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1

Tilted Bragg gratings in step-index polymer optical fiber.  

PubMed

We report the first slightly tilted Bragg gratings photo-inscription in polymer optical fiber (POF). For this, we make use of trans-4-stilbenemethanol-doped photosensitive step-index poly(methyl methacrylate) (PMMA) POFs. Tilted fiber Bragg gratings (TFBGs) are inscribed in the near-infrared wavelength range using the scanning phase mask technique with a tilted phase mask in the plane perpendicular to the laser beam direction. The transmitted amplitude spectrum evolution of a 3° TFBG is analyzed as a function of the surrounding refractive index. A maximum sensitivity close to 13??nm/RIU (refractive index unit) is obtained in the range 1.42-1.49. PMID:25503009

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

2014-12-15

2

A comparison of temperature sensing characteristics of SMS structures using step and graded index multimode fibers  

NASA Astrophysics Data System (ADS)

A comparative study of the temperature sensitivities of the single-multi-single mode (SMS) fiber structures employing step-index and graded-index multimode fibers (MMFs), for two different doping concentrations of GeO2 in MMF core, is carried out. The temperature sensitivity for graded-index MMF is found to be much larger (approx. 45-285 times) for the entire range of wavelength operation (0.7-1.6 ?m). A physical explanation of the observed behavior is also presented. The study should be useful in designing various fiber optic multimode interference based devices with high or low temperature sensitivities.

Kumar, Manoj; Kumar, Arun; Tripathi, Saurabh Mani

2014-02-01

3

High power modal instability measurements of very large mode area (VLMA) step index fibers  

NASA Astrophysics Data System (ADS)

High power (<0.5kW) experiments using low NA (~0.07), very large mode area (VLMA) step index fibers (SI) (with core/clad diameters: 45/375, 60/500um) and gain tailored step index (GT-SI) fibers (with doped-core/core/clad diameters: 38/60/400, 50/80/533um) are presented. In fiber amplifier experiments with multi-moded beam (M2 1.5- 3) outputs, Stimulated Thermal Rayleigh scattering (STRS) threshold is determined by comparing gain dependence of output mode quality between high power (<200W) and low power (<100W) experiments for a given fiber layout. Beam quality degradation with signal power is characterized well above the instability threshold where a saturation of the phenomena is observed. For SI fibers degree of beam quality degradation is found to be significantly worse for tighter fiber coil diameters. GT-SI fibers exhibit significantly less modal degradation compared to SI fibers. STRS instability threshold is further verified with signal power dependent multi-path interference spectrum (MPI) measurements which exhibited exponential broadening above the threshold. Strength of STRS nonlinear coupling coefficients are estimated from experimental data using a comprehensive 3-dimensional transverse spatial hole burning (TSHB) fiber MOPA numerical model, phenomenologicaly extended to include STRS.

Engin, Doruk; Lu, Wei; Verdun, Horacio; Gupta, Shantanu

2013-05-01

4

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

PubMed

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

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

2014-07-28

5

Influence of fiber design on light-guidance in step-index fibers for bundle applications in the UV-VIS-region  

NASA Astrophysics Data System (ADS)

Silica-based multimode fibers with a step-index refractive-index profile are commonly used for light transportation from 185 nm (DUV) up to 2300nm (NIR). Core diameters of such mono fibers range from 100 to 600 ?m and their clad-tocore- ratios (CCR) typically are 1.1 and larger. If bundles are required for applications in the UV- and VIS-region, fibers with smaller core diameter and thinner cladding thicknesses are desired to reduce coupling losses, as their light acceptance surface area is then relatively larger. However, using these bundles at higher wavelengths, e.g. in the NIR-region, change of light-guiding properties can be observed. In fiber-optic light delivery systems, the transmission including light acceptance and guidance can be described by the concept of pupil apodization. However in fiber characterization, the numerical aperture (NA) of specialty fibers is an useful key parameter, which will be determined using the inverse far-field method at two separate laser wavelengths with focused light excitation. With parallel light, skew rays/modes must be taken into account. In addition, the spectral fiber attenuation with Uniform Mode Distribution (UMD) illumination and mode-selective illumination will be discussed and compared with experimental NA results. As expected, the ratio of cladding thickness and wavelength is the most important parameter on the light-guiding properties in short-length applications with increasing wavelength.

Ohlmeyer, H.; Tobisch, T.; Voncken, M. M. A. J.; Prechtel, L.; Belz, M.; Klein, K.-F.

2014-05-01

6

1.9 octave supercontinuum generation in a As?S? step-index fiber driven by mid-IR OPCPA.  

PubMed

Using a 3.1-?m optical parametric chirped-pulse amplifier (OPCPA), we generate a supercontinuum in a step-index chalcogenide fiber that spans from 1.6 to 5.9 ?m at the -20??dB points. The rugged step-index geometry allows for long-term operation, while the spectral bandwidth is limited by the transmission of the As2S3 fiber. PMID:25360976

Hudson, Darren D; Baudisch, Matthias; Werdehausen, Daniel; Eggleton, Benjamin J; Biegert, Jens

2014-10-01

7

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

SciTech Connect

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

Yalin, Azer P; Joshi, Sachin

2014-06-03

8

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

NASA Astrophysics Data System (ADS)

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

Stepniak, G.; Siuzdak, J.

2014-08-01

9

High peak- and average-power pulse shaped fiber laser in the ns-regime applying step-index XLMA gain fibers  

NASA Astrophysics Data System (ADS)

Pulsed fiber lasers and continuous-wave (cw) fiber lasers have become the tool of choice in more and more laser based industrial applications like metal cutting and welding mainly because of their robustness, compactness, high brightness, high efficiency and reasonable costs. However, to further increase the productivity with those laser types there is a great demand for even higher laser power specifications. In this context we demonstrate a pulsed high peak- and averagepower fiber laser in a Master Oscillator Power Amplifier (MOPA) configuration with selectable pulse durations between 1 ns and several hundred nanoseconds. To overcome fiber nonlinearities such as stimulated Raman scattering (SRS) and self-phase-modulation (SPM) flexible Ytterbium doped extra-large mode area (XLMA) step index fibers, prepared by novel powder-sinter technology, have been used as gain fibers. As an example, for 12 ns pulses with a repetition rate of 10 kHz, a pump power limited average laser output power of more than 400 W in combination with peak powers of more than 3.5 MW (close to self-focusing-threshold) has been achieved in stable operation. The potentials of this laser system have been further explored towards longer pulse durations in order to achieve even higher pulse energies by means of pulse shaping techniques. In addition, investigations have been conducted with reduced pulse energies and repetition rates up to 500 kHz and average powers of more than 500 W at nearly diffraction limited beam quality.

Dinger, R.; Grundmann, F.-P.; Hapke, C.; Ruppik, S.

2014-03-01

10

40-Gbits transmission in dispersion-management links with step-index fiber and linear compensation.  

PubMed

The dynamic behavior of single-channel transmission in standard fibers with strong dispersion management and linear compensating devices was theoretically and numerically analyzed. We compared a single pulse and a pseudorandom sequence to highlight the relevant roles played by nonlinearity-induced spectrum distortion and pulse interaction. As a result, 40/Gbit/s transmission on an 1800-km dispersion-management link with 100-km spans of standard fiber was obtained. PMID:18073975

Zitelli, M; Matera, F; Settembre, M

1999-08-15

11

Fiber optic refractive index monitor  

DOEpatents

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

Weiss, Jonathan David (Albuquerque, NM)

2002-01-01

12

Fabrication of Bragg gratings in microstructured and step index Bi-SiO2 optical fibers using an ArF laser.  

PubMed

An ArF excimer laser was used to fabricate Bragg gratings in fibers with Bi-SiO(2) core and microstructured or F-doped claddings without fiber presensitization. Average and modulated refractive index changes of 2.7 × 10(-4) and 1.0 × 10(-4) were induced in pristine microstructured fiber while 1.0 × 10(-4) and 0.7 × 10(-4) were observed in the F-doped-cladding fiber. Fiber luminescence was also measured under 1064 nm pumping for both fibers. Photosensitivity and luminescence were compared to a Bi-Al(2)O(3)-SiO(2) core optical fiber. PMID:23262841

Violakis, Georgios; Limberger, Hans G; Zlenko, Alexander S; Semjonov, Sergey L; Bufetov, Igor A; Mashinsky, Valery M; Vel'miskin, Vladimir V; Dianov, Evgeny M

2012-12-10

13

High-bandwidth graded-index polymer optical fiber  

Microsoft Academic Search

High-bandwidth (2 GHz·km) graded-index polymer optical fiber (GI POF) was successfully obtained by the new interfacial-gel polymerization technique in which the unreactive component was used in order to obtain the quadratic refractive-index distribution. This high-bandwidth GI POF makes it possible to transmit high-speed optical signals in the short range network which was not covered by the step-index type POF commercially

Yasuhiro Koike; Takaaki Ishigure; E. Nihei

1995-01-01

14

Multimode interference refractive index sensor based on coreless fiber  

NASA Astrophysics Data System (ADS)

A multimode interference refractive index (RI) sensor based on the coreless fiber was numerically and experimentally demonstrated. Two identical single mode fibers (SMF) are spliced at both ends of a section of the coreless fiber which can be considered as the equivalent weakly guiding multimode fiber (MMF) with a step-index profile when the surrounding refractive index (SRI) is lower than that of the coreless fiber. Thus, it becomes the conventional single-mode multimode single-mode (SMS) fiber structure but with a larger core size. The output spectra will shift along with the changes in the SRI owing to the direct exposure of the coreless fiber. The output spectra under different SRIs were numerically studied, as well as the sensitivities with different lengths and diameters of the coreless fiber. The predication and calculation showed the good agreement with the experimental results. The proposed RI sensor proved to be feasible by verification experiments, and the relative error was merely 0.1% which occupied preferable sensing performance and practicability.

Li, Yang; Liu, Zhibo; Jian, Shuisheng

2014-03-01

15

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

16

Surface plasmon resonance based fiber optic refractive index sensors  

NASA Astrophysics Data System (ADS)

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

Hlubina, Petr; Kadulova, Miroslava; Ciprian, Dalibor

2014-12-01

17

Endface index profiling of optical fiber preforms.  

PubMed

A new method of obtaining the refractive-index profile of an optical fiber preform is described. The technique is based on the refraction of light emerging from an endface cut normal to the preform axis. Two forms have been developed. In one, quantitative index data are obtained by a spatial-filtering method. The result is displayed as a 3-D graphic plot. The other uses a new type of spatial modulation which permits a direct display of the 3-D index profile in the form of a visual image. PMID:20401050

Sasaki, I; Payne, D N; Mansfield, R J

1982-12-01

18

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

19

Highly birefringent index-guiding photonic crystal fibers  

Microsoft Academic Search

Photonic crystal fibers (PCFs) offer new possibilities of realizing highly birefringent fibers due to a higher intrinsic index contrast compared to conventional fibers. In this letter, we analyze theoretically the levels of birefringence that can be expected using relatively simple PCF designs. While extremely high degrees of birefringence may be obtained for the fibers, we demonstrate that careful design with

Theis P. Hansen; Jes Broeng; Stig E. B. Libori; Erik Knudsen; Anders Bjarklev; Jacob Riis Jensen; Harald Simonsen

2001-01-01

20

Refractive index sensor based on terahertz multimode interference fiber device  

NASA Astrophysics Data System (ADS)

A fiber-optic refractive index sensor based on terahertz multimode interference in a singlemode-multimode-singlemode fiber structure (SMS) is numerically demonstrated for the first time in the literature. The shift of spectral transmission is investigated as function of external refractive index. Moreover, the coupling efficiency between optical modes at singlemode and multimode sections are determined. The proposed sensor reaches average sensitivity of ~5 GHz/RIU (refractive index unit) over a refractive index range of 1.4-1.5.

Cruz, Alice L. S.; Migliano, Antonio C. C.; Franco, Marcos A. R.

2013-05-01

21

Spatial Frequency Multiplexing of Fiber-Optic Interferometric Refractive Index Sensors Based on Graded-Index Multimode Fibers  

PubMed Central

Fiber-optic interferometric sensors based on graded-index multimode fibers have very high refractive-index sensitivity, as we previously demonstrated. In this paper, spatial-frequency multiplexing of this type of fiber-optic refractive index sensors is investigated. It is estimated that multiplexing of more than 10 such sensors is possible. In the multiplexing scheme, one of the sensors is used to investigate the refractive index and temperature responses. The fast Fourier transform (FFT) of the combined reflective spectra is analyzed. The intensity of the FFT spectra is linearly related with the refractive index and is not sensitive to the temperature.

Liu, Li; Gong, Yuan; Wu, Yu; Zhao, Tian; Wu, Hui-Juan; Rao, Yun-Jiang

2012-01-01

22

Fiber Optic-Based Refractive Index Sensing at INESC Porto  

PubMed Central

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

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

2012-01-01

23

Fiber structure based on a depressed inner cladding fiber for bend, refractive index and temperature sensing  

NASA Astrophysics Data System (ADS)

A fiber-optic structure based on a section of a double-clad fiber with depressed inner cladding is investigated for bend, refractive index and temperature sensing. The structure is formed by splicing a section of SM630 fiber between two standard fibers SMF-28. The operation principle relies on the sensitivity of cladding modes that are induced at a splice of fibers having different refractive index profiles. The mode structure of the double cladding fiber and the mechanism of formation of dips in the transmission spectra are discussed. The transmission spectra of the structure are measured for different curvatures of the inserted fiber section. The shift of dips to long wavelengths with increasing curvature of the fiber is observed and its dependence on the fiber section length and the direction of bending is investigated. The sensitivities of the spectral dips to the external refractive index and temperature are also measured.

Ivanov, Oleg V.; Zlodeev, Ivan V.

2014-01-01

24

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

NASA Technical Reports Server (NTRS)

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

Kawalko, Stephen F.

1990-01-01

25

Theory of biaxial graded-index optical fiber  

NASA Technical Reports Server (NTRS)

The problem of wave propagation in a biaxial graded-index fiber with circular symmetry is considered. The problem is formulated in terms of four first-order differential equations for the tangential components of the electric and magnetic fields. A general solution method for solving systems of differential equations is presented. This solution method is then used to solve the system of equations for a particular example of a biaxial graded-index fiber. Numerical results for the propagation constant in the fiber are also given.

Kawalko, Stephen F.; Uslenghi, Piergiorgio L. E.

1990-01-01

26

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

27

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

28

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

NASA Astrophysics Data System (ADS)

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

Majumdar, Angshuman; Das, Satabdi; Gangopadhyay, Sankar

2014-12-01

29

Mode field diameters of index-guided microstructured optical fibers  

NASA Astrophysics Data System (ADS)

Using our earlier developed analytical field model, which retains the required azimuthal variation of field for the index-guiding microstructured optical fibers (MOFs), we show that Gaussian approximation based analysis for the mode field diameters (MFDs) is likely to give inaccurate results and suggest improvements.

Sharma, Dinesh Kumar; Sharma, Anurag

2013-06-01

30

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

31

Fiber-optic refractive index sensor based on surface plasmon resonance  

NASA Astrophysics Data System (ADS)

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

Hlubina, Petr; Ciprian, Dalibor; Kadulova, Miroslava

2015-01-01

32

Intermodal dispersion and mode coupling in perfluorinated graded-index plastic optical fiber  

Microsoft Academic Search

Graded-index multimode perfluorinated plastic optical fibers typically exhibit bandwidths much greater than would be expected from their index profiles. To resolve this discrepancy, we have conducted the first measurements of differential mode delay in such fibers. These measurements show intermodal dispersion that increases as the square root of fiber length, implying strong mode coupling in these fibers. Significant power transfer

W. R. White; Michael Dueser; W. A. Reed; Tsuyoshi Onishi

1999-01-01

33

Inline fiber interference-based refractive-index sensor  

NASA Astrophysics Data System (ADS)

We report two fiber multiple-mode interferometers formed in photonic crystal fiber (PCF). The interference between the core and the cladding modes of a PCF is utilized. We use two methods to form a coupling point, and the cladding modes are excited from the fundamental core mode. One method is blowing compressed gas into the air holes and discharging at the coupling point; the air holes will expand due to gas expansion in the discharge process. Similarly, the other is discharging at the coupling point after the air is exhausted from the air holes, and the holes will contract during the process. By making another coupling point at a different location along the fiber, the proposed PCF interferometers are implemented. Experimental results show that the sensitivities of the two devices can achieve 1.54 and 1.45 nm for a 0.01 refractive index change.

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

2014-11-01

34

One-step electrospinning of cross-linked chitosan fibers.  

PubMed

Chitin is a nitrogen-rich polysaccharide that is abundant in crustaceans, mollusks, insects, and fungi and is the second most abundant organic material found in nature next to cellulose. Chitosan, the N-deacetylated derivative of chitin, is environmentally friendly, nontoxic, biodegradable, and antibacterial. Fibrous mats are typically used in industries for filter media, catalysis, and sensors. Decreasing fiber diameters within these mats causes many beneficial effects such as increased specific surface area to volume ratios. When the intrinsically beneficial effects of chitosan are combined with the enhanced properties of nanofibrous mats, applications arise in a wide range of fields, including medical, packaging, agricultural, and automotive. This is particularly important as innovative technologies that focus around bio-based materials are currently of high urgency, as they can decrease dependencies on fossil fuels. We have demonstrated that Schiff base cross-linked chitosan fibrous mats can be produced utilizing a one-step electrospinning process that is 25 times faster and, therefore, more economical than a previously reported two-step vapor-cross-linking method. These fibrous mats are insoluble in acidic, basic, and aqueous solutions for 72 h. Additionally, this improved production method results in a decreased average fiber diameter, which measures 128 +/- 40 nm. Chemical and structural analyses were conducted utilizing Fourier transform infrared spectroscopy, solubility studies, and scanning electron microscopy. PMID:17696400

Schiffman, Jessica D; Schauer, Caroline L

2007-09-01

35

Fiber optic refractive index sensor based on ?-phase shifted fiber Bragg grating fabricated on etched side-hole fiber  

NASA Astrophysics Data System (ADS)

In this paper, we present a temperature-insensitive refractive index sensor based on ?-phase-shifted Bragg gratings fabricated on side-hole fibers processed by wet chemical etching technique. The reflection spectrum of the ?-phase shifted gratings on etched side-hole fiber features two notches with large spectral separation, which was used for refractive index (RI) detection in our application. The relative spectral notch separation exhibited a RI sensitivity of -278.5 pm/RIU (RIU: RI unit). Theoretical simulation obtained the temperature sensitivity of -0.00241 pm/°C, and experimental results also showed little sensitivity to temperature of our RI sensor.

Zhang, Qi; Hu, Lingling; Tian, Jiajun; Ianno, Natale J.; Han, Ming

2013-05-01

36

Reflectance Imaging by Graded-Index Short Multimode Fiber  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

37

Sensors and Actuators B 123 (2007) 594605 Fiber optic sensing of liquid refractive index  

E-print Network

Sensors and Actuators B 123 (2007) 594­605 Fiber optic sensing of liquid refractive index Argha is immersed, to a high degree of precision and over a wide range of refractive index. The slope of sensor of the fiber. The sensitivity of the sensor to refractive index change is dependent on cladding thickness

38

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

39

Rapid stabilization of pitch fiber precursor by multi-step thermal oxidation  

Microsoft Academic Search

A multi-step oxidation procedure was developed to stabilize an isotropic pitch fiber prior to carbonization. In the first step, the temperature was raised to 170–220 °C in 1 minute and kept isothermally for 4 minutes. The temperature was then increased in the same manner to 250, 300 and 350 °C. Stabilized fiber precursors were finally carbonized at 1000 °C. The

Jun-Ichiro Hayashi; Makoto Nakashima; Katsuki Kusakabe; Shigeharu Morooka; Susumu Mitsuda

1995-01-01

40

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

E-print Network

Organic Transistors on Fiber: A first step towards electronic textiles Josephine B. Lee and Vivek a significant step towards the realization of electronics textiles. Fiber transistors exhibit mobilities of >10. Introduction Recently, there has been interest in electronic textiles. E- textiles may be used to embed sensing

California at Irvine, University of

41

Benefits of a two-step cementation procedure for prefabricated fiber posts  

Microsoft Academic Search

Purpose: To determine whether two-step cementation of prefabricated fiber posts leads to higher bond strengths. Materials and Methods: Forty-eight human canine teeth were divided into six groups and fiber posts were cemented with DC Core, RelyX Unicem and Panavia F2.0, according to a one-step or two-step procedure. Per root, four cross-sections were prepared. The differences in push-out strength between procedure,

L. A. Jongsma; P. B. Bolhuis; P. Pallav; A. J. Feilzer; C. J. Kleverlaan

2010-01-01

42

Towards Silk Fiber Optics: Refractive Index Characterization, Fiber Spinning, and Spinneret Analysis  

NASA Astrophysics Data System (ADS)

Of the many biologically derived materials, whose historical record of use by humans underscores an ex-vivo utility, silk is interesting for it's contemporary repurposing from textile to biocompatible substrate. And while even within this category silk is one of several materials studied for novel repurposing, it has the unique character of being evolutionarily developed specifically for fiber spinning in vivo. The work discussed here is inspired by taking what nature has given, to explore the in vitro spinning of silk towards biocompatible fiber optics applications. A common formulation of silk used in biomedical studies for re-forming it into the various structures begins with the silkworm cocoon, which is degummed and dissolved into an aqueous solution of its miscible protein, fibroin, and post-treated to fabricate solid structures. In the first aim, the optical refractive index (RI) of various post-treatment methods is discussed towards determining RI design techniques. The methods considered in this work for re-forming a solid fiber from the reconstituted silk fibroin (RSF) solution borrow from the industrial techniques of gel spinning, and dry-spinning. In the second aim, methods are applied to RSF and quality of the spun fibers discussed. A feature common to spinning techniques is passing the (silk) material through a spinneret of specific shape. In the third aim, fluid flow through a simplified native silkworm spinneret is modeled towards bio-inspired lessons in design. In chapter 1 the history, reconstitution, are discussed towards understanding the fabrication of several optical device examples. Chapter 2 then prefaces the experiments and measurements in fiber optics by reviewing electromagnetic theory of waveguide function, and loss factors, to be considered in actual device fabrication. Chapter 3 presents results and discussion for the first aim, understanding design principles for the refractive index of RSF. From this point, industrial fiber-spinning approaches are reviewed from a theoretical and methodological perspective in chapter 4. Thus, chapter 5 presents results for the second aim, efforts to apply these techniques using RSF. Chapter 6 discusses the third aim, understanding the design of the silkworm spinneret by an idealized model of natural and reconstituted silk fibroin flow. While the ultimate goal of a structurally and optically smooth and uniform fiber remains elusive, this work serves as a guide for future efforts.

Spitzberg, Joshua David

43

A Highly Sensitive Fiber Optic Sensor Based on Two-Core Fiber for Refractive Index Measurement  

PubMed Central

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

2013-01-01

44

Simultaneous measurement of liquid level and surrounding refractive index using tilted fiber Bragg grating  

Microsoft Academic Search

In this paper, we present a novel fiber optic sensor for the simultaneous measurement of liquid level and surrounding refractive index based on tilted fiber Bragg grating (TFBG). The transmission loss and the bandwidth of cladding modes are two measures of the liquid level, while their resonance wavelengths are employed to determine the surrounding refractive index. A liquid level sensitivity

Qi Jiang; Debo Hu; Meng Yang

2011-01-01

45

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

46

One-step fabrication of high selective hollow fiber nanofiltration membrane module  

Microsoft Academic Search

A novel hollow fiber composite Nanofiltration (NF) membrane was fabricated by an improved preparation procedure. Using hollow\\u000a fiber ultrafiltration (UF) membrane modules as the supporting modules, hollow fiber composite NF modules were fabricated by\\u000a the one-step interfacial polymerization method. The effects of preparation conditions (such as concentration of the monomers,\\u000a reaction time of monomers and ambient relative humidity, etc.) on

Wei Wang; Guodong Li

2010-01-01

47

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...

48

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

PubMed

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

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

2015-02-15

49

Characteristics of a doubly clad optical fiber with a low-index inner cladding  

Microsoft Academic Search

This paper investigates a novel type of optical fiber which is composed of three portions: the core, inner cladding, and outer cladding. It is assumed that the core has the largest refractive index of the three, and the outer cladding index is the next largest. When the index difference between the core and the inner cladding is much larger than

S. Kawakami; S. Nishida

1974-01-01

50

Multiplex in-cylinder pressure measurement utilizing an optical fiber with specific refractive-index composition.  

PubMed

An approach to multiplex in-cylinder pressure measurement that utilizes a single-mode optical fiber with specific refractive-index composition has been proposed. The sensing fiber has been designed to show a certain amount of optical power loss with a small change in the fiber-local-bend radius. Along with pressure-transferring diaphragms the sensing fiber was embedded into the head gasket of a four-cylinder gasoline engine. The internal-pressure change in each combustion chamber was detected on the basis of bending power loss in the fiber. Combustion pressure peaks for each cylinder were clearly observed. PMID:21085226

Komachiya, M; Sonobe, H; Oho, S; Kurita, M; Nakazawa, T; Sasayama, T

1996-03-01

51

Mode field expansion in index-guiding microstructured optical fibers  

NASA Astrophysics Data System (ADS)

The mode-field expander (MFE) is a microstructured optical fiber (MOF) based device that enlarges the modal field distribution and can couple light from large mode area (LMA) fibers into small core fibers or vice-versa and other optical waveguides. Using our earlier developed analytical field model, we studied the mode-field expansion in MOFs having triangular lattice, and low-loss splicing of MOFs to standard single-mode fibers (SMFs), based on the controlled all airhole collapse method, which leads to an optimum mode-field match at the joint interface of the MOF-SMF. Comparisons with available experimental and simulation results have also been included.

Sharma, Dinesh Kumar; Sharma, Anurag

2013-05-01

52

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

PubMed Central

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

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

2013-01-01

53

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

NASA Astrophysics Data System (ADS)

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

Chen, Xiaogang; Hu, Xizhen; Huang, Dexiu

2014-09-01

54

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

NASA Astrophysics Data System (ADS)

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

Ge, Qiang

2014-12-01

55

Mechanical behavior of silica optical fibers coated with low index, low surface energy perfluorinated polymer  

E-print Network

Mechanical behavior of silica optical fibers coated with low index, low surface energy-curable coating has to be applied to the surface of optical fibers. The rate of wetting is critical due with vinyl groups. Failure to wet the surface will cause defects in the cured coatings known as fish eyes

Matthewson, M. John

56

Experimental study of liquid refractive index sensing based on a U-shaped optical fiber  

NASA Astrophysics Data System (ADS)

A U-shaped optical fiber sensing system designed to measure the refractive index of liquid had been proposed. The sensing mechanism of U-shaped optical fiber was discussed. A general single-mode fiber was bent into U-shaped and partially cladding of U-shaped fiber was corroded by HF acid buffer solution. Powers of different diameters of U-shaped fibers had been measured by many experiments. The results showed that the diameter of U-shaped fiber cladding 40 ?m and the diameter of U-shaped was 1 cm were suitable to measure liquid refractive index. Then, this U-shaped optical fiber was immersed in liquid, such as pure water, ethanol, acetone and isopropanol, respectively. The evanescent field of the U-shaped fiber should be modulated by the liquid. The optical signal in the U-shaped fiber was measured with the optical spectrum analyzers(OSA). Finally, the experimental results were analyzed, and the spectra in the air was selected as a reference. The relative intensity was obtained for the different liquid. These results showed that the relative intensity of the liquid had a good linear relationship. This sensing device could accurately demarcate refractive index of liquid. It is simple, low cost, and it can also be applied in measuring the level of liquid.

Zhang, Zhi; Yan, Haitao; Li, Liben; Wang, Ming

2013-12-01

57

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

NASA Astrophysics Data System (ADS)

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

Traore, Aboubakar

58

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

Microsoft Academic Search

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

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

1998-01-01

59

Simultaneous temperature and refractive index measurements using a 3° slanted multimode fiber Bragg grating  

Microsoft Academic Search

A novel and simple sensor based on a 3° slanted multimode fiber Bragg grating (MFBG) for simultaneous temperature and refractive index measurement is demonstrated. The 3° slanted MFBG shows two wavelength groups in its transmission spectrum: One group, due to the coupling from one core mode to cladding modes, is sensitive to both surrounding refractive index (SRI) and temperature and

Chun-Liu Zhao; Xiufeng Yang; M. S. Demokan; W. Jin

2006-01-01

60

Focusing Effects in Interferometric Analysis of Graded-index Optical Fibers.  

PubMed

The effects of ray bending due to graded refractive-index profiles have been studied in relation to the measurement of optical-fiber refractive-index profiles by microscopic interferometric techniques. In particular, the wavefront curvature produced by a simple parabolic profile has been calculated analytically. It is concluded that profile measurements by currently used methods require samples for which the fiber thickness (length) is much less than the effective focal length of the fiber. For parabolic profile fibers with diameter d greater, similar 100 microm, this poses no problem; however, for small-core versions of this fiber, sample thicknesses of 10-15 microm may be required and an alternate measurement technique is described. Interferograms made on a Leitz transmitted-light interference microscope are included in illustrations. PMID:20134845

Stone, J; Burrus, C A

1975-01-01

61

Electric control of state of polarization in index-guiding photonic liquid crystal fibers  

NASA Astrophysics Data System (ADS)

Photonic liquid crystal fibers allow for dynamic modification of their guiding and polarization properties. In particular it is possible to dynamically tune phase delay between two orthogonal polarization of the guided mode. In this work an index-guiding photonic liquid crystal fiber with highly tunable retardation, reaching value of 15? (or 30? in terms of phase difference) is presented. Electric tuning with two sets of electrodes is also discussed and demonstrated proving that photonic liquid crystal fibers can be utilized as a all-in-fiber polarization controllers.

Ertman, Slawomir; Siarkowska, Agata; Pysz, Dariusz; Buczy?ski, Ryszard; Nowinowski-Kruszelnicki, Edward; DÄ browski, Roman; Woli?ski, Tomasz R.

