Note: This page contains sample records for the topic step index fiber from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: August 15, 2014.
1

A modified vector mode solution of step index fiber  

NASA Astrophysics Data System (ADS)

For the sake of clarifying the characteristics of cylindrical travelling wave and step index fiber, the modified zero order Hankel function, which is an approximate harmonic complex function without singularity, is recommended as the eigen function of cylindrical travelling wave in homogeneous dielectric. As the modified zero order Neumann function avoids the singularity in the origin of coordinate, and the concept of the essence of mode field of fiber is engaged, both of zero order Bessel function and modified zero order Neumann function are recommend as the eigen functions of axial electric or magnetic component in the core layer of step index fiber. Then, the analysing method of vector mode of fiber is used for reference, a new eigen equation of step index fiber is recommended. These may provide a new method for analyzing the characteristics of cylindrical travelling wave and step index fiber.

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

2011-11-01

2

Skew modes in specialty fibers with step-index profile  

NASA Astrophysics Data System (ADS)

In step-index multimode-fibers, controlled excitation conditions are essential to achieve optimized transmission properties and control the output beam profile. Especially with lasers as a light-source, selective methods of mode excitation can be used easily. So far, fiber properties have been specified using meridional rays (modes), as proposed with the inverse far-field method. In addition to these meridional rays in step-index fibers, high-order skew rays can be selectively excited. Especially with excitation angles higher than the numerical aperture of the fiber, these skew rays can propagate with interesting properties. Based on these extreme test conditions, the core-cladding interface of large-core step-index fibers can be more efficiently controlled.

Klein, Karl-Friedrich; Gonschior, Cornell; Xia, Ruan; Hillrichs, Georg; Bloos, Martin; Poisel, Hans

2010-02-01

3

Influence of Numerical Aperture on Mode Coupling in Step-Index Plastic Optical Fibers  

Microsoft Academic Search

Using the power-flow equation, we have examined the state of mode coupling in step-index plastic optical fibers with different numerical apertures. Our results confirm that the coupling rates vary with the coupling coefficient of the fibers as the dominant parameter, especially in the early stage of coupling near the input fiber end. However, we show that the fiber's numerical aperture

Svetislav Savovic; Alexandar Djordjevich

2004-01-01

4

ASE and photostability measurements in dye doped step index, graded index and hollow polymer optical fiber  

NASA Astrophysics Data System (ADS)

Three categories of polymer optical fibers viz., step index (SI), graded index (GI) and hollow types doped with Rhodamine 6G (Rh6G) at specific concentrations were fabricated to study their optical properties. Detailed measurements were made to understand the amplified spontaneous emission (ASE) and photodegradation phenomena in these polymer optic fiber (POF) systems. Rh6G doped hollow POF shows maximum line narrowing for a given pump power at 532 nm when side illumination technique is employed. A redshift in ASE has been observed when propagation length is increased allowing a limited range of tuning of emission wavelength. Photostability studies show that GI POF has the maximum endurance at a given pump power.

Peter, Jaison; Vallabhan, C. P. G.; Radhakrishnan, P.; Nampoori, V. P. N.; Kailasnath, M.

2014-11-01

5

Scattering of the dominant guided mode due to end discontinuity in step index optical fibers  

Microsoft Academic Search

The electromagnetic scattering of the dominant guided mode of a step-index optical fiber due to a smoothed end discontinuity with free space is treated rigorously by using the mode-matching technique. The total field inside the optical fiber as well as in the free space region are expressed in terms of the complete spectrum modes of the optical fiber and the

M. A. Abdulalim; K. F. Hussein; F. M. Elhefnawi; E. A. Hashish

2005-01-01

6

Mode coupling in strained and unstrained step-index plastic optical fibers  

Microsoft Academic Search

Using the power-flow equation, we have examined the state of mode coupling in strained and unstrained step-index plastic optical fibers. The strained fibers show much stronger mode coupling than unstrained fibers of the same types. As a result, the coupling lengths where equilibrium mode distribution is achieved and the lengths of fiber required for achieving a steady-state mode distribution for

Svetislav Savovic; Alexandar Djordjevich

2006-01-01

7

Numerical and experimental study of microfluidic devices in step-index optical fibers.  

PubMed

Microfluidic devices composed of microslits in step-index optical fibers are thoroughly investigated. Numerical simulations are performed to explain scattering and power loss in such devices. Experimental results based on microslits fabricated by femtosecond laser processing corroborate theoretical data. Dependency of the device performance on the refractive index of fluid in the slit is further utilized to construct a refractive index sensor and an in-fiber attenuator. PMID:18382565

Petrovic, Jovana; Lai, Yicheng; Bennion, Ian

2008-04-01

8

Numerical and experimental study of microfluidic devices in step-index optical fibers  

NASA Astrophysics Data System (ADS)

Microfluidic devices composed of microslits in step-index optical fibers are thoroughly investigated. Numerical simulations are performed to explain scattering and power loss in such devices. Experimental results based on microslits fabricated by femtosecond laser processing corroborate theoretical data. Dependency of the device performance on the refractive index of fluid in the slit is further utilized to construct a refractive index sensor and an in-fiber attenuator.

Petrovic, Jovana; Lai, Yicheng; Bennion, Ian

2008-04-01

9

Investigation of mode coupling in step index plastic optical fibers using the power flow equation  

Microsoft Academic Search

Using the power flow equation, we have examined the mode coupling caused by intrinsic perturbation effects of the step index plastic optical fiber. A numerical solution has been obtained by the explicit finite difference method. Results show the state of mode coupling along the fiber. They indicate that the equilibrium mode distribution is achieved at much shorter lengths compared to

Alexander Djordjevich; S. Savovic

2000-01-01

10

Dye-doped step-index polymer optical fiber for broadband optical amplification  

Microsoft Academic Search

We report the development of a novel and simple technique for fabricating polymer optical fibers of good optical quality for special device applications. This technique aims at polymer fibers doped with various functional organic materials. On the basis of the technique, step-index polymer optical fibers doped with laser dyes have been fabricated. High-gain and high-efficiency optical amplification has been achieved

Gang Ding Peng; P. K. Chu; Zhengjun Xiong; Trevor W. Whitbread; Rod P. Chaplin

1996-01-01

11

Chalcogenide step index and microstructured single mode fibers  

Microsoft Academic Search

Chalcogenide glasses are known for their large transparency in the mid infrared, which includes the two atmospheric windows lying from 3–5?m and 8–12?m. Chalcogenide single mode fibers present numerous potential applications in the IR field, such as military countermeasures, LIDAR spectroscopy and spatial interferometry. Two routes can be considered for the elaboration of a single mode fiber. The first method

C. Conseil; Q. Coulombier; C. Boussard-Plédel; J. Troles; L. Brilland; G. Renversez; D. Mechin; B. Bureau; J. L. Adam; J. Lucas

2011-01-01

12

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

13

Measurements of lateral offset power losses in step-index optical fibers scanning point sources  

SciTech Connect

The authors report the results of an experimental study of optical power losses due to lateral offset of the input aperture of a step-index optical fiber used to scan a point source. Data were taken with hard-clad silica and plastic-clad silica fibers having core diameters ranging from 200 to 1000 ..mu..m. These results will be useful in establishing alignment criteria for the optical components used in the laser-based remote thermometry research program.

Dowell, L.J.; Gillies, G.T.; Allison, S.W.

1987-06-01

14

Measurements of lateral offset power losses in step-index optical fibers scanning point sources  

Microsoft Academic Search

The authors report the results of an experimental study of optical power losses due to lateral offset of the input aperture of a step-index optical fiber used to scan a point source. Data were taken with hard-clad silica and plastic-clad silica fibers having core diameters ranging from 200 to 1000 ..mu..m. These results will be useful in establishing alignment criteria

L. J. Dowell; G. T. Gillies; S. W. Allison

1987-01-01

15

Birefringence of standard step-index optical fiber with waveguide cladding microcrack  

NASA Astrophysics Data System (ADS)

In this article mathematical models for estimation calculation of birefringence components for step-index optical fiber with a microcrack on the waveguide cladding are considered. Dependences of geometrical and mechanical birefringence components and beat length on the geometrical microcrack size are received. Results of calculation indicate potential possibility of detection of local defects on the waveguide cladding.

Burdin, Vladimir A.; Dmitriev, Eugeniy V.; Praporshchikov, Denis E.

2014-04-01

16

Numerical solution of the power flow equation in step-index plastic optical fibers  

Microsoft Academic Search

The numerical solution of the complete power flow equation is reported and employed to investigate the state of mode coupling along a step-index plastic optical fiber. This solution is based on the explicit finite-difference method and, in contrast to earlier solutions, does not neglect absorption and scattering loss. It is the only solution that can accommodate any input condition throughout

Alexandar Djordjevich; Svetislav Savovic

2004-01-01

17

Discrete Multitone Modulation for Maximizing Transmission Rate in Step-Index Plastic Optical Fibers  

Microsoft Academic Search

The use of standard 1-mm core-diameter step-index plastic optical fiber (SI-POF) has so far been mainly limited to distances of up to 100 m and bit-rates in the order of 100 Mbit\\/s. By use of digital signal processing, transmission performance of such optical links can be improved. Among the different technical solutions proposed, a promising one is based on the

S. C. Jeffrey Lee; Florian Breyer; Sebastian Randel; Roberto Gaudino; Gabriella Bosco; Andreas Bluschke; Michael Matthews; Philipp Rietzsch; Rainer Steglich; Henrie P. A. van den Boom; Antonius M. J. Koonen

2009-01-01

18

Laser-induced damage studies on step-index multimode fibers  

NASA Astrophysics Data System (ADS)

A previous investigation of laser-induced damage mechanisms and corresponding thresholds in step-index, multimode fibers was motivated by an interest in optical systems for firing explosives. In the initial study, the output from a compact, multimode Nd/YAG laser was coupled into fiber cores of pure fused silica. End-face polishing steps were varied between successive fiber lots to produce improved finishes, and each fiber was subjected to a sequence of progressively increasing energy densities up to a value of more than 80 J/cm2. Essentially all of the tested fibers experienced a 'laser conditioning' process at the front fiber face, in which a visible plasma was generated for one or more laser shots. Rather than produce progressive damage at the front surface, however, this process would eventually cease and leave the surface with improved damage resistance. Once past this conditioning process, the majority of fibers damaged at the rear end face. Other modes of damage were observed either at locations of fixturing stresses or at a location of high static tensile stress resulting from bends introduced to the fiber. Although the previous results were encouraging in terms of achieving useful damage thresholds, a number of areas for further study were indicated. In the present study, a similar experimental procedure was used to address these areas. The relative permanence of front-surface laser conditioning was examined by re-testing fibers that had experienced this process at least a year previously. End-face mechanical polishing was again examined by testing fibers prepared using a refined polishing schedule. Attempts to use a single fixture to hold an entire lot of fibers throughout end-face polishing and damage testing met with mixed results, with fiber positions subjected to fixturing stresses likely sites for initial damage. In an effort to prepare fiber faces with the improved damage resistance observed with front faces following 'laser conditioning,' two schedules for CO2-laser polishing of end faces were developed and evaluated. Finally, to improve resistance to damage at sites with significant static stresses, fiber samples which passed a much higher tensile proof test during manufacturing were tested. The current experiments were conducted with a new laser having a shorter pulsewidth and a significantly different mode structure. The beam was injected into the fiber using a geometry that had been successful in the previous study in minimizing a damage mechanism which can occur at the core/cladding interface with the first few hundred fiber diameters. However, the different mode structure of the new laser apparently resulted in this mechanism dominating the current results.

Stechel, Ellen B.; Klingsporn, Paul E.

1992-07-01

19

Influence of launch-beam distribution on bandwidth in step-index plastic optical fibers.  

PubMed

The power-flow equation is employed to calculate bandwidth of step-index plastic optical fibers (POFs) for different launch conditions. The outcome specifies bandwidth as a function of the mean input angle and width of the launch-beam distribution. For small distribution widths, bandwidth is shown to decrease with increasing mean input angle of the launch-beam distribution. For large distribution widths, bandwidth becomes independent of the launch angle. Launch-beam distribution, mode-dependent attenuation, and mode dispersion and coupling in POFs strongly influence the bandwidth of data transmission systems. PMID:23434979

Savovi?, Svetislav; Drlja?a, Branko; Djordjevich, Alexandar

2013-02-20

20

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

Microsoft Academic Search

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

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

2005-01-01

21

Frequency response in step index plastic optical fibers obtained from the generalized power flow equation.  

PubMed

We present a method to obtain the frequency response of step index (SI) plastic optical fibers (POFs) based on the power flow equation generalized to incorporate the temporal dimension where the fibre diffusion and attenuation are functions of the propagation angle. To solve this equation we propose a fast implementation of the finite-difference method in matrix form. Our method is validated by comparing model predictions to experimental data. In addition, the model provides the space-time evolution of the angular power distribution when it is transmitted throughout the fibre which gives a detailed picture of the POFs capabilities for information transmission. Model predictions show that angular diffusion has a strong impact on temporal pulse widening with propagation. PMID:19219189

Mateo, J; Losada, M A; Zubia, J

2009-02-16

22

Equilibrium mode distribution and steady-state distribution in 100--400 ?m core step-index silica optical fibers  

NASA Astrophysics Data System (ADS)

Using the power flow equation, the state of mode coupling in 100--400 ?m core step-index silica optical fibers is investigated in this article. Results show the coupling length Lc at which the equilibrium mode distribution is achieved and the length zs of the fiber required for achieving the steady-state mode distribution. Functional dependences of these lengths on the core radius and wavelength are also given. Results agree well with those obtained using a long-established calculation method. Since large core silica optical fibers are used at short distances (usually at lengths of up to 10m), the light they transmit is at the stage of coupling that is far from the equilibrium and steady-state mode distributions.

Savovi?, Svetislav; Djordjevich, Alexandar; Simovi?, Ana; Drlja?a, Branko

2011-07-01

23

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

24

Photobleaching effects in step index pure silica optical fibers during in-situ irradiation at low temperatures  

NASA Astrophysics Data System (ADS)

This paper investigates photobleaching at a low temperature in a multimode step-index pure-silica-core optical fiber. Radiation-induced attenuation and subsequent recovery were measured over a wide range of transmitted optical power levels. These measurements were performed at a wavelength of 850 nm and a temperature of -55 C using the NATO/FOTP-49 test procedures. When low levels of optical power were used, the maximum attenuation increased by a factor of 10 and the recovery time increased by a factor of 30 compared with results at high optical power. Complete recovery required several hours at the lowest optical powers.

Johnston, A. H.; Evans, B. D.; Baze, M. P.; Greenwell, R. A.

25

Global characterization of optical power propagation in step-index plastic optical fibers  

Microsoft Academic Search

We propose to characterize optical power transmission in stepindex plastic optical fibers by estimating fiber diffusion and attenuation as functions of the propagation angle. We assume that power flow is described by Gloge´s differential equation and find a global solution that was fitted to experimental far field patterns registered using a CCD camera as a function of fiber length. The

Javier Mateo; M. Angeles Losada; Ignacio Garcés; Joseba Zubia

2006-01-01

26

Comment on "Influence of bending on power distribution in step-index plastic optical fibers and the calculation of bending loss"  

NASA Astrophysics Data System (ADS)

Arguments are presented that a recent paper on the topic of power distribution and mode coupling in curved step-index plastic optical fibers is incorrect and that the method proposed is conceptually flawed except for the special case when the fiber is straight, which was the case used to verify the calculations.

Djordjevich, Alexandar

2007-08-01

27

Comment on "Influence of bending on power distribution in step-index plastic optical fibers and the calculation of bending loss".  

PubMed

Arguments are presented that a recent paper on the topic of power distribution and mode coupling in curved step-index plastic optical fibers is incorrect and that the method proposed is conceptually flawed except for the special case when the fiber is straight, which was the case used to verify the calculations. PMID:17676088

Djordjevich, Alexandar

2007-08-01

28

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

29

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

PubMed

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

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

2011-05-23

30

Modeling of the loss and mode coupling due to an irregular core-cladding interface in step-index plastic optical fibers  

Microsoft Academic Search

The core-cladding boundary in step-index plastic optical fibers is imperfect. Surface irregularities locked in during the manufacturing process couple the guided modes by reflecting them in directions that deviate unpredictably from the expected directions. This causes an additional loss as the multiple reflections from surface elements with directions randomized around the nominal for the cylinder transfer the power to the

Milan S. Kovacevic; Dragoslav Nikezic; Alexandar Djordjevich

2005-01-01

31

Influence of bending on power distribution in step-index plastic optical fibers and the calculation of bending loss  

Microsoft Academic Search

A means of calculating optical power distribution in bent multimode optical fibers is proposed. It employs the power-flow equation approximated by the Fokker-Planck equation that is solved by the explicit finite-difference method. Conceptually important steps of this procedure include (i) dividing the full length of the bent optical fiber into a finite number of short, straight segments; (ii) solving the

M. S. Kovacevic; D. Nikezic

2006-01-01

32

Investigation and comparison of analytical, numerical, and experimentally measured coupling losses for multi-step index optical fibers.  

PubMed

The aim of the present paper is to provide a comprehensive analysis of the coupling losses in multi-step index (MSI) fibres. Their light power acceptance properties are investigated to obtain the corresponding analytical expressions taking into account longitudinal, transverse, and angular misalignments. For this purpose, a uniform power distribution is assumed. In addition, we perform several experimental measurements and computer simulations in order to calculate the coupling losses for two different MSI polymer optical fibres (MSI-POFs). These results serve us to validate the theoretical expressions we have obtained. PMID:19495312

Aldabaldetreku, Gotzon; Durana, Gaizka; Zubia, Joseba; Arrue, Jon; Poisel, Hans; Losada, María

2005-05-30

33

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) [Albuquerque, NM

2002-01-01

34

High Performance Graded Index Polymer Optical Fibers.  

National Technical Information Service (NTIS)

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

A. F. Garito

1998-01-01

35

Graded-index plastic optical fiber for deformation sensing  

Microsoft Academic Search

This paper proposes the use of imperfected graded-index plastic optical fibers as sensing elements in deformation sensors. Use of a graded-index fiber instead of a step-index fiber for bending measurements resulted in an increase in sensitivity. Multi-loop configuration led to an even greater increase in sensitivity, reaching saturation after 15 half-loops. Imperfections implemented on the fiber further increased the sensitivity,

Anatoly Babchenko; Jonathan Maryles

2007-01-01

36

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

37

Point-by-point fiber Bragg grating inscription in free-standing step-index and photonic crystal fibers using near-IR femtosecond laser.  

PubMed

We report what we believe to be the first highly symmetric first-order IR femtosecond laser fiber Bragg gratings within the telecommunications C band in free-standing optical fiber, fabricated with a relatively low NA lens and without use of oil immersion techniques. This grating features the smallest dimensions for a point-by-point fiber grating reported so far (to our knowledge). This achievement paves the way to rapid mass manufacturing of highly efficient and stable Bragg gratings using ultrafast lasers in any type of fiber. Mastering this femtosecond grating inscription technique also allowed the fabrication of the first Bragg gratings with direct near-IR femtosecond inscription in photonic crystal fibers, and without the use of techniques that rely on the compensation of the holey structure. PMID:20479837

Geernaert, Thomas; Kalli, Kyriacos; Koutsides, Charalambos; Komodromos, Michael; Nasilowski, Tomasz; Urbanczyk, Waclaw; Wojcik, Jan; Berghmans, Francis; Thienpont, Hugo

2010-05-15

38

Optical Fiber Sensor for Measuring Refractive Index  

Microsoft Academic Search

An optical fiber sensor for measuring a liquid refractive index is proposed. When an optical fiber is bent and part of its cladding is stripped off, the light energy (E) emerging from the fiber depends on the refractive index of the surrounding medium (nm). The change in nm can be found from E. The light output energy and the measuring

Takashi Takeo; Hajime Hattori

1982-01-01

39

High power gain guided index antiguided fiber lasers and amplifiers  

NASA Astrophysics Data System (ADS)

Increasing the core size of high-power fiber lasers and amplifiers is highly desired in order to mitigate the unwanted nonlinear optical effects and raise the optical damage threshold. If the core size of conventional index-guided (IG) optical fibers increases, the fiber will become multimode, because it is very difficult to control and fine-tune the index step between the core and cladding to satisfy the single mode condition. Siegman proposed Gain-guided index-antiguided (GG-IAG) fibers as a possible platform for ultra-large-core single-mode operation for lasers and amplifiers. In this thesis, the beam-quality factor M2 for the fundamental LP01 mode of a step-index fiber with finite and infinite cladding diameter is calculated in the presence of gain as a function of the complex generalized V number. The numerical results agree with analytical work that obtained in our group. It is shown that the M2 value of a single-mode gain-guided fiber laser can be arbitrarily large. The results are important for the interpretation of the beam-quality measurements in recent experiments on single-mode gain-guided fiber lasers. It is also shown that the conventional infinite cladding diameter approximation cannot be used for index-antiguided gain-guided fibers, and the rigorous analysis is required for accurate prediction of the beam quality factor, as reported in recent experimental measurements. We also highlight the key reasons behind the poor power efficiency observed in multiple experiments in gain guided index-antiguided (GG-IAG) fiber amplifiers and lasers. We show that by properly designing the fiber geometrical characteristics, it is possible to considerably improve the power efficiency of GG-IAG fiber amplifiers in end-pumping schemes.

Gandomkar Yarandi, Parisa

40

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

41

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

Microsoft Academic Search

The modal characteristics of photonic crystal fibers (PCFs), with guiding cores consisting of one or seven missing airholes, are investigated with the finite element method and compared to those of step-index fibers (SIFs). To extend the applicability of the classical SIF theories to PCFs, the effective refractive index of photonic crystal cladding and the effective core radius of a PCF

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

2007-01-01

42

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

43

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

NASA Astrophysics Data System (ADS)

We analytically explore a wide class of optical similariton solutions to the nonlinear Schrödinger 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 Schrödinger 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 Möbius transformation. Our procedure is applicable for both self-focusing and self-defocusing nonlinearities.

Raju, Thokala Soloman; Panigrahi, Prasanta K.

2011-09-01

44

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

45

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

46

Recent developments in microstructured fiber Bragg grating refractive index sensors  

NASA Astrophysics Data System (ADS)

Refractive index measurement by optical fiber sensors has proved to be effective in the research of biochemical and biomedical applications. The theoretical principles and technology underlying several microstructured fiber Bragg grating refractive index sensors developed over the past decade are classified and briefly summarized, and their future developments are considered.

Luo, Bin-Bin; Zhou, Xiao-jun; Zhao, Ming-fu; Zhong, Nianbing; Wang, Sao-fei

2010-01-01

47

Full-vectorial analysis of complex refractive index photonic crystal fibers  

Microsoft Academic Search

We investigated the modal properties of complex refractive-index core photonic crystal fibers (PCFs) with the supercell model. The validity of the approach is shown when we compare our results with those reported earlier on a step complex refractive-index profile. The imaginary part of the electric field results in wave-front distortion in the complex refractive-index profile PCFs, which means that the

Ren Guobin; Wang Zhi; Lou Shuqin; Liu Yan; Jian Shuisheng

2004-01-01

48

Refractive index profiling of a few-mode fiber from fundamental mode excitation  

NASA Astrophysics Data System (ADS)

The fundamental mode of a small-core step-index few-mode fiber, originally designed for single-mode operation at 1310/1550 nm, was selectively excited at visible wavelengths from a single-mode fiber by adiabatically tapering the fusion splice. A two-dimensional refractive index profile of the few-mode fiber was reconstructed directly from measured guided mode intensity distribution and its spatial partial derivatives with a modified end-fire coupling method using a differential inverse calculation algorithm, which applies only for single-mode guiding.

Tsai, Wan-Shao; Chang, Che-Kai; Sheu, Fang-Wen; Wang, Yao-Hsuan; Chen, Sy-Hann

2014-07-01

49

Graded-index characteristics in single-crystal fibers.  

PubMed

Single-crystal fibers of Ti(3+):Al(2)O (3)have been grown by the laser-heated pedestal growth technique and shown to exhibit radial refractive-index gradients. A refractive-index increase of approximately 12% in the fiber core with respect to the fiber sidewalls has been measured. The index profile can be fitted with a parabolic model. Postgrowth treatment of Cr(3+):Gd(3)Sc (2)Al (3)O(12)fibers has been shown to produce a uniform cladding region with a graded-index core. The core index is some 12.5% larger than the cladding region, with an index profile shape that is approximately parabolic in nature. PMID:18084428

Sharp, J H; Illingworth, R; Ruddock, I S

1998-01-15

50

Fiber optic-based refractive index sensing at INESC Porto.  

