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1

Equivalent step-index model of multifilament core fibers  

NASA Astrophysics Data System (ADS)

The accuracy of the recently presented1 equivalent step index approximation of multifilament core fibers is analyzed in terms of the effective refractive index, mode field area and bending losses of the fundamental mode. A modified Vparameter for this class of fibers as well as a single-mode condition is proposed. By comparison with a full-vectorial finite element method it is shown that the relative deviation of the effective refractive index and the mode field area are in the magnitude of 1 %. No significant decrease of bending losses is found for multifilament core fibers.

Spittel, Ron; Lorenz, Adrian; Jetschke, Sylvia; Jäger, Matthias; Bartelt, Hartmut

2013-03-01

2

Prototype for numerical aperture tester for step-index multimode specialty medical optical fiber  

Microsoft Academic Search

A prototype is to be designed, built, and evaluated for measuring the far-field and near-field numerical aperture (NA) values ranging from 0.10 to 0.65 for step-index multimode specialty medical optical fiber with various diameters ranging from 100 ?m to over 1000 ?m

B. J. Skutnik; M. B. Vollaro

2002-01-01

3

Design of mode scramblers for step-index and graded-index plastic optical fibers  

Microsoft Academic Search

We analyze the internal evolution of light power angular distribution in typical mode scrambling configurations by comparing the resultant far fields, obtained either experimentally or computationally, with the experimental equilibrium mode distribution (EMD) far field for the plastic optical fibers (POF) considered, so as to provide an insight that helps to adapt existing scramblers to new types of POF that

J. Arrue; G. Aldabaldetreku; G. Durana; J. Zubia; I. Garces; F. Jiménez

2005-01-01

4

1 Gbit/s transmission over step-index plastic optical fiber using an optical receiver with an integrated equalizer  

NASA Astrophysics Data System (ADS)

A single chip optical receiver with an integrated large-diameter photodiode, transimpedance amplifier, two stages active equalizer, post amplifier and 50 ? driver is used for gigabit transmission over PMMA step plastic optical fiber (SI-POF). The large-diameter photodiode with an antireflection coating optimized for red light. The integrated equalizer enables the presented optical receiver to reach 1 Gbit/s over 50 m SI-POF at bit error ratio of 10- 6. An error free (< 10- 9) 1 Gbit/s data rate over 40 m standard PMMA step-index plastic optical fiber is also achieved.

Atef, M.; Swoboda, R.; Zimmermann, H.

2011-10-01

5

Tunable supercontinuum generation in a high-index-step photonic-crystal fiber with a comma-shaped core  

Microsoft Academic Search

A fused silica high-index-step photonic-crystal fiber with a comma-shaped core is shown to upport two different types of guided modes with bell-shaped intensity profiles, efficiently transforming unamplified 30-fs Ti: sapphire laser pulses into supercontinuum emission through two different physical mechanisms. The modes of the first type provide broadly spanning supercontinuum emission with a smooth spectrum stretching from 450 to 1400

Ming-Lie Hu; Ching-Yue Wang; Yan-Feng Li; Lu Chai; Aleksei M. Zheltikov

2006-01-01

6

Space-time block code based MIMO encoding for large core step index plastic optical fiber transmission systems.  

PubMed

The performance of Space-Time Block Codes combined with Discrete MultiTone modulation applied in a Large Core Step-Index POF link is examined theoretically. A comparative study is performed considering several schemes that employ multiple transmitters/receivers and a fiber span of 100 m. The performance enhancement of the higher diversity order configurations is revealed by application of a Margin Adaptive Bit Loading technique that employs Chow's algorithm. Simulations results of the above schemes, in terms of Bit Error Rate as a function of the received Signal to Noise Ratio, are provided. An improvement of more than 6 dB for the required electrical SNR is observed for a 3 × 1 configuration, in order to achieve a 10(-3) BER value, as compared to a conventional Single Input Single output scheme. PMID:21643291

Raptis, Nikos; Grivas, Evangelos; Pikasis, Evangelos; Syvridis, Dimitris

2011-05-23

7

Analysis on Propagation Characteristics of Single-mode Step Index Linear and Nonlinear Optical Fiber with Revised Version of Improved Lorentzian Approximation for the Fundamental Mode  

NASA Astrophysics Data System (ADS)

In this paper, we approximate the fundamental mode of guided propagation by involving an extension of the previous version of Improved Lorentzian parameter for single mode step index liner and nonlinear optical fiber within the scalar variational framework. We show this version gives better performance in terms of field, propagation constants group delay and waveguide dispersion on wider scale of V-values in comparison to earlier ones and works better in low-V region.

Bandyopadhyay, Pratap Kumar; Sarkar, S. N.

2013-09-01

8

100 Mb\\/s Ethernet Transmission Over 275 m of Large Core Step Index Polymer Optical Fiber: Results From the POF-ALL European Project  

Microsoft Academic Search

We present our prototype solution for transmitting 100 Mb\\/s Ethernet data over large core (1 mm) step-index polymer optical fiber (POF), as one of the final results of the EU-funded project POF-ALL. The system is demonstrated over a record maximum distance of 275 m, largely outperforming CAT-5 systems and currently commercially available POF media converters. These results let us envision

Daniel Felipe Cardenas Lopez; Antonino Nespola; Stefano Camatel; Silvio Abrate; Roberto Gaudino

2009-01-01

9

Transmission of QAM signals over 100m step-index PMMA polymer optical fiber with 0.98mm core diameter  

Microsoft Academic Search

Polymer Optical Fiber (POF) is severely bandwidth-limited; to overcome this problem Quadrature Amplitude Modulation (QAM) was chosen for reaching high data rates because of its spectrum efficiency. In this paper we present Digital Video Broadcasting for Cables (DVB-c) transmission using 16-, 64- and 256-QAM modulation over up to 100m Step-Index PMMA POF. An LED as well as a laser source

Al Fiad; Xinkai Li; J Yang; AMJ Koonen; Boom van den HPA

2006-01-01

10

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

11

High Performance Graded Index Polymer Optical Fibers.  

National Technical Information Service (NTIS)

Experimental and theoretical studies of the optical properties of large core step index (SI) plastic optical fibers (POF) and graded index (GI) POFs are reported. A set of criteria and analyses of physical parameters are developed in context to the major ...

A. F. Garito

1998-01-01

12

Graded-Index Optical Fibers.  

National Technical Information Service (NTIS)

The imaging properties of graded-index fibers are determined theoretically and experimentally. Image location and resolution are measured for 1, 1.5, and 2.0 mm diameter fibers. Image quality is excellent for short fibers, generally within a factor of 3 o...

K. R. Hessel K. T. Stalker

1975-01-01

13

Ultrasensitive photonic crystal fiber refractive index sensor.  

PubMed

We introduce a microfluidic refractive index sensor based on a directional coupler architecture using solid-core photonic crystal fibers. The sensor achieves very high sensitivity by coupling the core mode to a mode in the adjacent fluid-filled waveguide that is beyond modal cutoff, and with strong field overlap. We demonstrate the device through the selective infiltration of a single hole with fluid along a microstructured optical fiber. A detection limit of 4.6x10(-7) refractive index units has been derived from measurements with a sensitivity of 30,100 nm per refractive index unit, which is the highest for a fiber device to date. PMID:19183645

Wu, Darran K C; Kuhlmey, Boris T; Eggleton, Benjamin J

2009-02-01

14

Multiwavelength optical fiber refractive index profiling  

NASA Astrophysics Data System (ADS)

Fourier transform spectroscopy and interference microscopy are combined to provide the world's first multi-wavelength optical fiber refractive index profile (RIP) measurements. The RIP and its spectral dependence are obtained with submicron spatial resolution across an octave stretching from about 500 nm to the 1 micron operating band of Yb-doped fiber lasers and amplifiers. In contrast to commercial Refracted Near Field (RNF) technology, which measures at a cleave, the technique described here measures transversely through the side of an uncleaved fiber, enabling measurements of axial fiber RIP variations found in fiber gratings, physical tapers, and fusion splices.

Yablon, Andrew D.

2010-02-01

15

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

16

Nondestructive measurement of refractive index profile for holey fiber preforms.  

PubMed

A non-destructive technique is presented to determine the refractive index profile of holey fiber preforms. The holes are filled with index matching oil and the holey preform deflection data is measured. An improved optical path-length formula and back projection method is used to reconstruct the two-dimensional filled holey fiber preform refractive index distribution. PMID:19471359

Zhao, Yucheng; Lyytikainen, Katja; van Eijkelenborg, Martijn; Fleming, Simon

2003-10-01

17

Raman fiber lasers and amplifiers based on multimode graded-index fibers and their application to beam cleanup  

NASA Astrophysics Data System (ADS)

Raman fiber lasers (RFLs) and Raman fiber amplifiers (RFAs) in multimode fibers were explored. The RFL based on a graded-index fiber was shown to be very efficient relative to RFLs based on singlemode fibers. Several configurations of the RFL were examined; the beam quality of the Stokes beam depended on the reflectivity of the output coupler and the Stokes power. When used as a beam combiner, the RFL was a highly efficient brightness converter. RFL configurations which used dichroic mirrors were shown to be potentially useful for RFLs based on very large fibers. The forward- and the backward-seeded geometries of an RFA based on a graded-index fiber were examined. The beam quality of the output was observed to depend on the beam quality of the input. A numerical model explains this behavior in terms of mode competition and explains why beam cleanup occurs in graded-index fibers but not in step-index fibers. The spectrum of the forward-seeded geometry was superior to the spectrum of the backward-seeded geometry. The RFA was used as a beam combiner.

Terry, Nathan B.

18

Organic transistors on fiber: a first step towards electronic textiles  

Microsoft Academic Search

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 >10-2 cm2\\/V-s measured at 20 V VDD. The entire transistor is fabricated without resorting to conventional lithography techniques. Patterning is achieved via shadowing from overwoven fibers. The process is compatible with textile

Josephine B. Lee; Vivek Subramanian

2003-01-01

19

Graded-index silver chlorobromide fibers for the mid-infrared.  

PubMed

We have developed and characterized graded-index optical fibers for the mid-IR spectral range, based on silver chlorobromide (AgClBr) crystals. A preform was fabricated by inserting a cylindrical rod made of AgCl(0.1)Br(0.9) into a tube made of AgCl(0.9)Br(0.1). The preform was heated in an oven, causing diffusion of Cl into the outer layer of the rod, thus reducing its index of refraction. The rod was removed from the tube and was then extruded through a die to form a graded-index fiber. Such a fiber was analyzed, investigated, and compared with a step-index fiber made of AgClBr. The attenuation of a 0.9-mm-diameter graded-index fiber was found to be 2.4 dB/m, and the attenuation of a 1.2-mm-diameter graded-index fiber was 4 dB/m at 10.6 microm. PMID:15943270

Dekel, Ben-Zion; Katzir, Abraham

2005-06-01

20

Analysis and Design of Photonic Crystal Fibers Based on an Improved Effective-Index Method  

NASA Astrophysics Data System (ADS)

The modal characteristics of photonic crystal fibers (PCFs), with guiding cores consisting of one or seven missing airholes, are investigated with the finite element method and compared to those of step-index fibers (SIFs). To extend the applicability of the classical SIF theories to PCFs, the effective refractive index of photonic crystal cladding and the effective core radius of a PCF are studied systematically, based on simple physically consistent concepts. With the new effective cladding index and core radius of PCFs, the classical definition of the V parameter for SIFs is extended to PCFs, and a highly efficient approach based on the effective-index method is developed for the design of PCFs. The new design approach has been successfully employed to analyze the modal properties of PCF lasers with depressed-index cores and further tested by using it to effectively estimate the number of guided modes for PCFs with large cores.

Li, Hongbo; Mafi, Arash; Schülzgen, Axel; Li, Li; Temyanko, Valery L.; Peyghambarian, Nasser; Moloney, Jerome V.

2007-05-01

21

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

22

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

23

Raman Fiber Lasers and Amplifiers Based on Multimode Graded-Index Fibers and Their Application to Beam Cleanup.  

National Technical Information Service (NTIS)

Raman fiber lasers (RFLs) and Raman fiber amplifiers (RFAs) in multimode fibers were explored. The RFL based on a graded-index fiber was shown to be very efficient relative to RFLs based on singlemode fibers. Several configurations of the RFL were examine...

N. B. Terry

2007-01-01

24

Refractive index measurement with optical fiber Mach-Zehnder interferometer  

Microsoft Academic Search

An interferometric technique for determination of the refractive index of liquids is described. The method is based on measurements of phase variations caused by the relative movement of an optical fiber tip in a liquid sample. The apparatus consists of two independent interferometers. A two-frequency Michelson interferometer is used to measure the liquid sample displacement in the air, while an

Alojz Suhadolnik; Ales Babnik; Janez Mozina

1993-01-01

25

Constant Refractive Index Multi-Core Fiber Laser  

SciTech Connect

A scalable fiber laser approach is described based on phase-locking multiple gain cores in an antiguided structure. The waveguide is comprised of periodic sequences of gain- and no-gain-loaded segments having uniform index, within the cladding region. Initial experimental results are presented.

Beach, R J; Feit, M D; Brasure, L D; Payne, S A; Mead, R W; Hayden, J S; Krashkevich, D; Alunni, D A

2002-03-18

26

Refractive Index Profile of Polymeric Fibers Characterized by Micro Interferometry  

NASA Astrophysics Data System (ADS)

Interference microscopy is the only non-destructive method which can measure orientation and crystallinity at different radial positions within a fiber. It has long been used to characterize the radial variation of fiber micro structure. However all past work has not considered fiber-liquid interfacial and fiber interior refraction correctly. The present research has developed a correct ray tracing method which takes consideration of both external and internal refraction. Based on the theory the systematic errors from the past work have been analyzed, and a numerical algorithm is developed to solve the refractive index profile using the correct optical path difference equation. In order to guarantee the precision of data acquisition process a new fringe extraction method based on interference principle has also been developed. The new method has been applied to fibers having either homogeneous or inhomogeneous structures. The experimental results indicate that the new algorithm greatly reduces effects of noise in interference fringe images and increases the accuracy of results. It is also found that the refractive index profile reduced from using this algorithm is adequately independent of immersion medium. The errors observed are almost within the calibration accuracy of the immersion media. When applied to high speed spun PET fibers, some previously unknown structural details have been revealed. The commercial POY (3500m/min.), due to low crystallinity, appears to have convex up refractive index profile n(r). On the other hand the n(r) of the higher speed spun (7000m/min.) fiber has concave down curvature.

Wu, Zhenqiu

27

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

28

Experiment study on measurement of the optical fiber refractive index based on digital holography  

NASA Astrophysics Data System (ADS)

The characteristics of optical fiber are quite important for improving the performance in various application of the optical fiber including communication and sensor systems. Based on optical Mach-Zehnder interferometer, a new measuring method of optical fiber refractive index profiling using digital holography is proposed in this paper, which simplifies the experimental setup compared to traditional holography. Several kinds of fiber samples such as multimode fiber, polarization-preserving fiber and special fiber are tested and their holograms are recorded by CCD. After filtering of the hologram, the phase distribution of fiber sample can be reconstructed and extracted. At last the experimental results of refractive index profiling of fiber are given.

Wang, Duocheng; Chang, Zheng; Huang, Sujuan

2012-11-01

29

Acoustic index of Ge-doped optical fibers.  

PubMed

A precise relation between the acoustic index and the amount of doped Ge in silica is established using both energy and wave dispersive spectroscopies on preform pieces and stimulated Brillouin scattering in optical fibers. It is shown that the relation is in very good agreement with a simple model involving only GeO(2) and SiO(2) bulk parameters. The change in the acoustic index is found to be 3.97x10(-3)/wt. %GeO(2) at 1550 nm. PMID:19953163

Herstrøm, Søren; Grüner-Nielsen, Lars; Pálsdóttir, Bera

2009-12-01

30

Influence of Connectors on the Performance of a VCSEL-Based Standard Step-Index POF Link  

Microsoft Academic Search

An experimental investigation on the influence of connectors in a large core step-index plastic optical fiber-based link, in terms of the available bandwidth, has been performed. A vertical-cavity surface-emitting laser with a small launch numerical aperture was used, while a number of subscriber connectors were placed into different positions of a 50-m link. Significant performance degradation was observed when the

Evangelos Grivas; Dimitris Syvridis; Giorgio Friedrich

2009-01-01

31

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

32

Investigation of refractive index profile and mode field distribution of optical fibers using digital holographic phase shifting interferometric method  

NASA Astrophysics Data System (ADS)

In this paper a digital holographic phase shifting interferometric method is used to characterize the graded index (GR-IN) optical fibers. Off-axis digital holographic Mach-Zehnder like arrangement in aid of phase shifting tool is applied. Numerical reconstruction of phase shifted holograms is applied to calculate the optical phase difference distribution in the image plane, and then the optical phase differences across GR-IN fibers are extracted considering image enhancement and noise reduction steps. Also, a simple algorithm is presented to modify the position of the extracted optical phase differences across the fibers to be perpendicular to x-axis, so that it becomes easy to calculate the mean optical phase differences along the fiber. The mean optical phase differences in combination with multilayer model are applied to calculate the refractive index profiles across GR-IN optical fibers. An analytical model is presented to predict the mode distribution associated with the effective indices and the propagation coefficient of the parabolic refractive index profile GR-IN fiber.

El-Din, M. A. Shams; Wahba, H. H.

2011-08-01

33

Reliability of low-index polymer coated double-clad fibers used in fiber lasers and amplifiers  

NASA Astrophysics Data System (ADS)

The reliability of low-index polymer coated double-clad (DC) fibers used in the manufacture of fiber lasers and amplifiers has not received adequate attention. This paper evaluates the mechanical reliability of fibers, using standard fiber optic test procedures, and compares the performance of the DC fibers to the GR-20-CORE standard adopted by the industry. An 85 °C hot water soak test is proposed as an accelerated test to evaluate a low-index polymer coated DC fiber performance with prolonged exposure to temperature and humidity conditions experienced during storage and operation of fiber lasers. The test is used to evaluate DC fibers with three different coatings, including a specially engineered coating, and benchmark fibers from competitors. The data in this paper demonstrate that a dual acrylate coated DC fiber, using the specially engineered coating, has median failure stress values of over 700 kpsi and an average stress corrosion parameter of 21, well exceeding the recommended industry minimum values of 550 kpsi and 18, respectively. The accelerated temperature and humidity aging test clearly demonstrates that DC fibers with specially engineered coatings have 2 to 3 orders of magnitude better optical reliability. Such remarkable optical and mechanical performance significantly alleviates long term reliability concerns of fiber lasers and amplifiers.

Tankala, Kanishka; Guertin, Douglas; Abramczyk, Jaroslaw; Jacobson, Nils

2011-11-01

34

A highly sensitive fiber optic sensor based on two-core fiber for refractive index measurement.  

PubMed

A simple and compact fiber optic sensor based on a two-core fiber is demonstrated for high-performance measurements of refractive indices (RI) of liquids. In order to demonstrate the suitability of the proposed sensor to perform high-sensitivity sensing in a variety of applications, the sensor has been used to measure the RI of binary liquid mixtures. Such measurements can accurately determine the salinity of salt water solutions, and detect the water content of adulterated alcoholic beverages. The largest sensitivity of the RI sensor that has been experimentally demonstrated is 3,119 nm per Refractive Index Units (RIU) for the RI range from 1.3160 to 1.3943. On the other hand, our results suggest that the sensitivity can be enhanced up to 3485.67 nm/RIU approximately for the same RI range. PMID:24152878

Guzmán-Sepúlveda, José Rafael; Guzmán-Cabrera, Rafael; Torres-Cisneros, Miguel; Sánchez-Mondragón, José Javier; May-Arrioja, Daniel Alberto

2013-10-22

35

Extrinsic fiber-optic Fabry-Perot interferometer sensor for refractive index measurement of optical glass  

SciTech Connect

A simple fiber-optic sensor based on Fabry-Perot interference for refractive index measurement of optical glass is investigated both theoretically and experimentally. A broadband light source is coupled into an extrinsic fiber Fabry-Perot cavity formed by the surfaces of a sensing fiber end and the measured sample. The interference signals from the cavity are reflected back into the same fiber. The refractive index of the sample can be obtained by measuring the contrast of the interference fringes. The experimental data meet with the theoretical values very well. The proposed technique is a new method for glass refractive index measurement with a simple, solid, and compact structure.

Chen Jihuan; Zhao Jiarong; Huang Xuguang; Huang Zhenjian

2010-10-10

36

Extrinsic fiber-optic Fabry-Perot interferometer sensor for refractive index measurement of optical glass.  

PubMed

A simple fiber-optic sensor based on Fabry-Perot interference for refractive index measurement of optical glass is investigated both theoretically and experimentally. A broadband light source is coupled into an extrinsic fiber Fabry-Perot cavity formed by the surfaces of a sensing fiber end and the measured sample. The interference signals from the cavity are reflected back into the same fiber. The refractive index of the sample can be obtained by measuring the contrast of the interference fringes. The experimental data meet with the theoretical values very well. The proposed technique is a new method for glass refractive index measurement with a simple, solid, and compact structure. PMID:20935706

Chen, Ji-Huan; Zhao, Jia-Rong; Huang, Xu-Guang; Huang, Zhen-Jian

2010-10-10

37

PHOSPHITE STABILIZATION EFFECTS ON TWO-STEP MELT-SPUN FIBERS OF POLYLACTIDE. (R826733)  

EPA Science Inventory

The effects of molecular weight stabilization on mechanical properties of polylactide (PLA) fibers are investigated. The textile-grade PLA contains a 98:02 ratio of L:D stereocenters and fibers are produced by the two step method, involving a primary quench and cold drawing. M...

38

Multimode fiber Mach-Zehnder interferometer for measurement of refractive index  

Microsoft Academic Search

A novel class of multimode optical fiber Mach-Zehnder interferometer suited for refractive index measurement is presented. The Mach-Zehnder interferometer was constructed by making two coupling points in a multimode optical fiber at localized regions with an electric arc system. The Mach-Zehnder interferometer as a high sensitive refractive-index sensor to detect changes in the surrounding refractive index was studied. The results

Chien-Hsing Chen; Yi-Chun Chen; Jian-Neng Wang; Lai-Kwan Chau; Jaw-Luen Tang; Wei-Te Wu

2010-01-01

39

Compact in-reflection fiber interferometer using thermally expanded core fiber and single-mode fiber and its applications as temperature and refractive index sensors  

NASA Astrophysics Data System (ADS)

We propose and experimentally demonstrate a compact in-reflection Mach-Zehnder fiber interferometer and applied the proposed device to temperature and refractive index sensing. By splicing a short section of an uncoated single-mode fiber with a thermally expanded core fiber, we obtained an interference pattern in the reflection spectrum of the device due to the effective index difference between the core mode and the cladding modes of the SMF which can be excited and re-collected due to the mode field mismatch at the splice point. We then demonstrate the use of this interferometer for temperature and refractive index sensing.

Nguyen, Linh Viet; Chung, Youngjoo

2009-10-01

40

Closed-loop phase stepping in a calibrated fiber-optic fringe projector for shape measurement  

NASA Astrophysics Data System (ADS)

Active homodyne feedback control can be used to stabilize an interferometer against unwanted phase drifts introduced by, for example, temperature gradients. The technique is commonly used in fiber-optic sensors to maintain the fiber at its most sensitive (quadrature) position. We describe an extension of the technique to introduce stabilized, pi/2-rad phase steps in a full-field interferometer. The technique was implemented in a single-mode, fiber-optic interference fringe projector used for shape measurement and can be easily applied to other fiber- or bulk-optic interferometers, for example, speckle pattern and holographic interferometers. Fresnel reflections from the distal fiber ends undergo a double pass in the fibers and interfere at the fourth port of a directional coupler. The interference intensity (and hence phase) is maintained at quadrature by feedback control to a phase modulator in one of the fiber arms. Stepping between quadrature positions (separated by pi rad for light undergoing a double pass) introduces stabilized phase steps in the projected fringes (separated by pi/2 rad for a single pass). A root-mean-square phase stability of 0.61 mrad in a 50-Hz bandwidth and phase step accuracy of 1.17 mrad were measured.

Moore, Andrew J.; McBride, Roy; Barton, James S.; Jones, Julian D. C.

2002-06-01

41

Low loss two-step ion-exchanged waveguides with high surface refractive index  

NASA Astrophysics Data System (ADS)

Two-step ion-exchanged waveguides with high surface refractive indices are fabricated under a variety of conditions. By modifying the conventional two-step ion exchange, the losses and the effective diffusion depth can be decreased without a significant effect on the surface refractive index. The influence of the first step, K+-Na+ ion exchange, performed time dependably on the surface refractive index change is investigated. Energy-dispersive x-ray spectroscopy is performed to establish the diffusion profiles of various ions.

Hassanzadeh, Abdollah; Mittler, Silvia

2011-07-01

42

Nonadiabatic fiber taper-based Mach-Zehnder interferometer for refractive index sensing  

NASA Astrophysics Data System (ADS)

A Mach-Zehnder interferometer based on a nonadiabatic fiber taper is proposed for refractive index (RI) sensing. Only the first order cladding guided mode is excited in the down-taper. The radius of the fiber core in the interference region is too thin (<1.64 ?m) to confine the fundamental mode in the fiber core, the fundamental core guided mode is converted to the fundamental cladding guided mode and interference occurs between it and the first order cladding guided mode. The sensitivity of the sensor is 980 nm per refractive index unit for the surrounding refractive index ranging from 1.332 to 1.392.

Xu, Linlin; Li, Ying; Li, Baojun

2012-10-01

43

Dietary glycemic index, glycemic load, insulin index, fiber and whole-grain intake in relation to risk of prostate cancer  

Microsoft Academic Search

Objective  Insulin may play a role in prostate cancer tumorigenesis. Postprandial blood glucose and insulin responses of foods depend\\u000a importantly on the carbohydrate quality and quantity, represented by glycemic index (GI), glycemic load (GL), fiber and whole-grain\\u000a content, but are also influenced by intake of protein and other characteristics. The recently developed insulin index (II)\\u000a quantifies the postprandial insulin secretion, also

K. Nimptsch; S. Kenfield; M. K. Jensen; M. J. Stampfer; M. Franz; L. Sampson; J. C. Brand-Miller; W. C. Willett; E. Giovannucci

2011-01-01

44

Two novel methods for liquid refractive index or concentration measurement using reflex fiber optic sensors  

NASA Astrophysics Data System (ADS)

Two novel content meters for liquid refractive index or concentration measurement are proposed based on the simple reflex fiber optic sensor configurations. One sensor exploits a reflex and concentrically arranged fiber probe structure which is very similar to the traditional intensity-modulated fiber optic displacement sensors, but the light captured by receiving fibers is modulated by the varied solute concentration, being in proportion to the liquid refractive index, instead of displacement. The other sensor works based on detecting the edge shift of the reflected light spot, which is modulated by the refractive index variation of the liquid. Theoretical analysis and simulations are carried out with the measurement range of refractive index from 1.0 to 1.5.

Peng, Bao-jin; Wan, Xu; Wang, Hui; Jin, Hong-zhen; Zhao, Yong

2006-01-01

45

Use of a continuous wave Raman fiber laser in graded-index multimode fiber for SRS beam combination.  

PubMed

We report using a Raman fiber laser (RFL) based on a multimode graded-index fiber as a novel method for beam combination of two continuous wave pump beams. Due to stimulated Raman scattering, the RFL generates a Stokes beam which can be up to 300% brighter than the pump beams. Up to 5.8 W of Stokes power is generated with an optical conversion efficiency of 56%. PMID:19532281

Terry, Nathan B; Engel, Kevin T; Alley, Thomas G; Russell, Timothy H

2007-01-22

46

Use of a continuous wave Raman fiber laser in graded-index multimode fiber for SRS beam combination  

NASA Astrophysics Data System (ADS)

We report using a Raman fiber laser (RFL) based on a multimode graded-index fiber as a novel method for beam combination of two continuous wave pump beams. Due to stimulated Raman scattering, the RFL generates a Stokes beam which can be up to 300% brighter than the pump beams. Up to 5.8 W of Stokes power is generated with an optical conversion efficiency of 56%.

Terry, Nathan B.; Engel, Kevin T.; Alley, Thomas G.; Russell, Timothy H.

2007-01-01

47

BPM-Numerical Study of Microstructured Fiber With High Difference Index Profile  

Microsoft Academic Search

A scalar beam propagation method is used to study confinement losses of air-clad fibers versus their geometrical parameters. The method is also applied to the computation of multimode guidance and pump absorption in two different microstructured fibers with high refractive index difference.

Laure Lavoute; Aude Roy; Philippe Leproux; Philippe Roy; Eric Suran

2008-01-01

48

Singularity avoidance of control moment gyros by one-step ahead singularity index  

NASA Astrophysics Data System (ADS)

A steering law of control moment gyros for spacecraft attitude control by using one-step ahead singularity index is addressed in this paper. In some recent studies, the null motion approaches or singularity robustness steering laws have been extensively investigated to avoid singular configurations for a control momentum gyro (CMG) cluster. As a novel approach different from them, the proposed approach is based on optimization technique by minimizing the one-step ahead singularity index. Modified approaches are also presented in this paper. The proposed one-step prediction method ultimately gives an optimized solution of gimbal rates with advanced ability to avoid a singularity. A singularity index for reliable computation of a gradient vector is also introduced. Finally, performance of the proposed algorithm is demonstrated by numerical simulations.

Leeghim, Henzeh; Bang, Hyochoong; Park, Jong-Oh

2009-05-01

49

The influence of index-depressions in core-pumped Yb-doped large pitch fibers.  

PubMed

Rare-earth doped photonic crystal fibers rely ideally on an index matching of the doped core to the surrounding glass to work properly. Obtaining a perfect index matching is technologically very challenging, and fiber manufacturers opt for targeting an index depression instead, which still ensures the influence of the photonic structure on the light propagation. In this paper the analysis of the influence of this core index depression on the higher-order mode discrimination and on the beam quality of the fundamental mode of different designs of core-pumped active large pitch photonic crystal fibers is discussed. The most promising design is evaluated in terms of mode area scaling with a view to mode field diameters above 100 µm. Detailed requirements on the accuracy of the core index matching are deduced. PMID:21196960

Jansen, Florian; Stutzki, Fabian; Otto, Hans-Jürgen; Baumgartl, Martin; Jauregui, Cesar; Limpert, Jens; Tünnermann, Andreas

2010-12-20

50

Fiber optics: A brief introduction  

Microsoft Academic Search

A basic introduction into the principles of fiber optics is presented. A review of both the underlying physical principles and the individual elements of typical fiber optic systems are presented. The optical phenomenon of total internal reflection is reviewed. The basic construction of the optical fiber is presented. Both step index and graded index fiber designs are reviewed. Multimode and

Michael E. Gruchalla

1989-01-01

51

Physical properties of poly(vinyl alcohol) fibers prepared from wet spinning\\/multi-step drawing  

Microsoft Academic Search

The preparation of poly(vinyl alcohol) (PVA) fibers by multi-step drawing was examined. The high draw ratio was attained when the drawing just before melting point was repeated. The influences of the draw ratio on mechanical and thermal properties of the fibers were studied. We utilized the wide angle x-ray diffraction (WAXD) as a medium to observe the erystallinity and the

Chin-An Link; Kuen-Shan Hwang; Chung-Hua Lin

1994-01-01

52

Propagation and scattering of light in optical fibers with index\\/gain Bragg grating: new class of exactly solvable diffraction problems  

Microsoft Academic Search

Interaction of electromagnetic guided modes with index\\/gain Bragg gratings in step-index round optical fibers is considered theoretically. The analysis includes the construction of exact solution of Maxwell equations in core and cladding regions, which strictly obeys the electromagnetic boundary conditions on core\\/cladding interface and on Bragg grating boundaries. The grating profiles, for which the exact solutions of Maxwell equations can

Victor I. Sokolov; Vladimir N. Seminogov

1995-01-01

53

Estimated glycemic index and dietary fiber content of cookies elaborated with extruded wheat bran.  

PubMed

The increasing demand for high-fiber products has favored the design of numerous bakery products rich in fiber such as bread, cookies, and cakes. The objective of this study was to evaluate the dietary fiber and estimated glycemic index of cookies containing extruded wheat bran. Wheat bran was subjected to extrusion process under three temperature profiles: TP1;(60, 75, 85 and 100 °C), TP2;(60, 80, 100 and 120 °C), and TP3;(60, 80, 110 and 140 °C) and three moisture contents: (15, 23, and 31 %). Cookies were elaborated using extruded wheat bran (30 %), separated into two fractions (coarse and fine). The dietary fiber content of cookies elaborated with extruded wheat bran was higher than the controls; C0 (100 % wheat flour) and C1 (30 % of no extruded bran coarse fraction) and C2 (30 % of no extruded bran fine fraction). The higher values of dietary fiber were observed on cookies from treatments 5 (TP1, 31 % moisture content and coarse fraction) and 11 (TP2, 31 % moisture content and coarse fraction). The estimated glycemic index of cookies ranged from 68.54 to 80.16. The dietary fiber content of cookies was increased and the lowest glycemic index corresponded to the cookies elaborated with extruded wheat bran. Cookie made with the treatment 11 had a better dietary fiber content and lower estimated glycemic index. PMID:23359085

Reyes-Pérez, Faviola; Salazar-García, María Guadalupe; Romero-Baranzini, Ana Lourdes; Islas-Rubio, Alma Rosa; Ramírez-Wong, Benjamín

2013-03-01

54

Dynamic matrix control for the step motion of synchronous motor based on the L? performance index  

Microsoft Academic Search

Based on the infinity norm performance index, dynamic matrix control (DMC) skillfully combines with the step motion, and a novel control technique of synchronous motor is proposed in this paper. It breaks the traditional control method of the drive, and uses the predictive model based on the dynamic information in the rotor position of the synchronous motor, rolling optimization strategy

Ge Baoming; Wang Xiangheng; Su Pengsheng; Jiang Jingping; Sun Hexu

2001-01-01

55

Tapered fiber Mach-Zehnder interferometer for simultaneous measurement of refractive index and temperature  

Microsoft Academic Search

An approach to achieve simultaneous measurement of refractive index and temperature is proposed by using a Mach-Zehnder interferometer realized on tapered single-mode optical fiber. The attenuation peak wavelength of the interference with specific order in the transmission spectrum shifts with changes in the environmental refractive index and temperature. By utilizing S-band and C\\/L-band light sources, simultaneous discrimination of refractive index

Ping Lu; Liqiu Men; Kevin Sooley; Qiying Chen

2009-01-01

56

Preparation of silicalite-1\\/glass fiber composites by one- and two-step hydrothermal syntheses  

Microsoft Academic Search

The crystallization of silicalite-1 on glass fiber supports by one- and two-step hydrothermal synthesis procedures was investigated. One-step synthesis (130, 150 or 170 °C) provided composites with an overall specific surface area of up to 200 m2\\/g. The effect of the starting composition and synthesis parameters on the physico-chemical properties of the composite was studied. The silicalite-1 content of the

O Larlus; V Valtchev; J Patarin; A.-C Faust; B Maquin

2002-01-01

57

Simple fiber optic refractive index sensor based on evanescent higher order modes  

NASA Astrophysics Data System (ADS)

This paper presents an optical fiber refractive index sensor based on the evanescent higher order modes. Its structure and principle are quite simple. The sensor is composed of two segments of optical fibers that are spliced together. An ordinary multimode fiber with a core diameter of 50 ?m is used to input the light. The functions of a second multimode fiber with a core diameter of 200 ?m are twofold. In the region of the splice, a section of the cladding a few centimetre long is removed by an electrical discharge. This part works as a sensing element, and the rest of the fiber is used to output the light. Once the light travels though the input fiber and crosses the splice to enter the second fiber, numerous modes both guided and leaky are generated due to the abrupt increase of the core diameter. The evanescent light fields of these guided modes are sensitive to changes in the refractive index of the material surrounding the fiber cladding. The evanescent field change directly causes a change in the output light intensity. The developed sensor is compact in size, simple to fabricate, promising in performance, and has a high potential for practical applications.

Chen, Jiahua; Bock, Wojtek J.; Mikulic, Predrag

2009-06-01

58

Highly sensitive refractive index sensor based on two cascaded special long-period fiber gratings with rotary refractive index modulation.  

PubMed

We present a refractive index (RI) sensor based on a fiber Mach-Zehnder interferometer (MZI) formed by two cascaded special long-period fiber gratings (LPFGs) with rotary refractive index modulation (RLPFGs), in which the coupling occurred between the guided mode and the high-order asymmetric cladding mode. The experimental results show that the RI sensitivity of a refractometer with an interaction length of 40?mm is up to 58.8?nm/RI in the range of 1.3344 to 1.3637, which is 3.5 times higher than that of an MZI formed by two normal LPFGs. The temperature sensitivity for the same parameters of an RLPFG-MZI is about 0.03?nm/°C. Such a kind of high-sensitivity, easy-to-fabricate and simple-structure interferometer may find applications in the chemical or biochemical sensing fields. PMID:21833138

Fan, Yan-en; Zhu, Tao; Shi, Leilei; Rao, Yun-Jiang

2011-08-10

59

Highly sensitive refractive index sensor based on two cascaded special long-period fiber gratings with rotary refractive index modulation  

NASA Astrophysics Data System (ADS)

We present a refractive index (RI) sensor based on a fiber Mach--Zehnder interferometer (MZI) formed by two cascaded special long-period fiber gratings (LPFGs) with rotary refractive index modulation (RLPFGs), in which the coupling occurred between the guided mode and the high-order asymmetric cladding mode. The experimental results show that the RI sensitivity of a refractometer with an interaction length of 40mm is up to 58.8nm/RI in the range of 1.3344 to 1.3637, which is 3.5 times higher than that of an MZI formed by two normal LPFGs. The temperature sensitivity for the same parameters of an RLPFG-MZI is about 0.03nm° C. Such a kind of high-sensitivity, easy-to-fabricate and simple-structure interferometer may find applications in the chemical or biochemical sensing fields.