2013-05-01

62

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

NASA Astrophysics Data System (ADS)

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

Huang, Jing; Li, Xueming; Yang, Jianchun

2013-12-01

63

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

E-print Network

The elongation of yeast prion fibers involves separable steps of association and conversion Thomas factor Sup35p is the basis for the prion [PSI ], a protein-based genetic element of Saccharomyces cerevisiae. In a process closely allied to in vivo conversion, the purified soluble, prion-determining region

Lindquist, Susan

64

Reflection based Extraordinary Optical Transmission Fiber Optic Probe for Refractive Index Sensing.  

PubMed

Fiber optic probes for chemical sensing based on the extraordinary optical transmission (EOT) phenomenon are designed and fabricated by perforating subwavelength hole arrays on the gold film coated optical fiber endface. The device exhibits a red shift in response to the surrounding refractive index increases with high sensitivity, enabling a reflection-based refractive index sensor with a compact and simple configuration. By choosing the period of hole arrays, the sensor can be designed to operate in the near infrared telecommunication wavelength range, where the abundant source and detectors are available for easy instrumentation. The new sensor probe is demonstrated for refractive index measurement using refractive index matching fluids. The sensitivity reaches 573 nm/RIU in the 1.333~1.430 refractive index range. PMID:24574579

Lan, Xinwei; Cheng, Baokai; Yang, Qingbo; Huang, Jie; Wang, Hanzheng; Ma, Yinfa; Shi, Honglan; Xiao, Hai

2014-03-31

65

Tunable high-resolution fiber optic WDMs using the high-index approach  

Microsoft Academic Search

High resolution (1 nm), low loss (< 0.2 dB) optical fiber WDMs based on evanescent field coupling between a single mode fiber, side polished close to the core, and a planar high index overlay have been reported previously. By using electro-optic materials in the role of either the overlay or superstrate (above the overlay) the wavelength characteristics may be dynamically

Walter Johnstone; David G. Moodie; G. Thursby; Kevin J. McCallion; Gordon Fawcett

1993-01-01

66

Photoinduced refractive-index changes in two-mode, elliptical-core fibers: sensing applications.  

PubMed

Photoinduced refractive-index changes in two-mode, elliptical-core optical fibers are shown to affect the differential phase modulation between the LP(01) and the LP(11)(even) modes. This change in beat length is dependent on the amount of strain induced in the fiber while the grating is being formed. We present experimental results that agree with conventional coupled-mode theory and propose the use of such sensors for weighted and distributed applications. PMID:19777027

Vengsarkar, A M; Greene, J A; Murphy, K A

1991-10-01

67

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

68

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

PubMed Central

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

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

2010-01-01

69

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

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

70

Refractive index and strain sensitivities of a long period fiber grating  

NASA Astrophysics Data System (ADS)

A long period fiber grating (LPFG) fabricated upon the all-solid photonic bandgap fiber by CO2 laser irradiation was investigated, and its resonance wavelength was at 1335.76 nm with a modulation depth of 15 dB and a 3-dB bandwidth of 2.6 nm. We studied its strain, temperature, and index sensor characteristics, the strain sensitivity of 0.992 pm/?? was obtained by using linear fit, and the relationship between the refractive index and wavelength obeyed the distribution of quadratic function. Also, we demonstrated its temperature response was relatively insensitive (21.51 pm/°).

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

2014-03-01

71

Femtosecond laser processing of fiber Bragg gratings with photo-induced gradient-index assisted focusing  

NASA Astrophysics Data System (ADS)

Gradient-index modulation prefabrication in the cladding of standard telecom fibers was proposed for femtosecond laser processing of Type II-IR fiber Bragg gratings. The refractive index of the prefabricated region in the cladding had a large gradient across the laser beam, which could act as a cylindrical lens to enhance the focusing of laser beam when writing Type II-IR gratings. With the help of prefabrication, the threshold pulse energy for processing Type II-IR FBGs was lowered from 750??J to 520??J. The fabricated FBGs showed good thermal stability at temperatures over 900?°C.

Cui, Wei; Chen, Tao; Si, Jinhai; Chen, Feng; Hou, Xun

2014-07-01

72

Refractive index profile of fused-fiber couplers cross-section.  

PubMed

We investigate the refractive index profile of the cross-section of fused type fiber-optic couplers by solving the convective diffusion equation. We assume the refractive index to be a linear function of the dopant concentration. The viscous sintering of the optical fibers is considered as the motion of an incompressible Newtonian fluid which is driven by the surface tension acting at the free boundary. The internal velocity field is obtained using conformal mapping methods. We present numerical solutions of the resulting equations and compare them with experimental observations. PMID:19474919

Pone, Elio; Daxhelet, Xavier; Lacroix, Suzanne

2004-03-22

73

In situ refraction index of liquid measurement using polymer optical fibers  

NASA Astrophysics Data System (ADS)

A device for the measure of index of refraction of liquids in situ based on polymer optical fibers (POFs) was demonstrated. It consists in a sensor head of three passive POFs where two are coupled to two detectors and an electronic unit for the differential measure of signals. A differential operating principle is utilized to reduce noise such as light intensity fluctuation. The device was successfully checked measuring refraction index changes of the water with different concentrations of sugar, salt and alcohol.

Lomer, Mauro; Zubia, Joseba; Conde, Olga M.; Mirapeix, Jesus M.; Cubillas, A. M.; Lopez-Higuera, Jose M.

2004-06-01

74

Novel bifunctional systems for measuring the refractive index profile and residual stress birefringence in optical fibers and preforms  

Microsoft Academic Search

Two measuring systems are presented enabling determination of the refractive index profile and its anisotropy as well as principal stress components in optical fibers and preforms, respectively. The systems for optical fibers is a scanning-type, differentiating interferometer used to directly measure the wavefront derivative, from which, after the inverse Abel transformation, the index profile is obtained. The required high sensitivity

Waclaw Urbanczyk; Kazimierz Pietraszkiewicz; Wladyslaw A. Wozniak

1992-01-01

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

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

77

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

PubMed Central

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

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

2013-01-01

78

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

2013-01-01

79

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

80

Thermally stable high-bandwidth graded-index polymer optical fiber  

Microsoft Academic Search

High-bandwidth poly (methyl methacrylate) PMMA base graded-index polymer optical fiber (GI POF) with high thermal stability is proposed. No distortion of bandwidth was observed even after more than 10000 hours aging at 85°C by selecting the large sized aromatic dopant which has a stable secondary interaction with PMMA matrix and maintains the high glass transition temperature (Tg) of the core

Masataka Sato; Takaaki Ishigure; Yasuhiro Koike

2000-01-01

81

Further analysis of focusing performance of an ultra-small gradient-index fiber probe  

NASA Astrophysics Data System (ADS)

In order to optimize ultra-small gradient-index (GRIN) fiber probes and provide a theoretical prediction for the fabrication of such probes with high performance, focusing performance of the GRIN fiber probe is further analyzed based on the optical characteristic parameters. According to the optical model of the GRIN fiber probe and its mathematical expressions of characteristic parameters, the three-dimensional (3-D) function diagram is used for analyzing the impact of the lengths of probe components on the characteristic parameters. Partial derivatives of the mathematical expressions of characteristics are derived to analyze the mutation of focusing performance caused by the different lengths of probe components. According to the analytical results, our predictions suggest that focusing performance could be reflected through the 3-D function diagram between the characteristic parameters and the continuous change of the lengths of probe components. In addition, mutation occurs in the focusing performance of the GRIN fiber probe when the length of probe components changes. The research results are of practical guiding significance for the fabrication of GRIN fiber probes requiring specific optical focusing performance.

Wang, Chi; Bi, Shubo; Xia, Xueqin; Yu, Yingjie

2014-01-01

82

Passive Q-switching of a fiber laser using a side-polished birefringent fiber with index matching gel spread on the flat side  

NASA Astrophysics Data System (ADS)

We experimentally demonstrate the use of a side-polished birefringent fiber with index matching gel spread on the flat side as a passive Q-switch for the implementation of an all-fiberized, erbium-doped fiber (EDF)-based Q-switched laser. It is shown that Q-switched pulses with a ~2.5-?s temporal width are readily achievable from an EDF ring cavity using the side-polished birefringent fiber-based Q-switch. The tuning capability of the pulse width and the repetition rate by changing the pump power is also investigated.

Koo, Joonhoi; Lee, Ju Han

2013-08-01

83

Use of optical fibers in spectrophotometry  

NASA Technical Reports Server (NTRS)

The use of single or small numbers of fiber optic fibers in astronomical spectroscopy with the goal of greater spectrophotometric and radial velocity accuracy is discussed. The properties of multimode step index fibers which are most important for this application are outlined, as are laboratory tests of currently available fibers.

Ramsey, Lawrence W.

1988-01-01

84

Side-polished fiber Bragg grating refractive index sensor with TbFeCo magnetoptic thin film  

Microsoft Academic Search

Fiber Bragg grating (FBG) is side-polished to enable interaction with sensitive materials around FBG fiber core. Using TbFeCo magneto-optic thin film deposited onto FBG fiber core as transducer, a FBG refractive index senor for magnetic field\\/current characterization is first proposed and demonstrated in this paper. Magnetic field sensing experiments show 19 pm of wavelength shift at a magnetic field intensity

Minghong Yang; Jixiang Dai; Xiaobin Li; Junjie Wang

2010-01-01

85

Performance of step index multimode waveguides with tuned numerical aperture for on-board optical links  

NASA Astrophysics Data System (ADS)

This paper discusses experimental results of optical characterization of low-loss, robust, high-speed optical link basing on step index (SI) polymeric multimode waveguides. In order to enhance the bandwidth of optical waveguides tuning of numerical aperture by material adoption has been implemented. However, trade-off between tolerance requirements, bandwidth and design rules have to be found. In this paper experimental performance evaluation of SI polymeric waveguides by insertion loss measurement, near- and far-field analysis and optical transmission measurements at high data rates will be investigated. The measurement results will be finally analyzed in order to derive design rules for onboard optical interconnects with multi Gbit/s × m performance.

Nieweglowski, Krzysztof; Henker, Ronny; Ellinger, Frank; Wolter, Klaus-Jürgen

2014-03-01

86

Quantitative estimates of mode coupling and differential modal attenuation in perfluorinated graded-index plastic optical fiber  

Microsoft Academic Search

The performance of plastic optical fiber is greatly influenced by the related but distinct effects of mode coupling and differential modal attenuation (DMA). We establish a method for estimating the matrix that governs both of these effects and allows us to distinguish the two. We obtain partial quantitative estimates of this matrix for a particular graded-index plastic optical fiber (GI-POF).

Steven E. Golowich; Whitney White; William A. Reed; Erik Knudsen

2003-01-01

87

Basics of fiber optics  

NASA Astrophysics Data System (ADS)

Fiber Optics are a medium for transmitting light. Think of having a garden hose five hundred meters long. When looking through it you are able to see 50% of the light. Now you understand the power of fiber optics. The wide variety of fiber optics presently available has advanced its use for sensing, process control and laser delivery applications. However, there is a strong need to understand fiber optics at the basic level. The focus of this paper will discuss the basics of fiber optics for step-index fibers.

Harrison, Craig D.

1992-08-01

88

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

89

Design and characteristics of refractive index sensor based on thinned and microstructure fiber Bragg grating  

NASA Astrophysics Data System (ADS)

A refractive index sensor based on the thinned and microstructure fiber Bragg grating (ThMs-FBG) was proposed and realized as a chemical sensing. The numerical simulation for the reflectance spectrum of the ThMs-FBG was calculated and the phase shift down-peak could be observed from the reflectance spectrum. Many factors influencing the reflectance spectrum were considered in detail for simulation, including the etched depth, length, and position. The sandwich-solution etching method was utilized to realize the microstructure of the ThMs-FBG, and the photographs of the microstructure were obtained. Experimental results demonstrated that the reflectance spectrum, phase shift down-peak wavelength, and reflected optical intensity of the ThMs-FBG all depended on the surrounding refractive index. However, only the down-peak wavelength of the ThMs-FBG changed with the surrounding temperature. Under the condition that the length and cladding diameter of the ThMs-FBG microstructure were 800 and 14 ?m, respectively, and the position of the microstructure of the ThMs-FBG is in the middle of grating region, the refractive index sensitivity of the ThMs-FBG was 0.79 nm/refractive index unit with the wide range of 1.33-1.457 and a high resolution of 1.2×10-3. The temperature sensitivity was 0.0103 nm/°C, which was approximately equal to that of common FBG.

Huang, Xue-Feng; Chen, Zhe-Min; Shao, Li-Yang; Cen, Ke-Fa; Sheng, De-Ren; Chen, Jun; Zhou, Hao

2008-02-01

90

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

91

Photonic crystal fiber refractive-index sensor based on multimode interferometry  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

92

Imaging of rat brain using short graded-index multimode fiber  

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

93

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

94

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

2012-01-01

95

Efficient excitation of surface plasmons in metal nanorods using large longitudinal component of high index nano fibers.  

PubMed

We report theoretical calculations of the mode fields of high index lead silicate and silicon nano fibers, and show that their strong longitudinal component enables efficient excitation of surface plasmons within a silver nanorod placed at the fiber tip. An excitation efficiency 1600 times higher than that of the standard single mode fibers has been achieved using a 350nm diameter silicon fiber at 1.1?m wavelength, while a factor of 640 times higher efficiency is achieved for a 400nm diameter lead silicate F2 glass fiber. The strong localized field emerging from the end of the rod serves as a nano-scale source with adjustable beam width, and such sources offer a new approach to high-resolution microscopy, particle manipulation and sensing. PMID:21747502

Ruan, Yinlan; Afshar, Shahraam V; Monro, Tanya M

2011-07-01

96

Monitoring of gamma-irradiated Yb-doped optical fibers through the pump induced refractive index change effect  

SciTech Connect

We report on the method for monitoring of the modifications in Yb-doped optical fibers irradiated by gamma-rays with the doses 1, 2, 4 and 8 kGy. This method is based on the refractive index change (RIC) effect induced in the tested fibers by square modulated optical pump pulses of 1 ms duration at 980 nm with the power up to 100 mW. The applied in-situ monitoring is based on interferometric technique and highlights the key parameters of the RIC effect that allows to characterize quantitatively the degree of the fiber degradation under the gamma irradiation. (authors)

Pekukhova, I. [Univ. of Mons, Mons 7000 (Belgium); Vrije Universiteit Brussel, Brussels 1050 (Belgium); Fotiadi, A. A. [Univ. of Mons, Mons 7000 (Belgium); Ioffe Physico-Technical Inst. of RAS, St. Petersburg (Russian Federation); Ulianovsk State Univ., Ulianovsk 432970 (Russian Federation); Shubin, A. V. [Fiber Optic Research Center of RAS, Moscow 119333 (Russian Federation); Tomashuk, A. L. [Ulianovsk State Univ., Ulianovsk 432970 (Russian Federation); Fiber Optic Research Center of RAS, Moscow 119333 (Russian Federation); Novikov, S. G.; Zolotovskiy, I. O. [Ulianovsk State Univ., Ulianovsk 432970 (Russian Federation); Antipov, O. L. [Inst. of Applied Physics of RAS, Nizhniy Novgorod 603950 (Russian Federation); Panajotov, K.; Thienpont, H. [Vrije Universiteit Brussel, Brussels 1050 (Belgium); Megret, P. [Univ. of Mons, Mons 7000 (Belgium)

2011-07-01

97

Side-polished fiber Bragg grating refractive index sensor with TbFeCo magnetoptic thin film  

NASA Astrophysics Data System (ADS)

Fiber Bragg grating (FBG) is side-polished to enable interaction with sensitive materials around FBG fiber core. Using TbFeCo magneto-optic thin film deposited onto FBG fiber core as transducer, a FBG refractive index senor for magnetic field/current characterization is first proposed and demonstrated in this paper. Magnetic field sensing experiments show 19 pm of wavelength shift at a magnetic field intensity of 50 mT, the average linearity of magnetic field response is 0.9877.

Yang, Minghong; Dai, Jixiang; Li, Xiaobin; Wang, Junjie

2010-08-01

98

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

99

Microstructured gradient-index antireflective coating fabricated on a fiber tip with direct laser writing.  

PubMed

We present a simple broadband gradient-index antireflective coating, fabricated directly on a single mode telecom fiber tip. A regular array of hemi-ellipsoidal protrusions significantly reduce the Fresnel reflection from the glass-air interface. The parameters of the structure were optimized with numerical simulation for the best performance at and around 1550 nm and the coating was fabricated with Direct Laser Writing. The measured reflectance decreased by a factor of 30 at 1550 nm and was below 0.28% for the 100 nm spectral band around the central wavelength. Compared to quarter wavelength antireflective coatings the demonstrated approach offers significantly reduced technological challenges, in particular processing of a single optical material with low sensitivity to imperfections in the fabrication process. PMID:24921372

Kowalczyk, Maciej; Haberko, Jakub; Wasylczyk, Piotr

2014-05-19

100

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. PMID:22736988

Wang, Jian-Neng; Tang, Jaw-Luen

2012-01-01

101

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

Microsoft Academic Search

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

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

2007-01-01

102

Long period fiber grating based refractive index sensor with enhanced sensitivity using Michelson interferometric arrangement  

NASA Astrophysics Data System (ADS)

The long period fiber grating (LPFG) is widely used as a sensor due to its high sensitivity and resolution. However, the broad bandwidth of the attenuation bands formed by the mode coupling between the fundamental core mode and the cladding modes constitutes a difficulty when the device is used as a conventional sensor. To overcome this limitation, a Michelson interferometer-type sensor configuration has been developed, using an LPFG grating pair formed by coating a mirror at the distal end of the LPFG. This sensor configuration is more convenient to use and is able to overcome the limitations of the single LPFG based sensor as the shifts in the attenuation bands being more easily detectable due to the formation of the sharp spectral fringe pattern in the LPFG based Michelson interferometer. In this work, I studied the LPFG based Michelson interferometer as the refractive index sensor and discussed the sensitivity enhancement of the LPFG based Michelson interferometer as a refractive index sensor by employing higher order cladding modes and by reducing the cladding radius. The results demonstrated the HE17 mode with a cladding radius of 62.5 ?m, in the range of surrounding refractive index (SRI) of 1-1.45, and its resonant peak showed a wavelength shift of 26.99 nm/RIU. When the cladding region was further reduced to 24 ?m, the resonant peak showed a wavelength shift of 569.88 nm/RIU, resulting in a sensitivity enhancement of nearly 21 times. However, as the cladding region was etched further, then the HE17 order cladding mode and higher mode would be cut off. Therefore, the implementation of high sensitivity for SRI sensing with the reduced cladding in the LPFG based Michelson interferometer is dependent on the proper combination of the cladding radius and cladding mode order.

Singh, Amit

2014-12-01

103

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

104

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

PubMed Central

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

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

2013-01-01

105

Novel design of a refractive index sensor based on a dual-core micro-structured optical fiber  

E-print Network

In the present work a new model of a refractive index (RI) sensor is exhibited. This is based on a dual core micro-structured optical fiber (MOF), where two holes are introduced at the core centers. In this way, the model enhances the interaction of the fiber modes propagated in the core region, providing the possibility of increasing the dimensions of the fiber sensor. Thus, the filling of the fiber holes with the fluid under study is facilitated, and generally the practical use of the system as a refractive index sensor is simplified. The influence of the core separation and the diameter of the central holes on the sensitivity of the sensor have been studied by a numerical simulation. The results are in agreement with the expected behavior as it is determined by the physics of the problem. Based on the same operating principle, it is verified that a dual-core conventional optical fiber with micro-fluidic channels at the center of the cores, can also operates as an RI sensor.

Tsigaridas, G; Persephonis, P

2014-01-01

106

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

EPA Science Inventory

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

107

Chalcogenide Glass Fibers for Infrared Sensing and Space Optics  

NASA Astrophysics Data System (ADS)

This review deals with chalcogenide glasses and fibers. Chemical compositions and physical properties are given for specific glasses well suited for fiber drawing. Fabrication techniques of glass perform are described. Single-index and step-index single-mode fibers are characterized in terms of optical losses in the infrared. Examples of applications of chalcogenide fibers are given, as well as optical sensors in the fields of environment, microbiology and health, and as mode-filters for infrared interferometry in space.

Bureau, Bruno; Maurugeon, Sébastien; Charpentier, Frederic; Adam, Jean-Luc; Boussard-Plédel, Catherine; Zhang, Xiang-Hua

108

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

109

Simultaneous measurement of the Raman gain coefficient and the nonlinear refractive index of optical fibers: theory and experiment  

NASA Astrophysics Data System (ADS)

We report for the first time, to our knowledge, a technique that has the capability to measure both the Raman gain coefficient and the nonlinear refractive index of an optical fiber, using the same experimental setup. This measurement utilizes the induced-grating autocorrelation (IGA) technique, which is based upon time-delayed four-beam coupling in a photorefractive crystal. The standard IGA trace, which is based upon two-beam coupling, fits a simple model based on pure self-phase modulation (SPM). We demonstrate that, in the negligible-dispersion regime of an optical fiber, the addition of stimulated Raman scattering (SRS) leads to a measurable distortion of the standard (pure SPM) IGA trace. We have developed a new IGA model from the analytical solution of the coupled-amplitude nonlinear Schrodinger equation. This new model successfully accounts for the effect of SRS on the IGA trace in the negligible-dispersive regime of the fiber and allows the direct determination of the Raman gain coefficient and the nonlinear refractive index from the fit of the SRS distorted IGA trace. The measured nonlinear refractive index and the Raman gain coefficient are in good agreement with published results.

Oguama, Ferdinand A.; Garcia, Hernando; Johnson, Anthony M.

2005-02-01

110

Extended step-out length fiber Bragg grating interrogation system for condition monitoring of electrical submersible pumps  

NASA Astrophysics Data System (ADS)

We present details of the design and laboratory evaluation of the fiber Bragg grating (FBG) interrogation system developed specifically for condition monitoring of electrical submersible pumps (ESPs). The system, based on the microelectromechanical systems (MEMS) Fabry-Pérot tunable filter, is capable of interrogating several FBG sensors placed around an ESP unit and configured to measure static and dynamic parameters, e.g., temperature, vibration signature and/or instantaneous voltage, and current. Sensor interrogation over the extended step-out length distance of 24 km is demonstrated in the laboratory in a simple experiment of multipoint dynamic strain monitoring in a vibrated cantilever beam.

Fusiek, G.; Niewczas, Pawel; McDonald, James R.

2005-03-01

111

Improved Optical Fiber Chemical Sensors  

NASA Technical Reports Server (NTRS)

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

Egalon, Claudio O.; Rogowski, Robert S.

1994-01-01

112

Refractive-index dispersion measurement of bulk optical materials using a fiber raman laser widely tunable in the visible and near-infrared  

Microsoft Academic Search

We propose a simple, highly sensitive fiber-optic autocollimation method for refractive-index dispersion measurement of solid-state\\u000a and liquid bulk optical materials using a double-pass fiber Raman laser with Littrow-prism-tuned emission. The optical fiber\\u000a is a key element of the scheme and serves simultaneously as a point laser source for the test, as a highly sensitive point\\u000a receiver (or spatial filter) of

Ilko K. Ilev; Hiroshi Kumagai; Koichi Toyoda

1997-01-01

113

Simultaneous measurement of temperature and external refractive index by use of a hybrid grating in D fiber with enhanced sensitivity by HF etching  

Microsoft Academic Search

We propose a dual-parameter optical sensor device achieved by UV inscription of a hybrid long-period grating-fiber Bragg grating structure in D fiber. The hybrid configuration permits the detection of the temperature from the latter's response and measurement of the external refractive index from the former's response. In addition, the host D fiber permits effective modification of the device's sensitivity by

Xianfeng Chen; Kaiming Zhou; Lin Zhang; Ian Bennion

2005-01-01

114

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

115

Novel bifunctional systems for measuring the refractive index profile and residual stress birefringence in optical fibers and preforms  

NASA Astrophysics Data System (ADS)

Two measuring systems are presented enabling determination of the refractive index profile and its anisotropy as well as principal stress components in optical fibers and preforms, respectively. The systems for optical fibers is a scanning-type, differentiating interferometer used to directly measure the wavefront derivative, from which, after the inverse Abel transformation, the index profile is obtained. The required high sensitivity of measurement is achieved by applying the sinusoidal modulation of the input beam ellipticity and the homodyne detection of the first harmonic component of the output intensity. After removing the Wollaston prism, the system can be used to measure the retardation function that is related to the fiber residual birefringence. The dynamic spatial-filtering technique, used until now to measure the ray deflection function, has been modified for testing the preforms. An optionally applied linear modulator of ellipticity of the input beam was added, to enable the measurement of the retardation function also. The system can be easily switched from the measurement of the ray deflection function to the measurement of the retardation function by moving only a single element.

Urbanczyk, Waclaw; Pietraszkiewicz, Kazimierz; Wozniak, Wladyslaw A.

1992-03-01

116

Novel bending-resistant design of two-layer low-index trench fiber with parabolic-profile core.  

PubMed

A novel design, two-layer low-index trench fiber with parabolic-profile core, is proposed and investigated numerically in this paper. Based on scalar FD-BPM algorithm, the excellent performance over other types of structures and great potential in mode area enlargement are demonstrated. The effective mode area of our design (D = 100?m) is approximately 890 ?m2. Both the high order mode (HOM) suppression and bending resistance of our design are better than that of Multi-Trench Fiber (MTF). The mode loss ratio and effective mode area are independent on the bending radius. Due to the circular symmetry of our proposed configuration design, the bending property is not varied with the changing of bending directions. PMID:25089423

Sun, Jiang; Kang, Zexin; Wang, Jing; Liu, Chao; Jian, Shuisheng

2014-07-28

117

Optimized graded index two-mode optical fiber with low DMD, large A(eff) and low bending loss.  

PubMed

An optimized two-mode optical fiber (TMF) with the graded index (GI) profile is designed and fabricated. We clarify an appropriate region of GI-TMF satisfying DMD = 0 ps/km, the large effective area A(eff), and the low bending loss for LP(11) at 1550 nm. According to our fiber design, GI-TMF is successfully fabricated to have the large effective area A(eff) of 150 ?m(2) for LP(01) mode, and low DMD below 36 ps/km including zero in the C-band. We expect that our design GI-TMF is suitable for MDM and can reduce MIMO-DSP complexity. PMID:23938473

Sato, Kiminori; Maruyama, Ryo; Kuwaki, Nobuo; Matsuo, Shoichiro; Ohashi, Masaharu

2013-07-15

118

Polarization dependent dispersion characteristics of high order modes in a cylindrical dual mode fiber with an arbitrary index profile  

NASA Astrophysics Data System (ADS)

For a cylindrical dual mode optical fiber, dispersion characteristics of the high order polarization modes, TE 01, TM 01, and HE 21, have been rigorously analyzed by solving the vectorial Maxwell equations numerically. The effects of the inner cladding index structure on the dispersion characteristics of the polarization modes are reported for the first time. In the matched cladding, the difference in chromatic dispersion, dispersion slope and modal delay among the polarization modes are found to increase for waveguide conditions optimized for a large negative dispersion. A new design of a cylindrical dual mode fiber with a depressed inner cladding that can intrinsically reduce the polarization dependence in the dispersion characteristics to improve the performance in dispersion compensation is proposed.

Oh, Kyunghwan; Seo, H. S.; Lee, J. K.; Paek, U. C.

1999-01-01

119

Simultaneous detection of liquid level and refractive index with a long-period fiber grating based sensor device  

NASA Astrophysics Data System (ADS)

In this study, a long-period fiber grating (LPFG)-based optical fiber sensor device is proposed for simultaneous detection of liquid level and refractive index (RI). When part of the grating was submerged in an unknown liquid, the resonant wavelength of each cladding mode of the LPFG sensor varied linearly with the submerged length and nonlinearly with the RI of the liquid. By retaining the first-order (sensitivity) and second-order (cross sensitivity) terms of a Taylor expansion of the nonlinear relation, the changes in submerged length (or liquid level) and RI can be simultaneously evaluated from the changes in resonant wavelength of two cladding modes. The sensitivity coefficients to liquid level, RI, their cross effect and environmental effects were studied both analytically and experimentally. The maximum prediction error by the proposed evaluation algorithm was found to be 1 mm for liquid level and 0.005 for RI.

Huang, Ying; Chen, Baokai; Chen, Genda; Xiao, Hai; Khan, Samee U.

2013-09-01

120

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

E-print Network

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

Burgoyne, Chris

121

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

122

MIMO equalization with adaptive step size for few-mode fiber transmission systems.  

PubMed

Optical multiple-input multiple-output (MIMO) transmission systems generally employ minimum mean squared error time or frequency domain equalizers. Using an experimental 3-mode dual polarization coherent transmission setup, we show that the convergence time of the MMSE time domain equalizer (TDE) and frequency domain equalizer (FDE) can be reduced by approximately 50% and 30%, respectively. The criterion used to estimate the system convergence time is the time it takes for the MIMO equalizer to reach an average output error which is within a margin of 5% of the average output error after 50,000 symbols. The convergence reduction difference between the TDE and FDE is attributed to the limited maximum step size for stable convergence of the frequency domain equalizer. The adaptive step size requires a small overhead in the form of a lookup table. It is highlighted that the convergence time reduction is achieved without sacrificing optical signal-to-noise ratio performance. PMID:24514973

van Uden, Roy G H; Okonkwo, Chigo M; Sleiffer, Vincent A J M; de Waardt, Hugo; Koonen, Antonius M J

2014-01-13

123

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

124

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

125

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

SciTech Connect

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

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

2014-09-14

126

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

127

High-speed (11 Gbit\\/s) data transmission using perfluorinated graded-index polymer optical fibers for short interconnects (<100 m)  

Microsoft Academic Search

Perfluorinated graded-index polymer optical fibers (GI-POF's) have been developed that offer low losses (0.3 GHz km) at data communication wavelengths (0.85 and 1.3 ?m). Here we demonstrate that such fibers can support data rates up to 11 Gbit\\/s for 100 m with low-power penalty and large-power margins. Although a restricted launch was used, differential mode delay measurements show that, in

Giorgio Giaretta; Whitney White; Mark Wegmuller; Tsuyoshi Onishi

2000-01-01

128

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

129

Ultra-Low Index and Rad-Hard Total Internal Reflection Claddings for High Numerical Aperture Scintillating, Waveshifting, Cerenkov, or Clear Optical Fibers, Capillaries, and Plates  

E-print Network

Novel low index (n less than 1.3)/high light trapping cladding films consisting of nanoporous alumina (sapphire), as formed by controlled anodization of aluminum, are described. These films are mechanically hard, intrinsically very rad-hard, and have an index of refraction n sufficiently small to triple the light capture of waveshifting or scintillating fibers and transparent plastic, glass or quartz core fibers. The low indices enable light-piping of water Cerenkov light. Applications are in Energy, Intensity, and Cosmic/Astroparticle detectors.