PubMed

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

51

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.

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

2012-01-01

52

Modeling multifilament core fibers by effective index method  

NASA Astrophysics Data System (ADS)

Multifilament core fibers (MCFs), a class of optical fibers whose core is made up of a number of strongly-coupled high-index rods surrounded by a low-index homogeneous cladding, can provide single mode operation and large mode area, desirable properties for high-power fiber lasers and amplifiers. We show that due to the low index contrast used in the fiber materials, an effective index method (EIM) can provide highly accurate results in modeling the mode properties of the MCFs such as the mode index and the normalized frequency V as compared with finite element calculation. The normalized frequency V can provide guidance for identifying the single mode regime of the MCFs. Furthermore, results based on the EIM also give good estimates of the mode area within a normalized wavelength range of 0.25-0.5. Thus, the EIM can be a simple yet accurate model for the design of MCFs.

Xie, Xinyi; Huang, Lili; Li, Yanfeng; Hu, Minglie

2013-07-01

53

Statistical Study of Graded-Index Perfluorinated Plastic Optical Fiber  

Microsoft Academic Search

Plastic fiber-based optical links have been proposed for a wide variety of high-speed short reach applications. Graded- index (GI) multimode plastic optical fiber (POF) that supports 10 Gb\\/s over 50 m is commercially available and 40 Gb\\/s over 100 m has beendemonstrated. However,unlikesingle-modefiber and like silica multimode fiber (MMF), GI POF exhibits a range of perfor- mance that depends on

Patrick J. Decker; Arup Polley; Joong H. Kim; Stephen E. Ralph

2011-01-01

54

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

55

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

NASA Astrophysics Data System (ADS)

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

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

2007-05-01

56

Accurate refractive index profiling in a graded-index plastic optical fiber exceeding gigabit transmission rates  

Microsoft Academic Search

An optimum index profile offering the highest bit rate communication was formed in a poly methyl methacrylate (PMMA)-based graded-index plastic optical fiber (GI-POF) by modifying the polymerization process. The interfacial-gel polymerization process we have proposed to fabricate the PMMA-based GI-POF is capable of forming a nearly optimum refractive index profile. However, the theoretically calculated bandwidth from the measured index profile

Takaaki Ishigure; Sho Tanaka; Eiji Kobayashi; Yasuhiro Koike

2002-01-01

57

On the Beam Profile and Beam Quality of Gain-Guided Index-Antiguided Fibers with Finite Cladding Boundary  

Microsoft Academic Search

The beam quality factor $M^2$ for the fundamental LP01 mode of a step-index fiber with a finite cladding diameter is calculated in the presence of gain, in a closed form, as a function of the complex generalized V-number. It is shown that the conventional infinite cladding diameter approximation cannot be used for index-antiguided gain-guided fibers, and the rigorous analysis presented

Parisa Gandomkar Yarandi; Krishna Mohan Gundu; Arash Mafi

2011-01-01

58

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

59

Self-similar propagation in a graded-index nonlinear-fiber amplifier with an external source  

SciTech Connect

We present exact analytical solutions describing spatial bright, trigonometric, and kink-type of self-similar waves, as well as the trains of such waves to the nonlinear Schroedinger equation appropriately modified to model beam propagation in graded-index, nonlinear fiber amplifier with an external source. We show that this model is appropriate for the self-similar propagation in asymmetric twin-core fiber amplifier. The asymmetric twin-core fiber is composed of two adjoining, closely spaced, single mode fibers in which the active one is a graded-index nonlinear fiber and the passive one is a step-index fiber. We obtain these self-similar waves using a Moebius transformation. Our procedure is applicable both for self-focusing and self-defocusing Kerr nonlinearities.

Raju, Thokala Soloman; Panigrahi, Prasanta K. [15647 Avenida Alcachofa, San Diego, California 92128 (United States); Indian Institute of Science Education and Research (IISER), Salt Lake, Kolkata 700106 (India)

2010-04-15

60

Tilted Fiber Bragg Grating photowritten in microstructured optical fiber for improved refractive index measurement.  

PubMed

We report what we believe to be the first Tilted short-period Fiber Bragg Grating photowritten in a microstructured optical fiber for refractive index measurement. We investigate the spectral sensitivity of Tilted Fiber Bragg Grating to refractive index liquid inserted into the holes of a multimode microstructured fiber. We measure the wavelength shift of the first four modes experimentally observed when calibrated oils are inserted into the fiber holes, and thus we determine the refractive index resolution for each of these modes. Moreover, a cross comparison between experimental and simulation results of a modal analysis is performed. Two simulation tools are used, respectively based on the localized functions method and on a finite element method. All results are in very good agreement. PMID:19529434

Phan Huy, Minh Châu; Laffont, Guillaume; Dewynter, Véronique; Ferdinand, Pierre; Labonté, Laurent; Pagnoux, Dominique; Roy, Philippe; Blanc, Wilfried; Dussardier, Bernard

2006-10-30

61

Intrinsic transmission bandwidths of graded-index plastic optical fibers.  

PubMed

We theoretically demonstrate that microscopic heterogeneous properties can enhance the transmission bandwidths of graded-index plastic optical fibers (POFs) for short-haul communication networks. The heterogeneities of the POF cores are quantitatively correlated with mode couplings by modifying the coupled power equation with consideration of the spatial correlation characteristics of the heterogeneities. Using the modified theory, we clarify that the larger fluctuation size and/or amplitude results in higher bandwidth because of greater forward scattering and/or higher scattering efficiency, respectively. This suggests that the multimode fiber bandwidths can depend on the macroscopically observed index profiles as well as on the microscopic material properties. PMID:22743462

Inoue, Azusa; Sassa, Takafumi; Makino, Kenji; Kondo, Atsushi; Koike, Yasuhiro

2012-07-01

62

Thinned fiber Bragg gratings as high sensitivity refractive index sensor  

Microsoft Academic Search

In this work, the numerical and experimental analysis on the use of thinned fiber Bragg gratings as refractive index sensors have been carried out. Wet chemical etching in a buffered hydrofluoric acid solution was used for sensor fabrication. Experimental characterization for an almost full etched cladding sensor is presented demonstrating good agreement with numerical results and resolutions of ?10-5 and

A. Iadicicco; A. Cusano; A. Cutolo; R. Bernini; M. Giordano

2004-01-01

63

High temperature resistant graded-index polymer optical fiber  

Microsoft Academic Search

The dopant system graded-index polymer optical fiber (GI POF) for high temperature stability both in bandwidth and attenuation is reported for the first time. We confirmed that the numerical aperture (NA) of the GI POF strongly influences the high temperature stability of the GI POF in the attenuation. It was confirmed in this paper that the attenuation increment was mainly

Masataka Sato; Miki Hirai; Takaaki Ishigure; Yasuhiro Koike

2000-01-01

64

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

65

Temperature-insensitive miniaturized fiber inline Fabry-Perot interferometer for highly sensitive refractive index measurement.  

PubMed

We report a miniaturized fiber inline Fabry-Perot interferometer (FPI), with an open micro-notch cavity fabricated by one-step fs laser micromachining, for highly sensitive refractive index measurement. The device was tested for measurement of the refractive indices of various liquids including isopropanol, acetone and methanol at room temperature, as well as the temperature-dependent refractive index of deionized water from 3 to 90 degrees C. The sensitivity for measurement of refractive index change of water was 1163 nm/RIU at the wavelength of 1550 nm. The temperature cross-sensitivity of the device was about 1.1x10(-6) RIU/degrees C. The small size, all-fiber structure, small temperature dependence, linear response and high sensitivity, make the device attractive for chemical and biological sensing. PMID:18542685

Wei, Tao; Han, Yukun; Li, Yanjun; Tsai, Hai-Lung; Xiao, Hai

2008-04-14

66

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

67

Improved fully vectorial effective index method for photonic crystal fibers: evaluation and enhancement  

NASA Astrophysics Data System (ADS)

In the effective index method, which models photonic crystal fibers by means of a step-index waveguide analogy, two critical parameters are the effective index of the cladding and the effective core radius. It has been shown that the use of an effective core radius as a function of the relative air hole diameter, or also of the relative wavelength, can improve the accuracy of this method. We show, by comparison with a rigorous finite-difference frequency-domain method, that the reported improved fully vectorial effective index methods have commonly adopted a radius of the equivalent circular unit cell, which does not give the best accurate effective cladding index as compared with the use of an equivalent circular unit cell having the same area as the hexagonal unit cell. Furthermore, by defining both the radius of the equivalent circular unit cell and the effective core radius as a function of the relative air hole diameter, and the relative wavelength, we believe that the fully vectorial effective index method can be further enhanced in terms of accuracy of both the effective cladding index and the modal index.

Li, Yanfeng; Yao, Yuhong; Hu, Minglie; Chai, Lu; Wang, Chingyue

2008-01-01

68

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

69

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

PubMed

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

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

2014-06-15

70

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

NASA Astrophysics Data System (ADS)

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

Hellwig, Tim; Walbaum, Till; Fallnich, Carsten

2013-09-01

71

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 ?m and a length of 5 mm. The field of view was about 80 ?m and the test pattern of 4.38 ?m 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

72

Power losses in deformed graded-index polymer optical fibers.  

PubMed

We investigate the power losses in bent and elongated graded-index polymer optical fibers (GI POFs). The variations of power losses in deformed GI POFs for various radii of curvature and elongations are measured. A simple tensile test result is used to calculate the average plastic energy density (APED) in a deformed GI POF at various elongations. The results indicate that the APED accumulated in a deformed GI POF can be considered as a key index to study the power loss in POF. Based on the experimental results, a curve-fitted equation is proposed to estimate the power loss using the APED for various radii of curvature. The maximum difference between the proposed equation and the experimental results is less than 3% for the deformed GI POFs. PMID:18806851

Chen, Li-Wen; Tsai, Hsun-Heng; Ke, Yi-Long; Chen, Yung-Chuan

2008-09-20

73

Refractive index sensors based on optical fiber hetero-core structures and Fabry-Pérot interferometers  

NASA Astrophysics Data System (ADS)

In this paper, several configurations of optical fiber refractive index sensors based on a hetero-core structure are presented. These sensors are made by splicing short lengths of several specialty fibers with different core and cladding diameters between two standard single-mode fibers. In addition, two fiber bragg gratings are inscribed in single-mode fiber at both sides of the specialty fibers in order to create an in-fiber Fabry-Perot interferometer and the behavior of the transmission spectra is analyzed. The sensitivities and spectral behavior of the sensors are obtained by immersion in solutions of different refractive index.

Bueno, A.; Caucheteur, C.; Kinet, D.; Mégret, P.

2013-05-01

74

High-bandwidth plastic optical fiber with W-refractive index profile  

Microsoft Academic Search

A plastic optical fiber having a W-shaped refractive index profile [W-shaped plastic optical fiber (POF)] was prepared for the first time to realize a higher bit rate transmission than those of the conventional silica-based multimode fiber and graded-index (GI) POF links. Since the W-shaped POF has a valley of the refractive index at the boundary of the core and cladding

Takaaki Ishigure; Hideki Endo; Kunihiro Ohdoko; Yasuhiro Koike

2004-01-01

75

Interferometric fiber-optic gyroscope performance owing to temperature-induced index fluctuations in the fiber: effect on bias modulation  

NASA Astrophysics Data System (ADS)

An analysis of the noise floor owing to temperature-induced index fluctuations in the fiber of a dynamically biased interferometric fiber-optic gyroscope is presented. A comparison with shot noise indicates that, for a harmonic bias modulation, thermal noise in the fiber dominates for fiber lengths longer than \\similar 1 - 2km when practical source power levels are considered. The noise can be reduced or eliminated by the proper choice of modulation frequency or waveform.

Knudsen, Sverre; Bløtekjær, Kjell

1995-06-01

76

Time variation of refractive index in the core of active fiber under pulsed optical pumping  

Microsoft Academic Search

The kinetics of refractive index change in active fiber under pulsed cladding-coupled optical pumping was investigated using interferometric technique. Relaxation processes after lasing threshold was observed.

V. V. Gainov; O. A. Ryabushkin

2008-01-01

77

Effects of the fiber releasing on step-climbing performance of the articulated tracks robots  

Microsoft Academic Search

For a robot used to deliver optical fiber for communication, its center of mass and load change over time. This may affect the robot's obstacle-surmounting capability. In this paper, step-climbing performance of articulated tracks robots was discussed, regarding the maximum height of the step in term of the length of fiber releasing that the robot carries and the swinging angle

Yunwang Li; Shirong Ge; Haifeng Fang; Chengcheng Chu; Yuanyuan Liu

2009-01-01

78

Characterization of fluids and fluid-fluid interaction by fiber optic refractive index sensor measurements  

NASA Astrophysics Data System (ADS)

A fiber optic refractive index sensor is tested for continuous monitoring of fluid-fluid and fluid-gas interactions within the frame of laboratory investigations of CO2 storage, monitoring and safety technology research (COSMOS project, "Geotechnologien" program). The sensor bases on a Fabry-Perot white light interferometer technique, where the refractive index (RI) of the solution under investigation is measured by variation of the liquid-filled Fabry-Perot optical cavity length. Such sensor system is typically used for measuring and controlling oil composition and also fluid quality. The aim of this study is to test the application of the fiber optic refractive index sensor for monitoring the CO2 dissolution in formation fluids (brine, oil, gas) of CO2 storage sites. Monitoring and knowledge of quantity and especially rate of CO2 dissolution in the formation fluid is important for any assessment of long-term risks of CO2 storage sites. It is also a prerequisite for any precise reservoir modelling. As a first step we performed laboratory experiments in standard autoclaves on a variety of different fluids and fluid mixtures (technical alcohols, pure water, CO2, synthetic brines, natural formation brine from the Ketzin test site). The RI measurements are partly combined with default electrical conductivity and sonic velocity measurements. The fiber optic refractive index sensor system allows for RI measurements within the range 1.0000 to 1.7000 RI with a resolution of approximately 0.0001 RI. For simple binary fluid mixtures first results indicate linear relationships between refractive indices and fluid composition. Within the pressure range investigated (up to 60 bar) the data suggest only minor changes of RI with pressure. Further, planned experiments will focus on the determination of i) the temperature dependency of RI, ii) the combined effects of pressure and temperature on RI, and finally iii) the kinetics of CO2 dissolution in realistic formation fluids.

Schmidt-Hattenberger, C.; Weiner, M.; Liebscher, A.; Spangenberg, E.

2009-04-01

79

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

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

80

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.

Guzman-Sepulveda, Jose Rafael; Guzman-Cabrera, Rafael; Torres-Cisneros, Miguel; Sanchez-Mondragon, Jose Javier; May-Arrioja, Daniel Alberto

2013-01-01

81

Investigation of modal properties of microstructured optical fibers with large depressed-index cores  

Microsoft Academic Search

We present what is, to the best of our knowledge, the first systematic study on how negative core-cladding index difference influences microstructured optical fiber's modal behavior. Single-mode lasing has been realized for short-length cladding-pumped phosphate glass microstructured fibers with large depressed-index Er3+-Yb3+-codoped cores.

L. Li; A. Schülzgen; V. L. Temyanko; H. Li; S. Sabet; M. M. Morrell; A. Mafi; J. V. Moloney; N. Peyghambarian

2005-01-01

82

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

PubMed

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

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

2010-10-10

83

Train communication system using graded-index leaky plastic optical fiber  

Microsoft Academic Search

We propose a new train communication system using optical wireless communication. In the proposed system, graded-index (GI) leaky plastic optical fiber (POF) is used as the communication medium. Since this fiber has the structure where scatterers are mixed in the core of normal GI-POF, the light which is entered through the end of this fiber from laser diode (LD) can

Akihiro Shimura; Yasuo Sugawara; Shinkhiro Haruyama; M. Nakagawa; Hiromrzsa Suzuki; Atsushi Kondo; Takmki Ishigure; Yasuhiro Koike

2004-01-01

84

Detailed Investigation of Mode-Field Adapters Utilizing Multimode-Interference in Graded Index Fibers  

Microsoft Academic Search

We present a detailed study of mode-field adapters (MFA) based on multimode interference in graded index multimode fibers. We have fabricated and characterized MFAs from a selection of commercially available single-mode and graded index fibers. Compared to existing techniques, the presented MFAs can be fabricated very quickly and are not limited to certain fiber types. Insertion losses of $< 0.5$

Peter Hofmann; Arash Mafi; Clémence Jollivet; Tobias Tiess; N. Peyghambarian; Axel Schulzgen

2012-01-01

85

Improved self-imaging for multi-mode optical fiber involving cladding refractive index  

NASA Astrophysics Data System (ADS)

In this work, improved self-imaging for optical fiber is proposed. For the first time, a precise formula of reimaging distance involving normalized frequency and cladding refractive index is given. By using our proposal, we can estimate the reimaging distance and evaluate the impact of cladding refractive index precisely and effectively. This method can be used to analyze multi-mode fiber interferences, especially no-core fiber interference.

Zheng, Jingjing; Li, Jing; Ning, Tigang; Pei, Li; Jian, Shuisheng; Wen, Yinghong

2013-01-01

86

Nonlinear propagation effects in antiresonant high-index inclusion photonic crystal fibers  

Microsoft Academic Search

We experimentally and numerically investigate femtosecond-pulse propagation in a microstructured optical fiber consisting of a silica core surrounded by airholes that are filled with a high-index fluid. This fiber combines the resonant properties of hollow-core bandgap fibers and the high nonlinearity of index-guiding waveguides. A range of nonlinear optical effects can be observed, including soliton propagation, dispersive wave generation, and

A. Fuerbach; P. Steinvurzel; J. A. Bolger; A. Nulsen; Benjamin J. Eggleton

2005-01-01

87

Modal bandwidth enhancement in a plastic optical fiber by W-refractive index profile  

Microsoft Academic Search

A plastic optical fiber (POF) having a W-shaped refractive index profile (W-shaped POF) was prepared for the first time that had a possibility to realize a higher bit rate transmission than those of the conventional silica-based multimode fiber and graded index (GI) POF links. Since the W-shaped POF has a valley of the refractive index at the boundary of the

Takaaki Ishigure; Hideki Endo; Kunihiro Ohdoko; Keita Takahashi; Yasuhiro Koike

2005-01-01

88

Numerical analysis of modal dispersion in graded-index plastic optical fibers  

Microsoft Academic Search

Modal dispersion properties of a fabricated plastic optical fiber are numerically calculated through a finite-element method. The modal index, group delay, impulse response, and output pulse shape are compared with those for the power-law profile plastic optical fiber; the influence of index profile deviations from the power-law profile is described. It is shown that index profile fluctuations in the actual

Masashi Eguchi

2005-01-01

89

Optimal Design of Multichannel Fiber Bragg Grating Filters With Small Dispersion and Low Index Modulation  

Microsoft Academic Search

We have proposed an effective method to synthesize and optimize multichannel fiber Bragg grating filters (MCFBGFs). The novel method contains two steps, i.e., the discrete layer peeling algorithm generates the excellent initial guess values and, successively, the nonlinear least squares method reconstructs and optimizes the expected fiber Bragg grating parameters from the initial guess in the previous step. Design examples

Yongkang Gong; Xueming Liu; Leiran Wang; Xiaohong Hu; Aoxiang Lin; Wei Zhao

2009-01-01

90

Index profile design for high-bandwidth W-shaped plastic optical fiber  

Microsoft Academic Search

Modal dispersion in plastic optical fibers with W-shaped refractive index profiles (W-shaped POFs) is investigated. The authors focus on the effect of the refractive index valley at the boundary of core and cladding on the group delay. In this paper, particularly, the relationship between the depth of the index valley and the modal dispersion is highlighted. In order to analyze

Keita Takahashi; Takaaki Ishigure; Yasuhiro Koike

2006-01-01

91

Split Step Fourier Method Based Pulse Propagation Model for Nonlinear Fiber Optics  

Microsoft Academic Search

A pulse propagation model is essential to investigate various effects in nonlinear optical fiber communications. Split step Fourier method (SSFM) is an efficient technique to implement nonlinear Schrodinger equation (NLSE) which describes pulse propagation phenomenon in optical fiber. We report some simulation results obtained using our developed model based on SSFM. Our results are in well accordance with the standard

M. Y. Hamza; S. Tariq

2007-01-01

92

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...

93

Nonlinear propagation effects in antiresonant high-index inclusion photonic crystal fibers.  

PubMed

We experimentally and numerically investigate femtosecond-pulse propagation in a microstructured optical fiber consisting of a silica core surrounded by airholes that are filled with a high-index fluid. This fiber combines the resonant properties of hollow-core bandgap fibers and the high nonlinearity of index-guiding waveguides. A range of nonlinear optical effects can be observed, including soliton propagation, dispersive wave generation, and a Raman self-frequency shift. Tuning the center wavelength of the laser and varying the refractive index of the fluid lead to different propagation effects, mediated by the strongly wavelength-dependent group-velocity dispersion in these photonic bandgap confining structures. PMID:15865369

Fuerbach, A; Steinvurzel, P; Bolger, J A; Nulsen, A; Eggleton, B J

2005-04-15

94

Refractive index profiling of a GRIN optical fiber using a modulated speckled sheet of light  

NASA Astrophysics Data System (ADS)

A method for calculating the refractive index of GRIN optical fiber from its transverse interference pattern is presented.In this method the transverse interference fringe pattern through an optical fiber using a sheet of light is applied to get the refractive index profile of it. The optical fiber is not immersed in a matching liquid as used in different techniques [Barakat N, El-Hennawi HA, El-Zaiat SY, Hassan R. Pure Appl Opt 1996;5:27]. In this method a sheet of He-Ne laser light is allowed to illuminate the fiber. The light sheet is divided into two parts, the first is refracted through the fiber while the second is used as a reference beam. Interference pattern will be obtained between these two rays displaying the refractive index variation along the fiber radius. The fringe shift of such interference pattern has been measured and used to calculate the deflection angle of light refracted by the fiber and the cladding. An equation is derived to calculate the refractive index profile difference ratio ?n at different positions across the fiber cross section in terms of the corresponding deflection angle and is verified experimentally. The optical path difference between these two rays (refracted and reference beam divided by the fiber) has been derived and the fringe shift obtained has been used to calculate the refractive index profile of the fiber. Introducing a ground glass screen on the passage of the two light beams (refracted and reference beam divided by the fiber), two superimposed identical speckle patterns are formed leading to the formation of a third speckle pattern modulated by a grid structure displaying the optical thickness of the fiber.

El-Ghandoor, H.; El-Ghafar, E. Abd.; Hassan, R.

1999-10-01

95

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

Microsoft Academic Search

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

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

2011-01-01

96

Core-cladding mode recoupling based fiber optic refractive index sensor  

NASA Astrophysics Data System (ADS)

We present a compact and robust fiber optic refractive index sensor based on a tilted fiber Bragg grating (TFBG) inscribed in a thin-core fiber that is spliced to a standard single-mode fiber (SSMF). Due to the core mismatch between the SSMF and the thin-core fiber, cladding modes generated from the TFBG can be back into SSMF for detection. Since the effective refractive index of a cladding mode is dependent on the surrounding refractive index (SRI), the cladding-mode resonances can be used for measurement. We fabricate the sensor probe and test it in a series solution with different SRIs, and the experimental results agree with the theoretical analysis. The repeatability of the sensor is also tested in the same SRI range. We demonstrate its capability and simplicity to use this sensor for a wide range SRI measurement.

Zhang, Xinpu; Peng, Wei; Liu, Yun; Pan, Lujun

2013-05-01

97

Reconstruction of fiber grating refractive-index profiles from complex bragg reflection spectra.  

