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1

Frequency response and bandwidth in low-numerical-aperture step-index plastic optical fibers.  

PubMed

By experimental measurement and from a numerical solution to the time-dependent power flow equation, the frequency response, bandwidth, mode coupling, and mode-dependent attenuation are determined for a low-numerical-aperture (NA) plastic optical fiber. Frequency response and bandwidth are specified as a function of fiber length. Numerical results are verified against experimental measurements. Mode coupling and modal attenuation are found to differ substantially between two fiber varieties of the same type (both low-NA, step-index, and plastic), implying their preferential suitability that is application-specific. PMID:25402786

Savovi?, Svetislav; Drlja?a, Branko; Kova?evi?, Milan S; Djordjevich, Alexandar; Baji?, Jovan S; Stupar, Dragan Z; Stepniak, Grzegorz

2014-10-20

2

Highly reflective Bragg gratings in slightly etched step-index polymer optical fiber.  

PubMed

During the past few years, a strong progress has been made in the photo-writing of fiber Bragg gratings (FBGs) in polymer optical fibers (POFs), animated by the constant wish to enhance the grating reflectivity and improve the sensing performances. In this paper, we report the photo-inscription of highly reflective gratings in step-index POFs, obtained thanks to a slight etching of the cladding. We demonstrate that a cladding diameter decrease of ~12% is an ideal trade-off to produce highly reflective gratings with enhanced axial strain sensitivity, while keeping almost intact their mechanical resistance. For this, we make use of Trans-4-stilbenemethanol-doped photosensitive step-index poly(methyl methacrylate) (PMMA) POFs. FBGs are inscribed at ~1550 nm by the scanning phase mask technique in POFs of different external diameters. Reflectivity reaching 97% is achieved for 6 mm long FBGs, compared to 25% for non-etched POFs. We also report that a cladding decrease enhances the FBG axial tension while keeping unchanged temperature and surrounding refractive index sensitivities. Finally and for the first time, a measurement is conducted in transmission with polarized light, showing that a photo-induced birefringence of 7 × 10(-6) is generated (one order of magnitude higher than the intrinsic fiber birefringence), which is similar to the one generated in silica fiber using ultra-violet laser. PMID:25089498

Hu, Xuehao; Pun, Chi-Fung Jeff; Tam, Hwa-Yaw; Mégret, Patrice; Caucheteur, Christophe

2014-07-28

3

Demonstration of ultra-low NA rare-earth doped step index fiber for applications in high power fiber lasers.  

PubMed

In this paper, we report the mode area scaling of a rare-earth doped step index fiber by using low numerical aperture. Numerical simulations show the possibility of achieving an effective area of ~700um2 (including bend induced effective area reduction) at a bend diameter of 32cm from a 35?m core fiber with a numerical aperture of 0.038. An effective single mode operation is ensured following the criterion of the fundamental mode loss to be lower than 0.1dB/m while ensuring the higher order modes loss to be higher than 10dB/m at a wavelength of 1060nm. Our optimized modified chemical vapor deposition process in conjunction with solution doping process allows fabrication of an Yb-doped step index fiber having an ultra-low numerical aperture of ~0.038. Experimental results confirm a Gaussian output beam from a 35?m core fiber validating our simulation results. Fiber shows an excellent laser efficiency of ~81%and aM2 less than 1.1. PMID:25837082

Jain, Deepak; Jung, Yongmin; Barua, Pranabesh; Alam, Shaiful; Sahu, Jayanta K

2015-03-23

4

Skew ray tracing in a step-index optical fiber using Geometric Algebra  

E-print Network

We used Geometric Algebra to compute the paths of skew rays in a cylindrical, step-index multimode optical fiber. To do this, we used the vector addition form for the law of propagation, the exponential of an imaginary vector form for the law of refraction, and the juxtaposed vector product form for the law of reflection. In particular, the exponential forms of the vector rotations enables us to take advantage of the addition or subtraction of exponential arguments of two rotated vectors in the derivation of the ray tracing invariants in cylindrical and spherical coordinates. We showed that the light rays inside the optical fiber trace a polygonal helical path characterized by three invariants that relate successive reflections inside the fiber: the ray path distance, the difference in axial distances, and the difference in the azimuthal angles. We also rederived the known generalized formula for the numerical aperture for skew rays, which simplifies to the standard form for meridional rays.

Ang, Angeleene; McNamara, Daniel J

2015-01-01

5

Delivery of high intensity beams with large clad step-index fibers for engine ignition  

NASA Astrophysics Data System (ADS)

We show, for the first time, that step-index silica fibers with a large clad (400 ?m core and 720 ?m clad) can be used to transmit nanosecond duration pulses in a way that allows reliable (consistent) spark formation in atmospheric pressure air by the focused output light from the fiber. The high intensity (>100 GW/cm2) of the focused output light is due to the combination of high output power (typical of fibers of this core size) with high output beam quality (better than that typical of fibers of this core size). The high output beam quality, which enables tight focusing, is due to the large clad which suppresses microbending-induced diffusion of modal power to higher order modes owing to the increased rigidity of the core-clad interface. We also show that extending the pulse duration provides a means to increase the delivered pulse energy (>20 mJ delivered for 50 ns pulses) without causing fiber damage. Based on this ability to deliver high energy sparks, we report the first reliable laser ignition of a natural gas engine including startup under typical procedures using silica fiber optics for pulse delivery.

Joshi, Sachin; Wilvert, Nick; Yalin, Azer P.

2012-09-01

6

Efficiency of various modulation types in Step Index Polymer Optical Fiber  

NASA Astrophysics Data System (ADS)

Efficiency of PAM, CAP/QAM and OFDM/DMT modulation for Step Index Polymer Optical Fiber channel is analyzed theoretically. It is shown that for the same transmitted optical power and same BER they offer similar data throughputs. However, when the light source has limited dynamics the crucial factor is the peak to average power ratio of the modulating signal. This is the greatest for OFDM/DMT and smaller for CAP and PAM. Consequently, the efficiency for PAM and CAP should be comparable whereas that of DMT - inferior. This conclusion was confirmed by experimental results.

Siuzdak, Jerzy; Stepniak, Grzegorz

2014-11-01

7

Estimation of angle-dependent mode coupling and attenuation in step-index plastic optical fibers from impulse responses.  

PubMed

We report on a method for estimation of angle-dependent mode coupling and attenuation in step-index plastic optical fibers (SI-POFs) from the shapes of impulse responses at two different fiber lengths. While alternating the fiber lengths, deviations between simulated and reference impulse responses are minimized by optimizing both mode coupling and attenuation parameters using pattern-search routines. Applying a matrix-based finite-difference approach to Gloge's time-dependent power flow equation fast computation of simulated impulse responses is enabled. We demonstrate that mode-dependent coupling and attenuation parameters converge to values that reconstruct fiber characteristics reported by other authors. We show that our results can be used for prediction of impulse responses, yielding determination of frequency responses, fiber bandwidths and coupling lengths. We conclude that our method enables characterization of SI-POFs from fiber impulse response measurements. PMID:23938556

Mundus, M; Hohl-Ebinger, J; Warta, W

2013-07-15

8

Solution of mode coupling in step-index optical fibers by the Fokker-Planck equation and the Langevin equation  

Microsoft Academic Search

The power-flow equation is approximated by the Fokker-Planck equation that is further transformed into a stochastic differential (Langevin) equation, resulting in an efficient method for the estimation of the state of mode coupling along step-index optical fibers caused by their intrinsic perturbation effects. The inherently stochastic nature of these effects is thus fully recognized mathematically. The numerical integration is based

Svetislav Savovic; Alexandar Djordjevich

2002-01-01

9

Transmission of laser pulses with high output beam quality using step-index fibers having large cladding  

SciTech Connect

An apparatus and method for transmission of laser pulses with high output beam quality using large core step-index silica optical fibers having thick cladding, are described. The thick cladding suppresses diffusion of modal power to higher order modes at the core-cladding interface, thereby enabling higher beam quality, M.sup.2, than are observed for large core, thin cladding optical fibers. For a given NA and core size, the thicker the cladding, the better the output beam quality. Mode coupling coefficients, D, has been found to scale approximately as the inverse square of the cladding dimension and the inverse square root of the wavelength. Output from a 2 m long silica optical fiber having a 100 .mu.m core and a 660 .mu.m cladding was found to be close to single mode, with an M.sup.2=1.6. Another thick cladding fiber (400 .mu.m core and 720 .mu.m clad) was used to transmit 1064 nm pulses of nanosecond duration with high beam quality to form gas sparks at the focused output (focused intensity of >100 GW/cm.sup.2), wherein the energy in the core was <6 mJ, and the duration of the laser pulses was about 6 ns. Extending the pulse duration provided the ability to increase the delivered pulse energy (>20 mJ delivered for 50 ns pulses) without damaging the silica fiber.

Yalin, Azer P; Joshi, Sachin

2014-06-03

10

Experimental investigation of PAM, CAP and DMT modulations efficiency over a double-step-index polymer optical fiber  

NASA Astrophysics Data System (ADS)

Investigated was the transmission over step index POF that is 50 m/100 m long with a red DVD laser as a source and a Si p-i-n commercial photo-detector. The maximum bit rates of three modulation formats: PAM, CAP and DMT were sought. Their constellation sizes and symbol rates were varied in order to maximize FEC limited throughputs for each modulation whereas the laser operating point and relevant optical powers were maintained constant for all the modulations. The maximum throughputs were similar for PAM and CAP, namely 3.3/2 Gbit/s for PAM, and 3.15/2.1 for CAP for 50/100 m fiber, respectively. The bit rates for DMT were 2.65/1.65 Gbit/s for the respective lengths of the fiber. We attribute the inferior performance of DMT to its high value of peak to average power ratio.

Stepniak, G.; Siuzdak, J.

2014-08-01

11

Fiber optic refractive index monitor  

DOEpatents

A sensor for measuring the change in refractive index of a liquid uses the lowest critical angle of a normal fiber optic to achieve sensitivity when the index of the liquid is significantly less than the index of the fiber core. Another embodiment uses a liquid filled core to ensure that its index is approximately the same as the liquid being measured.

Weiss, Jonathan David (Albuquerque, NM)

2002-01-01

12

Attenuation and bit error rate for four co-propagating spatially multiplexed optical communication channels of exactly same wavelength in step index multimode fibers  

NASA Astrophysics Data System (ADS)

Spatial domain multiplexing (SDM) utilizes co-propagation of exactly the same wavelength in optical fibers to increase the bandwidth by integer multiples. Input signals from multiple independent single mode pigtail laser sources are launched at different input angles into a single multimode carrier fiber. The SDM channels follow helical paths and traverse through the carrier fiber without interfering with each other. The optical energy from the different sources is spatially distributed and takes the form of concentric circular donut shaped rings, where each ring corresponds to an independent laser source. At the output end of the fiber these donut shaped independent channels can be separated either with the help of bulk optics or integrated concentric optical detectors. This presents the experimental setup and results for a four channel SDM system. The attenuation and bit error rate for individual channels of such a system is also presented.

Murshid, Syed H.; Chakravarty, Abhijit

2011-06-01

13

Towards mid-infrared supercontinuum generation: Ge-Sb-Se mid-infrared step-index small-core optical fiber  

NASA Astrophysics Data System (ADS)

In the 21st century, cancer has become a common and feared illness. Early detection is crucial for delivering the most effective treatment of patients, yet current diagnostic tests depend upon the skill of a consultant clinician and histologist for recognition of the cancerous cells. Therefore it is necessary to develop a medical diagnostic system which can analyze and image tissue instantly, removing the margin of human error and with the additional benefit of being minimally invasive. The molecular fingerprint of biological tissue lies within the mid-infrared (IR) region of the electromagnetic spectrum, 3-25?m wavelength. This can be used to determine a tissue spectral map and provide information about the absence or existence of disease, potentially in real-time and in vivo. However, current mid-IR broadband sources are not bright enough to achieve this. One alternative is to develop broadband, mid-IR, supercontinuum generation (SCG). Chalcogenide glass optical fibers have the potential to provide such mid-IR SC light. A popular chalcogenide glass fiber type is based on Ge-As-Se. For biomedical applications it is prudent to avoid the use of arsenic, on account of its toxicity. This paper investigates replacing arsenic with antimony, towards Ge-Sb-Se smallcore optical fibers for SCG. Physical properties of candidate glass pairs are investigated for glass stability via differential thermal analysis etc. and fiber optical loss measurements of associated fibers are assessed. These results are compared to analogous arsenic-containing chalcogenide glasses and optical fibers, and conclusions are drawn focusing on whether there is potential for antimony chalcogenide glass to be used for SCG for mid-infrared medical diagnostics.

Butterworth, J. H.; Jayasuriya, D.; Li, Q. Q.; Furniss, D.; Moneim, N. A.; Barney, E.; Sujecki, S.; Benson, T. M.; Sanghera, J. S.; Seddon, A. B.

2014-02-01

14

Surface plasmon resonance based fiber optic refractive index sensors  

NASA Astrophysics Data System (ADS)

Refractive index sensors based on surface plasmon resonance (SPR) in a thin metal film deposited on an unclad core of a multimode fiber are presented. The sensing element of the fiber optic SPR sensors is a bare core of a step-index optical fiber made of fused silica with a double-sided sputtered gold film. First, an in-line transmissionbased sensing scheme with the fiber optic SPR probe is used. Second, a reflection-based sensing scheme with a terminated fiber optic SPR probe is employed. The fiber optic SPR probes have different lengths and the thickness of the sputtered gold film is about 50 nm. Both sensing schemes utilize a wavelength interrogation method so that the refractive index of a liquid is sensed by measuring the position of the dip in the transmitted or reflected spectral intensity distribution. As an example, the aqueous solutions of ethanol with refractive indices in a range from 1.333 to 1.364 are measured. For the transmission-based sensing scheme a polarization-dependent response is revealed.

Hlubina, Petr; Kadulova, Miroslava; Ciprian, Dalibor

2014-12-01

15

Microstructured optical fiber refractive index sensor.  

PubMed

We describe a dual-core microstructured optical fiber designed for refractive index sensing of fluids. We show that by using the exponential dependence of intercore coupling on analyte refractive index, both large range and high sensitivity can be achieved in the one device. We also show that selective filling of the microstructure with analyte can increase the device sensitivity by approximately 1 order of magnitude. PMID:20237622

Town, Graham E; Yuan, Wu; McCosker, Ravi; Bang, Ole

2010-03-15

16

Graded-index optical fibers of methyl methacrylate-vinyl benzoate copolymer with low loss and high bandwidth  

NASA Astrophysics Data System (ADS)

The interfacial-gel copolymerization of 3/1, or 4/1 (wt/wt) methyl methacrylate-vinyl benzoate monomer mixture followed by heat drawing results in graded-index plastic optical fibers with attenuation loss of 212 and 134 dB/km at 652 nm, respectively, and with bandwidths of 170 and 260 MHz km, respectively, in comparison with 6 MHz km of the current step-index plastic optical fiber. Now, it has been confirmed experimentally that graded-index fibers are tremendously superior to step-index fibers for data-carrying capacity, while attenuation losses of both fibers are comparable.

Ohtsuka, Yasuji; Nihei, Eisuke; Koike, Yasuhiro

1990-07-01

17

Optical similaritons in a tapered graded-index nonlinear-fiber amplifier with an external source  

SciTech Connect

We analytically explore a wide class of optical similariton solutions to the nonlinear Schroedinger equation appropriately modified to model beam propagation in a tapered, graded-index nonlinear-fiber amplifier with an external source. Under certain physical conditions, we reduce the coupled nonlinear Schroedinger equations to a single-wave equation that aptly describes similariton propagation through asymmetric twin-core fiber amplifiers. The asymmetric twin-core fiber is composed of two adjoining, closely spaced, single-mode fibers in which the active one is a tapered, graded-index nonlinear-fiber and the passive one is a step-index fiber. We obtain these self-similar waves for different choices of tapered index profile, using a Moebius transformation. Our procedure is applicable for both self-focusing and self-defocusing nonlinearities.

Raju, Thokala Soloman; Panigrahi, Prasanta K. [Department of Electronics and Communication Engineering, Temple City Institute of Technology and Engineering, Bhubaneswar 752 057 (India); Indian Institute of Science Education and Research-Kolkata, Mohanpur, Nadia 741252 (India)

2011-09-15

18

Polymer microstructured fibers by one-step extrusion  

NASA Astrophysics Data System (ADS)

For the first time to our knowledge, polymer-based microstructured fibers with complex cross-sections are directly produced via melt extrusion. Two principal types of fibers were fabricated: a microstructured fiber of a single polymer with a hexagonal array of air holes and a bicomponent fiber consisting of approximately 60 coaxial rings. From the latter, strong visible iridescence was observed and is shown to exhibit a mechanochromic response. This approach, the mainstay of the textile trade for decades, offers a means of continuous high-volume low-cost manufacturing of polymer (and conceivably soft-glass) fibers. For example, in the present effort, 128 coaxially microstructured fibers were fabricated simultaneously at rates exceeding 1200 m/min from industrially mainstream polymers. This approach offers an important step forward towards commoditizing microstructured fibers and open new doors for optical engineering in fashion, marking/identification, and numerous military applications.

Mignanelli, M.; Wani, K.; Ballato, J.; Foulger, S.; Brown, P.

2007-05-01

19

Light propagation in graded-index optical fibers  

Microsoft Academic Search

An accurate numerical method is described for solving the Helmholtz equation for a general class of optical fibers. The method yields detailed information about the spatial and angular properties of the propagating beam as well as the modal propagation constants for the fiber. The method is applied to a practical graded-index fiber under the assumptions of both coherent and incoherent

M. D. Feit

1978-01-01

20

Fiber Optic-Based Refractive Index Sensing at INESC Porto  

PubMed Central

A review of refractive index measurement based on different types of optical fiber sensor configurations and techniques is presented. It addresses the main developments in the area, with particular focus on results obtained at INESC Porto, Portugal. The optical fiber sensing structures studied include those based on Bragg and long period gratings, on micro-interferometers, on plasmonic effects in fibers and on multimode interference in a large spectrum of standard and microstructured optical fibers. PMID:22969405

Jorge, Pedro A. S.; Silva, Susana O.; Gouveia, Carlos; Tafulo, Paula; Coelho, Luis; Caldas, Paulo; Viegas, Diana; Rego, Gaspar; Baptista, José M.; Santos, José L.; Frazão, Orlando

2012-01-01

21

Highly sensitive fiber Bragg grating refractive index sensors  

NASA Astrophysics Data System (ADS)

We combine fiber Bragg grating (FBG) technology with a wet chemical etch-erosion procedure and demonstrate two types of refractive index sensors using single-mode optical fibers. The first index sensor device is an etch-eroded single FBG with a radius of 3?m, which is used to measure the indices of four different liquids. The second index sensor device is an etch-eroded fiber Fabry-Pérot interferometer (FFPI) with a radius of ˜1.5?m and is used to measure the refractive indices of isopropyl alcohol solutions of different concentrations. Due to its narrower resonance spectral feature, the FFPI sensor has a higher sensitivity than the FBG sensor and can detect an index variation of 1.4×10-5. Since we can measure the reflection signal, these two types of sensors can be fabricated at the end of a fiber and used as point sensors.

Liang, Wei; Huang, Yanyi; Xu, Yong; Lee, Reginald K.; Yariv, Amnon

2005-04-01

22

Theory of biaxial graded-index optical fiber. M.S. Thesis  

NASA Technical Reports Server (NTRS)

A biaxial graded-index fiber with a homogeneous cladding is studied. Two methods, wave equation and matrix differential equation, of formulating the problem and their respective solutions are discussed. For the wave equation formulation of the problem it is shown that for the case of a diagonal permittivity tensor the longitudinal electric and magnetic fields satisfy a pair of coupled second-order differential equations. Also, a generalized dispersion relation is derived in terms of the solutions for the longitudinal electric and magnetic fields. For the case of a step-index fiber, either isotropic or uniaxial, these differential equations can be solved exactly in terms of Bessel functions. For the cases of an istropic graded-index and a uniaxial graded-index fiber, a solution using the Wentzel, Krammers and Brillouin (WKB) approximation technique is shown. Results for some particular permittivity profiles are presented. Also the WKB solutions is compared with the vector solution found by Kurtz and Streifer. For the matrix formulation it is shown that the tangential components of the electric and magnetic fields satisfy a system of four first-order differential equations which can be conveniently written in matrix form. For the special case of meridional modes, the system of equations splits into two systems of two equations. A general iterative technique, asymptotic partitioning of systems of equations, for solving systems of differential equations is presented. As a simple example, Bessel's differential equation is written in matrix form and is solved using this asymptotic technique. Low order solutions for particular examples of a biaxial and uniaxial graded-index fiber are presented. Finally numerical results obtained using the asymptotic technique are presented for particular examples of isotropic and uniaxial step-index fibers and isotropic, uniaxial and biaxial graded-index fibers.

Kawalko, Stephen F.

1990-01-01

23

STEP-INDEXED RELATIONAL REASONING FOR COUNTABLE NONDETERMINISM  

E-print Network

STEP-INDEXED RELATIONAL REASONING FOR COUNTABLE NONDETERMINISM JAN SCHWINGHAMMER AND LARS BIRKEDAL. Because countable choice introduces non-continuous behaviour, it is well-known that developing semantic and Lars Birkedal Creative Commons 1 #12;2 JAN SCHWINGHAMMER AND LARS BIRKEDAL and suggested that it would

Birkedal, Lars

24

Step-Indexed Relational Reasoning for Countable Nondeterminism  

E-print Network

Step-Indexed Relational Reasoning for Countable Nondeterminism Jan Schwinghammer1 and Lars Birkedal introduces non-continuous behaviour, it is well-known that developing semantic models for programming Schwinghammer and Lars Birkedal; licensed under Creative Commons License NC-ND Conference title on which

Birkedal, Lars

25

Simple index modulation profile with fast-converging design optimization for multichannel fiber Bragg grating filters  

NASA Astrophysics Data System (ADS)

In this paper, a novel hybrid algorithm featuring a simple index modulation profile with fast-converging optimization is proposed towards the design of dense wavelength-division-multiplexing systems (DWDM) multichannel fiber Bragg grating (FBG) filters. The approach is based on utilizing one of other FBG design approaches that may suffer from spectral distortion as the first step, then performing Lagrange multiplier optimization (LMO) for optimized correction of the spectral distortion. In our design examples, the superposition method is employed as the first design step for its merits of easy fabrication, and the discrete layer-peeling (DLP) algorithm is used to rapidly obtain the initial index modulation profiles for the superposition method. On account of the initially near-optimum index modulation profiles from the first step, the LMO optimization algorithm shows fast convergence to the target reflection spectra in the second step and the design outcome still retains the advantage of easy fabrication.

Hsin, Chen-Wei

2011-07-01

26

Influence of the power law index on the fiber breakage during injection molding by numerical simulations  

NASA Astrophysics Data System (ADS)

In predictive engineering for polymer processes, the proper prediction of material microstructure from known processing conditions and constituent material properties is a critical step forward properly predicting bulk properties in the finished composite. Operating within the context of long-fiber thermoplastics (LFT, length > 15mm) this investigation concentrates on the influence of the power law index on the final fiber length distribution within the injection molded part. To realize this, the Autodesk Simulation Moldflow Insight Scandium 2013 software has been used. In this software, a fiber breakage algorithm is available from this release on. Using virtual material data with realistic viscosity levels allows to separate the influence of the power law index on the fiber breakage from the other material and process parameters. Applying standard settings for the fiber breakage parameters results in an obvious influence on the fiber length distribution through the thickness of the part and also as function of position in the part. Finally, the influence of the shear rate constant within the fiber breakage model has been investigated illustrating the possibility to fit the virtual fiber length distribution to the possible experimentally available data.

Desplentere, Frederik; Six, Wim; Bonte, Hilde; Debrabandere, Eric

2013-04-01

27

A Simple Method for Prediction of Effective Core Area and Index of Refraction of Single-mode Graded Index Fiber in the Low V Region  

NASA Astrophysics Data System (ADS)

Based on the simple power series formulation of fundamental mode developed by Chebyshev formalism in the low V region, we prescribe analytical expression for effective core area of graded index fiber. Taking step and parabolic index fibers as examples, we estimate the effective core areas as well as effective refractive index for different normalized frequencies (V number) having low values. We also show that our estimations match excellently with the available exact results. The concerned predictions by our method require little computation. Thus, this simple but accurate formalism will be user friendly for the system engineers.

Majumdar, Angshuman; Das, Satabdi; Gangopadhyay, Sankar

2014-12-01

28

Observation of images in graded-index multimode fiber  

E-print Network

mismatch. Table I shows the results of the experiment. Reflected power is plotted against the length of the graded index multimode fiber in Fig, 22. Before tatdng data the laser output was coupled to a UDT amplifier which was recorded on a strip chart...OBSERVATION OF IMAGES IN GRADED-INDEX MULTIMODE FIBER A Thesis by SULTANA BEGUM Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE December 1992...

Begum, Sultana

1992-01-01

29

Single Step Sintered Calcium Phosphate Fibers from Avian EGG Shell  

NASA Astrophysics Data System (ADS)

Different forms of calcium-phosphate (Hydoxyapatite, ?-TCP, ?-TCP, CDHA) minerals are found to be major component of bone tissue. Development of calcium-phosphate (CaP) based fibrous microstructures is of significant research interest worldwide owing to its improved mechanical properties and higher interconnectivity. Here we represent a method for single step sintered wet-spun Fibers of calcium phosphate from avian egg shells for biomedical applications. Raw egg shell powder was mixed with chitosan solution and Phosphoric acid. The mixture is milled in a ball mill overnight and then filtered. The slurry was de-aired using 100 microliter 1-octanol per 100 ml of slurry as antifoaming and wet spun in coagulation bath. Fiber was dried overnight and sintered at different temperatures for microstructure and phase analysis. Both green and sintered Fibers were physico-chemical characterized by SEM, EDX, XRD, TGA, DSC, FTIR, and stereo-zoom microscopy. The fibers obtained in this procedure are found to have highly porous interconnected structures which can provide good cell adhesion and therefore can be used for bioactive scaffold making.

Dadhich, Prabhash; Das, Bodhisatwa; Dhara, Santanu

2013-11-01

30

Fiber-optic refractive index sensor based on surface plasmon resonance  

NASA Astrophysics Data System (ADS)

A fiber-optic refractive index sensor based on surface plasmon resonance (SPR) in a thin metal film deposited on an unclad core of a multimode fiber is presented. The sensing element of the SPR fiber-optic sensor is a bare core of a step-index optical fiber made of fused silica with a deposited gold film. First, a model of the SPR fiber-optic sensor based on the theory of attenuated total internal reflection is presented. The analysis is carried out in the frame of optics of multilayered media. The sensing scheme uses a wavelength interrogation method and the calculations are performed over a broad spectral range. Second, in a practical realization of the sensor with a double-sided sputtered gold film, a reflection-based sensing scheme to measure the refractive indices of liquids is considered. The refractive index of a liquid is sensed by measuring the position of the dip in the reflected spectral intensity distribution. As an example, the aqueous solutions of ethanol with refractive indices in a range from 1.333 to 1.364 are measured.

Hlubina, Petr; Ciprian, Dalibor; Kadulova, Miroslava

2015-01-01

31

Refractive index fiber sensor based on cladding modes interference  

NASA Astrophysics Data System (ADS)

We present the optical fiber sensor based on fused silica capillary as a sensing element spliced between the lead-in and lead-out singlemode (SM) fibers. In the region of the splice the cladding modes of capillary are excited from the fundamental mode of led-in SM fiber. The intermodal interference of the propagating cladding modes results in the formation of the resonant peaks in the transmission spectrum. With the variations of the external refractive index the shift of resonance wavelength of the peak can be observed. The sensitivity for the refractive index values around n=1.33 is observed and using the wet etching technique can be increased, what gives an assumption for its using in a biomedical sensing applications.

Tatar, Peter; Kacik, Daniel; Schuster, Kay

2014-12-01

32

Organic Transistors on Fiber: A first step towards electronic textiles Josephine B. Lee and Vivek Subramanian  

E-print Network

Organic Transistors on Fiber: A first step towards electronic textiles Josephine B. Lee and Vivek@eecs.berkeley.edu Abstract For the first time, we demonstrate flexible transistors formed directly on fibers. This represents a significant step towards the realization of electronics textiles. Fiber transistors exhibit mobilities of >10

California at Irvine, University of

33

Reflectivity enhanced refractive index sensor based on a fiber-integrated Fabry-Perot microresonator.  

PubMed

We discuss a fiber-integrated refractive index sensor with strongly improved detection performance. The resonator has been implemented by means of focused-ion beam milling of a step index fiber and shows a sensitivity of about 1.15µm/RIU. Coating the resonator walls led to a strongly improved mirror reflectivity by a factor of about 26. Design rules for device optimization and a detailed mathematical analysis are discussed, revealing that the sensor operates as an optimized Fabry-Perot resonator. We also show that the performance of such kind of Fabry-Perot sensors is, in general, limited by the detection limit function - a quantity depending on the cavitiy's finesse and on the measurement capabilities used. PMID:25401567

Wieduwilt, T; Dellith, J; Talkenberg, F; Bartelt, H; Schmidt, M A

2014-10-20

34

Reflection noise reduction effect of graded-index plastic optical fiber in multimode fiber link.  

PubMed

We experimentally demonstrate that a graded-index plastic optical fiber (GI POF) can significantly reduce reflection noise in a multimode fiber link with a vertical-cavity surface-emitting laser (VCSEL). By directly observing beams backreflected to the VCSEL, we show that the noise reduction effect is closely related to random mode coupling because of light scattering by microscopic heterogeneities in the GI POF core material. This suggests that intrinsic mode coupling can lower the self-coupling efficiency of the light backreflected to the VCSEL cavity through beam quality degradation. Using GI POFs, low-cost radio-over-fiber systems for indoor networks can be realized without optical isolators or fiber end-face polishing. PMID:24978562

Inoue, Azusa; Furukawa, Rei; Matsuura, Motoharu; Koike, Yasuhiro

2014-06-15

35

The elongation of yeast prion fibers involves separable steps of association and conversion  

E-print Network

of Sup35p (NM) converts to amyloid fibers by means of nucleated conformational conversion. First into amyloid fibers. To elucidate the nature of the polymerization step, we created single with amyloid assembly. These mutants provided a sensitive measure for the kinetics of fiber elongation

Lindquist, Susan

36

Optically induced mode conversion in graded-index fibers using ultra-short laser pulses  

NASA Astrophysics Data System (ADS)

We propose the use of graded-index few-mode fibers for mode conversion by long-period gratings (LPG) transiently written by ultrashort laser pulses using the optical Kerr effect. The mode interaction is studied by numerically solving the multi-mode coupled nonlinear Schrödinger equations. We present highly efficient conversion of the LP01- into the LP11-mode preserving the pulse shape in contrast to previous results in step-index fibers. Furthermore, mode conversion using different wavelengths for inducing and probing the LPG is shown. Due to the flat phase-matching curve of the examined modes in the graded-index fiber, mode conversion can be observed for probe center wavelengths of 1,100 nm up to 1,800 nm with a write beam centered around 1,030 nm. Therefore, a complete separation of the probe from the write beam should be possible as well as the application of optically induced guided-mode conversion for all-optical modulation across a broad wavelength range.

Hellwig, Tim; Walbaum, Till; Fallnich, Carsten

2013-09-01

37

Reflectance Imaging by Graded-Index Short Multimode Fiber  

NASA Astrophysics Data System (ADS)

The imaging condition and magnifications were measured using a graded-index multimode fiber for optical communication with a diameter of 140 µm and a length of 5 mm. The field of view was about 80 µm and the test pattern of 4.38 µm period was recognized. Reducing the background noise with the polarizer reflectance images of the weed surface were measured to show the cell shapes. There are problems such as background, distortion, and nonuniformity of image quality; however, the feasibility for minimally invasive endoscope has been shown.

Sato, Manabu; Kanno, Takahiro; Ishihara, Syoutarou; Suto, Hiroshi; Takahashi, Toshihiro; Nishidate, Izumi

2013-05-01

38

Two-dimensional scanning focused refractive-index microscopy and applications to refractive-index profiling of optical fibers  

NASA Astrophysics Data System (ADS)

The refractive-index profile (RIP) of optical fibers is of fundamental significance in determining critical fiber properties. Here, we present the application of a two-dimensional (2-D) scanning focused refractive-index microscopy (SFRIM) to accurately obtain the 2-D RIP of a graded-index optical fiber. Some modifications are made to SFRIM for better 2-D measurement. Quantitative RIP of the fiber is obtained with derivative total reflection method. The refractive-index accuracy is 0.002. The measured result is in good agreement with theoretical expectation. This method is straightforward, simple, repeatable, and free from signal distortion. This technique is suitable for symmetric and asymmetric optical fibers. The results indicate that this technique can be applied to obtain the RIPs of a wide range of materials and has broad application prospect in many fields.

Wang, Xiaowan; Ye, Qing; Sun, Tengqian; Wang, Jin; Deng, Zhichao; Mei, Jianchun; Zhou, Wenyuan; Zhang, Chunping; Tian, Jianguo

2015-01-01

39

Photonic crystal fiber filled with a high index electro-optic polymer  

NASA Astrophysics Data System (ADS)

We have investigated different possibilities to fill a Photonic Crystal Fibers (PCF) with an electro-optic (EO) polymer. As the EO polymers are generally solution processed, the solvents have to be removed from the holes of the PCF after filling with the liquid polymer, leaving a solid polymer layer. Repeated filling is required to create a multilayer of the EO polymer to fill about 80% of the volume of the holes. The remaining volume can be filled with a epoxy monomer and cured. Because of time consuming repeated steps in the solvent processing, solvent free single step filling processes are also presented. Polability of these different systems and their final attainable properties are compared. Considering the high refractive index of the polymer materials, possible applications e.g. for antiresonant guiding with variations of the transmission bandgaps are discussed.

Balakrishnan, Muralidharan; Spittel, Ron; Kobelke, Jens; Schuster, Kay; Reichel, Volker; Bartelt, Hartmut

2010-04-01

40

Thermo-optic effect of an index guiding photonic crystal fiber with elastomer inclusions  

E-print Network

-induced loss for a 6-cm long PDMS-filled PCF at 4 cm bend diameter. Keywords: Photonic crystal fiber, polymerThermo-optic effect of an index guiding photonic crystal fiber with elastomer inclusions C. Markos and experimentally the temperature dependence of a photonic crystal fiber (PCF) infiltrated with PDMS elastomer. We

Vlachos, Kyriakos G.

41

Characterization of the stress and refractive-index distributions in optical fibers and fiber-based devices  

NASA Astrophysics Data System (ADS)

Optical fiber technology continues to advance rapidly as a result of the increasing demands on communication systems and the expanding use of fiber-based sensing. New optical fiber types and fiber-based communications components are required to permit higher data rates, an increased number of channels, and more flexible installation requirements. Fiber-based sensors are continually being developed for a broad range of sensing applications, including environmental, medical, structural, industrial, and military. As optical fibers and fiber-based devices continue to advance, the need to understand their fundamental physical properties increases. The residual-stress distribution (RSD) and the refractive-index distribution (RID) play fundamental roles in the operation and performance of optical fibers. Custom RIDs are used to tailor the transmission properties of fibers used for long-distance transmission and to enable fiber-based devices such as long-period fiber gratings (LPFGs). The introduction and modification of RSDs enable specialty fibers, such as polarization-maintaining fiber, and contribute to the operation of fiber-based devices. Furthermore, the RSD and the RID are inherently linked through the photoelastic effect. Therefore, both the RSD and the RID need to be characterized because these fundamental properties are coupled and affect the fabrication, operation, and performance of fibers and fiber-based devices. To characterize effectively the physical properties of optical fibers, the RSD and the RID must be measured without perturbing or destroying the optical fiber. Furthermore, the techniques used must not be limited in detecting small variations and asymmetries in all directions through the fiber. Finally, the RSD and the RID must be characterized concurrently without moving the fiber to enable the analysis of the relationship between the RSD and the RID. Although many techniques exist for characterizing the residual stress and the refractive index in optical fibers, there is no existing methodology that meets all of these requirements. Therefore, the primary objective of the research presented in this thesis was to provide a methodology that is capable of characterizing concurrently the three-dimensional RSD and RID in optical fibers and fiber-based devices. This research represents a detailed study of the requirements for characterizing optical fibers and how these requirements are met through appropriate data analysis and experimental apparatus design and implementation. To validate the developed methodology, the secondary objective of this research was to characterize both unperturbed and modified optical fibers. The RSD and the RID were measured in a standard telecommunications-grade optical fiber, Corning SMF-28. The effects of cleaving this fiber were also analyzed and the longitudinal variations that result from cleaving were explored for the first time. The fabrication of carbon-dioxide-laser-induced (CO2 -laser-induced) LPFGs was also examined. These devices provide many of the functionalities required for fiber-based communications components as well as fiber-based sensors, and they offer relaxed fabrication requirements when compared to LPFGs fabricated by other methods. The developed methodology was used to perform the first measurements of the changes that occur in the RSD and the RID during LPFG fabrication. The analysis of these measurements ties together many of the existing theories of CO2-laser-induced LPFG fabrication to present a more coherent understanding of the processes that occur. In addition, new evidence provides detailed information on the functional form of the RSD and the RID in LPFGs. This information is crucial for the modeling of LPFG behavior, for the design of LPFGs for specific applications, for the tailoring of fabrication parameters to meet design requirements, and for understanding the limitations of LPFG fabrication in commercial optical fibers. Future areas of research concerning the improvement of the developed methodology, the need to characterize other fibers and f

Hebenstreit, Florian

2011-07-01

42

Plasmonic nanoshell functionalized etched fiber Bragg gratings for highly sensitive refractive index measurements.  

PubMed

A novel fiber optical refractive index sensor based on gold nanoshells immobilized on the surface of an etched single-mode fiber including a Bragg grating is demonstrated. The nanoparticle coating induces refractive index dependent waveguide losses, because of the variation of the evanescently guided part of the light. Hence the amplitude of the Bragg reflection is highly sensitive to refractive index changes of the surrounding medium. The nanoshell functionalized fiber optical refractive index sensor works in reflectance mode, is suitable for chemical and biochemical sensing, and shows an intensity dependency of 4400% per refractive index unit in the refractive index range between 1.333 and 1.346. Furthermore, the physical length of the sensor is smaller than 3 mm with a diameter of 6 ?m, and therefore offers the possibility of a localized refractive index measurement. PMID:25680146

Burgmeier, Jörg; Feizpour, Amin; Schade, Wolfgang; Reinhard, Björn M

2015-02-15

43

One-step preparation of ultrafine poly(acrylonitrile) fibers containing silver nanoparticles  

Microsoft Academic Search

A simple one-step method of preparing of ultrafine poly(acrylonitrile) (PAN) fibers containing Ag nanoparticles was developed. Ag+ ions in a PAN solution were directly reduced to produce Ag nanoparticles and the resulting solution was electrospun into ultrafine PAN fibers. N,N-dimethylformamide (DMF) was used as a solvent for PAN as well as a reducing agent for the Ag+ ions. The numbers

Hwang Kyu Lee; Eun Hwan Jeong; Chi Kyoung Baek; Ji Ho Youk

2005-01-01

44

Two-dimensional refractive index and stresses profiles of a homogenous bent optical fiber.  

PubMed

We present a significant contribution to the theory of determining the refractive index profile of a bent homogenous optical fiber. In this theory we consider two different processes controlling the index profile variations. The first is the linear index variation due to stress along the bent radius, and the second is the release of this stress on the fiber surface. This release process is considered to have radial dependence on the fiber radius. These considerations enable us to construct the index profile in two dimensions normal to the optical axis, considering the refraction of light rays traversing the fiber. This theory is applied to optical homogenous bent fiber with two bending radii when they are located orthogonal to the light path of the object arm in the holographic setup (like the Mach-Zehnder interferometer). Digital holographic phase shifting interferometry is employed in this study. The recorded phase shifted holograms have been combined, reconstructed, and processed to extract the phase map of the bent optical fiber. A comparison between the extracted optical phase differences and the calculated one indicates that the refractive index profile variation should include the above mentioned two processes, which are considered as a response for stress distribution across the fiber's cross section. The experimentally obtained refractive index profiles provide the stress induced birefringence profile. Thus we are able to present a realistic induced stress profile due to bending. PMID:25402912

Ramadan, W A; Wahba, H H; Shams El-Din, M A

2014-11-01

45

A Refractive Index Sensor Based on the Resonant Coupling to Cladding Modes in a Fiber Loop  

PubMed Central

We report an easy-to-build, compact, and low-cost optical fiber refractive index sensor. It consists of a single fiber loop whose transmission spectra exhibit a series of notches produced by the resonant coupling between the fundamental mode and the cladding modes in a uniformly bent fiber. The wavelength of the notches, distributed in a wavelength span from 1,400 to 1,700 nm, can be tuned by adjusting the diameter of the fiber loop and are sensitive to refractive index changes of the external medium. Sensitivities of 170 and 800 nm per refractive index unit for water solutions and for the refractive index interval 1.40–1.442, respectively, are demonstrated. We estimate a long range resolution of 3 × 10?4 and a short range resolution of 2 × 10?5 for water solutions. PMID:23979478

Reyes, Mauricio; Monzón-Hernández, David; Martínez-Ríos, Alejandro; Silvestre, Enrique; Díez, Antonio; Cruz, José Luis; Andrés, Miguel V.

2013-01-01

46

Performance Evaluation of Single Sideband Radio over Fiber System through Modulation Index Enhancement  

NASA Astrophysics Data System (ADS)

The transmission performance of single sideband (SSB) radio over fiber (RoF) system is evaluated through tuning the modulation index of Mach-Zehnder modulator, two different data modulation schemes and the influence of fiber dispersion are considered. The quantitative simulation results validate that there exist an optimum modulation index, and the system performance could be improved if the data signal is modulated on only optical carrier or sidebands.

Chen, Xiaogang; Hu, Xizhen; Huang, Dexiu

2014-09-01

47

Enhanced refractive index without absorption in optical fibers via an indirect incoherent pump field  

NASA Astrophysics Data System (ADS)

We demonstrate a scheme for realizing the refractive index with zero absorption in an Er3+-doped ZrF4-BaF2-LaF3-AlF3-NaF optical fiber. It is found that the refraction index of the probe laser can be easily controlled via adjusting properly the parameters of the corresponding system. Our scheme may provide some new possibilities for technological applications in optical-fiber communication.

Ge, Qiang

2014-12-01

48

One-step Tape Casting of Composites via Slurry on Fiber  

NASA Technical Reports Server (NTRS)

A process by which metal matrix composites can be made was presented. The process involves putting a powder slurry on fibers to make a precursor green tape. These green tapes are cut, stacked and hot pressed to form the fully dense composite. A computer program was presented which enables complete quantification and control of the process. Once some easily obtained properties of the slurry and its behavior are determined (such as the shrinkage from the wet to green state, and the density of the green tape) modification of the fiber spacing and blade height give the maker precise control of fiber volume fraction, and fiber architecture in the composite. The process was shown to be accurate and flexible through the production of a wide variety of volume fraction fiber composites made from a wide variety of fibers and powders. The most time consuming step of the tape casting process (other than hot pressing) was winding the fiber on the drum. The tape casting techniques developed resulted in high quality metal matrix composites, with ultimate tensile strength in the range of 215 ksi (1477 MPa), a strain at failure of 1.15 percent, and in fatigue at room temperature 0 to 120 ksi, n = 0.3 Hz, a 4-ply Ti-24Al-11Nb/SCS-6, 32 vol% fiber tape cast composite lasted 202,205 cycles with a maximum strain on the 100th cycle of 0.43 percent.

deGroh, Henry C., III

2001-01-01

49

Measurement of the nonlinear refractive index of tellurite glass fiber by using induced grating autocorrelation technique  

NASA Astrophysics Data System (ADS)

Nonlinear phenomena in optical fibers have been attracting considerable attention because of the rapid growth of the fiber optics communication industry. The increasing demand in internet use and the expansion of telecommunications in the developing world have triggered the need for high capacity and ultra-fast communication devices and also the need to increase the number of transmission channels in the fibers. Wavelength Division Multiplexing (WDM) and Dense Wavelength Division Multiplexing (DWDM) systems are capable of transmitting large volumes of data at very high rates into huge numbers of optical transmission channels. This ability is limited by the gain bandwidth of Silica based fiber optics amplifiers already installed in the communication networks. Tellurite based fiber amplifiers offer the necessary bandwidth for amplification of WDM and DWDM channels. To investigate the nonlinear properties of the optical fibers in this research, we used a 10 picoseconds pulse width passively mode-locked Nd:Vanadate ( Nd:YVO4) laser operating at 1342nm with a repetition rate of 76 MHz. We accurately measured the nonlinear refractive index of single mode silica fibers utilizing the Induced Grating Autocorrelation (IGA) technique. IGA technique was extended furthermore to study nonlinear effects in multimode fibers, and for the first time, we successfully measured the nonlinear refractive index (n2) of a multimode silica fiber. Confident of the ability of IGA technique for determining n 2 of multimode silica fibers, we measured the nonlinear refractive index of multimode Tellurite glass fibers with length as short as 0.5 meter. The goal of this work is to provide accurate and reliable information on the nonlinear optical properties of Tellurite glass fibers, novel fibers with promising future for developing ultrafast and high transmission capacity communication devices.

Traore, Aboubakar

50

Optical manipulation and rotation of liquid crystal drops using high-index fiber-optic tweezers  

NASA Astrophysics Data System (ADS)

We report an optical fiber tweezer based on high-index material for trapping and optical manipulation of microscale particles in water. The use of a high-index material increases the trapping force with respect to the more common silica, through tighter focusing of light. We demonstrate the potential of this simple and versatile device by trapping and rotating nematic liquid crystal drops. We monitor the rotation of the drop by detecting light modulation observed with the same fiber using backscattered light, which exhibits modulation in intensity due to the rotation of the drop; this further extends the capabilities of the fiber tweezers.

Abedin, Kazi Sarwar; Kerbage, Charles; Fernandez-Nieves, Alberto; Weitz, David A.

2007-08-01

51

Analysis of the response of long period fiber gratings to external index of refraction  

Microsoft Academic Search

This paper demonstrates that the change in wavelength of a long period fiber grating attenuation band with changes in external index of refraction can be enhanced by proper selection of the grating period. We calculate and experimentally verify that the wavelength shift caused by changing the external index from n=1 to n=1.44 of the attenuation band which appears in the

Heather J. Patrick; Alan D. Kersey; Frank Bucholtz

1998-01-01

52

Photonic crystal fiber modal interferometer for refractive index sensing of glycerine solution  

NASA Astrophysics Data System (ADS)

A photonic crystal fiber sensor was prepared for refractive index sensing. Based on modal interferometer theory, the relationships between the refractive index of glycerine solution and resonant wavelength shift of the sensor are analyzed by numerical simulation. A fiber optical device was designed to operate the sensing experiment. The sensing experiment shows that the resonant wavelength blued-shift for the sensor with refractive index in the range of 1.33~1.41 happens when increasing glycerine solution from 0.0% to 50.0% (v/v). The experimental results are approximately consistent with theory.

Huang, Jing; Li, Xueming; Yang, Jianchun

2013-12-01

53

Diffusion tensor imaging fiber tracking with reliable tracking orientation and flexible step size?  

PubMed Central

We propose a method of reliable tracking orientation and flexible step size fiber tracking. A new directional strategy was defined to select one optimal tracking orientation from each directional set, which was based on the single-tensor model and the two-tensor model. The directional set of planar voxels contained three tracking directions: two from the two-tensor model and one from the single-tensor model. The directional set of linear voxels contained only one principal vector. In addition, a flexible step size, rather than fixable step sizes, was implemented to improve the accuracy of fiber tracking. We used two sets of human data to assess the performance of our method; one was from a healthy volunteer and the other from a patient with low-grade glioma. Results verified that our method was superior to the single-tensor Fiber Assignment by Continuous Tracking and the two-tensor eXtended Streamline Tractography for showing detailed images of fiber bundles. PMID:25206444

Yao, Xufeng; Wang, Manning; Chen, Xinrong; Nie, Shengdong; Li, Zhexu; Xu, Xiaoping; Zhang, Xuelong; Song, Zhijian

2013-01-01

54

Prediction of Macrobending and Splice Losses for Photonic Crystal Fibers based on the Effective Index Method  

E-print Network

An index-guiding photonic crystal fiber (PCF) with an array of air holes surrounding the silica core region has special characteristics compared to conventional single-mode fibers (SMFs). Using the effective index method and the Gaussian beam propagation theory, the macro-bending and splice losses for PCFs are investigated. The wavelength dependence of the cladding index of the PCF has been taken properly into account. We obtain the effective spot size for different configurations of PCFs, which is used for computing the splice losses. The Gaussian approximation for the fundamental modal field leads to simple closed-form expressions for the splice losses produced by transverse, longitudinal and angular offsets. Calculations of macro-bending losses are based on antenna theory for bend standard fibers.

G. S. Kliros; J. Konstantinidis; C. Thraskias

2007-05-20

55

Determination of Diameter and Index of Refraction of Textile Fibers by Laser Backscattering  

SciTech Connect

A new method was developed to determine both diameters and indices of refraction and hence the birefringence of cylindrical textile and industrial fibers and bundles by measuring intensity patterns of the scattered light over an interval of scattering angles. The measured intensity patterns are compared with theoretical predictions (Mie theory) to determine fiber diameter and index of refraction. It is shown that the method is simple and accurate and may be useful as an on-line, noncontact diagnostic tool in real time.

