variable dispersion compensation. The GMPLS-based control scheme, which the authors called GMPLS-Plus, extended GMPLS's distributed control architecture with attributes for automatic discovery, advertisement, and signaling of chromatic dispersion. In this experiment, wavelength paths with distances of 24km and 360km were successfully established and error-free data transmission was verified. The experiment also confirmed path restoration with dynamic compensation adjustment upon fiber failure.

SDN architecture for optical packet and circuit integrated networks

NASA Astrophysics Data System (ADS)

Furukawa, Hideaki; Miyazawa, Takaya

2016-02-01

We have been developing an optical packet and circuit integrated (OPCI) network, which realizes dynamic optical path, high-density packet multiplexing, and flexible wavelength resource allocation. In the OPCI networks, a best-effort service and a QoS-guaranteed service are provided by employing optical packet switching (OPS) and optical circuit switching (OCS) respectively, and users can select these services. Different wavelength resources are assigned for OPS and OCS links, and the amount of their wavelength resources are dynamically changed in accordance with the service usage conditions. To apply OPCI networks into wide-area (core/metro) networks, we have developed an OPCI node with a distributed control mechanism. Moreover, our OPCI node works with a centralized control mechanism as well as a distributed one. It is therefore possible to realize SDN-based OPCI networks, where resource requests and a centralized configuration are carried out. In this paper, we show our SDN architecture for an OPS system that configures mapping tables between IP addresses and optical packet addresses and switching tables according to the requests from multiple users via a web interface. While OpenFlow-based centralized control protocol is coming into widespread use especially for single-administrative, small-area (LAN/data-center) networks. Here, we also show an interworking mechanism between OpenFlow-based networks (OFNs) and the OPCI network for constructing a wide-area network, and a control method of wavelength resource selection to automatically transfer diversified flows from OFNs to the OPCI network.

Cost-effective method of manufacturing a 3D MEMS optical switch

NASA Astrophysics Data System (ADS)

Carr, Emily; Zhang, Ping; Keebaugh, Doug; Chau, Kelvin

2009-02-01

growth of data and video transport networks. All-optical switching eliminates the need for optical-electrical conversion offering the ability to switch optical signals transparently: independent of data rates, formats and wavelength. It also provides network operators much needed automation capabilities to create, monitor and protect optical light paths. To further accelerate the market penetration, it is necessary to identify a path to reduce the manufacturing cost significantly as well as enhance the overall system performance, uniformity and reliability. Currently, most MEMS optical switches are assembled through die level flip-chip bonding with either epoxies or solder bumps. This is due to the alignment accuracy requirements of the switch assembly, defect matching of individual die, and cost of the individual components. In this paper, a wafer level assembly approach is reported based on silicon fusion bonding which aims to reduce the packaging time, defect count and cost through volume production. This approach is successfully demonstrated by the integration of two 6-inch wafers: a mirror array wafer and a "snap-guard" wafer, which provides a mechanical structure on top of the micromirror to prevent electrostatic snap-down. The direct silicon-to-silicon bond eliminates the CTEmismatch and stress issues caused by non-silicon bonding agents. Results from a completed integrated switch assembly will be presented, which demonstrates the reliability and uniformity of some key parameters of this MEMS optical switch.

Architecture design and performance evaluation of multigranularity optical networks based on optical code division multiplexing

NASA Astrophysics Data System (ADS)

Huang, Shaowei; Baba, Ken-Ichi; Murata, Masayuki; Kitayama, Ken-Ichi

2006-12-01

In traditional lambda-based multigranularity optical networks, a lambda is always treated as the basic routing unit, resulting in low wavelength utilization. On the basis of optical code division multiplexing (OCDM) technology, a novel OCDM-based multigranularity optical cross-connect (MG-OXC) is proposed. Compared with the traditional lambda-based MG-OXC, its switching capability has been extended to support fiber switching, waveband switching, lambda switching, and OCDM switching. In a network composed of OCDM-based MG-OXCs, a single wavelength can be shared by distinct label switched paths (LSPs) called OCDM-LSPs, and OCDM-LSP switching can be implemented in the optical domain. To improve the network flexibility for an OCDM-LSP provisioning, two kinds of switches enabling hybrid optical code (OC)-wavelength conversion are designed. Simulation results indicate that a blocking probability reduction of 2 orders can be obtained by deploying only five OCs to a single wavelength. Furthermore, compared with time-division-multiplexing LSP (TDM-LSP), owing to the asynchronous accessibility and the OC conversion, OCDM-LSPs have been shown to permit a simpler switch architecture and achieve better blocking performance than TDM-LSPs.

Wide range operation of regenerative optical parametric wavelength converter using ASE-degraded 43-Gb/s RZ-DPSK signals.

PubMed

Gao, Mingyi; Kurumida, Junya; Namiki, Shu

2011-11-07

For sustainable growth of the Internet, wavelength-tunable optical regeneration is the key to scaling up high energy-efficiency dynamic optical path networks while keeping the flexibility of the network. Wavelength-tunable optical parametric regenerator (T-OPR) based on the gain saturation effect of parametric amplification in a highly nonlinear fiber is promising for noise reduction in phase-shift keying signals. In this paper, we experimentally evaluated the T-OPR performance for ASE-degraded 43-Gb/s RZ-DPSK signals over a 20-nm input wavelength range between 1527 nm and 1547 nm. As a result, we achieved improved power penalty performance for the regenerated idler with a proper pump power range.

Performance evaluation of multi-stratum resources integration based on network function virtualization in software defined elastic data center optical interconnect.

PubMed

Yang, Hui; Zhang, Jie; Ji, Yuefeng; Tian, Rui; Han, Jianrui; Lee, Young

2015-11-30

Data center interconnect with elastic optical network is a promising scenario to meet the high burstiness and high-bandwidth requirements of data center services. In our previous work, we implemented multi-stratum resilience between IP and elastic optical networks that allows to accommodate data center services. In view of this, this study extends to consider the resource integration by breaking the limit of network device, which can enhance the resource utilization. We propose a novel multi-stratum resources integration (MSRI) architecture based on network function virtualization in software defined elastic data center optical interconnect. A resource integrated mapping (RIM) scheme for MSRI is introduced in the proposed architecture. The MSRI can accommodate the data center services with resources integration when the single function or resource is relatively scarce to provision the services, and enhance globally integrated optimization of optical network and application resources. The overall feasibility and efficiency of the proposed architecture are experimentally verified on the control plane of OpenFlow-based enhanced software defined networking (eSDN) testbed. The performance of RIM scheme under heavy traffic load scenario is also quantitatively evaluated based on MSRI architecture in terms of path blocking probability, provisioning latency and resource utilization, compared with other provisioning schemes.

Optical fiber network sensor system for monitoring methane concentration

NASA Astrophysics Data System (ADS)

Zhang, Zhi-wei; Zhang, Ji-long

2011-08-01

With regard to the high accuracy optic-fiber sensor for monitoring methane concentration, the choice of light source depends on methane peak values. Besides, the environment of mine should be considered, that is to say other gas should be considered, such as vapor, CO and CO2 etc, without absorbent spectrum in the decided wavelength. It has been reported that vapor, CO and CO2 have no obvious absorption in 0.85μm, 1.3μm and 1.66μm area, CH4 has no obvious absorption in 0.85μm area. So diode laser with 1.3μm or 1.66μm peak wavelength is chosen as the optic-fiber sensor's light source for detecting methane concentration. On the basis of the principle of optic absorption varied with methane concentration at its characteristic absorbent wavelength, the advantage of optic-fiber sensor technology and the circumstance characteristic of the coal mine. An optic-fiber sensor system is presented for monitoring methane concentration. Space Division Multiple Access Technology (SDMAT) and long optical path absorbent pool technology are combined in the study. Considering the circumstance characteristic of the coal mine, the optic-fiber network sensors for detecting methane concentration from mix gas of vapor, CO, CH4 and CO2 are used. It introduces the principle of an optic-fiber sensor system for monitoring methane concentration in coal mine. It contains the structure block diagram of monitoring system, the system is mainly made up of diode laser for monitoring methane concentration, Y-shaped photo-coupler with coupled rate 50:50, optical switch 1×2, gas absorbent cell, the computer data process and control system and photoelectric transformer. In this study, in order to decrease to the influence of the dark-current of photodiode, intensity in light sources and temperature drifts of processing circuit on the system accuracy in measurement, a beam of light is broken down into two beams in the coupler of Y-shaped coupler, the one acts as the reference optical path, the other is known as the sensing optical path. The experimental result shows that diode laser with 1654.141nm in wavelength is taken as the optic source for detecting methane concentration, the detective limit of the sensor is below 4.274mg/m3 when the optical path of absorbent pool is 20 centimeters, and the prevision and stability could satisfy practical application. The whole instrument can also reach on-line measurement with multiple points on different spot.

Blocking probability in the hose-model optical VPN with different number of wavelengths

NASA Astrophysics Data System (ADS)

Roslyakov, Alexander V.

2017-04-01

Connection setup with guaranteed quality of service (QoS) in the optical virtual private network (OVPN) is a major goal for the network providers. In order to support this we propose a QoS based OVPN connection set up mechanism over WDM network to the end customer. The proposed WDM network model can be specified in terms of QoS parameter such as blocking probability. We estimated this QoS parameter based on the hose-model OVPN. In this mechanism the OVPN connections also can be created or deleted according to the availability of the wavelengths in the optical path. In this paper we have considered the impact of the number of wavelengths on the computation of blocking probability. The goal of the work is to dynamically provide a best OVPN connection during frequent arrival of connection requests with QoS requirements.

Link Power Budget and Traffict QoS Performance Analysis of Gygabit Passive Optical Network

NASA Astrophysics Data System (ADS)

Ubaidillah, A.; Alfita, R.; Toyyibah

2018-01-01

Data service of telecommunication network is needed widely in the world; therefore extra wide bandwidth must be provided. For this case, PT. Telekomunikasi Tbk. applies GPON (Gigabit Passive Optical Network) as optical fibre based on telecommunication network system. GPON is a point to a multipoint technology of FTTx (Fiber to The x) that transmits information signals to the subscriber over optical fibre. In GPON trunking system, from OLT (Optical Line Terminal), the network is split to many ONT (Optical Network Terminal) of the subscribers, so it causes path loss and attenuation. In this research, the GPON performance is measured from the link power budget system and the Quality of Service (QoS) of the traffic. And the observation result shows that the link power budget system of this GPON is in good condition. The link power budget values from the mathematical calculation and direct measurement are satisfy the ITU-T G984 Class B standard, that the power level must be between -8 dBm to -27 dBm. While from the traffic performance, the observation result shows that the network resource utility of the subscribers of the observed area is not optimum. The mean of subscriber utility rate is 27.985 bps for upstream and 79.687 bps for downstream. While maximally, It should be 60.800 bps for upstream and 486.400 bps for downstream.

Performance evaluation of data center service localization based on virtual resource migration in software defined elastic optical network.

PubMed

Yang, Hui; Zhang, Jie; Ji, Yuefeng; Tan, Yuanlong; Lin, Yi; Han, Jianrui; Lee, Young

2015-09-07

Data center interconnection with elastic optical network is a promising scenario to meet the high burstiness and high-bandwidth requirements of data center services. In our previous work, we implemented cross stratum optimization of optical network and application stratums resources that allows to accommodate data center services. In view of this, this study extends the data center resources to user side to enhance the end-to-end quality of service. We propose a novel data center service localization (DCSL) architecture based on virtual resource migration in software defined elastic data center optical network. A migration evaluation scheme (MES) is introduced for DCSL based on the proposed architecture. The DCSL can enhance the responsiveness to the dynamic end-to-end data center demands, and effectively reduce the blocking probability to globally optimize optical network and application resources. The overall feasibility and efficiency of the proposed architecture are experimentally verified on the control plane of our OpenFlow-based enhanced SDN testbed. The performance of MES scheme under heavy traffic load scenario is also quantitatively evaluated based on DCSL architecture in terms of path blocking probability, provisioning latency and resource utilization, compared with other provisioning scheme.

Integrated RF/Optical Interplanetary Networking Preliminary Explorations and Empirical Results

NASA Technical Reports Server (NTRS)

Raible, Daniel E.; Hylton, Alan G.

2012-01-01

Over the last decade interplanetary telecommunication capabilities have been significantly expanded--specifically in support of the Mars exploration rover and lander missions. NASA is continuing to drive advances in new, high payoff optical communications technologies to enhance the network to Gbps performance from Mars, and the transition from technology demonstration to operational system is examined through a hybrid RF/optical approach. Such a system combines the best features of RF and optical communications considering availability and performance to realize a dual band trunk line operating within characteristic constraints. Disconnection due to planetary obscuration and solar conjunction, link delays, timing, ground terminal mission congestion and scheduling policy along with space and atmospheric weather disruptions all imply the need for network protocol solutions to ultimately manage the physical layer in a transparent manner to the end user. Delay Tolerant Networking (DTN) is an approach under evaluation which addresses these challenges. A multi-hop multi-path hybrid RF and optical test bed has been constructed to emulate the integrated deep space network and to support protocol and hardware refinement. Initial experimental results characterize several of these challenges and evaluate the effectiveness of DTN as a solution to mitigate them.

LCRD Update and Path to Optical Relay Operations

NASA Technical Reports Server (NTRS)

Israel, David

2017-01-01

Speaker and Presenter at the Lincoln Laboratory Communications Workshop on May 23, 2017 at the Massachusetts Institute of Technology Lincoln Laboratory in Lexington, MA. This presentation discusses a concept for an evolution of NASAs optical communications near-Earth relay architecture. NASA's Laser Communications Relay Demonstration (LCRD) is a joint project between NASAs Goddard Space Flight Center (GSFC), the Jet Propulsion Laboratory California Institute of Technology (JPL), and the Massachusetts Institute of Technology Lincoln Laboratory (MIT LL). LCRD will provide a minimum of two years of high data rate optical communications service experiments in geosynchronous orbit (GEO) following launch in 2019. This presentation will provide an update of the LCRD mission status and planned capabilities and experiments, followed by a discussion of the path from LCRD to operational network capabilities.

Unified study of Quality of Service (QoS) in OPS/OBS networks

NASA Astrophysics Data System (ADS)

Hailu, Dawit Hadush; Lema, Gebrehiwet Gebrekrstos; Yekun, Ephrem Admasu; Kebede, Samrawit Haylu

2017-07-01

With the growth of Internet traffic, an inevitable use of optical networks provide a large bandwidth, fast data transmission rates and Quality of Service (QoS) support. Currently, Optical Burst Switched (OBS)/Optical Packet Switched (OPS) networks are under study as future solutions for addressing the increase demand of Internet traffic. However, due to their high blocking probability in the intermediate nodes they have been delayed in the industries. Packet loss in OBS/OPS networks is mainly occur due to contention. Hence, the contribution of this study is to analyze the file loss ratio (FLR), packet overhead and number of disjoint paths, and processing delay over Coded Packet Transport (CPT) scheme for OBS/OPS network using simulation. The simulations show that CPT scheme reduces the FLR in OBS/OPS network for the evaluated scenarios since the data packets are chopped off into blocks of the data packet for transmission over a network. Simulation results for secrecy and survivability are verified with the help of the analytical model to define the operational range of CPT scheme.

Optical Interconnections for VLSI Computational Systems Using Computer-Generated Holography.

NASA Astrophysics Data System (ADS)

Feldman, Michael Robert

Optical interconnects for VLSI computational systems using computer generated holograms are evaluated in theory and experiment. It is shown that by replacing particular electronic connections with free-space optical communication paths, connection of devices on a single chip or wafer and between chips or modules can be improved. Optical and electrical interconnects are compared in terms of power dissipation, communication bandwidth, and connection density. Conditions are determined for which optical interconnects are advantageous. Based on this analysis, it is shown that by applying computer generated holographic optical interconnects to wafer scale fine grain parallel processing systems, dramatic increases in system performance can be expected. Some new interconnection networks, designed to take full advantage of optical interconnect technology, have been developed. Experimental Computer Generated Holograms (CGH's) have been designed, fabricated and subsequently tested in prototype optical interconnected computational systems. Several new CGH encoding methods have been developed to provide efficient high performance CGH's. One CGH was used to decrease the access time of a 1 kilobit CMOS RAM chip. Another was produced to implement the inter-processor communication paths in a shared memory SIMD parallel processor array.

End-to-end deep neural network for optical inversion in quantitative photoacoustic imaging.

PubMed

Cai, Chuangjian; Deng, Kexin; Ma, Cheng; Luo, Jianwen

2018-06-15

An end-to-end deep neural network, ResU-net, is developed for quantitative photoacoustic imaging. A residual learning framework is used to facilitate optimization and to gain better accuracy from considerably increased network depth. The contracting and expanding paths enable ResU-net to extract comprehensive context information from multispectral initial pressure images and, subsequently, to infer a quantitative image of chromophore concentration or oxygen saturation (sO 2 ). According to our numerical experiments, the estimations of sO 2 and indocyanine green concentration are accurate and robust against variations in both optical property and object geometry. An extremely short reconstruction time of 22 ms is achieved.

Overlapped optics induced perfect coherent effects.

PubMed

Li, Jian Jie; Zang, Xiao Fei; Mao, Jun Fa; Tang, Min; Zhu, Yi Ming; Zhuang, Song Lin

2013-12-20

For traditional coherent effects, two separated identical point sources can be interfered with each other only when the optical path difference is integer number of wavelengths, leading to alternate dark and bright fringes for different optical path difference. For hundreds of years, such a perfect coherent condition seems insurmountable. However, in this paper, based on transformation optics, two separated in-phase identical point sources can induce perfect interference with each other without satisfying the traditional coherent condition. This shifting illusion media is realized by inductor-capacitor transmission line network. Theoretical analysis, numerical simulations and experimental results are performed to confirm such a kind of perfect coherent effect and it is found that the total radiation power of multiple elements system can be greatly enhanced. Our investigation may be applicable to National Ignition Facility (NIF), Inertial Confined Fusion (ICF) of China, LED lighting technology, terahertz communication, and so on.

Stable radio-frequency transfer over optical fiber by phase-conjugate frequency mixing.

PubMed

He, Yabai; Orr, Brian J; Baldwin, Kenneth G H; Wouters, Michael J; Luiten, Andre N; Aben, Guido; Warrington, R Bruce

2013-08-12

We demonstrate long-distance (≥100-km) synchronization of the phase of a radio-frequency reference over an optical-fiber network without needing to actively stabilize the optical path length. Frequency mixing is used to achieve passive phase-conjugate cancellation of fiber-length fluctuations, ensuring that the phase difference between the reference and synchronized oscillators is independent of the link length. The fractional radio-frequency-transfer stability through a 100-km "real-world" urban optical-fiber network is 6 × 10(-17) with an averaging time of 10(4) s. Our compensation technique is robust, providing long-term stability superior to that of a hydrogen maser. By combining our technique with the short-term stability provided by a remote, high-quality quartz oscillator, this system is potentially applicable to transcontinental optical-fiber time and frequency dissemination where the optical round-trip propagation time is significant.

Optical datacenter network employing slotted (TDMA) operation for dynamic resource allocation

NASA Astrophysics Data System (ADS)

Bakopoulos, P.; Tokas, K.; Spatharakis, C.; Patronas, I.; Landi, G.; Christodoulopoulos, K.; Capitani, M.; Kyriakos, A.; Aziz, M.; Reisis, D.; Varvarigos, E.; Zahavi, E.; Avramopoulos, H.

2018-02-01

The soaring traffic demands in datacenter networks (DCNs) are outpacing progresses in CMOS technology, challenging the bandwidth and energy scalability of currently established technologies. Optical switching is gaining traction as a promising path for sustaining the explosive growth of DCNs; however, its practical deployment necessitates extensive modifications to the network architecture and operation, tailored to the technological particularities of optical switches (i.e. no buffering, limitations in radix size and speed). European project NEPHELE is developing an optical network infrastructure that leverages optical switching within a software-defined networking (SDN) framework to overcome the bandwidth and energy scaling challenges of datacenter networks. An experimental validation of the NEPHELE data plane is reported based on commercial off-the-shelf optical components controlled by FPGA boards. To facilitate dynamic allocation of the network resources and perform collision-free routing in a lossless network environment, slotted operation is employed (i.e. using time-division multiple-access - TDMA). Error-free operation of the NEPHELE data plane is verified for 200 μs slots in various scenarios that involve communication between Ethernet hosts connected to custom-designed top-of-rack (ToR) switches, located in the same or in different datacenter pods. Control of the slotted data plane is obtained through an SDN framework comprising an OpenDaylight controller with appropriate add-ons. Communication between servers in the optical-ToR is demonstrated with various routing scenarios, concerning communication between hosts located in the same rack or in different racks, within the same or different datacenter pods. Error-free operation is confirmed for all evaluated scenarios, underpinning the feasibility of the NEPHELE architecture.

Indoor communications networks realized through hybrid free-space optical and Wi-Fi links

NASA Astrophysics Data System (ADS)

Liverman, Spencer; Wang, Qiwei; Chu, Yu-Chung; Borah, Anindita; Wang, Songtao; Natarajan, Arun; Nguyen, Thinh; Wang, Alan X.

2018-01-01

Recently, free-space optical (FSO) networks have been investigated as a potential replacement for traditional WiFi networks due to their large bandwidth potentials. However, FSO networks often suffer from a lack of mobility. We present a hybrid free-space optical and radio frequency (RF) system that we have named WiFO, which seamlessly integrates free-space optical links with pre-existing WiFi networks. The free-space optical link in this system utilizes infrared LEDs operating at a wavelength of 850nm and is capable of transmitting 50Mbps over a three-meter distance. In this hybrid system, optical transmitters are embedded periodically throughout the ceiling of a workspace. Each transmitter directs an optical signal downward in a diffuse light cone, establishing a line of sight optical link. Line of sight communications links have an intrinsic physical layer of security due to the fact that a user must be directly in the path of transmission to access the link; however, this feature also poses a challenge for mobility. In our system, if the free-space optical link is interrupted, a control algorithm redirects traffic over a pre-existing WiFi link ensuring uninterrupted transmissions. After data packets are received, acknowledgments are sent back to a central access point via a WiFi link. As the demand for wireless bandwidth continues to increase exponentially, utilizing the unregulated bandwidth contained within optical spectrum will become necessary. Our fully functional hybrid free-space optical and WiFi prototype system takes full advantage of the untapped bandwidth potential in the optical spectrum, while also maintaining the mobility inherent in WiFi networks.

Heuristic approaches for energy-efficient shared restoration in WDM networks

NASA Astrophysics Data System (ADS)

Alilou, Shahab

In recent years, there has been ongoing research on the design of energy-efficient Wavelength Division Multiplexing (WDM) networks. The explosive growth of Internet traffic has led to increased power consumption of network components. Network survivability has also been a relevant research topic, as it plays a crucial role in assuring continuity of service with no disruption, regardless of network component failure. Network survivability mechanisms tend to utilize considerable resources such as spare capacity in order to protect and restore information. This thesis investigates techniques for reducing energy demand and enhancing energy efficiency in the context of network survivability. We propose two novel heuristic energy-efficient shared protection approaches for WDM networks. These approaches intend to save energy by setting on sleep mode devices that are not being used while providing shared backup paths to satisfy network survivability. The first approach exploits properties of a math series in order to assign weight to the network links. It aims at reducing power consumption at the network indirectly by aggregating traffic on a set of nodes and links with high traffic load level. Routing traffic on links and nodes that are already under utilization makes it possible for the links and nodes with no load to be set on sleep mode. The second approach is intended to dynamically route traffic through nodes and links with high traffic load level. Similar to the first approach, this approach computes a pair of paths for every newly arrived demand. It computes these paths for every new demand by comparing the power consumption of nodes and links in the network before the demand arrives with their potential power consumption if they are chosen along the paths of this demand. Simulations of two different networks were used to compare the total network power consumption obtained using the proposed techniques against a standard shared-path restoration scheme. Shared-path restoration is a network survivability method in which a link-disjoint backup path and wavelength is reserved at the time of call setup for a working path. However, in order to reduce spare capacity consumption, this reserved backup path and wavelength may be shared with other backup paths. Pool Sharing Scheme (PSS) is employed to implement shared-path restoration scheme [1]. In an optical network, the failure of a single link leads to the failure of all the lightpaths that pass through that particular link. PSS ensures that the amount of backup bandwidth required on a link to restore the failed connections will not be more than the total amount of reserved backup bandwidth on that link. Simulation results indicate that the proposed approaches lead to up to 35% power savings in WDM networks when traffic load is low. However, power saving decreases to 14% at high traffic load level. Furthermore, in terms of the total capacity consumption for working paths, PSS outperforms the two proposed approaches, as expected. In terms of total capacity consumption all the approaches behave similarly. In general, at low traffic load level, the two proposed approaches behave similar to PSS in terms of average link load, and the ratio of block demands. Nevertheless, at high traffic load, the proposed approaches result in higher ratio of blocked demands than PSS. They also lead to higher average link load than PSS for the equal number of generated demands.

Instant provisioning of wavelength service using quasi-circuit optical burst switching

NASA Astrophysics Data System (ADS)

Xie, Hongyi; Li, Yanhe; Zheng, Xiaoping; Zhang, Hanyi

2006-09-01

Due to the recent outstanding advancement of optical networking technology, pervasive Grid computing will be a feasible option in the near future. As Grid infrastructure, optical networks must be able to handle different Grid traffic patterns with various traffic characteristics as well as different QoS requirements. With current optical switching technology, optical circuit switching is suitable for data-intensive Grid applications while optical burst switching is suitable to submit small Grid jobs. However, there would be high bandwidth short-lived traffic in some emerging Grid applications such as multimedia editing. This kind of traffic couldn't be well supported by both OCS and conventional OBS because of considerable path setup delay and bandwidth waste in OCS and inherent loss in OBS. Quasi-Circuit OBS (QCOBS) is proposed in this paper to address this challenge, providing one-way reserved, nearly lossless, instant provisioned wavelength service in OBS networks. Simulation results show that QCOBS achieves lossless transmission at low and moderate loads, and very low loss probability at high loads with proper guard time configuration.

Architectural and engineering issues for building an optical Internet

NASA Astrophysics Data System (ADS)

St. Arnaud, Bill

1998-10-01

Recent developments in high density Wave Division Multiplexing fiber systems allows for the deployment of a dedicated optical Internet network for large volume backbone pipes that does not require an underlying multi-service SONET/SDH and ATM transport protocol. Some intrinsic characteristics of Internet traffic such as its self similar nature, server bound congestion, routing and data asymmetry allow for highly optimized traffic engineered networks using individual wavelengths. By transmitting GigaBit Ethernet or SONET/SDH frames natively over WDM wavelengths that directly interconnect high performance routers the original concept of the Internet as an intrinsically survivable datagram network is possible. Traffic engineering, restoral, protection and bandwidth management of the network must now be carried out at the IP layer and so new routing or switching protocols such as MPLS that allow for uni- directional paths with fast restoral and protection at the IP layer become essential for a reliable production network. The deployment of high density WDM municipal and campus networks also gives carriers and ISPs the flexibility to offer customers as integrated and seamless set of optical Internet services.

Optical implementation of polarization-independent, bidirectional, nonblocking Clos network using polarization control technique in free space

NASA Astrophysics Data System (ADS)

Yang, Junbo; Yang, Jiankun; Li, Xiujian; Chang, Shengli; Su, Xianyu; Ping, Xu

2011-04-01

The clos network is one of the earliest multistage interconnection networks. Recently, it has been widely studied in parallel optical information processing systems, and there have been many efforts to develop this network. In this paper, a smart and compact Clos network, including Clos(2,3,2) and Clos(2,4,2), is proposed by using polarizing beam-splitters (PBS), phase spatial light modulators (PSLM), and mirrors. PBS features that are s-component (perpendicular to the incident plane) of the incident light beam is reflected, and the p-component (parallel to the incident plane) passes through it. According to switching logic, under control of external electrical signals, PSLM functions to control routing paths of the signal beams, i.e., the polarization of each optical signal is rotated or not rotated 90° by a programmable PSLM. This new type of configuration grants the features of less optical components, compact in structure, efficient in performance, and insensitive to polarization of signal beam. In addition, the straight, the exchange, and the broadcast functions of the basic switch element are implemented bidirectionally in free-space. Furthermore, the new optical experimental module of 2×3 and 2×4 optical switch is also presented by a cascading polarization-independent bidirectional 2×2 optical switch. Simultaneously, the routing state-table of 2×3 and 2×4 optical switch to perform all permutation output and nonblocking switch for the input signal beam, is achieved. Since the proposed optical setup consists of only optical polarization elements, it is compact in structure, and possesses a low energy loss, a high signal-to-ratio, and an available large number of optical channels. Finally, the discussions and the experimental results show that the Clos network proposed here should be helpful in the design of large-scale network matrix, and may be used in optical communication and optical information processing.

Path coloring on the Mesh

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rabani, Y.

In the minimum path coloring problem, we are given a list of pairs of vertices of a graph. We are asked to connect each pair by a colored path. Paths of the same color must be edge disjoint. Our objective is to minimize the number of colors used. This problem was raised by Aggarwal et al and Raghavan and Upfal as a model for routing in all-optical networks. It is also related to questions in circuit routing. In this paper, we improve the O (ln N) approximation result of Kleinberg and Tardos for path coloring on the N x Nmore » mesh. We give an O(1) approximation algorithm to the number of colors needed, and a poly(ln ln N) approximation algorithm to the choice of paths and colors. To the best of our knowledge, these are the first sub-logarithmic bounds for any network other than trees, rings, or trees of rings. Our results are based on developing new techniques for randomized rounding. These techniques iteratively improve a fractional solution until it approaches integrality. They are motivated by the method used by Leighton, Maggs, and Rao for packet routing.« less

Scalable software-defined optical networking with high-performance routing and wavelength assignment algorithms.

PubMed

Lee, Chankyun; Cao, Xiaoyuan; Yoshikane, Noboru; Tsuritani, Takehiro; Rhee, June-Koo Kevin

2015-10-19

The feasibility of software-defined optical networking (SDON) for a practical application critically depends on scalability of centralized control performance. The paper, highly scalable routing and wavelength assignment (RWA) algorithms are investigated on an OpenFlow-based SDON testbed for proof-of-concept demonstration. Efficient RWA algorithms are proposed to achieve high performance in achieving network capacity with reduced computation cost, which is a significant attribute in a scalable centralized-control SDON. The proposed heuristic RWA algorithms differ in the orders of request processes and in the procedures of routing table updates. Combined in a shortest-path-based routing algorithm, a hottest-request-first processing policy that considers demand intensity and end-to-end distance information offers both the highest throughput of networks and acceptable computation scalability. We further investigate trade-off relationship between network throughput and computation complexity in routing table update procedure by a simulation study.

GMPLS-based control plane for optical networks: early implementation experience

NASA Astrophysics Data System (ADS)

Liu, Hang; Pendarakis, Dimitrios; Komaee, Nooshin; Saha, Debanjan

2002-07-01

Generalized Multi-Protocol Label Switching (GMPLS) extends MPLS signaling and Internet routing protocols to provide a scalable, interoperable, distributed control plane, which is applicable to multiple network technologies such as optical cross connects (OXCs), photonic switches, IP routers, ATM switches, SONET and DWDM systems. It is intended to facilitate automatic service provisioning and dynamic neighbor and topology discovery across multi-vendor intelligent transport networks, as well as their clients. Efforts to standardize such a distributed common control plane have reached various stages in several bodies such as the IETF, ITU and OIF. This paper describes the design considerations and architecture of a GMPLS-based control plane that we have prototyped for core optical networks. Functional components of GMPLS signaling and routing are integrated in this architecture with an application layer controller module. Various requirements including bandwidth, network protection and survivability, traffic engineering, optimal utilization of network resources, and etc. are taken into consideration during path computation and provisioning. Initial experiments with our prototype demonstrate the feasibility and main benefits of GMPLS as a distributed control plane for core optical networks. In addition to such feasibility results, actual adoption and deployment of GMPLS as a common control plane for intelligent transport networks will depend on the successful completion of relevant standardization activities, extensive interoperability testing as well as the strengthening of appropriate business drivers.

Dynamic routing and spectrum assignment based on multilayer virtual topology and ant colony optimization in elastic software-defined optical networks

NASA Astrophysics Data System (ADS)

Wang, Fu; Liu, Bo; Zhang, Lijia; Zhang, Qi; Tian, Qinghua; Tian, Feng; Rao, Lan; Xin, Xiangjun

2017-07-01

Elastic software-defined optical networks greatly improve the flexibility of the optical switching network while it has brought challenges to the routing and spectrum assignment (RSA). A multilayer virtual topology model is proposed to solve RSA problems. Two RSA algorithms based on the virtual topology are proposed, which are the ant colony optimization (ACO) algorithm of minimum consecutiveness loss and the ACO algorithm of maximum spectrum consecutiveness. Due to the computing power of the control layer in the software-defined network, the routing algorithm avoids the frequent link-state information between routers. Based on the effect of the spectrum consecutiveness loss on the pheromone in the ACO, the path and spectrum of the minimal impact on the network are selected for the service request. The proposed algorithms have been compared with other algorithms. The results show that the proposed algorithms can reduce the blocking rate by at least 5% and perform better in spectrum efficiency. Moreover, the proposed algorithms can effectively decrease spectrum fragmentation and enhance available spectrum consecutiveness.

Optical stabilization for time transfer infrastructure

NASA Astrophysics Data System (ADS)

Vojtech, Josef; Altmann, Michal; Skoda, Pavel; Horvath, Tomas; Slapak, Martin; Smotlacha, Vladimir; Havlis, Ondrej; Munster, Petr; Radil, Jan; Kundrat, Jan; Altmannova, Lada; Velc, Radek; Hula, Miloslav; Vohnout, Rudolf

2017-08-01

In this paper, we propose and present verification of all-optical methods for stabilization of the end-to-end delay of an optical fiber link. These methods are verified for deployment within infrastructure for accurate time and stable frequency distribution, based on sharing of fibers with research and educational network carrying live data traffic. Methods range from path length control, through temperature conditioning method to transmit wavelength control. Attention is given to achieve continuous control for relatively broad range of delays. We summarize design rules for delay stabilization based on the character and the total delay jitter.

Tunable ion-photon entanglement in an optical cavity.

PubMed

Stute, A; Casabone, B; Schindler, P; Monz, T; Schmidt, P O; Brandstätter, B; Northup, T E; Blatt, R

2012-05-23

Proposed quantum networks require both a quantum interface between light and matter and the coherent control of quantum states. A quantum interface can be realized by entangling the state of a single photon with the state of an atomic or solid-state quantum memory, as demonstrated in recent experiments with trapped ions, neutral atoms, atomic ensembles and nitrogen-vacancy spins. The entangling interaction couples an initial quantum memory state to two possible light-matter states, and the atomic level structure of the memory determines the available coupling paths. In previous work, the transition parameters of these paths determined the phase and amplitude of the final entangled state, unless the memory was initially prepared in a superposition state (a step that requires coherent control). Here we report fully tunable entanglement between a single (40)Ca(+) ion and the polarization state of a single photon within an optical resonator. Our method, based on a bichromatic, cavity-mediated Raman transition, allows us to select two coupling paths and adjust their relative phase and amplitude. The cavity setting enables intrinsically deterministic, high-fidelity generation of any two-qubit entangled state. This approach is applicable to a broad range of candidate systems and thus is a promising method for distributing information within quantum networks.

Distance Learning Partnerships for Underserved Learners.

ERIC Educational Resources Information Center

Chavkin, Nancy Feyl; And Others

1994-01-01

Describes a partnership that was formed to develop a fiber optic interactive network and its interface with the development of algebra curriculum and social services in the PATH (Partnership for Access to Higher) Mathematics project in Texas. Equipment connections, costs, and classroom layout are described; and social work components are…

A Neural Network Approach to Infer Optical Depth of Thick Ice Clouds at Night

NASA Technical Reports Server (NTRS)

Minnis, P.; Hong, G.; Sun-Mack, S.; Chen, Yan; Smith, W. L., Jr.

2016-01-01

One of the roadblocks to continuously monitoring cloud properties is the tendency of clouds to become optically black at cloud optical depths (COD) of 6 or less. This constraint dramatically reduces the quantitative information content at night. A recent study found that because of their diffuse nature, ice clouds remain optically gray, to some extent, up to COD of 100 at certain wavelengths. Taking advantage of this weak dependency and the availability of COD retrievals from CloudSat, an artificial neural network algorithm was developed to estimate COD values up to 70 from common satellite imager infrared channels. The method was trained using matched 2007 CloudSat and Aqua MODIS data and is tested using similar data from 2008. The results show a significant improvement over the use of default values at night with high correlation. This paper summarizes the results and suggests paths for future improvement.

Robust bidirectional links for photonic quantum networks

PubMed Central

Xu, Jin-Shi; Yung, Man-Hong; Xu, Xiao-Ye; Tang, Jian-Shun; Li, Chuan-Feng; Guo, Guang-Can

2016-01-01

Optical fibers are widely used as one of the main tools for transmitting not only classical but also quantum information. We propose and report an experimental realization of a promising method for creating robust bidirectional quantum communication links through paired optical polarization-maintaining fibers. Many limitations of existing protocols can be avoided with the proposed method. In particular, the path and polarization degrees of freedom are combined to deterministically create a photonic decoherence-free subspace without the need for any ancillary photon. This method is input state–independent, robust against dephasing noise, postselection-free, and applicable bidirectionally. To rigorously quantify the amount of quantum information transferred, the optical fibers are analyzed with the tools developed in quantum communication theory. These results not only suggest a practical means for protecting quantum information sent through optical quantum networks but also potentially provide a new physical platform for enriching the structure of the quantum communication theory. PMID:26824069

Energy-efficient routing, modulation and spectrum allocation in elastic optical networks

NASA Astrophysics Data System (ADS)

Tan, Yanxia; Gu, Rentao; Ji, Yuefeng

2017-07-01

With tremendous growth in bandwidth demand, energy consumption problem in elastic optical networks (EONs) becomes a hot topic with wide concern. The sliceable bandwidth-variable transponder in EON, which can transmit/receive multiple optical flows, was recently proposed to improve a transponder's flexibility and save energy. In this paper, energy-efficient routing, modulation and spectrum allocation (EE-RMSA) in EONs with sliceable bandwidth-variable transponder is studied. To decrease the energy consumption, we develop a Mixed Integer Linear Programming (MILP) model with corresponding EE-RMSA algorithm for EONs. The MILP model jointly considers the modulation format and optical grooming in the process of routing and spectrum allocation with the objective of minimizing the energy consumption. With the help of genetic operators, the EE-RMSA algorithm iteratively optimizes the feasible routing path, modulation format and spectrum resources solutions by explore the whole search space. In order to save energy, the optical-layer grooming strategy is designed to transmit the lightpath requests. Finally, simulation results verify that the proposed scheme is able to reduce the energy consumption of the network while maintaining the blocking probability (BP) performance compare with the existing First-Fit-KSP algorithm, Iterative Flipping algorithm and EAMGSP algorithm especially in large network topology. Our results also demonstrate that the proposed EE-RMSA algorithm achieves almost the same performance as MILP on an 8-node network.

All-optical two-way relaying free-space optical communications for HAP-based broadband backhaul networks

NASA Astrophysics Data System (ADS)

Vu, Minh Q.; Nguyen, Nga T. T.; Pham, Hien T. T.; Dang, Ngoc T.

2018-03-01

High-altitude platforms (HAPs) are flexible, non-pollutant and cost-effective infrastructures compared to satellite or old terrestrial systems. They are being researched and developed widely in Europe, USA, Japan, Korea, and so on. However, the current limited data rates and the overload of radio frequency (RF) spectrum are problems which the developers for HAPs are confronting because most of them use RF links to communicate with the ground stations (GSs) or each other. In this paper, we propose an all-optical two-way half-duplex relaying free-space optical (FSO) communication for HAP-based backhaul networks, which connect the base transceiver station (BTS) to the core network (CN) via a single HAP. Our proposed backhaul solution can be deployed quickly and flexibly for disaster relief and for serving users in both urban environments and remote areas. The key subsystem of HAP is an optical regenerate-and-forward (ORF) equipped with an optical hard-limiter (OHL) and an optical XOR gate to perform all-optical processing and help mitigate the background noise. In addition, two-way half-duplex relaying can be provided thanks to the use of network coding scheme. The closed-form expression for the bit error rate (BER) of our proposed system under the effect of path loss, atmospheric turbulence, and noise induced by the background light is formulated. The numerical results are demonstrated to prove the feasibility of our proposed system with the verification by using Monte-Carlo (M-C) simulations.

An experimental analysis on OSPF-TE convergence time

NASA Astrophysics Data System (ADS)

Huang, S.; Kitayama, K.; Cugini, F.; Paolucci, F.; Giorgetti, A.; Valcarenghi, L.; Castoldi, P.

2008-11-01

Open shortest path first (OSPF) protocol is commonly used as an interior gateway protocol (IGP) in MPLS and generalized MPLS (GMPLS) networks to determine the topology over which label-switched paths (LSPs) can be established. Traffic-engineering extensions (network states such as link bandwidth information, available wavelengths, signal quality, etc) have been recently enabled in OSPF (henceforth, called OSPF-TE) to support shortest path first (SPF) tree calculation upon different purposes, thus possibly achieving optimal path computation and helping improve resource utilization efficiency. Adding these features into routing phase can exploit the OSPF robustness, and no additional network component is required to manage the traffic-engineering information. However, this traffic-engineering enhancement also complicates OSPF behavior. Since network states change frequently upon the dynamic trafficengineered LSP setup and release, the network is easily driven from a stable state to unstable operating regimes. In this paper, we focus on studying the OSPF-TE stability in terms of convergence time. Convergence time is referred to the time spent by the network to go back to steady states upon any network state change. An external observation method (based on black-box method) is employed to estimate the convergence time. Several experimental test-beds are developed to emulate dynamic LSP setup/release, re-routing upon single-link failure. The experimental results show that with OSPF-TE the network requires more time to converge compared to the conventional OSPF protocol without TE extension. Especially, in case of wavelength-routed optical network (WRON), introducing per wavelength availability and wavelength continuity constraint to OSPF-TE suffers severe convergence time and a large number of advertised link state advertisements (LSAs). Our study implies that long convergence time and large number of LSAs flooded in the network might cause scalability problems in OSPF-TE and impose limitations on OSPF-TE applications. New solutions to mitigate the s convergence time and to reduce the amount of state information are desired in the future.

Statistical intensity variation analysis for rapid volumetric imaging of capillary network flux

PubMed Central

Lee, Jonghwan; Jiang, James Y.; Wu, Weicheng; Lesage, Frederic; Boas, David A.

2014-01-01

We present a novel optical coherence tomography (OCT)-based technique for rapid volumetric imaging of red blood cell (RBC) flux in capillary networks. Previously we reported that OCT can capture individual RBC passage within a capillary, where the OCT intensity signal at a voxel fluctuates when an RBC passes the voxel. Based on this finding, we defined a metric of statistical intensity variation (SIV) and validated that the mean SIV is proportional to the RBC flux [RBC/s] through simulations and measurements. From rapidly scanned volume data, we used Hessian matrix analysis to vectorize a segment path of each capillary and estimate its flux from the mean of the SIVs gathered along the path. Repeating this process led to a 3D flux map of the capillary network. The present technique enabled us to trace the RBC flux changes over hundreds of capillaries with a temporal resolution of ~1 s during functional activation. PMID:24761298

Hybrid protection algorithms based on game theory in multi-domain optical networks

NASA Astrophysics Data System (ADS)

Guo, Lei; Wu, Jingjing; Hou, Weigang; Liu, Yejun; Zhang, Lincong; Li, Hongming

2011-12-01

With the network size increasing, the optical backbone is divided into multiple domains and each domain has its own network operator and management policy. At the same time, the failures in optical network may lead to a huge data loss since each wavelength carries a lot of traffic. Therefore, the survivability in multi-domain optical network is very important. However, existing survivable algorithms can achieve only the unilateral optimization for profit of either users or network operators. Then, they cannot well find the double-win optimal solution with considering economic factors for both users and network operators. Thus, in this paper we develop the multi-domain network model with involving multiple Quality of Service (QoS) parameters. After presenting the link evaluation approach based on fuzzy mathematics, we propose the game model to find the optimal solution to maximize the user's utility, the network operator's utility, and the joint utility of user and network operator. Since the problem of finding double-win optimal solution is NP-complete, we propose two new hybrid protection algorithms, Intra-domain Sub-path Protection (ISP) algorithm and Inter-domain End-to-end Protection (IEP) algorithm. In ISP and IEP, the hybrid protection means that the intelligent algorithm based on Bacterial Colony Optimization (BCO) and the heuristic algorithm are used to solve the survivability in intra-domain routing and inter-domain routing, respectively. Simulation results show that ISP and IEP have the similar comprehensive utility. In addition, ISP has better resource utilization efficiency, lower blocking probability, and higher network operator's utility, while IEP has better user's utility.

Path Finding for Maximum Value of Information in Multi-Modal Underwater Wireless Sensor Networks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gjanci, Petrika; Petrioli, Chiara; Basagni, Stefano

Here, we consider underwater multi-modal wireless sensor networks (UWSNs) suitable for applications on submarine surveillance and monitoring, where nodes offload data to a mobile autonomous underwater vehicle (AUV) via optical technology, and coordinate using acoustic communication. Sensed data are associated with a value, decaying in time. In this scenario, we address the problem of finding the path of the AUV so that the Value of Information (VoI) of the data delivered to a sink on the surface is maximized. We define a Greedy and Adaptive AUV Path-finding (GAAP) heuristic that drives the AUV to collect data from nodes depending onmore » the VoI of their data. For benchmarking the performance of AUV path-finding heuristics, we define an integer linear programming (ILP) formulation that accurately models the considered scenario, deriving a path that drives the AUV to collect and deliver data with the maximum VoI. In our experiments GAAP consistently delivers more than 80 percent of the theoretical maximum VoI determined by the ILP model. We also compare the performance of GAAP with that of other strategies for driving the AUV among sensing nodes, namely, random paths, TSP-based paths and a “lawn mower”-like strategy. Our results show that GAAP always outperforms every other heuristic in terms of delivered VoI, also obtaining higher energy efficiency.« less

Path Finding for Maximum Value of Information in Multi-Modal Underwater Wireless Sensor Networks

DOE PAGES

Gjanci, Petrika; Petrioli, Chiara; Basagni, Stefano; ...

2017-05-19

Here, we consider underwater multi-modal wireless sensor networks (UWSNs) suitable for applications on submarine surveillance and monitoring, where nodes offload data to a mobile autonomous underwater vehicle (AUV) via optical technology, and coordinate using acoustic communication. Sensed data are associated with a value, decaying in time. In this scenario, we address the problem of finding the path of the AUV so that the Value of Information (VoI) of the data delivered to a sink on the surface is maximized. We define a Greedy and Adaptive AUV Path-finding (GAAP) heuristic that drives the AUV to collect data from nodes depending onmore » the VoI of their data. For benchmarking the performance of AUV path-finding heuristics, we define an integer linear programming (ILP) formulation that accurately models the considered scenario, deriving a path that drives the AUV to collect and deliver data with the maximum VoI. In our experiments GAAP consistently delivers more than 80 percent of the theoretical maximum VoI determined by the ILP model. We also compare the performance of GAAP with that of other strategies for driving the AUV among sensing nodes, namely, random paths, TSP-based paths and a “lawn mower”-like strategy. Our results show that GAAP always outperforms every other heuristic in terms of delivered VoI, also obtaining higher energy efficiency.« less

Frequency comb-based time transfer over a 159 km long installed fiber network

NASA Astrophysics Data System (ADS)

Lessing, M.; Margolis, H. S.; Brown, C. T. A.; Marra, G.

2017-05-01

We demonstrate a frequency comb-based time transfer technique on a 159 km long installed fiber link. Timing information is superimposed onto the optical pulse train of an ITU-channel-filtered mode-locked laser using an intensity modulation scheme. The environmentally induced optical path length fluctuations are compensated using a round-trip phase noise cancellation technique. When the fiber link is stabilized, a time deviation of 300 fs at 5 s and an accuracy at the 100 ps level are achieved.

Optical switch based on thermocapillarity

NASA Astrophysics Data System (ADS)

Sakata, Tomomi; Makihara, Mitsuhiro; Togo, Hiroyoshi; Shimokawa, Fusao; Kaneko, Kazumasa

2001-11-01

Space-division optical switches are essential for the protection, optical cross-connects (OXCs), and optical add/drop multiplexers (OADMs) needed in future fiber-optic communication networks. For applications in these areas, we proposed a thermocapillarity switch called oil-latching interfacial-tension variation effect (OLIVE) switch. An OLIVE switch is a micro-mechanical optical switch fabricated on planar lightwave circuits (PLC) using micro-electro-mechanical systems (MEMS) technology. It consists of a crossing waveguide that has a groove at each crossing point and a pair of microheaters. The groove is partially filled with the refractive-index-matching liquid, and optical signals are switched according to the liquid's position in the groove, i.e., whether it is passing straight through the groove or reflecting at the sidewall of the groove. The liquid is driven by thermocapillarity and latched by capillarity. Using the total internal reflection to switch the optical path, the OLIVE switch exhibits excellent optical characteristics, such as high transparency (insertion loss: < 2 dB), high extinction ratio (> 50 dB), and low crosstalk (< -50 dB). Moreover, since this switch has a simple structure and bi-stability, it has wide variety of applications in wavelength division multiplexing (WDM) networks.

Pre-configured polyhedron based protection against multi-link failures in optical mesh networks.

PubMed

Huang, Shanguo; Guo, Bingli; Li, Xin; Zhang, Jie; Zhao, Yongli; Gu, Wanyi

2014-02-10

This paper focuses on random multi-link failures protection in optical mesh networks, instead of single, the dual or sequential failures of previous studies. Spare resource efficiency and failure robustness are major concerns in link protection strategy designing and a k-regular and k-edge connected structure is proved to be one of the optimal solutions for link protection network. Based on this, a novel pre-configured polyhedron based protection structure is proposed, and it could provide protection for both simultaneous and sequential random link failures with improved spare resource efficiency. Its performance is evaluated in terms of spare resource consumption, recovery rate and average recovery path length, as well as compared with ring based and subgraph protection under probabilistic link failure scenarios. Results show the proposed novel link protection approach has better performance than previous works.

Photonic-powered cable assembly

DOEpatents

Sanderson, Stephen N.; Appel, Titus James; Wrye, IV, Walter C.

2013-01-22

A photonic-cable assembly includes a power source cable connector ("PSCC") coupled to a power receive cable connector ("PRCC") via a fiber cable. The PSCC electrically connects to a first electronic device and houses a photonic power source and an optical data transmitter. The fiber cable includes an optical transmit data path coupled to the optical data transmitter, an optical power path coupled to the photonic power source, and an optical feedback path coupled to provide feedback control to the photonic power source. The PRCC electrically connects to a second electronic device and houses an optical data receiver coupled to the optical transmit data path, a feedback controller coupled to the optical feedback path to control the photonic power source, and a photonic power converter coupled to the optical power path to convert photonic energy received over the optical power path to electrical energy to power components of the PRCC.

Photonic-powered cable assembly

DOEpatents

Sanderson, Stephen N; Appel, Titus James; Wrye, IV, Walter C

2014-06-24

A photonic-cable assembly includes a power source cable connector ("PSCC") coupled to a power receive cable connector ("PRCC") via a fiber cable. The PSCC electrically connects to a first electronic device and houses a photonic power source and an optical data transmitter. The fiber cable includes an optical transmit data path coupled to the optical data transmitter, an optical power path coupled to the photonic power source, and an optical feedback path coupled to provide feedback control to the photonic power source. The PRCC electrically connects to a second electronic device and houses an optical data receiver coupled to the optical transmit data path, a feedback controller coupled to the optical feedback path to control the photonic power source, and a photonic power converter coupled to the optical power path to convert photonic energy received over the optical power path to electrical energy to power components of the PRCC.

Optical system and method for gas detection and monitoring

NASA Technical Reports Server (NTRS)

Polzin, Kurt A. (Inventor); Sinko, John Elihu (Inventor); Korman, Valentin (Inventor); Witherow, William K. (Inventor); Hendrickson, Adam Gail (Inventor)

2011-01-01

A free-space optical path of an optical interferometer is disposed in an environment of interest. A light beam is guided to the optical interferometer using a single-mode optical fiber. The light beam traverses the interferometer's optical path. The light beam guided to the optical path is combined with the light beam at the end of the optical path to define an output light. A temporal history of the output light is recorded.

Four-fold increase in users of time-wavelength division multiplexing (TWDM) passive optical network (PON) by delayed optical amplitude modulation (AM) upstream

NASA Astrophysics Data System (ADS)

Kachhatiya, Vivek; Prince, Shanthi

2016-12-01

In this paper, we have proposed and simulated optical time division multiplexed passive optical network (TDM-PON) using delayed optical amplitude modulation (AM). Eight upstream wavelengths are demonstrated to show optical time wavelength division multiplexed (TWDM) by combining optical network units (ONU) users data at the remote node (RN). Each ONU generates 2.5 Gb/s user data, and it is modulated using novel return to zero (RZ) delayed AM. Optical TDM aggregates 10 Gb/s data per wavelength from four 2.5 Gb/s upstream user data, which facilitates four different ONU data on the same wavelength as 10 Gb/s per upstream wavelength and, simplify the laser requirements (2.5 Gb/s) at each optical network unit (ONU) transmitter. Upstream optical TWDM-PON is investigated for eight wavelengths with wavelength spacing of 100 GHz. Novel optical TDM for upstream increased the number of the simultaneous user to fourfold from conventional TWDM-PON using delayed AM with a high-quality-factor of received signal. Despite performance degradation due to different fiber reach and dispersion compensation technique, Optical TWDM link shows significant improvement regarding receiver sensitivity when compared with common TWDM link. Hence, it offers optimistic thinking to show optical TDM at this phase as one of the future direction, where complex digital signal processing (DSP) and coherent optical communication are frequently demonstrated to serve the access network. Downstream side conventional TWDM eight wavelengths are multiplexed at the OLT and sent downstream to serve distributed tunable ONU receivers through an optical distribution network (ODN). Each downstream wavelengths are modulated at the peak rate of 10 Gb/s using non-return to zero external modulation (NRZ-EM). The proposed architecture is cost efficient and supports high data rates as well as ;pay as you grow; network for both service providers and the users perspectives. Users are classified into two categories viz home-user and business-user, with an option for easy up-gradation. Proposed architecture operates on next generation passive optical network stage 2 (NG-PON2) wavelength plan, with symmetrical data rate. Downstream performance is investigated by comparing, high power laser source with a conventional laser source and the L-band Erbium-doped fiber amplifier (EDFA) of gain 10 dB and 20 dB. Downstream eight wavelengths perform error-free up to 40 Km fiber reach and 1024 splitting points. Power budget of the proposed architecture incorporates the N1, N2, E1 and E2 optical path loss class.

Exploration of optical classroom teaching by network platform

NASA Astrophysics Data System (ADS)

Jiao, Zheng; Ma, Kun

2017-08-01

The investigation shows that the difficulties students encounter in the course of optics are mainly due to the abstraction of the content of the optical course, and the problem that the description of the physical phenomenon and process is difficult to show in the classroom teaching. We consider to integrate information technology with classroom teaching. Teachers can set up course websites and create more teaching resources, such as videos of experimental processes, design of simulated optical paths, mock demonstration of optical phenomena, and so on. Teachers can use the courseware to link the resources of the website platform, and display the related resources to the students. After class, students are also able to learn through the website, which is helpful to their study.

A Novel Dynamic Physical Layer Impairment-Aware Routing and Wavelength Assignment (PLI-RWA) Algorithm for Mixed Line Rate (MLR) Wavelength Division Multiplexed (WDM) Optical Networks

NASA Astrophysics Data System (ADS)

Iyer, Sridhar

2016-12-01

The ever-increasing global Internet traffic will inevitably lead to a serious upgrade of the current optical networks' capacity. The legacy infrastructure can be enhanced not only by increasing the capacity but also by adopting advance modulation formats, having increased spectral efficiency at higher data rate. In a transparent mixed-line-rate (MLR) optical network, different line rates, on different wavelengths, can coexist on the same fiber. Migration to data rates higher than 10 Gbps requires the implementation of phase modulation schemes. However, the co-existing on-off keying (OOK) channels cause critical physical layer impairments (PLIs) to the phase modulated channels, mainly due to cross-phase modulation (XPM), which in turn limits the network's performance. In order to mitigate this effect, a more sophisticated PLI-Routing and Wavelength Assignment (PLI-RWA) scheme needs to be adopted. In this paper, we investigate the critical impairment for each data rate and the way it affects the quality of transmission (QoT). In view of the aforementioned, we present a novel dynamic PLI-RWA algorithm for MLR optical networks. The proposed algorithm is compared through simulations with the shortest path and minimum hop routing schemes. The simulation results show that performance of the proposed algorithm is better than the existing schemes.