PubMed

Reconstruction of the refractive-index profiles of fiber gratings from their complex Bragg reflection spectra is experimentally demonstrated. The amplitude and phase of the complex reflection spectrum were measured with a balanced Michelson interferometer. By integrating the coupled-mode equations, we built the relationship between the complex coupling coefficient and the complex reflection spectrum as an iterative algorithm for reconstructing the index profile. This method is expected to be useful for reconstructing the index profiles of fiber gratings with any apodization, chirp, or dc structures. An apodized chirped grating and a uniform grating with a depression of index modulation were used to demonstrate the technique. PMID:18323933

Huang, D W; Yang, C C

1999-07-20

98

Reconstruction of Fiber Grating Refractive-Index Profiles from Complex Bragg Reflection Spectra  

NASA Astrophysics Data System (ADS)

Reconstruction of the refractive-index profiles of fiber gratings from their complex Bragg reflection spectra is experimentally demonstrated. The amplitude and phase of the complex reflection spectrum were measured with a balanced Michelson interferometer. By integrating the coupled-mode equations, we built the relationship between the complex coupling coefficient and the complex reflection spectrum as an iterative algorithm for reconstructing the index profile. This method is expected to be useful for reconstructing the index profiles of fiber gratings with any apodization, chirp, or dc structures. An apodized chirped grating and a uniform grating with a depression of index modulation were used to demonstrate the technique.

Huang, Ding-Wei; Yang, Chih-Chung

1999-07-01

99

Cladding modes analysis of photonics crystal fiber for refractive index sensors using Finite Element method  

Microsoft Academic Search

We developed a Finite Element package to analyze cladding mode field extensions into the air-holes of photonics crystal fiber for refractive index sensing. Our analysis could determine the most sensitive cladding mode for liquid sensing.

Naeem Khurram; Linh Viet Nguyen; Kamal Alameh; Youngjoo Chung

2010-01-01

100

A refractive index sensor based on the resonant coupling to cladding modes in a fiber loop.  

PubMed

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

101

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.

Reyes, Mauricio; Monzon-Hernandez, David; Martinez-Rios, Alejandro; Silvestre, Enrique; Diez, Antonio; Cruz, Jose Luis; Andres, Miguel V.

2013-01-01

102

All-fiber coherent combining of Er-doped fiber amplifiers by active resonantly-induced refractive index control in Yb-doped fiber  

Microsoft Academic Search

We report on all-fiber coherent combining of 1.55 mum Er-doped single mode amplifiers achieved by means of active phase control that specifically employs the refractive index changes in Yb-doped fiber induced by 980 nm laser diode.

Andrei A. Fotiadi; Nikita G. Zakharov; Oleg L. Antipov; Patrice Mégret

2008-01-01

103

Qualitative measurement of average index profile of symmetrical microstructured optical fiber from microscopic imaging  

Microsoft Academic Search

Using a simple non-destructive and non-interferometric technique, we obtained an approximation of the average index profile for a partially symmetrical air-silica microstructured optical fiber. The method proposed in [1] for conventional fibers, where an image of the phase gradients is introduced into a transmitted optical field by a fiber sample, was used. An image of the phase gradients was obtained

Edgar Saucedo; Vladimir P. Minkovich

2007-01-01

104

Streak camera measurements of laser pulse temporal dispersion in short graded-index optical fibers  

SciTech Connect

Streak camera measurements were used to determine temporal dispersion in short (5 to 30 meter) graded-index optical fibers. Results show that 50-ps, 1.06-..mu..m and 0.53-..mu..m laser pulses can be propagated without significant dispersion when care is taken to prevent propagation of energy in fiber cladding modes.

Lerche, R.A.; Phillips, G.E.

1981-08-28

105

Hybrid long period fiber grating for measuring refractive index and pressure in downhole application  

Microsoft Academic Search

A hybrid long period fiber grating (HLPFG) sensor was utilized for sensing the refractive index and pressure for downhole applications. The HLPFG is fabricated by fattening and tapering on a single mode fiber, utilizing a standard fusion splicing and a CO2 laser, respectively. The limit of detection (LOD) of the HLPFG for the RI measurement in the range from 1.3150

J. Sadeghi; M. I. Zibaii; M. Kheiri; A. Ahmadlou; H. Latifi; M. H. Ghezelaiagh

2011-01-01

106

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

Microsoft Academic Search

Vertical-cavity surface-emitting lasers (VCSELs) with emission wavelengths in the range from 850 nm to 950 nm are highly attractive light sources for low-cost, high-speed data transmission over several hundred meters of perfluorinated graded-index plastic-optical fibers (GI- POFs). Multi-Gigabit\\/s data transmission over common PMA- based step-index POFs is generally limited to several meters predominantly due to dispersion. Here, we demonstrate 3

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

1999-01-01

107

Estimation of dispersion parameters involving Petermann II spot size using a Gaussian-type approximation in single-mode graded index fibers  

NASA Astrophysics Data System (ADS)

Based on a recently prescribed simple and novel approximation of the fundamental mode, we present analytic expressions for the Petermann II spot size, suitable for evaluating the dispersion parameters of single-mode graded-index fibers. With these expressions, we calculate the group delay dispersion factor and also the normalized waveguide dispersion coefficient. On comparison, our formulation is shown to be superior to the Gaussian approximation and predicts the parameters identically with the exact numerical techniques for step and parabolic index profiles.

Das, Gautam; Sarkar, Somenath N.

1997-09-01

108

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

109

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

110

Cyclic Steps and Antidunes : Relating Their Features to a Suspension Index  

NASA Astrophysics Data System (ADS)

Cyclic Steps and Antidunes : Relating Their Features to a Suspension Index Miwa Yokokawa (1), Yasushi Kishima (1), Gary Parker (2, 3) 1: Osaka Institute of Technology, Hirakata, Osaka, Japan 2: Dept. of Civil & Environmental Engineering, University of Illinois, Urbana, Illinois, U.S.A. 3: Dept. of Geology, University of Illinois, Urbana, Illinois, U.S.A. There are very few comparative studies of the differences in hydraulic conditions and morphologic features of bed- and water-surface-waves associated with cyclic steps and antidunes. In this study, the features of both the bed and the water surface, as well as hydraulic conditions are examined over the spectrum from antidune to cyclic steps. Experiments were performed using a flume at the Osaka Institute of Technology. The resultant features of the bedforms are as follows. In the case of antidunes, bed waves and water surface waves are in phase except when they collapse. Antidunes show several kinds of behavior; migrating downstream, standing, or migrating upstream. Upstream-migrating antidunes are divided into non-breaking, and breaking-types. Breaking antidunes appear alternatively with the plane bed state. Cyclic steps migrate upstream regularly associated with trains of hydraulic jumps, which divide each step. There is a significant change in water depth at the hydraulic jump, so that the phasing between the bed waves and water surface waves break at the each hydraulic jump. There is a kind of compromise between cyclic steps and antidunes, which we designate as “intermediate steps”. They move upstream and are associated with regular trains of hydraulic jumps. The jumps, however, occasionally collapse toward upstream. When this happens, bed waves move rapidly upstream; low-amplitude water surface waves and bed waves become in phase all over the bed shortly after the collapse. Then after some time, water surface waves become sufficiently prominent to yield regular hydraulic jumps. This cycle is then repeated.The hydraulic conditions for these bedfoms were examined using three non-dimensional parameters, i.e. the Froude Number, the Suspension Index, and the dimensionless particle size. The suspension index is a newly introduced parameter which is the ratio of the shear velocity divided by the settling velocity of the sediment (u*/Vs). Data from previous experimental studies are examined together with the present data in studying the characteristic regimes of bedform formation. In a diagram of Froude Number v.s. Suspension Index, antidunes, intermediate steps and cyclic steps can be divided along the axis of the Suspension Index. In the lowest range of the suspension index, downstream-migrating antidunes and upstream-migrating antidunes that do not break are found. The intermediate steps discussed above are located in the middle range. The highest range corresponds to cyclic steps and breaking antidunes. As described above, the Suspension Index can serve as a scale to quantify the spectrum between antidunes and cyclic steps. The use of the parameter also helps verify that suspension plays an important role in the formation and maintenance of cyclic steps.

Yokokawa, M.; Kishima, Y.; Parker, G.

2010-12-01

111

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

112

Waveguide parameter design of graded-index plastic optical fibers for bending-loss reduction  

Microsoft Academic Search

The waveguide structure of graded-index plastic optical fibers (GI POFs), such as index profile, numerical aperture (NA), and core diameter, is appropriately designed for eliminating bending losses, even under a severe bending condition. The bending loss of GI POFs under a severe bending condition is drastically reduced when the core diameter is smaller than 200 ?m and when the NA

Kenji Makino; Takaaki Ishigure; Yasuhiro Koike

2006-01-01

113

Dynamics of pump\\/signal-induced index change in Yb-doped fiber amplifier  

Microsoft Academic Search

The refractive index change in a Yb-doped fiber amplifier under diode pumping and pulse amplification is investigated using Mach-Zehnder interferometer operating in the spectral range far from Yb-ion transitions. A strong phase shift which indicate the change in the refractive index is observed both under pulsed and continuous wave pumping.

A. A. Fotiadi; O. L. Antipov; P. Megret

2007-01-01

114

Longitudinal versus transversal excitation in doped graded-index polymer optical fibers  

NASA Astrophysics Data System (ADS)

In this work we perform a detailed experimental and theoretical analysis of the properties of amplified spontaneous emission (ASE) in a rhodamine-6G-doped graded-index polymer optical fiber when the fiber is pumped either longitudinally or transversally with respect to the fiber axis. The dependence of the ASE threshold and efficiency on fiber length has been compared for both schemes of excitation. A theoretical model for longitudinal excitation has been carried out by means of the laser rate equations as functions of time, distance traveled by light and wavelength. The analysis takes into account that the fiber is a typical graded-index POF in which the radial distributions of light power density and dye concentration are not uniform. The theoretical calculations agree satisfactorily with the experimental results. The photodegradation of the ASE intensity has also been measured for both pumping schemes.

Illarramendi, M. A.; Arrue, J.; Ayesta, I.; Jiménez, F.; Zubia, J.; Bikandi, I.; Tagaya, A.; Koike, Y.

2014-03-01

115

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

116

Controlled modification and direct characterization of multimode-fiber refractive-index profiles.  

PubMed

A combination of controlled annealing and characterization by scanning probe microscopy (SPM) is used to demonstrate that the refractive-index proffle of a commercially available silica-based optical fiber can be accurately reconfigured for use as an evanescent field sensor. The process relies on the controlled relocation of the silica glass dopants across the fiber cross section through heat treatment and the accurate measurement of the resulting dopant redistribution with SPM and differential etching techniques. The effect of variable annealing along a length of fiber is to produce a mode transformer to couple light from a laser source into the sensing region of the fiber. PMID:12564481

Gibson, Brant C; Huntington, Shane T; Love, John D; Ryan, Tom G; Cahill, Laurence W; Elton, Darrell M

2003-02-01

117

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

118

Two-core transversally chirped microstructured optical fiber refractive index sensor.  

PubMed

We present a sensing architecture consisting of a two-core chirped microstructured optical fiber (MOF) for refractive index sensing of fluids. We show that by introducing a chirp in the hole size, the MOF can be a structure with decoupled cores, forming a Mach-Zehnder interferometer in which the analyte directly modulates the device transmittance by its differential influence on the effective refractive index of each core mode. We show that by filling all fiber holes with analyte, the sensing structure achieves high sensitivity (transmittance changes of 300 per RIU at 1.42) and has the potential for use over a wide range of analyte refractive index. PMID:24690846

Torres, Pedro; Reyes-Vera, Erick; Díez, Antonio; Andrés, Miguel V

2014-03-15

119

High-resolution refractive index anisotropy measurement in optical fibers through phase retardation modulation  

NASA Astrophysics Data System (ADS)

We present an improved, high-resolution method for the measurement of phase retardation induced by the material birefringence of optical fibers. Such a method can be used to retrieve information about the spatial distribution of refractive index anisotropy in the fiber by comparing the accumulated phase of a polarization component oriented along the fiber transmission axis and another located in the transverse plane. The method is based on the nonlinear regression of a phase modulated signal of known modulation amplitude altered by the sample. Experimental results obtained with our method for a standard telecommunications fiber (the Corning SMF-28) as well as photosensitive fibers (Fibercore PS1250 and PS1500) are presented with a noise-limited phase resolution below 10-4 radians and a spatial resolution below 1 ?m. An analysis of the limitation of such measurement methods is also presented including diffraction by the fibers.

Sévigny, Benoit; Busque, François; Godbout, Nicolas; Lacroix, Suzanne; Faucher, Mathieu

2008-03-01

120

Refractive index sensing characterization of a singlemode-claddingless-singlemode fiber structure based fiber ring cavity laser.  

PubMed

This paper firstly demonstrated the refractive index (RI) characteristics of a singlemode-claddingless-singlemode fiber structure filter based fiber ring cavity laser sensing system. The experiment shows that the lasing wavelength shifts to red side with the ambient RI increase. Linear and parabolic fitting are both done to the measurements. The linear fitting result shows a good linearity for applications in some areas with the determination coefficient of 0.993. And a sensitivity of ~131.64nm/RIU is experimentally achieved with the aqueous solution RI ranging from 1.333 to 1.3707, which is competitively compared to other existing fiber-optic sensors. While the 2 order polynomial fitting function, which determination relationship is higher than 0.999, can be used to some more rigorous monitoring. The proposed fiber laser has a SNR of ~50dB, and 3dB bandwidth ~0.03nm. PMID:24663842

Liu, Zhi-bo; Tan, Zhongwei; Yin, Bin; Bai, Yunlong; Jian, Shuisheng

2014-03-10

121

One-Step Tape Casting of Composites via Slurry on Fiber  

NASA Technical Reports Server (NTRS)

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

deGroh, Henry C., III

2001-01-01

122

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

PubMed

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

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

2011-08-10

123

A ray-transfer-matrix model for hybrid fiber Fabry-Perot sensor based on graded-index multimode fiber.  

PubMed

A theoretical model based on the ray-transfer-matrix method is developed for explaining the principle of a graded-index multimode fiber (GI-MMF) based hybrid fiber Fabry-Perot (GI-FFP) sensor. It is verified by the numerical simulations and experimental results that the high fringe contrast of the reflective spectrum of the sensor is due to the periodic self-focusing effect of the GI-MMF. The influence of the GI-MMF length on the shape of reflective spectrum and corresponding maximum fringe contrast are investigated. Experimental results are in good agreement with the theory. A typical GI-FFP sensor is fabricated and its response to the external refractive index is measured with a maximum sensitivity of approximately 160 dB/RIU (Refractive Index Unit). PMID:20720966

Gong, Yuan; Zhao, Tian; Rao, Yun-Jiang; Wu, Yu; Guo, Yu

2010-07-19

124

Glass of high refractive index for optics and optical fiber  

Microsoft Academic Search

Halide-chalcogenide glasses whose properties make them suitable for applications in modern optics and optical fiber technique are investigated. The object of examination were oxygen-free glasses in the Sb2Se3BaCl2-PbCl2 system. Because of the unconventional method of obtaining these glasses a special method of synthesizing these glasses is developed. Their characteristic temperatures and thermal stabilities are determined. Structural investigations using IR spectroscopy

Jan Wasylak; Maria Laczka; Jan Kucharski

1997-01-01

125

Fiber inline Michelson interferometer fabricated by CO2 laser irradiation for refractive index sensing  

NASA Astrophysics Data System (ADS)

A compact Michelson interferometer (MI) in a single-mode fiber (SMF) is successfully formed by CO2 laser irradiation to measure refractive index (RI) values. The fiber inline MI mainly consists of two parts: one is the waist region in fiber formed by CO2 laser irradiation and the other one is the fiber tip end facet with pure gold sputter coating. Based on the MI theory, the interference signal is generate between the core mode and the cladding mode excited by the core mode at the waist region. Reflective spectra at two different interference lengths of 5mm and 15mm are given and the calculated lengths based on theory are well verified. After the measurements of matching liquids with seven different refractive indices, the RI sensitivity of the MI sample is tested of -197.3+/-19.1nm/RIU (refractive index unit), which suggests well potential application in RI sensing.

Wu, Hongbin; Yuan, Lei; Zhao, Longjiang; Cao, Zhitao; Wang, Peng

2014-03-01

126

Nondestructive measurement of refractive index profile of optical fiber preforms using moire technique and phase shift method  

NASA Astrophysics Data System (ADS)

The refractive index profile of optical fiber preform is measured by a nondestructive technique based on Talbot interferometry. In this technique the preform is placed between two ronchi ruling gratings of 10 lines/mm and the system is illuminated by an expanded and collimated beam of He-Ne laser. In this arrangement the 2nd grating is positioned in the Talbot image of the 1st grating and the preform axis is parallel to the gratings planes. To eliminate the effect of clad on the light beam deflection during the measurements, the preform is immersed in an index matching liquid. The phase front of the laser light over the 2nd grating can be monitored by analysis of the moire pattern which is formed over there. The analysis is done by means of 4-step phase shift technique. In this technique the second grating is moved in four steps of 1/4 of the grating vector and in each step the intensity profile of the moire pattern is recorded. The phasefront can be specified by using the recorded intensities. The refractive index profile of the preform can be calculated from the changes on phasefront while the preform is placed between the gratings respect to the case when it is absent. The whole procedure is automated and computer controlled by using a CCD camera to record the moire fringes, a stepper motor for linear translation of the 2nd grating and a code in MATLAB to control the system and measurements.

Ranjbar, Samaneh; Khalesifard, Hamid R.; Rasouli, Saifollah

2006-01-01

127

Fabrication of graded-index plastic optical fiber by the diffusion-assisted coextrusion method  

Microsoft Academic Search

Recently, plastic optical fibers (POFs) have drawn significant attention as high-speed transmission media due to their advantages over conventional glass optical fibers such as flexibility and durability. In addition, Grade-Index (GRIN) POFs with smoothly varying refractive indices provide increased data transmission speeds suitable for the short-distance communications such as local area networking or home networking. In this research, the diffusion-assisted

In-Sung Sohn

2001-01-01

128

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

129

Electronic vs thermal index changes in pulsed and CW Yb-doped fiber amplifiers  

Microsoft Academic Search

The pump\\/signal induced refractive index changes (RICs) could strongly affect the generation of light in fiber lasers and amplifiers. The RICs in cw or quasi-cw pumped rare-earth-doped optical fibers can be caused both by the thermal mechanisms (due to thermalizatio n of the pumping energy) and a non-thermal effect due to population change of levels with a different polarizability (it

Maxim S. Kuznetsov; Oleg L. Antipov; Andrei A. Fotiadi; Patrice Megret

2011-01-01

130

Tension increase correlated to refractive-index change in fibers containing UV-written Bragg gratings  

NASA Astrophysics Data System (ADS)

A strong axial tension increase induced by UV laser radiation is observed in the cores of single-mode optical fibers containing Bragg gratings, independently of the initial core stress. The induced index modulation of the gratings is linearly correlated to stress changes with a slope of (0.8+/-0.2) \\times 10-4 mm 2/kg . The phenomenon can be explained by a structural change of the glass in the fiber core into a more compact configuration.

Fonjallaz, P. Y.; Limberger, H. G.; Salathé, R. P.; Cochet, F.; Leuenberger, B.

1995-06-01

131

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

132

Resonantly guided modes in microstructured optical fibers with a circular array of high-index rods.  

PubMed

A microstructured optical fiber with a new type of waveguiding mechanism is proposed. The fiber consists of a circular rod array of high index material (n=3.48) embedded in a low index background (n=1.44). The rod array exhibits guided-mode resonance (GMR) for cylindrical waves arriving from inside the array, and thus functions as a highly reflective circular wall. Through finite-difference time-domain (FDTD) simulations, we confirmed light confinement and guidance near the GMR wavelength. Basic optical characteristics such as dispersion relations, loss spectra, and mode field profiles were calculated. PMID:23903114

Ohtera, Yasuo; Hirose, Haruka; Yamada, Hirohito

2013-08-01

133

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

134

Efficient group delay averaging in graded-index plastic optical fiber with microscopic heterogeneous core.  

PubMed

Intrinsic mode coupling in a graded-index plastic optical fiber (GI POF) is investigated using the developed coupled power theory for a GI POF with a microscopic heterogeneous core. The results showed that the intrinsic material properties can induce random power transitions between all the guided modes, whereas the structural deformation of microbending results in nearest-neighbor coupling. It was numerically demonstrated that efficient group-delay averaging due to intrinsic mode coupling brings the pronounced bandwidth enhancement in fibers with much shorter length than the case of glass multimode fibers. PMID:23938585

Inoue, Azusa; Sassa, Takafumi; Furukawa, Rei; Makino, Kenji; Kondo, Atsushi; Koike, Yasuhiro

2013-07-15

135

Electronic and thermal refractive index changes in ytterbium-doped fiber amplifiers.  

PubMed

We develop a theoretical framework to analyze the mechanism of refractive index changes (RIC) in double-clad Yb³? doped optical fibers under resonant core or clad pumping, and with signal amplification. The model describes and compares thermal and electronic contributions to the phase shifts induced on the amplified signal at 1064 nm and the probe signal at 1550 nm, i.e. located inside and outside of the fiber amplification band, respectively. The ratio between the thermal and electronic phase shifts is evaluated as a function of the pump pulse duration, the gain saturation, the amplified beam power and for a variety of fiber parameters. PMID:24104127

Kuznetsov, M S; Antipov, O L; Fotiadi, A A; Mégret, P

2013-09-23

136

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

137

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

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

138

Optimization of index modulation profile of sampling period for sampled fiber Bragg gratings  

Microsoft Academic Search

Using the simple inverse Flourier transformation of the target channels, we can get the index modulation structure of the sampled period for the sampled fiber Bragg gratins (FBGs). In this method, the enable channels are identical wavelength operation while the unable channels are almost suppressed completely, and the enable and unable channels can be established at will based on the

Yumin Liu; Zhongyuan Yu; Hongbo Yang; Na Zhang

2004-01-01

139

Sensitivity of photonic crystal fiber grating sensors: biosensing, refractive index, strain, and temperature sensing  

Microsoft Academic Search

We study the sensitivity of fiber grating sensors in the applications of strain, temperature, internal label-free biosensing, and internal refractive index sensing. It is shown that optical dispersion plays a central role in determining the sensitivity, and the dispersion may enhance or suppress sensitivity as well as change the sign of the resonant wavelength shifts. We propose a quality factor,

Lars Rindorf; Ole Bang

2008-01-01

140

a Geometric Optical Investigation of Propagation of Polarization in Symmetric and Asymmetric Graded Index Fibers  

Microsoft Academic Search

Changes in polarization of the electromagnetic field along rays within symmetric and asymmetric parabolic index gradient fibers is investigated. The evolution of polarization in isotropic and inhomogeneous media is, of course, contained in Maxwell's equations. Within the approximation of geometrical optics, lambda_0to 0, the vector wave equations lead to geometrical optics: ray trajectories and transport equations for propagation of the

Mahmood Afzal

1991-01-01

141

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

PubMed

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

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

2009-11-15

142

Temperature and refractive index sensing characteristics of an MZI-based multimode fiber-dispersion compensation fiber-multimode fiber structure  

NASA Astrophysics Data System (ADS)

We proposed an optical fiber sensor with simple multimode fiber (MMF)-dispersion compensation fiber (DCF)-multimode fiber structure based on Mach-Zehnder Interferometer (MZI) and researched its temperature and refractive index (RI) sensing characteristics. The sensing principle is based on the interference between core and cladding modes of DCF due to the large core diameter mismatch. Spectral analyses demonstrate that the transmission spectrum is mainly formed by the interference between the dominant excited cladding mode and core modes. The experimental results show that the proposed sensor has high temperature sensitivity of 0.118 nm/°C in the range of 20-250 °C and RI sensitivity of 66.32 nm/RIU within the linear sensing range of 1.33-1.39 RIU. Therefore, the characteristics of compact size, low cost, easy fabrication, high sensitivities, and good anti-interference ability make this sensor have extensive application prospects.

Sun, Hao; Yang, Shen; Zhang, Jing; Rong, Qiangzhou; Liang, Lei; Xu, Qinfang; Xiang, Guanghua; Feng, Dingyi; Du, Yanying; Feng, Zhongyao; Qiao, Xueguang; Hu, Manli

2012-12-01

143

An automatic step adjustment method for average power analysis technique used in fiber amplifiers  

NASA Astrophysics Data System (ADS)

An automatic step adjustment (ASA) method for average power analysis (APA) technique used in fiber amplifiers is proposed in this paper for the first time. In comparison with the traditional APA technique, the proposed method has suggested two unique merits such as a higher order accuracy and an ASA mechanism, so that it can significantly shorten the computing time and improve the solution accuracy. A test example demonstrates that, by comparing to the APA technique, the proposed method increases the computing speed by more than a hundredfold under the same errors. By computing the model equations of erbium-doped fiber amplifiers, the numerical results show that our method can improve the solution accuracy by over two orders of magnitude at the same amplifying section number. The proposed method has the capacity to rapidly and effectively compute the model equations of fiber Raman amplifiers and semiconductor lasers.