H. Okuda; B. Stratton; L. Meixler; P. Efthimion; D.Mansfield

2003-07-24

56

A Multi-D-Shaped Optical Fiber for Refractive Index Sensing  

PubMed Central

A novel class of multi-D-shaped optical fiber suited for refractive index measurements is presented. The multi-D-shaped optical fiber was constructed by forming several D-sections in a multimode optical fiber at localized regions with femtosecond laser pulses. The total number of D-shaped zones fabricated could range from three to seven. Each D-shaped zone covered a sensor volume of 100 ?m depth, 250 ?m width, and 1 mm length. The mean roughness of the core surface obtained by the AFM images was 231.7 nm, which is relatively smooth. Results of the tensile test indicated that the fibers have sufficient mechanical strength to resist damage from further processing. The multi-D-shaped optical fiber as a high sensitive refractive-index sensor to detect changes in the surrounding refractive index was studied. The results for different concentrations of sucrose solution show that a resolution of 1.27 × 10?3–3.13 × 10?4 RIU is achieved for refractive indices in the range of 1.333 to 1.403, suggesting that the multi-D-shaped fibers are attractive for chemical, biological, and biochemical sensing with aqueous solutions. PMID:22399908

Chen, Chien-Hsing; Tsao, Tzu-Chein; Tang, Jaw-Luen; Wu, Wei-Te

2010-01-01

57

Elliptical-core two mode fiber sensors and devices incorporating photoinduced refractive index gratings  

NASA Technical Reports Server (NTRS)

Results of experiments performed using germanium-doped, elliptical core, two-mode optical fibers whose sensitivity to strain was spatially varied through the use of chirped, refractive-index gratings permanently induced into the core using Argon-ion laser light are presented. This type of distributed sensor falls into the class of eighted-fiber sensors which, through a variety of means, weight the strain sensitivity of a fiber according to a specified spatial profile. We describe results of a weighted-fiber vibration mode filter which successfully enhances the particular vibration mode whose spatial profile corresponds to the profile of the grating chirp. We report on the high temperature survivability of such grating-based sensors and discuss the possibility of multiplexing more than one sensor within a single fiber.

Greene, Jonathan A.; Miller, Mark S.; Starr, Suzanne E.; Fogg, Brian R.; Murphy, Kent A.; Claus, Richard O.; Vengsarkar, Ashish M.

1991-01-01

58

Improvement in refractive index sensitivity by means of internally curved long period fiber gratings  

NASA Astrophysics Data System (ADS)

A novel configuration of long period fiber grating (LPFG), based on a specially designed refractive index (RI) profile, was manufactured and studied. The internally manufactured geometric structure is characterized by grating planes tilted at increasing angles, as moving away from the center of symmetry of the structure towards its both edges. This structure reproduces the bending of an optical fiber and improves the RI sensitivity of an LPG to the external surrounding medium. A three-fold enhancement in the RI sensitivity was experimentally proved, thus giving a further contribution towards the development of more sensitive RI sensors based on optical fiber LPGs.

Chiavaioli, F.; Trono, C.; Baldini, F.

2014-05-01

59

Design of a long working distance graded index fiber lens with a low NA for fiber-optic probe in OCT application  

NASA Astrophysics Data System (ADS)

A fiber-optic probe for optical coherence tomography (OCT) applications typically includes a short section of graded index (GRIN) fiber fused onto a single-mode (SM) fiber. The GRIN fiber acts as a lens to focus the output of the SM fiber and to collect the reflected light from the sample. In this paper we will use the beam propagation method (BPM) to analyze the output beam characteristics such as beam radius and working distance, and then compare these with the measured results. With this tool we can design a GRIN fiber lens to achieve a long working distance without degrading the system performance.

Sun, Xiaoguang; Li, Jie

2014-02-01

60

Optical fiber sensor system for remote refractive index measurement based on Fresnel reflection using an OTDR  

NASA Astrophysics Data System (ADS)

In this work, we present an optical fiber sensor system for remote refractive index measurement using the optical time domain reflectometry technique as an interrogation method, and investigate the refractive index sensibility of the sensor system in detail. The sensor system operates based on Fresnel reflection at the fiber's end that is cleaved as a vertical planar surface. Surrounding refractive index from a long distance away can be measured easily through utilizing this sensor system. The experimental setup is simple and easy to handle. Experimental results show the feasibility of the remote measurement of refractive index. The range of this measurement can reach ~30km, moreover, to ensure its repeatability and accuracy, we retest the same sample for many times, some of which are artificially applied with disturbance. Lastly we make a comparative analysis to certify that the sensor system has a good potential to remote practical applications.

Yuan, Jianying; Zhao, Chun-Liu; Ye, Manping; Zhang, Zaixuan; Jin, Shangzhong

2013-12-01

61

Complete Analysis of the Characteristics of Propagation into Photonic Crystal Fibers, by the Finite Element Method  

Microsoft Academic Search

Using the finite element method, we propose an accurate vector analysis of the lowest electromagnetic modes of photonic crystal fibers. The likeness of their propagation characteristics to those of step index fibers is emphasized. Within the determined limits of a domain of validity, an equivalent step index fiber is defined. In addition, the single-mode broadband behavior of photonic crystal fibers

F. Brechet; J. Marcou; D. Pagnoux; P. Roy

2000-01-01

62

All-fiber coherent combining of Er-doped amplifiers through refractive index control in Yb-doped fibers.  

PubMed

We propose a simple all-fiber solution for coherent beam combining of Er-doped fiber amplifiers. This method, which we believe to be a new method, employs the effect of refractive index changes in Yb-doped fibers induced at approximately 1.55 microm by optical pumping at approximately 980 nm, which is performed for an active phase control in the fiber configuration. An algorithm based on population inversion in a two-level system supports the straightforward implementation of the effect into a feedback loop. Combining two 500 mW Er-doped amplifiers in a single-mode fiber is successfully demonstrated with control by approximately 120 mW laser diode. The method is shown to operate against the acoustic phase noise within the range of approximately pi rad and with a rate of approximately 2.6 pi rad/ms that potentially serves combining of at least 50 amplifiers similar to those used in practical work. PMID:19927215

Fotiadi, Andrei A; Zakharov, Nikita; Antipov, Oleg L; Mégret, Patrice

2009-11-15

63

Partial power recovery of bend-induced loss using a hybrid index-guiding photonic crystal fiber  

E-print Network

length [1]. Such fibers allow for the introduction of polymers (and other active materials such as liquidPartial power recovery of bend-induced loss using a hybrid index-guiding photonic crystal fiber crystals, high index fluids, etc.) into the air regions yielding hybrid polymer/silica waveguides

Vlachos, Kyriakos G.

64

Etching Bragg gratings in Panda fibers for the temperature-independent refractive index sensing.  

PubMed

We demonstrate the evolution of the Bragg gratings inscribed in Panda fibers with chemical etching. The resonance wavelengths can blueshift with cladding reduction similar to the conventional counterparts. But the wavelength separation between the two polarizations is co-determined by the stress and the asymmetric shape effects. The fast and slow axes of the fiber can be reversed with each other and zero birefringence can be achieved by chemical etching the structure. When the stress-applying parts of the fiber are removed, the finalizing grating can be exploited for the temperature-independent refractive index sensing, since the modes corresponding to the two polarizations exhibit the dissimilar responses to the external refractive index change but the same response to temperature. Our device is featured with easy achievement, spectral controllability, and relative robustness. PMID:25607160

Li, Jie; Wang, Hao; Sun, Li-Peng; Huang, Yunyun; Jin, Long; Guan, Bai-Ou

2014-12-29

65

Measurement of resonant and nonresonant induced refractive index changes in Yb-doped fiber grating amplifier.  

PubMed

We have measured the refractive index change (RIC) induced in a fiber Bragg grating (FBG) written in a Yb-doped fiber amplifier (YB-FBG) because of the amplifier pumping. The measurement was performed by exploiting the high sensitivity of the YD-FBG transmission to the RIC. We have separated between electronic and thermal contributions to the RIC based on the difference between the time-scales of the two effects. Because of high UV-induced loss in FBGs, the thermal contribution to the RIC is increased, in comparison with previously published work, where no grating was written in the fiber amplifier. The measurement method allows us to find the sign of each contribution to the RIC, and it requires only a few centimeters of fiber. Optimal pumping scheme for reducing the RIC in a YB-FBG is studied. PMID:25680141

Shapira, Y P; Oscar, D; Spektor, B; Smulakovsky, V; Horowitz, M

2015-02-15

66

A reflective fiber-optic refractive index sensor based on multimode interference in a coreless silica fiber  

NASA Astrophysics Data System (ADS)

A reflective fiber-optic refractive index (RI) sensor based on multimode interference (MMI) is presented and investigated in this paper. The sensor is made by splicing a small section of coreless silica fiber (CSF) to the standard single mode fiber (SMF). A wide-angle beam propagation method (WA-BPM) is employed for numerical simulation and design of the proposed RI sensor. Based on the simulation results, a RI sensor with a length of 1.7 cm of CSF is fabricated and experimentally studied. Experimental results show that the characteristic wavelength shift has an approximately linear relationship with the RI of the sample. A sensitivity of 141 nm/RIU (refractive index unit) and a resolution of 2.8×10-5 are obtained in the RI range from 1.33 to 1.38. As the RI value is higher than 1.38, the sensitivity of the sensor increase rapidly as the RI increase and a maximum sensitivity of 1561 nm/RIU can be achieved, corresponding to a resolution of 2.6×10-6. The experimental results fit well with the numerical simulation results.

Zhou, Xinlei; Chen, Ke; Mao, Xuefeng; peng, Wei; Yu, Qingxu

2015-04-01

67

Refractive index sensitivity of nano-film coated long-period fiber gratings.  

PubMed

We demonstrate the fabrication of long-period fiber gratings (LPFGs) coated with high index nano-film using the atomic layer deposition (ALD) technology. Higher index sensitivity can be achieved in the transition region of the coated LPFGs. For the LPFG coated by nano-film with a thickness of 100 nm, the high index sensitivity of 3000 nm/RIU and the expanded index sensitive range are obtained. The grating contrast of the over-coupled LPFGs and conventional LPFGs are measured and the over-coupled gratings are found to have a higher contrast in the transition region. The cladding modes transition is observed experimentally with increasing surrounding index using an infrared camera. The theoretical model of the hybrid modes in four-layer cylindrical waveguide is proposed for numerical simulation. The experimental results are well consistent with theoretical analysis. PMID:25835871

Zou, Fang; Liu, Yunqi; Deng, Chuanlu; Dong, Yanhua; Zhu, Shan; Wang, Tingyun

2015-01-26

68

Enhanced refractive index sensor using a combination of a long period fiber grating and a small core singlemode fiber structure  

NASA Astrophysics Data System (ADS)

An enhanced refractive index (RI) sensor based on a combination of a long period fiber grating (LPG) and a small core singlemode fiber (SCSMF) structure is proposed and developed. Since the LPG and SCSMF transmission spectra experience a blue and a red shift respectively as the surrounding RI (SRI) increases, the sensitivity is improved by measuring the separation between the resonant wavelengths of the LPG and SCSMF structures. Experimental results show that the sensor has a sensitivity of 1028 nm/SRI unit in the SRI range from 1.422 to 1.429, which is higher than individual sensitivities of either structure alone used in the experiment. Experimental results agree well with simulation results.

Wu, Qiang; Chan, Hai Ping; Yuan, Jinhui; Ma, Youqiao; Yang, Minwei; Semenova, Yuliya; Yan, Binbin; Wang, Pengfei; Yu, Chongxiu; Farrell, Gerald

2013-09-01

69

Numerical analysis of birefringence tuning in high index microstructured fiber selectively filled with liquid crystal  

NASA Astrophysics Data System (ADS)

In this paper we present the theoretical investigation of the phase birefringence in multi-component glasses photonic crystal fiber PCF14(6), selectively infiltrated with 5CB nematic liquid crystal (LC). The PCF14(6) used as a host in our numerical model is made of the PBG08 high-refractive index glass (~1.95). Refractive index of the fiber is much higher than then both ordinary and extraordinary refractive indices of the LC and as a result low-loss and index-guiding propagation is possible. In our calculations we assume that the host PCF is infiltrated with LC only in the center row of the air channels. Such selective infiltration induces initial phase birefringence in the fiber equal to 1.8 .10-5 when molecules are parallel to the fiber axis. The influence of the tilt angle of the liquid crystal molecules alignment on the PLCF birefringence is presented. We show possibility to tune the phase birefringence up to 6.2 .10-5 or down to -2.4 .10-5 depending on the direction of electric field.

Milenko, Karolina; Ertman, Slawomir; Woli?ski, Tomasz R.

2013-05-01

70

Walk Ratio (Step Length/Cadence) as a Summary Index of Neuromotor Control of Gait: Application to Multiple Sclerosis  

ERIC Educational Resources Information Center

In healthy adults, the step length/cadence ratio [walk ratio (WR) in mm/(steps/min) and normalized for height] is known to be constant around 6.5 mm/(step/min). It is a speed-independent index of the overall neuromotor gait control, in as much as it reflects energy expenditure, balance, between-step variability, and attentional demand. The speed…

Rota, Viviana; Perucca, Laura; Simone, Anna; Tesio, Luigi

2011-01-01

71

Refractive index sensor based on an abrupt taper Michelson interferometer in a single-mode fiber  

Microsoft Academic Search

A simple refractive index sensor based on a Michelson interferometer in\\u000a a single-mode fiber is constructed and demonstrated. The sensor consists\\u000a of a single symmetrically abrupt taper region in a short piece of\\u000a single-mode fiber that is terminated by similar to 500 nm thick gold\\u000a coating. The sensitivity of the new sensor is similar to that of a\\u000a long-period-grating-type sensor,

Zhaobing Tian; Scott S.-H. Yam; Hans-Peter Loock

2008-01-01

72

Nonlinear refractive index measurement utilizing bistable behavior of double coupling optical fiber ring resonator  

NASA Astrophysics Data System (ADS)

A novel approach for measuring the nonlinear refractive index of an optical fiber utlizing the bistable behavior of the double coupling optical fiber ring resonator was proposed and investigated. The switch-off or switch-on power decreases with an increase in the nonlinear refractive index n 2 (m2/W), and the dependence of swith-off or switch-on power on the nonlinear refractive index was analyzed numerically. Simulation results showed that the switch-off power and switch-on power (in dBW) decreased linearly with log10( n 2) in a 100-m-length fiber ring resonator, when n 2 changed from 3.2 × 10-20 m2/W to 2.5 × 10-17 m2/W or nearly n 2 = 3.2 × 10-20 m2/W. These mean that high accuracy as well as large-scale nonlinear refractive index measurement can be achieved by the proposed approach.

Yang, Lei; Pan, Wei; Luo, Bin; Yan, Lianshan

2015-03-01

73

Fabrication Quality Analysis of a Fiber Optic Refractive Index Sensor Created by CO2 Laser Machining  

PubMed Central

This study investigates the CO2 laser-stripped partial cladding of silica-based optic fibers with a core diameter of 400 ?m, which enables them to sense the refractive index of the surrounding environment. However, inappropriate treatments during the machining process can generate a number of defects in the optic fiber sensors. Therefore, the quality of optic fiber sensors fabricated using CO2 laser machining must be analyzed. The results show that analysis of the fiber core size after machining can provide preliminary defect detection, and qualitative analysis of the optical transmission defects can be used to identify imperfections that are difficult to observe through size analysis. To more precisely and quantitatively detect fabrication defects, we included a tensile test and numerical aperture measurements in this study. After a series of quality inspections, we proposed improvements to the existing CO2 laser machining parameters, namely, a vertical scanning pathway, 4 W of power, and a feed rate of 9.45 cm/s. Using these improved parameters, we created optical fiber sensors with a core diameter of approximately 400 ?m, no obvious optical transmission defects, a numerical aperture of 0.52 ± 0.019, a 0.886 Weibull modulus, and a 1.186 Weibull-shaped parameter. Finally, we used the optical fiber sensor fabricated using the improved parameters to measure the refractive indices of various solutions. The results show that a refractive-index resolution of 1.8 × 10?4 RIU (linear fitting R2 = 0.954) was achieved for sucrose solutions with refractive indices ranging between 1.333 and 1.383. We also adopted the particle plasmon resonance sensing scheme using the fabricated optical fibers. The results provided additional information, specifically, a superior sensor resolution of 5.73 × 10?5 RIU, and greater linearity at R2 = 0.999. PMID:23535636

Chen, Chien-Hsing; Yeh, Bo-Kuan; Tang, Jaw-Luen; Wu, Wei-Te

2013-01-01

74

Remote and high precision step height measurement with an optical fiber multiplexing interferometric system  

NASA Astrophysics Data System (ADS)

An optical fiber multiplexing low coherence and high coherence interferometric system, which includes a Fizeau interferometer as the sensing element and a Michelson interferometer as the demodulating element, is designed for remote and high precision step height measurement. The Fizeau interferometer is placed in the remote field for sensing the measurand, while the Michelson interferometer which works in both modes of low coherence interferometry and high coherence interferometry is employed for demodulating the measurand. The range of the step height is determined by the low coherence interferometry and the value of it is measured precisely by the high coherence interferometry. High precision has been obtained by searching precisely the peak of the low coherence interferogram symmetrically from two sides of the low coherence interferogram and stabilizing the Michelson interferometer with a feedback loop. The maximum step height that could be measured is 6 mm while the measurement resolution is less than 1 nm. The standard deviation of 10 times measurement results of a step height of 1 mm configurated with two gauge blocks is 0.5 nm.

Wang, Yunzhi; Xie, Fang; Ma, Sen; Chen, Liang

2015-03-01

75

Photonic crystal fiber refractive index sensor based on surface plasmon resonance  

NASA Astrophysics Data System (ADS)

This paper presents a photonic crystal fiber (PCF) refractive index sensor. The sensor structure is quite simple. It is composed of three segments of optical fibers spliced together. The multimode fibers with core diameter of 50 ?m are used for light input and output. The middle fiber is a short segment of PCF, ESM-12-01. Although it has some advantages such as being able to operate in single mode for a large number of light wavelengths and has great temperature stability, it also has a common drawback of the PCFs, that is, the tiny holes will collapse when they are spliced. This paper makes use of this drawback to facilitate the generation of the surface plasmon resonance. The spliced region of a PCF actually becomes a thin silica rod that is no longer a PCF or a traditional optical fiber. For this reason once the light travels into this region it diverts in all possible directions. Thus, the splice acts as a mode converter that converts the core modes of the multimode fiber into a set of the modes spreading into the PCF cladding. Among those modes some are suitable for SPR excitation. The width and the depth of the output spectrum dip depend on the length of the sensing part and the thickness and uniformity of the gold coating, and hence these parameters affect the properties of the sensor. The developed sensor is compact in size, simple to fabricate, promising in performance, and has a potential for practical applications.

Chen, Jiahua; Brabant, Daniel; Bock, Wojtek J.; Mikulic, Predrag; Eftimov, Tinko

2010-06-01

76

The adsorption of O and CO on low index Ni planes and stepped nickel surfaces  

NASA Astrophysics Data System (ADS)

The 5-parameter morse potential (5-MP) of interaction between an adatom and metal surface cluster is put forward and performed on O-Ni single crystal surface systems. The data of adsorption sites, adsorption geometry, binding energy and eigenvalues for vibration, etc. are obtained, also, several controversial questions have been discussed and analyzed for these systems. The extended LEPS potential energy surfaces of CO-Ni single crystal plane systems are constructed by means of 5-MP, both the adsorption and vibration of CO on Ni low index plane surface and stepped defective surface are investigated. The predictions for adsorption geometry, binding energy and vibrational frequency, etc. that we obtained are in good agreement with the experimental results. Meanwhile, the influence of step defect on Ni(1 0 0) surface for CO dissociation is also examined.

Xin Wang, Ze; Qiao, Qing-An; Gang Chen, Shou; Xia Zhang, Wen

2002-10-01

77

One-step electro-spinning/netting technique for controllably preparing polyurethane nano-fiber/net.  

PubMed

Electro-spinning/netting (ESN) as a cutting-edge technique evokes much interest because of its ability in the one-step preparation of versatile nano-fiber/net (NFN) membranes. Here, a controllable fabrication of polyurethane (PU) NFN membranes with attractive structures, consisting of common electrospun nanofibers and two-dimensional (2D) soap bubble-like structured nano-nets via an ESN process is reported. The unique nanoscaled NFN architecture can be finely controlled by regulating the solution properties and several ESN process parameters. The versatile PU nano-nets comprising interlinked nanowires with ultrathin diameters (5-40 nm) mean that the NFN structured membranes possess several excellent characteristics, such as an extremely large specific surface area, high porosity and large stacking density, which would be particularly useful for applications in ultrafiltration, special protective clothing, ultrasensitive sensors, catalyst support and so on. PMID:21858891

Hu, Juanping; Wang, Xianfeng; Ding, Bin; Lin, Jinyou; Yu, Jianyong; Sun, Gang

2011-11-01

78

Performance analysis simulation of new SPR microstructured D-type optical fiber sensor configurations for refractive index measurement  

NASA Astrophysics Data System (ADS)

This paper presents the performance analysis of two new sensing configurations of refractive index based on surface plasmon resonance (SPR) in microstructured D-type optical fiber with a thin gold layer using simulations obtained with COMSOL Multiphysics. The configurations are analyzed in terms of the intensity of the electric field. The results are compared with a conventional SPR D-type optical fiber sensor for refractive index measurement.

Santos, D. F.; Guerreiro, A.; Baptista, J. M.

2014-05-01

79

Sensitivity enhancement of fiber-optic refractive index sensor based on multimode interference with gold nanoparticles  

NASA Astrophysics Data System (ADS)

In this study, we investigated combinations of fiber-based multimode interference (MMI) sensors with gold nanoparticles (NPs). Gold NPs were synthesized and attached to the MMI sensor region using a silane-coupling agent. Light absorption due to the NPs was confirmed at wavelengths of 560 nm and longer, including the telecommunication band (1300–1600 nm). We examined the variation in the interfered wavelengths with changes in the medium surrounding the MMI sensor, both with and without NPs. The interfered wavelengths were redshifted when the refractive index (RI) increased, and the shift with NPs was almost twice as large as the shift without NPs. We determined the sensitivity of the MMI sensor with NPs to be approximately 218.28 nm/RIU (refractive index unit) in a refractive index range from 1.31535 to 1.35199.

Taue, Shuji; Daitoh, Hiroyuki; Fukano, Hideki

2015-04-01

80

Hybrid optical fiber Fabry-Perot interferometer for simultaneous measurement of gas refractive index and temperature.  

PubMed

We present a hybrid miniature optical fiber Fabry-Perot interferometer for simultaneous measurement of gas refractive index and temperature. The interferometer is fabricated by cascading two short sections of capillary tubes with different inner diameters. One extrinsic interferometer is based on the air gap cavity formed by the capillary tube with large diameter. Another section of capillary tube with small inner diameter performs as an intrinsic interferometer and also provides a channel enabling gas to enter and leave the extrinsic cavity freely. The experiment shows that the different dips or peaks in fringe exhibit different responses to the changes in gas refractive index and temperature. Owing to this feature, simultaneous measurement of the gas refractive index and temperature can be realized. PMID:25402996

Wang, Ruohui; Qiao, Xueguang

2014-11-10

81

Elementary Steps of the Cross-Bridge Cycle in Fast-Twitch Fiber Types from Rabbit Skeletal Muscles  

PubMed Central

To understand the molecular mechanism underlying the diversity of mammalian skeletal muscle fibers, the elementary steps of the cross-bridge cycle were investigated in three fast-twitch fiber types from rabbit limb muscles. Skinned fibers were maximally Ca2+-activated at 20°C and the effects of MgATP, phosphate (P, Pi), and MgADP were studied on three exponential processes by sinusoidal analysis. The fiber types (IIA, IID, and IIB) were determined by analyzing the myosin heavy-chain isoforms after mechanical experiments using high-resolution SDS-PAGE. The results were consistent with the following cross-bridge scheme: where A is actin, M is myosin, D is MgADP, and S is MgATP. All states except for those in brackets are strongly bound states. All rate constants of elementary steps (k2, 198–526 s?1; k?2, 51–328 s?1; k4, 13.6–143 s?1; k?4, 13.6–81 s?1) were progressively larger in the order of type IIA, type IID, and type IIB fibers. The rate constants of a transition from a weakly bound state to a strongly bound state (k?2, k4) varied more among fiber types than their reversals (k2, k?4). The equilibrium constants K1 (MgATP affinity) and K2 (=k2/k?2, ATP isomerization) were progressively less in the order IIA, IID, and IIB. K4 (=k4/k?4, force generation) and K5 (Pi affinity) were larger in IIB than IIA and IID fibers. K1 showed the largest variation indicating that the myosin head binds MgATP more tightly in the order IIA (8.7 mM?1), IID (4.9 mM?1), and IIB (0.84 mM?1). Similarly, the MgADP affinity (K0) was larger in type IID fibers than in type IIB fibers. PMID:16143633

Galler, Stefan; Wang, Brant Gang; Kawai, Masataka

2005-01-01

82

Few-mode fiber with inverse-parabolic graded-index profile for transmission of OAM-carrying modes.  

PubMed

A novel type of few-mode fiber, characterized by an inverse-parabolic graded-index profile, is proposed for the robust transmission of cylindrical vector modes as well as modes carrying quantized orbital angular momentum (OAM). Large effective index separations between vector modes (>2.1 × 10(-4)) are numerically calculated and experimentally confirmed in this fiber over the whole C-band, enabling transmission of OAM(+/-1,1) modes for distances up to 1.1 km. Simple design rules are provided for the optimization of the fiber parameters. PMID:25089424

Ung, B; Vaity, P; Wang, L; Messaddeq, Y; Rusch, L A; LaRochelle, S

2014-07-28

83

Optical fiber sensor based on capillary wall for highly-sensitive refractive index measurement  

NASA Astrophysics Data System (ADS)

This paper reports a temperature-compensated fiber-optic refractive index (RI) sensor for high sensitivity measurement. The sensor includes a piece of fused-silica capillary (FSC) and a fiber Bragg grating (FBG), both of which are sandwiched by single-mode fibers (SMFs). When light from the lead-in SMF enters into the wall of the FSC that acts as a RI sensing element, multiple modes are excited and interfere to form fringes collected by the lead-out SMF. The FBG is fabricated adjunct to the FSC to compensate its temperature sensitivity. The FSC based sensor prototype is fabricated and sealed in a flow cell to test its performance. Experimental results show that the sensor is highly sensitive to RI, and the sensitivity in the tested RI range from 1.33 to 1.35 is 698.52 nm/RIU and from 1.35 to 1.37 is 1061.78 nm/RIU. The temperature sensitivity of the FSC is -0.173 nm/°C, which is compensated by the FBG. This capillary wall based sensor can be further developed as a miniaturized fiber optic biosensor for biochemical application.

Liu, Yun; Peng, Wei; Zhang, Xinpu; Qian, Siyu

2014-05-01

84

Experimental analysis of distributed pump absorption and refractive index changes in Yb-doped fibers using acousto-optic interaction.  

PubMed

In-fiber acousto-optic interaction is used to characterize the refractive index changes at the C band in a single-mode ytterbium-doped optical fiber under 980 nm pumping. The transmission notch created by the acoustic-induced coupling between the core mode and a cladding mode shifts to longer wavelengths when the pump is delivered to the fiber. The electronic contribution to the refractive index change is quantified from the wavelength shift. Using a time-resolved acousto-optic method, we investigate the distribution of pump absorption, and the resulting refractive index change profile, along sections of ytterbium-doped fiber exceeding 1 m long under different pump power levels. PMID:25723408

Alcusa-Sáez, E P; Díez, A; Andrés, M V

2015-03-01

85

Single mode tapered fiber-optic interferometer based refractive index sensor and its application to protein sensing.  

PubMed

We demonstrate refractive index sensors based on single mode tapered fiber and its application as a biosensor. We utilize this tapered fiber optic biosensor, operating at 1550 nm, for the detection of protein (gelatin) concentration in water. The sensor is based on the spectroscopy of mode coupling based on core modes-fiber cladding modes excited by the fundamental core mode of an optical fiber when it transitions into tapered regions from untapered regions. The changes are determined from the wavelength shift of the transmission spectrum. The proposed fiber sensor has sensitivity of refractive index around 1500 nm/RIU and for protein concentration detection, its highest sensitivity is 2.42141 nm/%W/V. PMID:25321749

Yadav, T K; Narayanaswamy, R; Abu Bakar, M H; Kamil, Y Mustapha; Mahdi, M A

2014-09-22

86

An equivalent-stepped-index-coupled DFB semiconductor laser and laser array realized by stepping the duty cycle of the Sampled Bragg grating  

NASA Astrophysics Data System (ADS)

An equivalent-stepped-index-coupled (ESIC) distributed feedback semiconductor laser with an equivalent-stepped duty cycle (ESDC) is proposed and investigated numerically. The ESDC grating profile is realized by stepping the duty cycle of a Sampled Bragg grating (SBG) with the uniform seeding grating. Numerical results show that the light will be distributed in larger region along the laser cavity, that is to say, light field will be flattened and spatial hole burning can be suppressed in such flexible structure. Based on the ESDC structure, different sampling structures in a DFB laser array can also be obtained by stepping the sampling periods; therefore, multi-wavelength laser array can be designed and fabricated, which would simplify the fabrication process, and may be more suitable for the high precision and massive fabrication of DFB laser and laser array with reduced spatial hole burning.

Zheng, Junshou; Zhang, Yunshan; Li, Lianyan; Tang, Song; Sh, Yuechun; Chen, Xiangfei

2015-04-01

87

Highly sensitive fiber refractive index sensor based on side-core holey structure  

NASA Astrophysics Data System (ADS)

We propose a side-core holey fiber (SCHF)-based surface plasmon resonance (SPR) sensor to achieve high refractive index (RI) sensitivity. The SCHF structure can facilitate analyte filling and enhance the overlapping area of the core mode and surface plasmon polariton (SPP) mode. The coupling properties of the sensor are analyzed by numerical simulation. The maximum sensitivity of 5000 nm/RIU in an RI range of 1.33–1.44, and the average sensitivity of 9295 nm/RIU in an RI range from 1.44 to 1.54 can be obtained.

Han, Ya; Xia, Li; Liu, De-Ming

2014-10-01

88

Improvement of refractive index profiling of a small-core single-mode fiber under partially coherent light excitation  

NASA Astrophysics Data System (ADS)

The refractive index profile of a non-bending small-core single-mode fiber was first reconstructed from the measured guided mode intensity profile and its spatial derivatives. By combining a rotating diffuser with a coherent laser source, the resulting partially coherent light source overcomes the speckles on the guided mode image of a straight fiber, and the corresponding refractive index profile was successfully reconstructed. Furthermore, guided mode images of a bent fiber with a fiber coil at midway were also measured under different coherency light excitations for comparison. The slight asymmetry of the reconstructed index profile of a bent fiber measured under coherent light excitation was greatly improved when measured under partially coherent light excitation. The generated additional leaky modes propagating partly in both core and cladding induced by the effects of the fundamental core mode deformation at the intermediate fiber bending structure and the mode transition at the bent-to-straight fiber section were averaged out with a low coherence transformed light source.

Tsai, Wan-Shao; Huang, Bo-Ji; Sheu, Fang-Wen

2015-02-01

89

Birefringence and large mode area analysis of segmented cladding index-guiding photonic crystal fibers  

NASA Astrophysics Data System (ADS)

High birefringence and large mode area are the two paramount requirements of single-mode fibers to control polarization mode dispersion and nonlinear effects. We have investigated the birefringence, higher-order mode coupling loss of a fundamental mode (FM), and numerical aperture of index-guiding segmented cladding photonic crystal fibers in continuation to our previous analysis of the design for FM confinement and V parameter. High birefringence on the order of 10-4 to 10-3 over the near-infrared to short-wavelength infrared (0.75 to 2.3 ?m) spectral range has been obtained. The finite difference time domain method has been used for simulation. The center defect in the lattice forms the core and the remaining part represents the cladding. With phosphate glass (ngl=1.56) as a base material, cladding consists of different segments formed by varying the air hole diameter resulting in strong form birefringence and reduced numerical aperture which leads to a large mode area. We inferred a relation between fiber symmetry and birefringence by varying the duty cycle of the designs. A significant reduction in beat lengths shows reduced power losses in the FM due to higher-order mode coupling.

Kanungo, Vinay; Janyani, Vijay; Salim, Mohammad

2015-02-01

90

Experiences with a fiber linked spectrograph  

Microsoft Academic Search

A fiber linked spectrograph is described which was built for use at astronomical telescopes with apertures of less than 100 cm. The link between the telescope and the spectrograph was made by means of two single step index glass-on-glass fibers with a core diameter of 63 mum. The transmission of a 10 m fiber link lies between 65% and 4000

J. G. V. Schiffer

1984-01-01

91

A fiber tip refractive index sensor using FIB-milled gold-coated singlemode-multimode-singlemode structure  

NASA Astrophysics Data System (ADS)

A compact fiber tip refractive index sensor using FIB-milled gold-coated singlemode-multimode-singlemode structure is demonstrated. Focused ion beam (FIB) is exploited to cut the fiber tip to obtain a flat end-face and then a layer of gold is coated on the tip surface, to increase its reflection. An average sensitivity of 265 nm/RIU is obtained experimentally with a ~2.94 ?m diameter singlemode-multimode-singlemode fiber tip (SMST). Because of several advantages, including compactness, ease of fabrication, linear response, high sensitivity, easy connection with other fiberized optical components and low cost, this refractive index sensor could find various applications in chemical and biological area.

Ding, Ming; Wang, Pengfei; Wang, Junlong; Yuan, Heng; Brambilla, Gilberto

2014-05-01

92

Imaging of rat brain using short graded-index multimode fiber  

NASA Astrophysics Data System (ADS)

Clinically it is important to image structures of brain at deeper areas with low invasions, for example, the pathological information is not obtained enough from the white matter. Preliminarily we have measured transmission images of rat brain using the short graded-index multimode fiber (SMMF) with the diameter of 140?m and length of 5mm. SMMF (core diameter, 100?m) was cut using a fiber cleaver and was fixed in a jig. Fiber lengths inside and outside jig were 3mm and 2mm, respectively. The jig was attached at the 20x objective lens. The conventional optical microscope was used to measure images. In basic characteristics, it was confirmed that the imaging conditions almost corresponded to calculations with the ray-transfer matrix and the spatial resolution was evaluated at about 4.4?m by measuring the test pattern. After euthanasia the rat parietal brain was excised with thickness around 1.5mm and was set on the slide glass. The tissue was illuminated through the slide glass by the bundle fiber with Halogen lamp. The tip of SMMF was inserted into the tissue by lifting the sample stage. The transmission image at each depth from 0.1mm to 1.53mm was measured. Around the depth of 1.45mm, granular structures with sizes of 4-5?m were recognized and corresponded to images by HE stained tissue. Total measurement time was within 2 hours. The feasibilities to image the depth of 5 mm with SMMF have been shown.

Sato, Manabu; Kanno, Takahiro; Ishihara, Syoutarou; Suto, Hiroshi; Takahashi, Toshihiro; Kurotani, Reiko; Abe, Hiroyuki; Nishidate, Izumi

2014-03-01

93

Sex, Body Mass Index, and Dietary Fiber Intake Influence the Human Gut Microbiome  

PubMed Central

Increasing evidence suggests that the composition of the human gut microbiome is important in the etiology of human diseases; however, the personal factors that influence the gut microbiome composition are poorly characterized. Animal models point to sex hormone-related differentials in microbiome composition. In this study, we investigated the relationship of sex, body mass index (BMI) and dietary fiber intake with the gut microbiome in 82 humans. We sequenced fecal 16S rRNA genes by 454 FLX technology, then clustered and classified the reads to microbial genomes using the QIIME pipeline. Relationships of sex, BMI, and fiber intake with overall gut microbiome composition and specific taxon abundances were assessed by permutational MANOVA and multivariate logistic regression, respectively. We found that sex was associated with the gut microbiome composition overall (p=0.001). The gut microbiome in women was characterized by a lower abundance of Bacteroidetes (p=0.03). BMI (>25 kg/m2 vs. <25 kg/m2) was associated with the gut microbiome composition overall (p=0.05), and this relationship was strong in women (p=0.03) but not in men (p=0.29). Fiber from beans and from fruits and vegetables were associated, respectively, with greater abundance of Actinobacteria (p=0.006 and false discovery rate adjusted q=0.05) and Clostridia (p=0.009 and false discovery rate adjusted q=0.09). Our findings suggest that sex, BMI, and dietary fiber contribute to shaping the gut microbiome in humans. Better understanding of these relationships may have significant implications for gastrointestinal health and disease prevention. PMID:25874569

Dominianni, Christine; Sinha, Rashmi; Goedert, James J.; Pei, Zhiheng; Yang, Liying; Hayes, Richard B.; Ahn, Jiyoung

2015-01-01

94

Photonic crystal fiber refractive-index sensor based on multimode interferometry  

NASA Astrophysics Data System (ADS)

We report a type of multimode fiber interferometers (MMI) formed in photonic crystal fiber (PCF). To excite the cladding modes from the fundamental core mode of a PCF, a coupling point is formed. To form the coupling point, we used the method that is blowing compressed gas into the air-holes and discharging at one point, and the air-holes in this point will expand due to gas expansion in the discharge process. By placing two coupling points in series, a very simple all-fiber MMI can be implemented. The detailed fabrication process is that the one end of the PCF is tightly sealed by a short section of single mode fiber (SMF) spliced to the PCF. The other end of the PCF is sealed into a gas chamber and the opened air holes are pressurized. The PCF is then heated locally by the fusion splicer and the holes with higher gas pressure will expand locally where two bubbles formed. We tested the RI responses of fabricated sensors at room temperature by immersing the sensor into solutions with different NaCl concentration. Experimental results show that as refractive-index (RI) increases, the resonance wavelength of the MMI moves toward longer wavelengths. The sensitivity coefficients are estimated by the linear fitting line, which is 46nm/RIU, 154mn/RIU with the interferometer lengths (IL) of 3mm and 6mm. The interferometer with larger IL has higher RI sensitivity. The temperature cross-sensitivity of the sensor is also tested. The temperature sensitivity can be as low as -16.0pm/°C.

Gong, Zhenfeng; Zhang, Xinpu; Liu, Yun; Liu, Zigeng; Peng, Wei

2014-11-01

95

Development of a graded index microlens based fiber optical trap and its characterization using principal component analysis  

PubMed Central

We demonstrate a miniaturized single beam fiber optical trapping probe based on a high numerical aperture graded index (GRIN) micro-objective lens. This enables optical trapping at a distance of 200?m from the probe tip. The fiber trapping probe is characterized experimentally using power spectral density analysis and an original approach based on principal component analysis for accurate particle tracking. Its use for biomedical microscopy is demonstrated through optically mediated immunological synapse formation.

Nylk, J.; Kristensen, M. V. G.; Mazilu, M.; Thayil, A. K.; Mitchell, C. A.; Campbell, E. C.; Powis, S. J.; Gunn-Moore, F. J.; Dholakia, K.

2015-01-01

96

Fluorescence imaging of lattice re-distribution on step-index direct laser written Nd:YAG waveguide lasers  

NASA Astrophysics Data System (ADS)

The laser performance and crystalline micro-structural properties of near-infrared step-index channel waveguides fabricated inside Neodymium doped YAG laser ceramics by means of three-dimensional sub-picosecond pulse laser direct writing are reported. Fluorescence micro-mapping of the waveguide cross-sections reveals that an essential crystal lattice re-distribution has been induced after short pulse irradiation. Such lattice re-distribution is evidenced at the waveguide core corresponding to the laser written refractive index increased volume. The waveguides core surroundings also present diverse changes including slight lattice disorder and bi-axial strain fields. The step-index waveguide laser performance is compared with previous laser fabricated waveguides with a stress-optic guiding mechanism in absence of laser induced lattice re-distribution.

Martínez de Mendívil, Jon; Ródenas, Airán; Benayas, Antonio; Aguiló, Magdalena; Diaz, Francesc; Pérez Delgado, Alberto; Lifante, Ginés; Jaque, Daniel; Kar, Ajoy K.

2015-01-01

97

SMS fiber structure with a multimode fiber graded index type for a temperature measurement using an intensity-based interrogation system  

NASA Astrophysics Data System (ADS)

Temperature sensing based on a singlemode-multimode-singlemode (SMS) fiber structure with a graded index multimode fiber (GI-MMF) type using an intensity-based interrogation has been investigated numerically and experimentally. The effect of temperature on the SMS fiber structure with the MMF-GI type was modeled using a modal propagation analysis (MPA). The SMS fiber structures for temperature sensor was fabricated and tested with the MMF length of 57 mm. It is demonstrated experimentally, and supported with numerical results, that the sensor showed a sensitivity of 0.063 dB/°C with a temperature measurement range of 175-325°C. This sensor offers simple configuration and low cost of fabrication for the temperature measurement applications.

Mufarrikha, Ainun; Hatta, Agus M.; Koentjoro, Sekartedjo

2015-01-01

98

Single Step Generation of Micro and Radio Wave Signals in a Short Cavity Fiber Laser  

Microsoft Academic Search

Generation of stable micro or radio waves by fre- quency down-conversion has always been a challenging but rewarding task in radio over fiber systems. In this letter, a novel method for such a generation using a short-cavity fiber laser is demonstrated. For this purpose, an all-fiber laser is designed to have two stable longitudinal laser modes, each of them having

Udari Basnayaka; Xavier Fernando; Xijia Gu

2011-01-01

99

Gain-guided index-antiguided fiber with a Fabry-Perot layer for large mode area laser amplifiers.  

PubMed

We propose a modified gain-guided index-antiguided (GGIAG) fiber structure for large mode area laser amplifiers, in which a thin dielectric layer is placed between the low-index core and the high-index cladding. The introduced dielectric layer functions as a Fabry-Perot etalon. By letting the resonant wavelength of the Fabry-Perot layer coincide with the signal wavelength, the signal is gain-guided in the fiber core. Moreover, the pump is confined in the low-index core owing to the antiresonant reflection originated from the Fabry-Perot layer. Numerical results indicate that the leakage loss of the pump can be minified over two orders of magnitude in the proposed structure, and thus the end-pumping efficiency could be enhanced significantly. PMID:25836427

Lai, Chih-Hsien; Chen, Hsuan-Yu; Du, Cheng-Han; Chiou, Yih-Peng

2015-02-23

100

A Fresnel reflection-based optical fiber sensor system for remote refractive index measurement using an OTDR  

NASA Astrophysics Data System (ADS)

In this paper, we propose a Fresnel reflection-based optical fiber sensor system for remote refractive index measurement using the optical time domain reflectometry technique as an interrogation method. The surrounding refractive index from a long distance away can be measured easily by using this sensor system, which operates based on testing the Fresnel reflection intensity from the fiber-sample interface. This system is a simple configuration, which is easy to handle. Experimental results showed that the range of this measurement could reach about 100.8 km, and the refractive index sensitivities were from 38.71 dB/RIU to 304.89 dB/RIU in the refractive index (RI) range from 1.3486 to 1.4525.

Yuan, Jianying; Zhao, Chunliu; Ye, Manping; Kang, Juan; Zhang, Zaixuan; Jin, Shangzhong

2014-03-01

101

Low-temperature synthesis and characterization of helical carbon fibers by one-step chemical vapour deposition  

NASA Astrophysics Data System (ADS)

Helical carbon fibers (HCNFs) were synthesized by one-step chemical vapour deposition using cupric tartrate as a catalyst at temperature below 500 °C. The bound rubber of natural rubber (NR)/HCNFs were also prepared in this study. The results of thermogravimetry-differential scanning calorimetry (TG/DSC) for cupric tartrate nanoparticles show that the transformation of C4H4CuO6 ? Cu reaction occurs at ?250-310 °C. The characterization of scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) and Raman spectrum for the synthesized products confirms that the synthesis of HCNFs is highly temperature-dependent. The straight fibers with the fiber diameter of 100-400 nm are obtained at 280 °C and HCNFs can be synthesized at higher temperature, with the coil diameter of 0.5-1 ?m and fiber diameter of 100-200 nm at 380 °C, and the coil diameter of ?100 nm and fiber diameter of ?80 nm at 480 °C. The maximum of the bound-rubber content (37%) can be obtained with the addition of 100 wt.% HCNFs in NR, which indicates that the coiled configuration of HCNFs makes a noticeable contribution to the reinforcement of NR/CB system.

Jin, Yongzhong; Chen, Jian; Fu, Qingshan; Li, Binghong; Zhang, Huazhi; Gong, Yong

2015-01-01

102

Analysis of graded-index optical fibers by the spectral parameter power series method  

NASA Astrophysics Data System (ADS)

The spectral parameter power series (SPPS) method is a recently introduced technique (Kravchenko 2008 Complex Var. Elliptic Equ. 53 775–89, Kravchenko and Porter 2010 Math. Methods Appl. Sci. 33 459–68) for solving linear differential equations and related spectral problems. In this work we develop an approach based on the SPPS for analysis of graded-index optical fibers. The characteristic equation of the eigenvalue problem for calculation of guided modes is obtained in an analytical form in terms of SPPS. Truncation of the series and consideration in this way of the approximate characteristic equation gives us a simple and efficient numerical method for solving the problem. Comparison with the results obtained by other available techniques reveals clear advantages for the SPPS approach, in particular, with regards to accuracy. Based on the solution of the eigenvalue problem, parameters describing the dispersion are analyzed as well.

Castillo-Pérez, Raúl; Kravchenko, Vladislav V.; Torba, Sergii M.

2015-02-01

103

Supercontinuum generation in all-solid photonic crystal fibers with a low index subwavelength inclusion in the core  

NASA Astrophysics Data System (ADS)

All-solid photonic crystal fibers are novel fibers which allow us to control dispersion and nonlinear phenomena due to the possibility of using soft glasses and the high nonlinear coefficients of the fibers. We report on dispersion management and supercontinuum generation capabilities in all-solid photonic crystal fibers with a low index subwavelength inclusion in the core. The inclusion makes it possible to engineer the dispersion profile while maintaining a constant effective mode area. Numerical simulations are conducted to analyze dispersion control capability as a function of the geometrical parameters of the fiber cross-section. The structures of photonic crystal fibers have been developed from thermally matched pairs of soft glasses—SF6 lead glass and in-house developed silicate glass NC21—and have been subsequently analyzed. The dispersion characteristics are modeled for theoretical structures and for the developed fibers. Supercontinuum generation is expected and numerically confirmed for the developed fibers in the range 1150–1600 nm with flatness below 1 dB.

Pniewski, J.; Kasztelanic, R.; Pysz, D.; Stepien, R.; Buczynski, R.

2013-08-01

104

Spectral Behavior in Nano-Coated Tilted Fiber Bragg Gratings: Effect of Thickness and External Refractive Index  

Microsoft Academic Search

This work reports on the experimental investigation of the spectral effects induced by uniform high refractive index nano-coatings deposited on weakly tilted fiber Bragg gratings (TFBGs). To this aim, weakly TFBGs with different tilt angles were fabricated and then coated with thin overlays of syndiotactic polystyrene. Automated dip coating technique was used to obtain ring-shaped coatings with thickness ranging in

D. Paladino; A. Cusano; P. Pilla; S. Campopiano; C. Caucheteur; P. Megret

2007-01-01

105

A Sensitivity-Enhanced Refractive Index Sensor Using a Single-Mode Thin-Core Fiber Incorporating an Abrupt Taper  

PubMed Central

A sensitivity-enhanced fiber-optic refractive index (RI) sensor based on a tapered single-mode thin-core diameter fiber is proposed and experimentally demonstrated. The sensor head is formed by splicing a section of tapered thin-core diameter fiber (TCF) between two sections of single-mode fibers (SMFs). The cladding modes are excited at the first SMF-TCF interface, and then interfere with the core mode at the second interface, thus forming an inter-modal interferometer (IMI). An abrupt taper (tens of micrometers long) made by the electric-arc-heating method is utilized, and plays an important role in improving sensing sensitivity. The whole manufacture process only involves fiber splicing and tapering, and all the fabrication process can be achieved by a commercial fiber fusion splicer. Using glycerol and water mixture solution as an example, the experimental results show that the refractive index sensitivity is measured to be 0.591 nm for 1% change of surrounding RI. The proposed sensor structure features simple structure, low cost, easy fabrication, and high sensitivity. PMID:22666052

Shi, Jie; Xiao, Shilin; Yi, Lilin; Bi, Meihua

2012-01-01

106

A Modified EPA Method 1623 that Uses Tangential Flow Hollow-Fiber Ultrafiltration and Heat Dissociation Steps to Detect Waterborne Cryptosporidum and Giardia spp.  

EPA Science Inventory

This protocol describes the use of a tangential flow hollow-fiber ultrafiltration sample concentration system and a heat dissociation as alternative steps for the detection of waterborne Cryptosporidium and Giardia species using EPA Method 1623....

107

Single-step method for fiber-optic probe-based full-range spectral domain optical coherence tomography.  