Optical multi-species gas monitoring sensor and system

NASA Technical Reports Server (NTRS)

Korman, Valentin (Inventor); Polzin, Kurt A. (Inventor)

2012-01-01

The system includes at least one light source generating light energy having a corresponding wavelength. The system's sensor is based on an optical interferometer that receives light energy from each light source. The interferometer includes a free-space optical path disposed in an environment of interest. The system's sensor includes an optical device disposed in the optical path that causes light energy of a first selected wavelength to continue traversing the optical path whereas light energy of at least one second selected wavelength is directed away from the optical path. The interferometer generates an interference between the light energy of the first selected wavelength so-traversing the optical path with the light energy at the corresponding wavelength incident on the optical interferometer. A first optical detector detects the interference. At least one second detector detects the light energy at the at least one second selected wavelength directed away from the optical path.

Dynamic multicast routing scheme in WDM optical network

NASA Astrophysics Data System (ADS)

Zhu, Yonghua; Dong, Zhiling; Yao, Hong; Yang, Jianyong; Liu, Yibin

2007-11-01

During the information era, the Internet and the service of World Wide Web develop rapidly. Therefore, the wider and wider bandwidth is required with the lower and lower cost. The demand of operation turns out to be diversified. Data, images, videos and other special transmission demands share the challenge and opportunity with the service providers. Simultaneously, the electrical equipment has approached their limit. So the optical communication based on the wavelength division multiplexing (WDM) and the optical cross-connects (OXCs) shows great potentials and brilliant future to build an optical network based on the unique technical advantage and multi-wavelength characteristic. In this paper, we propose a multi-layered graph model with inter-path between layers to solve the problem of multicast routing wavelength assignment (RWA) contemporarily by employing an efficient graph theoretic formulation. And at the same time, an efficient dynamic multicast algorithm named Distributed Message Copying Multicast (DMCM) mechanism is also proposed. The multicast tree with minimum hops can be constructed dynamically according to this proposed scheme.

Retrievals of atmospheric columnar carbon dioxide and methane from GOSAT observations with photon path-length probability density function (PPDF) method

NASA Astrophysics Data System (ADS)

Bril, A.; Oshchepkov, S.; Yokota, T.; Yoshida, Y.; Morino, I.; Uchino, O.; Belikov, D. A.; Maksyutov, S. S.

2014-12-01

We retrieved the column-averaged dry air mole fraction of atmospheric carbon dioxide (XCO2) and methane (XCH4) from the radiance spectra measured by Greenhouse gases Observing SATellite (GOSAT) for 48 months of the satellite operation from June 2009. Recent version of the Photon path-length Probability Density Function (PPDF)-based algorithm was used to estimate XCO2 and optical path modifications in terms of PPDF parameters. We also present results of numerical simulations for over-land observations and "sharp edge" tests for sun-glint mode to discuss the algorithm accuracy under conditions of strong optical path modification. For the methane abundance retrieved from 1.67-µm-absorption band we applied optical path correction based on PPDF parameters from 1.6-µm carbon dioxide (CO2) absorption band. Similarly to CO2-proxy technique, this correction assumes identical light path modifications in 1.67-µm and 1.6-µm bands. However, proxy approach needs pre-defined XCO2 values to compute XCH4, whilst the PPDF-based approach does not use prior assumptions on CO2 concentrations.Post-processing data correction for XCO2 and XCH4 over land observations was performed using regression matrix based on multivariate analysis of variance (MANOVA). The MANOVA statistics was applied to the GOSAT retrievals using reference collocated measurements of Total Carbon Column Observing Network (TCCON). The regression matrix was constructed using the parameters that were found to correlate with GOSAT-TCCON discrepancies: PPDF parameters α and ρ, that are mainly responsible for shortening and lengthening of the optical path due to atmospheric light scattering; solar and satellite zenith angles; surface pressure; surface albedo in three GOSAT short wave infrared (SWIR) bands. Application of the post-correction generally improves statistical characteristics of the GOSAT-TCCON correlation diagrams for individual stations as well as for aggregated data.In addition to the analysis of the observations over 12 TCCON stations we estimated temporal and spatial trends (interannual XCO2 and XCH4 variations, seasonal cycles, latitudinal gradients) and compared them with modeled results as well as with similar estimates from other GOSAT retrievals.

Research on the Calculation Method of Optical Path Difference of the Shanghai Tian Ma Telescope

NASA Astrophysics Data System (ADS)

Dong, J.; Fu, L.; Jiang, Y. B.; Liu, Q. H.; Gou, W.; Yan, F.

2016-03-01

Based on the Shanghai Tian Ma Telescope (TM), an optical path difference calculation method of the shaped Cassegrain antenna is presented in the paper. Firstly, the mathematical model of the TM optics is established based on the antenna reciprocity theorem. Secondly, the TM sub-reflector and main reflector are fitted by the Non-Uniform Rational B-Splines (NURBS). Finally, the method of optical path difference calculation is implemented, and the expanding application of the Ruze optical path difference formulas in the TM is researched. The method can be used to calculate the optical path difference distributions across the aperture field of the TM due to misalignment like the axial and lateral displacements of the feed and sub-reflector, or the tilt of the sub-reflector. When the misalignment quantity is small, the expanding Ruze optical path difference formulas can be used to calculate the optical path difference quickly. The paper supports the real-time measurement and adjustment of the TM structure. The research has universality, and can provide reference for the optical path difference calculation of other radio telescopes with shaped surfaces.

Spreading paths in partially observed social networks

NASA Astrophysics Data System (ADS)

Onnela, Jukka-Pekka; Christakis, Nicholas A.

2012-03-01

Understanding how and how far information, behaviors, or pathogens spread in social networks is an important problem, having implications for both predicting the size of epidemics, as well as for planning effective interventions. There are, however, two main challenges for inferring spreading paths in real-world networks. One is the practical difficulty of observing a dynamic process on a network, and the other is the typical constraint of only partially observing a network. Using static, structurally realistic social networks as platforms for simulations, we juxtapose three distinct paths: (1) the stochastic path taken by a simulated spreading process from source to target; (2) the topologically shortest path in the fully observed network, and hence the single most likely stochastic path, between the two nodes; and (3) the topologically shortest path in a partially observed network. In a sampled network, how closely does the partially observed shortest path (3) emulate the unobserved spreading path (1)? Although partial observation inflates the length of the shortest path, the stochastic nature of the spreading process also frequently derails the dynamic path from the shortest path. We find that the partially observed shortest path does not necessarily give an inflated estimate of the length of the process path; in fact, partial observation may, counterintuitively, make the path seem shorter than it actually is.

Spreading paths in partially observed social networks.

PubMed

Onnela, Jukka-Pekka; Christakis, Nicholas A

2012-03-01

Understanding how and how far information, behaviors, or pathogens spread in social networks is an important problem, having implications for both predicting the size of epidemics, as well as for planning effective interventions. There are, however, two main challenges for inferring spreading paths in real-world networks. One is the practical difficulty of observing a dynamic process on a network, and the other is the typical constraint of only partially observing a network. Using static, structurally realistic social networks as platforms for simulations, we juxtapose three distinct paths: (1) the stochastic path taken by a simulated spreading process from source to target; (2) the topologically shortest path in the fully observed network, and hence the single most likely stochastic path, between the two nodes; and (3) the topologically shortest path in a partially observed network. In a sampled network, how closely does the partially observed shortest path (3) emulate the unobserved spreading path (1)? Although partial observation inflates the length of the shortest path, the stochastic nature of the spreading process also frequently derails the dynamic path from the shortest path. We find that the partially observed shortest path does not necessarily give an inflated estimate of the length of the process path; in fact, partial observation may, counterintuitively, make the path seem shorter than it actually is.

Multi-PON access network using a coarse AWG for smooth migration from TDM to WDM PON

NASA Astrophysics Data System (ADS)

Shachaf, Y.; Chang, C.-H.; Kourtessis, P.; Senior, J. M.

2007-06-01

An interoperable access network architecture based on a coarse array waveguide grating (AWG) is described, displaying dynamic wavelength assignment to manage the network load across multiple PONs. The multi-PON architecture utilizes coarse Gaussian channels of an AWG to facilitate scalability and smooth migration path between TDM and WDM PONs. Network simulations of a cross-operational protocol platform confirmed successful routing of individual PON clusters through 7 nm-wide passband windows of the AWG. Furthermore, polarization-dependent wavelength shift and phase errors of the device proved not to impose restrain on the routing performance. Optical transmission tests at 2.5 Gbit/s for distances up to 20 km are demonstrated.

Method and system for compact, multi-pass pulsed laser amplifier

DOEpatents

Erlandson, Alvin Charles

2014-11-25

A laser amplifier includes an input aperture operable to receive laser radiation having a first polarization, an output aperture coupled to the input aperture by an optical path, and a polarizer disposed along an optical path. A transmission axis of the polarizer is aligned with the first polarization. The laser amplifier also includes n optical switch disposed along the optical path. The optical switch is operable to pass the laser radiation when operated in a first state and to reflect the laser radiation when operated in a second state. The laser amplifier further includes an optical gain element disposed along the optical path and a polarization rotation device disposed along the optical path.

Optical mapping of prefrontal brain connectivity and activation during emotion anticipation.

PubMed

Wang, Meng-Yun; Lu, Feng-Mei; Hu, Zhishan; Zhang, Juan; Yuan, Zhen

2018-09-17

Accumulated neuroimaging evidence shows that the dorsal lateral prefrontal cortex (dlPFC) is activated during emotion anticipation. The aim of this work is to examine the brain connectivity and activation differences in dlPFC between the positive, neutral and negative emotion anticipation by using functional near-infrared spectroscopy (fNIRS). The hemodynamic responses were first assessed for all subjects during the performance of various emotion anticipation tasks. And then small-world analysis was performed, in which the small-world network indicators including the clustering coefficient, average path length, average node degree, and measure of small-world index were calculated for the functional brain networks associated with the positive, neutral and negative emotion anticipation, respectively. We discovered that compared to negative and neutral emotion anticipation, the positive one exhibited enhanced brain activation in the left dlPFC. Although the functional brain networks for the three emotion anticipation cases manifested the small-world properties regarding the clustering coefficient, average path length, average node degree, and measure of small-world index, the positive one showed significantly higher clustering coefficient and shorter average path length than those from the neutral and negative cases. Consequently, the small-world network indicators and brain activation in dlPPC were able to distinguish well between the positive, neutral and negative emotion anticipation. Copyright © 2018 Elsevier B.V. All rights reserved.

Inter-BSs virtual private network for privacy and security enhanced 60 GHz radio-over-fiber system

NASA Astrophysics Data System (ADS)

Zhang, Chongfu; Chen, Chen; Zhang, Wei; Jin, Wei; Qiu, Kun; Li, Changchun; Jiang, Ning

2013-06-01

A novel inter-basestations (inter-BSs) based virtual private network (VPN) for the privacy and security enhanced 60 GHz radio-over-fiber (RoF) system using optical code-division multiplexing (OCDM) is proposed and demonstrated experimentally. By establishing inter-BSs VPN overlaying the network structure of a 60 GHz RoF system, the express and private paths for the communication of end-users under different BSs can be offered. In order to effectively establish the inter-BSs VPN, the OCDM encoding/decoding technology is employed in the RoF system. In each BS, a 58 GHz millimeter-wave (MMW) is used as the inter-BSs VPN channel, while a 60 GHz MMW is used as the common central station (CS)-BSs communication channel. The optical carriers used for the downlink, uplink and VPN link transmissions are all simultaneously generated in a lightwave-centralized CS, by utilizing four-wave mixing (FWM) effect in a semiconductor optical amplifier (SOA). The obtained results properly verify the feasibility of our proposed configuration of the inter-BSs VPN in the 60 GHz RoF system.

Self-organization and solution of shortest-path optimization problems with memristive networks

NASA Astrophysics Data System (ADS)

Pershin, Yuriy V.; Di Ventra, Massimiliano

2013-07-01

We show that memristive networks, namely networks of resistors with memory, can efficiently solve shortest-path optimization problems. Indeed, the presence of memory (time nonlocality) promotes self organization of the network into the shortest possible path(s). We introduce a network entropy function to characterize the self-organized evolution, show the solution of the shortest-path problem and demonstrate the healing property of the solution path. Finally, we provide an algorithm to solve the traveling salesman problem. Similar considerations apply to networks of memcapacitors and meminductors, and networks with memory in various dimensions.

Quasi Path Restoration: A post-failure recovery scheme over pre-allocated backup resource for elastic optical networks

NASA Astrophysics Data System (ADS)

Yadav, Dharmendra Singh; Babu, Sarath; Manoj, B. S.

2018-03-01

Spectrum conflict during primary and backup routes assignment in elastic optical networks results in increased resource consumption as well as high Bandwidth Blocking Probability. In order to avoid such conflicts, we propose a new scheme, Quasi Path Restoration (QPR), where we divide the available spectrum into two: (1) primary spectrum (for primary routes allocation) and (2) backup spectrum (for rerouting the data on link failures). QPR exhibits three advantages over existing survivable strategies such as Shared Path Protection (SPP), Primary First Fit Backup Last Fit (PFFBLF), Jointly Releasing and re-establishment Defragmentation SPP (JRDSSPP), and Path Restoration (PR): (1) the conflict between primary and backup spectrum during route assignment is completely eliminated, (2) upon a link failure, connection recovery requires less backup resources compared to SPP, PFFBLF, and PR, and (3) availability of the same backup spectrum on each link improves the recovery guarantee. The performance of our scheme is analyzed with different primary backup spectrum partitions on varying connection-request demands and number of frequency slots. Our results show that QPR provides better connection recovery guarantee and Backup Resources Utilization (BRU) compared to bandwidth recovery of PR strategy. In addition, we compare QPR with Shared Path Protection and Primary First-Fit Backup Last Fit strategies in terms of Bandwidth Blocking Probability (BBP) and average frequency slots per connection request. Simulation results show that BBP of SPP, PFFBLF, and JRDSPP varies between 18.59% and 14.42%, while in QPR, BBP ranges from 2.55% to 17.76% for Cost239, NSFNET, and ARPANET topologies. Also, QPR provides bandwidth recovery between 93.61% and 100%, while in PR, the recovery ranges from 86.81% to 98.99%. It is evident from our analysis that QPR provides a reasonable trade-off between bandwidth blocking probability and connection recoverability.

Optical implementation of a parallel out-of-band controller for large broadband ATM switch applications

NASA Astrophysics Data System (ADS)

Cloonan, Thomas J.; Richards, Gaylord W.; Lentine, Anthony L.

1996-03-01

Asynchronous transfer mode (ATM) is rapidly becoming the transport mechanism of choice for the information superhighway, because it promises the bandwidth and flexibility needed for many voice, video and data service offerings. Some industry experts project that the required sizes for ATM switching equipment in the public-switched environment will reach the Tbps range by the beginning of the next decade. This paper analyzes the problems associated with controlling the flow of packets within a broadband ATM switch of this size. The analysis is based on the requirements of the growable packet switch architecture. The paper proposes a novel solution to the problem of hunting paths within an ATM packet switch network. The resulting control scheme is unconventional in two ways. First, it uses an out-of-band control algorithm instead of the more common self-routing approach. In particular, we explore the benefits of using a parallel processor as an out-of-band controller for a growable packet switch distribution network. The processor permits additional levels of parallelism to be added to the out-of-band control function so that path hunts can be performed for all N of the input ports within a single cell interval. The proposed approach is also unconventional because it uses free-space digital optics to guide signals between successive stages of the controller. The paper describes the underlying motivations for implementing an optical out-of-band controller for an ATM switch, and it also describes the logic within a controller node that has been fabricated using a hybrid Si CMOS/GaAs SEED technology. The node uses optical detectors (in GaAs), amplifiers and digital control logic (in Si), and optical modulators (in GaAs). Free-space optical connections between successive device arrays can be provided using either bulk optical elements or micro-optics, but the optical interconnects must provide massive fanout capability. An architectural analysis studying the feasibility of applying free-space optics in this proposed ATM switch controller also is presented.

A novel communication mechanism based on node potential multi-path routing

NASA Astrophysics Data System (ADS)

Bu, Youjun; Zhang, Chuanhao; Jiang, YiMing; Zhang, Zhen

2016-10-01

With the network scales rapidly and new network applications emerge frequently, bandwidth supply for today's Internet could not catch up with the rapid increasing requirements. Unfortunately, irrational using of network sources makes things worse. Actual network deploys single-next-hop optimization paths for data transmission, but such "best effort" model leads to the imbalance use of network resources and usually leads to local congestion. On the other hand Multi-path routing can use the aggregation bandwidth of multi paths efficiently and improve the robustness of network, security, load balancing and quality of service. As a result, multi-path has attracted much attention in the routing and switching research fields and many important ideas and solutions have been proposed. This paper focuses on implementing the parallel transmission of multi next-hop data, balancing the network traffic and reducing the congestion. It aimed at exploring the key technologies of the multi-path communication network, which could provide a feasible academic support for subsequent applications of multi-path communication networking. It proposed a novel multi-path algorithm based on node potential in the network. And the algorithm can fully use of the network link resource and effectively balance network link resource utilization.

US LHCNet: Transatlantic Networking for the LHC and the U.S. HEP Community

DOE Office of Scientific and Technical Information (OSTI.GOV)

Newman, Harvey B; Barczyk, Artur J

2013-04-05

US LHCNet provides the transatlantic connectivity between the Tier1 computing facilities at the Fermilab and Brookhaven National Labs and the Tier0 and Tier1 facilities at CERN, as well as Tier1s elsewhere in Europe and Asia. Together with ESnet, Internet2, and other R&E Networks participating in the LHCONE initiative, US LHCNet also supports transatlantic connections between the Tier2 centers (where most of the data analysis is taking place) and the Tier1s as needed. Given the key roles of the US and European Tier1 centers as well as Tier2 centers on both continents, the largest data flows are across the Atlantic, wheremore » US LHCNet has the major role. US LHCNet manages and operates the transatlantic network infrastructure including four Points of Presence (PoPs) and currently six transatlantic OC-192 (10Gbps) leased links. Operating at the optical layer, the network provides a highly resilient fabric for data movement, with a target service availability level in excess of 99.95%. This level of resilience and seamless operation is achieved through careful design including path diversity on both submarine and terrestrial segments, use of carrier-grade equipment with built-in high-availability and redundancy features, deployment of robust failover mechanisms based on SONET protection schemes, as well as the design of facility-diverse paths between the LHC computing sites. The US LHCNet network provides services at Layer 1(optical), Layer 2 (Ethernet) and Layer 3 (IPv4 and IPv6). The flexible design of the network, including modular equipment, a talented and agile team, and flexible circuit lease management, allows US LHCNet to react quickly to changing requirements form the LHC community. Network capacity is provisioned just-in-time to meet the needs, as demonstrated in the past years during the changing LHC start-up plans.« less

Observation of quasiperiodic dynamics in a one-dimensional quantum walk of single photons in space

NASA Astrophysics Data System (ADS)

Xue, Peng; Qin, Hao; Tang, Bao; Sanders, Barry C.

2014-05-01

We realize the quasi-periodic dynamics of a quantum walker over 2.5 quasi-periods by realizing the walker as a single photon passing through a quantum-walk optical-interferometer network. We introduce fully controllable polarization-independent phase shifters in each optical path to realize arbitrary site-dependent phase shifts, and employ large clear-aperture beam displacers, while maintaining high-visibility interference, to enable 10 quantum-walk steps to be reached. By varying the half-wave-plate setting, we control the quantum-coin bias thereby observing a transition from quasi-periodic dynamics to ballistic diffusion.

Optimisation of SOA-REAMs for hybrid DWDM-TDMA PON applications.

PubMed

Naughton, Alan; Antony, Cleitus; Ossieur, Peter; Porto, Stefano; Talli, Giuseppe; Townsend, Paul D

2011-12-12

We demonstrate how loss-optimised, gain-saturated SOA-REAM based reflective modulators can reduce the burst to burst power variations due to differential access loss in the upstream path in carrier distributed passive optical networks by 18 dB compared to fixed linear gain modulators. We also show that the loss optimised device has a high tolerance to input power variations and can operate in deep saturation with minimal patterning penalties. Finally, we demonstrate that an optimised device can operate across the C-Band and also over a transmission distance of 80 km. © 2011 Optical Society of America

Hybrid shearing and phase-shifting point diffraction interferometer

DOEpatents

Goldberg, Kenneth Alan; Naulleau, Patrick P.

2003-06-03

A new interferometry configuration combines the strengths of two existing interferometry methods, improving the quality and extending the dynamic range of both. On the same patterned mask, placed near the image-plane of an optical system under test, patterns for phase-shifting point diffraction interferometry and lateral shearing interferometry coexist. The former giving verifiable high accuracy for the measurement of nearly diffraction-limited optical systems. The latter enabling the measurement of optical systems with more than one wave of aberration in the system wavefront. The interferometry configuration is a hybrid shearing and point diffraction interferometer system for testing an optical element that is positioned along an optical path including: a source of electromagnetic energy in the optical path; a first beam splitter that is secured to a device that includes means for maneuvering the first beam splitter in a first position wherein the first beam splitter is in the optical path dividing light from the source into a reference beam and a test beam and in a second position wherein the first beam splitter is outside the optical path: a hybrid mask which includes a first section that defines a test window and at least one reference pinhole and a second section that defines a second beam splitter wherein the hybrid mask is secured to a device that includes means for maneuvering either the first section or the second section into the optical path positioned in an image plane that is created by the optical element, with the proviso that the first section of the hybrid mask is positioned in the optical path when first beam splitter is positioned in the optical path; and a detector positioned after the hybrid mask along the optical path.

Method and apparatus for timing of laser beams in a multiple laser beam fusion system

DOEpatents

Eastman, Jay M.; Miller, Theodore L.

1981-01-01

The optical path lengths of a plurality of comparison laser beams directed to impinge upon a common target from different directions are compared to that of a master laser beam by using an optical heterodyne interferometric detection technique. The technique consists of frequency shifting the master laser beam and combining the master beam with a first one of the comparison laser beams to produce a time-varying heterodyne interference pattern which is detected by a photo-detector to produce an AC electrical signal indicative of the difference in the optical path lengths of the two beams which were combined. The optical path length of this first comparison laser beam is adjusted to compensate for the detected difference in the optical path lengths of the two beams. The optical path lengths of all of the comparison laser beams are made equal to the optical path length of the master laser beam by repeating the optical path length adjustment process for each of the comparison laser beams. In this manner, the comparison laser beams are synchronized or timed to arrive at the target within .+-.1.times.10.sup.-12 second of each other.

Wavelength assignment algorithm considering the state of neighborhood links for OBS networks

NASA Astrophysics Data System (ADS)

Tanaka, Yu; Hirota, Yusuke; Tode, Hideki; Murakami, Koso

2005-10-01

Recently, Optical WDM technology is introduced into backbone networks. On the other hand, as the future optical switching scheme, Optical Burst Switching (OBS) systems become a realistic solution. OBS systems do not consider buffering in intermediate nodes. Thus, it is an important issue to avoid overlapping wavelength reservation between partially interfered paths. To solve this problem, so far, the wavelength assignment scheme which has priority management tables has been proposed. This method achieves the reduction of burst blocking probability. However, this priority management table requires huge memory space. In this paper, we propose a wavelength assignment algorithm that reduces both the number of priority management tables and burst blocking probability. To reduce priority management tables, we allocate and manage them for each link. To reduce burst blocking probability, our method announces information about the change of their priorities to intermediate nodes. We evaluate its performance in terms of the burst blocking probability and the reduction rate of priority management tables.

Optical path switching based differential absorption radiometry for substance detection

NASA Technical Reports Server (NTRS)

Sachse, Glen W. (Inventor)

2005-01-01

An optical path switch divides sample path radiation into a time series of alternating first polarized components and second polarized components. The first polarized components are transmitted along a first optical path and the second polarized components along a second optical path. A first gasless optical filter train filters the first polarized components to isolate at least a first wavelength band thereby generating first filtered radiation. A second gasless optical filter train filters the second polarized components to isolate at least a second wavelength band thereby generating second filtered radiation. A beam combiner combines the first and second filtered radiation to form a combined beam of radiation. A detector is disposed to monitor magnitude of at least a portion of the combined beam alternately at the first wavelength band and the second wavelength band as an indication of the concentration of the substance in the sample path.

Optical path switching based differential absorption radiometry for substance detection

NASA Technical Reports Server (NTRS)

Sachse, Glen W. (Inventor)

2003-01-01

An optical path switch divides sample path radiation into a time series of alternating first polarized components and second polarized components. The first polarized components are transmitted along a first optical path and the second polarized components along a second optical path. A first gasless optical filter train filters the first polarized components to isolate at least a first wavelength band thereby generating first filtered radiation. A second gasless optical filter train filters the second polarized components to isolate at least a second wavelength band thereby generating second filtered radiation. A beam combiner combines the first and second filtered radiation to form a combined beam of radiation. A detector is disposed to monitor magnitude of at least a portion of the combined beam alternately at the first wavelength band and the second wavelength band as an indication of the concentration of the substance in the sample path.

High efficiency diffraction grating technologies LPDL 900 and LPDL 1100 in telecommunications applications

NASA Astrophysics Data System (ADS)

Milner, Darrin; Didona, Kevin; Bannon, David

2005-04-01

With the introduction of wavelength division multiplexing and dense wavelength division multiplexing, equipment manufactures have sought to reduce design tradeoffs and costs while maintaining or increasing their product performance. With the need to reduce if not eliminate optical losses and create the all light path from source to destination, equipment manufactures are addressing the concerns of component manufactures to provide increased performance to support configurable designs for 100, 50, and eventually 12.5GHz. One of the most reliable, robust, and high performance devices is the low polarization dependent loss (LPDL) diffraction grating used to disperse wavelengths for channel blocking, add/drop functionality and real time light path reconfigurations. The networks today have a variety of factors which contribute to the optical loss budget and impact system design cost, facility requirements, maintenance or replacement costs. These factors include first and second order polarization mode dispersion (PMD), polarization dependent loss (PDL), wavelength dependent losses, and chromatic dispersion (CD). Network designers and equipment manufactures have to consider each component capability and its impact to the systems bit error rate (BER). In order to gain an understanding of the advantages of components with low polarization dependency, we will summarize the effects that interplay with these types of components.

Mini-lidar sensor for the remote stand-off sensing of chemical/biological substances and method for sensing same

DOEpatents

Ray, Mark D.; Sedlacek, Arthur J.

2003-08-19

A method and apparatus for remote, stand-off, and high efficiency spectroscopic detection of biological and chemical substances. The apparatus including an optical beam transmitter which transmits a beam having an axis of transmission to a target, the beam comprising at least a laser emission. An optical detector having an optical detection path to the target is provided for gathering optical information. The optical detection path has an axis of optical detection. A beam alignment device fixes the transmitter proximal to the detector and directs the beam to the target along the optical detection path such that the axis of transmission is within the optical detection path. Optical information gathered by the optical detector is analyzed by an analyzer which is operatively connected to the detector.

Scheduling with hop-by-hop priority increasing in meshed optical burst-switched network

NASA Astrophysics Data System (ADS)

Chang, Hao; Luo, Jiangtao; Zhang, Zhizhong; Xia, Da; Gong, Jue

2006-09-01

In OBS, JET (Just-Enough-Time) is the classical wavelength reservation scheme. But there is a phenomenon that the burst priority decreasing hop-by-hop in multi-hop networks that will waste the bandwidth that was used in the upstream. Based on the HPI (Hop-by-hop Priority Increasing) proposed in the former research, this paper will do an unprecedented simulation in 4×4 meshed topology, which is closer to the real network environment with the help of a NS2-based OBSN simulation platform constructed by ourselves. By contrasting, the drop probability and throughput on one of the longest end-to-end path lengths in the whole networks, it shows that the HPI scheme can improve the utilance of bandwidth better.

Circuity analyses of HSR network and high-speed train paths in China

PubMed Central

Zhao, Shuo; Huang, Jie; Shan, Xinghua

2017-01-01

Circuity, defined as the ratio of the shortest network distance to the Euclidean distance between one origin–destination (O-D) pair, can be adopted as a helpful evaluation method of indirect degrees of train paths. In this paper, the maximum circuity of the paths of operated trains is set to be the threshold value of the circuity of high-speed train paths. For the shortest paths of any node pairs, if their circuity is not higher than the threshold value, the paths can be regarded as the reasonable paths. With the consideration of a certain relative or absolute error, we cluster the reasonable paths on the basis of their inclusion relationship and the center path of each class represents a passenger transit corridor. We take the high-speed rail (HSR) network in China at the end of 2014 as an example, and obtain 51 passenger transit corridors, which are alternative sets of train paths. Furthermore, we analyze the circuity distribution of paths of all node pairs in the network. We find that the high circuity of train paths can be decreased with the construction of a high-speed railway line, which indicates that the structure of the HSR network in China tends to be more complete and the HSR network can make the Chinese railway network more efficient. PMID:28945757

Field-programmable logic devices with optical input-output.

PubMed

Szymanski, T H; Saint-Laurent, M; Tyan, V; Au, A; Supmonchai, B

2000-02-10

A field-programmable logic device (FPLD) with optical I/O is described. FPLD's with optical I/O can have their functionality specified in the field by means of downloading a control-bit stream and can be used in a wide range of applications, such as optical signal processing, optical image processing, and optical interconnects. Our device implements six state-of-the-art dynamically programmable logic arrays (PLA's) on a 2 mm x 2 mm die. The devices were fabricated through the Lucent Technologies-Advanced Research Projects Agency-Consortium for Optical and Optoelectronic Technologies in Computing (Lucent/ARPA/COOP) workshop by use of 0.5-microm complementary metal-oxide semiconductor-self-electro-optic device technology and were delivered in 1998. All devices are fully functional: The electronic data paths have been verified at 200 MHz, and optical tests are pending. The device has been programmed to implement a two-stage optical switching network with six 4 x 4 crossbar switches, which can realize more than 190 x 10(6) unique programmable input-output permutations. The same device scaled to a 2 cm x 2 cm substrate could support as many as 4000 optical I/O and 1 Tbit/s of optical I/O bandwidth and offer fully programmable digital functionality with approximately 110,000 programmable logic gates. The proposed optoelectronic FPLD is also ideally suited to realizing dense, statically reconfigurable crossbar switches. We describe an attractive application area for such devices: a rearrangeable three-stage optical switch for a wide-area-network backbone, switching 1000 traffic streams at the OC-48 data rate and supporting several terabits of traffic.

MIMO capacities and outage probabilities in spatially multiplexed optical transport systems.

PubMed

Winzer, Peter J; Foschini, Gerard J

2011-08-15

With wavelength-division multiplexing (WDM) rapidly nearing its scalability limits, space-division multiplexing (SDM) seems the only option to further scale the capacity of optical transport networks. In order for SDM systems to continue the WDM trend of reducing energy and cost per bit with system capacity, integration will be key to SDM. Since integration is likely to introduce non-negligible crosstalk between multiple parallel transmission paths, multiple-input multiple output (MIMO) signal processing techniques will have to be used. In this paper, we discuss MIMO capacities in optical SDM systems, including related outage considerations which are an important part in the design of such systems. In order to achieve the low-outage standards required for optical transport networks, SDM transponders should be capable of individually addressing, and preferably MIMO processing all modes supported by the optical SDM waveguide. We then discuss the effect of distributed optical noise in MIMO SDM systems and focus on the impact of mode-dependent loss (MDL) on system capacity and system outage. Through extensive numerical simulations, we extract scaling rules for mode-average and mode-dependent loss and show that MIMO SDM systems composed of up to 128 segments and supporting up to 128 modes can tolerate up to 1 dB of per-segment MDL at 90% of the system's full capacity at an outage probability of 10(-4). © 2011 Optical Society of America

Signal transmission in a human body medium-based body sensor network using a Mach-Zehnder electro-optical sensor.

PubMed

Song, Yong; Hao, Qun; Zhang, Kai; Wang, Jingwen; Jin, Xuefeng; Sun, He

2012-11-30

The signal transmission technology based on the human body medium offers significant advantages in Body Sensor Networks (BSNs) used for healthcare and the other related fields. In previous works we have proposed a novel signal transmission method based on the human body medium using a Mach-Zehnder electro-optical (EO) sensor. In this paper, we present a signal transmission system based on the proposed method, which consists of a transmitter, a Mach-Zehnder EO sensor and a corresponding receiving circuit. Meanwhile, in order to verify the frequency response properties and determine the suitable parameters of the developed system, in-vivo measurements have been implemented under conditions of different carrier frequencies, baseband frequencies and signal transmission paths. Results indicate that the proposed system will help to achieve reliable and high speed signal transmission of BSN based on the human body medium.

Signal Transmission in a Human Body Medium-Based Body Sensor Network Using a Mach-Zehnder Electro-Optical Sensor

PubMed Central

Song, Yong; Hao, Qun; Zhang, Kai; Wang, Jingwen; Jin, Xuefeng; Sun, He

2012-01-01

The signal transmission technology based on the human body medium offers significant advantages in Body Sensor Networks (BSNs) used for healthcare and the other related fields. In previous works we have proposed a novel signal transmission method based on the human body medium using a Mach-Zehnder electro-optical (EO) sensor. In this paper, we present a signal transmission system based on the proposed method, which consists of a transmitter, a Mach-Zehnder EO sensor and a corresponding receiving circuit. Meanwhile, in order to verify the frequency response properties and determine the suitable parameters of the developed system, in-vivo measurements have been implemented under conditions of different carrier frequencies, baseband frequencies and signal transmission paths. Results indicate that the proposed system will help to achieve reliable and high speed signal transmission of BSN based on the human body medium. PMID:23443393

Report on Technology Horizons: A Vision for Air Force Science and Technology During 2010-2030. Volume 1

DTIC Science & Technology

2010-05-15

flow and decision processes across the air and space domains. It thus comprises traditional wired and fiber-optic computer networks based on...dual flow path design allow high volumetric efficiency, and high cruise speed provides significantly increased survivability. Vertical takeoff...emerging “third-stream engine architectures” can enable for constant mass flow engines that can provide further reductions in fuel consumption. A wide

In-line optical fiber metallic mirror reflector for monolithic common path optical coherence tomography probes.

PubMed

Singh, Kanwarpal; Reddy, Rohith; Sharma, Gargi; Verma, Yogesh; Gardecki, Joseph A; Tearney, Guillermo

2018-03-01

Endoscopic optical coherence tomography probes suffer from various artifacts due to dispersion imbalance and polarization mismatch between reference and sample arm light. Such artifacts can be minimized using a common path approach. In this work, we demonstrate a miniaturized common path probe for optical coherence tomography using an inline fiber mirror. A common path optical fiber probe suitable for performing high-resolution endoscopic optical coherence tomography imaging was developed. To achieve common path functionality, an inline fiber mirror was fabricated using a thin gold layer. A commercially available swept source engine was used to test the designed probe in a cadaver human coronary artery ex vivo. We achieved a sensitivity of 104 dB for this probe using a swept source optical coherence tomography system. To test the probe, images of a cadaver human coronary artery were obtained, demonstrating the quality that is comparable to those obtained by OCT systems with separate reference arms. Additionally, we demonstrate recovery of ranging depth by use of a Michelson interferometer in the detection path. We developed a miniaturized monolithic inline fiber mirror-based common path probe for optical coherence tomography. Owing to its simplicity, our design will be helpful in endoscopic applications that require high-resolution probes in a compact form factor while reducing system complexity. Lasers Surg. Med. 50:230-235, 2018. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

R&D of a Next Generation LEO System for Global Multimedia Mobile Satellite Communications

NASA Astrophysics Data System (ADS)

Morikawa, E.; Motoyoshi, S.; Koyama, Y.; Suzuki, R.; Yasuda, Y.

2002-01-01

Next-generation LEO System Research Center (NeLS) was formed in the end of 1997 as a research group under the Telecommunications Advancement Organization of Japan, in cooperation with the telecommunications operators, manufacturers, universities and governmental research organization. The aim of this project is to develop new technology for global multimedia mobile satellite communications services with a user data rate around 2Mbps for handy terminals. component of the IMT-2000, and the second generation of the big-LEO systems. In prosecuting this project, two-phase approach, phase 1 and phase 2, is considered. Phase 1 is the system definition and development of key technologies. In Phase 2, we plan to verify the developed technology in Phase 1 on space. From this year we shifted the stage to Phase 2, and are now developing the prototype of on-board communication systems for flight tests, which will be planed at around 2006. The satellite altitude is assumed to be 1200 km in order to reduce the number of satellites, to avoid the Van Allen radiation belts and to increase the minimum elevation angle. Ten of the circular orbits with 55 degree of inclination are selected to cover the earth surface from -70 to 70 degree in latitude. 12 satellites are positioned at regular intervals in each orbit. In this case, the minimum elevation angle from the user terminal can be keep more than 20 degree for the visibility of the satellite, and 15 degree for simultaneous visibility of two satellites. Then, NeLS Research Center was focusing on the development of key technologies as the phase 1 project. Four kinds of key technologies; DBF satellite antenna, optical inter-satellite link system, satellite network technology with on-board ATM switch and variable rate modulation were selected. Satellite Antenna Technology: Development of on-board direct radiating active phased array antenna with digital beam forming technology would be one of the most important breakthroughs for the satellite communication systems. Therefore, the experimental DBF network with 16 radiating elements was developed for confirming a basic signal processing performance. A/D sampled data are processed by using FPGA circuit for beam forming by real-time basis. Optical Inter-Satellite Link Technology: The inter-satellite link (ISL) technology is also important, because the inter-satellite network is essential to realize the low delay network connection for multimedia services. The optical ISL simulator was developed for the study of optical modem and optical tracking mechanism. And the sensitivity of 56 photons/bit at 10-9 of error rate has been achieved by employing the Erbium doped fiber amplifier, polarizing filter and narrow band optical filter. Coude path type, the active universal joint (AUJ) type and two flat mirror type of optical antenna mechanism were developed. Satellite Network Technology: For constructing this optical ISL ring, the utilization of wavelength division multiplexing (WDM) technology is envisaged. By applying WDM technology to the optical intra-orbital ISL, logical mesh connections can be achieved by assigning the appropriate wavelength for the links among satellites. By using inclined orbit, inter-orbital ISL connection can be keep continuously. Therefore, WDM technology is also applicable to the inter-orbital ISL network. The satellite ATM network simulator was developed in order to investigate the effect of delay fluctuation caused by the satellite constellations. This simulator works as real-time basis by using commercial ATM switches and personal computers. This simulator was installed Dijkstra's algorithm to determine satellite routing path in order to minimize the end-to-end delay time from the source terminal to the destination terminal. The satellite IP network simulator has been developed in order to evaluate the congestion of the multimedia traffic. Variable Rate Modulation Technology: Considering the propagation impairments in the mobile conditions, we employ the variable rate transmission, which maintains the communication service by decreasing the data rate while the user link condition is degraded. CDMA and OFDM techniques are candidates for such a variable rate transmission scheme. In order to study the variable rate modem, the software simulation tools and hardware simulator were prepared. The hardware simulator can generate various kinds of propagation impairments, such as Rayleigh, multi-path, Doppler shift, etc by inputting satellite constellation parameters and fading models. In this paper, we briefly introduce the results of development in Phase 1and a current status in Phase 2.

A 2-dimensional optical architecture for solving Hamiltonian path problem based on micro ring resonators

NASA Astrophysics Data System (ADS)

Shakeri, Nadim; Jalili, Saeed; Ahmadi, Vahid; Rasoulzadeh Zali, Aref; Goliaei, Sama

2015-01-01

The problem of finding the Hamiltonian path in a graph, or deciding whether a graph has a Hamiltonian path or not, is an NP-complete problem. No exact solution has been found yet, to solve this problem using polynomial amount of time and space. In this paper, we propose a two dimensional (2-D) optical architecture based on optical electronic devices such as micro ring resonators, optical circulators and MEMS based mirror (MEMS-M) to solve the Hamiltonian Path Problem, for undirected graphs in linear time. It uses a heuristic algorithm and employs n+1 different wavelengths of a light ray, to check whether a Hamiltonian path exists or not on a graph with n vertices. Then if a Hamiltonian path exists, it reports the path. The device complexity of the proposed architecture is O(n2).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Joe Mambretti

This is the summary report of the third annual Optical Networking Testbed Workshop (ONT3), which brought together leading members of the international advanced research community to address major challenges in creating next generation communication services and technologies. Networking research and development (R&D) communities throughout the world continue to discover new methods and technologies that are enabling breakthroughs in advanced communications. These discoveries are keystones for building the foundation of the future economy, which requires the sophisticated management of extremely large qualities of digital information through high performance communications. This innovation is made possible by basic research and experiments within laboratoriesmore » and on specialized testbeds. Initial network research and development initiatives are driven by diverse motives, including attempts to solve existing complex problems, the desire to create powerful new technologies that do not exist using traditional methods, and the need to create tools to address specific challenges, including those mandated by large scale science or government agency mission agendas. Many new discoveries related to communications technologies transition to wide-spread deployment through standards organizations and commercialization. These transition paths allow for new communications capabilities that drive many sectors of the digital economy. In the last few years, networking R&D has increasingly focused on advancing multiple new capabilities enabled by next generation optical networking. Both US Federal networking R&D and other national R&D initiatives, such as those organized by the National Institute of Information and Communications Technology (NICT) of Japan are creating optical networking technologies that allow for new, powerful communication services. Among the most promising services are those based on new types of multi-service or hybrid networks, which use new optical networking technologies. Several years ago, when many of these optical networking research topics were first being investigated, they were the subject of controversial debate. The new techniques challenged many long-held concepts related to architecture and technology. However, today all major networking organizations are transitioning toward infrastructure that incorporates these new concepts. This progress has been assisted through the series of Optical Networking Testbed Workshops (ONT). The first (ONT1) outlined a general framework of key issues and topics and developed a series of recommendations (www.nren.nasa.gov/workshop7). The second (ONT2) developed a common vision of optical network technologies, services, infrastructure, and organizations (www.nren.nasa.gov/workshop8). Processes that allow for a common vision encourage widespread deployment of these types of resources among advanced networking communities. Also, such a shared vision enables key concepts and technologies to migrate from basic research testbeds to wider networking communities. The ONT-3 workshop built on these earlier activities by expanding discussion to include additional considerations of the international interoperability and of greater impact of optical networking technology on networking in general. In accordance with this recognition, the workshop confirmed that future-oriented research and development is indispensable to fundamentally change the current Internet architecture to create a global network incorporating completely new concepts. The workshop also recognized that the first priority to allow for this progress is basic research and development, including international collaborative activities, which are important for the global realization of interoperability of a new generation architecture.« less

Satellite networks in the ISDN era

NASA Astrophysics Data System (ADS)

Amadesi, P.; Haines, P.; Patacchini, A.

1986-12-01

The development of an integrated service digital network (ISDN) capable of supporting a wide range of services using a small set of standard multipurpose user-network interfaces is examined. The ISDN environment is expected to consist of functional elements such as, circuit switching, packet switching, and common channel signaling. The use of satellites or fiber optics in the ISDN is evaluated. The relation between satellites and the ISDN in the short-, medium-, and long-terms is analyzed. The recommendations of the consultative committee, CCIR, concerning the definition of the hypothetical reference digital path and the required quality and availability for ISDN applications, and the proposed plans of Eutelsat and Intelsat for satellite systems compatible with an ISDN are discussed. The application of business satellite networks and packet satellite networks to an ISDN is studied. The long-term objectives for an ISDN is a wideband system that accommodates digital transmission on circuit and packet switched bases.

All-optical, thermo-optical path length modulation based on the vanadium-doped fibers.

PubMed

Matjasec, Ziga; Campelj, Stanislav; Donlagic, Denis

2013-05-20

This paper presents an all-fiber, fully-optically controlled, optical-path length modulator based on highly absorbing optical fiber. The modulator utilizes a high-power 980 nm pump diode and a short section of vanadium-co-doped single mode fiber that is heated through absorption and a non-radiative relaxation process. The achievable path length modulation range primarily depends on the pump's power and the convective heat-transfer coefficient of the surrounding gas, while the time response primarily depends on the heated fiber's diameter. An absolute optical length change in excess of 500 µm and a time-constant as short as 11 ms, were demonstrated experimentally. The all-fiber design allows for an electrically-passive and remote operation of the modulator. The presented modulator could find use within various fiber-optics systems that require optical (remote) path length control or modulation.

An improved global dynamic routing strategy for scale-free network with tunable clustering

NASA Astrophysics Data System (ADS)

Sun, Lina; Huang, Ning; Zhang, Yue; Bai, Yannan

2016-08-01

An efficient routing strategy can deliver packets quickly to improve the network capacity. Node congestion and transmission path length are inevitable real-time factors for a good routing strategy. Existing dynamic global routing strategies only consider the congestion of neighbor nodes and the shortest path, which ignores other key nodes’ congestion on the path. With the development of detection methods and techniques, global traffic information is readily available and important for the routing choice. Reasonable use of this information can effectively improve the network routing. So, an improved global dynamic routing strategy is proposed, which considers the congestion of all nodes on the shortest path and incorporates the waiting time of the most congested node into the path. We investigate the effectiveness of the proposed routing for scale-free network with different clustering coefficients. The shortest path routing strategy and the traffic awareness routing strategy only considering the waiting time of neighbor node are analyzed comparatively. Simulation results show that network capacity is greatly enhanced compared with the shortest path; congestion state increase is relatively slow compared with the traffic awareness routing strategy. Clustering coefficient increase will not only reduce the network throughput, but also result in transmission average path length increase for scale-free network with tunable clustering. The proposed routing is favorable to ease network congestion and network routing strategy design.

Entropy-based link prediction in weighted networks

NASA Astrophysics Data System (ADS)

Xu, Zhongqi; Pu, Cunlai; Ramiz Sharafat, Rajput; Li, Lunbo; Yang, Jian

2017-01-01

Information entropy has been proved to be an effective tool to quantify the structural importance of complex networks. In the previous work (Xu et al, 2016 \\cite{xu2016}), we measure the contribution of a path in link prediction with information entropy. In this paper, we further quantify the contribution of a path with both path entropy and path weight, and propose a weighted prediction index based on the contributions of paths, namely Weighted Path Entropy (WPE), to improve the prediction accuracy in weighted networks. Empirical experiments on six weighted real-world networks show that WPE achieves higher prediction accuracy than three typical weighted indices.

A collaborative network middleware project by Lambda Station, TeraPaths, and Phoebus

NASA Astrophysics Data System (ADS)

Bobyshev, A.; Bradley, S.; Crawford, M.; DeMar, P.; Katramatos, D.; Shroff, K.; Swany, M.; Yu, D.

2010-04-01

The TeraPaths, Lambda Station, and Phoebus projects, funded by the US Department of Energy, have successfully developed network middleware services that establish on-demand and manage true end-to-end, Quality-of-Service (QoS) aware, virtual network paths across multiple administrative network domains, select network paths and gracefully reroute traffic over these dynamic paths, and streamline traffic between packet and circuit networks using transparent gateways. These services improve network QoS and performance for applications, playing a critical role in the effective use of emerging dynamic circuit network services. They provide interfaces to applications, such as dCache SRM, translate network service requests into network device configurations, and coordinate with each other to setup up end-to-end network paths. The End Site Control Plane Subsystem (ESCPS) builds upon the success of the three projects by combining their individual capabilities into the next generation of network middleware. ESCPS addresses challenges such as cross-domain control plane signalling and interoperability, authentication and authorization in a Grid environment, topology discovery, and dynamic status tracking. The new network middleware will take full advantage of the perfSONAR monitoring infrastructure and the Inter-Domain Control plane efforts and will be deployed and fully vetted in the Large Hadron Collider data movement environment.

Dynamically reconfigurable optical packet switch (DROPS)

NASA Astrophysics Data System (ADS)

Huang, Chi-Heng; Chou, Hsu-Feng; Bowers, John E.; Toudeh-Fallah, Farzam; Gyurek, Russ

2006-12-01

A novel Dynamically Reconfigurable Optical Packet Switch (DROPS) that combines both spectral and spatial switching capabilities is proposed and experimentally demonstrated for the first time. Compared with an Arrayed Waveguide Grating Router (AWGR), the added spatial switching capability provided by the microelectromechanical systems (MEMS) enables dynamically reconfigurable routing that is not possible with an AWGR alone. This methodology has several advantages over an AWGR including scalability, additional degrees of freedom in routing a packet from an ingress port to an egress port and more flexibility in path or line card recovery. The experimental demonstration implemented with 10-Gb/s packets shows that the added spatial switching does not degrade the bit-error-rate performance, indicating the promising potential of DROPS as a versatile and ultra-high capacity switch for optical packet-switched networks.

Fused smart sensor network for multi-axis forward kinematics estimation in industrial robots.

PubMed

Rodriguez-Donate, Carlos; Osornio-Rios, Roque Alfredo; Rivera-Guillen, Jesus Rooney; Romero-Troncoso, Rene de Jesus

2011-01-01

Flexible manipulator robots have a wide industrial application. Robot performance requires sensing its position and orientation adequately, known as forward kinematics. Commercially available, motion controllers use high-resolution optical encoders to sense the position of each joint which cannot detect some mechanical deformations that decrease the accuracy of the robot position and orientation. To overcome those problems, several sensor fusion methods have been proposed but at expenses of high-computational load, which avoids the online measurement of the joint's angular position and the online forward kinematics estimation. The contribution of this work is to propose a fused smart sensor network to estimate the forward kinematics of an industrial robot. The developed smart processor uses Kalman filters to filter and to fuse the information of the sensor network. Two primary sensors are used: an optical encoder, and a 3-axis accelerometer. In order to obtain the position and orientation of each joint online a field-programmable gate array (FPGA) is used in the hardware implementation taking advantage of the parallel computation capabilities and reconfigurability of this device. With the aim of evaluating the smart sensor network performance, three real-operation-oriented paths are executed and monitored in a 6-degree of freedom robot.

Improved graphite furnace atomizer

DOEpatents

Siemer, D.D.

1983-05-18

A graphite furnace atomizer for use in graphite furnace atomic absorption spectroscopy is described wherein the heating elements are affixed near the optical path and away from the point of sample deposition, so that when the sample is volatilized the spectroscopic temperature at the optical path is at least that of the volatilization temperature, whereby analyteconcomitant complex formation is advantageously reduced. The atomizer may be elongated along its axis to increase the distance between the optical path and the sample deposition point. Also, the atomizer may be elongated along the axis of the optical path, whereby its analytical sensitivity is greatly increased.

All-optical bidirectional neural interfacing using hybrid multiphoton holographic optogenetic stimulation.

PubMed

Paluch-Siegler, Shir; Mayblum, Tom; Dana, Hod; Brosh, Inbar; Gefen, Inna; Shoham, Shy

2015-07-01

Our understanding of neural information processing could potentially be advanced by combining flexible three-dimensional (3-D) neuroimaging and stimulation. Recent developments in optogenetics suggest that neurophotonic approaches are in principle highly suited for noncontact stimulation of network activity patterns. In particular, two-photon holographic optical neural stimulation (2P-HONS) has emerged as a leading approach for multisite 3-D excitation, and combining it with temporal focusing (TF) further enables axially confined yet spatially extended light patterns. Here, we study key steps toward bidirectional cell-targeted 3-D interfacing by introducing and testing a hybrid new 2P-TF-HONS stimulation path for accurate parallel optogenetic excitation into a recently developed hybrid multiphoton 3-D imaging system. The system is shown to allow targeted all-optical probing of in vitro cortical networks expressing channelrhodopsin-2 using a regeneratively amplified femtosecond laser source tuned to 905 nm. These developments further advance a prospective new tool for studying and achieving distributed control over 3-D neuronal circuits both in vitro and in vivo.

Analysis of multiuser mixed RF/FSO relay networks for performance improvements in Cloud Computing-Based Radio Access Networks (CC-RANs)

NASA Astrophysics Data System (ADS)

Alimi, Isiaka A.; Monteiro, Paulo P.; Teixeira, António L.

2017-11-01

The key paths toward the fifth generation (5G) network requirements are towards centralized processing and small-cell densification systems that are implemented on the cloud computing-based radio access networks (CC-RANs). The increasing recognitions of the CC-RANs can be attributed to their valuable features regarding system performance optimization and cost-effectiveness. Nevertheless, realization of the stringent requirements of the fronthaul that connects the network elements is highly demanding. In this paper, considering the small-cell network architectures, we present multiuser mixed radio-frequency/free-space optical (RF/FSO) relay networks as feasible technologies for the alleviation of the stringent requirements in the CC-RANs. In this study, we use the end-to-end (e2e) outage probability, average symbol error probability (ASEP), and ergodic channel capacity as the performance metrics in our analysis. Simulation results show the suitability of deployment of mixed RF/FSO schemes in the real-life scenarios.

Ethernet-Based Services for Next Generation Networks

NASA Astrophysics Data System (ADS)

Hernandez-Valencia, Enrique

Over the last few years, Ethernet technology and services have emerged as an indispensable component of the broadband networking and telecommunications infrastructure, both for network operators and service providers. As an example, Worldwide Enterprise customer demand for Ethernet services by itself is expected to hit the 30B US mark by year 2012. Use of Ethernet technology in the feeder networks that support residential applications, such as "triple play" voice, data, and video services, is equally on the rise. As the synergies between packet-aware transport and service oriented equipment continue to be exploited in the path toward transport convergence. Ethernet technology is expected to play a critical part in the evolution toward converged Optical/Packet Transport networks. Here we discuss the main business motivations, services, and technologies driving the specifications of so-called carrier Ethernet and highlight challenges associated with delivering the expectations for low implementation complexity, easy of use, provisioning and management of networks and network elements embracing this technology.

High Availability in Optical Networks

NASA Astrophysics Data System (ADS)

Grover, Wayne D.; Wosinska, Lena; Fumagalli, Andrea

2005-09-01

Call for Papers: High Availability in Optical Networks Submission Deadline: 1 January 2006 The Journal of Optical Networking (JON) is soliciting papers for a feature Issue pertaining to all aspects of reliable components and systems for optical networks and concepts, techniques, and experience leading to high availability of services provided by optical networks. Most nations now recognize that telecommunications in all its forms -- including voice, Internet, video, and so on -- are "critical infrastructure" for the society, commerce, government, and education. Yet all these services and applications are almost completely dependent on optical networks for their realization. "Always on" or apparently unbreakable communications connectivity is the expectation from most users and for some services is the actual requirement as well. Achieving the desired level of availability of services, and doing so with some elegance and efficiency, is a meritorious goal for current researchers. This requires development and use of high-reliability components and subsystems, but also concepts for active reconfiguration and capacity planning leading to high availability of service through unseen fast-acting survivability mechanisms. The feature issue is also intended to reflect some of the most important current directions and objectives in optical networking research, which include the aspects of integrated design and operation of multilevel survivability and realization of multiple Quality-of-Protection service classes. Dynamic survivable service provisioning, or batch re-provisioning is an important current theme, as well as methods that achieve high availability at far less investment in spare capacity than required by brute force service path duplication or 100% redundant rings, which is still the surprisingly prevalent practice. Papers of several types are envisioned in the feature issue, including outlook and forecasting types of treatments, optimization and analysis, new concepts for survivability, or papers on availability analysis methods or results. Customer, vendor, and researcher viewpoints and priorities will all be given consideration. Especially valuable to the community would be papers that include or provide measured data on actual reliability and availability performance of optical networking components or systems. The scope of the papers includes, but is not limited to, the following topics: Reliability and availability measurement techniques specific to optical network devices or services. Data on SRLG statistics and frequency of different actual failure causes. Real-life accounts or data on failure and repair rates or projected values for use in availability analysis. Availability analysis methods, especially for survivable networks with reconfigurable or adaptive failure-specific responses. Availability analysis and comparisons of basic schemes for survivability. Differentiated availability schemes. Design for Multiple Quality of Protection. Different schemes for on-demand survivable service provisioning. Basic comparisons or proposals of new survivability mechanisms and architectures. Concepts yielding higher than 1+1 protection switching availability at less than 100% redundancy. Survivable service provisioning in domains of optical transparency: dealing with signal impairments. To submit to this special issue, follow the normal procedure for submission to JON, indicating "Feature Issue: Optical Network Availability" in the "Comments" field of the online submission form. For all other questions relating to this feature issue, please send an e-mail to jon@osa.org, subject line "Feature Issue: Optical Network Availability." Additional information can be found on the JON website: http://www.osa-jon.org/submission/

A Novel Dual Separate Paths (DSP) Algorithm Providing Fault-Tolerant Communication for Wireless Sensor Networks.