Liu, Xue-Ming

2006-04-01

144

An integral split-step fourier method for digital back propagation to compensate fiber nonlinearity  

NASA Astrophysics Data System (ADS)

In optical fiber transmission systems, the split-step Fourier method (SSFM) has been widely used in digital back propagation (DBP) to compensate fiber nonlinearity. In this paper, by using the Lagrange's Integral Mean Value Theorem (LIMVT), we derive an analytical expression to calculate the optimal value of the nonlinearity calculation position (NLCP) for different systems and we propose an integral SSFM (I-SSFM) based on the expression. The I-SSFM can be performed more accurately and efficiently without parameter optimization. Simulations of various transmission links show that the I-SSFM outperforms the conventional asymmetric SSFM (A-SSFM) and the symmetric SSFM (S-SSFM) significantly, especially when we employ less amount of steps to ensure computation efficiency. The computation effort of the I-SSFM reaches as low as 50% of that of the S-SSFM.

Yang, Jie; Yu, Song; Li, Minliang; Chen, Zhixiao; Han, Yi; Gu, Wanyi

2014-02-01

145

Fiber-Laser-Based Sensor for Measuring Refractive Index and Solute Concentration of Aqueous Solutions  

NASA Astrophysics Data System (ADS)

We report a novel-principle fiber-laser intra-cavity sensor for measuring refractive index and solute concentration of aqueous solutions. The sensor operation is based on a variation of the laser oscillation relaxation frequency (RF, the measured parameter), sensitive to the intra-cavity loss. As the loss includes the reflection coefficient on the frontier aqueous solution-silica fiber cleaved cut, being the laser output coupler and simultaneously the sensor head, the RF becomes affected by the changes in refractive index of the aqueous solution; in turn, because the solution index is proportional to the solute concentration in water, the RF becomes also a function of the latter. The sensor capacity is demonstrated on the example of measurements of sugar concentration in water. A modeling of the sensor operation is presented, allowing its performance optimization.

Arellano-Sotelo, Héctor; Barmenkov, Yuri O.; Kir'yanov, Alexander V.

2008-10-01

146

Temperature and refractive index measurements using long-period fiber gratings fabricated by femtosecond laser  

NASA Astrophysics Data System (ADS)

Long period fiber gratings (LPFGs) with different periods in the standard single mode fiber were fabricated, using laser direct writing method, by femtosecond laser pulses with pulse width of 200 fs and the repetition rate of 250 kHz at a center wavelength of 800 nm in air. Comparative with bare LPFG in temperature sensor, LPFG had been encapsulated using large coefficient of thermal expansion of epoxy polymer and Aluminum to enhance the temperature sensitivity. The results showed that the temperature sensitivity of encapsulated LPFG was 2 times than that of bare LPFG. In addition, we also researched the relationship between resonant wavelength and surrounding refractive index (SRI) when LPFG immersed in refractive index of solution of different index at 20 degree Celsius.

Yu, Yongqin; Zheng, Jiarong; Yi, Kai; Ruan, Shuangchen; Du, Chenlin; Huang, Jianhui; Zhong, Wansheng

2011-11-01

147

Effects of average index variation in apodized long-period fiber gratings  

NASA Astrophysics Data System (ADS)

We analyze the effects of average index variation on the transmission characteristics of an index-apodized long-period fiber grating (LPFG) by the transfer matrix method and study how these effects depend on the grating length, the grating profile, the modal dispersion factor, and the duty cycle of the index modulation. Apart from shifting the resonance wavelength and modifying the rejection band, average index variation can give rise to significant side lobes that may appear on the short-wavelength or long-wavelength side of the rejection band, depending on the signs of the average index change and the modal dispersion factor. Our results provide general guidance for the writing of LPFGs for the minimization of side lobes. Our analysis compares well with published experimental results and should be useful for the design and fabrication of LPFGs.

Gu, Yanju; Chiang, Kin Seng

2013-06-01

148

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

NASA Astrophysics Data System (ADS)

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

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

2011-08-01

149

High-bandwidth, graded-index polymer optical fiber for near-infrared use  

NASA Astrophysics Data System (ADS)

We describe graded-index polymer optical fibers with high bandwidth (5.12 GHz for 100-m transmission) and low loss in the near-infrared region (56 and 115 dB km at wavelengths of 688 and 773 nm, respectively) that we successfully obtained with a new interfacial-gel polymerization technique using an all-deuterated methyl methacrylate monomer and a partially fluorinated acrylate monomer. The necessity for both low attenuation and high bandwidth for a polymer optical fiber is described for its use as a physical media in a high-speed multimedia network.

Nihei, Eisuke; Ishigure, Takaaki; Koike, Yasuhiro

1996-12-01

150

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.

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

2013-01-01

151

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

152

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

153

An analysis method for evaluating gradient-index fibers based on Monte Carlo method  

NASA Astrophysics Data System (ADS)

We propose a numerical analysis method for evaluating gradient-index (GRIN) optical fiber using the Monte Carlo method. GRIN optical fibers are widely used in optical information processing and communication applications, such as an image scanner, fax machine, optical sensor, and so on. An important factor which decides the performance of GRIN optical fiber is modulation transfer function (MTF). The MTF of a fiber is swayed by condition of manufacturing process such as temperature. Actual measurements of the MTF of a GRIN optical fiber using this method closely match those made by conventional methods. Experimentally, the MTF is measured using a square wave chart, and is then calculated based on the distribution of output strength on the chart. In contrast, the general method using computers evaluates the MTF based on a spot diagram made by an incident point light source. But the results differ greatly from those by experiment. In this paper, we explain the manufacturing process which affects the performance of GRIN optical fibers and a new evaluation method similar to the experimental system based on the Monte Carlo method. We verified that it more closely matches the experimental results than the conventional method.

Yoshida, S.; Horiuchi, S.; Ushiyama, Z.; Yamamoto, M.

2011-05-01

154

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

155

Hollow fiber taper with a silver micro-sphere used as refractive index sensor  

NASA Astrophysics Data System (ADS)

We have experimentally studied the plasmon resonance phenomenon of a silver micro-sphere with a diameter of 2.3 ?m in taper-shaped air cavity of a hollow fiber taper. To take insight into the plasmon resonance phenomenon, we move the micro-sphere along the fiber and observe the significant shift of the resonance peak. To explore this configuration as a sensor, we analyze the reflected optical spectrum changes as a function of the external refractive index by finite difference time domain method. The results show that this device can be used for a bio-chemical sensor to monitor the refractive index around it from 1.6 to 2.0. The further study supports that the variation was much more significantly for using the S polarized light as the incident source than P polarized light.

Li, Jin; Li, Hanyang; Zhao, Yong; Hu, Haifeng; Wang, Qi

2014-05-01

156

Poly(styrene)-based graded-index plastic optical fiber for home networks.  

PubMed

We investigated poly(styrene) (PSt)-based graded-index plastic optical fiber (GI-POF) with low loss and high bandwidth for home networks. To install the GI-POF in home networks, the attenuation must be below 200 dB/km at a 670-680 nm wavelength, and the bandwidth must be over 2.0 GHz for the 50 m fiber. In this study, we selected a dibenzothiophene (DBT) as a dopant to PSt, and we fabricated PSt-DBT-based GI-POF. We confirmed that the PSt-DBT-based GI-POF has high bandwidth (4.4 GHz) for 50 m fiber and low loss (166-193 dB/km) at a 670-680 nm wavelength and obtained the GI-POF that satisfied the requirements for home networks. PMID:22660051

Akimoto, Yoshihisa; Asai, Makoto; Koike, Kotaro; Makino, Kenji; Koike, Yasuhiro

2012-06-01

157

Using three different optical fiber designs to study humidity effect on the air refractive index  

NASA Astrophysics Data System (ADS)

Design and operation of three different optical designs based on the light intensity modulation for investigation of the humidity effects on the air index of refraction are described. The measurement variable is the transmitted power, which depends on the refractive index of the medium in the path of a fiber-to-fiber optical design. Three different probes (probe #1, #2, and #3) are tested in which probe #1 and probe #2 can also check the presence of water or any other transparent liquid in the gap between the two axial fibers. Performances of the new systems are tested as a refractive index monitoring mean and experimental results are given. The variations of the modulated powers as functions of the air humidity change in the light path are determined for the reported optical designs. For probe #1 for a power variation of 255-315 nW, the relative humidity changes from 32% to 41%. For probe #2 for 5 mm gap distance, for a power change of 2470-2754 nW, the relative humidity changes from 54.95% to 90.39%. For probe #3 for the 10 mm fiber gap, a power change 929.5-972.9 nW is noted for the relative humidity change of 33.0-76.75%. Power variations as a function of the axial fiber gap distances are also given and the optimum condition for the highest sensitivity is obtained. Probe #3 shows a higher sensitivity compared to probe #1 and it is superior to probe #2 because it operates in a fog-free condition. Finally, the calibration curve for each probe is given that can be used for the operation of the probe as a humidity sensor.

Golnabi, H.

2012-11-01

158

Sagnac interferometric intensity-dependent refractive-index measurements of polymer optical fiber  

NASA Astrophysics Data System (ADS)

We have applied a new modified Sagnac interferometric technique to measure the real part of the intensity-dependent refractive index of a single-mode polymer optical fiber. For a 0.1% by weight squaraine dye in a poly(methyl methacrylate) core, Re[ chi (3)11 11] is 12(+/-7) \\times 10-13 cm 3/erg at lambda =1064 nm. We discuss the effect of these measurements on all-optical devices.

Garvey, D. W.; Li, Q.; Kuzyk, M. G.; Dirk, Carl W.; Martinez, S.

1996-01-01

159

Electrostrictive contribution to the intensity-dependent refractive index of optical fibers  

Microsoft Academic Search

We show that electrostriction contributes significantly to self-action effects in optical fibers, adding 19% to the nonlinear refractive index for fields that vary slowly compared with the ,1-ns time scale of the acoustic response. Electrostriction also modifies the tensor nature of the nonlinear-optical response. The electrostrictive nonlinearity is the origin of the observed difference between measurements of n2 with cw

Eric L. Buckland; Robert W. Boyd

1996-01-01

160

Generation of infrared surface plasmon resonances with high refractive index sensitivity utilizing tilted fiber Bragg gratings  

NASA Astrophysics Data System (ADS)

We demonstrate the use of tilted fiber gratings to assist the generation of localized infrared surface plasmons with short propagation lengths and a sensitivity of d?/dn = 3365 nm in the aqueous index regime. It was also found that the resonances could be spectrally tuned over 1000 nm at the same spatial region with high coupling efficiency (in excess of 25 dB) by altering the polarization of the light illuminating the device.

Allsop, Tom; Neal, Ron; Rehman, Saeed; Webb, David J.; Mapps, Des; Bennion, Ian

2007-08-01

161

Generation of infrared surface plasmon resonances with high refractive index sensitivity utilizing tilted fiber Bragg gratings.  

PubMed

We demonstrate the use of tilted fiber gratings to assist the generation of localized infrared surface plasmons with short propagation lengths and a sensitivity of dlambda/dn = 3,365 nm in the aqueous index regime. It was also found that the resonances could be spectrally tuned over 1,000 nm at the same spatial region with high coupling efficiency (in excess of 25 dB) by altering the polarization of the light illuminating the device. PMID:17676162

Allsop, Tom; Neal, Ron; Rehman, Saeed; Webb, David J; Mapps, Des; Bennion, Ian

2007-08-01

162

LDPC-Coded OFDM Transmission Over Graded-Index Plastic Optical Fiber Links  

Microsoft Academic Search

The possibility of 10-Gb\\/s transmission over graded-index plastic optical fiber (GI-POF) using the orthogonal frequency-division multiplexing (OFDM) and iteratively decodable codes is demonstrated by simulations. Several classes of low-density parity-check (LDPC) codes suitable for use in LDPC-coded OFDM transmission over GI-POF are presented as well. Several power efficient OFDM schemes are introduced

Ivan B. Djordjevic

2007-01-01

163

Analysis of co-extrusion process for preparation of gradient index plastic optical fiber  

Microsoft Academic Search

The fabrication of gradient index plastic optical fiber in a closed co-extrusion process is simulated theoretically. The concentration dependency of the diffusivities of monomers in host polymer is taken into account on the basis of a modified free volume theory together with a generalized Flory–Huggins theory for a three-component polymer solution. The applicability of the model derived is justified by

Jyh-Ping Hsu; Sung-Hwa Lin

2003-01-01

164

High-Bandwidth Graded-Index Plastic Optical Fiber by the Dopant Diffusion Coextrusion Process  

Microsoft Academic Search

Today, the number of services, which includes large information contents like high-definition movies, is rapidly increasing. The graded-index plastic optical fiber (GI-POF) has been proposed as a solution. The conventional fabrication method of GI-POF, however, is unsuitable for mass production. Therefore, we propose the dopant diffusion coextrusion process for fabricating high-bandwidth GI-POF. It has been generally thought that formation mechanism

Makoto Asai; Ryoma Hirose; Atsushi Kondo; Yasuhiro Koike

2007-01-01

165

Graded-index plastic optical fiber with high mechanical properties enabling easy network installations. I  

Microsoft Academic Search

It was shown how high mechanical strength should be provided in the high numerical aperture (NA) graded-index plastic optical fiber (GI POF). In this newly developed GI POF, a copolymer of methyl methacrylate (MMA) and 2,2,2-trifluoroethyl methacrylate (3FMA) was used to increase the NA. The GI POF we proposed previ- ously was composed of a PMMA homopolymer cladding and a

Takaaki Ishigure; Miki Hirai; Masataka Sato; Yasuhiro Koike

2004-01-01

166

Numerical design and analysis of multimode fiber with high bend tolerance and bandwidth using refractive index optimization  

NASA Astrophysics Data System (ADS)

This paper presents a multimode optical fiber design that has high tolerance to bending. The fiber is designed by increasing refractive index difference between core and cladding and by the introduction of low index rod in the core. Average bending loss per mode for a standard 50 ?m graded index multimode fiber is 1.58E+08 dB/km for a bending radius of 1.25 mm and particularly for fundamental mode it is 3.793E+05 dB/km. Whereas, simulation results show that average bending loss per mode in the case of the proposed bend insensitive multimode fiber for a bending radius of 1.25 mm is about 7.409E-09 dB/km and particularly for the fundamental mode it is 4.985E-22 dB/km only. Selective mode launch phenomenon is used to excite only the bend insensitive modes of the proposed fiber. It is also observed that the proposed design is consistent with standard 50 ?m graded index multimode fiber in terms of bandwidth and interconnectivity. Thus both standard 50 ?m fiber and proposed fiber can be spliced with the proposed fiber in the bending section.

Mercy Kingsta, R.; Sivanantharaja, A.

2013-12-01

167

Stimulated Brillouin scattering in graded index multimode optical fiber by excitation of the fundamental mode only  

NASA Astrophysics Data System (ADS)

We investigate the suitability of silica graded index multimode fibers (MMF) for distributed Brillouin sensing in structural health monitoring, where the measurement range is limited by small bendings that appear during the integration process of the sensing fibers into the structures. For the investigation of stimulated Brillouin scattering (SBS) in MMF, we use an MMF connected on both ends to the SMF measurement setup by fusion splices to ensure that only the fundamental mode is transmitted. The SBS spectra in MMF are recorded using a 1319 nm single frequency (line width 5 kHz) laser. Results found for standard singlemode fibers and the fundamental mode in multimode silica optical fibers are compared. We present the gain spectra showing the dependence of frequency shift, attenuation and modal noise to both temperature and strain. The dependence of the attenuation due to bending is shown. Finally, the perspective of the excitation of SBS in polymer optical fibers is discussed against the background of our research on SBS in MMF.

Lenke, Philipp; Nöther, Nils

2007-05-01

168

Core-pumped gain-guided index-antiguided continuous wave lasing in dispersion-engineered erbium-doped fiber.  

PubMed

We demonstrate core-pumped gain-guided index-antiguided fiber lasers using a 22 cm long dispersion-engineered erbium-doped fiber. The erbium-doped fiber is dispersion-engineered using optical liquid to replace the most part of silica cladding so that the index of core turns out to be higher (lower) than that of new cladding at pump (lasing) wavelength, respectively. The pump light is confined to propagate in core based on an index-guiding mechanism to efficiently excite the gain medium running through the fiber whereas the cw lasing is constructed in a long, small-core waveguide under a gain-guided, index-antiguided situation. PMID:22859084

Chen, Nan-Kuang; Jian, Lian-Jiun

2012-08-01

169

Diode-pumped 200 ?m diameter core, gain-guided, index-antiguided single mode fiber laser  

Microsoft Academic Search

Single mode laser action in a diode-pumped gain-guided, index- antiguided Nd3+-doped phosphate glass fiber having a 200-?m-diameter core is demonstrated. Near-Gaussian beam quality was maintained, even\\u000a when pumped up to four times the threshold pump power, indicating robust lowest order mode oscillation. Subtle differences\\u000a associated with the effectiveness of diode pumping gain-guided, index-antiguided fibers are discussed.

V. Sudesh; T. McComb; Y. Chen; M. Bass; M. Richardson; J. Ballato; A. E. Siegman

2008-01-01

170

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

171

Impact of index change saturation on the growth behavior of higher-order type I ultrafast induced fiber Bragg gratings  

SciTech Connect

Ultrafast infrared induced fiber Bragg gratings in a hydrogen-loaded SMF-28 fiber are shown to exhibit complex and, what we believe to be, novel spectral evolutions. It is believed that the induced grating peak profile in the fiber is nonsinusoidal as a result of the nonlinear absorption required to modify the material. Rouard's method is used to show that the observed spectral evolution is a consequence of the saturation of the nonsinusoidal index change profile.

Smelser, Christopher W.; Mihailov, Stephen J.; Grobnic, Dan [Communications Research Centre Canada, 3701 Carling Ave., P.O. Box 11490, Station H, Ottawa, Ontario K2H 8S2 (Canada)

2008-05-15

172

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

173

Numerical analyses for thinned fiber Bragg grating under uneven surrounding refractive index environment  

NASA Astrophysics Data System (ADS)

Based on the fiber waveguide models, a modified transfer matrix method was utilized to calculate the reflection spectrum of the thinned fiber Bragg grating (ThFBG) under the uneven surrounding refractive index (SRI) environment. Tow SRI ranges, including the high SRI region (from 1.42 to the fiber cladding index) and the low ones (from 1.33 to about 1.36), were considered. Numerical results showed that the responsive characteristics of the reflectance spectrum of the ThFBG were closely related to the properties of the SRI distribution, first, the original reflection spectrum of the ThFBG would split into many tinny resonant peaks and the reflectance spectrums are asymmetric since the uneven SRI distributions, second, the number of the resonant peaks, the decline of the amplitude, and the degree of the asymmetric of the reflectance spectrums would increase as the increase in the SRI gradient and the D-value of the SRI between the tow ends of the ThFBG. The same numerical approach could be used to analyze the responsive characteristics of the ThFBG under the uneven medium environment where the SRI distribution was any other functions.

Luo, Bin-Bin; Zhao, Ming-Fu; Zhou, Xiao-Jun; Huang, De-Yi; Wang, Shao-Fei; Cao, Xue-Mei

2011-08-01

174

Fabrication of graded-index plastic optical fiber by the diffusion-assisted coextrusion method  

NASA Astrophysics Data System (ADS)

Recently, plastic optical fibers (POFs) have drawn significant attention as high-speed transmission media due to their advantages over conventional glass optical fibers such as flexibility and durability. In addition, Grade-Index (GRIN) POFs with smoothly varying refractive indices provide increased data transmission speeds suitable for the short-distance communications such as local area networking or home networking. In this research, the diffusion-assisted coextrusion process is introduced as a method to fabricate GRIN POFs. In this process, two or more polymeric materials containing additives for refractive index modification are fed separately into a coextrusion die where a concentric multi-layer structure is formed. Subsequently, the diffusion of additives take places in a diffusion zone creating a non-equilibrium concentration profile, hence the refractive index profile. A theoretical analysis for the prediction of the refractive index profile obtainable by this process indicates that it is difficult to obtain a near-parabolic refractive index profile with the tubular flow design unless a very large residence time in the diffusion zone is provided. However, significant changes in the refractive index profile can be induced by adopting a multi-layer approach and an annulus flow design. Furthermore, the bandwidth estimated by the ray analysis indicates that even a small variation of the refractive index profile created by the additive diffusion can result in a significant increase in the bandwidth. To verify the findings from theoretical analysis, poly(methyl methacrylate)-base GRIN POFs with diphenyl sulfide and diphenyl sulfoxide as refractive index-modifying dopants were prepared and the effects of various operating conditions such as melt temperatures, flow rates and core-cladding interface positions were investigated. The dopant concentration profile, thus the refractive index profile, characterized by FT-IR spectroscopy, has been shown to be controllable by adjusting the material and/or process variables. Through the theoretical analysis and experimental verifications, it was shown that bandwidth over 700 MHz at a 100 m distance could be obtained by this method, suggesting that the diffusion-assisted coextrusion process is a viable method to fabricate a high bandwidth GRIN POF that is applicable for short-distance communications.

Sohn, In-Sung

175

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

176

Refractive index and temperature sensitivity characteristics of a micro-slot fiber Bragg grating.  

PubMed

Fabrication and characterization of a UV inscribed fiber Bragg grating (FBG) with a micro-slot liquid core is presented. Femtosecond (fs) laser patterning/chemical etching technique was employed to engrave a micro-slot with dimensions of 5.74 ?m(h)×125 ?m(w)×1388.72 ?m(l) across the whole grating. The device has been evaluated for refractive index (RI) and temperature sensitivities and exhibited distinctive thermal response and RI sensitivity beyond the detection limit of reported fiber gratings. This structure has not just been RI sensitive, but also maintained the robustness comparing with the bare core FBGs and long-period gratings with the partial cladding etched off. PMID:22781247

Saffari, Pouneh; Yan, Zhijun; Zhou, Kaiming; Zhang, Lin

2012-07-10

177

Birefringent microfiber-based fiber loop mirrors for tunable filters and refractive index sensors  

NASA Astrophysics Data System (ADS)

Highly birefringent (Hi-Bi) microfiber-based fiber loop mirrors (FLMs) were studied for tunable comb filters and refractive index (RI) sensors. RI sensitivity of up to 15,441 nm/RIU was experimentally demonstrated for the RI sensors and, for the tunable filter a thermal tuning coefficient of ~-2.35nm/°C was obtained for temperature from 20 to 90°C when it was immersed into water. The use of two cascaded Hi-Bi micro-tapers within a Sagnac loop allows more flexibility in controlling the transmission/reflection spectraums of the FLM. The length of the tapered Hi-Bi microfibers is on the order of centimeters, two orders of magnitude shorter than the conventional Hi-Bi fiber-based devices.

Jin, Wa; Xuan, Haifeng; Jin, Wei

2013-05-01

178

Polarization mode preservation in elliptical index tailored optical fibers for apertureless scanning near-field optical microscopy  

NASA Astrophysics Data System (ADS)

We report on the development of elliptical, index tailored optical fibers for higher-order mode preservation for fiber-based, apertureless, internally illuminated scanning near-field optical microscopy (ai-SNOM). The fiber structure is simulated by the finite element method, showing large spreads of the effective indices for neighboring first higher-order modes. We demonstrate experimentally that due to this spread, the first higher-order modes do not couple, hence, the polarization is maintained, when the fiber is bent down to 1 cm radius. Further, we discuss the implications for ai-SNOM applications.

Zeh, Christoph; Spittel, Ron; Unger, Sonja; Opitz, Jörg; Köhler, Bernd; Kirchhof, Johannes; Bartelt, Hartmut; Eng, Lukas M.

2010-09-01

179

How to Measure Cortical Folding from MR Images: a Step-by-Step Tutorial to Compute Local Gyrification Index  

PubMed Central

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 colleagues2, 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 asymmetry3. 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 surface4. 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 Index5, a method originally used in comparative neuroanatomy to evaluate the cortical folding differences across species. In our implementation, which we name local Gyrification Index (lGI1), 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 expansion6, 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 study1. 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 colleagues7, 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.