PubMed

We propose a single-step method appropriated for a fiber-optic probe-based full-range spectral domain optical coherence tomography (OCT). The fiber-optic probe was scanned over a sample with a magnetically driven actuator. In the reference arm, a phase shift of ?/2 was applied during two neighbor axial scanning, from which the complex spectral interferogram was directly reconstructed. Since the complex-conjugate-free OCT image is obtained by doing just one Fourier transform on the complex interferogram, obtaining the full-range image is simple in algorithm and effective in computation time. Some full-range images of biological samples created with the proposed method are presented and the processing time is analyzed. PMID:23872759

Min, Eun Jung; Shin, Jun Geun; Lee, Jae Hwi; Yasuno, Yoshiaki; Lee, Byeong Ha

2013-07-20

108

Dietary fiber and the glycemic index: a background paper for the Nordic Nutrition Recommendations 2012  

PubMed Central

The aim of this study is to review recent data on dietary fiber (DF) and the glycemic index (GI), with special focus on studies from the Nordic countries regarding cardiometabolic risk factors, type 2 diabetes, cardiovascular disease, cancer, and total mortality. In this study, recent guidelines and scientific background papers or updates on older reports on DF and GI published between 2000 and 2011 from the US, EU, WHO, and the World Cancer Research Fund were reviewed, as well as prospective cohort and intervention studies carried out in the Nordic countries. All of the reports support the role for fiber-rich foods and DF as an important part of a healthy diet. All of the five identified Nordic papers found protective associations between high intake of DF and health outcomes; lower risk of cardiovascular disease, type 2 diabetes, colorectal and breast cancer. None of the reports and few of the Nordic papers found clear evidence for the GI in prevention of risk factors or diseases in healthy populations, although association was found in sub-groups, e.g. overweight and obese individuals and suggestive for prevention of type 2 diabetes. It was concluded that DF is associated with decreased risk of different chronic diseases and metabolic conditions. There is not enough evidence that choosing foods with low GI will decrease the risk of chronic diseases in the population overall. However, there is suggestive evidence that ranking food based on their GI might be of use for overweight and obese individuals. Issues regarding methodology, validity and practicality of the GI remain to be clarified. PMID:23538683

Øverby, Nina Cecilie; Sonestedt, Emily; Laaksonen, David E.; Birgisdottir, Bryndis Eva

2013-01-01

109

Improved Optical Fiber Chemical Sensors  

NASA Technical Reports Server (NTRS)

Calculations, based on exact theory of optical fiber, have shown how to increase optical efficiency sensitivity of active-core, step-index-profile optical-fiber fluorosensor. Calculations result of efforts to improve efficiency of optical-fiber chemical sensor of previous concept described in "Making Optical-Fiber Chemical Sensors More Sensitive" (LAR-14525). Optical fiber chemical detector of enhanced sensitivity made in several configurations. Portion of fluorescence or chemiluminescence generated in core, and launched directly into bound electromagnetic modes that propagate along core to photodetector.

Egalon, Claudio O.; Rogowski, Robert S.

1994-01-01

110

Refractive index sensing with Mach-Zehnder interferometer based on concatenating two single-mode fiber tapers  

Microsoft Academic Search

A novel refractive index (RI) sensor based on a fiber Mach-Zehnder\\u000a interferometer was realized by concatenating two single-mode fiber\\u000a tapers separated by a middle section. The proposed device had a minimum\\u000a insertion loss of 3 dB and maximum interferometric extinction ratio over\\u000a 20 dB. The resolution (0.171 nm) of the two-taper sensor to its\\u000a surrounding RI change (0.01) was found

Zhaobing Tian; Scott S.-H. Yam; Jack Barnes; Wojtek Bock; Patricia Greig; James M. Fraser; Hans-Peter Loock; Richard D. Oleschuk

2008-01-01

111

First steps in developing a multimetric macroinvertebrate index for the Ohio River  

USGS Publications Warehouse

The causes of degradation of aquatic systems are often complex and stem from a variety of human influences. Comprehensive, multimetric biological indices have been developed to quantify this degradation and its effect on aquatic communities, and measure subsequent recovery from anthropogenic stressors. Traditionally, such indices have concentrated on small-to medium-sized streams. Recently, however, the Ohio River Fish Index (ORFIn) was created to assess biotic integrity in the Ohio River. The goal of the present project was to begin developing a companion Ohio River multimetric index using benthic macroinvertebrates. Hester-Dendy multiplate samplers were used to evaluate benthic macroinvertebrate assemblages in relation to a gradient of water quality disturbance, represented by varying distances downstream of industrial and municipal wastewater outfalls in the Ohio River. In August 1999 and 2000, samplers were set every 100 m downstream of outfalls (12 outfalls in 1999, 22 in 2000) for 300-1000 m, as well as at upstream reference sites. Candidate metrics (n = 55) were examined to determine which have potential to detect changes in water quality downstream of outfalls. These individual measures of community structure were plotted against distance downstream of each outfall to determine their response to water quality disturbance. Values at reference and outfall sites were also compared. Metrics that are ecologically relevant and showed a response to outfall disturbance were identified as potentially valuable in a multimetric index. Multiple box plots of index scores indicated greater response to outfall disturbance during periods of low-flow, and longitudinal river-wide trends. Evaluation of other types of anthropogenic disturbance, as well as continued analysis of the effects of chemical water quality on macroinvertebrate communities in future years will facilitate further development of a multimetric benthic macroinvertebrate index to evaluate biotic integrity in the Ohio River. Copyright ?? 2007 John Wiley & Sons, Ltd.

Applegate, J.M.; Baumann, P.C.; Emery, E.B.; Wooten, M.S.

2007-01-01

112

Dependences of the polarization properties of polymer graded-index fibers of the Selfoc type  

Microsoft Academic Search

Temperature dependences of some polarization characteristics were determined for polymer Selfoc-type fibers. It was found that when plane-polarized light passed through a fiber of this kind, it emerged with elliptic polarization. The effective direction of the polarization of light emerging from a fiber was shifted by an angle from the plane of polarization of the incident wave. The temperature dependence

N. G. Gachechiladze; S. I. Grigorev; M. G. Zguladze; A. N. Mestvirishvili; V. R. Sagaradze

1983-01-01

113

Dependences of the polarization properties of polymer graded-index fibers of the Selfoc type  

Microsoft Academic Search

Temperature dependences of some polarization characteristics were determined for polymer Selfoc-type fibers. It was found that when plane-polarized light passed through a fiber of this kind, it emerged with elliptic polarization. The effective direction of the polarization of light emerging from a fiber was shifted by an angle ?? from the plane of polarization of the incident wave. The temperature

N G Gachechiladze; S I Grigorev; M G Zguladze; A N Mestvirishvili; V R Sagaradze

1983-01-01

114

The elongation of yeast prion fibers involves separable steps of association and conversion  

Microsoft Academic Search

A self-perpetuating change in the conformation of the translation termination factor Sup35p is the basis for the prion [PSI+], a protein-based genetic element of Saccharomyces cerevisiae. In a process closely allied to in vivo conversion, the purified soluble, prion-determining region of Sup35p (NM) converts to amyloid fibers by means of nucleated conformational conversion. First, oligomeric species convert to nuclei, and

Thomas Scheibel; Jesse Bloom; Susan L. Lindquist

2004-01-01

115

Variable optical attenuator for perfluorinated gradual index polymer optical fiber using a polymer dispersed liquid crystal cell  

Microsoft Academic Search

A Variable Optical Attenuator (VOA) based on a Polymer-Dispersed Liquid Crystal (PDLC) Cell is presented. The VOA's developed prototype has been successfully tested at 660nm, 850nm and 1300nm. This ability makes it strongly recommended for networks using Perfluorinated Gradual Index Polymer Optical Fiber (PF GI-POF) technology. The prototype has revealed a better than 12dBs dynamic range and losses of <1.2dB.

M. A. J. Pontes; C. Vázquez; J. M. S. Pena; P. C. Lallana; D. S. Montero

2005-01-01

116

Carbohydrate Intake, Glycemic Index, Glycemic Load, and Dietary Fiber in Relation to Risk of Stroke in Women  

Microsoft Academic Search

The associations of dietary carbohydrate, glycemic index, and glycemic load with stroke risk were examined among 78,779 US women who were free of cardiovascular disease and diabetes in 1980 and completed a food frequency questionnaire. During an 18-year follow-up, 1,020 stroke cases were documented (including 515 ischemic and 279 hemorrhagic). In analyses adjusting for nondietary risk factors and cereal fiber,

Kyungwon Oh; Frank B. Hu; Eunyoung Cho; Kathryn M. Rexrode; Meir J. Stampfer; JoAnn E. Manson; Simin Liu; Walter C. Willett

2005-01-01

117

The Influences of Fiber Feature and Polymer Melt Index on Mechanical Properties of Sugarcane Fiber/Polymer  

E-print Network

, vascular bundles, and pith (the paren- chyma). It contains cellulose (46.0%), hemicellulose (24.5%), lignin part, cellulose fibers account for 50%, while lig- nin and hemicellulose are 18 and 30%, respectively.6 be used for cellulose, plastics, fermenta- tion products, cane wax, paper and pulps, insulating board

118

FRPRCS-9 Sydney, Australia Monday 13 Wednesday 15 July 2009 STEPPED ISOSTRESS METHOD FOR ARAMID FIBERS  

E-print Network

Keywords: kevlar 49, technora, stepped isostress method, stress-rupture, accelerated testing, activation-term creep behaviour of Kevlar 49 and Technora. This method involves loading a single specimen, instead than TSSP, so offers several advantages. 2 MATERIALS AND EXPERIMENTAL SET-UP Kevlar 49 and Technora

Burgoyne, Chris

119

Content analysis of uterine cervix images: initial steps towards content based indexing and retrieval of cervigrams  

NASA Astrophysics Data System (ADS)

This work is motivated by the need for visual information extraction and management in the growing field of medical image archives. In particular the work focuses on a unique medical repository of digital cervicographic images ("Cervigrams") collected by the National Cancer Institute (NCI) in a longitudinal multi-year study carried out in Guanacaste, Costa Rica. NCI together with the National Library of Medicine (NLM) is developing a unique Web-based database of the digitized cervix images to study the evolution of lesions related to cervical cancer. Such a database requires specific tools that can analyze the cervigram content and represent it in a way that can be efficiently searched and compared. We present a multi-step scheme for segmenting and labeling regions of medical and anatomical interest within the cervigram, utilizing statistical tools and adequate features. The multi-step structure is motivated by the large diversity of the images within the database. The algorithm identifies the cervix region within the image. It than separates the cervix region into three main tissue types: the columnar epithelium (CE), the squamous epithelium (SE), and the acetowhite (AW), which is visible for a short time following the application of acetic acid. The algorithm is developed and tested on a subset of 120 cervigrams that were manually labeled by NCI experts. Initial segmentation results are presented and evaluated.

Gordon, Shiri; Zimmerman, Gali; Long, Rodney; Antani, Sameer; Jeronimo, Jose; Greenspan, Hayit

2006-03-01

120

Single-mode-fibers for fiberoptic-guided missiles: A comparison with graded-index multimode fibers  

Microsoft Academic Search

For a few years there have been activities in the application of optical fibers as a broadband, secure transmission medium between a ground-station and tactical missiles for ranges of about 10 km. The idea is to put the gunner's eye, i.e., a suitable imaging device, into the missile to provide a lock-on-after-launch capability together with a man-in-the-loop option. A key

K. H. Niederhofer; W. D. Schuck

1986-01-01

121

Dietary Fiber, Carbohydrates, Glycemic Index and Glycemic Load in Relation to Breast Cancer Prognosis in the HEAL Cohort  

PubMed Central

Background Dietary intake of fiber, carbohydrate, glycemic index (GI), and glycemic load (GL) may influence breast cancer survival, but consistent and convincing evidence is lacking. Methods We investigated associations of dietary fiber, carbohydrates, GI, and GL with breast cancer prognosis among n=688 stage 0 to IIIA breast cancer survivors in the Health, Eating, Activity, and Lifestyle (HEAL) study. Pre- and postmenopausal women from Western Washington State, Los Angeles County, and New Mexico participated. Usual diet was assessed with a food frequency questionnaire. Total mortality, breast cancer mortality, non-fatal recurrence and second occurrence data were obtained from SEER registries and medical records. Cox proportional hazards regression estimated multivariate-adjusted hazard ratios and 95% CIs. Results During a median of 6.7 years follow-up after diagnosis, n= 106 total deaths, n=83 breast cancer-specific deaths and n=82 non-fatal recurrences were confirmed. We observed an inverse association between fiber intake and mortality. Multivariate-adjusted HRRs comparing high to low intake were 0.53 (95% CI 0.23-1.23) and 0.75 (95% CI 0.43-1.31). A threshold effect was observed whereby no additional benefit was observed for intakes >9 g/day. Fiber intake was suggestively inversely associated with breast-cancer specific mortality (HRR=0.68, 95% CI 0.27-1.70) and risk of non-fatal recurrence or second occurrence (HRR=0.68, 95% CI 0.27-1.70), but results were not statistically significant. Conclusion Dietary fiber was associated with a non-significant inverse association with breast cancer events and total mortality. Further studies to assess and confirm this relationship are needed in order to offer effective dietary strategies for breast cancer patients. Impact Increasing dietary fiber may an effective lifestyle modification strategy for breast cancer survivors. PMID:21430298

Belle, Fabiën N.; Kampman, Ellen; McTiernan, Anne; Bernstein, Leslie; Baumgartner, Kathy; Baumgartner, Richard; Ambs, Anita; Ballard-Barbash, Rachel; Neuhouser, Marian L.

2011-01-01

122

Characterization of evolution of mode coupling in a graded-index polymer optical fiber by using Brillouin optical time-domain analysis.  

PubMed

A narrow bandwidth (2GHz) ?-phase-shift flattop fiber Bragg grating (FBG) is proposed to achieve Brillouin optical time-domain analysis (BOTDA) for perfluorinated graded-index polymer optical fibers (GI-POFs) for the first time to best of our knowledge. Using the technique of BOTDA, we explore the evolution of mode coupling in perfluorinated GI-POFs by analyzing the Brillouin frequency shift (BFS) variation along the whole fiber, and compare them with that of silica graded index multimode fibers (GI-MMFs). The characteristics of mode coupling of GI-POFs and GI-MMFs were also investigated in terms of the speckle patterns at the output face of the two fibers. The results show that compared with silica GI-MMFs, GI-POFs exhibit more efficient mode coupling and the excellent ablility of mode scrambling regardless of alignment conditions. PMID:25401802

Dong, Yongkang; Xu, Pengbai; Zhang, Hongying; Lu, Zhiwei; Chen, Liang; Bao, Xiaoyi

2014-11-01

123

Single-polarization single-mode photonic crystal fiber based on index-matching coupling with a single silica material  

NASA Astrophysics Data System (ADS)

We propose and analyze a novel design of single-polarization single-mode photonic crystal fiber based on index-matching coupling by using a finite-element method. The proposed fiber is designed such that there is a large differential loss between two polarizations of the fundamental mode by reducing two air holes in the cladding region which is composed of hexagonal structured air holes in pure silica. From the numerical analysis it is shown that single-polarization single-mode operation wavelength region can be tuned by adjusting the diameters of two defect air holes. In the proposed design, the spectral region over which the differential loss ratio is larger than 100 can be wider than 150 nm around the wavelength 1.55 or 1.31 ?m. Another novel design that allows simultaneous single-polarization single-mode guidance in two wavelength windows centered at 1.55 and 1.31 ?m is also proposed.

Lee, Sun-Goo; Lim, Sun Do; Lee, Kwanil; Lee, Sang Bae

2011-01-01

124

Anderson localized optical fibers  

NASA Astrophysics Data System (ADS)

Anderson localization has been a subject of fascination and intense research for more than fifty years. It is highly desirable to harness its curious and interesting properties in practical applications. We have taken a step in this direction by using this phenomenon as the wave guiding mechanism in optical fibers. We have shown, both experimentally and numerically, that for a moderate amount of disorder in optical fibers, transverse localization results in an effective propagating beam diameter that is comparable to that of a typical index-guiding optical fiber.1, 2 In this work, we investigate the effect of macro-bending on the localization properties in a disordered polymer optical fiber both experimentally and numerically. We show that macro-bending in ranges of practical interest does not significantly affect the beam propagation in Anderson localized fibers as long as the strong localization dominates the effect of bending.

Karbasi, Salman; Koch, Karl W.; Mafi, Arash

2013-02-01

125

Stack of PECVD silicon nitride nano-films on optical fiber end-face for refractive index sensing  

NASA Astrophysics Data System (ADS)

This paper presents a stack of silicon nitride (SiNx) nano-films deposited with radio-frequency plasma-enhanced chemical deposition (RF PECVD) method on single-mode fiber end-face for refractive index (RI) sensing. The stack consist of high (n~2.4) and low (n~1.9) refractive index (at ?=1550 nm) SiNx nano-films arranged alternately. As a result of the experiment where 5 nano-layers were deposited, we received down to -30 dB-deep resonance in reflection spectrum at about ?=1550 nm. In the proposed sensing scheme both reflected power and wavelength of the resonance can be used for external RI measurements.

?mietana, Mateusz; Koba, Marcin; Ró?ycki-Bakon, Radoslaw

2014-05-01

126

Fiber Optics  

NSDL National Science Digital Library

In this media-rich lesson plan, students investigate how the index of refraction of materials is related to fiber optics: they explore the phenomenon of total internal reflection and learn how dispersion can affect fiber optics.

WGBH Educational Foundation

2011-10-25

127

Highly nonlinear photonic crystal fiber with high refractive index core for dental OCT applications  

NASA Astrophysics Data System (ADS)

Optical coherence tomography is a technology which supplies the tomographic image using the optical interference. It uses the 1.31 ?m wavelength for dental applications. Resolution problems of such a technology can be improved by using supercontinuum light sources as low coherent broadband light is achievable from optical supercontinuum. Photonic crystal fibers have the ability to generate the supercontinuum light even with moderate input power levels. Only thing to consider is to ensure zero or nearly zero dispersion of such fibers at the target 1.31?m wavelength. This paper presents design of a high nonlinear photonic crystal fiber with near-zero dispersion around 1.31?m wavelength based on the finite difference method. Robustness of the design is confirmed numerically by generating wideband supercontinuum.

Koga, Taito; Namihira, Yoshinori; Kinjo, Tatsuya; Kaijage, Shubi F.; Razzak, S. M. Abdur; Nozaki, Shinya

2010-02-01

128

Bismuth-based optical fiber with nonlinear coefficient of 1360 W-1km-1  

Microsoft Academic Search

Abstract: We ,developed ,a conventional ,step-index type highly nonlinear bismuth ,oxide-based glass fiber. This ,fiber exhibits high nonlinearity (? =1360 W, [4]. This ,high nonlinearity originates from high nonlinearity of Bi2O3-based glass [5]. In addition to the high nonlinearity, this fiber shows relatively low propagation loss less

N. Sugimoto; T. Nagashima; T. Hasegawa; S. Ohara; K. Taira; K. Kikuchi

129

Theory of fiber optic radiometry, emissivity of fibers, and distributed thermal sensors  

NASA Astrophysics Data System (ADS)

The general radiometric theory of multimode fiber with a step index is presented, with emphasis on the region of mid- and far-IR optic fibers. The fibers are treated as passive waveguides for external radiation as well as active waveguides generating internal thermal radiation guided to both fiber endfaces. Thermal radiation emission from the fiber endfaces is formulated and compared to that of a blackbody. A fiber-optic distributed thermal sensor (FDTS) based on the self-generation of thermal radiation in a modified IR fiber is discussed. Sources of thermal radiation associated with fiber absorption in the fiber core, core bulk, and cladding are considered. Attention is given to the optimal sensor parameters yielding maximum sensitivity for each absorption profile of a FDTS.

Zur, Albert; Katzir, Abraham

1991-02-01

130

Treatment plan comparison of Linac step and shoot,Tomotherapy, RapidArc, and Proton therapy for prostate cancer using dosimetrical and biological index  

E-print Network

The purpose of this study was to use various dosimetrical indices to determine the best IMRT modality technique for treating patients with prostate cancer. Ten patients with prostate cancer were included in this study. Intensity modulated radiation therapy plans were designed to include different modalities, including the linac step and shoot, Tomotherapy, RapidArc, and Proton systems. Various dosimetrical indices, like the prescription isodose to target volume (PITV) ratio, conformity index (CI), homogeneity index (HI), target coverage index (TCI), modified dose homogeneity index (MHI), conformation number (CN), critical organ scoring index (COSI), and quality factor (QF) were determined to compare the different treatment plans. Biological indices such as the generalized equivalent uniform dose (gEUD), based tumor control probability (TCP), and normal tissue complication probability (NTCP) were also calculated and used to compare the treatment plans. The RapidArc plan attained better PTV coverage, as evidenc...

Lee, Suk; Chang, Kyung Hwan; Shim, Jang Bo; Kim, Kwang Hyeon; Lee, Nam Kwon; Park, Young Je; Kim, Chul Yong; Cho, Sam Ju; Lee, Sang Hoon; Min, Chul Kee; Kim, Woo Chul; Cho, Kwang Hwan; Huh, Hyun Do; Lim, Sangwook; Shin, Dongho

2015-01-01

131

One-step patterning of double tone high contrast and high refractive index inorganic spin-on resist  

SciTech Connect

A direct one-step and low temperature micro-fabrication process, enabling to realize large area totally inorganic TiO{sub 2} micro-patterns from a spin-on resist, is presented. High refractive index structures (up to 2 at 632?nm) without the need for transfer processes have been obtained by mask assisted UV lithography, exploiting photocatalytic titania properties. A distinctive feature not shared by any of the known available resists and boosting the material versatility, is that the system behaves either as a positive or as negative tone resist, depending on the process parameters and on the development chemistry. In order to explain the resist double tone behavior, deep comprehension of the lithographic process parameters optimization and of the resist chemistry and structure evolution during the lithographic process, generally uncommon in literature, is reported. Another striking property of the presented resist is that the negative tone shows a high contrast up to 19, allowing to obtain structures resolution down to 2??m wide. The presented process and material permit to directly fabricate different titania geometries of great importance for solar cells, photo-catalysis, and photonic crystals applications.

Zanchetta, E.; Della Giustina, G.; Brusatin, G. [Industrial Engineering Department and INSTM, Via Marzolo 9, 35131 Padova (Italy)

2014-09-14

132

Fiber-optic sensor tip for measuring temperature and liquid refractive index  

NASA Astrophysics Data System (ADS)

A fiber sensor tip was proposed for measuring temperature and liquid refractive indices (RI). The sensor tip was fabricated by dipping a solidification ultraviolet (SU-8) photoresist onto the end surface of a simple-mode optical fiber. Then the SU-8 photoresist was cured by an ultraviolet source. A Fabry-Perot (FP) cavity was formed on the end faces of the SU-8 and optical fiber, and it showed a perfect FP interference spectrum. The temperature and liquid RI can be independently measured by monitoring the shift and the loss variation of interference peaks. The liquid RI sensitivity is 96.07232 dB/RIU in the RI range of 1.333 to 1.3714, and the temperature sensitivity is 0.38052 nm/°C within the temperature range from 25 to 55°C. The cross-sensitivities of temperature and liquid RI can be ignored. The sensor tip can be used in harsh environments, including strong acid, strong alkali, and violent vibration liquids, as cross-linking SU-8 has excellent chemical corrosion resistance capacity and mechanical strength.

Li, Min; Liu, Yi; Qu, Shiliang; Li, Yan

2014-11-01

133

New insights into dopant design for graded-index plastic optical fibers for transmission at 850 nm  

NASA Astrophysics Data System (ADS)

To develop graded-index plastic optical fibers (GI POFs) which can be utilized for transmissions at 850 nm, not only do molecular vibrational absorptions of the base polymeric materials need to be considered, but also the dopants used. In this study, chlorinated aromatic dopants were synthesized and their effects on the optical and thermal properties of poly(pentafluorostyrene), which has the low-loss window at 850 nm, were studied. The polymers doped with chlorinated dopants showed no absorption peak and retained the broad windows around the source wavelength. Furthermore, they showed higher glass transition temperatures when compared at similar refractive indices than the polymer doped with diphenyl sulfide, which is the most common dopant for acrylates and styrenes-based GI POFs. However, as the chlorine content per dopant molecule increased, the compatibility with the base material became worse and the doped polymer exhibited a higher attenuation due to an increment of light scattering.

Sengupta, Arijit; Koike, Kotaro; Koike, Yasuhiro; Okamoto, Yoshiyuki

2014-02-01

134

Effects of Carbohydrate and Dietary Fiber Intake, Glycemic Index and Glycemic Load on HDL Metabolism in Asian Populations  

PubMed Central

High-density lipoprotein (HDL) is a lipoprotein which has anti-atherogenic property by reverse cholesterol transport from the peripheral tissues to liver. Low HDL-cholesterol (HDL-C) levels are associated with the development of coronary artery diseases (CADs). Various epidemiological studies have suggested that the development of CAD increase in individuals with less than 40 mg/dL of HDL-C. In spite of accumulation of evidences which suggest a significant association between low HDL-C and cardiovascular diseases, effects of dietary factors on HDL metabolism remained largely unknown. There may be interracial differences in effects of dietary factors on HDL metabolism. Here we reviewed published articles about effects of carbohydrate and dietary fiber intake, glycemic index (GI) and glycemic load (GL), on HDL-C metabolism, regarding meta-analyses and clinical studies performed in Asian population as important articles. Low carbohydrate intake, GI and GL may be beneficially associated with HDL metabolism. Dietary fiber intake may be favorably associated with HDL metabolism in Asian populations. PMID:25110535

Yanai, Hidekatsu; Katsuyama, Hisayuki; Hamasaki, Hidetaka; Abe, Shinichi; Tada, Norio; Sako, Akahito

2014-01-01

135

Chirped Gaussian pulse broadening induced by chromatic dispersion in the triple-clad single-mode fiber with a depressed index inner cladding  

Microsoft Academic Search

The chirped Gaussian pulse broadening induced by chromatic dispersion in two kinds of triple-clad single-mode fibers with a depressed index inner cladding was examined in this paper. In view of the impossibility to deduce the expression of chromatic dispersion directly due to the complexity of the characteristic equations, a feasible approach to calculate chromatic dispersion was established, and the influences

Xiaoping Zhang; Liya Xie; Xiangqing Tian; Shangling Hou

2004-01-01

136

Thulium fiber laser and application development  

NASA Astrophysics Data System (ADS)

Within the past 10 years, thulium (Tm)-doped fiber lasers have emerged as a flexible platform offering high average power as well as high peak power. Many of the benefits and limitations of Tm:fiber lasers are similar to those for ytterbium (Yb)-doped fiber lasers, however the ~2 µm emission wavelength posses unique challenges in terms of laser development as well as several benefits for applications. In this presentation, we will review the progress of laser development in CW, nanosecond, picosecond, and femtosecond regimes. As a review of our efforts in the development of power amplifiers, we will compare large mode area (LMA) stepindex and photonic crystal fiber (PCF) architectures. In our research, we have found Tm-doped step index LMA fibers to offer relatively high efficiency and average powers at the expense of fundamental mode quality. By comparison, Tm-doped PCFs provide the largest mode area and quasi diffraction-limited beam quality however they are approximately half as efficient as step-index fibers. In terms of defense related applications, the most prominent use of Tm:fiber lasers is to pump nonlinear conversion to the mid-IR such as supercontinuum generation and optical parametric oscillators/amplifiers (OPO/A). We have recently demonstrated Tm:fiber pumped OPOs which generate ~28 kW peak power in the mid-IR. In addition, we will show that Tm:fiber lasers also offer interesting capabilities in the processing of semiconductors.

Shah, Lawrence; Gaida, Christian; Gebhardt, Martin; Sincore, Alex; Bradford, Joshua D.; Gehlich, Nils; Mingareev, Ilya; Richardson, Martin

2014-06-01

137

Design of refractive index sensors based on the wavelength-selective resonant coupling phenomenon in dual-core photonic crystal fibers  

NASA Astrophysics Data System (ADS)

Design strategies for high-sensitivity refractive index sensors based on the principle of wavelength-selective resonant coupling in dual-core photonic crystal fibers are presented. Phase matching at a single wavelength can be achieved between an analyte-filled microstructured core and a small core with a down-doped rod or one small air hole in the center, thus enabling selectively directional resonant-coupling between the two cores. The transmission spectra of the output light presents a notch at the index-matched wavelength, yielding a resonant wavelength depending on the refractive index of the analyte. Numerical simulations demonstrate that both of the two proposed sensors can be used for highly sensitive detection of low-index analyte. In particular, the configuration realized by introducing the fiber with a small air hole in one core can be used to the detection of the analyte index around 1.33 and the sensitivity reach to 1.2×104 nm per refractive index unit (RIU). In addition, the detection limit is as low as 2.5×10-7 RIU at na=1.33.

Sun, Bing; Chen, Ming-Yang; Zhang, Yong-Kang; Yang, Ji-chang

2012-03-01

138

Egestion of asbestos fibers in Tetrahymena results in early morphological abnormalities. A step in the induction of heterogeneous cell lines?  

PubMed

In Tetrahymena populations exposed to crocidolite asbestos fibers, many cells develop morphological abnormalities within 1-2 hours. The abnormalities are mainly large or small protrusions or indentations, or flattened parts of the cell surface and most often located in the posterior part of the cell. They are formed repeatedly in all cells but are also continuously repaired so that the fraction of cells affected represents an equilibrium between these two processes. Their formation is connected with egestion of the large bundles of fibers formed by phagocytosis. Such effects of egestion of fibers do not seem to have been reported previously. Egestion of a bundle of fibers is much slower than for other types of undigestible residues. In contrast to normal exocytosis occurring invariably at the cytoproct, egestion of asbestos often occurs in the posterior part of the cell outside the cytoproct. To my knowledge this is the first reported case of either very slow or extra-cytoproctal egestion in Tetrahymena. Cells with large abnormalities have a greater tendency to develop into "early heterogeneous" cells than the average abnormal cell. Some of these give rise to hereditarily stable heterogeneous cell lines of Tetrahymena. The morphological abnormalities are probably caused by mechanical action of the crocidolite fibers resulting in local damage of the cytoskeletal elements responsible for normal cell shape. The heterogenous cell lines may arise when cellular structures carrying non-genic cytotactically inherited information are modified. The relevance of these ideas to the induction of cancer by asbestos is briefly discussed. PMID:2553916

Hjelm, K K

1989-01-01

139

One-step synthesis of polyaniline fibers with double-soft templates and evaluation of their doping process  

NASA Astrophysics Data System (ADS)

In this paper, we have developed a simple, facile, and efficient approach to synthesize polyaniline fibers (PANI fibers) from aniline in the presence of (NH4)2S2O8 with sodium dodecyl benzene sulfonate (SDBS) and L-camphorsulfonic acid (L-CSA) as double templates. The chemical constituents of the composites are characterized by Fourier transformation infrared spectroscopy (FTIR). The results demonstrate that the PANI fibers were synthesized successfully. The morphology of the composites was characterized by scanning electron microscopy (SEM). The SEM and UV-Vis images show an interesting growth and doping process. Moreover, cyclic voltammetry (CV) was used to characterize the electrochemical properties of PANI microfibers. They also give a pair of redox peaks and have better operation stability, which indicates that the composites show distinct electrochemical performance. So the PANI microfibers would have potential applications in the fields of analytical chemistry, bioanalysis, etc.

Chen, Yong; Zhao, Hui; Han, Bing

2014-12-01

140

Measurement of the nonlinear refractive index (n(2)) and stimulated Raman scattering in optical fibers as a function of germania content, using the photorefractive beam coupling technique  

NASA Astrophysics Data System (ADS)

One of the greatest challenges in optical communication is the understanding and control of optical fiber nonlinearities. While these nonlinearites limit the power handling capacity of optical fibers and can cause noise, signal distortion and cross talk in optically amplified transmission systems, they have been equally harnessed for the development of new generations of optical amplifiers and tunable laser sources. The two prominent parameters that characterize the nonlinear properties of an optical fiber are the nonlinear refractive index (n2) and the Raman gain coefficient (gR). These parameters are related to the third order nonlinear susceptibility [chi (3)]. In this work, the photorefractive beam coupling technique, also called induced grating autocorrelation (IGA), has been used to measure the nonlinear refractive index (n2) and the Raman gain coefficient (gR) of short lengths (z ˜ 20 m) of optical fibers. In the IGA experiment, a transform limited Gaussian pulse is propagated through a short length of an optical fiber, where it undergoes self-phase modulation (SPM) and other nonlinear distortions, and the output pulse is split into two. The two-excitation pulses are then coupled into a photorefractive crystal, where they interfere and form a photorefractive phase grating. The IGA response is determined by delaying one beam (the probe) and plotting the diffracted intensity of the probe versus the relative delay (tau). Analysis of the IGA response yields information about the nonlinear phase distortions and other calibration parameters of the fiber. Using the IGA technique the author has measured the nonlinear refractive index in several types of fibers, including pure silica, Er-Al-Ge doped fibers, DCF (dispersion compensating fiber) and the recently developed TrueWave Rs fiber, and investigated the dependence of n2 on the doping profiles of Er, Al, and Ge in optical fibers. The standard IGA model for n2 measurements was derived from the solution of the nonlinear wave equation for pulse propagation in the limit of pure self-phase modulation. This model assumed that GVD (group velocity dispersion) and other nonlinear processes such as SRS (stimulated Raman scattering) are negligible. This model has been successfully used to fit the experimental data and determine the n2 of the fiber from the time dependent phase shift. However, SRS has been observed to distort the IGA trace, thus leading to a breakdown of the standard IGA model. A new IGA model has been developed in this study from the solution of the coupled-amplitude nonlinear Schrodinger equation, using both analytical and numerical approaches. This new model successfully accounts for the SRS effects on the IGA trace, in the limit of zero GVD, and allows the direct determination of the Raman gain coefficient from the fit of the SRS-distorted IGA trace. The measured nonlinear refractive index and Raman gain coefficients are in good agreement with published results. It was also shown that in the limit of zero GVD and no Raman, the IGA technique reduces to the widely accepted spectral domain SPM technique pioneered by Stolen and Lin, but is readily applicable to shorter lengths of fiber and is sensitive to smaller phase shifts.

Oguama, Ferdinand Anayo

141

BRIEF COMMUNICATIONS: Dependences of the polarization properties of polymer graded-index fibers of the Selfoc type  

Microsoft Academic Search

Temperature dependences of some polarization characteristics were determined for polymer Selfoc-type fibers. It was found that when plane-polarized light passed through a fiber of this kind, it emerged with elliptic polarization. The effective direction of the polarization of light emerging from a fiber was shifted by an angle Deltavarphi from the plane of polarization of the incident wave. The temperature

N. G. Gachechiladze; S. I. Grigor'ev; M. G. Zguladze; A. N. Mestvirishvili; V. R. Sagaradze

1983-01-01

142

Simultaneous measurement of temperature and refractive index based on a core-offset Mach-Zehnder interferometer cascaded with a long-period fiber grating  

NASA Astrophysics Data System (ADS)

An all-fiber sensor based on a cascaded optical fiber device is proposed and demonstrated, and its sensor head is composed of a core-offset Mach-Zehnder interferometer (MZI) and a long-period fiber grating (LPFG). In the experiment, two dips shaped by the intermodulation between the interference fringe of MZI and the resonant wavelength of LPFG are monitored. Experimental results show that temperature sensitivities of two dips are 0.060 7 nm/°C and 0.056 3 pm/°C, and the refractive index (RI) sensitivities are -18.025 nm/RIU and -55.06 nm/RIU, respectively. The simultaneous measurement of the temperature and external RI is demonstrated based on the sensitive matrix. Its low fabrication cost, simple configuration and high sensitivity make this sensor have potential applications in chemical and biological sensing.

Cao, Ye; Liu, Hui-ying; Tong, Zheng-rong; Yuan, Shuo; Zhao, Shun

2015-01-01

143

Can spherical deconvolution provide more information than fiber orientations? Hindrance modulated orientational anisotropy, a true-tract specific index to characterize white matter diffusion.  

PubMed

Diffusion tensor imaging (DTI) methods are widely used to reconstruct white matter trajectories and to quantify tissue changes using the average diffusion properties of each brain voxel. Spherical deconvolution (SD) methods have been developed to overcome the limitations of the diffusion tensor model in resolving crossing fibers and to improve tractography reconstructions. However, the use of SD methods to obtain quantitative indices of white matter integrity has not been extensively explored. In this study, we show that the hindrance modulated orientational anisotropy (HMOA) index, defined as the absolute amplitude of each lobe of the fiber orientation distribution, can be used as a compact measure to characterize the diffusion properties along each fiber orientation in white matter regions with complex organization. We demonstrate that the HMOA is highly sensitive to changes in fiber diffusivity (e.g., myelination processes or axonal loss) and to differences in the microstructural organization of white matter like axonal diameter and fiber dispersion. Using simulations to describe diffusivity changes observed in normal brain development and disorders, we observed that the HMOA is able to identify white matter changes that are not detectable with conventional DTI indices. We also show that the HMOA index can be used as an effective threshold for in vivo data to improve tractography reconstructions and to better map white matter complexity inside the brain. In conclusion, the HMOA represents a true tract-specific and sensitive index and provides a compact characterization of white matter diffusion properties with potential for widespread application in normal and clinical populations. PMID:22488973

Dell'Acqua, Flavio; Simmons, Andrew; Williams, Steven C R; Catani, Marco

2013-10-01

144

Sol-gel preparation of hydrophobic silica antireflective coatings with low refractive index by base/acid two-step catalysis.  

PubMed

Hydrophobic antireflective coatings with a low refractive index were prepared via a base/acid-catalyzed two-step sol-gel process using tetraethylorthosilicate (TEOS) and methyltriethoxysilane (MTES) as precursors, respectively. The base-catalyzed hydrolysis of TEOS leads to the formation of a sol with spherical silica particles in the first step. In the second step, the acid-catalyzed MTES hydrolysis and condensation occur at the surface of the initial base-catalyzed spherical silica particles, which enlarge the silica particle size from 12.9 to 35.0 nm. By a dip-coating process, this hybrid sol gives an antireflective coating with a refractive index of about 1.15. Moreover, the water contact angles of the resulted coatings increase from 22.4 to 108.7° with the increases of MTES content, which affords the coatings an excellent hydrophobicity. A "core-shell" particle growth mechanism of the hybrid sol was proposed and the relationship between the microstructure of silica sols and the properties of AR coatings was investigated. PMID:24979297

Cai, Shuang; Zhang, Yulu; Zhang, Hongli; Yan, Hongwei; Lv, Haibing; Jiang, Bo

2014-07-23

145

Mode size converter between high-index-contrast waveguide and cleaved single mode fiber using SiON as intermediate material.  

PubMed

High-index-contrast (HIC) waveguide such as Si and Si3N4 has small mode size enabling compact integration. However, the coupling loss with single mode fiber is also remarkable owning to the mode mismatching. Therefore, mode size converter, as the interface between HIC waveguide and optical fiber, takes an important role in the field of integrated optics. The material with refractive index (RI) between HIC waveguide and optical fiber can be used as a bridge to reduce the mode mismatching loss. In this letter, we employ silicon oxynitride (SiON) with RI about 1.50 as the intermediate material and optimize the structure of the SiON waveguide to match with cleaved single mode fiber and HIC waveguide separately. Combined with inverse taper and suspended structure, the mismatching loss is reduced and the dependence to the dimension of the structure is also released. The coupling loss is 1.2 and 1.4 dB/facet for TE and TM mode, respectively, with 3 dB alignment tolerance of ± 3.5 ?m for Si(3)N(4) waveguide with just 200 nm-wide tip. While for Si waveguide, a critical dimension of 150 nm is applied due to the higher index contrast than Si(3)N(4) waveguide. Similar alignment tolerance is realized with coupling loss about 1.8 and 2.1 dB/facet for TE and TM mode. The polarization dependence loss (PDL) for both platforms is within 0.5 dB. PMID:25321831

Jia, Lianxi; Song, Junfeng; Liow, Tsung-Yang; Luo, Xianshu; Tu, Xiaoguang; Fang, Qing; Koh, Sing-Chee; Yu, Mingbin; Lo, Guoqiang

2014-09-22

146

Multiple-crack damage detection in multi-step beams by a novel local flexibility-based damage index  

NASA Astrophysics Data System (ADS)

In this article we address a simple method for detecting, localizing, and quantifying multiple cracks occurred in Euler-Bernoulli multi-stepped beams, using the measurement of natural frequencies and estimating the uncracked mode shapes. The analysis is based on energy method and Euler-Bernoulli beam theory. We model cracks as rotational springs and demonstrate a relationship among natural frequencies, crack locations and depths. This method can be applied to both forward and inverse problems. The main advantage of this method is that it has the power of detecting the unknown number of cracks. The concise and simple calculations, good accuracy and elimination of complicated matrix calculations are the other advantages. In addition, for reducing numerical complexity, we use global interpolation functions as is common in Rayleigh-Ritz method, instead of using piecewise continuous mode shapes for a multi-step beam. We present numerical examples for a two-step cantilever beam, including one, two, and three cracks to validate the method.

Maghsoodi, Ameneh; Ghadami, Amin; Reza Mirdamadi, Hamid

2013-01-01

147

Pump induced nonlinear refractive index [n2] change in erbium and ytterbium doped fibers-theory and experiments  

Microsoft Academic Search

Summary form only given. The increasingly demanding application of erbium-doped fiber amplifiers (EDFA) in fiber optic communication systems (including solitons), requires a deep understanding of the effects of the pump laser on the optical properties of the amplifier at the signal level. Amplification provides by EDFAs is produced by optically pumping an absorption band to provide signal gain in the

Hernando Garcia; Anthony M. Johnson; Sudhir Trivedi

2001-01-01

148

Development of one-step hollow fiber supported liquid phase sampling technique for occupational workplace air analysis using high performance liquid chromatography with ultra-violet detector.  

PubMed

In this study, a simple and novel one-step hollow-fiber supported liquid-phase sampling (HF-LPS) technique was developed for enriched sampling of gaseous toxic species prior to chemical analysis for workplace air monitoring. A lab-made apparatus designed with a gaseous sample generator and a microdialysis sampling cavity (for HF-LPS) was utilized and evaluated to simulate gaseous contaminant air for occupational workplace analysis. Gaseous phenol was selected as the model toxic species. A polyethersulfone hollow fiber dialysis module filled with ethylene glycol in the shell-side was applied as the absorption solvent to collect phenol from a gas flow through the tube-side, based on the concentration distribution of phenol between the absorption solvent and the gas flow. After sampling, 20 ?L of the extractant was analyzed by high performance liquid chromatography with ultraviolet detection (HPLC-UV). Factors that influence the generation of gaseous standards and the HF-LPS were studied thoroughly. Results indicated that at 25 °C the phenol (2000 ?g/mL) standard solution injected at 15-?L/min can be vaporized into sampling cavity under nitrogen flow at 780 mL/min, to generate gaseous phenol with concentration approximate to twice the permissible exposure limit. Sampling at 37.3 mL/min for 30 min can meet the requirement of the workplace air monitoring. The phenol in air ranged between 0.7 and 10 cm³/m³ (shows excellent linearity) with recovery between 98.1 and 104.1%. The proposed method was identified as a one-step sampling for workplace monitoring with advantages of convenience, rapidity, sensitivity, and usage of less-toxic solvent. PMID:22673811

Yan, Cheing-Tong; Chien, Hai-Ying

2012-07-13

149

Empirical relations to determine the normalized spot size of a single-mode trapezoidal index fiber and computation of its propagation characteristics  

NASA Astrophysics Data System (ADS)

Simple and complete empirical relations are presented here to determine a normalized spot size in terms of normalized frequencies over a long range and aspect ratio of a trapezoidal index single-mode fiber considering Gaussian approximation of the fundamental mode following the Marcuse method for the first time. After verification of their validity for arbitrary values of aspect ratio and normalized frequency, we calculate various propagation characteristics viz. dispersion and splice loss by using our formulations. Upon comparison, we observe an excellent match and the validity of our results with exact values and other results available in the literature. These formulas should attract the attention of experimentalists as a simple alternative to the rigorous methods of estimating the propagation characteristics of such fibers.

Mallick, Aswini Kumar; Sarkar, Somenath

2014-07-01

150

Microfluidic refractive index sensor based on an all-silica in-line Fabry-Perot interferometer fabricated with microstructured fibers.  

PubMed

We report a microfluidic fiber-optic refractive index (RI) sensor based on an in-line Fabry-Perot (FP) interferometer, which is formed by a silica tube sandwiched by two microstructured fibers (MFs). The sensor reported here can be fabricated at low cost, possess a robust structure, and has microfluidic capability. The micro-sized holes in the MFs naturally function as microfluidic channels through which liquid samples can be efficiently and conveniently delivered into and out of the FP cavity by a pressure/vacuum pump system for high-performance RI measurement. Due to the microfluidic capability enabled by the MFs, only sub microliter sample is required. We also experimentally study and demonstrate the superior performances of the sensor in terms of high RI sensitivity, good measurement repeatability, and low temperature cross-sensitivity. PMID:23482235

Tian, Jiajun; Lu, Yujie; Zhang, Qi; Han, Ming

2013-03-11

151

Phase-shift formed in a tapered long period fiber grating and its application to simultaneous measurements of temperature and refractive-index  

NASA Astrophysics Data System (ADS)

A novel approach to calibrate a phase-shift formed in a long-period fiber grating (LPG) is proposed and successfully demonstrated, which is based on the use of either a power- or a wavelength-interrogation technique to the loss-peak existed in the transmission spectrum of the phase-shifted LPG. Moreover, in this study, by tapering a LPG with CO2 laser, phase-shift is successfully created at central part of the LPG. Finally, base on the use of this kind of phase-shifted LPG, a simultaneous measurement for the temperature and the surrounding refractive index has been proposed and experimentally demonstrated.

Hishiki, Keisuke; Li, Hongpu

2013-09-01

152

Simulation-guided design and fabrication of long-period gratings in photonic crystal fiber as refractive index transduction platform for multi-parameter sensing  

NASA Astrophysics Data System (ADS)

Fiber optic sensing technology based on conventional, all-solid optical fiber has been broadly used for chemical and biological sensing and detection. The advent of photonic crystal fiber (PCF) offers transformative opportunities due to its unique waveguiding and microstructural features. Incorporating long period gratings (LPG) in PCF has the potential to further catapult LPG-PCF based sensing technology in terms of greatly improved sensing capabilities and significantly expanded field of applications. This doctoral dissertation aims to synergistically integrate LPG and index guiding PCF as refractive index transduction platform to explore its potential for multi-parameter sensing and measurements. The phase matching conditions, core mode to cladding mode coupling, and power overlap were theoretically simulated to aid in the design and fabrication of the LPG-PCF platform using CO2 laser. For sensing of aqueous solutions, we developed a novel means of LPG fabrication while maintaining a steady liquid flow in the PCF air channels. This approach greatly improves the quality and reproducibility of the fabrication process. More importantly, it helps preserve the general resonance coupling condition when an aqueous analyte solution is probed. We have theoretically predicted and experimentally achieved a sensitivity of ˜10-7 refractive index unit using our fabricated LPG-PCF platform due to the strong overlap between the cladding mode evanescent field and the analyte within the PCF air channels. For label-free biosensing, we integrated the LPG-PCF with a home-build microfluidic flow cell that can be optically coupled with the sensing platform while allowing continuous flow of the reagents. As a result, we have demonstrated the ability to monitor a series of surface binding events in situ. Our LPG-PCF is able to consistently detect monolayer biomolecular binding events with a measured resonance wavelength shift of about 0.75 nm per nanometer thick layer formed. Overall, theoretically and experimentally, we have shown that LPG-PCF represents a powerful refractive index transduction platform that can be used for sensing and measurements of multiple parameters. We have clearly shown that LPG-PCF has the potential to be a viable alternative to the surface plasmon resonance-based commercial refractometers for affinity-based biological measurements.

He, Zonghu

2011-12-01

153

1794 OPTICS LETTERS / Vol. 27, No. 20 / October 15, 2002 Gradient-index fiber-optic microprobes for minimally invasive  

E-print Network

and optical Doppler tomography.2,3 LCI is usually im- plemented as a fiber interferometer and has been used to study surface tissues such as skin4 or retina5 and hollow tissues6 such as respiratory or diges- tive

Schnitzer, Mark

154

Fiber Optics  

NSDL National Science Digital Library

SFGate: SBC and Microsofthttp://sfgate.com/cgi-bin/article.cgi?file=/c/a/2004/06/23/MNGVR7AI711.DTLSBC Communications Inc.http://www.sbc.com/gen/press-room?pid=5838How Stuff Works: How Fiber Optics Workhttp://electronics.howstuffworks.com/fiber-optic.htmFiber Optic Reference Guide: A Brief Historyhttp://www.fiber-optics.info/fiber-history.htmPC World: Has Your Broadband Had Its Fiber?http://www.pcworld.com/news/article/0,aid,117684,00.aspTelephony Onlinehttp://telephonyonline.com/ar/telecom_breaking_meg_barrier/index.htmThis article from SFGate reports on the recent negotiations between SBC and Microsoft (1) and the implications of the new technology for Internet and television access. This website from SBC (2) provides video footage and background information on their initiative called Project Lightspeed. This initiative is based largely on fiber technology, which is described further on this website from How Stuff Works (3). This website (4) provides a brief history of fiber optics technology along with links to sections on the applications of fiber optics and more basics on transmission. This article from PC World (5) discusses how fiber optics became a viable option. This article from Telephony Online 6)reviews some of the challenges that remain.