PubMed

Tien, Nguyen Xuan; Kim, Semog; Rhee, Jong Myung; Park, Sang Yoon

2017-07-25

Fault tolerance has long been a major concern for sensor communications in fault-tolerant cyber physical systems (CPSs). Network failure problems often occur in wireless sensor networks (WSNs) due to various factors such as the insufficient power of sensor nodes, the dislocation of sensor nodes, the unstable state of wireless links, and unpredictable environmental interference. Fault tolerance is thus one of the key requirements for data communications in WSN applications. This paper proposes a novel path redundancy-based algorithm, called dual separate paths (DSP), that provides fault-tolerant communication with the improvement of the network traffic performance for WSN applications, such as fault-tolerant CPSs. The proposed DSP algorithm establishes two separate paths between a source and a destination in a network based on the network topology information. These paths are node-disjoint paths and have optimal path distances. Unicast frames are delivered from the source to the destination in the network through the dual paths, providing fault-tolerant communication and reducing redundant unicast traffic for the network. The DSP algorithm can be applied to wired and wireless networks, such as WSNs, to provide seamless fault-tolerant communication for mission-critical and life-critical applications such as fault-tolerant CPSs. The analyzed and simulated results show that the DSP-based approach not only provides fault-tolerant communication, but also improves network traffic performance. For the case study in this paper, when the DSP algorithm was applied to high-availability seamless redundancy (HSR) networks, the proposed DSP-based approach reduced the network traffic by 80% to 88% compared with the standard HSR protocol, thus improving network traffic performance.

E-Center: A Collaborative Platform for Wide Area Network Users

NASA Astrophysics Data System (ADS)

Grigoriev, M.; DeMar, P.; Tierney, B.; Lake, A.; Metzger, J.; Frey, M.; Calyam, P.

2012-12-01

The E-Center is a social collaborative web-based platform for assisting network users in understanding network conditions across network paths of interest to them. It is designed to give a user the necessary tools to isolate, identify, and resolve network performance-related problems. E-Center provides network path information on a link-by-link level, as well as from an end-to-end perspective. In addition to providing current and recent network path data, E-Center is intended to provide a social media environment for them to share issues, ideas, concerns, and problems. The product has a modular design that accommodates integration of other network services that make use of the same network path and performance data.

Vibrational Analysis of a Shipboard Free Electron Laser Beam Path

DTIC Science & Technology

2011-12-01

2 Figure 2. Optical Extraction (η) vs. Separation and Electron Beam Tilt for a Notional FEL Oscillator . (From [1...in Figure 2. Figure 2. Optical Extraction (η) vs. Separation and Electron Beam Tilt for a Notional FEL Oscillator . (From [1]) The narrow beam...3 is a top down view of the entire electron beam path. Figure 3. Electron Beam Line of a Notional FEL Oscillator . 2. Optical Path The optical

Performance evaluation of multi-stratum resources integrated resilience for software defined inter-data center interconnect.

PubMed

Yang, Hui; Zhang, Jie; Zhao, Yongli; Ji, Yuefeng; Wu, Jialin; Lin, Yi; Han, Jianrui; Lee, Young

2015-05-18

Inter-data center interconnect with IP over elastic optical network (EON) is a promising scenario to meet the high burstiness and high-bandwidth requirements of data center services. In our previous work, we implemented multi-stratum resources integration among IP networks, optical networks and application stratums resources that allows to accommodate data center services. In view of this, this study extends to consider the service resilience in case of edge optical node failure. We propose a novel multi-stratum resources integrated resilience (MSRIR) architecture for the services in software defined inter-data center interconnect based on IP over EON. A global resources integrated resilience (GRIR) algorithm is introduced based on the proposed architecture. The MSRIR can enable cross stratum optimization and provide resilience using the multiple stratums resources, and enhance the data center service resilience responsiveness to the dynamic end-to-end service demands. The overall feasibility and efficiency of the proposed architecture is experimentally verified on the control plane of our OpenFlow-based enhanced SDN (eSDN) testbed. The performance of GRIR algorithm under heavy traffic load scenario is also quantitatively evaluated based on MSRIR architecture in terms of path blocking probability, resilience latency and resource utilization, compared with other resilience algorithms.

Planning and deployment of DWDM systems: a reality

NASA Astrophysics Data System (ADS)

Mishra, Data S.

2001-10-01

The new definition and implementation of new communication network architectures and elements in the present data-centric world are due to dramatic change in technology, explosive growth in bandwidth requirement and de-regulated, privatized and competitive telecommunication market. Network Convergence, Disruptive Technology and Convulsive Market are the basic forces who are pushing the future network towards Packet based Optical Core Network and varieties of Access Network along with integrated NMS. Well-known Moore's law governs the result of progress in silicon processing and accordingly the present capacity of network must be multiplied by 100 times in 10 years. To build a global network which is 100 times powerful than present one by scaling up today's technology can not be a practical solution due to requirement of 100 fold increase in cost, power and size. Today's two network (Low delay, fixed bandwidth, Poisson voice traffic based, circuit-switched PSTN/PLMN and variable delay, variable bandwidth, no-guaranteed QoS based packet switched internet) are converging towards two-layer network (IP and ATM in lower layer; DWDM in network layer). SDH Network which was well drafted before explosive data traffic and was best suitable for Interoperability, Survivability, Reliability and Manageability will be taken over by DWDM Network by 2005 due to 90% of data traffic. This paper describes the way to build the Communication Network (either by migration or by overlay) with an overview of the equipment and technologies required to design the DWDM Network. Service Providers are facing tough challenges for selection of emerging technologies and advances in network standard for bandwidth hungry, valued customers. The reduction of cost of services due to increased competition , explosive growth of internet and 10GbE Ethernet (which is being considered as an end-to-end network solution) have given surprise to many network architects and designers. To provide transparency to data-rate and data-format the gap between electrical layer and Optical backbone layer has to be filled. By partitioning the Optical Bandwidth of Optical Fibre Cable into the wavelengths (32 to 120) Wavelength Division Multiplexing can transport data rate from 10MB/s to 10GB/s on each wavelength. In this paper we will analyze the difficult strategies of suppliers and obstacles in the way of service providers to make DWDM a reality in the field either as Upgrade or Overlay or New Network. The difficult constraint of protection scheme with respect to compatibility with existing network and network under development has to sorted out along with present standard of Optical Fibre to carry DWDM signal in cost effective way to Access , Edge and Metro part of our network. The future of IP under DWDM is going to be key element for Network Planners in future. Fundamental limitation of bit manipulation in Photonic domain will have implication on the network design, cost and migration to all optical network because Photons are computer un-friendly and not mature enough to give memory and logic devices. In the environment of heterogeneous traffic the DWDM based All Optical Network should behave as per expectation of users whose primary traffic will be multi-media IP type. The quality of service (QoS), Virtual Path Network (VPN) over DWDM, OXC and intelligence at the edge will play a major role in future deployment of DWDM in our network . The development of improved fiber characteristics, EDFAs and Photonic component has led the carriers to go for Dense WDM Network.

A 16-bit Coherent Ising Machine for One-Dimensional Ring and Cubic Graph Problems

NASA Astrophysics Data System (ADS)

Takata, Kenta; Marandi, Alireza; Hamerly, Ryan; Haribara, Yoshitaka; Maruo, Daiki; Tamate, Shuhei; Sakaguchi, Hiromasa; Utsunomiya, Shoko; Yamamoto, Yoshihisa

2016-09-01

Many tasks in our modern life, such as planning an efficient travel, image processing and optimizing integrated circuit design, are modeled as complex combinatorial optimization problems with binary variables. Such problems can be mapped to finding a ground state of the Ising Hamiltonian, thus various physical systems have been studied to emulate and solve this Ising problem. Recently, networks of mutually injected optical oscillators, called coherent Ising machines, have been developed as promising solvers for the problem, benefiting from programmability, scalability and room temperature operation. Here, we report a 16-bit coherent Ising machine based on a network of time-division-multiplexed femtosecond degenerate optical parametric oscillators. The system experimentally gives more than 99.6% of success rates for one-dimensional Ising ring and nondeterministic polynomial-time (NP) hard instances. The experimental and numerical results indicate that gradual pumping of the network combined with multiple spectral and temporal modes of the femtosecond pulses can improve the computational performance of the Ising machine, offering a new path for tackling larger and more complex instances.

Universal method for crosstalk noise and transmission loss analysis for N-port nonblocking optical router for photonic networks-on-chip

NASA Astrophysics Data System (ADS)

Xie, Yiyuan; Zhang, Zhendong; Song, Tingting; He, Chao; Li, Jiachao; Wang, Guijin

2016-05-01

Crosstalk noise and transmission loss are two key elements in determining the performance of optical routers. We propose a universal method for crosstalk noise and transmission loss analysis for the N-port nonblocking optical router used in photonic networks-on-chip. Utilizing this method, we study the crosstalk noise and transmission loss for the five-, six-, seven-, and eight-port optical routers. We ascertain that the crosstalk noise and transmission loss are different for different input-output pairs. For the five-port optical router, the maximum crosstalk noise ranges from 0 to -7.07 dBm, and the transmission loss ranges from -9.05 to -0.51 dB. Furthermore, based on the crosstalk noise and transmission loss, we analyze optical signal-to-noise ratio (OSNR) and bit error ratio (BER) for the five-, six-, seven-, and eight-port nonblocking optical routers. As the number of ports increases, the minimum average OSNR decreases and the average BER increases. In addition, in order to present the performance of the routers more visually, a fiber-optic communications system is designed to simulate the transmission processes of the signals of the different paths of the routers in Optisystem. The results show that the power amplitude of the input signal is obviously higher than the corresponding output signal. With this method, we can easily evaluate the transmission loss, crosstalk noise, OSNR, and BER of high-radix nonblocking optical routers and conveniently study the performance of the N-port optical router.

The laser and optical system for the RIBF-PALIS experiment

NASA Astrophysics Data System (ADS)

Sonoda, T.; Iimura, H.; Reponen, M.; Wada, M.; Katayama, I.; Sonnenschein, V.; Takamatsu, T.; Tomita, H.; Kojima, T. M.

2018-01-01

This paper describes the laser and optical system for the Parasitic radioactive isotope (RI) beam production by Laser Ion-Source (PALIS) in the RIKEN fragment separator facility. This system requires an optical path length of 70 m for transporting the laser beam from the laser light source to the place for resonance ionization. To accomplish this, we designed and implemented a simple optical system consisting of several mirrors equipped with compact stepping motor actuators, lenses, beam spot screens and network cameras. The system enables multi-step laser resonance ionization in the gas cell and gas jet via overlap with a diameter of a few millimeters, between the laser photons and atomic beam. Despite such a long transport distance, we achieved a transport efficiency for the UV laser beam of about 50%. We also confirmed that the position stability of the laser beam stays within a permissible range for dedicated resonance ionization experiments.

Distributed multiple path routing in complex networks

NASA Astrophysics Data System (ADS)

Chen, Guang; Wang, San-Xiu; Wu, Ling-Wei; Mei, Pan; Yang, Xu-Hua; Wen, Guang-Hui

2016-12-01

Routing in complex transmission networks is an important problem that has garnered extensive research interest in the recent years. In this paper, we propose a novel routing strategy called the distributed multiple path (DMP) routing strategy. For each of the O-D node pairs in a given network, the DMP routing strategy computes and stores multiple short-length paths that overlap less with each other in advance. And during the transmission stage, it rapidly selects an actual routing path which provides low transmission cost from the pre-computed paths for each transmission task, according to the real-time network transmission status information. Computer simulation results obtained for the lattice, ER random, and scale-free networks indicate that the strategy can significantly improve the anti-congestion ability of transmission networks, as well as provide favorable routing robustness against partial network failures.

Nonadiabatic quantum path analysis of high-order harmonic generation: Role of the carrier-envelope phase on short and long paths

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sansone, G.; Stagira, S.; Nisoli, M.

2004-07-01

High-order harmonic generation process in the few- and multiple-optical-cycle regime is theoretically investigated, using the saddle-point method generalized to account for nonadiabatic effects. The influence of the carrier-envelope phase of the driving pulses on the various electron quantum paths is analyzed. We demonstrate that the short and long quantum paths are influenced in different ways by the carrier-envelope phase. In particular, we show that clear phase effects are visible on the long quantum paths even in the multiple-optical-cycle regime, while the short quantum paths are significantly influenced by the carrier-envelope phase only in the few-optical-cycle regime.

Path Network Recovery Using Remote Sensing Data and Geospatial-Temporal Semantic Graphs

DOE Office of Scientific and Technical Information (OSTI.GOV)

William C. McLendon III; Brost, Randy C.

Remote sensing systems produce large volumes of high-resolution images that are difficult to search. The GeoGraphy (pronounced Geo-Graph-y) framework [2, 20] encodes remote sensing imagery into a geospatial-temporal semantic graph representation to enable high level semantic searches to be performed. Typically scene objects such as buildings and trees tend to be shaped like blocks with few holes, but other shapes generated from path networks tend to have a large number of holes and can span a large geographic region due to their connectedness. For example, we have a dataset covering the city of Philadelphia in which there is a singlemore » road network node spanning a 6 mile x 8 mile region. Even a simple question such as "find two houses near the same street" might give unexpected results. More generally, nodes arising from networks of paths (roads, sidewalks, trails, etc.) require additional processing to make them useful for searches in GeoGraphy. We have assigned the term Path Network Recovery to this process. Path Network Recovery is a three-step process involving (1) partitioning the network node into segments, (2) repairing broken path segments interrupted by occlusions or sensor noise, and (3) adding path-aware search semantics into GeoQuestions. This report covers the path network recovery process, how it is used, and some example use cases of the current capabilities.« less

Evaluation of Acoustic Propagation Paths into the Human Head

DTIC Science & Technology

2005-04-01

pressure amplitude) via the alternate propagation paths. A 3D finite-element solid mesh was constructed using a digital image database of an adult...optics, rays are used to depict the path or paths taken as a light wave travels through a lens. However, in optics, the eikonal equation can be solved

Method and system for compact efficient laser architecture

DOEpatents

Bayramian, Andrew James; Erlandson, Alvin Charles; Manes, Kenneth Rene; Spaeth, Mary Louis; Caird, John Allyn; Deri, Robert J.

2015-09-15

A laser amplifier module having an enclosure includes an input window, a mirror optically coupled to the input window and disposed in a first plane, and a first amplifier head disposed along an optical amplification path adjacent a first end of the enclosure. The laser amplifier module also includes a second amplifier head disposed along the optical amplification path adjacent a second end of the enclosure and a cavity mirror disposed along the optical amplification path.

Attenuator And Conditioner

DOEpatents

Anderson, Gene R.; Armendariz, Marcelino G.; Carson, Richard F.; Bryan, Robert P.; Duckett, III, Edwin B.; Kemme, Shanalyn Adair; McCormick, Frederick B.; Peterson, David W.

2006-04-04

An apparatus and method of attenuating and/or conditioning optical energy for an optical transmitter, receiver or transceiver module is disclosed. An apparatus for attenuating the optical output of an optoelectronic connector including: a mounting surface; an array of optoelectronic devices having at least a first end; an array of optical elements having at least a first end; the first end of the array of optical elements optically aligned with the first end of the array of optoelectronic devices; an optical path extending from the first end of the array of optoelectronic devices and ending at a second end of the array of optical elements; and an attenuator in the optical path for attenuating the optical energy emitted from the array of optoelectronic devices. Alternatively, a conditioner may be adapted in the optical path for conditioning the optical energy emitted from the array of optoelectronic devices.

Optical Path Switching Based Differential Absorption Radiometry for Substance Detection

NASA Technical Reports Server (NTRS)

Sachse, Glen W. (Inventor)

2000-01-01

A system and method are provided for detecting one or more substances. An optical path switch divides sample path radiation into a time series of alternating first polarized components and second polarized components. The first polarized components are transmitted along a first optical path and the second polarized components along a second optical path. A first gasless optical filter train filters the first polarized components to isolate at least a first wavelength band thereby generating first filtered radiation. A second gasless optical filter train filters the second polarized components to isolate at least a second wavelength band thereby generating second filtered radiation. The first wavelength band and second wavelength band are unique. Further, spectral absorption of a substance of interest is different at the first wavelength band as compared to the second wavelength band. A beam combiner combines the first and second filtered radiation to form a combined beam of radiation. A detector is disposed to monitor magnitude of at least a portion of the combined beam alternately at the first wavelength band and the second wavelength band as an indication of the concentration of the substance in the sample path.

Method and apparatus for eliminating unsuccessful tries in a search tree

NASA Technical Reports Server (NTRS)

Peterson, John C. (Inventor); Chow, Edward (Inventor); Madan, Herb S. (Inventor)

1991-01-01

A circuit switching system in an M-ary, n-cube connected network completes a best-first path from an originating node to a destination node by latching valid legs of the path as the path is being sought out. Each network node is provided with a routing hyperswitch sub-network, (HSN) connected between that node and bidirectional high capacity communication channels of the n-cube network. The sub-networks are all controlled by routing algorithms which respond to message identification headings (headers) on messages to be routed along one or more routing legs. The header includes information embedded therein which is interpreted by each sub-network to route and historically update the header. A logic circuit, available at every node, implements the algorithm and automatically forwards or back-tracks the header in the network legs of various paths until a completed path is latched.

Two betweenness centrality measures based on Randomized Shortest Paths

PubMed Central

Kivimäki, Ilkka; Lebichot, Bertrand; Saramäki, Jari; Saerens, Marco

2016-01-01

This paper introduces two new closely related betweenness centrality measures based on the Randomized Shortest Paths (RSP) framework, which fill a gap between traditional network centrality measures based on shortest paths and more recent methods considering random walks or current flows. The framework defines Boltzmann probability distributions over paths of the network which focus on the shortest paths, but also take into account longer paths depending on an inverse temperature parameter. RSP’s have previously proven to be useful in defining distance measures on networks. In this work we study their utility in quantifying the importance of the nodes of a network. The proposed RSP betweenness centralities combine, in an optimal way, the ideas of using the shortest and purely random paths for analysing the roles of network nodes, avoiding issues involving these two paradigms. We present the derivations of these measures and how they can be computed in an efficient way. In addition, we show with real world examples the potential of the RSP betweenness centralities in identifying interesting nodes of a network that more traditional methods might fail to notice. PMID:26838176

Quasi-monolithic tunable optical resonator

NASA Technical Reports Server (NTRS)

Arbore, Mark (Inventor); Tapos, Francisc (Inventor)

2003-01-01

An optical resonator has a piezoelectric element attached to a quasi-monolithic structure. The quasi-monolithic structure defines an optical path. Mirrors attached to the structure deflect light along the optical path. The piezoelectric element controllably strains the quasi-monolithic structure to change a length of the optical path by about 1 micron. A first feedback loop coupled to the piezoelectric element provides fine control over the cavity length. The resonator may include a thermally actuated spacer attached to the cavity and a mirror attached to the spacer. The thermally actuated spacer adjusts the cavity length by up to about 20 microns. A second feedback loop coupled to the sensor and heater provides a coarse control over the cavity length. An alternative embodiment provides a quasi-monolithic optical parametric oscillator (OPO). This embodiment includes a non-linear optical element within the resonator cavity along the optical path. Such an OPO configuration is broadly tunable and capable of mode-hop free operation for periods of 24 hours or more.

Predictive modelling-based design and experiments for synthesis and spinning of bioinspired silk fibres

PubMed Central

Gronau, Greta; Jacobsen, Matthew M.; Huang, Wenwen; Rizzo, Daniel J.; Li, David; Staii, Cristian; Pugno, Nicola M.; Wong, Joyce Y.; Kaplan, David L.; Buehler, Markus J.

2016-01-01

Scalable computational modelling tools are required to guide the rational design of complex hierarchical materials with predictable functions. Here, we utilize mesoscopic modelling, integrated with genetic block copolymer synthesis and bioinspired spinning process, to demonstrate de novo materials design that incorporates chemistry, processing and material characterization. We find that intermediate hydrophobic/hydrophilic block ratios observed in natural spider silks and longer chain lengths lead to outstanding silk fibre formation. This design by nature is based on the optimal combination of protein solubility, self-assembled aggregate size and polymer network topology. The original homogeneous network structure becomes heterogeneous after spinning, enhancing the anisotropic network connectivity along the shear flow direction. Extending beyond the classical polymer theory, with insights from the percolation network model, we illustrate the direct proportionality between network conductance and fibre Young's modulus. This integrated approach provides a general path towards de novo functional network materials with enhanced mechanical properties and beyond (optical, electrical or thermal) as we have experimentally verified. PMID:26017575

Predictive modelling-based design and experiments for synthesis and spinning of bioinspired silk fibres.

PubMed

Lin, Shangchao; Ryu, Seunghwa; Tokareva, Olena; Gronau, Greta; Jacobsen, Matthew M; Huang, Wenwen; Rizzo, Daniel J; Li, David; Staii, Cristian; Pugno, Nicola M; Wong, Joyce Y; Kaplan, David L; Buehler, Markus J

2015-05-28

Scalable computational modelling tools are required to guide the rational design of complex hierarchical materials with predictable functions. Here, we utilize mesoscopic modelling, integrated with genetic block copolymer synthesis and bioinspired spinning process, to demonstrate de novo materials design that incorporates chemistry, processing and material characterization. We find that intermediate hydrophobic/hydrophilic block ratios observed in natural spider silks and longer chain lengths lead to outstanding silk fibre formation. This design by nature is based on the optimal combination of protein solubility, self-assembled aggregate size and polymer network topology. The original homogeneous network structure becomes heterogeneous after spinning, enhancing the anisotropic network connectivity along the shear flow direction. Extending beyond the classical polymer theory, with insights from the percolation network model, we illustrate the direct proportionality between network conductance and fibre Young's modulus. This integrated approach provides a general path towards de novo functional network materials with enhanced mechanical properties and beyond (optical, electrical or thermal) as we have experimentally verified.

Design and implementation of priority and time-window based traffic scheduling and routing-spectrum allocation mechanism in elastic optical networks

NASA Astrophysics Data System (ADS)

Wang, Honghuan; Xing, Fangyuan; Yin, Hongxi; Zhao, Nan; Lian, Bizhan

2016-02-01

With the explosive growth of network services, the reasonable traffic scheduling and efficient configuration of network resources have an important significance to increase the efficiency of the network. In this paper, an adaptive traffic scheduling policy based on the priority and time window is proposed and the performance of this algorithm is evaluated in terms of scheduling ratio. The routing and spectrum allocation are achieved by using the Floyd shortest path algorithm and establishing a node spectrum resource allocation model based on greedy algorithm, which is proposed by us. The fairness index is introduced to improve the capability of spectrum configuration. The results show that the designed traffic scheduling strategy can be applied to networks with multicast and broadcast functionalities, and makes them get real-time and efficient response. The scheme of node spectrum configuration improves the frequency resource utilization and gives play to the efficiency of the network.

Historical data learning based dynamic LSP routing for overlay IP/MPLS over WDM networks

NASA Astrophysics Data System (ADS)

Yu, Xiaojun; Xiao, Gaoxi; Cheng, Tee Hiang

2013-08-01

Overlay IP/MPLS over WDM network is a promising network architecture starting to gain wide deployments recently. A desirable feature of such a network is to achieve efficient routing with limited information exchanges between the IP/MPLS and the WDM layers. This paper studies dynamic label switched path (LSP) routing in the overlay IP/MPLS over WDM networks. To enhance network performance while maintaining its simplicity, we propose to learn from the historical data of lightpath setup costs maintained by the IP-layer integrated service provider (ISP) when making routing decisions. Using a novel historical data learning scheme for logical link cost estimation, we develop a new dynamic LSP routing method named Existing Link First (ELF) algorithm. Simulation results show that the proposed algorithm significantly outperforms the existing ones under different traffic loads, with either limited or unlimited numbers of optical ports. Effects of the number of candidate routes, add/drop ratio and the amount of historical data are also evaluated.

Accurate cell counts in live mouse embryos using optical quadrature and differential interference contrast microscopy

NASA Astrophysics Data System (ADS)

Warger, William C., II; Newmark, Judith A.; Zhao, Bing; Warner, Carol M.; DiMarzio, Charles A.

2006-02-01

Present imaging techniques used in in vitro fertilization (IVF) clinics are unable to produce accurate cell counts in developing embryos past the eight-cell stage. We have developed a method that has produced accurate cell counts in live mouse embryos ranging from 13-25 cells by combining Differential Interference Contrast (DIC) and Optical Quadrature Microscopy. Optical Quadrature Microscopy is an interferometric imaging modality that measures the amplitude and phase of the signal beam that travels through the embryo. The phase is transformed into an image of optical path length difference, which is used to determine the maximum optical path length deviation of a single cell. DIC microscopy gives distinct cell boundaries for cells within the focal plane when other cells do not lie in the path to the objective. Fitting an ellipse to the boundary of a single cell in the DIC image and combining it with the maximum optical path length deviation of a single cell creates an ellipsoidal model cell of optical path length deviation. Subtracting the model cell from the Optical Quadrature image will either show the optical path length deviation of the culture medium or reveal another cell underneath. Once all the boundaries are used in the DIC image, the subtracted Optical Quadrature image is analyzed to determine the cell boundaries of the remaining cells. The final cell count is produced when no more cells can be subtracted. We have produced exact cell counts on 5 samples, which have been validated by Epi-Fluorescence images of Hoechst stained nuclei.

Unbundling in Current Broadband and Next-Generation Ultra-Broadband Access Networks

NASA Astrophysics Data System (ADS)

Gaudino, Roberto; Giuliano, Romeo; Mazzenga, Franco; Valcarenghi, Luca; Vatalaro, Francesco

2014-05-01

This article overviews the methods that are currently under investigation for implementing multi-operator open-access/shared-access techniques in next-generation access ultra-broadband architectures, starting from the traditional "unbundling-of-the-local-loop" techniques implemented in legacy twisted-pair digital subscriber line access networks. A straightforward replication of these copper-based unbundling-of-the-local-loop techniques is usually not feasible on next-generation access networks, including fiber-to-the-home point-to-multipoint passive optical networks. To investigate this issue, the article first gives a concise description of traditional copper-based unbundling-of-the-local-loop solutions, then focalizes on both next-generation access hybrid fiber-copper digital subscriber line fiber-to-the-cabinet scenarios and on fiber to the home by accounting for the mix of regulatory and technological reasons driving the next-generation access migration path, focusing mostly on the European situation.

Structural factoring approach for analyzing stochastic networks

NASA Technical Reports Server (NTRS)

Hayhurst, Kelly J.; Shier, Douglas R.

1991-01-01

The problem of finding the distribution of the shortest path length through a stochastic network is investigated. A general algorithm for determining the exact distribution of the shortest path length is developed based on the concept of conditional factoring, in which a directed, stochastic network is decomposed into an equivalent set of smaller, generally less complex subnetworks. Several network constructs are identified and exploited to reduce significantly the computational effort required to solve a network problem relative to complete enumeration. This algorithm can be applied to two important classes of stochastic path problems: determining the critical path distribution for acyclic networks and the exact two-terminal reliability for probabilistic networks. Computational experience with the algorithm was encouraging and allowed the exact solution of networks that have been previously analyzed only by approximation techniques.

Limited-path-length entanglement percolation in quantum complex networks

NASA Astrophysics Data System (ADS)

Cuquet, Martí; Calsamiglia, John

2011-03-01

We study entanglement distribution in quantum complex networks where nodes are connected by bipartite entangled states. These networks are characterized by a complex structure, which dramatically affects how information is transmitted through them. For pure quantum state links, quantum networks exhibit a remarkable feature absent in classical networks: it is possible to effectively rewire the network by performing local operations on the nodes. We propose a family of such quantum operations that decrease the entanglement percolation threshold of the network and increase the size of the giant connected component. We provide analytic results for complex networks with an arbitrary (uncorrelated) degree distribution. These results are in good agreement with numerical simulations, which also show enhancement in correlated and real-world networks. The proposed quantum preprocessing strategies are not robust in the presence of noise. However, even when the links consist of (noisy) mixed-state links, one can send quantum information through a connecting path with a fidelity that decreases with the path length. In this noisy scenario, complex networks offer a clear advantage over regular lattices, namely, the fact that two arbitrary nodes can be connected through a relatively small number of steps, known as the small-world effect. We calculate the probability that two arbitrary nodes in the network can successfully communicate with a fidelity above a given threshold. This amounts to working out the classical problem of percolation with a limited path length. We find that this probability can be significant even for paths limited to few connections and that the results for standard (unlimited) percolation are soon recovered if the path length exceeds by a finite amount the average path length, which in complex networks generally scales logarithmically with the size of the network.

Analysis of optical route in a micro high-speed magneto-optic switch

NASA Astrophysics Data System (ADS)

Weng, Zihua; Yang, Guoguang; Huang, Yuanqing; Chen, Zhimin; Zhu, Yun; Wu, Jinming; Lin, Shufen; Mo, Weiping

2005-02-01

A novel micro high-speed 2x2 magneto-optic switch and its optical route, which is used in high-speed all-optical communication network, is designed and analyzed in this paper. The study of micro high-speed magneto-optic switch mainly involves the optical route and high-speed control technique design. The optical route design covers optical route design of polarization in optical switch, the performance analysis and material selection of magneto-optic crystal and magnetic path design in Faraday rotator. The research of high-speed control technique involves the study of nanosecond pulse generator, high-speed magnetic field and its control technique etc. High-speed current transients from nanosecond pulse generator are used to switch the magnetization of the magneto-optic crystal, which propagates a 1550nm optical beam. The optical route design schemes and electronic circuits of high-speed control technique are both simulated on computer and test by the experiments respectively. The experiment results state that the nanosecond pulse generator can output the pulse with rising edge time 3~35ns, voltage amplitude 10~90V and pulse width 10~100ns. Under the control of CPU singlechip, the optical beam can be stably switched and the switching time is less than 1μs currently.

Analysis of Mexico City urban air pollution using nitrogen dioxide column density measurements from UV/Visible spectroscopy

NASA Astrophysics Data System (ADS)

Garcia Payne, D. G.; Grutter, M.; Melamed, M. L.

2010-12-01

The differential optical absorption spectroscopy method (DOAS) was used to get column densities of nitrogen dioxide (NO2) from the analysis of zenith sky UV/visible spectra. Since the optical path length provides critical information in interpreting NO2 column densities, in conjunction with NO2 column densities, the oxygen dimer (O4) column density was retrieved to give insight into the optical path length. We report observations of year round NO2 and O4 column densities (from august 2009 to september 2010) from which the mean seasonal levels and the daily evolution, as well as the occurrence of elevated pollution episodes are examined. Surface nitric oxide (NO) and NO2 from the local monitoring network, as well as wind data and the vertical aerosol density from continuous Lidar measurements are used in the analysis to investigate specific events in the context of local emissions from vehicular traffic, photochemical production and transport from industrial emissions. The NO2 column density measurements will enhance the understanding Mexico City urban air pollution. Recent research has begun to unravel the complexity of the air pollution problem in Mexico City and its effects not only locally but on a regional and global scale as well.

On the optical path length in refracting media

NASA Astrophysics Data System (ADS)

Hasbun, Javier E.

2018-04-01

The path light follows as it travels through a substance depends on the substance's index of refraction. This path is commonly known as the optical path length (OPL). In geometrical optics, the laws of reflection and refraction are simple examples for understanding the path of light travel from source to detector for constant values of the traveled substances' refraction indices. In more complicated situations, the Euler equation can be quite useful and quite important in optics courses. Here, the well-known Euler differential equation (EDE) is used to obtain the OPL for several index of refraction models. For pedagogical completeness, the OPL is also obtained through a modified Monte Carlo (MC) method, versus which the various results obtained through the EDE are compared. The examples developed should be important in projects involving undergraduate as well as graduate students in an introductory optics course. A simple matlab script (program) is included that can be modified by students who wish to pursue the subject further.

Folded path LWIR system for SWAP constrained platforms

NASA Astrophysics Data System (ADS)

Fleet, Erin F.; Wilson, Michael L.; Linne von Berg, Dale; Giallorenzi, Thomas; Mathieu, Barry

2014-06-01

Folded path reflection and catadioptric optics are of growing interest, especially in the long wave infrared (LWIR), due to continuing demands for reductions in imaging system size, weight and power (SWAP). We present the optical design and laboratory data for a 50 mm focal length low f/# folded-path compact LWIR imaging system. The optical design uses 4 concentric aspheric mirrors, each of which is described by annular aspheric functions well suited to the folded path design space. The 4 mirrors are diamond turned onto two thin air-spaced aluminum plates which can be manually focused onto the uncooled LWIR microbolometer array detector. Stray light analysis will be presented to show how specialized internal baffling can be used to reduce stray light propagation through the folded path optical train. The system achieves near diffraction limited performance across the FOV with a 15 mm long optical train and a 5 mm back focal distance. The completed system is small enough to reside within a 3 inch diameter ball gimbal.

The study of optimization on process parameters of high-accuracy computerized numerical control polishing

NASA Astrophysics Data System (ADS)

Huang, Wei-Ren; Huang, Shih-Pu; Tsai, Tsung-Yueh; Lin, Yi-Jyun; Yu, Zong-Ru; Kuo, Ching-Hsiang; Hsu, Wei-Yao; Young, Hong-Tsu

2017-09-01

Spherical lenses lead to forming spherical aberration and reduced optical performance. Consequently, in practice optical system shall apply a combination of spherical lenses for aberration correction. Thus, the volume of the optical system increased. In modern optical systems, aspherical lenses have been widely used because of their high optical performance with less optical components. However, aspherical surfaces cannot be fabricated by traditional full aperture polishing process due to their varying curvature. Sub-aperture computer numerical control (CNC) polishing is adopted for aspherical surface fabrication in recent years. By using CNC polishing process, mid-spatial frequency (MSF) error is normally accompanied during this process. And the MSF surface texture of optics decreases the optical performance for high precision optical system, especially for short-wavelength applications. Based on a bonnet polishing CNC machine, this study focuses on the relationship between MSF surface texture and CNC polishing parameters, which include feed rate, head speed, track spacing and path direction. The power spectral density (PSD) analysis is used to judge the MSF level caused by those polishing parameters. The test results show that controlling the removal depth of single polishing path, through the feed rate, and without same direction polishing path for higher total removal depth can efficiently reduce the MSF error. To verify the optical polishing parameters, we divided a correction polishing process to several polishing runs with different direction polishing paths. Compare to one shot polishing run, multi-direction path polishing plan could produce better surface quality on the optics.

HIGH SPEED KERR CELL FRAMING CAMERA

DOEpatents

Goss, W.C.; Gilley, L.F.

1964-01-01

The present invention relates to a high speed camera utilizing a Kerr cell shutter and a novel optical delay system having no moving parts. The camera can selectively photograph at least 6 frames within 9 x 10/sup -8/ seconds during any such time interval of an occurring event. The invention utilizes particularly an optical system which views and transmits 6 images of an event to a multi-channeled optical delay relay system. The delay relay system has optical paths of successively increased length in whole multiples of the first channel optical path length, into which optical paths the 6 images are transmitted. The successively delayed images are accepted from the exit of the delay relay system by an optical image focusing means, which in turn directs the images into a Kerr cell shutter disposed to intercept the image paths. A camera is disposed to simultaneously view and record the 6 images during a single exposure of the Kerr cell shutter. (AEC)

Routing optimization in networks based on traffic gravitational field model

NASA Astrophysics Data System (ADS)

Liu, Longgeng; Luo, Guangchun

2017-04-01

For research on the gravitational field routing mechanism on complex networks, we further analyze the gravitational effect of paths. In this study, we introduce the concept of path confidence degree to evaluate the unblocked reliability of paths that it takes the traffic state of all nodes on the path into account from the overall. On the basis of this, we propose an improved gravitational field routing protocol considering all the nodes’ gravities on the path and the path confidence degree. In order to evaluate the transmission performance of the routing strategy, an order parameter is introduced to measure the network throughput by the critical value of phase transition from a free-flow phase to a jammed phase, and the betweenness centrality is used to evaluate the transmission performance and traffic congestion of the network. Simulation results show that compared with the shortest-path routing strategy and the previous gravitational field routing strategy, the proposed algorithm improves the network throughput considerably and effectively balances the traffic load within the network, and all nodes in the network are utilized high efficiently. As long as γ ≥ α, the transmission performance can reach the maximum and remains unchanged for different α and γ, which ensures that the proposed routing protocol is high efficient and stable.

Distributed Water Pollution Source Localization with Mobile UV-Visible Spectrometer Probes in Wireless Sensor Networks.

PubMed

Ma, Junjie; Meng, Fansheng; Zhou, Yuexi; Wang, Yeyao; Shi, Ping

2018-02-16

Pollution accidents that occur in surface waters, especially in drinking water source areas, greatly threaten the urban water supply system. During water pollution source localization, there are complicated pollutant spreading conditions and pollutant concentrations vary in a wide range. This paper provides a scalable total solution, investigating a distributed localization method in wireless sensor networks equipped with mobile ultraviolet-visible (UV-visible) spectrometer probes. A wireless sensor network is defined for water quality monitoring, where unmanned surface vehicles and buoys serve as mobile and stationary nodes, respectively. Both types of nodes carry UV-visible spectrometer probes to acquire in-situ multiple water quality parameter measurements, in which a self-adaptive optical path mechanism is designed to flexibly adjust the measurement range. A novel distributed algorithm, called Dual-PSO, is proposed to search for the water pollution source, where one particle swarm optimization (PSO) procedure computes the water quality multi-parameter measurements on each node, utilizing UV-visible absorption spectra, and another one finds the global solution of the pollution source position, regarding mobile nodes as particles. Besides, this algorithm uses entropy to dynamically recognize the most sensitive parameter during searching. Experimental results demonstrate that online multi-parameter monitoring of a drinking water source area with a wide dynamic range is achieved by this wireless sensor network and water pollution sources are localized efficiently with low-cost mobile node paths.

Distributed Water Pollution Source Localization with Mobile UV-Visible Spectrometer Probes in Wireless Sensor Networks

PubMed Central

Zhou, Yuexi; Wang, Yeyao; Shi, Ping

2018-01-01

Pollution accidents that occur in surface waters, especially in drinking water source areas, greatly threaten the urban water supply system. During water pollution source localization, there are complicated pollutant spreading conditions and pollutant concentrations vary in a wide range. This paper provides a scalable total solution, investigating a distributed localization method in wireless sensor networks equipped with mobile ultraviolet-visible (UV-visible) spectrometer probes. A wireless sensor network is defined for water quality monitoring, where unmanned surface vehicles and buoys serve as mobile and stationary nodes, respectively. Both types of nodes carry UV-visible spectrometer probes to acquire in-situ multiple water quality parameter measurements, in which a self-adaptive optical path mechanism is designed to flexibly adjust the measurement range. A novel distributed algorithm, called Dual-PSO, is proposed to search for the water pollution source, where one particle swarm optimization (PSO) procedure computes the water quality multi-parameter measurements on each node, utilizing UV-visible absorption spectra, and another one finds the global solution of the pollution source position, regarding mobile nodes as particles. Besides, this algorithm uses entropy to dynamically recognize the most sensitive parameter during searching. Experimental results demonstrate that online multi-parameter monitoring of a drinking water source area with a wide dynamic range is achieved by this wireless sensor network and water pollution sources are localized efficiently with low-cost mobile node paths. PMID:29462929

Interface between path and orbital angular momentum entanglement for high-dimensional photonic quantum information.

PubMed

Fickler, Robert; Lapkiewicz, Radek; Huber, Marcus; Lavery, Martin P J; Padgett, Miles J; Zeilinger, Anton

2014-07-30

Photonics has become a mature field of quantum information science, where integrated optical circuits offer a way to scale the complexity of the set-up as well as the dimensionality of the quantum state. On photonic chips, paths are the natural way to encode information. To distribute those high-dimensional quantum states over large distances, transverse spatial modes, like orbital angular momentum possessing Laguerre Gauss modes, are favourable as flying information carriers. Here we demonstrate a quantum interface between these two vibrant photonic fields. We create three-dimensional path entanglement between two photons in a nonlinear crystal and use a mode sorter as the quantum interface to transfer the entanglement to the orbital angular momentum degree of freedom. Thus our results show a flexible way to create high-dimensional spatial mode entanglement. Moreover, they pave the way to implement broad complex quantum networks where high-dimensionally entangled states could be distributed over distant photonic chips.

Link prediction based on local weighted paths for complex networks

NASA Astrophysics Data System (ADS)

Yao, Yabing; Zhang, Ruisheng; Yang, Fan; Yuan, Yongna; Hu, Rongjing; Zhao, Zhili

As a significant problem in complex networks, link prediction aims to find the missing and future links between two unconnected nodes by estimating the existence likelihood of potential links. It plays an important role in understanding the evolution mechanism of networks and has broad applications in practice. In order to improve prediction performance, a variety of structural similarity-based methods that rely on different topological features have been put forward. As one topological feature, the path information between node pairs is utilized to calculate the node similarity. However, many path-dependent methods neglect the different contributions of paths for a pair of nodes. In this paper, a local weighted path (LWP) index is proposed to differentiate the contributions between paths. The LWP index considers the effect of the link degrees of intermediate links and the connectivity influence of intermediate nodes on paths to quantify the path weight in the prediction procedure. The experimental results on 12 real-world networks show that the LWP index outperforms other seven prediction baselines.

Multipass optical device and process for gas and analyte determination

DOEpatents

Bernacki, Bruce E [Kennewick, WA

2011-01-25

A torus multipass optical device and method are described that provide for trace level determination of gases and gas-phase analytes. The torus device includes an optical cavity defined by at least one ring mirror. The mirror delivers optical power in at least a radial and axial direction and propagates light in a multipass optical path of a predefined path length.

Pheromone Static Routing Strategy for Complex Networks

NASA Astrophysics Data System (ADS)

Hu, Mao-Bin; Henry, Y. K. Lau; Ling, Xiang; Jiang, Rui

2012-12-01

We adopt the concept of using pheromones to generate a set of static paths that can reach the performance of global dynamic routing strategy [Phys. Rev. E 81 (2010) 016113]. The path generation method consists of two stages. In the first stage, a pheromone is dropped to the nodes by packets forwarded according to the global dynamic routing strategy. In the second stage, pheromone static paths are generated according to the pheromone density. The output paths can greatly improve traffic systems' overall capacity on different network structures, including scale-free networks, small-world networks and random graphs. Because the paths are static, the system needs much less computational resources than the global dynamic routing strategy.

Non-mechanical optical path switching and its application to dual beam spectroscopy including gas filter correlation radiometry

NASA Technical Reports Server (NTRS)

Sachse, Glen W. (Inventor); Wang, Liang-Guo (Inventor)

1992-01-01

A non-mechanical optical switch is developed for alternately switching a monochromatic or quasi-monochromatic light beam along two optical paths. A polarizer polarizes light into a single, e.g., vertical component which is then rapidly modulated into vertical and horizontal components by a polarization modulator. A polarization beam splitter then reflects one of these components along one path and transmits the other along the second path. In the specific application of gas filter correlation radiometry, one path is directed through a vacuum cell and one path is directed through a gas correlation cell containing a desired gas. Reflecting mirrors cause these two paths to intersect at a second polarization beam splitter which reflects one component and transmits the other to recombine them into a polarization modulated beam which can be detected by an appropriate single sensor.

SDN-based path hopping communication against eavesdropping attack

NASA Astrophysics Data System (ADS)

Zhang, Chuanhao; Bu, Youjun; Zhao, Zheng

2016-10-01

Network eavesdropping is one of the most popular means used by cyber attackers, which has been a severe threat to network communication security. Adversaries could capture and analyze network communication data from network nodes or links, monitor network status and steal sensitive data such as username and password etc. Traditional network usually uses static network configuration, and existing defense methods, including firewall, IDS, IPS etc., cannot prevent eavesdropping, which has no distinguishing characteristic. Network eavesdropping become silent during most of the time of the attacking process, which is why it is difficult to discover and to defend. But A successful eavesdropping attack also has its' precondition, which is the target path should be relatively stable and has enough time of duration. So, In order to resolve this problem, it has to work on the network architecture. In this paper, a path hopping communication(PHC) mechanism based on Software Define Network (SDN) was proposed to solve this problem. In PHC, Ends in communication packets as well as the routing paths were changed dynamically. Therefore, the traffic would be distributed to multiple flows and transmitted along different paths. so that Network eavesdropping attack could be prevented effectively. It was concluded that PHC was able to increase the overhead of Network eavesdropping, as well as the difficulty of communication data recovery.

Pulse stretcher

DOEpatents

Horton, J.A.

1994-05-03

Apparatus for increasing the length of a laser pulse to reduce its peak power without substantial loss in the average power of the pulse is disclosed. The apparatus uses a White cell having a plurality of optical delay paths of successively increasing number of passes between the field mirror and the objective mirrors. A pulse from a laser travels through a multi-leg reflective path between a beam splitter and a totally reflective mirror to the laser output. The laser pulse is also simultaneously injected through the beam splitter to the input mirrors of the optical delay paths. The pulses from the output mirrors of the optical delay paths go simultaneously to the laser output and to the input mirrors of the longer optical delay paths. The beam splitter is 50% reflective and 50% transmissive to provide equal attenuation of all of the pulses at the laser output. 6 figures.

Fused Smart Sensor Network for Multi-Axis Forward Kinematics Estimation in Industrial Robots

PubMed Central

Rodriguez-Donate, Carlos; Osornio-Rios, Roque Alfredo; Rivera-Guillen, Jesus Rooney; de Jesus Romero-Troncoso, Rene

2011-01-01

Flexible manipulator robots have a wide industrial application. Robot performance requires sensing its position and orientation adequately, known as forward kinematics. Commercially available, motion controllers use high-resolution optical encoders to sense the position of each joint which cannot detect some mechanical deformations that decrease the accuracy of the robot position and orientation. To overcome those problems, several sensor fusion methods have been proposed but at expenses of high-computational load, which avoids the online measurement of the joint’s angular position and the online forward kinematics estimation. The contribution of this work is to propose a fused smart sensor network to estimate the forward kinematics of an industrial robot. The developed smart processor uses Kalman filters to filter and to fuse the information of the sensor network. Two primary sensors are used: an optical encoder, and a 3-axis accelerometer. In order to obtain the position and orientation of each joint online a field-programmable gate array (FPGA) is used in the hardware implementation taking advantage of the parallel computation capabilities and reconfigurability of this device. With the aim of evaluating the smart sensor network performance, three real-operation-oriented paths are executed and monitored in a 6-degree of freedom robot. PMID:22163850

Adaptive Dynamics, Control, and Extinction in Networked Populations

DTIC Science & Technology

2015-07-09

network geometries. From the pre-history of paths that go extinct, a density function is created from the prehistory of these paths, and a clear local...density plots of Fig. 3b. Using the IAMM to compute the most probable path and comparing it to the prehistory of extinction events on stochastic networks

Using refraction in thick glass plates for optical path length modulation in low coherence interferometry.

PubMed

Kröger, Niklas; Schlobohm, Jochen; Pösch, Andreas; Reithmeier, Eduard

2017-09-01

In Michelson interferometer setups the standard way to generate different optical path lengths between a measurement arm and a reference arm relies on expensive high precision linear stages such as piezo actuators. We present an alternative approach based on the refraction of light at optical interfaces using a cheap stepper motor with high gearing ratio to control the rotation of a glass plate. The beam path is examined and a relation between angle of rotation and change in optical path length is devised. As verification, an experimental setup is presented, and reconstruction results from a measurement standard are shown. The reconstructed step height from this setup lies within 1.25% of the expected value.

Theoretical analysis for scaling law of thermal blooming based on optical phase deference

NASA Astrophysics Data System (ADS)

Sun, Yunqiang; Huang, Zhilong; Ren, Zebin; Chen, Zhiqiang; Guo, Longde; Xi, Fengjie

2016-10-01

In order to explore the laser propagation influence of thermal blooming effect of pipe flow and to analysis the influencing factors, scaling law theoretical analysis of the thermal blooming effects in pipe flow are carry out in detail based on the optical path difference caused by thermal blooming effects in pipe flow. Firstly, by solving the energy coupling equation of laser beam propagation, the temperature of the flow is obtained, and then the optical path difference caused by the thermal blooming is deduced. Through the analysis of the influence of pipe size, flow field and laser parameters on the optical path difference, energy scaling parameters Ne=nTαLPR2/(ρɛCpπR02) and geometric scaling parameters Nc=νR2/(ɛL) of thermal blooming for the pipe flow are derived. Secondly, for the direct solution method, the energy coupled equations have analytic solutions only for the straight tube with Gauss beam. Considering the limitation of directly solving the coupled equations, the dimensionless analysis method is adopted, the analysis is also based on the change of optical path difference, same scaling parameters for the pipe flow thermal blooming are derived, which makes energy scaling parameters Ne and geometric scaling parameters Nc have good universality. The research results indicate that when the laser power and the laser beam diameter are changed, thermal blooming effects of the pipeline axial flow caused by optical path difference will not change, as long as you keep energy scaling parameters constant. When diameter or length of the pipe changes, just keep the geometric scaling parameters constant, the pipeline axial flow gas thermal blooming effects caused by optical path difference distribution will not change. That is to say, when the pipe size and laser parameters change, if keeping two scaling parameters with constant, the pipeline axial flow thermal blooming effects caused by the optical path difference will not change. Therefore, the energy scaling parameters and the geometric scaling parameters can really describe the gas thermal blooming effect in the axial pipe flow. These conclusions can give a good reference for the construction of the thermal blooming test system of laser system. Contrasted with the thermal blooming scaling parameters of the Bradley-Hermann distortion number ND and Fresnel number NF, which were derived based on the change of far field beam intensity distortion, the scaling parameters of pipe flow thermal blooming deduced from the optical path deference variation are very suitable for the optical system with short laser propagation distance, large Fresnel number and obviously changed optical path deference.

Optical pumping in a whispering-mode optical waveguide

DOEpatents

Kurnit, N.A.

1981-08-11

A device and method for optical pumping in a whispering mode optical waveguide are described. Both a helical ribbon and cylinder are disclosed which incorporate an additional curvature for confining the beam to increase intensity. An optical pumping medium is disposed in the optical path of the beam as it propagates along the waveguide. Optical pumping is enhanced by the high intensities of the beam and long interaction path lengths which are achieved in a small volume.

Analysis of Tyman green detection system based on polarization interference

NASA Astrophysics Data System (ADS)

Huang, Yaolin; Wang, Min; Shao, Xiaoping; Kou, Yuanfeng

2018-02-01

The optical surface deviation of the lens can directly affect the quality of the optical system.In order to effectively and accurately detect the surface shape, an optical surface on-line detection system based on polarization interference technology is designed and developed. The system is based on Tyman-Green interference optical path, join the polarization interference measuring technology. Based on the theoretical derivation of the optical path and the ZEMAX software simulation, the experimental optical path is constructed. The parallel light is used to detect the concave lens. The parallel light is used as the light source, the size of the polarization splitting prism, detection radius of curvature, the relations between and among the size of the lens aperture, a detection range is given.

Apodization of beams in an optical interferometer

NASA Technical Reports Server (NTRS)

Ames, Lawrence L. (Inventor); Dutta, Kalyan (Inventor)

2006-01-01

An interferometry apparatus comprises one or more beam generators, a detector, and a plurality of optical paths along which one or more beams of light propagate. Disposed along at least one of the optical paths is an apodization mask to shape one of the beams.

An optically passive method that doubles the rate of 2-Ghz timing fiducials

NASA Astrophysics Data System (ADS)

Boni, R.; Kendrick, J.; Sorce, C.

2017-08-01

Solid-state optical comb-pulse generators provide a convenient and accurate method to include timing fiducials in a streak camera image for time base correction. Commercially available vertical-cavity surface-emitting lasers (VCSEL's) emitting in the visible currently in use can be modulated up to 2 GHz. An optically passive method is presented to interleave a time-delayed path of the 2-GHz comb with itself, producing a 4-GHz comb. This technique can be applied to VCSEL's with higher modulation rates. A fiber-delivered, randomly polarized 2-GHz VCSEL comb is polarization split into s-polarization and p-polarization paths. One path is time delayed relative to the other by twice the 2-GHz rate with +/-1-ps accuracy; the two paths then recombine at the fiber-coupled output. High throughput (>=90%) is achieved by carefully using polarization beam-splitting cubes, a total internal reflection beam-path-steering prism, and antireflection coatings. The glass path-length delay block and turning prism are optically contacted together. The beam polarizer cubes that split and recombine the paths are precision aligned and permanently cemented into place. We expect the palm-sized, inline fiber-coupled, comb-rate-doubling device to maintain its internal alignment indefinitely.

Modeling heading and path perception from optic flow in the case of independently moving objects

PubMed Central

Raudies, Florian; Neumann, Heiko

2013-01-01

Humans are usually accurate when estimating heading or path from optic flow, even in the presence of independently moving objects (IMOs) in an otherwise rigid scene. To invoke significant biases in perceived heading, IMOs have to be large and obscure the focus of expansion (FOE) in the image plane, which is the point of approach. For the estimation of path during curvilinear self-motion no significant biases were found in the presence of IMOs. What makes humans robust in their estimation of heading or path using optic flow? We derive analytical models of optic flow for linear and curvilinear self-motion using geometric scene models. Heading biases of a linear least squares method, which builds upon these analytical models, are large, larger than those reported for humans. This motivated us to study segmentation cues that are available from optic flow. We derive models of accretion/deletion, expansion/contraction, acceleration/deceleration, local spatial curvature, and local temporal curvature, to be used as cues to segment an IMO from the background. Integrating these segmentation cues into our method of estimating heading or path now explains human psychophysical data and extends, as well as unifies, previous investigations. Our analysis suggests that various cues available from optic flow help to segment IMOs and, thus, make humans' heading and path perception robust in the presence of such IMOs. PMID:23554589

Least loaded and route fragmentation aware RSA strategies for elastic optical networks

NASA Astrophysics Data System (ADS)

Batham, Deepak; Yadav, Dharmendra Singh; Prakash, Shashi

2017-12-01

Elastic optical networks (EONs) provide flexibility to assign wide range of spectral resources to the connection requests. In this manuscript, we address two issues related to spectrum assignment in EONs: the non uniform spectrum assignment along different links of the route and the spectrum fragmentation in the network. To address these issues, two routing and spectrum assignment (RSA) strategies have been proposed: Least Loaded RSA (LLRSA) and Route Fragmentation Aware RSA (RFARSA). The LLRSA allocates spectrum homogeneously along different links in the network, where as RFARSA accords priority to the routes which are less fragmented. To highlight the salient features of the two strategies, two new metrics, route fragmentation index (RFI) and standard deviation (SD) are introduced. RFI is defined as the ratio of non-contiguous FSs to the total available free FSs on the route, and SD relates to the measure of non-uniformity in the allocation of resources on the links in the network. A simulation program has been developed to evaluate the performance of the proposed (LLRSA and RFARSA) strategies, and the existing strategies of shortest path RSA (SPRSA) and spectrum compactness based defragmentation (SCD) strategies, on the metric of RFI, bandwidth blocking probability (BBP), network capacity utilized, and SD. The variation in the metrics on the basis of number of requests and the bandwidth (number of FSs) requested has been studied. It has been conclusively established that the proposed strategies (LLRSA and RFARSA) outperform the existing strategies in terms of all the metrics.