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

2012-01-01

180

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

181

Simultaneous measurement of refractive index and temperature by integrating an external Fabry-Perot cavity with a fiber Bragg grating.  

PubMed

A fiber sensor for simultaneous measurements of refractive index and temperature based on the integration of a fiber Bragg grating (FBG) with an external Fabry-Perot (F-P) cavity is presented. The fringe contrast of the interference spectrum generated by the F-P cavity is used to determine the external refractive index, while the wavelength shift of the FBG is used to measure temperature. The result showed that the refractive index and temperature sensitivity for the integrated sensor is 8.1 × 10(-6) and 0.01006 nm/°C, respectively. PMID:22667608

Chen, Luan Xiong; Huang, Xu Guang; Li, Jiao Yang; Zhong, Ze Bing

2012-05-01

182

Optical fiber Fabry-Perot interferometer cavity fabricated by femtosecond laser micromachining and fusion splicing for refractive index sensing.  

PubMed

We demonstrate a fiber in-line Fabry-Perot interferometer cavity sensor for refractive index measurement. The interferometer cavity is formed by drilling a micro-hole at the cleaved fiber end facet, followed by fusion splicing. A micro-channel is inscribed by femtosecond laser micromachining to vertically cross the cavity to allow liquid to flow in. The refractive index sensitivity obtained is ~994 nm/RIU (refractive index unit). Such a device is simple in configuration, easy for fabrication and reliable in operation due to extremely low temperature cross sensitivity of ~4.8 × 10(-6) RIU/°C. PMID:23037431

Liao, C R; Hu, T Y; Wang, D N

2012-09-24

183

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

PubMed Central

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

Regnier, M; Homsher, E

1998-01-01

184

[Spectral characteristics of refractive index based on nanocoated optical fiber F-P sensor].  

PubMed

An optical fiber Fabry-Perot (F-P) interferometer end surface was modified using layer-by-layer assembly and chemical covalent cross linking method, and the refractive index (RI) response characteristics of coated optical fiber F-P sensor were experimentally studied. Poly diallyldimethylammonium chloride (PDDA) and sodium polystyrene sulfonate (PSS) were chosen as nano-film materials. With the numbers of layers increasing, the reflection spectral contrast of optical fiber F-P sensor presents from high to low, then to high regularity. And the reflection spectral contrast has good temperature stability. The reflection spectra of the optical F-P sensor coated with 20 bilayers for a series of concentration of sucrose and inorganic solution were measured. Experimental results show that the inflection point extends from 1.457 to 1.462 3, and the reflection spectral contrast sensitivity to low RI material and high RI material is 24.53 and 3.60 dB x RI(-1), respectively, with good linearity. The results demonstrate that the functional coated optical F-P sensor provides a new method for biology and chemical material test. PMID:23586269

Jiang, Ming-Shun; Li, Qiu-Shun; Sui, Qing-Mei; Jia, Lei; Peng, Peng

2013-01-01

185

Indexing of the Step Adaptive Equalizer for Automatic Internal Correction in Microprocessors Inizializzazione Dell'Equalizzatore Adattativo a Passo di Correzione Interna Automatico Su Microprocessore.  

National Technical Information Service (NTIS)

An indexing subroutine (INI) is presented and analyzed. The use of the indexing subroutine is described, and an example given. The SHIFT subroutine for moving data contained in the memory one step forward is described.

F. Cascio G. Martinelli G. Orlandi M. Salerno

1980-01-01

186

Design and calibration of low-cost fiber optic sensors for refractive index measurement of turbid liquids  

NASA Astrophysics Data System (ADS)

An optical fiber, stripped partially out of its cladding is used to sense refractive index of a liquid to a precision to fifth place of decimal. The dependence of the light output of the sensor on the refractive index of the test liquid is nonlinear. The light output of the sensor depends on the thickness to which the cladding is stripped. It shows both positive and negative slope with increasing refractive index of the test liquid. The slope of the plot of sensor output against liquid refractive index shows a change of sign at around the fiber refractive index. The sensor is unaffected by the presence of absorption and is insensitive to the chemical nature of the solute. The sensor is sensitive in the whole of the tested range of refractive indices 1.33 to 1.52. Experiments that show the significance of cladding modes in sensing are described.

Gupta-Bhaya, Pinaki; Ghosh, Anjan Kumar; Saxena, Vishal; John, Joseph

2006-10-01

187

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

NASA Astrophysics Data System (ADS)

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

Mukawa, Yoshiki; Kondo, Atsushi; Koike, Yasuhiro

2012-04-01

188

Numerical analysis of plasmon polarition refractive index fiber sensors with hollow core and a long period grating  

NASA Astrophysics Data System (ADS)

The main principle of this design is based on the efficient energy transfer between the waveguide mode (WM) and the co-directional SPP provided by a properly designed fiber long period grating (LPG). This LPG is imprinted into a waveguide fiber layer of a specially designed hollow core optical fiber. The simulations are based on the finite element method (FEM) algorithm in electromagnetics and coupled mode theory for gratings. Compared to the previous proposed structure using a fiber Bragg grating (FBG), this novel kind of sensor can greatly enhance the refractive index sensitivity, e.g., from 5.93 nm/RIU (with FBG) to 817 nm/RIU (with LPG) at the sensing refractive index of 1.40. The other advantage is that the working conditions can be performed for the well-developed telecom wavelength windows 1500–1600 nm.

Xia, Li; Zhang, Yating; Zhou, Chi; Shuai, binbin; Liu, Deming

2011-06-01

189

Voltage-Controlled Optical Fiber Coupler Using a Layer of Low-Refractive-Index Liquid Crystal with Positive Dielectric Anisotropy  

NASA Astrophysics Data System (ADS)

A variable fiber directional coupler is made using liquid crystal as the intermediate cladding layer between two side-polished optical fibers. A nematic liquid crystal with low refractive index and positive dielectric anisotropy is used. An ac electric field is applied to the liquid crystal by applying a voltage across two parallel electrode stripes on the two sides of the fibers. The electric field rotates the molecular orientations and changes the refractive index of the liquid crystal. The coupling ratio between the two fibers is then controlled by the applied voltage. The dependence of the coupling ratio on the applied voltage is studied for various light wavelengths, including a continuous variable range between 1.272 µ m and 1.310 µ m.

Pan, Ru-Pin; Liou, Shyang-Rong; Lin, Chao-Ken

1995-12-01

190

Note: Optical fiber milled by focused ion beam and its application for Fabry-Pérot refractive index sensor.  

PubMed

We introduce a highly compact fiber-optic Fabry-Pérot refractive index sensor integrated with a fluid channel that is fabricated directly near the tip of a 32 ?m in diameter single-mode fiber taper. The focused ion beam technique is used to efficiently mill the microcavity from the fiber side and finely polish the end facets of the cavity with a high spatial resolution. It is found that a fringe visibility of over 15 dB can be achieved and that the sensor has a sensitivity of ~1731 nm/RIU (refractive index units) and a detection limit of ~5.78 × 10(-6) RIU. This miniature integrated all-in-fiber optofludic sensor may find use in minimal-invasive biomedical applications. PMID:21806237

Yuan, Wu; Wang, Fei; Savenko, Alexey; Petersen, Dirch Hjorth; Bang, Ole

2011-07-01

191

Fiber-Optic Level Sensor for Cryogens: Sharp bends in the fiber improve sensitivity with liquids of low refractive index, such as liquid hydrogen.  

National Technical Information Service (NTIS)

This citation summarizes a one-page announcement of technology available for utilization. A new fiber-optic liquid-level sensor is useful in cryogenic environments where liquids of very low index of refraction are encountered. It is a 'yes/no' indicator o...

1981-01-01

192

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

193

Threshold characteristics analysis of one-end-pumped Yb 3+-doped gain-guided and index-antiguided fiber laser  

NASA Astrophysics Data System (ADS)

An exact analytical expression of the threshold pump power for the one-end-pumped Yb 3+-doped gain-guided and index-antiguided (GG-IAG) fiber laser has been obtained by solving the improved rate equations (REs) with the additional leakage losses. The effects of Yb 3+ concentration, fiber length, core radius and mirror reflectivity on the threshold pump power are discussed. After optimizing, the results show that the laser threshold of GG-IAG fiber laser can be greatly reduced while maintaining single mode oscillation. Compared to the numerical methods, the analytical expression has easy calculation and distinct results.

Qu, Yibin; Zhu, Yonggang; Zhou, Enyu; Wei, Wei; Peng, Bo

2012-04-01

194

Radiation Hard Fiber Optics.  

National Technical Information Service (NTIS)

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

R. E. Jaeger M. Aslami

1981-01-01

195

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

196

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

PubMed

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

Rodenas, Airan; Kar, Ajoy K

2011-08-29

197

Optical characterization of radiation-resistant fibers  

Microsoft Academic Search

Various measurements have been made on step-index fibers having pure silica cores which are expected to have good radiation hardness properties. These measurements include spectral attenuation, numerical aperture, and bandwidth. Values for the preceding quantities are given for several step-index fibers of various diameters including the following: plastic-clad silica (PCS), OSF-AS, Raychem VCS, Dainichi Diaguide and Ensign-Bickford fiber. Computer-controlled instrumentation

V. N. Smiley; B. M. Whitcomb; M. A. Peressini; D. E. Whitaker; R. L. Flurer; C. W. Colburn; P. B. Lyons; J. W. Ogle; L. D. Looney

1984-01-01

198

Optical characterization of radiation-resistant fibers  

SciTech Connect

Various measurements have been made on step-index fibers having pure silica cores which are expected to have good radiation hardness properties. These measurements include spectral attenuation, numerical aperture, and bandwidth. Values for the preceding quantities are given for several step-index fibers of various diameters including the following: plastic-clad silica (PCS), OSF-AS, Raychem VCS, Dainichi Diaguide and Ensign-Bickford fiber. Computer-controlled instrumentation was developed for these measurements and is described.

Smiley, V.N.; Whitcomb, B.M.; Peressini, M.A.; Whitaker, D.E.; Flurer, R.L.; Colburn, C.W.; Lyons, P.B.; Ogle, J.W.; Looney, L.D.

1984-01-01

199

Novel approach for the refractive index gradient measurement in microliter volumes using fiber-optic technology  

NASA Astrophysics Data System (ADS)

The refractive index gradient (RIG) of hydrodynamically controlled profiles can be universally, yet sensitively, measured by carefully probing the radial RIG passing through a z-configuration flow cell. Fiber optic technology is applied in order to provide a narrow, collimated probe beam (100 micrometers diameter) that is deflected by a RIG and measured by a position sensitive detector. The fiber optic construction allows one to probe very small volumes (1 (mu) L to 3 (mu) L) amenable to microbore liquid chromatography ((mu) LC). The combination of (mu) LC and RIG detection is very useful for the analysis of trace quantities (ng injected amounts) of chemical species that are generally difficult to measure, i.e., species that are not amenable to absorbance detection or related techniques. Furthermore, the RIG detector is compatible with conventional mobile phase gradient and thermal gradient (mu) LC, unlike traditional RI detectors. A description of the RIG detector coupled with (mu) LC for the analysis of complex polymer samples is reported. Also, exploration into using the RIG detector for supercritical fluid chromatography is addressed.

Synovec, Robert E.; Renn, Curtiss N.

1991-07-01

200

A Miniature Fiber Optic Refractive Index Sensor Built in a MEMS-Based Microchannel  

PubMed Central

A small, highly sensitive, and electromagnetic interference (EMI)-immune refractive index (RI) sensor based on the Fabry-Perot (FP) interferometer is presented. The sensor’s FP cavity was fabricated by aligning two metal-deposited, single-mode optical fiber endfaces inside a microchannel on a silicon chip. The mirrors on the fiber endfaces were made of thermal-deposited metal films, which provided the high finesse necessary to produce a highly sensitive sensor. Microelectromechanical systems (MEMS) fabrication techniques, specifically photolithography and deep dry etching, were used to precisely control the profile and depth of the microchannel on the silicon chip with an accuracy of 2 ?m. The RI change within the FP cavity was determined by demodulating the transmission spectrum phase shift. The sensitivity and finesse of the transmission spectrum were controlled by adjusting the cavity length and the thickness of the deposited metal. Our experimental results showed that the sensor’s sensitivity was 665.90 nm/RIU (RI Unit), and the limit of detection was 6 × 10?6 RIU. Using MEMS fabrication techniques to fabricate these sensors could make high yield mass production a real possibility. Multiple sensors could be integrated on a single small silicon chip to simultaneously measure RI, temperature, and biomolecule targets.

Tian, Ye; Wang, Wenhui; Wu, Nan; Zou, Xiaotian; Guthy, Charles; Wang, Xingwei

2011-01-01

201

A miniature fiber optic refractive index sensor built in a MEMS-based microchannel.  

PubMed

A small, highly sensitive, and electromagnetic interference (EMI)-immune refractive index (RI) sensor based on the Fabry-Perot (FP) interferometer is presented. The sensor's FP cavity was fabricated by aligning two metal-deposited, single-mode optical fiber endfaces inside a microchannel on a silicon chip. The mirrors on the fiber endfaces were made of thermal-deposited metal films, which provided the high finesse necessary to produce a highly sensitive sensor. Microelectromechanical systems (MEMS) fabrication techniques, specifically photolithography and deep dry etching, were used to precisely control the profile and depth of the microchannel on the silicon chip with an accuracy of 2 ?m. The RI change within the FP cavity was determined by demodulating the transmission spectrum phase shift. The sensitivity and finesse of the transmission spectrum were controlled by adjusting the cavity length and the thickness of the deposited metal. Our experimental results showed that the sensor's sensitivity was 665.90 nm/RIU (RI Unit), and the limit of detection was 6 × 10(-6) RIU. Using MEMS fabrication techniques to fabricate these sensors could make high yield mass production a real possibility. Multiple sensors could be integrated on a single small silicon chip to simultaneously measure RI, temperature, and biomolecule targets. PMID:22344393

Tian, Ye; Wang, Wenhui; Wu, Nan; Zou, Xiaotian; Guthy, Charles; Wang, Xingwei

2011-01-01

202

Nonlinear-index-of-refraction measurement in a resonant region by the use of a fiber Mach-Zehnder interferometer  

NASA Astrophysics Data System (ADS)

The nonlinear index of refraction in a resonant region has been determined by the use of a fiber-based Mach-Zehnder interferometer to measure the temporal fringe shift between two signals. The measurement technique is direct and does not require additional amplitude information for the extraction of the nonlinear index of refraction. This technique has been used to measure the temporal response of an InGaAsP semiconductor optical amplifier at 1.313 mu m.

Kang, K. I.; Chang, T. G.; Glesk, I.; Prucnal, P. R.

1996-03-01

203

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

Microsoft Academic Search

Changes in the color of conodonts have long been used to assess thermal maturity. Color is a subjective measure, and color changes in conodonts are related to a subjective scale, the conodont alteration index or CAI. In this paper, we propose a simple, nondestructive method for objectively determining CAI and relating CAI to thermal maturity, the spectral reflectance of conodonts

B. C. Deaton; M. Nestell; W. L. Balsam

1996-01-01

204

Green productivity indexing : A practical step towards integrating environmental protection into corporate performance  

Microsoft Academic Search

Purpose – The purpose of the paper is to illustrate an approach for developing a framework of indicators for integrating environmental protection into corporate performance. This paper also highlights Green Productivity Index (GPI) of the Continuous Improvement (CI) performed in a foundry casting, which includes both economic and environmental performances. Design\\/methodology\\/approach – In the paper data were collected from a

N. Mohan Das Gandhi; V. Selladurai; P. Santhi

2006-01-01

205

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

USGS Publications Warehouse

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

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

2007-01-01

206

Accurate mode characterization of graded-index multimode fibers for the application of mode-noise analysis  

NASA Astrophysics Data System (ADS)

Guided modes in graded-index multimode optical fibers are accurately analyzed with the vector H-field finite-element method, aided by the use of the WKB method. As a result, exact mode-propagation constants and the corresponding modal eigenfield distributions are provided for the study of the modal noise that is due to the mode-coupling effect.

Liu, Yueai; Rahman, B. M. A.; Ning, Ya Nong; Grattan, K. T. V.

1995-03-01

207

40Gb\\/s transmission over 100m graded-index plastic optical fiber based on discrete multitone modulation  

Microsoft Academic Search

Spectral-efficient 40-Gb\\/s discrete multitone transmission over 100 m of graded-index plastic optical fiber is experimentally demonstrated by intensity-modulation of a 10-GHz DFB-laser (1302 nm) and direct-detection with a 25-mum large diameter photodetector.

H. Yang; S. C. J. Lee; E. Tangdiongga; F. Breyer; S. Randel; A. M. J. Koonen

2009-01-01

208

Pump\\/signal induced refractive index changes in Yb-doped fiber amplifier: The origin and properties  

Microsoft Academic Search

Refractive index changes induced by pump-signal operation in commercial Yb-doped fibers are shown to be of electronic origin with a strong contribution of UV-transitions to the polarizability difference explored for testing wavelength of 1460-1620 nm.

Andrei A. Fotiadi; Oleg L. Antipov; Patrice Mégret

2008-01-01

209

A sensitivity-enhanced refractive index sensor using a single-mode thin-core fiber incorporating an abrupt taper.  

PubMed

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

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

2012-01-01

210

Exact optical self-similar solutions in a tapered graded-index nonlinear-fiber amplifier with an external source  

NASA Astrophysics Data System (ADS)

We study the propagations of optical self-similar solutions in a tapered graded-index nonlinear-fiber amplifier with an external source through asymmetric twin-core fiber amplifiers. Various types of exact self-similar solutions, including the W-shaped and U-shaped solutions, trigonometric function solutions, and periodic wave solutions are found. The results show that these different types of self-similar optical structures can be generated and effectively controlled by modulating the amplitude of the source. The influences of nonlinear tunneling effects on the propagation of optical pulses are investigated as well. The obtained results may have potential applications in a tapered graded-index nonlinear-fiber amplifier with an external source.

He, Jun-Rong; Yi, Lin

2014-06-01

211

Lensed plastic optical fiber employing concave end filled with high-index resin  

Microsoft Academic Search

We propose an optical coupling scheme that uses a fiber-end lens to achieve efficient coupling of the plastic optical fiber with a light source and with a detector. Transparent resin filled in the concave end of the fiber is fixed by surface tension to form a biconvex lens that is automatically positioned relative to the fiber core. A simple ray-matrix

Hajime Sakata; Aya Imada

2002-01-01

212

Analyte-filled core self-calibration microstructured optical fiber based plasmonic sensor for detecting high refractive index aqueous analyte  

NASA Astrophysics Data System (ADS)

This paper presents a theoretical investigation on an analyte-filled core self-calibration microstructured optical fiber plasmonic refractive index sensor. The proposed microstructured optical fiber sensor introduces the concept of simultaneous detection in different ranges of wavelength because the sensing performance of the sensor in different wavelength ranges is relatively high, which will be useful for high accuracy measurement. The resonant peak 1 and peak 2 are stronger and more sensitive to the variation of analyte refractive index than any other peaks in this kind of microstructured optical fiber. An average refractive index sensitivity of ?4354.3 nm/RIU (refractive index unit) and 2280 nm/RIU in the dynamic index range from 1.46 to 1.485 as well as ?2660 nm/RIU and ?4240 nm/RIU from 1.50 to 1.52 corresponding to the peak 1 and peak 2 can be obtained, respectively. The self-calibration sensor demonstrates high linearity and accuracy. The influence of the structural parameters on the plasmonic excitations is also studied, with a view of turning and optimizing the resonant spectrum.

Qin, Wei; Li, Shuguang; Yao, Yuhong; Xin, Xujun; Xue, Jianrong

2014-07-01

213

Concurrent three-dimensional characterization of the refractive-index and residual-stress distributions in optical fibers.  

PubMed

A three-dimensional index-stress distribution (3DISD) measurement method for determining concurrently the refractive-index distributions (RIDs) and residual-stress distributions (RSDs) in optical fibers is presented. The method combines the quantitative-phase microscopy technique, the Brace-Köhler compensator technique, and computed tomography principles. These techniques are implemented on a common apparatus to enable concurrent characterization of the RID and the RSD. Measurements are performed on Corning SMF-28 fiber in an unperturbed section and in a section exposed to CO(2) laser radiation. The concurrent measurements allow for the first accurate comparison of the collocated RID and RSD. The resolutions of the refractive index and stress are estimated to be 2.34×10(-5) and 0.35 MPa, respectively. PMID:22859034

Hutsel, Michael R; Gaylord, Thomas K

2012-08-01

214

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

PubMed Central

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

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

2011-01-01

215

Multi-step adhesive cementation versus one-step adhesive cementation: push-out bond strength between fiber post and root dentin before and after mechanical cycling.  

PubMed

This study evaluated the effects of mechanical cycling on resin push-out bond strength to root dentin, using two strategies for fiber post cementation. Forty bovine roots were embedded in acrylic resin after root canal preparation using a custom drill of the fiber post system. The fiber posts were cemented into root canals using two different strategies (N = 20): a conventional adhesive approach using a three-step etch-and-rinse adhesive system combined with a conventional resin cement (ScotchBond Multi Purpose Plus + RelyX ARC ), or a simplified adhesive approach using a self-adhesive resin cement (RelyX U100). The core was built up with composite resin and half of the specimens from each cementation strategy were submitted to mechanical cycling (45 degree angle; 37 degrees C; 88 N; 4 Hz; 700,000 cycles). Each specimen was cross-sectioned and the disk specimens were pushed-out. The means from every group (n = 10) were statistically analyzed using a two-way ANOVA and a Tukey test (P = 0.05). The cementation strategy affected the push-out results (P < 0.001), while mechanical cycling did not (P = 0.3716). The simplified approach (a self-adhesive resin cement) had better bond performance despite the conditioning. The self-adhesive resin cement appears to be a good option for post cementation. Further trials are needed to confirm these results. PMID:22313828

Amaral, Marina; Rippe, Marilia Pivetta; Bergoli, Cesar Dalmolin; Monaco, Carlo; Valandro, Luiz Felipe

2011-01-01

216

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

PubMed

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

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

2013-01-01

217

Effect of temperature on optical fiber transmission  

Microsoft Academic Search

Results are presented concerning the effects of temperature on the transmission properties of various optical fibers including a silicone plastic clad, an acrylic plastic clad, and CVD step-index fibers both with and without polyurethane jackets. Results are presented for the normalized transmitted power vs temperature, the index of refraction vs temperature, and induced attenuation coefficients vs temperature. The data show

W. F. Yeung; A. R. Johnston

1978-01-01

218

Plastic-Clad Fiber Using Optical Transmission  

Microsoft Academic Search

Plastic-clad fiber is a fiber of the step-index type that consists of an inner core of high purity synthetic quartz and an outer coating clad of plastic material which has a lower refractive index than the inner core.

T. Kojima; K. Yagi; K. Shibuya; T. Sakanaka

1979-01-01

219

Gradient-index (GRIN) lens multimode fiber probe for laser-induced breakdown in the eye  

NASA Astrophysics Data System (ADS)

A model laser surgical probe was designed and built to employ laser induced breakdown (LIB) in cutting fibrovascular membranes within the vitreous cavity of the eye. The probe is a simple design of a gradient index (GRIN) lens attached to the tip of a multimode fiber. It is designed to fit through a sclerotomy incision and enter the vitreaous cavity for work anterior to the retina. The laser light is focused close to the tip of the probe without causing GRIN lens damage. Thus a widely divergent beam behind the focus will diminish potential laser damage posterior to the target tissue. A Nd:YAG 1064-nm 10-ns pulsed laser was used with the probe inserted into a cell of tap water. Threshold data for laser induced breakdown was taken ad fit to a probit curve. The data was compared with past LIB threshold data. The radiant exposure versus distance from the probe was plotted via spot size measurements. This measurement gave a rough indication of the distance the probe must remain from the retina to be well below retinal maximum permissible exposure (MPE) levels. In-vitro threshold measurements of bovine vitreous were taken and compared to the water threshold. Finally, collagen membranes were lased with the probe to demonstrate its functional application.

Toth, Cynthia A.; Hammer, Daniel X.; Slawinksi, Kim; Noojin, Gary D.