155

Diffraction-arrested soliton self-frequency shift of few-cycle laser pulses in a photonic-crystal fiber  

Microsoft Academic Search

The balance between diffraction and index-step guiding in photonic-crystal fibers is controlled by modifying the fiber structure, leading to different wavelength dependences of the effective mode area Seff(lambda) and providing a mechanism to control nonlinear-optical phenomena. In optical fibers with a steep Seff(lambda) profile, the guided mode of the light field tends to become much less compact with an increase

E. E. Serebryannikov; A. M. Zheltikov; S. Köhler; N. Ishii; C. Y. Teisset; T. Fuji; F. Krausz; A. Baltuska

2006-01-01

156

Nd3+-doped soft glass double-clad fibers with a hexagonal inner cladding  

NASA Astrophysics Data System (ADS)

The stack-and-draw technique was used to fabricate Nd3+-doped silicate and phosphate glass double-clad step-index fibers with a non-circular inner cladding. For the silicate fiber, a maximum output power of 7.7?W was obtained from a 94?cm fiber. An output power of 1.25?W was also realized with a short length fiber of 8?cm, confirming the application potential of this fiber in single frequency lasers and pulsed amplifiers where an efficient rare-earth-doped fiber with short length is desirable. For the phosphate fiber, a maximum output power of 2.78?W was obtained from a single-mode fiber with a core diameter of up to 35??m.

Wang, Longfei; He, Dongbing; Hu, Lili; Chen, Danping

2015-04-01

157

Tapered large-core 976 nm Yb-doped fiber laser with 10 W output power  

NASA Astrophysics Data System (ADS)

We report on a tapered large-core Yb fiber laser operating at 976 nm emission wavelength. It was realized using a high-numerical aperture large-core fiber with 126 ?m core diameter, which was fabricated by powder-sinter technology and shows a very homogeneous step-index profile. The end of the fiber is tapered down to match a single-mode fiber containing a fiber Bragg grating. Using the benefits of core-pumping and the feedback of the spliced fiber Bragg grating, we achieved efficient pump light absorption and wavelength stable 976 nm lasing with single-mode performance. We could demonstrate 10 W laser power out of a 10 ?m fiber core with a slope efficiency of 31% with respect to the launched pump power. The presented device is well-suited for fiber-coupled pumping of amplifiers for high peak power.

Leich, M.; Jäger, M.; Grimm, S.; Hoh, D.; Jetschke, S.; Becker, M.; Hartung, A.; Bartelt, H.

2014-04-01

158

Investigations on fibers for high-average power Nd:YAG-lasers for industrial applications  

SciTech Connect

For industrial applications of high-average power Nd:YAG-lasers the laser power is usually transmitted through all-silica optical fibers. The transmission properties of different types of step index and graded-index fibers are investigated, using a multimode high-power Nd:YAG rod laser with 2000 W output power in CW and Q-switch mode. The fibers are step index and graded-index fibers with 400 and 600 {mu}m core diameters, different cladding to core ratios and different types of coating materials. The dependence of the output beam parameters, waist diameter and divergence, and the resulting power transmission are given. The upper limits for the maximum beam parameters and maximum laser powers which can be coupled into fibers without loss, as well as the dependence of the output beam profiles upon the intensity distribution at the fiber input are briefly discussed. The end faces of polished and cleaved fibers are compared. Different setups for coupling several laser beams into one fiber, in order to increase the maximum laser power to be transmitted, are discussed. By these means more than 6 kW laser power could be transmitted.

Reng, N.; Beck, T. [Laser- und Medizin-Technologie GmbH, Berlin (Germany); Ostermeyer, M. [Optisches Institut, Berlin (Germany)

1997-12-01

159

Broadband, mid-infrared emission from Pr3+ doped GeAsGaSe chalcogenide fiber, optically clad  

NASA Astrophysics Data System (ADS)

We present a study of mid-infrared photoluminescence in the wavelength range 3.5-5.5 ?m emitted from Pr3+: GeAsGaSe core/GeAsGaSe cladding chalcogenide fiber. The Pr3+ doped fiber optic preform is fabricated using extrusion and is successfully drawn to low optical loss, step-index fiber. Broadband mid-infrared photoluminescence is observed from the fiber, both under 1.55 ?m or 1.94 ?m wavelength excitation. Absorption, and emission, spectra of bulk glass and fiber are presented. Luminescent lifetimes are measured for the fiber and the Judd-Ofelt parameters are calculated. The radiative transition rates calculated from Judd-Ofelt theory are compared with experimental lifetimes. The observed strong broadband emission suggests that this type of fiber is a good candidate for further development to realize both fiber lasers and amplified spontaneous emission fiber sources in the mid-infrared region.

Sójka, L.; Tang, Z.; Furniss, D.; Sakr, H.; Oladeji, A.; Bere?-Pawlik, E.; Dantanarayana, H.; Faber, E.; Seddon, A. B.; Benson, T. M.; Sujecki, S.

2014-04-01

160

Highly photosensitive polymethyl methacrylate microstructured polymer optical fiber with doped core.  

PubMed

In this Letter, we report the fabrication of a highly photosensitive, microstructured polymer optical fiber using benzyl dimethyl ketal as a dopant, as well as the inscription of a fiber Bragg grating in the fiber. A refractive index change in the core of at least 3.2×10(-4) has been achieved, providing a grating with a strong transmission rejection of -23 dB with an inscription time of only 13 min. The fabrication method has a big advantage compared to doping step index fiber since it enables doping of the fiber without using extra dopants to compensate for the index reduction in the core introduced by the photosensitive agent. PMID:24081048

Sáez-Rodríguez, D; Nielsen, K; Rasmussen, H K; Bang, O; Webb, D J

2013-10-01

161

Study of laser-induced damage to large core silica fiber by Nd:YAG and Alexandrite lasers  

NASA Astrophysics Data System (ADS)

As a continuation of our earlier study at 2.1 ?m wavelength, we have investigated the laser damage to several types of step-index, large core (1500 ?m) silica fibers at two new wavelengths by high power long pulsed Nd:YAG (1064 nm) and Alexandrite (755 nm) lasers. It was observed that fibers with different designs showed a significant difference in performance at these wavelengths. We will also report a correlation of damage to the fibers between the two laser wavelengths. The performance analyses of different fiber types under the given test conditions will enable optimization of fiber design for specific applications.

Sun, Xiaoguang; Li, Jie; Hokansson, Adam; Whelan, Dan; Clancy, Michael

2009-02-01

162

Depression of the glycemic index by high levels of ?-glucan fiber in two functional foods tested in type 2 diabetes  

Microsoft Academic Search

Objectives: To determine the extent to which ?-glucan reduces the glycemic index (GI) of oat products and whether high levels of ?-glucan impair palatability.Design: The study design was an open-label, randomized cross-over study with six treatment segments.Setting: Free-living outpatients.Subjects: Sixteen volunteers with type 2 diabetes (10 men, six women, 61±2 y, body mass index 29±2 kg\\/m2, HbA1c 7.4±0.4%) were recruited

AL Jenkins; DJA Jenkins; U Zdravkovic; P Würsch; V Vuksan

2002-01-01

163

Mid-infrared supercontinuum covering the 1.4–13.3??m molecular fingerprint region using ultra-high NA chalcogenide step-index fibre  

NASA Astrophysics Data System (ADS)

The mid-infrared spectral region is of great technical and scientific interest because most molecules display fundamental vibrational absorptions in this region, leaving distinctive spectral fingerprints. To date, the limitations of mid-infrared light sources such as thermal emitters, low-power laser diodes, quantum cascade lasers and synchrotron radiation have precluded mid-infrared applications where the spatial coherence, broad bandwidth, high brightness and portability of a supercontinuum laser are all required. Here, we demonstrate experimentally that launching intense ultra-short pulses with a central wavelength of either 4.5??m or 6.3??m into short pieces of ultra-high numerical-aperture step-index chalcogenide glass optical fibre generates a mid-infrared supercontinuum spanning 1.5??m to 11.7??m and 1.4??m to 13.3??m, respectively. This is the first experimental demonstration to truly reveal the potential of fibres to emit across the mid-infrared molecular ‘fingerprint region’, which is of key importance for applications such as early cancer diagnostics, gas sensing and food quality control.

Petersen, Christian Rosenberg; Møller, Uffe; Kubat, Irnis; Zhou, Binbin; Dupont, Sune; Ramsay, Jacob; Benson, Trevor; Sujecki, Slawomir; Abdel-Moneim, Nabil; Tang, Zhuoqi; Furniss, David; Seddon, Angela; Bang, Ole

2014-11-01

164

Index matching between passive and active tellurite glasses for use in microstructured fiber lasers: erbium doped lanthanum-tellurite glass.  

PubMed

Active and passive variants of La-containing tellurite glasses have been developed with matched refractive indices. The consequences of adding lanthanum to the glass was studied through measurements of the crystallization stability, glass viscosity and the loss of unstructured fibers. Doping the glass with erbium allowed for any spectroscopic changes to be observed through measurements of the absorption and energy level lifetimes. The fluorescence emission spectra were measured at 1.5 microm and, to the best of our knowledge, for the first time in tellurite glass at 2.7 microm. PMID:19724556

Oermann, Michael R; Ebendorff-Heidepriem, Heike; Li, Yahua; Foo, Tze-Cheung; Monro, Tanya M

2009-08-31

165

Mid-infrared supercontinuum generation to 12.5?m in large NA chalcogenide step-index fibres pumped at 4.5?m.  

PubMed

We present numerical modeling of mid-infrared (MIR) supercontinuum generation (SCG) in dispersion-optimized chalcogenide (CHALC) step-index fibres (SIFs) with exceptionally high numerical aperture (NA) around one, pumped with mode-locked praseodymium-doped (Pr(3+)) chalcogenide fibre lasers. The 4.5um laser is assumed to have a repetition rate of 4MHz with 50ps long pulses having a peak power of 4.7kW. A thorough fibre design optimisation was conducted using measured material dispersion (As-Se/Ge-As-Se) and measured fibre loss obtained in fabricated fibre of the same materials. The loss was below 2.5dB/m in the 3.3-9.4?m region. Fibres with 8 and 10?m core diameters generated an SC out to 12.5 and 10.7?m in less than 2m of fibre when pumped with 0.75 and 1kW, respectively. Larger core fibres with 20?m core diameters for potential higher power handling generated an SC out to 10.6?m for the highest NA considered but required pumping at 4.7kW as well as up to 3m of fibre to compensate for the lower nonlinearities. The amount of power converted into the 8-10?m band was 7.5 and 8.8mW for the 8 and 10?m fibres, respectively. For the 20?m core fibres up to 46mW was converted. PMID:25321003

Kubat, Irnis; Agger, Christian S; Møller, Uffe; Seddon, Angela B; Tang, Zhuoqi; Sujecki, Slawomir; Benson, Trevor M; Furniss, David; Lamrini, Samir; Scholle, Karsten; Fuhrberg, Peter; Napier, Bruce; Farries, Mark; Ward, Jon; Moselund, Peter M; Bang, Ole

2014-08-11

166

Fiber Optics  

NSDL National Science Digital Library

Optical fibers transmit light signals and are widely used in the telecommunications industry to transmit data over long distances. Light travels through the core material of an optical fiber by essentially repeatedly bouncing off the cladding material that surrounds the core. Understanding refraction and how light behaves at the boundary of two different materials is the basis for understanding how fiber optic lines work. In particular, total internal reflection occurs when light travels in a material with a higher index of refraction toward a material with a lower index of refraction and the angle of incidence is greater than the critical angle.In this lesson, students investigate through experimentation, discussion, and video the phenomenon of total internal reflection and its relationship to fiber optics. Students also watch a video about dispersion and discuss the implications for fiber optics.Note: This is the second of two optics lesson plans. You may want to precede this lesson with The Index of Refraction Lesson Plan.

167

Audio frequency pulse code modulation data link using an optical fiber  

Microsoft Academic Search

A simple, economical and inherently noise-immune asynchronous digital data link design that uses pulse code modulation and a fiber-optic cable is presented. Suitable for audio and instrumentation applications with typical bandwidths of dc-10 kHz, the system samples input signals at 20 kHz and converts them to a seven-bit binary code for transmission through a 20-foot length step index fiber-optic cable.

J. A. Blackburn

1981-01-01

168

Coupling analyses of LP0m modes with optical fiber gratings in multimode fiber and their application in mode-division multiplexing transmission  

NASA Astrophysics Data System (ADS)

Coupling characteristics of core higher-order modes LP0m with optical fiber gratings written in step-index multimode fiber (MMF) and their application in mode-division multiplexing (MDM) transmission are presented and analyzed in this article. Several long-period fiber gratings (LPFGs) cascaded in one MMF can realize conversion between any two core modes, HE1m(m=1,2,3,...,6) in other words and scalar mode LP0m, in mode order from low to high. These eigenmodes supported in fiber as independent data channels are theoretically proposed to be multiplexed in one MMF by the combination of LPFGs and fiber Bragg gratings (FBGs) united with optical circulators as both multiplexers and de-multiplexers. This method of flexible mode conversion using optical gratings can be practically significant on fiber communication as a mode-selective converter.

Fang, Liang; Jia, Hongzhi

2014-07-01

169

Development of on-fiber optical sensors utilizing chromogenic materials  

NASA Astrophysics Data System (ADS)

On-fiber optical sensors, designed with chromogenic materials used as the fiber modified cladding, were developed for sensing environmental conditions. The design was based on the previously developed on-fiber devices. It is known that the light propagation characteristics in optical fibers are strongly influenced by the refractive index of the cladding materials. Thus, the idea of the on- fiber devices is based on replacing the passive optical fiber cladding with active or sensitive materials. For example, temperature sensors can be developed by replacing the fiber clad material with thermochromic materials. In this paper, segmented polyurethane-diacetylene copolymer (SPU), was selected as the thermochromic material for temperature sensors applications. This material has unique chromogenic properties as well as the required mechanical behaviors. During UV exposure and heat treatment, the color of the SPU copolymer varies with its refractive index. The boundary condition between core and cladding changes due to the change of the refractive index of the modified cladding material. The method used for the sensor development presented involves three steps: (a) removing the fiber jacket and cladding from a small region, (b) coating the chromogenic materials onto the modified region, and (c) integrating the optical fiber sensor components. The experimental set-up was established to detect the changes of the output signal based on the temperature variations. For the sensor evaluation, real-time measurements were performed under different heating-cooling cycles. Abrupt irreversible changes of the sensor output power were detected during the first heating-cooling cycle. At the same time, color changes of the SPU copolymer were observed in the modified region of the optical fiber. For the next heating-cooling cycles, however, the observed changes were almost completely reversible. This result demonstrates that a low-temperature sensor can be built by utilizing the chromogenic SPU copolymer as the modified cladding material.

Yuan, Jianming; El-Sherif, Mahmoud A.

1999-01-01

170

Comparison of relation between visual function index and retinal nerve fiber layer structure by optical coherence tomography among primary open angle glaucoma and primary angle closure glaucoma eyes  

PubMed Central

Purpose: To compare the visual field index (VFI) in primary open angle glaucoma (POAG) and primary angle closure glaucoma (PACG) eyes, and to study the correlation with disc variables on optical coherence tomography (OCT) in all stages of severity. Materials and Methods: Thirty POAG and PACG underwent Humphrey visual field 24-2 along with detailed examination. They also underwent stratus OCT imaging of the optic nerve and retinal nerve fiber layer (RNFL). The correlation of VFI with RNFL thickness was compared in POAG and PACG. Results: The VFI significantly differed between POAG and PACG, with POAG eyes apparently having a better VFI at all severities of glaucoma. There were statistically significant differences in the superior max (Smax) and inferior max (Imax) in early and moderate POAG and PACG eyes. In early and moderate glaucoma, multivariate regression showed that maximum correlation of the VFI was seen with the mean deviation (b = 1.7, P < 0.001), average and superior RNFL thickness (b = 2.1, P < 0.001 and b = 1.8, P = 0.03, respectively), and age (b = 0.7, P = 0.04); while no correlation was seen with intraocular pressure (IOP), axial length, sex, or other clinical variables. VFI did not correlate well with RNFL thickness or other disc variables on OCT in severe glaucoma. Conclusion: VFI may not serve as a useful indicator of visual function in severe glaucoma. More useful indicators are required to monitor glaucoma patients with severe damage. PMID:24799794

Rao, Aparna

2014-01-01

171

Palladium particles embedded into silica optical fibers for hydrogen gas detection  

NASA Astrophysics Data System (ADS)

In this paper, we report the fabrication and characterization of a new concept of optical fibers whose cladding is composed of palladium particles embedded into the silica glass cladding. Since conventional fiber processes are not suitable for such realizations, we developed an original process based on powder technology to prepare our specific preforms. Step, graded index and photonic crystal optical fibers with original shapes were realized. The use of high purity powders as raw materials combined to a specific preforms heat treatment allowed the fabrication of resistant and long length metal-cladding optical fibers. Microstructured Pd-SiO2 composite cladding optical fibers with single-mode behavior and optical losses lower than 2 dB/m at 1530 nm were characterized. Hydrogen-induced attenuation sensitivity of these fibers at the 1245 nm wavelength was demonstrated after long H2 exposure. Dehydrogenation kinetics calculations and experiments were studied.

Leparmentier, Stéphanie; Auguste, Jean-Louis; Humbert, Georges; Delaizir, Gaëlle; Delepine-Lesoille, Sylvie; Bertrand, Johan; Buschaert, Stéphane; Perisse, Jocelyn; Macé, Jean Reynald

2014-05-01

172

Polarization dependence of Brillouin linewidth and peak frequency due to fiber inhomogeneity in single mode fiber and its impact on distributed fiber Brillouin sensing.  

PubMed

The dependence of Brillouin linewidth and peak frequency on lightwave state of polarization (SOP) due to fiber inhomogeneity in single mode fiber (SMF) is investigated by using Brillouin optical time domain analysis (BOTDA) system. Theoretical analysis shows fiber inhomogeneity leads to fiber birefringence and sound velocity variation, both of which can cause the broadening and asymmetry of the Brillouin gain spectrum (BGS) and thus contribute to the variation of Brillouin linewidth and peak frequency with lightwave SOP. Due to fiber inhomogeneity both in lateral profile and longitudinal direction, the measured BGS is the superposition of several spectrum components with different peak frequencies within the interaction length. When pump or probe SOP changes, both the peak Brillouin gain and the overlapping area of the optical and acoustic mode profile that determine the peak efficiency of each spectrum component vary within the interaction length, which further changes the linewidth and peak frequency of the superimposed BGS. The SOP dependence of Brillouin linewidth and peak frequency was experimentally demonstrated and quantified by measuring the spectrum asymmetric factor and fitting obtained effective peak frequency respectively via BOTDA system on standard step-index SMF-28 fiber. Experimental results show that on this fiber the Brillouin spectrum asymmetric factor and effective peak frequency vary in the range of 2% and 0.06MHz respectively over distance with orthogonal probe input SOPs. Experimental results also show that in distributed fiber Brillouin sensing, polarization scrambler (PS) can be used to reduce the SOP dependence of Brillouin linewidth and peak frequency caused by fiber inhomogeneity in lateral profile, however it maintains the effects caused by fiber inhomogeneity in longitudinal direction. In the case of non-ideal polarization scrambling using practical PS, the fluctuation of effective Brillouin peak frequency caused by fiber inhomogeneity provides another limit of sensing frequency resolution of distributed fiber Brillouin sensor. PMID:22418520

Xie, Shangran; Pang, Meng; Bao, Xiaoyi; Chen, Liang

2012-03-12

173

Simulating Optical Fibers.  

ERIC Educational Resources Information Center

Described is a demonstration of Snell's law using a laser beam and an optical fiber. Provided are the set-up method of the demonstration apparatus and some practical suggestions including "index matching" technique using vaseline. (YP)

Edgar, Dale

1988-01-01

174

Fabrication study of double-cladding structure in optical fibers using plasma channeling induced by a femtosecond laser  

NASA Astrophysics Data System (ADS)

Refractive index modification in multimode optical fibers is first demonstrated using the plasma channeling excited by a high-intensity femtosecond (110 fs) Ti:sapphire laser ((lambda) p equals 790 nm). The refractive index modification induced in a pure silica multimode step-index fiber with a 100/110 micrometers core/cladding diameter reaches the length of approximately 9 approximately 10 mm from the input face of the optical fiber with the diameters ranging from 5 to 8 micrometers at input intensities more than 1.5 X 1012 W/cm2. The graded refractive index profiles are fabricated to be a symmetric form from the center of a multimode fiber and a maximum value of refractive index change ((Delta) n) is measured to be 2.1 X 10-2. According to the electron spin resonance spectroscopic measurement, it is found that the defect concentration of SiE' center increased significantly in the modified region in relation to that of the region without modification. The plasma self-channeling would induced the refractive index modification with the defects. The intensity profile of the output beam transmitted through the modified multimode fibers shows that the bulk modification produces a double cladding structure. The fabrication method of the double cladding structure in optical fibers can be a useful tool for a variety of applications such as mode converters and single-mode connectors in the fields of optical communication and optical sensor.

Cho, Sung-Hak; Kumagai, Hiroshi; Midorikawa, Katsumi; Obara, Minoru

2000-02-01

175

Fabrication of double cladding structure in optical multimode fibers using plasma channeling excited by a high-intensity femtosecond laser  

NASA Astrophysics Data System (ADS)

Refractive index modification in multimode optical fibers was first demonstrated using the plasma channeling excited by a high-intensity femtosecond (110 fs) Ti: sapphire laser (? p=790 nm). The refractive index modification induced in a pure silica multimode step-index fiber with a 100/110 ?m core/cladding diameter reached a length of approximately 9˜10 mm from the input surface of the optical fiber with the diameters ranging from 5 to 8 ?m at input intensities more than 1.5×10 12 W/cm 2. The graded refractive index profiles were fabricated to be a symmetric form from the center of a multimode fiber and a maximum value of refractive index change (? n) was measured to be 2.1×10 -2. According to the electron spin resonance spectroscopic measurement, it was found that the defect concentration of SiE' center increased significantly in the modified region in relation to that of the region without modification. The plasma self-channeling would induce the refractive index modification with the defects. The intensity profile of the output beam transmitted through the modified multimode fibers showed that the bulk modification produced a double cladding structure. The fabrication method of the double cladding structure in optical fibers can be a useful tool for a variety of applications such as mode converters and single-mode connectors in the fields of optical communication and optical sensor.

Cho, Sung-Hak; Kumagai, Hiroshi; Midorikawa, Katsumi; Obara, Minoru

1999-09-01

176

Development of the multiwavelength monolithic integrated fiber optics terminal  

NASA Technical Reports Server (NTRS)

This paper describes the development of the Multiwavelength Monolithic Integrated Fiber Optic Terminal (MMIFOT) for the NASA Johnson Space Center. The program objective is to utilize guided wave optical technology to develop wavelength-multiplexing and -demultiplexing units, using a single mode optical fiber for transmission between terminals. Intensity modulated injection laser diodes, chirped diffraction gratings and thin film lenses are used to achieve the wavelength-multiplexing and -demultiplexing. The video and audio data transmission test of an integrated optical unit with a Luneburg collimation lens, waveguide diffraction grating and step index condensing lens is described.

Chubb, C. R.; Bryan, D. A.; Powers, J. K.; Rice, R. R.; Nettle, V. H.; Dalke, E. A.; Reed, W. R.

1982-01-01

177

Measurement of the nonlinear refractive index (n(2)) and stimulated Raman scattering in optical fibers as a function of germania content, using the photorefractive beam coupling technique  

Microsoft Academic Search

One of the greatest challenges in optical communication is the understanding and control of optical fiber nonlinearities. While these nonlinearites limit the power handling capacity of optical fibers and can cause noise, signal distortion and cross talk in optically amplified transmission systems, they have been equally harnessed for the development of new generations of optical amplifiers and tunable laser sources.

Ferdinand Anayo Oguama

2003-01-01

178

An all-fiber vacuum sensor based on thermo-optics' effect in vanadium-doped fiber  

NASA Astrophysics Data System (ADS)

This paper introduces an all-optical, fiber-optics vacuum sensor, which takes advantage of the thermo-optic effect within vanadium-co-doped fiber. This sensor utilizes a 980 nm pump-diode and a short section of highly absorbing vanadiumco- doped fiber produced by the flash vaporization process. The 980 nm source operates in pulse mode therefore the vanadium-co-doped fiber is periodically heated and self-cooled. The 980 nm pump-light is fully absorbed within the codoped fiber's core and relaxed as a heat, which changes the fiber's core refractive index. The heat-transfer between the heated fiber and surrounding gas depends on the gas pressure. Further, the doped-fiber is inserted into a Fabry-Perot interferometer which forms, in combination with a DFB laser diode at 1550 nm, a high coherence interferometer for optical path-length measurement. The time constant and absolute modulated optical path of the step response can be directly correlated with the gas pressure. The time constant is independent of the pump-diode's optical power, while the absolute modulated optical path also depends on the pump-diode's output of optical power and should thus be compensated. The vacuum sensor allows for a remote and fully dielectric measurement of the gas pressure and can be used in various industrial applications.

Matjasec, Ziga; Donlagic, Denis

2014-05-01

179

Aerogel-clad optical fiber  

DOEpatents

An optical fiber is surrounded by an aerogel cladding. For a low density aerogel, the index of refraction of the aerogel is close to that of air, which provides a high numerical aperture to the optical fiber. Due to the high numerical aperture, the aerogel clad optical fiber has improved light collection efficiency.

Sprehn, Gregory A. (Livermore, CA); Hrubesh, Lawrence W. (Pleasanton, CA); Poco, John F. (Livermore, CA); Sandler, Pamela H. (San Marino, CA)

1997-01-01

180

Aerogel-clad optical fiber  

DOEpatents

An optical fiber is surrounded by an aerogel cladding. For a low density aerogel, the index of refraction of the aerogel is close to that of air, which provides a high numerical aperture to the optical fiber. Due to the high numerical aperture, the aerogel clad optical fiber has improved light collection efficiency. 4 figs.

Sprehn, G.A.; Hrubesh, L.W.; Poco, J.F.; Sandler, P.H.

1997-11-04

181

Low-Cost and Robust 1-Gbit\\/s Plastic Optical Fiber Link Based on Light-Emitting Diode Technology  

Microsoft Academic Search

1-Gbit\\/s transmission is demonstrated over 50 m of step-index PMMA plastic optical fiber (1-mm core-diameter) using a commercial light-emitting diode. This is enabled by use of discrete multitone modulation with up to 64-QAM constellation mapping.

S. C. Lee; F. Breyer; S. Randel; O. Ziemann; H. P. A. van den Boom; A. M. J. Koonen

2008-01-01

182

Drawing robust infrared optical fibers from preforms produced by efficient multimaterial stacked coextrusion  

NASA Astrophysics Data System (ADS)

The utilization of infrared chalcogenide glass (ChG) fibers has long been hampered by the unfavorable mechanical characteristics typical of these glasses. Furthermore, the usual pathways to producing such fibers necessitate large-scale synthesis of high-purity glass, which represents a challenge in an academic environment, and thus presents an obstacle to the transfer of research results from academia to industry. Here we present our recent progress on multimaterial coextrusion technology that allows for high-efficiency disc-to-fiber manufacturing. A one-step extrusion from two glass discs (10-mm-diameter and 3-mm-thick) and a thermoplastic disc results in a robust step-index preform that is thermally drawn in an ambient atmosphere into continuous lengths of fiber with core diameters on the order of tens of micrometers. These results offer an alternative methodology that overcomes many of the traditional obstacles while potentially reducing the production cost.

Tao, Guangming; Abouraddy, Ayman F.

2014-03-01

183

Effect of constructional parameters on the performance of a surface plasmon resonance sensor based on a multimode polymer optical fiber.  

PubMed

We experimentally studied the influence of different constructional parameters on the performance of surface plasmon resonance (SPR) sensors based on a commercially available polymer step-index multimode fiber. For the first time, to the best of our knowledge, we experimentally investigated the influence of polishing depth on the characteristics of SPR sensors based on a straight multimode fiber. We also examined the impact of sensing length on the spectral position and strength of the SPR in side-polished straight fibers. To clarify literature contradictions concerning the effect of fiber bending on SPR, we experimentally investigated the performance of U-bent SPR sensing probes based on multimode fibers. We have shown that the SPR can be significantly amplified by bending the polymer fiber with stripped cladding. We also demonstrated that the side-polishing of U-bent sensing probes has little impact on their performance. PMID:25608056

Gasior, Katarzyna; Martynkien, Tadeusz; Urbanczyk, Waclaw

2014-12-10

184

Measurement of low-frequency ultrasonic wave in water using an acoustic fiber sensor.  

PubMed

An acoustic fiber sensor for measurement of ultrasonic waves, which used the approximate Raman-Nath diffraction effect where light diffraction waves were generated in an optical fiber by strain due to the ultrasonic waves, was proposed and examined. In order to characterize the acoustic fiber sensor as a basic study, measurements of low-frequency ultrasonic waves in water were examined using a step index fiber operating as a detection sensor. The results showed that characteristics of detected signals agreed with the theoretical prediction based on Fraunhofer diffraction. This indicates that our proposed fiber sensor can be used for the detection of low-frequency ultrasonic waves as well as the transmission of light diffraction signals. PMID:16615580

Sakoda, Tatsuya; Sonoda, Yoshito

2006-04-01

185

Temperature and strain characterization of long period gratings in air guiding fiber  

NASA Astrophysics Data System (ADS)

This paper reports on the fabrication of Long Period Gratings (LPGs) in hollow-core air-silica photonic bandgap fibers by using pressure assisted Electrode Arc Discharge (EAD) technique. In particular, the fabrication procedure relies on the combined use of EAD step, to locally heat the HC fiber, and of a static pressure (slightly higher than the external one) inside the fiber holes, to modify the holes. This procedure permits to preserve the holey structure of the host fiber avoiding any hole collapsing and it enables a local effective refractive index change due to the size and shape modifications of core and cladding holes. Periodically repeated EAD treatments permit the fabrication of LPGs based devices in hollow core optical fibers enabling new functionalities hitherto not possible. Here, the experimental fabrication of LPG prototypes with different periods and lengths are discussed. And, the HC-LPGs sensitivity to environmental parameters such as strain and temperature are investigated.

Iadicicco, Agostino; Cutolo, Antonello; Cusano, Andrea; Campopiano, Stefania

2013-05-01

186

Fiber bundle phase conjugate mirror  

DOEpatents

An improved method and apparatus for passively conjugating the phases of a distorted wavefronts resulting from optical phase mismatch between elements of a fiber laser array are disclosed. A method for passively conjugating a distorted wavefront comprises the steps of: multiplexing a plurality of probe fibers and a bundle pump fiber in a fiber bundle array; passing the multiplexed output from the fiber bundle array through a collimating lens and into one portion of a non-linear medium; passing the output from a pump collection fiber through a focusing lens and into another portion of the non-linear medium so that the output from the pump collection fiber mixes with the multiplexed output from the fiber bundle; adjusting one or more degrees of freedom of one or more of the fiber bundle array, the collimating lens, the focusing lens, the non-linear medium, or the pump collection fiber to produce a standing wave in the non-linear medium.

Ward, Benjamin G.

2012-05-01

187

Integrated Luneburg lens via ultra-strong index gradient on silicon.  

PubMed

Gradient index structures are gaining increased importance with the constant development of Transformation Optics and metamaterials. Our ability to fabricate such devices, while limited, has already demonstrated the extensive capabilities of those designs, in the forms of invisibility devices, as well as illusion optics and super-lensing. In this paper we present a low loss, high index contrast lens that is integrated with conventional nanophotonic waveguides to provide improved tolerance in fiber-to-chip optical links for future communication networks. This demonstration represents a positive step in making the extraordinary capabilities of gradient index devices available for integrated optics. PMID:21997023

Gabrielli, Lucas H; Lipson, Michal

2011-10-10

188

Next Step for STEP  

SciTech Connect

The Siletz Tribal Energy Program (STEP), housed in the Tribe’s Planning Department, will hire a data entry coordinator to collect, enter, analyze and store all the current and future energy efficiency and renewable energy data pertaining to administrative structures the tribe owns and operates and for homes in which tribal members live. The proposed data entry coordinator will conduct an energy options analysis in collaboration with the rest of the Siletz Tribal Energy Program and Planning Department staff. An energy options analysis will result in a thorough understanding of tribal energy resources and consumption, if energy efficiency and conservation measures being implemented are having the desired effect, analysis of tribal energy loads (current and future energy consumption), and evaluation of local and commercial energy supply options. A literature search will also be conducted. In order to educate additional tribal members about renewable energy, we will send four tribal members to be trained to install and maintain solar panels, solar hot water heaters, wind turbines and/or micro-hydro.

Wood, Claire [CTSI; Bremner, Brenda [CTSI

2013-08-09

189

ZBLAN Fiber  

NASA Technical Reports Server (NTRS)

Marshall Space Flight Center's researchers have conducted suborbital experiments with ZBLAN, an optical material capable of transmitting 100 times more signal and information than silica fibers. The next step is to process ZBLAN in a microgravity environment to stop the formation of crystallites, small crystals caused by a chemical imbalances. Scientists want to find a way to make ZBLAN an amorphous (without an internal shape) material. Producing a material such as this will have far-reaching implications on advanced communications, medical and manufacturing technologies using lasers, and a host of other products well into the 21st century.

2004-01-01

190

OPTOELECTRONICS, FIBER OPTICS, AND OTHER ASPECTS OF QUANTUM ELECTRONICS: Influence of the Rayleigh backscattering on the mode composition of radiation in multimode graded-index waveguides with a quadratic refractive-index profile  

Microsoft Academic Search

A method of coherent states is used to describe the process of Rayleigh scattering in a multimode graded-index waveguide with a quadratic refractive-index profile. Explicit expressions are obtained for the coefficients representing excitation of Gaussian-Hermite backscattering modes in two cases of practical importance: excitation of a waveguide by an extended noncoherent light source and selective excitation of different modes at

G. L. Esayan; S. G. Krivoshlykov

1989-01-01

191

High index contrast platform for silicon photonics  

E-print Network

This thesis focuses on silicon-based high index contrast (HIC) photonics. In addition to mature fiber optics or low index contrast (LIC) platform, which is often referred to as Planar Lightwave Cirrcuit (PLC) or Silica ...

Akiyama, Shoji, 1972-

2004-01-01

192

Robust fiber clustering of cerebral fiber bundles in white matter  

NASA Astrophysics Data System (ADS)

Diffusion tensor imaging fiber tracking (DTI-FT) has been widely accepted in the diagnosis and treatment of brain diseases. During the rendering pipeline of specific fiber tracts, the image noise and low resolution of DTI would lead to false propagations. In this paper, we propose a robust fiber clustering (FC) approach to diminish false fibers from one fiber tract. Our algorithm consists of three steps. Firstly, the optimized fiber assignment continuous tracking (FACT) is implemented to reconstruct one fiber tract; and then each curved fiber in the fiber tract is mapped to a point by kernel principal component analysis (KPCA); finally, the point clouds of fiber tract are clustered by hierarchical clustering which could distinguish false fibers from true fibers in one tract. In our experiment, the corticospinal tract (CST) in one case of human data in vivo was used to validate our method. Our method showed reliable capability in decreasing the false fibers in one tract. In conclusion, our method could effectively optimize the visualization of fiber bundles and would help a lot in the field of fiber evaluation.

Yao, Xufeng; Wang, Yongxiong; Zhuang, Songlin

2014-11-01

193

Micromachine Wedge Stepping Motor  

SciTech Connect

A wedge stepping motor, which will index a mechanism, has been designed and fabricated in the surface rnicromachine SUMMiT process. This device has demonstrated the ability to index one gear tooth at a time with speeds up to 205 teeth/see. The wedge stepper motor has the following features, whi:h will be useful in a number of applications. o The ability to precisely position mechanical components. . Simple pulse signals can be used for operation. o Only 2 drive signals are requixed for operation. o Torque and precision capabilities increase with device size . The device to be indexed is restrained at all times by the wedge shaped tooth that is used for actuation. This paper will discuss the theory of operation and desi=m of the wedge stepping motor. The fabrication and testing of I he device will also be presented.

Allen, J.J.; Schriner, H.K.

1998-11-04

194

Infrared single mode chalcogenide glass fiber for space.  

PubMed

An important measuring technique under study for the DARWIN planet finding mission, is nulling interferometry, enabling the detection of the weak infrared emission lines of an orbiting planet. This technique requires a perfect wavefront of the light beams to be combined in the interferometer. By using a single mode waveguide before detection, wavefront errors are filtered and a virtually perfect plane wavefront is obtained. In this paper the results on the development and the optical characterisation of suitable infrared transmitting chalcogenide glasses and mid-IR guiding optical fibers are reported. Two different perform techniques for manufacturing core-cladding chalcogenide fibers are described. Two types of step index fibers, prepared with Te(2)As(3)Se(5) chalcogenide glasses, offer single mode guidance at 10.6 mum. PMID:19547623

Houizot, P; Boussard-Plédel, C; Faber, A J; Cheng, L K; Bureau, B; Van Nijnatten, P A; Gielesen, W L M; Pereira do Carmo, J; Lucas, J

2007-09-17

195

Large-aperture, tapered fiber-coupled, 10-kHz particle-image velocimetry.  

PubMed

We demonstrate the design and implementation of a fiber-optic beam-delivery system using a large-aperture, tapered step-index fiber for high-speed particle-image velocimetry (PIV) in turbulent combustion flows. The tapered fiber in conjunction with a diffractive-optical-element (DOE) fiber-optic coupler significantly increases the damage threshold of the fiber, enabling fiber-optic beam delivery of sufficient nanosecond, 532-nm, laser pulse energy for high-speed PIV measurements. The fiber successfully transmits 1-kHz and 10-kHz laser pulses with energies of 5.3 mJ and 2 mJ, respectively, for more than 25 min without any indication of damage. It is experimentally demonstrated that the tapered fiber possesses the high coupling efficiency (~80%) and moderate beam quality for PIV. Additionally, the nearly uniform output-beam profile exiting the fiber is ideal for PIV applications. Comparative PIV measurements are made using a conventionally (bulk-optic) delivered light sheet, and a similar order of measurement accuracy is obtained with and without fiber coupling. Effective use of fiber-coupled, 10-kHz PIV is demonstrated for instantaneous 2D velocity-field measurements in turbulent reacting flows. Proof-of-concept measurements show significant promise for the performance of fiber-coupled, high-speed PIV using a tapered optical fiber in harsh laser-diagnostic environments such as those encountered in gas-turbine test beds and the cylinder of a combustion engine. PMID:23481818

Hsu, Paul S; Roy, Sukesh; Jiang, Naibo; Gord, James R

2013-02-11

196

Delivery of 800?W of nearly diffraction-limited laser power through a 100?m long multi-mode fiber  

NASA Astrophysics Data System (ADS)

We present the efficient propagation of a nearly diffraction-limited laser beam with a continuous wave power of 800?W through a multi-mode step-index delivery fiber with a core diameter of 30?µm and a numerical aperture of 0.056. The M2-value was measured to be 1.35 after 100?m of this passive fiber. This is an important advance as the delivery fiber length for high-brightness beams in the kilowatt range is usually limited to a few meters by the onset of nonlinear effects. For this demonstration a single-mode MOPA system was set-up consisting of a fiber oscillator and two amplifier stages. This source was coupled into the delivery fiber through a 500?mm long mode field adapter.

Negel, Jan-Philipp; Austerschulte, Armin; Vogel, Moritz M.; Rataj, Thomas; Voss, Andreas; Abdou Ahmed, Marwan; Graf, Thomas

2014-05-01

197

Congenital fiber type disproportion myopathy caused by LMNA mutations.  

PubMed

A boy, who had shown muscle weakness and hypotonia from early childhood and fiber type disproportion (FTD) with no dystrophic changes on muscle biopsy, was initially diagnosed as having congenital fiber type disproportion (CFTD). Subsequently, he developed cardiac conduction blocks. We reconsidered the diagnosis as possible LMNA-myopathy and found a heterozygous mutation in the LMNA gene. This encouraged us to search for LMNA mutations on 80 patients who met the diagnostic criteria of CFTD with unknown cause. Two patients including the above index case had heterozygous in-frame deletion mutations of c.367_369delAAG and c.99_101delGGA in LMNA, respectively. Four of 23 muscular dystrophy patients with LMNA mutation also showed fiber type disproportion (FTD). Importantly, all FTD associated with LMNA-myopathy were caused by hypertrophy of type 2 fibers as compared with age-matched controls, whereas CFTD with mutations in ACTA1 or TPM3 showed selective type 1 fiber atrophy but no type 2 fiber hypertrophy. Although FTD is not a constant pathological feature of LMNA-myopathy, we should consider the possibility of LMNA-myopathy whenever a diagnosis of CFTD is made and take steps to prevent cardiac insufficiency. PMID:24642510

Kajino, Sachiko; Ishihara, Kayo; Goto, Kanako; Ishigaki, Keiko; Noguchi, Satoru; Nonaka, Ikuya; Osawa, Makiko; Nishino, Ichizo; Hayashi, Yukiko K

2014-05-15

198

Specially designed long period grating with internal geometric bending for enhanced refractive index sensitivity  

NASA Astrophysics Data System (ADS)

We propose a long period grating (LPG) characterized by specially designed refractive index (RI) profile in which each grating plane is tilted at increasing angles, as moving away from the center of symmetry of the structure towards its both edges. This internally manufactured geometric structure, which basically simulates the bending of an optical fiber, increases the RI sensitivity of an LPG to the external medium. We experimentally demonstrate a three-fold improvement in the RI sensitivity, thus providing the basis for another step forward in the field of RI sensors based on optical fiber gratings.

Chiavaioli, F.; Trono, C.; Baldini, F.

2013-06-01

199

Scaling Fiber Lasers to Large Mode Area: An Investigation of Passive Mode-Locking Using a Multi-Mode Fiber  

PubMed Central

The mode-locking of dissipative soliton fiber lasers using large mode area fiber supporting multiple transverse modes is studied experimentally and theoretically. The averaged mode-locking dynamics in a multi-mode fiber are studied using a distributed model. The co-propagation of multiple transverse modes is governed by a system of coupled Ginzburg–Landau equations. Simulations show that stable and robust mode-locked pulses can be produced. However, the mode-locking can be destabilized by excessive higher-order mode content. Experiments using large core step-index fiber, photonic crystal fiber, and chirally-coupled core fiber show that mode-locking can be significantly disturbed in the presence of higher-order modes, resulting in lower maximum single-pulse energies. In practice, spatial mode content must be carefully controlled to achieve full pulse energy scaling. This paper demonstrates that mode-locking performance is very sensitive to the presence of multiple waveguide modes when compared to systems such as amplifiers and continuous-wave lasers. PMID:21731106

Ding, Edwin; Lefrancois, Simon; Kutz, Jose Nathan; Wise, Frank W.

2011-01-01

200

Parabolic pulse generation in a dispersion-decreasing solid-core photonic bandgap Bragg fiber  

NASA Astrophysics Data System (ADS)

We analyze the interplay of nonlinearity and dispersion in a dispersion-decreasing photonic bandgap Bragg fiber as a new platform for generating parabolic pulses. A suitably designed linearly tapered, low-index-contrast, solid-core Bragg fiber - amenable to fabrication by conventional modified chemical vapor deposition technology - is shown to yield stable parabolic pulses. The fiber design was optimized through a simple and accurate transfer-matrix formalism and pulse evolution was studied by the well-known split-step Fourier method. Our study revealed feasibility of generating parabolic pulses in such a dispersion-decreasing Bragg fiber of length as short as 1 m. We have also studied the effect of third order dispersion on generated parabolic pulse, which is an important deteriorating factor in such applications. The effective single-mode operation of the proposed device is achieved through appropriate tailoring of the outer cladding layers.

Nagaraju, B.; Varshney, R. K.; Agrawal, Govind P.; Pal, Bishnu P.

2010-06-01

201

Single mode fiber array for planet detection using a visible nulling interferometer  

NASA Technical Reports Server (NTRS)

We report the design, fabrication, and testing of a coherent large mode field diameter fiber array to be used as a spatial filter in a planet finding visible nulling interferometer. The array is a key component of a space instrument for visible-light detection and spectroscopy of Earth like extrasolar planets. In this concept, a nulling interferometer is synthesized from a pupil image of a single aperture which is then spatially filtered by a coherent array of single mode fibers to suppress the residual scattered star light. The use of the fiber array preserves spatial information between the star and planet. The fiber array uses a custom commercial large mode field or low NA step-index single mode fiber to relax alignment tolerances. A matching custom micro lens array is used to couple light into the fibers, and to recollimate the light out of the fiber array. The use of large mode field diameter fiber makes the fabrication of a large spatial filter array with 300 to 1000 elements feasible.

Liu, Duncan; Levine, B. Martin; Shao, Michael; Aguayo, Franciso

2005-01-01

202

Optical fiber sensor having a sol-gel fiber core and a method of making  

DOEpatents

A simple, economic wet chemical procedure is described for making sol-gel fibers. The sol-gel fibers made from this process are transparent to ultraviolet, visible and near infrared light. Light can be guided in these fibers by using an organic polymer as a fiber cladding. Alternatively, air can be used as a low refractive index medium. The sol-gel fibers have a micro pore structure which allows molecules to diffuse into the fiber core from the surrounding environment. Chemical and biochemical reagents can be doped into the fiber core. The sol-gel fiber can be used as a transducer for constructing an optical fiber sensor. The optical fiber sensor having an active sol-gel fiber core is more sensitive than conventional evanescent wave absorption based optical fiber sensors.

Tao, Shiquan; Jindal, Rajeev; Winstead, Christopher; Singh, Jagdish P.

2006-06-06

203

CBER-DETR Nevada Coincident and Leading Employment Two Steps Forward and One Step Back: The Nevada Recovery  

E-print Network

CBER-DETR Nevada Coincident and Leading Employment Indexes1 Two Steps Forward and One Step Back: The Nevada Recovery The Nevada Coincident Employment Index measures the ups and downs of the Nevada economy using an index of employment variables. The Nevada Leading Employment Index also measures the ups

Ahmad, Sajjad

204

Index of Refraction  

NSDL National Science Digital Library

Refraction is an important behavior of light that can be used to explain the operation of lenses, prisms, and optical fiber, as well as natural phenomena such as rainbows and mirages. The index of refraction, or refractive index, is defined as the ratio of the speed of light in a vacuum to the speed of light in a material. The index of refraction is an important property of optical materials and one that can be easily measured in the laboratory.This lesson begins with a video that introduces the concept of refraction. Students learn firsthand how when a wave of light travels from one medium to another, the change in the wave's speed leads to a change in its wavelength and the bending of the wave. Next, students investigate index of refraction through an interactive media asset, research, and a class discussion. Following a video about the index of refraction and Snell's law, students work in groups to conduct their own laboratory experiment to measure the index of refraction of gelatin (or plastic).Note: This is the first of two optics lesson plans. You may want to follow this lesson with the Fiber Optics Lesson Plan.

205

A wide-beam propagating fiber for embedding bulky optical devices  

Microsoft Academic Search

We report a compact, low-loss, and robust fiber collimator making use of a specific graded index fiber in which a wide Gaussian beam propagates. The fiber simplifies fabrication and alignment of collimators.

K. Shiraishi; Y. Tamura; H. Yoda; L. R. Nunes; K. Ohta; H. Kato; T. Yoshida

2004-01-01

206

Activated carbon fibers and engineered forms from renewable resources  

DOEpatents

A method of producing activated carbon fibers (ACFs) includes the steps of providing a natural carbonaceous precursor fiber material, blending the carbonaceous precursor material with a chemical activation agent to form chemical agent-impregnated precursor fibers, spinning the chemical agent-impregnated precursor material into fibers, and thermally treating the chemical agent-impregnated precursor fibers. The carbonaceous precursor material is both carbonized and activated to form ACFs in a single step. The method produces ACFs exclusive of a step to isolate an intermediate carbon fiber.

Baker, Frederick S

2013-02-19

207

Activated carbon fibers and engineered forms from renewable resources  

DOEpatents

A method of producing activated carbon fibers (ACFs) includes the steps of providing a natural carbonaceous precursor fiber material, blending the carbonaceous precursor material with a chemical activation agent to form chemical agent-impregnated precursor fibers, spinning the chemical agent-impregnated precursor material into fibers, and thermally treating the chemical agent-impregnated precursor fibers. The carbonaceous precursor material is both carbonized and activated to form ACFs in a single step. The method produces ACFs exclusive of a step to isolate an intermediate carbon fiber.

Baker, Frederick S.

2010-06-01

208

Air cavity-based Fabry-Perot interferometer sensor fabricated using a sawing technique for refractive index measurement  

NASA Astrophysics Data System (ADS)

We have demonstrated a refractive index sensor based on a fiber optic Fabry-Perot (FP) interferometer with an open air cavity fabricated using a one-step mechanical sawing technique. The sensor head consists of a short FP cavity near the fiber patch cord tip, which was assembled by joining a ceramic ferrule and a single-mode fiber together. Owing to the open air cavity in the sensor head, various liquid samples with different refractive index can fill in-line air cavity, which makes the device usable as a refractometer. Moreover, due to the sensor head encircled with the robust ceramic ferrule, the device is attractive for sensing measurement in harsh environments. The sensor was tested in different refractive index solutions. The experimental result shows that the attenuation peak wavelength of the sensor is shifted toward a shorter wavelength with increasing refractive index, and the refractive index sensitivity is ˜92.5 nm/refractive index unit (RIU) and 73.75 dB/RIU. The proposed sensor can be used as an in-line refractometer for many potential applications in the sensing field.