Optical Device for Converting a Laser Beam into Two Co-aligned but Oppositely Directed Beams

NASA Technical Reports Server (NTRS)

Jennings, Donald

2013-01-01

Optical systems consisting of a series of optical elements require alignment from the input end to the output end. The optical elements can be mirrors, lenses, sources, detectors, or other devices. Complex optical systems are often difficult to align from end-to-end because the alignment beam must be inserted at one end in order for the beam to traverse the entire optical path to the other end. The ends of the optical train may not be easily accessible to the alignment beam. Typically, when a series of optical elements is to be aligned, an alignment laser beam is inserted into the optical path with a pick-off mirror at one end of the series of elements. But it may be impossible to insert the beam at an end-point. It can be difficult to locate the pick-off mirror at the desired position because there is not enough space, there is no mounting surface, or the location is occupied by a source, detector, or other component. Alternatively, the laser beam might be inserted at an intermediate location (not at an end-point) and sent, first in one direction and then the other, to the opposite ends of the optical system for alignment. However, in this case, alignment must be performed in two directions and extra effort is required to co-align the two beams to make them parallel and coincident, i.e., to follow the same path as an end-to-end beam. An optical device has been developed that accepts a laser beam as input and produces two co-aligned, but counter-propagating beams. In contrast to a conventional alignment laser placed at one end of the optical path, this invention can be placed at a convenient position within the optical train and aligned to send its two beams simultaneously along precisely opposite paths that, taken together, trace out exactly the same path as the conventional alignment laser. This invention allows the user the freedom to choose locations within the optical train for placement of the alignment beam. It is also self-aligned by design and requires almost no adjustment.

Optical remote measurement of toxic gases

NASA Technical Reports Server (NTRS)

Grant, W. B.; Kagann, R. H.; McClenny, W. A.

1992-01-01

Enactment of the Clean Air Act Amendments (CAAA) of 1990 has resulted in increased ambient air monitoring needs for industry, some of which may be met efficiently using open-path optical remote sensing techniques. These techniques include Fourier transform spectroscopy, differential optical absorption spectroscopy, laser long-path absorption, differential absorption lidar, and gas cell correlation spectroscopy. With this regulatory impetus, it is an opportune time to consider applying these technologies to the remote and/or path-averaged measurement and monitoring of toxic gases covered by the CAAA. This article reviews the optical remote sensing technology and literature for that application.

Aerosol optical properties inferred from in-situ and path-averaged measurements

NASA Astrophysics Data System (ADS)

van Binsbergen, Sven A.; Grossmann, Peter; Cohen, Leo H.; van Eijk, Alexander M. J.; Stein, Karin U.

2017-09-01

This paper compares in-situ and path-averaged measurements of the electro-optical transmission, with emphasis on aerosol effects. The in-situ sensors consisted of optical particle counters (OPC) and a visibility meter, the path-averaged data was provided by a 7-wavelength transmissometer (MSRT) and a scintillometer (BLS). Data was collected at a test site in Northern Germany. A retrieval algorithm was developed to infer characteristics of the aerosol size distribution (Junge approximation) from the MSRT data. A comparison of the various sensors suggests that the optical particle counters are over-optimistic in their estimate of the transmission.

STEPP--Search Tool for Exploration of Petri net Paths: a new tool for Petri net-based path analysis in biochemical networks.

PubMed

Koch, Ina; Schueler, Markus; Heiner, Monika

2005-01-01

To understand biochemical processes caused by, e. g., mutations or deletions in the genome, the knowledge of possible alternative paths between two arbitrary chemical compounds is of increasing interest for biotechnology, pharmacology, medicine, and drug design. With the steadily increasing amount of data from high-throughput experiments new biochemical networks can be constructed and existing ones can be extended, which results in many large metabolic, signal transduction, and gene regulatory networks. The search for alternative paths within these complex and large networks can provide a huge amount of solutions, which can not be handled manually. Moreover, not all of the alternative paths are generally of interest. Therefore, we have developed and implemented a method, which allows us to define constraints to reduce the set of all structurally possible paths to the truly interesting path set. The paper describes the search algorithm and the constraints definition language. We give examples for path searches using this dedicated special language for a Petri net model of the sucrose-to-starch breakdown in the potato tuber.

STEPP - Search Tool for Exploration of Petri net Paths: A New Tool for Petri Net-Based Path Analysis in Biochemical Networks.

PubMed

Koch, Ina; Schüler, Markus; Heiner, Monika

2011-01-01

To understand biochemical processes caused by, e.g., mutations or deletions in the genome, the knowledge of possible alternative paths between two arbitrary chemical compounds is of increasing interest for biotechnology, pharmacology, medicine, and drug design. With the steadily increasing amount of data from high-throughput experiments new biochemical networks can be constructed and existing ones can be extended, which results in many large metabolic, signal transduction, and gene regulatory networks. The search for alternative paths within these complex and large networks can provide a huge amount of solutions, which can not be handled manually. Moreover, not all of the alternative paths are generally of interest. Therefore, we have developed and implemented a method, which allows us to define constraints to reduce the set of all structurally possible paths to the truly interesting path set. The paper describes the search algorithm and the constraints definition language. We give examples for path searches using this dedicated special language for a Petri net model of the sucrose-to-starch breakdown in the potato tuber. http://sanaga.tfh-berlin.de/~stepp/

From the physics of interacting polymers to optimizing routes on the London Underground

PubMed Central

Yeung, Chi Ho; Saad, David; Wong, K. Y. Michael

2013-01-01

Optimizing paths on networks is crucial for many applications, ranging from subway traffic to Internet communication. Because global path optimization that takes account of all path choices simultaneously is computationally hard, most existing routing algorithms optimize paths individually, thus providing suboptimal solutions. We use the physics of interacting polymers and disordered systems to analyze macroscopic properties of generic path optimization problems and derive a simple, principled, generic, and distributed routing algorithm capable of considering all individual path choices simultaneously. We demonstrate the efficacy of the algorithm by applying it to: (i) random graphs resembling Internet overlay networks, (ii) travel on the London Underground network based on Oyster card data, and (iii) the global airport network. Analytically derived macroscopic properties give rise to insightful new routing phenomena, including phase transitions and scaling laws, that facilitate better understanding of the appropriate operational regimes and their limitations, which are difficult to obtain otherwise. PMID:23898198

From the physics of interacting polymers to optimizing routes on the London Underground.

PubMed

Yeung, Chi Ho; Saad, David; Wong, K Y Michael

2013-08-20

Optimizing paths on networks is crucial for many applications, ranging from subway traffic to Internet communication. Because global path optimization that takes account of all path choices simultaneously is computationally hard, most existing routing algorithms optimize paths individually, thus providing suboptimal solutions. We use the physics of interacting polymers and disordered systems to analyze macroscopic properties of generic path optimization problems and derive a simple, principled, generic, and distributed routing algorithm capable of considering all individual path choices simultaneously. We demonstrate the efficacy of the algorithm by applying it to: (i) random graphs resembling Internet overlay networks, (ii) travel on the London Underground network based on Oyster card data, and (iii) the global airport network. Analytically derived macroscopic properties give rise to insightful new routing phenomena, including phase transitions and scaling laws, that facilitate better understanding of the appropriate operational regimes and their limitations, which are difficult to obtain otherwise.

Privacy-Preserving Relationship Path Discovery in Social Networks

NASA Astrophysics Data System (ADS)

Mezzour, Ghita; Perrig, Adrian; Gligor, Virgil; Papadimitratos, Panos

As social networks sites continue to proliferate and are being used for an increasing variety of purposes, the privacy risks raised by the full access of social networking sites over user data become uncomfortable. A decentralized social network would help alleviate this problem, but offering the functionalities of social networking sites is a distributed manner is a challenging problem. In this paper, we provide techniques to instantiate one of the core functionalities of social networks: discovery of paths between individuals. Our algorithm preserves the privacy of relationship information, and can operate offline during the path discovery phase. We simulate our algorithm on real social network topologies.

Traffic-engineering-aware shortest-path routing and its application in IP-over-WDM networks [Invited

NASA Astrophysics Data System (ADS)

Lee, Youngseok; Mukherjee, Biswanath

2004-03-01

Single shortest-path routing is known to perform poorly for Internet traffic engineering (TE) where the typical optimization objective is to minimize the maximum link load. Splitting traffic uniformly over equal-cost multiple shortest paths in open shortest path first and intermediate system-intermediate system protocols does not always minimize the maximum link load when multiple paths are not carefully selected for the global traffic demand matrix. However, a TE-aware shortest path among all the equal-cost multiple shortest paths between each ingress-egress pair can be selected such that the maximum link load is significantly reduced. IP routers can use the globally optimal TE-aware shortest path without any change to existing routing protocols and without any serious configuration overhead. While calculating TE-aware shortest paths, the destination-based forwarding constraint at a node should be satisfied, because an IP router will forward a packet to the next hop toward the destination by looking up the destination prefix. We present a mathematical problem formulation for finding a set of TE-aware shortest paths for the given network as an integer linear program, and we propose a simple heuristic for solving large instances of the problem. Then we explore the usage of our proposed algorithm for the integrated TE method in IP-over-WDM networks. The proposed algorithm is evaluated through simulations in IP networks as well as in IP-over-WDM networks.

Fault tolerant hypercube computer system architecture

NASA Technical Reports Server (NTRS)

Madan, Herb S. (Inventor); Chow, Edward (Inventor)

1989-01-01

A fault-tolerant multiprocessor computer system of the hypercube type comprising a hierarchy of computers of like kind which can be functionally substituted for one another as necessary is disclosed. Communication between the working nodes is via one communications network while communications between the working nodes and watch dog nodes and load balancing nodes higher in the structure is via another communications network separate from the first. A typical branch of the hierarchy reporting to a master node or host computer comprises, a plurality of first computing nodes; a first network of message conducting paths for interconnecting the first computing nodes as a hypercube. The first network provides a path for message transfer between the first computing nodes; a first watch dog node; and a second network of message connecting paths for connecting the first computing nodes to the first watch dog node independent from the first network, the second network provides an independent path for test message and reconfiguration affecting transfers between the first computing nodes and the first switch watch dog node. There is additionally, a plurality of second computing nodes; a third network of message conducting paths for interconnecting the second computing nodes as a hypercube. The third network provides a path for message transfer between the second computing nodes; a fourth network of message conducting paths for connecting the second computing nodes to the first watch dog node independent from the third network. The fourth network provides an independent path for test message and reconfiguration affecting transfers between the second computing nodes and the first watch dog node; and a first multiplexer disposed between the first watch dog node and the second and fourth networks for allowing the first watch dog node to selectively communicate with individual ones of the computing nodes through the second and fourth networks; as well as, a second watch dog node operably connected to the first multiplexer whereby the second watch dog node can selectively communicate with individual ones of the computing nodes through the second and fourth networks. The branch is completed by a first load balancing node; and a second multiplexer connected between the first load balancing node and the first and second watch dog nodes, allowing the first load balancing node to selectively communicate with the first and second watch dog nodes.

Simultaneous Water Vapor and Dry Air Optical Path Length Measurements and Compensation with the Large Binocular Telescope Interferometer

NASA Technical Reports Server (NTRS)

Defrere, D.; Hinz, P.; Downey, E.; Boehm, M.; Danchi, W. C.; Durney, O.; Ertel, S.; Hill, J. M.; Hoffmann, W. F.; Mennesson, B.;

System and Method for Measuring the Transfer Function of a Guided Wave Device

NASA Technical Reports Server (NTRS)

Froggatt, Mark E. (Inventor); Erdogan, Turan (Inventor)

2002-01-01

A method/system are provided for measuring the NxN scalar transfer function elements for an N-port guided wave device. Optical energy of a selected wavelength is generated at a source and directed along N reference optical paths having N reference path lengths. Each reference optical path terminates in one of N detectors such that N reference signals are produced at the N detectors. The reference signals are indicative of amplitude, phase and frequency of the optical energy carried along the N reference optical paths. The optical energy from the source is also directed to the N-ports of the guided wave device and then on to each of the N detectors such that N measurement optical paths are defined between the source and each of the N detectors. A portion of the optical energy is modified in terms of at least one of the amplitude and phase to produce N modified signals at each of the N detectors. At each of the N detectors, each of the N modified signals is combined with a corresponding one of the N reference signals to produce corresponding N combined signals at each of the N detectors. A total of N(sup 2) measurement signals are generated by the N detectors. Each of the N(sup 2) measurement signals is sampled at a wave number increment (Delta)k so that N(sup 2) sampled signals are produced. The NxN transfer function elements are generated using the N(sup 2) sampled signals. Reference and measurement path length constraints are defined such that the N combined signals at each of the N detectors are spatially separated from one another in the time domain.

Tracking trade transactions in water resource systems: A node-arc optimization formulation

NASA Astrophysics Data System (ADS)

Erfani, Tohid; Huskova, Ivana; Harou, Julien J.

2013-05-01

We formulate and apply a multicommodity network flow node-arc optimization model capable of tracking trade transactions in complex water resource systems. The model uses a simple node to node network connectivity matrix and does not require preprocessing of all possible flow paths in the network. We compare the proposed node-arc formulation with an existing arc-path (flow path) formulation and explain the advantages and difficulties of both approaches. We verify the proposed formulation model on a hypothetical water distribution network. Results indicate the arc-path model solves the problem with fewer constraints, but the proposed formulation allows using a simple network connectivity matrix which simplifies modeling large or complex networks. The proposed algorithm allows converting existing node-arc hydroeconomic models that broadly represent water trading to ones that also track individual supplier-receiver relationships (trade transactions).

Alternative Path Communication in Wide-Scale Cluster-Tree Wireless Sensor Networks Using Inactive Periods

PubMed Central

Leão, Erico; Montez, Carlos; Moraes, Ricardo; Portugal, Paulo; Vasques, Francisco

2017-01-01

The IEEE 802.15.4/ZigBee cluster-tree topology is a suitable technology to deploy wide-scale Wireless Sensor Networks (WSNs). These networks are usually designed to support convergecast traffic, where all communication paths go through the PAN (Personal Area Network) coordinator. Nevertheless, peer-to-peer communication relationships may be also required for different types of WSN applications. That is the typical case of sensor and actuator networks, where local control loops must be closed using a reduced number of communication hops. The use of communication schemes optimised just for the support of convergecast traffic may result in higher network congestion and in a potentially higher number of communication hops. Within this context, this paper proposes an Alternative-Route Definition (ARounD) communication scheme for WSNs. The underlying idea of ARounD is to setup alternative communication paths between specific source and destination nodes, avoiding congested cluster-tree paths. These alternative paths consider shorter inter-cluster paths, using a set of intermediate nodes to relay messages during their inactive periods in the cluster-tree network. Simulation results show that the ARounD communication scheme can significantly decrease the end-to-end communication delay, when compared to the use of standard cluster-tree communication schemes. Moreover, the ARounD communication scheme is able to reduce the network congestion around the PAN coordinator, enabling the reduction of the number of message drops due to queue overflows in the cluster-tree network. PMID:28481245

Alternative Path Communication in Wide-Scale Cluster-Tree Wireless Sensor Networks Using Inactive Periods.

PubMed

Leão, Erico; Montez, Carlos; Moraes, Ricardo; Portugal, Paulo; Vasques, Francisco

2017-05-06

The IEEE 802.15.4/ZigBee cluster-tree topology is a suitable technology to deploy wide-scale Wireless Sensor Networks (WSNs). These networks are usually designed to support convergecast traffic, where all communication paths go through the PAN (Personal Area Network) coordinator. Nevertheless, peer-to-peer communication relationships may be also required for different types of WSN applications. That is the typical case of sensor and actuator networks, where local control loops must be closed using a reduced number of communication hops. The use of communication schemes optimised just for the support of convergecast traffic may result in higher network congestion and in a potentially higher number of communication hops. Within this context, this paper proposes an Alternative-Route Definition (ARounD) communication scheme for WSNs. The underlying idea of ARounD is to setup alternative communication paths between specific source and destination nodes, avoiding congested cluster-tree paths. These alternative paths consider shorter inter-cluster paths, using a set of intermediate nodes to relay messages during their inactive periods in the cluster-tree network. Simulation results show that the ARounD communication scheme can significantly decrease the end-to-end communication delay, when compared to the use of standard cluster-tree communication schemes. Moreover, the ARounD communication scheme is able to reduce the network congestion around the PAN coordinator, enabling the reduction of the number of message drops due to queue overflows in the cluster-tree network.

Graph Coarsening for Path Finding in Cybersecurity Graphs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hogan, Emilie A.; Johnson, John R.; Halappanavar, Mahantesh

2013-01-01

n the pass-the-hash attack, hackers repeatedly steal password hashes and move through a computer network with the goal of reaching a computer with high level administrative privileges. In this paper we apply graph coarsening in network graphs for the purpose of detecting hackers using this attack or assessing the risk level of the network's current state. We repeatedly take graph minors, which preserve the existence of paths in the graph, and take powers of the adjacency matrix to count the paths. This allows us to detect the existence of paths as well as find paths that have high risk ofmore » being used by adversaries.« less

Temporal overlap estimation based on interference spectrum in CARS microscopy

NASA Astrophysics Data System (ADS)

Zhang, Yongning; Jiang, Junfeng; Liu, Kun; Huang, Can; Wang, Shuang; Zhang, Xuezhi; Liu, Tiegen

2018-01-01

Coherent Anti-Stokes Raman Scattering (CARS) microscopy has attracted lots of attention because of the advantages, such as noninvasive, label-free, chemical specificity, intrinsic three-dimension spatial resolution and so on. However, the temporal overlap of pump and Stokes has not been solved owing to the ultrafast optical pulse used in CARS microscopy. We combine interference spectrum of residual pump in Stokes path and nonlinear Schrodinger equation (NLSE) to realize the temporal overlap of pump pulse and Stokes pulse. At first, based on the interference spectrum of pump pulse and residual pump in Stokes path, the optical delay is defined when optical path difference between pump path and Stokes path is zero. Then the relative optical delay between Stokes pulse and residual pump in PCF can be calculated by NLSE. According to the spectrum interference and NLSE, temporal overlap of pump pulse and Stokes pulse will be realized easily and the imaging speed will be improved in CARS microscopy.

MAS Bulletin. GY-90 Fiber Optic Gyro

DTIC Science & Technology

1989-07-20

487 GY.9O Fiber Optic Gyro Background. Elettronica San Giorgio ELSAG S.p.A., Genoa, Italy, has developed a fiber optic gyro (FOG) for use on short...to the length of ELSAG S.p.A., Naval Systems Division, Via G. Puccini, 2-16154 the optical path and an extremely long optical path can be Genoa, Italy...Telephone 39 10/60011, Fax 39 10/607329, Telex achieved in a small size by using a many-turn coil of optical fiber. 270660/213847 ELSAG 1. There are

Turbulence effects in a horizontal propagation path close to ground: implications for optics detection

NASA Astrophysics Data System (ADS)

Sjöqvist, Lars; Allard, Lars; Gustafsson, Ove; Henriksson, Markus; Pettersson, Magnus

2011-11-01

Atmospheric turbulence effects close to ground may affect the performance of laser based systems severely. The variations in the refractive index along the propagation path cause effects such as beam wander, intensity fluctuations (scintillations) and beam broadening. Typical geometries of interest for optics detection include nearly horizontal propagation paths close to the ground and up to kilometre distance to the target. The scintillations and beam wander affect the performance in terms of detection probability and false alarm rate. Of interest is to study the influence of turbulence in optics detection applications. In a field trial atmospheric turbulence effects along a 1 kilometre horizontal propagation path were studied using a diode laser with a rectangular beam profile operating at 0.8 micrometer wavelength. Single-path beam characteristics were registered and analysed using photodetectors arranged in horizontal and vertical directions. The turbulence strength along the path was determined using a scintillometer and single-point ultrasonic anemometers. Strong scintillation effects were observed as a function of the turbulence strength and amplitude characteristics were fitted to model distributions. In addition to the single-path analysis double-path measurements were carried out on different targets. Experimental results are compared with existing theoretical turbulence laser beam propagation models. The results show that influence from scintillations needs to be considered when predicting performance in optics detection applications.

Method for Balancing Detector Output to a Desired Level of Balance at a Frequency

NASA Technical Reports Server (NTRS)

Sachse, Glenn W. (Inventor)

2003-01-01

A multi-gas sensor is provided which modulates a polarized light beam over a broadband of wavelengths between two alternating orthogonal polarization components. The two orthogonal polarization components of the polarization modulated beam are directed along two distinct optical paths. At least one optical path contains one or more spectral discrimination elements, with each spectral discrimination element having spectral absorption features of one or more gases of interest being measured. The two optical paths then intersect, and one orthogonal component of the intersected components is transmitted and the other orthogonal component is reflected. The combined polarization modulated beam is partitioned into one or more smaller spectral regions of interest where one or more gases of interest has an absorption band. The difference in intensity between the two orthogonal polarization components is then determined in each partitioned spectral region of interest as an indication of the spectral emission/absorption of the light beam by the gases of interest in the measurement path. The spectral emission/absorption is indicative of the concentration of the one or more gases of interest in the measurement path. More specifically, one embodiment of the present invention is a gas filter correlation radiometer which comprises a polarizer, a polarization modulator, a polarization beam splitter, a beam combiner, wavelength partitioning element, and detection element. The gases of interest are measured simultaneously and, further, can be measured independently or non-independently. Furthermore, optical or electronic element are provided to balance optical intensities between the two optical paths.

Multi-Gas Sensor

NASA Technical Reports Server (NTRS)

Sachse, Glenn W. (Inventor); Wang, Liang-Guo (Inventor); LeBel, Peter J. (Inventor); Steele, Tommy C. (Inventor); Rana, Mauro (Inventor)

1999-01-01

A multi-gas sensor is provided which modulates a polarized light beam over a broadband of wavelengths between two alternating orthogonal polarization components. The two orthogonal polarization components of the polarization modulated beam are directed along two distinct optical paths. At least one optical path contains one or more spectral discrimination element, with each spectral discrimination element having spectral absorption features of one or more gases of interest being measured. The two optical paths then intersect, and one orthogonal component of the intersected components is transmitted and the other orthogonal component is reflected. The combined polarization modulated beam is partitioned into one or more smaller spectral regions of interest where one or more gases of interest has an absorption band. The difference in intensity between the two orthogonal polarization components is then determined in each partitioned spectral region of interest as an indication of the spectral emission/absorption of the light beam by the gases of interest in the measurement path. The spectral emission/absorption is indicative of the concentration of the one or more gases of interest in the measurement path. More specifically, one embodiment of the present invention is a gas filter correlation radiometer which comprises a polarizer, a polarization modulator, a polarization beam splitter, a beam combiner, wavelength partitioning element, and detection element. The gases of interest are measured simultaneously and, further, can be measured independently or non-independently. Furthermore, optical or electronic element are provided to balance optical intensities between the two optical paths.

Rotational symmetric HMD with eye-tracking capability

NASA Astrophysics Data System (ADS)

Liu, Fangfang; Cheng, Dewen; Wang, Qiwei; Wang, Yongtian

2016-10-01

As an important auxiliary function of head-mounted displays (HMDs), eye tracking has an important role in the field of intelligent human-machine interaction. In this paper, an eye-tracking HMD system (ET-HMD) is designed based on the rotational symmetric system. The tracking principle in this paper is based on pupil-corneal reflection. The ET-HMD system comprises three optical paths for virtual display, infrared illumination, and eye tracking. The display optics is shared by three optical paths and consists of four spherical lenses. For the eye-tracking path, an extra imaging lens is added to match the image sensor and achieve eye tracking. The display optics provides users a 40° diagonal FOV with a ״ 0.61 OLED, the 19 mm eye clearance, and 10 mm exit pupil diameter. The eye-tracking path can capture 15 mm × 15 mm of the users' eyes. The average MTF is above 0.1 at 26 lp/mm for the display path, and exceeds 0.2 at 46 lp/mm for the eye-tracking path. Eye illumination is simulated using LightTools with an eye model and an 850 nm near-infrared LED (NIR-LED). The results of the simulation show that the illumination of the NIR-LED can cover the area of the eye model with the display optics that is sufficient for eye tracking. The integrated optical system HMDs with eye-tracking feature can help improve the HMD experience of users.

High-speed measurement of an air transect's temperature shift heated by laser beam

NASA Astrophysics Data System (ADS)

Li, WenYu; Jiang, ZongFu; Xi, Fengjie; Li, Qiang; Xie, Wenke

2005-02-01

Laser beam heat the air on the optic path, Beam-deflection optical tomography is a non-intrusive method to measure the 2-dimension temperature distribution in the transect. By means of linear Hartmann Sensor at the rate of 27kHz, the optic path was heated by a 2.7μm HF laser, continuous and high time resolution gradients of optic phase were obtained. the result of analysing and calculation showed the temperament shift in the heated beam path was not higher than 50K when the HF laser power was 9W. The experiment showed that it is a practical non-intrusive temperature shift measurement method for a small area aero-optical medium.

A link prediction method for heterogeneous networks based on BP neural network

NASA Astrophysics Data System (ADS)

Li, Ji-chao; Zhao, Dan-ling; Ge, Bing-Feng; Yang, Ke-Wei; Chen, Ying-Wu

2018-04-01

Most real-world systems, composed of different types of objects connected via many interconnections, can be abstracted as various complex heterogeneous networks. Link prediction for heterogeneous networks is of great significance for mining missing links and reconfiguring networks according to observed information, with considerable applications in, for example, friend and location recommendations and disease-gene candidate detection. In this paper, we put forward a novel integrated framework, called MPBP (Meta-Path feature-based BP neural network model), to predict multiple types of links for heterogeneous networks. More specifically, the concept of meta-path is introduced, followed by the extraction of meta-path features for heterogeneous networks. Next, based on the extracted meta-path features, a supervised link prediction model is built with a three-layer BP neural network. Then, the solution algorithm of the proposed link prediction model is put forward to obtain predicted results by iteratively training the network. Last, numerical experiments on the dataset of examples of a gene-disease network and a combat network are conducted to verify the effectiveness and feasibility of the proposed MPBP. It shows that the MPBP with very good performance is superior to the baseline methods.

Method and system for homogenizing diode laser pump arrays

DOEpatents

Bayramian, Andrew James

2016-05-03

An optical amplifier system includes a diode pump array including a plurality of semiconductor diode laser bars disposed in an array configuration and characterized by a periodic distance between adjacent semiconductor diode laser bars. The periodic distance is measured in a first direction perpendicular to each of the plurality of semiconductor diode laser bars. The diode pump array provides a pump output propagating along an optical path and characterized by a first intensity profile measured as a function of the first direction and having a variation greater than 10%. The optical amplifier system also includes a diffractive optic disposed along the optical path. The diffractive optic includes a photo-thermo-refractive glass member. The optical amplifier system further includes an amplifier slab having an input face and position along the optical path and separated from the diffractive optic by a predetermined distance. A second intensity profile measured at the input face of the amplifier slab as a function of the first direction has a variation less than 10%.

Method and system for homogenizing diode laser pump arrays

DOEpatents

Bayramian, Andy J

2013-10-01

An optical amplifier system includes a diode pump array including a plurality of semiconductor diode laser bars disposed in an array configuration and characterized by a periodic distance between adjacent semiconductor diode laser bars. The periodic distance is measured in a first direction perpendicular to each of the plurality of semiconductor diode laser bars. The diode pump array provides a pump output propagating along an optical path and characterized by a first intensity profile measured as a function of the first direction and having a variation greater than 10%. The optical amplifier system also includes a diffractive optic disposed along the optical path. The diffractive optic includes a photo-thermo-refractive glass member. The optical amplifier system further includes an amplifier slab having an input face and position along the optical path and separated from the diffractive optic by a predetermined distance. A second intensity profile measured at the input face of the amplifier slab as a function of the first direction has a variation less than 10%.

Comparison of primary optics in amonix CPV arrays

NASA Astrophysics Data System (ADS)

Nayak, Aditya; Kinsey, Geoffrey S.; Liu, Mingguo; Bagienski, William; Garboushian, Vahan

2012-10-01

The Amonix CPV system utilizes an acrylic Fresnel lens Primary Optical Element (POE) and a reflective Secondary Optical Element (SOE). Improvements in the optical design have contributed to more than 10% increase in rated power last year. In order to further optimize the optical power path, Amonix is looking at various trade-offs in optics, including, concentration, optical materials, reliability, and cost. A comparison of optical materials used for manufacturing the primary optical element and optical design trade off's used to maximize power output will be presented. Optimization of the power path has led to the demonstration of a module lens-area efficiency of 35% in outdoor testing at Amonix.

The "path" not taken: exploring structural differences in mapped- versus shortest-network-path school travel routes.

PubMed

Buliung, Ron N; Larsen, Kristian; Faulkner, Guy E J; Stone, Michelle R

2013-09-01

School route measurement often involves estimating the shortest network path. We challenged the relatively uncritical adoption of this method in school travel research and tested the route discordance hypothesis that several types of difference exist between shortest network paths and reported school routes. We constructed the mapped and shortest path through network routes for a sample of 759 children aged 9 to 13 years in grades 5 and 6 (boys = 45%, girls = 54%, unreported gender = 1%), in Toronto, Ontario, Canada. We used Wilcoxon signed-rank tests to compare reported with shortest-path route measures including distance, route directness, intersection crossings, and route overlap. Measurement difference was explored by mode and location. We found statistical evidence of route discordance for walkers and children who were driven and detected it more often for inner suburban cases. Evidence of route discordance varied by mode and school location. We found statistically significant differences for route structure and built environment variables measured along reported and geographic information systems-based shortest-path school routes. Uncertainty produced by the shortest-path approach challenges its conceptual and empirical validity in school travel research.

Improved Efficient Routing Strategy on Scale-Free Networks

NASA Astrophysics Data System (ADS)

Jiang, Zhong-Yuan; Liang, Man-Gui

Since the betweenness of nodes in complex networks can theoretically represent the traffic load of nodes under the currently used routing strategy, we propose an improved efficient (IE) routing strategy to enhance to the network traffic capacity based on the betweenness centrality. Any node with the highest betweenness is susceptible to traffic congestion. An efficient way to improve the network traffic capacity is to redistribute the heavy traffic load from these central nodes to non-central nodes, so in this paper, we firstly give a path cost function by considering the sum of node betweenness with a tunable parameter β along the actual path. Then, by minimizing the path cost, our IE routing strategy achieved obvious improvement on the network transport efficiency. Simulations on scale-free Barabási-Albert (BA) networks confirmed the effectiveness of our strategy, when compared with the efficient routing (ER) and the shortest path (SP) routing.

Detecting Topological Defect Dark Matter Using Coherent Laser Ranging System

PubMed Central

Yang, Wanpeng; Leng, Jianxiao; Zhang, Shuangyou; Zhao, Jianye

2016-01-01

In the last few decades, optical frequency combs with high intensity, broad optical bandwidth, and directly traceable discrete wavelengths have triggered rapid developments in distance metrology. However, optical frequency combs to date have been limited to determine the absolute distance to an object (such as satellite missions). We propose a scheme for the detection of topological defect dark matter using a coherent laser ranging system composed of dual-combs and an optical clock via nongravitational signatures. The dark matter field, which comprises a defect, may interact with standard model particles, including quarks and photons, resulting in the alteration of their masses. Thus, a topological defect may function as a dielectric material with a distinctive frequency-depend index of refraction, which would cause the time delay of a periodic extraterrestrial or terrestrial light. When a topological defect passes through the Earth, the optical path of long-distance vacuum path is altered, this change in optical path can be detected through the coherent laser ranging system. Compared to continuous wavelength(cw) laser interferometry methods, dual-comb interferometry in our scheme excludes systematic misjudgement by measuring the absolute optical path length. PMID:27389642

Extended shortest path selection for package routing of complex networks

NASA Astrophysics Data System (ADS)

Ye, Fan; Zhang, Lei; Wang, Bing-Hong; Liu, Lu; Zhang, Xing-Yi

The routing strategy plays a very important role in complex networks such as Internet system and Peer-to-Peer networks. However, most of the previous work concentrates only on the path selection, e.g. Flooding and Random Walk, or finding the shortest path (SP) and rarely considering the local load information such as SP and Distance Vector Routing. Flow-based Routing mainly considers load balance and still cannot achieve best optimization. Thus, in this paper, we propose a novel dynamic routing strategy on complex network by incorporating the local load information into SP algorithm to enhance the traffic flow routing optimization. It was found that the flow in a network is greatly affected by the waiting time of the network, so we should not consider only choosing optimized path for package transformation but also consider node congestion. As a result, the packages should be transmitted with a global optimized path with smaller congestion and relatively short distance. Analysis work and simulation experiments show that the proposed algorithm can largely enhance the network flow with the maximum throughput within an acceptable calculating time. The detailed analysis of the algorithm will also be provided for explaining the efficiency.

Large dynamic range optical vector analyzer based on optical single-sideband modulation and Hilbert transform

NASA Astrophysics Data System (ADS)

Xue, Min; Pan, Shilong; Zhao, Yongjiu

2016-07-01

A large dynamic range optical vector analyzer (OVA) based on optical single-sideband modulation is proposed and demonstrated. By dividing the optical signal after optical device under test into two paths, reversing the phase of one swept sideband using a Hilbert transformer in one path, and detecting the two signals from the two paths with a balanced photodetector, the measurement errors induced by the residual -1st-order sideband and the high-order sidebands can be eliminated and the dynamic range of the measurement is increased. In a proof-of-concept experiment, the stimulated Brillouin scattering and a fiber Bragg grating are measured by OVAs with and without the Hilbert transform and balanced photodetection. Results show that about 40-dB improvement in the measurement dynamic range is realized by the proposed OVA.

An Application of Multi-Criteria Shortest Path to a Customizable Hex-Map Environment

DTIC Science & Technology

2015-03-26

forces which could act as intermediate destinations or obstacles to movement through the network. This is similar to a traveling salesman problem ...118 Abstract The shortest path problem of finding the optimal path through a complex network is well-studied in the field of operations research. This...research presents an applica- tion of the shortest path problem to a customizable map with terrain features and enemy engagement risk. The PathFinder

Energy-Aware Multipath Routing Scheme Based on Particle Swarm Optimization in Mobile Ad Hoc Networks

PubMed Central

Robinson, Y. Harold; Rajaram, M.

2015-01-01

Mobile ad hoc network (MANET) is a collection of autonomous mobile nodes forming an ad hoc network without fixed infrastructure. Dynamic topology property of MANET may degrade the performance of the network. However, multipath selection is a great challenging task to improve the network lifetime. We proposed an energy-aware multipath routing scheme based on particle swarm optimization (EMPSO) that uses continuous time recurrent neural network (CTRNN) to solve optimization problems. CTRNN finds the optimal loop-free paths to solve link disjoint paths in a MANET. The CTRNN is used as an optimum path selection technique that produces a set of optimal paths between source and destination. In CTRNN, particle swarm optimization (PSO) method is primly used for training the RNN. The proposed scheme uses the reliability measures such as transmission cost, energy factor, and the optimal traffic ratio between source and destination to increase routing performance. In this scheme, optimal loop-free paths can be found using PSO to seek better link quality nodes in route discovery phase. PSO optimizes a problem by iteratively trying to get a better solution with regard to a measure of quality. The proposed scheme discovers multiple loop-free paths by using PSO technique. PMID:26819966

Network-Based Real-time Integrated Fire Detection and Alarm (FDA) System with Building Automation

NASA Astrophysics Data System (ADS)

Anwar, F.; Boby, R. I.; Rashid, M. M.; Alam, M. M.; Shaikh, Z.

2017-11-01

Fire alarm systems have become increasingly an important lifesaving technology in many aspects, such as applications to detect, monitor and control any fire hazard. A large sum of money is being spent annually to install and maintain the fire alarm systems in buildings to protect property and lives from the unexpected spread of fire. Several methods are already developed and it is improving on a daily basis to reduce the cost as well as increase quality. An integrated Fire Detection and Alarm (FDA) systems with building automation was studied, to reduce cost and improve their reliability by preventing false alarm. This work proposes an improved framework for FDA system to ensure a robust intelligent network of FDA control panels in real-time. A shortest path algorithmic was chosen for series of buildings connected by fiber optic network. The framework shares information and communicates with each fire alarm panels connected in peer to peer configuration and declare the network state using network address declaration from any building connected in network. The fiber-optic connection was proposed to reduce signal noises, thus increasing large area coverage, real-time communication and long-term safety. Based on this proposed method an experimental setup was designed and a prototype system was developed to validate the performance in practice. Also, the distributed network system was proposed to connect with an optional remote monitoring terminal panel to validate proposed network performance and ensure fire survivability where the information is sequentially transmitted. The proposed FDA system is different from traditional fire alarm and detection system in terms of topology as it manages group of buildings in an optimal and efficient manner.Introduction

Self-organizing path integration using a linked continuous attractor and competitive network: path integration of head direction.

PubMed

Stringer, Simon M; Rolls, Edmund T

2006-12-01

A key issue is how networks in the brain learn to perform path integration, that is update a represented position using a velocity signal. Using head direction cells as an example, we show that a competitive network could self-organize to learn to respond to combinations of head direction and angular head rotation velocity. These combination cells can then be used to drive a continuous attractor network to the next head direction based on the incoming rotation signal. An associative synaptic modification rule with a short term memory trace enables preceding combination cell activity during training to be associated with the next position in the continuous attractor network. The network accounts for the presence of neurons found in the brain that respond to combinations of head direction and angular head rotation velocity. Analogous networks in the hippocampal system could self-organize to perform path integration of place and spatial view representations.

CMPF: class-switching minimized pathfinding in metabolic networks.

PubMed

Lim, Kevin; Wong, Limsoon

2012-01-01

The metabolic network is an aggregation of enzyme catalyzed reactions that converts one compound to another. Paths in a metabolic network are a sequence of enzymes that describe how a chemical compound of interest can be produced in a biological system. As the number of such paths is quite large, many methods have been developed to score paths so that the k-shortest paths represent the set of paths that are biologically meaningful or efficient. However, these approaches do not consider whether the sequence of enzymes can be manufactured in the same pathway/species/localization. As a result, a predicted sequence might consist of groups of enzymes that operate in distinct pathway/species/localization and may not truly reflect the events occurring within cell. We propose a path weighting method CMPF (Class-switching Minimized Pathfinder) to search for routes in a metabolic network which minimizes pathway switching. In biological terms, a pathway is a series of chemical reactions which define a specific function (e.g. glycolysis). We conjecture that routes that cross many pathways are inefficient since different pathways define different metabolic functions. In addition, native routes are also well characterized within pathways, suggesting that reasonable paths should not involve too many pathway switches. Our method can be generalized when reactions participate in a class set (e.g., pathways, species or cellular localization) so that the paths predicted have minimal class crossings. We show that our method generates k-paths that involve the least number of class switching. In addition, we also show that native paths are recoverable and alternative paths deviates less from native paths compared to other methods. This suggests that paths ranked by our method could be a way to predict paths that are likely to occur in biological systems.

Observation of Biological Tissues Using Common Path Optical Coherence Tomography with Gold Coated Conical Tip Lens Fiber

NASA Astrophysics Data System (ADS)

Taguchi, K.; Sugiyama, J.; Totsuka, M.; Imanaka, S.

2012-03-01

In this paper, we proposed a high lateral resolution common-path Fourier domain optical coherence tomography(OCT) system with the use of a chemically etched single mode fiber. In our experiments, single mode optical fiber for 1310nm was used for preparing the tapered tips. Our system used a conical microlens that was chemically etched by selective chemical etching technique using an etching solution of buffered hydrofluoric acid (BHF). From experimental results, we verified that our proposed optical coherence tomography system could operate as a common-path Fourier domain OCT system and conical tip lens fiber was very useful for a high lateral resolution common-path Fourier domain OCT system. Furthermore, we could observe a surface of paramecium bursaria and symbiotic chlorella in the paramecium bursaria using gold coated conical-tip fiber in the water.

In-situ and path-averaged measurements of aerosol optical properties

NASA Astrophysics Data System (ADS)

van Binsbergen, Sven A.; Grossmann, Peter; February, Faith J.; Cohen, Leo H.; van Eijk, Alexander M. J.; Stein, Karin U.

2017-09-01

This paper compares in-situ and path-averaged measurements of the electro-optical transmission, with emphasis on aerosol effects. The in-situ sensors consisted of optical particle counters (OPC), the path-averaged data was provided by a 7-wavelength transmissometer (MSRT) and scintillometers (BLS). Data were collected at two sites: a homogeneous test site in Northern Germany, and over the inhomogeneous False Bay near Cape Town, South Africa. A retrieval algorithm was developed to infer characteristics of the aerosol size distribution (Junge approximation) from the MSRT data. A comparison of the various sensors suggests that the optical particle counters are over optimistic in their estimate of the transmission. For the homogeneous test site, in-situ and path-averaged sensors yield similar results. For the inhomogeneous test site, sensors may react differently or temporally separated to meteorological events such as a change in wind speed and/or direction.

Epidemic extinction paths in complex networks

NASA Astrophysics Data System (ADS)

Hindes, Jason; Schwartz, Ira B.

2017-05-01

We study the extinction of long-lived epidemics on finite complex networks induced by intrinsic noise. Applying analytical techniques to the stochastic susceptible-infected-susceptible model, we predict the distribution of large fluctuations, the most probable or optimal path through a network that leads to a disease-free state from an endemic state, and the average extinction time in general configurations. Our predictions agree with Monte Carlo simulations on several networks, including synthetic weighted and degree-distributed networks with degree correlations, and an empirical high school contact network. In addition, our approach quantifies characteristic scaling patterns for the optimal path and distribution of large fluctuations, both near and away from the epidemic threshold, in networks with heterogeneous eigenvector centrality and degree distributions.

Epidemic extinction paths in complex networks.

PubMed

Hindes, Jason; Schwartz, Ira B

2017-05-01

We study the extinction of long-lived epidemics on finite complex networks induced by intrinsic noise. Applying analytical techniques to the stochastic susceptible-infected-susceptible model, we predict the distribution of large fluctuations, the most probable or optimal path through a network that leads to a disease-free state from an endemic state, and the average extinction time in general configurations. Our predictions agree with Monte Carlo simulations on several networks, including synthetic weighted and degree-distributed networks with degree correlations, and an empirical high school contact network. In addition, our approach quantifies characteristic scaling patterns for the optimal path and distribution of large fluctuations, both near and away from the epidemic threshold, in networks with heterogeneous eigenvector centrality and degree distributions.

Aero-Optical Wavefront Propagation and Refractive Fluid Interfaces in Large-Reynolds-Number Compressible Turbulent Flows

DTIC Science & Technology

2005-12-31

are utilized with the eikonal equation of geometrical optics to propagate computationally the optical wavefronts in the near field. As long as the...aero-optical interactions. In terms of the refractive index field n and the optical path length (OPL), the eikonal equation is: |∇ (OPL)| = n , (9) (e.g...ray n(`, t) d` . (10) The OPL integral corresponds to inverting the eikonal equation 9. The physical distance along the beam propagation path for

A link-adding strategy for transport efficiency of complex networks

NASA Astrophysics Data System (ADS)

Ma, Jinlong; Han, Weizhan; Guo, Qing; Wang, Zhenyong; Zhang, Shuai

2016-12-01

The transport efficiency is one of the critical parameters to evaluate the performance of a network. In this paper, we propose an improved efficient (IE) strategy to enhance the network transport efficiency of complex networks by adding a fraction of links to an existing network based on the node’s local degree centrality and the shortest path length. Simulation results show that the proposed strategy can bring better traffic capacity and shorter average shortest path length than the low-degree-first (LDF) strategy under the shortest path routing protocol. It is found that the proposed strategy is beneficial to the improvement of overall traffic handling and delivering ability of the network. This study can alleviate the congestion in networks, and is helpful to design and optimize realistic networks.

Low-coherence interferometric sensor system utilizing an integrated optics configuration

NASA Astrophysics Data System (ADS)

Plissi, M. V.; Rogers, A. J.; Brassington, D. J.; Wilson, M. G. F.

1995-08-01

The implementation of a twin Mach-Zehnder reference interferometer in an integrated optics substrate is described. From measurements of the fringe visibilities, an identification of the fringe order is attempted as a way to provide an absolute sensor for any parameter capable of modifying the difference in path length between two interfering optical paths.

New Remote Gas Sensor Using Rapid Electro-Optical Path Switching

NASA Technical Reports Server (NTRS)

Sachse, G. W.; Lebel, P. J.; Wallio, H. A.; Vay, S. A.; Wang, L. G.

1994-01-01

Innovative gas filter correlation radiometer (GFCR) features nonmechanical switching of internal optical paths. Incoming radiation switched electro-optically, by means of polarization, between two optical paths, one of which contains correlation gas cell while other does not. Advantages include switching speed, 2 to 3 orders of magnitude faster than mechanical techniques, and high reliability. Applications include regional studies of atmospheric chemistry from either manned or unmanned aircraft as well as satellite studies of global distributions, sources and sink mechanisms for key species involved in chemistry of troposphere. Commercial applications: ability to survey many miles of natural gas pipelines rapidly from aircraft, pinpointing gas leaks by measuring methane at 2.3 micrometers.

Multiple frequency optical mixer and demultiplexer and apparatus for remote sensing

NASA Technical Reports Server (NTRS)

Chen, Jeffrey R. (Inventor)

2010-01-01

A pulsed laser system includes a modulator module configured to provide pulsed electrical signals and a plurality of solid-state seed sources coupled to the modulator module and configured to operate, responsive to the pulsed electrical signals, in a pulse mode. Each of the plurality of solid-state seed sources is tuned to a different frequency channel separated from any adjacent frequency channel by a frequency offset. The pulsed laser system also includes a combiner that combines outputs from each of the solid state seed sources into a single optical path and an optical doubler and demultiplexer coupled to the single optical path and providing each doubled seed frequency on a separate output path.

Road networks as collections of minimum cost paths

NASA Astrophysics Data System (ADS)

Wegner, Jan Dirk; Montoya-Zegarra, Javier Alexander; Schindler, Konrad

2015-10-01

We present a probabilistic representation of network structures in images. Our target application is the extraction of urban roads from aerial images. Roads appear as thin, elongated, partially curved structures forming a loopy graph, and this complex layout requires a prior that goes beyond standard smoothness and co-occurrence assumptions. In the proposed model the network is represented as a union of 1D paths connecting distant (super-)pixels. A large set of putative candidate paths is constructed in such a way that they include the true network as much as possible, by searching for minimum cost paths in the foreground (road) likelihood. Selecting the optimal subset of candidate paths is posed as MAP inference in a higher-order conditional random field. Each path forms a higher-order clique with a type of clique potential, which attracts the member nodes of cliques with high cumulative road evidence to the foreground label. That formulation induces a robust PN -Potts model, for which a global MAP solution can be found efficiently with graph cuts. Experiments with two road data sets show that the proposed model significantly improves per-pixel accuracies as well as the overall topological network quality with respect to several baselines.

On-chip passive three-port circuit of all-optical ordered-route transmission.

PubMed

Liu, Li; Dong, Jianji; Gao, Dingshan; Zheng, Aoling; Zhang, Xinliang

2015-05-13

On-chip photonic circuits of different specific functions are highly desirable and becoming significant demands in all-optical communication network. Especially, the function to control the transmission directions of the optical signals in integrated circuits is a fundamental research. Previous schemes, such as on-chip optical circulators, are mostly realized by Faraday effect which suffers from material incompatibilities between semiconductors and magneto-optical materials. Achieving highly functional circuits in which light circulates in a particular direction with satisfied performances are still difficult in pure silicon photonics platform. Here, we propose and experimentally demonstrate a three-port passive device supporting optical ordered-route transmission based on silicon thermo-optic effect for the first time. By injecting strong power from only one port, the light could transmit through the three ports in a strict order (1→2, 2→3, 3→1) while be blocked in the opposite order (1→3, 3→2, 2→1). The blocking extinction ratios and operation bandwidths have been investigated in this paper. Moreover, with compact size, economic fabrication process and great extensibility, this proposed photonic integrated circuit is competitive to be applied in on-chip all-optical information processing systems, such as path priority selector.

On-chip passive three-port circuit of all-optical ordered-route transmission

PubMed Central

Liu, Li; Dong, Jianji; Gao, Dingshan; Zheng, Aoling; Zhang, Xinliang

2015-01-01

On-chip photonic circuits of different specific functions are highly desirable and becoming significant demands in all-optical communication network. Especially, the function to control the transmission directions of the optical signals in integrated circuits is a fundamental research. Previous schemes, such as on-chip optical circulators, are mostly realized by Faraday effect which suffers from material incompatibilities between semiconductors and magneto-optical materials. Achieving highly functional circuits in which light circulates in a particular direction with satisfied performances are still difficult in pure silicon photonics platform. Here, we propose and experimentally demonstrate a three-port passive device supporting optical ordered-route transmission based on silicon thermo-optic effect for the first time. By injecting strong power from only one port, the light could transmit through the three ports in a strict order (1→2, 2→3, 3→1) while be blocked in the opposite order (1→3, 3→2, 2→1). The blocking extinction ratios and operation bandwidths have been investigated in this paper. Moreover, with compact size, economic fabrication process and great extensibility, this proposed photonic integrated circuit is competitive to be applied in on-chip all-optical information processing systems, such as path priority selector. PMID:25970855

Fast wavelength tuning techniques for external cavity lasers

DOEpatents

Wysocki, Gerard [Princeton, NJ; Tittel, Frank K [Houston, TX

2011-01-11

An apparatus comprising a laser source configured to emit a light beam along a first path, an optical beam steering component configured to steer the light beam from the first path to a second path at an angle to the first path, and a diffraction grating configured to reflect back at least a portion of the light beam along the second path, wherein the angle determines an external cavity length. Included is an apparatus comprising a laser source configured to emit a light beam along a first path, a beam steering component configured to redirect the light beam to a second path at an angle to the first path, wherein the optical beam steering component is configured to change the angle at a rate of at least about one Kilohertz, and a diffraction grating configured to reflect back at least a portion of the light beam along the second path.

High-yield sol-gel synthesis of well-dispersed, colorless ZrO(2) nanocrystals.

PubMed

Mizuno, Mikihisa; Sasaki, Yuichi; Lee, Sungkil; Katakura, Hitoshi

2006-08-15

A 93% high-yield synthesis of well-dispersed, colorless zirconium dioxide (ZrO(2)) nanocrystals is reported. In this synthesis, hydrolysis and condensation reactions of zirconium(IV) tert-butoxide in the presence of oleic acid (100 degrees C) formed ZrO(2) precursors. The ZrO(2) precursors were made of -Zr-O-Zr- networks surrounded by oleic acid molecules. Annealing (280 degrees C) the precursors dispersed in dioctyl ether caused crystallization of the -Zr-O-Zr- networks, thereby generating 4 nm ZrO(2) nanocrystals stabilized with oleic acid. The particles were highly crystalline and tetragonal phase. A dense ZrO(2) nanocrystal dispersion in toluene (280 mg/mL) showed a transmittance of about 90% (3 mm optical path length) in the whole visible region.

Terrestrial Planet Finder cryogenic delay line development

NASA Technical Reports Server (NTRS)

Smythe, Robert F.; Swain, Mark R.; Alvarez-Salazar, Oscar; Moore, James D.

2004-01-01

Delay lines provide the path-length compensation that makes the measurement of interference fringes possible. When used for nulling interferometry, the delay line must control path-lengths so that the null is stable and controlled throughout the measurement. We report on a low noise, low disturbance, and high bandwidth optical delay line capable of meeting the TPF interferometer optical path length control requirements at cryogenic temperatures.

HIGH TEMPERATURE MICROSCOPE AND FURNACE

DOEpatents

Olson, D.M.

1961-01-31

A high-temperature microscope is offered. It has a reflecting optic situated above a molten specimen in a furnace and reflecting the image of the same downward through an inert optic member in the floor of the furnace, a plurality of spaced reflecting plane mirrors defining a reflecting path around the furnace, a standard microscope supported in the path of and forming the end terminus of the light path.

Detailed Comparisons of COMBAT Data to Wave-Optics Simulations

DTIC Science & Technology

2015-10-18

2010 along the path between Mauna Loa and Haleakala and is one of many to investigate atmospheric effects in long horizontal optical paths [1-7]. The...Relatively strong jitter sources near transmitter ( atmosphere or telescope). Rationale: Turbulence -induced scintillation alone does not explain the...Characterization of atmospheric turbulence effects over 149 km propagation path using multi-wavelength laser beacons,” in Proceedings of the 2010 AMOS

128×128 three-dimensional MEMS optical switch module with simultaneous optical path connection for optical cross-connect systems.

PubMed

Mizukami, Masato; Yamaguchi, Joji; Nemoto, Naru; Kawajiri, Yuko; Hirata, Hirooki; Uchiyama, Shingo; Makihara, Mitsuhiro; Sakata, Tomomi; Shimoyama, Nobuhiro; Oda, Kazuhiro

2011-07-20

A 128×128 three-dimensional MEMS optical switch module and a switching-control algorithm for high-speed connection and optical power stabilization are described. A prototype switch module enables the simultaneous switching of all optical paths. The insertion loss is less than 4.6 dB and is 2.3 dB on average. The switching time is less than 38 ms and is 8 ms on average. We confirmed that the maximum optical power can be obtained and optical power stabilization control is possible. The results confirm that the module is suitable for practical use in optical cross-connect systems. © 2011 Optical Society of America

The aquatic real-time monitoring network; in-situ optical sensors for monitoring the nation's water quality

USGS Publications Warehouse

Pellerin, Brian A.; Bergamaschi, Brian A.; Murdoch, Peter S.; Downing, Bryan D.; Saraceno, John Franco; Aiken, George R.; Striegl, Robert G.

2011-01-01

Floods, hurricanes, and longer-term changes in climate and land use can have profound effects on water quality due to shifts in hydrologic flow paths, water residence time, precipitation patterns, connectivity between rivers and uplands, and many other factors. In order to understand and respond to changes in hydrology and water quality, resource managers and policy makers have a need for accurate and early indicators, as well as the ability to assess possible mechanisms and likely outcomes. In-situ optical sensors-those making continuous measurements of constituents by absorbance or fluorescence properties in the environment at timescales of minutes to years-have a long history in oceanography for developing highly resolved concentrations and fluxes, but are not commonly used in freshwater systems. The United States Geological Survey (USGS) has developed the Aquatic Real-Time Monitoring Network, with high-resolution optical data collection for organic carbon, nutrients, and sediment in large coastal rivers, along with continuous measurements of discharge, water temperature, and dissolved inorganic carbon. The collecting of continuous water-quality data in the Nation?s waterways has revealed temporal trends and spatial patterns in constituents that traditional sampling approaches fail to capture, and will serve a critical role in monitoring, assessment and decision-making in a rapidly changing landscape.

Passive and electro-optic polymer photonics and InP electronics integration

NASA Astrophysics Data System (ADS)

Zhang, Z.; Katopodis, V.; Groumas, P.; Konczykowska, A.; Dupuy, J.-.; Beretta, A.; Dede, A.; Miller, E.; Choi, J. H.; Harati, P.; Jorge, F.; Nodjiadjim, V.; Dinu, R.; Cangini, G.; Vannucci, A.; Felipe, D.; Maese-Novo, A.; Keil, N.; Bach, H.-.; Schell, Martin; Avramopoulos, H.; Kouloumentas, Ch.

2015-05-01

Hybrid photonic integration allows individual components to be developed at their best-suited material platforms without sacrificing the overall performance. In the past few years a polymer-enabled hybrid integration platform has been established, comprising 1) EO polymers for constructing low-complexity and low-cost Mach-Zehnder modulators (MZMs) with extremely high modulation bandwidth; 2) InP components for light sources, detectors, and high-speed electronics including MUX drivers and DEMUX circuits; 3) Ceramic (AIN) RF board that links the electronic signals within the package. On this platform, advanced optoelectronic modules have been demonstrated, including serial 100 Gb/s [1] and 2x100 Gb/s [2] optical transmitters, but also 400 Gb/s optoelectronic interfaces for intra-data center networks [3]. To expand the device functionalities to an unprecedented level and at the same time improve the integration compatibility with diversified active / passive photonic components, we have added a passive polymer-based photonic board (polyboard) as the 4th material system. This passive polyboard allows for low-cost fabrication of single-mode waveguide networks, enables fast and convenient integration of various thin-film elements (TFEs) to control the light polarization, and provides efficient thermo-optic elements (TOEs) for wavelength tuning, light amplitude regulation and light-path switching.

Pulse stretcher

DOEpatents

Horton, James A.

1994-01-01

Apparatus (20) for increasing the length of a laser pulse to reduce its peak power without substantial loss in the average power of the pulse. The apparatus (20) uses a White cell (10) having a plurality of optical delay paths (18a-18d) of successively increasing number of passes between the field mirror (13) and the objective mirrors (11 and 12). A pulse (26) from a laser (27) travels through a multi-leg reflective path (28) between a beam splitter (21) and a totally reflective mirror (24) to the laser output (37). The laser pulse (26) is also simultaneously injected through the beam splitter (21) to the input mirrors (14a-14d) of the optical delay paths (18a-18d). The pulses from the output mirrors (16a-16d) of the optical delay paths (18a-18d) go simultaneously to the laser output (37) and to the input mirrors ( 14b-14d) of the longer optical delay paths. The beam splitter (21) is 50% reflective and 50% transmissive to provide equal attenuation of all of the pulses at the laser output (37).