Sanzeni, C; Winn, D R

2013-01-01

130

Refractive index modulation in photo-thermo-refractive fibers Eugeniu Rotari, Larissa Glebova, and Leonid Glebov  

E-print Network

atomic silver forms colloidal silver containing particle. Negative refractive index change is caused by absorption of the glass matrix, cerium ions, colloidal silver and scattering by crystalline phase photo-thermo-refractive (PTR) glass. PTR glass is a fluorosilicate glass doped with cerium and silver

Glebov, Leon

131

Modification of carbon-fiber-composite surface emissivity/reflectance by high-index interference films  

NASA Astrophysics Data System (ADS)

High strength/weight carbon fiber-reinforced composites (CFRCs) are finding applications where control of surface infrared emission or reflection is desirable. A quarter wave sputtered Ge film has been shown to reduce the normal emittance of a bismaleimide CFRC in the 8 - 14 micrometers band by 39%, with angle dependence theoretically constant out to 80% off-axis. A three-layer HLH stack is predicted to reduce emittance of less than 0.1. For thermal IR polymer curing, a single-layer coating optimizing emissivity in the polymer's absorption band while suppressing emission at longer wavelengths may yield electric power savings in the 10 - 20% range.

Pike, John N.; Matthews, Linn H.

1997-10-01

132

Optical fiber Fabry-Perot interferometer cavity fabricated by femtosecond laser-induced water breakdown for refractive index sensing.  

PubMed

The Fabry-Perot interferometer (FPI) cavity in a single-mode fiber with two open faces was fabricated by using the method of femtosecond laser-induced water breakdown. Then the FPI cavity was annealed by the arc discharge to greatly smooth its internal surface. The whole fabrication process features simple operation and high efficiency. The fabricated FPI cavity exhibits a perfect interferometer spectrum with reflection loss of only -3 dB and fringe visibility of almost 30 dB. It can be used as a perfectly reliable liquid refractive index sensor, as it exhibits high sensitivity (1147.48 nm/RIU), good linearity (99.93%), good repeatability, high actual measurement accuracy (1.29×10(-4)RIU), large measurement range, and good temperature insensitive characteristic. PMID:24514135

Liu, Yi; Qu, Shiliang

2014-01-20

133

Mapping the refractive index of optically transparent samples by means of optical nanoantenna attached to fiber microaxicon.  

PubMed

We demonstrate analytically and numerically that the detection of the spectral response of a single spherical Au nanoantenna allows one to map very small (down to 5·10(-4) RIU) variations of the refractive index of an optically transparent sample. Spectral shift of the dipole local plasmon resonance wavelength of the nanoantenna and the spectral sensitivity of the method developed was estimated by using simple analytical quasi-static model. A pointed scanning probe based on fiber microaxicon with the Au spherical nanoantenna attached to its tip was proposed to realize the RI mapping method. Finite-difference time-domain numerical simulations of the spectral properties of the proposed probe are in good agreement with the theoretical quasi-electrostatic estimations for a radius of the nanoantenna not exceeding the skin depth of Au. PMID:24921510

Kuchmizhak, Aleksandr A; Pavlov, Dmitriy V; Kulchin, Yuri N; Vitrik, Oleg B

2014-06-01

134

Fiber Optics  

NSDL National Science Digital Library

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

2011-05-02

135

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

136

Analysis According to Gender and Body Mass Index of the Number of Steps Taken by Sedentary Workers as Measured by a Pedometer  

PubMed Central

[Purpose] The purpose of this study was to determine according to gender and body mass index the number of steps taken by the sedentary workers as measured by a pedometer. [Subjects] Thirty-six sedentary workers in their twenties in Ulsan city were enrolled in for this study and their step counts were investigated. [Methods] Step counts at the workplace between 9 am and 6 pm everyday for 2 weeks were measured by a pedometer. Data were analyzed using SPSS 20.0 to compare step count according to gender and BMI on different days of the week. [Results] Females showed a higher step count than males on every day of the week except Fridays and Sundays. The step count was higher among the low weight group than overweight group on every day of the week. [Conclusion] Future studies should examine ways of helping sedentary workers to increase their step count. Also, more effort should be made to find practical ways of improving the number of steps taken in the workplace to keep workers in good health, as additional benefit would accrue, such as improved work efficiency. PMID:24259885

Cho, Sung-Hyoun; Oh, Byoung-Don; Cho, Byung-Jun

2013-01-01

137

Fabrication and characterization of a hybrid four-hole AsSe?-As?S? microstructured optical fiber with a large refractive index difference.  

PubMed

A hybrid four-hole AsSe2-As2S5 microstructured optical fiber (MOF) with a large refractive index difference is fabricated by the rod-in-tube drawing technique. The core and the cladding are made from the AsSe2 glass and As2S5 glass, respectively. The propagation loss is ~1.8 dB/m and the nonlinear coefficient is ~2.03 × 10(4) km(-1)W(-1) at 2000 nm. Raman scattering is observed in the normal dispersion regime when the fiber is pumped by a 2 ?m mode-locked picosecond fiber laser. Additionally, soliton is generated in the anomalous dispersion regime when the fiber is pumped by an optical parametric oscillator (OPO) at the pump wavelength of ~3000 nm. PMID:24921526

Cheng, Tonglei; Kanou, Yasuhire; Deng, Dinghuan; Xue, Xiaojie; Matsumoto, Morio; Misumi, Takashi; Suzuki, Takenobu; Ohishi, Yasutake

2014-06-01

138

The bending and temperature characteristics of long period gratings written in elliptical core step-index fibre  

Microsoft Academic Search

A fibre long period grating (LPG) is an axially periodic refractive index variation inscribed in the core of a photosensitive single-mode optical fibre by ultra-violet irradiation, which couples light from the core of the fibre into the fibre cladding modes at discrete wavelengths. The index modulation change within the core of a single mode optical fibre is approximately 10-4 and

T. Allsop; F. Floreani; D. J. Webb; Ian Bennion

2005-01-01

139

Refractive-index dispersion measurement of bulk optical materials using a fiber raman laser widely tunable in the visible and near-infrared  

NASA Astrophysics Data System (ADS)

We propose a simple, highly sensitive fiber-optic autocollimation method for refractive-index dispersion measurement of solid-state and liquid bulk optical materials using a double-pass fiber Raman laser with Littrow-prism-tuned emission. The optical fiber is a key element of the scheme and serves simultaneously as a point laser source for the test, as a highly sensitive point receiver (or spatial filter) of the autocollimation backreflectance signal and as a medium for nonlinear frequency conversion and generation of a broadband continuum spectrum. When the Raman medium is a graded-index multimode fiber with powerful pumping (over 100 kW) using the second harmonic of a Q-switched Nd:YAG laser (?p=532nm), we obtain widely tunable (0.54-1.01 ?m) generation in both the visible and near-IR ranges. The results obtained in the refractive-index dispersion measurements are fitted to the Sellmeier dispersion equation and the standard deviation of the experimental data from the analytical curve does not exceed 5x10-5.

Ilev, Ilko K.; Kumagai, Hiroshi; Toyoda, Koichi

1997-01-01

140

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

NASA Astrophysics Data System (ADS)

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

Oguama, Ferdinand Anayo

141

Generation of Megawatt Optical Solitons in Hollow-Core Photonic BandGap Fibers  

Microsoft Academic Search

The measured dispersion of a low-loss, hollow-core photonic band-gap fiber is anomalous throughout most of the transmission band, and its variation with wavelength is large compared with that of a conventional step-index fiber. For an air-filled fiber, femtosecond self-frequency-shifted fundamental solitons with peak powers greater than 2 megawatts can be supported. For Xe-filled fibers, nonfrequency-shifted temporal solitons with peak powers

Dimitre G. Ouzounov; Faisal R. Ahmad; Dirk Müller; Natesan Venkataraman; Michael T. Gallagher; Malcolm G. Thomas; John Silcox; Karl W. Koch; Alexander L. Gaeta

2003-01-01

142

Fiber Bragg grating cladding mode resonance liquid-level sensor  

Microsoft Academic Search

A Fiber-optic liquid-level sensor based on etched fiber Bragg grating (FBG) cladding mode resonance is proposed and demonstrated both theoretically and experimentally. The theoretical model of the FBG cladding mode liquid-level sensor is built under a three-layer step-index fiber geometry. Response of cladding mode resonance spectra to the variation of ambient liquid level are studied and simulated numerically with couple

Na Chen; Binfeng Yun; Yiping Cui

2009-01-01

143

Thermo-optic coefficient measurement of liquids based on simultaneous temperature and refractive index sensing capability of a two-mode fiber interferometric probe.  

PubMed

A fiber-optic interferometric probe based on a two-mode fiber (TMF) is proposed and demonstrated for measuring the thermo-optic coefficients (TOCs) of liquid samples. The proposed probe can be simply fabricated by fusion-splicing a short piece of TMF to a lead single mode fiber (SMF) with small lateral offset, which makes interference between LP(01) and LP(02) modes. The sensing responses of the probe to temperature and surrounding refractive index (SRI) have been experimentally investigated to show the capability of simultaneous measurements; the phase change of the reflection spectrum was related to temperature variation and the intensity change was to SRI variation. The data analysis is made not only in the spectral domain but in the Fourier domain also to effectively quantify the measurements. The TOCs of several liquid samples including water, ethanol, and acetone have been obtained with the proposed method. PMID:23188340

Kim, Young Ho; Park, Seong Jun; Jeon, Sie-Wook; Ju, Seongmin; Park, Chang-Soo; Han, Won-Taek; Lee, Byeong Ha

2012-10-01

144

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

145

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

PubMed

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

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

2014-07-23

146

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

NASA Astrophysics Data System (ADS)

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

Chen, Yong; Zhao, Hui; Han, Bing

2014-12-01

147

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

148

Conversion of Modified Commercial Polyacrylonitrile Fibers to Carbon Fibers  

Microsoft Academic Search

Carbon fibers are fabricated from different materials, such as special polyacrylonitrile (PAN) fibers, rayon fibers and pitch. Among these three groups of materials, PAN fibers are the most widely used precursor for the manufacture of carbon fibers. The process of fabrication carbon fibers from special PAN fibers includes two steps; oxidative stabilization at low temperature and carbonization at high temperatures

R. Eslami Farsani; A. Shokuhfar; A. Sedghi

2007-01-01

149

In-line open-cavity Fabry-Pérot interferometer formed by C-shaped fiber fortemperature-insensitive refractive index sensing.  

PubMed

We report an open-cavity optical fiber Fabry-Pérot interferometer (FPI) capable of measuring refractive index with very low temperature cross-sensitivity. The FPI was constructed by splicing a thin piece of C-shaped fiber between two standard single-mode fibers. The refractive index (RI) response of the FPI was characterized using water-ethanol mixtures with RI in the range of 1.33 to 1.36. The RI sensitivity was measured to be 1368 nm/RIU at the wavelength of 1600 nm with good linearity. Thanks to its all-glass structure, the FPI exhibits very low temperature cross-sensitivity of 3.04 × 10?? RIU/°C. The effects of cavity length on the performance of the sensor were also studied. A shorter cavity gives rise to broader measurement range while offering larger detection limit, and vice versa. What's more, the effect of material dispersion of analyte on the sensitivity of open-cavity FPIs was identified for the first time. The sensor is compact in size and easy to fabricate. It is potentially useful for label-free optical sensing of chemical and biological samples. PMID:25321551

Wu, Chuang; Liu, Zhengyong; Zhang, A Ping; Guan, Bai-Ou; Tam, Hwa-Yaw

2014-09-01

150

Pretreatment based on two-step steam explosion combined with an intermediate separation of fiber cells--optimization of fermentation of corn straw hydrolysates.  

PubMed

Pretreatment is necessary for lignocellulose to achieve a highly efficient enzymatic hydrolysis and fermentation. However, coincident with pretreatment, compounds inhibiting microorganism growth are formed. Some tissues or cells, such as thin-walled cells that easily hydrolyze, will be excessively degraded because of the structural heterogeneity of lignocellulose, and some inhibitors will be generated under the same pretreatment conditions. Results showed, compared with one-step steam explosion (1.2 MPa/8 min), two-step steam explosion with an intermediate separation of fiber cells (ISFC) (1.1 Mpa/4 min-ISFC-1.2 MPa/4 min) can increase enzymatic hydrolyzation by 12.82%, reduce inhibitor conversion by 33%, and increase fermentation product (2,3-butanediol) conversion by 209%. Thus, the two-step steam explosion with ISFC process is proposed to optimize the hydrolysis process of lignocellulose by modifying the raw material from the origin. This novel process reduces the inhibitor content, promotes the biotransformation of lignocellulose, and simplifies the process of excluding the detoxification unit operation. PMID:22858472

Zhang, Yuzhen; Fu, Xiaoguo; Chen, Hongzhang

2012-10-01

151

Birefringence-induced splitting of the zero-dispersion wavelength in nonlinear photonic crystal fibers  

Microsoft Academic Search

We investigate how the strongly wavelength-dependent birefringence in nonlinear photonic crystal fibers leads to a splitting in the zero-dispersion wavelength for the two polarizations. We translate the requirements for the maximum splitting of the zero-dispersion wavelength to requirements for transverse structural uniformity by adopting a simple effective-index approach in which the birefringence is calculated in a step-index fiber with an

K. P. Hansen; A. Petersson; J. R. Folkenberg; M. Albertsen; A. Bjarklev

2004-01-01

152

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

153

Microstructure-assisted grating inscription in photonic crystal fibers  

NASA Astrophysics Data System (ADS)

One of the recent methods of grating inscription is based on inducing an array of highly localized index changes in the silica core of a fiber by tightly focused high intensity laser pulses. There were already several reports of such point-by-point gratings in conventional step index fibers. Applying this technique to photonic crystal fibers (PCFs) is still not straightforward. The main reason is the air holed microstructure which distorts the wave front of the inscribing laser beam and counters the focusing of the light in the core. We propose a new concept of microstructure-assisted grating inscription in photonic crystal fibers by introducing a focusing microstructure in the cladding of the fiber. We designed special types of photonic crystal fibers with a photonic crystal Mikaelian lens (PCML) in their cladding. Such a PCML is the implementation of a conventional Mikaelian or gradient index lens in a photonic crystal lattice. The effective index variation in a PCML is achieved via a variable air hole radius. In a fiber that is equipped with a PCML the inscribing laser beam can be tightly focused to the fiber core. This concept allows increasing optical power densities in the core of a PCF by an order of magnitude. We present a numerical model of a PCF with a PCML designed for 800 nm wavelength 125 femtosecond laser pulses.

Baghdasaryan, Tigran; Geernaert, Thomas; Berghmans, Francis; Thienpont, Hugo

2012-04-01

154

Flax Fiber - Interfacial Bonding  

Technology Transfer Automated Retrieval System (TEKTRAN)

Measured flax fiber physical and chemical properties potentially impact bonding and thus stress transfer between the matrix and fiber within composites. These first attempts at correlating flax fiber quality and biofiber composites contain the initial steps towards identifying key flax fiber charac...

155

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

E-print Network

. Using a laser source, a power meter, and a thermo-couple we measured the amount of power recovered from. Increasing the temperature, the refractive index contrast between cladding and core also increases, allowing, R. S. Windeler, and G. L. Burdge, "Cladding-Mode-Resonances in Air-Silica Microstructure Optical

Vlachos, Kyriakos G.

156

Tilted Fiber Bragg Grating photowritten in Microstructured Optical Fiber  

E-print Network

Tilted Fiber Bragg Grating photowritten in Microstructured Optical Fiber for improved refractive optical fiber for refrac- tive index measurement. We investigate the spectral sensitivity of Tilted Fi codes: (050.2770) Gratings; (060.0060) Fiber optics and optical communications; (060.2280) Fiber design

Paris-Sud XI, Université de

157

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

PubMed

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

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

2014-08-11

158

Interlaboratory comparison of radiation-induced attenuation in optical fibers  

SciTech Connect

A comparison of the losses induced in step index multimode, graded index multimode and single mode fibers by pulsed radiation exposure has been made among 12 laboratories over a period of 5 years. The recoveries of the incremental attenuations from 10{sup -9} to 10{sup 1} s are reported. Although a standard set of measurement parameters was attempted, differences between the laboratories are evident; possible origins for these are discussed. 18 refs., 18 figs., 7 tabs.

Friebele, E.J.; Lyons, P.B.; Blackburn, J.C.; Henschel, H.; Johan, A.; Krinsky, J.A.; Robinson, A.; Schneider, W.; Smith, D.; Taylor, E.W. (Naval Research Lab., Washington, DC (USA); Los Alamos National Lab., NM (USA); Harry Diamond Labs., Adelphi, MD (USA); Fraunhofer-Institut fuer Naturwissenschaftlich-Technische Trendanalysen (INT), Euskirchen (Germany, F.R.); Direction des Recherches, Etudes et Techni

1989-08-01

159

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

160

Splice Losses in Microstructured Optical Fibers: An Analytical Approach  

NASA Astrophysics Data System (ADS)

We have recently developed a simple method based on variational principle for the scalar analytical approach to study the propagation characteristics of MOFs. The model retains required azimuthal variation of field unlike Effective index method (EIM). We have analyzed, based on this model, the splice loss between two MOFs and that between an MOF and a conventional step-index fiber (SMF-28). As expected, the splicing between two MOFs depends on the relative orientation of air-holes. For typical fibers, this loss could be as high as 0.23 dB.

Sharma, Dinesh Kumar; Sharma, Anurag

2011-10-01

161

Spectrally efficient polymer optical fiber transmission  

NASA Astrophysics Data System (ADS)

The step-index polymer optical fiber (SI-POF) is an attractive transmission medium for high speed communication links in automotive infotainment networks, in industrial automation, and in home networks. Growing demands for quality of service, e.g., for IPTV distribution in homes and for Ethernet based industrial control networks will necessitate Gigabit speeds in the near future. We present an overview on recent advances in the design of spectrally efficient and robust Gigabit-over-SI-POF transmission systems.

Randel, Sebastian; Bunge, Christian-Alexander

2011-01-01

162

Fiber Bragg grating cladding mode resonance liquid-level sensor  

NASA Astrophysics Data System (ADS)

A Fiber-optic liquid-level sensor based on etched fiber Bragg grating (FBG) cladding mode resonance is proposed and demonstrated both theoretically and experimentally. The theoretical model of the FBG cladding mode liquid-level sensor is built under a three-layer step-index fiber geometry. Response of cladding mode resonance spectra to the variation of ambient liquid level are studied and simulated numerically with couple mode theory and transmission matrix method. In the experiments, a chemical etching method is adopted to diminish the fiber cladding diameter and increase the sensitivity of cladding mode resonances to the ambient refractive index change. Dependences of FBG cladding mode resonance spectra on the liquid-level variation are measured and the experiments data match the model well.

Chen, Na; Yun, Binfeng; Cui, Yiping

2009-10-01

163

Multimode optical fiber  

SciTech Connect

A depressed graded-index multimode optical fiber includes a central core, an inner depressed cladding, a depressed trench, an outer depressed cladding, and an outer cladding. The central core has an alpha-index profile. The depressed claddings limit the impact of leaky modes on optical-fiber performance characteristics (e.g., bandwidth, core size, and/or numerical aperture).

Bigot-Astruc, Marianne; Molin, Denis; Sillard, Pierre

2014-11-04

164

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

2012-01-01

165

Arc fusion splicing of hollow-core photonic bandgap fibers for gas-filled fiber cells.  

PubMed

The difficulty of fusion splicing hollow-core photonic bandgap fiber (PBGF) to conventional step index single mode fiber (SMF) has severely limited the implementation of PBGFs. To make PBGFs more functional we have developed a method for splicing a hollow-core PBGF to a SMF using a commercial arc splicer. A repeatable, robust, low-loss splice between the PBGF and SMF is demonstrated. By filling one end of the PBGF spliced to SMF with acetylene gas and performing saturation spectroscopy, we determine that this splice is useful for a PBGF cell. PMID:19529347

Thapa, R; Knabe, K; Corwin, K L; Washburn, B R

2006-10-16

166

Mid-infrared supercontinuum generation in fluoroindate fiber.  

PubMed

We report the generation of mid-infrared supercontinua in a step-index fluoroindate-based fiber. The large core of the fluoroindate fiber allows the guiding of multiwatt laser power over a broad spectral range. These fibers exhibit zero dispersion at 1.83 ?m, minimal loss of 0.1 dB/m at 3.2 ?m up to only 0.8 dB/m at 5 ?m. These specifications enable mid-infrared supercontinuum generation and propagation with low loss. By using mid-infrared ultrashort laser pulses from an optical parametric amplifier, we demonstrate generation of a 20 dB spectral flatness supercontinua from 2.7 to 4.7 ?m in the fluoroindate fiber, which is twice the spectral broadening compared to a ZBLAN fiber under similar conditions. PMID:24322105

Théberge, Francis; Daigle, Jean-François; Vincent, Denis; Mathieu, Pierre; Fortin, Jean; Schmidt, Bruno E; Thiré, Nicolas; Légaré, François

2013-11-15

167

Theoretical and experimental evaluation of the modal field shift and the associated transition loss in perturbed index-profile single-mode optical fiber with application of Fizeau interferometry.  

PubMed

Fizeau micro-interferometry is applied to evaluate some parameters of a curved single-mode optical fiber. The field shift of the fundamental mode and the associated transition loss in a perturbed index-profile fiber due to bending are determined. The preceding fiber parameters are determined as a function of the shift of multiple-beam Fizeau fringes. For a curvature range between 0.13 and 0.053 mm(-1), a range of field shift between 0.44 and 0.21 microm is determined. A fraction of the transition loss ranging between 0.0056 and 0.028 is calculated within the same curvature range. Because our method has high index resolution and spatial resolution, it shows good agreement with theory. The results and the agreement with theory indicate that the use of multiple-beam Fizeau fringes is a promising technique that is capable of determining with high accuracy some guidance parameters of the optical fibers. PMID:15330478

El-Diasty, Fouad

2004-08-01

168

High-resolution Fiber-fed Spectrograph for the 2.16-m Reflector  

Microsoft Academic Search

We present the design of a high-resolution fiber-fed spectrograph for the 2.16-m reflector at Xinglong Station, National Astronomical Observatories. The front-end optics box of the spectrograph was mounted on the Cassegrain focus (f\\/9) of the telescope, together with the CCD guiding system inside, yielding 6' × 6' guiding field of view. After careful tests, we chose the step-index STU fibers

X. J. Jiang

2002-01-01

169

1052 IEEE JOURNAL OF QUANTUM ELECTRONICS, VOL. QE-18, NO. 7 , JULY 1982 Aer and a step-index multimode fiber, was investigated. As a  

E-print Network

. An electromagnet surrounds the plasma tube,providing an axial magnetic field up to4.2 kG that helps to direct previously [l]- [ 3 ] . The electron beam is injected into a plasma tube 1.1 cm in diameter and 100 cm long

Rocca, Jorge J.

170

Fast Ethernet system with high-speed plastic optical fiber data links  

Microsoft Academic Search

In summary, we have achieved a 156 Mbps 100-m transmission with low numerical aperture (NA) step index plastic optical fiber (SI-POF) and low launch NA red LED. By using these technologies, a POF-based fast Ethernet system was successfully demonstrated. This system exhibited the advantages of cost and EMI tolerance of a POF link.

T. Nyu; M. Momona; S. Yamazaki; A. K. Dutta; A. Suzuki

1996-01-01

171

Comparison of higher-order mode suppression and Q-switched laser performance in thulium-doped large mode area and photonic crystal fibers.  

PubMed

We report the influence of higher order modes (HOMs) in large mode fibers operation in Q-switched oscillator configurations at ~2 ?m wavelength. S(2) measurements confirm guiding of LP(11) and LP(02) fiber modes in a large mode area (LMA) step-index fiber, whereas a prototype photonic crystal fiber (PCF) provides nearly single-mode performance with a small portion of light in the LP(11) mode. The difference in HOM content leads to a significant difference in Q-switched oscillator performance. In the step-index fiber, the percentage of cladding light increases by 20% to >40% with increasing pulse energy to ~250 µJ. We accredit this degradation to saturation of the gain in the fundamental mode leading to more light generated in the HOMs, which is eventually converted into cladding light. No such degradation is seen in PCF laser system for >400 µJ energies. PMID:23187192

Kadwani, Pankaj; Jollivet, Clemence; Sims, R Andrew; Schülzgen, Axel; Shah, Lawrence; Richardson, Martin

2012-10-22

172

Twist-induced birefringence in hexagonal photonic fibers  

NASA Astrophysics Data System (ADS)

Photonic crystal optical fibers have much more degrees of freedom concerning the geometries and index contrasts than step-index fibers; therefore, the theoretical analysis of their performance is usually based on the finite element method. In this work, taking advantage of the similarities observed for twisted single-mode fibers: standard (SMF-28 and SMF- 28e) and hexagonal photonic fibers, we propose that in regard with polarization performance, photonic fibers can be described using a simpler model based on classical polarization optics. The main advantages of the matrix model we propose lie in its accuracy and generality: for each one of the selected wavelengths and input states of polarization, it allows a precise prediction of the output polarization state. The comparison of the experimental results measured for standard and photonic fibers with the theoretical model predictions indicates that in both cases, twist induced birefringence is produced not only by the medium's photoelasticity, but also by the waveguide (cladding/core structure and asymmetry) modification. In addition, for the photonic fiber, the non-symmetrical response to right and left twist allowed the identification of an initial twist as part of the residual elliptical birefringence.

Tentori, D.; Garcia-Weidner, A.; Torres-Gómez, I.

2011-09-01

173

Security: Step by Step  

ERIC Educational Resources Information Center

This article provides a list of the essential steps to keeping a school's or district's network safe and sound. It describes how to establish a security architecture and approach that will continually evolve as the threat environment changes over time. The article discusses the methodology for implementing this approach and then discusses the…

Svetcov, Eric

2005-01-01

174

Fiber optic laser rod  

DOEpatents

A laser rod is formed from a plurality of optical fibers, each forming an individual laser. Synchronization of the individual fiber lasers is obtained by evanescent wave coupling between adjacent optical fiber cores. The fiber cores are dye-doped and spaced at a distance appropriate for evanescent wave coupling at the wavelength of the selected dye. An interstitial material having an index of refraction lower than that of the fiber core provides the optical isolation for effective lasing action while maintaining the cores at the appropriate coupling distance. 2 figs.

Erickson, G.F.

1988-04-13

175

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

176

Flat fiber: the flexible format for distributed lab-on-a-chip  

NASA Astrophysics Data System (ADS)

Integrated optical devices offer dense, multifunctional capability in a single robust package but are rarely considered compatible with the fields of remote or distributed sensing or compete in the long-haul with conventional 'one-dimensional' fibers. Here we aim to change that by introducing a 'flat-fiber' process that combines the advantages of of existing low-cost fiber drawing with the functionality of planar lightwave circuits in a novel hybrid format. Adapted from MCVD fiber fabrication, our preforms are deposited and collapsed into a rectangular geometry before drawing, resulting in extended lengths of mechanically flexible flat-fiber material with a photosensitive germanium-doped planar core. Direct UV writing is then used to create arrays of channel waveguides within the core layer, using a 5?m focused laser spot that literally 'draws' refractive index patterns into the flat fiber as it moves. Having recently demonstrated simple building blocks for integrated optical circuits in millimeter-wide flat-fibers (including; channel waveguides, power junctions and splitters, and planar Bragg gratings), our next step is to incorporate structured windows at strategic points along the fiber to allow fluidic access to the evanescent field for local refractive-index-based chemical measurements. By taking this approach, we hope to extend beyond the limitations of traditional planar and fiber substrates, allowing exotic material compositions, device layouts, and local sensing functions to be distributed over extended distances with no coupling or compatibility concerns in highly functional distributed lab-on-a-chip devices.

Gawith, Corin B. E.; Webb, Andrew S.; Standish, Robert J.; Sahu, Jayanta K.; Adikan, F. Rafiq M.; Gates, James C.; Smith, Peter G. R.

2007-05-01

177

Aerogel-clad optical fiber  

DOEpatents

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

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

1997-11-04

178

Aerogel-clad optical fiber  

DOEpatents

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

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

1997-01-01

179

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

NASA Astrophysics Data System (ADS)

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

Tao, Guangming; Abouraddy, Ayman F.

2014-03-01

180

High-power monolithic fiber amplifiers based on advanced photonic crystal fiber designs  

NASA Astrophysics Data System (ADS)

We report on the development and performance of a fully monolithic PCF amplifier that has achieved over 400 W with near diffraction limited beam quality with an approximately 1GHz phase modulated input. The key components for these amplifiers are an advanced PCF fiber design that combines segmented acoustically tailored (SAT) fiber that is gain tailored, a novel multi fiber-coupled laser diode stack and a monolithic 6+1x1 large fiber pump/signal multiplexer. The precisely aligned 2-D laser diode emitter array found in laser diode stacks is utilized by way of a simple in-line imaging process with no mirror reflections to process a 2-D array of 380-450 elements into 3 400/440?m 0.22NA pump delivery fibers. The fiber combiner is an etched air taper design that transforms low numerical aperture (NA), large diameter pump radiation into a high NA, small diameter format for pump injection into an air-clad large mode area PCF, while maintaining a constant core size through the taper for efficient signal coupling and throughput. The fiber combiner has 6 400/440/0.22 core/clad/NA pump delivery fibers and a 25/440 PM step-index signal delivery fiber on the input side and a 40/525 PM undoped PCF on the output side. The etched air taper transforms the six 400/440 ?m 0.22 NA pump fibers to the 525 ?m 0.55 NA core of the PCF fiber with a measured pump combining efficiency of over 95% with a low brightness drop. The combiner also operates as a stepwise mode converter via a 30 ?m intermediate core region in the combiner between the 20 ?m core of the input fiber and the 40 ?m fiber core of the PCF with a measured signal efficiency of 60% to 70% while maintaining polarization with a measured PER of 20 dB. These devices were integrated in to a monolithic fiber amplifier with high efficiency and near diffraction limited beam quality.