1994-06-01

220

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

SciTech Connect

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

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

1996-07-01

221

Relation of dietary glycemic index, glycemic load, and fiber and whole-grain intakes during puberty to the concurrent development of percent body fat and body mass index.  

PubMed

The authors prospectively examined whether change in dietary glycemic index (GI), glycemic load (GL), fiber intake, or whole-grain intake during puberty is associated with concurrent change in percentage of body fat (%BF) or body mass index (BMI; weight (kg)/height)(2). Linear mixed-effects regression analyses were performed in 215 participants from the Dortmund Nutritional and Anthropometric Longitudinally Designed (DONALD) Study (Dortmund, Germany) who possessed weighed 3-day dietary records and anthropometric data at puberty onset (defined by age at takeoff) and over the subsequent 4 years (1988-2007). Neither changes in dietary GI, GL, fiber intake, nor whole-grain intake were associated with concurrent changes in %BF throughout puberty (change in %BF: -0.03 (standard error (SE), 0.11) per standard deviation (SD) increase in GI (P = 0.8); -0.01 (SE, 0.11) per SD increase in GL (P = 0.9); 0.02 (SE, 0.14) per SD increase in fiber intake (P = 0.9); and 0.09 (SE, 0.13) per SD increase in whole-grain intake (P = 0.5)). Similarly, no concurrent associations were observed between these dietary factors and BMI SD scores. Associations of dietary GI with %BF and BMI SD score differed between overweight and normal-weight adolescents (for concurrent association, P for interaction was 0.03 for %BF and 0.08 for BMI SD score). Dietary GI, GL, and fiber and whole-grain intakes in healthy, free-living adolescents do not appear to be relevant to the development of %BF or BMI during puberty. PMID:19126582

Cheng, Guo; Karaolis-Danckert, Nadina; Libuda, Lars; Bolzenius, Katja; Remer, Thomas; Buyken, Anette E

2009-03-15

222

Two-steps fabrication of single-mode fiber couplers with a CO2 laser source  

Microsoft Academic Search

We have used a CO2 laser as a heating source to fabricate a single-mode fiber couplers. The process consists of fusing and stretching two standard single model fibers initially maintained in lateral contact. We have fabricated 3 dB couplers at 1500 nm with insertion loss 30dB with a bandwidth of 30 nm at -30dB. Finally, a coupler with a long

Georges J. Humbert; Abdelrafik Malki

2003-01-01

223

Dynamics of pump-induced refractive index changes in single-mode Yb-doped optical fibers.  

PubMed

We quantify the refractive index changes (RIC) in single-mode ytterbium-doped optical fibers induced by optical pulses at 980 nm and, for the first time, report details of the effect dynamics. The RIC dynamics is shown to follow that of the population of the excited/unexcited ion states with a factor proportional to their polarizability difference (PD). The absolute PD value is evaluated in the spectral range of 1460-1620 nm for different fiber samples and is found to be independent on the fiber geometry and on the ion concentration. The PD dispersion profile indicates to a predominant far-resonance UV rather than near-resonant IR transitions contribution to the RIC. PMID:18711503

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

2008-08-18

224

Numerical simulation on multimode fiber Bragg gratings with non-uniform transverse profile of refractive index change  

NASA Astrophysics Data System (ADS)

The reflection characteristics of Multi-mode fiber Bragg grating (MM-FBG) with non-uniform profile of index change were numerically studied in this work. The reflection spectrum of MM-FBG was obtained by solving the coupled mode equations (CMEs) using shooting method. For a standard multimode fiber with 342 guided modes, the initial problem within the shooting method frame is very slow when it was solved using numerical methods. We obtained the analytical solution of the initial problem of the CMEs by diagonalization so that the numerical simulation is fast enough to be finished within several hours using personal computer. The reflection was obtained for a standard multimode fiber with diameter of 62.5 micron. There are 35 reflection peaks in the spectrum where 18 of them are corresponding to forward-propagation mode coupled to same order backward mode and the other 17 peaks are corresponding to forward mode coupled to backward mode with neighboring order.

Gao, Feng; Yang, Chun

2005-11-01

225

Design of Low-Loss Graded-Index Plastic Optical Fiber Based on Partially Fluorinated Methacrylate Polymer  

Microsoft Academic Search

As a promising candidate of optical home network, a novel Gigabit Ethernet prepared by inexpensive partially fluorinated polymer-based graded-index plastic optical fiber (GI POF) was proposed. Poly (2,2,2-trifluoroethyl methacrylate) (P3FMA) was selected as a base material for the GI POF because of its high transparency, low material dispersion, and low cost. The transmission characteristics were investigated, and it was clarified

Kotaro Koike; Yasuhiro Koike

2009-01-01

226

Transmission of return-to-zero pulses in an optical split-step system based on reflecting fiber gratings  

NASA Astrophysics Data System (ADS)

A new variety of the "soliton management" in heterogeneous optical media is proposed. The system is composed as a periodic chain of nonlinear fibers with negligible intrinsic group-velocity dispersion (GVD), alternating with sections of unchirped fiber Bragg gratings (FBGs) operating in the reflection regime. Losses due to incomplete reflection are compensated by linear amplifiers. The model may apply to fiber-optic telecommunication links with periodically installed FBG modules, and it may be used for the design of laser setups. By means of extended simulations, we identify small regions in the underlying parameter space where this model, featuring the periodic separation of the Kerr nonlinearity and FBG-induced GVD (hence the name of the "split-step" system), supports stable transmission of RZ (return-to-zero) pulses, i.e., quasi-solitons. The effect of nonzero fiber's GVD on the stable transmission regime is considered too. Moderately unstable (partly usable) transmission regimes are found in larger regions of the parameter space; they may be of two different types, with the average nonlinearity either undercompensating or overcompensating the GVD. Interactions between the stable RZ pulses are also studied, leading to the identification of a minimum separation between them necessary for the suppression of interaction effects.

Tsaraf, Yoram; Malomed, Boris A.

2009-10-01

227

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....

228

High resolution, all-fiber, micro-machined sensor for simultaneous measurement of refractive index and temperature.  

PubMed

This paper presents a highly-sensitive, miniature, all-silica, dual parameter fiber-optic Fabry-Perot sensor, which is suitable for independent measurement of the refractive index and the temperature of the fluid surrounding the sensor. The experimental sensor was produced by a micromachining process based on the selective etching of doped silica glass and a simple assembly procedure that included fiber cleaving, splicing and etching of optical fibers. The presented sensor also allows for direct compensation of the temperature's effect on the fluid's refractive index change and consequently provides opportunities for the detection of very small changes in the surrounding fluid's composition. A measurement resolution of 2x10-7RIU was demonstrated experimentally for a component of the refractive index that is related purely to the fluid's composition. This resolution was achieved under non-stabilized temperature conditions. The temperature resolution of the sensor proved to be about 10-3°C. These high resolution measurements were obtained by phase-tracking of characteristic components in a Fourier transform of sensor's optical spectrum. PMID:24977875

Pevec, Simon; Donlagic, Denis

2014-06-30

229

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

Microsoft Academic Search

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

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

2009-01-01

230

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

231

Theoretical analysis on the refractive-index distribution and bandwidth of gradient-index polymer optical fibers from a centrifugal field.  

PubMed

Theoretical analysis was applied to analyze the refractive-index distribution (RID) and bandwidth (BW) of gradient-index polymer optical fibers (GI POFs) prepared by a centrifugal field process. The RID of the prepared GI POF could be represented by the equation of n(r) = n1[1 - 2delta(r/alpha)g](1/2). The studied material systems were poly(hexafluoroisopropyl 2-fluoroacrylate) (PHFIP 2-FA)/dibutyl phthalate (DBP) and poly(methyl methacrylate) (PMMA)/benzyl benzoate (BEN). The RID and the BW were significantly affected by an essential parameter k, which was related to thematerial properties (density difference and molecular weight) and processing properties (rotating speed, temperature, and radius). As k increased, the characteristic constant of RID, g, decreased to a minimum and then increased sharply, owing to the separation of the polymer and the dopant. On the other hand, the relative refractive-index difference of RID, delta, increased to a steady value after k increased to a certain value. The variation of RID with k resulted in a local minimum of intermodal dispersion, and thus a maximum bandwidth was obtained. The maximum BW of the PHFIP 2-FA/DBP and PMMA/BEN systems at 1550 nm (100-m fiber length and 2-nm spectral width) for the case of k not equal to 0 were 6.7 and 3.2 Gb/s, respectively. The wavelength of light source affects the BW significantly only at k around zero because of the importance of the intramodal dispersion in this case. PMID:12716159

Wei, Ming-Hsin; Chen, Wen-Chang

2003-04-20

232

A high-quality Mach-Zehnder interferometer fiber sensor by femtosecond laser one-step processing.  

PubMed

During new fiber sensor development experiments, an easy-to-fabricate simple sensing structure with a trench and partially ablated fiber core is fabricated by using an 800 nm 35 fs 1 kHz laser. It is demonstrated that the structure forms a Mach-Zehnder interferometer (MZI) with the interference between the laser light passing through the air in the trench cavity and that in the remained fiber core. The fringe visibilities are all more than 25 dB. The transmission spectra vary with the femtosecond (fs) laser ablation scanning cycle. The free spectral range (FSR) decreases as the trench length increases. The MZI structure is of very high fabrication and sensing repeatability. The sensing mechanism is theoretically discussed, which is in agreement with experiments. The test sensitivity for acetone vapor is about 10(4) nm/RIU, and the temperature sensitivity is 51.5 pm/°C at 200 ? 875 °C with a step of 25 °C. PMID:22346567

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

2011-01-01

233

Single-ended long period fiber grating refractive index sensor based on metal-coated surface plasma resonance  

NASA Astrophysics Data System (ADS)

A novel single-ended reflecting long period fiber grating (LPFG) sensor with thin metal film overlay and the sensing system is described. An all-fiber reflection based surface plasma resonance (SPR) LPFG sensor with three-layer structure (core, cladding and metal) is established experimentally and fabricated with a pulsed CO2 laser writing system and vacuum evaporation coating system. Different nm-thick thin metal films are deposited on the reflected LPFG sensor for the excitation of surface plasma waves (SPWs) and the characteristics of the reflection resonance spectra of the LPFG sensor for measuring refractive index of fluids are studied. It is found that different thicknesses of different metal films show different measuring sensitivity. Through the comparison of the resonance wavelength obtained in air, water, alcohol, glycerin and their mixture solution, different sensitivities of the reflected SPR-LPFG sensor have been achieved. The proposed SPR-LPFG sensing scheme offers an efficient platform for achieving high performance fiber sensors for the measurement of ambient refractive index.

Zhao, Minfu; Zhang, Guiju; Ma, Difeng; Wang, Chinhua

2008-12-01

234

Bending Characteristics of Fiber Long-Period Gratings With Cladding Index Modified by Femtosecond Laser  

NASA Astrophysics Data System (ADS)

A femtosecond laser has been used to asymmetrically modify the cladding of fiber containing long-period gratings. Following modification, devices in single-mode fiber are shown to be capable of sensing the magnitude and direction of bending in one plane by producing blue and red wavelength shifts depending upon the orientation of the bend. The resulting curvature sensitivities were -1.62 and +3.82 nm · m. Devices have also been produced using an elliptical core fiber to study the effects of the cladding modification on the two polarization eigenstates. A cladding modification applied on the fast axis of the fiber is shown to affect the light in the fast axis much more significantly than the light in the orthogonal state; this behavior may ultimately lead to a sensor capable of detecting the direction of bending in two dimensions for applications in shape sensing.

Allsop, T.; Dubov, M.; Martinez, A.; Floreani, F.; Khrushchev, I.; Webb, D. J.; Bennion, I.

2006-08-01

235

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

236

State of polarization and propagation factor of a stochastic electromagnetic beam in a gradient-index fiber.  

PubMed

With the help of a tensor method, we investigate the evolution properties of the state of polarization of an electromagnetic Gaussian Schell-model beam propagating through a gradient-index (GRIN) fiber. We find that the Stokes parameters and the polarization ellipse exhibit periodicity. The initial beam parameters affect the values of the Stokes parameters and the parameters of the polarization ellipse. Furthermore, based on the second-order moments of the Wigner distribution function, the explicit expression for the propagation factor (known as the M(2) factor) in the GRIN fiber is derived. It is shown that the M(2) factor remains invariant on propagation and is determined only by the initial beam parameters. PMID:24322929

Zhu, Shijun; Liu, Lin; Chen, Yahong; Cai, Yangjian

2013-11-01

237

Temperature-induced index gratings and their impact on mode instabilities in high-power fiber laser systems.  

PubMed

Mode-interference along an active fiber in high-power operation gives rise to a longitudinally oscillating temperature profile which, in turn, is converted into a strong index grating via the thermo-optic effect. In the case of mode beating between the fundamental mode and a radially anti-symmetric mode such a grating exhibits two periodic features: a main one which is radially symmetric and has half the period of the modal beating, and a second one that closely follows the mode interference pattern and has its same period. In the case of modal beating between two radially symmetric modes the thermally induced grating only has radially symmetric features and exhibits the same period of the mode interference. The relevance of such gratings in the context of the recently observed mode instabilities of high-power fiber laser systems is discussed. PMID:22274367

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

2012-01-01

238

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

239

Phase-stepping fiber-optic projected fringe system for surface topography measurements  

NASA Technical Reports Server (NTRS)

A projected fringe interferometer for measuring the topography of an object is presented. The interferometer periodically steps the phase angle between a pair of light beams emanating from a common source. The steps are pi/2 radians (90 deg) apart, and at each step a video image of the fringes is recorded and stored. Photodetectors measure either the phase and theta of the beams or 2(theta). Either of the measures can be used to control one of the light beams so that the 90 deg theta is accurately maintained. A camera, a computer, a phase controller, and a phase modulator established closed-loop control of theta. Measuring the phase map of a flat surface establishes a calibration reference.

Mercer, Carolyn R. (inventor); Beheim, Glenn (inventor)

1992-01-01

240

In-fiber reflection mode interferometer based on a long-period grating for external refractive-index measurement.  

PubMed

We present two novel schemes for refractometry based on a long-period fiber grating- (LPG-) based Michelson interferometer. These schemes are designed to overcome the measurement dependence of previously demonstrated LPG-based refractometry on the immersion depth. The first utilizes an unshielded LPG and the second, a shielded one. Both schemes were tested over a certain refractive-index range, and the measurement of glucose concentration in water was experimentally demonstrated. In addition, the temperature sensitivity of the two schemes is discussed. PMID:16161647

Kim, Dae Woong; Zhang, Yan; Cooper, Kristie L; Wang, Anbo

2005-09-10

241

Surface plasmon resonance refractive index sensor based on polymer photonic crystal fibers with nano-composite materials  

NASA Astrophysics Data System (ADS)

A study of polymer photonic crystal fiber (PCF) sensor coated with smart composite materials for measurements of refractive index of analyte is presented in this paper. The proposed sensor combines the characteristics of polymer PCF and composite material, which can make the confinement loss lower than the silica PCF duo to the double interaction of the polymer and silver film. The results obtained in this study demonstrate that polymer PCF sensors coated with composite material and with the polymer PCF's advantages, the sensor's feasibility can be improved further and it can be applied in a broad field, especially in biosensing platforms.

Hao, Congjing; Lu, Ying; Wu, Baoqun; Duan, Liangcheng; Wang, Mintuo; Yao, Jianquan

2013-09-01

242

Optic sensors of high refractive-index responsivity and low thermal cross sensitivity that use fiber Bragg gratings of >80 degrees tilted structures.  

PubMed

For the first time to the authors' knowledge, fiber Bragg gratings (FBGs) with >80 degrees tilted structures have been fabricated and characterized. Their performance in sensing temperature, strain, and the surrounding medium's refractive index was investigated. In comparison with normal FBGs and long-period gratings (LPGs), >80 degrees tilted FBGs exhibit significantly higher refractive-index responsivity and lower thermal cross sensitivity. When the grating sensor was used to detect changes in refractive index, a responsivity as high as 340 nm/refractive-index unit near an index of 1.33 was demonstrated, which is three times higher than that of conventional LPGs. PMID:16642056

Zhou, Kaiming; Zhang, Lin; Chen, Xianfeng; Bennion, Ian

2006-05-01

243

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

244

Ceria-based electrospun fibers for renewable fuel production via two-step thermal redox cycles for carbon dioxide splitting.  

PubMed

Zirconium-doped ceria (Ce1-xZrxO2) was synthesized through a controlled electrospinning process as a promising approach to cost-effective, sinter-resistant material structures for high-temperature, solar-driven thermochemical redox cycles. To approximate a two-step redox cycle for solar fuel production, fibrous Ce1-xZrxO2 with relatively low levels of Zr-doping (0 < x < 0.1) were cycled in an infrared-imaging furnace with high-temperature (up to 1500 °C) partial reduction and lower-temperature (?800 °C) reoxidation via CO2 splitting to produce CO. Increases in Zr content improve reducibility and sintering resistance, and, for x? 0.05, do not significantly slow reoxidation kinetics for CO production. Cycle stability of the fibrous Ce1-xZrxO2 (with x = 0.025) was assessed for a range of conditions by measuring rates of O2 release during reduction and CO production during reoxidation and by assessing post-cycling fiber crystallite sizes and surface areas. Sintering increases with reduction temperature but occurs primarily along the fiber axes. Even after 108 redox cycles with reduction at 1400 °C and oxidation with CO2 at 800 °C, the fibers maintain their structure with surface areas of ?0.3 m(2) g(-1), higher than those observed in the literature for other ceria-based structures operating at similarly high temperature conditions. Total CO production and peak production rate stabilize above 3.0 mL g(-1) and 13.0 mL min(-1) g(-1), respectively. The results show the potential for electrospun oxides as sinter-resistant material structures with adequate surface area to support rapid CO2 splitting in solar thermochemical redox cycles. PMID:24914875

Gibbons, William T; Venstrom, Luke J; De Smith, Robert M; Davidson, Jane H; Jackson, Gregory S

2014-07-21

245

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

NASA Astrophysics Data System (ADS)

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

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

2003-10-01

246

Fiber density index, fractional anisotropy, adc and clinical motor findings in the white matter of patients with glioblastoma.  

PubMed

Whether fractional anisotropy (FA), apparent diffusion coefficient (ADC), and fiber density index (FDi) values differ in the white matter close to glioblastomas of both symptomatic and asymptomatic patients was investigated. Twenty patients with glioblastomas underwent magnetic resonance imaging study. The FDi, FA and ADC values were calculated in areas of white matter in close proximity to the tumor (perWM) and encompassing fibers of cortico-spinal tract and in the contralateral normal-appearing white matter (nWM). The clinical compromise of the cortico-spinal tract was graded using Brunnstrom's criteria. FA and FDi were significantly decreased and ADC increased in perWM compared with the contralateral. Mean FDi, FA, and ADC values comparing perWM and nWM in symptomatic patients showed similar differences. Comparing the perWM of symptomatic and asymptomatic patients, mean FDi and ADC values were lower in symptomatic patients than in asymptomatic ones. A positive correlation was found between the clinical score (CS) and, separately, FDi, FA and ADC per WM values. In a multiple stepwise regression among the same factors, only the ADC of perWM values showed a positive correlation with the CS. An increased ADC plays a major role in reducing the number of fibers (reduced FDi) in symptomatic patients. PMID:17899109

Romano, Andrea; Fasoli, Fabrizio; Ferrante, Michele; Ferrante, Luigi; Fantozzi, Luigi Maria; Bozzao, Alessandro

2008-02-01

247

Power flow equation analysis of graded-index polymer optical fibers  

Microsoft Academic Search

We have succeeded in development of a simulation specialized for GI POF. In this study, we investigated the propagation characteristics of GI POF by use of this simulation. Propagation properties of multi-mode optical fibers can be calculated by the scalar-wave equation derived from Maxwell's equations. However, calculated impulse response disagrees with measured results. The factors of this disagreement have been

Kazuma Nehashi; Yasuhiro Koike

2009-01-01

248

Influence of non-linear index on coherent passive beam combining of fiber lasers  

Microsoft Academic Search

Coherent laser beam combining is potentially attractive way to increase the output beam brightness beyond the limits imposed on single-mode lasers by technological problems. Passive phase locking does not need complex external management. A specific feature of fiber amplifiers and lasers is that they possess optical path differences of many wavelengths magnitude. Cold-cavity theory of coherent laser beam combining predicts

A. P. Napartovich; N. N. Elkin; D. V. Vysotsky

2011-01-01

249

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

PubMed Central

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

Wang, Ke; Pickrell, Gary

2011-01-01

250

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

251

Spatial beam properties of combined lasers' delivery fibers.  

PubMed

The superiority of parabolic-index fibers over step-index fibers in delivering high-beam-quality light out of incoherently combined lasers is demonstrated numerically and experimentally. By utilizing the tapered fused bundle-combining approach and connecting it with delivery fiber, we point to an efficient, rugged, all-glass, integrated, and nearly brightness-preserving device that is capable of transmitting high-quality output beams. PMID:22555688

Shamir, Yariv; Zuitlin, Roey; Sintov, Yoav; Shtaif, Mark

2012-05-01

252

Highly birefringence low loss index guiding photonic crystal fiber with differently sized air-holes in cladding  

NASA Astrophysics Data System (ADS)

An analysis of highly birefringence low losss index-guiding phptonic crystal fiber composed of different sized circular air-holes in cladding and adjacent to the two ellipital air-holes x-diraction in the first inner rings is carried out in this work using voul fector finite element method.The birefringence properities in terms of various parameters,e.g,pitch length,air-hole size and ellipticity ratio are calculated.Form the numerical results confirm that the size control of these air holes and pitch length is the key to reaching high model birefringnce.The proposed struture at wavelength 1.55?m shows a birefringence of up to 3.02x10-2 and at the same time can get the confinement loss of less than 1.9x10-7dB/m, which is a reference significance in useful to dessign temperature sensors.

Mayilamu, Musideke; Lu, Ying; Hao, Congjing; Duan, Liangcheng; Yao, Jianquan

2013-12-01

253

Propagation in a tropospheric duct with a single-step discontinuity in the refractive index in the direction of propagation  

NASA Astrophysics Data System (ADS)

A Green's function approach is used to derive an expression for the field inside a laterally inhomogeneous duct. The laterally inhomogeneous duct is assumed to have a single step, and convergence criteria for the step size and number of modes are discussed.

Ott, R. H.

1980-06-01

254

Mathematical analysis of adaptive step-size techniques when solving the nonlinear Schrödinger equation for simulating light-wave propagation in optical fibers  

NASA Astrophysics Data System (ADS)

In optics the nonlinear Schrödinger equation (NLSE) which modelizes light-wave propagation in an optical fibre is the most widely solved by the Symmetric Split-Step method. The practical efficiency of the Symmetric Split-Step method is highly dependent on the computational grid points distribution along the fiber and therefore an efficient adaptive step-size control strategy is mandatory. A lot of adaptive step-size methods designed to be used in conjunction with the Symmetric Split-Step method for solving the various forms taken by the NLSE can be found in the literature dedicated to optics. These methods can be gathered together into two groups. Broadly speaking, a first group of methods is based on the observation along the propagation length of the behavior of a given optical quantity (e.g. the photons number) and the step-size at each computational step is set so as to guarantee that the known properties of the quantity are preserved. Most of the time these approaches are derived under specific assumptions and the step-size selection criterion depends on the fiber parameters. The second group of methods makes use of some mathematical concepts to estimate the local error at each computational grid point and the step-size is set so as to maintain it lower than a prescribed tolerance. This approach should be preferred due to its generality of use but suffers from a lack of understanding in the mathematical concepts of numerical analysis it involves. The aim of this paper is to present an analysis of local error estimate and adaptive step-size control techniques for solving the NSLE by the Symmetric Split-Step method with all the unavoidable mathematical rigor required for a comprehensive understanding of the topic.