Simultaneous water vapor and dry air optical path length measurements and compensation with the large binocular telescope interferometer

NASA Astrophysics Data System (ADS)

Defrère, D.; Hinz, P.; Downey, E.; Böhm, M.; Danchi, W. C.; Durney, O.; Ertel, S.; Hill, J. M.; Hoffmann, W. F.; Mennesson, B.; Millan-Gabet, R.; Montoya, M.; Pott, J.-U.; Skemer, A.; Spalding, E.; Stone, J.; Vaz, A.

2016-08-01

The Large Binocular Telescope Interferometer uses a near-infrared camera to measure the optical path length variations between the two AO-corrected apertures and provide high-angular resolution observations for all its science channels (1.5-13 microns). There is however a wavelength dependent component to the atmospheric turbulence, which can introduce optical path length errors when observing at a wavelength different from that of the fringe sensing camera. Water vapor in particular is highly dispersive and its effect must be taken into account for high-precision infrared interferometric observations as described previously for VLTI/MIDI or the Keck Interferometer Nuller. In this paper, we describe the new sensing approach that has been developed at the LBT to measure and monitor the optical path length fluctuations due to dry air and water vapor separately. After reviewing the current performance of the system for dry air seeing compensation, we present simultaneous H-, K-, and N-band observations that illustrate the feasibility of our feedforward approach to stabilize the path length fluctuations seen by the LBTI nuller.

Long-distance thermal temporal ghost imaging over optical fibers

NASA Astrophysics Data System (ADS)

Yao, Xin; Zhang, Wei; Li, Hao; You, Lixing; Wang, Zhen; Huang, Yidong

2018-02-01

A thermal ghost imaging scheme between two distant parties is proposed and experimentally demonstrated over long-distance optical fibers. In the scheme, the weak thermal light is split into two paths. Photons in one path are spatially diffused according to their frequencies by a spatial dispersion component, then illuminate the object and record its spatial transmission information. Photons in the other path are temporally diffused by a temporal dispersion component. By the coincidence measurement between photons of two paths, the object can be imaged in a way of ghost imaging, based on the frequency correlation between photons in the two paths. In the experiment, the weak thermal light source is prepared by the spontaneous four-wave mixing in a silicon waveguide. The temporal dispersion is introduced by single mode fibers of 50 km, which also could be looked as a fiber link. Experimental results show that this scheme can be realized over long-distance optical fibers.

Evanescent-wave photoacoustic spectroscopy with optical micro/nano fibers.

PubMed

Cao, Yingchun; Jin, Wei; Ho, Lut Hoi; Liu, Zhibo

2012-01-15

We demonstrate gas detection based on evanescent-wave photoacoustic (PA) spectroscopy with tapered optical fibers. Evanescent-field instead of open-path absorption is exploited for PA generation, and a quartz tuning fork is used for PA detection. A tapered optical fiber with a diameter down to the wavelength scale demonstrates detection sensitivity similar to an open-path system but with the advantages of easier optical alignment, smaller insertion loss, and multiplexing capability.

Procedure Enabling Simulation and In-Depth Analysis of Optical Effects in Camera-Based Time-Of Sensors

NASA Astrophysics Data System (ADS)

Baumgart, M.; Druml, N.; Consani, M.

2018-05-01

This paper presents a simulation approach for Time-of-Flight cameras to estimate sensor performance and accuracy, as well as to help understanding experimentally discovered effects. The main scope is the detailed simulation of the optical signals. We use a raytracing-based approach and use the optical path length as the master parameter for depth calculations. The procedure is described in detail with references to our implementation in Zemax OpticStudio and Python. Our simulation approach supports multiple and extended light sources and allows accounting for all effects within the geometrical optics model. Especially multi-object reflection/scattering ray-paths, translucent objects, and aberration effects (e.g. distortion caused by the ToF lens) are supported. The optical path length approach also enables the implementation of different ToF senor types and transient imaging evaluations. The main features are demonstrated on a simple 3D test scene.

Three layers multi-granularity OCDM switching system based on learning-stateful PCE

NASA Astrophysics Data System (ADS)

Wang, Yubao; Liu, Yanfei; Sun, Hao

2017-10-01

In the existing three layers multi-granularity OCDM switching system (TLMG-OCDMSS), F-LSP, L-LSP and OC-LSP can be bundled as switching granularity. For CPU-intensive network, the node not only needs to compute the path but also needs to bundle the switching granularity so that the load of single node is heavy. The node will paralyze when the traffic of the node is too heavy, which will impact the performance of the whole network seriously. The introduction of stateful PCE(S-PCE) will effectively solve these problems. PCE is composed of two parts, namely, the path computation element and the database (TED and LSPDB), and returns the result of path computation to PCC (path computation clients) after PCC sends the path computation request to it. In this way, the pressure of the distributed path computation in each node is reduced. In this paper, we propose the concept of Learning PCE (L-PCE), which uses the existing LSPDB as the data source of PCE's learning. By this means, we can simplify the path computation and reduce the network delay, as a result, improving the performance of network.

The “Path” Not Taken: Exploring Structural Differences in Mapped- Versus Shortest-Network-Path School Travel Routes

PubMed Central

Larsen, Kristian; Faulkner, Guy E. J.; Stone, Michelle R.

2013-01-01

Objectives. School route measurement often involves estimating the shortest network path. We challenged the relatively uncritical adoption of this method in school travel research and tested the route discordance hypothesis that several types of difference exist between shortest network paths and reported school routes. Methods. We constructed the mapped and shortest path through network routes for a sample of 759 children aged 9 to 13 years in grades 5 and 6 (boys = 45%, girls = 54%, unreported gender = 1%), in Toronto, Ontario, Canada. We used Wilcoxon signed-rank tests to compare reported with shortest-path route measures including distance, route directness, intersection crossings, and route overlap. Measurement difference was explored by mode and location. Results. We found statistical evidence of route discordance for walkers and children who were driven and detected it more often for inner suburban cases. Evidence of route discordance varied by mode and school location. Conclusions. We found statistically significant differences for route structure and built environment variables measured along reported and geographic information systems–based shortest-path school routes. Uncertainty produced by the shortest-path approach challenges its conceptual and empirical validity in school travel research. PMID:23865648

Design of physical and logical topologies with fault-tolerant ability in wavelength-routed optical network

NASA Astrophysics Data System (ADS)

Chen, Chunfeng; Liu, Hua; Fan, Ge

2005-02-01

In this paper we consider the problem of designing a network of optical cross-connects(OXCs) to provide end-to-end lightpath services to label switched routers (LSRs). Like some previous work, we select the number of OXCs as our objective. Compared with the previous studies, we take into account the fault-tolerant characteristic of logical topology. First of all, using a Prufer number randomly generated, we generate a tree. By adding some edges to the tree, we can obtain a physical topology which consists of a certain number of OXCs and fiber links connecting OXCs. It is notable that we for the first time limit the number of layers of the tree produced according to the method mentioned above. Then we design the logical topologies based on the physical topologies mentioned above. In principle, we will select the shortest path in addition to some consideration on the load balancing of links and the limitation owing to the SRLG. Notably, we implement the routing algorithm for the nodes in increasing order of the degree of the nodes. With regarding to the problem of the wavelength assignment, we adopt the heuristic algorithm of the graph coloring commonly used. It is clear our problem is computationally intractable especially when the scale of the network is large. We adopt the taboo search algorithm to find the near optimal solution to our objective. We present numerical results for up to 1000 LSRs and for a wide range of system parameters such as the number of wavelengths supported by each fiber link and traffic. The results indicate that it is possible to build large-scale optical networks with rich connectivity in a cost-effective manner, using relatively few but properly dimensioned OXCs.

Path statistics, memory, and coarse-graining of continuous-time random walks on networks

PubMed Central

Kion-Crosby, Willow; Morozov, Alexandre V.

2015-01-01

Continuous-time random walks (CTRWs) on discrete state spaces, ranging from regular lattices to complex networks, are ubiquitous across physics, chemistry, and biology. Models with coarse-grained states (for example, those employed in studies of molecular kinetics) or spatial disorder can give rise to memory and non-exponential distributions of waiting times and first-passage statistics. However, existing methods for analyzing CTRWs on complex energy landscapes do not address these effects. Here we use statistical mechanics of the nonequilibrium path ensemble to characterize first-passage CTRWs on networks with arbitrary connectivity, energy landscape, and waiting time distributions. Our approach can be applied to calculating higher moments (beyond the mean) of path length, time, and action, as well as statistics of any conservative or non-conservative force along a path. For homogeneous networks, we derive exact relations between length and time moments, quantifying the validity of approximating a continuous-time process with its discrete-time projection. For more general models, we obtain recursion relations, reminiscent of transfer matrix and exact enumeration techniques, to efficiently calculate path statistics numerically. We have implemented our algorithm in PathMAN (Path Matrix Algorithm for Networks), a Python script that users can apply to their model of choice. We demonstrate the algorithm on a few representative examples which underscore the importance of non-exponential distributions, memory, and coarse-graining in CTRWs. PMID:26646868

Horizontal Line-of-Sight Turbulence Over Near-Ground Paths and Implications for Adaptive Optics Corrections in Laser Communications.

PubMed

Levine, B M; Martinsen, E A; Wirth, A; Jankevics, A; Toledo-Quinones, M; Landers, F; Bruno, T L

1998-07-20

Atmospheric turbulence over long horizontal paths perturbs phase and can also cause severe intensity scintillation in the pupil of an optical communications receiver, which limits the data rate over which intensity-based modulation schemes can operate. The feasibility of using low-order adaptive optics by applying phase-only corrections over horizontal propagation paths is investigated. A Shack-Hartmann wave-front sensor was built and data were gathered on paths 1 m above ground and between a 1- and 2.5-km range. Both intensity fluctuations and optical path fluctuation statistics were gathered within a single frame, and the wave-front reconstructor was modified to allow for scintillated data. The temporal power spectral density for various Zernike polynomial modes was used to determine the effects of the expected corrections by adaptive optics. The slopes of the inertial subrange of turbulence were found to be less than predicted by Kolmogorov theory with an infinite outer scale, and the distribution of variance explained by increasing order was also found to be different. Statistical analysis of these data in the 1-km range indicates that at communications wavelengths of 1.3 mum, a significant improvement in transmitted beam quality could be expected most of the time, to a performance of 10% Strehl ratio or better.

Local multipoint distribution system (LDMS) versus free-space optical (FSO) networks

NASA Astrophysics Data System (ADS)

Willebrand, Heinz A.; Clark, Gerald R.; Willson, Bryan; Andreu von Euw, Christian G.; Roy, Joe; Mayhew, Laurel M.

2001-11-01

This paper compares two emerging broadband access methodologies, Free Space Optics (FSO) and Local Multipoint Distribution System (LMDS) and the atmospheric propagation characteristics of each when exposed to a dynamically changing channel. The comparison focuses on bandwidth, availability, and distance requirements for the new broadband market and how LMDS and FSO can be used to meet these requirements. Possible network topologies and their associated costs are examined. This comparison takes into account the total cost of deployment, including equipment costs, installation fees, access fees, and spectrum licensing fees. LMDS and FSO are compared on speed of deployment, scalability, aggregate bandwidth, and bandwidth per customer. Present and projected capabilities of each technology are considered for their suitability in different locations in the network, from the Wide Area Network (WAN), to the Metropolitan Area Network (MAN), all the way to Last Mile Access. There is a discussion on the relative performance of LMDS and FSO, focusing on the different factors that can affect link availability. Since network design is a large factor in assuring overall reliability, the flexibility of each technology with regard to network design is compared. LMDS and FSO are both line of sight, space-propagated technologies, and as such, they are both susceptible to path impediments and atmospheric attenuation, dispersion, scattering, and absorption. LMDS and FSO are affected very differently by different meteorological phenomena. Problematic atmospheric conditions are, specifically scintillation, rainfall, and fog, are examined. In addition to a discussion of these conditions, various techniques for minimizing atmospheric and environmental effects are investigated. The paper concludes with a summary of findings and recommendations for a number of broadband wireless applications.

Modeling and optimization of Quality of Service routing in Mobile Ad hoc Networks

NASA Astrophysics Data System (ADS)

Rafsanjani, Marjan Kuchaki; Fatemidokht, Hamideh; Balas, Valentina Emilia

2016-01-01

Mobile ad hoc networks (MANETs) are a group of mobile nodes that are connected without using a fixed infrastructure. In these networks, nodes communicate with each other by forming a single-hop or multi-hop network. To design effective mobile ad hoc networks, it is important to evaluate the performance of multi-hop paths. In this paper, we present a mathematical model for a routing protocol under energy consumption and packet delivery ratio of multi-hop paths. In this model, we use geometric random graphs rather than random graphs. Our proposed model finds effective paths that minimize the energy consumption and maximizes the packet delivery ratio of the network. Validation of the mathematical model is performed through simulation.

Modelling cointegration and Granger causality network to detect long-term equilibrium and diffusion paths in the financial system.

PubMed

Gao, Xiangyun; Huang, Shupei; Sun, Xiaoqi; Hao, Xiaoqing; An, Feng

2018-03-01

Microscopic factors are the basis of macroscopic phenomena. We proposed a network analysis paradigm to study the macroscopic financial system from a microstructure perspective. We built the cointegration network model and the Granger causality network model based on econometrics and complex network theory and chose stock price time series of the real estate industry and its upstream and downstream industries as empirical sample data. Then, we analysed the cointegration network for understanding the steady long-term equilibrium relationships and analysed the Granger causality network for identifying the diffusion paths of the potential risks in the system. The results showed that the influence from a few key stocks can spread conveniently in the system. The cointegration network and Granger causality network are helpful to detect the diffusion path between the industries. We can also identify and intervene in the transmission medium to curb risk diffusion.

Modelling cointegration and Granger causality network to detect long-term equilibrium and diffusion paths in the financial system

PubMed Central

Huang, Shupei; Sun, Xiaoqi; Hao, Xiaoqing; An, Feng

2018-01-01

Microscopic factors are the basis of macroscopic phenomena. We proposed a network analysis paradigm to study the macroscopic financial system from a microstructure perspective. We built the cointegration network model and the Granger causality network model based on econometrics and complex network theory and chose stock price time series of the real estate industry and its upstream and downstream industries as empirical sample data. Then, we analysed the cointegration network for understanding the steady long-term equilibrium relationships and analysed the Granger causality network for identifying the diffusion paths of the potential risks in the system. The results showed that the influence from a few key stocks can spread conveniently in the system. The cointegration network and Granger causality network are helpful to detect the diffusion path between the industries. We can also identify and intervene in the transmission medium to curb risk diffusion. PMID:29657804

Parallel multiplex laser feedback interferometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Song; Tan, Yidong; Zhang, Shulian, E-mail: zsl-dpi@mail.tsinghua.edu.cn

2013-12-15

We present a parallel multiplex laser feedback interferometer based on spatial multiplexing which avoids the signal crosstalk in the former feedback interferometer. The interferometer outputs two close parallel laser beams, whose frequencies are shifted by two acousto-optic modulators by 2Ω simultaneously. A static reference mirror is inserted into one of the optical paths as the reference optical path. The other beam impinges on the target as the measurement optical path. Phase variations of the two feedback laser beams are simultaneously measured through heterodyne demodulation with two different detectors. Their subtraction accurately reflects the target displacement. Under typical room conditions, experimentalmore » results show a resolution of 1.6 nm and accuracy of 7.8 nm within the range of 100 μm.« less

Generation of elliptical and circular vector hollow beams with different polarizations by a Mach-Zehnder-type optical path

NASA Astrophysics Data System (ADS)

Wang, Zhizhang; Pei, Chunying; Xia, Meng; Yin, Yaling; Xia, Yong; Yin, Jianping

2018-01-01

We present an experimental approach to convert linearly polarized Gaussian beams into elliptical and circular vector hollow beams (VHBs) with different polarization states. The scheme employed is based on a Mach-Zehnder-type optical path combined with a reflective spatial light modulator (SLM) in each path. The resulting VHBs have radial, azimuthal, and other polarization states. Our studies also show that the size of the generated VHBs remains constant during the propagation in free space over a certain distance, and can be controlled by the axial ratio of the SLM’s binary phase plate. These studies deliver great optical parameters and hold promising applications in the fields of optical trapping and manipulation of particles.

Prism Window for Optical Alignment

NASA Technical Reports Server (NTRS)

Tang, Hong

2008-01-01

A prism window has been devised for use, with an autocollimator, in aligning optical components that are (1) required to be oriented parallel to each other and/or at a specified angle of incidence with respect to a common optical path and (2) mounted at different positions along the common optical path. The prism window can also be used to align a single optical component at a specified angle of incidence. Prism windows could be generally useful for orienting optical components in manufacture of optical instruments. "Prism window" denotes an application-specific unit comprising two beam-splitter windows that are bonded together at an angle chosen to obtain the specified angle of incidence.

Modelling information flow along the human connectome using maximum flow.

PubMed

Lyoo, Youngwook; Kim, Jieun E; Yoon, Sujung

2018-01-01

The human connectome is a complex network that transmits information between interlinked brain regions. Using graph theory, previously well-known network measures of integration between brain regions have been constructed under the key assumption that information flows strictly along the shortest paths possible between two nodes. However, it is now apparent that information does flow through non-shortest paths in many real-world networks such as cellular networks, social networks, and the internet. In the current hypothesis, we present a novel framework using the maximum flow to quantify information flow along all possible paths within the brain, so as to implement an analogy to network traffic. We hypothesize that the connection strengths of brain networks represent a limit on the amount of information that can flow through the connections per unit of time. This allows us to compute the maximum amount of information flow between two brain regions along all possible paths. Using this novel framework of maximum flow, previous network topological measures are expanded to account for information flow through non-shortest paths. The most important advantage of the current approach using maximum flow is that it can integrate the weighted connectivity data in a way that better reflects the real information flow of the brain network. The current framework and its concept regarding maximum flow provides insight on how network structure shapes information flow in contrast to graph theory, and suggests future applications such as investigating structural and functional connectomes at a neuronal level. Copyright © 2017 Elsevier Ltd. All rights reserved.

Multiple-Path-Length Optical Absorbance Cell

NASA Technical Reports Server (NTRS)

2001-01-01

An optical absorbance cell that offers a selection of multiple optical path lengths has been developed as part of a portable spectrometric instrument that measures absorption spectra of small samples of water and that costs less than does a conventional, non-portable laboratory spectrometer. The instrument is intended, more specifically, for use in studying colored dissolved organic matter (CDOM) in seawater, especially in coastal regions. Accurate characterization of CDOM is necessary for building bio-optical mathematical models of seawater. The multiple path lengths of the absorption cell afford a wide range of sensitivity needed for measuring the optical absorbances associated with the wide range of concentrations of CDOM observed in nature. The instrument operates in the wavelength range of 370 to 725 nm. The major subsystems of the instrument (see figure) include a color-balanced light source; the absorption cell; a peristaltic pump; a high-precision, low-noise fiber optic spectrometer; and a laptop or other personal computer. A fiber-optic cable transmits light from the source to the absorption cell. Other optical fibers transmit light from the absorption cell to the spectrometer,

Tortuous Pore Path Through the Glaucomatous Lamina Cribrosa.

PubMed

Wang, Bo; Lucy, Katie A; Schuman, Joel S; Sigal, Ian A; Bilonick, Richard A; Lu, Chen; Liu, Jonathan; Grulkowski, Ireneusz; Nadler, Zachary; Ishikawa, Hiroshi; Kagemann, Larry; Fujimoto, James G; Wollstein, Gadi

2018-05-08

The lamina cribrosa is a primary site of damage in glaucoma. While mechanical distortion is hypothesized to cause reduction of axoplasmic flow, little is known about how the pores, which contains the retinal ganglion cell axons, traverse the lamina cribrosa. We investigated lamina cribrosa pore paths in vivo to quantify differences in tortuosity of pore paths between healthy and glaucomatous eyes. We imaged 16 healthy, 23 glaucoma suspect and 48 glaucomatous eyes from 70 subjects using a swept source optical coherence tomography system. The lamina cribrosa pores were automatically segmented using a previously described segmentation algorithm. Individual pore paths were automatically tracked through the depth of the lamina cribrosa using custom software. Pore path convergence to the optic nerve center and tortuosity was quantified for each eye. We found that lamina cribrosa pore pathways traverse the lamina cribrosa closer to the optic nerve center along the depth of the lamina cribrosa regardless of disease severity or diagnostic category. In addition, pores of glaucoma eyes take a more tortuous path through the lamina cribrosa compared to those of healthy eyes, suggesting a potential mechanism for reduction of axoplasmic flow in glaucoma.

Multi-criteria robustness analysis of metro networks

NASA Astrophysics Data System (ADS)

Wang, Xiangrong; Koç, Yakup; Derrible, Sybil; Ahmad, Sk Nasir; Pino, Willem J. A.; Kooij, Robert E.

2017-05-01

Metros (heavy rail transit systems) are integral parts of urban transportation systems. Failures in their operations can have serious impacts on urban mobility, and measuring their robustness is therefore critical. Moreover, as physical networks, metros can be viewed as topological entities, and as such they possess measurable network properties. In this article, by using network science and graph theory, we investigate ten theoretical and four numerical robustness metrics and their performance in quantifying the robustness of 33 metro networks under random failures or targeted attacks. We find that the ten theoretical metrics capture two distinct aspects of robustness of metro networks. First, several metrics place an emphasis on alternative paths. Second, other metrics place an emphasis on the length of the paths. To account for all aspects, we standardize all ten indicators and plot them on radar diagrams to assess the overall robustness for metro networks. Overall, we find that Tokyo and Rome are the most robust networks. Rome benefits from short transferring and Tokyo has a significant number of transfer stations, both in the city center and in the peripheral area of the city, promoting both a higher number of alternative paths and overall relatively short path-lengths.

Towards Scalable Cost-Effective Service and Survivability Provisioning in Ultra High Speed Networks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bin Wang

Optical transport networks based on wavelength division multiplexing (WDM) are considered to be the most appropriate choice for future Internet backbone. On the other hand, future DOE networks are expected to have the ability to dynamically provision on-demand survivable services to suit the needs of various high performance scientific applications and remote collaboration. Since a failure in aWDMnetwork such as a cable cut may result in a tremendous amount of data loss, efficient protection of data transport in WDM networks is therefore essential. As the backbone network is moving towards GMPLS/WDM optical networks, the unique requirement to support DOE’s sciencemore » mission results in challenging issues that are not directly addressed by existing networking techniques and methodologies. The objectives of this project were to develop cost effective protection and restoration mechanisms based on dedicated path, shared path, preconfigured cycle (p-cycle), and so on, to deal with single failure, dual failure, and shared risk link group (SRLG) failure, under different traffic and resource requirement models; to devise efficient service provisioning algorithms that deal with application specific network resource requirements for both unicast and multicast; to study various aspects of traffic grooming in WDM ring and mesh networks to derive cost effective solutions while meeting application resource and QoS requirements; to design various diverse routing and multi-constrained routing algorithms, considering different traffic models and failure models, for protection and restoration, as well as for service provisioning; to propose and study new optical burst switched architectures and mechanisms for effectively supporting dynamic services; and to integrate research with graduate and undergraduate education. All objectives have been successfully met. This report summarizes the major accomplishments of this project. The impact of the project manifests in many aspects: First, the project addressed many essential problems that arisen in current and future WDM optical networks, and provided a host of innovative solutions though there was no invention or patent filing. This project resulted in more than 2 dozens publications in major journals and conferences (including papers in IEEE Transactions and journals, as well as a book chapter). Our publications have been cited by many peer researchers. In particular, one of our conference papers was nominated for the best paper award of IEEE/Create-Net Broadnets (International Conference on Broadband Communications, Networks, and Systems) 2006. Second, the results and solutions of this project were well received by DOE Labs where presentations were given by the PI. We hope to continue the collaboration with DOE Labs in the future. Third, the project was the first to propose and extensively study multicast traffic grooming, new traffic models such as sliding scheduled traffic model and scheduled traffic model. Our research has sparkled a flurry of recent studies and publications by the research community in these areas. Fourth, the project has benefited a diverse population of students by motivating, engaging, enhancing their learning and skills. The project has been conducted in a manner conducive to the training of students both at graduate and undergraduate levels. As a result, one Ph.D., Dr. Abdur Billah, was graduated. Another Ph.D. student, Tianjian Li, will graduate in January 2007. In addition, four MS students were graduated. One undergraduate student, Jeffrey Alan Shininger, completed his university honors project. Fifth, thanks to the support of this ECPI project, the PI has obtained additional funding from the National Science Foundation, the Air Force Research Lab, and other sources. A few other proposals are pending. Finally, this project has also significantly impacted the curricula and resulted in the enhancement of courses at the graduate and undergraduate levels, therefore strengthening the bond between research and education.« less

Cross-Polarization Optical Coherence Tomography with Active Maintenance of the Circular Polarization of a Sounding Wave in a Common Path System

NASA Astrophysics Data System (ADS)

Gelikonov, V. M.; Romashov, V. N.; Shabanov, D. V.; Ksenofontov, S. Yu.; Terpelov, D. A.; Shilyagin, P. A.; Gelikonov, G. V.; Vitkin, I. A.

2018-05-01

We consider a cross-polarization optical coherence tomography system with a common path for the sounding and reference waves and active maintenance of the circular polarization of a sounding wave. The system is based on the formation of birefringent characteristics of the total optical path, which are equivalent to a quarter-wave plate with a 45° orientation of its optical axes with respect to the linearly polarized reference wave. Conditions under which any light-polarization state can be obtained using a two-element phase controller are obtained. The dependence of the local cross-scattering coefficient of light in a model medium and biological tissue on the sounding-wave polarization state is demonstrated. The necessity of active maintenance of the circular polarization of a sounding wave in this common path system (including a flexible probe) is shown to realize uniform optimal conditions for cross-polarization studies of biological tissue.

Performance analysis of visible light communication using the STBC-OFDM technique for intelligent transportation systems

NASA Astrophysics Data System (ADS)

Li, Changping; Yi, Ying; Lee, Kyujin; Lee, Kyesan

2014-08-01

Visible light communication (VLC) applied in an intelligent transportation system (ITS) has attracted growing attentions, but it also faces challenges, for example deep path loss and optical multi-path dispersion. In this work, we modelled an actual outdoor optical channel as a Rician channel and further proposed space-time block coding (STBC) orthogonal frequency-division multiplexing (OFDM) technology to reduce the influence of severe optical multi-path dispersion associated with such a mock channel for achieving the effective BER of 10-6 even at a low signal-to-noise ratio (SNR). In this case, the optical signals transmission distance can be extended as long as possible. Through the simulation results of STBC-OFDM and single-input-single-output (SISO) counterparts in bit error rate (BER) performance comparison, we can distinctly observe that the VLC-ITS system using STBC-OFDM technique can obtain a strongly improved BER performance due to multi-path dispersion alleviation.

Adaptive Reliable Routing Protocol Using Combined Link Stability Estimation for Mobile Ad hoc Networks

NASA Astrophysics Data System (ADS)

Vadivel, R.; Bhaskaran, V. Murali

2010-10-01

The main reason for packet loss in ad hoc networks is the link failure or node failure. In order to increase the path stability, it is essential to distinguish and moderate the failures. By knowing individual link stability along a path, path stability can be identified. In this paper, we develop an adaptive reliable routing protocol using combined link stability estimation for mobile ad hoc networks. The main objective of this protocol is to determine a Quality of Service (QoS) path along with prolonging the network life time and to reduce the packet loss. We calculate a combined metric for a path based on the parameters Link Expiration Time, Node Remaining Energy and Node Velocity and received signal strength to predict the link stability or lifetime. Then, a bypass route is established to retransmit the lost data, when a link failure occurs. By simulation results, we show that the proposed reliable routing protocol achieves high delivery ratio with reduced delay and packet drop.

Modeling the average shortest-path length in growth of word-adjacency networks

NASA Astrophysics Data System (ADS)

Kulig, Andrzej; DroŻdŻ, Stanisław; Kwapień, Jarosław; OświÈ©cimka, Paweł

2015-03-01

We investigate properties of evolving linguistic networks defined by the word-adjacency relation. Such networks belong to the category of networks with accelerated growth but their shortest-path length appears to reveal the network size dependence of different functional form than the ones known so far. We thus compare the networks created from literary texts with their artificial substitutes based on different variants of the Dorogovtsev-Mendes model and observe that none of them is able to properly simulate the novel asymptotics of the shortest-path length. Then, we identify the local chainlike linear growth induced by grammar and style as a missing element in this model and extend it by incorporating such effects. It is in this way that a satisfactory agreement with the empirical result is obtained.

An automatic alignment system for measuring optical path of transmissometer based on light beam scanning

NASA Astrophysics Data System (ADS)

Zhou, Shudao; Ma, Zhongliang; Wang, Min; Peng, Shuling

2018-05-01

This paper proposes a novel alignment system based on the measurement of optical path using a light beam scanning mode in a transmissometer. The system controls both the probe beam and the receiving field of view while scanning in two vertical directions. The system then calculates the azimuth angle of the transmitter and the receiver to determine the precise alignment of the optical path. Experiments show that this method can determine the alignment angles in less than 10 min with errors smaller than 66 μrad in the azimuth. This system also features high collimation precision, process automation and simple installation.

Statistical analysis of measured free-space laser signal intensity over a 2.33 km optical path.

PubMed

Tunick, Arnold

2007-10-17

Experimental research is conducted to determine the characteristic behavior of high frequency laser signal intensity data collected over a 2.33 km optical path. Results focus mainly on calculated power spectra and frequency distributions. In addition, a model is developed to calculate optical turbulence intensity (C(n)/2) as a function of receiving and transmitting aperture diameter, log-amplitude variance, and path length. Initial comparisons of calculated to measured C(n)/2 data are favorable. It is anticipated that this kind of signal data analysis will benefit laser communication systems development and testing at the U.S. Army Research Laboratory (ARL) and elsewhere.

[Not Available].

PubMed

Yanashima, Ryoji; Kitagawa, Noriyuki; Matsubara, Yoshiya; Weatheritt, Robert; Oka, Kotaro; Kikuchi, Shinichi; Tomita, Masaru; Ishizaki, Shun

2009-01-01

The scale-free and small-world network models reflect the functional units of networks. However, when we investigated the network properties of a signaling pathway using these models, no significant differences were found between the original undirected graphs and the graphs in which inactive proteins were eliminated from the gene expression data. We analyzed signaling networks by focusing on those pathways that best reflected cellular function. Therefore, our analysis of pathways started from the ligands and progressed to transcription factors and cytoskeletal proteins. We employed the Python module to assess the target network. This involved comparing the original and restricted signaling cascades as a directed graph using microarray gene expression profiles of late onset Alzheimer's disease. The most commonly used method of shortest-path analysis neglects to consider the influences of alternative pathways that can affect the activation of transcription factors or cytoskeletal proteins. We therefore introduced included k-shortest paths and k-cycles in our network analysis using the Python modules, which allowed us to attain a reasonable computational time and identify k-shortest paths. This technique reflected results found in vivo and identified pathways not found when shortest path or degree analysis was applied. Our module enabled us to comprehensively analyse the characteristics of biomolecular networks and also enabled analysis of the effects of diseases considering the feedback loop and feedforward loop control structures as an alternative path.

Peano-like paths for subaperture polishing of optical aspherical surfaces.

PubMed

Tam, Hon-Yuen; Cheng, Haobo; Dong, Zhichao

2013-05-20

Polishing can be more uniform if the polishing path provides uniform coverage of the surface. It is known that Peano paths can provide uniform coverage of planar surfaces. Peano paths also contain short path segments and turns: (1) all path segments have the same length, (2) path segments are mutually orthogonal at the turns, and (3) path segments and turns are uniformity distributed over the domain surface. These make Peano paths an attractive candidate among polishing tool paths because they enhance multidirectional approaches of the tool to each surface location. A method for constructing Peano paths for uniform coverage of aspherical surfaces is proposed in this paper. When mapped to the aspherical surface, the path also contains short path segments and turns, and the above attributes are approximately preserved. Attention is paid so that the path segments are still well distributed near the vertex of the surface. The proposed tool path was used in the polishing of a number of parabolic BK7 specimens using magnetorheological finishing (MRF) and pitch with cerium oxide. The results were rather good for optical lenses and confirm that a Peano-like path was useful for polishing, for MRF, and for pitch polishing. In the latter case, the surface roughness achieved was 0.91 nm according to WYKO measurement.

Evolvable Neuronal Paths: A Novel Basis for Information and Search in the Brain

PubMed Central

Fernando, Chrisantha; Vasas, Vera; Szathmáry, Eörs; Husbands, Phil

2011-01-01

We propose a previously unrecognized kind of informational entity in the brain that is capable of acting as the basis for unlimited hereditary variation in neuronal networks. This unit is a path of activity through a network of neurons, analogous to a path taken through a hidden Markov model. To prove in principle the capabilities of this new kind of informational substrate, we show how a population of paths can be used as the hereditary material for a neuronally implemented genetic algorithm, (the swiss-army knife of black-box optimization techniques) which we have proposed elsewhere could operate at somatic timescales in the brain. We compare this to the same genetic algorithm that uses a standard ‘genetic’ informational substrate, i.e. non-overlapping discrete genotypes, on a range of optimization problems. A path evolution algorithm (PEA) is defined as any algorithm that implements natural selection of paths in a network substrate. A PEA is a previously unrecognized type of natural selection that is well suited for implementation by biological neuronal networks with structural plasticity. The important similarities and differences between a standard genetic algorithm and a PEA are considered. Whilst most experiments are conducted on an abstract network model, at the conclusion of the paper a slightly more realistic neuronal implementation of a PEA is outlined based on Izhikevich spiking neurons. Finally, experimental predictions are made for the identification of such informational paths in the brain. PMID:21887266

Diversified Control Paths: A Significant Way Disease Genes Perturb the Human Regulatory Network

PubMed Central

Wang, Bingbo; Gao, Lin; Zhang, Qingfang; Li, Aimin; Deng, Yue; Guo, Xingli

2015-01-01

Background The complexity of biological systems motivates us to use the underlying networks to provide deep understanding of disease etiology and the human diseases are viewed as perturbations of dynamic properties of networks. Control theory that deals with dynamic systems has been successfully used to capture systems-level knowledge in large amount of quantitative biological interactions. But from the perspective of system control, the ways by which multiple genetic factors jointly perturb a disease phenotype still remain. Results In this work, we combine tools from control theory and network science to address the diversified control paths in complex networks. Then the ways by which the disease genes perturb biological systems are identified and quantified by the control paths in a human regulatory network. Furthermore, as an application, prioritization of candidate genes is presented by use of control path analysis and gene ontology annotation for definition of similarities. We use leave-one-out cross-validation to evaluate the ability of finding the gene-disease relationship. Results have shown compatible performance with previous sophisticated works, especially in directed systems. Conclusions Our results inspire a deeper understanding of molecular mechanisms that drive pathological processes. Diversified control paths offer a basis for integrated intervention techniques which will ultimately lead to the development of novel therapeutic strategies. PMID:26284649

Optical modeling based on mean free path calculations for quantum dot phosphors applied to optoelectronic devices.

PubMed

Shin, Min-Ho; Kim, Hyo-Jun; Kim, Young-Joo

2017-02-20

We proposed an optical simulation model for the quantum dot (QD) nanophosphor based on the mean free path concept to understand precisely the optical performance of optoelectronic devices. A measurement methodology was also developed to get the desired optical characteristics such as the mean free path and absorption spectra for QD nanophosphors which are to be incorporated into the simulation. The simulation results for QD-based white LED and OLED displays show good agreement with the experimental values from the fabricated devices in terms of spectral power distribution, chromaticity coordinate, CCT, and CRI. The proposed simulation model and measurement methodology can be applied easily to the design of lots of optoelectronics devices using QD nanophosphors to obtain high efficiency and the desired color characteristics.

Accuracy enhanced distance measurement system using double-sideband modulated frequency scanning interferometry

NASA Astrophysics Data System (ADS)

Chen, Xilun; Wang, Xiangchuan; Pan, Shilong

2017-03-01

An implementation of a distance measurement system using double-sideband with suppressed carrier modulation (DSB-SC) frequency scanning interferometry is proposed to reduce the variations in the optical path and improve the measurement accuracy. In this proposed system, the electro-optic DSB-SC is used to create dual-swept signals with opposite scanning directions. For each swept signal, the relative distance between the reference arm and the measuring arm is determined by the beat frequency of signals from two arms. By multiplying both beat signals, measurement errors caused by variations in the optical path can be greatly reduced. As an experimental demonstration, a vibration was introduced in the optical path length. The experimental results show that the variations can be suppressed for over 19.9 dB.

Modeling learning in brain stem and cerebellar sites responsible for VOR plasticity

NASA Technical Reports Server (NTRS)

Quinn, K. J.; Didier, A. J.; Baker, J. F.; Peterson, B. W.

1998-01-01

A simple model of vestibuloocular reflex (VOR) function was used to analyze several hypotheses currently held concerning the characteristics of VOR plasticity. The network included a direct vestibular pathway and an indirect path via the cerebellum. An optimization analysis of this model suggests that regulation of brain stem sites is critical for the proper modification of VOR gain. A more physiologically plausible learning rule was also applied to this network. Analysis of these simulation results suggests that the preferred error correction signal controlling gain modification of the VOR is the direct output of the accessory optic system (AOS) to the vestibular nuclei vs. a signal relayed through the cerebellum via floccular Purkinje cells. The potential anatomical and physiological basis for this conclusion is discussed, in relation to our current understanding of the latency of the adapted VOR response.

WDM-PON Architecture for FTTx Networks

NASA Astrophysics Data System (ADS)

Iannone, E.; Franco, P.; Santoni, S.

Broadband services for residential users in European countries have until now largely relied on xDSL technologies, while FTTx technologies have been mainly exploited in Asia and North America. The increasing bandwidth demand and the growing penetration of new services are pushing the deployment of optical access networks, and major European operators are now announcing FTTx projects. While FTTH is recognized as the target solution to bring broadband services to residential users, the identification of an FTTx evolutionary path able to seamlessly migrate to FTTH is key to enabling a massive deployment, easing the huge investments needed. WDM-PON architecture is an interesting solution that is able to accommodate the strategic need of building a new fiber-based access infrastructure with the possibility of adapting investments to actual demands and evolving to FTTH without requiring further interventions on fiber infrastructures.

Non-common path aberration correction in an adaptive optics scanning ophthalmoscope.

PubMed

Sulai, Yusufu N; Dubra, Alfredo

2014-09-01

The correction of non-common path aberrations (NCPAs) between the imaging and wavefront sensing channel in a confocal scanning adaptive optics ophthalmoscope is demonstrated. NCPA correction is achieved by maximizing an image sharpness metric while the confocal detection aperture is temporarily removed, effectively minimizing the monochromatic aberrations in the illumination path of the imaging channel. Comparison of NCPA estimated using zonal and modal orthogonal wavefront corrector bases provided wavefronts that differ by ~λ/20 in root-mean-squared (~λ/30 standard deviation). Sequential insertion of a cylindrical lens in the illumination and light collection paths of the imaging channel was used to compare image resolution after changing the wavefront correction to maximize image sharpness and intensity metrics. Finally, the NCPA correction was incorporated into the closed-loop adaptive optics control by biasing the wavefront sensor signals without reducing its bandwidth.

A new routing enhancement scheme based on node blocking state advertisement in wavelength-routed WDM networks

NASA Astrophysics Data System (ADS)

Hu, Peigang; Jin, Yaohui; Zhang, Chunlei; He, Hao; Hu, WeiSheng

2005-02-01

The increasing switching capacity brings the optical node with considerable complexity. Due to the limitation in cost and technology, an optical node is often designed with partial switching capability and partial resource sharing. It means that the node is of blocking to some extent, for example multi-granularity switching node, which in fact is a structure using pass wavelength to reduce the dimension of OXC, and partial sharing wavelength converter (WC) OXC. It is conceivable that these blocking nodes will have great effects on the problem of routing and wavelength assignment. Some previous works studied the blocking case, partial WC OXC, using complicated wavelength assignment algorithm. But the complexities of these schemes decide them to be not in practice in real networks. In this paper, we propose a new scheme based on the node blocking state advertisement to reduce the retry or rerouting probability and improve the efficiency of routing in the networks with blocking nodes. In the scheme, node blocking state are advertised to the other nodes in networks, which will be used for subsequent route calculation to find a path with lowest blocking probability. The performance of the scheme is evaluated using discrete event model in 14-node NSFNET, all the nodes of which employ a kind of partial sharing WC OXC structure. In the simulation, a simple First-Fit wavelength assignment algorithm is used. The simulation results demonstrate that the new scheme considerably reduces the retry or rerouting probability in routing process.

Full optical model of micro-endoscope with optical coherence microscopy, multiphoton microscopy and visible capabilities

NASA Astrophysics Data System (ADS)

Vega, David; Kiekens, Kelli C.; Syson, Nikolas C.; Romano, Gabriella; Baker, Tressa; Barton, Jennifer K.

2018-02-01

While Optical Coherence Microscopy (OCM), Multiphoton Microscopy (MPM), and narrowband imaging are powerful imaging techniques that can be used to detect cancer, each imaging technique has limitations when used by itself. Combining them into an endoscope to work in synergy can help achieve high sensitivity and specificity for diagnosis at the point of care. Such complex endoscopes have an elevated risk of failure, and performing proper modelling ensures functionality and minimizes risk. We present full 2D and 3D models of a multimodality optical micro-endoscope to provide real-time detection of carcinomas, called a salpingoscope. The models evaluate the endoscope illumination and light collection capabilities of various modalities. The design features two optical paths with different numerical apertures (NA) through a single lens system with a scanning optical fiber. The dual path is achieved using dichroic coatings embedded in a triplet. A high NA optical path is designed to perform OCM and MPM while a low NA optical path is designed for the visible spectrum to navigate the endoscope to areas of interest and narrowband imaging. Different tests such as the reflectance profile of homogeneous epithelial tissue were performed to adjust the models properly. Light collection models for the different modalities were created and tested for efficiency. While it is challenging to evaluate the efficiency of multimodality endoscopes, the models ensure that the system is design for the expected light collection levels to provide detectable signal to work for the intended imaging.

Low-latency optical parallel adder based on a binary decision diagram with wavelength division multiplexing scheme

NASA Astrophysics Data System (ADS)

Shinya, A.; Ishihara, T.; Inoue, K.; Nozaki, K.; Kita, S.; Notomi, M.

2018-02-01

We propose an optical parallel adder based on a binary decision diagram that can calculate simply by propagating light through electrically controlled optical pass gates. The CARRY and CARRY operations are multiplexed in one circuit by a wavelength division multiplexing scheme to reduce the number of optical elements, and only a single gate constitutes the critical path for one digit calculation. The processing time reaches picoseconds per digit when we use a 100-μm-long optical path gates, which is ten times faster than a CMOS circuit.

Non-contact measurement of electrical activity in neurons using magnified image spatial spectrum (MISS) microscopy (Conference Presentation)

NASA Astrophysics Data System (ADS)

Majeed, Hassaan; Lee, Young J.; Best-Popescu, Catherine; Popescu, Gabriel; Jang, Sung-Soo; Chung, Hee Jung

2017-02-01

Traditionally the measurement of electrical activity in neurons has been carried out using microelectrode arrays that require the conducting elements to be in contact with the neuronal network. This method, also referred to as "electrophysiology", while being excellent in terms of temporal resolution is limited in spatial resolution and is invasive. An optical microscopy method for measuring electrical activity is thus highly desired. Common-path quantitative phase imaging (QPI) systems are good candidates for such investigations as they provide high sensitivity (on the order of nanometers) to the plasma membrane fluctuations that can be linked to electrical activity in a neuronal circuit. In this work we measured electrical activity in a culture of rat cortical neurons using MISS microscopy, a high-speed common-path QPI technique having an axial resolution of around 1 nm in optical path-length, which we introduced at PW BIOS 2016. Specifically, we measured the vesicular cycling (endocytosis and exocytosis) occurring at axon terminals of the neurons due to electrical activity caused by adding a high K+ solution to the cell culture. The axon terminals were localized using a micro-fluidic device that separated them from the rest of the culture. Stacks of images of these terminals were acquired at 826 fps both before and after K+ excitation and the temporal standard deviation maps for the two cases were compared to measure the membrane fluctuations. Concurrently, the existence of vesicular cycling was confirmed through fluorescent tagging and imaging of the vesicles at and around the axon terminals.

Design of EPON far-end equipment based on FTTH

NASA Astrophysics Data System (ADS)

Feng, Xiancheng; Yun, Xiang

2008-12-01

Now, most favors fiber access is mainly the EPON fiber access system. Inheriting from the low cost of Ethernet, usability and bandwidth of optical network, EPON technology is one of the best technologies in fiber access and is adopted by the carriers all over the world widely. According to the scheme analysis to FTTH fan-end equipment, hardware design of ONU is proposed in this paper. The FTTH far-end equipment software design deference modulation design concept, it divides the software designment into 5 function modules: the module of low-layer driver, the module of system management, the module of master/slave communication, and the module of main/Standby switch and the module of command line. The software flow of the host computer is also analyzed. Finally, test is made for Ethernet service performance of FTTH far-end equipment, E1 service performance and the optical path protection switching, and so on. The results of test indicates that all the items are accordance with technical request of far-end ONU equipment and possess good quality and fully reach the requirement of telecommunication level equipment. The far-end equipment of FTTH divides into several parts based on the function: the control module, the exchange module, the UNI interface module, the ONU module, the EPON interface module, the network management debugging module, the voice processing module, the circuit simulation module, the CATV module. In the downstream direction, under the protect condition, we design 2 optical modules. The system can set one group optical module working and another group optical module closure when it is initialized. When the optical fiber line is cut off, the LOS warning comes out. It will cause MUX to replace another group optical module, simultaneously will reset module 3701/3711 and will make it again test the distance, and will give the plug board MPC850 report through the GPIO port. During normal mode, the downstream optical signal is transformed into the electrical signal by the optical module. In the upstream direction, the upstream Ethernet data is retransmitted through the exchange chip BCM5380 to the GMII/MII in module 3701/3711, and then is transmitted to EPON port. The 2MB data are transformed the Ethernet data packet in the plug board TDM, then it's transmitted to the interface MII of the module 3701/3711. The software design of FTTH far-end equipment compiles with modulation design concept. According to the system realization duty, the software is divided into 5 function modules: low-level driver module, system management module, master/slave communication module, the man/Standby switch module and the command line module. The FTTH far-end equipment test, is mainly the Ethernet service performance test, E1 service performance test and the optical path protection switching test and so on the key specification test.

Microscopic optical path length difference and polarization measurement system for cell analysis

NASA Astrophysics Data System (ADS)

Satake, H.; Ikeda, K.; Kowa, H.; Hoshiba, T.; Watanabe, E.

2018-03-01

In recent years, noninvasive, nonstaining, and nondestructive quantitative cell measurement techniques have become increasingly important in the medical field. These cell measurement techniques enable the quantitative analysis of living cells, and are therefore applied to various cell identification processes, such as those determining the passage number limit during cell culturing in regenerative medicine. To enable cell measurement, we developed a quantitative microscopic phase imaging system based on a Mach-Zehnder interferometer that measures the optical path length difference distribution without phase unwrapping using optical phase locking. The applicability of our phase imaging system was demonstrated by successful identification of breast cancer cells amongst normal cells. However, the cell identification method using this phase imaging system exhibited a false identification rate of approximately 7%. In this study, we implemented a polarimetric imaging system by introducing a polarimetric module to one arm of the Mach-Zehnder interferometer of our conventional phase imaging system. This module was comprised of a quarter wave plate and a rotational polarizer on the illumination side of the sample, and a linear polarizer on the optical detector side. In addition, we developed correction methods for the measurement errors of the optical path length and birefringence phase differences that arose through the influence of elements other than cells, such as the Petri dish. As the Petri dish holding the fluid specimens was transparent, it did not affect the amplitude information; however, the optical path length and birefringence phase differences were affected. Therefore, we proposed correction of the optical path length and birefringence phase for the influence of elements other than cells, as a prerequisite for obtaining highly precise phase and polarimetric images.

Barriers Keep Drops Of Water Out Of Infrared Gas Sensors

NASA Technical Reports Server (NTRS)

Murray, Sean K.

1996-01-01

Infrared-sensor cells used for measuring partial pressures of CO(2) and other breathable gases modified to prevent entry of liquid water into sensory optical paths of cells. Hydrophobic membrane prevents drops of water entrained in flow from entering optical path from lamp to infrared detectors.

OPEN PATH AMBIENT MEASUREMENTS OF POLLUTANTS WITH A DOAS SYSTEM

EPA Science Inventory

A differential optical absorption spectrometer (DOAS) has been in operation since August 1991 at the U.S. EPA in RTP, NC. he analyzer unit is located in an environmentally-controlled shelter in the EPA parking lot. our separate open optical paths have been established, ranging fr...

SIMULATION STUDY FOR GASEOUS FLUXES FROM AN AREA SOURCE USING COMPUTED TOMOGRAPHY AND OPTICAL REMOTE SENSING

EPA Science Inventory

The paper presents a new approach to quantifying emissions from fugitive gaseous air pollution sources. Computed tomography (CT) and path-integrated optical remote sensing (PI-ORS) concentration data are combined in a new field beam geometry. Path-integrated concentrations are ...

Differential phase contrast X-ray imaging system and components

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stutman, Daniel; Finkenthal, Michael

2017-11-21

A differential phase contrast X-ray imaging system includes an X-ray illumination system, a beam splitter arranged in an optical path of the X-ray illumination system, and a detection system arranged in an optical path to detect X-rays after passing through the beam splitter.

Applying self-organizing map and modified radial based neural network for clustering and routing optimal path in wireless network

NASA Astrophysics Data System (ADS)

Hoomod, Haider K.; Kareem Jebur, Tuka

2018-05-01

Mobile ad hoc networks (MANETs) play a critical role in today’s wireless ad hoc network research and consist of active nodes that can be in motion freely. Because it consider very important problem in this network, we suggested proposed method based on modified radial basis function networks RBFN and Self-Organizing Map SOM. These networks can be improved by the use of clusters because of huge congestion in the whole network. In such a system, the performance of MANET is improved by splitting the whole network into various clusters using SOM. The performance of clustering is improved by the cluster head selection and number of clusters. Modified Radial Based Neural Network is very simple, adaptable and efficient method to increase the life time of nodes, packet delivery ratio and the throughput of the network will increase and connection become more useful because the optimal path has the best parameters from other paths including the best bitrate and best life link with minimum delays. Proposed routing algorithm depends on the group of factors and parameters to select the path between two points in the wireless network. The SOM clustering average time (1-10 msec for stall nodes) and (8-75 msec for mobile nodes). While the routing time range (92-510 msec).The proposed system is faster than the Dijkstra by 150-300%, and faster from the RBFNN (without modify) by 145-180%.

Path scanning for the detection of anomalous subgraphs and use of DNS requests and host agents for anomaly/change detection and network situational awareness

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neil, Joshua Charles; Fisk, Michael Edward; Brugh, Alexander William

A system, apparatus, computer-readable medium, and computer-implemented method are provided for detecting anomalous behavior in a network. Historical parameters of the network are determined in order to determine normal activity levels. A plurality of paths in the network are enumerated as part of a graph representing the network, where each computing system in the network may be a node in the graph and the sequence of connections between two computing systems may be a directed edge in the graph. A statistical model is applied to the plurality of paths in the graph on a sliding window basis to detect anomalousmore » behavior. Data collected by a Unified Host Collection Agent ("UHCA") may also be used to detect anomalous behavior.« less

Quality of service routing in wireless ad hoc networks

NASA Astrophysics Data System (ADS)

Sane, Sachin J.; Patcha, Animesh; Mishra, Amitabh

2003-08-01

An efficient routing protocol is essential to guarantee application level quality of service running on wireless ad hoc networks. In this paper we propose a novel routing algorithm that computes a path between a source and a destination by considering several important constraints such as path-life, availability of sufficient energy as well as buffer space in each of the nodes on the path between the source and destination. The algorithm chooses the best path from among the multiples paths that it computes between two endpoints. We consider the use of control packets that run at a priority higher than the data packets in determining the multiple paths. The paper also examines the impact of different schedulers such as weighted fair queuing, and weighted random early detection among others in preserving the QoS level guarantees. Our extensive simulation results indicate that the algorithm improves the overall lifetime of a network, reduces the number of dropped packets, and decreases the end-to-end delay for real-time voice application.

Analyzing Water's Optical Absorption

NASA Technical Reports Server (NTRS)

2002-01-01

A cooperative agreement between World Precision Instruments (WPI), Inc., and Stennis Space Center has led the UltraPath(TM) device, which provides a more efficient method for analyzing the optical absorption of water samples at sea. UltraPath is a unique, high-performance absorbance spectrophotometer with user-selectable light path lengths. It is an ideal tool for any study requiring precise and highly sensitive spectroscopic determination of analytes, either in the laboratory or the field. As a low-cost, rugged, and portable system capable of high- sensitivity measurements in widely divergent waters, UltraPath will help scientists examine the role that coastal ocean environments play in the global carbon cycle. UltraPath(TM) is a trademark of World Precision Instruments, Inc. LWCC(TM) is a trademark of World Precision Instruments, Inc.

Zero-Slack, Noncritical Paths

ERIC Educational Resources Information Center

Simons, Jacob V., Jr.

2017-01-01

The critical path method/program evaluation and review technique method of project scheduling is based on the importance of managing a project's critical path(s). Although a critical path is the longest path through a network, its location in large projects is facilitated by the computation of activity slack. However, logical fallacies in…

Modified multiblock partial least squares path modeling algorithm with backpropagation neural networks approach

NASA Astrophysics Data System (ADS)

Yuniarto, Budi; Kurniawan, Robert

2017-03-01

PLS Path Modeling (PLS-PM) is different from covariance based SEM, where PLS-PM use an approach based on variance or component, therefore, PLS-PM is also known as a component based SEM. Multiblock Partial Least Squares (MBPLS) is a method in PLS regression which can be used in PLS Path Modeling which known as Multiblock PLS Path Modeling (MBPLS-PM). This method uses an iterative procedure in its algorithm. This research aims to modify MBPLS-PM with Back Propagation Neural Network approach. The result is MBPLS-PM algorithm can be modified using the Back Propagation Neural Network approach to replace the iterative process in backward and forward step to get the matrix t and the matrix u in the algorithm. By modifying the MBPLS-PM algorithm using Back Propagation Neural Network approach, the model parameters obtained are relatively not significantly different compared to model parameters obtained by original MBPLS-PM algorithm.

A mathematical model for adaptive transport network in path finding by true slime mold.

PubMed

Tero, Atsushi; Kobayashi, Ryo; Nakagaki, Toshiyuki

2007-02-21

We describe here a mathematical model of the adaptive dynamics of a transport network of the true slime mold Physarum polycephalum, an amoeboid organism that exhibits path-finding behavior in a maze. This organism possesses a network of tubular elements, by means of which nutrients and signals circulate through the plasmodium. When the organism is put in a maze, the network changes its shape to connect two exits by the shortest path. This process of path-finding is attributed to an underlying physiological mechanism: a tube thickens as the flux through it increases. The experimental evidence for this is, however, only qualitative. We constructed a mathematical model of the general form of the tube dynamics. Our model contains a key parameter corresponding to the extent of the feedback regulation between the thickness of a tube and the flux through it. We demonstrate the dependence of the behavior of the model on this parameter.

Path integration of head direction: updating a packet of neural activity at the correct speed using axonal conduction delays.

PubMed

Walters, Daniel; Stringer, Simon; Rolls, Edmund

2013-01-01

The head direction cell system is capable of accurately updating its current representation of head direction in the absence of visual input. This is known as the path integration of head direction. An important question is how the head direction cell system learns to perform accurate path integration of head direction. In this paper we propose a model of velocity path integration of head direction in which the natural time delay of axonal transmission between a linked continuous attractor network and competitive network acts as a timing mechanism to facilitate the correct speed of path integration. The model effectively learns a "look-up" table for the correct speed of path integration. In simulation, we show that the model is able to successfully learn two different speeds of path integration across two different axonal conduction delays, and without the need to alter any other model parameters. An implication of this model is that, by learning look-up tables for each speed of path integration, the model should exhibit a degree of robustness to damage. In simulations, we show that the speed of path integration is not significantly affected by degrading the network through removing a proportion of the cells that signal rotational velocity.