Sipes, Donald L.; Tafoya, Jason D.; Schulz, Daniel S.; Alkeskjold, Thomas Tanggaard; Weirich, Johannes; Olausson, Christina B.

2014-03-01

181

High index contrast platform for silicon photonics  

E-print Network

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

Akiyama, Shoji, 1972-

2004-01-01

182

Next Step for STEP  

SciTech Connect

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

Wood, Claire [CTSI; Bremner, Brenda [CTSI

2013-08-09

183

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.

184

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

185

Highly nonlinear tellurite fiber with engineered chromatic dispersion for broadband optical parametric amplification  

NASA Astrophysics Data System (ADS)

We present here the broadband and parametric gain for tellurite/phospho-tellurite optical fiber by carefully engineering the chromatic dispersion for optical parametric amplifier. This optical parametric amplification with broad bandwidth promises significant solutions for wavelength division multiplexing (WDM) and advanced ultrafast optical telecommunication systems. The parametric gain has been obtained with inclusion of higher and even order dispersion parameters in phase-mismatching factor (??). The results have been obtained for step index fiber (SI) and hybrid microstructured optical fiber (HMOF) with engineered chromatic dispersion, having one zero dispersion wavelength (ZDW) and two ZDWs. The HMOF with a core diameter of 1.1 ?m and chromatic dispersions having two ZDWs at 1262 and 1559 nm provides broadest parametric gain bandwidth (280 nm). This broad bandwidth advents due to the high nonlinear coefficient of tellurite/phospho-tellurite hybrid microstructured optical fiber. The paper explores variation in dispersion parameters, supercontinuum spectra and bandwidth of the parametric gains for these fibers.

Samuel, Edmund P.; Tuan, Tong Hoang; Asano, Koji; Suzuki, Takenobu; Ohishi, Yasutake

2013-05-01

186

Generation of megawatt optical solitons in hollow-core photonic band-gap fibers.  

PubMed

The measured dispersion of a low-loss, hollow-core photonic band-gap fiber is anomalous throughout most of the transmission band, and its variation with wavelength is large compared with that of a conventional step-index fiber. For an air-filled fiber, femtosecond self-frequency--shifted fundamental solitons with peak powers greater than 2megawatts can be supported. For Xe-filled fibers, nonfrequency-shifted temporal solitons with peak powers greater than 5.5 megawatts can be generated, representing an increase in the power that can be propagated in an optical fiber of two orders of magnitude. The results demonstrate a unique capability to deliver high-power pulses in a single spatial mode over distances exceeding 200 meters. PMID:14500976

Ouzounov, Dimitre G; Ahmad, Faisal R; Müller, Dirk; Venkataraman, Natesan; Gallagher, Michael T; Thomas, Malcolm G; Silcox, John; Koch, Karl W; Gaeta, Alexander L

2003-09-19

187

Optical fiber gyroscopes - Sagnac or Fizeau effect  

Microsoft Academic Search

Optical fiber gyroscopes consist of a multiturn coil of a single-mode fiber in an interferometer arrangement. The fringe shift (scale factor) depends on the effective index of refraction and on the dispersion of the fiber. The paper is intended to show that the scale factor is independent of the fiber properties and that the fringe shift obeys the Sagnac formula.

W. R. Leeb; Gerhard Schiffner; Eduard Scheiterer

1979-01-01

188

Robust multimaterial tellurium-based chalcogenide glass fibers for mid-wave and long-wave infrared transmission.  

PubMed

We describe an approach for producing robust multimaterial chalcogenide glass fibers for mid-wave and long-wave mid-infrared transmission. By combining the traditional rod-in-tube process with multimaterial coextrusion, we prepare a hybrid glass-polymer preform that is drawn continuously into a robust step-index fiber with a built-in, thermally compatible polymer jacket. Using tellurium-based chalcogenides, the fibers have a transparency window covering the 3-12 ?m spectral range, making them particularly attractive for delivering quantum cascade laser light and in space applications. PMID:24978794

Tao, Guangming; Shabahang, Soroush; Ren, He; Khalilzadeh-Rezaie, Farnood; Peale, Robert E; Yang, Zhiyong; Wang, Xunsi; Abouraddy, Ayman F

2014-07-01

189

Longitudinally Graded Optical Fibers  

NASA Astrophysics Data System (ADS)

Described herein, for the first time to the best of our knowledge, are optical fibers possessing significant compositional gradations along their length due to longitudinal control of the core glass composition. More specifically, MCVD-derived germanosilicate fibers were fabricated that exhibited a gradient of up to about 0.55 weight percent GeO2 per meter. These gradients are about 1900 times greater than previously reported for fibers possessing longitudinal changes in composition. The refractive index difference is shown to change by about 0.001, representing a numerical aperture change of about 10%, over a fiber length of less than 20 m. The lowest attenuation measured from the present longitudinally-graded fiber (LGF) was 82 dB/km at a wavelength of 1550 nm, though this is shown to result from extrinsic process-induced factors and could be reduced with further optimization. The stimulated Brillouin scattering (SBS) spectrum from the LGF exhibited a 4.4 dB increase in the spectral width, and thus reduction in Brillouin gain, relative to a standard commercial single mode fiber, over a fiber length of only 17 m. Fibers with longitudinally uniform (i.e., not gradient) refractive index profiles but differing chemical compositions among various core layers were also fabricated to determine acoustic effects of the core slug method. The refractive index of the resulting preform varies by about +/- 0.00013 from the average. Upon core drilling, it was found that the core slugs had been drilled off-center from the parent preform, resulting in semi-circular core cross sections that were unable to guide light. As a result, optical analysis could not be conducted. Chemical composition data was obtained, however, and is described herein. A third fiber produced was actively doped with ytterbium (Yb3 ) and fabricated similarly to the previous fibers. The preforms were doped via the solution doping method with a solution of 0.015 M Yb 3 derived from ytterbium chloride hexahydrate and 0.30 M Al 3 derived from aluminum chloride hexahydrate. The doped preform was engineered to have two core layers of differing chemical composition, resulting in both a gradient refractive index profile as well as a gradient acoustic profile. While exhibiting higher loss than the original LGF, the Yb 3-doped fiber showed slightly better SBS suppression with preliminary calculations showing at least 6 dB reduction in Brillouin gain. Lastly, 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 developed to produce longitudinally-graded optical fibers, 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. Possible applications of longitudinally graded optical fibers and future improvements are also discussed. The methods employed are very straight-forward and technically simple, providing for a wide variety of longitudinal refractive index and acoustic velocity profiles, as well as core shapes, that could be especially valuable for SBS suppression in high energy laser systems. Next generation analogs, with longitudinally-graded compositional profiles that are very reasonable to fabricate, are shown computationally to be more effective at suppressing SBS than present alternatives, such as externally-applied temperature or strain gradients.

Evert, Alexander George

190

ZBLAN Fiber  

NASA Technical Reports Server (NTRS)

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

2004-01-01

191

Robust fiber clustering of cerebral fiber bundles in white matter  

NASA Astrophysics Data System (ADS)

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

Yao, Xufeng; Wang, Yongxiong; Zhuang, Songlin

2014-11-01

192

Improved deep UV fiber for medical and spectroscopy applications  

NASA Astrophysics Data System (ADS)

An effort to reduce UV-induced defect centers and improve the UV solarization resistance in a high -OH synthetic fused silica step index multimode optical fiber, designated as FDP, was successfully completed at Polymicro Technologies. The development achieved significant reduction in the 214 and 265nm absorption bands typically associated with solarization effects in fused silica. The improvements were applied to fiber core diameters from 68 to 600?m. Characterization of the solarization resistance was performed with added attenuation from UV exposure demonstrated to be less than 1dB per two meters tested for all fibers in the core size range. Results of spectral performance and UV degradation are presented along with a description of the test protocols. Potential applications in the medical and spectroscopy fields also will be discussed.

Khalilov, Valery; Shannon, John; Timmerman, Richard

2014-02-01

193

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

194

Index of Refraction  

NSDL National Science Digital Library

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

2012-05-24

195

Fiber-optic level indicator for liquid hydrogen  

NASA Astrophysics Data System (ADS)

This paper describes a fiber-optic level indicator designed to detect the liquid interface in the liquid-hydrogen storage tanks. The considerations which led to the choice of the particular fiber-optic sensor and the construction of the measurement system are discussed. A fiber-optic refractometric transducer with the detection element of ellipsoidal form was developed which features a step-like response to the external refractive index in the narrow interval of this quantity between unity (gas) and 1.0974 (liquid hydrogen). The fiber-optic inputs to the storage system secure the reduced heat ingress in the liquid-hydrogen in comparison to sensors with electrical wires. The fiber-optic transducer features small dimensions, is strong mechanically, and supports multiple cycles of cooling to 20 K and heating to the ambient temperature. The device successfully indicated the level of liquid interface in a liquid-hydrogen storage tank under the maximum excess pressure in the tank of 4 MPa. The paper discusses a number of prospective applications of the developed fiber-optic transducer in the liquid-hydrogen storage systems.

Khotiaintsev, Sergei; Svyryd, Volodymyr

2008-04-01

196

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

PubMed Central

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

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

2011-01-01

197

Spatial coherence in optical fibers  

Microsoft Academic Search

The spatial degree of coherence on the cross-section of a graded-index optical fiber is evaluated under the assumption that all the propagating modes are uncorrelated among themselves. A detailed example for the case of parabolic fibers is given.

S. Piazzolla; G. de Marchis

1980-01-01

198

Effect of pulses from a high-power ytterbium fiber laser on a material with a nonuniform refractive index. I. Irradiation of yttrium oxide targets  

NASA Astrophysics Data System (ADS)

The irradiation of Nd:Y2O3 targets with an absorption coefficient of 13-1.7 × 103 cm-1 using laser pulses with a duration of 0.1-3.5 ms and peak power of 200-700 W at a power density of (0.2-1.3) × 106 W/cm2 is studied. A relatively large spread of the delay times of laser plume, spike emission of the laser plume, cleavage of the front surface of the target, and greater ejection of substance from the crater in comparison with the effect of the CO2-laser radiation with almost the same power are demonstrated. A numerical model of the effect of radiation on a target with a nonuniform refractive index is proposed to interpret the destruction of dielectric material (cleavage of the front surface) and the large spread of the delay times of the plume.

Osipov, V. V.; Lisenkov, V. V.; Platonov, V. V.; Orlov, A. N.; Podkin, A. V.; Savvin, I. A.

2014-05-01

199

Step Pultrusion  

NASA Astrophysics Data System (ADS)

The pultrusion process is an efficient technology for the production of composite material profiles. Thanks to this positive feature, several studies have been carried out, either to expand the range of products made using the pultrusion technology, or improve its already high production rate. This study presents a process derived from the traditional pultrusion technology named "Step Pultrusion Process Technology" (SPPT). Using the step pultrusion process, the final section of the composite profiles is obtainable by means of a progressive cross section increasing through several resin cure stations. This progressive increasing of the composite cross section means that a higher degree of cure level can be attained at the die exit point of the last die. Mechanical test results of the manufactured pultruded samples have been used to compare both the traditional and the step pultrusion processes. Finally, there is a discussion on ways to improve the new step pultrusion process even further.

Langella, A.; Carbone, R.; Durante, M.

2012-12-01

200

Irrigation Retrofit Program Steps to Improving sprinkler system efficiency  

E-print Network

jlomeli@ufl.edu EFFICIENT Electric Valves INEFFICIENT Indexing Valve Step 2. Add one of these irrigation of Indexing valve with electric valves $400 #12;Steps to Improving sprinkler system efficiency Visit ourIrrigation Retrofit Program Steps to Improving sprinkler system efficiency Step 1. Replace

Jawitz, James W.

201

Optimized fiber delivery system for Q-switched Nd:YAG lasers  

NASA Astrophysics Data System (ADS)

Interest in the transmission of high intensities through optical fibers is being motivated by an increasing number of applications. Using different laser types and fiber materials, various studies are encountering transmission limitations due to laser-induced damage processes. For a number of years we have been investigating these limiting processes during the transmission of Q-switched, multimode, 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 can result in subtle surface modifications that leave the entrance face more resistant to further breakdown or damage events. Catastrophic fiber damage can also occur as a result of a variety of mechanisms, with damage appearing at fiber entrance and exit faces, within the initial 'entry' segment of the fiber path, and at other internal sites due to fiber fixturing and routing effects. System attributes that will affect breakdown and damage thresholds include laser characteristics, the design and alignment of laser-to-fiber injection optics, and fiber end-face preparation. In the present work we have combined insights gained in past studies in order to establish what thresholds can be achieved if all system attributes can be optimized to some degree. Our multimode laser utilized past modifications that produced a relatively smooth, quasi-Gaussian profile. The laser-to-fiber injection system achieved a relatively low value for the ratio of peak-to-average fluences at the fiber entrance face, incorporated a mode scrambler to generate a broad mode power distribution within the initial segment of the fiber path, and had improved fixturing to insure that the fiber axis was collinear with the incident laser beam. Test fibers were from a particular production lot for which initial-strength characteristics were established and a high-stress proof test was performed. Fiber end faces were prepared by a careful mechanical polishing schedule followed by surface conditioning using a CO2 laser. In combination, these factors resulted in higher thresholds for breakdown and damage than we had achieved previously in studies that utilized a simple lens injection system. Probability distribution functions were fitted to the threshold data, providing a means for estimating the probability for transmission failure at lower laser energies.

Setchell, Robert E.

1997-05-01

202

Next Steps  

Cancer.gov

Next Steps 27 September 2002 Michael W. Vannier NCI - B IP Action items • P ut agenda on website and link slide presentations • E nroll attendees on archive-comm-l listserver • U pdate links to database projects on BIP webpage • P repare reports for

203

Activated carbon fibers and engineered forms from renewable resources  

DOEpatents

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

Baker, Frederick S

2013-02-19

204

Chiral fiber sensors  

NASA Astrophysics Data System (ADS)

We have fabricated a variety of chiral fiber sensors by twisting one or more standard or custom optical fibers with noncircular or nonconcentric core as they pass though a miniature oven. The resulting structures are as stable as the glass material and can be produced with helical pitch ranging from microns to hundreds of microns. The polarization selectivity of the chiral gratings is determined by the geometry of the fiber cross section. Single helix structures are polarization insensitive, while double helix gratings interact only with a single optical polarization component. Both single and double helix gratings may function as a fiber long period grating, coupling core and cladding modes or as a diffraction grating scattering light from the fiber core out of the fiber. The resulting dips in the transmission spectrum are sensitive to fiber elongation, twist and temperature, and (in the case of the long period gratings) to the refractive index of the surrounding medium. The suitability of chiral gratings for sensing temperature, elongation, twist and liquid levels will be discussed. Gratings made of radiation sensitive glass can be used to measure the cumulative radiation dose, while gratings made of radiation-hardened glass are suitable for stable sensing of the environment in nuclear power plants. Excellent temperature stability up to 900°C is found in pure silica chiral diffraction grating sensors.

Kopp, Victor I.; Churikov, Victor M.; Singer, Jonathan; Neugroschl, Daniel; Genack, Azriel Z.

2010-04-01

205

Investigation of optical fibers for coherent anti-Stokes Raman scattering (CARS) spectroscopy in reacting flows  

NASA Astrophysics Data System (ADS)

The objective of this work is to investigate the feasibility of intense laser-beam propagation through optical fibers for temperature and species concentration measurements in gas-phase reacting flows using coherent anti-Stokes Raman scattering (CARS) spectroscopy. In particular, damage thresholds of fibers, nonlinear effects during beam propagation, and beam quality at the output of the fibers are studied for the propagation of nanosecond (ns) and picosecond (ps) laser beams. It is observed that ps pulses are better suited for fiber-based nonlinear optical spectroscopic techniques, which generally depend on laser irradiance rather than fluence. A ps fiber-coupled CARS system using multimode step-index fibers is developed. Temperature measurements using this system are demonstrated in an atmospheric pressure, near-adiabatic laboratory flame. Proof-of-concept measurements show significant promise for fiber-based CARS spectroscopy in harsh combustion environments. Furthermore, since ps-CARS spectroscopy allows the suppression of non-resonant background, this technique could be utilized for improving the sensitivity and accuracy of CARS thermometry in high-pressure hydrocarbon-fueled combustors.

Hsu, Paul S.; Patnaik, Anil K.; Gord, James R.; Meyer, Terrence R.; Kulatilaka, Waruna D.; Roy, Sukesh

2010-10-01

206

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

PubMed

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

Swiderski, Jacek; Michalska, Maria

2014-02-15

207

A New Type of Motor: Pneumatic Step Motor  

PubMed Central

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

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

2011-01-01

208

Nonlinear analysis of nano-cluster doped fiber  

Microsoft Academic Search

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

Gang Liu; Ru Zhang

2007-01-01

209

5 CFR 591.222 - How does OPM use the expenditure weights to combine price indexes?  

Code of Federal Regulations, 2012 CFR

...does OPM use the expenditure weights to combine price indexes? 591.222 Section 591...does OPM use the expenditure weights to combine price indexes? OPM uses a three-step process to combine price indexes. (a) Step 1....

2012-01-01

210

5 CFR 591.222 - How does OPM use the expenditure weights to combine price indexes?  

...does OPM use the expenditure weights to combine price indexes? 591.222 Section 591...does OPM use the expenditure weights to combine price indexes? OPM uses a three-step process to combine price indexes. (a) Step 1....

2014-01-01

211

5 CFR 591.222 - How does OPM use the expenditure weights to combine price indexes?  

Code of Federal Regulations, 2013 CFR

...does OPM use the expenditure weights to combine price indexes? 591.222 Section 591...does OPM use the expenditure weights to combine price indexes? OPM uses a three-step process to combine price indexes. (a) Step 1....

2013-01-01

212

5 CFR 591.222 - How does OPM use the expenditure weights to combine price indexes?  

Code of Federal Regulations, 2011 CFR

...does OPM use the expenditure weights to combine price indexes? 591.222 Section 591...does OPM use the expenditure weights to combine price indexes? OPM uses a three-step process to combine price indexes. (a) Step 1....

2011-01-01

213

Stepped nozzle  

DOEpatents

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

Sutton, G.P.

1998-07-14

214

Stepped nozzle  

DOEpatents

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

Sutton, George P. (Danville, CA)

1998-01-01

215

Modal frequencies of vertical-cavity lasers determined by an effective-index model  

SciTech Connect

Previously, an effective-index optical model was introduced for the analysis of lateral waveguiding effects in vertical-cavity surface-emitting lasers. We show that the resultant transverse equation obtained in that model is almost identical to the one typically obtained in the analysis of dielectric waveguide problems, such as a step-index optical fiber. In this letter, we extend the effective-index model to obtain predictions of the discrete frequencies of the microcavity modes. As an example, we apply the analysis to vertical-cavity lasers that contain thin-oxide apertures. The model intuitively explains our experimental data and makes quantitative predictions in good agreement with a highly accurate numerical model. (c) 2000 American Institute of Physics.

Serkland, Darwin K. [Sandia National Laboratories, P.O. Box 5800, MS 0603, Albuquerque, New Mexico 87185 (United States)] [Sandia National Laboratories, P.O. Box 5800, MS 0603, Albuquerque, New Mexico 87185 (United States); Hadley, G. R. [Sandia National Laboratories, P.O. Box 5800, MS 0603, Albuquerque, New Mexico 87185 (United States)] [Sandia National Laboratories, P.O. Box 5800, MS 0603, Albuquerque, New Mexico 87185 (United States); Choquette, K. D. [Sandia National Laboratories, P.O. Box 5800, MS 0603, Albuquerque, New Mexico 87185 (United States)] [Sandia National Laboratories, P.O. Box 5800, MS 0603, Albuquerque, New Mexico 87185 (United States); Geib, K. M. [Sandia National Laboratories, P.O. Box 5800, MS 0603, Albuquerque, New Mexico 87185 (United States)] [Sandia National Laboratories, P.O. Box 5800, MS 0603, Albuquerque, New Mexico 87185 (United States); Allerman, A. A. [Sandia National Laboratories, P.O. Box 5800, MS 0603, Albuquerque, New Mexico 87185 (United States)] [Sandia National Laboratories, P.O. Box 5800, MS 0603, Albuquerque, New Mexico 87185 (United States)

2000-07-03

216

FLAX FIBERS  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

217

Index Numbers  

Microsoft Academic Search

Index numbers are used to aggregate detailed information on prices and quantities into scalar measures of price and quantity levels or their growth. The paper reviews four main approaches to bilateral index number theory where two price and quantity vectors are to be aggregated: fixed basket and average of fixed baskets, stochastic, test or axiomatic and economic approaches. The paper

Erwin Diewert

2007-01-01

218

Birefringent all-solid hybrid microstructured fiber.  

PubMed

We report the characterization of a birefringent all-solid hybrid microstructured fiber, in which the core-modes are guided by both the photonic bandgap (PBG) effect and total internal reflection (TIR). Due to the twofold symmetry, modal birefringence of 1.5 x 10(-4) and group birefringence of 2.1 x 10(-4) were measured at 1.31 microm, which is in the middle of the second bandgap. The band structure was calculated to be different from conventional 2-D PBG fibers due to the 1-D arrangement of high-index regions. The bend loss has a strong directional dependence due to the coexistence of the two guiding mechanisms. The fiber has two important properties pertinent to PBG fibers; spectral filtering, and chromatic dispersion specific to PBG fibers. The number of high-index regions, which trap pump power (by index guiding) when the fiber is used in cladding-pumped fiber lasers, is greatly reduced so that this fiber should enable efficient cladding pumping. This structure is suitable for linearly-polarized, cladding-pumped fiber lasers utilizing the properties of PBG fibers. PMID:19581962

Goto, Ryuichiro; Jackson, Stuart D; Fleming, Simon; Kuhlmey, Boris T; Eggleton, Benjamin J; Himeno, Kuniharu

2008-11-10

219

Phase-Compensating System For Fiber-Optic Holography  

NASA Technical Reports Server (NTRS)

Phase-compensating system controls relative phase of laser light emitted from two optical fibers. Stabilized for conventional holographic applications, or stepped through sequence of 90 degree phase shifts for phase-stepping holographic interferometry. Closed-loop system compensates for phase fluctuations caused by mechanical stresses and temperature changes in fibers, providing long-term phase stability and phase steps accurate to within 0.02 degrees. Controls environmental fluctuations in phases of light emitted by output fibers.

Mercer, Carolyn R.; Beheim, Glenn

1990-01-01

220

Fiber Bragg grating inscription in novel highly strains sensitive microstructured fiber  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

221

[Carbohydrates and fiber].  

PubMed

Dietary carbohydrates comprise two fractions that may be classified as digestible, and which are useful as energy sources (simple and complex carbohydrates) and fiber, which is presumed to be of no use to the human body. There are insufficient epidemiologic data on the metabolic effects of simple carbohydrates and it is not advisable to make quantitative recommendations of intake. It is questionable to recommend in developing countries that a fixed proportion of dietary energy be derived from simple sugars, due to the high prevalence of deficient energy intake, cultural habits, and regional differences in food intake and physical activity. In relation to recommendations of complex carbohydrates, it should be considered that their absorption is influenced by many factors inherent to the individual and to the foods. Fiber is defined as a series of different substances derived from tissue structures, cellular residues and undigested chemical substances that may be partially utilized after intestinal bacteria have acted on them. There is not a clear definition of the chemical composition of fiber, but it consists mainly of polysaccharides (such as cellulose, hemicellulose and pectins), lignin and end products of the interactions of various food components. The effects of fiber, such as control of food intake, regulation of gastrointestinal transit, post-prandial blood concentrations of cholesterol, glucose and insulin, flatulence and alterations in nutrient bioavailability are due to various physical properties inherent to its chemical components. Impairment of nutrient absorption may be harmful, mainly among populations whose food intake is lower than their energy needs, and with a high fiber content. This may be particularly important in pregnant women, growing children and the elderly, and should be considered when making nutrient recommendations. A precise knowledge of fiber is also important to calculate the real energy value of foods, mainly for two reasons: 1) the proportion of "crude fiber" (as measured by acid and alkaline digestion) leads to an over-estimation of the proportion of digestible carbohydrates calculated by difference; 2) fiber may alter the polysaccharide utilization of some foods, as shown by the "glycemic index". It is difficult to make recommendations on dietary fiber due to insufficient data on intake, fiber composition, its physiological effects, and epidemiological studies. However, a preliminary evaluation of the diets from most Latin American countries shows large intakes of vegetable foods and, consequently, an adequate fiber intake may be expected. PMID:2856370

Lajolo, F M; de Menezes, E W; Filisetti-Cozzi, T M

1988-09-01

222

Carbon Fibers Conductivity Studies  

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

223

Simple method of fabrication tapered fiber  

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

224

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.

225

Holey optical fibers: an efficient modal model  

Microsoft Academic Search

A new model for light propagation in holey optical fibers is developed in which the transverse index profile and the modal field are decomposed using different orthogonal functions. It is an efficient and accurate alternative to previous techniques, and is an invaluable tool to aid fabrication efforts. Using this model, a number of regimes of interest in these fibers are

Tanya M. Monro; D. J. Richardson; N. G. R. Broderick; P. J. Bennett

1999-01-01

226

Fiber optic level sensor for cryogens  

NASA Technical Reports Server (NTRS)

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

Sharma, M.

1981-01-01

227

Transmission measurements of hollow-core THz Bragg fibers  

E-print Network

Transmission measurements of hollow-core THz Bragg fibers Alexandre Dupuis,* Karen Stoeffler, Bora 135293); published March 23, 2011 We report on the terahertz (THz) spectral characteristics of hollow-core THz Bragg fibers. Two types of high-index contrast Bragg fibers were fabricated: one based

Skorobogatiy, Maksim

228

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

229

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

PubMed Central

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

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

2014-01-01

230

Jung Index  

NSDL National Science Digital Library

Compiled by Matthew Clapp of the University of Georgia, the Jung Index is a collection of more than 300 online resources about and related to the life and work of Carl Jung, the Swiss psychologist and psychiatrist who founded analytic psychology. Resources are indexed into ten major topic areas and include sections such as Research Resources, Jungian Psychology, and Psychoanalysis, among others. A What's New? section, a What's Cool? section, and the JungNet Newsletter keep frequent visitors up to date on the latest and greatest resources in analytic psychology. In addition, the site provides a glossary of Jungian terms, a gallery of Jungian images, and a moderated forum for Jungian discussion.

1999-01-01

231

Advances in low index polymer cladding materials  

NASA Astrophysics Data System (ADS)

Low index polymer claddings were developed and tested for use with silica core fibers. Polymers with varying indices of refraction were developed, so that numerical apertures useful for multiple applications were produced. High transmission over a wide wavelength range was obtained, both for films and for clad fibers. A refractive index as low as 1.363 was achieved, which results in a numerical aperture of 0.50 (at 852 nm) when used in cladding silica cores. Results for fibers clad with 1.373 index material under high temperatures (150 °C) show that worst case change in loss was within 0.084 dB, even over a time frame of 6400 hours.

Clark, Timothy E.; Kwak, Seung-Jo

2010-10-01

232

Geochemistry Index  

NSDL National Science Digital Library

This site is the index of a book used in a geochemistry course taught by W. M. White at Cornell University. There are 15 chapters and a table of contents available. All of the chapters are large PDF files and take some time to download. Figures and exercises accompany the text.

William M. White

233

Population Index  

NSDL National Science Digital Library

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

1986-01-01

234

Surface Porosity of Lignin\\/PP Blend Carbon Fibers  

Microsoft Academic Search

The surface porosities of carbon fibers derived from the polymer blend fibers of hardwood kraft lignin, HKL and polypropylene, PP, were discussed using thermal analyses, FTIR, and nitrogen adsorption. HKL\\/PP carbon fibers were prepared by two?step thermal processing, thermostabilization, and carbonization. During the thermostabilization process, pores are created by oxidative degradation of the PP component. After thermostabilization some crystalline and

Satoshi Kubo; Takahiro Yoshida; John F. Kadla

2007-01-01

235

Dual-parameter sensor based on a no-core fiber and fiber Bragg grating  

NASA Astrophysics Data System (ADS)

A dual-parameter fiber sensor achieved by cascading a fiber Bragg grating with a no-core fiber (NCF) is used for simultaneously detecting both the temperature and index physical parameters. The main index sensing mechanism of NCF is based on the wavelength shift of multimode signals' interference (MMI), and the temperature-sensing mechanism is determined by the Bragg wavelength shift and MMI wavelength shift. As the testing index value approaches the cladding index of the optical fiber, an MMI-induced loss-dip is thus created with a sensitivity of 899 nm/RIU due to the phase-match condition of MMI being satisfied. By coating the thin films of different materials, this kind of sensor can be applied in a wide range of different sensing systems.

Lin, Guei-Ru; Fu, Ming-Yue; Lee, Cheng-Ling; Liu, Wen-Fung

2014-05-01

236

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

PubMed

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

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

2014-10-01

237

Interferometric Fiber Optic Sensors  

PubMed Central

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

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

2012-01-01

238

Optical Fiber Protection  

NASA Technical Reports Server (NTRS)

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

1999-01-01

239

Two Fiber Optical Fiber Thermometry  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

240

Fiber optic fluid detector  

DOEpatents

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

Angel, S.M.