Fan, Yan-En; Zhu, Tao; Shi, Leilei; Rao, Yun-Jiang

2011-08-01

60

Optical fiber bend sensor based on fiber Bragg grating in germano-silicate glass optical fiber with depressed-index structure  

NASA Astrophysics Data System (ADS)

An optical fiber bend sensor based on a fiber Bragg grating by using a germano-silicate glass optical fiber with depressed-index structure has been developed and its novel bend sensing characteristics was demonstrated. With the increase of bending, the transmission spectrum was linearly blue-shifted without change of optical transmission loss. Total blue-shift of the Bragg reflection wavelength upon bending in the radius of curvature from 20 m-1 to 133 m-1 was - 0.13 nm.

Ju, Seongmin; Jeong, Seongmook; Kim, Youngwoong; Jang, Myoung-Jin; Kim, Onyu; Han, Won-Taek

2013-05-01

61

Laser emission from the whispering gallery modes of a graded index fiber.  

PubMed

Whispering gallery mode (WGM) laser emission has been observed from rhodamine B doped polymer optical graded index (GI) fiber by transverse pumping with a frequency doubled Q-switched Nd:YAG laser. The propagation and confinement of these modes were also observed. A variation in the free spectral range from 0.29 to 1.24 nm is obtained along the length due to the confinement of WGMs in the GI fiber. PMID:23988929

Linslal, C L; Mathew, S; Radhakrishnan, P; Nampoori, V P N; Girijavallabhan, C P; Kailasnath, M

2013-09-01

62

Fringe Visibility Enhanced Extrinsic Fabry–Perot Interferometer Using a Graded Index Fiber Collimator  

Microsoft Academic Search

We report a fringe visibility-enhanced extrinsic Fabry-Perot interferometer (EFPI) by fusion splicing a quarter-pitch length of a graded-index fiber (GIF) to the lead-in single mode fiber (SMF). The performance of the GIF collimator is theoretically analyzed using a ray matrix model and experimentally verified through beam divergence angle measurements. The fringe visibility of the GIF-collimated EFPI is measured as a

Yinan Zhang; Yanjun Li; Tao Wei; Xinwei Lan; Ying Huang; Genda Chen; Hai Xiao

2010-01-01

63

Estimation of nonlinear refractive index in various silica-based glasses for optical fibers  

NASA Astrophysics Data System (ADS)

The dependence of the nonlinear refractive index n2 on glass compositions for optical fibers is clarified. The relation between n2 and germanium- or fluorine-doped SiO2 is calculated on the basis of the measurement of n 2 at 1.55 mu m with the improved cross-phase-modulation method, taking into account the radial distribution of the optical power in the fibers.

Kato, T.; Suetsugu, Y.; Nishimura, M.

1995-11-01

64

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

65

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.

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

2010-01-01

66

Gradient-index fiber-optic microprobes for minimally invasive in vivo low-coherence interferometry  

NASA Astrophysics Data System (ADS)

We describe the design, construction, and application of what are believed to be the smallest fiber-optic probes used to date during imaging or diagnosis involving low-coherence interferometry (LCI). The probes use novel fiber-optic gradient-index (GRIN) lenses fabricated by a recently developed modified chemical-vapor-deposition (MCVD) process that avoids on-axis aberrations commonly marring MCVD-fabricated GRIN substrate. Fusing GRIN fiber lenses onto single-mode fiber yields automatically aligned all-fiber probes that insert into tissue through hypodermic needles as small as 31-gauge (inner diameter, 127 ?m). We demonstrate the use of such probes with LCI by measuring microscopic brain motions in vivo.

Reed, William A.; Yan, Man F.; Schnitzer, Mark J.

2002-10-01

67

Chalcogenide double index fibers: fabrication, design, and application as a chemical sensor  

SciTech Connect

Double index chalcogenide fibers, based on tellurium, arsenic, and selenium, have been made by an original technique. This technique, based on the build-in-casting method, is achieved in a sealed silica ampoule. In view of the low attenuation obtained in the mid-infrared (IR), these fibers are used to implement Fiber Evanescent Wave Spectroscopy (FEWS). As the IR light is only propagated through the core of the waveguide, a chemical etching is applied in order to remove the glassy cladding of the sensing zone. IR spectra of ethanol and chloroform, recorded with such sensor, are presented showing the high sensitivity of the method.

Le Coq, D.; Boussard-Pledel, C.; Fonteneau, G.; Pain, T.; Bureau, B.; Adam, J.L

2003-10-30

68

Numerical investigation of a refractive index SPR D-type optical fiber sensor using COMSOL multiphysics  

NASA Astrophysics Data System (ADS)

Recently, many programs have been developed for simulation or analysis of the different parameters of light propagation in optical fibers, either for sensing or for communication purposes. In this paper, it is shown the COMSOL Multiphysics as a fairly robust and simple program, due to the existence of a graphical environment, to perform simulations with good accuracy. Results are compared with other simulation analysis, focusing on the surface plasmon resonance (SPR) phenomena for refractive index sensing in a D-type optical fiber, where the characteristics of the material layers, in terms of the type and thickness, and the residual fiber cladding thickness are optimized.

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

2013-03-01

69

ZnO films grown on cotton fibers surface at low temperature by a simple two-step process  

Microsoft Academic Search

Zinc oxide (ZnO) films have been synthesized and deposited onto cotton fiber surface using a simple two-step process. At first step, the cotton fiber surface was coated with a conductive layer of zinc–cellulose complex by rinsing the fibers in zinc chloride solution. After that, the growth of ZnO films was carried out in zinc acetate aqueous solution at room temperature,

Hongjun Wang; Anvar Zakirov; Shavkat U. Yuldashev; Jaechun Lee; Dejun Fu; Taewon Kang

2011-01-01

70

Fiber-Optic Probe Based on a Bifunctional Lensed Photonic Crystal Fiber for Refractive Index Measurements of Liquids  

Microsoft Academic Search

We report a fiber-optic sensor for measuring the re- fractive index (RI) of a liquid sample. The sensing probe is con- structed from an extrinsic cavity formed by a micromirror and a lensedphotoniccrystalfiber(PCF)tip.WeshowthatPCFlenswith an unconventionally large radius of curvature is bifunctional ;a n effective reflector as well as a collimator and thus suitable for re- alizing long single-arm interferometers, with

Gopinath Mudhana; Kwan Seob Park; Seon Young Ryu; Byeong Ha Lee

2011-01-01

71

Femtosecond laser fabricated all-optical fiber sensors with ultrahigh refractive index sensitivity: modeling and experiment  

NASA Astrophysics Data System (ADS)

All-optical fiber sensors based on ultracompact fiber inline Mach-Zehnder interferometer (MZI) are fabricated by side-ablating a U-shape microcavity in a single-mode optical fiber with the fiber core partially removed using femtosecond (fs) laser pulses, in which the two light paths are accordingly formed in the remaining D-type fiber core and the U-shape microcavity. Beam propagation method (BPM) analysis is utilized to illustrate the dependences of good transmission spectra on parameters including the ablation depth, ablation length and the refractive index of U-shape micocavity, which gives some guidelines to optimize parameters for fs laser micromachining and predicts RI (refractive index) sensitivities within given RI ranges. The modeling results of ultrahigh RI sensitivities for gases and solutions are -3243.75 ± 0.65nm/RIU (refractive index unit) and -10789.29 ± 18.91nm/RIU, respectively. In RI testing experiments, the sensor exhibits ultrahigh RI sensitivities of -3754.79 ± 44.24nm/RIU with refractive indices ranging from 1.0001143 to 1.0002187 by testing different mixture ratios of N2 and He gases, and -12162.01 ± 173.92nm/RIU with refractive indices ranging from 1.3330 to 1.33801 by testing different concentrations of sucrose solutions, which is essentially in agreement with the modeling results.

Jiang, Lan; Zhao, Longjiang; Wang, Sumei; Yang, Jinpeng; Xiao, Hai

2011-08-01

72

Effects of the asymmetric refractive index change profile on the reflection spectra of multimode fiber Bragg gratings  

Microsoft Academic Search

In this paper, the effects of the asymmetric refractive index change profile on the reflection spectra of multimode fiber Bragg gratings (MMFBGs) are experimentally and theoretically investigated. Different guided modes in a multimode fiber (MMF) are coupled with each other and the sub-reflection peaks are generated if the refractive index change profile of the MMFBG is asymmetric in the cross

Hong-Gang Yu; Yong Wang; Chun Yang; Qing-Yang Xu; Xiao-Le Yang; Chang-Qing Xu

2005-01-01

73

Graded-index fiber tip optical tweezers: numerical simulation and trapping experiment.  

PubMed

Optical fiber tweezers based on a graded-index multimode fiber (GIMMF) tip is proposed. Light propagation characteristics and gradient force distribution near the GIMMF tip are numerically investigated, which are further compared with that of optical fiber tips based on conventional single mode fibers. The simulated results indicated that by selecting optimal GIMMF length, the gradient force of the GIMMF tip tweezers is about 4 times higher than that of the SMF tip tweezers with a same shape. To prove the feasibility of such a new concept, optical trapping of yeast cells with a diameter of ~5 ?m using the chemically-etched GIMMF tip is experimentally demonstrated and the trapping force is also calculated. PMID:23842403

Gong, Yuan; Ye, Ai-Yan; Wu, Yu; Rao, Yun-Jiang; Yao, Yao; Xiao, Song

2013-07-01

74

Monte Carlo simulation of Goos-Hänchen shifts in multimode step-index plastic optical fibres  

NASA Astrophysics Data System (ADS)

A quantitative example is given for the Goos-Hänchen (GH) shift effect on the ray transit time along a plastic optical fibre (POF) with a step-index profile. A three-dimensional ray-tracing method based on Monte Carlo simulation reported earlier (Kovacevic et al 2005 Appl. Opt. 44 3898) has been adapted for this purpose. The GH shift is considered as a cumulative effect along the length of the optical fibre. Correcting the pulse dispersion in POFs for this shift was found necessary only when the angle ? was near the critical angle ?c.

Kova?evi?, M. S.; Nikezi?, D.

2012-05-01

75

Modeling refractive index change in writing long-period fiber gratings using mid-infrared laser radiation  

NASA Astrophysics Data System (ADS)

The research on the use of fiber sensors based on long-period fiber gratings inscribed by CO2 laser mid-infrared radiation has increased in the last years. In this paper, a set of analytical expressions are used to model the interaction between laser radiation and an optical fiber and to determine the resulting refractive index change. Thermal and residual stress analysis is exemplified for a standard single mode fiber, demonstrating the capability of these models to point out the necessary parameters to achieve proper optical fiber devices based on long period fiber gratings. Experimental results are also presented.

Coelho, João M. P.; Nespereira, Marta C.; Abreu, Manuel; Rebordão, José M.

2013-03-01

76

Dietary fiber intake, dietary glycemic index and load, and body mass index: a cross-sectional study of 3931 Japanese women aged 18–20 years  

Microsoft Academic Search

Objective:Few observational studies have investigated dietary fiber intake and dietary glycemic index (GI) and glycemic load (GL) simultaneously in relation to obesity, particularly in non-Western populations. We examined the associations between dietary fiber intake and dietary GI and GL, and body mass index (BMI) in young Japanese women.Design:Cross-sectional study.Subjects:A total of 3931 female Japanese dietetic students aged 18–20 years from

K Murakami; S Sasaki; H Okubo; Y Takahashi; Y Hosoi; M Itabashi

2007-01-01

77

LLNL Measurements of Graded-Index Multi-Mode Fiber (ITF 47)  

SciTech Connect

The Russian Federal Nuclear Center-All Russian Research Institute of Technical Physics, located in the Nuclear City of Snezhinsk, east of the Ural mountains and the Lawrence Livermore National Laboratories have been investigating the possibility of establishing a commercial optical fiber manufacturing facility. These discussions began in the summer of 1998. At that time three samples (single mode and multi-mode) of optical fiber were left at the Sandia National Laboratory. Sandia measured two of the segments and sent them to LLNL. The optical loss at 1550 nm and 1300 nm were higher than commercially available fiber. The measurements were complicated because the geometry of the fibers also did not meet specification. Since the core was not adequately centered coupling of optical energy into the fiber being tested varied widely depending on which end of the fiber was used for insertion. The results of these measurements were summarized in the informal report dated June 11, 1999, which was hand carried by Dr. Paul Herman during his July 1999 visit. During the July visit a 1.2-km long section of graded-index multimode fiber, ITF 47, was given to Herman. We had requested samples longer than the earlier ones (which were {approx}0.1 km long) in order that a cutback method could be used for the transmission measurements. The optical loss using the cutback technique and the transmission spectral measurements in the 600-1700 mn region are reported. Also physical measurements are reported of the fiber's diameter, concentricity, ellipticity and tensile strength (proof test). The test results are summarized in Table 1, ''Comparative Data for Multi-mode Optical Fiber.'' The table includes the values from the Industrial specification TIA/EIA 402AAAB, the commercial specification for Corning's 50/125 CPC6, the values measured on ITF-47 and provided by C-70, and LLNL's values for ITF-47 as well as the multimode values from the June 1999 samples.

Saito, T.T.

2000-05-01

78

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

79

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

80

Nanowire-based refractive index sensor on the tip of an optical fiber  

NASA Astrophysics Data System (ADS)

This letter presents a refractive index sensor created at the tip of an optical fiber that utilizes silica nanowire within a radius of between 225 nm and 600 nm, as a sensing element. Sensitivity in excess of 800 nm/RIU was demonstrated within an aquatic medium, while the entire sensor structure was shorter than 1 mm with a diameter equal to or less than the standard fiber diameter. The presented sensor structure is made entirely from silica and provides the mechanical protection of sensitive nanowire. The proposed sensor is thus a robust and self-sustained structure, which does not require any complex packing.

Pevec, Simon; Donlagic, Denis

2013-05-01

81

Fabrication quality analysis of a fiber optic refractive index sensor created by CO2 laser machining.  

PubMed

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

2013-03-26

82

Microstructured fiber based plasmonic index sensor with optimized accuracy and calibration relation in large dynamic range  

NASA Astrophysics Data System (ADS)

A novel surface plasmon resonance photonic sensor is proposed using an index-guided microstructured fiber with an analyte channel introduced into the central core. Compared with the previous designs of porous fiber core, variation of the signal amplitude with exterior refractive index is demonstrated to be contrary to that of the sensitivity in the proposed fiber, contributing to optimized detecting accuracy over a large refractive index range of 1.33 to 1.42. By carefully choosing the central channel size, the analyte-filled core can achieve narrower resonance spectral width and higher signal to noise ratio (SNR) than the air-filled core. Sensor responses are also studied in this paper based on two spectral interrogation methods, including monitoring single resonance shift and measuring change in the resonance separation. For both methods, response linearity has been improved considerably through partially filling the core with analyte. The maximal sensitivity reaches 10- 6 refractive index unit (RIU). The linear sensing performance along with the broad measurement range is very promising in the application of the proposed sensor as sensitive refractometer.

Zhang, Yating; Xia, Li; Zhou, Chi; Yu, Xia; Liu, Hairong; Liu, Deming; Zhang, Ying

2011-08-01

83

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

84

Fiber optic based multiparametric spectroscopy in vivo: toward a new quantitative tissue vitality index  

NASA Astrophysics Data System (ADS)

In our previous publication (Mayevsky et al SPIE 5326: 98-105, 2004) we described a multiparametric fiber optic system enabling the evaluation of 4 physiological parameters as indicators of tissue vitality. Since the correlation between the various parameters may differ in various pathophysiological conditions there is a need for an objective quantitative index that will integrate the relative changes measured in real time by the multiparametric monitoring system into a single number-vitality index. Such an approach to calculate tissue vitality index is critical for the possibility to use such an instrument in clinical environments. In the current presentation we are reporting our preliminary results indicating that calculation of an objective tissue vitality index is feasible. We used an intuitive empirical approach based on the comparison between the calculated index by the computer and the subjective evaluation made by an expert in the field of physiological monitoring. We used the in vivo brain of rats as an animal model in our current studies. The rats were exposed to anoxia, ischemia and cortical spreading depression and the responses were recorded in real time. At the end of the monitoring session the results were analyzed and the tissue vitality index was calculated offline. Mitochondrial NADH, tissue blood flow and oxy-hemoglobin were used to calculate the vitality index of the brain in vivo, where each parameter received a different weight, in each experiment type based on their significance. It was found that the mitochondrial NADH response was the main factor affected the calculated vitality index.

Kutai-Asis, Hofit; Barbiro-Michaely, Efrat; Deutsch, Assaf; Mayevsky, Avraham

2006-03-01

85

Hyperspectral optical fiber refractive index measurement spanning 2.5 octaves  

NASA Astrophysics Data System (ADS)

Optical fiber refractive index profiles were measured across a 2.5 octave wavelength range (from 375 nm to 2100 nm) using a single phase-shifting interferometer. This spectral range is more than a factor of 2 larger than previously reported multi-wavelength interferometers, and includes the pump and amplification bands of Er-doped, Yb-doped, Er:Yb-doped, and Tm-doped fibers. The apparatus can measure the material dispersion in a spatially-resolved manner that permits more accurate prediction of the fiber's waveguide properties. The measurement wavelength can be tailored to optimize the beneficial or deleterious effects of material dispersion, optical resolution, and interferometric phase ambiguities.

Yablon, Andrew D.; Jasapara, Jayesh

2013-02-01

86

Nonlinear refractive index of multicomponent glasses designed for fabrication of photonic crystal fibers  

NASA Astrophysics Data System (ADS)

The second order nonlinear refractive index n 2 of various multicomponent glasses was measured at the wavelength of 1240 nm close to the 1.3-?m fiber transmission window. With the refractive index covering the range from 1.45 to 2.3, a comparatively broad range of n 2 with values from 1.1×10-20 m2/W for boro-silicate based glass NC21 to 4.3×10-19 m2/W for lead-bismuth-gallate based glass PBG08 was measured using the Z-scan method. Considering the broad infrared transmission range of multicomponent glasses, these materials pose a great potential for future applications as photonic crystal fiber sources of infrared supercontinuum.

Lorenc, D.; Aranyosiova, M.; Buczynski, R.; Stepien, R.; Bugar, I.; Vincze, A.; Velic, D.

2008-11-01

87

Microchanneled Chirped Fiber Bragg Grating Formed by Femtosecond Laser-Aided Chemical Etching for Refractive Index and Temperature Measurements  

Microsoft Academic Search

In this work, a microchanneled chirped fiber Bragg grating (MCFBG) is proposed and fabricated through the femtosecond laser-assisted chemical etching. The microchannel ( $sim$550 $mu$ m) gives access to the external index liquid, thus inducing refractive index (RI) sensitivity to the structure. In the experiment, the transmission bands induced by the reduced effective index in the microchannel region were used

Hongyan Fu; Kaiming Zhou; Pouneh Saffari; Chengbo Mou; Lin Zhang; Sailing He; Ian Bennion

2008-01-01

88

Top-hat beam output of a single-mode microstructured optical fiber: Impact of core index depression.  

PubMed

A new strategy to obtain a single-mode fiber with a flattened intensity profile distribution is presented. It is based on the use of an OVD-made high index ring deposited on a silica rod having a refractive index slightly lower than the silica used for the microstructured cladding. Using this strategy, we realized the first single-mode fiber with a quasi-perfect top-hat intensity profile around 1 µm. Numerical studies clearly demonstrate the advantage of using a core index depression to insure the single-mode operation of the fiber at the working wavelength. PMID:24104239

Valentin, Constance; Calvet, Pierre; Quiquempois, Yves; Bouwmans, Géraud; Bigot, Laurent; Coulombier, Quentin; Douay, Marc; Delplace, Karen; Mussot, Arnaud; Hugonnot, Emmanuel

2013-10-01

89

Application of the coupled-mode theory to a specialized graded-index optical fiber coupler.  

PubMed

A specialized coupler formed by two identical multimode graded-index slab fibers is described. This special coupler can be used to examine the tilt or the roughness of a surface through the reflected beam. It may also find applications as a mode filter, an alignment sensor, or a feed component of an optical monopulse tracking radar. Coupled-mode theory is generalized for this application. The coupling length for maximum power transfer of the higher-order modes from the excited to the coupled fiber, leaving as much power of the lowest mode as possible to continue in the excited fiber, is computed. The fields are computed at the output of the system for incident optical beams with different axial displacements and beams launched on axis with tilted wavefronts. This desired coupling length is shown to be substantially independent of characteristics of the incident light beam. To compute the fields propagated through the tapered section introduced to separate the slab fibers, the stairwise approximation is used, and mode matching is used to connect the fields at the junctions between the successive segments. An optimum taper to separate the coupled fibers, with minimal perturbation of the fields, is present at the right-hand end of the coupling section. PMID:20725210

Kahn, W K; Saleh, S A

1992-05-20

90

Refractive-Index-Based Sorting of Colloidal Particles Using a Subwavelength Optical Fiber in a Static Fluid  

NASA Astrophysics Data System (ADS)

An optical-fiber-based technique is presented for refractive-index-based sorting of colloidal particles in a static fluid. The method employs the different optical scattering forces exerted by a subwavelength optical fiber on colloidal particles with different refractive indices. By launching two counterpropagating laser beams at wavelengths of 808 and 1047 nm into a fiber of 800 nm diameter, the resultant scattering forces acting on polystyrene and SiO2 particles can be in opposite directions, which leads to a countertransport of the particles along the fiber. Experiments are performed using the fiber to sort the particles of 650 nm size.

Zhang, Yao; Lei, Hongxiang; Li, Baojun

2013-07-01

91

Analysis on the saturation of refractive index modulation in fiber Bragg gratings (FBGs) written by partially coherent UV beams.  

PubMed

We present an analysis on the saturation of refractive index modulation of fiber Bragg gratings written in nonhydrogenated Ge-B co-doped single-mode photosensitive optical fiber by partially coherent pulsed UV beams. The UV beams of different spatial coherence properties were generated by second harmonic conversion of high repetition rate, high average power copper vapor laser (CVL) oscillators with different optical resonators. It is observed that for UV beams of higher spatial coherence, the fiber Bragg grating reflectivity growth was faster and saturation of refractive index modulation was higher. The experimental results are explained with the help of a physical model based on exponential decay of defect centers per unit volume on UV absorption in the fiber core. The subsequent increase in the refractive index was attributed to the structural modification and densification of the fiber core. PMID:22534886

Mahakud, Ramakanta; Prakash, Om; Nakhe, Shankar V; Dixit, Sudhir Kumar

2012-04-20

92

Sensitivity-enhanced refractive index sensor by using tapered thin-core fiber based inline Mach-Zehnder interferometer  

NASA Astrophysics Data System (ADS)

A sensitivity-enhanced optical fiber refractive index sensor based on inline Mach-Zehnder interferometer is proposed. The sensor head is formed by splicing a tapered thin-core diameter fiber between two sections of single mode fibers. The taper (less than 1 mm) plays an important role in improving the sensitivity of the sensor. The sensitivity of refractive index is measured to be 0.447 nm for a 1% change of refractive index in the typical refractive index range of 1.333- 1.3725. The whole fabrication process (including splicing and tapering) can be operated by a commercial fiber splicing machine. The proposed sensor also shows the merits of simple structure, low cost, and easy fabrication.

Shi, Jie; Xiao, Shilin; Bi, Meihua

2011-11-01

93

Estimation of the modal field profile of single mode graded-index fibers from the far-field pattern  

NASA Astrophysics Data System (ADS)

We give a method to estimate the transverse modal field profile of weakly guiding single mode graded-index fibers from the far-field radiation pattern. We also show that if the parameter koa is known, then the q and V values of the fiber can also be determined; here ko is the free space wave number, a the radius of the fiber core, q the profile parameter, and V the normalised frequency.

Tewari, Ramanand; Thyagarajan, K.; Pal, B. P.; Ghatak, A. K.

1982-12-01

94

Fiber In-Line Mach–Zehnder Interferometer Embedded in FBG for Simultaneous Refractive Index and Temperature Measurement  

Microsoft Academic Search

An ultracompact optical fiber sensor based on a Mach-Zehnder interferometer (MZI) embedded in fiber Bragg grating (FBG) is proposed and experimentally demonstrated for simultaneous refractive index (RI) and temperature measurement. By use of the resonant wavelength of the FBG and the interference dip of the MZI, the RI and temperature of the surrounding medium can be unambiguously determined. The interesting

C. R. Liao; Ying Wang; D. N. Wang; M. W. Yang

2010-01-01

95

Investigation of refractive index distribution in different photonic crystal fiber elements  

NASA Astrophysics Data System (ADS)

The paper presents the last data regarding new elements based on photonic crystal fibers such as the low-loss patch cord with a single mode fiber, the fused coupler, the asymmetric coupler for an active fiber power pump. Their fundamental optical characteristics including wavelength depending loss as a coupling ratio are presented in this paper as well as their inner structure (cross section) obtained by SEM. However, the use of SEM for the investigation of the inner element structure is destructive, thus in the last part of the paper we present the tomographic in-line determination of geometry and refractive index distribution changes along the investigated photonic structure. The analysis of different approaches to the photonic crystal fiber data capture with a sufficient optical resolution is given. The data obtained from the Mach-Zehnder interferometer with different laser sources as well as from the in-line digital holographic setup are presented and compared. The further enhancement required for the digital in-line holography is discussed.

Jaroszewicz, Leszek R.; Kujawi?ska, Ma?gorzata; Stasiewicz, Karol; Mar?, Pawe?; Nasi?owski, Tomasz; Murawski, Micha?; Szyma?ski, Micha?; Siwicki, Bart?omiej; Krauze, Wojciech

2011-08-01

96

Time domain measurement of the nonlinear refractive index in optical fibers and semiconductor films  

NASA Astrophysics Data System (ADS)

A new technique to measure the nonlinear refractive index n 2 in optical fibers and semiconductor films has been developed. It is based on the time delay two-beam coupling of very intense picosecond laser pulses that have been self-phase modulated in the nonlinear optical medium. The two beams are coupled in a slow responding medium that is sensitive to time dependent phase distortions. We determine that the amount of phase distortion experienced by the pulse is proportional to the nonlinear refractive index of the medium. This time domain approach can also be applied to optical fiber amplifiers in the presence of gain and to semiconductor films. Because the technique is based on pure refraction the measurement of n 2 is insensitive to nonlinear absorption, thermal effects, and surface roughness. With this technique we have measured n2 in 20-m length of Silica- glass, Ytterbium-doped, and Erbium-doped optical fibers at 1.064-?m. Also we have measured the change of n 2 at 1.064-?m in the presence of a 980-nm pump laser in Yb 3+- doped and Er3+-doped fibers. Finally we have extended the technique to measure n2 in 2-mm thick samples of GaAs, CdTe and ZnTe semiconductors. In the language of ultrafast spectroscopist, if the best tool to characterize an ultrashort optical pulse is the pulse itself, then the best tool to characterize an optical nonlinear medium is a pulse that has been modified by the medium.

Garcia, Hernando

2000-11-01

97

The effect of ATP analogs on posthydrolytic and force development steps in skinned skeletal muscle fibers.  

PubMed Central

ATP, 2-deoxy ATP (dATP), CTP, and UTP support isometric force and unloaded shortening velocity (Vu) to various extents (Regnier et al., Biophys. J. 74:3044-3058). Vu correlated with the rate of cross-bridge dissociation after the power stroke and the steady-state hydrolysis rate in solution, whereas force was modulated by NTP binding and cleavage. Here we studied the influence of posthydrolytic cross-bridge steps on force and fiber shortening by measuring isometric force and stiffness, the rate of tension decline (kPi) after Pi photogeneration from caged Pi, and the rate of tension redevelopment (ktr) after a sudden release and restretch of fibers. The slope of the force versus [Pi] relationship was the same for ATP, dATP, and CTP, but for UTP it was threefold less. ktr and kPi increased with increasing [Pi] with a similar slope for ATP, dATP, and CTP, but had an increasing magnitude of the relationship ATP < dATP < CTP. UTP reduced ktr but increased kPi. The results suggest that the rate constant for the force-generating isomerization increases with the order ATP < dATP < CTP < UTP. Simulations using a six-state model suggest that increasing the force-generating rate accounts for the faster kPi in dATP, CTP, and UTP. In contrast, ktr appears to be strongly affected by the rates of NTP binding and cleavage and the rate of the force-generating isomerization.

Regnier, M; Homsher, E

1998-01-01

98

Effects of thickness and external refractive index in coated tilted fiber Bragg gratings  

NASA Astrophysics Data System (ADS)

In this work, an experimental analysis on the spectral effects induced by depositing a uniform high refractive index (HRI) thin coating on weakly tilted fiber Bragg gratings (TFBGs) is carried out. First, two weakly TFBGs presenting different tilt angles were fabricated. Successively, by using dip-coating technique, two different coating thicknesses were deposited on each of them. The transmission spectra of the obtained structures were collected as the surrounding refractive index (SRI) changed in the range 1÷1.47. The coated gratings present some differences in their spectral evolution, that can be opportunely exploited. The coated configuration could improve some aspects of previous demodulation techniques exploited in the case of bare TFBGs. Moreover, an important effect of HRI coatings is to enhance the SRI sensitivity of the spectral position of the dips corresponding to cladding modes coupling, leading to a different interrogation method for sensing applications.

Paladino, D.; Pilla, P.; Cutolo, A.; Campopiano, S.; Giordano, M.; Cusano, A.; Caucheteur, C.; Mégret, P.

2007-07-01

99

How to measure cortical folding from MR images: a step-by-step tutorial to compute local gyrification index.  

PubMed

Cortical folding (gyrification) is determined during the first months of life, so that adverse events occurring during this period leave traces that will be identifiable at any age. As recently reviewed by Mangin and colleagues(2), several methods exist to quantify different characteristics of gyrification. For instance, sulcal morphometry can be used to measure shape descriptors such as the depth, length or indices of inter-hemispheric asymmetry(3). These geometrical properties have the advantage of being easy to interpret. However, sulcal morphometry tightly relies on the accurate identification of a given set of sulci and hence provides a fragmented description of gyrification. A more fine-grained quantification of gyrification can be achieved with curvature-based measurements, where smoothed absolute mean curvature is typically computed at thousands of points over the cortical surface(4). The curvature is however not straightforward to comprehend, as it remains unclear if there is any direct relationship between the curvedness and a biologically meaningful correlate such as cortical volume or surface. To address the diverse issues raised by the measurement of cortical folding, we previously developed an algorithm to quantify local gyrification with an exquisite spatial resolution and of simple interpretation. Our method is inspired of the Gyrification Index(5), a method originally used in comparative neuroanatomy to evaluate the cortical folding differences across species. In our implementation, which we name local Gyrification Index (lGI(1)), we measure the amount of cortex buried within the sulcal folds as compared with the amount of visible cortex in circular regions of interest. Given that the cortex grows primarily through radial expansion(6), our method was specifically designed to identify early defects of cortical development. In this article, we detail the computation of local Gyrification Index, which is now freely distributed as a part of the FreeSurfer Software (http://surfer.nmr.mgh.harvard.edu/, Martinos Center for Biomedical Imaging, Massachusetts General Hospital). FreeSurfer provides a set of automated reconstruction tools of the brain's cortical surface from structural MRI data. The cortical surface extracted in the native space of the images with sub-millimeter accuracy is then further used for the creation of an outer surface, which will serve as a basis for the lGI calculation. A circular region of interest is then delineated on the outer surface, and its corresponding region of interest on the cortical surface is identified using a matching algorithm as described in our validation study(1). This process is repeatedly iterated with largely overlapping regions of interest, resulting in cortical maps of gyrification for subsequent statistical comparisons (Fig. 1). Of note, another measurement of local gyrification with a similar inspiration was proposed by Toro and colleagues(7), where the folding index at each point is computed as the ratio of the cortical area contained in a sphere divided by the area of a disc with the same radius. The two implementations differ in that the one by Toro et al. is based on Euclidian distances and thus considers discontinuous patches of cortical area, whereas ours uses a strict geodesic algorithm and include only the continuous patch of cortical area opening at the brain surface in a circular region of interest. PMID:22230945

Schaer, Marie; Cuadra, Meritxell Bach; Schmansky, Nick; Fischl, Bruce; Thiran, Jean-Philippe; Eliez, Stephan

2012-01-02

100

Optimization of the Refractive-Index Distribution of Graded-Index Polymer Optical Fiber by the Diffusion-Assisted Fabrication Process  

NASA Astrophysics Data System (ADS)

Graded-index polymer optical fiber (GI-POF) is a promising high-speed communication medium for very-short-reach networks, such as home or office networks. The refractive-index distribution of GI-POF needs to be accurately controlled to maximize the bandwidth. We attempted to control the refractive-index distribution by developing a simulation for dopant diffusion. In the rod-in-tube method, GI-POF with an optimal refractive-index distribution was obtained by adjusting the diffusion temperature and the diffusion time, whereas in the coextrusion process, GI-POF with an optimal refractive-index distribution was fabricated by controlling the length of the diffusion tube and the rate of discharge of polymer.

Mukawa, Yoshiki; Kondo, Atsushi; Koike, Yasuhiro

2012-04-01

101

Effect of fiber tapering in LPG-based Mach-Zehnder modal interferometers for refractive-index sensing  

Microsoft Academic Search

In this work, an LPG-based Mach-Zehnder modal interferometer with a tapered fiber section between the two LPGs is studied as a sensing structure for measuring environmental refractive index. To interrogate this sensing device, coherence addressing and pseudo-heterodyne processing were used. A fiber taper was made between the two LPGs to improve and tailor the sensitivity of the sensor. Experimental results

P. Caldas; P. A. S. Jorge; F. Araújo; L. A. Ferreira; G. Rego; J. L. Santos

2009-01-01

102

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 interferometer was realized by concatenating two single-mode fiber tapers separated by a middle section. The proposed device had a minimum insertion loss of 3 dB and maximum interferometric extinction ratio over 20 dB. The resolution (0.171 nm) of the two-taper sensor to its 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

103

Using of Intelligent Particle Swarm Optimization Algorithm to Synthesis the Index Modulation Profile of Narrow Ban Fiber Bragg Grating Filter  

Microsoft Academic Search

A new method for synthesis of fiber Bragg gratings based filter is proposed. By combining the transmission matrix method and\\u000a the particles swarm optimization algorithm, we obtain a novel method for the inverse problem of the synthesizing fiber gratings.\\u000a With adjusting the parameters of the PSO algorithm we can get the demand index modulation for the target reflection spectrums\\u000a including

Yumin Liu; Zhongyuan Yu

2006-01-01

104

Radiation Hard Fiber Optics.  

National Technical Information Service (NTIS)

A study of radiation-inducted absorption in low-loss optical waveguides is reported. Step-index optical fibers were prepared from preforms fabricated by the CVD method. The germanium silicate core glass in the fibers was doped with varying amounts of anti...

R. E. Jaeger M. Aslami

1981-01-01

105

Fiber Optic Sensor for the Measurement of Concentration and Refractive Index of Liquids Based on Intensity Modulation  

NASA Astrophysics Data System (ADS)

This paper reports the use of fiber optic sensor consists of two-fiber probe and reflector for the measurement of concentration and refractive index of liquids based on the reflective intensity modulation. Conventionally such a sensor is used for measuring micro-displacement of fiber tip with reference to the reflector. In one of the previously reported work we have established that if the separation between fiber tips and reflector is maintained constant the same arrangement can be directly used for sensing refractive index changes of medium. The liquid under test fills the gap between probe and reflector. Depending upon the refractive index of liquid, angle of emittance will change which will decide the received output power by receiving fiber. Apart from pure solvents which have different refractive indices, there are mixtures of various types which also alter the refractive index of a given medium. The developed sensor is used to detect the concentration of the alcohols like methanol & ethylene glycol in mixture with water.

Chaudhari, A. L.; Shaligram, A. D.

106

Refractive index profiles of Ge-doped optical fibers with nanometer spatial resolution using atomic force microscopy.  

PubMed

We show a quantitative connection between Refractive Index Profiles (RIP) and measurements made by an Atomic Force Microscope (AFM). Germanium doped fibers were chemically etched in hydrofluoric acid solution (HF) and the wet etching characteristics of germanium were studied using an AFM. The AFM profiles were compared to both a concentration profile of the preform determined using a Scanning Electron Microscope (SEM) and a RIP of the fiber measured using a commercial profiling instrument, and were found to be in excellent agreement. It is now possible to calculate the RIP of a germanium doped fiber directly from an AFM profile. PMID:19474968

Pace, P; Huntington, Shane; Lyytikäinen, K; Roberts, A; Love, J

2004-04-01

107

Influence of the drawing process on the defect generation in multistep-index germanium-doped optical fibers.  

PubMed

Variation of germanium lone pair center (GLPC) concentration in germanosilicate multistep-index optical fibers and preforms was studied using confocal microscopy luminescence technique. The experimental results provide evidence that in the central core region ([Ge] approximately 11 wt.%) of our specific canonical samples the ratio [GLPC]/[Ge] is five times larger in fiber than in preforms. The relative influence of the glass composition and of the drawing process on the generation efficiency of the GLPC defects that drive the glass photosensitivity is discussed. The radial distribution of these defects suggests a possible enhancement of the defect creation related to the internal stress of the fiber core. PMID:19649071

Origlio, G; Cannas, M; Girard, S; Boscaino, R; Boukenter, A; Ouerdane, Y

2009-08-01

108

Brillouin gain spectrum dependence on large strain in perfluorinated graded-index polymer optical fiber.  

PubMed

We investigate the dependence of Brillouin gain spectra on large strain of > 20% in a perfluorinated graded-index polymer optical fiber, and prove, for the first time, that the dependence of Brillouin frequency shift (BFS) is highly non-monotonic. We predict that temperature sensors even with zero strain sensitivity can be implemented by use of this non-monotonic nature. Meanwhile, the Stokes power decreases rapidly when the applied strain is > ~10%. This behavior seems to originate from the propagation loss dependence on large strain. By exploiting the Stokes power dependence, we can probably solve the problem of how to identify the applied strain, when the identification is difficult only by BFS because of its non-monotonic nature. PMID:23037233

Hayashi, Neisei; Mizuno, Yosuke; Nakamura, Kentaro

2012-09-10

109

Surface plasmon resonance based fiber optic refractive index sensor utilizing silicon layer: Effect of doping  

NASA Astrophysics Data System (ADS)

We present an experimental study on the surface plasmon resonance (SPR) based fiber optic refractive index sensor utilizing a high index silicon layer between a metal layer and sensing medium using the wavelength interrogation mode of operation. Both n- and p-type silicon have been used. For the metal layer, silver and gold have been used. For a given metal, experimental results predict higher sensitivity of the sensor for the n-type silicon than for the p-type silicon layer. Further, for a given type of silicon, the sensitivity for the gold coated probe is higher than that of the silver coated probe. Numerically, the sensitivity of the n-type silicon with silver as the metal layer is approximately 1.39 times higher than that of the p-type silicon. In the case of gold as the metal layer, the sensitivity of the n-type silicon is approximately 1.50 times that of the p-type silicon. Since the refractive index of both p-type and n-type silicon is the same it appears that the majority charge carriers in silicon play an important role in the sensitivity of the surface plasmon resonance based sensor. The charge carriers are either affecting the field in the analyte region or may be somehow affecting the propagation constant of the surface plasmon wave which is solely due to oscillation of free electrons in the metal layer. In addition, the sensitivity of only the metal coated probes is found to lie between their p-type and n-type silicon coated probes. This suggests that the effect of charge carriers on sensitivity is more than the refractive index of the silicon layer. The effects of charge carriers in silicon, electrons and holes appears to be opposite.