Path Integration of Head Direction: Updating a Packet of Neural Activity at the Correct Speed Using Axonal Conduction Delays

PubMed Central

Walters, Daniel; Stringer, Simon; Rolls, Edmund

2013-01-01

The head direction cell system is capable of accurately updating its current representation of head direction in the absence of visual input. This is known as the path integration of head direction. An important question is how the head direction cell system learns to perform accurate path integration of head direction. In this paper we propose a model of velocity path integration of head direction in which the natural time delay of axonal transmission between a linked continuous attractor network and competitive network acts as a timing mechanism to facilitate the correct speed of path integration. The model effectively learns a “look-up” table for the correct speed of path integration. In simulation, we show that the model is able to successfully learn two different speeds of path integration across two different axonal conduction delays, and without the need to alter any other model parameters. An implication of this model is that, by learning look-up tables for each speed of path integration, the model should exhibit a degree of robustness to damage. In simulations, we show that the speed of path integration is not significantly affected by degrading the network through removing a proportion of the cells that signal rotational velocity. PMID:23526976

Method and apparatus for optical communication by frequency modulation

DOEpatents

Priatko, Gordon J.

1988-01-01

Laser optical communication according to this invention is carried out by producing multi-frequency laser beams having different frequencies, splitting one or more of these constituent beams into reference and signal beams, encoding information on the signal beams by frequency modulation and detecting the encoded information by heterodyne techniques. Much more information can be transmitted over optical paths according to the present invention than with the use of only one path as done previously.

Network Design for Reliability and Resilience to Attack

DTIC Science & Technology

2014-03-01

attacker can destroy n arcs in the network SPNI Shortest-Path Network-Interdiction problem TSP Traveling Salesman Problem UB upper bound UKR Ukraine...elimination from the traveling salesman problem (TSP). Literature calls a walk that does not contain a cycle a path [19]. The objective function in...arc lengths as random variables with known probability distributions. The m-median problem seeks to design a network with minimum average travel cost

The current development status of the Orbiting Carbon Observatory (OCO) instrument optical design

NASA Technical Reports Server (NTRS)

Haring, Robert; Sutin, Brian; Crisp, David; Pollock, Randy; Sundstrand, Hamilton

2005-01-01

The status of the OCO instrument optical design is presented in this paper. The optical bench assembly comprises three cooled grating spectrometers coupled to an all-reflective telescope/relay system. Dichroic beam splitters are used to separate the light from a common telescope into the three spectral bands. The three bore sighted spectrometers allow the total column CO2 absorption path to be corrected for optical path and surface pressure uncertainties, aerosols, and water vapor. The design of the instrument is based on classic flight proven technologies.

Two instruments based on differential optical absorption spectroscopy (DOAS) to measure accurate ammonia concentrations in the atmosphere

NASA Astrophysics Data System (ADS)

Volten, H.; Bergwerff, J. B.; Haaima, M.; Lolkema, D. E.; Berkhout, A. J. C.; van der Hoff, G. R.; Potma, C. J. M.; Wichink Kruit, R. J.; van Pul, W. A. J.; Swart, D. P. J.

2011-08-01

We present two Differential Optical Absorption Spectroscopy (DOAS) instruments built at RIVM, the RIVM DOAS and the miniDOAS. Both instruments provide virtually interference free measurements of NH3 concentrations in the atmosphere, since they measure over an open path, without suffering from inlet problems or interference problems by ammonium aerosols dissociating on tubes or filters. They measure concentrations up to at least 200 μg m-3, have a fast response, low maintenance demands, and a high up-time. The RIVM DOAS has a high accuracy of typically 0.15 μg m-3 for ammonia over 5-min averages and over a total light path of 100 m. The miniDOAS has been developed for application in measurement networks such as the Dutch National Air Quality Monitoring Network (LML). Compared to the RIVM DOAS it has a similar accuracy, but is significantly reduced in size, costs, and handling complexity. The RIVM DOAS and miniDOAS results showed excellent agreement (R2 = 0.996) during a field measurement campaign in Vredepeel, the Netherlands. This measurement site is located in an agricultural area and is characterized by highly variable, but on average high ammonia concentrations in the air. The RIVM-DOAS and miniDOAS results were compared to the results of the AMOR instrument, a continuous-flow wet denuder system, which is currently used in the LML. Averaged over longer time spans of typically a day the (mini)DOAS and AMOR results agree reasonably well, although an offset of the AMOR values compared to the (mini)DOAS results exists. On short time scales the (mini)DOAS shows a faster response and does not show the memory effects due to inlet tubing and transport of absorption fluids encountered by the AMOR. Due to its high accuracy, high uptime, low maintenance and its open path, the (mini)DOAS shows a good potential for flux measurements by using two (or more) systems in a gradient set-up and applying the aerodynamic gradient technique.

Two instruments based on differential optical absorption spectroscopy (DOAS) to measure accurate ammonia concentrations in the atmosphere

NASA Astrophysics Data System (ADS)

Volten, H.; Bergwerff, J. B.; Haaima, M.; Lolkema, D. E.; Berkhout, A. J. C.; van der Hoff, G. R.; Potma, C. J. M.; Wichink Kruit, R. J.; van Pul, W. A. J.; Swart, D. P. J.

2012-02-01

We present two Differential Optical Absorption Spectroscopy (DOAS) instruments built at RIVM: the RIVM DOAS and the miniDOAS. Both instruments provide virtually interference-free measurements of NH3 concentrations in the atmosphere, since they measure over an open path, without suffering from inlet problems or interference problems by ammonium aerosols dissociating on tubes or filters. They measure concentrations up to at least 200 μg m-3, have a fast response, low maintenance demands, and a high up-time. The RIVM DOAS has a high accuracy of typically 0.15 μg m-3 for ammonia for 5-min averages and over a total light path of 100 m. The miniDOAS has been developed for application in measurement networks such as the Dutch National Air Quality Monitoring Network (LML). Compared to the RIVM DOAS it has a similar accuracy, but is significantly reduced in size, costs, and handling complexity. The RIVM DOAS and miniDOAS results showed excellent agreement (R2 = 0.996) during a field measurement campaign in Vredepeel, the Netherlands. This measurement site is located in an agricultural area and is characterized by highly variable, but on average high ammonia concentrations in the air. The RIVM-DOAS and miniDOAS results were compared to the results of the AMOR instrument, a continuous-flow wet denuder system, which is currently used in the LML. Averaged over longer time spans of typically a day, the (mini)DOAS and AMOR results agree reasonably well, although an offset of the AMOR values compared to the (mini)DOAS results exists. On short time scales, the (mini)DOAS shows a faster response and does not show the memory effects due to inlet tubing and transport of absorption fluids encountered by the AMOR. Due to its high accuracy, high uptime, low maintenance and its open path, the (mini)DOAS shows a good potential for flux measurements by using two (or more) systems in a gradient set-up and applying the aerodynamic gradient technique.

Non-common path aberration correction in an adaptive optics scanning ophthalmoscope

PubMed Central

Sulai, Yusufu N.; Dubra, Alfredo

2014-01-01

The correction of non-common path aberrations (NCPAs) between the imaging and wavefront sensing channel in a confocal scanning adaptive optics ophthalmoscope is demonstrated. NCPA correction is achieved by maximizing an image sharpness metric while the confocal detection aperture is temporarily removed, effectively minimizing the monochromatic aberrations in the illumination path of the imaging channel. Comparison of NCPA estimated using zonal and modal orthogonal wavefront corrector bases provided wavefronts that differ by ~λ/20 in root-mean-squared (~λ/30 standard deviation). Sequential insertion of a cylindrical lens in the illumination and light collection paths of the imaging channel was used to compare image resolution after changing the wavefront correction to maximize image sharpness and intensity metrics. Finally, the NCPA correction was incorporated into the closed-loop adaptive optics control by biasing the wavefront sensor signals without reducing its bandwidth. PMID:25401020

PathCase-SB architecture and database design

PubMed Central

2011-01-01

Background Integration of metabolic pathways resources and regulatory metabolic network models, and deploying new tools on the integrated platform can help perform more effective and more efficient systems biology research on understanding the regulation in metabolic networks. Therefore, the tasks of (a) integrating under a single database environment regulatory metabolic networks and existing models, and (b) building tools to help with modeling and analysis are desirable and intellectually challenging computational tasks. Description PathCase Systems Biology (PathCase-SB) is built and released. The PathCase-SB database provides data and API for multiple user interfaces and software tools. The current PathCase-SB system provides a database-enabled framework and web-based computational tools towards facilitating the development of kinetic models for biological systems. PathCase-SB aims to integrate data of selected biological data sources on the web (currently, BioModels database and KEGG), and to provide more powerful and/or new capabilities via the new web-based integrative framework. This paper describes architecture and database design issues encountered in PathCase-SB's design and implementation, and presents the current design of PathCase-SB's architecture and database. Conclusions PathCase-SB architecture and database provide a highly extensible and scalable environment with easy and fast (real-time) access to the data in the database. PathCase-SB itself is already being used by researchers across the world. PMID:22070889

Multi-point laser ignition device

DOEpatents

McIntyre, Dustin L.; Woodruff, Steven D.

2017-01-17

A multi-point laser device comprising a plurality of optical pumping sources. Each optical pumping source is configured to create pumping excitation energy along a corresponding optical path directed through a high-reflectivity mirror and into substantially different locations within the laser media thereby producing atomic optical emissions at substantially different locations within the laser media and directed along a corresponding optical path of the optical pumping source. An output coupler and one or more output lenses are configured to produce a plurality of lasing events at substantially different times, locations or a combination thereof from the multiple atomic optical emissions produced at substantially different locations within the laser media. The laser media is a single continuous media, preferably grown on a single substrate.

Simulation and modeling of the temporal performance of path-based restoration schemes in planar mesh networks

NASA Astrophysics Data System (ADS)

Bhardwaj, Manish; McCaughan, Leon; Olkhovets, Anatoli; Korotky, Steven K.

2006-12-01

We formulate an analytic framework for the restoration performance of path-based restoration schemes in planar mesh networks. We analyze various switch architectures and signaling schemes and model their total restoration interval. We also evaluate the network global expectation value of the time to restore a demand as a function of network parameters. We analyze a wide range of nominally capacity-optimal planar mesh networks and find our analytic model to be in good agreement with numerical simulation data.

Demonstrating Fermat's Principle in Optics

ERIC Educational Resources Information Center

Paleiov, Orr; Pupko, Ofir; Lipson, S. G.

2011-01-01

We demonstrate Fermat's principle in optics by a simple experiment using reflection from an arbitrarily shaped one-dimensional reflector. We investigated a range of possible light paths from a lamp to a fixed slit by reflection in a curved reflector and showed by direct measurement that the paths along which light is concentrated have either…

Results from SIM's Thermo-Opto-Mechanical (TOM3) Testbed

NASA Technical Reports Server (NTRS)

Goullioud, Renaud; Lindensmith, C. A.; Hahn, I.

2006-01-01

Future space-based optical interferometers, such as the Space Interferometer Mission Planet Quest (SIM), require thermal stability of the optical wavefront to the level of picometers in order to produce astrometric data at the micro-arc-second level. In SIM, the internal path of the interferometer will be measured with a small metrology beam whereas the starlight fringe position is estimated from a large concentric annular beam. To achieve the micro-arc-second observation goal for SIM, it is necessary to maintain the optical path difference between the central and the outer annulus portions of the wavefront of the front-end telescope optics to a few tens of picometers. The Thermo-Opto-Mecha nical testbed (TOM3) was developed at the Jet Propulsion Laboratory to measure thermally induced optical deformations of a full-size flight-like beam compressor and siderostat, the two largest optics on SIM, in flight-like thermal environments. A Common Path Heterodyne Interferometer (COPHI) developed at JPL was used for the fine optical path difference measurement as the metrology sensor. The system was integrated inside a large vacuum chamber in order to mitigate the atmospheric and thermal disturbances. The siderostat was installed in a temperature-controlled thermal shroud inside the vacuum chamber, creating a flight-like thermal environment. Detailed thermal and structural models of the test articles (siderostat and compressor) were also developed for model prediction and correlation of the thermal deformations. Experimental data shows SIM required thermal stability of the test articles and good agreement with the model predictions.

Time signal distribution in communication networks based on synchronous digital hierarchy

NASA Technical Reports Server (NTRS)

Imaoka, Atsushi; Kihara, Masami

1993-01-01

A new method that uses round-trip paths to accurately measure transmission delay for time synchronization is proposed. The performance of the method in Synchronous Digital Hierarchy networks is discussed. The feature of this method is that it separately measures the initial round trip path delay and the variations in round-trip path delay. The delay generated in SDH equipment is determined by measuring the initial round-trip path delay. In an experiment with actual SDH equipment, the error of initial delay measurement was suppressed to 30ns.

Hopfield networks for solving Tower of Hanoi problems

NASA Astrophysics Data System (ADS)

Kaplan, G. B.; Güzeliş, Cüneyt

2001-08-01

In this paper, Hopfield neural networks have been considered in solving the Tower of Hanoi test which is used in the determining of deficit of planning capability of the human prefrontal cortex. The main difference between this paper and the ones in the literature which use neural networks is that the Tower of Hanoi problem has been formulated here as a special shortest-path problem. In the literature, some Hopfield networks are developed for solving the shortest path problem which is a combinatorial optimization problem having a diverse field of application. The approach given in this paper gives the possibility of solving the Tower of Hanoi problem using these Hopfield networks. Also, the paper proposes new Hopfield network models for the shortest path and hence the Tower of Hanoi problems and compares them to the available ones in terms of the memory and time (number of steps) needed in the simulations.

pathChirp: Efficient Available Bandwidth Estimation for Network Paths

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cottrell, Les

2003-04-30

This paper presents pathChirp, a new active probing tool for estimating the available bandwidth on a communication network path. Based on the concept of ''self-induced congestion,'' pathChirp features an exponential flight pattern of probes we call a chirp. Packet chips offer several significant advantages over current probing schemes based on packet pairs or packet trains. By rapidly increasing the probing rate within each chirp, pathChirp obtains a rich set of information from which to dynamically estimate the available bandwidth. Since it uses only packet interarrival times for estimation, pathChirp does not require synchronous nor highly stable clocks at the sendermore » and receiver. We test pathChirp with simulations and Internet experiments and find that it provides good estimates of the available bandwidth while using only a fraction of the number of probe bytes that current state-of-the-art techniques use.« less

Selection of test paths for solder joint intermittent connection faults under DC stimulus

NASA Astrophysics Data System (ADS)

Huakang, Li; Kehong, Lv; Jing, Qiu; Guanjun, Liu; Bailiang, Chen

2018-06-01

The test path of solder joint intermittent connection faults under direct-current stimulus is examined in this paper. According to the physical structure of the circuit, a network model is established first. A network node is utilised to represent the test node. The path edge refers to the number of intermittent connection faults in the path. Then, the selection criteria of the test path based on the node degree index are proposed and the solder joint intermittent connection faults are covered using fewer test paths. Finally, three circuits are selected to verify the method. To test if the intermittent fault is covered by the test paths, the intermittent fault is simulated by a switch. The results show that the proposed method can detect the solder joint intermittent connection fault using fewer test paths. Additionally, the number of detection steps is greatly reduced without compromising fault coverage.

Synchronization of Clocks Through 12 km of Strongly Turbulent Air Over a City.

PubMed

Sinclair, Laura C; Swann, William C; Bergeron, Hugo; Baumann, Esther; Cermak, Michael; Coddington, Ian; Deschênes, Jean-Daniel; Giorgetta, Fabrizio R; Juarez, Juan C; Khader, Isaac; Petrillo, Keith G; Souza, Katherine T; Dennis, Michael L; Newbury, Nathan R

2016-10-15

We demonstrate real-time, femtosecond-level clock synchronization across a low-lying, strongly turbulent, 12-km horizontal air path by optical two-way time transfer. For this long horizontal free-space path, the integrated turbulence extends well into the strong turbulence regime corresponding to multiple scattering with a Rytov variance up to 7 and with the number of signal interruptions exceeding 100 per second. Nevertheless, optical two-way time transfer is used to synchronize a remote clock to a master clock with femtosecond-level agreement and with a relative time deviation dropping as low as a few hundred attoseconds. Synchronization is shown for a remote clock based on either an optical or microwave oscillator and using either tip-tilt or adaptive-optics free-space optical terminals. The performance is unaltered from optical two-way time transfer in weak turbulence across short links. These results confirm that the two-way reciprocity of the free-space time-of-flight is maintained both under strong turbulence and with the use of adaptive optics. The demonstrated robustness of optical two-way time transfer against strong turbulence and its compatibility with adaptive optics is encouraging for future femtosecond clock synchronization over very long distance ground-to-air free-space paths.

Synchronization of Clocks Through 12 km of Strongly Turbulent Air Over a City

PubMed Central

Sinclair, Laura C.; Swann, William C.; Bergeron, Hugo; Baumann, Esther; Cermak, Michael; Coddington, Ian; Deschênes, Jean-Daniel; Giorgetta, Fabrizio R.; Juarez, Juan C.; Khader, Isaac; Petrillo, Keith G.; Souza, Katherine T.; Dennis, Michael L.; Newbury, Nathan R.

2018-01-01

We demonstrate real-time, femtosecond-level clock synchronization across a low-lying, strongly turbulent, 12-km horizontal air path by optical two-way time transfer. For this long horizontal free-space path, the integrated turbulence extends well into the strong turbulence regime corresponding to multiple scattering with a Rytov variance up to 7 and with the number of signal interruptions exceeding 100 per second. Nevertheless, optical two-way time transfer is used to synchronize a remote clock to a master clock with femtosecond-level agreement and with a relative time deviation dropping as low as a few hundred attoseconds. Synchronization is shown for a remote clock based on either an optical or microwave oscillator and using either tip-tilt or adaptive-optics free-space optical terminals. The performance is unaltered from optical two-way time transfer in weak turbulence across short links. These results confirm that the two-way reciprocity of the free-space time-of-flight is maintained both under strong turbulence and with the use of adaptive optics. The demonstrated robustness of optical two-way time transfer against strong turbulence and its compatibility with adaptive optics is encouraging for future femtosecond clock synchronization over very long distance ground-to-air free-space paths. PMID:29348695

Raman scattering in a whispering mode optical waveguide

DOEpatents

Kurnit, Norman A.

1982-01-01

A device and method for Raman scattering in a whispering mode optical waveguide. Both a helical ribbon and cylinder are disclosed which incorporate an additional curvature .rho. p for confining the beam to increase intensity. A Raman scattering medium is disposed in the optical path of the beam as it propagates along the waveguide. Raman scattering is enhanced by the high intensities of the beam and long interaction path lengths which are achieved in a small volume.

Automatic cell identification and visualization using digital holographic microscopy with head mounted augmented reality devices.

PubMed

O'Connor, Timothy; Rawat, Siddharth; Markman, Adam; Javidi, Bahram

2018-03-01

We propose a compact imaging system that integrates an augmented reality head mounted device with digital holographic microscopy for automated cell identification and visualization. A shearing interferometer is used to produce holograms of biological cells, which are recorded using customized smart glasses containing an external camera. After image acquisition, segmentation is performed to isolate regions of interest containing biological cells in the field-of-view, followed by digital reconstruction of the cells, which is used to generate a three-dimensional (3D) pseudocolor optical path length profile. Morphological features are extracted from the cell's optical path length map, including mean optical path length, coefficient of variation, optical volume, projected area, projected area to optical volume ratio, cell skewness, and cell kurtosis. Classification is performed using the random forest classifier, support vector machines, and K-nearest neighbor, and the results are compared. Finally, the augmented reality device displays the cell's pseudocolor 3D rendering of its optical path length profile, extracted features, and the identified cell's type or class. The proposed system could allow a healthcare worker to quickly visualize cells using augmented reality smart glasses and extract the relevant information for rapid diagnosis. To the best of our knowledge, this is the first report on the integration of digital holographic microscopy with augmented reality devices for automated cell identification and visualization.

High power regenerative laser amplifier

DOEpatents

Miller, John L.; Hackel, Lloyd A.; Dane, Clifford B.; Zapata, Luis E.

1994-01-01

A regenerative amplifier design capable of operating at high energy per pulse, for instance, from 20-100 Joules, at moderate repetition rates, for instance from 5-20 Hertz is provided. The laser amplifier comprises a gain medium and source of pump energy coupled with the gain medium; a Pockels cell, which rotates an incident beam in response to application of a control signal; an optical relay system defining a first relay plane near the gain medium and a second relay plane near the rotator; and a plurality of reflectors configured to define an optical path through the gain medium, optical relay and Pockels cell, such that each transit of the optical path includes at least one pass through the gain medium and only one pass through the Pockels cell. An input coupler, and an output coupler are provided, implemented by a single polarizer. A control circuit coupled to the Pockels cell generates the control signal in timed relationship with the input pulse so that the input pulse is captured by the input coupler and proceeds through at least one transit of the optical path, and then the control signal is applied to cause rotation of the pulse to a polarization reflected by the polarizer, after which the captured pulse passes through the gain medium at least once more and is reflected out of the optical path by the polarizer before passing through the rotator again to provide an amplified pulse.

High power regenerative laser amplifier

DOEpatents

Miller, J.L.; Hackel, L.A.; Dane, C.B.; Zapata, L.E.

1994-02-08

A regenerative amplifier design capable of operating at high energy per pulse, for instance, from 20-100 Joules, at moderate repetition rates, for instance from 5-20 Hertz is provided. The laser amplifier comprises a gain medium and source of pump energy coupled with the gain medium; a Pockels cell, which rotates an incident beam in response to application of a control signal; an optical relay system defining a first relay plane near the gain medium and a second relay plane near the rotator; and a plurality of reflectors configured to define an optical path through the gain medium, optical relay and Pockels cell, such that each transit of the optical path includes at least one pass through the gain medium and only one pass through the Pockels cell. An input coupler, and an output coupler are provided, implemented by a single polarizer. A control circuit coupled to the Pockels cell generates the control signal in timed relationship with the input pulse so that the input pulse is captured by the input coupler and proceeds through at least one transit of the optical path, and then the control signal is applied to cause rotation of the pulse to a polarization reflected by the polarizer, after which the captured pulse passes through the gain medium at least once more and is reflected out of the optical path by the polarizer before passing through the rotator again to provide an amplified pulse. 7 figures.

CFO compensation method using optical feedback path for coherent optical OFDM system

NASA Astrophysics Data System (ADS)

Moon, Sang-Rok; Hwang, In-Ki; Kang, Hun-Sik; Chang, Sun Hyok; Lee, Seung-Woo; Lee, Joon Ki

2017-07-01

We investigate feasibility of carrier frequency offset (CFO) compensation method using optical feedback path for coherent optical orthogonal frequency division multiplexing (CO-OFDM) system. Recently proposed CFO compensation algorithms provide wide CFO estimation range in electrical domain. However, their practical compensation range is limited by sampling rate of an analog-to-digital converter (ADC). This limitation has not drawn attention, since the ADC sampling rate was high enough comparing to the data bandwidth and CFO in the wireless OFDM system. For CO-OFDM, the limitation is becoming visible because of increased data bandwidth, laser instability (i.e. large CFO) and insufficient ADC sampling rate owing to high cost. To solve the problem and extend practical CFO compensation range, we propose a CFO compensation method having optical feedback path. By adding simple wavelength control for local oscillator, the practical CFO compensation range can be extended to the sampling frequency range. The feasibility of the proposed method is experimentally investigated.

The CHARA array adaptive optics I: common-path optical and mechanical design, and preliminary on-sky results

NASA Astrophysics Data System (ADS)

Che, Xiao; Sturmann, Laszlo; Monnier, John D.; ten Brummelaar, Theo A.; Sturmann, Judit; Ridgway, Stephen T.; Ireland, Michael J.; Turner, Nils H.; McAlister, Harold A.

2014-07-01

The CHARA array is an optical interferometer with six 1-meter diameter telescopes, providing baselines from 33 to 331 meters. With sub-milliarcsecond angular resolution, its versatile visible and near infrared combiners offer a unique angle of studying nearby stellar systems by spatially resolving their detailed structures. To improve the sensitivity and scientific throughput, the CHARA array was funded by NSF-ATI in 2011 to install adaptive optics (AO) systems on all six telescopes. The initial grant covers Phase I of the AO systems, which includes on-telescope Wavefront Sensors (WFS) and non-common-path (NCP) error correction. Meanwhile we are seeking funding for Phase II which will add large Deformable Mirrors on telescopes to close the full AO loop. The corrections of NCP error and static aberrations in the optical system beyond the WFS are described in the second paper of this series. This paper describes the design of the common-path optical system and the on-telescope WFS, and shows the on-sky commissioning results.

Monolithic mm-wave phase shifter using optically activated superconducting switches

NASA Technical Reports Server (NTRS)

Romanofsky, Robert R. (Inventor); Bhasin, Kul B. (Inventor)

1992-01-01

A phase shifter is disclosed having a reference path and a delay path, light sources, and superconductive switches. Each of the superconductive switches is terminated in a virtual short circuit, which may be a radial stub. Switching between the reference path and delayed path is accomplished by illuminating the superconductive switches connected to the desired path, while not illuminating the superconductive switches connected to the other path.

On Channel-Discontinuity-Constraint Routing in Wireless Networks☆

PubMed Central

Sankararaman, Swaminathan; Efrat, Alon; Ramasubramanian, Srinivasan; Agarwal, Pankaj K.

2011-01-01

Multi-channel wireless networks are increasingly deployed as infrastructure networks, e.g. in metro areas. Network nodes frequently employ directional antennas to improve spatial throughput. In such networks, between two nodes, it is of interest to compute a path with a channel assignment for the links such that the path and link bandwidths are the same. This is achieved when any two consecutive links are assigned different channels, termed as “Channel-Discontinuity-Constraint” (CDC). CDC-paths are also useful in TDMA systems, where, preferably, consecutive links are assigned different time-slots. In the first part of this paper, we develop a t-spanner for CDC-paths using spatial properties; a sub-network containing O(n/θ) links, for any θ > 0, such that CDC-paths increase in cost by at most a factor t = (1−2 sin (θ/2))−2. We propose a novel distributed algorithm to compute the spanner using an expected number of O(n log n) fixed-size messages. In the second part, we present a distributed algorithm to find minimum-cost CDC-paths between two nodes using O(n2) fixed-size messages, by developing an extension of Edmonds’ algorithm for minimum-cost perfect matching. In a centralized implementation, our algorithm runs in O(n2) time improving the previous best algorithm which requires O(n3) running time. Moreover, this running time improves to O(n/θ) when used in conjunction with the spanner developed. PMID:24443646

Adaptive Bio-Inspired Wireless Network Routing for Planetary Surface Exploration

NASA Technical Reports Server (NTRS)

Alena, Richard I.; Lee, Charles

2004-01-01

Wireless mobile networks suffer connectivity loss when used in a terrain that has hills, and valleys when line of sight is interrupted or range is exceeded. To resolve this problem and achieve acceptable network performance, we have designed an adaptive, configurable, hybrid system to automatically route network packets along the best path between multiple geographically dispersed modules. This is very useful in planetary surface exploration, especially for ad-hoc mobile networks, where computational devices take an active part in creating a network infrastructure, and can actually be used to route data dynamically and even store data for later transmission between networks. Using inspiration from biological systems, this research proposes to use ant trail algorithms with multi-layered information maps (topographic maps, RF coverage maps) to determine the best route through ad-hoc network at real time. The determination of best route is a complex one, and requires research into the appropriate metrics, best method to identify the best path, optimizing traffic capacity, network performance, reliability, processing capabilities and cost. Real ants are capable of finding the shortest path from their nest to a food source without visual sensing through the use of pheromones. They are also able to adapt to changes in the environment using subtle clues. To use ant trail algorithms, we need to define the probability function. The artificial ant is, in this case, a software agent that moves from node to node on a network graph. The function to calculate the fitness (evaluate the better path) includes: length of the network edge, the coverage index, topology graph index, and pheromone trail left behind by other ant agents. Each agent modifies the environment in two different ways: 1) Local trail updating: As the ant moves between nodes it updates the amount of pheromone on the edge; and 2) Global trail updating: When all ants have completed a tour the ant that found the shortest route updates the edges in its path.

Chain-Based Communication in Cylindrical Underwater Wireless Sensor Networks

PubMed Central

Javaid, Nadeem; Jafri, Mohsin Raza; Khan, Zahoor Ali; Alrajeh, Nabil; Imran, Muhammad; Vasilakos, Athanasios

2015-01-01

Appropriate network design is very significant for Underwater Wireless Sensor Networks (UWSNs). Application-oriented UWSNs are planned to achieve certain objectives. Therefore, there is always a demand for efficient data routing schemes, which can fulfill certain requirements of application-oriented UWSNs. These networks can be of any shape, i.e., rectangular, cylindrical or square. In this paper, we propose chain-based routing schemes for application-oriented cylindrical networks and also formulate mathematical models to find a global optimum path for data transmission. In the first scheme, we devise four interconnected chains of sensor nodes to perform data communication. In the second scheme, we propose routing scheme in which two chains of sensor nodes are interconnected, whereas in third scheme single-chain based routing is done in cylindrical networks. After finding local optimum paths in separate chains, we find global optimum paths through their interconnection. Moreover, we develop a computational model for the analysis of end-to-end delay. We compare the performance of the above three proposed schemes with that of Power Efficient Gathering System in Sensor Information Systems (PEGASIS) and Congestion adjusted PEGASIS (C-PEGASIS). Simulation results show that our proposed 4-chain based scheme performs better than the other selected schemes in terms of network lifetime, end-to-end delay, path loss, transmission loss, and packet sending rate. PMID:25658394

Novel techniques for optical performance monitoring in optical systems

NASA Astrophysics Data System (ADS)

Ku, Yuen Ching

The tremendous increase of data traffic in the worldwide Internet has driven the rapid development of optical networks to migrate from numerous point-to-point links towards meshed, transparent optical networks with dynamically routed light paths. This increases the need for appropriate network supervision methods. In view of this, optical performance monitoring (OPM) has emerged as an indispensable element for the quality assurance of an optical network. This thesis is devoted to the proposal of several new and accurate techniques to monitor different optical impairments so as to enhance proper network management. When the optical signal is carried on fiber links with optical amplifiers, the accumulated amplified spontaneous emission (ASE) noise will result in erroneous detection of the received signals. The first part of the thesis presents a novel, simple, and robust in-band optical signal to noise ratio (OSNR) monitoring technique using phase modulator embedded fiber loop mirror (PM-FLM). This technique measures the in-band OSNR accurately by observing the output power of a fiber loop mirror filter, where the transmittance is adjusted by an embedded phase modulator driven by a low-frequency periodic signal. The robustness against polarization mode dispersion, chromatic dispersion, bit-rate, and partially polarized noise is experimentally demonstrated. Chromatic dispersion (CD) is due to the fact that light with different frequencies travel at different speeds inside fiber. It causes pulse spreading and intersymbol interference (ISI) which would severely degrade the transmission performance. By feeding a signal into a fiber loop which consists of a high-birefringence (Hi-Bi) fiber, we experimentally show that the amount of experienced dispersion can be deduced from the RF power at a specific selected frequency which is determined by the length of the Hi-Bi fiber. Experimental results show that this technique can provide high monitoring resolution and dynamic range. Polarization mode dispersion (PMD) splits an optical pulse into two orthogonally polarized pulses traveling along the fiber at different speeds, causing crosstalk and ISI. The third part of the thesis demonstrates two different PMD monitoring schemes. The first one is based on the analysis of frequency-resolved state-of-polarization (SOP) rotation, with signal spectrum broadened by self-phase modulation (SPM) effect. Experimental results show that the use of broadened signal spectrum induced by SPM not only relaxes the filter requirement and reduces the computational complexity, but also improves the estimation accuracy, and extends the monitoring range of the pulsewidth. The second one is based on the delay-tap asynchronous waveform sampling technique. By examining the statistical distribution of the measured scatter plot, unambiguous PMD measurement range up to 50% of signal bit-period is demonstrated. The final part of the thesis focuses on the monitoring of alignment status between the pulse carver and data modulator in an optical system. We again employ the two-tap asynchronous sampling technique to perform such kind of monitoring in RZ-OOK transmission system. Experimental results show that both the misalignment direction and magnitude can be successfully determined. Besides, we propose and experimentally demonstrate the use of off-center optical filtering technique to capture the amount of spectrum broadening induced by the misalignment between the pulse-carver and the data modulator in RZ-DPSK transmission system. The same technique was also applied to monitor the synchronization between the old and the new data in synchronized phase re-modulation (SPRM) system.

Integrating cell on chip—Novel waveguide platform employing ultra-long optical paths

NASA Astrophysics Data System (ADS)

Fohrmann, Lena Simone; Sommer, Gerrit; Pitruzzello, Giampaolo; Krauss, Thomas F.; Petrov, Alexander Yu.; Eich, Manfred

2017-09-01

Optical waveguides are the most fundamental building blocks of integrated optical circuits. They are extremely well understood, yet there is still room for surprises. Here, we introduce a novel 2D waveguide platform which affords a strong interaction of the evanescent tail of a guided optical wave with an external medium while only employing a very small geometrical footprint. The key feature of the platform is its ability to integrate the ultra-long path lengths by combining low propagation losses in a silicon slab with multiple reflections of the guided wave from photonic crystal (PhC) mirrors. With a reflectivity of 99.1% of our tailored PhC-mirrors, we achieve interaction paths of 25 cm within an area of less than 10 mm2. This corresponds to 0.17 dB/cm effective propagation which is much lower than the state-of-the-art loss of approximately 1 dB/cm of single mode silicon channel waveguides. In contrast to conventional waveguides, our 2D-approach leads to a decay of the guided wave power only inversely proportional to the optical path length. This entirely different characteristic is the major advantage of the 2D integrating cell waveguide platform over the conventional channel waveguide concepts that obey the Beer-Lambert law.

The routing, modulation level, and spectrum allocation algorithm in the virtual optical network mapping

NASA Astrophysics Data System (ADS)

Wang, Yunyun; Li, Hui; Liu, Yuze; Ji, Yuefeng; Li, Hongfa

2017-10-01

With the development of large video services and cloud computing, the network is increasingly in the form of services. In SDON, the SDN controller holds the underlying physical resource information, thus allocating the appropriate resources and bandwidth to the VON service. However, for some services that require extremely strict QoT (quality of transmission), the shortest distance path algorithm is often unable to meet the requirements because it does not take the link spectrum resources into account. And in accordance with the choice of the most unoccupied links, there may be more spectrum fragments. So here we propose a new RMLSA (the routing, modulation Level, and spectrum allocation) algorithm to reduce the blocking probability. The results show about 40% less blocking probability than the shortest-distance algorithm and the minimum usage of the spectrum priority algorithm. This algorithm is used to satisfy strict request of QoT for demands.

The Abcd Formula of Phase Definition in Optical Interferometry: Combined Effect of Air Dispersion and Broad Passband

NASA Astrophysics Data System (ADS)

Mathar, Richard J.

Long-baseline interferometry detects fringes created by superposition of two beams of light collected by two telescopes pointing into a common direction. The external path difference is commonly compensated by adding a variable optical path length (delay) through air for one beam such that the optical path difference between the beams remains close to zero near the detector. The ABCD formula assigns a (wrapped) phase to the signals A to D of an interference pattern shifted by multiples of 90 degrees in phase. We study the interplay between a broad spectral passband of the optics and the dispersion of the air in the compensating delay, which leads to small deviations between the ABCD phase and the reduced, monochromatic group-delay representation of the wave packets. This adds dispersion to the effects that have been discussed for evacuated interferometers before (Milman 2005).

A study of the high-precision displacement laser probe

NASA Astrophysics Data System (ADS)

Fan, Yuming; Zhang, Guoxiong

2006-06-01

On the basis of the measuring principle of the dynamic active optical confocal probe based on time difference measurement that has a reference path, a dynamic active optical confocal probe based on time difference measurement but has no reference path is developed. In this paper, the working principle of this optical confocal probe is dissertated. A large-scale integrated measuring system is designed to simplify the structure of the probe and to enhance the stability of the probe. Single-chip microcomputer system with a high-speed ADC is selected in the measurement and control system of the probe. At the end of the paper, experiments on the performance of the optical confocal probe based on time difference measurement with no reference path are carried out. Experiment results show that the probe has a measuring resolution of 0.05μm, a measuring range of 0.2mm and a linearity of 0.4μm.

Optical path design of phase contrast imaging on HL-2A tokamak

NASA Astrophysics Data System (ADS)

Qiyun, CHENG; Yi, YU; Shaobo, GONG; Min, XU; Tao, LAN; Wei, JIANG; Boda, YUAN; Yifan, WU; Lin, NIE; Rui, KE; Ting, LONG; Dong, GUO; Minyou, YE; Xuru, DUAN

2017-12-01

A phase contrast imaging (PCI) diagnostic has recently been developed on HL-2A tokamak. It can diagnose plasma density fluctuations with maximum wave number of 15 cm-1 and wave number resolution of 2 cm-1. The time resolution reaches 2 μs. A 10.6 μm CO2 laser is expanded to a beam with a diameter of 30 mm and injected into the plasma as an incident beam, injecting into plasma. The emerging scattered and unscattered beams are contrasted by a phase plate. The ideas of optical path design are presented in this paper, together with the parameters of the main optical components. The whole optical path of PCI is not only carefully designed, but also constructed on HL-2A. First calibration results show the ability of this system to catch plasma turbulence in a wide frequency domain.

Polarization feedback laser stabilization

DOEpatents

Esherick, Peter; Owyoung, Adelbert

1988-01-01

A system for locking two Nd:YAG laser oscillators includes an optical path for feeding the output of one laser into the other with different polarizations. Elliptical polarization is incorporated into the optical path so that the change in polarization that occurs when the frequencies coincide may be detected to provide a feedback signal to control one laser relative to the other.

Visualizing Transmedia Networks: Links, Paths and Peripheries

ERIC Educational Resources Information Center

Ruppel, Marc Nathaniel

2012-01-01

'Visualizing Transmedia Networks: Links, Paths and Peripheries' examines the increasingly complex rhetorical intersections between narrative and media ("old" and "new") in the creation of transmedia fictions, loosely defined as multisensory and multimodal stories told extensively across a diverse media set. In order…

Light-driven phase shifter

DOEpatents

Early, James W.

1990-01-01

A light-driven phase shifter is provided for modulating a transmission light beam. A gaseous medium such as argon is provided with electron energy states excited to populate a metastable state. A tunable dye laser is selected with a wavelength effective to deplete the metastable electron state and may be intensity modulated. The dye laser is directed through the gaseous medium to define a first optical path having an index of refraction determined by the gaseous medium having a depleted metastable electron state. A transmission laser beam is also directed through the gaseous medium to define a second optical path at least partially coincident with the first optical path. The intensity of the dye laser beam may then be varied to phase modulate the transmission laser beam.

Complete description of the optical path difference of a novel spectral zooming imaging spectrometer

NASA Astrophysics Data System (ADS)

Li, Jie; Wu, Haiying; Qi, Chun

2018-03-01

A complete description of the optical path difference of a novel spectral zooming imaging spectrometer (SZIS) is presented. SZIS is designed based on two identical Wollaston prisms with an adjustable air gap. Thus, interferogram with arbitrary spectral resolution and great reduction of spectral image size can be conveniently formed to adapt to different application requirements. Ray tracing modeling in arbitrary incidence with a quasi-parallel-plate approximation scheme is proposed to analyze the optical path difference of SZIS. In order to know the characteristics of the apparatus, exact calculations of the corresponding spectral resolution and field of view are both derived and analyzed in detail. We also present a comparison of calculation and experiment to prove the validity of the theory.

Optical path difference microscopy with a Shack-Hartmann wavefront sensor.

PubMed

Gong, Hai; Agbana, Temitope E; Pozzi, Paolo; Soloviev, Oleg; Verhaegen, Michel; Vdovin, Gleb

2017-06-01

In this Letter, we show that a Shack-Hartmann wavefront sensor can be used for the quantitative measurement of the specimen optical path difference (OPD) in an ordinary incoherent optical microscope, if the spatial coherence of the illumination light in the plane of the specimen is larger than the microscope resolution. To satisfy this condition, the illumination numerical aperture should be smaller than the numerical aperture of the imaging lens. This principle has been successfully applied to build a high-resolution reference-free instrument for the characterization of the OPD of micro-optical components and microscopic biological samples.

Aerosol mass spectrometry systems and methods

DOEpatents

Fergenson, David P.; Gard, Eric E.

2013-08-20

A system according to one embodiment includes a particle accelerator that directs a succession of polydisperse aerosol particles along a predetermined particle path; multiple tracking lasers for generating beams of light across the particle path; an optical detector positioned adjacent the particle path for detecting impingement of the beams of light on individual particles; a desorption laser for generating a beam of desorbing light across the particle path about coaxial with a beam of light produced by one of the tracking lasers; and a controller, responsive to detection of a signal produced by the optical detector, that controls the desorption laser to generate the beam of desorbing light. Additional systems and methods are also disclosed.

Path integrals and large deviations in stochastic hybrid systems.

PubMed

Bressloff, Paul C; Newby, Jay M

2014-04-01

We construct a path-integral representation of solutions to a stochastic hybrid system, consisting of one or more continuous variables evolving according to a piecewise-deterministic dynamics. The differential equations for the continuous variables are coupled to a set of discrete variables that satisfy a continuous-time Markov process, which means that the differential equations are only valid between jumps in the discrete variables. Examples of stochastic hybrid systems arise in biophysical models of stochastic ion channels, motor-driven intracellular transport, gene networks, and stochastic neural networks. We use the path-integral representation to derive a large deviation action principle for a stochastic hybrid system. Minimizing the associated action functional with respect to the set of all trajectories emanating from a metastable state (assuming that such a minimization scheme exists) then determines the most probable paths of escape. Moreover, evaluating the action functional along a most probable path generates the so-called quasipotential used in the calculation of mean first passage times. We illustrate the theory by considering the optimal paths of escape from a metastable state in a bistable neural network.

Stray magnetic-field response of linear birefringent optical current sensors

NASA Astrophysics Data System (ADS)

MacDougall, Trevor W.; Hutchinson, Ted F.

1995-07-01

It is well known that the line integral, describing Faraday rotation in an optical medium, reduces to zero at low frequencies for a closed path that does not encircle a current source. If the closed optical path possesses linear birefringence in addition to Faraday rotation, the cumulative effects on the state of polarization result in a response to externally located current-carrying conductors. This effect can induce a measurable error of the order of 0.3% during certain steady-state operating conditions.

Path-length-resolved dynamic light scattering in highly scattering random media: The transition to diffusing wave spectroscopy

NASA Astrophysics Data System (ADS)

Bizheva, Kostadinka K.; Siegel, Andy M.; Boas, David A.

1998-12-01

We used low coherence interferometry to measure Brownian motion within highly scattering random media. A coherence gate was applied to resolve the optical path-length distribution and to separate ballistic from diffusive light. Our experimental analysis provides details on the transition from single scattering to light diffusion and its dependence on the system parameters. We found that the transition to the light diffusion regime occurs at shorter path lengths for media with higher scattering anisotropy or for larger numerical aperture of the focusing optics.

Optimizing Retransmission Threshold in Wireless Sensor Networks

PubMed Central

Bi, Ran; Li, Yingshu; Tan, Guozhen; Sun, Liang

2016-01-01

The retransmission threshold in wireless sensor networks is critical to the latency of data delivery in the networks. However, existing works on data transmission in sensor networks did not consider the optimization of the retransmission threshold, and they simply set the same retransmission threshold for all sensor nodes in advance. The method did not take link quality and delay requirement into account, which decreases the probability of a packet passing its delivery path within a given deadline. This paper investigates the problem of finding optimal retransmission thresholds for relay nodes along a delivery path in a sensor network. The object of optimizing retransmission thresholds is to maximize the summation of the probability of the packet being successfully delivered to the next relay node or destination node in time. A dynamic programming-based distributed algorithm for finding optimal retransmission thresholds for relay nodes along a delivery path in the sensor network is proposed. The time complexity is OnΔ·max1≤i≤n{ui}, where ui is the given upper bound of the retransmission threshold of sensor node i in a given delivery path, n is the length of the delivery path and Δ is the given upper bound of the transmission delay of the delivery path. If Δ is greater than the polynomial, to reduce the time complexity, a linear programming-based (1+pmin)-approximation algorithm is proposed. Furthermore, when the ranges of the upper and lower bounds of retransmission thresholds are big enough, a Lagrange multiplier-based distributed O(1)-approximation algorithm with time complexity O(1) is proposed. Experimental results show that the proposed algorithms have better performance. PMID:27171092

Spectrum-efficient multipath provisioning with content connectivity for the survivability of elastic optical datacenter networks

NASA Astrophysics Data System (ADS)

Gao, Tao; Li, Xin; Guo, Bingli; Yin, Shan; Li, Wenzhe; Huang, Shanguo

2017-07-01

Multipath provisioning is a survivable and resource efficient solution against increasing link failures caused by natural or man-made disasters in elastic optical datacenter networks (EODNs). Nevertheless, the conventional multipath provisioning scheme is designed only for connecting a specific node pair. Also, it is obvious that the number of node-disjoint paths between any two nodes is restricted to network connectivity, which has a fixed value for a given topology. Recently, the concept of content connectivity in EODNs has been proposed, which guarantees that a user can be served by any datacenter hosting the required content regardless of where it is located. From this new perspective, we propose a survivable multipath provisioning with content connectivity (MPCC) scheme, which is expected to improve the spectrum efficiency and the whole system survivability. We formulate the MPCC scheme with Integer Linear Program (ILP) in static traffic scenario and a heuristic approach is proposed for dynamic traffic scenario. Furthermore, to adapt MPCC to the variation of network state in dynamic traffic scenario, we propose a dynamic content placement (DCP) strategy in the MPCC scheme for detecting the variation of the distribution of user requests and adjusting the content location dynamically. Simulation results indicate that the MPCC scheme can reduce over 20% spectrum consumption than conventional multipath provisioning scheme in static traffic scenario. And in dynamic traffic scenario, the MPCC scheme can reduce over 20% spectrum consumption and over 50% blocking probability than conventional multipath provisioning scheme. Meanwhile, benefiting from the DCP strategy, the MPCC scheme has a good adaption to the variation of the distribution of user requests.

Slant-path coherent free space optical communications over the maritime and terrestrial atmospheres with the use of adaptive optics for beam wavefront correction.

PubMed

Li, Ming; Gao, Wenbo; Cvijetic, Milorad

2017-01-10

As a continuation of our previous work [Appl. Opt.54, 1453 (2015)APOPAI0003-693510.1364/AO.54.001453] in which we have studied the performance of coherent free space optical (FSO) communication systems operating over a horizontal path, in this paper we study the coherent FSO system operating over a general slant path. We evaluated system bit-error-rate (BER) in the case when the quadrature phase-shift keying (QPSK) modulation format is applied and when an adaptive optics (AO) system is employed to mitigate the air turbulence effects for both maritime and terrestrial air transmission scenarios. We adopted a multiple-layer scheme to efficiently model the FSO slant-path links. The atmospheric channel fading was characterized by the wavefront phase distortions and the log-amplitude fluctuations. We derived analytical expressions to characterize log-amplitude fluctuations of air turbulence by asserting the aperture averaging within the frame of the multiple-layer model. The obtained results showed that use of AO enabled improvement of system performance for both uplinks and downlinks, and also revealed that it is more beneficial for the FSO downlinks. Also, AO employment brought larger enhancements in BER performance for the maritime slant-path FSO links than for the terrestrial ones, with an additional striking increase in performance when the AO correction is combined with the aperture averaging.

Advanced laser architectures for high power eyesafe illuminators

NASA Astrophysics Data System (ADS)

Baranova, N.; Pati, B.; Stebbins, K.; Bystryak, I.; Rayno, M.; Ezzo, K.; DePriest, C.

2018-02-01

Q-Peak has demonstrated a novel pulsed eyesafe laser architecture operating with >50 mJ pulse energies at Pulse Repetition Frequencies (PRFs) as high as 320 Hz. The design leverages an Optical Parametric Oscillator (OPO) and Optical Parametric Amplifier (OPA) geometry, which provides the unique capability for high power in a comparatively compact package, while also offering the potential for additional eyesafe power scaling. The laser consists of a Commercial Off-the-Shelf (COTS) Q-switched front-end seed laser to produce pulse-widths around 10 ns at 1.06-μm, which is then followed by a pair of Multi-Pass Amplifier (MPA) architectures (comprised of side-pumped, multi-pass Nd:YAG slabs with a compact diode-pump-array imaging system), and finally involving two sequential nonlinear optical conversion architectures for transfer into the eyesafe regime. The initial seed beam is first amplified through the MPA, and then split into parallel optical paths. An OPO provides effective nonlinear conversion on one optical path, while a second MPA further amplifies the 1.06-μm beam for use in pumping an OPA on the second optical path. These paths are then recombined prior to seeding the OPA. Each nonlinear conversion subsystem utilizes Potassium Titanyl Arsenate (KTA) for effective nonlinear conversion with lower risk to optical damage. This laser architecture efficiently produces pulse energies of >50 mJ in the eyesafe band at PRFs as high as 320 Hz, and has been designed to fit within a volume of 4,500 in3 (0.074 m3 ). We will discuss theoretical and experimental details of the nonlinear optical system for achieving higher eyesafe powers.

Path finding methods accounting for stoichiometry in metabolic networks

PubMed Central

2011-01-01

Graph-based methods have been widely used for the analysis of biological networks. Their application to metabolic networks has been much discussed, in particular noting that an important weakness in such methods is that reaction stoichiometry is neglected. In this study, we show that reaction stoichiometry can be incorporated into path-finding approaches via mixed-integer linear programming. This major advance at the modeling level results in improved prediction of topological and functional properties in metabolic networks. PMID:21619601

Optimization of OSPF Routing in IP Networks

NASA Astrophysics Data System (ADS)

Bley, Andreas; Fortz, Bernard; Gourdin, Eric; Holmberg, Kaj; Klopfenstein, Olivier; Pióro, Michał; Tomaszewski, Artur; Ümit, Hakan

The Internet is a huge world-wide packet switching network comprised of more than 13,000 distinct subnetworks, referred to as Autonomous Systems (ASs) autonomous system AS . They all rely on the Internet Protocol (IP) internet protocol IP for transport of packets across the network. And most of them use shortest path routing protocols shortest path routing!protocols , such as OSPF or IS-IS, to control the routing of IP packets routing!of IP packets within an AS. The idea of the routing is extremely simple — every packet is forwarded on IP links along the shortest route between its source and destination nodes of the AS. The AS network administrator can manage the routing of packets in the AS by supplying the so-called administrative weights of IP links, which specify the link lengths that are used by the routing protocols for their shortest path computations. The main advantage of the shortest path routing policy is its simplicity, allowing for little administrative overhead. From the network engineering perspective, however, shortest path routing can pose problems in achieving satisfactory traffic handling efficiency. As all routing paths depend on the same routing metric routing!metric , it is not possible to configure the routing paths for the communication demands between different pairs of nodes explicitly or individually; the routing can be controlled only indirectly and only as a whole by modifying the routing metric. Thus, one of the main tasks when planning such networks is to find administrative link weights that induce a globally efficient traffic routing traffic!routing configuration of an AS. It turns out that this task leads to very difficult mathematical optimization problems. In this chapter, we discuss and describe exact integer programming models and solution approaches as well as practically efficient smart heuristics for such shortest path routing problems shortest path routing!problems .

Fiber-Optic Terahertz Data-Communication Networks

NASA Technical Reports Server (NTRS)

Chua, Peter L.; Lambert, James L.; Morookian, John M.; Bergman, Larry A.

1994-01-01

Network protocols implemented in optical domain. Fiber-optic data-communication networks utilize fully available bandwidth of single-mode optical fibers. Two key features of method: use of subpicosecond laser pulses as carrier signals and spectral phase modulation of pulses for optical implementation of code-division multiple access as multiplexing network protocol. Local-area network designed according to concept offers full crossbar functionality, security of data in transit through network, and capacity about 100 times that of typical fiber-optic local-area network in current use.

Polarization feedback laser stabilization

DOEpatents

Esherick, P.; Owyoung, A.

1987-09-28

A system for locking two Nd:YAG laser oscillators includes an optical path for feeding the output of one laser into the other with different polarizations. Elliptical polarization is incorporated into the optical path so that the change in polarization that occurs when the frequencies coincide may be detected to provide a feedback signal to control one laser relative to the other. 4 figs.

Report on Research

DTIC Science & Technology

1989-06-01

Force systems require a resolved information on the optical thorough understanding of the propaga- extinction coefficient. Measurements of tion path , the...Depolarization as Function of Snow Density. Measurement System ). (It correlated well with the ( Multi -scatter scale length information is usable to extinction ...data on the effect of optically thin cirrus clouds on long - path infrared transmit- tance. Future system designers will have access to this new

Simulation of the fixed optical path difference of near infrared wind imaging interferometer

NASA Astrophysics Data System (ADS)

Rong, Piao; Zhang, Chunmin; Yan, Tingyu; Liu, Dongdong; Li, Yanfen

2017-02-01

As an important part of the earth, atmosphere plays a vital role in filtering the solar radiation, adjusting the temperature and organizing the water circulation and keeping human survival. The passive atmospheric wind measurement is based on the imaging interferometer technology and Doppler effect of electromagnetic wave. By using the wind imaging interferometer to get four interferograms of airglow emission lines, the atmospheric wind velocity, temperature, pressure and emission rate can be derived. Exploring the multi-functional and integrated innovation of detecting wind temperature, wind velocity and trace gas has become a research focus in the field. In the present paper, the impact factors of the fixed optical path difference(OPD) of near infrared wind imaging interferometer(NIWII) are analyzed and the optimum value of the fixed optical path difference is simulated, yielding the optimal results of the fixed optical path difference is 20 cm in near infrared wave band (the O2(a1Δg) airglow emission at 1.27 microns). This study aims at providing theoretical basis and technical support for the detection of stratosphere near infrared wind field and giving guidance for the design and development of near infrared wind imaging interferometer.

Quantum correlation in degenerate optical parametric oscillators with mutual injections

NASA Astrophysics Data System (ADS)

Takata, Kenta; Marandi, Alireza; Yamamoto, Yoshihisa

2015-10-01

We theoretically and numerically study the quantum dynamics of two degenerate optical parametric oscillators with mutual injections. The cavity mode in the optical coupling path between the two oscillator facets is explicitly considered. Stochastic equations for the oscillators and mutual injection path based on the positive P representation are derived. The system of two gradually pumped oscillators with out-of-phase mutual injections is simulated, and its quantum state is investigated. When the incoherent loss of the oscillators other than the mutual injections is small, the squeezed quadratic amplitudes p ̂ in the oscillators are positively correlated near the oscillation threshold. It indicates finite quantum correlation, estimated via Gaussian quantum discord, and the entanglement between the intracavity subharmonic fields. When the loss in the injection path is low, each oscillator around the phase transition point forms macroscopic superposition even under a small pump noise. It suggests that the squeezed field stored in the low-loss injection path weakens the decoherence in the oscillators.

Predictions of first passage times in sparse discrete fracture networks using graph-based reductions

NASA Astrophysics Data System (ADS)

Hyman, J.; Hagberg, A.; Srinivasan, G.; Mohd-Yusof, J.; Viswanathan, H. S.

2017-12-01

We present a graph-based methodology to reduce the computational cost of obtaining first passage times through sparse fracture networks. We derive graph representations of generic three-dimensional discrete fracture networks (DFNs) using the DFN topology and flow boundary conditions. Subgraphs corresponding to the union of the k shortest paths between the inflow and outflow boundaries are identified and transport on their equivalent subnetworks is compared to transport through the full network. The number of paths included in the subgraphs is based on the scaling behavior of the number of edges in the graph with the number of shortest paths. First passage times through the subnetworks are in good agreement with those obtained in the full network, both for individual realizations and in distribution. Accurate estimates of first passage times are obtained with an order of magnitude reduction of CPU time and mesh size using the proposed method.