1987-02-27

241

Dietary Fiber and Weight Loss  

MedlinePLUS Videos and Cool Tools

... weight loss results of the American Heart Association diet versus a one-step high fiber diet. 240 adults who were at risk for developing ... The remainder were asked to follow the AHA diet, which includes 13 components from limiting calories, reducing ...

242

Pragmatic Approach to Subject Indexing: A New Concept.  

ERIC Educational Resources Information Center

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

Dutta, S.; Sinha, P. K.

1984-01-01

243

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. 4 figs.

Van`t Hof, J.

1998-09-01

244

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

245

MESH-BASED SPHERICAL DECONVOLUTION FOR PHYSICALLY VALID FIBER ORIENTATION RECONSTRUCTION VIA DIFFUSION-WEIGHTED MRI  

E-print Network

University of California, Los Angeles ABSTRACT High angular resolution diffusion imaging (HARDI) meth- ods fiber geometry. Index Terms-- Deconvolution, magnetic resonance imaging, inverse problems, optimizationMESH-BASED SPHERICAL DECONVOLUTION FOR PHYSICALLY VALID FIBER ORIENTATION RECONSTRUCTION VIA

Thompson, Paul

246

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

PubMed Central

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

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

2012-01-01

247

Aberration-limited coupling efficiency from a plano-convex lens into an optical fiber.  

PubMed

Ray-tracing calculations of the coupling efficiency from a plano-convex lens of relatively low f/number ( approximately 2.35) into highly multimode step-index optical fibers have been performed for both orientations of the lens. The results of the calculations yield surprising discontinuities and asymmetries in the slope of the coupling efficiency versus longitudinal displacement. These features are explained in terms of the multiplicity of roots in the mapping of incident-ray heights onto the fiber core radius. In addition, it is found that the paraxial coupling efficiency result is in marked qualitative and quantitative disagreement with exact theoretical results, except at coupling efficiencies of less than a few percent. The relationship of these features to longitudinal spherical aberration, paraxial coupling, and the ray caustic is discussed. PMID:20717357

Wanser, K H; Lewotsky, K

1991-12-20

248

A fast segmentation method for high-resolution color images of foreign fibers in cotton  

Microsoft Academic Search

Foreign fibers in cotton seriously affect the quality of cotton products. The identification of foreign fibers in cotton is a critical step in the automated inspection of foreign fibers in cotton; image segmentation is crucial in this identification process. This paper presents a new approach for segmenting images of foreign fibers in cotton. Firstly, color images were captured, and the

Xin Zhang; Daoliang Li; Wenzhu Yang; Jinxing Wang; Shuangxi Liu

2011-01-01

249

Cumulative Index  

E-print Network

CUMULATIVE INDEX I. Articles (i) By Author Abate, Charles J. "Has Dretske Really Refuted Skepticism?", v.4, n.3 (June, 1977), pp. 169- 175. Abugattas, Juan A. "On the Relation Between Morality and the Notion of God". v.7, n.l (November, 1979...), pp. 47-81. Algeo, Donald. "Why Art?", v.7, n.2 (Spring, 1980), pp. 105-129. Austin, James W. "Rorty's Materialism", v.3, n.l (November, 1975), pp. 20-28. Bell, Gary. "A Characterization of Mathematics". v.8, n.2 (Summer, 1981), pp. 96-104. Bell...

1981-12-01

250

Processing and characterization of core-clad tellurite glass preforms and fibers fabricated by rotational casting  

NASA Astrophysics Data System (ADS)

We report results on the processing and characterization of tellurite-based glass preforms (core and cladding bulk glasses) and fibers within the TeO 2-Bi 2O 3-ZnO glass system. The core-clad fiber has been drawn from a core-clad preform prepared via rotational casting. Using Cu as a tracer to assess interface quality between the core and clad layers, we show excellent cladding layer thickness uniformity across lengths of up to 40 mm in a 65 mm long perform. No measurable diffusion of Cu between the core and the clad has been observed, within the accuracy of measurement, indicating good stability and interface quality during casting of melted glass. Micro-Raman spectroscopy has been used to identify subtle post-draw structural modification induced in the preform following the fiber drawing. These changes have been attributed to modification to the bulk glass' thermal history upon drawing and small scale molecular orientation of chain units within the tellurite glass matrix produced during the fiber drawing process. The resulting fiber was found to have an index step of (0.009 ± 0.002) between the fiber core and clad composition at 632 nm and propagation losses of (3.2 ± 0.1) dB/m at 632 nm and (2.1 ± 0.1) dB/m at 1.5 ?m. The primary source of loss in the near-IR (NIR) is associated with residual hydroxyl (OH -) groups in the bulk preform which remain in the glass fiber.

Massera, J.; Haldeman, A.; Milanese, D.; Gebavi, H.; Ferraris, M.; Foy, P.; Hawkins, W.; Ballato, J.; Stolen, R.; Petit, L.; Richardson, K.

2010-03-01

251

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

252

Concentric core optical fiber with multiple-mode signal transmission  

DOEpatents

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

Muhs, J.D.

1997-05-06

253

Concentric core optical fiber with multiple-mode signal transmission  

DOEpatents

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

Muhs, Jeffrey D. (Lenoir City, TN)

1997-01-01

254

Thinned fiber Bragg grating magnetic field sensor with magnetic fluid  

Microsoft Academic Search

The refractive index of magnetic fluid may be changed by external magnetic field. Therefore, through measuring its refractive index, the intensity of the magnetic field can be obtained. Fiber Bragg grating (FBG) is sensitive to the refractive index surrounding its cladding when the diameter of cladding is reduced to a certain degree. In order to prove the sensitivity of the

Ciming Zhou; Li Ding; Dongli Wang; Yaqi Kuang; Desheng Jiang

2011-01-01

255

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

PubMed

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

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

2014-01-15

256

Longitudinal strain sensing with photonic crystal fibers and fiber Bragg gratings  

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

257

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

258

High temperature sensing with fiber Bragg gratings in sapphire-derived all-glass optical fibers.  

PubMed

A structured sapphire-derived all-glass optical fiber with an aluminum content in the core of up to 50 mol% was used for fiber Bragg grating inscription. The fiber provided a parabolic refractive index profile. Fiber Bragg gratings were inscribed by means of femtosecond-laser pulses with a wavelength of 400 nm in combination with a two-beam phase mask interferometer. Heating experiments demonstrated the stability of the gratings for temperatures up to 950°C for more than 24 h without degradation in reflectivity. PMID:25401829

Elsmann, Tino; Lorenz, Adrian; Yazd, Nazila Safari; Habisreuther, Tobias; Dellith, Jan; Schwuchow, Anka; Bierlich, Jörg; Schuster, Kay; Rothhardt, Manfred; Kido, Ladislav; Bartelt, Hartmut

2014-11-01

259

Fiber receptacle _ Collection optics  

E-print Network

Fiber receptacle _ Collection optics lymer optical fiber Optoelectronics Controlled impedance-1077 USA ABSTRACT Our work discusses the tolerance modeling of an optical fiber that is inserted. Keywords: Modeling and simulation, optical data interconnect, fiber-optic modules, optics 1. INTRODUCTON

Miller, Ethan L.

260

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

261

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

262

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

263

Inverse Variation: Step By Step Lesson  

NSDL National Science Digital Library

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

2012-08-29

264

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

265

Photovoltaic fibers  

NASA Astrophysics Data System (ADS)

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

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

2006-08-01

266

Miniature fiber optic surface plasmon resonance biosensors  

NASA Astrophysics Data System (ADS)

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

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

1999-01-01

267

Two-Dimensional Finite-Element Modal Analysis of Brillouin Gain Spectra in Optical Fibers  

Microsoft Academic Search

A modal analysis based on two-dimensional (2-D) finite-element method for the Brillouin gain spectra (BGS) in optical fibers is demonstrated. This method enables the evaluation of optical fibers with 2-D complicated geometry and\\/or refractive-index profile. The BGS of two fiber samples, a single-mode fiber and a PANDA polarization-maintaining fiber (PMF) of the same design except the stress-applying elements in the

Weiwen Zou; Zuyuan He; Kazuo Hotate

2006-01-01

268

Photonic lantern with cladding-removable fibers  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

269

Optimization of laser fibers for high pump light absorption  

NASA Astrophysics Data System (ADS)

For the implementation of novel fiber laser concepts, such as extra-large mode area (X-LMA) fiber lasers or multi-core fiber lasers alternative manufacturing processes for highly-doped silica glasses and the laser fibers fabricated from it are required. For efficient laser operation a high absorption of pump power in the active fiber core is a necessary condition. To increase the pump light absorption the fiber development aimed at the preparation of laser-active and adapted passive single-large core fibers up to multi-core structures with 7 large cores showing broken circular fiber symmetry. The optimization of the optical fibers which will be shown in detail is based on the combination of several innovative manufacturing methods such as the powder sintering technology (REPUSIL), the preform preparation by stack-and-draw technique and the fiber drawing process. The described procedure is particularly suitable to produce multifilament glass preforms resp. laser fibers with large cores in which the radial and lateral indices of refraction can be adjusted homogeneously and reproducibly. Due to the realized increase of the laser-active core volume in these fibers the pump light absorption could be considerably increased and the resulting shorter fiber length allows the use of fibers with a moderate attenuation. The results concerning the characterization of materials science and the optical aspects e. g. the dopant concentration distributions and related refractive index profiles as well attenuation and pump absorption spectra will be presented.

Bierlich, Jörg; Kobelke, Jens; Jetschke, Sylvia; Grimm, Stephan; Unger, Sonja; Schuster, Kay

2014-03-01

270

Photovoltaic fibers  

Microsoft Academic Search

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

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

2006-01-01

271

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

272

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

273

1088 IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 18, NO. 9, MAY 1, 2006 Switchable Multiwavelength Erbium-Doped Fiber  

E-print Network

Erbium-Doped Fiber Laser With a Multimode Fiber Bragg Grating and Photonic Crystal Fiber Xinhuan Feng, a simple switchable multiwavelength erbium-doped fiber laser is proposed and demonstrated. The wavelengths or wavelength switching modes by varying the states of polarizations of the laser cavity. Index Terms--Erbium

Wai, Ping-kong Alexander

274

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

275

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

276

Soft capacitor fibers using conductive polymers for electronic textiles  

E-print Network

A novel, highly flexible, conductive polymer-based fiber with high electric capacitance is reported. In its crossection the fiber features a periodic sequence of hundreds of conductive and isolating plastic layers positioned around metallic electrodes. The fiber is fabricated using fiber drawing method, where a multi-material macroscopic preform is drawn into a sub-millimeter capacitor fiber in a single fabrication step. Several kilometres of fibers can be obtained from a single preform with fiber diameters ranging between 500um -1000um. A typical measured capacitance of our fibers is 60-100 nF/m and it is independent of the fiber diameter. For comparison, a coaxial cable of the comparable dimensions would have only ~0.06nF/m capacitance. Analysis of the fiber frequency response shows that in its simplest interrogation mode the capacitor fiber has a transverse resistance of 5 kOhm/L, which is inversely proportional to the fiber length L and is independent of the fiber diameter. Softness of the fiber materials...

Gu, Jian Feng; Skorobogatiy, Maksim

2010-01-01

277

Bringing Nanotechnology into Fiber Opticsinto Fiber Optics  

E-print Network

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

Skorobogatiy, Maksim

278

Photonic Crystal Fibers Advances in Fiber Optics  

E-print Network

Photonic Crystal Fibers Advances in Fiber Optics Elliott L. VonWeller March 1, 2005 Applied Optics of communication for decades. The transition to optical systems was a giant leap forward. These fiber optic lines and are immune to electromagnetic interference that plaques electronic signal lines. These fiber optics

La Rosa, Andres H.

279

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

NASA Astrophysics Data System (ADS)

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

Singh, Amit

2014-12-01

280

Environmental stability of intercalated graphite fibers  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

281

A novel inventory classification approach based on fuzzy membership degrees of evaluation indexes  

Microsoft Academic Search

A novel inventory classification approach based on fuzzy membership degrees of evaluation indexes is proposed in this paper. The approach includes six steps: the selection of the evaluation indexes, the formulation of the fuzzy membership functions of evaluation indexes, the calculation of the fuzzy membership degrees of evaluation indexes, the sequencing of the fuzzy membership degrees of evaluation indexes, the

Hua-Li Sun; Yao-Feng Xue

2009-01-01

282

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

283

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

284

Photonic Crystal Fibers: A New Class of Optical Waveguides  

Microsoft Academic Search

Remarkable properties of optical fibers with a high-index core region and a surrounding silica\\/air photonic crystal cladding have recently been reported. Here we discuss the physics, the special guiding properties, and the theoretical tools developed for the modeling of these photonic crystal fibers. With an emphasis on the applicational aspects of the fibers, we study their single-mode operation, bending losses,

Jes Broeng; Dmitri Mogilevstev; Stig E. Barkou; Anders Bjarklev

1999-01-01

285

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

286

Wavelength division multiplexed fiber optic absolute position encoder  

Microsoft Academic Search

A wavelength division multiplexing (WDM) method for fiber optic sensors is proposed which uses a broadband light source and narrow bandpass thin film optical filter coatings on cylindrical graded index lenses. In the WDM system described here, all bits are multiplexed onto a single signal return fiber by assigning each bit a unique wavelength. A multielement photodetector array is used

Eric D. Park; Erann Gat

1989-01-01

287

Soft glasses for photonic crystal fibers and microstructured optical components  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

288

Fiber Optics Introduction  

E-print Network

Fiber Optics #12;Introduction · History of Fiber Optics · Types and Structure of Fibers · Loss_464- 564/Projects_Presented/Projects-2008/Optical_fiber_SMF- 28_Datasheet_%289microns-125microns%29.pdf · http://www.sff.net/people/Jeff.Hecht/history.htm · http://www.timbercon.com/History-of-Fiber-Optics

La Rosa, Andres H.

289

Index des mots-cls Keywords index  

E-print Network

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

Boyer, Edmond

290

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

291

High NA-fibers: silica-based fibers for new applications  

NASA Astrophysics Data System (ADS)

For medical and analytical applications, thick-core fibers based on synthetic silica are widely spread. In many cases, the fibers are used as a light-guiding medium only; therefore, the coupling efficiency between the light-emitting area and the accepting fiber is of great importance described easily by the light acceptance cone related to the numerical aperture of the fiber. In the past, all-silica fibers with un-doped silica core and fluorine-doped silica cladding have been used for different applications. However, these fibers are restricted in respect to a low numerical aperture of typically 0.22. To increase the numerical aperture, different polymers can be used for cladding material. In addition to standard polymers, Teflon-AF is an attractive candidate for significantly higher NAs of approx. 0.65. In parallel, a new class of all-silica fibers was developed with high NA, the so-called "Air-clad" or microstructured fibers. Longitudinal microstructured holes, in the order of the wavelength, form the cladding-region together with the surrounding silica. The dimensions of the microstructure dictate the critical angle for light transmission in the core, rather than the refractive index of the cladding material. The light guiding properties of different fibers will be compared. Especially the optical transmission from the UV-region up to the NIR-region will be discussed. Due to the wavelength-dependent mean value of the refractive index (RI) in the cladding, the definition of numerical aperture has to be adjusted. Especially, the UV-damage within Teflon-coated fibers and the microstructured fibers will be described in detail.

Klein, Karl-Friedrich; Eckhardt, Hanns S.; Vincze, Christiane; Grimm, Stephan; Kirchhof, Johannes; Kobelke, Jens; Clarkin, Jim; Nelson, Gary

2005-03-01

292

Analysis of a new measurement for electromagnetic field with the DGD of fiber grating  

Microsoft Academic Search

Fiber grating is sensitive to the stress, temperature and other entironmental factors. It has caused much attention and has been used widely. In this paper a new magnetic field measurement using different group delay (DGD) of fiber grating is proposed. When the magnetic field applied the refractive index difference of the two circularly polarized light in fiber grating will be

Yang Su; Hui Peng; Yuquan Li

2008-01-01

293

Impact of fiber core diameter on dispersion and multiplexing in multimode-fiber links.  

PubMed

Large-core silica multimode fibers, whose core diameters are generally 50 ?m or 62.5 ?m, form the bulk of short and medium haul optical fiber links in existence today, owing to their low cost and ease of deployment. However, modal dispersion significantly limits the maximum data rates that they support. Recently, the ability to multiplex several streams of data through optical fibers has spawned the development of few-mode multimode fibers. These fibers possess the low-dispersion characteristics of single-mode fibers and the ability to multiplex several data streams using multiple-input multiple-output (MIMO) techniques and mode-specific filtering to increase data rates. While fibers with larger core diameters possess a larger number of spatial modes, they do not support data rates as high as few-mode fibers. In this paper, we describe a simulation based approach to characterize the tradeoffs between fiber diameter, achievable data rates and alignment tolerances of coherent links that employ graded-index multimode fibers (MMFs) of various dimensions, using the information theoretic outage capacity as the metric. The simulations used fibers' intermodal coupling characteristics to measure its multiplexing abilities and dispersion limitations with mode-specific filters and launch and detection spatial filter arrays. The simulations indicate that the bandwidth-length product achievable over few-mode fibers with MIMO techniques can exceed 250 Gb/s-km, while heavy mode spreading and limited mode selectivity limits the bandwidth-length product to under 25 Gb/s-km in fibers core diameters larger than 50 ?m. PMID:25090530

Appaiah, Kumar; Vishwanath, Sriram; Bank, Seth R

2014-07-14

294

Toxin detection using a fiber-optic-based biosensor  

NASA Astrophysics Data System (ADS)

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

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

1993-05-01

295

Fiber-optic level indicator for liquid hydrogen  

Microsoft Academic Search

This paper describes a fiber-optic level indicator designed to detect the liquid interface in the liquid-hydrogen storage tanks. The considerations which led to the choice of the particular fiber-optic sensor and the construction of the measurement system are discussed. A fiber-optic refractometric transducer with the detection element of ellipsoidal form was developed which features a step-like response to the external

Sergei Khotiaintsev; Volodymyr Svyryd

2008-01-01

296

Polyethylene fiber drawing optimization  

E-print Network

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

Chiloyan, Vazrik

2011-01-01

297

Step by Step Instructions Adding an Individual Description of Work  

E-print Network

Step by Step Instructions Adding an Individual Description of Work To a Job Hazards Analysis of Work to a Job Hazards Analysis (JHA). Step 1: Log In Step 2: Create a Draft JHA Step 3: Update Description of Work Step 4: Create Hazards Profile Step 5: Confirm Creation of JHA Adding Description of Work

298

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.

299

Fiber optic quasi-distributed temperature sensor  

Microsoft Academic Search

The subject of this paper is an optical fiber temperature sensor using the techniques of optical time domain reflectometry. The sensor uses the dependence between the refractive index of epoxy resins and temperature and allows us to develop sensors working in transmission as well as in reflective mode.

Ryszard Hypszer; Bogdan B. Kosmowski; Jerzy Plucinski; Pawel Wierzba

1997-01-01

300

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

301

Characterization of Polarization-Maintaining Fiber Using High-Sensitivity Optical-Frequency-Domain Reflectometry  

NASA Astrophysics Data System (ADS)

Optical-frequency-domain reflectometry is used to measure the group-index difference and the refractive-index difference (i.e., beat length) between the fast and slow modes in polarization-maintaining optical fiber. The Rayleigh scatter normally present in the fiber is measured in reflection. This measurement, in turn, enables a distributed measurement of the fiber's birefringence that is rapid and completely nondestructive.

Froggatt, Mark E.; Gifford, Dawn K.; Kreger, Steven; Wolfe, Matthew; Soller, Brian J.

2006-11-01

302

Fiber Bragg grating inscription in few-mode highly birefringent microstructured fiber.  

PubMed

In this Letter, we present the technology of fiber Bragg grating (FBG) inscription in highly birefringent (HB) few-mode microstructured fibers (MSFs) with two different (nanosecond and femtosecond) lasers in a Talbot interferometer setup. The spectral characteristics of FBGs written in the core region of the investigated fiber, with particular modes represented by dual peaks, are presented and discussed. Furthermore, we calculate the fundamental fiber parameters (mode effective refractive index and phase modal birefringence) from the spectral characteristics and show very good agreement with the performed numerical fiber characterization. We expect the results of our experiments to be very useful in future development of FBG sensors based on novel HB MSFs, with enhanced strain sensitivity of higher-order modes. PMID:23811884

Tenderenda, Tadeusz; Murawski, Michal; Szymanski, Michal; Szostkiewicz, Lukasz; Becker, Martin; Rothhardt, Manfred; Bartelt, Hartmut; Mergo, Pawel; Skorupski, Krzysztof; Marc, Pawel; Jaroszewicz, Leszek R; Nasilowski, Tomasz

2013-07-01

303

Concatenation of surface plasmon resonance sensors in a single optical fiber using tilted fiber Bragg gratings.  

PubMed

An inline multichannel surface plasmon resonance (SPR) sensor scheme excited with tilted fiber Bragg gratings (TFBG) in a chromium- and gold-coated fiber is demonstrated. The channels have different operating wavelengths, different TFBG tilt angles, and hence different refractive index operating ranges. The polarization state of each channel based on the TFBG orientation can be used to switch each SPR sensor on or off as required. This system provides an operating range of 1.40-1.44 RIU and a sensitivity of around 500??nm/RIU. The multiplexing in a single optical fiber of a number of TFBG-SPR sensors is demonstrated for the first time. PMID:25531623

Baiad, Mohamad Diaa; Kashyap, Raman

2015-01-01

304

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

305

Design procedures for fiber composite box beams  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

306

Investigation of structural transformations taking place during oxidative stabilization of viscose rayon precursor fibers prior to carbonization and activation  

NASA Astrophysics Data System (ADS)

An investigation was carried out on the physical and structural transformations occurring during oxidative stabilization of viscose rayon precursor fibers impregnated with diammonium hydrogen phosphate (DAP). Structural characterization was performed using optical microscopy, X-ray diffraction, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and infrared (IR) spectroscopy techniques. The results indicated that the use of DAP impregnation improved the thermal stability of viscose rayon fibers prior to carbonization and activation steps. Analysis of the equatorial X-ray diffraction traces demonstrated gradual loss of crystalline structure due to the disordering processes caused by the interruption of intermolecular hydrogen bonds. A novel X-ray stabilization index for the evaluation of oxidative stabilization was devised specifically for the oxidized viscose rayon fibers. The results obtained from DSC and TGA measurements demonstrated that there was an improvement in the thermal stability due to the formation of an increasing amount of ladder-like structures containing aromatic entities with progressing temperature. The results obtained from the analysis of IR spectra showed the gradual and continuous loss of intramolecular and intermolecular hydrogen bonds associated with dehydrogenation and dehydration reactions. IR spectra demonstrated the loss of crystallinity with progressing temperature confirming the results obtained from X-ray diffraction measurements. IR spectra also demonstrated the formation of double bonded Cdbnd C bonds attributed to the formation of a crosslinked ladder-like structure. DSC and TGA measurements show that the sample oxidized at 250 °C possesses high thermal stability which can be used for the subsequent carbonization and activation steps.

Karacan, ?smail; Soy, Taner

2013-06-01

307

About Segmentation Step in Content-based Image Retrieval Systems  

E-print Network

About Segmentation Step in Content-based Image Retrieval Systems J´er^ome Da Rugna, Gael Chareyron informations during this first segmentation step. Index Terms--Content-based image retrieval, segmentation. THE SEGMENTATION DEBATE Many systems use segmentation to calculate image features[10], [11], [12]. In fact

Paris-Sud XI, Université de

308

Integrated environmental index for application in land-use zoning  

NASA Astrophysics Data System (ADS)

This paper describes the development of an integrated environmental index that may serve as a representation of the general environmental quality at a certain location. This index is meant to be used by local administrators to strike a balance between the development of industrial activities and the protection of sensitive land-uses (housing). The approach used to arrive at this index, based on health considerations, is described, detailing the different steps in the construction of the index: identification, assessment, summation, valuation and aggregation. The index combines environmental quality information concerning noise, odor, air pollution, and risk of industrial calamities. The resulting integrated environmental index is illustrated using data of a pilot project.

Sol, Veronica M.; Lammers, Petronella E. M.; Aiking, Harry; de Boer, Joop; Feenstra, Jan F.

1995-05-01

309

Gene-rich islands for fiber development in the cotton genome  

Technology Transfer Automated Retrieval System (TEKTRAN)

Cotton fiber is an economically important seed trichome and the world's leading natural fiber used in the manufacture of textiles. As a step towards elucidating the genomic organization and distribution of gene networks responsible for cotton fiber development, we investigated the distribution of f...

310

A new fiber optic accelerometer based on fiber Bragg grating  

NASA Astrophysics Data System (ADS)

High sensitivity is an important index of an accelerometer for seismic monitoring. In this paper, we have designed a new fiber Bragg grating accelerometer and, a theoretical structure is given. The theoretical analysis of the sensor is established, and the results show that the sensitivity of accelerometer device is 2131.5pm/g and resonance frequency is 28.01Hz theoretically. It has a higher precision than traditional accelerometer on magnitude. In the experiment, we have found that the output will react as a cosine signal while the input is a cosine signal. It indicates that the sensor has a good linear relationship between output and response. We demonstrated a strain sensing test of measuring central wavelength shifting by fiber Bragg grating.

Liang, Qianliang; Sun, Qizhen; Xu, Jun; Yu, Li; Zhang, Manliang

2012-01-01

311

A new fiber optic accelerometer based on fiber Bragg grating  

NASA Astrophysics Data System (ADS)

High sensitivity is an important index of an accelerometer for seismic monitoring. In this paper, we have designed a new fiber Bragg grating accelerometer and, a theoretical structure is given. The theoretical analysis of the sensor is established, and the results show that the sensitivity of accelerometer device is 2131.5pm/g and resonance frequency is 28.01Hz theoretically. It has a higher precision than traditional accelerometer on magnitude. In the experiment, we have found that the output will react as a cosine signal while the input is a cosine signal. It indicates that the sensor has a good linear relationship between output and response. We demonstrated a strain sensing test of measuring central wavelength shifting by fiber Bragg grating.

Liang, Qianliang; Sun, Qizhen; Xu, Jun; Yu, Li; Zhang, Manliang

2011-11-01

312

Creating the Solar System step by step  

NSDL National Science Digital Library

The goal of this lesson is to encourage the clarification and understanding of the processes involved in the creation of our solar system. The lesson is part of a larger unit of astronomy which addresses the MA Science Curriculum Framework Standard concerning gravity and its' role in the formation of the planets, stars, and the solar system. The lesson is a springboard to other standards including; describing the layers of the earth lithosphere, mantle, and core, and differentiating among radiation, convection, and conduction- heat transfer in the earth's system. The lesson begins with a lecture describing the complex process of creation from molecular cloud to planetesimals to planets to organized solar system. The lecture is followed up with a draw/write activity in which the students are required to put in pictures or writing their interpretation of the series of steps that have been presented. The activity involves the students, working in pairs to create a visual model of one of the steps in the series. Their phase in the process will be assigned and the class as a whole will be creating a timeline in entirety. It is important to make clear that this process is not linear but certain steps overlap. In addition, this process is ongoing and is occurring in many places in the universe even today.

Curtin, Karen

313

Chemical Sensing Using Fiber Cavity Ring-Down Spectroscopy  

PubMed Central

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

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

2010-01-01

314

Post-exposed fiber Bragg gratings  

NASA Astrophysics Data System (ADS)

This thesis explains the development and characterization of a novel technique to fabricate weak fiber Bragg gratings for highly specific multi-element sensor arrays. This method, termed the "rescan technique," involves re-exposing a local region of a grating to fringeless ultraviolet light to "trim" unwanted portions of the reflection spectrum. The spectral effects that result from a rescan can only be adequately described by inventing the concept of a three-dimensional index growth surface, where induced index is a function of both the writing intensity and the exposure time. Using this information, it is possible to predict the spectral response of a rescanned grating using a numerical model. For our model, we have modified the piecewise-uniform approach to include coefficients within the coupled-mode formulism that imitate the same scattering properties as the actual grating. By taking high accuracy measurements of the refractive index change in germanosilicate fiber, we have created the necessary 3D map of photoinduced index to accurately model gratings and their post-exposure spectra. We will also demonstrate that optical fiber exhibits what we call "exposure history"; the final index change in a region depends on the previous exposures conditions.

Miller, Gary A.

315

STEP Experiment Requirements  

NASA Technical Reports Server (NTRS)

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

Brumfield, M. L. (compiler)

1984-01-01

316

Tools for Printing Indexes  

Microsoft Academic Search

SUMMARY This paper describes a set of programs for processing and printing the index for a book or a manual. The input consists of lines containing index terms and page numbers. The programs collect multiple occurrences of the same terms, compress runs of page numbers, create permutations (e.g., 'index, book' from 'book index'), and sort them into proper alphabetic order.

Jon Louis Bentley; Brian W. Kernighan

1988-01-01

317

KSC Construction Cost Index  

NASA Technical Reports Server (NTRS)

Kennedy Space Center cost Index aids in conceptual design cost estimates. Report discusses development of KSC Cost Index since January 1974. Index since January 1974. Index provides management, design engineers, and estimators an up-to-data reference for local labor and material process. Also provides mount and rate of change in these costs used to predict future construction costs.

Brown, J. A.

1983-01-01

318

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

319

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

320

Quaker Resources Online Index.  