Bhatia, Priya; Gupta, , Banshi D.

2013-01-01

110

Photonic Crystal Fiber Mach-Zehnder Interferometer for Refractive Index Sensing  

PubMed Central

We report on a refractive index sensor using a photonic crystal fiber (PCF) interferometer which was realized by fusion splicing a short section of PCF (Blaze Photonics, LMA-10) between two standard single mode fibers. The fully collapsed air holes of the PCF at the spice regions allow the coupling of PCF core and cladding modes that makes a Mach-Zehnder interferometer. The transmission spectrum exhibits sinusoidal interference pattern which shifts differently when the cladding/core surface of the PCF is immersed with different RI of the surrounding medium. Experimental results using wavelength-shift interrogation for sensing different concentrations of sucrose solution show that a resolution of 1.62 × 10?4–8.88 × 10?4 RIU or 1.02 × 10?4–9.04 × 10?4 RIU (sensing length for 3.50 or 5.00 cm, respectively) was achieved for refractive indices in the range of 1.333 to 1.422, suggesting that the PCF interferometer are attractive for chemical, biological, biochemical sensing with aqueous solutions, as well as for civil engineering and environmental monitoring applications.

Wang, Jian-Neng; Tang, Jaw-Luen

2012-01-01

111

Photonic crystal fiber Mach-Zehnder interferometer for refractive index sensing.  

PubMed

We report on a refractive index sensor using a photonic crystal fiber (PCF) interferometer which was realized by fusion splicing a short section of PCF (Blaze Photonics, LMA-10) between two standard single mode fibers. The fully collapsed air holes of the PCF at the spice regions allow the coupling of PCF core and cladding modes that makes a Mach-Zehnder interferometer. The transmission spectrum exhibits sinusoidal interference pattern which shifts differently when the cladding/core surface of the PCF is immersed with different RI of the surrounding medium. Experimental results using wavelength-shift interrogation for sensing different concentrations of sucrose solution show that a resolution of 1.62 × 10(-4)-8.88 × 10(-4) RIU or 1.02 × 10(-4)-9.04 × 10(-4) RIU (sensing length for 3.50 or 5.00 cm, respectively) was achieved for refractive indices in the range of 1.333 to 1.422, suggesting that the PCF interferometer are attractive for chemical, biological, biochemical sensing with aqueous solutions, as well as for civil engineering and environmental monitoring applications. PMID:22736988

Wang, Jian-Neng; Tang, Jaw-Luen

2012-03-02

112

Multigigabit/s perfluorinated graded-index plastic-optical-fiber data links with butt-coupled single-mode InGaAs VCSEL  

NASA Astrophysics Data System (ADS)

Vertical-cavity surface-emitting lasers (VCSELs) with emission wavelengths in the range from 850 nm to 950 nm are highly attractive light sources for low-cost, high-speed data transmission over several hundred meters of perfluorinated graded-index plastic-optical fibers (GI- POFs). Multi-Gigabit/s data transmission over common PMA- based step-index POFs is generally limited to several meters predominantly due to dispersion. Here, we demonstrate 3 Gbit/s and 7 Gbit/s pseudo-random-bit-sequence non-return- to-zero data transmission over 80 m perfluorinated GI-POF made of CYTOP using a single mode butt-coupled selectively oxidized InGaAs VCSEL source emitting at 935 nm emission wavelength. For 3 Gbit/s data rather the received optical power for a bit error rate (BER) of 10-11 is -22.5 dBm for back-to-back (BTB). A power penalty of 1 dB is found for transmission over 100 m graded-index multimode glass fiber and 2 dB for 80 m GI-POF for 80 m GI- POF transmission. Reduced power penalty observed at 7 Gbit/s is attributed to the restricted modulation bandwidth of the VCSEL used in the experiment.

Mederer, Felix; Jaeger, Roland; Schnitzer, Peter; Unold, Heiko J.; Kicherer, Max; Ebeling, Karl J.; Naritomi, Masaki; Yoshida, Ryouta

1999-11-01

113

Design and fabrication of efficient diffraction transmission gratings on step-index optical waveguides  

Microsoft Academic Search

High-efficiency and low-loss constant periodicity gratings have been fabricated and evaluated on single-mode planar optical waveguides. The most important parameters that will affect the lens performance are the coupling coefficient and the Q (or rho) factor. The coupling coefficient has been found to depend on the mode-index change. An investigation of the mode-index change has shown that for small groove

J.-M. P. Delavaux; W. S. C. Chang

1984-01-01

114

A High-Quality Mach-Zehnder Interferometer Fiber Sensor by Femtosecond Laser One-Step Processing  

PubMed Central

During new fiber sensor development experiments, an easy-to-fabricate simple sensing structure with a trench and partially ablated fiber core is fabricated by using an 800 nm 35 fs 1 kHz laser. It is demonstrated that the structure forms a Mach-Zehnder interferometer (MZI) with the interference between the laser light passing through the air in the trench cavity and that in the remained fiber core. The fringe visibilities are all more than 25 dB. The transmission spectra vary with the femtosecond (fs) laser ablation scanning cycle. The free spectral range (FSR) decreases as the trench length increases. The MZI structure is of very high fabrication and sensing repeatability. The sensing mechanism is theoretically discussed, which is in agreement with experiments. The test sensitivity for acetone vapor is about 104 nm/RIU, and the temperature sensitivity is 51.5 pm/°C at 200 ? 875 °C with a step of 25 °C.

Zhao, Longjiang; Jiang, Lan; Wang, Sumei; Xiao, Hai; Lu, Yongfeng; Tsai, Hai-Lung

2011-01-01

115

High-contrast step-index waveguides in borate nonlinear laser crystals by 3D laser writing  

NASA Astrophysics Data System (ADS)

We report the ultrafast fabrication of high-contrast step-index channel waveguides in Nd3+:YCa4O(BO3)3 borate laser crystals by means of 3D direct laser writing. Guiding up to 3.4 ?m wavelength is demonstrated for the first time in a laser written crystalline waveguide. Modeling the measured fundamental modes at the wavelengths of 1.9 ?m and 3.4 ?m allowed us to estimate the high laser-induced refractive index increments (index contrasts) to be 0.010 (0.59%), and 0.005 (0.29%), respectively. Confocal ?-Raman spectral imaging of the waveguides cross-sections confirmed that the cores have very well defined step profiles, and that the increase in the refractive index can be linked to the localized creation of permanent intrinsic defects. These results indicate that this crystalline waveguides are a potential candidate for the development of 3D active waveguide circuits, due to the laser and electro-optic properties of rare earth doped borate crystals.

Rodenas, Airan; Kar, Ajoy K.

2011-08-01

116

High-contrast step-index waveguides in borate nonlinear laser crystals by 3D laser writing.  

PubMed

We report the ultrafast fabrication of high-contrast step-index channel waveguides in Nd(3+):YCa(4)O(BO(3))(3) borate laser crystals by means of 3D direct laser writing. Guiding up to 3.4 ?m wavelength is demonstrated for the first time in a laser written crystalline waveguide. Modeling the measured fundamental modes at the wavelengths of 1.9 µm and 3.4 µm allowed us to estimate the high laser-induced refractive index increments (index contrasts) to be 0.010 (0.59%), and 0.005 (0.29%), respectively. Confocal µ-Raman spectral imaging of the waveguides cross-sections confirmed that the cores have very well defined step profiles, and that the increase in the refractive index can be linked to the localized creation of permanent intrinsic defects. These results indicate that this crystalline waveguides are a potential candidate for the development of 3D active waveguide circuits, due to the laser and electro-optic properties of rare earth doped borate crystals. PMID:21935150

Rodenas, Airan; Kar, Ajoy K

2011-08-29

117

Modal Interferometer Based on a C-Shaped Ultrathin Fiber Taper for High-Sensitivity Refractive Index Measurement  

NASA Astrophysics Data System (ADS)

The ultrathin fiber taper fabricated by adiabatically stretching a heated single-mode optical fiber (SMF) is made in a C-shape bent to form a modal interferometer. The interference fringes due to the mode beating in the multimode taper waist are dependent on the bending radius. Under an optimized bending radius, a maximum 18 dB interference depth can be obtained. The influence of the fiber taper geometry on the interference fringes is discussed. The proposed modal interferometer has a high refractive index (RI) sensitivity of ˜658 nm/RIU (refractive index unit) for RI= 1.333{--}1.353, which is expected to be useful for precision bio/chemical sensing applications.

Luo, Haimei; Li, Xinwan; Zou, Weiwen; Jiang, Wenning; Chen, Jianping

2012-01-01

118

Elementary steps of the cross-bridge cycle in fast-twitch fiber types from rabbit skeletal muscles.  

PubMed

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 Ca(2+)-activated at 20 degrees C and the effects of MgATP, phosphate (P, P(i)), 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 (k(2), 198-526 s(-1); k(-2), 51-328 s(-1); k(4), 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), k(4)) varied more among fiber types than their reversals (k(2), k(-4)). The equilibrium constants K(1) (MgATP affinity) and K(2) (=k(2)/k(-2), ATP isomerization) were progressively less in the order IIA, IID, and IIB. K(4) (=k(4)/k(-4), force generation) and K(5) (P(i) affinity) were larger in IIB than IIA and IID fibers. K(1) 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 (K(0)) was larger in type IID fibers than in type IIB fibers. PMID:16143633

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

2005-09-02

119

A Simplified Technique for Efficient Fiber-Polymer-Waveguide Power Coupling Using a Customized Cladding With Tunable Index of Refraction  

NASA Astrophysics Data System (ADS)

A novel technique to minimize the mode mismatch between the fiber and waveguide modes in integrating optical fiber to polymer waveguides is presented. The mode fields at the facets of the waveguides were tailored, optimizing the waveguide geometry as well as tuning the index of refraction of the lower cladding near the facets, by chemical composition. No additional processes were required after the core was deposited. The modified lower cladding can be integrated efficiently with any other lower-cladding material used in the remaining portion of the waveguide, resulting in hybrid waveguides. A power-coupling loss as low as 0.46 dB at the fiber-waveguide interfaces was demonstrated with the available fiber.

Sanghadasa, Mohan; Ashley, Paul R.; Webster, Eric L.; Cocke, Carys; Lindsay, Geoffrey A.; Guenthner, Andrew J.

2006-10-01

120

An optical continuous phase FSK modulation scheme with an arbitrary modulation index over long-haul transmission fiber link  

NASA Astrophysics Data System (ADS)

This paper presents an optical continuous phase frequency shift keying (CPFSK) modulation scheme with an arbitrary modulation index. The detailed principle on the optical CPFSK generation is derived and analyzed, which includes the special case of the minimum-shift keying (MSK) with a modulation index h = 1/2. The differential detection and the coherent detection of CPFSK are also depicted. The performances of the four kinds of the optical CPFSK modulated system with a 40 Gb/s modulation rate whose modulation index are h = 1/2, h = 2/3, h = 3/4 and h = 1 are simulated via the spectral efficiency and the receiver sensitivity over fiber link respectively. In addition, comparison with the differential phase shift keying (DPSK) is taken. Through the calculation of the spectral efficiency of each modulation formats, CPFSK has higher spectral efficiency than DPSK with the same optical devices. The transmission performances of our CPFSK over the fiber link change better as the modulation index increases under the condition of the first order dispersion of the fiber link is completely compensated. Through simulations, a 1200 km transmission distance can be achieved with a modulation index h = 1.

Zou, Ning; Li, Wei; Huang, Benxiong; Xu, Zhengguang; Xu, Shuhua; Yang, Caihong

2012-05-01

121

FIBER AND INTEGRATED OPTICS: Experimental investigation of energy transfer between modes in a graded-index fiber waveguide with periodic microbending of the axis  

NASA Astrophysics Data System (ADS)

An experimental investigation was made of energy transfer between the lowest axially symmetric modes in a multimode graded-index fiber waveguide as a function of the amplitude of periodic bending of its axis. Selective excitation and detection of given modes in a waveguide was induced with the aid of synthesized holograms. The experimental curves were in satisfactory agreement with the results of a theoretical calculation and confirmed that the sensitivity of a mode to bending of the axis of a graded-index waveguide increased on increase in the mode number.

Garichev, V. P.; Krivoshlykov, S. G.; Jahn, I.-U.

1990-08-01

122

Simultaneous measurement of temperature and refractive index using a simplified modal interferometer composed of tilted long-period fiber grating and fiber bitaper  

NASA Astrophysics Data System (ADS)

A simplified long-period fiber-grating-based Mach-Zehnder interferometer (MZI) for simultaneous temperature and refractive index (RI) measurement is presented. The sensing element is constructed by connecting a waist-enlarged fiber bitaper after a tilted long-period fiber grating written by high-frequency CO2 laser pulses, which has higher writing efficiency than the conventional long-period fiber grating (LPFG). By employing the proposed MZI, the transmission bandwidth for each resonant wavelength of the fiber grating could be conveniently reduced without the presence of the LPFG pair. Experimental results indicate that the MZI has good temperature sensitivity (70.42 pm °C-1) and RI sensitivity (-37.43 nm/RIU, in the RI range from 1.3425 to 1.3750). Besides, the extinction ratio of interference fringes could reach 20 dB at the resonant wavelength. With several advantages such as narrow bandwidth, large extinction ratio, simple structure and ease of fabrication, the proposed device would be a promising candidate for precise large-capacity dual-parameter sensing application.

Xue, Xiaolin; Zhang, Weigang; Zhang, Hao; Gao, Shecheng; Geng, Pengcheng; Bai, Zhiyong; Li, Jieliang

2013-06-01

123

All fiber chirped-pulse amplification system based on compression in air-guiding photonic bandgap fiber  

Microsoft Academic Search

We report on the experimental demonstration of an all fiber CPA system based on a step-index fiber stretcher and an air-guiding photonic crystal fiber compressor. The ultrafast fiber laser system producing an average power of 6.0 W with 100-fs pulses at 73 MHz, what corresponds to a peak power out of the compressor fiber of 0.82 MW. This completely fiber

J. Limpert; T. Schreiber; S. Nolte; H. Zellmer; A. Tünnermann

2003-01-01

124

Content analysis of uterine cervix images: initial steps toward 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

125

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....

126

Inline core-cladding intermodal interferometer based on nano-coated photonic crystal fiber for refractive-index sensing  

NASA Astrophysics Data System (ADS)

The paper presents a modification of the refractive-index (RI) response of a photonic crystal fiber (PCF) based intermodal interferometer using a thin plasma-deposited silicon nitride (SiNx) overlay with a high refractive index. We show that the film overlay can effectively change the distribution of the cladding modes and thus tune the RI sensitivity of the interferometer. Thanks to the nano-coating we were able to increase RI sensitivity eightfold in the range required for biosensors (nD~1.33). Due to the extreme hardness of SiNx films and their excellent adhesion to the fiber surface, we believe that after the deposition the device can still maintain its advantages, i.e. lack of degradation over time or with temperature.

Smietana, Mateusz; Brabant, Daniel; Bock, Wojtek J.; Mikulic, Predrag; Eftimov, Tinko

2011-05-01

127

Optimum index profile of the perfluorinated polymer-based GI polymer optical fiber and its dispersion properties  

Microsoft Academic Search

The significant advantages in bandwidth and low material dispersion of perfluorinated (PF) polymer-based graded-index polymer optical fiber (GI POF) are theoretically and experimentally reported for the first time. It is confirmed that the low attenuation and low material dispersion of the PF polymer enables 1 Gb\\/s km and 10 Gb\\/s km transmission at 0.85-?m and 1.3-?m wavelengths, respectively. The PF

Takaaki Ishigure; Yasuhiro Koike; James W. Fleming

2000-01-01

128

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

129

Solid-Core Photonic Bandgap Fibers for High-Power Fiber Lasers  

Microsoft Academic Search

An overview of various designs of large-mode-area photonic bandgap fibers (PBGFs) is presented in this paper. Bending properties of these structures are discussed and compared with those of step-index and air-silica microstructured fibers. Peculiarities of active PBGF fabrication are considered, and novel high-power laser architecture based on such fibers is described.

Evgeny M. Dianov; Mikhail E. Likhachev; S. Fevrier

2009-01-01

130

Spectral reflectance of conodonts: A step toward quantitative color alteration and thermal maturity indexes  

SciTech Connect

Changes in the color of conodonts have long been used to assess thermal maturity. Color is a subjective measure, and color changes in conodonts are related to a subjective scale, the conodont alteration index or CAI. In this paper, we propose a simple, nondestructive method for objectively determining CAI and relating CAI to thermal maturity, the spectral reflectance of conodonts (SRC). The diffuse reflectance of about 30 large conodont fragments arranged on a barium-sulfate slide was determined with a total reflectance spectrophotometer in the wavelength range of 300-850 nm. By examining conodonts that ranged form a CAI of 1 to a CAI of 6 we found that the average slope of the reflectance curve from 550 to 800 nm is a good proxy for CAI. A second-order regression equation estimates CAI from this slope with high accuracy (correlation coefficient = 0.99). These estimates appear most accurate for a CAI of 1 to a CAI of 4, where the slopes change most rapidly, but give reasonable results up to a CAI of 6. Based on the results of our analysis of two samples with known thermal maturities form the Valles Caldera region of New Mexico, we propose a preliminary relationship among SRC slope, CAI, and in-situ alteration temperature.

Deaton, B.C. [Texas Wesleyan Univ., Fort Worth, TX (United States); Nestell, M.; Balsam, W.L. [Univ. of Texas, Arlington, TX (United States)

1996-07-01

131

Effects of the absorption coefficient on the refractive index of germanium in a fiber optic-semiconductor temperature sensor  

NASA Astrophysics Data System (ADS)

This paper introduces a theoretical model which reveals the relation between the absorption and the refractive index of germanium within absorption region, which is crucial to a new fiber optic-semiconductor film temperature sensor developed lately in our lab. The new designed sensor is based on the effect of the temperature dependence of the refractive index of semiconductor. Many efforts on the effect of the temperature-dependent refractive index of semiconductor are reported in transparent region mostly by empirical model such as Sellmeier model[1]. We analyze the temperature dependence of the refractive index of semiconductor near the absorption edge other than in the transparent region. From the Kramers-Kronig relations, the refractive index is an integral of the absorption coefficient over the whole energy spectrum.Taking advantage of the model that explained the contribution of the integral cloesd to the absorption edge to the refractive index by Frank Stern [2] we are able to calculate the variation of the refractive index due to the thermal shift of absorption edge. The contribution of the temperature-dependent absorption coefficient to the refractive index is enhanced dramatically at the absorption edge of semiconductor, where the temperature dependence of the energy gap Eg can be used to get the absorption edge shift with Yu-Brook's model[3]. While the contribution of the absorption shift far away from the absorption edge to ?n is negligible comparing to that near the edge according to Frank Stern[2]. Further demonstration experiments will be carried out to support our theory, in which refractive indexes of germanium are measured at specific wavelengths of 1310nm, 1550nm and 2000nm. Since the direct absorption edge of germanium is at about 0.82eV, corresponding to the wavelength of 1550nm, we estimate that the thermo-optic coefficient dn/dT of germanium at 1550nm would be larger than that at 1310nm and 2000nm.

Peng, Liu; Min, Li; Zhong, Pan

2011-11-01

132

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.

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

2011-01-01

133

Modal dispersion, pulse broadening and maximum transmission rate in GRIN optical fibers encompass a central dip in the core index profile  

NASA Astrophysics Data System (ADS)

Intermodal and intramodal dispersions signify one of the problems in graded-index multi-mode optical fibers (GRIN) used for LAN communication systems and for sensing applications. A central index dip (depression) in the profile of core refractive-index may occur due to the CVD fabrication processes. The index dip may also be intentionally designed to broaden the fundamental mode field profile toward a plateau-like distribution, which have advantages for fiber-source connections, fiber amplifiers and self-imaging applications. Effect of core central index dip on the propagation parameters of GRIN fiber, such as intermodal dispersion, intramodal dispersion and root-mean-square broadening, is investigated. The conventional methods usually study optical signal propagation in optical fiber in terms of mode characteristics and the number of modes, but in this work multiple-beam Fizeau interferometry is proposed as an inductive but alternative methodology to afford a radial approach to determine dispersion, pulse broadening and maximum transmission rate in GRIN optical fiber having a central index dip.

El-Diasty, Fouad; El-Hennawi, H. A.; El-Ghandoor, H.; Soliman, Mona A.

2013-12-01

134

Ambient refractive index-independent bending vector sensor based on seven-core photonic crystal fiber using lateral offset splicing.  

PubMed

A novel, simple, and compact optical fiber directional bending vector sensor based on Mach-Zehnder interferometer (MZI) is proposed and experimentally demonstrated. The device consists of a piece of seven-core photonic crystal fiber (PCF) sandwiched between two single mode fibers (SMFs) with a lateral offset splicing joint that covering two cores of PCF. Bending sensitivity of the seven-core PCF based MZI is changed by an axial rotation angle, which shows its capacity for recognizing positive and negative directions. Within a curvature range of -7.05 m-1 to 7.05 m-1, the calculated bending sensitivities of two resonant central wavelengths with opposite fiber orientations are 1.232 nm/m-1 and 1.174 nm/m-1, respectively. This novel MZI is formed by invoking interference between the LP01-like supermode and other higher order supermodes in the core, which leads to insensitive to ambient refractive index (ARI). We have also investigated the transmission characteristics of the sensor with the temperature change. PMID:24104292

Ou, Zhilong; Yu, Yongqin; Yan, Peiguang; Wang, Jishun; Huang, Quandong; Chen, Xue; Du, Chenlin; Wei, Huifeng

2013-10-01

135

Measurable refractive index range for a doubly cladding single mode fiber sensor and its application in temperature and humidity sensing  

NASA Astrophysics Data System (ADS)

A new type of evanescent field sensors based on a doubly cladding single mode fiber is proposed. The theoretical analysis shows that the measurable refractive index (RI) ranges for the sensors are limited in the single mode in the fiber becoming leaky and the range is less than the RI difference between the core and the cladding of the fibers. Two temperature sensors and a humidity sensor were fabricated. One temperature sensor showed a good linear response in a range of 60°C, the modulation depth of 40 dB, and the insertion loss of -1.4 dB. The humidity sensors fabricated by agarose gel had a measurable moisture range of 16 ~ 100% of RH. Its optical power variation with humidity is 8.5 dB and insertion loss is 3.9 dB. We confirmed that the DC single mode fiber sensors became a new type of intensity sensors characterized in good linear response, low insertion loss, high modulation depth, and low cost in fabrication.

Zhang, Xiao-Kang; Lan, Lu; Kong, Zhen; Chen, Lihua; Ye, Zhiren

2010-11-01

136

Comparison between a graded and step-index optical cavity in InGaN MQW laser diodes  

NASA Astrophysics Data System (ADS)

In this paper we theoretically analysed the influence of the number of QWs in the active region and the cladding layer width on the confinement factor, near field patterns and far field patterns. A comparison between the conventional step separate confinement heterostructure (SCH) and a graded-index separate structure (GRIN-SCH) is done regarding these parameters. We found that in the case of single quantum well structure the step cavity gives the highest values of the confinement factor. As the number of wells (N) in the active region is increased the superiority of one structure or the other depends on the cladding layer width and the value of N, but for values of N higher than six, the confinement factor is always higher in the structure with a GRIN cavity, independent of the cladding layer width. In general the far field patterns in GRIN structure have lower values of the full width half-maximum (FWHM). The cutoff condition for a mono mode optical cavity is also calculated in both structures.

Martín, Juan A.; Sánchez, M.

2005-03-01

137

Nonlinear pulse reshaping in a designed erbium-doped fiber amplifier with a multicladded index profile  

NASA Astrophysics Data System (ADS)

A multicladded normally dispersive erbium-doped fiber amplifier (ND-EDFA) is designed for a short length to operate at the wavelength of 1550 nm with a dispersion of -6.5 ps/km nm and parabolic pulse generation through the proposed fiber is studied. The proposed ND-EDFA shows a flattened gain spectrum in C-band. The nonlinear Schrödinger equation is solved numerically in presence of fiber gain, nonlinearity, and dispersion to investigate the pulse propagation through the proposed fiber. While continuous wave (CW) sources are considered, parabolic self-similar pulses with structure factor of 0.072 are created at suitable values of optimum fiber length when input pulse properties and fiber parameters are optimized accordingly. Side by side with a low repetition rate laser source, the pulse propagation equation is controlled by the gain dispersion term and dipole relaxation time, such that the evolution of Gaussian pulses may lead to nonparabolic regime. The effects of pulse parameters like power level, pulse width, and dipole relaxation time on the propagation of input Gaussian pulses through the so-designed ND-EDFA are investigated. Our results depict that the pulses with same input energy reshape into exactly parabolic shape for CW laser source or nonparabolic profile for a laser source with low repetition rate.

Bose, Navonil; Ghosh, Dipankar; Mukherjee, Sampad; Basu, Mousumi

2013-08-01

138

New phospho-tellurite glasses with optimization of transition temperature and refractive index for hybrid microstructured optical fibers  

NASA Astrophysics Data System (ADS)

The glass formation and compositional dependences of glass thermal properties and optical properties were investigated in TeO2-ZnO-Na2O-P2O5 system. The refractive index at 1.55 ?m and glass transition temperature varied in a wide range from 1.513 to 2.036 and from 265 °C to 376 °C by controlling of the TeO2/P2O5 and ZnO/Na2O content, respectively. These properties enable phospho-tellurite glasses with large freedom in designing and fabrication of hybrid microstructured optical fiber. The structures of glasses were investigated by Raman spectra to understand their dependence of structure on composition. Using the present glasses, some hybrid microstructured optical fibers with various dispersion profiles were designed.

Duan, Zhongchao; Tong, Hoang Tuan; Liao, Meisong; Cheng, Tonglei; Erwan, Motillon; Suzuki, Takenobu; Ohishi, Yasutake

2013-10-01

139

Refractive index sensing based on Mach-Zehnder interferometer formed by three cascaded single-mode fiber tapers.  

PubMed

We report a highly sensitive refractive index (RI) sensor based on three cascaded single-mode fiber tapers, in which a weak taper is sandwiched between the two tapers to improve the sensitivity of the sensor. Experimental results show that the sensitivity of the device is 0.286 nm for a 0.01 RI change, which is about four times higher than that of the normal two-cascaded-taper-based Mach-Zehnder interferometer. In addition, the sensitivity of the device could be enhanced by tapering a longer and thinner middle weak taper. Such kinds of low-cost and highly sensitive fiber-optic RI sensors would find applications in chemical or biochemical sensing fields. PMID:21478927

Wu, Di; Zhu, Tao; Deng, Ming; Duan, De-Wen; Shi, Lei-Lei; Yao, Jun; Rao, Yun-Jiang

2011-04-10

140

Errors of optical fiber chromatic dispersion calculation caused by line approximation of silica glass refraction index as a function of dopant concentration  

NASA Astrophysics Data System (ADS)

Errors of optical fiber chromatic dispersion calculation caused by line approximation of silica glass refraction index as a function of dopant concentration are investigated. Calculation of chromatic dispersion for fibers with refractive index profiles, for which experimental data of chromatic dispersion are known, is performed by an investigated method. Errors of chromatic dispersion calculation are estimated by deviation evaluated results from data of measuring for samples of optical fiber. On the basis of the comparative analysis the estimation of adequacy of the cosidered method is given.

Burdin, Vladimir A.

2009-12-01

141

Radiation hard fiber optics  

Microsoft Academic Search

A study of radiation-inducted absorption in low-loss optical waveguides is reported. Step-index optical fibers were prepared from preforms fabricated by the CVD method. The germanium silicate core glass in the fibers was doped with varying amounts of antimony, cerium, boron, phosphorus and hydroxyl groups. The effects of such variations in the glass chemistry on the radiation inducted attenuation of the

R. E. Jaeger; M. Aslami

1981-01-01

142

Kinetics of the refractive index change in the core of active fibers, doped with Yb3+ and Er3+ ions, under pulsed optical pumping  

NASA Astrophysics Data System (ADS)

The kinetics of refractive index change (RIC) in the core of Yb3+/Er3+ fibers at a radiation wave-length lying beyond the range of resonant absorption of active ions under pulsed pumping of fiber laser has been analyzed. The measurement of RIC kinetics with a Mach-Zehnder interferometer makes it possible to separate the contributions of the electronic and thermal RIC mechanisms and determine quantitatively the temperature profile inhomogeneity in the fiber. The measured values are compared with the numerical estimates derived from the spectral properties of the active medium in order to check the modern models of RIC in active fibers.

Gainov, V. V.; Ryabushkin, O. A.

2012-03-01

143

Glycemic index, carbohydrate and fiber intakes and risk of reflux esophagitis, Barrett’s esophagus, and esophageal adenocarcinoma  

Microsoft Academic Search

Objective  To examine the association between dietary glycemic index (GI), glycemic load (GL), total carbohydrate, sugars, starch, and\\u000a fiber intakes and the risk of reflux esophagitis, Barrett’s esophagus, and esophageal adenocarcinoma.\\u000a \\u000a \\u000a \\u000a Methods  In an all-Ireland study, dietary information was collected from patients with esophageal adenocarcinoma (n = 224), long-segment Barrett’s esophagus (n = 220), reflux esophagitis (n = 219), and population-based controls (n = 256). Multiple logistic regression analysis examined

Helen G. Mulholland; Marie M. Cantwell; Lesley A. Anderson; Brian T. Johnston; R. G. Peter Watson; Seamus J. Murphy; Heather R. Ferguson; Jim McGuigan; John V. Reynolds; Harry Comber; Liam J. Murray

2009-01-01

144

Surface plasmon resonance based fiber optic refractive index sensor utilizing Cu/ZnO layer  

NASA Astrophysics Data System (ADS)

Modeling of a miniaturized fiber optic sensor based on surface plasmon resonance (SPR) utilizing Cu/ZnO layer is presented. Attenuated total internal reflection with Kretschmann configuration is the basis of the theoretical model. The performance of the sensor is evaluated in terms of sensitivity and detection accuracy.

Mishra, Satyendra Kr; Varshney, Charul; Gupta, Banshi D.

2013-06-01

145

New approach to the measurement of the nonlinear refractive index of short (<25 m) lengths of silica and erbium-doped fibers.  

PubMed

The nonlinear refractive index n2 of silica fiber (24 m) and erbium-doped fiber (10 m) is measured to within an accuracy of 5% by use of time-delayed photorefractive beam coupling of intense 53-ps, 1.064-microm pulses that experience self-phase modulation in the fibers. The resultant induced grating autocorrelation response yields a value of n2/A(eff) and a calibration standard for the fiber. A phase shift of the order of 0.19pi can be detected and is limited only by laser amplitude fluctuations. A unique advantage of this technique is its ability to measure n2 accurately in short lengths (z < or = 25 m) of fiber, whereas other approaches typically use much longer lengths of fiber (z > or = 100 m). PMID:14514104

Garcia, Hernando; Johnson, Anthony M; Oguama, Ferdinand A; Trivedi, Sudhir

2003-10-01

146

Automation for monitoring of the refractive index profile of vapor-phase-deposited soot preforms for optical fiber  

SciTech Connect

The vapor-phase axial deposition process is currently one of the most advantageous methods to produce preforms for optical fibers, due to its high efficiency and reduced production cost. However, this method has great difficulty in determining the refractive index profile, since it is influenced by too many process parameters. In this work, an automation system to determine the refractive index profile by monitoring the preform deposition surface profile during the soot preform deposition stage is presented. Based on a previous study that showed a strong correlation between these two profiles, an automation system was developed in LABVIEW to monitor the deposition surface profile during the preform deposition stage in order to estimate the preform germanium doping profile and refractive index profile, as well as a theoretical study to develop this system in order to minimize the performance impairment. As a result, not only preforms with a predetermined index profile were produced but also a reduction in production cost was obtained by decreasing the number of preform rejects.

Santos, J.S. dos; Ono, E.; Suzuki, C.K. [Laboratory of Integrated Quartz Cycle (LIQC), Faculty of Mechanical Engineering, Department of Materials Engineering, State University of Campinas, P.O. Box 6122, 13083-970, Campinas-Sao Paulo (Brazil)

2006-05-15

147

Dispersion optimization of photonic crystal fiber long-period gratings for a high-sensitivity refractive index sensing  

NASA Astrophysics Data System (ADS)

Photonic crystal fiber long-period gratings (PCF-LPGs) operating near the phase-matching turning point to achieve high sensitivity to the refractive index of gas and liquid analytes infiltrated into cladding air holes are designed by numerical optimization. The vectorial finite element method is employed for the modal analysis of an index-guiding PCF and the calculation of the phase matching curves. The geometrical parameters of PCF (pitch and diameter of air holes arranged in a periodic triangular array) are optimized by using the down-hill simplex technique to engineer the dispersion of modes coupled by a LPG to obtain the turning point in the phase-matching curve at a desired wavelength for a given analyte refractive index. The resonant wavelength is subsequently extremely sensitive to the analyte refractive index, however, its large shifts can be detected with a substantially reduced resolution because the resonance dip in the LPG transmission spectrum is very broad. On the other hand, the broad resonance provides a broadband operation of a PCF-LPG sensor and its high sensitivity to the refractive index can still be achieved by relying on changes in the coupling strength (and consequently in the transmission loss) rather than in the resonant wavelength of LPG. We consider coupling between the fundamental core mode and the first-order symmetric cladding mode. We also explore an alternative approach based on coupling between the fundamental core mode and the fundamental space-filling mode instead of the individual cladding mode. The PCF-LPG structure optimized for refractive-index sensing is also assessed for label-free biosensing.

Kanka, Jiri

2011-05-01

148

Analysis of performance index of fiber-optic liquid-level sensor based on an extrinsic Fabry-Perot interferometer  

NASA Astrophysics Data System (ADS)

A novel configuration of fiber-optic liquid-level sensor based on an extrinsic Fabry-Perot cavity is presented and demonstrated in this paper. The main principle of this sensor is that output intensity will vary linearly in a locally special linear region with liquid-level increasing and cavity length decreasing. The experimental results prove that the actual curve of extrinsic Fabry-Perot cavity is approximate cosine curve, and that the peak values of the fringes slowly decrease with increased cavity length. Consequently, cavity length loss influences on performance indexes of extrinsic Fabry-Perot cavity optical fiber sensors operating in linear region such as measurement range, sensitivity, minimum resolution, and linearity. To obtain high finesse and throughout for reducing the complexity of signal processing system, the loss must be kept as small as possible by selecting an appropriate cavity length in view of different sensing surface and reflectivity. Otherwise, the sensor with too small initial cavity length can output more intensity, perform wider range of measurands, possess higher minimum resolution, and is more sensitive, but the linearity becomes worse and the measurement errors are maybe unavoidable to rise. On the contrary, with bigger original cavity length, the things are opposite. Hence, the original cavity length and the end reflectivity must be selected appropriately to meet with the requirements for performance indexes of the liquid-level sensor in realistic circumstance.

Lü, Tao; Li, Zhengjia; Xia, Danqing

2008-12-01

149

Relation of dietary glycemic index, glycemic load, added sugar intake, or fiber intake to the development of body composition between ages 2 and 7 y1-3  

Microsoft Academic Search

Background:Observationalstudiesinadultssuggestthatadietwith a high glycemic index (GI) or glycemic load (GL), a high intake of sugary foods, or a low fiber intake may increase the risk of over- weight. Objectives:WeaimedtoexamineprospectivelywhetherdietaryGI, GL, added sugar intake, or fiber intake between age 2 an d7ya re associated with the development of body composition. If so, we aimed to ascertain whether these associations are modified

Anette E Buyken; Guo Cheng; Anke LB Gunther; Angela D Liese; Thomas Remer; Nadina Karaolis-Danckert

150

Long Period Gratings in Random Hole Optical Fibers for Refractive Index Sensing  

PubMed Central

We have demonstrated the fabrication of long period gratings in random hole optical fibers. The long period gratings are fabricated by a point-by-point technique using a CO2 laser. The gratings with a periodicity of 450 ?m are fabricated and a maximum coupling efficiency of ?9.81 dB has been achieved. Sensing of different refractive indices in the surrounding mediums is demonstrated by applying standard liquids with refractive indices from 1.400 to 1.440 to the long period grating.

Wang, Ke; Pickrell, Gary

2011-01-01

151

Radiation damage in optical fibers  

SciTech Connect

While plastic-clad-silica (PCS) fiber shows the greatest radiation resistance, PCS fiber has been difficult to reliably connectorize for routine field operations. For this reason, all-glass fibers have been studied as an alternative to PCS. Based on available literature and some preliminary tests at Los Alamos, we have concentrated on fluorosilicate clad, step index, pure silica core fibers. This paper reviews recent laboratory data for these fibers relative to the PCS fibers. This paper also discusses use of a fiber (or any optical medium) on a Cerenkov radiation-to-light transducer. Since the radiation induces attenuation in the medium, the light output is not proportional to the radiation input. The nonlinearity introduced by this attenuation is calculated.

Lyons, P.B.; Looney, L.D.; Ogle, J.W.