Balac, Stéphane; Fernandez, Arnaud

2014-10-01

255

Differences in the architecture of low-grade and high-grade gliomas evaluated using fiber density index and fractional anisotropy  

Microsoft Academic Search

Accurate pre-operative assessment of tumor grade is important for the selection of appropriate treatment strategies. The aim of this study was to retrospectively evaluate whether the fiber density index (FDi) and fractional anisotropy (FA) via diffusion tensor MRI (DTI) could assist with pre-operative diagnosis of glioma grade. A total of 31 patients who had histologically confirmed gliomas underwent DTI performed

Yiyong Chen; Yonghong Shi; Zhijian Song

2010-01-01

256

Record 5.3 Gbit\\/s transmission over 50m 1mm core diameter graded-index plastic optical fiber  

Microsoft Academic Search

We report multi-Gbit\\/s capacity in 1-mm diameter graded index plastic optical fiber exploiting low-cost eye safe compliant transceivers. Transmission rates between 5.3 and 7.6 Gbit\\/s are achieved for lengths between 10 and 50 m using DMT.

D. Visani; C. M. Okonkwo; S. Loquai; H. Yang; Y. Shi; H. P. A. van den Boom; A. M. H. Ditewig; G. Tartarini; B. Schmauss; S. Randel; A. M. J. Koonen; E. Tangdiongga

2010-01-01

257

Fiber optics: A brief introduction  

SciTech Connect

A basic introduction into the principles of fiber optics is presented. A review of both the underlying physical principles and the individual elements of typical fiber-optic systems are presented. The optical phenomenon of total internal reflection is reviewed. The basic construction of the optical fiber is presented. Both step-index and graded-index fiber designs are reviewed. Multimode and single-mode fiber constructions are considered and typical performance parameters given. Typical optical-fiber bandwidth and loss characteristics are compared to various common coaxial cables, waveguides, and air transmission. The constructions of optical-fiber cables are reviewed. Both loose-tube and tightly-buffered designs are considered. Several optical connection approaches are presented. Photographs of several representative optical connectors are included. Light Emitting Diode and Laser Diode emitters for fiber-optic applications are reviewed, and some advantages and shortcomings of each are considered. The phenomenon of modal noise is briefly explained. Both PIN and Avalanche photodetectors are reviewed and their performance parameters compared. Methods of data transmission over optical fiber are introduced. Principles of Wavelength, Frequency, and Time Division Multiplexing are briefly presented. The technology of fiber-optic sensors is briefly reviewed with basic principles introduced. The performance of a fiber-optic strain sensor is included as a practical example. 7 refs., 10 figs.

Gruchalla, M.E.

1989-01-01

258

Fiber post adhesion to radicular dentin: The use of acid etching prior to a one-step self-etching adhesive.  

PubMed

The aim of this study was to evaluate the bond strength of fiber posts luted with a one-step self-etching adhesive with the push-out test after phosphoric acid conditioning of the root dentin. Thirty-six single-rooted teeth were endodontically treated. Teeth were sectioned perpendicularly to the cementoenamel junction, and a 10-mm post space was prepared with a calibrated bur. Specimens were then divided into three groups according to the adhesive protocol: A, total-etch three steps; B, self-etch one step; and C, 32% phosphoric acid conditioning and self-etch one step. Fiber posts were luted with self-curing resin-based cement. Teeth were cut in 1-mm slices and pushed until failure with an Instron machine. Results were statistically analyzed with the ANOVA and Bonferroni tests (P < .05). Two additional specimens from each group were examined under the scanning electron microscope (SEM). The 32% phosphoric acid significantly influenced the push-out bond strength of fiber posts luted with self-etch adhesives (P < .05). SEM analysis showed a continuous hybrid layer with resin tags and lateral branches in groups A and C, while group B showed smear layer dissolution with poor infiltration of the tubules. PMID:22670257

Scotti, Nicola; Rota, Riccardo; Scansetti, Marco; Migliaretti, Giuseppe; Pasqualini, Damiano; Berutti, Elio

2012-01-01

259

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.

Foundation, Wgbh E.

2011-10-25

260

Dependence of Bending Losses on Cladding Thickness in Plastic Optical Fibers  

Microsoft Academic Search

Our main goal is to provide a comprehensive explanation of the existing differences in bending losses arising from having step-index multimode plastic optical fibers with different cladding thicknesses and under different types of conditions, namely, the variable bend radius R , the number of fiber turns, or the fiber diameter. For this purpose, both experimental and numerical results of bending

Gaizka Durana; Joseba Zubia; Jon Arrue; Gotzon Aldabaldetreku; Javier Mateo

2003-01-01

261

Mode coupling and equilibrium mode distribution conditions in plastic optical fibers  

Microsoft Academic Search

The equilibrium mode distribution (EMD) condition is critical for optical fiber measurements. In this letter, we examine the achievement of EMD condition inside plastic optical fibers (POF's) under different launch conditions. Our pulse broadening measurements of step-index (SI) POF's as a function of fiber length show that the EMD condition can readily be achieved in an SI POF much shorter

G. Jiang; R. F. Shi; A. F. Garito

1997-01-01

262

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

263

Development of a two-step tier-2 dissolution method for blinded overencapsulated erlotinib tablets using UV fiber optic detection.  

PubMed

Measuring dissolution of a comparator drug overencapsulated in a hard gelatin shell is necessary when determining performance of the native and blinded formulations. However, the gelatin in the shell may form cross-links upon storage at stressed conditions, resulting in slow dissolution of the encapsulated drug. The aim of this study was to develop a dissolution approach for a hard-gelatin overencapsulated formulation of a comparator drug, erlotinib, which can overcome cross linking of the capsule shell. In this case, following the USP two-tier dissolution test by simply adding an enzyme did not dissolve the cross-linked capsules because the medium used in the method for erlotinib described in the FDA Dissolution Database contains sodium dodecyl sulfate that inhibits the activity of the enzyme. Changing the method by using different surfactants was not considered acceptable because it is preferable to closely follow the compendial method for the comparator. A two-step tier-2 method was developed as a solution, without significant change to the compendial method conditions. It uses 0.1N HCl + pepsin as the initial medium to help capsule break-up. SDS is added at 15 min after the testing starts to ensure dissolution of the drug. This may be a useful general approach for dealing with cross-linking in over-encapsulated comparators. A UV fiber optic spectrophotometer was used for in situ, real-time detection of the dissolution profile during method development studies. The fast sampling rate available with this type of detection was important in elucidating the events occurring during dissolution and determining the optimal time of the SDS addition. PMID:21620602

Lu, Xujin; Xiao, Baiming; Lo, Lili; Bolgar, Mark S; Lloyd, David K

2011-08-25

264

Fiber  

MedlinePLUS

... short period of time can cause intestinal gas ( flatulence ), bloating , and abdominal cramps . This usually goes away ... Food and Nutrition Board. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and ...

265

Narrow Bandwidth 850-nm Fiber Bragg Gratings in Few-Mode Polymer Optical Fibers  

Microsoft Academic Search

We report on the inscription and characterization of narrow bandwidth fiber Bragg gratings (FBGs) with 850-nm res- onance wavelength in polymer optical fibers (POFs). We use two fibers: an in-house fabricated microstructured POF (mPOF) with relative hole size of 0.5 and a commercial step-index POF, which supports six modes at 850 nm. The gratings have been written with the phase-mask

Alessio Stefani; Wu Yuan; Christos Markos; Ole Bang

2011-01-01

266

Real-index-guided AlGaInP red laser with high-power characteristics grown by one-step MOVPE  

NASA Astrophysics Data System (ADS)

We have developed a one-step-grown real-index-guided AlGaInP/GaInAsP red laser called a self-aligned stepped substrate (S3) laser. This S3-laser has a double- hetero structure formed on a stepped nonplanar substrate and an active layer inclined at an angle to the horizontal. The fabrication process of the laser utilizes the following two key techniques: (1) a lateral p-n junction formed during the growth of the nonplanar substrate by alternate doping with Zn and Se that have strong impurity incorporation dependencies on the substrate's orientation, and (2) a natural (411)A-like growth facet formation on the nonplanar substrate by metal organic vapor phase epitaxy (MOVPE). The real-index waveguide structure with an inclined active layer provided the laser with a stable lateral-mode and good beam characteristics (a small astigmatism and a small aspect ratio). Its optical-loss- free structure leads to a low threshold current of about 20 mA, a high quantum efficiency of about 1.2 W/A, and a high characteristic temperature of about 150K within 25 degrees Celsius to 50 degrees Celsius. A low operating current of the laser with the wavelength of 680 nm under 70 degrees Celsius, 35 mW conditions, would make it highly reliable for optical storage applications.

Anayama, Chikashi; Furuya, Akira; Tanahashi, Toshiyuki

1998-04-01

267

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

268

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

NASA Astrophysics Data System (ADS)

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

Zur, Albert; Katzir, Abraham

1991-02-01

269

Photoinduced refractive-index change in Sm(+2)/Sm(+3) codoped aluminosilicate fiber by irradiation of an Ar-ion laser.  

PubMed

A Sm(+2)/Sm(+3) codoped aluminosilicate glass optical fiber was fabricated by use of modified chemical-vapor deposition in conjunction with an aerosol-delivery technique. A permanent index change of 7.6 x 10(-5) was induced in the fiber by irradiation of 1 W of multiline output from an Ar-ion laser. Bleaching of a broad absorption band of Sm(+2) in the visible range was also observed, and it is believed that photoionization of Sm(+2)? Sm(+3)+e plays an important role in the induced photorefractivity. PMID:18185792

Oh, K; Paek, U C; Morse, T F; Reinhart, L; Kilian, A

1997-08-01

270

Distinct Docking and Stabilization Steps of the Pseudopilus Conformational Transition Path Suggest Rotational Assembly of Type IV Pilus-like Fibers.  

PubMed

The closely related bacterial type II secretion (T2S) and type IV pilus (T4P) systems are sophisticated machines that assemble dynamic fibers promoting protein transport, motility, or adhesion. Despite their essential role in virulence, the molecular mechanisms underlying helical fiber assembly remain unknown. Here, we use electron microscopy and flexible modeling to study conformational changes of PulG pili assembled by the Klebsiella oxytoca T2SS. Neural network analysis of 3,900 pilus models suggested a transition path toward low-energy conformations driven by progressive increase in fiber helical twist. Detailed predictions of interprotomer contacts along this path were tested by site-directed mutagenesis, pilus assembly, and protein secretion analyses. We demonstrate that electrostatic interactions between adjacent protomers (P-P+1) in the membrane drive pseudopilin docking, while P-P+3 and P-P+4 contacts determine downstream fiber stabilization steps. These results support a model of a spool-like assembly mechanism for fibers of the T2SS-T4P superfamily. PMID:24685147

Nivaskumar, Mangayarkarasi; Bouvier, Guillaume; Campos, Manuel; Nadeau, Nathalie; Yu, Xiong; Egelman, Edward H; Nilges, Michael; Francetic, Olivera

2014-05-01

271

New high performance plastic optical fibers for data communications  

Microsoft Academic Search

Summary form only given. In this study we introduce an approach to form a gradient of refractive index in the polymeric fibers, namely, radial diffusion of low-refractive-index (lower than polymer) modifier. Two steps of preform manufacturing by this method include synthesis of the polymeric cladding tube doped with low-refractive-index plasticizers. During the second step the cladding tube is filled with

V. Ilyashenko

1998-01-01

272

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

273

Dual-peak long-period fiber gratings with enhanced refractive index sensitivity by finely tailored mode dispersion that uses the light cladding etching technique  

NASA Astrophysics Data System (ADS)

We have experimentally investigated the mode dispersion property and refractive index sensitivity of dual-peak long-period fiber gratings (LPGs) that were sensitized by hydrofluoric acid (HF) etching. The nature of the coupled cladding modes close to the dispersion turning point makes the dual-peak LPGs ultrasensitive to cladding property, permitting a fine tailoring of the mode dispersion and index sensitivity by the light cladding etching method using HF acid of only 1% concentration. As an implementation of an optical biosensor, the etched device was used to detect the concentration of hemoglobin protein in a sugar solution, showing a sensitivity as high as 20 nm/1%.

Chen, Xianfeng; Zhou, Kaiming; Zhang, Lin; Bennion, Ian

2007-02-01

274

Dual-peak long-period fiber gratings with enhanced refractive index sensitivity by finely tailored mode dispersion that uses the light cladding etching technique.  

PubMed

We have experimentally investigated the mode dispersion property and refractive index sensitivity of dual-peak long-period fiber gratings (LPGs) that were sensitized by hydrofluoric acid (HF) etching. The nature of the coupled cladding modes close to the dispersion turning point makes the dual-peak LPGs ultrasensitive to cladding property, permitting a fine tailoring of the mode dispersion and index sensitivity by the light cladding etching method using HF acid of only 1% concentration. As an implementation of an optical biosensor, the etched device was used to detect the concentration of hemoglobin protein in a sugar solution, showing a sensitivity as high as 20 nm/1%. PMID:17230235

Chen, Xianfeng; Zhou, Kaiming; Zhang, Lin; Bennion, Ian

2007-02-01

275

Temperature-insensitive refractive index sensing by use of micro Fabry-Pérot cavity based on simplified hollow-core photonic crystal fiber.  

PubMed

A temperature-insensitive micro Fabry-Pérot (FP) cavity based on simplified hollow-core (SHC) photonic crystal fiber (PCF) is demonstrated. Such a device is fabricated by splicing a section of SHC PCF with single mode fibers at both cleaved ends. An extremely low temperature sensitivity of ~0.273 pm/°C is obtained between room temperature and 900°C. By drilling vertical micro-channels using a femtosecond laser, the micro FP cavity can be filled with liquids and functions as a sensitive refractometer and the refractive index sensitivity obtained is ~851.3 nm/RIU (refractive index unit), which indicates an ultra low temperature cross-sensitivity of ~3.2×10(-7) RIU/°C. PMID:23381407

Wang, Ying; Wang, D N; Liao, C R; Hu, Tianyi; Guo, Jiangtao; Wei, Huifeng

2013-02-01

276

Simultaneous measurement of external refractive index and temperature based on long-period-grating-inscribed Sagnac interferometer and fiber Bragg grating  

NASA Astrophysics Data System (ADS)

A compact Sagnac interferometer with a long-period grating (LPG) inscribed in a polarization-maintaining fiber (PMF-LPG) and a fiber Bragg grating (FBG) is proposed. The PMF-LPG is intrinsically sensitive to the external refractive index (ERI) and temperature, whereas the FBG is only sensitive to temperature. Simultaneous measurement of the ERI and temperature can be achieved by detecting wavelength shifts in the interference patterns of the Sagnac interferometer and the FBG. Because a Sagnac interference structure is used, a high ERI sensitivity of -21.07 nm/refractive index unit in measurement range 1.33-1.43 is obtained, which is about three times higher than for the normal LPG ERI sensor.

Gao, Peng; Chen, Xiuyan; Feng, Wenjiang

2012-10-01

277

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

278

47.4 Gb\\/s Transmission Over 100 m Graded-Index Plastic Optical Fiber Based on Rate-Adaptive Discrete Multitone Modulation  

Microsoft Academic Search

We experimentally demonstrate a bit-rate of 47.4 Gb\\/s over 100 m of perfluorinated multimode graded-index plastic optical fiber (GI-POF) by exploiting discrete multitone (DMT) modulation with rate-adaptive bit-loading. The maximum achieved aggregate bit rate is 51.8 Gb\\/s including DMT transmission overhead (cyclic prefix and preambles) and the standard of 7% of forward-error-correction (FEC) overhead. This is achieved over an intensity-modulated

Hejie Yang; S. C. Jeffrey Lee; Eduward Tangdiongga; Chigo Okonkwo; Henrie P. A. van den Boom; Florian Breyer; Sebastian Randel; A. M. J. Koonen

2010-01-01

279

Excitation of Single-mode Circular Core Parabolic Index Fiber by Laser Diode via Upside Down Tapered Hemispherical Microlens on the Tip of the Fiber: Estimation of Coupling Efficiency by Application of ABCD Matrix Formalism  

NASA Astrophysics Data System (ADS)

The ABCD matrix prescribed for a upside down tapered hemispherical microlens end drawn from a parabolic index circular core fiber is used to formulate analytical expression of coupling efficiency of excitation of this optical device by a laser diode. In our analysis, we assume Gaussian field distribution for both the source and the fiber. For maximum coupling efficiency, the lens transmitted spot size of the source should match with the fiber spot size. In our investigations, we employ two different laser diodes emitting wavelengths 1.3 ?m and 1.5 ?m respectively. It is found that the wavelength 1.5 ?m is more efficient in the context of present coupling optics. Our formalism predicts the concerned coupling optics excellently and the execution of our formalism requires little computations. This simple but accurate technique is expected to benefit the system designers and packagers concerned with optimum launch optics.

Das, Bishuddhananda; Maiti, Anup Kumar; Gangopadhyay, Sankar

2014-06-01

280

Design guidelines and characteristics for a kind of four-layer large flattened mode fibers  

NASA Astrophysics Data System (ADS)

A theoretical method to analyze a kind of four-layer large flattened mode (LFM) fibers is presented. The properties of the fiber, including the fundamental and higher-order modal fields, effective area and bending loss are discussed by comparison. At the same time, the reasons for the different characteristics are considered. The obtained results indicate that the effective area of the four-layer LFM fiber is about 1.3 times larger than that of the conventional standard step-index fiber and the fiber can suppress the higher-order modes via bending effectively. The four-layer LFM fiber has less efficient bend-induced filtering ability than the conventional step-index fiber; however, it has more efficient filtering ability than the three-layer LFM fiber.

Zhao, Chujun; Tang, Zhixiang; Ye, Yunxia; Shen, Lei; Fan, Dianyuan

2008-11-01

281

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

Microsoft Academic Search

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,

Grzegorz Fusiek; Pawel Niewczas; James R. McDonald

2005-01-01

282

Acceptance-angle measurement of multimode fibers - A comparison of techniques  

Microsoft Academic Search

A number of techniques for measuring multimode fiber acceptance angle are described, and the general requirements and problems particular to each technique are discussed. An experimental comparison is presented of a fiber acceptance-angle technique and a fiber radiation-angle technique. Results are presented on quasi-step index and also plastic-clad silica fibers. It is concluded that the radiation-angle technique offers simplicity of

R. Worthington

1982-01-01

283

Equalization and mode partition noise in all-plastic optical fiber data links  

Microsoft Academic Search

High-speed, short-distance data transmission over all-plastic step-index fiber (plastic optical fiber, or POF) is normally considered to be limited by intermodal dispersion. Theoretical calculations in this letter show that the baseband frequency response can be significantly improved using simple linear equalization. However, as the fiber length is increased, the sharp absorption attenuation peaks of PMMA fiber can potentially introduce mode

Richard J. S. Bates

1992-01-01

284

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

285

Excitation efficiency of an optical fiber core source  

NASA Technical Reports Server (NTRS)

The exact field solution of a step-index profile fiber is used to determine the excitation efficiency of a distribution of sources in the core of an optical fiber. Previous results of a thin-film cladding source distribution to its core source counterpart are used for comparison. The behavior of power efficiency with the fiber parameters is examined and found to be similar to the behavior exhibited by cladding sources. It is also found that a core-source fiber is two orders of magnitude more efficient than a fiber with a bulk distribution of cladding sources. This result agrees qualitatively with previous ones obtained experimentally.

Egalon, Claudio O.; Rogowski, Robert S.; Tai, Alan C.

1992-01-01

286

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

PubMed

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

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

2013-03-11

287

Optical fibers for optical communication  

Microsoft Academic Search

Optical fiber fabrication technology is described with particular attention given to the coating of fibers. Consideration is given to the plastic-cladded fiber, the graded-index fiber, and the single-mode fiber with respect to mechanical strength, attenuation, and dispersion. The sensitivity of these fibers to bending and microbending, and the offset when coupling two fibers are also discussed.

W. Eickhoff; H.-P. Huber; O. Krumpholz; K. Petermann

1979-01-01

288

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

NASA Astrophysics Data System (ADS)

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

Hishiki, Keisuke; Li, Hongpu

2013-09-01

289

Suppression of Dynamic Laser Speckle Signals in Multimode Fibers of Various Lengths  

NASA Astrophysics Data System (ADS)

The effects of fiber coupling and fiber length on photocurrent fluctuations are studied when the light of a laser diode transmitted to and from a dynamic turbid medium by a step-index multimode fiber is studied. When the laser light is coupled asymmetrically, filling only the higher-order modes, the photocurrent fluctuations are suppressed significantly when fiber lengths of as much as 16 m are added between the laser and the medium. Addition of as much as 16 m of detection fiber, or any fiber in the case of symmetric light coupling, leads to much less or no suppression of the photocurrent fluctuations.

Petoukhova, Anna L.; Cleven, Ester; de Mul, Frits F. M.; Steenbergen, Wiendelt

2004-04-01

290

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

291

a Reformulation of Coupled Mode Theory for Multimode Guides with Application to a Specialized Graded-Index Optical Fiber Coupler  

Microsoft Academic Search

Coupled mode theory for parallel dielectric waveguides is reformulated for the case of a multimode multiwaveguide system. This theory is derived on the basis of a generalized reciprocity theorem. Analytical relations among the coupling coefficients are derived and applied to the coupled mode equations. It is found that even for lossless identical fibers the coupling coefficients from the m^ {th}

Salama Abul-Seoud Saleh

1991-01-01

292

Effect of temperature on optical fiber transmission. [for spacecraft communication  

NASA Technical Reports Server (NTRS)

Results are presented concerning the effects of temperature on the transmission properties of various optical fibers including a silicone plastic clad, an acrylic plastic clad, and CVD step-index fibers both with and without polyurethane jackets. Results are presented for the normalized transmitted power vs temperature, the index of refraction vs temperature, and induced attenuation coefficients vs temperature. The data show that the intrinsic transmission of a CVD fiber is independent of temperature over the -110 to +150 C range. Plastic clad fused silica fibers are subject to transmission losses at lower temperatures due to changes in the optical index of the cladding polymer. Acrylic-clad and plastic-clad silica fibers also show transmission losses at lower temperatures, but to lesser extents.

Yeung, W. F.; Johnston, A. R.

1978-01-01

293

A rigorous analysis of the power distribution in plastic clad annular core optical fibers  

Microsoft Academic Search

Using Maxwell's field equations, an analytical investigation is presented of the relative power distributions in the different sections of a step-index plastic clad annular core optical fiber (ACF) operating in the infrared region of the electromagnetic (EM) spectrum. It is assumed that the fiber cross-section is made of two concentric circles, and the EM waves propagate through the annular region.

P. K. Choudhury; Toshihiko Yoshino

2002-01-01

294

On the application of optical-fiber image scramblers to astronomical spectroscopy  

Microsoft Academic Search

Single, step-index optical fibers, when properly employed, can function as optically efficient image scramblers. Their use as optical feeds for astronomical slit spectrographs can reduce zonal error levels in those instruments by orders of magnitude. As a consequence, the application of optical-fiber couplers to new and existing spectrographs may greatly increase the wavelength metric quality of conventional astronomical spectroscopy. The

W. D. Heacox

1986-01-01

295

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

PubMed

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

Yan, Cheing-Tong; Chien, Hai-Ying

2012-07-13

296

Real-Time implementation of a 1.25-Gbit\\/s DMT transmitter for robust and Low-cost LED-based plastic optical fiber applications  

Microsoft Academic Search

Real-time implementation of a DMT transmitter in FPGA is demonstrated for low-cost, standard 1-mm step-index plastic optical fiber applications based on commercial resonant-cavity LED and large-diameter (540 mum) photodiode.

Sian Lee; F. Breyer; D. Cardenas; S. Randel; T. Koonen

2009-01-01

297

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

298

The spectrum of a bent fiber Fabry-Perot interferometer under small variations of the refractive index of the environment  

NASA Astrophysics Data System (ADS)

The phase of light propagating through a bent optical fibre is shown to depend on the refractive index of the medium surrounding the fibre cladding when there is resonance coupling between the guided core mode and cladding modes. This shifts the spectral maxima in the bent fibre-optic Fabry-Perot interferometer. The highest phase and spectral sensitivities achieved with this interferometer configuration are 0,71 and 0,077, respectively, and enable changes in the refractive index of the ambient medium down to 5·10-6 to be detected. This makes the proposed approach potentially attractive for producing highly stable, precision refractive index sensors capable of solving a wide range of liquid refractometry problems.

Gurbatov, Stanislav O.; Kulchin, Yury N.; Vitrik, Oleg B.

299

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

Microsoft Academic Search

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

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

2002-01-01

300

Fabrication of corrugated Ge-doped silica fibers.  