ERIC Educational Resources Information Center

The Quaker Resources Online Index is a World Wide Web-based index, including author, title, subject, and meeting indexes, that provides access to Quaker materials available on the Web. Given the current failings and shortcomings of search engines and automated key word searches, this index brings together information from a variety of sources and…

Beke-Harrigan, Heidi

321

Optical fiber liquid-level sensor using a surface plasmon resonance  

Microsoft Academic Search

A liquid-level optical fiber sensor based on refractive index sensitivity of surface plasmon resonance has been proposed and demonstrated. The sensor can continuously measure a wide distance range in the liquids with a single fiber element, since the sensing interface is characterized on the fiber-cladding surface. The fiber element, having the gold film thickness of 70nm on the sensing surface,

Mitsuhiro Iga; Atsushi Seki; Kazuhiro Watanabe

2005-01-01

322

Polymer Optical Fiber Sensors for Distributed Strain Measurement and Application in Structural Health Monitoring  

Microsoft Academic Search

Polymer optical fiber (POF) sensors have the unique ability to measure high strain distributed along the fiber up to 40% using the optical time-domain reflectometry (OTDR) technique. Both, standard PMMA fibers and perfluorinated (PF) graded-index (GI) POF are introduced and evaluated in potential use and applicability. Further, distributed length change measurement based on cross-correlation analysis of the characteristic fiber signature

Sascha Liehr; Philipp Lenke; Mario Wendt; Katerina Krebber; Monika Seeger; Elke Thiele; Heike Metschies; Berhane Gebreselassie; Johannes Christian Munich

2009-01-01

323

Prediction of fiber composite mechanical behavior made simple. [using a rocket calculator  

NASA Technical Reports Server (NTRS)

The elastic properties and failure stresses of angleplied fiber composite laminates were determined using a pocket calculator. The procedure uses simple equations and appropriate graphs of elastic properties versus angle plies, and can handle all types of fiber composites including hybrids. The versatility and generality of the method is illustrated in several step-by-step numerical examples.

Chamis, C. C.

1980-01-01

324

Polarization-dependent effects in point-by-point fiber Bragg gratings enable simple, linearly polarized fiber lasers.  

PubMed

Fiber Bragg gratings inscribed with a femtosecond laser using the point-by-point (PbP) technique have polarization dependent grating strength (PDGS) and exhibit birefringence. In this paper we quantify the dependence of these two properties on the ellipticity, position in the core and size of the micro-voids at the center of each refractive index modulation. We demonstrate that the effective modal index for type II gratings written with a femtosecond laser using the PbP method must be lower than that of the pristine fiber, and for the first time associate an axis with a polarization such that the long axis of the elliptically-shaped index modulations corresponds to the slow axis of the gratings. We exploit the PDGS of two gratings used as frequency-selective feedback elements as well as appropriate coiling, to realize a linearly-polarized fiber laser with a low birefringence fiber cavity. We show that the polarization-dependent grating strength is a function of the writing pulse energy and that only gratings optimized for this property will linearly polarize the fiber laser. The fiber lasers have high extinction ratios (>30 dB) for fiber lengths of up to 10 m and very stable polarized output powers (<0.5% amplitude fluctuations) in the range of 20-65 mW at 1540 nm. This method of polarization discrimination allows the realization of highly robust and simplified linearly polarized fiber lasers. PMID:19365431

Jovanovic, Nemanja; Thomas, Jens; Williams, Robert J; Steel, M J; Marshall, Graham D; Fuerbach, Alexander; Nolte, Stefan; Tünnermann, Andreas; Withford, Michael J

2009-04-13

325

Step by Step Instructions Adding a Description of Work  

E-print Network

Step by Step Instructions Adding a Description of Work Work Group Revision 1f, August 12, 2009 In order to add a Description of Work to a Work Group Profile, you must be an Owner of that Work Group. Step 1: Log In Step 2: Go to My Work Groups Step 3: Open Work Group Step 4: Update Description of Work

326

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

E-print Network

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

Sharma, Mohit; Konar, S

2015-01-01

327

Fabrication and characterization of special microstructured fibers  

NASA Astrophysics Data System (ADS)

Microstructured optical fibers (MOFs) as a novel type of light guiding media typically combine structural elements with very different chemical and optical behavior, e.g. silica - air, silica - high refractive index glasses. The applicative potential is very manifold: devices for telecommunication, nonlinear optics, sensing devices, fiber based gas lasers, etc. We report about preparation and characterization of selected total internal reflection (TIR) guiding MOFs: Air Clad Fiber, Suspended Core Fiber and heavy metal oxide (HMO) glass core MOFs. We fabricated Air Clad Fibers with extreme air fraction. The bridge width of about 0.13 ?m corresponds to a numerical aperture (NA) of about 0.6. Suspended core fibers for evanescent sensing were prepared by pressurized drawing of arrangements of three and four capillaries. By inflating the cavities the NA was increased up to 0.68. Material combined MOFs were prepared for nonlinear application (e.g. supercontinuum generation) with lanthanum aluminum silicate glass core. Thermochemical and optical behaviors of high nonlinear core glass candidates were investigated for alumina concentration up to 20 mol% and lanthanum oxide concentration up to 24 mol% in silica matrix. The manufactured HMO glass core MOF with a La2O3 concentration of 10 mol% shows a similar background loss level like the unstructured HMO glass fiber about 1 dB/m.

Kobelke, J.; Schuster, K.; Schwuchow, A.; Litzkendorf, D.; Spittel, R.; Kirchhof, J.; Bartelt, H.

2011-05-01

328

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

329

Photonic crystal fibers  

Microsoft Academic Search

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

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

2003-01-01

330

Fiber Sensor Technology Today  

Microsoft Academic Search

Fiber sensor technologies are overviewed. Since the early 1970s, this field has been developed, on the basis of the same devices and photonic principles as fiber communication technologies. Besides simple configurations, in which the fiber acts only as a data transmission line, sophisticated configurations have also been developed, in which the fiber is used as a device to realize unique

Kazuo Hotate

2006-01-01

331

Photonic crystal fiber coupler  

Microsoft Academic Search

Fiber couplers made with photonic crystal fibers (PCF) are reported. Two types of PCF were fabricated by means of stacking a group of silica tubes around a silica rod and drawing them. The fiber couplers were made by use of the fused biconical tapered method. With a fiber that had five hexagonally stacked layers of air holes, a 33\\/67 coupling

Byeong Ha Lee; Joo Beom Eom; Jinchae Kim; Dae Seung Moon; Un-Chul Paek; Gil-Ho Yang

2002-01-01

332

Fiber optic connector  

DOEpatents

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

Rajic, S.; Muhs, J.D.

1996-10-22

333

Fiber optic temperature sensor  

NASA Technical Reports Server (NTRS)

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

Sawatari, Takeo (Inventor); Gaubis, Philip A. (Inventor); Mattes, Brenton L. (Inventor); Charnetski, Clark J. (Inventor)

1999-01-01

334

Fiber optic temperature sensor  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

335

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

336

Coatings for graphite fibers  

NASA Technical Reports Server (NTRS)

Graphite fibers released from composites during burning or an explosion caused shorting of electrical and electronic equipment. Silicon carbide, silica, silicon nitride and boron nitride were coated on graphite fibers to increase their electrical resistances. Resistances as high as three orders of magnitude higher than uncoated fiber were attained without any significant degradation of the substrate fiber. An organo-silicone approach to produce coated fibers with high electrical resistance was also used. Celion 6000 graphite fibers were coated with an organo-silicone compound, followed by hydrolysis and pyrolysis of the coating to a silica-like material. The shear and flexural strengths of composites made from high electrically resistant fibers were considerably lower than the shear and flexural strengths of composites made from the lower electrically resistant fibers. The lower shear strengths of the composites indicated that the coatings on these fibers were weaker than the coating on the fibers which were pyrolyzed at higher temperature.

Galasso, F. S.; Scola, D. A.; Veltri, R. D.

1980-01-01

337

Active Fibers: Matching Deformable Tract Templates to Diffusion Tensor Images  

PubMed Central

Reliable quantitative analysis of white matter connectivity in the brain is an open problem in neuroimaging, with common solutions requiring tools for fiber tracking, tractography segmentation and estimation of intersubject correspondence. This paper proposes a novel, template matching approach to the problem. In the proposed method, a deformable fiber-bundle model is aligned directly with the subject tensor field, skipping the fiber tracking step. Furthermore, the use of a common template eliminates the need for tractography segmentation and defines intersubject shape correspondence. The method is validated using phantom DTI data and applications are presented, including automatic fiber-bundle reconstruction and tract-based morphometry. PMID:19457360

Eckstein, Ilya; Shattuck, David W.; Stein, Jason L.; McMahon, Katie L.; de Zubicaray, Greig; Wright, Margaret J.; Thompson, Paul M.; Toga, Arthur W.

2009-01-01

338

What the Index Medicus Indexes, and Why *  

PubMed Central

The main criterion for selecting journals for indexing in Index Medicus, and thereby largely in MEDLARS, is quality. Subject scope varies with the voiced needs of the biomedical community. The Index aims to cover the best journals in all relevant subject fields, but the percentage of journals on a subject indexed depends on the quality of each journal. Country and language coverage depends on quality, even in the case of the best journals of each, although American biases may affect such selection. While a number of guidelines exist for identifying quality journals, information necessary to apply them confidently is often difficult to obtain. The National Library of Medicine is advised by an Ad Hoc Panel on the Selection of Journals for Index Medicus, composed both of NLM officers and extramural members. Criticism has been voiced that too many titles are indexed, compared with titles actually used, but no meaningful statistics of use exist which can identify titles which should be excluded from indexing. Continuing suggestions from users regarding titles indexed would benefit everyone. PMID:5922258

Truelson, Stanley D.

1966-01-01

339

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

340

Alumina fiber strength improvement  

NASA Technical Reports Server (NTRS)

The effective fiber strength of alumina fibers in an aluminum composite was increased to 173,000 psi. A high temperature heat treatment, combined with a glassy carbon surface coating, was used to prevent degradation and improve fiber tensile strength. Attempts to achieve chemical strengthening of the alumina fiber by chromium oxide and boron oxide coatings proved unsuccessful. A major problem encountered on the program was the low and inconsistent strength of the Dupont Fiber FP used for the investigation.

Pepper, R. T.; Nelson, D. C.

1982-01-01

341

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

342

Step Barrier Scattering Model  

NSDL National Science Digital Library

The Step Barrier Scattering model shows a quantum mechanical experiment in which an incident wave (particle) traveling from the left is transmitted and reflected from a potential step at x=0.  Although the analytic solution to this standard problem is well known, its visualization shows how the incident and reflected waves form an interference pattern and how the incident wave penetrates the classically forbidden region when its energy is less than the barrier height Vâ

Christian, Wolfgang

2008-10-09

343

Large effective area fiber for DWDM systems  

NASA Astrophysics Data System (ADS)

In this paper, we analyze and propose an exponentially modulated refractive index profile for large effective area fibers with non-zero dispersion characteristics. A linear finite element method is used for computing the modal propagation characteristics and modal field distributions of an optical fiber having an arbitrary refractive index profile. The core effective area and the dispersion characteristics are optimized by optimizing a constraint objective function in the profile parametric space. The optimum refractive index profile can give a core effective area of 110 micrometers 2. The dispersion varies linearly from 2.5 ps/nm-km to 4.5 ps/nm-km with a dispersion slope of 0.065 ps/nm2-km over 1.53 micrometers -1.56 micrometers wavelength range. Manufacturing tolerance analysis for the designed fiber characteristics is also studied. The bending loss for the fiber is around 0.003 dB/m for a bend radius of 100mm.

Survaiya, Sunil P.; Shevgaonkar, R. K.

2001-09-01

344

Optical D-fiber-based volatile organic compound sensor  

NASA Astrophysics Data System (ADS)

A fiber-optic sensor used to detect volatile organic compounds is described. The sensor consists of a single-mode D-fiber with a 2.5 ?m polydimethylsiloxane layer. The layer is applied to the fiber flat after removal of a section of the fiber's cladding to increase evanescent interaction of the light with the layer. Absorption of volatile organic compounds into the polymer alters the refractive index of the layer, resulting in a birefringent change of the fiber. This change is observed as a shift in polarization of the light carried by the fiber. The sensor has a short length of 3 cm and a response time of around 1 s. The sensor is naturally reversible and gives an exponential response for gas and liquid concentrations of dichloromethane and acetone, respectively.

Gordon, John D.; Lowder, Tyson L.; Selfridge, Richard H.; Schultz, Stephen M.

2007-11-01

345

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

346

AGU index terms updated  

NASA Astrophysics Data System (ADS)

AGU has just completed a major revision of its Index Terms. The last major revision of the Index Terms was conducted in 1995. AGU Index Terms are used for classification of both AGU publications and meetings programs. The new Index Terms will be available for use by the AGU community on 17 December (http://www.agu.org/pubs/indexterms).A 15-person working group, representing various disciplinary groups across the AGU, was established by, and reports to, the Publications Committee. The Index Committee members consulted with their constituencies and considered term-by-term usage of the old Index Term list in creating the new list.

Kodama, Kenneth P.

2004-12-01

347

The Database Index.  

ERIC Educational Resources Information Center

Describes the characteristics of System Development Corporation's (SDC) online index to its database, "Database Index," and presents the results of various test searches to demonstrate the limitations and benefits of the new online file. (JD)

Antony, Arthur

1979-01-01

348

RF over fiber PD IF over fiber  

E-print Network

#12;#12;fRF RF over fiber PD EOM Light Source fRF fIF IF over fiber +O/E Mixer Light Source PD EOM fRF Light Source MOD DEMOD PD EOM fRF Baseband over fiber (a) (b) (c) - 1094 - 2014 #12;LOp.40 5.42 5.44 -140 -120 -100 -80 Frequency (GHz) 200 MHz LD: Laser Diode EOM: Electrooptic Modulator MMF

Choi, Woo-Young

349

A machine learning based lecture video segmentation and indexing algorithm  

NASA Astrophysics Data System (ADS)

Video segmentation and indexing are important steps in multi-media document understanding and information retrieval. This paper presents a novel machine learning based approach for automatic structuring and indexing of lecture videos. By indexing video content, we can support both topic indexing and semantic querying of multimedia documents. In this paper, our proposed approach extracts features from video images and then uses these features to construct a model to label video frames. Using this model, we are able to segment and indexing videos with accuracy of 95% on our test collection.

Ma, Di; Xie, Bingqing; Agam, Gady

2013-12-01

350

A fiber-optic density sensor for monitoring the state-of-change of a lead acid battery  

Microsoft Academic Search

A fiber-optic technique for measuring specific gravity is described. This method relies on the optical power loss exhibited by fibers bent beyond a critical radius. For such fibers the loss depends on the refractive index of the surrounding medium, which is proportional to the specific gravity of this medium. The amount of leakage can be measured and related to the

Hancke

1990-01-01

351

Observing transverse Anderson localization in random air line based fiber  

NASA Astrophysics Data System (ADS)

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

Chen, Minghan; Li, Ming-Jun

2014-02-01

352

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.

353

California Nitrogen Index  

Technology Transfer Automated Retrieval System (TEKTRAN)

The California N Index User Manual is designed to help you become accustomed to the software environment in which the N Index runs. This manual will use an example scenario to demonstrate how to use the N Index to assess nitrogen losses. The objective of this theoretical example is to guide you towa...

354

The Europe 2020 Index  

ERIC Educational Resources Information Center

This paper presents a new index to quantify, measure and monitor the progress towards the objectives of the Europe 2020 strategy. This index is based on a set of relevant, accepted, credible, easy to monitor and robust indicators presented by the European Commission at the time the strategy was launched. The internal analysis of the index shows…

Pasimeni, Paolo

2013-01-01

355

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

356

Design of fiber optic probes for laser light scattering  

NASA Technical Reports Server (NTRS)

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

Dhadwal, Harbans S.; Chu, Benjamin

1989-01-01

357

Measurement of modal dispersion in optical fiber by means of acousto-optic coupling.  

PubMed

We show that frequency-wavelength tuning characteristics of acousto-optic coupling can be used for measuring the difference of effective index, group index, and chromatic dispersion between core and cladding modes in single-mode fibers. Chromatic dispersion measurements of a 30-cm-long conventional single-mode fiber, a nonzero dispersion-shifted fiber, and a dispersion-compensating fiber with this new method are presented for the wavelength range 1500-1600 nm. Qualitative agreement with independently measured data is obtained. PMID:12656490

Li, Qun; Dashti, Pedram Zare; Tomov, I V; Lee, H P

2003-01-15

358

The second oncogenic step.  

PubMed

Three theories of the development of a malignant change which each involve two successive steps are described. Armitage, Doll (1957) proposed that two homologous chromosomes each contained a region which was critical in the control of cell division. The two steps were mutations in these regions brought about by random exposure to carcinogenic agents. Comings (1973) proposed a similar theory but the two steps were considered to be spontaneous mutatons. This paper points out that if one mutation has occurred this can become dominant in at least six ways which mostly involve chromosome translocations. The synergism between oncogenic agents and ionizing radiation and the ability to breed out high and low cancer incidence stocks of animals from a common stock can be explained on the same lines. PMID:1063921

Read, J

1976-02-11

359

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

SciTech Connect

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 H{sub 2} and CH{sub 4} evolved by scission of Si-CH{sub 3} and Si-H and by rearrangement reactions, and the second step was at 1,000--1,700 K where H{sub 2} evolved by reactions related to C atoms in the PCS main chain. H{sub 2} evolution in the first step was reduced with increasing oxygen content in the cured PCS fibers.

Sugimoto, Masaki; Seguchi, Tadao [Japan Atomic Energy Research Inst., Gunma (Japan). Takasaki Radiation Chemistry Research Establishment; Shimoo, Toship; Okamura, Kiyohito [Japan Atomic Energy Research Inst., Gunma (Japan). Takasaki Radiation Chemistry Research Establishment]|[Univ. of Osaka Prefecture, Sakai (Japan)

1995-04-01

360

Ceramic fiber reinforced filter  

DOEpatents

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

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

1991-01-01

361

Moisture Properties of Coolmax Fiber Blended with Regenerated Cellulose Fibers  

Microsoft Academic Search

7 kinds of Coolmax fibers blended with regenerated cellulose fibers were chosen. Static moisture transfer and moisture comfort ability were tested and analyzed. The regenerated cellulose fibers were pearl fiber, tencel, modal, especially the pearl fiber was a creative cellulose fiber. The experimental contained wicking effect test, drop-proliferation test, regains test, water vapor permeability test, permeability test and quick dry

Dongping Li; Mai Ni

2009-01-01

362

On noninferior performance index vectors  

Microsoft Academic Search

The noninferior vector index problem of optimal control theory is investigated in an effort to establish some basic properties of the noninferior index surface in the generalN-dimensional index problem. The vector performance index problem is first converted to a family of scalar index problems by forming an auxiliary scalar index as a function of the vector index and a vector

R. W. Reid; S. J. Citron

1971-01-01

363

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

364

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.

365

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

366

Fiber bundle fluorescence endomicroscopy  

E-print Network

An improved design for fiber bundle fluorescence endomicroscopy is demonstrated. Scanned illumination and detection using coherent fiber bundles with 30,000 elements with 3 ?m resolution enables high speed imaging with ...

Tsai, Tsung-Han

367

Soluble vs. insoluble fiber  

MedlinePLUS

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

368

Fiber Optics 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

369

Fiber Optics Instrumentation Development  

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

370

Multimaterial fiber electronics  

E-print Network

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

Lestoquoy, Guillaume

2014-01-01

371

Fiber draw synthesis  

E-print Network

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

Orf, Nicholas D.

372

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/

373

CONVERGING RCC STEPPED SPILLWAYS  

Technology Transfer Automated Retrieval System (TEKTRAN)

To meet current dam safety requirements, roller compacted concrete (RCC) stepped spillways has become a popular choice is dam rehabilitation. In many cases, urbanization has changed the hazard classification of these aging watershed structures, and land rights are often not obtainable for widening ...

374

Deep ultraviolet femtosecond laser tuning of fiber Bragg gratings  

NASA Astrophysics Data System (ADS)

A deep ultraviolet femtosecond laser operating at wavelength 258 nm was demonstrated to be effective in trimming fiber Bragg gratings in telecommunication fibers. A smooth tunable resonance wavelength shift of up to 0.52 nm has been observed, corresponding to a refractive index change of ˜5 × 10 -4 after an accumulated laser fluence of 63.3 kJ/cm 2 at a single pulse fluence of 124 mJ/cm 2. The ultrafast laser enhancement of ultraviolet photosensitivity response and modification of anisotropic index profile in silica fiber is a powerful technique to precise control of the performance of fiber Bragg grating devices for applications in optical filtering and polarization mode dispersion management.

Chen, Qiying; Chen, Kevin P.; Xu, Wei; Nikumb, Suwas

2006-03-01

375

Fiber pulling apparatus modification  

NASA Technical Reports Server (NTRS)

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

Smith, Guy A.; Workman, Gary L.

1992-01-01

376

Helical Fiber Amplifier  

DOEpatents

A multi-mode gain fiber is provided which affords substantial improvements in the maximum pulse energy, peak power handling capabilities, average output power, and/or pumping efficiency of fiber amplifier and laser sources while maintaining good beam quality (comparable to that of a conventional single-mode fiber source). These benefits are realized by coiling the multimode gain fiber to induce significant bend loss for all but the lowest-order mode(s).

Koplow, Jeffrey P. (Washington, DC); Kliner, Dahy (San Ramon, CA); Goldberg, Lew (Fairfax, VA)

2002-12-17

377

Fiber optic coupled optical sensor  

DOEpatents

A displacement sensor includes a first optical fiber for radiating light to a target, and a second optical fiber for receiving light from the target. The end of the first fiber is adjacent and not axially aligned with the second fiber end. A lens focuses light from the first fiber onto the target and light from the target onto the second fiber.

Fleming, Kevin J. (Albuquerque, NM)

2001-01-01

378

Oxynitride glass fibers  

NASA Technical Reports Server (NTRS)

Research at the Army Materials Technology Laboratory (AMTL) and elsewhere has shown that many glass properties including elastic modulus, hardness, and corrosion resistance are improved markedly by the substitution of nitrogen for oxygen in the glass structure. Oxynitride glasses, therefore, offer exciting opportunities for making high modulus, high strength fibers. Processes for making oxynitride glasses and fibers of glass compositions similar to commercial oxide glasses, but with considerable enhanced properties, are discussed. We have made glasses with elastic moduli as high as 140 GPa and fibers with moduli of 120 GPa and tensile strengths up to 2900 MPa. AMTL holds a U.S. patent on oxynitride glass fibers, and this presentation discusses a unique process for drawing small diameter oxynitride glass fibers at high drawing rates. Fibers are drawn through a nozzle from molten glass in a molybdenum crucible at 1550 C. The crucible is situated in a furnace chamber in flowing nitrogen, and the fiber is wound in air outside of the chamber, making the process straightforward and commercially feasible. Strengths were considerably improved by improving glass quality to minimize internal defects. Though the fiber strengths were comparable with oxide fibers, work is currently in progress to further improve the elastic modulus and strength of fibers. The high elastic modulus of oxynitride glasses indicate their potential for making fibers with tensile strengths surpassing any oxide glass fibers, and we hope to realize that potential in the near future.

Patel, Parimal J.; Messier, Donald R.; Rich, R. E.

1991-01-01

379

Microstrutured fibers with germanium doped core components  

NASA Astrophysics Data System (ADS)

The paper reports preparation and applicative aspects of two types of index guiding microstructured fibers (MOFs) with germanium doped cores. The first fiber type has a solid core with graded germanium profile. It shows a high photosensitivity compared to pure silica MOFs. We inscribed high-quality Bragg gratings with a reflectivity of 73% without hydrogen loading. The solid core germanium doped MOF was spliced with standard silica fiber. The minimum splice loss was about 1 dB at 1550 ?m wavelength. A more complex MOF type was prepared with germanium doped holey core in a silica holey cladding. The germanium doped core area includes seven holes in hexagonal arrangement with equal diameter and pitch sizes. The holey core propagates a large area annulus mode. We show the suitability of this MOF for chemical gas sensing by filling the core cavities with hydrocarbon analytes.

Kobelke, J.; Schuster, K.; Schwuchow, A.; Wang, Y.; Brückner, S.; Becker, M.; Rothhardt, M.; Kirchhof, J.; Ecke, W.; Willsch, R.; Bartelt, H.

2009-05-01

380

Liquid level measurement sensor using a long-period fiber grating  

NASA Astrophysics Data System (ADS)

A liquid level sensor based on a long-period fiber grating is proposed. The principle of this type of sensor is based on the refractive index sensitivity of long-period fiber grating. As the cladding mode's effective refractive index depends on the refractive index of the surrounding material, the resonant wavelengths of the long period fiber grating will shift when the surrounding refractive index changes. By monitoring a given attenuation band's resonant wavelength shifts, one can measure the immersed lengths of long period fiber gratings and then the liquid level. A direct liquid level measurement is demonstrated by using a long-period fiber grating which was fabricated in a photosensitive B-Ge co-doped optical fiber from Fibercore Inc. (Fibercore PS 1250/1500). The long-period fiber grating was immersed in two solutions which have different refractive indexes. A maximum shift of 7.69 nm for 50 mm of solution which has the highest refractive index has been observed.

Mao, Barerem-Melgueba; Zhou, Bin

2012-02-01

381

Optical fiber sensor based on localized surface plasmon resonance using silver nanoparticles photodeposited on the optical fiber end.  

PubMed

This paper reports the implementation of an optical fiber sensor to measure the refractive index in aqueous media based on localized surface plasmon resonance (LSPR). We have used a novel technique known as photodeposition to immobilize silver nanoparticles on the optical fiber end. This technique has a simple instrumentation, involves laser light via an optical fiber and silver nanoparticles suspended in an aqueous medium. The optical sensor was assembled using a tungsten lamp as white light, a spectrometer, and an optical fiber with silver nanoparticles. The response of this sensor is such that the LSPR peak wavelength is linearly shifted to longer wavelengths as the refractive index is increased, showing a sensitivity of 67.6 nm/RIU. Experimental results are presented. PMID:25302813

Ortega-Mendoza, J Gabriel; Padilla-Vivanco, Alfonso; Toxqui-Quitl, Carina; Zaca-Morán, Placido; Villegas-Hernández, David; Chávez, Fernando

2014-01-01

382

Optical Fiber Sensor Based on Localized Surface Plasmon Resonance Using Silver Nanoparticles Photodeposited on the Optical Fiber End  

PubMed Central

This paper reports the implementation of an optical fiber sensor to measure the refractive index in aqueous media based on localized surface plasmon resonance (LSPR). We have used a novel technique known as photodeposition to immobilize silver nanoparticles on the optical fiber end. This technique has a simple instrumentation, involves laser light via an optical fiber and silver nanoparticles suspended in an aqueous medium. The optical sensor was assembled using a tungsten lamp as white light, a spectrometer, and an optical fiber with silver nanoparticles. The response of this sensor is such that the LSPR peak wavelength is linearly shifted to longer wavelengths as the refractive index is increased, showing a sensitivity of 67.6 nm/RIU. Experimental results are presented. PMID:25302813

Ortega-Mendoza, J. Gabriel; Padilla-Vivanco, Alfonso; Toxqui-Quitl, Carina; Zaca-Morán, Placido; Villegas-Hernández, David; Chávez, Fernando

2014-01-01

383

Design concept for optical fibers with enhanced SBS threshold  

Microsoft Academic Search

We propose a criterion to predict the relative value of the stimulated Brillouin scattering (SBS) threshold in single-mode optical fibers with different refractive index profiles. We confirm our results by several representative measurements. We show that with the proper profile design one can achieve more than 3 dB increase in the SBS threshold compared to the standard single-mode optical fiber.

Andrey Kobyakov; Shiva Kumar; Dipak Q. Chowdhury; A. Boh Ruffin; Micheal Sauer; Scott R. Bickham; Raj Mishra

2005-01-01

384

Wavelength division multiplexed fiber optic absolute position encoder  

NASA Technical Reports Server (NTRS)

A wavelength division multiplexing (WDM) method for fiber optic sensors is proposed which uses a broadband light source and narrow bandpass thin film optical filter coatings on cylindrical graded index lenses. In the WDM system described here, all bits are multiplexed onto a single signal return fiber by assigning each bit a unique wavelength. A multielement photodetector array is used as the encoded position information is in parallel. Preliminary prototype test results are presented.

Park, Eric D.; Gat, Erann

1989-01-01

385

All-fiber-optic sensor for liquid level measurement  

Microsoft Academic Search

An experimental realization of a simple all-fiber-optic sensor for liquid level measurement is demonstrated. It is an intensity-modulated on-off switching sensor whose operating principle is based on the frustrated-total-internal-reflection effect caused by the refractive-index change of the surrounding medium. The basic optical element in the scheme is a sensing single fiber which serves simultaneously to transmit both the forward laser

Ilko K. Ilev; Ronald W. Waynant

1999-01-01

386

All-fiber-optic sensor for liquid level measurement  

Microsoft Academic Search

An experimental realization of a simple all-fiber-optic sensor for liquid level measurement is demonstrated. It is an intensity-modulated on–off switching sensor whose operating principle is based on the frustrated-total-internal-reflection effect caused by the refractive-index change of the surrounding medium. The basic optical element in the scheme is a sensing single fiber which serves simultaneously to transmit both the forward laser

Ilko K. Ilev; Ronald W. Waynant

1999-01-01

387

Monitoring of Temperature Fatigue Failure Mechanism for Polyvinyl Alcohol Fiber Concrete Using Acoustic Emission Sensors  

PubMed Central

The applicability of acoustic emission (AE) techniques to monitor the mechanism of evolution of polyvinyl alcohol (PVA) fiber concrete damage under temperature fatigue loading is investigated. Using the temperature fatigue test, real-time AE monitoring data of PVA fiber concrete is achieved. Based on the AE signal characteristics of the whole test process and comparison of AE signals of PVA fiber concretes with different fiber contents, the damage evolution process of PVA fiber concrete is analyzed. Finally, a qualitative evaluation of the damage degree is obtained using the kurtosis index and b-value of AE characteristic parameters. The results obtained using both methods are discussed. PMID:23012555

Li, Dongsheng; Cao, Hai

2012-01-01

388

Resonant optical nonlinearity of Nb-doped silica fiber measured with LPFG interferometer  

NASA Astrophysics Data System (ADS)

Recently, specialty fibers with various functional material doping have attracted significant attention. In this paper, we fabricated Nb-doped silica fiber and measured its resonant optical nonlinearity with long-period fiber gratings (LPFG) interferometer. The Nb-doped fiber was made with a combined MCVD and ALD technology. Then, we fabricated a pair of LPFGs and cascaded them as a Mach-Zehnder interferometer (MZI).By measuring the wavelength shifts of the interference fringe with the 532nm laser pump power, the resonant nonlinear refractive index of Nb-doped silica fiber around 1537 nm was estimated to be 8.12×10-16m2/W.