1983-01-01

152

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

153

Fiber optics: A brief introduction  

NASA Astrophysics Data System (ADS)

A basic introduction into the principles of fiber optics is presented. A review of both the underlying physical principles and the individual elements of typical fiber optic systems are presented. The optical phenomenon of total internal reflection is reviewed. The basic construction of the optical fiber is presented. Both step index and graded index fiber designs are reviewed. Multimode and single mode fiber constructions are considered and typical performance parameters given. Typical optical fiber bandwidth and loss characteristics are compared to various common coaxial cables, waveguides, and air transmission. The constructions of optical fiber cables are reviewed. Both loose tube and tightly buffered designs are considered. Several optical connection approaches are presented. Photographs of several representative optical connectors are included. Light Emitting Diode and Laser Diode emitters for fiber optic applications are reviewed, and some advantages and shortcomings of each are considered. The phenomenon of modal noise is briefly explained. Both PIN and Avalanche photodetectors are reviewed and their performance parameters compared. Methods of data transmission over optical fiber are introduced. Principles of Wavelength, Frequency, and Time Division Multiplexing are briefly presented. The technology of fiber optic sensors is briefly reviewed with basic principles introduced. The performance of a fiber optic strain sensor is included as a practical example.

Gruchalla, Michael E.

154

Glycemic index, glycemic load, and dietary fiber intake and incidence of type 2 diabetes in younger and middle-aged women1-3  

Microsoft Academic Search

Background: Increasing evidence suggests an important role of carbohydrate quality in the development of type 2 diabetes. Objective: Our objective was to prospectively examine the associ- ation between glycemic index, glycemic load, and dietary fiber and the risk of type 2 diabetes in a large cohort of young women. Design: In 1991, 91 249 women completed a semiquantitative food- frequency

Matthias B Schulze; Simin Liu; Eric B Rimm; JoAnn E Manson; Walter C Willett; Frank B Hu

155

Self-Tuning Multi-Step Prediction of Strength Index in an Iron-Ore Sintering Process.  

National Technical Information Service (NTIS)

A method which predicts sinter strength index (ISO) with reasonable accuracy several hours in advance is presented. The sintering process is characterized by a discrete time stochastic model, using ISO records and coke percentage in the raw mix. Practical...

P. P. Kanjilal E. Rose

1982-01-01

156

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

157

Photocatalytic degradation of methylene blue in a sparged tube reactor with TiO 2 fibers prepared by a properly two-step method  

Microsoft Academic Search

The photocatalytic oxidation of methylene blue has been performed in the presence of suspended TiO2 fibers prepared by a properly two-step method in an air-sparged tube reactor. The key factors affecting the methylene blue oxidation efficiency were investigated, including the initial concentration of methylene blue, the pH value and the electric power of UV lamp. For photodegradation of methylene blue,

Shiying Zhang; Zhenhua Chen; Yunlong Li; Qun Wang; Long Wan

2008-01-01

158

All fiber chirped-pulse amplification system based on compression in air-guiding photonic bandgap fiber.  

PubMed

We report on the experimental demonstration of an all fiber CPA system based on a step-index fiber stretcher and an air-guiding photonic crystal fiber compressor. The ultrafast fiber laser system producing an average power of 6.0 W with 100-fs pulses at 73 MHz, what corresponds to a peak power out of the compressor fiber of 0.82 MW. This completely fiber integrated approach has the potential to be scaled to significantly higher peak powers. PMID:19471462

Limpert, J; Schreiber, T; Nolte, S; Zellmer, H; Tünnermann, A

2003-12-01

159

A standardized core set for systemic sclerosis clinical trials. First step in development of combined response index  

PubMed Central

SSc can be associated with a high morbidity and mortality. Due to the complexity and heterogeneity of the disease, a composite response measure that will capture differing organ involvements and patient-reported outcomes is desirable. Recently, with participation of the Scleroderma Clinical Trial Consortium, a standardized core set of items were proposed for SSc clinical trials using a structured Delphi exercise. The Delphi exercise identified 11 domains relevant to SSc clinical trials. Currently, efforts are under way to develop a combined response index for clinical trials in diffuse cutaneous SSc.

2008-01-01

160

Mid-infrared supercontinuum generation in As2S3-silica "nano-spike" step-index waveguide.  

PubMed

Efficient generation of a broad-band mid-infrared supercontinuum spectrum is reported in an arsenic trisulphide waveguide embedded in silica. A chalcogenide "nano-spike", designed to transform the incident light adiabatically into the fundamental mode of a 2-mm-long uniform section 1 µm in diameter, is used to achieve high launch efficiencies. The nano-spike is fully encapsulated in a fused silica cladding, protecting it from the environment. Nano-spikes provide a convenient means of launching light into sub-wavelength scale waveguides. Ultrashort (65 fs, repetition rate 100 MHz) pulses at wavelength 2 µm, delivered from a Tm-doped fiber laser, are launched with an efficiency ~12% into the sub-wavelength chalcogenide waveguide. Soliton fission and dispersive wave generation along the uniform section result in spectral broadening out to almost 4 µm for launched energies of only 18 pJ. The spectrum generated will have immediate uses in metrology and infrared spectroscopy. PMID:23669953

Granzow, N; Schmidt, M A; Chang, W; Wang, L; Coulombier, Q; Troles, J; Toupin, P; Hartl, I; Lee, K F; Fermann, M E; Wondraczek, L; Russell, P St J

2013-05-01

161

Thermal lens spectroscopy using a diode laser and optical fibers  

Microsoft Academic Search

A compact thermal lens spectrometer was developed using optical fibers and a diode laser for measurements of rare earth species in aqueous solutions. A cw GaAlAs diode laser coupled with a multimode step-index fiber was used as the excitation source. The thermal lens was probed with a He-Ne laser using a multimode 200 μm diameter core optical fiber as the

Dorys Rojas; Robert J. Silva; Richard E. Russo

1992-01-01

162

A high-fiber, moderate-glycemic-index, Mexican style diet improves dyslipidemia in individuals with type 2 diabetes  

Microsoft Academic Search

The typical Mexican diet includes beans and tortillas, which are foods with a low glycemic index. The objective of this paper was to compare the effects of a lower and a higher glycemic index Mexican style diet on metabolic control. In a randomized, controlled crossover design, eight subjects with type 2 diabetes were assigned to either a high glycemic index

Arturo Jiménez-Cruz; Wilfred H. Turnbull; Montserrat Bacardi-Gascón

2004-01-01

163

Dispersion-shifted all-solid high index-contrast microstructured optical fiber for nonlinear applications at 1.55 microm.  

PubMed

We report the fabrication of an all-solid highly nonlinear microstructured optical fiber. The structured preform was made by glass extrusion using two types of commercial lead silicate glasses that provide high index-contrast. Effectively single-moded guidance was observed in the fiber at 1.55 microm. The effective nonlinearity and the propagation loss at this wavelength were measured to be 120 W(-1)km(-1) and 0.8 dB/m, respectively. Numerical simulations indicate that the fiber is dispersion-shifted with a zero-dispersion-wavelength of 1475 nm and a dispersion slope of 0.16 ps/nm(2)/km respectively at 1.55 microm. These predictions are consistent with the experimentally determined dispersion of + 12.5 ps/nm/km at 1.55 microm. Tunable and efficient four-wave-mixing based wavelength conversion was demonstrated at wavelengths around 1.55 microm using a 1.5m-length of the fiber. PMID:19997250

Feng, Xian; Poletti, Francesco; Camerlingo, Angela; Parmigiani, Francesca; Horak, Peter; Petropoulos, Periklis; Loh, Wei H; Richardson, David J

2009-10-26

164

Coupling characteristics between fundamental mode square waveguide and fiber  

NASA Astrophysics Data System (ADS)

Based on the weakly waveguide approximation, the eigen mode field distribution of fundamental mode step index square waveguide is suggested, and the overlap integral formula between two mode field distributions is employed, the expression of coupling efficiency between fundamental mode step index square waveguide and fiber is suggested. As the values of beam propagation factors of fundamental mode step index square waveguide and fiber are closed to unit in a certain range of normalized frequency, it is rational to express the mode field distributions of fundamental mode square waveguide and fiber by the Gaussian approximation in some range of normalized frequency. As the equivalent mode field size which defined by the geometric mean of second moment mode field size and differential operator mode field size is employed to express the waist sizes of Gaussian approximation for fundamental mode step index square waveguide and fiber, the coupling characteristics between fundamental mode step index square waveguide and fiber is discussed, and a useful optimum coupling condition is suggested. The conclusions would be beneficial to the assembling technology of optical waveguide device.

Guo, Fuyuan; Li, Lianhuang; Zheng, Hua; Wang, Yi; Ke, Jinrui; Dai, Tiangui; Lin, Xiaoming

2012-11-01

165

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

166

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

2012-05-11

167

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

168

Very high intensity fiber transmission systems  

SciTech Connect

Various applications are currently motivating interest in the transmission of very high laser intensities through optical fibers. As intensities within a fiber are increased, however, laser breakdown or laser-induced fiber damage will eventually occur and interrupt fiber transmission. For a number of years we have been studying these effects during the transmission of Q-switched, Nd/YAG laser pulses through step-index, multimode, fused-silica fiber. We have found that fiber transmission is often limited by a plasma-forming breakdown occurring at the fiber entrance face. This breakdown results in subtle surface modifications that can leave the surface more resistant to further breakdown or damage events. Catastrophic fiber damage can also occur as a result of a number of different mechanisms, with damage appearing at fiber end faces, within the initial ``entry`` segment of the fiber path, and at other internal sites due to effects related to the particular fiber routing. An overview of these past observations is presented, and issues requiring further study are identified.

Setchell, R.E.

1995-12-31

169

Microwave fiber delay line performance simulation research  

NASA Astrophysics Data System (ADS)

The design, component selection, fabrication, testing, and evaluation of an optically-switched, binary, fiber optic programmable delay line are discussed. The basic building blocks, including laser diode which is based on a rate equation model, external modulated transmitter, transmission fiber and receiver, are explained. The system comprises eight delay stages, has a maximum delay of 6.4?s with a 100ps step and operates over the 1-18 GHz band. This computer controlled prototype used low-cost commercially available components in conjunction with graded-index, single-mode fiber. Its overall performance is satisfied with the simulation result.

Zhang, Xiaoqing; Zhang, Chunxi; Hu, Shuling; Ou, Pan; Wei, Limin

2008-11-01

170

Glycemic Index, Glycemic Load, and Cereal Fiber Intake and Risk of Type 2 Diabetes in US Black Women  

Microsoft Academic Search

associated with the risk of diabetes: the IRR for the high- est quintile relative to the lowest was 1.23 (95% confi- dence interval (CI), 1.05-1.44). Cereal fiber intake was inversely associated with risk of diabetes, with an IRR of 0.82 (95% CI, 0.70-0.96) for the highest vs lowest quin- tiles of intake. Stronger associations were seen among women with a

Supriya Krishnan; Lynn Rosenberg; Martha Singer; Frank B. Hu; Luc Djousse ´; L. Adrienne Cupples; Julie R. Palmer

2007-01-01

171

Analysis of performance index of fiber-optic liquid-level sensor based on an extrinsic Fabry-Perot interferometer  

Microsoft Academic Search

A novel configuration of fiber-optic liquid-level sensor based on an extrinsic Fabry-Perot cavity is presented and demonstrated in this paper. The main principle of this sensor is that output intensity will vary linearly in a locally special linear region with liquid-level increasing and cavity length decreasing. The experimental results prove that the actual curve of extrinsic Fabry-Perot cavity is approximate

Tao Lü; Zhengjia Li; Danqing Xia

2008-01-01

172

Redox-active ionic-liquid-assisted one-step general method for preparing gold nanoparticle thin films: applications in refractive index sensing and catalysis.  

PubMed

We describe a general one-step facile method for depositing gold nanoparticle (GNP) thin films onto any type of substrates by the in situ reduction of AuCl(3) using a newly designed redox-active ionic liquid (IL), tetrabutylphosphonium citrate ([TBP][Ci]). Various substrates such as positively charged glass, negatively charged glass/quartz, neutral hydrophobic glass, polypropylene, polystyrene, plain paper, and cellophane paper are successfully coated with a thin film of GNPs. This IL ([TBP][Ci]) is prepared by the simple neutralization of tetrabutylphosphonium hydroxide with citric acid. We also demonstrate that the [TBP][Ci] ionic liquid can be successfully used to generate GNPs in an aqueous colloidal suspension in situ. The deposited GNP thin films on various surfaces are made up of mostly discrete spherical GNPs that are well distributed throughout the film, as confirmed by field-emission scanning electron microscopy. However, it seems that some GNPs are arranged to form arrays depending on the nature of surface. We also characterize these GNP thin films via UV-vis spectroscopy and X-ray diffractometry. The as-formed GNP thin films show excellent stability toward solvent washing. We demonstrate that the thin film of GNPs on a glass/quartz surface can be successfully used as a refractive index (RI) sensor for different polar and nonpolar organic solvents. The as-formed GNP thin films on different surfaces show excellent catalytic activity in the borohydride reduction of p-nitrophenol. PMID:20942449

Dinda, Enakshi; Rashid, Md Harunar; Biswas, Mrinmoy; Mandal, Tarun K

2010-10-13

173

Active fibers from sol-gel derived granulated silica: state of the art and potential  

Microsoft Academic Search

In the recent past we have studied the granulated silica method as a versatile and cost effective way of fiber preform production. We have used the sol-gel technology combined with a laser-assisted remelting step to produce high homogeneity Rare Earth or Transition Metal - activated microsized particles for the fiber core. For the fiber cladding pure or index-raised granulated Silica

Valerio Romano; Frederic Sandoz

2010-01-01

174

High-temperature effects in fluorine-doped, fused synthetic silica fibers  

Microsoft Academic Search

Effects caused by exposure of large-core, fluorine-doped, step-index silica optical fibers to high temperatures were studied experimentally in controlled laboratory conditions. A fiber was located partially inside a temperature-controlled electric tube furnace and irradiated from the end by a light source. The light source was either an incandescent halogen lamp or a blackbody radiator. The influence of fiber temperature on

Risto Oikari; Toni Laurila; Rolf Hernberg

1997-01-01

175

APOGEE fiber development and FRD testing  

NASA Astrophysics Data System (ADS)

Development of the Apache Point Observatory Galactic Evolution Experiment (APOGEE) near-infrared spectrograph has motivated thorough investigation into the properties and performance of optical fibers. The fiber selected for APOGEE is a step index, multi-mode fiber, developed by PolyMicro, with a 120?m low OH, fused silica core, 25?m cladding, and 10?m buffer. The instrument design includes a 40 meter fiber run, connecting the spectrograph to the 2.5m Sloan Digital Sky Survey (SDSS) telescope, and an additional 2.5 meter fiber segment located within the instrument dewar, a vacuum-sealed, cryogenic environment. This light path is convoluted and includes many transitions and connections where the beam is susceptible irrevocable loss. To optimize the spectrograph performance it is necessary to minimize the losses incurred in the fiber system, especially those resulting in focal ratio degradation (FRD). The focus of this research has been to identify potential sources of loss and where applicable, select material components to minimize this effect. There is little previous documented work concerning the performance of optical fibers within this wavelength band (1.5-1.7?m). Consequently, the following includes comprehensive explanations of the APOGEE fiber system components, our experimental design and optical test bed set-up, beam alignment procedures, fiber terminating and polishing techniques, and results from our examination of FRD as correlated with source wavelength, fiber length and termination, and environmental conditions.

Brunner, Sophia; Burton, Adam; Crane, Jeff; Zhao, Bo; Hearty, Fred R.; Wilson, John C.; Carey, Larry; Leger, French; Skrutskie, Mike; Schiavon, Ricardo; Majewski, Steven R.

2010-07-01

176

Slow-light in photonic crystal waveguides/fibers: dispersion tailoring schemes for obtaining a high group index with wide band and low GVD  

NASA Astrophysics Data System (ADS)

Phenomenon of slow light has long been a hot research topic due to its promising and potential applications in communication networks, signal processing, optical sensors and nonlinear interactions. Particularly, photonic crystal devices, being capable of supporting slow-light propagation, are much attractive owing to its room-temperature operation and tunable dispersion features. Among them, photonic crystal waveguides (PCWs) are specially used in compact devices, while photonic band-gap fibers (PBGFs) are usually used in short-distance propagation and high sensitive interferometers. In this paper, dispersion tailoring schemes for obtaining a high group index with the wide band and low group velocity dispersion (GVD) are reviewed in both PCWs and PBGFs. For the same purpose, we propose schemes for the slow-pulse propagation in PCWs based on the air-hole shifting method and in PBGFs based on the microfluid infiltration method, respectively. Simulation results using 2D plane wave expansion method and finite-difference timedomain (FDTD) method are given. Pulse distortion and design optimization are also discussed in some detail with the consideration of the practical fabrication errors. Slow-light pulse propagation in photonic crystal fiber is also demonstrated in the experiment based on stimulated Brillouin scattering.

Ren, Liyong; Liang, Jian; Liu, Yu; Ju, Haijuan; Yun, Maojin; Ma, Chengju; Han, Xu; Lin, Xiao; Tomita, Yasuo

2012-02-01

177

Production of a human monoclonal IgM directed against human cardiac myosin in a hollow-fiber bioreactor for membrane anion exchange chromatography one-step purification.  

PubMed

Purification of human IgM monoclonal antibodies (MAbs) has proved to be difficult. Since IgM Mabs tend to bind strongly to a variety of resin support surfaces, the number of chromatographic steps used in the purification of these biomolecules should be minimized. Here we describe procedures developed for the optimal production and purification of the human monoclonal IgM B7, which specifically binds to the myosin heavy chain of human ventricular myocardium. This property makes this antibody potentially useful for the diagnosis of myocardial necrosis. Several chromatographic techniques were evaluated (size exclusion, ion exchange, affinity chromatography). The best results were obtained with anion exchange membrane chromatography using Sartobind Q15 (98% purity, 30% recovery). IgM production was improved by the hollow fiber technology which permitted the use of serum-reduced medium and an increase in antibody concentration to an average production of 300-400 microg/ml, compared to 20 microg/ml in flask culture. Several flow-rates were also evaluated, the optimal being 20 ml/minute for 30% of recovery. Importantly, the purified IgM molecule was able to bind to human myosin in ELISA and Western-blotting, thus allowing the IgM to be kept intact for further radiolabeling. PMID:15598987

Jacobin, Marie-Josée; Santarelli, Xavier; Laroche-Traineau, Jeanny; Clofent-Sanchez, Gisèle

2004-01-01

178

Active fibers from sol-gel derived granulated silica: state of the art and potential  

NASA Astrophysics Data System (ADS)

In the recent past we have studied the granulated silica method as a versatile and cost effective way of fiber preform production. We have used the sol-gel technology combined with a laser-assisted remelting step to produce high homogeneity Rare Earth or Transition Metal - activated microsized particles for the fiber core. For the fiber cladding pure or index-raised granulated Silica has been employed. Silica glass tubes, appropriately filled with these granular materials, are then drawn to fibers, eventually after an optional quality enhancing vitrification step. The process offers a high degree of compositional flexibility with respect to dopants; it further facilitates to achieve high concentrations even in cases when several dopants are used. By this "rapid preform production" technique, that is also ideally suited for the preparation of microstructured optical fibers, several fibers ranging from broadband emitters, PCFs and large mode area fibers have been produced and will be presented here.

Romano, Valerio; Sandoz, Frederic

2010-10-01

179

Luminescent polymer optical fibers: linear and nonlinear spectroscopy and lasing  

Microsoft Academic Search

We have reported on optical gain and blue lasing from a step index glass-clad polymer optical fibre that uses a novel fluorescent stilbenoid compound, 1,4-bis(4diphenylamino-styryl)-benzene. Our results will open the door to the development of compact polymer fiber lasers and amplifiers for such diverse applications as polymer optical fiber-based networks, spectroscopy and sensing.

T. Kobayashi; G. Jordan; W. J. Blau; H. Tillmann; H.-H. Horhold

2002-01-01

180

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

181

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

182

Exact derivation of the coupling coefficient in corrugated waveguides with arbitrary cross-section: application to optical fibers  

Microsoft Academic Search

Expressions for the coupling coefficient in corrugated waveguides with rectangular tooth shape are derived based on local mode expansion. The expressions are exact to first order in the tooth height (or index difference) for any waveguide cross-section. When applied to slab waveguides, the familiar expressions are obtained. Specializing to weakly guiding fibers, with step index profile, result in simple expressions

Amos Hardy

1995-01-01

183

Fabrication of large flattened mode optical fiber for high power laser  

NASA Astrophysics Data System (ADS)

Large flattened mode optical fiber with raised index ring around the outer edge of the fiber core has been fabricated through modified chemical vapour deposition process to raise the threshold for non-linear interaction in high power laser fiber. The conversion of the fundamental mode shape from a Bessel function to a top hat function, enhances the effective area of the core intersected by the mode without increasing the physical size of the core. The shape of the fundamental mode is observed to be strongly dependent on the width of the raised index ring from the modal analysis. Suitable fiber parameters have also been estimated through the modal field analysis. Fabrication process steps have been optimized to achieve the desired fiber parameters. Modal field distribution, transmission properties and bending loss of the fabricated fibers have been characterized.

Das, S.; Pal, A.; Paul, M. C.; Sen, R.

2010-12-01

184

Fiber optics in the BNL booster radiation environment  

SciTech Connect

The Booster instrumentation uses analog and digital fiber optic links, designed to withstand at least 50 krads without performance degradation. The links use inexpensive and commercially available components that operate at a center wavelength of 820 nm. The analog link operates to 30 MHz over a 200 m fiber and can provide insertion gain. The digital link provides 60 ns timing pulses without the dispersive effects of coaxial cables. The optical fiber is a step-index hard clad silica type with a 200 micron core. This paper presents the component selection criteria, link design, installation, testing and performance for the optical links in the Booster instrumentation systems. 7 refs., 4 figs.

Beadle, E.R.

1991-01-01

185

A modified EPA Method 1623 that uses tangential flow hollow-fiber ultrafiltration and heat dissociation steps to detect waterborne Cryptosporidium and Giardia spp.  

PubMed

Cryptosporidium and Giardia species are two of the most prevalent protozoa that cause waterborne diarrheal disease outbreaks worldwide. To better characterize the prevalence of these pathogens, EPA Method 1623 was developed and used to monitor levels of these organisms in US drinking water supplies (12). The method has three main parts; the first is the sample concentration in which at least 10 L of raw surface water is filtered. The organisms and trapped debris are then eluted from the filter and centrifuged to further concentrate the sample. The second part of the method uses an immunomagnetic separation procedure where the concentrated water sample is applied to immunomagnetic beads that specifically bind to the Cryptosporidium oocysts and Giardia cysts allowing for specific removal of the parasites from the concentrated debris. These (oo)cysts are then detached from the magnetic beads by an acid dissociation procedure. The final part of the method is the immunofluorescence staining and enumeration where (oo)cysts are applied to a slide, stained, and enumerated by microscopy. Method 1623 has four listed sample concentration systems to capture Cryptosporidium oocysts and Giardia cysts in water: Envirochek filters (Pall Corporation, Ann Arbor, MI), Envirochek HV filters (Pall Corporation), Filta-Max filters (IDEXX, Westbrook, MA), or Continuous Flow Centrifugation (Haemonetics, Braintree, MA). However, Cryptosporidium and Giardia (oo)cyst recoveries have varied greatly depending on the source water matrix and filters used(1,14). A new tangential flow hollow-fiber ultrafiltration (HFUF) system has recently been shown to be more efficient and more robust at recovering Cryptosporidium oocysts and Giardia cysts from various water matrices; moreover, it is less expensive than other capsule filter options and can concentrate multiple pathogens simultaneously(1-3,5-8,10,11). In addition, previous studies by Hill and colleagues demonstrated that the HFUF significantly improved Cryptosporidium oocysts recoveries when directly compared with the Envirochek HV filters(4). Additional modifications to the current methods have also been reported to improve method performance. Replacing the acid dissociation procedure with heat dissociation was shown to be more effective at separating Cryptosporidium from the magnetic beads in some matrices(9,13) . This protocol describes a modified Method 1623 that uses the new HFUF filtration system with the heat dissociation step. The use of HFUF with this modified Method is a less expensive alternative to current EPA Method 1623 filtration options and provides more flexibility by allowing the concentration of multiple organisms. PMID:22805201

Rhodes, Eric R; Villegas, Leah Fohl; Shaw, Nancy J; Miller, Carrie; Villegas, Eric N

2012-07-09

186

Random hole optical fibers  

Microsoft Academic Search

Conventional telecommunications fibers rely on a refractive index difference between the core and cladding region to confine light to the central core region. The refractive index difference is produced by different compositions of glass in the core and cladding regions. In contrast, holey optical fibers rely on an array of air holes in the cladding to confine light to the

Gary R. Pickrell; Daniel Kominsky; Roger Stolen

2004-01-01

187

FIBER AND INTEGRATED OPTICS: Use of the offset method in an analysis of a non-Gaussian field distribution in single-mode fiber waveguides  

NASA Astrophysics Data System (ADS)

An offset method is modified to allow an analysis of the distribution of fields in a single-mode fiber waveguide without recourse to the Gaussian approximation. A new approximation for the field is obtained for fiber waveguides with a step refractive index profile and a special analysis employing the Hankel transformation is applied to waveguides with a distributed refractive index. The field distributions determined by this method are compared with the corresponding distributions calculated from the refractive index of a preform from which the fibers are drawn. It is shown that these new approaches can be used to determine the dimensions of a mode spot defined in different ways and to forecast the dispersion characteristics of single-mode fiber waveguides.

Belov, A. V.; Kurkov, Andrei S.; Chikolini, A. V.

1990-08-01

188

Investigations on the Bragg grating recording in all-silica, standard and microstructured optical fibers using 248 nm 5 ps, laser radiation  

NASA Astrophysics Data System (ADS)

The fabrication of Bragg reflectors in hydrogenated, all-silica, fluorine cladding depressed and microstructured optical fibers using 248 nm, 5 ps laser radiation, is investigated here. Comparative Bragg grating recordings are performed in both optical fibers, for investigating effects related to the scattering induced by the capillary micro-structure, to the photosensitivity and index engineering yield. Further, finite difference time domain method is employed for simulating the scattering from the above capillary structure and the nominal intensity reaching the fiber core for side-illumination. The maximum modulated refractive index changes inscribed in the standard, step-index fiber were of the order of 8.3x10-5, while the maximum refractive index changes inscribed in one of the microstructured optical fibers was 32% lower and 5.7x10-5, for nominal pulse intensities of 20 GW/cm2 and modest accumulated energy densities.

Pissadakis, S.; Livitziis, M.; Tsibidis, G. D.

2009-12-01

189

Fiber design and realization of point-by-point written fiber Bragg gratings in polymer optical fibers  

NASA Astrophysics Data System (ADS)

An increasing interest in making sensors based on fiber Bragg gratings (FBGs) written in polymer optical fibers (POFs) has been seen recently. Mostly microstructured POFs (mPOFs) have been chosen for this purpose because they are easier to fabricate compared, for example, to step index fibers and because they allow to tune the guiding parameters by modifying the microstructure. Now a days the only technique used to write gratings in such fibers is the phase mask technique with UV light illumination. Despite the good results that have been obtained, a limited flexibility on the grating design and the very long times required for the writing of FBGs raise some questions about the possibility of exporting POF FBGs and the sensors based on them from the laboratory bench to the mass production market. The possibility of arbitrary design of fiber Bragg gratings and the very short time required to write the gratings make the point-by-point grating writing technique very interesting and would appear to be able to fill this technological gap. On the other end this technique is hardly applicable for microstructured fibers because of the writing beam being scattered by the air-holes. We report on the design and realization of a microstructured polymer optical fiber made of PMMA for direct writing of FBGs. The fiber was designed specifically to avoid obstruction of the writing beam by air-holes. The realized fiber has been used to point-by-point write a 5 mm long fourth order FBG with a Bragg wavelength of 1518 nm. The grating was inspected under Differential Interferometric Contrast microscope and the reflection spectrum was measured. This is, to the best of our knowledge, the first FBGs written into a mPOF with the point-by-point technique and also the fastest ever written into a polymer optical fiber, with less than 2.5 seconds needed.

Stefani, Alessio; Stecher, Matthias; Town, Graham E.; Bang, Ole

2012-05-01

190

Radiation hard fiber optics. Final technical report 24 Apr 78-24 Apr 80  

Microsoft Academic Search

A study of radiation-inducted absorption in low-loss optical waveguides is reported. Step-index optical fibers were prepared from preforms fabricated by the CVD method. The germanium silicate core glass in the fibers was doped with varying amounts of antimony, cerium, boron, phosphorus and hydroxyl groups. The effects of such variations in the glass chemistry on the radiation inducted attenuation of the

R. E. Jaeger; M. Aslami

1981-01-01

191

Fiber-based pulse stretcher for narrowband terahertz pulse generation with a chirped-pulse beating method  

NASA Astrophysics Data System (ADS)

We theoretically show that it is possible to generate chirp-free terahertz (THz) pulses with a chirped-pulse beating method by using an optical fiber as a pulse stretcher. Proper choices of the core radius and the dopant fraction of the core material of a step-index single-mode optical fiber eliminate the third-order spectral phase of the fiber, thus giving the pump laser pulse a purely linear chirp. We also show that even a standard commercial single-mode optical fiber can give THz pulses of lower chirp than the lower limit for a grating pair. We perform experiments to verify our theory.

Yoshida, Tetsuya; Kamada, Shohei; Murata, Shuhei; Aoki, Takao

2013-10-01

192

Silyl-acetylene polymers for use as precursors to silicon carbide fibers  

SciTech Connect

The steps involved in production of silicon carbide fiber using silyl acetylene polymer precursors can be separated into four processing steps: polymer synthesis, fiber spinning, fiber crosslinking, and pyrolysis. Practical experimental considerations in each step are discussed.

Meyer, M.K.

1991-12-20

193

Silyl-acetylene polymers for use as precursors to silicon carbide fibers  

Microsoft Academic Search

The steps involved in production of silicon carbide fiber using silyl acetylene polymer precursors can be separated into four processing steps: polymer synthesis, fiber spinning, fiber crosslinking, and pyrolysis. Practical experimental considerations in each step are discussed.

1991-01-01

194

Estimation of cut-off wavelength of rare earth doped single-mode fibers  

NASA Astrophysics Data System (ADS)

A new empirical relation is proposed describing spectral variation of mode-field radius (MFR) as inferred from measurements in the far-field of the fiber. It is shown that using this relation, it is possible to estimate the cut-off wavelength (?c) of the fiber. The proposed technique is successfully tested through measurements made on two standard step index single-mode fibers, as well as on an erbium doped fiber (EDF) having ?c falling within its strong absorption band around 980 nm. This empirical formula is more accurate than the widely used Marcuse's formula to describe spectral dependence of MFR determined through measurements made in the fiber's far-field. The proposed technique is especially suited for estimation of ?c of doped fibers in which ?c falls within an absorption band.

Kaur, J.; Thyagarajan, K.; Pal, B. P.

1999-11-01

195

Power scaling of ytterbium(3+)-doped phosphate fiber lasers and amplifiers  

NASA Astrophysics Data System (ADS)

The initial motivation for this work was to build a high-power single-frequency, single-mode, linearly polarized fiber MOPA for gravitational-wave detection. Although spectacular progress has been made over the past few years in the development of single-frequency Yb3+-doped silica fiber laser sources, their maximum output powers are still limited by the onset of stimulated Brillouin scattering. To further scale the output power of single-frequency silica fiber laser sources with step-index single-mode fibers, increasing the ion concentration in the gain fiber is required. Unfortunately, excessive amounts of rare-earth ions in silica fibers cause concentration quenching, photodarkening, and crystallization. To this end, phosphate glass is a good alternative because of the high solubility of rare-earth oxides in this host. For example, the solubility of Yb2O3 in phosphate glass is at least 26 wt.%, i.e., 10 times higher than in silica. Such a high ion concentration significantly reduces the required fiber length and enables the use of a short step-index single-mode fiber without suffering from SBS up to very high output powers. To investigate the feasibility of extracting high powers from this gain medium, we measured several key material properties of the Yb3+-doped phosphate fibers, including the SBS gain coefficient, photodarkening resistance, and fiber background loss. Our experimental results showed that, compared to silica fibers, phosphate fibers exhibit a 50% weaker SBS gain coefficient and allow a 6-times-higher Yb3+ concentration without the onset of photodarkening. We measured the scattering and absorption loss of the phosphate fiber by using an integrating sphere and a fiber calorimeter, respectively. The results showed that 77% of the fiber background loss originates from impurity absorption, and the rest from scattering. It indicates that absorption loss must be reduced to improve the efficiency of the fiber laser. The studies of these material properties allow us to precisely evaluate the potential for power scaling of phosphate fiber lasers and amplifiers. As a proof of principle, we experimentally demonstrate truly single-mode fiber lasers and amplifiers with record output powers of several tens of watts. These laser sources include a 57-W multiple-frequency 1.06-mum fiber laser with a slope efficiency of 52.7%, and a 16-W single-frequency fiber MOPA. This is the first report of a watt-level CW Yb3+-doped phosphate fiber amplifier. We showed through numerical simulations that the exceptional characteristics of phosphate fibers can be extended to a ˜700-W single-frequency fiber amplifier from a step-index single-mode fiber. The peak thermal load of this 700-W phosphate fiber MOPA was calculated to be ˜800 W/m, which can be handled by suitable cooling. In summary, all results presented in this dissertation confirm that Yb3+-doped phosphate fibers constitute a promising gain element for power-scaling truly single-mode single-frequency fiber laser amplifiers.

Lee, Yin-Wen

196

Interlaboratory comparison of radiation-induced attenuation in optical fibers. III. Transient exposures  

Microsoft Academic Search

For pt.II see ibid., p.967-76 (1990). A comparison made over a period of five years of the losses induced in step-index multimode, graded-index multimode, and single-mode fibers by pulsed radiation exposure by 12 laboratories is discussed. The recoveries of the incremental attenuations from 10-9 to 101 s are reported. Although a standard set of measurement parameters was attempted, differences between

E. J. Friebele; P. B. Lyons; J. Blackburn; H. Henschel; A. Johan; J. A. Krinsky; A. Robinson; W. Scheneider; D. Smith; E. W. Taylor; G. Y. Turquet de Beauregard; R. H. West; P. Zagarino

1990-01-01

197

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

198

Optimization of activated carbon production from empty fruit bunch fibers in one-step steam pyrolysis for cadmium removal from aqueous solution  

Microsoft Academic Search

The fast growth of the palm oil industry in Malaysia is associated with various waste products, namely the empty fruit bunches\\u000a (EFB), which have a negative impact on the environment. Therefore, these wastes were utilized as a cheap raw material for\\u000a the production of activated carbon (AC) with less energy consumption. One-step steam pyrolysis was used to produce AC from

Ma’an F. Alkhatib; Suleyman A. Muyibi; Jeminat Omotayo Amode

199

Nonsilica glasses for holey fibers  

Microsoft Academic Search

The authors of this paper investigated the thermal properties and optical properties of typical nonsilica glasses, including viscosity, surface tension, thermal conductivity, transmission, linear and nonlinear refractive index, and fiber attenuation in order to judge the feasibility of using nonsilica glasses as the background material of holey fibers (HFs). Novel techniques were presented to fabricate the nonsilica glass microstructured fiber

Xian Feng; Arshad K. Mairaj; Daniel W. Hewak; Tanya M. Monro

2005-01-01

200

Cellulosic Fibers: Effect of Processing on Fiber Bundle Strength  

Microsoft Academic Search

A range of differently processed cellulosic fibers from flax and hemp plants were investigated to study the relation between processing of cellulosic fibers and fiber bundle strength. The studied processing methods are applied for yarn production and include retting, scutching, carding, and cottonization. There was a monotonically decreasing relationship between the strength and the number of processing steps, which was

Anders Thygesen; Bo Madsen; Anne Belinda Bjerre; Hans Lilholt

2011-01-01

201

Calculating a Biodiversity Index  

NSDL National Science Digital Library

In this Biodiversity Counts activity, students learn how scientists calculate a biodiversity index using a page from the phone book as their data source. The printable five-page PDF handout includes a series of inquiry-based questions to get students thinking about what they already know about biodiversity and how living and non-living things are connected, step-by-step directions for calculating a biodiversity index, and a worksheet that includes brainstorming questions and areas for recording answers.

202

Research on the NO gas-sensitive effect of long-period fiber gratings coated with film  

Microsoft Academic Search

The spectral characteristics of long period fiber grating (LPFG) coated with sensitive film whose refractive index is higher than that of cladding is analyzed based on four-layer-step geometrical model both theoretically and experimentally. It is pointed out that the resonant wavelength of LPFG has a regular variation with the refractive indices of both ambience and the film besides film thickness.

Yong Peng; Min Sun

2008-01-01

203

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

204

A step-zoom probe for laser endophotocoagulation: I. Design.  

PubMed

A step-zoom probe for laser endophotocoagulation of the eye has been developed, using fiber optics and a gradient index (GRIN) rod lens. It provides the operator with five or more focused spots ranging in size from 50 to 500 microns, and the spot size on the target is independent of the media filling the vitreous cavity, i.e., fluid or air. Each spot is located at the waist of the beam and therefore can be easily placed on the target, reducing the potential for overtreatment. A prototype model is currently undergoing animal testing. PMID:3561940

Pankratov, M M; Pomerantzeff, O; Pflibsen, K P; Bearse, G R

1987-01-01

205

A monolithic pump signal multiplexer for air-clad photonic crystal fiber amplifiers  

NASA Astrophysics Data System (ADS)

We report on the performance of a monolithic 6+1X1 fiber pump signal multiplexer for use in fiber amplifiers. The key component of this coupler design is an etched taper that transforms the low-numerical aperture large diameter pump radiation into a high numerical aperture small diamter format for injection into the pump cladding of an air-clad fiber while maintaining a constant refractive index profile in the core for efficient signal coupling. This taper was then fused onto the 6+1 fiber bundle at the large end and to the air-clad large mode area polarization maintaining photonic crystal fiber at the small end. We employed 6 pump delivery fibers in a 200/220/0.22 core/clad/NA format and a 25/250 polarization maintaining step index signal delivery fiber for the bundle. The large end of the taper had a cladding diameter of 650 ?m while the small end had a cladding diameter of 300 ?m to match the pump cladding diameter of the PCF which was 314 ?m. The core within the taper had a constant diameter of 40 ?m and NA of 0.07 achieved through a step index profile. The mode field diameter of the PCF was 54 ?m. Signal coupling efficiency at 1550 nm was measured to be 90% with a polarization extinction ratio > 20dB while pump coupling efficiency was measured to be 87% at 1532nm. The low pump coupling efficiency was found to be due to pump delivery fibers that had a numerical aperture of 0.24, higher than the specification of 0.22. A simple calculation shows that with 0.22 NA pump fibers, the pump coupling efficiency would increase to 94%.