Jung, Eun Joo; Lee, Woo-Jin; Kim, Myoung Jin; Hwang, Sung Hwan; Rho, Byung Sup

2014-01-01

209

High-power supercontinuum generation in a ZBLAN fiber with very efficient power distribution toward the mid-infrared.  

PubMed

We report high-power supercontinuum (SC) generation in a step-index fluorozirconate (ZBLAN) fiber with a zero-dispersion wavelength shifted to ~1.9???m. Pumping the fluoride fiber with 2.75 W of power provided by a thulium-doped fiber amplifier, a continuous spectrum extending from ~0.85 to 4.2 ?m with 2.24 W of average output power was achieved. Over 61% (1.37 W) of the total output power corresponds to wavelengths longer than 3 ?m, which shows, to the best of our knowledge, the highest power conversion efficiency toward the mid-IR spectral band in relation to the output spectrum width. A linear SC power scalability up to 5.24 W, with a spectral band of ~0.9-4???m, with repetition rate and pump power provided by a 1.55 ?m fiber master-oscillator power amplifier system, is also demonstrated. PMID:24562239

Swiderski, Jacek; Michalska, Maria

2014-02-15

210

Interaction and dispersion of waveguide modes in an optical fiber with microirregularities of the core surface  

NASA Astrophysics Data System (ADS)

A self-consistent linear model is proposed for the transformation of the average intensity of the mode spectrum I( z) of the waveguide field in a multimode optical fiber with a stepped refractive index profile and the core having a rough surface. The model is based on the concept of the intermodal dispersion matrix of an elementary segment of the fiber, ?, whose elements characterize the mutual transfer of energy between the waveguide modes, as well as their conversion to radiation modes on the specified interval. On this basis, the features of the transformation of the mode spectrum I( z) in a multimode optical fiber with a stepped refractive index profile are considered that is due to the effects of multiple dispersion of the signal by the stochastic irregularities of the duct. The effect of self-filtering of I( z) is described that results in the formation of a stable (normalized) distribution I*. The features of the normalization of the radiative damping of a group of modes I i ( z) in an optical fiber are considered.

Zadorin, A. S.; Kruglov, R. S.; Surkova, G. A.

2012-08-01

211

Nonlinear analysis of nano-cluster doped fiber  

Microsoft Academic Search

There are prominent nonlinear characteristics that we hope for the semiconductor nano-clusters doped fiber. Refractive index\\u000a of fiber core can be effectively changed by adulteration. This technology can provide a new method for developing photons\\u000a components. Because the semiconductor nano-cluster has quantum characteristics, Based on first-order perturbation theory and\\u000a classical theory of fiber, we deduced refractive index expressions of fiber

Gang Liu; Ru Zhang

2007-01-01

212

A New Type of Motor: Pneumatic Step Motor  

PubMed Central

This paper presents a new type of pneumatic motor, a pneumatic step motor (PneuStep). Directional rotary motion of discrete displacement is achieved by sequentially pressurizing the three ports of the motor. Pulsed pressure waves are generated by a remote pneumatic distributor. The motor assembly includes a motor, gearhead, and incremental position encoder in a compact, central bore construction. A special electronic driver is used to control the new motor with electric stepper indexers and standard motion control cards. The motor accepts open-loop step operation as well as closed-loop control with position feedback from the enclosed sensor. A special control feature is implemented to adapt classic control algorithms to the new motor, and is experimentally validated. The speed performance of the motor degrades with the length of the pneumatic hoses between the distributor and motor. Experimental results are presented to reveal this behavior and set the expectation level. Nevertheless, the stepper achieves easily controllable precise motion unlike other pneumatic motors. The motor was designed to be compatible with magnetic resonance medical imaging equipment, for actuating an image-guided intervention robot, for medical applications. For this reason, the motors were entirely made of nonmagnetic and dielectric materials such as plastics, ceramics, and rubbers. Encoding was performed with fiber optics, so that the motors are electricity free, exclusively using pressure and light. PneuStep is readily applicable to other pneumatic or hydraulic precision-motion applications. PMID:21528106

Stoianovici, Dan; Patriciu, Alexandru; Petrisor, Doru; Mazilu, Dumitru; Kavoussi, Louis

2011-01-01

213

A New Type of Motor: Pneumatic Step Motor.  

PubMed

This paper presents a new type of pneumatic motor, a pneumatic step motor (PneuStep). Directional rotary motion of discrete displacement is achieved by sequentially pressurizing the three ports of the motor. Pulsed pressure waves are generated by a remote pneumatic distributor. The motor assembly includes a motor, gearhead, and incremental position encoder in a compact, central bore construction. A special electronic driver is used to control the new motor with electric stepper indexers and standard motion control cards. The motor accepts open-loop step operation as well as closed-loop control with position feedback from the enclosed sensor. A special control feature is implemented to adapt classic control algorithms to the new motor, and is experimentally validated. The speed performance of the motor degrades with the length of the pneumatic hoses between the distributor and motor. Experimental results are presented to reveal this behavior and set the expectation level. Nevertheless, the stepper achieves easily controllable precise motion unlike other pneumatic motors. The motor was designed to be compatible with magnetic resonance medical imaging equipment, for actuating an image-guided intervention robot, for medical applications. For this reason, the motors were entirely made of nonmagnetic and dielectric materials such as plastics, ceramics, and rubbers. Encoding was performed with fiber optics, so that the motors are electricity free, exclusively using pressure and light. PneuStep is readily applicable to other pneumatic or hydraulic precision-motion applications. PMID:21528106

Stoianovici, Dan; Patriciu, Alexandru; Petrisor, Doru; Mazilu, Dumitru; Kavoussi, Louis

2007-02-01

214

Tunable random fiber laser  

SciTech Connect

An optical fiber is treated as a natural one-dimensional random system where lasing is possible due to a combination of Rayleigh scattering by refractive index inhomogeneities and distributed amplification through the Raman effect. We present such a random fiber laser that is tunable over a broad wavelength range with uniquely flat output power and high efficiency, which outperforms traditional lasers of the same category. Outstanding characteristics defined by deep underlying physics and the simplicity of the scheme make the demonstrated laser a very attractive light source both for fundamental science and practical applications.

Babin, S. A.; Podivilov, E. V. [Institute of Automation and Electrometry, SB RAS, Novosibirsk 630090 (Russian Federation); El-Taher, A. E.; Harper, P.; Turitsyn, S. K. [Photonics Research Group, Aston University, Birmingham, B4 7ET (United Kingdom)

2011-08-15

215

Fiber optic sensor for angular position measurement: application for an electrical power-assisted steering system  

NASA Astrophysics Data System (ADS)

To achieve a very effective automotive power steering system, we need two important data, the angular position of the wheel and the torque applied on the shaft by the driver of the car. We present a new accurate optical fiber angular position sensor connected to an automotive power steering column. In this new design, the sensor allows the measurement of the angular position of a car steering wheel over a large and adjustable range (± several turns of the wheel). The wheel rotation induces micro-bending in the transducer part of the optical fiber sensing system. This system operates as an amplitude modulation sensor based on mode coupling in the transducing fiber in the case when all the modes are equally excited. We study the sensor response both theoretically and experimentally with a multimode step index optical fiber [rf (fiber radius) = 300 ?m rc (core radius) = 50 ?m nc (core index) = 1,457; N.A. = 0, 22 and the wavelength is 632,8 nm at the ambient Temperature (20°C)]. We show that the sensitivity can be controlled as a function of the sensor's length. We compare modeling and experimental validation and we conclude with a perspective on what could soon be an industrial sensor.

Javahiraly, Nicolas; Chakari, Ayoub

2013-05-01

216

Nonlinear pulse propagation through an optical fiber: Theory and experiment  

NASA Astrophysics Data System (ADS)

Pulse propagation through optical fibers is studied for two different phenomena, (i) the evolution of four-wave-mixing and (ii) the interplay between self- and cross-phase modulation for ultra-short pulses in a polarization maintaining fiber. For the four-wave-mixing case, we present the results of a study of the dynamical evolution of multiple four-wave-mixing processes in a single mode optical fiber with spatially and temporally delta-correlated phase noise. A nonlinear Schrodinger equation (NLSE) with stochastic phase fluctuations along the length of the fiber is solved using the Split-Step Fourier method. Good agreement is obtained with previous experimental and computational results based on a truncated-ODE model in which stochasticity was seen to play a key role in determining the nature of the dynamics. The full NLSE allows for simulations with high frequency resolution (60MHz) and frequency span (16THz) compared to the truncated ODE model (300GHz and 2.8THz respectively), thus enabling a more detailed comparison with observations. Fluctuations in the refractive index of the fiber core are found to be a possible source for this phase noise. It is found that index fluctuations as small as 1 part per billion are sufficient to explain observed features of the evolution of the four-wave-mixing sidebands. These measurements and numerical models thus may provide a technique for estimating these refractive index fluctuations which are otherwise difficult to measure. For the case of self- and cross-phase modulation, the evolution of orthogonal polarizations of asymmetric femtosecond pulses (810nm) propagating through a birefringent single-mode optical fiber (6.9cm) is studied both experimentally (using GRENOUILLE) and numerically (using a set of coupled NLSEs). A linear optical spectrogram representation is derived from the electric field of the pulses and juxtaposed with the optical spectrum and optical time-trace. The simulations are in good qualitative agreement with the experiments. Input temporal pulse asymmetry is found to be the dominant cause of output spectral asymmetry. The results indicate that it is possible to modulate short pulses both temporally and spectrally by passage through polarization maintaining optical fibers with specified orientation and length.

Khubchandani, Bhaskar

217

Indexing Images.  

ERIC Educational Resources Information Center

Focuses on access to digital image collections by means of manual and automatic indexing. Contains six sections: (1) Studies of Image Systems and their Use; (2) Approaches to Indexing Images; (3) Image Attributes; (4) Concept-Based Indexing; (5) Content-Based Indexing; and (6) Browsing in Image Retrieval. Contains 105 references. (AEF)

Rasmussen, Edie M.

1997-01-01

218

FLAX FIBERS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Flax (Linum usitatissimum L.) is a versatile plant, supplying both fiber and seed for industrial uses. The long, strong fibers processed for linen are prized for comfort and appearance in textiles, while shorter fibers are used in textile blends and for specialty paper, reinforced composites, and a...

219

Investigations on birefringence effects in polymer optical fiber Bragg gratings  

NASA Astrophysics Data System (ADS)

Step-index polymer optical fiber Bragg gratings (POFBGs) and microstructured polymer optical fiber Bragg gratings (mPOFBGs) present several attractive features, especially for sensing purposes. In comparison to FBGs written in silica fibers, they are more sensitive to temperature and pressure because of the larger thermo-optic coefficient and smaller Young's modulus of polymer materials. (M)POFBGs are most often photowritten in poly(methylmethacrylate) (PMMA) materials using a continuous-wave 325 nm HeCd laser. For the first time to the best of our knowledge, we study photoinduced birefringence effects in (m)POFBGs. To achieve this, highly reflective gratings were inscribed with the phase mask technique. They were then monitored in transmission with polarized light. For this, (m)POF sections a few cm in length containing the gratings were glued to angled silica fibers. Polarization dependent loss (PDL) and differential group delay (DGD) were computed from the Jones matrix eigenanalysis using an optical vector analyser. Maximum values exceeding several dB and a few picoseconds were obtained for the PDL and DGD, respectively. The response to lateral force was finally investigated. As it induces birefringence in addition to the photo-induced one, an increase of the PDL and DGD values were noticed.

Hu, X.; Sáez-Rodríguez, D.; Bang, O.; Webb, D. J.; Caucheteur, C.

2014-05-01

220

Stepped nozzle  

DOEpatents

An insert which allows a supersonic nozzle of a rocket propulsion system to operate at two or more different nozzle area ratios. This provides an improved vehicle flight performance or increased payload. The insert has significant advantages over existing devices for increasing nozzle area ratios. The insert is temporarily fastened by a simple retaining mechanism to the aft end of the diverging segment of the nozzle and provides for a multi-step variation of nozzle area ratio. When mounted in place, the insert provides the nozzle with a low nozzle area ratio. During flight, the retaining mechanism is released and the insert ejected thereby providing a high nozzle area ratio in the diverging nozzle segment.

Sutton, George P. (Danville, CA)

1998-01-01

221

Stepped nozzle  

DOEpatents

An insert is described which allows a supersonic nozzle of a rocket propulsion system to operate at two or more different nozzle area ratios. This provides an improved vehicle flight performance or increased payload. The insert has significant advantages over existing devices for increasing nozzle area ratios. The insert is temporarily fastened by a simple retaining mechanism to the aft end of the diverging segment of the nozzle and provides for a multi-step variation of nozzle area ratio. When mounted in place, the insert provides the nozzle with a low nozzle area ratio. During flight, the retaining mechanism is released and the insert ejected thereby providing a high nozzle area ratio in the diverging nozzle segment. 5 figs.

Sutton, G.P.

1998-07-14

222

Fiber Bragg grating inscription in novel highly strains sensitive microstructured fiber  

NASA Astrophysics Data System (ADS)

Microstructured optical fibers (MOF) sometimes also referred to as photonic crystal fibers (PCF) have been a subject of extensive research for over a decade. This is mainly due to the fact that by changing the microstructure geometry (e.g. distribution and size of the air-holes) fiber properties can be significantly modified to better fit specific applications. In this manuscript we present a novel fiber design with three large air-holes neighboring the core and report on how the air-hole diameter influences the effective refractive index strain sensitivity. As direct measurement of the effective refractive index change may be complex and challenging, we propose to use fiber Bragg gratings (FBG) in our sensing set up. The Bragg wavelength is a function of the effective refractive index, hence the external strain changes can be monitored through the Bragg wavelength shift with a simple optical spectrometer. Furthermore we also include an analysis of the fibers temperature sensitivity.

Stepien, K.; Tenderenda, T.; Murawski, M.; Szymanski, M.; Szostkiewicz, L.; Becker, M.; Rothhardt, M.; Bartelt, H.; Mergo, P.; Poturaj, K.; Jaroszewicz, L. R.; Nasilowski, T.

2014-05-01

223

Optical and spectroscopic characterization of Er3+-Yb3+co-doped tellurite glasses and fibers  

NASA Astrophysics Data System (ADS)

Optical and spectroscopic properties of Er3+-Yb3+ co-doped TeO2-WO3-Nb2O5-Na2O-Al2O3 glasses and fibers were investigated. Emission spectra and fluorescence lifetimes of 4I13/2 level of Er3+ion as a function of rare earth concentration and fiber length were measured in glasses. Results show that the self-absorption effect broadens the spectral bandwidth of 4I13/2?4I15/2 transition and lengthens the lifetime significantly from 3.5 to 4.6 ms. Fibers were fabricated by the rod-in-tube technique using a Heathway drawing tower. The emission power of these Er3+-Yb3+ co-doped Step Index Tellurite Fibers (SITFs; lengths varying from 2 to 60 cm) were generated by a 980 nm diode laser pump and then the emission power spectra were acquired with an OSA. The maximum emission power spectra, within the 1530-1560 nm region, were observed for fiber lengths ranging from 3 to 6 cm. The highest bandwidth obtained was 108 nm for 8 cm fiber length around 1.53 µm.

Narro-García, R.; Desirena, H.; Chillcce, E. F.; Barbosa, L. C.; Rodriguez, E.; De la Rosa, E.

2014-04-01

224

OTDR fiber-optical chemical sensor system for detection and location of hydrocarbon leakage.  

PubMed

A distributed sensing system for apolar hydrocarbons is presented which is built from a polymer-clad silica fiber adapted to an optical time domain reflectometer (OTDR) set-up. OTDR measurements allow locating and detecting chemicals by measuring the time delay between short light pulses entering the fiber and discrete changes in the backscatter signals that are caused by local extraction of hydrocarbons into the fiber cladding. The light guiding properties of the fiber are affected by interaction of the extracted chemicals with the evanescent wave light field extending into the fiber cladding. Distributed sensing of pure liquid hydrocarbons (HC) and aqueous HC solutions with a commercially available mini-OTDR adapted to sensing fibers of up to 1km length could be demonstrated. A pulsed laser diode emitting at the 850 nm telecommunication wavelength was applied in the mini-OTDR to locate the HCs by analyzing the step drop (light loss) in the backscatter signal, which is induced by local refractive index (RI) increase in the silicone cladding due to the extracted HC. The prototype instrument can be applied for monitoring hydrocarbon leakage in large technical installations, such as tanks, chemical pipelines or chemical waste disposal containments. PMID:12963280

Buerck, J; Roth, S; Kraemer, K; Mathieu, H

2003-08-15

225

Carbon Fibers Conductivity Studies  

NASA Technical Reports Server (NTRS)

In an attempt to understand the process of electrical conduction in polyacrylonitrile (PAN)-based carbon fibers, calculations were carried out on cluster models of the fiber consisting of carbon, nitrogen, and hydrogen atoms using the modified intermediate neglect of differential overlap (MINDO) molecular orbital (MO) method. The models were developed based on the assumption that PAN carbon fibers obtained with heat treatment temperatures (HTT) below 1000 C retain nitrogen in a graphite-like lattice. For clusters modeling an edge nitrogen site, analysis of the occupied MO's indicated an electron distribution similar to that of graphite. A similar analysis for the somewhat less stable interior nitrogen site revealed a partially localized II electron distribution around the nitrogen atom. The differences in bonding trends and structural stability between edge and interior nitrogen clusters led to a two-step process proposed for nitrogen evolution with increasing HTT.

Yang, C. Y.; Butkus, A. M.

1980-01-01

226

Simple method of fabrication tapered fiber  

NASA Astrophysics Data System (ADS)

This paper presents a simple method for manufacturing fiber tapered through elongation, by the combination of heating with a butane torch and controlled stretch. Reducing the diameter of the multimode fiber of 100 microns to 10 microns, the displacement of the fiber is performed through bipolar stepping motors with one driver L293B and one PIC16F628A microcontroller for controlling movement. The system allows control of the desired fiber diameter up to 10 microns; the results are seen in a microscope and a rule of separation 2.5?m micrometer to calculate the diameter of the fiber.

Vega, Fabio; Torres, Cesar; Diaz, Leonardo; Mattos, L.

2013-11-01

227

Fiber optic level sensor for cryogens  

NASA Technical Reports Server (NTRS)

Sensor is useful in cryogenic environments where liquids of very low index of refraction are encountered. It is "yes/no" indication of whether liquid is in contact with sensor. Sharp bends in fiber alter distribution of light among propagation modes. This amplifies change in light output observed when sensor contacts liquid, without requiring long fiber that would increse insertion loss.

Sharma, M.

1981-01-01

228

Rotational multiphoton endoscopy with a 1 m fiber laser system  

E-print Network

Rotational multiphoton endoscopy with a 1 m fiber laser system Gangjun Liu,1 Tuqiang Xie,1 Ivan V-based femtosecond laser. The rotational probe is based on a double-clad photonic crystal fiber, a gradient index a diameter of 2.2 mm and can provide 360° full-view rotation. The fiber laser provides ultrashort pulses

Chen, Zhongping

229

Supercontinuum Generation in Optical Fibers  

NASA Astrophysics Data System (ADS)

1. Introduction and history J. R. Taylor; 2. Supercontinuum generation in microstructure fiber - an historical note J. K. Ranka; 3. Nonlinear fiber optics overview J. C. Travers, M. H. Frosz and J. M. Dudley; 4. Fiber supercontinuum generation overview J. M. Dudley; 5. Silica fibers for supercontinuum generation J. C. Knight and W. Wadsworth; 6. Supercontinuum generation and nonlinearity in soft glass fibers J. H. V. Price and D. J. Richardson; 7. Increasing the blue-shift of a picosecond pumped supercontinuum M. H. Frosz, P. M. Moselund, P. D. Rasmussen, C. L. Thomsen and O. Bang; 8. Continuous wave supercontinuum generation J. C. Travers; 9. Theory of supercontinuum and interactions of solitons with dispersive waves D. V. Skryabin and A. V. Gorbach; 10. Interaction of four-wave mixing and stimulated Raman scattering in optical fibers S. Coen, S. G. Murdoch and F. Vanholsbeeck; 11. Nonlinear optics in emerging waveguides: revised fundamentals and implications S. V. Afshar, M. Turner and T. M. Monro; 12. Supercontinuum generation in dispersion varying fibers G. Genty; 13. Supercontinuum generation in chalcogenide glass waveguides Dong-Il Yeom, M. R. E. Lamont, B. Luther Davies and B. J. Eggleton; 14. Supercontinuum generation for carrier-envelope phase stabilization of mode-locked lasers S. T. Cundiff; 15. Biophotonics applications of supercontinuum generation C. Dunsby and P. M. W. French; 16. Fiber sources of tailored supercontinuum in nonlinear microspectroscopy and imaging A. M. Zheltikov; Index.

Dudley, J. M.; Taylor, J. R.

2010-04-01

230

Experiments on room temperature optical fiber-fiber direct bonding  

NASA Astrophysics Data System (ADS)

High quality permanent connection between optical fibers is a significant issue in optics and communication. Studies on room temperature optical large diameter fiber-fiber direct bonding, which is essentially surface interactions of glass material, are presented here. Bonded fiber pairs are obtained for the first time through the bonding technics illustrated here. Two different kinds of bonding technics are provided-fresh surface (freshly grinded and polished) bonding and hydrophobic surface (activated by H2SO4 and HF) bonding. By means of fresh surface bonding, a bonded fiber pair with light transmitting efficiency of 98.1% and bond strength of 21.2 N is obtained. Besides, in the bonding process, chemical surface treatment of fibers' end surfaces is an important step. Therefore, various ways of surface treatment are analyzed and compared, based on atomic force microscopy force curves of differently disposed surfaces. According to the comparison, fresh surfaces are suggested as the prior choice in room temperature optical fiber-fiber bonding, owing to their larger adhesive force, attractive force, attractive distance, and adhesive range.

Hao, Jinping; Yan, Ping; Xiao, Qirong; Wang, Yaping; Gong, Mali

2012-08-01

231

Beyond Crossing Fibers: Bootstrap Probabilistic Tractography Using Complex Subvoxel Fiber Geometries  

PubMed Central

Diffusion magnetic resonance imaging fiber tractography is a powerful tool for investigating human white matter connectivity in vivo. However, it is prone to false positive and false negative results, making interpretation of the tractography result difficult. Optimal tractography must begin with an accurate description of the subvoxel white matter fiber structure, includes quantification of the uncertainty in the fiber directions obtained, and quantifies the confidence in each reconstructed fiber tract. This paper presents a novel and comprehensive pipeline for fiber tractography that meets the above requirements. The subvoxel fiber geometry is described in detail using a technique that allows not only for straight crossing fibers but for fibers that curve and splay. This technique is repeatedly performed within a residual bootstrap statistical process in order to efficiently quantify the uncertainty in the subvoxel geometries obtained. A robust connectivity index is defined to quantify the confidence in the reconstructed connections. The tractography pipeline is demonstrated in the human brain. PMID:25389414

Campbell, Jennifer S. W.; MomayyezSiahkal, Parya; Savadjiev, Peter; Leppert, Ilana R.; Siddiqi, Kaleem; Pike, G. Bruce

2014-01-01

232

Effects of UV exposure on the attenuation of silica optical fibers  

Microsoft Academic Search

The influence of fiber processing parameters on the ultraviolet (UV)-visible properties of optical fibers and hence their suitability for applications in this wavelength region was investigated. The effect of fiber draw conditions, which include fiber diameter, fiber speed, and in-line UV radiation exposure, were determined for depressed-index glass-clad synthetic-silica-core optical fibers. Core materials containing 1000 p.p.m. and 5.0 p.p.m. [OH

Michael E. Mills; Richard L. Lehman

1989-01-01

233

Coating Carbon Fibers With Platinum  

NASA Technical Reports Server (NTRS)

A process for coating carbon fibers with platinum has been developed. The process may also be adaptable to coating carbon fibers with other noble and refractory metals, including rhenium and iridium. The coated carbon fibers would be used as ingredients of matrix/fiber composite materials that would resist oxidation at high temperatures. The metal coats would contribute to oxidation resistance by keeping atmospheric oxygen away from fibers when cracks form in the matrices. Other processes that have been used to coat carbon fibers with metals have significant disadvantages: Metal-vapor deposition processes yield coats that are nonuniform along both the lengths and the circumferences of the fibers. The electrical resistivities of carbon fibers are too high to be compatible with electrolytic processes. Metal/organic vapor deposition entails the use of expensive starting materials, it may be necessary to use a furnace, and the starting materials and/or materials generated in the process may be hazardous. The present process does not have these disadvantages. It yields uniform, nonporous coats and is relatively inexpensive. The process can be summarized as one of pretreatment followed by electroless deposition. The process consists of the following steps: The surfaces of the fiber are activated by deposition of palladium crystallites from a solution. The surface-activated fibers are immersed in a solution that contains platinum. A reducing agent is used to supply electrons to effect a chemical reduction in situ. The chemical reduction displaces the platinum from the solution. The displaced platinum becomes deposited on the fibers. Each platinum atom that has been deposited acts as a catalytic site for the deposition of another platinum atom. Hence, the deposition process can also be characterized as autocatalytic. The thickness of the deposited metal can be tailored via the duration of immersion and the chemical activity of the solution.

Effinger, Michael R.; Duncan, Peter; Coupland, Duncan; Rigali, Mark J.

2007-01-01

234

DIETARY FIBER  

Technology Transfer Automated Retrieval System (TEKTRAN)

This chapter explores the role of dietary fiber in human diets, health, and medicine. Dietary fiber contributes to human health by maintenance of normal gastrointestinal tract function. The polysaccharides and lignin present in cell walls of plant-derived foods are the primary source of dietary fibe...

235

Broadband 1×2 liquid crystal router with low thermal dependence for polymer optical fiber networks  

NASA Astrophysics Data System (ADS)

A 1×2 optical router based on an achromatic liquid crystal polarization rotator has been designed and experimentally tested. The router can work in the spectral range used in step-index polymer optical fiber networks (400-700 nm) with low wavelength and temperature dependences. The theoretical design is fast and simple and has good agreement with experimental results. Experimental crosstalk is lower than -18.68 dB for both outputs, even with thermal variations of 10 °C. Performance improvement with respect to previously reported devices with similar structure has also been analyzed.

Pinzón, Plinio Jesús; Pérez, Isabel; Vázquez, Carmen; Sánchez-Pena, José Manuel

2014-12-01

236

Interferometric Fiber Optic Sensors  

PubMed Central

Fiber optic interferometers to sense various physical parameters including temperature, strain, pressure, and refractive index have been widely investigated. They can be categorized into four types: Fabry-Perot, Mach-Zehnder, Michelson, and Sagnac. In this paper, each type of interferometric sensor is reviewed in terms of operating principles, fabrication methods, and application fields. Some specific examples of recently reported interferometeric sensor technologies are presented in detail to show their large potential in practical applications. Some of the simple to fabricate but exceedingly effective Fabry-Perot interferometers, implemented in both extrinsic and intrinsic structures, are discussed. Also, a wide variety of Mach-Zehnder and Michelson interferometric sensors based on photonic crystal fibers are introduced along with their remarkable sensing performances. Finally, the simultaneous multi-parameter sensing capability of a pair of long period fiber grating (LPG) is presented in two types of structures; one is the Mach-Zehnder interferometer formed in a double cladding fiber and the other is the highly sensitive Sagnac interferometer cascaded with an LPG pair. PMID:22736961

Lee, Byeong Ha; Kim, Young Ho; Park, Kwan Seob; Eom, Joo Beom; Kim, Myoung Jin; Rho, Byung Sup; Choi, Hae Young

2012-01-01

237

Optical Fiber Protection  

NASA Technical Reports Server (NTRS)

F&S Inc. developed and commercialized fiber optic and microelectromechanical systems- (MEMS) based instrumentation for harsh environments encountered in the aerospace industry. The NASA SBIR programs have provided F&S the funds and the technology to develop ruggedized coatings and coating techniques that are applied during the optical fiber draw process. The F&S optical fiber fabrication facility and developed coating methods enable F&S to manufacture specialty optical fiber with custom designed refractive index profiles and protective or active coatings. F&S has demonstrated sputtered coatings using metals and ceramics and combinations of each, and has also developed techniques to apply thin coatings of specialized polyimides formulated at NASA Langley Research Center. With these capabilities, F&S has produced cost-effective, reliable instrumentation and sensors capable of withstanding temperatures up to 800? C and continues building commercial sales with corporate partners and private funding. More recently, F&S has adapted the same sensing platforms to provide the rapid detection and identification of chemical and biological agents

1999-01-01

238

Low threshold mid-infrared supercontinuum generation in short fluoride-chalcogenide multimaterial fibers.  

PubMed

Mid-infrared supercontinuum generation (SCG) is mostly studied in fluoride glass fibers in which long fibers and high power pump sources are needed. Taking advantages of high nonlinearity and transparency, chalcogenide glass is also applied for SCG in mid-infrared region, where specific strategy is needed to compensate large normal material dispersion. We investigate multimaterial fibers (MMFs) combined with fluoride and chalcogenide glasses for SCG. The high refraction contrast allows the zero dispersion point of the fiber to shift to below 2 ?m without air holes. These two materials have similar glass transition temperatures and thermal expansion coefficients. They are possible to be drawn together. Both step-index MMFs and microstructured MMFs (MS-MMFs) are considered. The chromatic dispersions and supercontinuum spectra are studied. A 20 dB bandwidth of over one octave SCG with high coherence can be obtained from a 1 cm MS-MMF at 1.95 ?m with a pumping peak power of 175 W. As the pump power increased, the spectrum can extend to 5 ?m. In this scheme the fiber is so short that the high level of loss, which is the feature of MMFs, will not cause problems. PMID:25321993

Li, Xia; Chen, Wei; Xue, Tianfeng; Gao, Juanjuan; Gao, Weiqing; Hu, Lili; Liao, Meisong

2014-10-01

239

Two Fiber Optical Fiber Thermometry  

NASA Technical Reports Server (NTRS)

An optical fiber thermometer consists of an optical fiber whose sensing tip is given a metallic coating. The sensing tip of the fiber is essentially an isothermal cavity, so the emission from this cavity will be approximately equal to the emission from a blackbody. Temperature readings are obtained by measuring the spectral radiative heat flux at the end of the fiber at two wavelengths. The ratio of these measurements and Planck's Law are used to infer the temperature at the sensing tip. Optical fiber thermometers have high accuracy, excellent long-term stability and are immune to electromagnetic interference. In addition, they can be operated for extended periods without requiring re-calibration. For these reasons. it is desirable to use optical fiber thermometers in environments such as the International Space Station. However, it has recently been shown that temperature readings are corrupted by emission from the fiber when extended portions of the probe are exposed to elevated temperatures. This paper will describe several ways in which the reading from a second fiber can be used to correct the corrupted temperature measurements. The accuracy and sensitivity to measurement uncertainty will be presented for each method.

Jones, Mathew R.; Farmer, Jeffery T.; Breeding, Shawn P.

2000-01-01

240

Fiber optic fluid detector  

DOEpatents

Particular gases or liquids are detected with a fiber optic element having a cladding or coating of a material which absorbs the fluid or fluids and which exhibits a change of an optical property, such as index of refraction, light transmissiveness or fluoresence emission, for example, in response to absorption of the fluid. The fluid is sensed by directing light into the fiber optic element and detecting changes in the light, such as exit angle changes for example, that result from the changed optical property of the coating material. The fluid detector may be used for such purposes as sensing toxic or explosive gases in the atmosphere, measuring ground water contamination or monitoring fluid flows in industrial processes, among other uses. 10 figs.

Angel, S.M.

1987-02-27

241

Fiber optic fluid detector  

DOEpatents

Particular gases or liquids are detected with a fiber optic element (11, 11a to 11j) having a cladding or coating of a material (23, 23a to 23j) which absorbs the fluid or fluids and which exhibits a change of an optical property, such as index of refraction, light transmissiveness or fluoresence emission, for example, in response to absorption of the fluid. The fluid is sensed by directing light into the fiber optic element and detecting changes in the light, such as exit angle changes for example, that result from the changed optical property of the coating material. The fluid detector (24, 24a to 24j) may be used for such purposes as sensing toxic or explosive gases in the atmosphere, measuring ground water contamination or monitoring fluid flows in industrial processes, among other uses.

Angel, S. Michael (Livermore, CA)

1989-01-01

242

Optical Fibers  

NASA Astrophysics Data System (ADS)

With the development of extremely low-loss optical fibers and their application to communication systems, a revolution has taken fiber glass place during the last 40 years. In 2001, using glass fibers as the transmission medium and lightwaves as carrier wave waves, information was transmitted at a rate more than 1 Tbit/s (which is roughly equivalent to transmission of about 15 million simultaneous telephone conversations) through one hair thin optical fiber. Experimental demonstration of transmission at the rate of 14 Tbit/s over a 160 km long single fiber was demonstrated in 2006, which is equivalent to sending 140 digital high definition movies in 1 s. Very recently record transmission of more than 100 Tbit/s over 165 km single mode fiber has been reported. These can be considered as extremely important technological achievements. In this chapter we will discuss the propagation characteristics of optical fibers with special applications to optical communication systems and also present some of the noncommunication applications such as sensing.

Ghatak, Ajoy; Thyagarajan, K.

243

Optical fiber to waveguide coupling technique  

NASA Astrophysics Data System (ADS)

A technique for permanently coupling optical fibers edge-on to thin film waveguides was investigated and its feasibility demonstrated. It offers the fine micropositioner adjustment via a needle vacuum chuck for maximum optical coupling, offers robust mechanical support to the fibers from etched Si V-grooves, separates the support and fine adjustment cementing steps to minimize curing and thermal stresses, relaxes the requirements on fiber circularity and concentricity, is compatible with waveguide devices, and is suitable for close-spaced arrays of fibers.

Albares, D. J.; Trask, T. W.

1990-03-01

244

In-Line Fiber Optic Interferometric Sensors in Single-Mode Fibers  

PubMed Central

In-line fiber optic interferometers have attracted intensive attention for their potential sensing applications in refractive index, temperature, pressure and strain measurement, etc. Typical in-line fiber-optic interferometers are of two types: Fabry-Perot interferometers and core-cladding-mode interferometers. It's known that the in-line fiber optic interferometers based on single-mode fibers can exhibit compact structures, easy fabrication and low cost. In this paper, we review two kinds of typical in-line fiber optic interferometers formed in single-mode fibers fabricated with different post-processing techniques. Also, some recently reported specific technologies for fabricating such fiber optic interferometers are presented. PMID:23112608

Zhu, Tao; Wu, Di; Liu, Min; Duan, De-Wen

2012-01-01

245

Automation of fiber-optic pigtailing process: Laser welding demonstration program  

NASA Astrophysics Data System (ADS)

This demonstration program is intended to demonstrate the feasibility of coupling a commercially available Nd:YAG laser with the Kaptron POLYTROPE 3000 automatic alignment system for the production of single mode fiber pigtailed semiconductor lasers. It has been demonstrated that 30 watts of Nd:YAG laser power can produce repeatable welds of 0.18mm thick Kovar saddles to gold plated substrates of the type used for semiconductor laser modules. It has also been shown that beam geometry stabilization by passing the beam through a step index fiber (or reflective tube channel) is essential for reliable and repeatable welding with this type of multimode laser. Laser and delivery system requirements for a production Nd:YAG laser welding accessory for the Polytrope 3000 have been defined, and recommendations for such an accessory are included in this report.

Unterleitner, F. C.

1989-05-01

246

Immigration Index  

NSDL National Science Digital Library

Striving to become the "immigration resource directory on the net," the Immigration Index is a newly launched Website dedicated to news and information about immigration worldwide. Along with breaking headlines from a variety of news sources about immigration-related issues such as asylum, migration, trafficking and women, and much more, the site contains a fully annotated collection of links to immigration materials all around the World Wide Web. Only a month old, some of the categories in the Index's hierarchy still need some filling in. In time, however, the Immigration Index promises to become an invaluable resource for interested parties.

247

Soft capacitor fibers using conductive polymers for electronic textiles  

NASA Astrophysics Data System (ADS)

A novel, highly flexible, conductive polymer-based fiber with high electric capacitance is reported. In its cross section the fiber features a periodic sequence of hundreds of conductive and isolating plastic layers positioned around metallic electrodes. The fiber is fabricated using the fiber drawing method, where a multi-material macroscopic preform is drawn into a sub-millimeter capacitor fiber in a single fabrication step. Several kilometers of fibers can be obtained from a single preform with fiber diameters ranging between 500 and 1000 µm. A typical measured capacitance of our fibers is 60-100 nF m-1 and it is independent of the fiber diameter. Analysis of the fiber frequency response shows that in its simplest interrogation mode the capacitor fiber has a transverse resistance of 5 k? m L-1, which is inversely proportional to the fiber length L and is independent of the fiber diameter. Softness of the fiber materials, the absence of liquid electrolyte in the fiber structure, ease of scalability to large production volumes and high capacitance of our fibers make them interesting for various smart textile applications ranging from distributed sensing to energy storage.

Gu, Jian Feng; Gorgutsa, Stephan; Skorobogatiy, Maksim

2010-11-01

248

Concentric core optical fiber with multiple-mode signal transmission  

DOEpatents

A concentric core optical fiber provides for the simultaneous but independent transmission of signals over a single optical fiber. The concentric optical fiber is constructed of a single-mode or multimode inner optical fiber defined by a core and a cladding of a lower index of refraction than the core and an outer optical fiber defined by additional cladding concentrically disposed around the cladding and of an index of refraction lower than the first mentioned cladding whereby the latter functions as the core of the outer optical fiber. By employing such an optical fiber construction with a single-mode inner core or optical fiber, highly sensitive interferometric and stable less sensitive amplitude based sensors can be placed along the same length of a concentric core optical fiber. Also, by employing the concentric core optical fiber secure telecommunications can be achieved via the inner optical fiber since an intrusion of the concentric optical fiber will first cause a variation in the light being transmitted through the outer optical fiber and this variation of light being used to trigger a suitable alarm indicative of the intrusion. 3 figs.

Muhs, J.D.

1997-05-06

249

Concentric core optical fiber with multiple-mode signal transmission  

DOEpatents

A concentric core optical fiber provides for the simultaneous but independent transmission of signals over a single optical fiber. The concentric optical fiber is constructed of a single-mode or multimode inner optical fiber defined by a core and a cladding of a lower index of refraction than the core and an outer optical fiber defined by additional cladding concentrically disposed around the cladding and of an index of refraction lower than the first mentioned cladding whereby the latter functions as the core of the outer optical fiber. By employing such an optical fiber construction with a single-mode inner core or optical fiber, highly sensitive interferometric and stable less sensitive amplitude based sensors can be placed along the same length of a concentric core optical fiber. Also, by employing the concentric core optical fiber secure telecommunications can be achieved via the inner optical fiber since an intrusion of the concentric optical fiber will first cause a variation in the light being transmitted through the outer optical fiber and this variation of light being used to trigger a suitable alarm indicative of the intrusion.

Muhs, Jeffrey D. (Lenoir City, TN)

1997-01-01

250

Design of All-Solid Bandgap Fiber With Improved Confinement and Bend Losses  

Microsoft Academic Search

We propose a new design of low-contrast all-solid bandgap fiber with low confinement and bend losses within low-order bandgaps. By introducing an index depressed layer around the high index rod in fiber cladding, we theoretically predict that the confinement loss of the proposed all-solid bandgap fiber would be significantly improved. Due to the enlarged index mismatch of the guided core

Guobin Ren; Ping Shum; Liren Zhang; Min Yan; Xia Yu; Weijun Tong; Jie Luo

2006-01-01

251

Fibers comprised of epitaxially grown single-wall carbon nanotubes, and a method for added catalyst and continuous growth at the tip  

DOEpatents

The present invention is directed to fibers of epitaxially grown single-wall carbon nanotubes (SWNTs) and methods of making same. Such methods generally comprise the steps of: (a) providing a spun SWNT fiber; (b) cutting the fiber substantially perpendicular to the fiber axis to yield a cut fiber; (c) etching the cut fiber at its end with a plasma to yield an etched cut fiber; (d) depositing metal catalyst on the etched cut fiber end to form a continuous SWNT fiber precursor; and (e) introducing feedstock gases under SWNT growth conditions to grow the continuous SWNT fiber precursor into a continuous SWNT fiber.

Kittrell, W. Carter; Wang, Yuhuang; Kim, Myung Jong; Hauge, Robert H.; Smalley, Richard E.; Marek leg, Irene Morin

2010-06-01

252

Relaxation after a voltage step of inhibitory synaptic current elicited by nerve stimulation (crayfish neuromuscular junction)  

Microsoft Academic Search

The clamped membrane potential of small crayfish muscle fibers was shifted in rapid steps between potentials of about -60 and -120 mV, and the clamp currents measured after de-and hyperpolarizing steps were averaged. In addition, the inhibitory nerver fiber was stimulated either synchronously or asynchronously with the averaging. Synchronous stimulation yielded the usual IPSCs, and asynchronous stimulation a steady state

J. Dudel

1978-01-01

253

Triple-clad large-pitch fibers for compact high-power pulsed fiber laser systems.  

PubMed

We present a novel ytterbium (Yb)-doped large-pitch fiber design with significantly increased pump absorption and higher energy storage/gain per unit length, which enables high-peak-power fiber laser systems with smaller footprints. Up to now index matching between core and surrounding material in microstructured fibers was achieved by co-doping the active core region with fluorine. Here we carry out the index matching by passively doping the cladding with germanium, thus raising its index of refraction. Hence, the fluorine in the core can be omitted, which leads to an effective increase of the core doping concentration, while detrimental effects such as photo-darkening and lifetime quenching are avoided by maintaining the bulk Yb concentration. Experiments and simulations show that a gain higher than 50 dB/m and an output average power higher than 100 W with excellent beam quality are feasible even with a fiber length of only 40 cm. PMID:24562108

Gaida, Christian; Stutzki, Fabian; Jansen, Florian; Otto, Hans-Jürgen; Eidam, Tino; Jauregui, Cesar; de Vries, Oliver; Limpert, Jens; Tünnermann, Andreas

2014-01-15

254

Effective index model predicts modal frequencies of vertical-cavity lasers  

SciTech Connect

Previously, an effective index optical model was introduced for the analysis of lateral waveguiding effects in vertical-cavity surface-emitting lasers. The authors show that the resultant transverse equation is almost identical to the one typically obtained in the analysis of dielectric waveguide problems, such as a step-index optical fiber. The solution to the transverse equation yields the lateral dependence of the optical field and, as is recognized in this paper, the discrete frequencies of the microcavity modes. As an example, they apply this technique to the analysis of vertical-cavity lasers that contain thin-oxide apertures. The model intuitively explains the experimental data and makes quantitative predictions in good agreement with a highly accurate numerical model.

SERKLAND,DARWIN K.; HADLEY,G. RONALD; CHOQUETTE,KENT D.; GEIB,KENT M.; ALLERMAN,ANDREW A.

2000-04-18

255

Longitudinal strain sensing with photonic crystal fibers and fiber Bragg gratings  

NASA Astrophysics Data System (ADS)

Photonic crystal fibers (PCF), sometimes also referred to as microstructured fibers (MSF), have been a subject of extensive research for over a decade. This is mainly due to the fact that by changing the geometry and distribution of the air holes the fiber properties can be significantly modified and tailored to specific applications. In this paper we present the results of a numerical analysis of the influence of the air-hole distribution on the sensitivity of the propagated modes' effective refractive index to externally applied longitudinal strain. We propose an optimal strain sensitive fiber design, with a number of fibers drawn and experimentally evaluated to confirm the theoretical results. Furthermore as the direct measurement of the effective refractive index change may be complex and challenging in field environment, we propose to use fiber Bragg gratings (FBG) in our sensing set-up. As the Bragg wavelength is a function of the effective refractive index, the external strain changes can be monitored through the Bragg wavelength shift with a simple optical spectrometer. Moreover, since the PCF is also optimized for low-loss splicing with standard single mode fiber, our novel sensor head can be used with standard off-the-shelf components in complex multiplexed sensing arrays, with the measured signal transmitted to and from the sensor head by standard telecom fibers, which significantly reduces costs.

Tenderenda, T.; Murawski, M.; Szymanski, M.; Szostkiewicz, L.; Becker, M.; Rothhardt, M.; Bartelt, H.; Mergo, P.; Poturaj, Kl; Makara, M.; Skorupski, K.; Marc, P.; Jaroszewicz, L. R.; Nasilowski, T.

2014-03-01

256

Analysis of mode transitions in a long-period fiber grating with a nano-overlay of diamond-like carbon  

NASA Astrophysics Data System (ADS)

This work presents optimization analysis of the sensitivity to variations of the external refractive index (RI) of long-period fiber grating (LPFG) coated with a nano-overlay of diamond-like carbon (DLC) material. Through numerical simulations, we have shown that both the dual-resonance and mode transition phenomena can be simultaneously exploited to substantially increase the sensitivity to variations of the external RI. The tuning of the DLC layer thickness to displace the dual-resonance band into a more suitable region of the spectrum is also reported. To perform this analysis, we implemented a novel pseudo-heuristic simulation model based on a 4-layer step-index fiber layer model and coupled mode theory. The dispersion dependence on the DLC overlay thickness was modeled from experimental data. LPFG parameters were fitted to an experimental transmission spectrum. The simulation model and the obtain results provides guidance for the fabrication of the device.

Brabant, D.; Koba, M.; Smietana, Mateusz; Bock, Wojtek J.

2014-09-01

257

Pragmatic Approach to Subject Indexing: A New Concept.  

ERIC Educational Resources Information Center

Describes adoption at Sorghum and Millets Information Center (India) of Pragmatic Approach to Subject Index (PASI), computer-manipulative indexing procedure in which key words are arranged in meaningful sequence. Indexing problems, search for suitable system, PASI indexing steps, and computerization are discussed. Thirteen references and…

Dutta, S.; Sinha, P. K.

1984-01-01

258

Photovoltaic fibers  

NASA Astrophysics Data System (ADS)

It was realized early in the history of Konarka that the ability to produce fibers that generate power from solar energy could be applied to a wide variety of applications where fabrics are utilized currently. These applications include personal items such as jackets, shirts and hats, to architectural uses such as awnings, tents, large covers for cars, trucks and even doomed stadiums, to indoor furnishings such as window blinds, shades and drapes. They may also be used as small fabric patches or fiber bundles for powering or recharging batteries in small sensors. Power generating fabrics for clothing is of particular interest to the military where they would be used in uniforms and body armor where portable power is vital to field operations. In strong sunlight these power generating fabrics could be used as a primary source of energy, or they can be used in either direct sunlight or low light conditions to recharge batteries. Early in 2002, Konarka performed a series of proof-of-concept experiments to demonstrate the feasibility of building a photovoltaic cell using dye-sensitized titania and electrolyte on a metal wire core. The approach taken was based on the sequential coating processes used in making fiber optics, namely, a fiber core, e.g., a metal wire serving as the primary electrode, is passed through a series of vertically aligned coating cups. Each of the cups contains a coating fluid that has a specific function in the photocell. A second wire, used as the counter electrode, is brought into the process prior to entering the final coating cup. The latter contains a photopolymerizable, transparent cladding which hardens when passed through a UV chamber. Upon exiting the UV chamber, the finished PV fiber is spooled. Two hundred of foot lengths of PV fiber have been made using this process. When the fiber is exposed to visible radiation, it generates electrical power. The best efficiency exhibited by these fibers is 6% with an average value in the 4-5 % range.

Gaudiana, Russell; Eckert, Robert; Cardone, John; Ryan, James; Montello, Alan

2006-08-01

259

Miniature fiber optic surface plasmon resonance biosensors  

NASA Astrophysics Data System (ADS)

A novel design of surface plasmon resonance fiber optic sensor is reported which leads to a compact, highly miniaturized sensing element with excellent sensitivity. The sensing device is based on a side-polished single-mode optical fiber with a thin metal overlayer supporting surface plasmon waves. The strength of interaction between a fiber mode and a surface plasmon wave depends strongly on the refractive index near the sensing surface. Therefore, refractive index changes associated with biospecific interaction between antibodies immobilized on the sensor and antigen molecules can be monitored by measuring light intensity variations. Detection of horse radish peroxidase (HRP) of the concentration of 100 ng/ml has been accomplished using the fiber optic sensor with a matrix of monoclonal antibodies against HRP immobilized on the sensor surface.