Wang, Litao; Chen, Na; Guo, Qiang; Chen, Zhenyi; Liu, Yunqi; Wang, Tingyun

2012-11-01

389

Characterization of fluorescence lifetime of Tm-doped fibers with increased quantum conversion efficiency  

NASA Astrophysics Data System (ADS)

In this work we report on the fluorescence lifetime characterization of the experimentally prepared Tm-doped silica optical fibers with increased quantum conversion efficiency (QE). Optical fibers were drawn from preforms prepared by conventional solution-doping of thulium and aluminium chlorides and by deposition of dispersed alumina nanoparticles with thulium chloride. Prepared preforms and optical fibers were characterized by means of thulium and aluminium concentrations, refractive index profiles, optical spectral attenuations (absorptions) and fluorescence lifetimes. Highly aluminium-codoped optical fiber prepared from alumina nanoparticles exhibited fluorescence lifetime of about 690 ?s, which is about 40% higher compared to the conventionally prepared Tm-doped silica fiber.

Cajzl, Jakub; Peterka, Pavel; Honzátko, Pavel; Mrázek, Jan; Podrazký, Ond?ej; Todorov, Filip; Gladkov, Petar; Sahu, Jayanta K.; Nunez-Velazquez, Miguel; Nekvindová, Pavla; Kašík, Ivan

2015-01-01

390

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 temperature fatigue loading is investigated. Using the temperature fatigue test, real-time AE monitoring data of PVA fiber concrete is achieved. Based on the AE signal characteristics of the whole test process and comparison of AE signals of PVA fiber concretes with different fiber contents, the damage evolution process of PVA fiber concrete is analyzed. Finally, a qualitative evaluation of the damage degree is obtained using the kurtosis index and b-value of AE characteristic parameters. The results obtained using both methods are discussed. PMID:23012555

Li, Dongsheng; Cao, Hai

2012-01-01

391

Relating Multi-step and Single-step Microprocessor  

E-print Network

Relating Multi-step and Single-step Microprocessor Correctness Statements Relating Multi-step and Single-step Microprocessor Correctness Statements MarkMark AagaardAagaard Nancy DayNancy Day MengMeng LouLou University of Waterloo #12;MotivationMotivation Ã?Ã?highhigh--level microprocessor correctnesslevel

Day, Nancy

392

Working with Documents Step-By-Step Procedure  

E-print Network

Proposal Management All Roles Working with Documents Step-By-Step Procedure Last updated: 11/18/11 1 of 5 http://eresearch.umich.edu Working with Documents This procedure details how to: Attach;Proposal Management All Roles Working with Documents Step-By-Step Procedure Last updated: 11/18/11 2 of 5

Shyy, Wei

393

Gradient-index lenses as flux concentrators  

NASA Astrophysics Data System (ADS)

While gradient-index lenses are usually analyzed in terms of image fidelity, they are also capable of high flux concentration. In the first part of this presentation, the simplest class of gradient-index problems is revisited. An alterative way to obtain established solution of the refractive index profiles that produce perfect imaging is derived form the method of Fermat's strings and skewness conservation. The degree to which difference classes of such spherical lenses can realize the thermodynamic limit to flux concentration is explored. An answer is also sought to the intriguing question of the extent to which the spherical gradient-index lens of the fish eye is a modified Luneburg lens optimized subject to material constraints. The second half of this presentation addresses gradient-index rod lense. Both analytic methods and computer raytrace simulations are used for a comprehensive evaluation of their concentration and collection efficiency. They appear to be well suited as concentrators for the distal end of laser fiber-optic surgical units.

Gordon, Jeffrey M.

2001-11-01

394

pH biosensor with plastic fiber optic doped with carbone nanotubes used sol-gel technique  

NASA Astrophysics Data System (ADS)

We prepare optrodes of fiber optic plastic with sol-gel technique. Suitable concentration of carbone nanotubes (CNTs), phenol red, bromophenol blue and cresol red, design optrodes with fiber optic plastic. The surface charge of silica and the refractive index, which play an important roll on the fiber, modifies the conditions of light propagation into the plastic optical fiber. We use the transmittance to measure the pH of a solution or fluid in a range between 3 and 9.

Alvarado-Méndez, E.; Flores-Rangel, S. D.; Hernández-Cruz, D.; Trejo-Durán, M.; Andrade-Lucio, J. A.; Rojas-Laguna, R.; Estudillo-Ayala, J. M.; Vargas-Rodríguez, E.; Mata Chávez, R. I.; García-Hernández, M. G.

2010-10-01

395

Dopants concentration effects on the wavelength shift of long-period fiber gratings used as liquid level detectors  

Microsoft Academic Search

Two liquid level sensors based on different long-period fiber gratings are proposed and compared. The long-period gratings have the same characteristics (length, grating period) but are fabricated in different optical fibers (photosensitive B-Ge codoped optical fibers with different dopants concentrations). The principle of this type of sensor is based on the refractive index sensitivity of long-period fiber gratings. By monitoring

Barerem-Melgueba Mao; Bin Zhoua

2011-01-01

396

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

397

Fiber coating method  

DOEpatents

A coating is applied to reinforcing fibers arranged into a tow by coaxially aligning the tow with an adjacent separation layer and winding or wrapping the tow and separation layer onto a support structure in an interleaved manner so that the separation layer separates a wrap of the tow from an adjacent wrap of the tow. A coating can then be uniformly applied to the reinforcing fibers without defects caused by fiber tow to fiber tow contact. The separation layer can be a carbon fiber veil.

Corman, Gregory Scot (Ballston Lake, NY)

2003-04-15

398

Fiber coating method  

DOEpatents

A coating is applied to reinforcing fibers arranged into a tow by coaxially aligning the tow with an adjacent separation layer and winding or wrapping the tow and separation layer onto a support structure in an interleaved manner so that the separation layer separates a wrap of the tow from an adjacent wrap of the tow. A coating can then be uniformly applied to the reinforcing fibers without defects caused by fiber tow to fiber tow contact. The separation layer can be a carbon fiber veil.

Corman, Gregory Scot (Ballston Lake, NY)

2001-01-01

399

Multimaterial Acoustic Fibers  

NASA Astrophysics Data System (ADS)

The emergence of multimaterial fibers that combine a multiplicity of solid materials with disparate electrical, optical, and mechanical properties into a single fiber presents new opportunities for extending fiber applications well beyond optical transmission. Fiber reflectors, thermal detectors, photodetectors, chemical sensors, surface-emitting fiber lasers, fiber diodes, and other functional fiber devices have been demonstrated with this approach. Yet, throughout this development and indeed the development of fibers in general, a key premise has remained unchanged : that fibers are essentially static devices incapable of controllably changing their properties at high frequencies. Unique opportunities would arise if a rapid, electrically-driven mechanism for changing fiber properties existed. A wide spectrum of hitherto passive fiber devices could at once become active with applications spanning electronics, mechanics, acoustics, and optics, with the benefits of large surface-area, structural robustness, and mechanical flexibility. This thesis addresses the challenges and opportunities associated with the realization of electromechanical transduction in fibers through the integration of internal piezoelectric and electrostrictive domains. The fundamental challenges related to the fabrication of piezoelectric devices in fiber form are analyzed from a materials perspective, and candidate materials and geometries are selected that are compatible with the thermal drawing process. The first realization of a thermally drawn piezoelectric fiber device is reported and its piezoelectric response is established over a wide range of frequencies. The acoustic properties of piezoelectric fiber devices are characterized and related to their mechanical and geometric properties. Collective effects in multi-fiber constructs are discussed and demonstrated by the realization of a linear phased array of piezoelectric fibers capable of acoustic beam steering. High strain actuation capabilities in a fiber are demonstrated based on the integration of a highly electrostrictive relaxor ferroelectric polymer. The potential of this approach to realize integrated microelectromechanical systems in fibers is illustrated by the fabrication of a hybrid fiber comprising an electrostrictive device and an adjacent Fabry-Perot optical filter. Amplitude modulation of the light reflected from the Fabry-Perot cavity is demonstrated through electric field induced tuning of the cavity resonance. (Copies available exclusively from MIT Libraries, libraries.mit.edu/docs - docs@mit.edu)

Chocat, Noemie

400

Superconducting tin core fiber  

NASA Astrophysics Data System (ADS)

In this study, we demonstrated superconductivity in a fiber with a tin core and fused silica cladding. The fibers were fabricated via a modified melt-draw technique and maintained core diameters ranging from 50-300 microns and overall diameters of 125-800 microns. 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 3.8 K. The synthesis route and fiber design are perquisites to ongoing research dedicated all-fiber optoelectronics and the relationships between superconductivity and the material structures, as well as corresponding fabrication techniques.

Homa, Daniel; Liang, Yongxuan; Hill, Cary; Kaur, Gurbinder; Pickrell, Gary

2015-01-01

401

All-fiber Mach-Zehnder interferometers for sensing applications.  

PubMed

We propose and demonstrate a thinned fiber based Mach-Zehnder interferometer for multi-purpose sensing applications. The sensor head is formed by all-fiber in-line singlemode-multimode-thinned-singlemode (SMTS) fiber structure, only using the splicing method. The principle of operation relies on the effect that the thinned fiber cladding modes interference with the core mode by employing a multimode fiber as a mode coupler. Experimental results showed that the liquid refractive index information can be simultaneously provided from measuring the sensitivity of the liquid level. A 9.00 mm long thinned fiber sensor at a wavelength of 1538.7228 nm exhibits a water level sensitivity of -175.8 pm/mm, and refractive index sensitivity as high as -1868.42 (pm/mm)/RIU, respectively. The measuring method is novel, for the first time to our knowledge. In addition, it also demonstrates that by monitoring the wavelength shift, the sensor at a wavelength of 1566.4785 nm exhibits a refractive index sensitivity of -25.2935 nm/RIU, temperature sensitivity of 0.0615 nm/°C, and axial strain sensitivity of -2.99 pm/??, respectively. Moreover, the sensor fabrication process is very simple and cost effective. PMID:22565734

Li, Lecheng; Xia, Li; Xie, Zhenhai; Liu, Deming

2012-05-01

402

Wide range optofluidically tunable multimode interference fiber laser  

NASA Astrophysics Data System (ADS)

An optofluidically tunable fiber laser based on multimode interference (MMI) effects with a wide tuning range is proposed and demonstrated. The tunable mechanism is based on an MMI fiber filter fabricated using a special fiber known as no-core fiber, which is a multimode fiber (MMF) without cladding. Therefore, when the MMI filter is covered by liquid the optical properties of the no-core fiber are modified, which allow us to tune the peak wavelength response of the MMI filter. Rather than applying the liquid on the entire no-core fiber, we change the liquid level along the no-core fiber, which provides a highly linear tuning response. In addition, by selecting the adequate refractive index of the liquid we can also choose the tuning range. We demonstrate the versatility of the optofluidically tunable MMI filter by wavelength tuning two different gain media, erbium doped fiber and a semiconductor optical amplifier, achieving tuning ranges of 55 and 90?nm respectively. In both cases, we achieve side-mode suppression ratios (SMSR) better than 50?dBm with output power variations of less than 0.76?dBm over the whole tuning range.

Antonio-Lopez, J. E.; Sanchez-Mondragon, J. J.; LiKamWa, P.; May-Arrioja, D. A.

2014-08-01

403

Multioctave infrared supercontinuum generation in large-core As2S3 fibers.  

PubMed

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

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

2014-11-15

404

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.

United Nations

405

Passive and active data porting to composite integrated optical fibers via integrated optics  

NASA Astrophysics Data System (ADS)

Novel methods for remote coupling of light into optical fibers embedded in composite structures has been explored. A passive technique in which light is coupled via a 45° angled mirror manufactured at the end of a plastic optical fiber (POF) was explored as well as an active technique in which a dye-impregnated POF was used to couple light to immersed fibers without physical connectorization. The fibers were immersed in fluids with different refractive indices to determine the effect of index on the coupling efficiency and simulate optical fibers embedded in a polymer composite. The passive technique proved much more efficient with a maximum efficiency of 91.4% achieved in an index of 1.33. The dye-impregnated POF was much less efficient with typical values ranging from 1%-2% for various indexes.

Teitelbaum, M. E.; O'Brien, D. J.; Wetzel, E. D.; Goossen, K. W.

2008-03-01

406

Fiber optic vibration sensor  

DOEpatents

A fiber optic vibration sensor utilizes two single mode optical fibers supported by a housing with one optical fiber fixedly secured to the housing and providing a reference signal and the other optical fiber having a free span length subject to vibrational displacement thereof with respect to the housing and the first optical fiber for providing a signal indicative of a measurement of any perturbation of the sensor. Damping or tailoring of the sensor to be responsive to selected levels of perturbation is provided by altering the diameter of optical fibers or by immersing at least a portion of the free span length of the vibration sensing optical fiber into a liquid of a selected viscosity.

Dooley, Joseph B. (Harriman, TN); Muhs, Jeffrey D. (Lenoir City, TN); Tobin, Kenneth W. (Harriman, TN)

1995-01-01

407

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

408

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

409

Fiber optic vibration sensor  

DOEpatents

A fiber optic vibration sensor utilizes two single mode optical fibers supported by a housing with one optical fiber fixedly secured to the housing and providing a reference signal and the other optical fiber having a free span length subject to vibrational displacement thereof with respect to the housing and the first optical fiber for providing a signal indicative of a measurement of any perturbation of the sensor. Damping or tailoring of the sensor to be responsive to selected levels of perturbation is provided by altering the diameter of optical fibers or by immersing at least a portion of the free span length of the vibration sensing optical fiber into a liquid of a selected viscosity. 2 figures.

Dooley, J.B.; Muhs, J.D.; Tobin, K.W.

1995-01-10

410

Nano-fiber diameters as liquid concentration sensors  

NASA Astrophysics Data System (ADS)

Manufacturing technologies of nano-fiber sensors offer a number of approved properties of optical fiber sensors utilized in various sensory applications. The nano-fiber sensor is utilized to sense the difference in the concentration of D-glucose in double-distilled deionized water and to measure the refractive index (RI) of a sugar solution. Our proposed method exhibited satisfactory capability based on bimolecular interactions in the biological system. The response of the nano-fiber sensors indicates a different kind of interaction among various groups of AAs. These results can be interpreted in terms of solute-solute and solute-solvent interactions and the structure making or breaking ability of solutes in the given solution. This study utilized spectra photonics to measure the transmission of light through different concentrations of sugar solution, employing cell cumber and nano-optical fibers as sensors.

Chyad, Radhi M.; Mat Jafri, Mohd Zubir; Ibrahim, Kamarulazizi

2013-05-01

411

Fiber Optic Switch For Broadband Emission Spectroscopy  

NASA Technical Reports Server (NTRS)

Many high-temperature processes comprise large-scale phenomena. Studying spatial and temporal correlations of physical processes between several locations within characteristic scales provides desired information on macroscopic physical processes. Achieved with emission spectroscopy by use of multiple optical fibers. Simultaneous coupling of light from these fibers into single available spectrometer and/or monochromator not accomplished without added expense of two-dimensional array and increased complexity of calibration. Quasi-simultaneous coupling, while maintaining optimum alignment and maximum throughput of broadband emission, achieved by use of fiber optic multiscanner. Instrument used successfully in study of frozen-flow losses internal to flow of plasma inside nozzle of arc jet. Instrument includes two hollow disks of different sizes and stepping motor.

De Groot, Wim; Myers, Roger; Zube, Dieter

1994-01-01

412

SMS fiber structure for temperature measurement using an OTDR  

NASA Astrophysics Data System (ADS)

A singlemode-multimode-singlemode (SMS) fiber structure for temperature measurement using an optical time domain reflectometer (OTDR)-based interrogation system is proposed. A temperature measurement range of 40 °C-195 °C with a resolution of 0.12 °C and a linearity of 0.992 could be achieved for the multimode fiber (MMF) graded index with a length of 60 mm. It was also demonstrated that two-point temperature measurement with two SMS fiber structures as temperature sensors could be made. The proposed temperature measurement system offered a high resolution and also benefited from a simple configuration with a capability of multi-point temperature measurement.

Hatta, A. M.; Indriawati, K.; Bestariyan, T.; Humada, T.; Sekartedjo

2013-09-01

413

Antiresonant reflecting microstructured optical fibers for the mid-infrared  

NASA Astrophysics Data System (ADS)

We report on the demonstration of silver halide (AgClxBr1-x) microstructured optical fibers (MOFs) based on the antiresonant reflecting optical waveguide (ARROW) model, for the mid-infrared. MOFs with low index core surrounded by an octagonal structure of high index rods were designed and fabricated. The fibers exhibited transmission spectra with narrow stopband frequencies in the 9-11 ?m range. The location of the transmission minima matched the theoretical predictions by the ARROW model. The measured propagation losses in the maximum transmission range were ˜60 dB/m. Imaging the output of the MOFs at the passband wavelengths revealed single mode guidance in the core.

Lewi, T.; Ofek, J.; Katzir, A.

2013-03-01

414

Tunable multi-wavelength fiber lasers based on novel fiber-optic components  

NASA Astrophysics Data System (ADS)

Multi-wavelength laser sources are of great interest in optical communications, spectroscopic measurements, optical sensors, and biomedical images and diagnoses. As the number and complexity of wavelength division multiplexing channels increase, multi-wavelength generation technology becomes more important in the optical communication systems. However, the tunability and application of multi-wavelength output of conventional systems remain quite limited. In this dissertation, tunable multi-wavelength lasers are proposed to achieve simultaneous multiple wavelength lasing in a single all-optical fiber laser cavity. The single cavity laser system is composed of two main fiber optic sections that include (1) comb filter section to define multiple lasing wavelengths, and (2) cavity section to provide the gain at several wavelengths simultaneously. As a comb filter, cascaded long period fiber gratings interferometer and fiber Sagnac loop interferometer are theoretically and experimentally demonstrated for fast wavelength tuning and discrete channel space tuning. To fabricate high performance fiber gratings devices, specially designed optical fibers are fabricated with a novel method, and the mechanism of refractive index change is discussed rigorously. In regard to the polarization dependency of polarization-maintaining fiber, the absolute wavelength and relative channel space of transmission spectrum are controlled by adjusting the effective fiber length in Sagnac loop filter. Multi-wavelength lasings are demonstrated in both erbium-doped fiber ring cavity and Raman fiber ring cavity configurations. In the case of the erbium-doped fiber ring laser, both continuous wave and pulsed mode outputs are considered for various laser operations and applications. Several designs of fiber Raman laser ring laser are developed based on a broad generation of cascaded Raman Stokes wave and nonlinear phenomena. Detailed numerical models are analysed to optimise the laser cavity. Absolute wavelength tuning and the relative channel space tuning of multi-lasing peaks are demonstrated through the control of optical fiber comb filter, and other characteristics of the lasers are demonstrated. The applications of tunable multi-wavelength laser are also discussed for an optical soliton pulse-train generator, an interleaved wavelength-selective switch, a fast wavelength-swept laser, a biomedical optical coherence tomography source, a temperature and strain sensor, and a differential absorption lidar.

Kim, Chang-Seok

415

Graded-index planar waveguide solar concentrator.  

PubMed

Planar waveguides are useful to transport, concentrate and distribute light uniformly over large dimensions. Their capacity to collect and gather light efficiently over a large distance is interesting for many applications, like backlighting and solar concentration. For these reasons, the possibility of making them even more efficient could be of considerable interest for the community. The observation of the ray path inside a graded-index (GRIN) fiber inspired the development of a similar technology inside planar waveguides. In this Letter, we show that it has the potential to dramatically increase the efficiency of planar waveguide-based solar concentrators or backlighting using GRIN planar waveguides. PMID:24690705

Bouchard, Sébastien; Thibault, Simon

2014-03-01

416

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.

Lipinski, Ronald J. [Advanced Nuclear Concepts Department, Sandia National Laboratories, P.O Box 5800, Albuquerque, NM 87185 (United States); Hensen, Danielle L. [Risk and Reliability Department Sandia National Laboratories, P.O Box 5800, Albuquerque, NM 87185 (United States)

2008-01-21

417

Temperature- and strain-independent torsion sensor using a fiber loop mirror based on suspended twin-core fiber.  

PubMed

In this Letter, we present a fiber loop mirror configuration based on a suspended twin-core fiber for sensing applications. Using the suspended twin-core fiber, the fringe pattern is due to the differential optical patch of the light in the two cores associated with a refractive index difference of approximately 10(-3), which indicates an advantage of this approach compared with those based on high-birefringent fibers, namely, the possibility of using a small length of fiber. The sensing configuration was characterized for torsion, temperature, and strain. Using the fast Fourier transform technique, it is possible to obtain measurand-induced amplitude variations of the fringe pattern. The results obtained indicate the viability of a temperature- and strain-independent torsion sensor. PMID:20717454

Frazão, Orlando; Silva, Ricardo M; Kobelke, Jens; Schuster, Kay

2010-08-15

418

Mechanical behavior of lightweight thermoplastic fiber–metal laminates  

Microsoft Academic Search

Lightweight thermoplastic-based fiber–metal laminates were developed based on self-reinforced polypropylene and glass fiber-reinforced polypropylene composite materials and an aluminum alloy 2024-T3. The laminates were manufactured using a fast one-step cold press manufacturing procedure. The mechanical behavior of the laminates was then investigated under tensile and fatigue loading conditions. The tensile properties of the plain aluminum, the composite materials and the

G. Reyes; H. Kang

2007-01-01

419

Decay time and light yield measurements for plastic scintillating fibers  

Microsoft Academic Search

We have studied light production and propagation in three different samplesof plastic scintillating fibers manufactured by Kyowa Gas Co.: SCSF-81, SCSF-38 and SCSF-38 with afquenching additive. The emissio time distribution is described phenomenologically by a fast two-step scintillation process and an additional slow component, the time constants of which are determined. The light yield from the fibers is measured as

C. M. Hawkes; M. Kuhlen; B. Milliken; R. Stroynowski; E. Wicklund; T. Shimizu; O. Shinji

1990-01-01

420

Carbon fibers from electrospun polymeric phenolic resin precursors  

Microsoft Academic Search

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

Diane L. Gee

2003-01-01

421

Fabrication and Measurement of Few-Mode Cr4+:YAG Crystal Fibers.  

E-print Network

??In this study, a few-mode chromium doped yttrium aluminum garnet(Cr4+:YAG) crystalline fiber with high-index glass cladding has been demonstrated by employing laser heated pedestal growth(LHPG)… (more)

Chuang, Chih-Wei

2013-01-01

422

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. PMID:22408510

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

2009-01-01

423

Gradient index retroreflector  

DOEpatents

A retroreflector is formed of a graded index lens with a reflective coating at one end. The lens has a length of an odd multiple of a quarter period thereof. Hexagonally shaped graded index lenses may be closely packed in an array to form a retroreflecting surface.

Layne, Clyde B. (Livermore, CA)

1988-01-01

424

A Computer Calculated Index.  

ERIC Educational Resources Information Center

The Gunning Fog Index of readability indicates both the average length of words and the difficult words (three or more syllables) in written material. This document describes a business communication course at Wayne State University in which students calculate the Gunning Fog Index of two of their writing assignments with the aid of the…

Brown, Francis J.

425

Universal Index System  

NASA Technical Reports Server (NTRS)

The Universal Index System (UIS) is an index management system that uses a uniform interface to solve the heterogeneity problem among database management systems. UIS provides an easy-to-use common interface to access all underlying data, but also allows different underlying database management systems, storage representations, and access methods.

Kelley, Steve; Roussopoulos, Nick; Sellis, Timos; Wallace, Sarah

1993-01-01

426

Consumer Price Index  

NSDL National Science Digital Library

According to the Consumer Price Index for March 2000, the Consumer Price Index for All Urban Consumers (CPI-U) rose 0.8 percent in March. This is a 3.7 percent increase since March 1999. After seasonal adjustments, the CPI-U rose 0.7 percent, after a 0.5 percent increase in February 2000.

427

Exploring Volumetrically Indexed Cups  

ERIC Educational Resources Information Center

This article was inspired by a set of 12 cylindrical cups, which are volumetrically indexed; that is to say, the volume of cup "n" is equal to "n" times the volume of cup 1. Various sets of volumetrically indexed cylindrical cups are explored. I demonstrate how this children's toy is ripe for mathematical investigation, with connections to…

Jones, Dustin L.

2011-01-01

428

The Users of Indexes.  

ERIC Educational Resources Information Center

Problems of indexing and index use lie at the heart of information use. They determine maximum possible use of information systems and sources, affect communication with users, influence the use of retrieved documents, and should form a more important field of research than past history indicates. Previous research provides some clues to user…

Beal, Christina

429

EMMSE Media Index.  

ERIC Educational Resources Information Center

This index provides a topical taxonomy of media which have been selected for their relevance in the teaching of materials science and engineering. The index is keyed to a matrix which matches topical and/or class material with six classifications of media: print, 16mm film, super 8 film, slide/tape, videotape, and other (including interactive…

Hewitt, Clifford A., Comp.; McKinstry, Herbert A., Comp.

430

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 ...

431

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 ...

432

AUDIO INDEXING Gal RICHARD  

E-print Network

AUDIO AUDIO INDEXING Gaël RICHARD Ecole Nationale Supérieure des Télécommunications (ENST) Speech and Image Processing Department 37-39, rue Dareau, 75014 Paris, France #12;Audio Indexing Gaël RICHARD Ecole audio data available nowadays and the spread of its use as a data source in many applications

Richard, Gaël

433

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

434

On creep of unidirectional fiber composites with fiber damage  

Microsoft Academic Search

The roles of broken fibers in the creep of continuous fiber reinforced composites are studied theoretically. The unidirectional fiber composite is modeled using a cylindrical cell consisting of a single broken fiber and a shell of the fiber material embedded in an elastic-power law creeping matrix. The time-dependent creep behavior of the composite is calculated using finite elements; both longitudinal

Y. Song; G. Bao; C. Y. Hui

1995-01-01

435

Photonic crystal fibers based on chalcogenide glasses  

NASA Astrophysics Data System (ADS)

Chalcogenide glasses are known for their large transparency in the mid-infrared and their high refractive index (>2). They present also a high non-linear coefficient (n2), 100 to 1000 times larger than for silica, depending on the composition. An original way to obtain single-mode fibers is to design microstructured optical fibers (MOFs). These fibers present unique optical properties thanks to the high degree of freedom in the design of their geometrical structure. A classical method to realize MOFs is the stack-and-draw technique. However, with chalcogenide glasses, that technique induces optical losses at the interfaces in the stack of capillaries. In consequence, we have developed a new casting method to fabricate the chalcogenide preform. This method permits to obtain optical losses around 1 dB/m at 1.55 ?m and 0.3 dB/m in the mid-IR region. Various chalcogenide microstructured fibers working in the IR range were prepared in order to take advantage of the non-linear properties of these glasses and of the original MOF properties. For example, fibers with small effective mode area (Aeff < 10 ?m2) have been realized to exacerbate the non-linear optical properties. Such fibers will find applications for signal regeneration in telecom, and for the generation of supercontinuum sources. On the contrary, for military applications in the 3-5 and 8-12 ?m windows, large effective mode area and single mode fibers have been designed to permit the propagation of high-power gaussian laser beams.

Adam, J. L.; Troles, J.; Brilland, L.; Coulombier, Q.; Chartier, T.

2010-10-01

436

Low-temperature hermetic sealing of optical fiber components  

DOEpatents

A method for manufacturing low-temperature hermetically sealed optical fiber components is provided. The method comprises the steps of: inserting an optical fiber into a housing, the optical fiber having a glass core, a glass cladding and a protective buffer layer disposed around the core and cladding; heating the housing to a predetermined temperature, the predetermined temperature being below a melting point for the protective buffer layer and above a melting point of a solder; placing the solder in communication with the heated housing to allow the solder to form an eutectic and thereby fill a gap between the interior of the housing and the optical fiber; and cooling the housing to allow the solder to form a hermetic compression seal between the housing and the optical fiber. 5 figs.

Kramer, D.P.

1996-10-22

437

Fiber optic temperature sensor  

NASA Technical Reports Server (NTRS)

A temperature sensor has been developed that utilizes the temperature dependent absorption of a rare earth doped optical fiber. The temperature measurement is localized at a remote position by splicing a short section of the rare earth fiber into a loop of commercial data communication fiber that sends and returns an optical probe signal to the temperature sensitive section of fiber. The optical probe signal is generated from two different wavelength filtered LED sources. A four port fiber optic coupler combines the two separate wavelength signals into the fiber sensing loop. Time multiplexing is used so that each signal wavelength is present at a different time. A reference signal level measurement is also made from the LED sources and a ratio taken with the sensor signal to produce a transmission measurement of the fiber loop. The transmission is affected differently at each wavelength by the rare earth temperature sensitive fiber. The temperature is determined from a ratio of the two transmission measurements. This method eliminates any ambiguity with respect to changes in signal level in the fiber loop such as mating and unmating optical connectors. The temperature range of the sensor is limited to about 800 C by the temperature limit fo the feed fibers.

Morey, W. W.; Glenn, W. H.; Snitzer, E.

1983-01-01

438

Coatings for Graphite Fibers  

NASA Technical Reports Server (NTRS)

Several approaches for applying high resistance coatings continuously to graphite yarn were investigated. Two of the most promising approaches involved (1) chemically vapor depositing (CVD) SiC coatings on the surface of the fiber followed by oxidation, and (2) drawing the graphite yarn through an organo-silicone solution followed by heat treatments. In both methods, coated fibers were obtained which exhibited increased electrical resistances over untreated fibers and which were not degraded. This work was conducted in a previous program. In this program, the continuous CVD SiC coating process used on HTS fiber was extended to the coating of HMS, Celion 6000, Celion 12000 and T-300 graphite fiber. Electrical resistances three order of magnitude greater than the uncoated fiber were measured with no significant degradation of the fiber strength. Graphite fibers coated with CVD Si3N4 and BN had resistances greater than 10(exp 6) ohm/cm. Lower pyrolysis temperatures were used in preparing the silica-like coatings also resulting in resistances as high as three orders of magnitude higher than the uncoated fiber. The epoxy matrix composites prepared using these coated fibers had low shear strengths indicating that the coatings were weak.