Ward, Benjamin G.; Sipes, Donald L., Jr.; Tafoya, Jason D.

2010-02-01

206

Pulse shepherding in nonlinear fiber optics  

Microsoft Academic Search

In a wavelength division multiplexed fiber system, where pulses on different wavelength beams may copropagate in a single mode fiber, the cross-phase-modulation (CPM) effects caused by the nonlinearity of the optical fiber are unavoidable. In other words, pulses on different wavelength beams can interact with and affect each other through the intensity dependence of the refractive index of the fiber.

C. Yeh; L. Bergman

1996-01-01

207

A highly non-linear tellurite microstructure fiber with multi-ring holes for supercontinuum generation.  

PubMed

We have fabricated a highly nonlinear complex microstructure tellurite fiber with a 1.8 micron core surrounded by four rings of holes. The cane for the fiber was prepared by combining the methods of cast rod in tube and stacking. In the process of fiber-drawing a positive pressure was pumped into the holes of cane to overcome the collapse of holes and reshape the microstructure. The correlations among pump pressure, hole size, surface tension and temperature gradient were investigated. The temperature gradient at the bottom of the preform's neck region was evaluated quantitatively by an indirect method. The chromatic dispersion of this fiber was compared with that of a step-index air-clad fiber. It was found that this fiber has a much more flattened chromatic dispersion. To the best of our knowledge this is the first report about a soft glass microstructure fiber which has such a small core together with four rings of holes for the dispersion engineering. The SC generation from this fiber was investigated under the pump of a 1557 nm femtosecond fiber laser. Infrared supercontinuum generation, free of fine structure, together with visible third harmonic generation was obtained under the pump of a femtosecond fiber laser with a pulse energy of several hundred pJ. PMID:19724545

Liao, Meisong; Yan, Xin; Qin, Guanshi; Chaudhari, Chitrarekha; Suzuki, Takenobu; Ohishi, Yasutake

2009-08-31

208

High-order modes suppression in large mode area active fibers by controlling the radial distribution of the rare earth dopant  

NASA Astrophysics Data System (ADS)

Many high power fiber laser applications require doped fibers having large mode area but still working in the single mode regime. The most common techniques to keep a large mode area fiber in the single mode regime are to reduce the core numerical aperture, to strip the high order modes by coiling the fiber, to launch only a single transverse mode, or to use photonic crystal fibers. All these methods have limits and disadvantages. In this paper we demonstrate by simulation the effectiveness of another method to suppress the high order modes in large mode area active fibers by optimizing the rare earth dopant concentration across the core while keeping the step index structure of the core of the fiber. This method was not previously employed because the traditional doped fiber manufacturing technologies do not have the required capability to radially control the dopant concentration. However, Direct Nanoparticle Deposition (DND) can be used to manufacture large mode area fibers having any radial distribution of active element concentration and any refractive index profile. Thus, DND fibers can be designed to benefit from this high order mode suppression technique. The simulation results presented in this paper have been obtained using Liekki Application Designer v3.1, a software simulator for fiber lasers and amplifiers.

Hotoleanu, Mircea; Söderlund, Miko; Kliner, Dahv; Koplow, Jeffrey; Tammela, Simo; Philipov, Valery

2006-03-01

209

The Glycemic Index: Methodology and Use  

Microsoft Academic Search

The glycemic index concept owes much to the dietary fiber hypothesis that fiber would reduce the rate of nutrient absorption and increase the value of carbohydrate foods in the maintenance of health and treatment of disease. However, properties and components of food other than its fiber content contribute to the glycemic and endocrine responses postprandially. The aim of the glycemic

C. Kendall; L. Augustin; A. Emam; A. Josse; N. Saxena; D. Jenkins

2006-01-01

210

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

211

Silyl-acetylene polymers for use as precursors to silicon carbide fibers.  

National Technical Information Service (NTIS)

The steps involved in production of silicon carbide fiber using silyl acetylene polymer precursors can be separated into four processing steps: polymer synthesis, fiber spinning, fiber crosslinking, and pyrolysis. Practical experimental considerations in ...

M. K. Meyer

1991-01-01

212

Fiber optic testing laboratory  

NASA Astrophysics Data System (ADS)

The TIA and the EIA have developed a set of standardized test procedures for optical loss of fiber, cables, connectors and splices under many varying environmental conditions called FOTPs. We have implemented the experimental setup corresponding to four of these FOTPs. The firs test allows to measure the change in optical transmittance for devices used in optical fiber systems, between an initial condition and a new condition induced by exposure of the device to physical or environmental changes. The second test determines the quality of the ends for both, bare and connectorized fiber using an interferometric microscope. The third one measures the cutoff wavelength for single-mode fibers. Finally, the capacity of a fiber cable to resist simultaneously torsion and traction are determined measuring the changes in optical transmittance when the cable is properly installed in a special tower. This work is considered as the first step towards the settlement of a regional center for fiber optic testing.

Gualdron Gonzalez, Oscar; Lasprilla Alvarez, Maria del Carmen; Torres, Yezid

2001-08-01

213

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

214

Modeling compact high power fiber lasers and vecsels  

NASA Astrophysics Data System (ADS)

Compact high power fiber lasers and the vertical-external-cavity surface-emitting lasers (VECSELs) are promising candidates for high power laser sources with diffraction-limited beam quality and are currently the subject of intensive research and development. Here three large mode area fiber lasers, namely, the photonic crystal fiber (PCF) laser, the multicore fiber (MCF) laser, and the multimode interference (MMI) fiber laser, as well as the VECSEL are modeled and designed. For the PCF laser, the effective refractive index and the effective core radius of the PCF are investigated using vectorial approaches and reformulated. Then, the classical step-index fiber theory is extended to PCFs, resulting in a highly efficient vectorial effective-index method for the design and analysis of PCFs. The new approach is employed to analyze the modal properties of the PCF lasers with depressed-index cores and to effectively estimate the number of guided modes for PCFs. The MCF laser, consisting of an active MCF and a passive coreless fiber, is modeled using the vectorial mode expansion method developed in this work. The results illustrate that the mode selection in the MCF laser by the coreless fiber section is determined by the MMI effect, not the Talbot effect. Based on the MMI and self-imaging in multimode fibers, the vectorial mode expansion approach is employed to design the first MMI fiber laser demonstrated experimentally. For the design and modeling of VECSELs, the optical, thermal, and structural properties of common material systems are investigated and the most reliable material models are summarized. The nanoscale heat transport theory is applied for the first time, to the best of my knowledge, to design and model VECSELs. In addition, the most accurate strain compensation approach is selected for VECSELs incorporating strained quantum wells to maintain structural stability. The design principles for the VECSEL subcavity are elaborated and applied to design a 1040nm VECSEL subcavity that has been demonstrated for high power operation of VECSELs where near diffraction-limited output over 20 W is obtained. Physical modeling of the VECSEL is also discussed and used to compare VECSEL subcavity designs on the laser level.

Li, Hongbo

215

Mode evolution in long tapered fibers with high tapering ratio.  

PubMed

We have experimentally studied fundamental mode propagation in few meters long, adiabatically tapered step-index fibers with high numerical aperture, core diameter up to 117 ?m (V = 38) and tapering ratio up to 18. The single fundamental mode propagation was confirmed by several techniques that reveal no signature of higher-order mode excitation. It can be, therefore, concluded that adiabatic tapering is a powerful method for selective excitation of the fundamental mode in highly multimode large-mode-area fibers. Annular near field distortion observed for large output core diameters was attributed to built-in stress due to thermal expansion mismatch between core and cladding materials. The mechanical stress could be avoided by an appropriate technique of fiber preform fabrication and drawing, which would prevent the mode field deformation and lead to reliable diffraction-limited fundamental mode guiding for very large core diameters. PMID:23187363

Kerttula, Juho; Filippov, Valery; Ustimchik, Vasily; Chamorovskiy, Yuri; Okhotnikov, Oleg G

2012-11-01

216

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

217

Nanoscopic tip sensors fabricated by gas phase etching of optical glass fibers  

NASA Astrophysics Data System (ADS)

Silica-based fiber tips are used in a variety of spectroscopic, micro- or nano-scopic optical sensor applications and photonic micro-devices. The miniaturization of optical sensor systems and the technical implementation using optical fibers can provide new sensor designs with improved properties and functionality for new applications. The selective-etching of specifically doped silica fibers is a promising method in order to form complex photonic micro structures at the end or within fibers such as tips and cavities in various shapes useful for the all-fiber sensor and imaging applications. In the present study, we investigated the preparation of geometrically predefined, nanoscaled fiber tips by taking advantage of the dopant concentration profiles of highly doped step-index fibers. For this purpose, a gas phase etching process using hydrofluoric acid (HF) vapor was applied. The shaping of the fiber tips was based on very different etching rates as a result of the doping characteristics of specific optical fibers. Technological studies on the influence of the etching gas atmosphere on the temporal tip shaping and the final geometry were performed using undoped and doped silica fibers. The influence of the doping characteristics was investigated in phosphorus-, germanium-, fluorine- and boron-doped glass fibers. Narrow exposed as well as protected internal fiber tips in various shapes and tip radiuses down to less than 15 nm were achieved and characterized geometrically and topologically. For investigations into surface plasmon resonance effects, the fiber tips were coated with nanometer-sized silver layers by means of vapour deposition and finally subjected to an annealing treatment.

Bierlich, Jörg; Kobelke, Jens; Brand, David; Kirsch, Konstantin; Dellith, Jan; Bartelt, Hartmut

2012-12-01

218

Optimum Geometry of Stepped-Taper Beams.  

National Technical Information Service (NTIS)

An application of the parametric load index approach is presented which yields a general least weight formulation for stepped taper beams optimized for any prescribed number of stepped segments. The method provides for treating all cross-sectional dimensi...

L. Spunt

1981-01-01

219

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.

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

2011-01-01

220

Recent Results From the EU POF-PLUS Project: Multi-Gigabit Transmission Over 1 mm Core Diameter Plastic Optical Fibers  

Microsoft Academic Search

Recent activity to achieve multi-gigabit transmission over 1 mm core diameter graded-index and step-index plastic optical fibers for distances up to 50 meters is reported in this paper. By employing a simple intensity-modulated direct-detec- tion system with pulse amplitude or digital multi-tone modulation techniques, low-cost transceivers and easy to install large-core POFs, it is demonstrated that multi-gigabit transmission up to

C. M. Okonkwo; E. Tangdiongga; H. Yang; D. Visani; S. Loquai; R. Kruglov; B. Charbonnier; M. Ouzzif; I. Greiss; O. Ziemann; R. Gaudino; A. M. J. Koonen

2011-01-01

221

Compound activity in sensory nerve fibers is related to intensity of sensation evoked by air-puff stimulation of the index finger in man.  

PubMed

An analysis of a population response recorded from the primary afferents was undertaken to study the neural signs of intensity coding in the peripheral somatosensory system. Short air-puff stimuli were applied to the volar aspect of the tip of the index finger to obtain both neural and psychophysical responses. The detection threshold (So) was first determined and 6 levels of stimulus intensity above threshold (So + 0.25 kg/cm2, So + 1.25 kg/cm2, So + 2.50 kg/cm2, So + 3.75 kg/cm2, So + 5.00 kg/cm2, and So + 6.25 kg/cm2) were adopted for magnitude estimation using the stimulus level of So + 2.50 kg/cm2 as the standard stimulus. The subject was asked to give a numerical estimate of the intensity of a series of stimuli randomly presented. Compound sensory nerve action potentials (SNAPs) were also recorded from surface electrodes over the median nerve at the wrist for the 6 stimulus intensities. Eight SNAP components (4 positive and 4 negative) were recorded within 10 msec following stimulation. A simple power function with an exponent of 0.85 provided an adequate description of the magnitude estimation function, as was verified by the high correlation coefficient (r = 0.89, P less than 0.001). Similarly, stimulus-amplitude functions of individual SNAP components were well represented by straight lines in double logarithmic plots. The function of the late N2-P3 component had the highest power exponent (0.80) and also the highest correlation coefficient (r = 0.59, P less than 0.001). The functions of other SNAP components had considerably lower power exponents with lower correlation coefficients. Thus, a mismatch between neural and psychophysical functions was obvious when individual neural functions were compared with the psychophysical function. Conversely, it was found likely that the total number or time-integral of peaks in the population response was a more pertinent parameter of neural activity and, thus, had a closer correlation with the psychophysical response. PMID:1710966

Hashimoto, I; Gatayama, T; Yoshikawa, K; Sasaki, M; Nomura, M

1991-06-01

222

Natural fibers  

Treesearch

Description: The term “natural fibers” covers a broad range of vegetable, ... These fibers often contribute greatly to the structural performance of the plant and, ... One of the largest areas of recent growth in natural fiber plastic composites is the  ...

223

Fiber resources  

Treesearch

Almost all pulp and paper fiber resources are plant materials obtained from trees or agricultural crops. ... and fibers recovered from recycled paper or paperboard. ... papermaking (e.g., synthetic plastic fibers) but very small quantities and only ...

224

Dispersion tailoring in single mode optical fiber by doping silver nanoparticle  

NASA Astrophysics Data System (ADS)

We propose an optical fiber which has very low dispersion loss (typically ~ 6.7 ps2/km at 1,550 nm) that can be achieved by doping Ag nanoparticle into the core glass. At low absorption loss approximation, dispersion free propagation can be achieved up to 64 km for a 20 ps pulse. Enhanced third order nonlinearity due to the presence of Ag nanoparticle (typically ~ 3.82 × 10-20 W/m2) compensates for long length dispersion broadening that is not possible in conventional fused silica step index fiber.

Chattopadhyay, Rik; Bhadra, Shyamal K.

2013-05-01

225

Enhancing the locality of optical interrogation with photonic-crystal fibers  

NASA Astrophysics Data System (ADS)

Small-core photonic-crystal fibers (PCFs) are shown to enhance the locality of optical interrogation in fiber-probe-based imaging. We demonstrate that, in a typical fluorescence imaging experiment, the longitudinal dimension of the interrogated region closely follows the amtan-1?d scaling with the effective mode radius am and the beam-divergence angle ?d. The confinement of optical interrogation provided by small-core, high-index-step PCF probes is high enough to enable interrogation of individual neurons in a typical brain imaging experiment.

Doronina-Amitonova, Lyubov V.; Fedotov, Il'ya V.; Ivashkina, Olga I.; Zots, Marina A.; Fedotov, Andrei B.; Anokhin, Konstantin V.; Zheltikov, Aleksei M.

2012-07-01

226

Fiber optics  

Microsoft Academic Search

Topics discussed include the dispersion characteristics of three-layer elliptical fiber-optic waveguides; the coherence and polarization properties of radiation in single-mode fiber-optic waveguides; information transmission via optical solitons; the strength of long glass optical fibers; and heat-resistant optical fiber cables. Consideration is also given to the optical properties of germanium silicate glass for low-loss fiber-optic waveguides; nonlinear effects in single-mode fiber-optic

E. M. Dianov

1987-01-01

227

Effects of chemical modification on fusion splicing of optical fiber and preparation of fiber corrosion sensor  

NASA Astrophysics Data System (ADS)

It is very important for hydrofluoric acid to improve the performance of fused optical fiber and to prepare the fiber sensor. A novel transmitted-light differential interference contrast (DIC) system was used to nondestructively measure the refractive index profile (RIP) of an optical fiber. A hydrofluoric acid solution effectively enhanced some performances after fusion occurring. Furthermore, it also can remove the cladding of a optical fiber for constructing a fiber sensor to monitor corrosion of steel and aluminum.

Dong, Saying; Liao, Yanbiao; Zhang, Min; Tian, Qian

2004-11-01

228

An analytical study of the modal characteristics of annular step-index waveguide of elliptical cross section with two conducting helical windings on the two boundary surfaces between the guiding and the non guiding regions  

Microsoft Academic Search

We study an optical fiber with a guiding region bounded by two ellipses. There are two conducting helical windings on the two interfaces between the annular guiding region and the inner and outer cladding regions. The field components are determined for the different regions and they are matched at the boundaries using appropriate boundary conditions. This leads to an eighth

Deepak Kumar; O SINGHII

2002-01-01

229

Thin film-based optical fiber sensors  

Microsoft Academic Search

Optical thin films can be deposited on side- and end-face of optical fiber, if these films are sensitive to ambient environments, optical refractive index changes in thin films will finally result to variation of optical signals transmitted in the optical fiber. Here thin films work as sensitive elements and transducer to get response and feedback from environments, optical fiber here

Minghong Yang; Dai Jixiang; Wang Min; Xinling Tong; Desheng Jiang

2010-01-01

230

Developmental Single-Mode Fiber Transmission System.  

National Technical Information Service (NTIS)

The frequency response of data links transmitting analog signals over kilometer-length graded-index optical fibers is limited to 1 GHz by fiber bandwidth. System bandwidths can be substantially increased if single-mode fibers are used. In the developmenta...

K. Hagans R. Heritsch B. Pruett R. Neurath

1986-01-01

231

Effects of Accelerated Aging on Fiber Damage Thresholds  

SciTech Connect

Laser-induced damage mechanisms that can occur during high-intensity fiber transmission have been under study for a number of years. Our particular interest in laser initiation of explosives has led us to examine damage processes associated with the transmission of Q-switched, Nd:YAG pulses at 1.06 {micro}m through step-index, multimode, fused silica fiber. Laser breakdown at the fiber entrance face is often the first process to limit fiber transmission but catastrophic damage can also occur at either fiber end face, within the initial entry segment of the fiber, and at other internal sites along the fiber path. Past studies have examined how these various damage mechanisms depend upon fiber end-face preparation, fiber fixturing and routing, laser characteristics, and laser-to-fiber injection optics. In some applications of interest, however, a fiber transmission system may spend years in storage before it is used. Consequently, an important additional issue for these applications is whether or not there are aging processes that can result in lower damage thresholds over time. Fiber end-face contamination would certainly lower breakdown and damage thresholds at these surfaces, but careful design of hermetic seals in connectors and other end-face fixtures can minimize this possibility. A more subtle possibility would be a process for the slow growth of internal defects that could lead to lower thresholds for internal damage. In the current study, two approaches to stimulating the growth of internal defects were used in an attempt to produce observable changes in internal damage thresholds. In the first approach test fibers were subjected to a very high tensile stress for a time sufficient for some fraction to fail from static fatigue. In the second approach, test fibers were subjected to a combination of high tensile stress and large, cyclic temperature variations. Both of these approaches were rather arbitrary due to the lack of an established growth mechanism for internal defects. Damage characteristics obtained from fibers subjected to each of these aging environments were compared to results from fresh fibers tested under identical conditions. A surprising result was that internal damage was not observed in any of the tested fibers. Only breakdown at the fiber entrance face and catastrophic damage at both end faces were observed. Fiber end faces were not sealed during the accelerated aging environments, and thresholds at these faces were significantly lower in the aged fibers. However, most fibers transmitted relatively high pulse energies before damaging, and a large fraction never damaged before we reached the limits of our test laser. The absence of any observable affect on internal damage thresholds is encouraging, but the current results do not rule out the possibility that some other approach to accelerated aging could reveal a growth mechanism for internal defects.

Setchell, R.E.

1999-02-15

232

Optical fiber laser  

SciTech Connect

This patent describes an optical fiber laser comprising: a gain cavity including a single mode optical fiber of given length and index of refraction and a cladding surrounding the core and having an index of refraction lower than that of the core. The core comprising a host material having incorporated therein a predetermined concentration of just erbium oxide having a fluorescence spectrum with a peak emission line at 1.54 micrometers; filter means optically coupled to each end of the fiber gain cavity for providing feedback in the cavity at the peak emission line of the erbium oxide and for permitting energy to be introduced into the cavity at the absorption band of the erbium oxide in the region of 1.45 to 1.53 micrometers; and a laser diode optically coupled to one end of the core for pumping energy into the end of the gain cavity so that the gain cavity oscillates at just the peak emission line.

Snitzer, E.

1988-10-25

233

Carbon nanotubes coated fiber optic ammonia gas sensor  

NASA Astrophysics Data System (ADS)

We report, intrinsic fiber optic carbon nanotubes coated sensor for the detection of ammonia gas at room temperature. Multimode step index polymethyl methacrylate (PMMA) optical fiber passive cladding is partly replaced by an active coating of single and multi-walled carbon nanotubes following the dip coating technique and the reaction with ammonia is studied by measuring the change in output intensity from the optical fiber under various ammonia gas concentrations in the range 0-500 ppm in step of 50 ppm. The sensitivity is calculated for different wavelengths in the range 200-1100 nm both for single and multi-walled carbon nanotubes coated fiber. Higher sensitivities are obtained as 0.26 counts/ppm and 0.31 counts/ppm for single-walled (average diameter 1.3 nm, 30 wt.% purity) and multi-walled (average diameter 10-15 nm, 95 wt.% purity) carbon nanotubes respectively. The role of diameter and purity of carbon nanotubes towards the ammonia sensing is studied and the results are discussed.

Manivannan, S.; Shobin, L. R.; Saranya, A. M.; Renganathan, B.; Sastikumar, D.; Park, Kyu Chang

2011-02-01

234

A simple interrogation technique for refractive index measurement using multimode interference structure  

Microsoft Academic Search

A simple interrogation technique for refractive index measurement is proposed, using a multimode interference-based fiber tip structure. The fiber probe is a section of a multimode fiber, spliced to a single-mode fiber and interrogated in reflection. The interrogation technique uses two fiber Bragg gratings as discrete optical sources; by means of relative intensity variation of the reflected signals, those sources

Susana Silva; O. Frazão; J. L. Santos; F. X. Malcata

2011-01-01

235

End-face preparation methods for high-intensity fiber applications  

SciTech Connect

High laser intensities are being transmitted through optical fibers in a growing number of applications. The author`s interest in laser initiation of explosives has led him to examine the transmission of Q-switched, Nd:YAG laser pulses through step-index, multimode, fused-silica fibers for a number of years. A common limiting process is a plasma-forming breakdown occurring at the fiber entrance face. The breakdown threshold at this face depends on the surface characteristics that result from the particular method of end-face preparation. In previous studies he examined entrance-face breakdown thresholds for several different mechanical polishing schedules, and also for several schedules of CO{sub 2}-laser conditioning following mechanical polishing. In the present study he examined three end-face preparation methods that were based on the recent availability of exceptionally good cleaved surfaces for the fibers of interest. Using test procedures similar to those in past studies, he examined the cleaved fibers directly, fibers with cleaved surfaces that were subsequently flame polished, and fibers with cleaved surfaces that were subsequently conditioned with a CO{sub 2} laser. All of these preparation methods resulted in fibers that showed a broader range of entrance-face breakdown conditions than found in past studies, together with a susceptibility to subsurface exit-face damage. By introducing additional cleaning steps with the cleaved surfaces, he was able to reduce the variability in breakdown thresholds observed after subsequent CO{sub 2}-laser conditioning. A consistent location of exit-face damage sites indicates that subsurface fracturing occurs during the cleaving process, and that the subsequent end-face processing steps were not effective in mitigating damage at these sites. Threshold energies for entrance-face breakdown are also affected by the relation between incident laser energy and the resulting peak local fluence at this surface.

Setchell, R.E.

1997-10-01

236

Natural fibers  

Treesearch

Description: The term “natural fibers” covers a broad range of vegetable, animal, ... it usually refers to wood fiber and plant-based bast, leaf, seed, and stem fibers. ... One of the largest areas of recent growth in natural fiber plastic composites is ...

237

Method of thermochemically treating silicon carbide fibers derived from polymers  

Microsoft Academic Search

A method is described of thermochemically treating polymeric-derived silicon carbide fiber comprising the step of: annealing a silicon carbide fiber derived from organosilicon polymeric precursors said fiber further including at least: (1) excess carbon and oxygen, (2) excess silicon and oxygen, or (3) nitrogen, at a temperature between 800 C and 1,800 C, thus outgassing from said silicon carbide fiber

J. S. Wallace; B. A. Bender; D. Schrodt

1993-01-01

238

Selected Bibliography on Fiber-Reinforced Cement and Concrete.  

National Technical Information Service (NTIS)

A listing of 660 references with author index is given for fiber reinforced cement and gypsum matrices, mortars, and concretes. Fiber types include steel, glass, plastic, asbestos, organic, carbon, and others. (Author)

C. M. Fontenot G. C. Hoff J. G. Tom

1976-01-01

239

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

240

Chemiluminescent optical fiber immunosensor for detecting cholera antitoxin  

NASA Astrophysics Data System (ADS)

A chemiluminescent-based optical fiber immunosensor is developed to detect the presence of jejunal cholera antitoxin IgA immunoglobulins. This was accomplished using optical fiber tips, conjugated with the cholera toxin B subunit. The cholera antitoxin analyte is marked by a secondary antibody labeled with horseradish peroxidase. A photoelectronic setup is designed specifically to monitor the signal. This immunosensor system is shown to be specific, sensitive, and fast to run, without requiring a purification step. The lowest titer detected was 1:1,310,720. When the luminol-containing buffer solution was replaced by air, thus dramatically lowering the index of refraction of the surrounding medium, sensitivity increased and cholera antitoxin was detected at an additional titer dilution at 1:2,621,440.

Marks, Robert S.; Bassis, Effim; Bychenko, Alexei; Levine, Myron M.

1997-12-01

241

Radiation Effects and Propagation in Optical Fibers and Components.  

NASA Astrophysics Data System (ADS)

The power series expansion method was used to solve the wave equation in step-index optical fiber. The cut off frequencies were calculated using 200 coefficients. The cutoff frequencies of TM modes were found to differ from those of TE modes. This difference, which is the error due to the approximations made, was calculated as a function of the relative refractive index difference (Delta ). The intermodal delay between the TE and TM mode was also calculated. The dispersion curves were plotted for several modes and values of Delta. A polarization control system was designed to be used in a coherent optical communication system, to restore the state of polarization (SOP) of the light output of a singlemode fiber. Rotating quarter wave and half wave plates were used to compensate for the changes in SOP. The sensitivity of the system was greatly improved by utilizing the heterodyne principle. The effects of neutron irradiation were studied on fiber optic materials (glasses), optical fibers, and photodetectors. In case of the heavy metal fluoride glasses, a red shift was found in the UV edge, which increased with neutron fluence. A very small amount of recovery was observed after three weeks. The shift could be due to the occurrence of color centers on irradiation and/or due to the shift in the urbach edge itself. The optical fibers showed an increase in the attenuation in the visible/near IR part of the spectrum. Fibers doped with P in the core showed more induced loss compared to the fibers doped with P in the cladding, and showed little or no recovery after a day. Radiation hardened fibers suffered far less induced loss on irradiation compared to the other fibers and also recovered in attenuation by a factor of 3 to 6 after a day. The responsivity of Si-PIN and Ge-PIN photodiodes degraded after irradiation. The relative responsivity was found to have a spectral dependence in case of Si-photodiode but was found to be independent of wavelength in case of Ge-photodiode. The primary photocurrent and current gain of Si-APD degraded after irradiation. This degradation is explained in terms of the defects introduced in the depletion region.

Gedam, Subhash Ganpatrao

1987-09-01

242

Vectorial wave analysis of stress-applied polarization-maintaining optical fibers by the finite-element method  

Microsoft Academic Search

A vectorial wave analysis of stress-applied polarization-maintaining optical fibers is presented using a vectorH-field finite-element method. In this approach, the divergence-free constraint forHis imposed and the spurious, nonphysical solutions which are included in the solutions of earlier vectorial finite-element methods do not appear in a guided region. In order to verify the accuracy of solutions, numerical results for a step-index

K. Hayata; M. Koshiba; M. Suzuki

1986-01-01

243

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.

244

Latest advancements in the acetylation of wood fibers to improve ...  

Treesearch

The acetylated fiber is then stripped in a first step with superheated vapor of ... more stable to dimensional changes in both high relative humidity and liquid water ... Keywords: Fibers, acetylation, dimensional stability, equilibrium moisture  ...

245

UK Index  

NSDL National Science Digital Library

The UK Index provides a searchable index of resources in or about the United Kingdom. The Quick Reference section offers links to News Resources in the UK such as the BBC, weather information, UK record charts, and UK related USENET newsgroups. The Foreign & Commonwealth Office provides good advice for travelers. The search engine allows the selection of categories such as arts or business to restrict the search to pages included in one category or a combination of categories.

246

Wavelength dependent measurements of optical fiber transit time, material dispersion, and attenuation  

SciTech Connect

A new method for measuring the wavelength dependence of the transit time, material dispersion, and attenuation of an optical fiber is described. The authors inject light from a 4-ns risetime pulsed broad-band flashlamp into various length fibers and record the transmitted signals with a time-resolved spectrograph. Segments of data spanning an approximately 3,000 {angstrom} range are recorded from a single flashlamp pulse. Comparison of data acquired with short and long fibers enables the determination of the transit time and the material dispersion as functions of wavelength dependence for the entire recorded spectrum simultaneously. The wavelength dependent attenuation is also determined from the signal intensities. The method is demonstrated with experiments using a step index 200-{micro}m-diameter SiO{sub 2} fiber. The results agree with the transit time determined from the bulk glass refractive index to within {+-} 0.035% for the visible (4,000--7,200 {angstrom}) spectrum and 0.12% for the ultraviolet (2,650--4,000 {angstrom}) spectrum, and with the attenuation specified by the fiber manufacturer to within {+-} 10%.

COCHRANE,KYLE ROBERT; BAILEY,JAMES E.; LAKE,PATRICK WAYNE; CARLSON,ALAN L.

2000-04-18

247

Characterization of nanolayer LPG refractometer according surrounding refractive index  

NASA Astrophysics Data System (ADS)

In this work the behavior of an optical fiber Long Period Grating (LPG) refractometer with the variations of the surrounding refractive index is discussed. The objective is to characterize optical fiber refractometers sensitive to surrounding refractive index, higher and lower than the cladding. For values of surrounding refractive index higher than the cladding, the LPG does not show enough sensitivity. For this reason, a nanolayer of an organic material was coated onto the fiber, using the Langmuir-Blodgett technique. We characterized LPG covered with different nanolayers thickness (110 and 120 nm) relatively to changes in surrounding refractive index.

Simões, E.; Abe, I.; Oliveira, J.; Pinto, J. L.; Caldas, P.; Frazão, O.

2010-09-01

248

Microstructured fibers for sensing applications  

NASA Astrophysics Data System (ADS)

Microstructured fibers (MOFs) are among the most innovative developments in optical fiber technology in recent years. These fibers contain arrays of tiny air holes that run along their length and define the waveguiding properties. Optical confinement and guidance in MOFs can be obtained either through modified total internal reflection, or photonic bandgap effects; correspondingly, they are classified into index-guiding Holey Fibers (HFs) and Photonic Bandgap Fibers (PBGFs). MOFs offer great flexibility in terms of fiber design and, by virtue of the large refractive index contrast between glass/air and the possibility to make wavelength-scale features, offer a range of unique properties. In this paper we review the current status of air/silica MOF design and fabrication and discuss the attractions of this technology within the field of sensors, including prospects for further development. We focus on two primary areas, which we believe to be of particular significance. Firstly, we discuss the use of fibers offering large evanescent fields, or, alternatively, guidance in an air core, to provide long interaction lengths for detection of trace chemicals in gas or liquid samples; an improved fibre design is presented and prospects for practical implementation in sensor systems are also analysed. Secondly, we discuss the application of photonic bandgap fibre technology for obtaining fibres operating beyond silica's transparency window, and in particular in the 3?m wavelength region.

Petrovich, M. N.; van Brakel, A.; Poletti, F.; Mukasa, K.; Austin, E.; Finazzi, V.; Petropoulos, P.; O'Driscoll, E.; Watson, M.; DelMonte, T.; Monro, T. M.; Dakin, J. P.; Richardson, D. J.

2005-11-01

249

Effect of carbon fiber dispersion on the mechanical properties of carbon fiber-reinforced cement-based composites  

Microsoft Academic Search

The preparation of carbon fiber-reinforced cement-based composites involved two-step dispersions of carbon fibers. Both steps affected greatly the mechanical properties of the composites. With the aid of ultrasonic wave, a new dispersant hydroxyethyl cellulose was used to help fiber dispersion in the first step. The fracture surface of the composites was observed by scanning electron microscopy. The distribution of major

Chuang Wang; Ke-Zhi Li; He-Jun Li; Geng-Sheng Jiao; Jinhua Lu; Dang-She Hou

2008-01-01

250

Reconstruction of refractive index profile of optical waveguides by the finite element method  

NASA Astrophysics Data System (ADS)

We show that the refractive-index profile (RIP) of optical waveguides can be determined by analyzing the transmitted near-field pattern with the finite element method. The first step consists in determine the initial guess for the RIP. Then, the selected guess is improved applying a reconstruction procedure with the finite element method. The procedure has been evaluated by comparing the obtained results with experimental measurements obtained by the RNF and m-lines techniques on a pure-silica single-mode fiber and slab waveguide, respectively.

Solano G., Sigifredo; Ramirez, Catalina A.; Morales, Javier; Torres, Pedro I.; Gomez Montoya, Nicolas A.

2004-10-01

251

INDEXING MECHANISM  

DOEpatents

A device is presented for loading and unloading fuel elements containing material fissionable by neutrons of thermal energy. The device comprises a combination of mechanical features Including a base, a lever pivotally attached to the base, an Indexing plate on the base parallel to the plane of lever rotation and having a plurality of apertures, the apertures being disposed In rows, each aperture having a keyway, an Index pin movably disposed to the plane of lever rotation and having a plurality of apertures, the apertures being disposed in rows, each aperture having a keyway, an index pin movably disposed on the lever normal to the plane rotation, a key on the pin, a sleeve on the lever spaced from and parallel to the index pin, a pair of pulleys and a cable disposed between them, an open collar rotatably attached to the sleeve and linked to one of the pulleys, a pin extending from the collar, and a bearing movably mounted in the sleeve and having at least two longitudinal grooves in the outside surface.

Kock, L.J.

1959-09-22

252

Automating metadata generation: the simple indexing interface  

Microsoft Academic Search

In this paper, we focus on the development of a framework for automatic metadata generation. The first step towards this framework is the definition of an Application Programmer Interface (API), which we call the Simple Indexing Interface (SII). The second step is the definition of a framework for implementation of the SII. Both steps are presented in some detail in

Kris Cardinaels; Michael Meire; Erik Duval

2005-01-01

253

All-Optical Polymer Fiber Devices.  

National Technical Information Service (NTIS)

The goal of our research was to build an ultrafast all-optical switching device in a single mode polymer optical fiber. We have concentrated on both extensive processing and characterization studies. Activities included characterizing: refractive index pr...

M. G. Kuzyk

1998-01-01

254

Microstructured multimode optical fiber for differential mode delay compensation  

NASA Astrophysics Data System (ADS)

Design of differential mode delay compensating microstructured multimode fiber (MMF-DCF) and microstructured multimode fiber optimized for 0,85 mkm wavelength window which imitate ideal graded refractive index profile of conventional multimode fiber are presented in this paper. The main feature of the proposed fibers is that they are capable of being constructed without the need of germanium doping, this type of fibers are known as microstructured fibers. The axially oriented small air holes, that run the entire fiber length, are configured to provide required refractive index profile and more focused interaction with selected modes. Results of microstructured multimode fiber and differential mode delay compensating microstructured multimode fiber design and results of group velocity calculation for selected modes with full vector finite element method are presented. It is shown that the proposed approach enables the synthesis of microstructured MMF-DCFs and provides resulting group velocities diagram of the excited modes, close to the desired optimal.

Bourdine, Anton V.; Burdin, Vladimir A.; Delmukhametov, Oleg R.

2010-12-01

255

Superconducting fiber  

NASA Astrophysics Data System (ADS)

In this study, we demonstrated superconductivity in a fiber with a lead core and fused silica cladding. The fibers were fabricated via a melt-draw technique and maintained overall diameters ranging from 200-900 ?m and core diameters of 100-800 ?m. Superconductivity of this fiber design was validated via the traditional four probe test method in a bath of liquid helium at temperatures on the order of 4 K. The superconducting fiber paves the way for applications in power transmission, magnetic sensing, and fundamental studies in the fields of electromagnetism.

Homa, D.; Liang, Y.; Pickrell, G.

2013-08-01

256

Method of thermochemically treating silicon carbide fibers derived from polymers  

SciTech Connect

A method is described of thermochemically treating polymeric-derived silicon carbide fiber comprising the step of: annealing a silicon carbide fiber derived from organosilicon polymeric precursors said fiber further including at least: (1) excess carbon and oxygen, (2) excess silicon and oxygen, or (3) nitrogen, at a temperature between 800 C and 1,800 C, thus outgassing from said silicon carbide fiber at least one member selected from the group consisting of nitrogen, silicon monoxide and carbon monoxide, in intimate contact with carbon particles and in the presence of a gas capable of reacting in the presence of said carbon particles and said silicon carbide fiber, with products and byproducts formed as a result of said outgassing to form silicon carbide, so that said annealing step provides an annealed fiber wherein at least said silicon of the silicon carbide at said modified surface of said annealed fiber was originally present in said fiber prior to said annealing step.

Wallace, J.S.; Bender, B.A.; Schrodt, D.

1993-07-27

257

Bragg gratings photoinduced in ZBLAN fibers by femtosecond pulses at 800 nm.  

PubMed

Fiber Bragg gratings were written in thulium-doped and undoped single-mode ZBLAN fibers by focusing femtosecond laser pulses on the fiber core through a phase mask. Maximum index modulation of the order of 1 x 10(-3) was induced in both types of fibers. Measurements of the transverse refractive index changes across the core and cladding regions indicate that the grating formation originates from a negative index change. PMID:17392885

Bernier, M; Faucher, D; Vallée, R; Saliminia, A; Androz, G; Sheng, Y; Chin, S L

2007-03-01

258

Long period gratings in photonic crystal fibers  

NASA Astrophysics Data System (ADS)

The authors review the recent advances in fabricating long-period gratings (LPGs) in photonic crystal fibers (PCFs). The novel light-guiding properties of the PCFs allow the demonstration of novel sensors and devices based on such LPGs. The sensitivity of these PCF LPGs to temperature, strain and refractive index is discussed and compared with LPGs made on conventional single-mode fibers. In-fiber devices such as tunable band rejection filters, Mach-Zehnder interferometers are discussed.