Predictions of first passage times in sparse discrete fracture networks using graph-based reductions

NASA Astrophysics Data System (ADS)

Hyman, Jeffrey D.; Hagberg, Aric; Srinivasan, Gowri; Mohd-Yusof, Jamaludin; Viswanathan, Hari

2017-07-01

We present a graph-based methodology to reduce the computational cost of obtaining first passage times through sparse fracture networks. We derive graph representations of generic three-dimensional discrete fracture networks (DFNs) using the DFN topology and flow boundary conditions. Subgraphs corresponding to the union of the k shortest paths between the inflow and outflow boundaries are identified and transport on their equivalent subnetworks is compared to transport through the full network. The number of paths included in the subgraphs is based on the scaling behavior of the number of edges in the graph with the number of shortest paths. First passage times through the subnetworks are in good agreement with those obtained in the full network, both for individual realizations and in distribution. Accurate estimates of first passage times are obtained with an order of magnitude reduction of CPU time and mesh size using the proposed method.

Development of large field-of-view two photon microscopy for imaging mouse cortex (Conference Presentation)

NASA Astrophysics Data System (ADS)

Bumstead, Jonathan; Côté, Daniel C.; Culver, Joseph P.

2017-02-01

Spontaneous neuronal activity has been measured at cellular resolution in mice, zebrafish, and C. elegans using optical sectioning microscopy techniques, such as light sheet microscopy (LSM) and two photon microscopy (TPM). Recent improvements in these modalities and genetically encoded calcium indicators (GECI's) have enabled whole brain imaging of calcium dynamics in zebrafish and C. elegans. However, these whole brain microscopy studies have not been extended to mice due to the limited field of view (FOV) of TPM and the cumbersome geometry of LSM. Conventional TPM is restricted to diffraction limited imaging over this small FOV (around 500 x 500 microns) due to the use of high magnification objectives (e.g. 1.0 NA; 20X) and the aberrations introduced by relay optics used in scanning the beam across the sample. To overcome these limitations, we have redesigned the entire optical path of the two photon microscope (scanning optics and objective lens) to support a field of view of Ø7 mm with relatively high spatial resolution (<10 microns). Using optical engineering software Zemax, we designed our system with commercially available optics that minimize astigmatism, field curvature, chromatic focal shift, and vignetting. Performance of the system was also tested experimentally with fluorescent beads in agarose, fixed samples, and in vivo structural imaging. Our large-FOV TPM provides a modality capable of studying distributed brain networks in mice at cellular resolution.

Topological Vulnerability Analysis

NASA Astrophysics Data System (ADS)

Jajodia, Sushil; Noel, Steven

Traditionally, network administrators rely on labor-intensive processes for tracking network configurations and vulnerabilities. This requires a great deal of expertise, and is error prone because of the complexity of networks and associated security data. The interdependencies of network vulnerabilities make traditional point-wise vulnerability analysis inadequate. We describe a Topological Vulnerability Analysis (TVA) approach that analyzes vulnerability dependencies and shows all possible attack paths into a network. From models of the network vulnerabilities and potential attacker exploits, we compute attack graphs that convey the impact of individual and combined vulnerabilities on overall security. TVA finds potential paths of vulnerability through a network, showing exactly how attackers may penetrate a network. From this, we identify key vulnerabilities and provide strategies for protection of critical network assets.

Novel Diffusivity Measurement Technique

NASA Technical Reports Server (NTRS)

Rashidnia, Nasser

2001-01-01

A common-path interferometer (CPI) system was developed to measure the diffusivity of liquid pairs. The CPI is an optical technique that can be used to measure changes in the gradient of the refraction index of transparent materials. This system uses a shearing interferometer that shares the same optical path from a laser light source to the final imaging plane. Hence, the molecular diffusion coefficient of liquids can be determined using the physical relations between changes in the optical path length and the liquid phase properties. The data obtained with this interferometer were compared with similar results from other techniques and demonstrated that the instrument is superior in measuring the diffusivity of miscible liquids while keeping the system very compact and robust. CPI can also be used for studies in interface dynamics and other diffusion-dominated-process applications.

Monitoring of vapor phase polycyclic aromatic hydrocarbons

DOEpatents

Vo-Dinh, Tuan; Hajaligol, Mohammad R.

2004-06-01

An apparatus for monitoring vapor phase polycyclic aromatic hydrocarbons in a high-temperature environment has an excitation source producing electromagnetic radiation, an optical path having an optical probe optically communicating the electromagnetic radiation received at a proximal end to a distal end, a spectrometer or polychromator, a detector, and a positioner coupled to the first optical path. The positioner can slidably move the distal end of the optical probe to maintain the distal end position with respect to an area of a material undergoing combustion. The emitted wavelength can be directed to a detector in a single optical probe 180.degree. backscattered configuration, in a dual optical probe 180.degree. backscattered configuration or in a dual optical probe 90.degree. side scattered configuration. The apparatus can be used to monitor an emitted wavelength of energy from a polycyclic aromatic hydrocarbon as it fluoresces in a high temperature environment.

Scanning optical microscope with long working distance objective

DOEpatents

Cloutier, Sylvain G.

2010-10-19

A scanning optical microscope, including: a light source to generate a beam of probe light; collimation optics to substantially collimate the probe beam; a probe-result beamsplitter; a long working-distance, infinity-corrected objective; scanning means to scan a beam spot of the focused probe beam on or within a sample; relay optics; and a detector. The collimation optics are disposed in the probe beam. The probe-result beamsplitter is arranged in the optical paths of the probe beam and the resultant light from the sample. The beamsplitter reflects the probe beam into the objective and transmits resultant light. The long working-distance, infinity-corrected objective is also arranged in the optical paths of the probe beam and the resultant light. It focuses the reflected probe beam onto the sample, and collects and substantially collimates the resultant light. The relay optics are arranged to relay the transmitted resultant light from the beamsplitter to the detector.

Understanding and applying open-path optical sensing data

NASA Astrophysics Data System (ADS)

Virag, Peter; Kricks, Robert J.

1999-02-01

During the last 10 years, open-path air monitors have evolved to yield reliable and effective measurements of single and multiple compounds on a real-time basis. To many individuals within the optical remote sensing community, the attributes of open-path and its the potential uses seem unlimited. Then why has the market has been stagnant for the last few years? The reason may center on how open-path information is applied and how well the end user understands that information. We constantly try to compare open-path data to risk/health or safety levels that are based for use at a single point and for a specific averaging period often far longer than a typical open-path data point. Often this approach is perceived as putting a square peg in a round hole. This perception may be well founded, as open-path data at times may need to go through extensive data manipulation and assumptions before it can be applied. This paper will review pervious open-path monitoring programs and their success in applying the data collected. We will also look at how open-path data is being currently used, some previous pitfalls in data use, alternate methods of data interpretation, and how open-path data can be best practically applied to fit current needs.

Real-time video streaming using H.264 scalable video coding (SVC) in multihomed mobile networks: a testbed approach

NASA Astrophysics Data System (ADS)

Nightingale, James; Wang, Qi; Grecos, Christos

2011-03-01

Users of the next generation wireless paradigm known as multihomed mobile networks expect satisfactory quality of service (QoS) when accessing streamed multimedia content. The recent H.264 Scalable Video Coding (SVC) extension to the Advanced Video Coding standard (AVC), offers the facility to adapt real-time video streams in response to the dynamic conditions of multiple network paths encountered in multihomed wireless mobile networks. Nevertheless, preexisting streaming algorithms were mainly proposed for AVC delivery over multipath wired networks and were evaluated by software simulation. This paper introduces a practical, hardware-based testbed upon which we implement and evaluate real-time H.264 SVC streaming algorithms in a realistic multihomed wireless mobile networks environment. We propose an optimised streaming algorithm with multi-fold technical contributions. Firstly, we extended the AVC packet prioritisation schemes to reflect the three-dimensional granularity of SVC. Secondly, we designed a mechanism for evaluating the effects of different streamer 'read ahead window' sizes on real-time performance. Thirdly, we took account of the previously unconsidered path switching and mobile networks tunnelling overheads encountered in real-world deployments. Finally, we implemented a path condition monitoring and reporting scheme to facilitate the intelligent path switching. The proposed system has been experimentally shown to offer a significant improvement in PSNR of the received stream compared with representative existing algorithms.

Allocation of spectral and spatial modes in multidimensional metro-access optical networks

NASA Astrophysics Data System (ADS)

Gao, Wenbo; Cvijetic, Milorad

2018-04-01

Introduction of spatial division multiplexing (SDM) has added a new dimension in an effort to increase optical fiber channel capacity. At the same time, it can also be explored as an advanced optical networking tool. In this paper, we have investigated the resource allocation to end-users in multidimensional networking structure with plurality of spectral and spatial modes actively deployed in different networking segments. This presents a more comprehensive method as compared to the common practice where the segments of optical network are analyzed independently since the interaction between network hierarchies is included into consideration. We explored the possible transparency from the metro/core network to the optical access network, analyzed the potential bottlenecks from the network architecture perspective, and identified an optimized network structure. In our considerations, the viability of optical grooming through the entire hierarchical all-optical network is investigated by evaluating the effective utilization and spectral efficiency of the network architecture.

Quantifying Cell Fate Decisions for Differentiation and Reprogramming of a Human Stem Cell Network: Landscape and Biological Paths

PubMed Central

Li, Chunhe; Wang, Jin

2013-01-01

Cellular reprogramming has been recently intensively studied experimentally. We developed a global potential landscape and kinetic path framework to explore a human stem cell developmental network composed of 52 genes. We uncovered the underlying landscape for the stem cell network with two basins of attractions representing stem and differentiated cell states, quantified and exhibited the high dimensional biological paths for the differentiation and reprogramming process, connecting the stem cell state and differentiated cell state. Both the landscape and non-equilibrium curl flux determine the dynamics of cell differentiation jointly. Flux leads the kinetic paths to be deviated from the steepest descent gradient path, and the corresponding differentiation and reprogramming paths are irreversible. Quantification of paths allows us to find out how the differentiation and reprogramming occur and which important states they go through. We show the developmental process proceeds as moving from the stem cell basin of attraction to the differentiation basin of attraction. The landscape topography characterized by the barrier heights and transition rates quantitatively determine the global stability and kinetic speed of cell fate decision process for development. Through the global sensitivity analysis, we provided some specific predictions for the effects of key genes and regulation connections on the cellular differentiation or reprogramming process. Key links from sensitivity analysis and biological paths can be used to guide the differentiation designs or reprogramming tactics. PMID:23935477

Path Searching Based Fault Automated Recovery Scheme for Distribution Grid with DG

NASA Astrophysics Data System (ADS)

Xia, Lin; Qun, Wang; Hui, Xue; Simeng, Zhu

2016-12-01

Applying the method of path searching based on distribution network topology in setting software has a good effect, and the path searching method containing DG power source is also applicable to the automatic generation and division of planned islands after the fault. This paper applies path searching algorithm in the automatic division of planned islands after faults: starting from the switch of fault isolation, ending in each power source, and according to the line load that the searching path traverses and the load integrated by important optimized searching path, forming optimized division scheme of planned islands that uses each DG as power source and is balanced to local important load. Finally, COBASE software and distribution network automation software applied are used to illustrate the effectiveness of the realization of such automatic restoration program.

Cloud Droplet Size and Liquid Water Path Retrievals From Zenith Radiance Measurements: Examples From the Atmospheric Radiation Measurement Program and the Aerosol Robotic Network

NASA Technical Reports Server (NTRS)

Chiu, J. C.; Marshak, A.; Huang, C.-H.; Varnai, T.; Hogan, R. J.; Giles, D. M.; Holben, B. N.; Knyazikhin, Y.; O'Connor, E. J.; Wiscombe, W. J.

2012-01-01

The ground-based Atmospheric Radiation Measurement Program (ARM) and NASA Aerosol Robotic Network (AERONET) routinely monitor clouds using zenith radiances at visible and near-infrared wavelengths. Using the transmittance calculated from such measurements, we have developed a new retrieval method for cloud effective droplet size and conducted extensive tests for non-precipitating liquid water clouds. The underlying principle is to combine a water-absorbing wavelength (i.e. 1640 nm) with a nonwater-absorbing wavelength for acquiring information on cloud droplet size and optical depth. For simulated stratocumulus clouds with liquid water path less than 300 g/sq m and horizontal resolution of 201m, the retrieval method underestimates the mean effective radius by 0.8 m, with a root-mean-squared error of 1.7 m and a relative deviation of 13 %. For actual observations with a liquid water path less than 450 gm.2 at the ARM Oklahoma site during 2007-2008, our 1.5 min-averaged retrievals are generally larger by around 1 m than those from combined ground-based cloud radar and microwave radiometer at a 5min temporal resolution. We also compared our retrievals to those from combined shortwave flux and microwave observations for relatively homogeneous clouds, showing that the bias between these two retrieval sets is negligible, but the error of 2.6 m and the relative deviation of 22% are larger than those found in our simulation case. Finally, the transmittance-based cloud effective droplet radii agree to better than 11% with satellite observations and have a negative bias of 1 m. Overall, the retrieval method provides reasonable cloud effective radius estimates, which can enhance the cloud products of both ARM and AERONET.

Energy-Efficient Next-Generation Passive Optical Networks Based on Sleep Mode and Heuristic Optimization

NASA Astrophysics Data System (ADS)

Zulai, Luis G. T.; Durand, Fábio R.; Abrão, Taufik

2015-05-01

In this article, an energy-efficiency mechanism for next-generation passive optical networks is investigated through heuristic particle swarm optimization. Ten-gigabit Ethernet-wavelength division multiplexing optical code division multiplexing-passive optical network next-generation passive optical networks are based on the use of a legacy 10-gigabit Ethernet-passive optical network with the advantage of using only an en/decoder pair of optical code division multiplexing technology, thus eliminating the en/decoder at each optical network unit. The proposed joint mechanism is based on the sleep-mode power-saving scheme for a 10-gigabit Ethernet-passive optical network, combined with a power control procedure aiming to adjust the transmitted power of the active optical network units while maximizing the overall energy-efficiency network. The particle swarm optimization based power control algorithm establishes the optimal transmitted power in each optical network unit according to the network pre-defined quality of service requirements. The objective is controlling the power consumption of the optical network unit according to the traffic demand by adjusting its transmitter power in an attempt to maximize the number of transmitted bits with minimum energy consumption, achieving maximal system energy efficiency. Numerical results have revealed that it is possible to save 75% of energy consumption with the proposed particle swarm optimization based sleep-mode energy-efficiency mechanism compared to 55% energy savings when just a sleeping-mode-based mechanism is deployed.

Report of the Interagency Optical Network Testbeds Workshop 2, NASA Ames Research Center, September 12-14, 2005

NASA Technical Reports Server (NTRS)

2005-01-01

The Optical Network Testbeds Workshop 2 (ONT2), held on September 12-14, 2005, was cosponsored by the Department of Energy Office of Science (DOE/SC) and the National Aeronautics and Space Administration (NASA), in cooperation with the Joint Engineering Team (JET) of the Federal Networking and Information Technology Research and Development (NITRD) Program's Large Scale Networking (LSN) Coordinating Group. The ONT2 workshop was a follow-on to an August 2004 Workshop on Optical Network Testbeds (ONT1). ONT1 recommended actions by the Federal agencies to assure timely development and implementation of optical networking technologies and infrastructure. Hosted by the NASA Ames Research Center in Mountain View, California, the ONT2 workshop brought together representatives of the U.S. advanced research and education (R&E) networks, regional optical networks (RONs), service providers, international networking organizations, and senior engineering and R&D managers from Federal agencies and national research laboratories. Its purpose was to develop a common vision of the optical network technologies, services, infrastructure, and organizations needed to enable widespread use of optical networks; recommend activities for transitioning the optical networking research community and its current infrastructure to leading-edge optical networks over the next three to five years; and present information enabling commercial network infrastructure providers to plan for and use leading-edge optical network services in that time frame.

Multi-access laser communications terminal

NASA Technical Reports Server (NTRS)

1992-01-01

The Optical Multi-Access (OMA) Terminal is capable of establishing up to six simultaneous high-data-rate communication links between low-Earth-orbit satellites and a host satellite at synchronous orbit with only one 16-inch-diameter antenna on the synchronous satellite. The advantage over equivalent RF systems in space weight, power, and swept volume is great when applied to NASA satellite communications networks. A photograph of the 3-channel prototype constructed under the present contract to demonstrate the feasibility of the concept is presented. The telescope has a 10-inch clear aperture and a 22 deg full field of view. It consists of 4 refractive elements to achieve a telecentric focus, i.e., the focused beam is normal to the focal plane at all field angles. This feature permits image pick-up optics in the focal plane to track satellite images without tilting their optic axes to accommodate field angle. The geometry of the imager-pick-up concept and the coordinate system of the swinging arm and disk mechanism for image pick-up are shown. Optics in the arm relay the telescope focus to a communications and tracking receiver and introduce the transmitted beacon beam on a path collinear with the receive path. The electronic circuits for the communications and tracking receivers are contained on the arm and disk assemblies and relay signals to an associated PC-based operator's console for control of the arm and disk motor drive through a flexible cable which permits +/- 240 deg travel for each arm and disk assembly. Power supplies and laser transmitters are mounted in the cradle for the telescope. A single-mode fiber in the cable is used to carry the laser transmitter signal to the arm optics. The promise of the optical multi-access terminal towards which the prototype effort worked is shown. The emphasis in the prototype development was the demonstration of the unique aspect of the concept, and where possible, cost avoidance compromises were implemented in areas already proven on other programs. The design details are described in section 2, the prototype test results in section 3, additional development required in section 4, and conclusions in section 5.

Estimating nocturnal opaque ice cloud optical depth from MODIS multispectral infrared radiances using a neural network method

NASA Astrophysics Data System (ADS)

Minnis, Patrick; Hong, Gang; Sun-Mack, Szedung; Smith, William L.; Chen, Yan; Miller, Steven D.

2016-05-01

Retrieval of ice cloud properties using IR measurements has a distinct advantage over the visible and near-IR techniques by providing consistent monitoring regardless of solar illumination conditions. Historically, the IR bands at 3.7, 6.7, 11.0, and 12.0 µm have been used to infer ice cloud parameters by various methods, but the reliable retrieval of ice cloud optical depth τ is limited to nonopaque cirrus with τ < 8. The Ice Cloud Optical Depth from Infrared using a Neural network (ICODIN) method is developed in this paper by training Moderate Resolution Imaging Spectroradiometer (MODIS) radiances at 3.7, 6.7, 11.0, and 12.0 µm against CloudSat-estimated τ during the nighttime using 2 months of matched global data from 2007. An independent data set comprising observations from the same 2 months of 2008 was used to validate the ICODIN. One 4-channel and three 3-channel versions of the ICODIN were tested. The training and validation results show that IR channels can be used to estimate ice cloud τ up to 150 with correlations above 78% and 69% for all clouds and only opaque ice clouds, respectively. However, τ for the deepest clouds is still underestimated in many instances. The corresponding RMS differences relative to CloudSat are ~100 and ~72%. If the opaque clouds are properly identified with the IR methods, the RMS differences in the retrieved optical depths are ~62%. The 3.7 µm channel appears to be most sensitive to optical depth changes but is constrained by poor precision at low temperatures. A method for estimating total optical depth is explored for estimation of cloud water path in the future. Factors affecting the uncertainties and potential improvements are discussed. With improved techniques for discriminating between opaque and semitransparent ice clouds, the method can ultimately improve cloud property monitoring over the entire diurnal cycle.

APPLYING OPEN-PATH OPTICAL SPECTROSCOPY TO HEAVY-DUTY DIESEL EMISSIONS

EPA Science Inventory

Non-dispersive infrared absorption has been used to measure gaseous emissions for both stationary and mobile sources. Fourier transform infrared spectroscopy has been used for stationary sources as both extractive and open-path methods. We have applied the open-path method for bo...

Optical remote diagnostics of atmospheric propagating beams of ionizing radiation

DOEpatents

Karl JR., Robert R.

1990-03-06

Data is obtained for use in diagnosing the characteristics of a beam of ionizing radiation, such as charged particle beams, neutral particle beams, and gamma ray beams. In one embodiment the beam is emitted through the atmosphere and produces nitrogen fluorescence during passage through air. The nitrogen fluorescence is detected along the beam path to provide an intensity from which various beam characteristics can be calculated from known tabulations. Optical detecting equipment is preferably located orthogonal to the beam path at a distance effective to include the entire beam path in the equipment field of view.

Optical remote diagnostics of atmospheric propagating beams of ionizing radiation

DOEpatents

Karl, Jr., Robert R.

1990-01-01

Data is obtained for use in diagnosing the characteristics of a beam of ionizing radiation, such as charged particle beams, neutral particle beams, and gamma ray beams. In one embodiment the beam is emitted through the atmosphere and produces nitrogen fluorescence during passage through air. The nitrogen fluorescence is detected along the beam path to provide an intensity from which various beam characteristics can be calculated from known tabulations. Optical detecting equipment is preferably located orthogonal to the beam path at a distance effective to include the entire beam path in the equipment field of view.

Resonant optical scattering in nanoparticle-doped polymer photonic crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baumberg, J. J.; Pursiainen, O. L.; Spahn, P.

2009-11-15

A broadband hyperspectral technique is used to measure the coherent optical backscatter across a wide spectral bandwidth, showing the resonant suppression of the photon transport mean free path around the photonic bandgap of a shear-assembled polymer photonic crystal. By doping with carbon nanoscale scatterers that reside at specific points within the photonic crystal lattice, the ratio between photon mean free path and optical penetration is tuned from 10 to 1, enhancing forward scatter at the expense of back-scatter. The back-scattering strength of different polarisations is not explained by any current theory.

Reflection-induced linear polarization rotation and phase modulation between orthogonal waves for refractive index variation measurement.

PubMed

Twu, Ruey-Ching; Wang, Jhao-Sheng

2016-04-01

An optical phase interrogation is proposed to study reflection-induced linear polarization rotation in a common-path homodyne interferometer. This optical methodology can also be applied to the measurement of the refractive index variation of a liquid solution. The performance of the refractive index sensing structure is discussed theoretically, and the experimental results demonstrated a very good ability based on the proposed schemes. Compared with a conventional common-path heterodyne interferometer, the proposed homodyne interferometer with only a single channel reduced the usage of optic elements.

Why Does Mptcp Have To Make Things So Complicated : Cross Path Nids Evasion And Countermeasures

DTIC Science & Technology

2016-09-01

previously only establish communication channels over single network paths to communicate over multiple network paths. MPTCP is an enhancement toTCP that...the attacker would fail to create a Command and Control (C2) channel unless the attacker had created a new mapping to the target on the splicing...machine. This would allow the attacker to conduct C2 over a spliced channel . This may even make the attacker’s C2 more evasive. In fact, the effect

Periscopic Spine Surgery

DTIC Science & Technology

2005-03-01

Guided Technologies, Boulder, CO; motion path built from three orthogonal sinusoidal paths is Optotrak , Northern Digital, Waterloo, ON) optical tracking...Hopkins University using an Optotrak to evaluate the simulated motions. The Optotrak (Northern Digital, Inc.) is an optical high- precision 3-D motion...verify the accuracy of the RMS, tests were carried out using the Optotrak , which was placed about 2 m from the simulator. For each test, two sets of data

High frequency modulation circuits based on photoconductive wide bandgap switches

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sampayan, Stephen

Methods, systems, and devices for high voltage and/or high frequency modulation. In one aspect, an optoelectronic modulation system includes an array of two or more photoconductive switch units each including a wide bandgap photoconductive material coupled between a first electrode and a second electrode, a light source optically coupled to the WBGP material of each photoconductive switch unit via a light path, in which the light path splits into multiple light paths to optically interface with each WBGP material, such that a time delay of emitted light exists along each subsequent split light path, and in which the WBGP materialmore » conducts an electrical signal when a light signal is transmitted to the WBGP material, and an output to transmit the electrical signal conducted by each photoconductive switch unit. The time delay of the photons emitted through the light path is substantially equivalent to the time delay of the electrical signal.« less

Method and apparatus for routing data in an inter-nodal communications lattice of a massively parallel computer system by employing bandwidth shells at areas of overutilization

DOEpatents

Archer, Charles Jens; Musselman, Roy Glenn; Peters, Amanda; Pinnow, Kurt Walter; Swartz, Brent Allen; Wallenfelt, Brian Paul

2010-04-27

A massively parallel computer system contains an inter-nodal communications network of node-to-node links. An automated routing strategy routes packets through one or more intermediate nodes of the network to reach a final destination. The default routing strategy is altered responsive to detection of overutilization of a particular path of one or more links, and at least some traffic is re-routed by distributing the traffic among multiple paths (which may include the default path). An alternative path may require a greater number of link traversals to reach the destination node.

Path selection rules for droplet trains in single-lane microfluidic networks

NASA Astrophysics Data System (ADS)

Amon, A.; Schmit, A.; Salkin, L.; Courbin, L.; Panizza, P.

2013-07-01

We investigate the transport of periodic trains of droplets through microfluidic networks having one inlet, one outlet, and nodes consisting of T junctions. Variations of the dilution of the trains, i.e., the distance between drops, reveal the existence of various hydrodynamic regimes characterized by the number of preferential paths taken by the drops. As the dilution increases, this number continuously decreases until only one path remains explored. Building on a continuous approach used to treat droplet traffic through a single asymmetric loop, we determine selection rules for the paths taken by the drops and we predict the variations of the fraction of droplets taking these paths with the parameters at play including the dilution. Our results show that as dilution decreases, the paths are selected according to the ascending order of their hydrodynamic resistance in the absence of droplets. The dynamics of these systems controlled by time-delayed feedback is complex: We observe a succession of periodic regimes separated by a wealth of bifurcations as the dilution is varied. In contrast to droplet traffic in single asymmetric loops, the dynamical behavior in networks of loops is sensitive to initial conditions because of extra degrees of freedom.

Analysis of blocking probability for OFDM-based variable bandwidth optical network

NASA Astrophysics Data System (ADS)

Gong, Lei; Zhang, Jie; Zhao, Yongli; Lin, Xuefeng; Wu, Yuyao; Gu, Wanyi

2011-12-01

Orthogonal Frequency Division Multiplexing (OFDM) has recently been proposed as a modulation technique. For optical networks, because of its good spectral efficiency, flexibility, and tolerance to impairments, optical OFDM is much more flexible compared to traditional WDM systems, enabling elastic bandwidth transmissions, and optical networking is the future trend of development. In OFDM-based optical network the research of blocking rate has very important significance for network assessment. Current research for WDM network is basically based on a fixed bandwidth, in order to accommodate the future business and the fast-changing development of optical network, our study is based on variable bandwidth OFDM-based optical networks. We apply the mathematical analysis and theoretical derivation, based on the existing theory and algorithms, research blocking probability of the variable bandwidth of optical network, and then we will build a model for blocking probability.

Experimental demonstration of a quantum router

PubMed Central

Yuan, X. X.; Ma, J.-J.; Hou, P.-Y.; Chang, X.-Y.; Zu, C.; Duan, L.-M.

2015-01-01

The router is a key element for a network. We describe a scheme to realize genuine quantum routing of single-photon pulses based on cascading of conditional quantum gates in a Mach-Zehnder interferometer and report a proof-of-principle experiment for its demonstration using linear optics quantum gates. The polarization of the control photon routes in a coherent way the path of the signal photon while preserving the qubit state of the signal photon represented by its polarization. We demonstrate quantum nature of this router by showing entanglement generated between the initially unentangled control and signal photons, and confirm that the qubit state of the signal photon is well preserved by the router through quantum process tomography. PMID:26197928

Current-Sensitive Path Planning for an Underactuated Free-Floating Ocean Sensorweb

NASA Technical Reports Server (NTRS)

Dahl, Kristen P.; Thompson, David R.; McLaren, David; Chao, Yi; Chien, Steve

2011-01-01

This work investigates multi-agent path planning in strong, dynamic currents using thousands of highly under-actuated vehicles. We address the specific task of path planning for a global network of ocean-observing floats. These submersibles are typified by the Argo global network consisting of over 3000 sensor platforms. They can control their buoyancy to float at depth for data collection or rise to the surface for satellite communications. Currently, floats drift at a constant depth regardless of the local currents. However, accurate current forecasts have become available which present the possibility of intentionally controlling floats' motion by dynamically commanding them to linger at different depths. This project explores the use of these current predictions to direct float networks to some desired final formation or position. It presents multiple algorithms for such path optimization and demonstrates their advantage over the standard approach of constant-depth drifting.

Pseudo paths towards minimum energy states in network dynamics

NASA Astrophysics Data System (ADS)

Hedayatifar, L.; Hassanibesheli, F.; Shirazi, A. H.; Vasheghani Farahani, S.; Jafari, G. R.

2017-10-01

The dynamics of networks forming on Heider balance theory moves towards lower tension states. The condition derived from this theory enforces agents to reevaluate and modify their interactions to achieve equilibrium. These possible changes in network's topology can be considered as various paths that guide systems to minimum energy states. Based on this theory the final destination of a system could reside on a local minimum energy, ;jammed state;, or the global minimum energy, balanced states. The question we would like to address is whether jammed states just appear by chance? Or there exist some pseudo paths that bound a system towards a jammed state. We introduce an indicator to suspect the location of a jammed state based on the Inverse Participation Ratio method (IPR). We provide a margin before a local minimum where the number of possible paths dramatically drastically decreases. This is a condition that proves adequate for ending up on a jammed states.

AERONET-Based Nonspherical Dust Optical Models and Effects on the VIIRS Deep Blue/SOAR Over Water Aerosol Product

NASA Astrophysics Data System (ADS)

Lee, Jaehwa; Hsu, N. Christina; Sayer, Andrew M.; Bettenhausen, Corey; Yang, Ping

2017-10-01

Aerosol Robotic Network (AERONET)-based nonspherical dust optical models are developed and applied to the Satellite Ocean Aerosol Retrieval (SOAR) algorithm as part of the Version 1 Visible Infrared Imaging Radiometer Suite (VIIRS) NASA "Deep Blue" aerosol data product suite. The optical models are created using Version 2 AERONET inversion data at six distinct sites influenced frequently by dust aerosols from different source regions. The same spheroid shape distribution as used in the AERONET inversion algorithm is assumed to account for the nonspherical characteristics of mineral dust, which ensures the consistency between the bulk scattering properties of the developed optical models and the AERONET-retrieved microphysical and optical properties. For the Version 1 SOAR aerosol product, the dust optical model representative for Capo Verde site is used, considering the strong influence of Saharan dust over the global ocean in terms of amount and spatial coverage. Comparisons of the VIIRS-retrieved aerosol optical properties against AERONET direct-Sun observations at five island/coastal sites suggest that the use of nonspherical dust optical models significantly improves the retrievals of aerosol optical depth (AOD) and Ångström exponent by mitigating the well-known artifact of scattering angle dependence of the variables, which is observed when incorrectly assuming spherical dust. The resulting removal of these artifacts results in a more natural spatial pattern of AOD along the transport path of Saharan dust to the Atlantic Ocean; that is, AOD decreases with increasing distance transported, whereas the spherical assumption leads to a strong wave pattern due to the spurious scattering angle dependence of AOD.

Robot-assisted three-dimensional registration for cochlear implant surgery using a common-path swept-source optical coherence tomography probe

NASA Astrophysics Data System (ADS)

Gurbani, Saumya S.; Wilkening, Paul; Zhao, Mingtao; Gonenc, Berk; Cheon, Gyeong Woo; Iordachita, Iulian I.; Chien, Wade; Taylor, Russell H.; Niparko, John K.; Kang, Jin U.

2014-05-01

Cochlear implantation offers the potential to restore sensitive hearing in patients with severe to profound deafness. However, surgical placement of the electrode array within the cochlea can produce trauma to sensorineural components, particularly if the initial turn of the cochlea is not successfully navigated as the array is advanced. In this work, we present a robot-mounted common-path swept-source optical coherence tomography endoscopic platform for three-dimensional (3-D) optical coherence tomography (OCT) registration and preoperative surgical planning for cochlear implant surgery. The platform is composed of a common-path 600-μm diameter fiber optic rotary probe attached to a five degrees of freedom robot capable of 1 μm precision movement. The system is tested on a dry fixed ex vivo human temporal bone, and we demonstrate the feasibility of a 3-D OCT registration of the cochlea to accurately describe the spatial and angular profiles of the canal formed by the scala tympani into the first cochlear turn.

Noninvasive imaging of oral mucosae with optical coherence tomography

NASA Astrophysics Data System (ADS)

Lee, Cheng-Yu; Chen, Wei-Chuan; Tsai, Meng-Tsan

2017-04-01

In this study, a swept-source optical coherence tomography (OCT) system is developed for in vivo visualization of structural and vascular morphology oral mucosa. For simplification of optical probe fabrication, probe weight, and system setup, the body of the scanning probe is fabricated by a 3D printer to fix the optical components and the mechanical scanning device, and a partially reflective slide is attached at the output end of probe to achieve a common-path configuration. Aside from providing the ability of 3D structural imaging with the developed system, 3D vascular images of oral mucosa can be simultaneously obtained. Then, different locations of oral mucosa are scanned with common-path OCT. The results show that epithelium and lamina propria layers as well as fungiform papilla can be identified and microvascular images can be acquired. With the proposed probe, the system cost and volume can be greatly reduced. Experimental results indicate that such common-path OCT system could be further implemented for oral cancer diagnosis.

Laser modulator for LISA pathfinder

NASA Astrophysics Data System (ADS)

Voland, C.; Lund, G.; Coppoolse, W.; Crosby, P.; Stadler, M.; Kudielka, K.; Özkan, C.

2017-11-01

LISA Pathfinder is an ESA experiment to demonstrate the key technologies needed for the LISA mission to detect gravitational waves in space. The LISA Pathfinder spacecraft represents one arm of the LISA interferometer, containing an optical metrology system and two proof masses as inertial references for the drag-free control system. The LISA Pathfinder payload consists of two drag-free floating test masses located in the inertial sensors with their control electronics and an optical metrology subsystem. The optical metrology subsystem monitors the movement of both test masses relative to each other and to the spacecraft with very high sensitivity and resolution. This is achieved with a heterodyne Mach- Zehnder interferometer. This interferometer requires as input two coherent laser beams with a heterodyne frequency difference of a few kHz. To generate the two laser beams with a heterodyne frequency difference a Nd:YAG laser is used together with the Laser Modulator. The Nd:YAG laser generates a single coherent laser signal at a wavelength of 1064nm which is fibre coupled to the Laser Modulator. The Laser Modulator then generates the two optical beams with the required heterodyne frequency offset. In addition, the Laser Modulator is required to perform laser amplitude stabilization and optical path difference control for the two optical signals. The Laser Modulator consists of an optical unit - the LMU - and RF synthesiser, power amplification and control electronics. These electronics are all housed in the Laser Modulator Electronics (LME). The LMU has four primary functions: • Splitting of the input laser beam into two paths for later superposition in the interferometer. • Applying different frequency shifts to each of the beams. • Providing amplitude modulation control to each of the beams. • Providing active control of the optical path length difference between the two optical paths. The present paper describes the design and performance of the LMU together with a summary of the results of the Laser Modulator engineering model test campaign.

Physarum solver: A biologically inspired method of road-network navigation

NASA Astrophysics Data System (ADS)

Tero, Atsushi; Kobayashi, Ryo; Nakagaki, Toshiyuki

2006-04-01

We have proposed a mathematical model for the adaptive dynamics of the transport network in an amoeba-like organism, the true slime mold Physarum polycephalum. The model is based on physiological observations of this species, but can also be used for path-finding in the complicated networks of mazes and road maps. In this paper, we describe the physiological basis and the formulation of the model, as well as the results of simulations of some complicated networks. The path-finding method used by Physarum is a good example of cellular computation.

Metabolic PathFinding: inferring relevant pathways in biochemical networks.

PubMed

Croes, Didier; Couche, Fabian; Wodak, Shoshana J; van Helden, Jacques

2005-07-01

Our knowledge of metabolism can be represented as a network comprising several thousands of nodes (compounds and reactions). Several groups applied graph theory to analyse the topological properties of this network and to infer metabolic pathways by path finding. This is, however, not straightforward, with a major problem caused by traversing irrelevant shortcuts through highly connected nodes, which correspond to pool metabolites and co-factors (e.g. H2O, NADP and H+). In this study, we present a web server implementing two simple approaches, which circumvent this problem, thereby improving the relevance of the inferred pathways. In the simplest approach, the shortest path is computed, while filtering out the selection of highly connected compounds. In the second approach, the shortest path is computed on the weighted metabolic graph where each compound is assigned a weight equal to its connectivity in the network. This approach significantly increases the accuracy of the inferred pathways, enabling the correct inference of relatively long pathways (e.g. with as many as eight intermediate reactions). Available options include the calculation of the k-shortest paths between two specified seed nodes (either compounds or reactions). Multiple requests can be submitted in a queue. Results are returned by email, in textual as well as graphical formats (available in http://www.scmbb.ulb.ac.be/pathfinding/).

A common-path optical coherence tomography based electrode for structural imaging of nerves and recording of action potentials

NASA Astrophysics Data System (ADS)

Islam, M. Shahidul; Haque, Md. Rezuanul; Oh, Christian M.; Wang, Yan; Park, B. Hyle

2013-03-01

Current technologies for monitoring neural activity either use different variety of electrodes (electrical recording) or require contrast agents introduced exogenously or through genetic modification (optical imaging). Here we demonstrate an optical method for non-contact and contrast agent free detection of nerve activity using phase-resolved optical coherence tomography (pr-OCT). A common-path variation of the pr-OCT is recently implemented and the developed system demonstrated the capability to detect rapid transient structural changes that accompany neural spike propagation. No averaging over multiple trials was required, indicating its capability of single-shot detection of individual impulses from functionally stimulated Limulus optic nerve. The strength of this OCT-based optical electrode is that it is a contactless method and does not require any exogenous contrast agent. With further improvements in accuracy and sensitivity, this optical electrode will play a complementary role to the existing recording technologies in future.

Applications of Temporal Graph Metrics to Real-World Networks

NASA Astrophysics Data System (ADS)

Tang, John; Leontiadis, Ilias; Scellato, Salvatore; Nicosia, Vincenzo; Mascolo, Cecilia; Musolesi, Mirco; Latora, Vito

Real world networks exhibit rich temporal information: friends are added and removed over time in online social networks; the seasons dictate the predator-prey relationship in food webs; and the propagation of a virus depends on the network of human contacts throughout the day. Recent studies have demonstrated that static network analysis is perhaps unsuitable in the study of real world network since static paths ignore time order, which, in turn, results in static shortest paths overestimating available links and underestimating their true corresponding lengths. Temporal extensions to centrality and efficiency metrics based on temporal shortest paths have also been proposed. Firstly, we analyse the roles of key individuals of a corporate network ranked according to temporal centrality within the context of a bankruptcy scandal; secondly, we present how such temporal metrics can be used to study the robustness of temporal networks in presence of random errors and intelligent attacks; thirdly, we study containment schemes for mobile phone malware which can spread via short range radio, similar to biological viruses; finally, we study how the temporal network structure of human interactions can be exploited to effectively immunise human populations. Through these applications we demonstrate that temporal metrics provide a more accurate and effective analysis of real-world networks compared to their static counterparts.

Tracing Technological Development Trajectories: A Genetic Knowledge Persistence-Based Main Path Approach.

PubMed

Park, Hyunseok; Magee, Christopher L

2017-01-01

The aim of this paper is to propose a new method to identify main paths in a technological domain using patent citations. Previous approaches for using main path analysis have greatly improved our understanding of actual technological trajectories but nonetheless have some limitations. They have high potential to miss some dominant patents from the identified main paths; nonetheless, the high network complexity of their main paths makes qualitative tracing of trajectories problematic. The proposed method searches backward and forward paths from the high-persistence patents which are identified based on a standard genetic knowledge persistence algorithm. We tested the new method by applying it to the desalination and the solar photovoltaic domains and compared the results to output from the same domains using a prior method. The empirical results show that the proposed method can dramatically reduce network complexity without missing any dominantly important patents. The main paths identified by our approach for two test cases are almost 10x less complex than the main paths identified by the existing approach. The proposed approach identifies all dominantly important patents on the main paths, but the main paths identified by the existing approach miss about 20% of dominantly important patents.

Tracing Technological Development Trajectories: A Genetic Knowledge Persistence-Based Main Path Approach

PubMed Central

2017-01-01

The aim of this paper is to propose a new method to identify main paths in a technological domain using patent citations. Previous approaches for using main path analysis have greatly improved our understanding of actual technological trajectories but nonetheless have some limitations. They have high potential to miss some dominant patents from the identified main paths; nonetheless, the high network complexity of their main paths makes qualitative tracing of trajectories problematic. The proposed method searches backward and forward paths from the high-persistence patents which are identified based on a standard genetic knowledge persistence algorithm. We tested the new method by applying it to the desalination and the solar photovoltaic domains and compared the results to output from the same domains using a prior method. The empirical results show that the proposed method can dramatically reduce network complexity without missing any dominantly important patents. The main paths identified by our approach for two test cases are almost 10x less complex than the main paths identified by the existing approach. The proposed approach identifies all dominantly important patents on the main paths, but the main paths identified by the existing approach miss about 20% of dominantly important patents. PMID:28135304

Intelligentization: an efficient means to get more from optical networking

NASA Astrophysics Data System (ADS)

Chen, Zhi Yun

2001-10-01

Infocom is a term used to describe the merger of Information and Communications and is used to show the radical changes in today's network traffic. The continuous growth of Infocom traffic, especially that of Internet, is driving Infocom networks to expand rapidly. To service providers, the traffic is consuming the bandwidth of their network. Simultaneously, users are complaining too slow, the net never stopped in China. It is the reality faced by both the service providers and equipment vendors. Demands from both the customers and competition in market call for an efficient network infrastructure. What should a Service Provider do? This paper will first analyze the development trends of optical networking and the formation of the concepts of Intelligent Optical Network (ION) and Automatic Switched Optical Network (ASON) as a solution to this problem. Next it will look at the ways to bring intelligence into optical networks, discussing the benefits to service providers by showing some application examples. Finally, it concludes that the development of optical networking has arrived at a point of introducing intelligence into optical networks. The intelligent optical networks and Automatic Switched Optical Networks will immediately bring a wide range of benefit to service providers, equipment vendors, and, of course, the end users.

Influence of visual path information on human heading perception during rotation.

PubMed

Li, Li; Chen, Jing; Peng, Xiaozhe

2009-03-31

How does visual path information influence people's perception of their instantaneous direction of self-motion (heading)? We have previously shown that humans can perceive heading without direct access to visual path information. Here we vary two key parameters for estimating heading from optic flow, the field of view (FOV) and the depth range of environmental points, to investigate the conditions under which visual path information influences human heading perception. The display simulated an observer traveling on a circular path. Observers used a joystick to rotate their line of sight until deemed aligned with true heading. Four FOV sizes (110 x 94 degrees, 48 x 41 degrees, 16 x 14 degrees, 8 x 7 degrees) and depth ranges (6-50 m, 6-25 m, 6-12.5 m, 6-9 m) were tested. Consistent with our computational modeling results, heading bias increased with the reduction of FOV or depth range when the display provided a sequence of velocity fields but no direct path information. When the display provided path information, heading bias was not influenced as much by the reduction of FOV or depth range. We conclude that human heading and path perception involve separate visual processes. Path helps heading perception when the display does not contain enough optic-flow information for heading estimation during rotation.

Optical network democratization.

PubMed

Nejabati, Reza; Peng, Shuping; Simeonidou, Dimitra

2016-03-06

The current Internet infrastructure is not able to support independent evolution and innovation at physical and network layer functionalities, protocols and services, while at same time supporting the increasing bandwidth demands of evolving and heterogeneous applications. This paper addresses this problem by proposing a completely democratized optical network infrastructure. It introduces the novel concepts of the optical white box and bare metal optical switch as key technology enablers for democratizing optical networks. These are programmable optical switches whose hardware is loosely connected internally and is completely separated from their control software. To alleviate their complexity, a multi-dimensional abstraction mechanism using software-defined network technology is proposed. It creates a universal model of the proposed switches without exposing their technological details. It also enables a conventional network programmer to develop network applications for control of the optical network without specific technical knowledge of the physical layer. Furthermore, a novel optical network virtualization mechanism is proposed, enabling the composition and operation of multiple coexisting and application-specific virtual optical networks sharing the same physical infrastructure. Finally, the optical white box and the abstraction mechanism are experimentally evaluated, while the virtualization mechanism is evaluated with simulation. © 2016 The Author(s).

Teleconnection Paths via Climate Network Direct Link Detection.

PubMed

Zhou, Dong; Gozolchiani, Avi; Ashkenazy, Yosef; Havlin, Shlomo

2015-12-31

Teleconnections describe remote connections (typically thousands of kilometers) of the climate system. These are of great importance in climate dynamics as they reflect the transportation of energy and climate change on global scales (like the El Niño phenomenon). Yet, the path of influence propagation between such remote regions, and weighting associated with different paths, are only partially known. Here we propose a systematic climate network approach to find and quantify the optimal paths between remotely distant interacting locations. Specifically, we separate the correlations between two grid points into direct and indirect components, where the optimal path is found based on a minimal total cost function of the direct links. We demonstrate our method using near surface air temperature reanalysis data, on identifying cross-latitude teleconnections and their corresponding optimal paths. The proposed method may be used to quantify and improve our understanding regarding the emergence of climate patterns on global scales.

High bandwidth underwater optical communication.

PubMed

Hanson, Frank; Radic, Stojan

2008-01-10

We report error-free underwater optical transmission measurements at 1 Gbit/s (10(9) bits/s) over a 2 m path in a laboratory water pipe with up to 36 dB of extinction. The source at 532 nm was derived from a 1064 nm continuous-wave laser diode that was intensity modulated, amplified, and frequency doubled in periodically poled lithium niobate. Measurements were made over a range of extinction by the addition of a Mg(OH)(2) and Al(OH)(3) suspension to the water path, and we were not able to observe any evidence of temporal pulse broadening. Results of Monte Carlo simulations over ocean water paths of several tens of meters indicate that optical communication data rates >1 Gbit/s can be supported and are compatible with high-capacity data transfer applications that require no physical contact.

Characterizing the propagation path in moderate to strong optical turbulence.

PubMed

Vetelino, Frida Strömqvist; Clare, Bradley; Corbett, Kerry; Young, Cynthia; Grant, Kenneth; Andrews, Larry

2006-05-20

In February 2005 a joint atmospheric propagation experiment was conducted between the Australian Defence Science and Technology Organisation and the University of Central Florida. A Gaussian beam was propagated along a horizontal 1500 m path near the ground. Scintillation was measured simultaneously at three receivers of diameters 1, 5, and 13 mm. Scintillation theory combined with a numerical scheme was used to infer the structure constant C2n, the inner scale l0, and the outer scale L0 from the optical measurements. At the same time, C2n measurements were taken by a commercial scintillometer, set up parallel to the optical path. The C2n values from the inferred scheme and the commercial scintillometer predict the same behavior, but the inferred scheme consistently gives slightly smaller C2n values.

Global Coordinates and Exact Aberration Calculations Applied to Physical Optics Modeling of Complex Optical Systems

NASA Astrophysics Data System (ADS)

Lawrence, G.; Barnard, C.; Viswanathan, V.

1986-11-01

Historically, wave optics computer codes have been paraxial in nature. Folded systems could be modeled by "unfolding" the optical system. Calculation of optical aberrations is, in general, left for the analyst to do with off-line codes. While such paraxial codes were adequate for the simpler systems being studied 10 years ago, current problems such as phased arrays, ring resonators, coupled resonators, and grazing incidence optics require a major advance in analytical capability. This paper describes extension of the physical optics codes GLAD and GLAD V to include a global coordinate system and exact ray aberration calculations. The global coordinate system allows components to be positioned and rotated arbitrarily. Exact aberrations are calculated for components in aligned or misaligned configurations by using ray tracing to compute optical path differences and diffraction propagation. Optical path lengths between components and beam rotations in complex mirror systems are calculated accurately so that coherent interactions in phased arrays and coupled devices may be treated correctly.

Detection, Evaluation, and Optimization of Optical Signals Generated by Fiber Optic Bragg Gratings Under Dynamic Excitations

NASA Technical Reports Server (NTRS)

Adamovsky, Grigory; Lekki, John; Lock, James A.

2002-01-01

The dynamic response of a fiber optic Bragg grating to mechanical vibrations is examined both theoretically and experimentally. The theoretical expressions describing the consequences of changes in the grating's reflection spectrum are derived for partially coherent beams in an interferometer. The analysis is given in terms of the dominant wavelength, optical bandwidth, and optical path difference of the interfering signals. Changes in the reflection spectrum caused by a periodic stretching and compression of the grating were experimentally measured using an unbalanced Michelson interferometer, a Michelson interferometer with a non-zero optical path difference. The interferometer's sensitivity to changes in dominant wavelength of the interfering beams was measured as a function of interferometer unbalance and was compared to theoretical predictions. The theoretical analysis enables the user to determine the optimum performance for an unbalanced interferometer.

Caching Joint Shortcut Routing to Improve Quality of Service for Information-Centric Networking.

PubMed

Huang, Baixiang; Liu, Anfeng; Zhang, Chengyuan; Xiong, Naixue; Zeng, Zhiwen; Cai, Zhiping

2018-05-29

Hundreds of thousands of ubiquitous sensing (US) devices have provided an enormous number of data for Information-Centric Networking (ICN), which is an emerging network architecture that has the potential to solve a great variety of issues faced by the traditional network. A Caching Joint Shortcut Routing (CJSR) scheme is proposed in this paper to improve the Quality of service (QoS) for ICN. The CJSR scheme mainly has two innovations which are different from other in-network caching schemes: (1) Two routing shortcuts are set up to reduce the length of routing paths. Because of some inconvenient transmission processes, the routing paths of previous schemes are prolonged, and users can only request data from Data Centers (DCs) until the data have been uploaded from Data Producers (DPs) to DCs. Hence, the first kind of shortcut is built from DPs to users directly. This shortcut could release the burden of whole network and reduce delay. Moreover, in the second shortcut routing method, a Content Router (CR) which could yield shorter length of uploading routing path from DPs to DCs is chosen, and then data packets are uploaded through this chosen CR. In this method, the uploading path shares some segments with the pre-caching path, thus the overall length of routing paths is reduced. (2) The second innovation of the CJSR scheme is that a cooperative pre-caching mechanism is proposed so that QoS could have a further increase. Besides being used in downloading routing, the pre-caching mechanism can also be used when data packets are uploaded towards DCs. Combining uploading and downloading pre-caching, the cooperative pre-caching mechanism exhibits high performance in different situations. Furthermore, to address the scarcity of storage size, an algorithm that could make use of storage from idle CRs is proposed. After comparing the proposed scheme with five existing schemes via simulations, experiments results reveal that the CJSR scheme could reduce the total number of processed interest packets by 54.8%, enhance the cache hits of each CR and reduce the number of total hop counts by 51.6% and cut down the length of routing path for users to obtain their interested data by 28.6⁻85.7% compared with the traditional NDN scheme. Moreover, the length of uploading routing path could be decreased by 8.3⁻33.3%.

FIELD EVALUATION OF A METHOD FOR ESTIMATING GASEOUS FLUXES FROM AREA SOURCES USING OPEN-PATH FTIR

EPA Science Inventory

The paper gives preliminary results from a field evaluation of a new approach for quantifying gaseous fugitive emissions of area air pollution sources. The approach combines path-integrated concentration data acquired with any path-integrated optical remote sensing (PI-ORS) ...

FIELD EVALUATION OF A METHOD FOR ESTIMATING GASEOUS FLUXES FROM AREA SOURCES USING OPEN-PATH FOURIER TRANSFORM INFRARED

EPA Science Inventory

The paper describes preliminary results from a field experiment designed to evaluate a new approach to quantifying gaseous fugitive emissions from area air pollution sources. The new approach combines path-integrated concentration data acquired with any path-integrated optical re...

Remote atmospheric probing by ground to ground line of sight optical methods

NASA Technical Reports Server (NTRS)

Lawrence, R. S.

1969-01-01

The optical effects arising from refractive-index variations in the clear air are qualitatively described, and the possibilities are discussed of using those effects for remotely sensing the physical properties of the atmosphere. The effects include scintillations, path length fluctuations, spreading of a laser beam, deflection of the beam, and depolarization. The physical properties that may be measured include the average temperature along the path, the vertical temperature gradient, and the distribution along the path of the strength of turbulence and the transverse wind velocity. Line-of-sight laser beam methods are clearly effective in measuring the average properties, but less effective in measuring distributions along the path. Fundamental limitations to the resolution are pointed out and experiments are recommended to investigate the practicality of the methods.

Network Analysis Tools: from biological networks to clusters and pathways.

PubMed

Brohée, Sylvain; Faust, Karoline; Lima-Mendez, Gipsi; Vanderstocken, Gilles; van Helden, Jacques

2008-01-01

Network Analysis Tools (NeAT) is a suite of computer tools that integrate various algorithms for the analysis of biological networks: comparison between graphs, between clusters, or between graphs and clusters; network randomization; analysis of degree distribution; network-based clustering and path finding. The tools are interconnected to enable a stepwise analysis of the network through a complete analytical workflow. In this protocol, we present a typical case of utilization, where the tasks above are combined to decipher a protein-protein interaction network retrieved from the STRING database. The results returned by NeAT are typically subnetworks, networks enriched with additional information (i.e., clusters or paths) or tables displaying statistics. Typical networks comprising several thousands of nodes and arcs can be analyzed within a few minutes. The complete protocol can be read and executed in approximately 1 h.

Interactogeneous: Disease Gene Prioritization Using Heterogeneous Networks and Full Topology Scores

PubMed Central

Gonçalves, Joana P.; Francisco, Alexandre P.; Moreau, Yves; Madeira, Sara C.

2012-01-01

Disease gene prioritization aims to suggest potential implications of genes in disease susceptibility. Often accomplished in a guilt-by-association scheme, promising candidates are sorted according to their relatedness to known disease genes. Network-based methods have been successfully exploiting this concept by capturing the interaction of genes or proteins into a score. Nonetheless, most current approaches yield at least some of the following limitations: (1) networks comprise only curated physical interactions leading to poor genome coverage and density, and bias toward a particular source; (2) scores focus on adjacencies (direct links) or the most direct paths (shortest paths) within a constrained neighborhood around the disease genes, ignoring potentially informative indirect paths; (3) global clustering is widely applied to partition the network in an unsupervised manner, attributing little importance to prior knowledge; (4) confidence weights and their contribution to edge differentiation and ranking reliability are often disregarded. We hypothesize that network-based prioritization related to local clustering on graphs and considering full topology of weighted gene association networks integrating heterogeneous sources should overcome the above challenges. We term such a strategy Interactogeneous. We conducted cross-validation tests to assess the impact of network sources, alternative path inclusion and confidence weights on the prioritization of putative genes for 29 diseases. Heat diffusion ranking proved the best prioritization method overall, increasing the gap to neighborhood and shortest paths scores mostly on single source networks. Heterogeneous associations consistently delivered superior performance over single source data across the majority of methods. Results on the contribution of confidence weights were inconclusive. Finally, the best Interactogeneous strategy, heat diffusion ranking and associations from the STRING database, was used to prioritize genes for Parkinson’s disease. This method effectively recovered known genes and uncovered interesting candidates which could be linked to pathogenic mechanisms of the disease. PMID:23185389

Path integration of head direction: updating a packet of neural activity at the correct speed using neuronal time constants.

PubMed

Walters, D M; Stringer, S M

2010-07-01

A key question in understanding the neural basis of path integration is how individual, spatially responsive, neurons may self-organize into networks that can, through learning, integrate velocity signals to update a continuous representation of location within an environment. It is of vital importance that this internal representation of position is updated at the correct speed, and in real time, to accurately reflect the motion of the animal. In this article, we present a biologically plausible model of velocity path integration of head direction that can solve this problem using neuronal time constants to effect natural time delays, over which associations can be learned through associative Hebbian learning rules. The model comprises a linked continuous attractor network and competitive network. In simulation, we show that the same model is able to learn two different speeds of rotation when implemented with two different values for the time constant, and without the need to alter any other model parameters. The proposed model could be extended to path integration of place in the environment, and path integration of spatial view.