Galasso, F. S.; Scola, D. A.; Veltri, R. D.

1980-01-01

439

Space Flight Qualification on a Multi-Fiber Ribbon Cable and Array Connector Assembly  

Microsoft Academic Search

ABSTRACT NASA’s Goddard Space Flight Center (GSFC) cooperatively with Sandia National Laboratories completed,a series of tests on three separate configurations of multi-fiber ribbon cable and MTP connector assemblies. These tests simulate the aging process of components,during launch,and long-term space environmental exposure. The multi-fiber ribbon cable assembly was constructed of non-outgassing materials, with radiation-hardened, graded index 100\\/140-micron optical fiber. The results

Xiaodan Jin; Melanie N. Ott; Frank V. Larocca; Ronald M. Baker; Bianca E. N. Keeler; Patricia R. Friedberg; Richard F. Chuska; Mary C. Malenab; L Shawn

440

Mechanism analysis on biofouling detection based on optical fiber sensing technique  

Microsoft Academic Search

More attention is paid to on-line monitoring of biofouling in industrial water process systems. Based on optical fiber sensing technology, biofouling detection mechanism is put forward in the paper. With biofouling formation, optical characteristics and the relation between light intensity and refractive index studied, schematic diagram of optical fiber self-referencing detecting system and technological flowchart are presented. Immunity to electromagnetic

Huiping Ma; Feng Yuan; Yongmeng Liu; Xiuzhen Jiang

2010-01-01

441

Analyzing Multi-Fiber Reconstruction in High Angular Resolution Diffusion Imaging using the Tensor Distribution Function  

E-print Network

Analyzing Multi-Fiber Reconstruction in High Angular Resolution Diffusion Imaging using the Tensor. Index Terms-- High Angular Resolution Diffusion Imaging, Tensor Distribution Function, multi-fiber protocols with higher angular and radial resolutions, such as the high- angular resolution diffusion imaging

Thompson, Paul

442

Multimode fibered photodetectors for high-power high-speed applications beyond 10 Gb\\/s  

Microsoft Academic Search

We report the development of top illuminated InGaAs photodetectors pigtailed to 50 mum core multimode (MM) fibers. These PIN diodes, in conjunction with low dispersion graded index MM fibers, allow for low cost and rugged solutions for high speed digital and analog applications. Our PIN diodes have previously demonstrated high optical power handling capability at large signal bandwidths. Coupled with

Roy Howard; Xinde Wang; Abhay Joshi; Don Becker; Shubhashish Datta; Christoph Wree

2007-01-01

443

Observation of pulse delaying and advancement in optical fibers using stimulated Brillouin scattering  

Microsoft Academic Search

We demonstrate experimentally that it is possible to control optically the group velocity of an optical pulse as it travels along an optical fiber. To achieve this control we use the effect of Stimulated Brillouin Scattering. In our experiments we have achieved changes in the group index of 10 -3 in several kilometer-length fibers, thus leading to pulse delaying and

Kwang Yong Song; Miguel González Herráez; Luc Thévenaz

2005-01-01

444

Guiding and birefringent properties of a hybrid PDMS/Silica photonic crystal fiber  

E-print Network

and studied by filling liquid crystal, high index fluids, metals9 as well as other materials into the airGuiding and birefringent properties of a hybrid PDMS/Silica photonic crystal fiber Christos Markos-Bi) photonic crystal fiber (PCF) infiltrated with PDMS elastomer in order to enhance the sensitivity

Vlachos, Kyriakos G.

445

Mode-field radius of photonic crystal fibers expressed by the V parameter  

Microsoft Academic Search

We numerically calculate the equivalent mode-field radius of the fundamental mode in a photonic crystal fiber (PCF) and show that this is a function of the V parameter only and not the relative hole size. This dependence is similar to what is found for graded-index standard fibers, and we furthermore show that the relation for the PCF can be excellently

Martin Dybendal Nielsen; Niels Asger Mortensen; Jacob Riis Folkenberg; Anders Bjarklev

2003-01-01

446

Light coupling and propagation in composite optical fiber-slab waveguides  

Microsoft Academic Search

A theoretical investigation of evanescent coupling between an optical fiber and a slab waveguide with an asymmetric geometry is presented. The characteristics of right propagation and coupling are obtained through numerical calculations based on simplified coupled-mode and compound-mode equations and found to be highly dependent not only on the relative values of refractive index of the fiber core and slab,

Shu Zheng; L. N. Binh; George P. Simon

1995-01-01

447

Investigation of mode coupling in optical fiber with controlled volume disorder  

E-print Network

configurations of controlled disorder in optical fibers suitable for such applications as random fiber lasers benefits observed when disorder is induced into a mundane system. A random laser1 , where laser action diameter is 7.66 microns, the cladding diameter is 125 microns, NA = 0.13 with the refractive indexes

Yamilov, Alexey

448

Preform For Producing An Optical Fiber And Method Therefor  

DOEpatents

The present invention provides a simple method for fabricating fiber-optic glass preforms having complex refractive index configurations and/or dopant distributions in a radial direction with a high degree of accuracy and precision. The method teaches bundling together a plurality of glass rods of specific physical, chemical, or optical properties and wherein the rod bundle is fused in a manner that maintains the cross-sectional composition and refractive-index profiles established by the position of the rods.

Kliner, Dahv A. V. (San Ramon, CA); Koplow, Jeffery P. (Washington, DC)

2005-04-19

449

Preform For Producing An Optical Fiber And Method Therefor  

DOEpatents

The present invention provides a simple method for fabricating fiber-optic glass preforms having complex refractive index configurations and/or dopant distributions in a radial direction with a high degree of accuracy and precision. The method teaches bundling together a plurality of glass rods of specific physical, chemical, or optical properties and wherein the rod bundle is fused in a manner that maintains the cross-sectional composition and refractive-index profiles established by the position of the rods.

Kliner, Dahv A. V. (San Ramon, CA); Koplow, Jeffery P. (Washington, DC)

2004-08-10

450

Refractive index measurements by adaptive techniques (RIMDAPT: Phases 1 and 1A)  

Microsoft Academic Search

A method for the adaptive computation of ray traces directly without going through the intermediate step of determining refractive indices or refractive index gradients is demonstrated. The basis of the new method of direct ray tracing is presented together with an exposition of the inherent difficulty of using measured or computed refractive index or refractive index gradients for ray tracing

F. W. Vanstraten; R. L. Barron; R. F. Snyder

1974-01-01

451

Raman Imaging with a Fiber-Coupled Multichannel Spectrograph  

PubMed Central

Until now, spatially resolved Raman Spectroscopy has required to scan a sample under investigation in a time-consuming step-by-step procedure. Here, we present a technique that allows the capture of an entire Raman image with only one single exposure. The Raman scattering arising from the sample was collected with a fiber-coupled high-performance astronomy spectrograph. The probe head consisting of an array of 20 × 20 multimode fibers was linked to the camera port of a microscope. To demonstrate the high potential of this new concept, Raman images of reference samples were recorded. Entire chemical maps were received without the need for a scanning procedure. PMID:25420149

Schmälzlin, Elmar; Moralejo, Benito; Rutowska, Monika; Monreal-Ibero, Ana; Sandin, Christer; Tarcea, Nicolae; Popp, Jürgen; Roth, Martin M.

2014-01-01

452

Fiber optic sensors  

NASA Astrophysics Data System (ADS)

Fiber sensors are surveyed, and basic fiber theory is treated, as well as numerous sensor principles. These sensors can be made completely nonmetallic and without any electrical signals. Two acoustic sensor types are reviewed: the microbendsensor and the Mach-Lehnder interferometer. A fiber optical reflection sensor for acoustic detection is described; this device is not fully developed, technical problems appeared with the end diaphragm.

Bengtsson, J. P.

1986-03-01

453

Fiber composite flywheel rim  

DOEpatents

A flywheel 2 comprising a hub 4 having at least one radially projecting disc 6, an annular rim 14 secured to said disc and providing a surface circumferential to said hub, a first plurality of resin-impregnated fibers 22 wound about said rim congruent to said surface, and a shell 26 enclosing said first plurality of fibers and formed by a second plurality of resin-impregnated fibers wound about said rim tangentially to said surface.

Davis, Donald E. (Thousand Oaks, CA); Ingham, Kenneth T. (Woodland Hills, CA)

1987-01-01

454

Fiber-optic reflectometer  

Microsoft Academic Search

A reflectometer that studies the properties of optical-fiber waveguides on the basis of a backscattering technique is described. The device includes a pulsed double-heterostructure Al(x)Ga(1-x)As laser making it possible to inject a radiation power of 150 mW into the fiber at a wavelength of 0.85 micron; a fiber-optic directional coupler; and a silicon avalanche photodiode. The spatial resolution for the

V. I. Borodulin; V. A. Vlasov; Iu. V. Guliaev; V. P. Koniaev; A. V. Kulymanov; V. T. Potapov; V. P. Sosnin; I. I. Taubkin; A. A. Timofeev; V. I. Shveikin

1981-01-01

455

A spatial indexing approach based on linear referencing system  

NASA Astrophysics Data System (ADS)

To 3D visualization of terrain data with large ranges, we often use the strategy as follows: terrain model is firstly divided into regular patches and then index mechanism is set up on the basis of data patches. Next, we load batches of data patches around the viewpoint dynamically. However, when many road networks are nested into terrain models, it is difficult for terrain models to divide into regular patches in an original way. It is well known that the data is along the road in a linear way and the roads connect to each other. According to the above feature, a hybrid index mechanism combining connectivity with dynamic segmentation is proposed in this paper, which can realize the process of query in two steps. The first step is to search roughly by means of connectivity index. Based on the results of the first step, the second step can finish the process of exact query satisfactorily using dynamic segmentation index. This index mechanism with high query speed guarantees speed of loading data dynamically, and meets the demand of visualization of road network. Finally, we implement the algorithm by means of some experiments, and give a comparison in space efficiency and time efficiency with R-tree index.

Zuo, Xiao qing; Fang, Yuan min

2006-10-01

456

The game chromatic index and game coloring index of graphs  

E-print Network

The game chromatic index and game coloring index of graphs Leizhen Cai Department of Computer@math.nsysu.edu.tw May, 1998. y Abstract This paper discusses the game chromatic index and game coloring index of graphs. We prove that if a graph G is k-degenerate, then its game coloring index is at most #1;+ 3k 1

Zhu, Xuding

457

Managing Employee Development: A Step-By-Step Approach.  

ERIC Educational Resources Information Center

A guide for agencies in setting up new employee development programs or a tool for assessing existing ones, the paper presents an eight-step process for organizational training. Step 1 commences with the identification and ranking of learning needs, or conducting a needs assessment. Step 2, selection of learning objectives, includes a job analysis…

Wright, Chester; And Others

458

Green Schools Energy Project: A Step-by-Step Manual.  

ERIC Educational Resources Information Center

This publication contains a step-by-step guide for implementing an energy-saving project in local school districts: the installation of newer, more energy-efficient "T-8" fluorescent tube lights in place of "T-12" lights. Eleven steps are explained in detail: (1) find out what kind of lights the school district currently uses; (2) form a group to…

Quigley, Gwen

459

A new supersymmetric index  

NASA Astrophysics Data System (ADS)

We show that Tr(-1) FFe ?H is an index for N = 2 supersymmetric theories in two dimensions, in the sense that it is independent of almost all deformations of the theory. This index is related to the geometry of the vacua (Berry's curvature) and satisfies an exact differential equation as a function of ?. For integrable theories we can also compute the index thermodynamically, using the exact S-matrix. The equivalence of these two results implies a highly non-trivial equivalence of a set of coupled integral equations with these differential equations, among them Painlevé III and the affine Toda equations.

Cecotti, Sergio; Fendley, Paul; Intriligator, Ken; Vafa, Cumrun

1992-11-01

460

Integration of microfluidics with grating coupled silicon photonic sensors by one-step combined photopatterning and molding of OSTE.  

PubMed

We present a novel integration method for packaging silicon photonic sensors with polymer microfluidics, designed to be suitable for wafer-level production methods. The method addresses the previously unmet manufacturing challenges of matching the microfluidic footprint area to that of the photonics, and of robust bonding of microfluidic layers to biofunctionalized surfaces. We demonstrate the fabrication, in a single step, of a microfluidic layer in the recently introduced OSTE polymer, and the subsequent unassisted dry bonding of the microfluidic layer to a grating coupled silicon photonic ring resonator sensor chip. The microfluidic layer features photopatterned through holes (vias) for optical fiber probing and fluid connections, as well as molded microchannels and tube connectors, and is manufactured and subsequently bonded to a silicon sensor chip in less than 10 minutes. Combining this new microfluidic packaging method with photonic waveguide surface gratings for light coupling allows matching the size scale of microfluidics to that of current silicon photonic biosensors. To demonstrate the new method, we performed successful refractive index measurements of liquid ethanol and methanol samples, using the fabricated device. The minimum required sample volume for refractive index measurement is below one nanoliter. PMID:24104003

Errando-Herranz, Carlos; Saharil, Farizah; Romero, Albert Mola; Sandström, Niklas; Shafagh, Reza Zandi; van der Wijngaart, Wouter; Haraldsson, Tommy; Gylfason, Kristinn B

2013-09-01

461

Electrospinning of nanocomposite fibers  

NASA Astrophysics Data System (ADS)

Physical properties of a novel biocompatible nanocomposite fiber are investigated. The fibers are fabricated by incorporation of organically modified clay in a fiber electrospinning process. Commercially available Montmorillonite type organoclays with different extent of miscibility with the polymer matrix are employed to study the effect of organic modifier/matrix interactions. The nanocomposite fibers are prepared by electrospinning a suspension of organoclay/dichloromethane with poly(L-lactic acid), PLLA, a widely used biodegradable synthetic polyester. Effect of clay incorporation on fiber diameter, crystallinity and mechanical properties are studied. A high degree of birefringence in polarized light microscopy suggested that the polymer chains in as-spun fibers are highly aligned. However, wide angle x-ray scattering (WAXS) data revealed no crystalline peaks in as-spun fibers. Annealing the samples above the glass transition temperature induces high degree of crystallinity. Based on Scanning electron microscopy (SEM), spun fibers are highly porous, which may be beneficial in biomedical applications, membranes, and reinforcement matrices. Transmission electron microscopy (TEM) data show the ordering of silicate platelets along the fiber axis, consistent with the d-spacings obtained from WAXS. Cold crystallization behavior of as spun nanofibers studied via in-situ Fourier Transform Infrared spectroscopy (FTIR) will also be presented.

Krikorian, Vahik

2005-03-01

462

ZBLAN, Silica Fiber Comparison  

NASA Technical Reports Server (NTRS)

This graph depicts the increased signal quality possible with optical fibers made from ZBLAN, a family of heavy-metal fluoride glasses (fluorine combined zirconium, barium, lanthanum, aluminum, and sodium) as compared to silica fibers. NASA is conducting research on pulling ZBLAN fibers in the low-g environment of space to prevent crystallization that limits ZBLAN's usefulness in optical fiber-based communications. In the graph, a line closer to the black theoretical maximum line is better. Photo credit: NASA/Marshall Space Flight Center

1998-01-01

463

AMPHIBOLE FIBER CONCENTRATION DETERMINATION FOR A SERIES OF COMMUNITY AIR SAMPLES: USE OF X-RAY DIFFRACTION TO SUPPLEMENT ELECTRON MICROSCOPE ANALYSIS  

EPA Science Inventory

The accurate measurement of annual average mineral fiber concentrations at various air sampling sites provides the best index of non-occupational inhalation exposure to fibers in a community located near an industrial source of airborne amphibole fibers. The transmission electron...

464

CAD Centre - Index Searcher  

NSDL National Science Digital Library

A searchable index of the CAD Centre, a postgraduate teaching and research unit in design manufacture and engineering management, with research focused on design methods and computer support of the design process for engineering applications.

2007-10-11

465

Gradient index metamaterials.  

PubMed

Metamaterials--artificially structured materials with tailored electromagnetic response--can be designed to have properties difficult or impossible to achieve with traditional materials fabrication methods. Here we present a structured metamaterial, based on conducting split ring resonators (SRRs), which has an effective index of refraction with a constant spatial gradient. We experimentally confirm the gradient by measuring the deflection of a microwave beam by a planar slab of the composite metamaterial over a range of microwave frequencies. The gradient index metamaterial may prove an advantageous alternative approach to the development of gradient index lenses and similar optics, especially at higher frequencies. In particular, the gradient index metamaterial we propose may be suited for terahertz applications, where the magnetic resonant response of SRRs has recently been demonstrated. PMID:15903607

Smith, D R; Mock, J J; Starr, A F; Schurig, D

2005-03-01

466

The Index of Refraction  

NSDL National Science Digital Library

In this media-rich lesson plan, students explore the refraction of light at the boundary between materials: they learn about the refractive indices of various materials and measure the index of refraction of plastic or gelatin.

2011-05-02

467

Genetics of Cotton Fiber Elongation  

E-print Network

include: Palmeri, Morilli, Richmondii, Yucatenanse, Punctatum, Marie galante and Latifolium (Iqbal et al., 2001 and Khadi et al., 2010). 8 Cotton fiber classing Cotton fiber is a variable product. Development of every single fiber on cotton...

Ng, Eng Hwa

2013-05-29

468

Strength development of high-strength ductile concrete incorporating Metakaolin and PVA fibers.  

PubMed

The mechanical properties of high-strength ductile concrete (HSDC) have been investigated using Metakaolin (MK) as the cement replacing material and PVA fibers. Total twenty-seven (27) mixes of concrete have been examined with varying content of MK and PVA fibers. It has been found that the coarser type PVA fibers provide strengths competitive to control or higher than control. Concrete with coarser type PVA fibers has also refined microstructure, but the microstructure has been undergone with the increase in aspect ratio of fibers. The microstructure of concrete with MK has also more refined and packing of material is much better with MK. PVA fibers not only give higher stiffness but also showed the deflection hardening response. Toughness Index of HSDC reflects the improvement in flexural toughness over the plain concrete and the maximum toughness indices have been observed with 10% MK and 2% volume fraction of PVA fibers. PMID:24707202

Nuruddin, Muhammad Fadhil; Khan, Sadaqat Ullah; Shafiq, Nasir; Ayub, Tehmina

2014-01-01

469

Strength Development of High-Strength Ductile Concrete Incorporating Metakaolin and PVA Fibers  

PubMed Central

The mechanical properties of high-strength ductile concrete (HSDC) have been investigated using Metakaolin (MK) as the cement replacing material and PVA fibers. Total twenty-seven (27) mixes of concrete have been examined with varying content of MK and PVA fibers. It has been found that the coarser type PVA fibers provide strengths competitive to control or higher than control. Concrete with coarser type PVA fibers has also refined microstructure, but the microstructure has been undergone with the increase in aspect ratio of fibers. The microstructure of concrete with MK has also more refined and packing of material is much better with MK. PVA fibers not only give higher stiffness but also showed the deflection hardening response. Toughness Index of HSDC reflects the improvement in flexural toughness over the plain concrete and the maximum toughness indices have been observed with 10% MK and 2% volume fraction of PVA fibers. PMID:24707202

Nuruddin, Muhammad Fadhil; Shafiq, Nasir

2014-01-01

470

STEPS: JPL's Astrometric Exoplanet Survey  

NASA Technical Reports Server (NTRS)

Presentation topics include: STEPS ground-based astrometry at Hale Telescope; the instrument; why astronomy and why M-dwarfs; motion of center of light about center of mass in photocentric orbit; photocentric motion vs. fractional mass; high-resolution imaging of STEPS targets; GU 802 p one possible orbit plotted with data, Keplerian frame; GJ 802 results; STEPS future; and a bibliography of STEPS papers.

Shaklan, Stuart; Pravdo, Steve

2008-01-01

471

Electrospun Fibers for Energy, Electronic, & Environmental Applications  

NASA Astrophysics Data System (ADS)

Electrospinning is an established method for creating polymer and bio-polymer fibers of dimensions ranging from ˜10 nanometers to microns. The process typically involves applying a high voltage between a solution source (usually at the end of a capillary or syringe) and a substrate on which the nanofibers are deposited. The high electric field distorts the shape of the liquid droplet, creating a Taylor cone. Additional applied voltage ejects a liquid jet of the polymer solution in the Taylor cone toward the counter electrode. The formation of fibers is generated by the rapid electrostatic elongation and solvent evaporation of this viscoelastic jet, which typically generates an entangled non-woven mesh of fibers with a high surface area to volume ratio. Electrospinning is an attractive alternative to other processes for creating nano-scale fibers and high surface area to volume ratio surfaces due to its low start up cost, overall simplicity, wide range of processable materials, and the ability to generate a moderate amount of fibers in one step. It has also been demonstrated that coaxial electrospinning is possible, wherein the nanofiber has two distinct phases, one being the core and another being the sheath. This method is advantageous because properties of two materials can be combined into one fiber, while maintaining two distinct material phases. Materials that are inherently electrospinable could be made into fibers using this technique as well. The most common applications areas for electrospun fibers are in filtration and biomedical areas, with a comparatively small amount of work done in energy, environmental, and sensor applications. Furthermore, the use of biologically materials in electrospun fibers is an avenue of research that needs more exploration, given the unique properties these materials can exhibit. The research aim of this thesis is to explore the use of electrospun fibers for energy, electrical and environmental applications. For energy applications, fibers consisting of the commonly used organic photovoltaic electron donor/acceptor pair P3HT:PCBM were made by coaxial electrospinning. The inclusion of P3HT:PCBM fibers into an active layer of a organic photovoltaic device led to a ˜ 50% increase in power conversion efficiency over a thin film device of identical chemical composition and thickness. The inclusion of biological photosynthetic moieties into electrically relevant conjugated polymers was also explored for electrical applications. Polymeric fibers consisting largely of PEDOT:PSS were doped with thylakoid vesicles from spinach, and were found to act as photo-detectors. Native PEDOT:PSS does not exhibit such properties. For environmental applications, photocatalytic degradation membranes were also created by electrospinning cellulosic fibers which could be used as platforms to efficiently bind the photocatalyst TiO2. Employing different fiber-titania binding strategies, titania nanoparticles of various sizes and band gap configurations were successfully incorporated into mats of non-woven cellulosic nanofibers. These mats were found to successfully degrade dyes and relevant fresh water toxins such as microcystin-LR.

Bedford, Nicholas M.

472

Engineering metal oxide nanostructures for the fiber optic sensor platform.  

PubMed

This paper presents an effective integration scheme of nanostructured SnO2 with the fiber optic platform for chemical sensing applications based on evanescent optical interactions. By using a triblock copolymer as a structure directing agent as the means of nano-structuring, the refractive index of SnO2 is reduced from >2.0 to 1.46, in accordance with effective medium theory for optimal on-fiber integration. High-temperature stable fiber Bragg gratings inscribed in D-shaped fibers were used to perform real-time characterization of optical absorption and refractive index modulation of metal oxides in response to NH3 from the room temperature to 500 °C. Measurement results reveals that the redox reaction of the nanostructured metal oxides exposed to a reactive gas NH3 induces much stronger changes in optical absorption as opposed to changes in the refractive index. Results presented in this paper provide important guidance for fiber optic chemical sensing designs based on metal oxide nanomaterials. PMID:24663558

Poole, Zsolt L; Ohodnicki, Paul; Chen, Rongzhang; Lin, Yuankun; Chen, Kevin P

2014-02-10

473

Integrated hollow-core fibers for nonlinear optofluidic applications.  

PubMed

A method to fabricate all-in-fiber liquid microcells has been demonstrated which allows for the incorporation of complex hollow-core photonic crystal fibers (HCPCFs). The approach is based on a mechanical splicing method in which the hollow-core fibers are pigtailed with telecoms fibers to yield devices that have low insertion losses, are highly compact, and do not suffer from evaporation of the core material. To isolate the PCF cores for the infiltration of low index liquids, a pulsed CO2 laser cleaving technique has been developed which seals only the very ends of the cladding holes, thus minimizing degradation of the guiding properties at the coupling region. The efficiency of this integration method has been verified via strong cascaded Raman scattering in both toluene (high index) core capillaries and ethanol (low index) core HCPCFs, for power thresholds up to six orders of magnitude lower than previous results. We anticipate that this stable, robust all-fiber integration approach will open up new possibilities for the exploration of optofluidic interactions. PMID:24514387

Xiao, Limin; Wheeler, Natalie V; Healy, Noel; Peacock, Anna C

2013-11-18

474

Effect of weight loss on muscle fiber type, fiber size, capillarity, and succinate dehydrogenase activity in humans.  

PubMed

To examine the effects of weight loss on muscle oxidative properties, nine obese subjects (body mass index, 34 +/- 1.5) had muscle biopsies before and after weight loss and weight stabilization. Weight loss ranged from 13-32 kg and represented 20.8 +/- 2.1% of initial weight. After weight loss, there was no change in the proportions of oxidative (type I and type IIa) fibers and also no change in mean fiber cross-sectional area, whereas there was a small, but significant, decrease in the relative interstitial space (P < 0.05). However, weight loss resulted in a 32 +/- 6% (mean +/- SEM) increase in capillary/fiber ratio and a 54% increase in capillary density (P < 0.05). In addition, there was a 41 +/- 13% increase in succinate dehydrogenase (SDH) activity (P < 0.05). This increase in muscle capillarization and SDH activity was seen in all fiber types, even the relatively lower oxidative type IIx fibers. There was a strong correlation between the change in capillary/fiber ratio and the change in SDH activity (r = 0.82; P < 0.02). Thus, weight loss resulted in no change in muscle fiber type or cross-sectional area, but produced increases in capillary/fiber ratio, capillary density, and SDH activity, suggesting an increase in muscle oxidative capacity. PMID:10566670

Kern, P A; Simsolo, R B; Fournier, M

1999-11-01

475

Formulation of resource depletion index  

Microsoft Academic Search

A resource depletion index can serve as a quantitative tool to evaluate the level of depletion for natural resources. This study introduces two types of resource depletion indices, the global resource depletion index and the local resource depletion index. Global resource depletion index mainly concerns global reserves and the annual consumption rate of these resources. The local resource depletion index

C.-H. Lee

1998-01-01

476

SPAR-H Step-by-Step Guidance  

SciTech Connect

Step-by-step guidance was developed recently at Idaho National Laboratory for the US Nuclear Regulatory Commission on the use of the Standardized Plant Analysis Risk-Human Reliability Analysis (SPAR-H) method for quantifying Human Failure Events (HFEs). This work was done to address SPAR-H user needs, specifically requests for additional guidance on the proper application of various aspects of the methodology. This paper overviews the steps of the SPAR-H analysis process and highlights some of the most important insights gained during the development of the step-by-step directions. This supplemental guidance for analysts is applicable when plant-specific information is available, and goes beyond the general guidance provided in existing SPAR-H documentation. The steps highlighted in this paper 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.

April M. Whaley; Dana L. Kelly; Ronald L. Boring; William J. Galyean

2012-06-01

477

Fiber optic sensor employing successively destroyed coupled points or reflectors for detecting shock wave speed and damage location  

DOEpatents

A shock velocity and damage location sensor providing a means of measuring shock speed and damage location. The sensor consists of a long series of time-of-arrival "points" constructed with fiber optics. The fiber optic sensor apparatus measures shock velocity as the fiber sensor is progressively crushed as a shock wave proceeds in a direction along the fiber. The light received by a receiving means changes as time-of-arrival points are destroyed as the sensor is disturbed by the shock. The sensor may comprise a transmitting fiber bent into a series of loops and fused to a receiving fiber at various places, time-of-arrival points, along the receiving fibers length. At the "points" of contact, where a portion of the light leaves the transmitting fiber and enters the receiving fiber, the loops would be required to allow the light to travel backwards through the receiving fiber toward a receiving means. The sensor may also comprise a single optical fiber wherein the time-of-arrival points are comprised of reflection planes distributed along the fibers length. In this configuration, as the shock front proceeds along the fiber it destroys one reflector after another. The output received by a receiving means from this sensor may be a series of downward steps produced as the shock wave destroys one time-of-arrival point after another, or a nonsequential pattern of steps in the event time-of-arrival points are destroyed at any point along the sensor.

Weiss, Jonathan D. (Albuquerque, NM)

1995-01-01

478

Fiber optic sensor employing successively destroyed coupled points or reflectors for detecting shock wave speed and damage location  

DOEpatents

A shock velocity and damage location sensor providing a means of measuring shock speed and damage location is disclosed. The sensor consists of a long series of time-of-arrival ``points`` constructed with fiber optics. The fiber optic sensor apparatus measures shock velocity as the fiber sensor is progressively crushed as a shock wave proceeds in a direction along the fiber. The light received by a receiving means changes as time-of-arrival points are destroyed as the sensor is disturbed by the shock. The sensor may comprise a transmitting fiber bent into a series of loops and fused to a receiving fiber at various places, time-of-arrival points, along the receiving fibers length. At the ``points`` of contact, where a portion of the light leaves the transmitting fiber and enters the receiving fiber, the loops would be required to allow the light to travel backwards through the receiving fiber toward a receiving means. The sensor may also comprise a single optical fiber wherein the time-of-arrival points are comprised of reflection planes distributed along the fibers length. In this configuration, as the shock front proceeds along the fiber it destroys one reflector after another. The output received by a receiving means from this sensor may be a series of downward steps produced as the shock wave destroys one time-of-arrival point after another, or a nonsequential pattern of steps in the event time-of-arrival points are destroyed at any point along the sensor. 6 figs.

Weiss, J.D.

1995-08-29

479

JSC document index  

NASA Technical Reports Server (NTRS)

The Johnson Space Center (JSC) document index is intended to provide a single source listing of all published JSC-numbered documents their authors, and the designated off