Ju, Jian; Jin, Wei

2012-03-01

259

Semi-guiding high-aspect-ratio core (SHARC) fiber providing single-mode operation and an ultra-large core area in a compact coilable package.  

PubMed

A new class of optical fiber is presented that departs from the circular-core symmetry common to conventional fibers. By using a high-aspect-ratio (~30:1) rectangular core, the mode area can be significantly expanded well beyond 10,000 ?m2. Moreover, by also specifying a very small refractive-index step at the narrow core edges, the core becomes "semi-guiding," i.e. it guides in the narrow dimension and is effectively un-guiding in the wide mm-scale dimension. The mode dependence of the resulting Fresnel leakage loss in the wide dimension strongly favors the fundamental mode, promoting single-mode operation. Since the modal loss ratios are independent of mode area, this core structure offers nearly unlimited scalability. The implications of using such a fiber in fiber laser and amplifier systems are also discussed. PMID:21934837

Rockwell, David A; Shkunov, Vladimir V; Marciante, John R

2011-07-18

260

Radiation damage effects on liquid scintillating fibers  

Microsoft Academic Search

The effects of radiation on liquid scintillating fibers composed of borosilicate glass (Pyrex) tubing in combination with a high refractive index liquid scintillator are investigated. The fiber components (tubes, liquids and liquids in tubes), were irradiated in a nuclear reactor with doses exceeding 100 megarads. It was found that the discoloration of the glass tubing does not degrade the optical

Mei Gui; F. R. Huson; Tina Ostrovsky; Dan Reese; Dan Suson; J. T. White

1993-01-01

261

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...

262

Microstructures made in optical fiber with femtosecond laser  

Microsoft Academic Search

Different types of microstructures including microchannels and microslots were made in optical fibers using femtosecond laser inscription and chemical etching. Integrated with UV-inscribed fiber Bragg gratings, these microstructures have miniature, robustness and high sensitivity features and have been used to implement novel devices for various sensing applications. The fiber microchannels were used to detect the refractive index change of liquid

Kaiming Zhou; Lin Zhang; Xianfeng Chen; Vladimir Mezentsev; Ian Bennion

2010-01-01

263

Fiber Optic Interferometer Configuration with Pump-Induced Phase Carrier.  

National Technical Information Service (NTIS)

An interferometric fiber optic sensor and method are provided for controlling the optical phase of a fiber interferometer by an optically induced change in the refractive index for one arm of the fiber interferometer and providing a passive all-optical ph...

A. D. Kersey C. A. Villarruel

1992-01-01

264

Selective multi-chemical fiber optic sensor  

NASA Astrophysics Data System (ADS)

A fiber optic sensor for detecting at least one chemical by evanescent wave spectroscopy comprises a generator of a light signal, a mirror for introducing the light signal into a fiber, a clad optical chalcogenide glass fiber, a mirror for directing the light signal from the fiber into a detector, and a detector for detecting chemicals by the fiber. The fiber comprises a core and a clad having lower refractive index than the core enveloping and being in continuous contact with the core, at least one region on the fiber completely or partially devoid of the clad, and a polymer disposed in the region having affinity for the chemical(s). There being a different polymer in each region if there is more than one region.

Sanghera, Jasbinder; Pureza, Pablo C.; Aggarwal, Ishwar D.; Nau, Gregory

1994-10-01

265

Fabrication and measurements of plastic scintillating fibers  

Microsoft Academic Search

Sixty kilometers of plastic scintillating fibers, 1mm in diameter, have been manufactured using a preform\\/tube technology. The fibers consist of a polystyrene core surrounded by a polymethylmethacrylate cladding. The fabrication method is described and evaluated both qualitatively and quantitatively. A great effort has been made in order to measure the optical properties of the polymer at the different steps of

P. P. Rebourgeard; F. Rondeaux; J. P Baton; G. Besnard; H. Blumenfeld; M. Bourdinaud; J. Calvet; J.-C Cavan; R. Chipaux; A. Giganon; J. Heitzmann; C. Jeanney; P. Micolon; M. Neveu; T. Pedrol; D. Pierrepont; J.-C Thévenin

1999-01-01

266

Applications of MIR fibers for medical diagnostics  

NASA Astrophysics Data System (ADS)

In this work only first steps in blood glucose measurements were made and possibilities of tissue analysis were demonstrated with a MIR fiber probe. Spectroscopic measurements with the same objects by ATR (attenuated total reflectance) elements were made before, but advantages make fiber use more attractive.

Artjushenko, Vjacheslav G.; Konov, Vitaly I.; Lerman, Alexander A.; Kryukov, Alexander P.; Kuzin, Eugenii A.; Plotnichenko, V. G.; Neuberger, Wolfgang

1993-05-01

267

PNSI Wizards: Step-by-Step Instructions  

Center for Food Safety and Applied Nutrition (CFSAN)

Step-by-Step Instructions for submitting Prior Notice for Food Articles using FDA's PNSI (Prior Notice System Interface) Version 1.9. More results from www.fda.gov/food/guidanceregulation/importsexports

268

Few modes in infrared photonic crystal fibers  

NASA Astrophysics Data System (ADS)

Photonic crystal fibers guide light by trapping it in a periodic array of elements in the cladding area. We fabricated photonic crystal fibers by multiple extrusions of silver halide (AgClxBr1-x) crystals which are highly transparent in the middle infrared. The core of such a fiber consisted of pure silver bromide AgBr (n=2.16 at 10.6 ?m), and the cladding area consisted of concentric rings of fiber-optic elements made of pure silver chloride AgCl (n=1.98 at 10.6 ?m), which lowered the refractive index of the clad. Two types of photonic crystal fibers were fabricated, one with two concentric rings and one with five concentric rings of fiber-optic elements around the core. The characterization of the fibers, such as the power distribution, the attenuation, and the numerical aperture were measured. Both fibers behaved like regular core-clad structures. Simulations on these structures showed that each of these fibers guided a small number of modes and that adding rings to the structure lowered the number of bound modes in the core. This would pave the way for the fabrication of single-mode fibers. Photonic crystal fibers offer many advantages compared to conventional fibers, and they will be extremely useful for many applications in the middle and far infrared.

Rave, E.; Sade, S.; Millo, A.; Katzir, A.

2005-02-01

269

Wide-band dual-mode operation of multi-core fibers with air-hole structure  

NASA Astrophysics Data System (ADS)

A novel multi-core dual-mode fiber consisting of 11 cores with eight air holes for wide-band dual-mode operation is proposed in this paper. Modal properties, operation range and effective area affected by core-to-core distance, core-to-pitch ratio, relative index difference and center core diameter are investigated systematically. For 11-core dual-mode fiber with air-hole structure, simulation shows that it can support both a strict dual-mode operation (propagation in HE11 mode and HE21 mode only) and low bending losses (less than 0.8 dB/m at R>0.20 m), meanwhile maintaining a large effective area up to 1120.33 ?m2. With a proper design of structural parameters the effective area of the 11-core dual-mode could be even higher. It has great advantages over conventional few-mode fibers, multi-core fibers and step-index single-mode fibers in terms of less mode coupling, larger effective area and lower bending loss.

Lin, Zhen; Ren, Guobin; Zheng, Siwen; Jian, Shuisheng

2013-10-01

270

Fabrication of highly nonlinear optical fibers with tellurite glass core and phosphate glass cladding  

NASA Astrophysics Data System (ADS)

We perform a systematic investigation of phosphate glasses containing alkaline earth, alkali and mixed-alkali oxides proposed as cladding glasses for tellurite-glass core to realize highly nonlinear optical fibers with tailored chromatic dispersion. The effects of glass composition on the optical and thermal properties of phosphate glasses are studied in this work. The phosphate glasses containing alkali oxides exhibit transmission windows in the range of 0.2-3.5 ?m and refractive indices as low as 1.500 at 1544 nm. The coefficient of thermal expansion, viscosity, glass transition temperature, deformation temperature and crystallization temperature of those glasses are optimized to allow successful fiber drawing with tellurite-glass cores. We propose the 40P2O5-30ZnO-20Na2O-10K2O mol% (PZNK) mixed-alkali phosphate glass as a suitable cladding material for the 78TeO2-5ZnO-12Li2O-5Bi2O3 mol% (TZLB) tellurite-glass used as a core material since they have nearly identical thermal characteristics. A successful fabrication of step-index optical fibers composed of TZLB and PZNK glasses and numerical calculations in chromatic dispersion and nonlinear coefficient are demonstrated. The large refractive index difference of 0.49 between TZLB and PZNK glasses confirms the high nonlinearity and freely-tailored chromatic dispersion profiles of these new fibers.

Tong, Hoang Tuan; Kito, Chihiro; Suzuki, Takenobu; Ohishi, Yasutake

2012-09-01

271

Dietary Fiber and Weight Gain  

Microsoft Academic Search

To the Editor: The study by Dr Ludwig and colleagues 1 pro- vides evidence that a high intake of low-fiber foods is a key me- diator of the epidemic of obesity in the United States. The au- thors plausibly suggest that this effect is primarily attributable to the often high glycemic index of such foods. A secondary but no less

Robert J. L. Waugh

2010-01-01

272

Tunable photonic band gap fiber  

Microsoft Academic Search

The ability to change the photonic band gap structure continuously and reversibly by modifying the index thermally allows the band gap features to be sensitively tuned, allowing for a thorough investigation of the various band gap guiding properties. Furthermore, it may be possible to use this type of band gap fiber as a tunable filter. Investigations of the dispersion properties

R. T. Bise; R. S. Windeler; K. S. Kranz; C. Kerbage; B. J. Eggleton; D. J. Trevor

2002-01-01

273

Progress in crystalline semiconductor core optical fibers  

NASA Astrophysics Data System (ADS)

Recently developed glass-clad crystalline semiconductor core optical fibers potentially offer a series of advantages over present optical fiber materials including greatly enhanced Raman cross-sections and extended infrared transparency. Indeed, the low-cost high-through-put fiberization of crystalline materials could permit a step-jump in performance critical for use in high energy laser, infrared counter-measure, communication, and sensor systems. Further, the high degree of crystallinity is of considerable scientific value since optical fiber fabrication is a highly non-equilibrium process and so achieving high degrees of crystallinity is very counter-intuitive and offers new insight into crystal growth mechanisms. This talk will review progress in glass-clad fibers possessing cores of highly crystalline silicon and germanium including anomalies in Si and Ge that may benefit fiber fabrication as well as paths forward to optimization of fiber design and performance.

Ballato, J.; Hawkins, T.; Foy, P.; McMillen, C.; Stolen, R.; Rice, R.

2010-02-01

274

Accurate modal gain control in a multimode erbium doped fiber amplifier incorporating ring doping and a simple LP?? pump configuration.  

PubMed

We experimentally validate a numerical model to study multimode erbium-doped fiber amplifiers (MM-EDFAs). Using this model, we demonstrate the improved performance achievable in a step index MM-EDFA incorporating a localized erbium doped ring and its potential for Space Division Multiplexed (SDM) transmission. Using a pure LP?? pump beam, which greatly simplifies amplifier construction, accurate modal gain control can be achieved by carefully tuning the thickness of the ring-doped layer in the active fiber and the pump power. In particular, by optimizing the erbium-ring-doped structure and the length of active fiber used, over 20dB gain for both LP?? and LP?? signals with a maximum gain difference of around 2 dB across the C band are predicted for a pure LP?? pump beam delivering 250 mW power at 980 nm. PMID:23037207

Kang, Qiongyue; Lim, Ee-Leong; Jung, Yongmin; Sahu, Jayanta K; Poletti, Francesco; Baskiotis, Catherine; Alam, Shaif-Ul; Richardson, David J

2012-09-10

275

Interferometric fiber optic sensors.  

PubMed

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

2012-02-23

276

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.

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

2012-01-01

277

Modification in optical fibers using high-intensity femtosecond lasers  

Microsoft Academic Search

Refractive index modification in optical multimode fibers was firstly demonstrated, as a fabrication method of double cladding structure, using plasma channeling excited by a high intensity femtosecond Ti:Sapphire laser. The induced refractive index modification in a pure silica multimode fiber with 100\\/110 micrometers core\\/cladding diameter was reached to the length of approximately 9-10 mm from the end of optical fiber

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

1999-01-01

278

Automated alignment of microstructured optical fibers and conventional single-mode fibers  

NASA Astrophysics Data System (ADS)

Aligning two optical fibers is a crucial step in designing good optical fiber-based systems and networks. Good alignment optimizes the power transmitted between the fibers, especially when a microstructured optical fiber (MOF) is interfaced with a single-mode fiber (SMF). In this paper, we present a self-alignment algorithm based on particle swarm optimization (PSO). The PSO algorithm is used to locate the optimal coupling position with the highest optical power for alignments with multiple degrees of freedom. The proposed algorithm is validated by applying it for two different sources and checking the achieved alignment of SMF and MOF and that of two SMFs.

Landry, Marc; Kaddouri, Azeddine; Bouslimani, Yassine; Ghribi, Mohsen

2013-06-01

279

Synthesis of silver chloride nanocrystal on silk fibers  

Microsoft Academic Search

The synthesis of silver chloride nanocrystals on silk fiber is reported. The growth of the nanocrystal was achieved by sequential dipping of the silk fibers in alternating solution of either silver nitrate or sodium chloride followed by a rinse step. The negative charge present at the surface of the fibers can immobilize silver ions which react in the next sodium

Pranut Potiyaraj; Panittamat Kumlangdudsana; Stephan T. Dubas

2007-01-01

280

Benefits of glass fibers in solar fiber optic lighting systems.  

PubMed

The transmission properties and coupling of solar light have been studied for glass core multimode fibers in order to verify their benefits for a solar fiber optic lighting system. The light transportation distance can be extended from 20 m with plastic fibers to over 100 m with the kind of glass fibers studied here. A high luminous flux, full visible spectrum, as well as an outstanding color rendering index (98) and correlated color temperature similar to the direct sun light outside have been obtained. Thus the outstanding quality of solar light transmitted through these fibers would improve the visibility of all kinds of objects compared to fluorescent and other artificial lighting. Annual relative lighting energy savings of 36% in Uppsala, Sweden, and 76% in Dubai were estimated in an office environment. The absolute savings can be doubled by using glass optical fibers, and are estimated to be in the order of 550??kWh/year in Sweden and 1160??kWh/year in Dubai for one system of only 0.159??m2 total light collecting area. The savings are dependent on the fiber length, the daily usage time of the interior, the type of artificial lighting substituted, the system light output flux, and the available time of sunny weather at the geographic location. PMID:24085167

Volotinen, Tarja T; Lingfors, David H S

2013-09-20

281

Technique to prepare high-reflectance optical fiber Bragg gratings with single exposure in-line or fiber draw tower  

NASA Astrophysics Data System (ADS)

A process for making an optical reflection grating in a glass fiber includes exposing all unjacketed optic fiber to a single writing pulse from a pair of interfering light beams that form an interference pattern in the fiber. A novel optical fiber has at least one optical grating with a preselected Bragg spacing in at least one region of the fiber, with a periodic modulation in its index of refraction, with high thermal stability and narrow linewidth. A process for making an array of optical reflection gratings in a glass fiber includes exposing a fiber to a plurality of writing pulse from a pair of interfering light beams that form an interference pattern in the fiber, where these pulses are applied sequentially as the fiber is drawn from a draw furnace. A novel optical fiber has a plurality of unspliced gratings with high thermal stability and narrow linewidth.

Askins, Charles G.; Friebele, Edward J.

1995-03-01

282

Optical fiber lasers and amplifiers  

SciTech Connect

An optical fiber is described, which comprises: a substantially single-mode core having an index of refraction n/sub 1/ comprised of laser material disposed within a multi-mode cladding having an index of refraction n/sub 2/; and a further cladding having an index of refraction n/sub 3/ surrounding the multi-mode cladding with substantially no space between the further cladding and the multi-mode cladding; wherein the single-mode core is disposed at an offset from the geometric center of the multi-mode cladding.

Snitzer, E.; Po, H.; Tumminelli, R.P.; Hakimi, F.

1989-03-21

283

Brillouin characterization of holey optical fibers  

NASA Astrophysics Data System (ADS)

We report the results of detailed measurements on the Brillouin frequency shift (BFS), gain bandwidth, and gain coefficients of several small-core holey optical fibers (HFs) of both uniform and axially varying structural characteristics and compare these with measurements on more conventional fibers. Our measurements show that the BFS of HFs is first-order proportional to the modal index for light propagating along the fiber and is thus extremely sensitive to its precise structural parameters. Our results highlight the possibility of using distributed Brillouin scattering measurements to perform nondestructive structural characterization of HFs, and the possibility of producing Brillouin-suppressed HFs using controlled structural variation along the fiber length.

Furusawa, K.; Yusoff, Z.; Poletti, F.; Monro, T. M.; Broderick, N. G. R.; Richardson, D. J.

2006-09-01

284

Liquid optical fibers.  

PubMed

A small-diameter jet of a transparent liquid having a refractive index greater than the surrounding medium can entrap a light beam and act as an optical fiber. The liquid stream can be bent through quite large angles and will still retain the light. Electrically controlled bending of the liquid stream, and hence the light beam, has been achieved directly by means of electrostatic forces and indirectly by the use of hydraulic devices and associated transducers. Several ways have been demonstrated for separating the light from the liquid stream. The liquid optical fiber principle can be used for building both analog and digital one-or two-dimensional light deflectors. PMID:20119046

Taylor, G W

1972-04-01

285

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

286

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

287

Pulsed radiation-induced attenuation in certain optical fibers  

Microsoft Academic Search

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

Jonathan D. Weiss

1992-01-01

288

Pulsed radiation-induced attenuation in certain optical fibers  

Microsoft Academic Search

Using the X-ray pulse from the HERMES II simulation machine at Sandia National Laboratories, the author measured the pulsed radiation-induced attenuation in two optical fibers considered to be `non-rad-hard': the 50 ?m 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

J. D. Weiss

1992-01-01

289

Optical fiber laser  

SciTech Connect

An optical fiber laser is described comprising: a gain cavity including a single mode optical fiber of given length having a core with a given index of refraction and a cladding surrounding the core and having an index of refraction lower than that of the core. The core comprises a host glass having incorporated a laser gain material with a fluorescence spectrum having at least one broadband region in which there is at least one peak emission line; filter means optically coupled to one end of the gain cavity and reflective to radiation emitted from the gain material over a predetermined wavelength interval about the peak emission line to provide feedback in the gain cavity; an etalon filter section butt coupled to the remaining end of the gain cavity optical fiber, the etalon filter section comprising a pair of filters spaced apart in parallel by a predetermined length of material transparent to any radiation emitted from the gain cavity. The predetermined length of the transparent material is such that the etalon filter section is no longer than the distance over which the wave train energy from the fiber core remains substantially planar so that the etalon filter section is inside the divergent region to enhance feedback in the gain cavity; and means for pumping energy into the gain cavity to raise the interval energy level such that only a small part of the ion population, corresponding to a predetermined bandwidth about the peak emission line, is raised above laser threshold. The laser emits radiation only over narrow lines over a narrow wavelength interval centered about the peak emission line.

Hakimi, F.; Po, H.; Snitzer, E.

1987-07-14

290

Multiparameter sensor using fiber in-line MZ interferometer embedded in fiber Bragg grating  

Microsoft Academic Search

We propose an ultra compact optical fiber sensor integrating a Mach-Zehnder interferometer (MZI) in fiber Bragg grating (FBG) for simultaneous refractive index (RI) and temperature measurement. By use of the resonant wavelength of the FBG and the interference dip of the MZI, the RI and temperature of the surrounding medium can be unambiguously determined. The interesting properties of the sensor

C. R. Liao; Ying Wang; D. N. Wang; Minwei Yang

2010-01-01

291

Deposition of Man-Made Fibers in a Human Nasal Airway  

Microsoft Academic Search

Many occupational lung diseases are associated with exposure to aerosolized fibers in the workplace. The nasal airway is a critical route for fiber aerosol to enter the human respiratory tract. The fiber deposition efficiency in the nasal airway could be used as an index to indicate the fraction of the inhaled fibers potentially transported to the lower airways. In this

Wei-Chung Su; Jun Wu; Jan C. M. Marijnissen; Yung Sung Cheng

2008-01-01

292

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

293

Estimation of ovular fiber production in cotton  

SciTech Connect

The present invention is a method for rendering cotton fiber cells that are post-anthesis and pre-harvest available for analysis of their physical properties. The method includes the steps of hydrolyzing cotton fiber cells and separating cotton fiber cells from cotton ovules thereby rendering the cells available for analysis. The analysis of the fiber cells is through any suitable means, e.g., visual inspection. Visual inspection of the cells can be accomplished by placing the cells under an instrument for detection, such as microscope or other means. 4 figs.

Van`t Hof, J.

1998-09-01

294

Estimation of ovular fiber production in cotton  

DOEpatents

The present invention is a method for rendering cotton fiber cells that are post-anthesis and pre-harvest available for analysis of their physical properties. The method includes the steps of hydrolyzing cotton fiber cells and separating cotton fiber cells from cotton ovules thereby rendering the cells available for analysis. The analysis of the fiber cells is through any suitable means, e.g., visual inspection. Visual inspection of the cells can be accomplished by placing the cells under an instrument for detection, such as microscope or other means.

Van' t Hof, Jack (Brookhaven, NY)

1998-09-01

295

Optimum 3-step step-stress tests  

Microsoft Academic Search

Optimum simple step-stress accelerated life testing plans have practical limitations. They highly depend upon the assumption of a linear relationship between stress and time-to-failure and use only two extreme stresses that can cause irrelevant failure modes. Thus, 3-step plans are preferable. In this paper, the authors derive the optimum quadratic plan and propose and evaluate a 3-step test plan, the

Imad I. H. Khamis; James J. Higgins

1996-01-01

296

INDEXING WORKSHOP: HOW TO ASSIGN KEYWORDS  

Microsoft Academic Search

You have heard about issues surrounding indexing and retrieval of nuclear records and automation and micrographics of these records. Now we are going to get each of you involved in indexing and assigning keywords. The first part of this hands-on workshop will be a very basic, elementary step-by-step introduction, concentrating on how to assign keywords. It is a workshop for

1979-01-01

297

Infuence of fiber terminal face reflection on fiber optical confocal scanning microscope  

NASA Astrophysics Data System (ADS)

In fiber optical confocal scanning imaging system of reflection mode, interference of the reflection light beams from terminal face of the fiber coupling tip and from the surface of the sample will always destroy the image of low reflection index samples, such as CD-R pregroove basal disc and biotic samples. A quantitative analysis was given to find out the influence of fiber terminal face reflection on the system axial response. In order to avoid the influence of the fiber reflected light, the reflectivity ratio of the fiber tip to the sample should be low. Interference noise was effectively reduced by immersing the unused fiber tip into glycerol and cleaving the fiber tip end face at an angle. The proof experimental results of axial response have been shown. Finally, good quality confocal images of the recordable CD pregroove and the chromosome were presented.

Yang, Li-Song; Wang, Guiying; Wang, Jiangang; Xu, Zhizhan

1999-09-01

298

In-line fiber optic interferometric sensors in single-mode fibers.  

PubMed

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

2012-08-02

299

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

300

Introduction to Step Dynamics and Step Instabilities  

Microsoft Academic Search

This paper provides an elementary introduction to the basic concepts used in describing epitaxial crystal growth in terms of the thermodynamics and kinetics of atomic steps. Selected applications to morphological instabilities of stepped surfaces are reviewed, and some open problems are outlined.

Joachim Krug

2004-01-01

301

One Step Forward, Half a Step Backward?  

ERIC Educational Resources Information Center

|More than thirty cases involving desegregation of public school systems handed down in the first 25 years after Brown v. Board of Education, Topeka, Kansas, by the U.S. Supreme Court are discussed. However, the last 25 years have resulted in a situation of having the nation taking one step forward and half a step backwards, due to the conditions…

Russo, Charles J.

2004-01-01

302

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.

2012-01-01

303

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

304

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

305

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

306

Improving fiber to waveguide coupling efficiency by use of a highly germanium-doped thermally expanded core fiber  

NASA Astrophysics Data System (ADS)

Possessing a gradient refractive index (RI), thermally expanded core (TEC) fibers have been studied to be able to improve coupling efficiency of waveguide-fiber or LD-fiber according to the qualitative analysis of geometrical optics. The experiments show that the mode field radius (MFR) expansion of single-mode fiber with highly Germanium-doped (HGD) is more effective than that of conventional single-mode fiber (SMF). The coupling efficiency of a fabricated TEC fiber with HGD can enhance 5%-6% compared with that of a conventional-SMF. So the TEC fiber with HGD is a good candidate for the coupling of waveguide-fiber or LD-fiber.

Chen, Huaixi; Qiu, Yishen; Li, Gaoming; Zhang, Hao; Chen, Qun

2012-04-01

307

Optical amplification of Eu(DBM)3Phen-doped polymer optical fiber.  

PubMed

A preform technique is used to prepare a step-index (SI) polymer optical fiber (POF) doped with Eu(DBM)3Phen. The gain (5.7 dB) at 613 nm of the doped SI POF with Eu3+ content of 4000 in 10(6) wt., 0.4-mm core diameter, and 30-cm fiber length is observed at ambient temperature by end pumping with a YAG at 355 nm. The input signal light is approximately 0.2 W. The results show the possibility of signal gain in a rare-earth-doped POF amplifier and the potential of a polymer doped with rare-earth ions as an active optical device. PMID:15005198

Liang, Hao; Zhang, Qijin; Zheng, Zhiqiang; Ming, Hai; Li, Zengchang; Xu, Jie; Chen, Biao; Zhao, Hui

2004-03-01

308

Mid-infrared ZBLAN fiber supercontinuum source using picosecond diode-pumping at 2 µm.  

PubMed

We present the first demonstration of mid-IR supercontinuum generation directly pumped with picosecond pulses from a Thulium fiber-amplified gain-switched laser diode at 2 µm. We achieve more than two octaves of bandwidth from 750 - 4000 nm in step-index ZBLAN fiber with Watt-level average power and spectral flatness of less than 1.5 dB over a 1300 nm range in the mid-IR from 2450 - 3750 nm. The system offers high stability, power-scaling capability to the 10 W regime, and demonstrates an attractive route towards relatively inexpensive, versatile and practical sources of high power broadband mid-IR radiation. PMID:24104337

Heidt, A M; Price, J H V; Baskiotis, C; Feehan, J S; Li, Z; Alam, S U; Richardson, D J

2013-10-01

309

Efficient fiber Bragg gratings in 2D all-solid photonic bandgap fiber.  

PubMed

Fiber Bragg Gratings with reflectivity up to 25 dB have been photo-written in the core of a 2D all-solid Photonic Bandgap Fiber without modification of the guiding properties of the fiber. This result is obtained by combining an appropriate glass composition for the high index inclusions constituting the micro-structured cladding and a photosensitive low index core. Couplings of the fundamental core guided mode with cladding modes are investigated and compared to theoretical predictions. PMID:19506663

Bigot, Laurent; Bouwmans, Géraud; Quiquempois, Yves; Le Rouge, Antoine; Pureur, Vincent; Vanvincq, Olivier; Douay, Marc

2009-06-01

310

High-fiber foods  

MedlinePLUS

Dietary fiber - self-care ... Fiber is a substance found in plants. Dietary fiber -- the kind you eat -- is found in fruits, vegetables, and grains. Your body cannot digest fiber, so it passes through your intestines quickly.

311

Soluble vs. insoluble fiber  

MedlinePLUS

Insoluble vs. soluble fiber; Fiber - soluble vs. insoluble ... There are two different types of fiber -- soluble and insoluble. Both are important for health, digestion, and preventing diseases. Soluble fiber attracts water and turns to gel during digestion. ...

312

Improved High Modulus Fibers.  

National Technical Information Service (NTIS)

The purpose of this investigation was to find ways of reducing the electrical conductivity of carbon fibers without diminishing fiber strength or stiffness, or greatly increasing fiber weight. Polyacrylonitrile (PAN)-based carbon fibers are studied, while...

G. S. Ansell S. Chen R. J. Diefendorf C. Kim

1987-01-01

313

Bragg gratings photoinduced in ZBLAN fibers by femtosecond pulses at 800 nm  

Microsoft Academic Search

Fiber Bragg gratings were written in thulium-doped and undoped single-mode ZBLAN fibers by focusing femtosecond laser pulses on the fiber core through a phase mask. Maximum index modulation of the order of 1×10-3 was induced in both types of fibers. Measurements of the transverse refractive index changes across the core and cladding regions indicate that the grating formation originates from

M. Bernier; D. Faucher; R. Vallée; A. Saliminia; G. Androz; Y. Sheng; S. L. Chin

2007-01-01

314

Chirped rectilinear core longitudinally-graded optical fibers  

NASA Astrophysics Data System (ADS)

Reported here is a straight-forward and flexible method to fabricate silica optical fibers of circular cladding cross-section and rectilinear cores whose aspect ratio and refractive index profile changes with position along the fiber in a deterministic way. Specifically, a modification to the process recently developed to produce longitudinally-graded optical fibers, LGFs [Opt. Express 20 (2012) 17394–17402], was employed. Herein reported are MCVD-derived germanosilicate fibers with rectangular cores where the aspect ratio changes by nearly 200% and the average refractive index changed by about 5%. Fiber losses were measured to be about 50 dB/km. Such rectangular core fibers are useful for a variety of telecommunication and biomedical applications and the dimensional and optical chirp provides a deterministic way to control further the modal properties of the fiber.

Evert, A.; Hawkins, T.; Stolen, R.; Dragic, P.; Rice, R.; Ballato, J.

2013-10-01

315

Artificially disordered birefringent optical fibers.  

PubMed

We develop and experimentally verify a theory of evolution of polarization in artificially-disordered multi-mode optical fibers. Starting with a microscopic model of photo-induced index change, we obtain the first and second order statistics of the dielectric tensor in a Ge-doped fiber, where a volume disorder is intentionally inscribed via UV radiation transmitted through a diffuser. A hybrid coupled-power & coupled-mode theory is developed to describe the transient process of de-polarization of light launched into such a fiber. After certain characteristic distance, the power is predicted to be equally distributed over all co-propagating modes of the fiber regardless of their polarization. Polarization-resolved experiments, confirm the predicted evolution of the state of polarization. Complete mode mixing in a segment of fiber as short as ? 10cm after 3.6dB insertion loss is experimentally observed. Equal excitation of all modes in such a multi-mode fiber creates the conditions to maximize the information capacity of the system under e.g. multiple-input-multiple-output (MIMO) transmission setup. PMID:22418121

Herath, S; Puente, N P; Chaikina, E I; Yamilov, A

2012-02-13

316

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

2006-11-01

317

Accelerating XPath location steps  

Microsoft Academic Search

This work is a proposal for a database index structure that has been specifically designed to support the evaluation of XPath queries. As such, the index is capable to support all XPath axes (including ancestor, following, preceding-sibling, descendant-or-self, etc.). This feature lets the index stand out among related work on XML indexing structures which had a focus on regular path

Torsten Grust

2002-01-01

318

Temperature-controlled transformation in fiber types of fluid-filled photonic crystal fibers and applications  

NASA Astrophysics Data System (ADS)

We investigated experimentally and theoretically an invertible fiber-type transformation from a photonic bandgap fiber into a nonideal waveguide and then into an index-guiding photonic crystal fiber via the thermo-optic effect of the fluid filled in the air holes. Such a transformation could be used to develop an in-fiber optical switch/attenuator with a high-extinction ratio of more than 35 dB over an extremely broad wavelength range from 600to1700 nm via a small temperature adjustment.

Wang, Yiping; Tan, Xiaoling; Ying, Diqing; Hoo, Yeuk Lai; Liu, Shujing

2009-12-01

319

Structural characterization of hair fiber by optical coherence tomography (OCT)  

NASA Astrophysics Data System (ADS)

In this work we use the optical coherence tomography (OCT) technique to produce in vitro transversal section images of human hair. It was possible to identify in the A-scan protocol its principal structures: cuticle, cortex and medulla. The mean diameter of medulla was 29 +/- 7 ?m and hair diameter was 122 +/- 16 ?m in our samples of standard Afro-ethnic hair. We also compared the OCT signal before and after chemical treatment with 18% w/w ammonium thioglycolate solution. After chemical treatment, it was not possible to identify the main structures of hair fiber, due the index matching promoted by deleterious action of chemical agent. A tridimensional image was built starting from 601 cross-sectional images (slices). Each slice was taken in steps of 6.0 ?m at 8 frames per second, and the whole 3D image was built in 60 seconds.

Freitas, Anderson Zanardi; Robes Velasco, Maria Valeria; Paulo Raele, Marcus; Kaneko, Telma Mary; Vieira, Nilson Dias, Jr.; Baby, Andre Rolim

2008-12-01

320

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

321

Step by Step: Avoiding Spiritual Bypass in 12-Step Work  

ERIC Educational Resources Information Center

With spirituality as a cornerstone, 12-step groups serve a vital role in the recovery community. It is important for counselors to be mindful, however, of the potential for clients to be in spiritual bypass, which likely will undermine the recovery process.

Cashwell, Craig S.; Clarke, Philip B.; Graves, Elizabeth G.

2009-01-01

322

Carbon fiber from natural biopolymer Bombyx mori silk fibroin with iodine treatment  

Microsoft Academic Search

Carbon fibers were prepared from silk fibers after an iodine treatment and the carbon yield, fiber morphology, structure and mechanical properties were investigated. A single or multi-step carbonization process was used for the preparation. In the single step process, silk fibroin (SF) fibers were heated from 25 to 800°C with a heating rate of 5°Cmin?1 under Ar atmosphere. However, the

Yasuo Gotoh; Hideaki Morikawa; Mikihiko Miura; Yoshie Fujimori; Masanobu Nagura

2007-01-01

323

STEP: A Status Report  

Microsoft Academic Search

This paper presents an overview of the current technical status of STEP, the Satellite Test of the Equivalence Principle.\\u000a STEP was originally presented as a candidate for ESA’s M2 mission as a joint mission with NASA, and has since been studied\\u000a as an M3 candidate, and under NASA as QuickSTEP and MiniSTEP. Studies especially during the last two years have

Nick Lockerbie; John C. Mester; Rodney Torii; Stefano Vitale; Paul W. Worden

2001-01-01

324

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 ...

Reddish, Ms.

2011-09-30

325

Spiro-oxazine photochromic fiber optical switch  

NASA Astrophysics Data System (ADS)

A photochromic all-optical switch in telecommunication-grade fiber is fabricated by filling a fiber Bragg grating Fabry-Pérot resonator with a spiro-oxazine solution. The narrow linewidth of the resonator allows for a high sensitivity of the resonance wavelengths to the index change. The switch is controlled by low intensity UV light exposure, and operation at infrared telecommunication wavelengths is demonstrated. The switching speed on the order of minutes has been achieved.

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

2006-05-01

326

Dietary Carbohydrates, Fiber, and Breast Cancer Risk  

Microsoft Academic Search

Dietary fiber, fiber fractions, carbohydrate, glycemic index, and glycemic load were prospectively assessed five times over 18 years with a validated food frequency questionnaire in relation to breast cancer risk among 88,678 women (aged 34-59 years at baseline) in the Nurses' Health Study. Incident breast cancer occurred in 4,092 of these women between 1980 and 1998. The authors observed no

Michelle D. Holmes; Simin Liu; Susan E. Hankinson; Graham A. Colditz; David J. Hunter; Walter C. Willett

2004-01-01

327

Fiber delivery and diagnostics of laser spark ignition for natural gas engines  

NASA Astrophysics Data System (ADS)

Laser ignition via fiber optic delivery is challenging because of the need to deliver pulsed laser beam with relatively high energy and sufficient beam quality to refocus the light to the intensity required for creating spark. This dissertation presents work undertaken towards the development of a multiplexed fiber delivered laser ignition system for advanced lean-burn natural gas engines. It also describes the use of laser ignition system to perform in-cylinder optical diagnostics in gas engines. Key elements of the dissertation includes: (i) time resolved emission spectroscopy (TRES) of laser sparks in air to investigate the dependence of spark temperatures and electron number densities on ambient gas pressures, (ii) optical characterization of hollow core fibers, step-index silica fibers, photonic crystal fibers (PCFs) and fiber lasers, (iii) development and on-engine demonstration of a multiplexer to deliver the laser beam from a single laser source to two engine cylinders via optical fibers, and (iv) demonstration of simultaneous use of laser sparks for ignition and Laser Induced Breakdown Spectroscopy (LIBS) to measure in-cylinder equivalence ratios in a Cooperative Fuel Research (CFR) engine. For TRES of laser sparks, the ambient gas pressure is varied from 0.85 bar to 48.3 bar (high pressures to simulate elevated motored in-cylinder pressures at time of ignition in advanced gas engines). At later stages (˜1mus) of spark evolution, spark temperatures become comparable at all pressures. Electron number densities increase initially with increasing ambient gas pressure but become comparable at pressures greater than ˜20 bar. The effects of launch conditions and bending for 2-m long hollow core fibers are studied and an optimum launch f/# of ˜55 is shown to form spark in atmospheric pressure air. Spark formation using the output of a pulsed fiber laser is shown and delivery of 0.55 mJ nanosecond pulses through PCFs is achieved. Successful multiplexed laser ignition of a CAT G3516C gas engine via hollow core fibers is shown. LIBS analysis conducted at equivalence ratios from 0.6 to 0.95 in the CFR engine show a linear variation and linear correlation (R 2 > 0.99) of line intensity ratio (Halpha/O777 and Halpha/Ntot) with equivalence ratio.

Joshi, Sachin

328

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

329

Analysis and characterization of Er-Yb codoped-depressed inner cladding fiber.  

PubMed

A 125 ?m-diameter erbium-ytterbium-codoped single-mode fiber is reported. The utilization of depressed inner cladding guarantees the improvement of trade-off between the effective area and bending sensitivity compared to step-index profiles. Changes of cutoff wavelength, effective area, and macrobend loss under the influence of various structural parameters, and the balancing selection of core radius and subsidence layer width are investigated systematically. For the laboratory-made depressed inner cladding fiber, a macrobend loss of 0.06 dB/loop for a bending radius as tight as 10 mm was achieved, while maintaining an effective area of 164.22 ?m² with intact single-mode properties at 1550 nm. The maximum small signal gain was achieved at 40.9 dB, and the gain fluctuation was less than 1 dB at the C-band. The fiber is suitable for high-power, small, portable, and handy optical fiber devices. PMID:23938442

Lin, Zhen; Ren, Guobin; Zheng, Siwen; Jian, Wei; Zheng, Jingjing; Jian, Shuisheng

2013-08-10

330

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.; Vizcaino Lizaola, Rogelio.