Slavik, Radan; Brynda, Eduard; Homola, Jiri; Ctyroky, Jiri

1999-01-01

260

Photonic lantern with cladding-removable fibers  

NASA Astrophysics Data System (ADS)

Recently, spectral measurement becomes an important tool in astronomy to find exoplanets etc. The fibers are used to transfer light from the focal plate to spectrometers. To get high-resolution spectrum, the input slits of the spectrometers should be as narrow as possible. In opposite, the light spots from the fibers are circle, which diameters are clearly wider than the width of the spectrometer slits. To reduce the energy loss of the fiber-guide star light, many kinds of image slicers were designed and fabricated to transform light spot from circle to linear. Some different setup of fiber slicers are introduced by different research groups around the world. The photonic lanterns are candidates of fiber slicers. Photonic lantern includes three parts: inserted fibers, preform or tubing, taped part of the preform or tubing. Usually the optical fields concentrate in the former-core area, so the light spots are not uniform from the tapered end of the lantern. We designed, fabricated and tested a special kind of photonic lantern. The special fibers consist polymer cladding and doped high-index core. The polymer cladding could be easily removed using acetone bath, while the fiber core remains in good condition. We inserted the pure high-index cores into a pure silica tubing and tapered it. During the tapering process, the gaps between the inserted fibers disappeared. Finally we can get a uniform tapered multimode fiber end. The simulation results show that the longer the taper is, the lower the loss is. The shape of the taper should be controlled carefully. A large-zone moving-flame taper machine was fabricated to make the special photonic lantern. Three samples of photonic lanterns were fabricated and tested. The lanterns with cladding-removable fibers guide light uniform in the tapered ends that means these lanterns could collect more light from those ends.

Sun, Weimin; Yan, Qi; Bi, Yao; Yu, Haijiao; Liu, Xiaoqi; Xue, Jiuling; Tian, He; Liu, Yongjun

2014-07-01

261

Rib index.  

PubMed

This article analyzes the double rib contour sign (DRCS) and the rib index (RI). The analyzed topics are 1. the history of presentations - publication of DRCS-RI, 2. the study source origin: school screening for idiopathic scoliosis (IS), 3. what the DRCS and the RI are- Description, 4. the quantification of the DRCS - RI, 5. a reliability study for RI 6. how much the rib index is affected by the distance between the radiation source and the irradiated individual, 7. the implications on IS aetiology, 8. the applications of Rib index for a. documentation of the deformity, b. assessment of physiotherapy, c. assessment of brace treatment and d. pre- and post-operative assessment; assessment of the rib-cage deformity correction on the transverse plane, 9. the use of RI and implications for screening policies 10. the reference of the RI method in spinal textbooks and finally 11. the citations in Google Scholar. PMID:25635184

Grivas, Theodoros B

2014-01-01

262

Fiber optical turbulence sensing system  

NASA Astrophysics Data System (ADS)

A novel fiber optical turbulence sensing system based on phase generated carrier technique is developed for measuring the intensity and structure of local atmospheric optical turbulence. The turbulence-induced air refractive index fluctuations are detected through fiber optical turbulence sensor array and demodulated by the algorithm of correlation. The system's dynamic range is 10-18 ~ 10-12, which satisfies most of the sceneries in the boundary atmosphere. Time series of the measured refractive index fluctuations and its power spectrum up to the frequency of 500Hz in different conditions such as sealed box or free turbulent atmosphere are illuminated and analyzed. In the end, some of its applications are briefly outlined.

Xiao, Shu-mei; Mei, Hai-ping; Huang, Qi-kai; Rao, Rui-zhong

2012-10-01

263

Step-Growth Polymerization.  

ERIC Educational Resources Information Center

Following a comparison of chain-growth and step-growth polymerization, focuses on the latter process by describing requirements for high molecular weight, step-growth polymerization kinetics, synthesis and molecular weight distribution of some linear step-growth polymers, and three-dimensional network step-growth polymers. (JN)

Stille, J. K.

1981-01-01

264

Stepping motor controller  

DOEpatents

A stepping motor is microprocessor controlled by digital circuitry which monitors the output of a shaft encoder adjustably secured to the stepping motor and generates a subsequent stepping pulse only after the preceding step has occurred and a fixed delay has expired. The fixed delay is variable on a real-time basis to provide for smooth and controlled deceleration.

Bourret, S.C.; Swansen, J.E.

1982-07-02

265

Stepping motor controller  

DOEpatents

A stepping motor is microprocessingly controlled by digital circuitry which monitors the output of a shaft encoder adjustably secured to the stepping motor and generates a subsequent stepping pulse only after the preceding step has occurred and a fixed delay has expired. The fixed delay is variable on a real-time basis to provide for smooth and controlled deceleration.

Bourret, Steven C. (Los Alamos, NM); Swansen, James E. (Los Alamos, NM)

1984-01-01

266

Fabrication of nonlinear plastic optical fiber (POF) and application  

NASA Astrophysics Data System (ADS)

We have developed a fabrication technique for plastic optical fiber (POF) using nonlinear organic materials. The fabrication technique is the direct core solution injection into the hole of cladding preform formed by polymerization of cladding solution. The cladding solution was made of MMA, BBP, and BPO. The preform of fiber was drawn into fiber following polymerization of core solution in cladding preform. We used DR1 to control the refractive index of fiber and investigated the sensor characteristics. The sensitivity of fabricated fiber is about 0.11 W/°C in the temperature range from 20 °C to 100 °C.

Kim, Eung Soo; Kinoshita, Takeshi; Yu, Yun Sik; Jeong, Myung Yung

2007-04-01

267

Inverse Variation: Step By Step Lesson  

NSDL National Science Digital Library

This step by step lesson from the Math Ops website explains inverse variation. Students can read the text or follow along as it is read out loud. The lesson includes nine slides which explain what an inverse variation equation is, and include several real world examples of this type of mathematical model.

2012-08-29

268

PAF Changes Step-By-Step Procedure  

E-print Network

Proposal Management Reviewer PAF Changes Step-By-Step Procedure Last updated: 4/1/2013 1 of 6 http://eresearch.umich.edu Reviewer - PAF Changes In the state of Unit Review, a Reviewer or a Reviewer Who Can Sign (Approver) can make and submit their own changes or request that the project team make and submit the changes. When

Shyy, Wei

269

Acknowledge Changes Step by Step Procedure  

E-print Network

Proposal Management Reviewer Acknowledge Changes Step by Step Procedure Last updated: 03/20/09 1 of 4 http://eresearch.umich.edu Acknowledge Changes Acknowledge is used to confirm that you are aware of the PAF changes have been made after your approval, and that you do not wish to suspend your prior

Shyy, Wei

270

Photovoltaic fibers  

Microsoft Academic Search

It was realized early in the history of Konarka that the ability to produce fibers that generate power from solar energy could be applied to a wide variety of applications where fabrics are utilized currently. These applications include personal items such as jackets, shirts and hats, to architectural uses such as awnings, tents, large covers for cars, trucks and even

Russell Gaudiana; Robert Eckert; John Cardone; James Ryan; Alan Montello

2006-01-01

271

Intrinsic Fabry-Perot optical fiber sensors and their multiplexing  

DOEpatents

An intrinsic Fabry-Perot optical sensor includes a thin film sandwiched between two fiber ends. When light is launched into the fiber, two reflections are generated at the two fiber/thin film interfaces due to a difference in refractive indices between the fibers and the film, giving rise to the sensor output. In another embodiment, a portion of the cladding of a fiber is removed, creating two parallel surfaces. Part of the evanescent fields of light propagating in the fiber is reflected at each of the surfaces, giving rise to the sensor output. In a third embodiment, the refractive index of a small portion of a fiber is changed through exposure to a laser beam or other radiation. Interference between reflections at the ends of the small portion give rise to the sensor output. Multiple sensors along a single fiber are multiplexed using an optical time domain reflectometry method.

Wang, Anbo (Blacksburg, VA)

2007-12-11

272

1784 JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 20, NO. 9, MAY 1, 2014 A Dual-Wavelength Fiber Ring Laser Incorporating  

E-print Network

--A novel configuration for a dual-wavelength fiber ring laser with improved lasing stability realized at an ultra-high speed. Index Terms--Dual-wavelength laser, fiber laser, fiber optic sen- sor, laser stability) signal generation [5]. Such applications can take advantage of the inherent properties of a fiber laser

Yao, Jianping

273

Influence of scattering on transmission through long-period fiber gratings and tunable microstructure fibers.  

PubMed

Controlled optical scattering within or around an optical fiber provides a potentially useful mean for adjusting its transmission characteristic. This approach can complement conventional methods based on the establishment of well-defined variations in the index of refraction of the core or the cladding of the fiber. We describe the use of a highly scattering submonolayer of nanoparticles deposited onto the fiber surface for adjusting the resonance wavelength, depth, and width of an in-fiber long-period grating filter. We also introduce a polymer-dispersed liquid-crystal material that has a thermally tunable scattering cross section and can be incorporated into the channels of a microstructure optical fiber; this system may provide the means for a fiber-based scattering switch. PMID:12463247

Mach, Peter; Kerbage, Charles; Ramanathan, Sharad; Windeler, Robert S; Eggleton, Benjamin J; Rogers, John A

2002-11-20

274

Consumption of total fiber and types of fiber are associated with a lower prevalence of obesity and abdominal adiposity in US adults. NHANES 1999-2006.  

Technology Transfer Automated Retrieval System (TEKTRAN)

In this cross-sectional study, an inverse association was found between intakes of total dietary fiber and five types of fiber with Body Mass Index, waist circumference, and percent obese, and with increased waist circumference. Intake of vegetable fiber was not associated with any of the weight mea...

275

Toxicity of fibers and fiber composites. January 1980-August 1991 (Citations from the NTIS data base). Rept. for Jan 80-Aug 91  

SciTech Connect

The bibliography contains citations concerning the toxicity of exposure to such fibers as glass, wood, cotton, carbon, fiber- reinforced plastics, and asbestos. Topics include health hazard survey reports; respiratory diseases associated with occupational exposure; and methods and equipment for the detection, control, and removal of airborne fibers. (Contains 157 citations with title list and subject index.)

Not Available

1991-07-01

276

The segal crystallinity index as it relates to crystallite size  

Technology Transfer Automated Retrieval System (TEKTRAN)

Cotton fibers are composed of crystals of cellulose that yield a diffraction pattern, although fibers from varying sources and histories are said to have different degrees of crystallinity. There are many methods to assess this crystallinity. One of the most popular is the Segal Crystallinity Index ...

277

Population Index  

NSDL National Science Digital Library

Two excellent bibliographic resources for population studies are the "Population Index" from the Office of Population Research at Princeton University, and "Population Organizations: Finder's Guide" from the Center for Demography and Ecology at the University of Wisconsin-Madison. "Population Index" is a quarterly publication that has been available since 1935. It "covers all fields of interest to demographers, including fertility, mortality, population size and growth, migration, nuptiality and the family, research methodology, projections and predictions, historical demography, and demographic and economic interrelations. Input is derived from original publications including monographs, journal articles, other serial publications, working papers, doctoral dissertations, machine-readable data files, and relevant acquisitions lists and bibliographies." About 3,500 citations are produced annually. Full text for the Index is available at the "Population Index" Web site for 1986-present (Vol. 52-present). Indexes can be searched by author, subject matter, geographical region, or publication year. There is now an experimental free text search capability for the 1994-present issues. "Population Organizations: Finder's Guide" is a no frills "practical tool for population professionals who need a single source for the quick location of organizations that publish and distribute or post population or family planning documents." It contains hundreds of citations, providing organization addresses, phone and FAX numbers, and Internet addresses when available. The Guide is updated every six months and is maintained by Ruth Sandor, Director of the Library of the Center for Demography and Ecology. Office of Population Research, Princeton University: http://opr.princeton.edu/ "Population Organizations: Finder's Guide": gopher://cde2.ssc.wisc.edu:70/00/addazlis gopher to: cde2.ssc.wisc.edu select: Population Organizations: Finder's Guide Center for Demography and Ecology, University of Wisconsin-Madison: http://www.ssc.wisc.edu/cde/

278

The effect of processing on the structure and properties of carbon fibers  

Microsoft Academic Search

Even though the same three process steps (fiber formation, stabilization, and carbonization) are used to produce both polyacrylonitrile-based (PAN-based) and pitch-based carbon fibers, their final properties differ significantly. This is a direct result of the precursors used to produce these two types of carbon fibers (polymeric versus liquid-crystalline). Liquid-crystalline materials readily orient during fiber formation, creating fibers with a high

D. D. Edie

1998-01-01

279

Bringing Nanotechnology into Fiber Opticsinto Fiber Optics  

E-print Network

Bringing Nanotechnology into Fiber Opticsinto Fiber Optics Prof. Maksim Skorobogatiy www.photonics.phys.polymtl.ca Canada Research Chair in Micro and Nano Photonics � l P l h i d M é l�cole Polytechnique de Montréal www.photonics.phys.polymtl.ca #12;Total Internal Reflection (conventional) optical fibers Very efficient guiding in the fiber core

Skorobogatiy, Maksim

280

Study of modeling aspects of long period fiber grating using three-layer fiber geometry  

NASA Astrophysics Data System (ADS)

The author studied and demonstrated the various modeling aspects of long period fiber grating (LPFG) such as the core effective index, cladding effective index, coupling coefficient, coupled mode theory, and transmission spectrum of the LPFG using three-layer fiber geometry. Actually, there are two different techniques used for theoretical modeling of the long period fiber grating. The first technique was used by Vengsarkar et al who described the phenomenon of long-period fiber gratings, and the second technique was reported by Erdogan who revealed the inaccuracies and shortcomings of the original method, thereby providing an accurate and updated alternative. The main difference between these two different approaches lies in their fiber geometry. Venserkar et al used two-layer fiber geometry which is simple but employs weakly guided approximation, whereas Erdogan used three-layer fiber geometry which is complex but also the most accurate technique for theoretical study of the LPFG. The author further discussed about the behavior of the transmission spectrum by altering different grating parameters such as the grating length, ultraviolet (UV) induced-index change, and grating period to achieve the desired flexibility. The author simulated the various results with the help of MATLAB.

Singh, Amit

2015-03-01

281

Optical fibers for high-resolution in vivo microendoscopic fluorescence imaging  

NASA Astrophysics Data System (ADS)

Optical fiber-based high-resolution fluorescence imaging techniques have promising applications in clinical practice and preclinical research using animals. Here we review the instrumentation and applications of microendoscopy based on various types of optical fibers. Single-mode fibers and double-clad fibers have been widely used for delivering light from light sources to tissues and collecting light from tissues to photodetectors. Coherent fiber bundles, cylindrical graded-index lenses, and multi-mode fibers have been employed in both beam-scanning and non-scanning microscopy. With continuing advances of optical fiber technologies, further innovations in optical microendoscopy are expected.

Oh, Gyungseok; Chung, Euiheon; Yun, Seok H.

2013-12-01

282

Studies on pyrolysis of Nomex polyaramid fibers  

Microsoft Academic Search

The pyrolysis behavior of Nomex [poly(m-phenylene isophtalamide)] fibers under argon was studied using thermoanalytical and infrared spectroscopic methods to get direct information on the progressive changes undergone by the solid material and its carbon fiber residues. Simultaneous thermogravimetry (TG)–differential thermal analysis (DTA) measurements were carried out in a thermobalance in order to establish the different steps in the thermal degradation

S. Villar-Rodil; A. Mart??nez-Alonso; J. M. D. Tascón

2001-01-01

283

Environmental stability of intercalated graphite fibers  

NASA Technical Reports Server (NTRS)

Graphite fibers intercalated with bromine, iodine monochloride, ferric chloride, and cupric chloride were subjected to stability tests under four environments which are encountered by engineering materials in the aerospace industry: ambient laboratory conditions, as would be experienced during handling operations and terrestrial applications; high vacuum, as would be experienced in space applications; high humidity, as would be experienced in marine applications; and high temperature, as would be experienced in some processing steps and applications. Monitoring the resistance of the fibers at ambient laboratory conditions revealed that only the ferric chloride intercalated fibers were unstable, due to absorption of water from the air. All four types of intercalated fibers were unstable, due to absorption of water from the air. All four types of intercalated fibers were stable for long periods under high vacuum. Ferric chloride, cupric chloride, and iodine monochloride intercalated fibers were sensitive to high humidity conditions. All intercalated fibers began to degrade above 250 C. The order of their thermal stability, from lowest to highest, was cupric chloride, iodine monochloride, bromine, and ferric chloride. Of the four types of intercalated fibers tested, the bromine intercalated fibers appear to have the most potential for application, based on environmental stability.

Gaier, J. R.; Jaworskie, D. A.

1985-01-01

284

Polyimide Fibers  

NASA Technical Reports Server (NTRS)

A polyimide fiber having textile physical property characteristics and the process of melt extruding same from a polyimide powder. Polyimide powder formed as the reaction product of the monomers 3.4'-ODA and ODPA, and end- capped with phthalic anhydride to control the molecular weight thereof, is melt extruded in the temperature range of 340 C. to 360 C. and at heights of 100.5 inches. 209 inches and 364.5 inches. The fibers obtained have a diameter in the range of 0.0068 inch to 0.0147 inch; a mean tensile strength in the range of 15.6 to 23.1 ksi; a mean modulus of 406 to 465 ksi, and a mean elongation in the range of 14 to 103%.

St.Clair, Terry L. (Inventor); Fay, Catharine C. (Inventor); Working, Dennis C. (Inventor)

1998-01-01

285

Polyimide Fibers  

NASA Technical Reports Server (NTRS)

A polyimide fiber having textile physical property characteristics and the process of melt extruding same from a polyimide powder. Polyimide powder formed as the reaction product of the monomers 3.4'-ODA and ODPA, and endcapped with phthalic anhydride to control the molecular weight thereof, is melt extruded in the temperature range of 340? C. to 360? C. and at heights of 100.5 inches, 209 inches and 364.5 inches. The fibers obtained have a diameter in the range of 0.0068 inch to 0.0147 inch; a mean tensile strength in the range of 15.6 to 23.1 ksi; a mean modulus of 406 to 465 ksi; and a mean elongation in the range of 14 to 103%.

St.Clair, Terry L. (Inventor); Fay, Catharine C. (Inventor); Working, Dennis C. (Inventor)

1997-01-01

286

Restoration of images transmitted through coherent fiber bundles  

NASA Astrophysics Data System (ADS)

The use of coherent fiber-optic bundles as image conduits has increased significantly in recent years. Fiber bundles permit optical inspection of small, previously inaccessible places. Applications in industrial vision, medicine, aerospace instrumentation and other areas are developing rapidly. The resolution of the image transmitted by fiber bundles is primarily limited by the diameter of the individual fibers. The image is further distorted by a number of factors such as the wide and occasionally skewed point spread function of each fiber and the non-uniformity of fiber characteristics throughout the bundle. Additionally, the appearance of the characteristic circular or hexagonal fiber walls is distracting and objectionable to viewers and increases the complexity of machine vision algorithms. We report a sequence of image processing steps on digitized coherent bundle images which results in complete removal of the fiber wall patterns from the transmitted images; along with corrections for factors creating distortion. The processing steps essentially involve 1) calibrating the fiber bundle under uniform illumination, 2) locating the center of each fiber and extracting the centroid value, 3) disseminating the centroid values onto a uniform grid, and 4) reconstructing the complete image by interpolating between nearest neighbor points on the uniform grid. The process has been applied to both monochrome and color images by applying the above steps individually to each of the red, green and blue components. Future work needs to be performed to correct for a visible moire pattern and the inherent smoothing caused by the interpolation process.

Gazerro, Robert; Katz, Norman P.; Nelson, Mark R.

1990-07-01

287

Education Index  

NSDL National Science Digital Library

The Education Index Web site provides a guide to "the most useful education-related sites on the Web." The links can be browsed by subject such as astronomy, chemistry, geology, and physics (among many others), or by lifestage, from prenatal and infant all the way to college and continuing education. Although the sites described do not have a date of review or rating system, users should still find the resource worthwhile.

288

Carbon fiber manufacturing via plasma technology  

DOEpatents

The disclosed invention introduces a novel method of manufacturing carbon and/or graphite fibers that avoids the high costs associated with conventional carbonization processes. The method of the present invention avoids these costs by utilizing plasma technology in connection with electromagnetic radiation to produce carbon and/or graphite fibers from fully or partially stabilized carbon fiber precursors. In general, the stabilized or partially stabilized carbon fiber precursors are placed under slight tension, in an oxygen-free atmosphere, and carbonized using a plasma and electromagnetic radiation having a power input which is increased as the fibers become more carbonized and progress towards a final carbon or graphite product. In an additional step, the final carbon or graphite product may be surface treated with an oxygen-plasma treatment to enhance adhesion to matrix materials.

Paulauskas, Felix L. (Knoxville, TN); Yarborough, Kenneth D. (Oak Ridge, TN); Meek, Thomas T. (Knoxville, TN)

2002-01-01

289

The influence of the fiber drawing process on intrinsic stress and the resulting birefringence optimization of PM fibers  

NASA Astrophysics Data System (ADS)

The propagation properties of optical fibers can be significantly influenced by intrinsic stress. These effects are often undesired but in some cases essential for certain applications, e.g. in polarization maintaining (PM) fibers. In this paper, we present systematic studies on the influence of the fiber drawing process on the generated stress and demonstrate an approach to significantly increase the stress induced birefringence of PM-fibers. It is shown that the thermal stress caused by the material composition is superimposed with the mechanical stress caused by the fiber fabrication process. This intrinsic stress has a strong effect on the optical and mechanical properties of the glass and thus influences the fiber stability and modal behavior. By applying a thermal annealing step, the mechanical stress due to the fiber drawing process can be canceled. It is shown that this annealing step compensates the stress reducing influence of the drawing process on the birefringence of PM-fibers with panda structure. The comparison of the intrinsic stress states after fabrication with the state after the additional high temperature annealing step clearly shows that it is possible to improve the overall birefringence of panda fibers using appropriate preparation steps.

Just, Florian; Spittel, Ron; Bierlich, Jörg; Grimm, Stephan; Jäger, Matthias; Bartelt, Hartmut

2015-04-01

290

A two-mode fiber optic-bending sensor  

E-print Network

It is shown that a small slope in the refractive index profile of an optical fiber causes the two lowest order spatial modes to travel different distances from the geometrical center of the fiber. This effect increases by orders of magnitude...

Covington, Charles Eric

1993-01-01

291

Soft glasses for photonic crystal fibers and microstructured optical components  

NASA Astrophysics Data System (ADS)

Thermally stable tellurite, lead-bismuth-gallium oxides based boron-silicate and lead-silicate glasses dedicated for multiple thermal processing are presented. The glasses are successfully used for the development of photonic crystal fibers, nanostructured gradient index lenses, all-solid microstructured fibers as well as refractive or diffractive micro-optical elements with ultra-broadband transmission.

Stepien, Ryszard; Cimek, Jaroslaw; Pysz, Dariusz; Kujawa, Ireneusz; Klimczak, Mariusz; Buczynski, Ryszard

2014-07-01

292

Power coupling between fiber and multimode slab composite waveguide  

Microsoft Academic Search

We discuss power coupling in devices composed of a fiber with partly or completely removed cladding and multimode slab overlay waveguide of any complexity. A fiber mode excites with a high efficiency only one mode of the composite structure in the wide range of system parameters. But only when the effective refractive index of this mode almost equals to the

Valeri V. Kapoustine; Sergey O. Yarovikov

2002-01-01

293

Continuous Fiber Ceramic Composites (CFCC)  

SciTech Connect

This report summarizes work to develop CFCC's for various applications in the Industries of the Future (IOF) and power generation areas. Performance requirements range from relatively modest for hot gas filters to severe for turbine combustor liners and infrared burners. The McDermott Technology Inc. (MTI) CFCC program focused on oxide/oxide composite systems because they are known to be stable in the application environments of interest. The work is broadly focused on dense and porous composite systems depending on the specific application. Dense composites were targeted at corrosion resistant components, molten aluminum handling components and gas turbine combustor liners. The development work on dense composites led to significant advances in fiber coatings for oxide fibers and matrix densification. Additionally, a one-step fabrication process was developed to produce low cost composite components. The program also supported key developments in advanced oxide fibers that resulted in an improved version of Nextel 610 fiber (commercially available as Nextel 650) and significant progress in the development of a YAG/alumina fiber. Porous composite development focused on the vacuum winding process used to produce hot gas filters and infrared burner components.

R. A. Wagner

2002-12-18

294

Evaluation of Small Form Factor Fiber Optic Interconnects for the NASA Electronics Parts and Packaging Program (NEPP)  

NASA Technical Reports Server (NTRS)

The Diamond AVIM optical fiber connector has been used for over a decade in flight environments. AVIM which stands for Aviation Intermediate Maintenance is always referenced as a fiber optic connector type from the DIN (Deutsches Institut fur Normung) family of optical fiber connectors. The newly available Mini AVIM and DMI (Definition Multimedia Interface) connectors also by Diamond provide similar features as the high performance AVIM with the added benefits of being small form factor for board mount and internal box use where long connectors and strain relief can not be accommodated. Transceiver, fiber laser technology and receiver optic technology based on small sized constraints will benefit the most by the reduction in connector form factor. It is for this reason that the Mini AVIM is being evaluated for multimode and single mode optical fiber use in both fiber based and cable based packaging configurations. In a fiber based termination, there are no cable materials to bond to the connector. The only bonding that is conducted is the mounting of the fiber with epoxy to the connector ferrules (which are called DMI ferrules). In a cable configuration, the compatibility of the connector subcomponents along with the upjacketing materials of the cable around the fiber needs to be considered carefully for termination fabrication. Cabled terminations will show greater insertion loss and high probability of failures during thermal cycling testing. This is due to the stressing of the combination of materials that each have different Coefficients of Thermal Expansion (CTE's) and that are bonded together to the connector subcomponents. As the materials flex during thermal excursions, forces are applied to the termination and can make the system fail if the grouping of materials (per their CTE's) are not compatible and this includes cable materials, epoxies, ferrule and connector body components. For this evaluation, multimode 100 micron core step index fiber was used for the fiber terminated condition, and single mode SMF-28 upjacketed with W.L. Gore Flexlite was used for the cabled configuration. For background purposes, a comparison is presented here for information purposes between the high performance AVIM connector features and the Mini AVIM small form factor connectors. Basic connector features are described here.

Ott, Melanie; Thomes, W. Joe; Blair, Diana; Chuska, Rick; Switzer, Rob

2010-01-01

295

Solving Single Step Equations  

NSDL National Science Digital Library

This is to practice and review single step equations. Have fun. Complete the following two sites. Follow the directions given for each site. One-Step Equations Add/Subtract One-Step Equations Mult/Division When you have finished the sites above, enter equation buster and work through level one. Equation buster ...

Ms. Reddish

2011-09-30

296

Step by Step tutorial Powder XRD Short-Arm  

E-print Network

Step by Step tutorial for Powder XRD Short-Arm Data Collection #12;Creating the Parameter File Step to Step 5 directly. 1. Click on the XRD wizard icon #12;Step 2. You will get the XRD Wizard program window

Meagher, Mary

297

Packaging of high density fiber\\/laser modules using passive alignment techniques  

Microsoft Academic Search

A method for packaging a laser-fiber module is explored in which the critical laser-fiber alignment is carried out, not with the laser activated, but by a passive method based on the registration principles of photolithography. The method relies on an index scheme in which fiducial marks are lithographically placed on the laser chip and on a fiber carrier. At 850

M. S. Cohen; M. F. Cina; E. Bassous; M. M. Opyrsko; J. L. Speidell; F. J. Canora; M. J. DeFranza

1992-01-01

298

Optical-Fiber Refractometric Sensor with Semicylindrical Optical Detection Element for Measuring the Level of Gasoline  

Microsoft Academic Search

We present a novel optical fiber refractometric sensor with semi-cylindrical optical detection element. A pair of the multimode optical fibers is attached symmetrically to the element's flat plane. The optical coupling of the two fibers due to internal reflection of light from the element's cylindrical surface is sensitive to the refractive index of the surrounding medium. We exploit several internal

Sergei Khotiaintsev; Enrique Llanito-Caudillo; Selene Perez-Garcia; Jordi Morales-Farah

2009-01-01

299

Low loss porous terahertz fibers containing multiple subwavelength holes Alireza Hassani, Alexandre Dupuis, and Maksim Skorobogatiya  

E-print Network

wavelengths, covering the range of 30­3000 m, have strong potential for applications in bio- medical sensing groups have stud- ied a wide variety of dielectric waveguides, such as plastic solid core holey fibers,4,5 Bragg bandgap fibers,6 subwave- length plastic fibers,7 and low index discontinuity waveguides.8

Skorobogatiy, Maksim

300

Polyethylene fiber drawing optimization  

E-print Network

Polymer fiber drawing creates fibers with enhanced thermal conductivity and strength compared to bulk polymer because drawing aligns the molecular chains. I optimize the polymer fiber drawing method in order to achieve ...

Chiloyan, Vazrik

2011-01-01

301

Multimaterial acoustic fibers  

E-print Network

The emergence of multimaterial fibers that combine a multiplicity of solid materials with disparate electrical, optical, and mechanical properties into a single fiber presents new opportunities for extending fiber applications ...

Chocat, Noémie

2012-01-01

302

Toxin detection using a fiber-optic-based biosensor  

NASA Astrophysics Data System (ADS)

Using an evanescent wave fiber optic-based biosensor developed at Naval Research Laboratory, ricin toxin can be detected in the low ng/ml range. Sensitivity was established at 1 - 5 ng/ml using a two-step assay. The two-step assay showed enhanced signal levels in comparison to a one-step assay. A two-step assay utilizes a 10 minute incubation of an immobilized affinity purified anti-ricin antibody fiber optic probe in the ricin sample before placement in a solution of fluorophore-labeled goat anti-ricin antibodies. The specific fluorescent signal is obtained by the binding of the fluorophore-labeled antibodies to ricin which is bound by the immobilized antibodies on the fiber optic probe. The toxin can be detected directly from urine and river water using this fiber optic assay.

Ogert, Robert A.; Shriver-Lake, Lisa C.; Ligler, Frances S.

1993-05-01

303

Advanced CSS Layouts: Step by Step  

NSDL National Science Digital Library

Most Web sites are designed with HTML tables, which can be an arduous task. Making sites that are accessible and standards-compliant requires a separation of markup and content, and CSS is the best way to accomplish this. This Web page by Rogelio Vizcaino Lizaola and Andy King offers a step-by-step CSS layout tutorial on how to create WebReference table-like layouts (that behave well with small window sizes and large fonts), while avoiding some of the bugs and problems discovered in other implementations. Target browsers include all of the generation five and greater browsers on both Windows and Macintosh platforms.

King, Andy.

304

Fiber distributed feedback laser  

NASA Technical Reports Server (NTRS)

Utilizing round optical fibers as communication channels in optical communication networks presents the problem of obtaining a high efficiency coupling between the optical fiber and the laser. A laser is made an integral part of the optical fiber channel by either diffusing active material into the optical fiber or surrounding the optical fiber with the active material. Oscillation within the active medium to produce lasing action is established by grating the optical fiber so that distributed feedback occurs.

Elachi, C.; Evans, G. A.; Yeh, C. (inventors)

1976-01-01

305

Continuous, linearly intermixed fiber tows and composite molded article thereform  

NASA Technical Reports Server (NTRS)

The instant invention involves a process used in preparing fibrous tows which may be formed into polymeric plastic composites. The process involves the steps of (a) forming a carbon fiber tow; (b) forming a thermoplastic polymeric fiber tow; (c) intermixing the two tows; and (d) withdrawing the intermixed tow for further use.

McMahon, Paul E. (Inventor); Chung, Tai-Shung (Inventor); Ying, Lincoln (Inventor)

2000-01-01

306

Tunable Fabry-Perot filter in cobalt doped fiber formed by optically heated fiber Bragg gratings pair  

NASA Astrophysics Data System (ADS)

In this paper, a tunable fiber Fabry-Perot (F-P) filter by all-optical heating is proposed. Two high reflective fiber Bragg gratings (FBG) fabricated in cobalt doped single mode fiber form the F-P cavity. The cobalt-doped fiber used here is an active fiber, and it transforms optical power from a control laser into heat effectively due to the nonradiative processes. The generated heat raises the refraction index of the fiber and enlarges the F-P cavity's length, realizing the all-optical tuning characteristics. By adjusting the power of the control laser, the resonant wavelength of our proposed fiber F-P filter can be high precisely controlled. The cavity length of the filter is carefully designed to make sure the longitude mode spacing is comparable to the grating bandwidth, making it single mode operating.

Li, Ying; Zhou, Bin; Zhang, Liang; He, Sailing

2015-06-01

307

Longitudinal fiber parameter measurements of multi-core fiber using OTDR.  

PubMed

A novel technique is proposed for measuring the longitudinal fiber parameters of multi-core fiber (MCF). The mode field diameter (MFD)of a fiber link composed of MCF is successfully estimated with a modified optical time domain reflectometer (OTDR). The measurement accuracy of the MFD distribution is revealed by simulation as a function of the mode coupling coefficient. It is also shown that the relative-index difference and chromatic dispersion of MCF can be estimated with the present technique. PMID:25606943

Ohashi, Masaharu; Miyoshi, Yuji; Kubota, Hirokazu; Maruyama, Ryo; Kuwaki, Nobuo

2014-12-01

308

Strong fibers  

SciTech Connect

This program was directed to a new and generic approach to the development of new materials with novel and interesting properties, and to the precision fabrication of these materials in one and two-dimensional forms. Advanced deposition processes and microfabrication technology were used to produce fibers and grids of metals, semiconductors, ceramics, and mixtures of controlled composition and structure, and with new and interesting mechanical and physical properties. Deposition processes included electron beam evaporation, co-deposition of mixtures by dual electron beam evaporation, thermal evaporation, sputtering of a single element or compound, sputtering of a single element in a gaseous atmosphere to produce compounds, plasma enhanced chemical vapor deposition (PECVD), low pressure chemical vapor deposition (LPCVD), and selective tungsten chemical vapor deposition (W-CVD). The approach was to use the deposition processes in coordination with patterns generated by optical lithography to produce fibers with transverse dimensions in the micron range, and lengths from less than a millimeter to several centimeters. The approach is also applicable to the production of two-dimensional grids and particulates of controlled sizes and geometries.

Li, Che-Yu.

1991-03-01

309

Design Procedures for Fiber Composite Box Beams  

NASA Technical Reports Server (NTRS)

Step-by-step procedures are described which can be used for the preliminary design of fiber composite box beams subjected to combined loadings. These procedures include a collection of approximate closed-form equations so that all the required calculations can be performed using pocket calculators. Included is an illustrated example of a tapered cantilever box beam subjected to combined loads. The box beam is designed to satisfy strength, displacement, buckling, and frequency requirements.

Chamis, Christos C.; Murthy, Pappu L. N.

1988-01-01

310

High gain ytterbium doped Ge pedestal large pitch fiber  

NASA Astrophysics Data System (ADS)

Large mode area rod-type fibers have enabled amplification of ultra-short pulses to mJ pulse energy and MW peak powers. For very large mode field areas, fibers have to be designed as rigid rods with typical fiber lengths of around 1 m for efficient operation. A shorter fiber length can be desirable to reduce the packaging size of commercial systems and to decrease the impact of parasitic nonlinear effects for peakpower scaling. The fiber design presented here is based on a modified large-pitch fiber with an effectively higher ytterbium concentration in the fiber core. To achieve index matching the cladding index needs to be changed. In this contribution we propose to co-dope the passive host material with germanium to match both indices and to obtain a higher Yb-concentration within the active core. Compared to standard LPF, where the core index is reduced by co-doping the core with Flourine, the ytterbium doping concentration of this novel germanium-pedestal LPF is doubled. A detailed numerical and experimental investigation shows that with short fiber lengths <40cm is feasible to achieve output powers beyond 100W with 10W seed. Significantly higher gains, of nearly 30 dB, can be achieved for fiber lengths in the order of 60cm. A similar gain can be expected in a conventional LPF with 1.20 m length. In conclusion, we demonstrate a fiber design for significantly enhanced energy storage per fiber length and improved pump absorption. This concept will notably reduce the footprint of ultra-short fiber laser systems.

Gaida, Christian; Stutzki, Fabian; Jansen, Florian; Otto, Hans-Jürgen; Eidam, Tino; Jauregui, Cesar; Limpert, Jens; Tünnermann, Andreas

2014-03-01

311

How Many Steps?  

NSDL National Science Digital Library

In this lesson activity students use nonstandard units (baby steps) to measure lengths of different types of "steps" (giant, regular, umbrella, scissor, wooden-soldier, and backwards steps). Once each student gathers this data they will display their own data on a bar graph. Then the class will discuss the data and compare graphs among students. A students worksheet for data collection is included in PDF format.

Helene Silverman

2008-01-01

312

Computer-aided fiber analysis for crime scene forensics  

NASA Astrophysics Data System (ADS)

The forensic analysis of fibers is currently completely manual and therefore time consuming. The automation of analysis steps can significantly support forensic experts and reduce the time, required for the investigation. Moreover, a subjective expert belief is extended by objective machine estimation. This work proposes the pattern recognition pipeline containing the digital acquisition of a fiber media, the pre-processing for fiber segmentation, and the extraction of the distinctive characteristics of fibers. Currently, basic geometrical features like width, height, area of optically dominant fibers are investigated. In order to support the automatic classification of fibers, supervised machine learning algorithms are evaluated. The experimental setup includes a car seat and two pieces clothing of a different fabric. As preliminary work, acrylic as synthetic and sheep wool as natural fiber are chosen to be classified. While sitting on the seat, a test person leaves textile fibers. The test aims at automatic distinguishing of clothes through the fiber traces gained from the seat with the help of adhesive tape. The digitalization of fiber samples is provided by a contactless chromatic white light sensor. First test results showed, that two optically very different fibers can be properly assigned to their corresponding fiber type. The best classifier achieves an accuracy of 75 percent correctly classified samples for our suggested features.

Hildebrandt, Mario; Arndt, Christian; Makrushin, Andrey; Dittmann, Jana

2012-03-01

313

Giant Steps in Cefalù  

NASA Astrophysics Data System (ADS)

Giant steps is a technique to accelerate Monte Carlo radiative transfer in optically-thick cells (which are isotropic and homogeneous in matter properties and into which astrophysical atmospheres are divided) by greatly reducing the number of Monte Carlo steps needed to propagate photon packets through such cells. In an optically-thick cell, packets starting from any point (which can be regarded a point source) well away from the cell wall act essentially as packets diffusing from the point source in an infinite, isotropic, homogeneous atmosphere. One can replace many ordinary Monte Carlo steps that a packet diffusing from the point source takes by a randomly directed giant step whose length is slightly less than the distance to the nearest cell wall point from the point source. The giant step is assigned a time duration equal to the time for the RMS radius for a burst of packets diffusing from the point source to have reached the giant step length. We call assigning giant-step time durations this way RMS-radius (RMSR) synchronization. Propagating packets by series of giant steps in giant-steps random walks in the interiors of optically-thick cells constitutes the technique of giant steps. Giant steps effectively replaces the exact diffusion treatment of ordinary Monte Carlo radiative transfer in optically-thick cells by an approximate diffusion treatment. In this paper, we describe the basic idea of giant steps and report demonstration giant-steps flux calculations for the grey atmosphere. Speed-up factors of order 100 are obtained relative to ordinary Monte Carlo radiative transfer. In practical applications, speed-up factors of order ten and perhaps more are possible. The speed-up factor is likely to be significantly application-dependent and there is a trade-off between speed-up and accuracy. This paper and past work suggest that giant-steps error can probably be kept to a few percent by using sufficiently large boundary-layer optical depths while still maintaining large speed-up factors. Thus, giant steps can be characterized as a moderate accuracy radiative transfer technique. For many applications, the loss of some accuracy may be a tolerable price to pay for the speed-ups gained by using giant steps.

Jeffery, David J.; Mazzali, Paolo A.

2007-08-01

314

Does topology drive fiber polymerization?  

PubMed

We have developed new procedures to examine the early steps in fibrin polymerization. First, we isolated fibrinogen monomers from plasma fibrinogen by gel filtration. Polymerization of fibrinogen monomers differed from that of plasma fibrinogen. The formation of protofibrils was slower and the transformation of protofibrils to fibers faster for the fibrinogen monomers. Second, we used formaldehyde to terminate the polymerization reactions. The formaldehyde-fixed products obtained at each time point were examined by dynamic light scattering and transmission electron microscopy (TEM). The data showed the formaldehyde-fixed products were stable and representative of the reaction intermediates. TEM images showed monomers, short oligomers, protofibrils, and thin fibers. The amount and length of these species varied with time. Short oligomers were less than 5% of the molecules at all times. Third, we developed models that recapitulate the TEM images. Fibrin monomer models were assembled into protofibrils, and protofibrils were assembled into two-strand fibers using Chimera software. Monomers were based on fibrinogen crystal structures, and the end-to-end interactions between monomers were based on D-dimer crystal structures. Protofibrils assembled from S-shaped monomers through asymmetric D:D interactions were ordered helical structures. Fibers were modeled by duplicating a protofibril and rotating the duplicate 120° around its long axis. No specific interactions were presumed. The two protofibrils simply twisted around one another to form a fiber. This model suggests that the conformation of the protofibril per se promotes the assembly into fibers. These findings introduce a novel mechanism for fibrin assembly that may be relevant to other biopolymers. PMID:25419972

Huang, Lihong; Hsiao, Joe Ping-Lin; Powierza, Camilla; Taylor, Russell M; Lord, Susan T

2014-12-16

315

All-solid all-chalcogenide microstructured optical fiber.  

PubMed

The realization of an all-solid microstructured optical fiber based on chalcogenide glasses was achieved. The fiber presents As(2)S(3) inclusions selected as low refractive index material (n = 2.4) embedded in a As(38)Se(62) glass matrix (n = 2.8). The single mode regime of the fiber was demonstrated both theoretically by multipole method calculations and experimentally by near field measurements. Optical transmission measurements of the microstructured fiber and single index fibers made of the initial glasses reveal an excess of losses as high as 6-7 dB/m. This excess is not due to the guide geometry but can be explained by the presence of defects in the glass interface regions. PMID:23787652

Toupin, Perrine; Brilland, Laurent; Renversez, Gilles; Troles, Johann

2013-06-17

316

Fabrication of fiber Bragg gratings with 267 nm femtosecond radiation.  

PubMed

Strong high-quality fiber Bragg gratings with photoinduced refractive-index modulation of more than 10-(3) were written in a Corning SMF-28 fiber, a P(2)O5-doped-core fiber and a pure-silica-core fluorine-doped-cladding fiber by third-harmonic radiation (267 nm, 150 fs and 1.2-1.8x1011 W/cm(2)) of a femtosecond Ti:sapphire laser using a phase mask. We compare the 267-nm photosensitivity responses with the results of irradiation by 193-nm ArF and 157-nm F(2) excimer lasers. The dependence of the refractive-index change on the exposure dose and the annealing characteristics of the fabricated gratings are typical for Type-I UV-written fiber gratings. PMID:19488241

Zagorulko, K; Kryukov, P; Larionov, Yu; Rybaltovsky, A; Dianov, E; Chekalin, S; Matveets, Yu; Kompanets, V

2004-11-29

317

FOA Lecture 22: Mode Power Distribution in Multimode Fibers  

NSDL National Science Digital Library

This is Lecture 22 in the Fiber Optics Association's lecture series on multimode fibers. In this lecture, the presenter briefly reviews modes in graded-index multimode fibers then shows how you can actually see the modes by using visible laser light from a VFL (visual fault locator.) The presenter will also show the effect of a mandrel wrap on the fiber, allowing you to actually see how the higher order modes are removed by the mandrel wrap. Running time for the lecture is 8:29. Flash is required to view the video.

318

Fabrication of fiber Bragg gratings with 267 nm femtosecond radiation  

Microsoft Academic Search

Strong high-quality fiber Bragg gratings with photoinduced refractive-index modulation of more than 10-mu were written in a Corning SMF-28 fiber, a PmuO5-doped-core fiber and a pure-silica-core fluorine-doped-cladding fiber by third-harmonic radiation (267 nm, 150 fs and 1.2-1.8×1011 W\\/cmmu) of a femtosecond Ti:sapphire laser using a phase mask. We compare the 267-nm photosensitivity responses with the results of irradiation by 193-nm

K. A. Zagorulko; P. G. Kryukov; Yu. V. Larionov; A. A. Rybaltovsky; E. M. Dianov; S. V. Chekalin; Yu. A. Matveets; V. O. Kompanets

2004-01-01

319

Improvement of the coupling efficiency between LEDs and optical fibers.  

PubMed

A truncated spherical lens geometry is evaluated for layered lenses with various index profiles to determine power coupling efficiency between an LED and an optical fiber. The equations for the efficiency calculation through multiple boundaries are discussed, and numerical results are presented for optical fibers with numerical aperture values of 0.14, 0.23, and 0.35. The layered Luneburg profile is found to give the highest efficiency when the lens and fiber have a significantly larger size than the LED. The layered Maxwell fisheye profile is most efficient when the lens, fiber, and LED are of similar radius. PMID:20212603

Solomin, A Z; Alexopoulos, N G

1979-06-15

320

Chemical Sensing Using Fiber Cavity Ring-Down Spectroscopy  

PubMed Central

Waveguide-based cavity ring-down spectroscopy (CRD) can be used for quantitative measurements of chemical concentrations in small amounts of liquid, in gases or in films. The change in ring-down time can be correlated to analyte concentration when using fiber optic sensing elements that change their attenuation in dependence of either sample absorption or refractive index. Two types of fiber cavities, i.e., fiber loops and fiber strands containing reflective elements, are distinguished. Both types of cavities were coupled to a variety of chemical sensor elements, which are discussed and compared. PMID:22294895

Waechter, Helen; Litman, Jessica; Cheung, Adrienne H.; Barnes, Jack A.; Loock, Hans-Peter

2010-01-01

321

Measuring optical fiber length by use of a short-pulse optical fiber ring laser in a self-injection seeding scheme.  

PubMed

A method for measuring the length of an optical fiber by use of an optical fiber ring laser pulse source is proposed and demonstrated. The key element of the optical fiber ring laser is a gain-switched Fabry-Perot laser diode operated in a self-injection seeding scheme. This method is especially suitable for measuring a medium or long fiber, and a resolution of 0.1 m is experimentally achieved. The measurement is implemented by accurately determining the pulse frequency that can maximize the output power of the fiber ring laser. The measurement results depend only on the refractive index of the fiber corresponding to this single wavelength, instead of the group index of the fiber, which represents a great advantage over both optical time-domain reflectometry and optical low-coherence reflectometry methods. PMID:16912784

Wang, Yi-Ping; Wang, Dong Ning; Jin, Wei

2006-09-01

322

Producing regenerated gratings in hydrogen-loaded single mode fiber by heat treatment  

NASA Astrophysics Data System (ADS)

The fiber Bragg grating (FBG) is a passive optical fiber component with the refractive index modulated along the fiber length and has been widely applied in fiber sensing systems. High-temperature stable fiber gratings are promising for uses at high temperatures and attract extensive attention. In this paper, FBGs were inscribed in hydrogen loaded standard single mode fibers with the 248-nm excimer laser, and regenerated gratings were obtained through heat treatment. The shift of the central wavelength of the regenerated FBG had a good linearity with temperature, and the reflectivity of the regenerated FBG could almost keep unchanged at 800 °C.

Yu, Haihu; Li, Gengmin; Li, Xiaofu; Guo, Huiyong

2014-06-01

323

Nanoporous polystyrene fibers for oil spill cleanup  

Microsoft Academic Search

The development of oil sorbents with high sorption capacity, low cost, scalable fabrication, and high selectivity is of great significance for water environmental protection, especially for oil spillage on seawater. In this work, we report nanoporous polystyrene (PS) fibers prepared via a one-step electrospinning process used as oil sorbents for oil spill cleanup. The oleophilic-hydrophobic PS oil sorbent with highly

Jinyou Lin; Yanwei Shang; Bin Ding; Jianmao Yang; Jianyong Yu

324

Multioctave infrared supercontinuum generation in large-core As?S? fibers.  

PubMed

We report on infrared supercontinuum (SC) generation through laser filamentation and subsequent nonlinear propagation in a step-index As2S3 fiber. The 100 ?m core and high-purity As2S3 fiber used exhibit zero-dispersion wavelength around 4.5 ?m, a mid-infrared background loss of 0.2??dB/m, and a maximum loss of only 0.55??dB/m at the S-H absorption peak around 4.05 ?m. When pumping with ultrashort laser pulses slightly above the S-H absorption band, broadband infrared supercontinua were generated with a 20 dB spectral flatness spanning from 1.5 up to 7 ?m. The efficiency and spectral shape of the SC produced by ultrashort pulses in large-core As2S3 fiber are mainly determined by its dispersion, the S-H contaminant absorption, and the mid-infrared nonlinear absorption. PMID:25490497

Théberge, Francis; Thiré, Nicolas; Daigle, Jean-François; Mathieu, Pierre; Schmidt, Bruno E; Messaddeq, Younès; Vallée, Réal; Légaré, François

2014-11-15

325

Supercontinuum Generation in Photonic Crystal Fibers Possessing High Birefringence and Large Optical Nonlinearity  

E-print Network

This paper presents the design of an index guided highly birefringent photonic crystal fiber which promises to yield very large birefringence ~3.33 X 10^(-2) at 1550 nm and ~1.75 X 10^(-2) at 1064 nm as well as large effective nonlinearity ~80 W^(-1)km^(-1). Optical supercontinuum generation in the proposed fiber using a 1064 nm pump source with peak power of 1kW has been also presented. Finite difference time domain method (FDTD) has been employed to examine the optical properties such as fiber birefringence, mode field, V-parameter, walk-off and optical nonlinearity, while the Split-step Fourier method is used to solve the nonlinear Schrodinger equation felicitating the study of supercontinuum generation. Simulation results indicate that horizontal input pulse yields superior continuum in comparison to that of the vertically polarized input. However, the broadening of the continuum is about 1450 nm in case of horizontally polarized input light whereas it is approximately 2350 nm for vertically polarized.