An Efficient Wireless Recharging Mechanism for Achieving Perpetual Lifetime of Wireless Sensor Networks

PubMed Central

Yu, Hongli; Chen, Guilin; Zhao, Shenghui; Chang, Chih-Yung; Chin, Yu-Ting

2016-01-01

Energy recharging has received much attention in recent years. Several recharging mechanisms were proposed for achieving perpetual lifetime of a given Wireless Sensor Network (WSN). However, most of them require a mobile recharger to visit each sensor and then perform the recharging task, which increases the length of the recharging path. Another common weakness of these works is the requirement for the mobile recharger to stop at the location of each sensor. As a result, it is impossible for recharger to move with a constant speed, leading to inefficient movement. To improve the recharging efficiency, this paper takes “recharging while moving” into consideration when constructing the recharging path. We propose a Recharging Path Construction (RPC) mechanism, which enables the mobile recharger to recharge all sensors using a constant speed, aiming to minimize the length of recharging path and improve the recharging efficiency while achieving the requirement of perpetual network lifetime of a given WSN. Performance studies reveal that the proposed RPC outperforms existing proposals in terms of path length and energy utilization index, as well as visiting cycle. PMID:28025567

Entanglement-Gradient Routing for Quantum Networks.

PubMed

Gyongyosi, Laszlo; Imre, Sandor

2017-10-27

We define the entanglement-gradient routing scheme for quantum repeater networks. The routing framework fuses the fundamentals of swarm intelligence and quantum Shannon theory. Swarm intelligence provides nature-inspired solutions for problem solving. Motivated by models of social insect behavior, the routing is performed using parallel threads to determine the shortest path via the entanglement gradient coefficient, which describes the feasibility of the entangled links and paths of the network. The routing metrics are derived from the characteristics of entanglement transmission and relevant measures of entanglement distribution in quantum networks. The method allows a moderate complexity decentralized routing in quantum repeater networks. The results can be applied in experimental quantum networking, future quantum Internet, and long-distance quantum communications.

Optical RRH working in an all-optical fronthaul network

NASA Astrophysics Data System (ADS)

Zakrzewski, Zbigniew

2017-12-01

The paper presents an example of an optical RRH (Remote Radio Head) design, which is equipped with photonic components for direct connection to an all-optical network. The features that can be fulfilled by an all-optical network are indicated to support future 5G mobile networks. The demand for optical bandwidth in fronthaul/midhaul distribution network links, working in D-RoF and A-RoF formats was performed. The increase in demand is due to the very large traffic generated by the Optical Massive-MIMO RRH/RRU will work in format of an Active-Distributed Antenna System (A-DAS). An exemplary next-generation mobile network that will utilize O-RRH and an all-optical backbone is presented. All components of presented network will work in the Centralized/Cloud Radio Access Network (C-RAN) architecture, which is achievable by control with the use of the OpenFlow (OF).

Remote Sensing of the Optical and Physical Densities of Smoke, Dust, and Water Clouds.

DTIC Science & Technology

1982-12-01

systems to measure variability of aerosol concentration distributions along horizontal optical paths . Analysis of backscatter... extinction measurements using a single- laser lidar system operating at 1.06- and 0.53-pm wavelengths. For larger mean particle sizes the extinction ratio...clear air paths and The transmissometers were mounted across a 10-m complete blockage of the source energy. Transmisso- long aerosol tunnel that

Ejecta Experiments at the Pegasus Pulsed Power Facility

DTIC Science & Technology

1997-06-01

Laboratory (LANL ). The facility provides both radial and axial access for making measurements. There exist optical, laser , and X-Ray paths for performing...and axial access for making measurements. There exist optical, laser , and X-Ray paths for performing measurements on the target assembly located near...surface variations, microjets can be formed thus contributing to the amount of ejecta. In addition to material properties which contribute to ejecta

Advances in stereomicroscopy

NASA Astrophysics Data System (ADS)

Schnitzler, H.; Zimmer, Klaus-Peter

2008-09-01

Similar to human's binocular vision, stereomicroscopes are comprised of two optical paths under a convergence angle providing a full perspective insight into the world's microstructure. The numerical aperture of stereomicroscopes has continuously increased over the years, reaching the point where the lenses of left and right perspective paths touched each other. This constraint appeared as an upper limit for the resolution of stereomicroscopes, as the resolution of a stereomicroscope was deduced from the numerical apertures of the two equally sized perspective channels. We present the optical design and advances in resolution of the world's first asymmetrical stereomicroscope, which is a technological breakthrough in many aspects of stereomicroscopes. This unique approach uses a large numerical aperture and thus an, so far, unachievable high lateral resolution in the one path, and a small aperture in the other path, which provides a high depth of field ("Fusion Optics"). This new concept is a technical challenge for the optical design of the zoom system as well as for the common main objectives. Furthermore, the new concept makes use of the particular way in which perspective information by binocular vision is formed in the human's brain. In conjunction with a research project at the University of Zurich, Leica Microsystems consolidated the functionality of this concept in to a new generation of stereomicroscopes.

Phase-Shifted Laser Feedback Interferometry

NASA Technical Reports Server (NTRS)

Ovryn, Benjie

1999-01-01

Phase-shifted, laser feedback interferometry is a new diagnostic tool developed at the NASA Lewis Research Center under the Advanced Technology Development (ATD) Program directed by NASA Headquarters Microgravity Research Division. It combines the principles of phase-shifting interferometry (PSI) and laser-feedback interferometry (LFI) to produce an instrument that can quantify both optical path length changes and sample reflectivity variations. In a homogenous medium, the optical path length between two points is the product of the index of refraction and the geometric distance between the two points. LFI differs from other forms of interferometry by using the laser as both the source and the phase detector. In LFI, coherent feedback of the incident light either reflected directly from a surface or reflected after transmission through a region of interest will modulate the output intensity of the laser. The combination of PSI and LFI has produced a robust instrument, based on a low-power helium-neon (HeNe) gas laser, with a high dynamic range that can be used to measure either static or oscillatory changes of the optical path length. Small changes in optical path length are limited by the fraction of a fringe that can be measured; we can measure nonoscillatory changes with a root mean square (rms) error of the wavelength/1000 without averaging.

Far off-resonance laser frequency stabilization using multipass cells in Faraday rotation spectroscopy.

PubMed

Quan, Wei; Li, Yang; Li, Rujie; Shang, Huining; Fang, Zishan; Qin, Jie; Wan, Shuangai

2016-04-01

We propose a far off-resonance laser frequency stabilization method by using multipass cells in Rb Faraday rotation spectroscopy. Based on the detuning equation, if multipass cells with several meters optical path length are used in the conventional Faraday spectroscopy, the detuning of the lock point can be extended much further from the alkali metal resonance. A plate beam splitter was used to generate two different Faraday signals at the same time. The transmitted optical path length was L=50  mm and the reflected optical path length was 2L=100  mm. When the optical path length doubled, the detuning of the lock points moved further away from the atomic resonance. The temperature dependence of the detuning of the lock point was also analyzed. A temperature-insensitive lock point was found near resonance when the cell temperature was between 110°C and 130°C. We achieved an rms fluctuation of 0.9 MHz/23 h at a detuning of 0.5 GHz. A frequency drift of 16 MHz/h at a detuning of -5.6  GHz and 4 MHz/h at a detuning of -5.2  GHz were also obtained for the transmitted and reflected light Faraday signal.

High-contrast fast Fourier transform acousto-optical tomography of phantom tissues with a frequency-chirp modulation of the ultrasound.

PubMed

Forget, Benoît-Claude; Ramaz, François; Atlan, Michaël; Selb, Juliette; Boccara, Albert-Claude

2003-03-01

We report new results on acousto-optical tomography in phantom tissues using a frequency chirp modulation and a CCD camera. This technique allows quick recording of three-dimensional images of the optical contrast with a two-dimensional scan of the ultrasound source in a plane perpendicular to the ultrasonic path. The entire optical contrast along the ultrasonic path is concurrently obtained from the capture of a film sequence at a rate of 200 Hz. This technique reduces the acquisition time, and it enhances the axial resolution and thus the contrast, which are usually poor owing to the large volume of interaction of the ultrasound perturbation.

Semi-monolithic cavity for external resonant frequency doubling and method of performing the same

NASA Technical Reports Server (NTRS)

Hemmati, Hamid (Inventor)

1999-01-01

The fabrication of an optical cavity for use in a laser, in a frequency doubling external cavity, or any other type of nonlinear optical device, can be simplified by providing the nonlinear crystal in combination with a surrounding glass having an index of refraction substantially equal to that of the nonlinear crystal. The closed optical path in this cavity is formed in the surrounding glass and through the nonlinear crystal which lies in one of the optical segments of the light path. The light is transmitted through interfaces between the surrounding glass in the nonlinear crystal through interfaces which are formed at the Brewster-angle to minimize or eliminate reflection.

Cyber Fighter Associate

DTIC Science & Technology

2016-01-01

accomplish a patch- management mission while securing a critical path. As a first proof of concept a simulation with a network of 10 nodes and 4...software-agility walk of the “PERFORMANCE Each Threat Managed ” tree is slightly more complex than the network -agility walk. The original design of the...CyFiA was tested to accomplish a patch- management mission while securing a critical path. As a first proof of concept a simulation with a network of 10

Design and performance evaluation of an OpenFlow-based control plane for software-defined elastic optical networks with direct-detection optical OFDM (DDO-OFDM) transmission.

PubMed

Liu, Lei; Peng, Wei-Ren; Casellas, Ramon; Tsuritani, Takehiro; Morita, Itsuro; Martínez, Ricardo; Muñoz, Raül; Yoo, S J B

2014-01-13

Optical Orthogonal Frequency Division Multiplexing (O-OFDM), which transmits high speed optical signals using multiple spectrally overlapped lower-speed subcarriers, is a promising candidate for supporting future elastic optical networks. In contrast to previous works which focus on Coherent Optical OFDM (CO-OFDM), in this paper, we consider the direct-detection optical OFDM (DDO-OFDM) as the transport technique, which leads to simpler hardware and software realizations, potentially offering a low-cost solution for elastic optical networks, especially in metro networks, and short or medium distance core networks. Based on this network scenario, we design and deploy a software-defined networking (SDN) control plane enabled by extending OpenFlow, detailing the network architecture, the routing and spectrum assignment algorithm, OpenFlow protocol extensions and the experimental validation. To the best of our knowledge, it is the first time that an OpenFlow-based control plane is reported and its performance is quantitatively measured in an elastic optical network with DDO-OFDM transmission.

Hop Optimization and Relay Node Selection in Multi-hop Wireless Ad-Hoc Networks

NASA Astrophysics Data System (ADS)

Li, Xiaohua(Edward)

In this paper we propose an efficient approach to determine the optimal hops for multi-hop ad hoc wireless networks. Based on the assumption that nodes use successive interference cancellation (SIC) and maximal ratio combining (MRC) to deal with mutual interference and to utilize all the received signal energy, we show that the signal-to-interference-plus-noise ratio (SINR) of a node is determined only by the nodes before it, not the nodes after it, along a packet forwarding path. Based on this observation, we propose an iterative procedure to select the relay nodes and to calculate the path SINR as well as capacity of an arbitrary multi-hop packet forwarding path. The complexity of the algorithm is extremely low, and scaling well with network size. The algorithm is applicable in arbitrarily large networks. Its performance is demonstrated as desirable by simulations. The algorithm can be helpful in analyzing the performance of multi-hop wireless networks.

Predictions of first passage times in sparse discrete fracture networks using graph-based reductions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hyman, Jeffrey De'Haven; Hagberg, Aric Arild; Mohd-Yusof, Jamaludin

Here, we present a graph-based methodology to reduce the computational cost of obtaining first passage times through sparse fracture networks. We also derive graph representations of generic three-dimensional discrete fracture networks (DFNs) using the DFN topology and flow boundary conditions. Subgraphs corresponding to the union of the k shortest paths between the inflow and outflow boundaries are identified and transport on their equivalent subnetworks is compared to transport through the full network. The number of paths included in the subgraphs is based on the scaling behavior of the number of edges in the graph with the number of shortest paths.more » First passage times through the subnetworks are in good agreement with those obtained in the full network, both for individual realizations and in distribution. We obtain accurate estimates of first passage times with an order of magnitude reduction of CPU time and mesh size using the proposed method.« less

Predictions of first passage times in sparse discrete fracture networks using graph-based reductions

DOE PAGES

Hyman, Jeffrey De'Haven; Hagberg, Aric Arild; Mohd-Yusof, Jamaludin; ...

2017-07-10

Here, we present a graph-based methodology to reduce the computational cost of obtaining first passage times through sparse fracture networks. We also derive graph representations of generic three-dimensional discrete fracture networks (DFNs) using the DFN topology and flow boundary conditions. Subgraphs corresponding to the union of the k shortest paths between the inflow and outflow boundaries are identified and transport on their equivalent subnetworks is compared to transport through the full network. The number of paths included in the subgraphs is based on the scaling behavior of the number of edges in the graph with the number of shortest paths.more » First passage times through the subnetworks are in good agreement with those obtained in the full network, both for individual realizations and in distribution. We obtain accurate estimates of first passage times with an order of magnitude reduction of CPU time and mesh size using the proposed method.« less

A Random Walk into Optical Signal Processing and Integrated Optofluidics

NASA Astrophysics Data System (ADS)

Baylor, Martha-Elizabeth

2013-04-01

As a young child, I knew that I wanted to be a paleontologist. My parents, both artists, did their best to encourage me in my quest to dig for dinosaurs. However, decisions during my late high school and early college years serendipitously shifted my path so that I ended up pursuing a career in applied physics. In particular, my career path has been centered in optics with an emphasis on holography and signal processing. This talk will discuss my research in the areas of opto-electronic blind source separation and holographic photopolymers as well as the non-linear path that has gotten me to this point.

NACA Flight-Path Angle and Air-Speed Recorder

NASA Technical Reports Server (NTRS)

Coleman, Donald G

1926-01-01

A new trailing bomb-type instrument for photographically recording the flight-path angle and air speed of aircraft in unaccelerated flight is described. The instrument consists essentially of an inclinometer, air-speed meter and a film-drum case. The inclinometer carries an oil-damped pendulum which records optically the flight-path angle upon a rotating motor-driven film drum. The air-speed meter consists of a taut metal diaphragm of high natural frequency which is acted upon by the pressure difference of a Prandtl type Pitot-static tube. The inclinometer record and air-speed record are made optically on the same sensitive film. Two records taken by this instrument are shown.

Study on system for extracted type infrared gas analysis

NASA Astrophysics Data System (ADS)

Gu, Ruirui; Yao, Jun; Li, Wei; Li, Wenzhong; Zhang, Shaohua; Liu, Zhe; Wen, Qiang

2015-12-01

Based on the Beer-Lambert law and the characteristic IR absorption spectrum of CO, a system for extracted type infrared gas analysis has been designed and manufactured, which utilizes different absorptive degrees infrared light gain under different concentration degrees of the gas to be measured to the value of detect CO concentration, including optical path, electric circuit and gas path. A forward and backward gas detection chamber equipped with a micro flow sensor has been used in the optical path as well as a multistage high precision amplifier and filter circuit has been used in the electric circuit. The experimental results accord with the testing standard.

On the Resource Efficiency of Virtual Concatenation in SDH/SONET Mesh Transport Networks Bearing Protected Scheduled Connections

NASA Astrophysics Data System (ADS)

Kuri, Josu�; Gagnaire, Maurice; Puech, Nicolas

2005-10-01

Virtual concatenation (VCAT) is a Synchronous Digital Hierarchy (SDH)/Synchronous Optical Network (SONET) network functionality recently standardized by the International Telecommunication Union Telecommunication Standardization Sector (ITU-T). VCAT provides the flexibility required to efficiently allocate network resources to Ethernet, Fiber Channel (FC), Enterprise System Connection (ESCON), and other important data traffic signals. In this article, we assess the resources' gain provided by VCAT with respect to contiguous concatenation (CCAT) in SDH/SONET mesh transport networks bearing protected scheduled connection demands (SCDs). As explained later, an SCD is a connection demand for which the set-up and tear-down dates are known in advance. We define mathematical models to quantify the add/drop and transmission resources required to instantiate a set of protected SCDs in VCAT-and CCAT-capable networks. Quantification of transmission resources requires a routing and slot assignment (RSA) problem to be solved. We formulate the RSA problem in VCAT-and CCAT-capable networks as two different combinatorial optimization problems: RSA in VCAT-capable networks (RSAv) and RSA in CCAT-capable networks (RSAc), respectively. Protection of the SCDs is considered in the formulations using a shared backup path protection (SBPP) technique. We propose a simulated annealing (SA)-based meta-heuristic algorithm to compute approximate solutions to these problems (i.e., solutions whose cost approximates the cost of the optimal ones). The gain in transmission resources and the cost structure of add/drop resources making VCAT-capable networks more economical are analyzed for different traffic scenarios.

An object-based storage model for distributed remote sensing images

NASA Astrophysics Data System (ADS)

Yu, Zhanwu; Li, Zhongmin; Zheng, Sheng

2006-10-01

It is very difficult to design an integrated storage solution for distributed remote sensing images to offer high performance network storage services and secure data sharing across platforms using current network storage models such as direct attached storage, network attached storage and storage area network. Object-based storage, as new generation network storage technology emerged recently, separates the data path, the control path and the management path, which solves the bottleneck problem of metadata existed in traditional storage models, and has the characteristics of parallel data access, data sharing across platforms, intelligence of storage devices and security of data access. We use the object-based storage in the storage management of remote sensing images to construct an object-based storage model for distributed remote sensing images. In the storage model, remote sensing images are organized as remote sensing objects stored in the object-based storage devices. According to the storage model, we present the architecture of a distributed remote sensing images application system based on object-based storage, and give some test results about the write performance comparison of traditional network storage model and object-based storage model.

On/off ratio enhancement in single-walled carbon nanotube field-effect transistor by controlling network density via sonication

NASA Astrophysics Data System (ADS)

Jang, Ho-Kyun; Choi, Jun Hee; Kim, Do-Hyun; Kim, Gyu Tae

2018-06-01

Single-walled carbon nanotube (SWCNT) is generally used as a networked structure in the fabrication of a field-effect transistor (FET) since it is known that one-third of SWCNT is electrically metallic and the remains are semiconducting. In this case, the presence of metallic paths by metallic SWCNT (m-SWCNT) becomes a significant technical barrier which hinders the networks from achieving a semiconducting behavior, resulting in a low on/off ratio. Here, we report on an easy method of controlling the on/off ratio of a FET where semiconducting SWCNT (s-SWCNT) and m-SWCNT constitute networks between source and drain electrodes. A FET with SWCNT networks was simply sonicated under water to control the on/off ratio and network density. As a result, the FET having an almost metallic behavior due to the metallic paths by m-SWCNT exhibited a p-type semiconducting behavior. The on/off ratio ranged from 1 to 9.0 × 104 along sonication time. In addition, theoretical calculations based on Monte-Carlo method and circuit simulation were performed to understand and explain the phenomenon of a change in the on/off ratio and network density by sonication. On the basis of experimental and theoretical results, we found that metallic paths contributed to a high off-state current which leads to a low on/off ratio and that sonication formed sparse SWCNT networks where metallic paths of m-SWCNT were removed, resulting in a high on/off ratio. This method can open a chance to save the device which has been considered as a failed one due to a metallic behavior by a high network density leading to a low on/off ratio.

Integrated Model for Performance Analysis of All-Optical Multihop Packet Switches

NASA Astrophysics Data System (ADS)

Jeong, Han-You; Seo, Seung-Woo

2000-09-01

The overall performance of an all-optical packet switching system is usually determined by two criteria, i.e., switching latency and packet loss rate. In some real-time applications, however, in which packets arriving later than a timeout period are discarded as loss, the packet loss rate becomes the most dominant criterion for system performance. Here we focus on evaluating the performance of all-optical packet switches in terms of the packet loss rate, which normally arises from the insufficient hardware or the degradation of an optical signal. Considering both aspects, we propose what we believe is a new analysis model for the packet loss rate that reflects the complicated interactions between physical impairments and system-level parameters. On the basis of the estimation model for signal quality degradation in a multihop path we construct an equivalent analysis model of a switching network for evaluating an average bit error rate. With the model constructed we then propose an integrated model for estimating the packet loss rate in three architectural examples of multihop packet switches, each of which is based on a different switching concept. We also derive the bounds on the packet loss rate induced by bit errors. Finally, it is verified through simulation studies that our analysis model accurately predicts system performance.

Exploring crosstalk noise generated in the N-port router used in the WDM-based ONoC

NASA Astrophysics Data System (ADS)

Zhang, Zhendong; Xie, Yiyuan; Song, Tingting; He, Chao; Li, Jiachao; Liu, Yong

2017-07-01

Compared with optical network-on-chip (ONoC) with single wavelength, ONoC adopting wavelength division multiplexing (WDM) technology possesses a very prominent advantage-higher bandwidth. Therefore, WDM-based ONoC has been considered one of the most promising ways to relieve the rapidly increasing traffic load in communication systems. A WDM-based router, as the core equipment of WDM-based ONoC, is influenced by crosstalk noise, especially the nonlinear crosstalk noise generated by the four-wave mixing effect. Thus, to explore the performance of the N-port nonblocking optical router using WDM, we propose a universal analytic model to analyze the transmission loss, crosstalk noise, optical signal-to-noise ratio (OSNR), and bit error ratio (BER). The research results show that crosstalk noise varies along with signals at different wavelengths in the same channel. For signals with the same wavelength, the noises generated in the different transmission paths are obviously different from each other. For research of transmission loss, OSNR, and BER, similar results can be obtained. Based on the eye diagrams, we can learn that crosstalk noise will cause signal distortion to a certain extent. With this model, capability of this kind of multiport optical router using WDM can be understood conveniently.

High-resolution laser spectroscopy of hot Cs and Rb vapor confined in a thin optical cell

NASA Astrophysics Data System (ADS)

Todorov, P.; Krasteva, A.; Vartanyan, T.; Todorov, G.; Sarkisyan, D.; Cartaleva, S.

2018-03-01

We propose a novel use of an optical cell of micrometer thickness filled with Cs vapor in view of studying the collisions between two different alkali atoms of strongly different densities. We demonstrate narrow and good-contrast sub-Doppler resonances at the Rb D2 line for a mean-free-path of the Cs atoms comparable to the optical cell longitudinal dimension; the resonances are completely destroyed when the mean-free-path of the Cs atoms is more than two orders of magnitude shorter than the longitudinal dimension of the thin cell.

Multiple-wavelength tunable laser

NASA Technical Reports Server (NTRS)

Barnes, Norman P. (Inventor); Walsh, Brian M. (Inventor); Reichle, Donald J. (Inventor)

2010-01-01

A tunable laser includes dispersion optics for separating generated laser pulses into first and second wavelength pulses directed along first and second optical paths. First and second reflective mirrors are disposed in the first and second optical paths, respectively. The laser's output mirror is partially reflective and partially transmissive with respect to the first wavelength and the second wavelength in accordance with provided criteria. A first resonator length is defined between the output mirror and the first mirror, while a second resonator length is defined between the output mirror and the second mirror. The second resonator length is a function of the first resonator length.

Low-Coherence light source design for ESPI in-plane displacement measurements

NASA Astrophysics Data System (ADS)

Heikkinen, J. J.; Schajer, G. S.

2018-01-01

The ESPI method for surface deformation measurements requires the use of a light source with high coherence length to accommodate the optical path length differences present in the apparatus. Such high-coherence lasers, however, are typically large, delicate and costly. Laser diodes, on the other hand, are compact, mechanically robust and inexpensive, but unfortunately they have short coherence length. The present work aims to enable the use of a laser diode as an illumination source by equalizing the path lengths within an ESPI interferometer. This is done by using a reflection type diffraction grating to compensate for the path length differences. The high optical power efficiency of such diffraction gratings allows the use of much lower optical power than in previous interferometer designs using transmission gratings. The proposed concept was experimentally investigated by doing in-plane ESPI measurements using a high-coherence single longitudinal mode (SLM) laser, a laser diode and then a laser diode with path length optimization. The results demonstrated the limitations of using an uncompensated laser diode. They then showed the effectiveness of adding a reflection type diffraction grating to equalize the interferometer path lengths. This addition enabled the laser diode to produce high measurement quality across the entire field of view, rivaling although not quite equaling the performance of a high-coherence SLM laser source.

Minimum-Risk Path Finding by an Adaptive Amoebal Network

NASA Astrophysics Data System (ADS)

Nakagaki, Toshiyuki; Iima, Makoto; Ueda, Tetsuo; Nishiura, Yasumasa; Saigusa, Tetsu; Tero, Atsushi; Kobayashi, Ryo; Showalter, Kenneth

2007-08-01

When two food sources are presented to the slime mold Physarum in the dark, a thick tube for absorbing nutrients is formed that connects the food sources through the shortest route. When the light-avoiding organism is partially illuminated, however, the tube connecting the food sources follows a different route. Defining risk as the experimentally measurable rate of light-avoiding movement, the minimum-risk path is exhibited by the organism, determined by integrating along the path. A model for an adaptive-tube network is presented that is in good agreement with the experimental observations.

Critical path method applied to research project planning: Fire Economics Evaluation System (FEES)

Treesearch

Earl B. Anderson; R. Stanton Hales

1986-01-01

The critical path method (CPM) of network analysis (a) depicts precedence among the many activities in a project by a network diagram; (b) identifies critical activities by calculating their starting, finishing, and float times; and (c) displays possible schedules by constructing time charts. CPM was applied to the development of the Forest Service's Fire...

Mathematical modeling of a radio-frequency path for IEEE 802.11ah based wireless sensor networks

NASA Astrophysics Data System (ADS)

Tyshchenko, Igor; Cherepanov, Alexander; Dmitrii, Vakhnin; Popova, Mariia

2017-09-01

This article discusses the process of creating the mathematical model of a radio-frequency path for an IEEE 802.11ah based wireless sensor networks using M atLab Simulink CAD tools. In addition, it describes occurring perturbing effects and determining the presence of a useful signal in the received mixture.

Iterative deep convolutional encoder-decoder network for medical image segmentation.

PubMed

Jung Uk Kim; Hak Gu Kim; Yong Man Ro

2017-07-01

In this paper, we propose a novel medical image segmentation using iterative deep learning framework. We have combined an iterative learning approach and an encoder-decoder network to improve segmentation results, which enables to precisely localize the regions of interest (ROIs) including complex shapes or detailed textures of medical images in an iterative manner. The proposed iterative deep convolutional encoder-decoder network consists of two main paths: convolutional encoder path and convolutional decoder path with iterative learning. Experimental results show that the proposed iterative deep learning framework is able to yield excellent medical image segmentation performances for various medical images. The effectiveness of the proposed method has been proved by comparing with other state-of-the-art medical image segmentation methods.

Multi-layer service function chaining scheduling based on auxiliary graph in IP over optical network

NASA Astrophysics Data System (ADS)

Li, Yixuan; Li, Hui; Liu, Yuze; Ji, Yuefeng

2017-10-01

Software Defined Optical Network (SDON) can be considered as extension of Software Defined Network (SDN) in optical networks. SDON offers a unified control plane and makes optical network an intelligent transport network with dynamic flexibility and service adaptability. For this reason, a comprehensive optical transmission service, able to achieve service differentiation all the way down to the optical transport layer, can be provided to service function chaining (SFC). IP over optical network, as a promising networking architecture to interconnect data centers, is the most widely used scenarios of SFC. In this paper, we offer a flexible and dynamic resource allocation method for diverse SFC service requests in the IP over optical network. To do so, we firstly propose the concept of optical service function (OSF) and a multi-layer SFC model. OSF represents the comprehensive optical transmission service (e.g., multicast, low latency, quality of service, etc.), which can be achieved in multi-layer SFC model. OSF can also be considered as a special SF. Secondly, we design a resource allocation algorithm, which we call OSF-oriented optical service scheduling algorithm. It is able to address multi-layer SFC optical service scheduling and provide comprehensive optical transmission service, while meeting multiple optical transmission requirements (e.g., bandwidth, latency, availability). Moreover, the algorithm exploits the concept of Auxiliary Graph. Finally, we compare our algorithm with the Baseline algorithm in simulation. And simulation results show that our algorithm achieves superior performance than Baseline algorithm in low traffic load condition.

A scaling law for random walks on networks

PubMed Central

Perkins, Theodore J.; Foxall, Eric; Glass, Leon; Edwards, Roderick

2014-01-01

The dynamics of many natural and artificial systems are well described as random walks on a network: the stochastic behaviour of molecules, traffic patterns on the internet, fluctuations in stock prices and so on. The vast literature on random walks provides many tools for computing properties such as steady-state probabilities or expected hitting times. Previously, however, there has been no general theory describing the distribution of possible paths followed by a random walk. Here, we show that for any random walk on a finite network, there are precisely three mutually exclusive possibilities for the form of the path distribution: finite, stretched exponential and power law. The form of the distribution depends only on the structure of the network, while the stepping probabilities control the parameters of the distribution. We use our theory to explain path distributions in domains such as sports, music, nonlinear dynamics and stochastic chemical kinetics. PMID:25311870

A scaling law for random walks on networks

NASA Astrophysics Data System (ADS)

Perkins, Theodore J.; Foxall, Eric; Glass, Leon; Edwards, Roderick

2014-10-01

The dynamics of many natural and artificial systems are well described as random walks on a network: the stochastic behaviour of molecules, traffic patterns on the internet, fluctuations in stock prices and so on. The vast literature on random walks provides many tools for computing properties such as steady-state probabilities or expected hitting times. Previously, however, there has been no general theory describing the distribution of possible paths followed by a random walk. Here, we show that for any random walk on a finite network, there are precisely three mutually exclusive possibilities for the form of the path distribution: finite, stretched exponential and power law. The form of the distribution depends only on the structure of the network, while the stepping probabilities control the parameters of the distribution. We use our theory to explain path distributions in domains such as sports, music, nonlinear dynamics and stochastic chemical kinetics.

Topology and static response of interaction networks in molecular biology

PubMed Central

Radulescu, Ovidiu; Lagarrigue, Sandrine; Siegel, Anne; Veber, Philippe; Le Borgne, Michel

2005-01-01

We introduce a mathematical framework describing static response of networks occurring in molecular biology. This formalism has many similarities with the Laplace–Kirchhoff equations for electrical networks. We introduce the concept of graph boundary and we show how the response of the biological networks to external perturbations can be related to the Dirichlet or Neumann problems for the corresponding equations on the interaction graph. Solutions to these two problems are given in terms of path moduli (measuring path rigidity with respect to the propagation of interaction along the graph). Path moduli are related to loop products in the interaction graph via generalized Mason–Coates formulae. We apply our results to two specific biological examples: the lactose operon and the genetic regulation of lipogenesis. Our applications show consistency with experimental results and in the case of lipogenesis check some hypothesis on the behaviour of hepatic fatty acids on fasting. PMID:16849230

A scaling law for random walks on networks.

PubMed

Perkins, Theodore J; Foxall, Eric; Glass, Leon; Edwards, Roderick

2014-10-14

The dynamics of many natural and artificial systems are well described as random walks on a network: the stochastic behaviour of molecules, traffic patterns on the internet, fluctuations in stock prices and so on. The vast literature on random walks provides many tools for computing properties such as steady-state probabilities or expected hitting times. Previously, however, there has been no general theory describing the distribution of possible paths followed by a random walk. Here, we show that for any random walk on a finite network, there are precisely three mutually exclusive possibilities for the form of the path distribution: finite, stretched exponential and power law. The form of the distribution depends only on the structure of the network, while the stepping probabilities control the parameters of the distribution. We use our theory to explain path distributions in domains such as sports, music, nonlinear dynamics and stochastic chemical kinetics.

Cloud Optical Depths and Liquid Water Paths at the NSA CART

DOE Office of Scientific and Technical Information (OSTI.GOV)

Doran, J C.; Barnard, James C.; Zhong, Shiyuan

2000-03-14

Cloud optical depths have been measured using multifilter rotating shadowband radiometers (MFRSRs) at Barrow and Atqasuk, and liquid water paths have been measured at Barrow using a microwave radiometer (MWR) during the warm season (June-September) in 1999. Comparisons have been made between these quantities and the corresponding ones determined from the ECMWF GCM. Hour-by-hour comparisons of cloud optical depths show considerable scatter. The scatter is reduced, but is still substantial, when the averaging period is increased to ''daily'' averages, i.e., the time period each day over which the MFRSR can make measurements. This period varied between 18 hours in Junemore » and 6 hours in September. Preliminary results indicate that, for measured cloud optical depths less than approximately 25, the ECMWF has a low bias in its predictions, consistent with a low bias in predicted liquid water path. Based on a more limited set of data, the optical depths at Atqasuk were found to be generally lower than those at Barrow, a trend at least qualitatively captured by the ECMWF model. Analyses to identify the cause of the biases and the considerable scatter in the predictions are continuing.« less

Comparison of weighted and unweighted network analysis in the case of a pig trade network in Northern Germany.

PubMed

Büttner, Kathrin; Krieter, Joachim

2018-08-01

The analysis of trade networks as well as the spread of diseases within these systems focuses mainly on pure animal movements between farms. However, additional data included as edge weights can complement the informational content of the network analysis. However, the inclusion of edge weights can also alter the outcome of the network analysis. Thus, the aim of the study was to compare unweighted and weighted network analyses of a pork supply chain in Northern Germany and to evaluate the impact on the centrality parameters. Five different weighted network versions were constructed by adding the following edge weights: number of trade contacts, number of delivered livestock, average number of delivered livestock per trade contact, geographical distance and reciprocal geographical distance. Additionally, two different edge weight standardizations were used. The network observed from 2013 to 2014 contained 678 farms which were connected by 1,018 edges. General network characteristics including shortest path structure (e.g. identical shortest paths, shortest path lengths) as well as centrality parameters for each network version were calculated. Furthermore, the targeted and the random removal of farms were performed in order to evaluate the structural changes in the networks. All network versions and edge weight standardizations revealed the same number of shortest paths (1,935). Between 94.4 to 98.9% of the unweighted network and the weighted network versions were identical. Furthermore, depending on the calculated centrality parameters and the edge weight standardization used, it could be shown that the weighted network versions differed from the unweighted network (e.g. for the centrality parameters based on ingoing trade contacts) or did not differ (e.g. for the centrality parameters based on the outgoing trade contacts) with regard to the Spearman Rank Correlation and the targeted removal of farms. The choice of standardization method as well as the inclusion or exclusion of specific farm types (e.g. abattoirs) can alter the results significantly. These facts have to be considered when centrality parameters are to be used for the implementation of prevention and control strategies in the case of an epidemic. Copyright © 2018 Elsevier B.V. All rights reserved.

Optical reset modulation in the SiO2/Cu conductive-bridge resistive memory stack

NASA Astrophysics Data System (ADS)

Kawashima, T.; Zhou, Y.; Yew, K. S.; Ang, D. S.

2017-09-01

We show that the negative photoconductivity property of the nanoscale filamentary breakdown path in the SiO2 electrolyte of the SiO2/Cu conductive bridge resistive random access memory (CBRAM) stack is affected by the number of positive-voltage sweeps applied to the Cu electrode (with respect to a non-metal counter electrode). The path's photo-response to white light, of a given intensity, is suppressed with an increasing number of applied positive-voltage sweeps. When this occurs, the path may only be disrupted by the light of a higher intensity. It is further shown that the loss of the path's photosensitivity to the light of a given intensity can be recovered using a negative-voltage sweep (which eliminates the path), followed by the reformation of the path by a positive-voltage sweep. The above behavior is, however, not seen in the SiO2/Si stack (which involves a non-metal Si electrode), suggesting that the photo-response modulation effect is related to the Cu electrode. The demonstrated reversible electrical modulation of the path's photo-response may afford greater flexibility in the electro-optical control of the CBRAM device.

Architecture Design and Experimental Platform Demonstration of Optical Network based on OpenFlow Protocol

NASA Astrophysics Data System (ADS)

Xing, Fangyuan; Wang, Honghuan; Yin, Hongxi; Li, Ming; Luo, Shenzi; Wu, Chenguang

2016-02-01

With the extensive application of cloud computing and data centres, as well as the constantly emerging services, the big data with the burst characteristic has brought huge challenges to optical networks. Consequently, the software defined optical network (SDON) that combines optical networks with software defined network (SDN), has attracted much attention. In this paper, an OpenFlow-enabled optical node employed in optical cross-connect (OXC) and reconfigurable optical add/drop multiplexer (ROADM), is proposed. An open source OpenFlow controller is extended on routing strategies. In addition, the experiment platform based on OpenFlow protocol for software defined optical network, is designed. The feasibility and availability of the OpenFlow-enabled optical nodes and the extended OpenFlow controller are validated by the connectivity test, protection switching and load balancing experiments in this test platform.

Design alternatives for wavelength routing networks

NASA Astrophysics Data System (ADS)

Miliotis, K.; Papadimitriou, G. I.; Pomportsis, A. S.

2003-03-01

This paper attempts to provide a high level overview of many of the technologies employed in optical networks with a focus on wavelength-routing networks. Optical networks involve a number of technologies from the physics of light through protocols and networks architectures. In fact there is so much technology and know-how that most people involved with optical networks only have a full understanding of the narrow area they deal with. We start first examining the principles that govern light and its use as a wave guide, and then turn our focus to the various components that constitute an optical network and conclude with the description of all optical networks and wavelength-routed networks in greater detail.

Improved passive optical network architectures to support local area network emulation and protection

NASA Astrophysics Data System (ADS)

Wong, Elaine; Nadarajah, Nishaanthan; Chae, Chang-Joon; Nirmalathas, Ampalavanapillai; Attygalle, Sanjeewa M.

2006-01-01

We describe two optical layer schemes which simultaneously facilitate local area network emulation and automatic protection switching against distribution fiber breaks in passive optical networks. One scheme employs a narrowband fiber Bragg grating placed close to the star coupler in the feeder fiber of the passive optical network, while the other uses an additional short length distribution fiber from the star coupler to each customer for the redirection of the customer traffic. Both schemes use RF subcarrier multiplexed transmission for intercommunication between customers in conjunction with upstream access to the central office at baseband. Failure detection and automatic protection switching are performed independently by each optical network unit that is located at the customer premises in a distributed manner. The restoration of traffic transported between the central office and an optical network unit in the event of the distribution fiber break is performed by interconnecting adjacent optical network units and carrying out signal transmissions via an independent but interconnected optical network unit. Such a protection mechanism enables multiple adjacent optical network units to be simultaneously protected by a single optical network unit utilizing its maximum available bandwidth. We experimentally verify the feasibility of both schemes with 1.25 Gb/s upstream baseband transmission to the central office and 155 Mb/s local area network data transmission on a RF subcarrier frequency. The experimental results obtained from both schemes are compared, and the power budgets are calculated to analyze the scalability of each scheme.

INNOVATIVE APPROACH FOR MEASURING AMMONIA AND METHANE FLUXES FROM A HOG FARM USING OPEN-PATH FOURIER TRANSFORM INFRARED SPECTROSCOPY

EPA Science Inventory

The paper describes a new approach to quantify emissions from area air pollution sources. The approach combines path-integrated concentration data acquired with any path-integrated optical remote sensing (PI-ORS) technique and computed tomography (CT) technique. In this study, an...

Newberry EGS Seismic Velocity Model

DOE Data Explorer

Templeton, Dennise

2013-10-01

We use ambient noise correlation (ANC) to create a detailed image of the subsurface seismic velocity at the Newberry EGS site down to 5 km. We collected continuous data for the 22 stations in the Newberry network, together with 12 additional stations from the nearby CC, UO and UW networks. The data were instrument corrected, whitened and converted to single bit traces before cross correlation according to the methodology in Benson (2007). There are 231 unique paths connecting the 22 stations of the Newberry network. The additional networks extended that to 402 unique paths crossing beneath the Newberry site.

Computer aided manufacturing for complex freeform optics

NASA Astrophysics Data System (ADS)

Wolfs, Franciscus; Fess, Ed; Johns, Dustin; LePage, Gabriel; Matthews, Greg

2017-10-01

Recently, the desire to use freeform optics has been increasing. Freeform optics can be used to expand the capabilities of optical systems and reduce the number of optics needed in an assembly. The traits that increase optical performance also present challenges in manufacturing. As tolerances on freeform optics become more stringent, it is necessary to continue to improve methods for how the grinding and polishing processes interact with metrology. To create these complex shapes, OptiPro has developed a computer aided manufacturing package called PROSurf. PROSurf generates tool paths required for grinding and polishing freeform optics with multiple axes of motion. It also uses metrology feedback for deterministic corrections. ProSurf handles 2 key aspects of the manufacturing process that most other CAM systems struggle with. The first is having the ability to support several input types (equations, CAD models, point clouds) and still be able to create a uniform high-density surface map useable for generating a smooth tool path. The second is to improve the accuracy of mapping a metrology file to the part surface. To perform this OptiPro is using 3D error maps instead of traditional 2D maps. The metrology error map drives the tool path adjustment applied during processing. For grinding, the error map adjusts the tool position to compensate for repeatable system error. For polishing, the error map drives the relative dwell times of the tool across the part surface. This paper will present the challenges associated with these issues and solutions that we have created.

An industrial robot singular trajectories planning based on graphs and neural networks

NASA Astrophysics Data System (ADS)

Łęgowski, Adrian; Niezabitowski, Michał

2016-06-01

Singular trajectories are rarely used because of issues during realization. A method of planning trajectories for given set of points in task space with use of graphs and neural networks is presented. In every desired point the inverse kinematics problem is solved in order to derive all possible solutions. A graph of solutions is made. The shortest path is determined to define required nodes in joint space. Neural networks are used to define the path between these nodes.

Graphene-based battery electrodes having continuous flow paths

DOEpatents

Zhang, Jiguang; Xiao, Jie; Liu, Jun; Xu, Wu; Li, Xiaolin; Wang, Deyu

2014-05-24

Some batteries can exhibit greatly improved performance by utilizing electrodes having randomly arranged graphene nanosheets forming a network of channels defining continuous flow paths through the electrode. The network of channels can provide a diffusion pathway for the liquid electrolyte and/or for reactant gases. Metal-air batteries can benefit from such electrodes. In particular Li-air batteries show extremely high capacities, wherein the network of channels allow oxygen to diffuse through the electrode and mesopores in the electrode can store discharge products.

A compact CCD-monitored atomic force microscope with optical vision and improved performances.

PubMed

Mingyue, Liu; Haijun, Zhang; Dongxian, Zhang

2013-09-01

A novel CCD-monitored atomic force microscope (AFM) with optical vision and improved performances has been developed. Compact optical paths are specifically devised for both tip-sample microscopic monitoring and cantilever's deflection detecting with minimized volume and optimal light-amplifying ratio. The ingeniously designed AFM probe with such optical paths enables quick and safe tip-sample approaching, convenient and effective tip-sample positioning, and high quality image scanning. An image stitching method is also developed to build a wider-range AFM image under monitoring. Experiments show that this AFM system can offer real-time optical vision for tip-sample monitoring with wide visual field and/or high lateral optical resolution by simply switching the objective; meanwhile, it has the elegant performances of nanometer resolution, high stability, and high scan speed. Furthermore, it is capable of conducting wider-range image measurement while keeping nanometer resolution. Copyright © 2013 Wiley Periodicals, Inc.

Direct view zoom scope with single focal plane and adaptable reticle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bagwell, Brett

A direct view telescopic sight includes objective lens, eyepiece, and prism erector assemblies. The objective lens assembly is mounted to receive light of an image from an object direction and direct the light along an optical path. The eyepiece assembly is mounted to receive the light along the optical path and to emit the light of the image along an eye-ward direction. The prism erector assembly is positioned between the objective lens and eyepiece assemblies and includes first and second prism elements through which the optical path passes. The first and second prism elements invert the image. A reticle elementmore » is disposed on or adjacent to a surface of one of the first or second prism elements to combine a reticle on the image. The image is brought into focus at only a single focal plane between the objective lens and eyepiece assemblies at a given time.« less

Arbitrary unitary transformations on optical states using a quantum memory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Campbell, Geoff T.; Pinel, Olivier; Hosseini, Mahdi

2014-12-04

We show that optical memories arranged along an optical path can perform arbitrary unitary transformations on frequency domain optical states. The protocol offers favourable scaling and can be used with any quantum memory that uses an off-resonant Raman transition to reversibly transfer optical information to an atomic spin coherence.

Slant Path Low Visibility Atmospheric Conditions.

DTIC Science & Technology

1980-09-01

situation. a) An optical propagation slant test path , of a length over which infrared transmissometer measurements can be made that are in a magnitude...transmission measure - ments which are close to 100% and therefore do not accurately relate to absolute transmissivity. A path which is too long will result in...is available for measurement of backscatter cross section along the chosen transmissometer path . 3. Rough Cross Cut of the Works unde Contract in

Joint Energy Supply and Routing Path Selection for Rechargeable Wireless Sensor Networks.

PubMed

Tang, Liangrui; Cai, Jinqi; Yan, Jiangyu; Zhou, Zhenyu

2018-06-17

The topic of network lifetime has been attracting much research attention because of its importance in prolonging the standing operation of battery-restricted wireless sensor networks, and the rechargeable wireless sensor network has emerged as a promising solution. In this paper, we propose a joint energy supply and routing path selection algorithm to extend the network lifetime based on an initiative power supply. We develop a two-stage energy replenishment strategy to supplement the energy consumption of nodes as much as possible. Furthermore, the influence of charging factors on the selection of next-hop nodes in data routing is considered. The simulation results show that our algorithm effectively prolong the network lifetime, and different demands of network delay and energy consumption can be obtained by dynamically adjusting parameters.

Graph modeling systems and methods

DOEpatents

Neergaard, Mike

2015-10-13

An apparatus and a method for vulnerability and reliability modeling are provided. The method generally includes constructing a graph model of a physical network using a computer, the graph model including a plurality of terminating vertices to represent nodes in the physical network, a plurality of edges to represent transmission paths in the physical network, and a non-terminating vertex to represent a non-nodal vulnerability along a transmission path in the physical network. The method additionally includes evaluating the vulnerability and reliability of the physical network using the constructed graph model, wherein the vulnerability and reliability evaluation includes a determination of whether each terminating and non-terminating vertex represents a critical point of failure. The method can be utilized to evaluate wide variety of networks, including power grid infrastructures, communication network topologies, and fluid distribution systems.

Optimal solution for travelling salesman problem using heuristic shortest path algorithm with imprecise arc length

NASA Astrophysics Data System (ADS)

Bakar, Sumarni Abu; Ibrahim, Milbah

2017-08-01

The shortest path problem is a popular problem in graph theory. It is about finding a path with minimum length between a specified pair of vertices. In any network the weight of each edge is usually represented in a form of crisp real number and subsequently the weight is used in the calculation of shortest path problem using deterministic algorithms. However, due to failure, uncertainty is always encountered in practice whereby the weight of edge of the network is uncertain and imprecise. In this paper, a modified algorithm which utilized heuristic shortest path method and fuzzy approach is proposed for solving a network with imprecise arc length. Here, interval number and triangular fuzzy number in representing arc length of the network are considered. The modified algorithm is then applied to a specific example of the Travelling Salesman Problem (TSP). Total shortest distance obtained from this algorithm is then compared with the total distance obtained from traditional nearest neighbour heuristic algorithm. The result shows that the modified algorithm can provide not only on the sequence of visited cities which shown to be similar with traditional approach but it also provides a good measurement of total shortest distance which is lesser as compared to the total shortest distance calculated using traditional approach. Hence, this research could contribute to the enrichment of methods used in solving TSP.

Study on multiple-hops performance of MOOC sequences-based optical labels for OPS networks

NASA Astrophysics Data System (ADS)

Zhang, Chongfu; Qiu, Kun; Ma, Chunli

2009-11-01

In this paper, we utilize a new study method that is under independent case of multiple optical orthogonal codes to derive the probability function of MOOCS-OPS networks, discuss the performance characteristics for a variety of parameters, and compare some characteristics of the system employed by single optical orthogonal code or multiple optical orthogonal codes sequences-based optical labels. The performance of the system is also calculated, and our results verify that the method is effective. Additionally it is found that performance of MOOCS-OPS networks would, negatively, be worsened, compared with single optical orthogonal code-based optical label for optical packet switching (SOOC-OPS); however, MOOCS-OPS networks can greatly enlarge the scalability of optical packet switching networks.

Time Shared Optical Network (TSON): a novel metro architecture for flexible multi-granular services.

PubMed

Zervas, Georgios S; Triay, Joan; Amaya, Norberto; Qin, Yixuan; Cervelló-Pastor, Cristina; Simeonidou, Dimitra

2011-12-12

This paper presents the Time Shared Optical Network (TSON) as metro mesh network architecture for guaranteed, statistically-multiplexed services. TSON proposes a flexible and tunable time-wavelength assignment along with one-way tree-based reservation and node architecture. It delivers guaranteed sub-wavelength and multi-granular network services without wavelength conversion, time-slice interchange and optical buffering. Simulation results demonstrate high network utilization, fast service delivery, and low end-to-end delay on a contention-free sub-wavelength optical transport network. In addition, implementation complexity in terms of Layer 2 aggregation, grooming and optical switching has been evaluated. © 2011 Optical Society of America

Experimental performance evaluation of software defined networking (SDN) based data communication networks for large scale flexi-grid optical networks.

PubMed

Zhao, Yongli; He, Ruiying; Chen, Haoran; Zhang, Jie; Ji, Yuefeng; Zheng, Haomian; Lin, Yi; Wang, Xinbo

2014-04-21

Software defined networking (SDN) has become the focus in the current information and communication technology area because of its flexibility and programmability. It has been introduced into various network scenarios, such as datacenter networks, carrier networks, and wireless networks. Optical transport network is also regarded as an important application scenario for SDN, which is adopted as the enabling technology of data communication networks (DCN) instead of general multi-protocol label switching (GMPLS). However, the practical performance of SDN based DCN for large scale optical networks, which is very important for the technology selection in the future optical network deployment, has not been evaluated up to now. In this paper we have built a large scale flexi-grid optical network testbed with 1000 virtual optical transport nodes to evaluate the performance of SDN based DCN, including network scalability, DCN bandwidth limitation, and restoration time. A series of network performance parameters including blocking probability, bandwidth utilization, average lightpath provisioning time, and failure restoration time have been demonstrated under various network environments, such as with different traffic loads and different DCN bandwidths. The demonstration in this work can be taken as a proof for the future network deployment.

A Dynamic Bayesian Observer Model Reveals Origins of Bias in Visual Path Integration.

PubMed

Lakshminarasimhan, Kaushik J; Petsalis, Marina; Park, Hyeshin; DeAngelis, Gregory C; Pitkow, Xaq; Angelaki, Dora E

2018-06-20

Path integration is a strategy by which animals track their position by integrating their self-motion velocity. To identify the computational origins of bias in visual path integration, we asked human subjects to navigate in a virtual environment using optic flow and found that they generally traveled beyond the goal location. Such a behavior could stem from leaky integration of unbiased self-motion velocity estimates or from a prior expectation favoring slower speeds that causes velocity underestimation. Testing both alternatives using a probabilistic framework that maximizes expected reward, we found that subjects' biases were better explained by a slow-speed prior than imperfect integration. When subjects integrate paths over long periods, this framework intriguingly predicts a distance-dependent bias reversal due to buildup of uncertainty, which we also confirmed experimentally. These results suggest that visual path integration in noisy environments is limited largely by biases in processing optic flow rather than by leaky integration. Copyright © 2018 Elsevier Inc. All rights reserved.

a Modified Genetic Algorithm for Finding Fuzzy Shortest Paths in Uncertain Networks

NASA Astrophysics Data System (ADS)

Heidari, A. A.; Delavar, M. R.

2016-06-01

In realistic network analysis, there are several uncertainties in the measurements and computation of the arcs and vertices. These uncertainties should also be considered in realizing the shortest path problem (SPP) due to the inherent fuzziness in the body of expert's knowledge. In this paper, we investigated the SPP under uncertainty to evaluate our modified genetic strategy. We improved the performance of genetic algorithm (GA) to investigate a class of shortest path problems on networks with vague arc weights. The solutions of the uncertain SPP with considering fuzzy path lengths are examined and compared in detail. As a robust metaheuristic, GA algorithm is modified and evaluated to tackle the fuzzy SPP (FSPP) with uncertain arcs. For this purpose, first, a dynamic operation is implemented to enrich the exploration/exploitation patterns of the conventional procedure and mitigate the premature convergence of GA technique. Then, the modified GA (MGA) strategy is used to resolve the FSPP. The attained results of the proposed strategy are compared to those of GA with regard to the cost, quality of paths and CPU times. Numerical instances are provided to demonstrate the success of the proposed MGA-FSPP strategy in comparison with GA. The simulations affirm that not only the proposed technique can outperform GA, but also the qualities of the paths are effectively improved. The results clarify that the competence of the proposed GA is preferred in view of quality quantities. The results also demonstrate that the proposed method can efficiently be utilized to handle FSPP in uncertain networks.

Receiver-Based Ad Hoc On Demand Multipath Routing Protocol for Mobile Ad Hoc Networks

PubMed Central

Al-Nahari, Abdulaziz; Mohamad, Mohd Murtadha

2016-01-01

Decreasing the route rediscovery time process in reactive routing protocols is challenging in mobile ad hoc networks. Links between nodes are continuously established and broken because of the characteristics of the network. Finding multiple routes to increase the reliability is also important but requires a fast update, especially in high traffic load and high mobility where paths can be broken as well. The sender node keeps re-establishing path discovery to find new paths, which makes for long time delay. In this paper we propose an improved multipath routing protocol, called Receiver-based ad hoc on demand multipath routing protocol (RB-AOMDV), which takes advantage of the reliability of the state of the art ad hoc on demand multipath distance vector (AOMDV) protocol with less re-established discovery time. The receiver node assumes the role of discovering paths when finding data packets that have not been received after a period of time. Simulation results show the delay and delivery ratio performances are improved compared with AOMDV. PMID:27258013

An Energy-Efficient and Robust Multipath Routing Protocol for Cognitive Radio Ad Hoc Networks.

PubMed

Singh, Kishor; Moh, Sangman

2017-09-04

Routing in cognitive radio ad hoc networks (CRAHNs) is a daunting task owing to dynamic topology, intermittent connectivity, spectrum heterogeneity, and energy constraints. Other prominent aspects such as channel stability, path reliability, and route discovery frequency should also be exploited. Several routing protocols have been proposed for CRAHNs in the literature. By stressing on one of the aspects more than any other, however, they do not satisfy all requirements of throughput, energy efficiency, and robustness. In this paper, we propose an energy-efficient and robust multipath routing (ERMR) protocol for CRAHNs by considering all prominent aspects including residual energy and channel stability in design. Even when the current routing path fails, the alternative routing path is immediately utilized. In establishing primary and alternative routing paths, both residual energy and channel stability are exploited simultaneously. Our simulation study shows that the proposed ERMR outperforms the conventional protocol in terms of network throughput, packet delivery ratio, energy consumption, and end-to-end delay.

An Energy-Efficient and Robust Multipath Routing Protocol for Cognitive Radio Ad Hoc Networks

PubMed Central

Singh, Kishor

2017-01-01

Routing in cognitive radio ad hoc networks (CRAHNs) is a daunting task owing to dynamic topology, intermittent connectivity, spectrum heterogeneity, and energy constraints. Other prominent aspects such as channel stability, path reliability, and route discovery frequency should also be exploited. Several routing protocols have been proposed for CRAHNs in the literature. By stressing on one of the aspects more than any other, however, they do not satisfy all requirements of throughput, energy efficiency, and robustness. In this paper, we propose an energy-efficient and robust multipath routing (ERMR) protocol for CRAHNs by considering all prominent aspects including residual energy and channel stability in design. Even when the current routing path fails, the alternative routing path is immediately utilized. In establishing primary and alternative routing paths, both residual energy and channel stability are exploited simultaneously. Our simulation study shows that the proposed ERMR outperforms the conventional protocol in terms of network throughput, packet delivery ratio, energy consumption, and end-to-end delay. PMID:28869551

Receiver-Based Ad Hoc On Demand Multipath Routing Protocol for Mobile Ad Hoc Networks.

PubMed

Al-Nahari, Abdulaziz; Mohamad, Mohd Murtadha

2016-01-01

Decreasing the route rediscovery time process in reactive routing protocols is challenging in mobile ad hoc networks. Links between nodes are continuously established and broken because of the characteristics of the network. Finding multiple routes to increase the reliability is also important but requires a fast update, especially in high traffic load and high mobility where paths can be broken as well. The sender node keeps re-establishing path discovery to find new paths, which makes for long time delay. In this paper we propose an improved multipath routing protocol, called Receiver-based ad hoc on demand multipath routing protocol (RB-AOMDV), which takes advantage of the reliability of the state of the art ad hoc on demand multipath distance vector (AOMDV) protocol with less re-established discovery time. The receiver node assumes the role of discovering paths when finding data packets that have not been received after a period of time. Simulation results show the delay and delivery ratio performances are improved compared with AOMDV.