2002-01-01

331

Preparation and characterization of semi-crystalline poly(ether ether ketone) hollow fiber membranes  

Microsoft Academic Search

Semi-crystalline poly(ether ether ketone) (PEEK) hollow fiber membranes were successfully prepared utilizing a two step membrane preparation process. In the first step, precursory hollow fibers were formed from blends of PEEK and poly(ether imide) (PEI) by melt extrusion. In the second step, porous PEEK hollow fiber membranes were formed by selective decomposition and removal of the polyimide phase utilizing a

Yong Ding; Benjamin Bikson

2010-01-01

332

Radiation damage effects on liquid scintillating fibers  

NASA Astrophysics Data System (ADS)

The effects of radiation on liquid scintillating fibers composed of borosilicate glass (Pyrex) tubing in combination with a high refractive index liquid scintillator are investigated. The fiber components (tubes, liquids and liquids in tubes), were irradiated in a nuclear reactor with doses exceeding 100 megarads. It was found that the discoloration of the glass tubing does not degrade the optical properties of the fibers - in fact, the attenuation length of fibers using irradiated tubes are longer than those using non irradiated tubes. The attenuation lengths of the liquids in this study appeared to be shortened by the radiation. However, it was found that no deposits or other surface damage occurred on the surfaces of the tubes containing the liquids so the irradiated fibers could be rejuvenated by simply adding fresh liquid.

Gui, Mei; Huson, F. R.; Ostrovsky, Tina; Reese, Dan; Suson, Dan; White, J. T.

1993-01-01

333

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

334

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

335

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

336

Mechanically induced long period fiber gratings in Er3+ fiber for structural health monitoring  

NASA Astrophysics Data System (ADS)

This work presents preliminary results on wavelength sensitivity due to mechanically induced long period fiber grating (LPFG) on both standard single-mode and Er-doped fibers. The work presents and compares results for both types of fibers under different torsion conditions. In order to apply the torsion one of the fiber ends is fixed while torsion is applied on the other end. A LPFG whose period is 503?m is used to press on the fiber after the torsion, this will allow for micro curvatures to be formed on the fiber, which will in turn generate a periodical index perturbation on it. Here, it was noted that the rejection band shifts to shorter wavelengths for Er-doped fibers. It was detected that for torsion of 6 turns applied to 10cm doped fiber the wavelength peaks can shift up to 25nm, which is longer than similar results reported on standard fibers. Therefore, by using Er-doped fibers this technique will give more sensitive and accurate results on the real conditions of the structure under study. These results can be employed for sensing applications, especially for small to medium size structures, being these structures mechanical, civil or aeronautical. Theoretical calculations and simulations are employed for experimental results validation.

Pulido-Navarro, M. G.; Alvarez-Chavez, J. A.; Ceballos-Herrera, D. E.; Escamilla-Ambrosio, P. J.

2013-09-01

337

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.

338

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

339

Electrically tunable efficient broad-band fiber filter  

Microsoft Academic Search

We demonstrate a new type of fiber-optic electrically tunable filter that enables a tuning range of 60 mm with an electrical power of 0.17 W, corresponding to a tuning efficiency of approximately 320 nm\\/W. The device is based on a metal coated long-period fiber grating written in a specially designed “air-clad” fiber that is filled with a polymer whose index

Anatoli A. Abramov; Benjamin J. Eggleton; John A. Rogers; Rolando P. Espindola; Arturo Hale; Robert S. Windeler; Thomas A. Strasser

1999-01-01

340

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

341

Fiber optic sensing system for smart materials and structures  

Microsoft Academic Search

In this work, a fiber optic multiparameter sensing system is presented It could be used for process and structural health monitoring in concrete structures. Reflectometric technique has been implemented for refractive index measurements by using as transducer the fiber end\\/host interface. Results on the capability of the developed sensor to monitor the curing process of thermoset based composites are presented.

Andrea Cusano; Giovanni Breglio; Michele Giordano; A. Calabro; Luigi Nicolais; A. Cutolo

2001-01-01

342

Dietary carbohydrates, fiber, and breast cancer risk in Chinese  

Microsoft Academic Search

Background: Few studies have investigated the association of di- etary carbohydrate and fiber intake with breast cancer risk in women in China, where carbohydrate intake is traditionally high. Objective: The objective was to prospectively evaluate the associ- ation of dietary carbohydrates, glycemic index, glycemic load, and dietary fiber with breast cancer risk and to determine whether the effect of these

Wanqing Wen; Xiao Ou Shu; Honglan Li; Gong Yang; Bu-Tian Ji; Hui Cai; Yu-Tang Gao; Wei Zheng

343

Direct functionalization of an optical fiber by a plasmonic nanosensor.  

PubMed

We explore a rapid route for fabricating silver nanoparticles (NPs) at the end of an optical fiber. The size and number of silver NPs can be controlled by varying the exposure doses. The effect of the refractive index of different solvents on the extinction spectra have been studied as a proof of concept of a fiber integrated plasmon-based sensor. PMID:21808358

Zeng, X; Jradi, S; Proust, J; Bachelot, R; Zhang, Z P; Royer, P; Plain, J

2011-08-01

344

Optical fibers with dual coatings for high-temperature applications  

NASA Astrophysics Data System (ADS)

We describe a new optical fiber coating, comprising layers of UV-curable silicone and high-temperature acrylate, with and without hermetic carbon. Optical and mechanical properties of graded index 50/125 ?m multimode fibers drawn with the new coating are examined. The new coatings display superior thermal stability in comparison with conventional dual acrylate coatings.

Stolov, Andrei A.; Simoff, Debra A.; Lindholm, Eric A.; Ciardiello, Catherine R.

2010-10-01

345

The design of erbium-doped fiber amplifiers  

Microsoft Academic Search

An accurate model for the erbium-doped fiber amplifier is presented. The model is used to design the index profile of the doped fiber, optimizing with regard to efficiency for inline- and preamplifiers as well as for power booster amplifiers. The predicted pump efficiencies (maximum gain to pump power ratios) are in agreement with experimental results presented in the literature. The

Bo Pedersen; Anders Bjarklev; J. H. Povlsen; Kristen Dybdal; Carl Christian Larsen

1991-01-01

346

Antiresonant guiding microstructured optical fibers for sensing applications  

NASA Astrophysics Data System (ADS)

A novel refractometric sensor utilizing unique spectral properties of antiresonant-guiding microstructured optical fibers is proposed. The sensor operation is based on the wavelength shift of the transmission spectrum in response to the refractive index change of a sample loaded in the air-holes of the microstructured optical fiber. Refractive index changes on the order of 0.1% can be detected using less than a nanoliter of a sample.

Litchinitser, N. M.; Poliakov, E.

2005-07-01

347

Optical Fiber Fabrication by the Out-Diffusion Method  

Microsoft Academic Search

Single-mode optical fibers with triangular index profile are successfully fabricated by a new fabrication technique, the ``out-diffusion method''. Evaporation and diffusion of fluorine by heating and subsequent collapsing of the fluorine-doped silica glass tubes result in formation of the core in the center of the collapsed preforms. Optical fibers with refractive index difference of 0.67% are obtained with an optical

Takeshi Kitagawa; Shuichi Shibata; Masaharu Horiguchi

1987-01-01

348

Arrays of Regenerated Fiber Bragg Gratings in Non-Hydrogen-Loaded Photosensitive Fibers for High-Temperature Sensor Networks  

PubMed Central

We report about the possibility of using regenerated fiber Bragg gratings generated in photosensitive fibers without applying hydrogen loading for high temperature sensor networks. We use a thermally induced regenerative process which leads to a secondary increase in grating reflectivity. This refractive index modification has shown to become more stable after the regeneration up to temperatures of 600 °C. With the use of an interferometric writing technique, it is possible also to generate arrays of regenerated fiber Bragg gratings for sensor networks.

Lindner, Eric; Chojetztki, Christoph; Brueckner, Sven; Becker, Martin; Rothhardt, Manfred; Vlekken, Johan; Bartelt, Hartmut

2009-01-01

349

Python fiber optic seal.  

National Technical Information Service (NTIS)

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...

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

1993-01-01

350

Antimicrobial Acrylic Fiber.  

National Technical Information Service (NTIS)

Fibers have been produced from a blend of poly(acrylonitrile) and poly(styrene hydantoin). The fibers were extruded from a single solvent, dimenthyl acetamide. The fibers could be chlorinated to produce halamines and thus rendered antimicrobial. The abili...

J. Lee R. M. Broughton J. Liang S. D. Worley T. S. Huang

2006-01-01

351

Numerical study of single mode Er-doped microstructured fibers: influence of geometrical parameters on amplifier performances  

NASA Astrophysics Data System (ADS)

A theoretical study of optimized single mode Er-doped MOFs designed for high efficiency amplification at 1550nm is carried out, deriving benefit from the demonstrated very low decrease of the overlap factor versus wavelength. In spite of this potential advantage, classical single mode MOFs are first shown to be less efficient than usual Er-doped step index fibers (SIF). However, novel single mode large core MOFs (LCMOFs) are designed, providing overlap factors higher than 0.9 at both the pump and the signal wavelengths. To obtain the same gain, the necessary length of LCMOF is reduced by up to 40% compared to that of Er-doped SIF. Such a highly efficient amplifying fiber is attractive for short pulse and soliton amplification.

Hilaire, Stéphane; Pagnoux, Dominique; Roy, Philippe; Février, Sébastien

2006-10-01

352

Detecting Stepping Stones  

Microsoft Academic Search

One widely-used technique by which network attackers attain anonymity and complicate their apprehension is by employing stepping stones: they launch attacks not from their own computer but from intermediary hosts that they previously compromised. We develop an effi- cient algorithm for detecting stepping stones by monitor- ing a site' s Internet access link. The algorithm is based on the distinctive

Vern Paxson

353

Plane Wave: Step Scattering  

NSDL National Science Digital Library

The Plane Wave: Step Scattering model simulates the time evolution of a free-particle plane wave in position space when it is incident on a potential energy step.  The position-space wave functions are depicted using three colors on the graph: black depicting the absolute square of the wave function, blue depicting the real part of the wave function, and red depicting the imaginary part of the wave function. The user may change the height of the potential step or the plane wave energy by dragging circles on the energy graph. Also shown is the calculated transmission and reflection coefficients. The Plane Wave: Step Scattering model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_qm_plane_step.jar file will run the program if Java is installed.

Palop, Jose I.

2010-12-13

354

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

355

Effect of Strain on Actomyosin Kinetics in Isometric Muscle Fibers  

Microsoft Academic Search

Investigations were conducted into the biochemical and mechanical states of cross-bridges during isometric muscle contraction. Rapid length steps (3 or 6nmhs?1) were applied to rabbit psoas fibers, permeabilized and isometric, at either 12°C or 20°C. Fibers were activated by photolysis of P3-1-(2-nitrophenyl)-ethyl ester of ATP infused into rigor fibers at saturating Ca2+. Sarcomere length, tension, and phosphate release were recorded—the

V. B. Siththanandan; J. L. Donnelly; M. A. Ferenczi

2006-01-01

356

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

357

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

358

Modal Interferometer Based on ARROW Fiber for Strain and Temperature Measurement  

Microsoft Academic Search

In this letter, interferometric sensors based on antiresonance reflecting optical waveguide (ARROW) fibers were developed, and used to sense strain and temperature. Two types of solid-core ARROW fibers were considered and signal demodulation was achieved by using the white light interferometric technique. The ARROW fibers have two rings of high index rods arranged in a hexagonal structure with a lattice

S. H. Aref; O. Frazao; P. Caldas; L. A. Ferreira; F. M. Araujo; J. L. Santos; H. Latifi; P. Foy; T. Hawkins; J. Ballato; T. Her; F. Farahi

2009-01-01

359

Analysis in indexing: document and domain centered approaches  

Microsoft Academic Search

The paper discusses the notion of steps in indexing and reveals that the document-centered approach to indexing is prevalent and argues that the document-centered approach is problematic because it blocks out context-dependent factors in the indexing process. A domain-centered approach to indexing is presented as an alternative and the paper discusses how this approach includes a broader range of analyses

Jens-erik Mai

2005-01-01

360

Design of large-core single-mode Yb3+-doped photonic crystal fiber  

NASA Astrophysics Data System (ADS)

The effective index of the cladding fundamental space-filling mode in photonic crystal fiber (PCF) is simulated by the effective index method. The variation of the effective index with the structure parameters of the fiber is achieved. For the first time, the relations of the V parameter of Yb3+-doped PCF with the refractive index of core and the structure parameters of the fiber are provided. The single-mode characteristics of large-core Yb3+-doped photonic crystal fibers with 7 and 19 missing air holes in the core are analyzed. The large-core single-mode Yb3+-doped photonic crystal fibers with core diameters of 50 ?m, 100 ?m and 150 ?m are designed. The results provide theory instruction for the design and fabrication of fiber.

Zhao, Xing-tao; Zheng, Yi; Liu, Xiao-xu; Zhou, Gui-yao; Liu, Zhaolun; Hou, Lan-tian

2012-05-01

361

Ribbon Fiber Laser-Theory and Experiment  

SciTech Connect

A scalable fiber laser approach is described based on phase-locking multiple gain cores in an antiguided structure. The waveguide is comprised of periodic sequences of gain- and no-gain-loaded segments having uniform index, within the cladding region. Initial experimental results are presented.

Beach, R J; Feit, M D; Brasure, L D; Payne, S A

2002-05-10

362

Hydrogen storage on pyrolyzed chicken feather fibers  

Microsoft Academic Search

Pyrolyzed chicken feather fibers (PCFF) that were prepared by two-step process (215 °C\\/15 h + 400–450 °C\\/1 h) demonstrated a significant H2 adsorption uptake due to their microporous nature. Considering their large availability, cost and H2 storage capability, PCFF can be a significant, environmentally friendly and bio-renewable candidate to address the H2 storage problem. A wide range of microporosities was obtained when the second step pyrolysis

Erman Senoz; Richard P. Wool

2011-01-01

363

10 GbE and Radio over Fiber Dual Transmission through Polymer Optical Fiber  

NASA Astrophysics Data System (ADS)

The study reported here deals with the exploitation of the perfluorinated graded index polymer optical fiber bandwidth to add further services in a home/office network. An extension of the classical baseband existing network is proposed to reach a dual concept allowing the indoor coverage of wireless signals transmitted using the radio over fiber (RoF) technology. The simultaneous transmission of a 10 GbE signal and a wireless signal is done, respectively, at 850 and 1300 nm on a plastic fiber. The penalties have been evaluated both in digital (bit error rate measurement) and radiofrequency (error vector magnitude measurement) domains.

Lethien, Christophe; Loyez, Christophe; Vilcot, Jean-Pierre; Rolland, Nathalie; Rolland, Paul Alain

2011-11-01

364

A STUDY OF TWO-STEP THROTTLE IN WATER HYDRAULICS  

Microsoft Academic Search

In water hydraulic valve, cavitation is more likely to happen than in oil hydraulic one. Two-step throttle, which consists of two orifices, is an effective form to avoid or reduce cavitation damage. In this paper, cavitation index of two-step throttle is analyzed. For throttles with different structure, experiments are conducted for the research of flow and pressure characteristics. Test results

Liu Yinshui; Huang Yan; Qiu Hongli; Li Zhuangyun

365

Reaction mechanisms of silicon carbide fiber synthesis by heat treatment of polycarbosilane fibers cured by radiation. 1: Evolved gas analysis  

Microsoft Academic Search

SiC fibers were synthesized from polycarbosilane (PCS) fibers by heat treatment after electron beam irradiation curing. The pyrolysis reaction mechanisms from the organic PCS to ceramic SiC were investigated by the analysis of gases evolved during heat treatment. There were two steps in the major reaction: the first step was at 800--1,200 K where Hâ and CHâ evolved by scission

Masaki Sugimoto; Tadao Seguchi; Toship Shimoo; Kiyohito Okamura

1995-01-01

366

Environmental Application of Chitosan?Supported Catalysts: Catalytic Hollow Fibers for the Degradation of Phenolic Derivatives  

Microsoft Academic Search

Hollow fibers made of chitosan were prepared and tested for the immobilization of palladium, a catalytic metal widely used for reductive reactions. Hollow chitosan fibers were prepared by extrusion of chitosan into a coagulating solution followed by a final conditioning step to increase the stability of chitosan in acidic solutions. The fibers were then contacted with palladium solution at pH

Eric Guibal; Thierry Vincent; Sylvie Spinelli

2005-01-01

367

Hybrid recycled glass fiber\\/wood flour thermoplastic composites: Manufacturing and mechanical characterization  

Microsoft Academic Search

Hybrid thermoplastic composites from wood flour and recycled glass fibers were manufactured through a two-step process involving a kinetic mixer and a compression molding machine. To evaluate the effect of recycled glass fibers, hybrid composites containing virgin glass fibers were also manufactured and tested. Mechanical properties of the composites including flexural modulus and strength, hardness as a function of temperature,

Marco Valente; Fabrizio Sarasini; Francesco Marra; Jacopo Tirillò; Giovanni Pulci

2011-01-01

368

Tellurium halide IR fibers for remote spectroscopy  

NASA Astrophysics Data System (ADS)

The new family of IR transmitting glasses, the TeX glasses, based on the association of tellurium and halide (Cl, Br, or I) are characterized by a wide optical window extending from 2 to 18 micrometers and a strong stability towards devitrification. Optical fibers drawn from these glasses exhibit low losses in the 7 - 10 micrometers range (less than 1 dB/m for single index fibers, 1 - 2 dB/m for fibers having a core-clad structure). The TeX glass fibers have been used in a remote analysis set-up which is mainly composed of a FTIR spectrometer coupled with a HgCdTe detector. This prototype system permits qualitative and quantitative analysis in a wide wavelength region lying from 3 to 13 micrometers , covering the fundamental absorption of more organic species. The evolution of a lactic and an alcoholic fermentation has been monitored by means of this set-up.

Zhang, Xhang H.; Ma, Hong-Li; Blanchetiere, Chantal; Le Foulgoc, K.; Lucas, Jacques; Heuze, Jean; Colardelle, P.; Froissard, P.; Picque, D.; Corrieu, G.

1994-07-01

369

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

2001-01-01

370

High precision fiber development  

Microsoft Academic Search

The improvement of single-mode precision fiber is critical to the efficient use of these fibers in connectors and to allow for low loss splices. Similarly, the alignment of fibers to integrated optic devices demands high precision. Likewise, the precision of large core multimode fibers affects coupler and connector losses as well as overall optical and physical performance. In accordance with

F. I. Akers; H. D. Shepherd

1981-01-01

371

Microstructured Polymer Optical Fibers  

Microsoft Academic Search

The fabrication, materials, properties and applications of microstructured polymer optical fibers are reviewed. Microstructured polymer optical fibers formed the basis of extensive work on the physics of microstructured fibers, and an outline of the contribution to the wider field of microstructured fibers is also presented.

Alexander Argyros

2009-01-01

372

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

373

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

374

Modeling of transient modal instability in fiber amplifiers.  

PubMed

A model of transient modal instability in fiber amplifiers is presented. This model combines an optical beam propagation method that incorporates laser gain through local solution of the rate equations and refractive index perturbations caused by the thermo-optic effect with a time-dependent thermal solver with a quantum defect heating source term. This model predicts modal instability a fiber amplifier operating at 241, 270, and 287 Watts of output power characterized by power coupling to un-seeded modes, the presence of stable and unstable regions within the fiber, and rapid intensity variations along the fiber. The instability becomes more severe as the power is increased. PMID:23736426

Ward, Benjamin G

2013-05-20

375

Reversible low-loss fiber optic hydrazine sensor  

NASA Astrophysics Data System (ADS)

This paper reports the development of a hydrazine fiber optic reversible sensor that operates, for the first time to our knowledge, in the lowest attenuation wavelength range of commercial silica fibers. A pentacenediquinone (PDQ) and polymer mix, with an index of refraction adjusted to closely match that of silica, was used as an active sensing material replacing the cladding of a silica core optical fiber. The optical signal passing through this modified cladding type fiber sensor exhibited a reversible intensity change in the presence hydrazine at different concentrations.

Andrawis, Alfred; Ranjitkar, Barun; Yan, Xingzhong; Peng, Yuelin

2010-04-01

376

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

377

Angle of arrival detection through artificial neural network analysis of optical fiber intensity patterns  

NASA Astrophysics Data System (ADS)

The optical sensors of United States Air Force reconnaissance vehicles, such as satellites, are subject to temporary or permanent blinding from hostile (or threat) laser radiation. By detecting and determining the angle of arrival (AOA) of the hostile radiation, the reconnaissance vehicle may be able to protect its optical sensors by taking evasive maneuvers or by shutting down the optical sensor (such as closing a shutter) until the threat has passed. In addition, the vehicle can relay information to its ground terminal allowing the intelligence community to determine the source of the hostile laser radiation. This thesis demonstrated that an intensity pattern out of a short piece of optical fiber could be used to determine the angle of arrival (AOA), to within 0.1 deg, of the incident laser energy on the front of the optical fiber. The optical fiber was a one-inch-long, 3mm-diameter, multimode, step-index, plastic fiber. The optical fiber was mounted to the front end of a charge injection device (CID) camera. The CID camera's angle with respect to the incident laser energy, a uniform amplitude plan wave, would be varied by a computer controlled rotational stage. The output of the CID camera was captured by Spiricon software. Captured outputs representing various AOAs were processed to provide template or test feature vectors. The processing method used a fast Fourier transform routine to create a 24 component low frequency feature vector. Two classification methodologies were used: a Eucledian distance method and a radial basis function neural network.

Thomas, Scott

1990-12-01

378

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

379

A simple all-solid tellurite microstructured optical fiber.  

PubMed

A simple all-solid tellurite microstructured optical fiber which has only one layer of high-index rods in the cladding is proposed and fabricated in the paper. The core and the cladding with the low index are made from the TeO(2)-ZnO-Na(2)O-La(2)O(3) glass, and the high-index rods are made from the TeO(2)-Li(2)O-WO(3)-MoO(3)-Nb(2)O(5) glass. The guiding regime in this fiber can be explained by ARROW model. The fiber can support the near- and mid-infrared light transmitting in the core within the transmission bands while the all-solid silica microstructured optical fiber cannot. When the pump light is outside the transmission bands, the light will transmit in six TLWMN rods. PMID:23481791

Cheng, Tonglei; Duan, Zhongchao; Liao, Meisong; Gao, Weiqing; Deng, Dinghuan; Suzuki, Takenobu; Ohishi, Yasutake

2013-02-11

380

Apparatus for Teaching Physics: Optical Fiber Communications.  

ERIC Educational Resources Information Center

|Describes a demonstration of the transmission of data signals from one microcomputer to another using an optical fiber line. Discusses the set-up method and demonstration steps for sending program and graphics. Provides a block diagram of the system and two circuit diagrams. (YP)|

Throckmorton, Carl; Dey, Joe

1988-01-01

381

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

382

Dietary fiber and the glycemic response.  

PubMed

Addition of purified fiber to carbohydrate test meals has been shown to flatten the glycemic response in both normal and diabetic volunteers, reduce the insulin requirement in patients on the artificial pancreas and in the longer term reduce urinary glucose loss and improve diabetes control. In the context of high fiber-high carbohydrate diets these findings have had a major impact in influencing recommendations for the dietary management of diabetes internationally. The mechanism of action appears in part to be due to the effect of fiber in slowing absorption rather than by increasing colonic losses of carbohydrate. Consequently postprandial GIP and insulin levels are reduced and the more viscous purified fibers (e.g., guar and pectin) appear most effective. In addition it has been suggested that colonic fermentation products of fiber may enhance glucose utilization. More recently it has become clear that many aspects of carbohydrate foods (food form, antinutrients, etc.) in addition to fiber may influence the rate of digestion and has led to a classification especially of starchy foods in terms of glycemic index to define the degree to which equicarbohydrate portions of different foods raise the blood glucose. Use of such data may maximize the effectiveness of high carbohydrate and high fiber diets in the management of diabetes and related disorders. PMID:3001740

Jenkins, D J; Jenkins, A L

1985-12-01

383

Microbend fiber-optic temperature sensor  

DOEpatents

A temperature sensor is made of optical fiber into which quasi-sinusoidal microbends have been permanently introduced. In particular, the present invention includes a graded-index optical fiber directing steady light through a section of the optical fiber containing a plurality of permanent microbends. The microbend section of the optical fiber is contained in a thermally expansive sheath, attached to a thermally expansive structure, or attached to a bimetallic element undergoing temperature changes and being monitored. The microbend section is secured to the thermally expansive sheath which allows the amplitude of the microbends to decrease with temperature. The resultant increase in the optical fiber's transmission thus allows temperature to be measured. The plural microbend section of the optical fiber is secured to the thermally expansive structure only at its ends and the microbends themselves are completely unconstrained laterally by any bonding agent to obtain maximum longitudinal temperature sensitivity. Although the permanent microbends reduce the transmission capabilities of fiber optics, the present invention utilizes this phenomenon as a transduction mechanism which is optimized to measure temperature.

Weiss, Jonathan D. (Albuquerque, NM)

1995-01-01

384

Investigation of pulse broadening in Gradan optical fibers  

Microsoft Academic Search

Measurements were made of the optical pulse dispersion in Gradan optical fibers having different refractive index profiles. The dependence of the pulse broadening on the waveguide length was also studied. It was established that, for one group of graded-index waveguides, the pulse broadening increased linearly with length (for waveguide lengths of less than 1 km) in agreement with the regular

T. V. Babkina; S. A. Bagaev; M. A. Beskorskaya; V. V. Grigor'yants; M. E. Zhabotinskii; G. A. Ivanov; N. A. Koreneva; D. K. Sattarov; Valerii B. Smirnov; S. V. Shreiber; K. M. Freivert

1980-01-01

385

High-Temperature Sensing Using Miniaturized Fiber In-Line Mach–Zehnder Interferometer  

Microsoft Academic Search

A miniaturized single fiber in-line Mach-Zehnder interferometer is proposed for high-temperature sensing. The interferometer has a microcavity in one of its arms, formed by removing part of the fiber core and cladding, while the other arm remains in the fiber core. Because the fiber core exhibits a temperature coefficient of refractive index which is different from that of air, the

Ying Wang; Yuhua Li; Changrui Liao; D. N. Wang; Minwei Yang; Peixiang Lu

2010-01-01

386

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

387

Generation of Cerenkov radiation at 850 nm in higher-order-mode fiber  

PubMed Central

We demonstrate generation of Cerenkov radiation at 850 nm in a higher-order-mode (HOM) fiber. The LP02 mode in this solid, silica-based fiber has anomalous dispersion from 690 nm to 810 nm. Cerenkov radiation with 3 nJ pulse energy is generated in this module, exhibiting 60% energy conversion efficiency from the input. The HOM fiber provides a valuable fiber platform for nonlinear wavelength conversion with pulse energies in-between index-guided silica-core photonic crystal fibers and air-core photonic bandgap fibers.

Cheng, Ji; Lee, Jennifer H.; Wang, Ke; Xu, Chris; Jespersen, Kim G.; Garmund, Martin; Gruner-Nielsen, Lars; Jakobsen, Dan

2011-01-01

388

Indexed Bibliography on Tracking.  

National Technical Information Service (NTIS)

This document comprises a bibliography about tracking and related literature, with corresponding documentation in the form of indexed author and subject listings. Indexing was performed to enhance its utility as a reference. Topical subjects were distingu...

S. P. Schipani

1990-01-01

389

Audio Indexing for Efficiency  

ERIC Educational Resources Information Center

This article describes Zimdex, an audio indexing system developed to solve the problem of indexing audio materials for individual instruction in the content area of the mathematics of life insurance. (Author)

Rahnlom, Harold F.; Pedrick, Lillian

1978-01-01

390

Glycemic Index and Diabetes  

MedlinePLUS

... food? Is the GI a better tool than carbohydrate counting? Glycemic index examples of foods. What is ... The glycemic index, or GI, measures how a carbohydrate-containing food raises blood glucose. Foods are ranked ...

391

Indexing of Feminist Periodicals  

Microsoft Academic Search

During the last twelve years there has been a phenomenal increase in the number of periodicals focusing on women's studies and feminism. Initially these titles were ignored by most indexing and abstracting services. The earliest indexing, by the Alternative Press Index and Women Studies Abstracts appeared in 1971 and 1972. Since 1975 there has been a marked increase in the

Mary Alice Sanguinetti

1984-01-01

392

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.

393

Indexing multiversion databases  

Microsoft Academic Search

An ecient management of multiversion data with branched evolution is crucial for many applications. It requires databa- se designers aware of tradeos among index structures and policies. This paper defines a framework and an analysis method for understanding the behavior of dierent indexing policies. Given data and query characteristics the analysis allows determining the most suitable index structure. The analysis

Khaled Jouini; Geneviève Jomier

2007-01-01

394

Generalized Partial Indexes  

Microsoft Academic Search

This paper demonstrates the use of generalized par- tial indexes for efficient query processing. We propose that partial indexes be built on those portions of the database that are statistically likely to be the most useful for query processing. We identify three classes of statistical infor- mation, and two levels at which it may be available. We describe indexing strategies

Praveen Seshadri; Arun N. Swami

1995-01-01

395

Kaiser's Systematic Indexing.  

ERIC Educational Resources Information Center

|Describes a system of subject indexing developed by Julius Kaiser (1868-1927) which is based on "concretes" and "processes" to govern the form of subject headings and subdivisions. Elements of amplification, guides for the subject index, and criticism of Kaiser's systematic indexing are noted. Five sources are given. (EJS)|

Rodriguez, Robert D.

1984-01-01

396

Innovative fiber coating systems based on organic modified ceramics  

NASA Astrophysics Data System (ADS)

We describe the application of inorganic organic hybrid materials (ORMOCERs) as optical fiber coatings for use in Fiber Bragg Grating sensors and high power transmission fibers. The materials are UV curable, enable a single layer thickness of about 50 ?m and show high a high peak temperature stability >300 °C. Regarding the fiber protection the coatings have been investigated using tensile strength measurements before and after temperature load. Best coatings maintain the high tensile strength of 68 N (125 ?m fiber) with a Weibull parameter of 182 after a temperature cycling up to 300 °C. For the first time a low refractive index ORMOCER will be presented showing a numerical aperture of 0.47 at a wavelength of 1000 nm on a pure silica fiber. This corresponds to a refractive index of 1.37. The fiber possesses a fiber loss of 18 dB/km at a wavelength of 1000 nm. The fibers have been coated using a gravity as well as pressure technology. The latter possesses extremely minimized die equipment and is therefore well applicable for small coating amounts. The so called dead volume within the coating die is about 1 ml. The overall dead volume is only influenced by the supply pipe and can be reduced down to 5 ml.

Schuster, Kay; Kobelke, Jens; Rose, Klaus; Helbig, Manfred; Zoheidi, Mohammad; Heinze, Alexander

2010-02-01

397

Direct generation of polarization-entangled photon pairs in a poled fiber.  

PubMed

We experimentally demonstrate the direct generation of polarization-entangled photon pairs in an optical fiber at room temperature by exploiting type-II phase-matched spontaneous parametric down-conversion. A second-order nonlinearity is artificially induced in the 17-cm-long weakly birefringent step-index fiber through the process of thermal poling, and quasi-phase-matching allows for the generation of entangled photons in the 1.5-micron telecom band when the fiber is pumped at 775 nm. A greater-than 80:1 coincidence-to-accidental ratio is achieved, limited mainly by multiphoton pair generation. Without the need to subtract accidentals or to compensate for walk-off, the raw two-photon interference visibility is found to be better than 95%, and violation of Bell's inequality is observed by more than 18 standard deviations. This makes for a truly alignment-free, plug-and-play source of polarization-entangled photon pairs. PMID:23003253

Zhu, Eric Y; Tang, Zhiyuan; Qian, Li; Helt, Lukas G; Liscidini, Marco; Sipe, J E; Corbari, Costantino; Canagasabey, Albert; Ibsen, Morten; Kazansky, Peter G

2012-05-21

398

Direct Generation of Polarization-Entangled Photon Pairs in a Poled Fiber  

NASA Astrophysics Data System (ADS)

We experimentally demonstrate the direct generation of polarization-entangled photon pairs in an optical fiber at room temperature by exploiting type-II phase-matched spontaneous parametric down-conversion. A second-order nonlinearity is artificially induced in the 17-cm-long weakly birefringent step-index fiber through the process of thermal poling, and quasi-phase-matching allows for the generation of entangled photons in the 1.5-micron telecom band when the fiber is pumped at 775 nm. A greater-than 80?1 coincidence-to-accidental ratio is achieved, limited mainly by multiphoton pair generation. Without the need to subtract accidentals or to compensate for walk-off, the raw two-photon interference visibility is found to be better than 95%, and violation of Bell’s inequality is observed by more than 18 standard deviations. This makes for a truly alignment-free, plug-and-play source of polarization-entangled photon pairs.

Zhu, Eric Y.; Tang, Zhiyuan; Qian, Li; Helt, Lukas G.; Liscidini, Marco; Sipe, J. E.; Corbari, Costantino; Canagasabey, Albert; Ibsen, Morten; Kazansky, Peter G.

2012-05-01

399

Over an octave cascaded Raman scattering in short highly germanium-doped silica fiber.  

PubMed

In this paper, we report on cascaded Raman scattering (RS) in a highly germanium-doped silica fiber (HGDF) pumped by a picosecond pulsed master oscillator power amplifier (MOPA) system at 1064 nm in the normal dispersion regime. Benefited by the higher Raman gain of germanium (GeO2) than silica in the core, the length of the HGDF is only several meters. The broadest output spectrum comprises of 10 orders Raman stokes waves and eventually evolves into a supercontinuum (SC) spanning from 1000 to beyond 2100 nm with an output average power up to Watt scale. To the best of our knowledge, this is the first time to obtain such a broad cascaded RS spectrum in a short length of GeO2-doped step index silica fiber. We also numerically investigate the propagation of picosecond pulses in this HGDF based on the generalized nonlinear Schrödinger equation (GNLSE) which includes most of the dispersive and nonlinear effects, and the simulation results are in fairly good agreement with our experiments. It is believed that the numerical approach adopted in this paper is very beneficial for designing customized cascaded Raman fiber lasers before experimental implementations. PMID:23842385

Yin, Ke; Zhang, Bin; Yang, Weiqiang; Chen, Hongwei; Hou, Jing

2013-07-01

400

Impact of fiber outer boundaries on leaky mode losses in leakage channel fibers.  

PubMed

In a leakage channel fiber, the desired fundamental mode (FM) has negligible waveguide loss. Higher-order modes (HOM) are designed to have much higher waveguide losses so that they are practically eliminated during propagation. Coherent reflection at the fiber outer boundary can lead to additional confinement especially for highly leaky HOM, leading to lower HOM losses than what are predicted by conventional FEM mode solver considering infinite cladding. In this work, we conducted, for the first time, careful measurements of HOM losses in two leakage channel fibers (LCF) with circular and rounded hexagonal boundary shapes respectively. Impact on HOM losses from coiling, fiber boundary shapes and coating indexes were studied in comparison to simulations. This work, for the first time, demonstrates the limit of the simulation method commonly used in the large-mode-area fiber designs and the need for an improved approach. More importantly, this work also demonstrates that a deviation from circular fiber outer shape may be an effective method to mitigate HOM loss reduction from coherent reflection from fiber outer boundary, even in double-clad fibers, with HOM losses in excess of 20dB/m measured in the hexagonal LCF with ~50µm core diameter while keeping FM loss negligible. PMID:24104313

Gu, Guancheng; Kong, Fanting; Hawkins, Thomas W; Foy, Paul; Wei, Kanxian; Samson, Bryce; Dong, Liang

2013-10-01

401

Nanowires at Steps  

NASA Astrophysics Data System (ADS)

Nanowires can now be synthesized at stepped surfaces with atomic precision, from 10 nm wide silicide wires all the way down to strings of single atoms. The basic idea is the decoration of straight steps by adsorbed atoms and the resulting step flow growth. Conducting Gd disilicide wires longer than 1 micron grow along [-110] step edges on Si(111) [1]. Such controlled nucleation of nanowires represents a first step towards self-assembled interconnects in nano-electronics. Strings of metal atoms tend to form on Si(111) at low coverage and lead to a ground state with broken three-fold symmetry. A single domain can be stabilized at a stepped surface. Examples are nx1 and nx2 structures of Ag, Au [2-5], Gd [6], alkali metals, and alkaline earths. The variety of adsorbates and the option of vicinal Si(557)substrates [3-5] provide opportunities for systematically tailoring one-dimensional electron systems via intra-chain and inter-chain coupling, Coulomb interaction, magnetic moment, and band occupancy. Angle-resolved photoemission with synchrotron radiation reveals interesting electronic features, such as a band of mixed dimensionality [2] and a pair of one-dimensional bands with metallic character defying the Peierls theorem [3,4]. The search for the predicted spin-charge separation of one-dimensional electrons is on. [1] J. L. McChesney, et al., Nanotechnology, submitted. [2] R. Losio et al., Phys. Rev. Lett. 85, 808 (2000). [3] R. Losio et al., Phys. Rev. Lett. 86, 4632 (2001). [4] K. N. Altmann et al., Phys. Rev. B 64, 035406 (2001). [5] I. K. Robinson, et al., Phys. Rev. Lett., submitted. [6] A. Kirakosian et al., Surf. Sci. Lett., in press.

Himpsel, F. J.