Sharma, Mohit; Konar, S

2015-01-01

326

Nonlinear mode competition and phasing in Yb-doped fiber amplifier  

Microsoft Academic Search

We used coupled-mode theory in an Yb-doped multimode fiber amplifier to compute the effects of gain saturation, nonlinear index, and fiber curvature on the evolution of the field. A positive nonlinear index results in power transfer to lower-order modes, usually the fundamental LP10 mode, and for negative nonlinear index the reverse is predicted. The nonlinear interaction between modes breaks the

Erik J. Bochove; Robert R. Rice; Philip R. Cunningham

2004-01-01

327

Electrospinning of nanocomposite fibers  

Microsoft Academic Search

Physical properties of a novel biocompatible nanocomposite fiber are investigated. The fibers are fabricated by incorporation of organically modified clay in a fiber electrospinning process. Commercially available Montmorillonite type organoclays with different extent of miscibility with the polymer matrix are employed to study the effect of organic modifier\\/matrix interactions. The nanocomposite fibers are prepared by electrospinning a suspension of organoclay\\/dichloromethane

Vahik Krikorian

2005-01-01

328

Python fiber optic seal  

Microsoft Academic Search

Sandia National Laboratories has developed a high security fiber optic seal that incorporates tamper resistance features that are not available in commercial fiber optic seals. The Python Seal is a passive fiber optic loop seal designed to give indication of unauthorized entry. The seal includes a fingerprint feature that provides seal identity information in addition to the unique fiber optic

K. Ystesund; J. Bartberger; C. Brusseau; P. Fleming; K. Insch; K. Tolk

1993-01-01

329

Photonic crystal fibers  

Microsoft Academic Search

Photonic crystal fibers having a complex microstructure in the transverse plane constitute a new and promising class of optical fibers. Such fibers can either guide light through total internal reflection or the photonic bandgap effect, In this paper, we review the different types and applications of photonic crystal fibers with particular emphasis on recent advances in the field.

J. Laegsgaard; K. P. Hansen; M. D. Nielsen; T. P. Hansen; J. Riishede; K. Hougaard; T. Sorensen; T. T. Larsen; N. A. Mortensent; J. Broeng; J. B. Jensen; A. Bjarklev

2003-01-01

330

STEP Experiment Requirements  

NASA Technical Reports Server (NTRS)

A plan to develop a space technology experiments platform (STEP) was examined. NASA Langley Research Center held a STEP Experiment Requirements Workshop on June 29 and 30 and July 1, 1983, at which experiment proposers were invited to present more detailed information on their experiment concept and requirements. A feasibility and preliminary definition study was conducted and the preliminary definition of STEP capabilities and experiment concepts and expected requirements for support services are presented. The preliminary definition of STEP capabilities based on detailed review of potential experiment requirements is investigated. Topics discussed include: Shuttle on-orbit dynamics; effects of the space environment on damping materials; erectable beam experiment; technology for development of very large solar array deployers; thermal energy management process experiment; photovoltaic concentrater pointing dynamics and plasma interactions; vibration isolation technology; flight tests of a synthetic aperture radar antenna with use of STEP.

Brumfield, M. L. (compiler)

1984-01-01

331

Design of large mode area, mode selection fiber  

NASA Astrophysics Data System (ADS)

The paper study on the effect of index distribution on the mode field and calculated the mode distribution in various index profiles. A single mode gaussian hybrid multicore fiber with 19 hexagonally arranged high index quartz rods is designed and investigated. Theoretical and simulative results are presented and compared to the conventional large mode area double clad fiber, the fundamental mode (FM) area can be reached 694.28 ?m2, the confinement loss of FM and high order modes (HOMs) are 0.186 dB/m and 1.48 dB/m respectively with the bending radius of 20 cm at 1.064 ?m wavelength, moreover, the index distribution can resistant the mode field distortion, which caused by fiber bending. So the FM delivery can be formed and the beam quality can be improved.

Jin, Liang; Xu, Li; Zhang, He; Zou, Yonggang; Ding, Ye; Ma, Xiaohui

2014-12-01

332

Fiber optic connector  

DOEpatents

A fiber optic connector and method for connecting composite materials within which optical fibers are imbedded. The fiber optic connector includes a capillary tube for receiving optical fibers at opposing ends. The method involves inserting a first optical fiber into the capillary tube and imbedding the unit in the end of a softened composite material. The capillary tube is injected with a coupling medium which subsequently solidifies. The composite material is machined to a desired configuration. An external optical fiber is then inserted into the capillary tube after fluidizing the coupling medium, whereby the optical fibers are coupled.

Rajic, Slobodan (Knoxville, TN); Muhs, Jeffrey D. (Lenior City, TN)

1996-01-01

333

Fiber optic connector  

DOEpatents

A fiber optic connector and method for connecting composite materials within which optical fibers are imbedded are disclosed. The fiber optic connector includes a capillary tube for receiving optical fibers at opposing ends. The method involves inserting a first optical fiber into the capillary tube and imbedding the unit in the end of a softened composite material. The capillary tube is injected with a coupling medium which subsequently solidifies. The composite material is machined to a desired configuration. An external optical fiber is then inserted into the capillary tube after fluidizing the coupling medium, whereby the optical fibers are coupled. 3 figs.

Rajic, S.; Muhs, J.D.

1996-10-22

334

Fiber optic temperature sensor  

NASA Technical Reports Server (NTRS)

A fiber optic temperature sensor uses a light source which transmits light through an optical fiber to a sensor head at the opposite end of the optical fiber from the light source. The sensor head has a housing coupled to the end of the optical fiber. A metallic reflective surface is coupled to the housing adjacent the end of the optical fiber to form a gap having a predetermined length between the reflective surface and the optical fiber. A detection system is also coupled to the optical fiber which determines the temperature at the sensor head from an interference pattern of light which is reflected from the reflective surface.

Sawatari, Takeo (Inventor); Gaubis, Philip A. (Inventor)

2000-01-01

335

Dispersion properties of all-solid photonic crystal fibers with nanostructured core  

NASA Astrophysics Data System (ADS)

The development of all-solid photonic crystal fibers for nonlinear optics is an alternative approach to the air-glass solid core photonic crystal fibers. The use of soft glasses ensures a high refractive index contrast (>0.1) and a high nonlinear coefficient of the fibers. In addition, the manipulation of the subwavelength structure of the core of a photonic crystal fiber allows significant modification of its dispersion characteristics and efficient generation of supercontinuum with various femtosecond and nanosecond sources. The development of all-solid photonic crystal fiber allows very accurate control of all the parameters of the developed fiber in very good agreement with the design criteria. In this paper, we report on the dispersion management capabilities in all-solid photonic crystal fibers with nanostructured cores using thermally matched glasses, which can be jointly processed using the stack-and-draw fiber fabrication technology. We consider a photonic crystal fiber made of the high index lead-silicate glass SF6 and the in-house synthesized low index silicate glass NC21. The NC21 glass plays the role of low index inclusion in the photonic cladding and a nano-inclusion in the core of the fiber. The final dispersion profile of the photonic crystal fiber is determined by the low index nano-inclusion in the core with diameter in the range 100-500nm. The dispersion profiles are modeled for a theoretical structure and for the developed fiber. Supercontinuum generation is expected and numerically confirmed for the developed fiber in the range 1150-1500nm with flatness below 1dB. The fiber is dedicated for supercontinuum generation with 1550nm laser sources.

Pniewski, J.; Pysz, D.; Stepien, R.; Kujawa, I.; Waddie, A. J.; Taghizadeh, M. R.; Buczynski, R.

2012-04-01

336

Fiber optic monitoring device  

DOEpatents

A device for the purpose of monitoring light transmissions in optical fibers comprises a fiber optic tap that optically diverts a fraction of a transmitted optical signal without disrupting the integrity of the signal. The diverted signal is carried, preferably by the fiber optic tap, to a lens or lens system that disperses the light over a solid angle that facilitates viewing. The dispersed light indicates whether or not the monitored optical fiber or system of optical fibers is currently transmitting optical information.

Samborsky, James K. (605 Groves Blvd., N. Augusta, SC 29841)

1993-01-01

337

Giant Steps in Cefalu  

E-print Network

Giant steps is a technique to accelerate Monte Carlo radiative transfer in optically-thick cells of astrophysical atmospheres by greatly reducing the number of Monte Carlo steps needed to propagate photon packets through such cells. Giant steps replaces the exact diffusion treatment of ordinary Monte Carlo radiative transfer in the cells by an approximate diffusion treatment. In this paper, we describe the basic idea of giant steps and report demonstration giant-steps flux calculations for the grey atmosphere. Speed-up factors of order 100 are obtained relative to ordinary Monte Carlo radiative transfer. In practical applications, speed-up factors of order ten (Mazzali et al. 2001) and perhaps more are possible. The speed-up factor is likely to be significantly application-dependent and there is a trade-off between speed-up and accuracy. This paper and past work (Mazzali et al. 2001) suggest that giant-steps error can probably be kept to a few percent by using sufficiently large boundary-layer optical depths while still maintaining large speed-up factors. Thus, giant steps can be characterized as a moderate accuracy radiative transfer technique.

David J. Jeffery; Paolo A. Mazzali

2006-10-31

338

Biorefining of wood: combined production of ethanol and xylanase from waste fiber sludge  

Microsoft Academic Search

The possibility to utilize fiber sludge, waste fibers from pulp mills and lignocellulose-based biorefineries, for combined\\u000a production of liquid biofuel and biocatalysts was investigated. Without pretreatment, fiber sludge was hydrolyzed enzymatically\\u000a to monosaccharides, mainly glucose and xylose. In the first of two sequential fermentation steps, the fiber sludge hydrolysate\\u000a was fermented to cellulosic ethanol with the yeast Saccharomyces cerevisiae. Although

Adnan Cavka; Björn Alriksson; Shaunita H. Rose; Willem H. van Zyl; Leif J. Jönsson

339

Experimental and Numerical Investigation of Single Frequency Amplifier with Photonic Bandgap Fiber at 1178 nm  

NASA Astrophysics Data System (ADS)

A single frequency photonic bandgap fiber amplifier at 1178 nm is investigated experimentally and numerically. With a pump power of 81 W, a single frequency 1178 nm fiber laser of 10.3 W is obtained with a 3W seed laser and a 20 m gain fiber. Numerical simulation is conducted with a rate equation model taking amplified spontaneous emission and stimulated Brillouin scattering (SBS) into consideration. Temperature distribution along the fiber is applied for SBS suppression, more than 50 W single frequency fiber laser at 1178 nm is predicted theoretically with a 5W seed laser and a 40 m long gain fiber with five temperature steps.

Wang, Jian-Hua; Cui, Shu-Zhen; Hu, Jin-Meng; Cao, Fen; Fang, Yong; Lu, Hui-Ling

2014-06-01

340

Progress in the development of scintillating optical fibers  

SciTech Connect

Starting with 1 inch diameter PVT scintillator as a preform, the authors have drawn fibers of several diameters ranging from 1 to 4 mm. These fibers have been coated in line with the draw to form optical fibers. Several cladding materials whose index of refraction ranges from 1.35 to 1.55 have been used. The most successful fiber has been obtained with an extra thick (200 micron) cladding of silicone in combination with a linear draw, as opposed to a spool draw. This fiber is acceptable, but it is extremely fragile and its quality is difficult to control. The authors are currently constructing a 12 channel hodoscope with 1 mm spatial resolution using 4 mm diameter fibers. An account is also given of the progress made in using the Avalanche Photo Diode (APD) operated in the Geiger mode as the photo detector.

Borenstein, S.R.; Strand, R.C.

1983-01-01

341

Complex Faraday rotation in microstructured magneto-optical fiber waveguides.  

PubMed

Magneto-optical glasses are of considerable current interest, primarily for applications in fiber circuitry, optical isolation, all-optical diodes, optical switching and modulation. While the benchmark materials are still crystalline, glasses offer a variety of unique advantages, such as very high rare-earth and heavy-metal solubility and, in principle, the possibility of being produced in fiber form. In comparison to conventional fiber-drawing processes, pressure-assisted melt-filling of microcapillaries or photonic crystal fibers with magneto-optical glasses offers an alternative route to creating complex waveguide architectures from unusual combinations of glasses. For instance, strongly diamagnetic tellurite or chalcogenide glasses with high refractive index can be combined with silica in an all-solid, microstructured waveguide. This promises the implementation of as-yet-unsuitable but strongly active glass candidates as fiber waveguides, for example in photonic crystal fibers. PMID:21823263

Schmidt, Markus A; Wondraczek, Lothar; Lee, Ho W; Granzow, Nicolai; Da, Ning; St J Russell, Philip

2011-06-17

342

Deflection of stepped shafts  

E-print Network

4 5 6 7 8 C I . 02 Q o o . 03 Figure 14. Eccentricity curve of both stepped shafts. 36 Figure 15. Typical oscillogram record showing how the radius of whirl and rotational speed wete obtained. . 20 16 17 18 19 20 21 22 23 24 26... 35 15. Typical oscillogram record showing how the radius of whirl and rotational speed were obtained 36 16. Radius of whirl of the one-stepped shaft, station number 1 37 17. Radius of whirl of the one-stepped shaft, station number 3 38 18...

Alexander, Richard Marvin

1967-01-01

343

Deposition of continuous silicalite-1 films on inorganic fibers  

Microsoft Academic Search

Silicalite-fiber composites were prepared by a new method for the synthesis of molecular sieve films. The method consists of two steps: in the first one, the surface charge of the support is reversed by treatment with a cationic polymer solution and a monolayer of negatively charged colloidal molecular sieve seed crystals is adsorbed on the surface. The second step consists

V. Valtchev; J. Hedlund; B. J. Schoeman; J. Sterte; S. Mintova

1997-01-01

344

EXTENDING FIBER RESOURCES: FIBER LOADING RECYCLED FIBER AND MECHANICAL PULPS FOR LIGHTWEIGHT, HIGH OPACITY PAPER  

E-print Network

alkalinity, precipitates calcium carbonate (PCC) in situ within pulp fibers. Because paper made from fiberEXTENDING FIBER RESOURCES: FIBER LOADING RECYCLED FIBER AND MECHANICAL PULPS FOR LIGHTWEIGHT, HIGH and extend most types of wood fibers. Fiber loading, a process carried out at high consistency and high

Abubakr, Said

345

Indexing Consistency and Quality.  

ERIC Educational Resources Information Center

A measure of indexing consistency is developed based on the concept of 'fuzzy sets'. It assigns a higher consistency value if indexers agree on the more important terms than if they agree on less important terms. Measures of the quality of an indexer's work and exhaustivity of indexing are also proposed. Experimental data on indexing consistency…

Zunde, Pranas; Dexter, Margaret E.

346

Stepping Motor Control System  

E-print Network

This paper describes a hardware system designed to facilitate position and velocity control of a group of eight stepping motors using a PDP-11. The system includes motor driver cards and other interface cards in addition ...

Larson, Noble G.

347

Tuning of an erbium-doped fiber ring laser based on heating a tapered fiber filter  

NASA Astrophysics Data System (ADS)

An erbium-doped fiber ring laser (EDFRL) with wavelength tuning is reported. The laser has a Mach-Zehnder fiber interferometer (MZFI) based on tapers as an intracavity filter, which spectral interference transmission spectrum is modified by external refractive index changes induced by temperature variations in the 25-110 °C range. The MZFI is immersed in a glycerol solution, which refractive index is modified by controlled temperature changes, which allows the tuning of the laser wavelength determined by the interference fringes. Wavelength tuning of 12 nm was measured. This approach is very simple, portable and inexpensive over traditional methods to tune a fiber laser. In addition, the tuning mechanism do not require a solution replacement to operate.

Selvas-Aguilar, R.; Martínez-Rios, A.; Anzueto-Sánchez, G.; Castillo-Guzmán, A.; Hernández-Luna, M. C.; Robledo-Fava, R.

2014-08-01

348

Enhanced Sulfur Removal of Coal Via Carbon Fiber Production  

SciTech Connect

The characterization of highly graphitic vapor-grown carbon fiber (VGCF) produced by the floating catalyst method was determined to evaluate the effect of processing changes on the VGCF properties. Properties examined were bulk density, bulk resistivity of compressed fiber bundles, UV absorption of acetone extractables, graphitic index, pH value, and ASTM dibutyl phthalate absorption number. The data show the properties do not vary significantly from three different reactor tubes used to produce the fibers. Of the properties examined, only graphitic index, density and UV absorption of acetone extractables appear to be independent of sampling handling. Resistivity is directly correlated to the pressure exerted to from the fiber pellet due to the layering of the fiber bundles. The pH of fiber samples suspended in water does not vary significantly. The dibutyl phthalate absorption number is strongly affected by the compression of the material. Thus, only the graphitic index, the UV absorption of acetone extractables, and the apparent density will be used to aid in process quality control and to determine the process conditions required to produce carbon fiber with properties optimized for specific conditions using high sulfur coal dust.

Alesha Patterson; David Grffith; Delbert Buffinger; Edward Asikele; Herbert Smitherman; Osagie Evbuoma

1997-05-30

349

Index des mots-cls Keywords index  

E-print Network

Index des mots-clés Keywords index A Abies, 823 Abies alba, 265 acacia, 93 Acacia cyanophylla Lindl., 335 Acacia mearnsii De Wild., 833 acclimation, 19 AFLP, 627 AFLP, SSR, EST markers, 637 Agrobacterium

Boyer, Edmond

350

Design, fabrication and validation of an OAM fiber supporting 36 states.  

PubMed

We present an optical fiber supporting 36 information bearing orbital angular momentum (OAM) states spanning 9 OAM orders. We introduce design techniques to maximize the number of OAM modes supported in the fiber; while avoiding LP mode excitation. We fabricate such a fiber with an air core and an annular index profile using the MCVD process. We introduce a new technique for shaping OAM beams in free-space to obtain better coupling efficiency with fiber with annular index profiles. We excite 9 orders of OAM in the fiber, using interferometry to verify the OAM state on exiting the fiber. Using polarization multiplexing and both signs for the topological charge, we confirm support of 36 states, exploiting to our knowledge the highest number of OAM modes ever transmitted in optical fiber. PMID:25401644

Brunet, Charles; Vaity, Pravin; Messaddeq, Younès; LaRochelle, Sophie; Rusch, Leslie A

2014-10-20

351

Computing discharge using the index velocity method  

USGS Publications Warehouse

Application of the index velocity method for computing continuous records of discharge has become increasingly common, especially since the introduction of low-cost acoustic Doppler velocity meters (ADVMs) in 1997. Presently (2011), the index velocity method is being used to compute discharge records for approximately 470 gaging stations operated and maintained by the U.S. Geological Survey. The purpose of this report is to document and describe techniques for computing discharge records using the index velocity method. Computing discharge using the index velocity method differs from the traditional stage-discharge method by separating velocity and area into two ratings—the index velocity rating and the stage-area rating. The outputs from each of these ratings, mean channel velocity (V) and cross-sectional area (A), are then multiplied together to compute a discharge. For the index velocity method, V is a function of such parameters as streamwise velocity, stage, cross-stream velocity, and velocity head, and A is a function of stage and cross-section shape. The index velocity method can be used at locations where stage-discharge methods are used, but it is especially appropriate when more than one specific discharge can be measured for a specific stage. After the ADVM is selected, installed, and configured, the stage-area rating and the index velocity rating must be developed. A standard cross section is identified and surveyed in order to develop the stage-area rating. The standard cross section should be surveyed every year for the first 3 years of operation and thereafter at a lesser frequency, depending on the susceptibility of the cross section to change. Periodic measurements of discharge are used to calibrate and validate the index rating for the range of conditions experienced at the gaging station. Data from discharge measurements, ADVMs, and stage sensors are compiled for index-rating analysis. Index ratings are developed by means of regression techniques in which the mean cross-sectional velocity for the standard section is related to the measured index velocity. Most ratings are simple-linear regressions, but more complex ratings may be necessary in some cases. Once the rating is established, validation measurements should be made periodically. Over time, validation measurements may provide additional definition to the rating or result in the creation of a new rating. The computation of discharge is the last step in the index velocity method, and in some ways it is the most straight-forward step. This step differs little from the steps used to compute discharge records for stage-discharge gaging stations. The ratings are entered into database software used for records computation, and continuous records of discharge are computed.

Levesque, Victor A.; Oberg, Kevin A.

2012-01-01

352

IEEE JOURNAL OF QUANTUM ELECTRONICS, VOL. 36, NO. 4, APRIL 2000 465 Pulse-Train Uniformity in Optical Fiber Lasers  

E-print Network

in Optical Fiber Lasers Passively Mode-Locked by Nonlinear Polarization Rotation A. D. Kim, J. N. Kutz, and D has been experimentally demonstrated in a birefringent fiber laser with a passive polarizer. Numerical. Index Terms--Mode-locked lasers, optical fibers, solitons. I. INTRODUCTION IN A SIMPLE additive pulse

Kim, Arnold D.

353

Full-vector analysis of photonic crystal fiber and 2D plane photonic crystals waveguides by finite difference method  

Microsoft Academic Search

An important class of optical waveguides are those refractive index profile is not continuous, such as Bragg fiber, photonic crystal fiber and 2-D photonic crystal waveguides. These microstructure fibers and waveguides become more and more important in the future optical devices for their novel and spurious optical characteristics. To give a full understand of these devices, the exact mode fields

Yumin Liu; Zhongyuan Yu

2005-01-01

354

Observing transverse Anderson localization in random air line based fiber  

NASA Astrophysics Data System (ADS)

The concept of Anderson localization has been applied to electromagnetic waves for decades and strong photon localization effect has been observed in many two-dimensional systems including optical lattice and optical fibers. Among different types of optical fibers, both fibers with and without air hole were investigated. Air hole based fiber has significant higher refractive index contrast than other fibers which allow much lower filling fraction in order to observe Anderson localization. In a previous research, Anderson localization was observed near the fiber edge with an air fillfraction of 5.5%. At the fiber center region with only 2.2% air fill-fraction, Anderson localization disappeared. However, we observed Anderson localization in fibers with much lower air fill-fraction. In our experiments, random air line fibers with 150, 250 and 350 ?m diameters were fabricated and characterized by scanning electronic microscopy (SEM). Averaged air line diameters were 177, 247 and 387 nm for the 150, 250 and 350 ?m diameter fibers, respectively. Air fill-fraction was also measured at fiber center, middle and edge regions. Beam profiles were imaged into a charge couple device (CCD) and Anderson localization was observed. Unlike the previous research in which Anderson localization was only observed at the fiber edge due to non-uniform air line distribution, we observed Anderson localization within the fiber area with air fill-fraction significantly lower than the previous investigation. This is because with smaller air line diameter our fiber has higher air lines density than the previous report.

Chen, Minghan; Li, Ming-Jun

2014-02-01

355

An LD-pumped Raman fiber laser operating below 1 ?m  

NASA Astrophysics Data System (ADS)

A CW Raman fiber laser (RFL) operating below 1 ?m with direct pumping by a high-power multimode laser diode at 938 nm has been demonstrated for the first time. The laser cavity is formed by a normally cleaved fiber end and a highly reflective fiber Bragg grating (FBG) inscribed at the opposite end of a 4.5 km long multimode graded-index fiber. Low-index transverse modes are generated at the first Stokes wavelength of ˜980 nm with an output power of ˜3 W, while the second Stokes wave at 1025 nm also starts to be generated, thus limiting the 980 nm output.

Kablukov, S. I.; Dontsova, E. I.; Zlobina, E. A.; Nemov, I. N.; Vlasov, A. A.; Babin, S. A.

2013-08-01

356

Design of fiber optic probes for laser light scattering  

NASA Technical Reports Server (NTRS)

A quantitative analysis is presented of the role of optical fibers in laser light scattering. Design of a general fiber optic/microlens probe by means of ray tracing is described. Several different geometries employing an optical fiber of the type used in lightwave communications and a graded index microlens are considered. Experimental results using a nonimaging fiber optic detector probe show that due to geometrical limitations of single mode fibers, a probe using a multimode optical fiber has better performance, for both static and dynamic measurements of the scattered light intensity, compared with a probe using a single mode fiber. Fiber optic detector probes are shown to be more efficient at data collection when compared with conventional approaches to measurements of the scattered laser light. Integration of fiber optic detector probes into a fiber optic spectrometer offers considerable miniaturization of conventional light scattering spectrometers, which can be made arbitrarily small. In addition static and dynamic measurements of scattered light can be made within the scattering cell and consequently very close to the scattering center.

Dhadwal, Harbans S.; Chu, Benjamin

1989-01-01

357

Mechanized selection of fiber optic arrays for spectroscopy measurements  

SciTech Connect

A 400-fiber optic bundle has been installed as part of the beam emission spectroscopy diagnostic for measuring density fluctuations in Tokamak Fusion Test Reactor. One hundred bundles, each composed of four 1-mm-diam fibers, transmit {ital H}{sub {alpha}} light 50 m away to 20 detectors located outside the radiation area. To shorten the time spent manually switching the bundles among the 20 detectors, a mechanized fiber selector was installed. The fiber bundles were separated into radial and poloidal groups of 220 and 180 fibers and coupled by a computer-controlled, motorized precision translation stage. The fibers were fastened to a plate and placed less than 0.003 in. from an identical plate that holds a similar array of fibers which transmits the light to the detectors. Holding the fiber spacing tolerance to 0.001 in., and using refractive index matching fluid, the highest measured loss was less than 0.5 dB, and generally was very small compared to the fiber's insertion loss. The stages are actuated with precision encoded micrometers and controlled by the beam emission spectroscopy VAX-resident software via a RS-232/CAMAC interface allowing arbitrary selections of fibers between plasma discharges with a 5 min repetition rate.

Paul, S.F.; Cylinder, D.; Durst, R.D.; Fonck, R.J. (Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States))

1992-10-01

358

Trapping efficiency of fluorescent optical fibers  

NASA Astrophysics Data System (ADS)

Fluorescent optical fibers are used in nuclear detection and other forms of fiber-optic sensors. The trapping efficiency of a fluorescent optical fiber is defined by the optical energy trapped (or guided) by the fiber divided by the total energy emitted within it by the fluorescers that dope the fiber core. This characteristic is clearly important in determining the size of signals from these devices. A calculation of the trapping efficiency has been performed under the assumption that the fluorescence radiation is emitted isotropically by the individual fluorescers that are uniformly distributed throughout the core and are equally likely to be excited by particles or shorter-wavelength light. At the price of increased complexity, nothing in the analysis precludes the lifting of these restrictions. What is included in this analysis is the contribution of skew rays, which, to the author's knowledge, is not presented elsewhere. A very simple expression for the trapping efficiency as a function of the cladding-to-core index ratio is derived. Also important in determining signal size is the transmission loss of the fluorescence radiation to either end of the fiber from the point of its generation. However, as it is a separate matter, it is not discussed here.

Weiss, Jonathan D.

2015-02-01

359

Index Funds Online  

NSDL National Science Digital Library

Matthew Roberts recently released Index Funds Online in response to the lack of index investment fund information on the Internet. Site features include the market performance newsletter Indexing Quarterly, background and definitional information on major US Indexes such as the S&P 500, and a library of new and interesting financial Websites, articles, and book reviews. Links to current index performance figures are also provided as well as a simple site search system and index fund discussion board.

360

Job Hazard Analysis Step by Step Instructions for Individuals  

E-print Network

Job Hazard Analysis Step by Step Instructions for Individuals Step by Step Instructions ­ Page 1 of 4 Helpful Information STEP 1. Log in to the EH&S Job Hazards Analysis (JHA) system at https responses will result in having no individual work information in your Job Hazards Analysis

Knowles, David William

361

Ceramic fiber reinforced filter  

DOEpatents

A filter for removing particulate matter from high temperature flowing fluids, and in particular gases, that is reinforced with ceramic fibers. The filter has a ceramic base fiber material in the form of a fabric, felt, paper of the like, with the refractory fibers thereof coated with a thin layer of a protective and bonding refractory applied by chemical vapor deposition techniques. This coating causes each fiber to be physically joined to adjoining fibers so as to prevent movement of the fibers during use and to increase the strength and toughness of the composite filter. Further, the coating can be selected to minimize any reactions between the constituents of the fluids and the fibers. A description is given of the formation of a composite filter using a felt preform of commercial silicon carbide fibers together with the coating of these fibers with pure silicon carbide. Filter efficiency approaching 100% has been demonstrated with these filters. The fiber base material is alternately made from aluminosilicate fibers, zirconia fibers and alumina fibers. Coating with Al.sub.2 O.sub.3 is also described. Advanced configurations for the composite filter are suggested.

Stinton, David P. (Knoxville, TN); McLaughlin, Jerry C. (Oak Ridge, TN); Lowden, Richard A. (Powell, TN)

1991-01-01

362

Fiber-coupled surface-emitting photonic crystal band edge laser for biochemical sensor applications  

NASA Astrophysics Data System (ADS)

We report on a refractive index sensor platform based on a surface-emitting photonic crystal (PC) ?-point band edge laser (BEL). A simple butt-end fiber coupling makes the BEL system compact, while the translational symmetry of the PC pattern removes the necessity of fiber alignment. The laser wavelength shifts linearly to longer wavelengths as the refractive index of the environmental medium increases. Our BEL system had an index resolution of ˜10-3. Taking into account the alignment-free nature, as well as its ultracompactness and high fiber-coupled laser output, the BEL system is well suited to a label-free sensor platform for biochemical applications.

Kim, Sunghwan; Lee, Jeongkug; Jeon, Heonsu; Kim, Hyo Jin

2009-03-01

363

CBER-DETR Nevada Coincident and Leading Employment Is It a Recovery? One Small Step after Another  

E-print Network

CBER-DETR Nevada Coincident and Leading Employment Indexes1 Is It a Recovery? One Small Step after Another The Nevada Coincident Employment Index measures the ups and downs of the Nevada economy using an index of employment variables. The Nevada Leading Employment Index also measures the ups and downs

Ahmad, Sajjad

364

Fiber Optics Technology.  

ERIC Educational Resources Information Center

Discusses various applications of fiber optics technology: information systems, industrial robots, medicine, television, transportation, and training. Types of jobs that will be available with fiber optics training (such as electricians and telephone cable installers and splicers) are examined. (CT)

Burns, William E.

1986-01-01

365

Multimaterial fiber electronics  

E-print Network

As the number of materials that are thermally-drawable into fibers is rapidly expending, numerous new multimaterial fiber architectures can be envisioned and fabricated. High-melting temperature metals, compound materials, ...

Lestoquoy, Guillaume

2014-01-01

366

Fiber draw synthesis  

E-print Network

The synthesis of a high-melting temperature semiconductor in a low-temperature fiber drawing process is demonstrated, substantially expanding the set of materials that can be incorporated into fibers. Reagents in the solid ...

Orf, Nicholas D.

367

Soluble vs. insoluble fiber  

MedlinePLUS

... soluble and insoluble. Both are important for health, digestion, and preventing diseases. Soluble fiber attracts water and turns to gel during digestion. This slows digestion. Soluble fiber is found in ...

368

Fiber Optics Instrumentation Development  

NASA Technical Reports Server (NTRS)

This is a general presentation of fiber optics instrumentation development work being conducted at NASA Dryden for the past 10 years and recent achievements in the field of fiber optics strain sensors.

Chan, Patrick Hon Man; Parker, Allen R., Jr.; Richards, W. Lance

2010-01-01

369

Omnidirectional fiber optic tiltmeter  

DOEpatents

A tiltmeter is provided which is useful in detecting very small movements such as earth tides. The device comprises a single optical fiber, and an associated weight affixed thereto, suspended from a support to form a pendulum. A light source, e.g., a light emitting diode, mounted on the support transmits light through the optical fiber to a group of further optical fibers located adjacent to but spaced from the free end of the single optical fiber so that displacement of the single optical fiber with respect to the group will result in a change in the amount of light received by the individual optical fibers of the group. Photodetectors individually connectd to the fibers produce corresponding electrical outputs which are differentially compared and processed to produce a resultant continuous analog output representative of the amount and direction of displacement of the single optical fiber.

Benjamin, B.C.; Miller, H.M.

1983-06-30

370

Tapered fiber optic sensor for potassium detection in distilled water  

NASA Astrophysics Data System (ADS)

A simple sensor is proposed and demonstrated using a silica tapered fiber for sensing different concentration of potassium in de-ionized water. The tapered fiber is fabricated using a flame brushing technique to achieve a waist diameter and length of 10 ?m and 80 mm, respectively. For a concentration change from 0 to 50 %, the ouput signal of the sensor decreases exponentially from -10.04 dBm to -11.11 dBm with linearity of more than 92%. The increment of potassium concentration increases the refractive index of the solution, which in turn reduces the index difference between core and cladding of the tapered fiber and thus allows more light to be leaked out from the fiber. This new potassium monitoring system provides numerous advantages such as simplicity of design and low cost of production.

Yasin, M.; Pujiyanto, .; Apsari, R.; Tanjung, M.

2015-01-01

371

Method of identifying features in indexed data  

DOEpatents

The present invention is a method of identifying features in indexed data, especially useful for distinguishing signal from noise in data provided as a plurality of ordered pairs. Each of the plurality of ordered pairs has an index and a response. The method has the steps of: (a) providing an index window having a first window end located on a first index and extending across a plurality of indices to a second window end; (b) selecting responses corresponding to the plurality of indices within the index window and computing a measure of dispersion of the responses; and (c) comparing the measure of dispersion to a dispersion critical value. Advantages of the present invention include minimizing signal to noise ratio, signal drift, varying baseline signal and combinations thereof.

Jarman, Kristin H. (Richland, WA) [Richland, WA; Daly, Don Simone (Richland, WA) [Richland, WA; Anderson, Kevin K. (Richland, WA) [Richland, WA; Wahl, Karen L. (Richland, WA) [Richland, WA

2001-06-26

372

Adaptive step size random search  

Microsoft Academic Search

Fixed step size random search for minimization of functions of several parameters is described and compared with the fixed step size gradient method for a particular surface. A theoretical technique, using the optimum step size at each step, is analyzed. A practical adaptive step size random search algorithm is then proposed, and experimental experience is reported that shows the superiority

M. Schumer; K. Steiglitz

1968-01-01

373

Fiber pulling apparatus modification  

NASA Technical Reports Server (NTRS)

A reduced gravity fiber pulling apparatus (FPA) was constructed in order to study the effects of gravity on glass fiber formation. The apparatus was specifically designed and built for use on NASA's KC-135 aircraft. Four flights have been completed to date during which E-glass fiber was successfully produced in simulated zero, high, and lunar gravity environments. In addition simulated lunar soil samples were tested for their fiber producing properties using the FPA.

Smith, Guy A.; Workman, Gary L.

1992-01-01

374

Nonlinear Fiber Optics  

Microsoft Academic Search

Nonlinear fiber optics concerns with the nonlinear optical phenomena occurring inside optical fibers. Although the field ofnonlinear\\u000a optics traces its beginning to 1961, when a ruby laser was first used to generate the second-harmonic radiation inside a crystal\\u000a [1], the use ofoptical fibers as a nonlinear medium became feasible only after 1970 when fiber losses were reduced to below\\u000a 20

Govind P. Agrawal

2006-01-01

375

Photonic Crystal Fibers  

Microsoft Academic Search

Photonic crystal fibers guide light by corralling it within a periodic array of microscopic air holes that run along the entire fiber length. Largely through their ability to overcome the limitations of conventional fiber optics-for example, by permitting low-loss guidance of light in a hollow core-these fibers are proving to have a multitude of important technological and scientific applications spanning

Philip Russell

2003-01-01

376

Helical Fiber Amplifier  

DOEpatents

A multi-mode gain fiber is provided which affords substantial improvements in the maximum pulse energy, peak power handling capabilities, average output power, and/or pumping efficiency of fiber amplifier and laser sources while maintaining good beam quality (comparable to that of a conventional single-mode fiber source). These benefits are realized by coiling the multimode gain fiber to induce significant bend loss for all but the lowest-order mode(s).

Koplow, Jeffrey P. (Washington, DC); Kliner, Dahy (San Ramon, CA); Goldberg, Lew (Fairfax, VA)

2002-12-17

377

Fiber Laser Applications  

NSDL National Science Digital Library

This pdf from OP-TEC, the National Center for Optics and Photonics Education, addresses basic concepts underlying the operation of fiber lasers. This free 19 page document supplements the fiber laser material presented in an Elements of Photonics Course by provided a more current and detailed description of how lasers operate. This course covers an introduction to fiber laser application, established laser types, advantages of fiber lasers, application in materials processing, and other applications.

378

Fiber Optics Basics  

NSDL National Science Digital Library

This pdf from OP-TEC, the National Center for Optics and Photonics Education, addresses basic concepts underlying the operation of fiber lasers. This free 26 page document supplements the fiber laser material presented in an Elements of Photonics Course by provided a more current and detailed description of how lasers operate. This course covers basic laser operations, basic structure of fiber lasers, pulsing methods, output characteristics of fiber lasers, and advanced structures.

379

Fiber optic coupled optical sensor  

DOEpatents

A displacement sensor includes a first optical fiber for radiating light to a target, and a second optical fiber for receiving light from the target. The end of the first fiber is adjacent and not axially aligned with the second fiber end. A lens focuses light from the first fiber onto the target and light from the target onto the second fiber.

Fleming, Kevin J. (Albuquerque, NM)

2001-01-01

380

Preparation and characterization of Bragg fibers with air cores for transfer of laser radiation  

NASA Astrophysics Data System (ADS)

This paper presents results of preparation and characterization of Bragg fibers with silica and air cores designed for delivery of laser radiation at 1060 nm. The fibers consist of cores with a refractive index equal to that of air or silica which is surrounded by three pairs of Bragg layers. Each pair is composed of one layer with a high and one layer with a low refractive index and is characterized by a refractive-index contrast up to 0.03. Three structures of Bragg fibers are presented in the paper, namely the structure with a silica core of 26 ?m in diameter, structure with an air core of 5 ?m in diameter and that with an air core of a diameter of 72 ?m. Preforms of the Bragg fibers in the form of a rod or tube have been prepared by the MCVD method using germanium dioxide, phosphorous pentoxide and fluorine as silica dopants. The fibers have been drawn from the preforms under controlled temperatures in order to obtain fibers with air or solid cores. Results of characterization of prepared fibers with optical microscopy and by measuring their refractive-index profiles, losses and angular distributions of the output optical power are presented. The characterization of fibers for delivery radiation of a Nd:YAG laser with nanosecond pulses at 1060 nm, namely the transmission, attenuation coefficient, spatial profiles of transmitted beams, and bending losses are also presented. Fiber damage thresholds in a range 25-30 GW/cm2 have been determined.

Mat?jec, Vlastimil; Kašík, Ivan; Podrazký, Ond?ej; Aubrecht, Jan; Frank, Milan; Jelínek, Michal; Kube?ek, Václav

2013-05-01

381

SINGLE COTTON FIBER PROPERTIES  

Technology Transfer Automated Retrieval System (TEKTRAN)

The Favimat, a single fiber testing machine, it used to measure fibers from samples consisting of cottons containing two different parents FM832 AND MD51neOK) and their progeny. In order to get a representation of certain fibers within these samples, the cotton is further divided into the 17 and 19...

382

Oxynitride glass fibers  

NASA Technical Reports Server (NTRS)

Research at the Army Materials Technology Laboratory (AMTL) and elsewhere has shown that many glass properties including elastic modulus, hardness, and corrosion resistance are improved markedly by the substitution of nitrogen for oxygen in the glass structure. Oxynitride glasses, therefore, offer exciting opportunities for making high modulus, high strength fibers. Processes for making oxynitride glasses and fibers of glass compositions similar to commercial oxide glasses, but with considerable enhanced properties, are discussed. We have made glasses with elastic moduli as high as 140 GPa and fibers with moduli of 120 GPa and tensile strengths up to 2900 MPa. AMTL holds a U.S. patent on oxynitride glass fibers, and this presentation discusses a unique process for drawing small diameter oxynitride glass fibers at high drawing rates. Fibers are drawn through a nozzle from molten glass in a molybdenum crucible at 1550 C. The crucible is situated in a furnace chamber in flowing nitrogen, and the fiber is wound in air outside of the chamber, making the process straightforward and commercially feasible. Strengths were considerably improved by improving glass quality to minimize internal defects. Though the fiber strengths were comparable with oxide fibers, work is currently in progress to further improve the elastic modulus and strength of fibers. The high elastic modulus of oxynitride glasses indicate their potential for making fibers with tensile strengths surpassing any oxide glass fibers, and we hope to realize that potential in the near future.

Patel, Parimal J.; Messier, Donald R.; Rich, R. E.

1991-01-01

383

Linearly polarized fiber amplifier  

DOEpatents

Optically pumped rare-earth-doped polarizing fibers exhibit significantly higher gain for one linear polarization state than for the orthogonal state. Such a fiber can be used to construct a single-polarization fiber laser, amplifier, or amplified-spontaneous-emission (ASE) source without the need for additional optical components to obtain stable, linearly polarized operation.

Kliner, Dahv A.; Koplow, Jeffery P.

2004-11-30

384

The Fiber Optic Connection.  

ERIC Educational Resources Information Center

Describes the fiber optics programs at the Career and Technical Center in Berlin, Pennsylvania and the Charles S. Monroe Technology Center in Loudoun County, Virginia. Discusses the involvement of the Fiber Optic Association with education, research and development, manufacturing, sales, distribution, installation, and maintenance of fiber optic…

Reese, Susan

2003-01-01

385

All-round joining method with carbon fiber reinforced interface  

NASA Astrophysics Data System (ADS)

Carbon fiber reinforced polymer (CFRP) has been recently applied to not only wing, but also fan blades of turbo fan engines. To prevent impact force, leading edge of titanium was often mounted on the CFRP fan blades with adhesive force. In order to enhance the joining strength, a joining method with carbon fiber reinforced interface has been developed. By using nickel-coated carbon fibers, a joining sample with carbon fiber-reinforced interface between CFRP and CFRM has been successfully developed. The joining sample with nickel-coated carbon fiber interface exhibits the high tensile strength, which was about 10 times higher than that with conventional adhesion. On the other hand, Al-welding methods to steel, Cu and Ti with carbon fiber reinforced interface have been successfully developed to lighten the parts of machines of racing car and airplane. Carbon fibers in felt are covered with metals to protect the interfacial reaction. The first step of the welding method is that the Al coated felt is contacted and wrapped with molten aluminum solidified under gravity pressure, whereas the second step is that the felt with double layer of Ni and Al is contacted and wrapped with molten steel (Cu or Ti) solidified under gravity pressure. Tensile strength of Al-Fe (Cu or Ti) welded sample with carbon fiber reinforced interface is higher than those of Al-Fe (Cu or Ti) welded sample.

Miwa, Noriyoshi; Tanaka, Kazunori; Kamiya, Yoshiko; Nishi, Yoshitake

2008-08-01

386

Optical Fiber Sensor Based on Localized Surface Plasmon Resonance Using Silver Nanoparticles Photodeposited on the Optical Fiber End  

PubMed Central

This paper reports the implementation of an optical fiber sensor to measure the refractive index in aqueous media based on localized surface plasmon resonance (LSPR). We have used a novel technique known as photodeposition to immobilize silver nanoparticles on the optical fiber end. This technique has a simple instrumentation, involves laser light via an optical fiber and silver nanoparticles suspended in an aqueous medium. The optical sensor was assembled using a tungsten lamp as white light, a spectrometer, and an optical fiber with silver nanoparticles. The response of this sensor is such that the LSPR peak wavelength is linearly shifted to longer wavelengths as the refractive index is increased, showing a sensitivity of 67.6 nm/RIU. Experimental results are presented. PMID:25302813

Ortega-Mendoza, J. Gabriel; Padilla-Vivanco, Alfonso; Toxqui-Quitl, Carina; Zaca-Morán, Placido; Villegas-Hernández, David; Chávez, Fernando

2014-01-01

387

Wide bandwidth slow light using a Raman fiber amplifier  

Microsoft Academic Search

We demonstrate an all-optical tunable pulse delay scheme that utilizes the power-dependent variation of the refractive index that accompanies stimulated Raman scattering in an optical fiber. Using this technique, we delay 430-fs pulses by up to 85% of a pulse width. The ability to accommodate the bandwidth of pulses shorter than 1 ps in a fiber-based system makes this technique

Jay E. Sharping; Yoshitomo Okawachi; Alexander L. Gaeta

2005-01-01

388

Optomechanical behavior of embedded fiber Bragg grating strain sensors  

NASA Astrophysics Data System (ADS)

Fiber Bragg gratings (FBGs) can provide extremely sensitive strain measurements for various materials and structures. The main functionality of the Bragg grating is along the fiber's main axis, where changes in the grating's spacing can be converted into strain measurements. Previous work from a number of researchers has identified bifurcation and broadening of the Bragg signal under transverse loading. The work presented in this thesis highlights efforts to relate transverse loading to changes in index of refraction in the fiber core cross section, and then ultimately to predicted changes in Bragg signals. The background of FBGs, their application, manufacturing, and operation is outlined. In addition, background on the general concept of photoelasticity, the relationship of stress and index of refraction, in glass materials is presented. A theoretical analysis was performed for uncoated silica fiber to calculate the stresses within an optical fiber core under transverse loading. The transverse loading profile ranged from pure diametric point loading to a more distributed profile. The stresses calculated were translated into changes of index of refraction and FBG signal values. The analysis was then simulated utilizing a numerical model, calculating stress, change of index of refraction, and change in FBG signal with various transverse loading profiles. In addition to an uncoated fiber, a polymer coated fiber system was analyzed. The model was verified by performing a laboratory experiment where FBGs were loaded transversely and their signal monitored. A special loading rig was designed and fabricated to impart transverse loading to the fiber while monitoring the compression load and deflection of the loading plates. The laboratory experienced showed reasonable agreement with the numerical model. The data show that side loading of the FBG caused a bifurcation of the signal, and that this effect can be predicted by the theoretical model. The modeling work completed provides a useful tool in predicting effects on FBGs of potential transverse loading scenarios, whether these effects are undesirable, or sought after.

Mastro, Stephen A.

2005-11-01

389

Optical fiber refractometer using narrowband cladding-mode resonance shifts  

Microsoft Academic Search

Short-period fiber Bragg gratings with weakly tilted grating planes generate multiple strong resonances in transmission. Our experimental results show that the wavelength separation between selected resonances allows the measurement of the refractive index of the medium surrounding the fiber for values between 1.25 and 1.44 with an accuracy approaching 1×10-4. The sensor element is 10 mm long and made from

Chun-Fan Chan; Chengkun Chen; Amir Jafari; Albane Laronche; Douglas J. Thomson; Jacques Albert

2007-01-01

390

Critical Coupling Between Optical Fibers and WGM Resonators  

NASA Technical Reports Server (NTRS)

Two recipes for ensuring critical coupling between a single-mode optical fiber and a whispering-gallery-mode (WGM) optical resonator have been devised. The recipes provide for phase matching and aperture matching, both of which are necessary for efficient coupling. There is also a provision for suppressing intermodal coupling, which is detrimental because it drains energy from desired modes into undesired ones. According to one recipe, the tip of the single-mode optical fiber is either tapered in diameter or tapered in effective diameter by virtue of being cleaved at an oblique angle. The effective index of refraction and the phase velocity at a given position along the taper depend on the diameter (or effective diameter) and the index of refraction of the bulk fiber material. As the diameter (or effective diameter) decreases with decreasing distance from the tip, the effective index of refraction also decreases. Critical coupling and phase matching can be achieved by placing the optical fiber and the resonator in contact at the proper point along the taper. This recipe is subject to the limitation that the attainable effective index of refraction lies between the indices of refraction of the bulk fiber material and the atmosphere or vacuum to which the resonator and fiber are exposed. The other recipe involves a refinement of the previously developed technique of prism coupling, in which the light beam from the optical fiber is collimated and focused onto one surface of a prism that has an index of refraction greater than that of the resonator. Another surface of the prism is placed in contact with the resonator. The various components are arranged so that the collimated beam is focused at the prism/resonator contact spot. The recipe includes the following additional provisions:

Matsko, Andrey; Maleki, Lute; Itchenko, Vladimir; Savchenkov, Anatoliy

2009-01-01

391

The Capitol Steps  

NSDL National Science Digital Library

The Capitol Steps, the Washington-based troupe of Congressional staffers turned songwriters, have a WWW home page featuring music and political satire. Hear selections from recent albums (Lord of the Fries, The Joy of Sax, etc.) plus pre-releases of the latest songs. http://www.capsteps.com/

392

CONVERGING RCC STEPPED SPILLWAYS  

Technology Transfer Automated Retrieval System (TEKTRAN)

To meet current dam safety requirements, roller compacted concrete (RCC) stepped spillways has become a popular choice is dam rehabilitation. In many cases, urbanization has changed the hazard classification of these aging watershed structures, and land rights are often not obtainable for widening ...

393

Stepped inlet optical panel  

DOEpatents

An optical panel includes stacked optical waveguides having stepped inlet facets collectively defining an inlet face for receiving image light, and having beveled outlet faces collectively defining a display screen for displaying the image light channeled through the waveguides by internal reflection.

Veligdan, James T. (6 Stephanie La., Manorville, NY 11949)

2001-01-01

394

STEP electronic system design  

NASA Technical Reports Server (NTRS)

The STEP electronic system design is discussed. The purpose of the design is outlined. The electronic system design is summarized and it is found that: an effective conceptual system design is developed; the design represents a unique set of capabilities; makes efficient use of available orbiter resources; the system capabilities exceed identified potential experiment needs.

Couch, R. H.; Johnson, J. W.

1984-01-01

395

Characterization of fluorescence lifetime of Tm-doped fibers with increased quantum conversion efficiency  

NASA Astrophysics Data System (ADS)

In this work we report on the fluorescence lifetime characterization of the experimentally prepared Tm-doped silica optical fibers with increased quantum conversion efficiency (QE). Optical fibers were drawn from preforms prepared by conventional solution-doping of thulium and aluminium chlorides and by deposition of dispersed alumina nanoparticles with thulium chloride. Prepared preforms and optical fibers were characterized by means of thulium and aluminium concentrations, refractive index profiles, optical spectral attenuations (absorptions) and fluorescence lifetimes. Highly aluminium-codoped optical fiber prepared from alumina nanoparticles exhibited fluorescence lifetime of about 690 ?s, which is about 40% higher compared to the conventionally prepared Tm-doped silica fiber.

Cajzl, Jakub; Peterka, Pavel; Honzátko, Pavel; Mrázek, Jan; Podrazký, Ond?ej; Todorov, Filip; Gladkov, Petar; Sahu, Jayanta K.; Nunez-Velazquez, Miguel; Nekvindová, Pavla; Kašík, Ivan

2015-01-01

396

Monitoring of Temperature Fatigue Failure Mechanism for Polyvinyl Alcohol Fiber Concrete Using Acoustic Emission Sensors  

PubMed Central

The applicability of acoustic emission (AE) techniques to monitor the mechanism of evolution of polyvinyl alcohol (PVA) fiber concrete damage under temperature fatigue loading is investigated. Using the temperature fatigue test, real-time AE monitoring data of PVA fiber concrete is achieved. Based on the AE signal characteristics of the whole test process and comparison of AE signals of PVA fiber concretes with different fiber contents, the damage evolution process of PVA fiber concrete is analyzed. Finally, a qualitative evaluation of the damage degree is obtained using the kurtosis index and b-value of AE characteristic parameters. The results obtained using both methods are discussed. PMID:23012555

Li, Dongsheng; Cao, Hai

2012-01-01

397

Dynamic of HNLS Solitons using Compact Split Step Padé Scheme  

NASA Astrophysics Data System (ADS)

In this communication, we use a compact split step Pade scheme (CSSPS) to solve the scalar higher-order nonlinear Schrodinger equation (HNLS) with higher-order linear and nonlinear effects. The second part, consisting of two sections, the first section is dedicated to the study numerically the stabilization of high-order solitons dynamic in optical fibers by compensation or by the interplay of higher order nonlinearity – especially quintic nonlinearity- and the self-steepening. In the second section we study also numerically the propagation of conventional chirped or unchirped solitons in optical fibers with to the management of the nonlinearity, dispersion and loss (gain).

Smadi, Moussa; Bahloul, Derradji

2015-01-01

398

Nucleic acid indexing  

DOEpatents

A restriction site indexing method for selectively amplifying any fragment generated by a Class II restriction enzyme includes adaptors specific to fragment ends containing adaptor indexing sequences complementary to fragment indexing sequences near the termini of fragments generated by Class II enzyme cleavage. A method for combinatorial indexing facilitates amplification of restriction fragments whose sequence is not known.

Guilfoyle, Richard A. (Madison, WI); Guo, Zhen (Bellevue, WA)

1999-01-01

399

Nucleic acid indexing  

DOEpatents

A restriction site indexing method for selectively amplifying any fragment generated by a Class II restriction enzyme includes adaptors specific to fragment ends containing adaptor indexing sequences complementary to fragment indexing sequences near the termini of fragments generated by Class II enzyme cleavage. A method for combinatorial indexing facilitates amplification of restriction fragments whose sequence is not known.

Guilfoyle, Richard A. (Madison, WI); Guo, Zhen (Bellevue, WA)

2001-01-01

400

Indexing Consistency and Quality.  

ERIC Educational Resources Information Center

Proposed is a measure of indexing consistency based on the concept of "fuzzy sets." By this procedure a higher consistency value is assigned if indexers agree on the more important terms than if they agree on less important terms. Measures of the quality of an indexer's work and exhaustivity of indexing are also proposed. Experimental data on…

Zunde, Pranas; Dexter, Margaret E.

401

Tools for Printing Indexes  

Microsoft Academic Search

SUMMARY This paper describes a set of programs for processing and printing the index for a book or a manual. The input consists of lines containing index terms and page numbers. The programs collect multiple occurrences of the same terms, compress runs of page numbers, create permutations (e.g., 'index, book' from 'book index'), and sort them into proper alphabetic order.

Jon Louis Bentley; Brian W. Kernighan

1988-01-01

402

Universal light source for optical fiber sensors  

Microsoft Academic Search

A multifunction light source based on index-guided AlGaAs heterostructure with three isolated electrodes is realized. Three different operation modes are available by a simple change of the electrode's connection, namely LD, SLD, and mode-locking LD. The output power in single- mode fiber pigtail is about 500 uW for SLD, more than 5 mW for LD, and 1 - 2 W

Alexandr T. Semenov; Boris B. Elenkrig; Valerii N. Logozinskii

1991-01-01

403

Extending single mode performance of all-solid large-mode-area single trench fiber.  

PubMed

We report a novel "single trench fiber" design for mode area scaling of the fundamental mode while offering effective single mode operation for a compact fiber laser device. This fiber design allows very high suppression of the higher order modes by offering high loss and power delocalization. It has the advantages of low cost and easy fabrication thanks to all solid fiber design, cylindrical symmetry, and higher refractive index of core as that of the cladding. A Yb-doped single trench fiber with a 40 µm core diameter has been fabricated from modified chemical vapor deposition process in conjunction with solution-doping offering an effective mode area of as large as ~1,000 µm(2) at 1,060 nm for the bend radius of 20 cm. Detailed characterizations confirm a robust single mode behavior of the fiber. Comparative analysis with other fiber designs shows significant performance enhancement of effective single mode operation suitable for fiber laser applications. PMID:25607057

Jain, D; Jung, Y; Nunez-Velazquez, M; Sahu, J K

2014-12-15

404

The effect of commercial refining steps on the rancidity measures of soybean and canola oils  

Microsoft Academic Search

The effect of commercial refining steps on the peroxide value (PV), acid value (AV), carbonyl value (CV), total polar compounds (TPC) content, polar compounds distribution, and oil\\/oxidative stability index (OSI) of soybean and canola oils was studied. The PVs were changed during the different refining steps. The AVs significantly decreased after the neutralisation step. The CVs continuously increased during the

Reza Farhoosh; Soodabeh Einafshar; Parvin Sharayei

2009-01-01

405

Optical fiber sensor for water detection using a side-polished fiber coupler with a planar glass-overlay-waveguide  

Microsoft Academic Search

For monitoring the presence of water at the splicing points of an optical fiber, the water detection sensors based on a side-polished fiber coupler with a commercial microscope-cover-glass are proposed. The sensors are very sensitive to the variation of an upper cladding layer’s index on the overlay waveguide. When the sensors detect water, the coupling wavelengths shift to longer wavelength

Kyung-Rak Sohn; Kwang-Taek Kim; Jae-Won Song

2002-01-01

406

Circulation Take Steps to  

E-print Network

with rest · Leg or foot pain that disturbs sleep · Sores, wounds, or ulcers on the toes, feet, or legs: 140/90 mmHg or higher ANKLE-BRACHIAL INDEX (ABI) A test that compares the blood pressure readings in your ankles and arms to help determine whether you have P.A.D. Normal: 1.0­1.3 Possible P.A.D.: 0

Bandettini, Peter A.

407

Fiber coating method  

DOEpatents

A coating is applied to reinforcing fibers arranged into a tow by coaxially aligning the tow with an adjacent separation layer and winding or wrapping the tow and separation layer onto a support structure in an interleaved manner so that the separation layer separates a wrap of the tow from an adjacent wrap of the tow. A coating can then be uniformly applied to the reinforcing fibers without defects caused by fiber tow to fiber tow contact. The separation layer can be a carbon fiber veil.

Corman, Gregory Scot (Ballston Lake, NY)

2001-01-01

408

Hybrid matrix fiber composites  

DOEpatents

Hybrid matrix fiber composites having enhanced compressive performance as well as enhanced stiffness, toughness and durability suitable for compression-critical applications. The methods for producing the fiber composites using matrix hybridization. The hybrid matrix fiber composites include two chemically or physically bonded matrix materials, whereas the first matrix materials are used to impregnate multi-filament fibers formed into ribbons and the second matrix material is placed around and between the fiber ribbons that are impregnated with the first matrix material and both matrix materials are cured and solidified.

Deteresa, Steven J.; Lyon, Richard E.; Groves, Scott E.

2003-07-15

409

Fiber optic monitoring device  

DOEpatents

A device for the purpose of monitoring light transmissions in optical fibers comprises a fiber optic tap that optically diverts a fraction of a transmitted optical signal without disrupting the integrity of the signal. The diverted signal is carried, preferably by the fiber optic tap, to a lens or lens system that disperses the light over a solid angle that facilitates viewing. The dispersed light indicates whether or not the monitored optical fiber or system of optical fibers is currently transmitting optical information. 4 figures.

Samborsky, J.K.

1993-10-05

410

A highly-nonlinear three-core chalcogenide-tellurite fiber  

NASA Astrophysics Data System (ADS)

A novel highly nonlinear three-core chalcogenide-tellurite fiber is proposed and fabricated in the paper. Each core with high index is made of chalcogenide glass (Ge15Ga3Sb13S69). The background with low index is made of TeO2-ZnO-Li2O-Bi2O3 (TZLB) glass. Each core of this fiber can be considered as a single core. And it can be used for the high power transmission. The effective modal refractive index and the chromatic dispersion are calculated with the light beam coupled in one core of the fiber, respectively. Supercontinuum generation from 1400 nm to 3536 nm in this fiber is investigated under the pump of a 2200 nm femtosecond fiber laser.

Cheng, Tonglei; Asyikin, Nur; Gao, Weiqing; Liao, Meisong; Deng, Dinghuan; Matsumoto, Morio; Misumi, Takashi; Suzuki, Takenobu; Ohishi, Yasutake

2014-03-01

411

Pulsed radiation-induced attenuation in certain optical fibers  

SciTech Connect

Using the X-ray pulse from the HERMES II simulation machine at Sandia National Laboratories, the pulsed radiation-induced attenuation was measured in two optical fibers considered to be 'nonrad-hard': the 50-micron-core, graded-index fiber from Corning and the plastic (PMMA) fiber from the Mitsubishi Rayon Company. These fibers were exposed to radiation up to doses of 19.5 and 28 krad(Si), respectively. In addition, fits of their post-radiation recovery were made to the geminate recombination model, from which the recombination-rate and generation constants, characteristic of this theory, were determined. These parameters should be useful in determining the response of the fibers to radiation conditions other than those encountered here. 18 refs.

Weiss, J.D. (Sandia National Laboratories, Albuquerque, NM (United States))

1992-05-01

412

Fiber optic moisture sensor  

DOEpatents

A method and apparatus for sensing moisture changes by utilizing optical fiber technology. One embodiment uses a reflective target at the end of an optical fiber. The reflectance of the target varies with its moisture content and can be detected by a remote unit at the opposite end of the fiber. A second embodiment utilizes changes in light loss along the fiber length. This can be attributed to changes in reflectance of cladding material as a function of its moisture content. It can also be affected by holes or inserts interposed in the cladding material and/or fiber. Changing light levels can also be coupled from one fiber to another in an assembly of fibers as a function of varying moisture content in their overlapping lengths of cladding material.

Kirkham, R.R.

1984-08-03

413

Fiber draw synthesis  

PubMed Central

The synthesis of a high-melting temperature semiconductor in a low-temperature fiber drawing process is demonstrated, substantially expanding the set of materials that can be incorporated into fibers. Reagents in the solid state are arranged in proximate domains within a fiber preform. The preform is fluidized at elevated temperatures and drawn into fiber, reducing the lateral dimensions and bringing the domains into intimate contact to enable chemical reaction. A polymer preform containing a thin layer of selenium contacted by tin–zinc wires is drawn to yield electrically contacted crystalline ZnSe domains of sub-100-nm scales. The in situ synthesized compound semiconductor becomes the basis for an electronic heterostructure diode of arbitrary length in the fiber. The ability to synthesize materials within fibers while precisely controlling their geometry and electrical connectivity at submicron scales presents new opportunities for increasing the complexity and functionality of fiber structures.

Orf, Nicholas D.; Shapira, Ofer; Sorin, Fabien; Danto, Sylvain; Baldo, Marc A.; Joannopoulos, John D.; Fink, Yoel

2011-01-01

414

Fiber optic vibration sensor  

DOEpatents

A fiber optic vibration sensor utilizes two single mode optical fibers supported by a housing with one optical fiber fixedly secured to the housing and providing a reference signal and the other optical fiber having a free span length subject to vibrational displacement thereof with respect to the housing and the first optical fiber for providing a signal indicative of a measurement of any perturbation of the sensor. Damping or tailoring of the sensor to be responsive to selected levels of perturbation is provided by altering the diameter of optical fibers or by immersing at least a portion of the free span length of the vibration sensing optical fiber into a liquid of a selected viscosity.

Dooley, Joseph B. (Harriman, TN); Muhs, Jeffrey D. (Lenoir City, TN); Tobin, Kenneth W. (Harriman, TN)

1995-01-01

415

Fiber optic vibration sensor  

DOEpatents

A fiber optic vibration sensor utilizes two single mode optical fibers supported by a housing with one optical fiber fixedly secured to the housing and providing a reference signal and the other optical fiber having a free span length subject to vibrational displacement thereof with respect to the housing and the first optical fiber for providing a signal indicative of a measurement of any perturbation of the sensor. Damping or tailoring of the sensor to be responsive to selected levels of perturbation is provided by altering the diameter of optical fibers or by immersing at least a portion of the free span length of the vibration sensing optical fiber into a liquid of a selected viscosity. 2 figures.

Dooley, J.B.; Muhs, J.D.; Tobin, K.W.

1995-01-10

416

Ribbon Fiber with Multiple Antiguided Phase-Locked Gain Cores  

SciTech Connect

We report on the first experimental demonstration of a scalable fiber laser approach based on phase-locking multiple gain cores in an antiguided structure. A novel fabrication technology is used with soft glass components to construct the multiple core fiber used in our experiments. The waveguide region is rectangular in shape and comprised of a periodic sequence of gain and no-gain segments having nearly uniform refractive index. The rectangular waveguide is itself embedded in a lower refractive index cladding region. Experimental results confirm that our five-core Nd doped glass prototype structure runs predominantly in two spatial antiguided modes as predicted by our modeling.

Beach, R J; Feit, M D; Mitchell, S C; Cutter, K P; Dawson, J W; Payne, S A

2002-11-20

417

Antiresonant reflecting microstructured optical fibers for the mid-infrared  

NASA Astrophysics Data System (ADS)

We report on the demonstration of silver halide (AgClxBr1-x) microstructured optical fibers (MOFs) based on the antiresonant reflecting optical waveguide (ARROW) model, for the mid-infrared. MOFs with low index core surrounded by an octagonal structure of high index rods were designed and fabricated. The fibers exhibited transmission spectra with narrow stopband frequencies in the 9-11 ?m range. The location of the transmission minima matched the theoretical predictions by the ARROW model. The measured propagation losses in the maximum transmission range were ˜60 dB/m. Imaging the output of the MOFs at the passband wavelengths revealed single mode guidance in the core.

Lewi, T.; Ofek, J.; Katzir, A.

2013-03-01

418

Fiber optic sensor for methanol quantification in biodiesel  

NASA Astrophysics Data System (ADS)

In this work a refractometric sensor for assessment of methanol presence in biodiesel is reported. The transducer relies on the interference between the forward and back propagating modes of a single long period grating, written close to an end-face mirror optical fiber. The sensing method is thermally assisted in order to overcome the drawback caused by the high refractive index (close to the fiber cladding index) of methanol-biodiesel blends at low temperatures. Sensor showed a combined standard uncertainty of 0.6 % v/v of methanol in biodiesel for a confidence level of 68.27%, within the methanol concentration ranging from 0 to 25 % v/v.

Kawano, Marianne S.; Kamikawachi, Ricardo Canute; Fabris, José L.; Müller, Marcia

2014-05-01

419

Dual-mode fiber-optic interferometer: a novel design  

NASA Astrophysics Data System (ADS)

We describe a simple and novel single-arm two-mode fiber interferometer in which the directional couplers and the fiber-grating couplers are replaced with microbends caused by point mechanical squeezing. The interferometer works with incident light in the LP02 mode. While the input microbend couples the LP 02 mode to the LP21 mode, the output microbend behaves as an attenuator that is sensitive to the orientation of LP02 - LP21 interference intensity field inside the fiber. The application of this device for measuring the core-cladding refractive-index difference and as an interferometric temperature sensor between 20 and 400 deg C is demonstrated.

Sharma, A.; Posey, R.

1995-11-01

420

Relating Multi-step and Single-step Microprocessor  

E-print Network

Relating Multi-step and Single-step Microprocessor Correctness Statements Relating Multi-step and Single-step Microprocessor Correctness Statements MarkMark AagaardAagaard Nancy DayNancy Day MengMeng LouLou University of Waterloo #12;MotivationMotivation Ã?Ã?highhigh--level microprocessor correctnesslevel

Day, Nancy

421

Fiber Optic Switch For Broadband Emission Spectroscopy  

NASA Technical Reports Server (NTRS)

Many high-temperature processes comprise large-scale phenomena. Studying spatial and temporal correlations of physical processes between several locations within characteristic scales provides desired information on macroscopic physical processes. Achieved with emission spectroscopy by use of multiple optical fibers. Simultaneous coupling of light from these fibers into single available spectrometer and/or monochromator not accomplished without added expense of two-dimensional array and increased complexity of calibration. Quasi-simultaneous coupling, while maintaining optimum alignment and maximum throughput of broadband emission, achieved by use of fiber optic multiscanner. Instrument used successfully in study of frozen-flow losses internal to flow of plasma inside nozzle of arc jet. Instrument includes two hollow disks of different sizes and stepping motor.

De Groot, Wim; Myers, Roger; Zube, Dieter

1994-01-01

422

A machine learning based lecture video segmentation and indexing algorithm  

NASA Astrophysics Data System (ADS)

Video segmentation and indexing are important steps in multi-media document understanding and information retrieval. This paper presents a novel machine learning based approach for automatic structuring and indexing of lecture videos. By indexing video content, we can support both topic indexing and semantic querying of multimedia documents. In this paper, our proposed approach extracts features from video images and then uses these features to construct a model to label video frames. Using this model, we are able to segment and indexing videos with accuracy of 95% on our test collection.

Ma, Di; Xie, Bingqing; Agam, Gady

2013-12-01

423

Polarization and modal filters based on W-fibers Panda for fiber-optic gyroscopes and high-power fiber lasers  

NASA Astrophysics Data System (ADS)

Polarizing Panda-type W-fibers, practical realizations are presented for fiber-optic gyroscope (FOG) sensing coil (500-m length, 8-?m fundamental mode field diameter) and for polarization/modal filtering at the FOG loop interferometer input (˜1-m length, 10-?m fundamental mode field diameter). Using these fibers, two different mathematical models for light propagation are tested and applied for further dichroism spectral band spreading of polarizing W-fibers with fundamental mode field diameter (MFD) of 6 to 10 ?m for FOG coil and at least with MFD=8 to 10 ?m for input filtering in loop interferometer. Also, some fibers with large MFD are considered, which may be useful for high-power fiber lasers, requiring the low nonlinear effects. One is a practically realized single-mode 200-m W-fiber Panda with dichroism and MFD=12.4 ?m at 1.06 ?m, which is bend resistant for 60-mm diameters. For further MFD increase a straight 100-mm length modal and polarization filters are suggested with MFD=30 to 70 ?m at 1.06 ?m, based on a pure silica core fiber, narrow/shallow fluorine cladding, and stress-applying parts. The latter are used for core refractive index regulation by birefringence (W-profile forming), which is more precise than with core germanium doping.

Kurbatov, Alexander. M.; Kurbatov, Roman. A.

2013-03-01

424

Mode area scaling for high-power fiber lasers with all-solid photonic bandgap fibers  

NASA Astrophysics Data System (ADS)

There are very strong interests for power scaling in high power fiber lasers for a wide range of applications in medical, industry, defense and science. In many of these lasers, fiber nonlinearities are the main limits to further scaling. Although numerous specific techniques have studied for the suppression of the wide range of nonlinearities, the fundamental solution is scaling mode areas in fibers while maintaining sufficient single mode operation. Here the key problem is that more modes are supported once physical dimensions of waveguides are increased. There are two basic approaches, lower refractive index contrast to counter the increase of waveguide dimension or/and introduction of additional losses to suppress higher order modes. Lower index contrast leads to weak waveguides, resulting in fibers no longer being coil-able. Our research has been focused on designs for significant higher mode suppression. In conventional waveguides, modes are increasingly guided in the center of the waveguides when waveguide dimensions are increased. It is hard to couple the modes out to suppress them. This severely limits the scalability of all designs based conventional fibers. In an all-solid photonic bandgap fiber, modes are guided due to anti-resonance of cladding photonic crystal lattice. This leads strongly mode-dependent guidance. Our theoretical study has shown that it can have some of the highest differential mode losses among all designs with equivalent mode areas. Our design and experimental works have shown the potential of this approach for all-glass fibers with >50?m core which can be coiled for high power applications.

Dong, Liang; Saitoh, Kunimasa; Kong, Fanting; Foy, Paul; Hawkins, Thomas; McClane, Devon

2012-06-01

425

Zero–group-velocity modes in chalcogenide holey photonic-crystal fibers  

E-print Network

We demonstrate that a holey photonic-crystal fiber with chalcogenide-glass index contrast can be designed to have a complete gap at a propagation constant ?=0 that also extends into the non-zero ? region. This type of ...

Oskooi, Ardavan F.

426

Modeling fiber dynamics and transport in the carding process  

NASA Astrophysics Data System (ADS)

A carding machine processes short, crimped fibers by feeding disorganized tufts onto a rotating cylinder coated with wires that engage the fibers. This cylinder works in conjunction with pun of smaller cylinders (carding stations) dig are simply coated and rotating at carefully calibrated speeds in order to separate, redistribute, align and straighten the fibers. This process produces a relatively uniform sheet of fibers with properties desirable for the textile industry. One method used to analyze the processing of the fibers is to insert a small number of easily identified tracer fibers in the card and observe their behavior at different stages throughout the card. In a similar manner, this research develops a technique to follow a representative sampling of theoretical fibers through a structure simulating the card, complete with forces attributable to the presence of other fibers, the surrounding air, and the wires on the surfaces. In this work a model of the card is proposed consisting of three essential elements. First, equations are developed to estimate the density and velocity of the overall fiber mass with a partial differential equation (PDE) derived from a random-walk formulation of the fiber motion in an interface between two surfaces. Next, a numerical solution is obtained for the steady state Navier-Stokes equations for air-flow in the space between the three rotating cylinders of a single carding station. Finally, these velocities and densities are applied to the dynamics of individual fibers, each represented as a chain of elastic-jointed segments in a moving fluid, subject to viscous drag, with the possibility of being tugged at some point with a fixed velocity by either a wire on the surface or another fiber. All of these elements are tied into the overall structure of a simple card with three rotating Cylinders, interfaces between cylinders, triangular cavity, fiber input and output points and the transfer of fibers between surfaces. Fibers are then propagated through the card with positions calculated at each successive time step and the appropriate fraction extracted at the doffer to form an output fiber stream. The resulting output of simulated tracer fibers is then analyzed for a variety of statistical properties such as alignment, length, width, change in position, and the presence or magnitude of certain geometrical features. This allows various conclusions to be drawn concerning the overall behavior of the bulk fiber mass and the effectiveness of the carding machine for a given set of parameters.

Wibberly, Leonard Daniel

1999-12-01

427

The toxic spill index (emergency response index)  

Microsoft Academic Search

An index has been devised to indicate the magnitude of a toxic spill. The index is a product calculation that varies from 0–96. It incorporates an estimate of the magnitude of the spill, the spill type (unknown, leak, spill), the medium affected, and the magnitude of the hazard represented. The method of calculation appears to be straightforward, based upon a

Dean F. Martin; M. Christine Flynn; Charles D. Norris; Barbara B. Martin

1990-01-01

428

Review of recent advances in index flood estimation Hydrology and Earth System Sciences, 7(3), 283296 (2003) EGU  

E-print Network

the conceptual basis of the index flood method. This requires a two-step procedure. The first step requires. The estimation of the index flood is crucial to design flood prediction and it requires the merging of conceptsReview of recent advances in index flood estimation 283 Hydrology and Earth System Sciences, 7

Paris-Sud XI, Université de

429

Coatings for Graphite Fibers  

NASA Technical Reports Server (NTRS)

Several approaches for applying high resistance coatings continuously to graphite yarn were investigated. Two of the most promising approaches involved (1) chemically vapor depositing (CVD) SiC coatings on the surface of the fiber followed by oxidation, and (2) drawing the graphite yarn through an organo-silicone solution followed by heat treatments. In both methods, coated fibers were obtained which exhibited increased electrical resistances over untreated fibers and which were not degraded. This work was conducted in a previous program. In this program, the continuous CVD SiC coating process used on HTS fiber was extended to the coating of HMS, Celion 6000, Celion 12000 and T-300 graphite fiber. Electrical resistances three order of magnitude greater than the uncoated fiber were measured with no significant degradation of the fiber strength. Graphite fibers coated with CVD Si3N4 and BN had resistances greater than 10(exp 6) ohm/cm. Lower pyrolysis temperatures were used in preparing the silica-like coatings also resulting in resistances as high as three orders of magnitude higher than the uncoated fiber. The epoxy matrix composites prepared using these coated fibers had low shear strengths indicating that the coatings were weak.

Galasso, F. S.; Scola, D. A.; Veltri, R. D.

1980-01-01

430

CENDI Indexing Workshop  

NASA Technical Reports Server (NTRS)

The CENDI Indexing Workshop held at NASA Headquarters, Two Independence Square, 300 E Street, Washington, DC, on September 21-22, 1994 focused on the following topics: machine aided indexing, indexing quality, an indexing pilot project, the MedIndEx Prototype, Department of Energy/Office of Scientific and Technical Information indexing activities, high-tech coding structures, category indexing schemes, and the Government Information Locator Service. This publication consists mostly of viewgraphs related to the above noted topics. In an appendix is a description of the Government Information Locator Service.

1994-01-01

431

Modal analysis for optimization of single-mode waveguide pigtailing and fiber splicing.  

PubMed

We examine the waveguide dimension and refractive-index difference space for the optimization of single-mode channel waveguide pigtails and optical fiber splices, and we explain these results using modal analysis. We present closed-form equations for the evaluation of the optimal index difference and the allowable variation in its value in any material. We provide a novel way of viewing common waveguide physical parameters and translating them into information that determines the efficacy of a fiber connection. PMID:18301613

Eldada, L; Yardley, J T

1998-11-20

432

Low-temperature hermetic sealing of optical fiber components  

SciTech Connect

A method for manufacturing low-temperature hermetically sealed optical fiber components is provided. The method comprises the steps of: inserting an optical fiber into a housing, the optical fiber having a glass core, a glass cladding and a protective buffer layer disposed around the core and cladding; heating the housing to a predetermined temperature, the predetermined temperature being below a melting point for the protective buffer layer and above a melting point of a solder; placing the solder in communication with the heated housing to allow the solder to form an eutectic and thereby fill a gap between the interior of the housing and the optical fiber; and cooling the housing to allow the solder to form a hermetic compression seal between the housing and the optical fiber.

Kramer, D.P.

1995-12-31

433

In-Line Polarization Controller Based on Liquid-Crystal Photonic Crystal Fibers  

Microsoft Academic Search

Compact polarization control elements based on index-guiding soft-glass photonic crystal fibers infiltrated with nematic liquid crystals are proposed and thoroughly studied. The nematic director profiles atthefiber'scross section are consistently calculated by solving the coupled electrostatic and elastic problem, in the context of an analysis on the tunability of liquid-crystal-in- filtrated photonic crystal fibers. The fiber's dispersive properties and light propagation

Alexandros K. Pitilakis; Dimitrios C. Zografopoulos; Emmanouil E. Kriezis

2011-01-01

434

Design and performance of Gaussian-profile dispersion-shifted fibers manufactured by VAD process  

Microsoft Academic Search

Design and manufacturing of dispersion-shifted fibers with a Gaussian profile, which is compatible to the VAD process, are studied. From the viewpoint of stable cabling, the parametric analysis is made with emphasis on the bending loss. To make the bending sensitivity of the Gaussian core fibers comparable with the conventional 1.3- ?m zero-dispersion fibers, an 0.8 percent or higher index

Ryozo Yamauchi; Matsuhiro Miyamoto; Tomio Abiru; Kenji Nishide; Tatsuyuki Ohashi; Osamu Fukuda; Koichi Inada

1986-01-01

435

SPAR-H Step-by-Step Guidance  

SciTech Connect

This guide provides step-by-step guidance on the use of the SPAR-H method for quantifying Human Failure Events (HFEs). This guide is intended to be used with the worksheets provided in: 'The SPAR-H Human Reliability Analysis Method,' NUREG/CR-6883, dated August 2005. Each step in the process of producing a Human Error Probability (HEP) is discussed. These steps are: Step-1, Categorizing the HFE as Diagnosis and/or Action; Step-2, Rate the Performance Shaping Factors; Step-3, Calculate PSF-Modified HEP; Step-4, Accounting for Dependence, and; Step-5, Minimum Value Cutoff. The discussions on dependence are extensive and include an appendix that describes insights obtained from the psychology literature.

W. J. Galyean; A. M. Whaley; D. L. Kelly; R. L. Boring

2011-05-01

436

Preform For Producing An Optical Fiber And Method Therefor  

DOEpatents

The present invention provides a simple method for fabricating fiber-optic glass preforms having complex refractive index configurations and/or dopant distributions in a radial direction with a high degree of accuracy and precision. The method teaches bundling together a plurality of glass rods of specific physical, chemical, or optical properties and wherein the rod bundle is fused in a manner that maintains the cross-sectional composition and refractive-index profiles established by the position of the rods.

Kliner, Dahv A. V. (San Ramon, CA); Koplow, Jeffery P. (Washington, DC)

2004-08-10

437

Preform For Producing An Optical Fiber And Method Therefor  

DOEpatents

The present invention provides a simple method for fabricating fiber-optic glass preforms having complex refractive index configurations and/or dopant distributions in a radial direction with a high degree of accuracy and precision. The method teaches bundling together a plurality of glass rods of specific physical, chemical, or optical properties and wherein the rod bundle is fused in a manner that maintains the cross-sectional composition and refractive-index profiles established by the position of the rods.

Kliner, Dahv A. V. (San Ramon, CA); Koplow, Jeffery P. (Washington, DC)

2005-04-19

438

KERATIN FIBER-POLYMER COMPOSITES  

Technology Transfer Automated Retrieval System (TEKTRAN)

Short-fiber reinforced composites are made from keratin fibers and polyethylene (PE) and polypropylene (PP). The keratin fibers are obtained from poultry feathers. It is shown that PE and PP are reinforced by the keratin fibers. There is good compatibility between the polymer and fiber without th...

439

Optical Fibers Optics and Photonics  

E-print Network

Optical Fibers Optics and Photonics Dr. Palffy-Muhoray Ines Busuladzic Department of Theoretical and Applied Mathematics The University of Akron April 21, 2008 #12;Outline · History of optical fibers · What are optical fibers? · How are optical fibers made? · Light propagation through optical fibers · Application

Palffy-Muhoray, Peter

440

Kinetic model for step flow growth of [100] steps  

SciTech Connect

A kinetic model for the step flow growth of [100] steps is derived. This model extends the implicit close-to-equilibrium assumption in the classical Burton-Cabrera-Frank theory to out-of-equilibrium growth regimes common in molecular beam epitaxy. In equilibrium, the kink density coincides with Burton, Cabrera, and Frank [Philos. Trans. R. Soc. London, Ser. A 243, 299 (1951)] but in a planar steady state solution for a periodic sequence of steps the kink density derivates and we analyze its scaling behavior with the step Peclet number. Furthermore, we observe a discontinuity of adatoms on the steps that might give a new explanation for step bunching.

Balykov, Lev; Voigt, Axel [Crystal Growth Group, Research Center caesar, Ludwig-Erhard-Allee 2, 53175 Bonn (Germany)

2005-08-01

441

Experimentation: the next step  

PubMed Central

General practice has entered a period of accelerating change, and those responsible for planning its development now put forward a variety of promising proposals. Unless provision is made for large scale experimentation and scientific evaluation, the direction of future change will be determined not by evidence but by rhetoric. A framework for creating and evaluating a substantial programme of experimentation is suggested. The programme is the logical next step in the process of change which was given impetus by the publication of the government green paper. It should be seen as a professional, moral and political priority. PMID:3681850

Marinker, Marshall

1987-01-01

442

Steps to the moon  

USGS Publications Warehouse

On July 20, 1969, man walked on the surface of the Moon and began a new chapter of his studies that will eventually disclose the geologic nature of the Earth's nearest neighbor. Although he has finally reached the Moon and sampled its substance, much work and study remain before he will know the full scientific significance of the first landing. This booklet briefly summarizes the steps man has taken to understand the Moon and what he thinks he has learned to date as a result of his centuries-long speculations and studies.

U.S. Geological Survey; Dale, Alvin E.

1976-01-01

443

2 Step Equation  

NSDL National Science Digital Library

Now that you know how to solve simple Algebra equations, we\\'re going to make it a little more challenging! These equations have two or more steps to solving them. Grab your worksheet and ready, set, go! Let\\'s start by doing a virtual hands-on activity. The object here is to add things to each side of the scale to make it balance, and then perform operations to reduce the equation until the variable is alone. After entering the site, place the appropriate objects on each ...

Mr. Elmer

2011-06-10

444

Raman Imaging with a Fiber-Coupled Multichannel Spectrograph  

PubMed Central

Until now, spatially resolved Raman Spectroscopy has required to scan a sample under investigation in a time-consuming step-by-step procedure. Here, we present a technique that allows the capture of an entire Raman image with only one single exposure. The Raman scattering arising from the sample was collected with a fiber-coupled high-performance astronomy spectrograph. The probe head consisting of an array of 20 × 20 multimode fibers was linked to the camera port of a microscope. To demonstrate the high potential of this new concept, Raman images of reference samples were recorded. Entire chemical maps were received without the need for a scanning procedure. PMID:25420149

Schmälzlin, Elmar; Moralejo, Benito; Rutowska, Monika; Monreal-Ibero, Ana; Sandin, Christer; Tarcea, Nicolae; Popp, Jürgen; Roth, Martin M.

2014-01-01

445

Fiber optic micro accelerometer  

DOEpatents

An accelerometer includes a wafer, a proof mass integrated into the wafer, at least one spring member connected to the proof mass, and an optical fiber. A Fabry-Perot cavity is formed by a partially reflective surface on the proof mass and a partially reflective surface on the end of the optical fiber. The two partially reflective surfaces are used to detect movement of the proof mass through the optical fiber, using an optical detection system.

Swierkowski, Steve P.

2005-07-26

446

E-band fiber Raman amplifier in nonzero dispersion fiber  

Microsoft Academic Search

An E-band fiber Raman amplifier in nonzero dispersion fiber is demonstrated with a 39 dB peak gain. Gain fiber water absorption is not observed to significantly hinder amplification. Such a device could extend the telecommunications bandwidth.

D. A. Chestnut; J. R. Taylor

2003-01-01

447

Low Cost Carbon Fiber Production Carbon Fiber Manufacturing Cost Modeling  

E-print Network

Low Cost Carbon Fiber Production Carbon Fiber Manufacturing Cost Modeling Oak Ridge National spinning, and the low mass conversion yield of precursor to carbon fiber. Alternative precursors have22725 Research Areas Freight Flows Passenger Flows Supply Chain Efficiency Transportation: Energy

448

AMPHIBOLE FIBER CONCENTRATION DETERMINATION FOR A SERIES OF COMMUNITY AIR SAMPLES: USE OF X-RAY DIFFRACTION TO SUPPLEMENT ELECTRON MICROSCOPE ANALYSIS  

EPA Science Inventory

The accurate measurement of annual average mineral fiber concentrations at various air sampling sites provides the best index of non-occupational inhalation exposure to fibers in a community located near an industrial source of airborne amphibole fibers. The transmission electron...

449

IEEE JOURNAL ON SELECTED TOPICS IN QUANTUM ELECTRONICS, VOL. 7, NO. 3, MAY/JUNE 2001 425 Novel Multimode Fiber for Narrow-Band  

E-print Network

with angular harmonic parameter = 1. Index Terms--Fiber Bragg gratings, multimode fiber, optical fiber and polarization character- istics. MMFGs are also useful for tuning solid-state lasers, in Manuscript received Bragg grating in MMF would enable the use of wavelength-division multiplexing (WDM) in LANs. Other

Sipe,J. E.

450

The Europe 2020 Index  

ERIC Educational Resources Information Center

This paper presents a new index to quantify, measure and monitor the progress towards the objectives of the Europe 2020 strategy. This index is based on a set of relevant, accepted, credible, easy to monitor and robust indicators presented by the European Commission at the time the strategy was launched. The internal analysis of the index shows…

Pasimeni, Paolo

2013-01-01

451

Dow Jones Internet Indexes  

NSDL National Science Digital Library

Dow Jones Indexes has created the Dow Jones Internet Index (DJII) to bring "an ordered perspective" to "the seeming chaos of Internet stocks." The new index includes companies that generate a minimum of 50 percent of their revenues from the Internet. Complete documentation of DJII components, data, historical values, and news are provided on-site.

452

ZBLAN, Silica Fiber Comparison  

NASA Technical Reports Server (NTRS)

This graph depicts the increased signal quality possible with optical fibers made from ZBLAN, a family of heavy-metal fluoride glasses (fluorine combined zirconium, barium, lanthanum, aluminum, and sodium) as compared to silica fibers. NASA is conducting research on pulling ZBLAN fibers in the low-g environment of space to prevent crystallization that limits ZBLAN's usefulness in optical fiber-based communications. In the graph, a line closer to the black theoretical maximum line is better. Photo credit: NASA/Marshall Space Flight Center

1998-01-01

453

Design of Vibration Absorbers for Step Motions and Step Disturbances  

E-print Network

Design of Vibration Absorbers for Step Motions and Step Disturbances Joel Fortgang William Singhose or from external disturbances. The technique of adding a vibration ab- sorber has proven useful at eliminating vibrations from external disturbances and rotational imbalances. Traditionally, vibration

Singhose, William

454

Integration of microfluidics with grating coupled silicon photonic sensors by one-step combined photopatterning and molding of OSTE.  

PubMed

We present a novel integration method for packaging silicon photonic sensors with polymer microfluidics, designed to be suitable for wafer-level production methods. The method addresses the previously unmet manufacturing challenges of matching the microfluidic footprint area to that of the photonics, and of robust bonding of microfluidic layers to biofunctionalized surfaces. We demonstrate the fabrication, in a single step, of a microfluidic layer in the recently introduced OSTE polymer, and the subsequent unassisted dry bonding of the microfluidic layer to a grating coupled silicon photonic ring resonator sensor chip. The microfluidic layer features photopatterned through holes (vias) for optical fiber probing and fluid connections, as well as molded microchannels and tube connectors, and is manufactured and subsequently bonded to a silicon sensor chip in less than 10 minutes. Combining this new microfluidic packaging method with photonic waveguide surface gratings for light coupling allows matching the size scale of microfluidics to that of current silicon photonic biosensors. To demonstrate the new method, we performed successful refractive index measurements of liquid ethanol and methanol samples, using the fabricated device. The minimum required sample volume for refractive index measurement is below one nanoliter. PMID:24104003

Errando-Herranz, Carlos; Saharil, Farizah; Romero, Albert Mola; Sandström, Niklas; Shafagh, Reza Zandi; van der Wijngaart, Wouter; Haraldsson, Tommy; Gylfason, Kristinn B

2013-09-01

455

Tapered fiber bundle couplers for high-power fiber amplifiers  

NASA Astrophysics Data System (ADS)

In this work, we would like to demonstrate our results on performing (6+1)x1 tapered fiber bundle combiners using a trielectrode fiber splicing system. In our combiners we have used 9/80 ?m (core/clad) diameter fibers as single-mode signal input ports. Using this fiber, instead of a conventional 9/125 ?m single-mode fiber allowed us to reduce the taper ratio and therefore significantly increase the signal transmission. We have also performed power combiner which is based on the LMA fibers: input signal fiber 20/125?m and passive double clad fiber 25/300 ?m at the output.

Sliwinska, Dorota; Kaczmarek, Pawel; Abramski, Krzysztof M.

2014-12-01

456

Strength development of high-strength ductile concrete incorporating Metakaolin and PVA fibers.  

PubMed

The mechanical properties of high-strength ductile concrete (HSDC) have been investigated using Metakaolin (MK) as the cement replacing material and PVA fibers. Total twenty-seven (27) mixes of concrete have been examined with varying content of MK and PVA fibers. It has been found that the coarser type PVA fibers provide strengths competitive to control or higher than control. Concrete with coarser type PVA fibers has also refined microstructure, but the microstructure has been undergone with the increase in aspect ratio of fibers. The microstructure of concrete with MK has also more refined and packing of material is much better with MK. PVA fibers not only give higher stiffness but also showed the deflection hardening response. Toughness Index of HSDC reflects the improvement in flexural toughness over the plain concrete and the maximum toughness indices have been observed with 10% MK and 2% volume fraction of PVA fibers. PMID:24707202

Nuruddin, Muhammad Fadhil; Khan, Sadaqat Ullah; Shafiq, Nasir; Ayub, Tehmina

2014-01-01

457

Strength Development of High-Strength Ductile Concrete Incorporating Metakaolin and PVA Fibers  

PubMed Central

The mechanical properties of high-strength ductile concrete (HSDC) have been investigated using Metakaolin (MK) as the cement replacing material and PVA fibers. Total twenty-seven (27) mixes of concrete have been examined with varying content of MK and PVA fibers. It has been found that the coarser type PVA fibers provide strengths competitive to control or higher than control. Concrete with coarser type PVA fibers has also refined microstructure, but the microstructure has been undergone with the increase in aspect ratio of fibers. The microstructure of concrete with MK has also more refined and packing of material is much better with MK. PVA fibers not only give higher stiffness but also showed the deflection hardening response. Toughness Index of HSDC reflects the improvement in flexural toughness over the plain concrete and the maximum toughness indices have been observed with 10% MK and 2% volume fraction of PVA fibers. PMID:24707202

Nuruddin, Muhammad Fadhil; Shafiq, Nasir

2014-01-01

458

Interferometric microstructured polymer optical fiber ultrasound sensor for optoacoustic endoscopic imaging in biomedical applications  

NASA Astrophysics Data System (ADS)

We report a characterization of the acoustic sensitivity of microstructured polymer optical fiber interferometric sensors at ultrasonic frequencies from 100kHz to 10MHz. The use of wide-band ultrasonic fiber optic sensors in biomedical ultrasonic and optoacoustic applications is an open alternative to conventional piezoelectric transducers. These kind of sensors, made of biocompatible polymers, are good candidates for the sensing element in an optoacoustic endoscope because of its high sensitivity, its shape and its non-brittle and non-electric nature. The acoustic sensitivity of the intrinsic fiber optic interferometric sensors depends strongly of the material which is composed of. In this work we compare experimentally the intrinsic ultrasonic sensitivities of a PMMA mPOF with other three optical fibers: a singlemode silica optical fiber, a single-mode polymer optical fiber and a multimode graded-index perfluorinated polymer optical fiber.

Gallego, Daniel; Sáez-Rodríguez, David; Webb, David; Bang, Ole; Lamela, Horacio

2014-05-01

459

Preparation and hydrogen storage of activated rayon-based carbon fibers with high specific surface area  

Microsoft Academic Search

Activated carbon fibers were prepared from rayon-based carbon fibers by two step activations with steam and KOH treatments. Hydrogen storage properties of the activated rayon-based carbon fibers with high specific surface area and micropore volume have been investigated. SEM, XRD and Brunauer–Emmett–Teller (BET) were used to characterize the samples. The adsorption performance and porous structure were investigated by nitrogen adsorption

Fen Gao; Dong-Lin Zhao; Yan Li; Xing-Guo Li

2010-01-01

460

Fiber Supply Associate Company Overview  

E-print Network

materials acquisition, harvesting, logistics coordination, contract negotiations, and inventory management leadership roles such as Fiber Specialist, Fiber Supply Manager, Region Manager, Director, General Manager. A Fiber Supply Associate may also oversee relationships with vendors to insure compliance with contracts

Mazzotti, Frank

461

USDA Flax fiber utilization research  

Technology Transfer Automated Retrieval System (TEKTRAN)

The United States is pursuing natural fibers as sustainable, environmentally friendly sources for a variety of industrial applications. Flax (Linum usitatissimum L.) fiber offers many possibilities towards this goal. Research on flax fiber production, processing, and standards development is urgen...

462

Green Schools Energy Project: A Step-by-Step Manual.  

ERIC Educational Resources Information Center

This publication contains a step-by-step guide for implementing an energy-saving project in local school districts: the installation of newer, more energy-efficient "T-8" fluorescent tube lights in place of "T-12" lights. Eleven steps are explained in detail: (1) find out what kind of lights the school district currently uses; (2) form a group to…

Quigley, Gwen

463

Fiber optic sensor employing successively destroyed coupled points or reflectors for detecting shock wave speed and damage location  

DOEpatents

A shock velocity and damage location sensor providing a means of measuring shock speed and damage location is disclosed. The sensor consists of a long series of time-of-arrival ``points`` constructed with fiber optics. The fiber optic sensor apparatus measures shock velocity as the fiber sensor is progressively crushed as a shock wave proceeds in a direction along the fiber. The light received by a receiving means changes as time-of-arrival points are destroyed as the sensor is disturbed by the shock. The sensor may comprise a transmitting fiber bent into a series of loops and fused to a receiving fiber at various places, time-of-arrival points, along the receiving fibers length. At the ``points`` of contact, where a portion of the light leaves the transmitting fiber and enters the receiving fiber, the loops would be required to allow the light to travel backwards through the receiving fiber toward a receiving means. The sensor may also comprise a single optical fiber wherein the time-of-arrival points are comprised of reflection planes distributed along the fibers length. In this configuration, as the shock front proceeds along the fiber it destroys one reflector after another. The output received by a receiving means from this sensor may be a series of downward steps produced as the shock wave destroys one time-of-arrival point after another, or a nonsequential pattern of steps in the event time-of-arrival points are destroyed at any point along the sensor. 6 figs.

Weiss, J.D.

1995-08-29

464

Fiber optic sensor employing successively destroyed coupled points or reflectors for detecting shock wave speed and damage location  

DOEpatents

A shock velocity and damage location sensor providing a means of measuring shock speed and damage location. The sensor consists of a long series of time-of-arrival "points" constructed with fiber optics. The fiber optic sensor apparatus measures shock velocity as the fiber sensor is progressively crushed as a shock wave proceeds in a direction along the fiber. The light received by a receiving means changes as time-of-arrival points are destroyed as the sensor is disturbed by the shock. The sensor may comprise a transmitting fiber bent into a series of loops and fused to a receiving fiber at various places, time-of-arrival points, along the receiving fibers length. At the "points" of contact, where a portion of the light leaves the transmitting fiber and enters the receiving fiber, the loops would be required to allow the light to travel backwards through the receiving fiber toward a receiving means. The sensor may also comprise a single optical fiber wherein the time-of-arrival points are comprised of reflection planes distributed along the fibers length. In this configuration, as the shock front proceeds along the fiber it destroys one reflector after another. The output received by a receiving means from this sensor may be a series of downward steps produced as the shock wave destroys one time-of-arrival point after another, or a nonsequential pattern of steps in the event time-of-arrival points are destroyed at any point along the sensor.

Weiss, Jonathan D. (Albuquerque, NM)

1995-01-01

465

Tunable fiber polarizing filter based on a single-hole-infiltrated polarization maintaining photonic crystal fiber.  

PubMed

A tunable fiber polarizing filter based on selectively filling a single hole of a solid-core polarization maintaining photonic crystal fiber with high index liquid are proposed and demonstrated. Two groups of polarization-dependent resonance dips in the transmission spectrum of the single-hole-infiltrated photonic crystal fiber are observed. Theoretical and experimental investigations reveal that these resonant dips result from the couplings between the silica core fundamental mode at x or y polarization and high order modes (TM(01), TE(01) and HE(11)) in the liquid core. Especially, a distinctive characteristic near the strongest resonant point (SRP) is demonstrated and revealed. The transmission loss and spectral shape at the SRP wavelength are extremely sensitive to the filling length and temperature (or Refractive Index, RI), which permits a fiber bandpass or bandstop polarizing filter with a good performance on tunability and controllability. Furthermore, the narrowband dips on both sides of the SRP wavelength have wavelength-dependent tuning velocities, providing a method to achieve flexible and controllable filters as well as two- or multi-parameter sensors with a compact structure. PMID:24718135

Guo, Junqi; Liu, Yan-ge; Wang, Zhi; Han, Tingting; Huang, Wei; Luo, Mingming

2014-04-01