2002-03-01

402

In-line optical fiber-sensors based on low-loss semi-reflective in-fiber mirrors  

NASA Astrophysics Data System (ADS)

This paper presents the design and fabrication of semi-reflective in-fiber mirrors and their usage for the realization of different miniature fiber sensors. The fabrication of a semi-reflective in-fiber mirror is based on the selective chemical etching and splicing of standard single-mode fibers (SMF). The mirror's reflectance can be set precisely in between any range between 0.1% and 9.5 %. The practical usability of the produced in-fiber mirrors was evaluated by the fabrication of an in-line temperature sensor and evanescent field refractive index (RI) sensor. A temperature sensor is an intrinsic type of in-line FPI, formed between an in-fiber mirror and a flat-cleaved optical fiber tip. As an example, a temperature sensor that was optimized within a range from 0 to 100°C showed a temperature resolution better than 0.1 °C, and a repeatability better than 0.2 °C. The evanescent RI sensor was created by the splicing of a small-diameter SMF between two in-fiber mirrors and removing of the intermediate fiber-cladding by chemical etching. The effective index of the fundamental mode depended on the surrounding-medium RI, which was interrogated by a spectrally-resolved technique. A high sensitivity of 830 nm/RIU was measured at RI of 1.444.

Cibula, E.; Donlagic, D.

2012-05-01

403

Development of a biotechnological process for the production of high quality linen fibers  

Microsoft Academic Search

A novel biotechnological process for the production of high-quality flax fibers was developed. In this process, decorticated\\u000a fibers from green flax were washed with 0.5% soda solution and treated with the pectinolytic strain Geobacillus thermoglucosidasius PB94A. Before drying the fibers, they were treated with the textile softener Adulcinol BUN. If the fibers contained contaminant\\u000a shives, a bleaching step with hydrogen

Ana Gabriela Valladares Juárez; Gernot Rost; Uwe Heitmann; Egon Heger; Rudolf Müller

404

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

405

Long-term blood cholesterol–lowering effects of a dietary fiber supplement  

Microsoft Academic Search

Background: The study evaluated the blood cholesterol–lowering effects of a dietary supplement of water-soluble fibers (guar gum, pectin) and mostly non-water-soluble fibers (soy fiber, pea fiber, corn bran) in subjects with mild to moderate hypercholesterolemia (LDL cholesterol, 3.37–4.92 mmol\\/L).Methods: After stabilization for 9 weeks on a National Cholesterol Education Program Step 1 Diet, subjects were randomly assigned to receive 20

Robert H Knopp; H. Robert Superko; Michael Davidson; William Insull; Carlos A Dujovne; Peter O Kwiterovich; James H Zavoral; Kevin Graham; Robert R O’Connor; David A Edelman

1999-01-01

406

Specialty optical fibers: revisited  

NASA Astrophysics Data System (ADS)

The paper contains description of chosen aspects of analysis and design of tailored optical fibers. By specialty optical fibers we understand here the fibers which have complex construction and which serve for the functional processing of optical signal rather than long distance transmission. Thus, they are called also instrumentation optical fibers. The following issues are considered: transmission properties, transformation of optical signal, fiber characteristics, fiber susceptibility to external reactions. The technology of tailored optical fibers offers a wider choice of the design tools for the fiber itself, and then various devices made from these fiber, than classical technology of communication optical fibers. The consequence is different fiber properties, nonstandard dimensions and different metrological problems. The price to be paid for wider design possibilities are bigger optical losses of these fibers and weaker mechanical properties, and worse chemical stability. These fibers find their applications outside the field of telecommunications. The applications of instrumentation optical fibers combine other techniques apart from the photonics ones like: electronic, chemical and mechatronic.

Romaniuk, Ryszard S.

2011-06-01

407

A fiber-optic light-scattering spectrometer  

NASA Astrophysics Data System (ADS)

A new fiber-optic light-scattering spectrometer, which uses fiber-optic detector probes each comprising an optical fiber and a graded index microlens, is described. The fiber-optic detectors form an integral part of the scattering cell, which no longer requires transparent windows for the exit (or entrance) light beam. This feature eliminates the need for a goniometer, which is one of the most bulky and expensive components of a conventional light-scattering spectrometer. Thus, the spectrometer, unlike all of its predecessors, has no moving parts. The fiber-optic light-scattering spectrometer can utilize a reaction vessel of whichever shape or composition as the scattering cell for light-scattering measurements because the fiber-optic detector probes are directly immersed in the scattering medium.

Dhadwal, H. S.; Chu, Benjamin

1989-05-01

408

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

409

Sensing characteristics of polymer highly birefringent side-hole fiber  

NASA Astrophysics Data System (ADS)

This paper presents the sensor characteristics of highly birefringent polymer side-hole optical fiber. The fiber core with greater refractive index was made of copolymer PMMA-PS, while the cladding of pure PMMA. The fabricated fiber showed relatively low losses of the order of 6 dB/m in the visible range. We measured several sensing characteristics in the fabricated fiber, including birefringence and polarimetric sensitivity to pressure and temperature. The fiber showed high polarimetric sensitivity to pressure, which is directly related to the presence of two large holes transferring symmetrical load applied to the cladding into nonsymmetric stress distribution in the core region. This in turn changes modal birefringence of the investigated fiber and increases the sensitivity to pressure.

Mergo, Pawe?; Klimek, Jacek; Skorupski, Krzysztof; Gasior, Katarzyna; Grzondko, Mateusz; Martynkien, Tadeusz; Wójcik, Grzegorz; Walewski, Aleksander; Pédzisz, Janusz; Kope?, Jaros?aw; Urba?czyk, Wac?aw

2013-07-01

410

Ophthalmoscopic observation of the retinal nerve fiber layer.  

PubMed

Alterations of the retinal nerve fiber layer occur as a result of diseases affecting the anterior visual pathway. Optimal viewing conditions, familiarity with the appearance of the normal nerve fiber layer, precise focus, and a high index of suspicion are necessary for the ophthalmoscopic observation of pathologic alteration in the nerve fiber layer. The observer must learn to differentiate pseudodefects (reflexes) from true defects (areas of nerve fiber layer atrophy). Nerve fiber layer changes appear ophthalmoscopically as generalized attrition, slit defects, sector defects (all types of atrophic change), or changes in the appearance of the nerve fiber layer itself. These alterations, which occur in numerous conditions including congenital hemianopia, ocular hypertension and glaucoma, multiple sclerosis, acute Leber optic neuropathy, trauma, severe hypertension, congenital and heredity optic atrophy, toxic amblyopia, papilledema, retinochoroiditis, and following photocoagulation, may be of critical diagnostic importance. PMID:929796

Newman, N M

411

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

412

Steps towards photonic antennas  

Microsoft Academic Search

Summary form only given. Photonics are basically replacing conventional components, such as the coaxial lead that would have interconnected the antenna and electronics. In the replacement stage, the design of the electronics is largely, if not completely, unaffected by the photonics. A second step in the evolution, of which we are beginning to see signs already, is the integration of

2000-01-01

413

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/

414

Step Prototype Development Status  

Microsoft Academic Search

STEP, the Satellite Test of the Equivalence Principle [1], proposes to test the Equivalence Principle to a part in 1018 by comparing the free-fall acceleration of cylindrical shaped test masses [2] in Earth orbit. Magnetic bearings constrain the test mass motion to their axis of symmetry [3]. The displacement of the test masses is measured using a DC SQUID and

C. Mehls; C. Bayart; J. Bower; B. Clarke; C. Cox; D. Gill; D. Stricker; N. Vora; S. Wang; P. Zhou; R. Torii; P. Worden; D. Debra; H. Dittus; F. Loeffler

2008-01-01

415

Composite Random Fiber Networks  

NASA Astrophysics Data System (ADS)

Systems made from fibers are common in the biological and engineering worlds. In many instances, as for example in skin, where elastin and collagen fibers are present, the fiber network is composite, in the sense that it contains fibers of very different properties. The relationship between microstructural parameters and the elastic moduli of random fiber networks containing a single type of fiber is understood. In this work we address a similar target for the composite networks. We show that linear superposition of the contributions to stiffness of individual sub-networks does not apply and interesting non-linear effects are observed. A physical basis of these effects is proposed.

Picu, Catalin; Shahsavari, Ali

2013-03-01

416

Semiparametric Single-index Poisson Regression Model with Unobserved Heterogeneity  

Microsoft Academic Search

We propose a two-step semiparametric pseudo-maximum likelihood procedure forsingle-index regression models where the conditional variance is a known function of theregression and an additional parameter. The Poisson single-index regression model withmultiplicative unobserved heterogeneity is an example of such a semiparametric model.Our procedure is based on linear exponential densities with nuisance parameter. Thenuisance parameter is estimated in a preliminary step and

Jérôme Foncel; Marian Hristache; Valentin Patilea

2004-01-01

417

Highly sensitive refractive index sensor based on two cascaded long period gratings with rotary refractive index modulation  

Microsoft Academic Search

We present a refractive index (RI) sensor based on a fiber Mach-Zehnder interferometer, which is realized by two cascaded special long period gratings with rotary refractive index modulation (C-RLPFG). The wavelength shift of the refractometer behaves good linear response in a RI range of 1.3342 to 1.3362, and the sensitivity of 14.5pm\\/mm for 0.01SRI change has been obtained. The sensitivity

Tao Zhu; Yanen Fan; Ming Deng; Yunjiang Rao

2011-01-01

418

Passive coherent phasing of fiber laser arrays  

NASA Astrophysics Data System (ADS)

Theoretical and numerical analyses are presented of the passive coherent phasing of an array of fiber lasers that are combined in a single laser cavity by an Nx1 coupler. In an initial linear analysis it is found that the brightness gain of the passive coherent array grows linearly for a small number of fibers, however, for practical parameters, the coherent brightness gain saturates at ~ 8 - 12 for large arrays. An intensity dependent index (Kerr) nonlinearity is then introduced and it is shown that the expected maximum improvement is modest, with the coherent brightness gain saturating at 10 - 14, depending on the strength of the nonlinearity. These results are compared with recent experiments.

Rothenberg, Joshua E.

2008-03-01

419

Rigorous sufficient conditions for index-guided modes in microstructured dielectric waveguides  

Microsoft Academic Search

We derive a sufficient condition for the existence of index-guided modes in a very general class of dielectric waveguides, including photonic-crystal fibers (arbitrary periodic claddings, such as ``holey fibers''), anisotropic materials, and waveguides with periodicity along the propagation direction. This condition provides a rigorous guarantee of cutoff-free index-guided modes in any such structure where the core is formed by increasing

Karen K. Y. Lee; Yehuda Avniel; Steven G. Johnson

2008-01-01

420

Extended-length fiber optic carbon dioxide monitoring  

NASA Astrophysics Data System (ADS)

This paper discusses the design and performance of fiber optic distributed intrinsic sensors for dissolved carbon dioxide, based on the use optical fibers fabricated so that their entire lengths are chemically sensitive. These fibers use a polymer-clad, silica-core structure where the cladding undergoes a large, reversible, change in optical absorbance in the presence of CO2. The local "cladding loss" induced by this change is thus a direct indication of the carbon dioxide concentration in any section of the fiber. To create these fibers, have developed a carbon dioxide-permeable polymer material that adheres well to glass, is physically robust, has a refractive index lower than fused silica, and acts as excellent hosts for a unique colorimetric indicator system that respond to CO2. We have used this proprietary material to produce carbon-dioxide sensitive fibers up to 50 meters long, using commercial optical fiber fabrication techniques. The sensors have shown a measurement range of dissolved CO2 of 0 to 1,450 mg/l (0 to 100% CO2 saturation), limit of detection of 0.3 mg/l and precision of 1.0 mg/l in the 0 to 50 mg/l dissolved CO2 range, when a 5 meter-long sensor fiber segment is used. Maximum fiber length, minimum detectable concentration, and spatial resolution can be adjusted by adjusting indicator concentration and fiber design.

Delgado-Alonso, Jesus; Lieberman, Robert A.

2013-05-01

421

Moving Objects Indexing  

NASA Astrophysics Data System (ADS)

For querying large amounts of moving objects, a key problem is to create efficient indexing structures that make it possible to effectively answer various types of queries. Traditional spatial indexing approaches cannot be used because the locations of moving objects are highly dynamic, which leads to frequent updates of index structures, which in turn will cause huge overheads. In this chapter, we first introduce a few of the underlying spatial index structures including the R-tree, Grid File, and Quad-tree. Then, we propose the indexing methods for moving objects in Euclidean space and in spatial networks. Finally, we describe techniques that index the past, present, and anticipated future positions of moving objects.

Chen, Jidong; Meng, Xiaofeng

422

Step Prototype Development Status  

NASA Astrophysics Data System (ADS)

STEP, the Satellite Test of the Equivalence Principle [1], proposes to test the Equivalence Principle to a part in 1018 by comparing the free-fall acceleration of cylindrical shaped test masses [2] in Earth orbit. Magnetic bearings constrain the test mass motion to their axis of symmetry [3]. The displacement of the test masses is measured using a DC SQUID and superconducting coils [4], enabling a displacement sensitivity as small as 10-15 m. In combination with a small spring stiffness a differential acceleration sensitivity of 10-18 g is achievable. Residual satellite acceleration is reduced to better than 10-14 g by compensating satellite drag forces with thrust provided by helium gas. We report on recent progress in the development of STEP prototype flight accelerometers, in particular the development of the high precision quartz housing for the engineering inner accelerometer and the testing of SQUID and capacitive readout systems using 'brass board' accelerometer prototypes.

Mehls, C.; Bayart, C.; Bower, J.; Clarke, B.; Cox, C.; Gill, D.; Stricker, D.; Vora, N.; Wang, S.; Zhou, P.; Torii, R.; Worden, P.; Debra, D.; Dittus, H.; Loeffler, F.

2008-09-01

423

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

424

Fiber Optic Smart Structures.  

National Technical Information Service (NTIS)

A brief review of research carried out at the Fiber Optic Smart Structure Laboratory at the Institute for Aerospace Studies is provided. The use of Michaelson fiber optic sensors embedded within composite structures as optical strain gauges has been teste...

R. M. Measures K. Liu W. E. R. Davies K. F. Mcewen N. D. Glossop

1989-01-01

425

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

426

Conducting fiber compression tester  

DOEpatents

The invention measures the resistance across a conductive fiber attached to a substrate place under a compressive load to determine the amount of compression needed to cause the fiber to fail. 3 figs.

DeTeresa, S.J.

1989-12-07

427

Patterned Electrospray Fiber Structures.  

National Technical Information Service (NTIS)

Electrospun fibers have useful filtration properties for chemical protective clothing and filter masks. Techniques for the patterned deposition of these fibers have been developed based on varying the conductivity of the target substrate. We are investiga...

P. Gibson H. Schreuder-Gibson

2005-01-01

428

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

429

Eco-Index  

NSDL National Science Digital Library

Eco-Index, a project of the Rainforest Alliance, is "a searchable almanac of current and past conservation projects in Mesoamerica, with project descriptions, goals, achievements, lessons learned, and more." With current, well-presented features covering a range of biodiversity conservation issues, Eco-Index offers an excellent way for conservation researchers and practitioners to keep abreast of activity in their field. Users are encouraged to add their own project descriptions to the Eco-Index database. Available in English or Spanish.

430

The Healthy Eating Index  

Microsoft Academic Search

Objective To develop an index of overall diet quality.Design The Healthy Eating Index (HEI) was developed based on a 10-component system of five food groups, four nutrients, and a measure of variety in food intake. Each of the 10 components has a score ranging from 0 to 10, so the total possible index score is 100.Methods\\/subjects Data from the 1989

EILEEN T KENNEDY; JAMES OHLS; STEVEN CARLSON; KATHRYN FLEMING

1995-01-01

431

Fully automated, quantitative, noninvasive assessment of collagen fiber content and organization in thick collagen gels  

NASA Astrophysics Data System (ADS)

Collagen is the most prominent protein of human tissues. Its content and organization define to a large extent the mechanical properties of tissue as well as its function. Methods that have been used traditionally to visualize and analyze collagen are invasive, provide only qualitative or indirect information, and have limited use in studies that aim to understand the dynamic nature of collagen remodeling and its interactions with the surrounding cells and other matrix components. Second harmonic generation (SHG) imaging emerged as a promising noninvasive modality for providing high-resolution images of collagen fibers within thick specimens, such as tissues. In this article, we present a fully automated procedure to acquire quantitative information on the content, orientation, and organization of collagen fibers. We use this procedure to monitor the dynamic remodeling of collagen gels in the absence or presence of fibroblasts over periods of 12 or 14 days. We find that an adaptive thresholding and stretching approach provides great insight to the content of collagen fibers within SHG images without the need for user input. An additional feature-erosion and feature-dilation step is useful for preserving structure and noise removal in images with low signal. To quantitatively assess the orientation of collagen fibers, we extract the orientation index (OI), a parameter based on the power distribution of the spatial-frequency-averaged, two-dimensional Fourier transform of the SHG images. To measure the local organization of the collagen fibers, we access the Hough transform of small tiles of the image and compute the entropy distribution, which represents the probability of finding the direction of fibers along a dominant direction. Using these methods we observed that the presence and number of fibroblasts within the collagen gel significantly affects the remodeling of the collagen matrix. In the absence of fibroblasts, gels contract, especially during the first few days, in a manner that allows the fibers to remain mostly disoriented, as indicated by small OI values. Subtle changes in the local organization of fibers may be taking place as the corresponding entropy values of these gels show a small decrease. The presence of fibroblasts affects the collagen matrix in a manner that is highly dependent on their number. A low density of fibroblasts enhances the rate of initial gel contraction, but ultimately leads to degradation of collagen fibers, which start to organize in localized clumps. This degradation and reorganization is seen within the first days of incubation with fibroblasts at a high density and is followed by de novo collagen fiber deposition by the fibroblasts. These collagen fibers are more highly oriented and organized than the fibers of the original collagen gel. These initial studies demonstrate that SHG imaging in combination with automated image analysis approaches offer a noninvasive and easily implementable method for characterizing important features of the content and organization of collagen in tissuelike specimens. Therefore, these studies could offer important insights for improving tissue engineering and disease diagnostic efforts.

Bayan, Christopher; Levitt, Jonathan M.; Miller, Eric; Kaplan, David; Georgakoudi, Irene

2009-05-01

432

Silica Fiber/Core-Sheath Fiber.  

National Technical Information Service (NTIS)

The report describes work on a program which called for (1) a study of fused quartz fiber forming from a fluid melt contained in a bushing of tungsten and other materials in an argon atmosphere, and (2) the development of a composite ceramic-glass fiber o...

D. Plaskon D. Bradford W. H. Otto

1965-01-01

433

Human Development Index Data  

NSDL National Science Digital Library

This data set traces the varying patterns of national progress in recent decades, documenting impressive long-term Human Development Index (HDI) gains even in most low-income countries. The data set also includes three innovative new measurements: the Inequality-adjusted Human Development Index (IHDI), the Gender Inequality Index (GII) and the Multidimensional Poverty Index (MPI). The data set is available in both CSV and SDMX file formats and contains more than 100 indicators that measure quality of life for all UN member states.

Nations, United

434

Fiber pulling apparatus modification  

NASA Astrophysics Data System (ADS)

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.

1992-11-01

435

PLASTIC FIBER ROLLINGFOR CONCRETEREINFORCEMENT  

Microsoft Academic Search

ABSTRACT Fiber reinforced concrete is gaining in acceptance and usage as its strength and toughness,benefits are realized. Polypropylene fibers are currently the most commonly,used fibers. However~,the cost of virgin plastics limits the percent content that can be economically,added to concrete. One would,first believe that recycled plastics could offer a viable alternative to virgin-plastic fibers, but at present time extra selection

JEFF SCOTT THOMAS

1996-01-01

436

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

437

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

438

FIBER LOADING: THEORY AND APPLICATIONS  

Microsoft Academic Search

Fiber loading is a method for manufacturing precipitated calcium carbonate (PCC) within the pulp processing system. The fiber-loading process results in PCC being partly deposited within the fiber, which results in potential fiber savings. Although fiber loading is applicable to all printing and writing papers, this study focuses on recycling mixed office wastepaper into printing and writing papers. Fiber loading

John H. Klungness; Marguerite S. Sykes

439

eBooks with indexes that reorganize conceptually  

Microsoft Academic Search

Subject indexes were an important step forward for books because they enabled the comparison and correlations of information without extensive reading, re-reading and memorization. In this short paper, we focus on the user interaction and usage scenario of a new system called ScentIndex that enhances the subject index of an eBook by conceptually reorganizing it to suit particular information needs.

Ed Huai-hsin Chi; Lichan Hong; Julie Heiser; Stuart K. Card

2004-01-01

440

Carbon fibers from electrospun polymeric phenolic resin precursors  

NASA Astrophysics Data System (ADS)

This dissertation presents a technique for producing carbon fibers of nano- to micro-sized dimension by utilizing a non-conventional fiber spinning approach with refractory polymers, followed by post-processing steps, to create new carbon materials with distinctive chemical/physical property characteristics. Phenolic resins, novolak and resole, are selected for this study because of their low cost, marketability, environmental friendliness, and high char yield upon pyrolysis. The new carbon fibers are at least an order of magnitude smaller than their conventionally processed counterpart, and possess significant advantages. Phenolic resin fibers, consisting of a blend of novolak and resole, are generated via electrospinning and are subsequently cured and pyrolyzed at temperatures from 800°C to 2000°C to form carbon fibers having diameters of ˜1 mum. Fiber analysis by scanning electron microscopy confirms that the morphology generated during the electrospinning processing is retained throughout the curing and carbonization processes. X-ray diffraction suggests the presence of highly graphitized carbon, which is further validated by high-resolution transmission electron microscopy (HRTEM) analysis. There is evidence of crystalline graphite, which may have nucleated on aligned sheets presence on the fiber surface. The physical characteristics of electrospun fibers are contrary to those exhibited by pyrolyzed phenolic resins, which fall into the classification of non-graphitizing. It is likely that the thin electrospun fibers offer a template that encourages ordering not usually seen in thicker fibers or bulk samples of carbonized phenolic resins.

Gee, Diane L.

441

Isolation of cellulose fibers from kenaf using electron beam  

NASA Astrophysics Data System (ADS)

Cellulose fibers were isolated from a kenaf bast fiber using a electron beam irradiation (EBI) treatment. The methods of isolation were based on a hot water treatment after EBI and two-step bleaching processes. FT-IR spectroscopy demonstrated that the content of lignin and hemicellulose in the bleached cellulose fibers treated with various EBI doses decreased with increasing doses of EBI. Specifically, the lignin in the bleached cellulose fibers treated at 300 kGy, was almost completely removed. Moreover, XRD analyses showed that the bleached cellulose fibers treated at 300 kGy presented the highest crystallinity of all the samples treated with EBI. Finally, the morphology of the bleached fiber was characterized by SEM imagery, and the studies showed that the separated degree of bleached cellulose fibers treated with various EBI doses increased with an increase of EBI dose, and the bleached cellulose fibers obtained by EBI treatment at 300 kGy was separated more uniformly than the bleached cellulose fiber obtained by alkali cooking with non-irradiated kenaf fiber.

Shin, Hye Kyoung; Pyo Jeun, Joon; Bin Kim, Hyun; Hyun Kang, Phil

2012-08-01

442

Gated fiber optic transmission  

Microsoft Academic Search

A gated fiber optic sensor system is disclosed for increasing the effective optical path of a length of optical fiber cable. A pulse of polarized light having a known optical wavelength is directed into a length of optical fiber cable for propagation therethrough in a cyclic path. A planar semiconductor member is mounted in the path of the polarized light

L. C. Bobb

1984-01-01

443

Fiber grating spectra  

Microsoft Academic Search

In this paper, we describe the spectral characteristics that can be achieved in fiber reflection (Bragg) and transmission gratings. Both principles for understanding and tools for designing fiber gratings are emphasized. Examples are given to illustrate the wide variety of optical properties that are possible in fiber gratings. The types of gratings considered include uniform, apodized, chirped, discrete phase-shifted, and

T. Erdogan

1997-01-01

444

Steps that Count - The Association Between the Number and Intensity of Steps Accumulated and Fitness and Health Measures.  

PubMed

BACKGROUND: Pedometer-based recommendations for accumulating steps/d largely focus on volume, with less emphasis on intensity and fitness/health outcomes. We aim to examine this relationship. METHODS: A convenience sample (N=70, 35 men, 32+8yrs) wore a pedometer (4-days). The pedometer classified steps as "aerobic" (>60steps/minute, minimum duration of 1-minute) or "non-aerobic" (<60steps/minute and/or <1-minute). Estimated maximal oxygen uptake (VO2max) derived from a 12 minute sub-maximal step-test, and health outcomes (blood pressure (BP), body mass index (BMI), percentage body fat (%BF), waist circumference (WC)) were correlated with pedometer data. Participants were grouped according to number and intensity of steps: LOW (<5,000 steps/day), HIGH-LOW (>5,000 steps/day, no aerobic steps), HIGH-HIGH (>5,000 steps/day, including some aerobic steps). Analyses of co-variance, adjusting for age, gender and total steps/day were used to compare groups. RESULTS: Average steps/day was 6,520+2,306; Total steps/day and total time spent accumulating "aerobic" steps (minutes/day) were inversely associated with %BF, BMI, WC and systolic BP (p<0.05). After adjusting for gender and total steps/day, %BF was different between all 3 groups, VO2max was different between the LOW and HIGH-HIGH groups, WC was lower in the HIGH-HIGH versus the other 2 groups (p<0.03, respectively). CONCLUSION: Intensity seems an important factor to consider in steps/day cut-points. PMID:23249564

Pillay, Julian David; Kolbe-Alexander, Tracy L; van Mechelen, Willem; Lambert, Estelle Vicki

2012-12-17

445

Characterization of mineral population by index particle: implication for the Stanton hypothesis.  

PubMed

Fibers from seven crocidolite samples used by M. F. Stanton et al. (J. Natl. Cancer Inst. 67, 965-975 (1981] were measured from STEM and optical images. Their masses were computed. From these data, the population was normalized to a sample mass of 1 micrograms, and the number of fibers in various size categories of a 1-microgram sample was compared to the tumor probability for each sample. The purposes of this study were (1) to evaluate errors in and the utility of population characterization by index number (log of the number of particles longer than 8 micron with widths equal to or less than 0.25 micron) and (2) to review the Stanton hypothesis in view of this analysis. The study found that in most cases the index number is a reliable population parameter. However, index numbers between 0 and 2.5 cannot be obtained. Therefore, populations of mineral fibers will fall into two groups: those without index particles, which have indeterminant index numbers, and those with index numbers between 2.5 and 6.0. Within Stanton's populations that contain index particles, where y equals logit tumor probability and x equals index number, r equals 0.307 (insignificant). Where y equals tumor probability and x equals index number, r equals 0.503 (significant). The correlation coefficients are low enough to suggest the possibility that factors other than size and shape play a role in mineral fiber carcinogenicity. PMID:3038512

Wylie, A G; Virta, R L; Segreti, J M

1987-08-01

446

Probabilistic latent semantic indexing  

Microsoft Academic Search

Probabilistic Latent Semantic Indexing is a novel approach to automated document indexing which is based on a statistical latent class model for factor analysis of count data. Fitted from a training corpus of text documents by a generalization of the Expectation Maximization algorithm, the utilized model is able to deal with domain-specific synonymy as well as with polysemous words. In

Thomas Hofmann

1999-01-01

447

TIGR Drosophila Gene Index  

NSDL National Science Digital Library

The Institute for Genomic Resources (TIGR) placed online the Drosophila Gene Index (version 1.1) in 1999. The index is searchable by nucleotide or protein sequence, identifier (TC, ET, EST, GB), tissue, or gene product name. Note that this resource is available free of charge "only to researchers at non-profit institutions using it for non-commercial purposes."

448

HUMAN USE INDEX (FUTURE)  

EPA Science Inventory

Human land uses may have major impacts on ecosystems, affecting biodiversity, habitat, air and water quality. The human use index (also known as U-index) is the percentage of human land use in an area, including agriculture, urban and suburban development, and mining. Low values ...

449

HUMAN USE INDEX  

EPA Science Inventory

Human land uses may have major impacts on ecosystems, affecting biodiversity, habitat, air and water quality. The human use index (also known as U-index) is the percentage of human land use in an area, including agriculture, urban and suburban development, and mining. Low values ...

450

Indexing Transitional Knowledge  

Microsoft Academic Search

Various indexes have been proposed to mark when a child is on the verge of acquiring new knowledge. This article described a new method for indexing this point of transition, which is based on the specificity of children's verbal explanations. The degree to which children were specific in their verbal explanations was related to whether they benefited from instruction. In

Theresa Graham; Michelle Perry

1993-01-01

451

Machine-Aided Indexing.  

National Technical Information Service (NTIS)

Progress is reported at the 1,000,000 word level on the development of a partial syntactic analysis technique for indexing text. A new indexing subroutine for hyphens is provided. New grammars written and programmed for MAI are discussed. (Author)

C. R. Jacobs

1972-01-01

452

Indexing Editorial Cartoons.  

ERIC Educational Resources Information Center

Discusses access to editorial cartoons, including the importance and worth of editorial cartoons; sources, including newspapers, museums, and special cartoon collections; indexing and classification; subject access; indexing by illustrator and subject; technology and access, including digital data; access to special collections; and access to…

Chapple-Sokol, Angie

1996-01-01

453

Generalization for Estrada Index  

NASA Astrophysics Data System (ADS)

In this paper the Estrada index of Hermite matrix is firstly defined and investigated. In fact this is a natural generalization of Estrada, distance Estrada and Laplacian Estrada indices. Thus all properties about them can be handled by this new index.

Güngör, A. Dilek; Çevik, A. Sinan; Karpuz, Eylem G.; Ate?, Firat; Cangül, I. Naci

2010-09-01

454

Broadband excitation and collection in fiber-optic nonlinear endomicroscopy  

NASA Astrophysics Data System (ADS)

Broadband excitation and collection in a fiber-optic nonlinear endomicroscope are realized by using a single hollow-core double-clad photonic crystal fiber and a gradient index lens. Femtosecond pulses with central wavelengths in the range of 750-850 nm can be directly delivered through the core of the fiber for nonlinear excitation without pre-chirping. A gradient index lens with numerical aperture 0.8 designed to operate over the near-infrared wavelength range is used for focusing the laser beam from the fiber for nonlinear excitation and for collecting the fluorescent signal from the sample. This compact system is suitable to perform nonlinear imaging of multiple fluorophors in the wavelength range of 750-850 nm.

Prakash Ghimire, Navin; Bao, Hongchun; Gu, Min

2013-08-01

455

A Reconfigurable Stepping Motor  

NASA Astrophysics Data System (ADS)

Multiphase brushless actuators, commonly known as the stepper motors, are ubiquitous for many precision control applications. Developments in the microelectronics have lead to their use as efficient drive motors for modern electric vehicles. Understanding the physics and the control logic for interfacing these transducers continues to be important for scientists and engineers. An overview of the stepping motor principles and interfacing requirements is presented and a simple working model used to teach the concepts of stepper motors is described and demonstrated. This model was used to design a much larger stepper motor required to precisely rotate a massive optical system in the undergraduate advanced physics laboratory.

Rogers, Charles; Selvaggi, Richard

2009-04-01

456

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.

Marinker, Marshall

1987-01-01

457

New photolithography stepping machine  

SciTech Connect

A joint development project to design a new photolithography steeping machine capable of 150 nanometer overlay accuracy was completed by Ultratech Stepper and the Lawrence Livermore National Laboratory. The principal result of the project is a next-generation product that will strengthen the US position in step-and-repeat photolithography. The significant challenges addressed and solved in the project are the subject of this report. Design methods and new devices that have broader application to precision machine design are presented in greater detail while project specific information serves primarily as background and motivation.

Hale, L.; Klingmann, J. [Lawrence Livermore National Lab., CA (United States); Markle, D. [Ultratech Stepper Inc. (United States)

1995-03-08

458

UV Bragg grating inscription in germanium-doped photonic crystal fibers  

NASA Astrophysics Data System (ADS)

The design flexibility of photonic crystal fibers has accelerated the development of specialty optical fibers for a wide variety of applications. Optical fiber sensor applications for instance can benefit from this fiber technology. Fiber Bragg grating inscriptions in photonic crystal fibers have been reported with inscription setups that go from continuous-wave to femtosecond pulsed laser sources. However, the compatibility of the microstructures in these fibers with conventional ultraviolet inscription techniques was never before investigated in a broad range of (Germanium doped) fibers. We present UV laser induced dynamics of Bragg gratings growths in photonic crystal fibers with a hexagonal arrangement of 6 rings of airholes around a Germanium doped core region. The average refractive index increase and the refractive index modulation by the grating inscription process are compared for microstructures with several doping levels, airhole filling factors, airhole pitch distance and fiber orientation. We show how the parameters of the microstructure can influence the Bragg grating inscriptions. In addition we expand the range of fibers in which Bragg gratings, with reflection strengths that are useable for sensing purposes, can be inscribed to fibers with Germanium doping concentrations as low as 1.36 and 0.45 mol%.

Geernaert, Thomas; Becker, Martin; Mergo, Pawel; Nasilowski, Tomasz; Wojcik, Jan; Urbanczyk, Waclaw; Rothhardt, Manfred; Chojetzki, Christoph; Bartelt, Hartmut; Berghmans, Francis; Thienpont, Hugo

2010-04-01

459

Electrooptic modulation in optical fiber with liquid crystalline core  

NASA Astrophysics Data System (ADS)

This thesis investigates a novel electrooptic fiber waveguide using a liquid crystalline core. The electrooptic fibers are fabricated by filling liquid crystal materials into hollow-core fibers. Liquid crystal molecules in the fiber core can be modulated by electric fields, which results in a change of refractive index. A new variety of electrooptic devices can be fabricated using such liquid crystal fiber waveguides. The molecular alignment of liquid crystal molecules in a fiber core is a critical issue in obtaining electrooptic modulation. Photo-alignment technique is used to obtain uniform parallel liquid crystal molecular alignment inside hollow-core optical fibers, as a rubbing method is not physically possible. The scattering loss of nematic liquid crystals in the fiber structure is measured to be ~3 dB/cm, which makes it suitable for the potential electrooptic applications. To demonstrate the fundamental feasibility of electrooptic modulation, both intensity- and phase modulators are constructed using liquid crystal fibers. The normal waveguide modes of the parallel-aligned liquid crystal fiber are obtained by directly solving the Maxwell's equations. The single-mode cut-off condition of a liquid crystal fiber is found to be dependent on the anisotropy of the liquid crystal material. The deformation of the liquid crystal molecular profile due to the application of an electric field is obtained numerically. Finite element method is employed to study the waveguide mode characteristics of the liquid crystal fibers under the perturbation of an electric field. Finally, a novel polarization controller using a liquid crystal fiber is proposed and analyzed in detail. Directions of future research are presented at the end of this thesis.

Wong, Charles Seng-Ieong

1997-09-01

460

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

461

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

462

Refractive index profiling of an optical waveguide from the determination of the effective index with measured differential fields.  

PubMed

The evanescent tails of a guiding mode as well as its first and second derivatives were measured by a modified end-fire coupling method. The effective index of the waveguide can be obtained by simultaneously fitting these three fields using single parameter. Combined with an inverse calculation algorithm, the fields with fitted evanescent tails showed great improvement in the refractive index profiling of the optical waveguide, especially at the substrate region. Single-mode optical fibers and planar waveguides of proton-exchanged (PE) and titanium-indiffusion (Ti:LiNbO3) on lithium niobate substrates with different refractive index profiles were measured for the demonstration. PMID:23187531

Tsai, Wan-Shao; Ting, San-Yu; Wei, Pei-Kuen

2012-11-19

463

Criticality calculations for Step-2 GPHS modules.  

SciTech Connect

The Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) will use an improved version of the General Purpose Heat Source (GPHS) module as its source of thermal power. This new version, referred to as the Step-2 GPHS Module, has additional and thicker layers of carbon fiber material (Fine Weaved Pierced Fabric) for increased strength over the original GPHS module. The GPHS uses alpha decay of {sup 238}Pu in the oxide form as the primary source of heat, and small amounts of other actinides are also present in the oxide fuel. Criticality calculations have been performed by previous researchers on the original version of the GPHS module (Step 0). This paper presents criticality calculations for the present Step-2 version. The Monte Carlo N-Particle eXtended code (MCNPX) was used for these calculations. Numerous configurations of GPHS module arrays surrounded by wet sand and other materials (to reflect the neutrons back into the stack with minimal absorption) were modeled. For geometries with eight GPHS modules (from a single MMRTG) surrounded by wet sand, the configuration is extremely sub-critical; k{sub eff} is about 0.3. It requires about 1000 GPHS modules (from 125 MMRTGs) in a close-spaced stack to approach criticality (k{sub eff} = 1.0) when surrounded by wet sand. The effect of beryllium in the MMRTG was found to be relatively small.

Hensen, Danielle Lynn; Lipinski, Ronald J.

2007-08-01

464

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

465

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

466

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

467

Characterization of novel optical fibers for use in laser detonators  

NASA Astrophysics Data System (ADS)

A system for launching flyers using a Q-switched Nd: YAG laser has been developed for shock initiation of secondary explosives. Flyers have been launched at velocities approaching 6 km s-1. Optical fibers are used to transport the optical energy from the laser to the detonator. The launch of these flyers with sufficient velocity requires a fluence in the region of 35 J cm-2, significantly above the damage threshold of most optical fibers. This damage is typically caused by laser absorption at the input face due to imperfections in the surface polishing. A variety of optical fibers with high quality input faces have been tested at fluences up to 50 J cm-2, and their damage thresholds and beam profiles have been measured. The standard fiber used in this system is a low hydroxyl (-OH) content, 400?m diameter core silica fiber, with CO2 laser polished faces. In addition to this, fibers tapering down to 300?m and 200?m core diameter were investigated, as a means of increasing the efficiency of the system, along with mechanically polished fibers. The fiber currently enters the detonator body from the rear. Depending on the application, it may be required for the fiber to enter from the side. To facilitate this, fibers with a machined output face, designed to produce an output at approximately 90 degrees to the fiber axis were tested. Finally, a 2:1 fiber splitter was tested, as a first step to enable simultaneous firing of several detonators. Multiple initiation points are desirable for applications such as programmable initiation, and it is intended to study fiber splitters with a higher split ratio, such as 4:1 and 8:1. The results of these experiments are presented, and assessments made of suitability for transmission of high-power Qswitched Nd:YAG laser pulses.

Bowden, M. D.; Drake, R. C.; Singleton, C. A.

2006-09-01

468

Monitoring of temperature fatigue failure mechanism for polyvinyl alcohol fiber concrete using acoustic emission sensors.  

PubMed

The applicability of acoustic emission (AE) techniques to monitor the mechanism of evolution of polyvinyl alcohol (PVA) fiber concrete damage under tem