PubMed

We present a method of fabricating Ge-doped SiO2 fibers with corrugations around their full circumference for a desired length in the longitudinal direction. The procedure comprises three steps: hydrogenation of Ge-doped SiO2 fibers to increase photosensitivity, recording of Bragg gratings with ultraviolet light to achieve modulation of refractive index, and chemical etching. Finite-length, radially corrugated fibers may be used as couplers. Corrugated tapered fibers are used as high energy throughput probes in scanning near-field optical microscopy. PMID:22714512

Wróbel, P; Stefaniuk, T; Antosiewicz, T J; Libura, A; Nowak, G; Wejrzanowski, T; Andrzejczuk, M; Kurzyd?owski, K J; Jedrzejewski, K; Szoplik, T

2012-06-18

301

Thermally induced optical phase effects in fiber optic sensors.  

PubMed

Induced optical phase effects attributed to time varying temperatures at the fiber surface in single-mode fiber optic interferometric sensors are calculated. A Green's function approach is used for predicting temperature distributions within fibers for general time-dependent external temperatures. Analytic expressions for temperature distributions within fibers exposed to external linear, step, and sinusoidal temperature variations are derived using standard differential equation methods, assuming heat conduction to be the only heat transfer mechanism. With these expressions, thermally induced optical phase effects are predicted for an infinitely long uniform-index fiber. Plots are given that show the significance of fiber diameter and thermal properties on the time-dependent behavior of thermally induced phase effects for specific external temperature variations. It is shown that thermally induced phase effects can be reduced by jacketing fibers with elastomers having certain thermal properties. PMID:20221060

Hughes, R; Priest, R

1980-05-01

302

Efficient and short-range light coupling to index-matched liquid-filled hole in a solid-core photonic crystal fiber.  

PubMed

A photonic crystal fiber (PCF) with a section of one of the holes next to the solid core filled with an index-matched liquid is studied. Liquid filling alters the core geometry, which locally comprises the original silica core, the liquid channel and the silica around it. It is demonstrated that when light reaches the filled section, it periodically and efficiently couples to the liquid, via the excitation of a number of modes of the composite core, with coupling lengths ranging from tens to hundreds of microns. The resulting modal-interference-modulated spectrum shows temperature sensitivity as high as 5.35 nm/°C. The proposed waveguide geometry presents itself as an interesting way to pump and/or to probe liquid media within the fiber, combining advantages usually found separately in liquid-filled hollow-core PCFs (high light-liquid overlap) and in solid-core PCFs (low insertion losses). Therefore, pumping and luminescence guiding with a PCF filled with a Rhodamine solution is also demonstrated. PMID:22109496

Gerosa, Rodrigo M; Spadoti, Danilo H; de Matos, Christiano J S; Menezes, Leonardo de S; Franco, Marcos A R

2011-11-21

303

Mode coupling in low NA plastic optical fibers  

NASA Astrophysics Data System (ADS)

Using the power flow equation and experimental measurements, investigated in this article is the state of mode coupling in low NA (0.3) step-index plastic optical fibers for laser beam launch. Results show the coupling length Lc at which the equilibrium mode distribution is achieved and the length zs of the fiber required for achieving the steady-state mode distribution. Numerical results obtained using the power flow equation agree well with experimental measurements.

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

2014-08-01

304

Optical power flow in plastic-clad silica fibers  

Microsoft Academic Search

Using the time-independent power-flow equation, we have examined the mode coupling caused by intrinsic perturbation effects of step-index plastic clad silica fiber carrying more than 105 modes. Results show that the equilibrium mode distribution for this fiber is achieved at a length of approximately 550 m, which is longer than reported previously. While this coupling length is much longer than

Svetislav Savovic; Alexandar Djordjevich

2002-01-01

305

Low-loss hybrid fiber with zero dispersion wavelength shifted to 1 ?m  

NASA Astrophysics Data System (ADS)

We propose a novel cylindrically symmetric hybrid fiber design that allows combining properties of the both fibers guiding light due to total internal reflection (low optical losses) and photonic bandgap fibers (anomalous dispersion at 1 ?m). Refractive index profile of these fibers consist of the only few layers: low-index core (ncore-nsilica>0) surrounded with one or more high-index ring layers (nhigh-ncore>0), a depressed layer (ndepress-nsilica<0) and silica cladding. Operating mode is one of the high-order modes (depending on high-index ring layers number) with intensity maximum at fiber axis. Because the other modes (including the fundamental mode LP01) are guided in the high-index ring layer(s) the hybrid mode can be easily excited by splicing hybrid fiber and standard single-mode (?~1?m) step-index fiber with appropriate mode field diameter. Moreover method of achievement of asymptotically singlemode regime of light propagation (suppression of the high-index ring layer modes) has been proposed. The main idea of it is doping narrow strong absorbing layer where hybrid mode has intensity of electric field closed to zero. Furthermore we have considered possibility to increase anomalous dispersion of the hybrid fiber (up to 100 ps/nm km) by usage more complicated refractive index profile with two high-index ring layers. In this work we have fabricated the technologically simplest hybrid fiber with the only one high-index layer. The hybrid LP02 core mode had dispersion of 13 ps/(nm km) and optical loss of about 6 dB/km. Propagation of chirped pulses through the fabricated hybrid fiber allowed us to compress them from 8ps to 330fs.

Aleshkina, Svetlana S.; Likhachev, Mikhail E.; Senatorov, Andrei K.; Bubnov, Mikhail M.; Salaganskii, Mikhail Yu.; Guryanov, Alexei N.

2014-03-01

306

Dependence of beating dynamics on the ellipticity of a Gaussian beam in graded-index absorbing nonlinear fibers  

NASA Astrophysics Data System (ADS)

Using the collective variable approach technique, we analyze propagation of elliptical Gaussian beams in nonlinear waveguides with a parabolic graded-index (GRIN) profile. We considered both saturable and cubic-quintic models to describe the nonlinearity, taking into account both linear and nonlinear absorption. For lossless media, we construct diagrams, which define regions of self-focusing and self-diffractive beam propagation for both models in GRIN waveguides and compare them with those for nongraded waveguides. The widths of the propagating elliptic beam exhibit an oscillatory pattern, similar to the “breathing” and “beating” behavior found in nongraded media. Two types of beating oscillations are observed in both models. We calculate the dependence of Lbeat/Lbr, the ratio of the “beating” to “breathing” oscillation periods, on the beam ellipticity ? and the GRIN index g. We find that there is a remarkable difference in this dependence between saturable and cubic-quintic media: in the saturable model, Lbeat/Lbr is a monotonic function of ?, whereas in the cubic-quintic model, it is characterized by singularities, which correspond to transitions between the types of beat oscillations. For lossy media, we discuss the difference between the breathing behavior in nongraded and GRIN waveguides.

Ianetz, D.; Kaganovskii, Yu.; Wilson-Gordon, A. D.

2013-04-01

307

A single step technique for preparation of porous solid phase microextraction fibers by electrochemically co-deposited silica based sol-gel/Cu nanocomposite.  

PubMed

In this study, electrochemically co-deposited 3-trimethoxysilyl propyl methacrylate (3TMSPMA)/Cu nanocomposite is introduced as a novel and single-step technique for preparation of efficient and unbreakable solid phase microextraction (SPME) fibers; having strong interaction between the substrate and the coating. The applicability of prepared nanocomposite films was evaluated through extraction of some aromatic pollutants as model compounds from the headspace of aqueous samples in combination with gas chromatography-mass spectrometry (GC-MS). Different parameters affecting the structure and composition of the deposited films including applied potential, electrodeposition time, and precursor concentration; and the parameters affecting extraction efficiency such as extraction temperature, extraction time, and salt content were investigated. The results showed that morphology and grain size of the films are strongly affected by the ratio between the sol-gel precursor and Cu(2+) ions. Furthermore, potential of deposition influences the composition of films as it controls the kinetics of sol-gel/Cu co-deposition. Finally, characterization of the deposited films was accomplished by scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). PMID:23336939

Saber Tehrani, Mohammad; Aberoomand Azar, Parviz; Mohammadiazar, Sirwan

2013-02-22

308

Fabrication and characterization of a hybrid four-hole AsSe2-As2S5 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 × 104 km-1W-1at 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

309

Spectral and polarization selective fiber-optic elements  

Microsoft Academic Search

A pair of coupled step-index waveguides is analyzed. Characteristic equations are obtained and used to evaluate the cutoff frequencies and coupling constants. Mode transformation at tapers is analyzed. The spectral properties of fused couplers and tapered filters for which cutoff frequencies of higher modes were observed are studied. A fiber polarization splitter is realized. A semiconductor laser with an external

A. G. Bulushev; Y. V. Gurov; E. M. Dianov; O. G. Kuznetsov; O. G. Okhotnikov; V. M. Paramonov

1988-01-01

310

[Noninvasive assessment of wall stress related velocity of circumferential fiber shortening as an index of left ventricular contractility in children].  

PubMed

Assessment of the myocardial contractility in terms of the velocity of circumferential fiber shortening appropriate to the actual left ventricular endsystolic wall stress requires endsystolic pressure measurement usually done invasively. But for noninvasive evaluation of this parameter, we elaborated an algorithm to derive the endsystolic pressure in the ascending aorta from oscillometric blood pressure measurements. In 99 infants, children, adolescents, and young adults (1 day-37 years, median 5.5 years) we performed direct pressure recordings in the ascending aorta while measuring the arterial blood pressure at the upper arm by the Dinamap 8100 Blood Pressure Monitor. If measured directly, endsystolic (ESP(direct)) and mean aortic pressure (MAP(direct)) correlated well: ESP(direct)) = 1, 04 * MAP(direct))-2.18; r(2) = 0.91; s(y.x.) = 5.1 mm Hg. Comparison between the endsystolic and the mean arterial pressure (MAP(Dinamap) resulted in: ESP(direct) = 1.19 * MAP(Dinamap)-4.8; r(2) = 0.74; s(y. x.) = 8.3 mm Hg. In 52 patients this equation was used to derive the endsystolic pressure from the mean arterial pressure. Then the endsystolic wall stress was determined using the calculated (ESSm(Dinamap)) as well as the directly measured endsystolic pressure (ESSm(direct)): mean difference (ESSm(Dinamap) - ESSm(direct)) = -2.1 kdyn/cm(2); 95% confidence limits: -16.2 to 12. 1 kdyn/cm(2); linear regression: ESSm(direct = 1.07 * ESSm(Dinamap) - 2.22; r(2) = 0.91; s(y.x.) = 7.1 kdyn/cm(2). In n = 12 infants with complex heart defects and severe congestive heart failure due to pulmonary hyperperfusion the contractility was monitored noninvasively to assess the effects of propranolol (1.5 to 2 mg/kg/day) given complementary to digoxin and diuretics. The advantage of noninvasive assessment of the contractility in clinical routine was confirmed by the result that long-term propranolol does not impair myocardial contractility in this setting. PMID:10552183

Wessel, A; Buchhorn, R; Löber, M; Eigster, G; Hulpke-Wette, M; Bürsch, J

1999-10-01

311

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

312

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

NASA Astrophysics Data System (ADS)

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

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

2009-02-01

313

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

PubMed Central

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

Rao, Aparna

2014-01-01

314

Description of ultrashort pulse propagation in multimode optical fibers  

SciTech Connect

The guided, single-mode propagation of ultrashort optical pulses is commonly described by a well studied and understood generalized nonlinear Schroedinger equation. Here we present and discuss an extended version for multimode optical fibers and waveguides including polarization effects, high-order dispersion, Kerr and Raman nonlinearities, self-steepening effects, as well as wavelength-dependent mode coupling and nonlinear coefficients. We then investigate the symmetry properties of the nonlinear coupling coefficients for the cases of step-index and circularly symmetric conventional fibers and for microstructured fibers with hexagonal symmetry. Finally, we study the computational complexity of the proposed algorithm.

Poletti, Francesco; Horak, Peter [Optoelectronics Research Centre, University of Southampton, Southampton SO17 1BJ (United Kingdom)

2008-10-15

315

Bidirectional optical coupler for plastic optical fibers.  

PubMed

We have developed a low-loss bidirectional optical coupler for high-speed optical communication with plastic optical fibers (POFs). The coupler, which is fabricated by an injection molding method that uses poly (methyl methacrylate), has an antisymmetric tapered shape. We show that the coupler has low insertion and branching losses. The tapered shape of the receiving branch reduces beam diameter and increases detection efficiency coupling to a photodetector, whose area is smaller than that of the plastic optical fiber. The possibility of more than 15-m bidirectional transmission with a signaling bit rate up to 500 Mbits/s for simplex step-index POFs is demonstrated. PMID:15929280

Sugita, Tatsuya; Abe, Tomiya; Hirano, Kouki; Itoh, Yuzo

2005-05-20

316

Numerical diffraction modeling of light propagation in multicore fiber  

NASA Astrophysics Data System (ADS)

Modern technology allows for manufacturing of multicore fibers composed of a number of microcores placed on a circle and doped with Nd3+ ions. The construction is attractive because of effective absorption of diode laser pump radiation. High-power conditions are easily achievable, and phase coupling between microcore lasers looks very promising for receiving high-brightness radiation from compact fiber lasers. To understand in detail coupling between microcores and evaluate an opportunity to achieve phase-locked operation of the array, a mathematical code describing light propagation in this composed fiber was developed. A numerical code performs direct integration of scalar wave equation in paraxial approximation. Refractive index profile corresponds to N index-guiding microcores. The composite fiber was embedded into square region imitating fiber cladding with lower index. The wave equation was solved using a splitting technique for diffraction/refraction processes on every propagation step. Calculations on the diffraction step were made with help of 2D FFT technique on Cartesian mesh. Numerical accuracy was checked by special tests. Results on simulations of microcore array excitation by injection of a beam into one of microcores will be reported. For realizable in experiments conditions coupling lengths are found. Evolution of far-field patterns for different fiber lengths was studied.

Napartovich, Anatoly P.; Elkin, Nickolai N.; Sukharev, Alexander G.; Troshchieva, Vera N.; Vysotsky, Dmitri V.

2000-04-01

317

Investigations on fibers for high-peak power pulsed Nd:YAG-lasers for laser detonator  

NASA Astrophysics Data System (ADS)

For laser detonator application, high-peak power pulsed Nd:YAG laser is transmitted through all-silica optical fiber. The transmission properties of step-index fibers are investigated, using a high-peak power pulsed Nd: YAG rod laser with beyond 1MW power and Q-switch mode. The fibers are step-index multimode fibers with 400 or 600 ?m core diameters, 440 or 660 ?m cladding diameters. The power delivery characteristics were studied by theory and experiments. The results show that the fiber core diameter, NA, length and so on affect the transmission efficiency for high power laser. When the laser power is beyond a certain threshold, the SRS and SBS will be serious; the quantity of fiber end-face limits to the raising of laser power passing through fibers; the zero-probability damage threshold is calculated according to ISO/DIS standard 11254-1.2, which is 58.6J/cm2. Energy distribution of output beam from fibers will be uniform. Even the fiber end-face was partly damaged, laser power is still deliverable, and the transmission efficiency is related to the fiber damage grade.

Gao, Yang; Zhao, Xing-hai; Su, Wei; Cheng, Yong-sheng; Xu, Mei-jian; Duan, Wen-tao; Yu, Hai-wu

2008-05-01

318

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

PubMed Central

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 used1,14. A new tangential flow hollow-fiber ultrafiltration (HFUF) system has recently been shown to be more efficient and more robust at recovering Cryptosporidium oocystsand Giardia cysts from various water matrices; moreover, it is less expensive than other capsule filter options and can concentrate multiple pathogens simultaneously1-3,5-8,10,11. In addition, previous studies by Hill and colleagues demonstrated that the HFUF significantly improved Cryptosporidium oocysts recoveries when directly compared with the Envirochek HV filters4. 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 matrices9,13 . 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.

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

2012-01-01

319

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

320

Fiber Optics  

NSDL National Science Digital Library

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

2012-05-24

321

Spatially resolved modal spectroscopy of Er:Yb doped multifilament-core fiber amplifier.  

PubMed

The spatially resolved spectral (S2) imaging method is applied on an active microstructured fiber, with a multi-filament core (MFC). This type of fiber has been designed to be the last amplifying stage of a source for a long range coherent lidar. Studying the influence of the bending radius on the modal content with or without gain, we demonstrate that an upper-bound of the high-order modes content can be found by performing the S2 imaging on the bleached fiber. S2 imaging is then used to verify that the output beam of the MFC fiber can be made effectively single-mode. We also show that it can be simply adapted for measuring the fiber birefringence. Finally, a comparison of the MFC fiber mode area with that of a standard large mode area Erbium doped step index fiber illustrates the interest of the MFC structure for high power amplifiers. PMID:22418363

Le Gouët, Julien; Delaporte, Julien; Lombard, Laurent; Canat, Guillaume

2012-02-27

322

Dual-mode fiber optic SPR chemical microsensor  

NASA Astrophysics Data System (ADS)

A fiber optic microsensor is described which utilizes the surface plasmon resonance (SPR) effect to detect the chemical environment surrounding the fiber. The sensor is a multimode step index optic fiber, which is constructed by removing the fiber cladding layer with hot sulfuric acid and coated with gold film on fiber core and on distal end. The changes in the light reflectivity are recorded as SPR spectra, which are highly sensitive to the optical properties of the samples adjacent to the sensor surface. The incident light is guided through a splitter to excite and record SPR in both visible and near infrared (NIR) regions. The NIR spectrum has a larger and sharper resonant peak than visible one. It thus provides a more sensitive mechanism to probe the vicinity of interface for biochip applications.

Lin, Chii-Wann; Liou, Yug-Tsuen; Huang, Chii-Yu; Chiu, Jyh-Perng; Kou, Te-Son

2001-10-01

323

Preparation and characterisation of optical fiber tips for nanoscopic applications  

NASA Astrophysics Data System (ADS)

Silica-based fiber tips are used in a variety of spectroscopic, micro- or nanoscopic optical sensor applications. The efficiency of such measurement systems is dependent on the tip geometry and the diameter of the tapered fiber end. In the present study we investigated the preparation of geometrically predefined, nanoscaled fiber tips by taking advantage of the dopant concentration profiles of highly doped step-index fibers. For this purpose, a gas phase etching process using hydrofluoric acid (HF) vapor was applied. The shaping of the fiber tips was based on very different etching rates as a result of the doping characteristics of specific optical fibers. Technological studies on the influence of the etching gas atmosphere on the temporal tip shaping and the final geometry were performed using undoped and doped silica fibers. The influence of the doping characteristics was investigated in phosphorus-, germanium-, fluorine- and boron-doped glass fibers. Narrow exposed as well as protected internal fiber tips in various shapes and tip radiuses down to less than 15 nm were achieved and characterized geometrically and topologically. For investigations of surface plasmon resonance effects the fiber tips were coated with nanometer-sized silver layers by means of vapour deposition and finally subjected to an annealing treatment.

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

2012-05-01

324

Fiber Fuse Phenomenon in Triangular-Profile Single-Mode Optical Fibers  

NASA Astrophysics Data System (ADS)

The unsteady-state thermal conduction processes in triangular-profile (TP) optical fibers, which exhibited zero chromatic dispersion near 1.55 µm, were studied theoretically with the explicit finite-difference method (FDM). It was estimated that these fibers would exhibit a high-temperature optical absorption on the basis of the high-temperature loss-increase mechanism proposed for step-index (SI) optical fibers. The core-center temperature of the TP fibers changed suddenly and reached over 7 × 105K when a 1.064-µm laser power of 1 W was inputted into the core layer heated at 2608 K. This rapid heating of the core initiated the"fiber fuse"phenomenon. The propagation rates of the fiber fuse, estimated at 1.064 µm, were in fairly good agreement with the experimentally determined values. It was found that the threshold powers for initiating the fiber fuse are linearly proportional to the roots of the effective core areas of both the SI and the TP optical fibers. This coincides the experimental result reported by Seo .

Shuto, Yoshito; Yanagi, Shuichi; Asakawa, Shuichiro; Kobayashi, Masaru; Nagase, Ryo

2006-02-01

325

Beam Quality Factor of Single-Mode Gain-Guided Fiber Lasers  

Microsoft Academic Search

The beam quality factor M^2 for the fundamental LP01 mode of a step-index fiber is calculated in the presence of gain, in a closed form, as a function of the complex generalized V-number. It is shown that the M^2 value of a single-mode gain-guided fiber laser can be arbitrary large. The results are important for the interpretation of the beam

Krishna Mohan Gundu; Parisa Gandomkar Yarandi; Arash Mafi

2010-01-01

326

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

NASA Astrophysics Data System (ADS)

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

Fang, Liang; Jia, Hongzhi

2014-07-01

327

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

328

A rigorous analysis of the distribution of power in plastic clad linear tapered fibers  

Microsoft Academic Search

An analytical investigation is presented of the propagation of power in a step-index plastic clad tapered optical fiber operating in the infrared region of the electromagnetic (EM) spectrum. The chosen materials are widely used in low cost optical links. It is assumed that the taper section has a linear profile. Following rigorous analytical approach, the general expressions for power in

S. C. Yeow; M. H. Lim; P. K. Choudhury

2006-01-01

329

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

330

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

331

Palladium particles embedded into silica optical fibers for hydrogen gas detection  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

332

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.

333

Fiber-optic epoxy composite cure sensor. I. Dependence of refractive index of an autocatalytic reaction epoxy system at 850 nm on temperature and extent of cure  

NASA Astrophysics Data System (ADS)

We discuss the behavior of the refractive index of a typical epoxy-aromatic diamine system. Near 850 nm the index of refraction is found to be largely controlled by the density of the epoxy. Models are derived to describe its dependence on temperature and extent of cure. Within the range of temperatures studied, the refractive index decreases linearly with increasing temperature. In addition, as the epoxy is cured, the refractive index increases linearly with conversion to the gel point. >From then on, shrinkage in the volume of the epoxy is restricted by local viscosity. Therefore the linear relationship between the refractive index and the extent of cure does not hold beyond the gel point.

Lam, Kai-Yuen; Afromowitz, Martin A.

1995-09-01

334

Fiber-optic epoxy composite cure sensor. I. Dependence of refractive index of an autocatalytic reaction epoxy system at 850 nm on temperature and extent of cure.  

PubMed

We discuss the behavior of the refractive index of a typical epoxy-aromatic diamine system. Near 850 nm the index of refraction is found to be largely controlled by the density of the epoxy. Models are derived to describe its dependence on temperature and extent of cure. Within the range of temperatures studied, the refractive index decreases linearly with increasing temperature. In addition, as the epoxy is cured, the refractive index increases linearly with conversion to the gel point. From then on, shrinkage in the volume of the epoxy is restricted by local viscosity. Therefore the linear relationship between the refractive index and the extent of cure does not hold beyond the gel point. PMID:21060391

Lam, K Y; Afromowitz, M A

1995-09-01

335

Titanium-based transition-edge photon number resolving detector with 98% detection efficiency with index-matched small-gap fiber coupling.  

PubMed

We have realized a high-detection-efficiency photon number resolving detector at an operating wavelength of about 850 nm. The detector consists of a titanium superconducting transition edge sensor in an optical cavity, which is directly coupled to an optical fiber using an approximately 300-nm gap. The gap reduces the sensitive area and heat capacity of the device, leading to high photon number resolution of 0.42 eV without sacrificing detection efficiency or signal response speed. Wavelength dependent efficiency in fiber-coupled devices, which is due to optical interference between the fiber and the device, is also decreased to less than 1% in this configuration. The overall system detection efficiency is 98%±1% at wavelengths of around 850 nm, which is the highest value ever reported in this wavelength range. PMID:21263626

Fukuda, Daiji; Fujii, Go; Numata, Takayuki; Amemiya, Kuniaki; Yoshizawa, Akio; Tsuchida, Hidemi; Fujino, Hidetoshi; Ishii, Hiroyuki; Itatani, Taro; Inoue, Shuichiro; Zama, Tatsuya

2011-01-17

336

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

337

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

PubMed

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

Gabrielli, Lucas H; Lipson, Michal

2011-10-10

338

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

339

Maximal Upstroke Velocity as an Index of Available Sodium Conductance Comparison of Maximal Upstroke Velocity and Voltage Clamp Measurements of Sodium Current in Rabbit Purkinje Fibers  

Microsoft Academic Search

SUMMARY. We compared the maximal upstroke velocity of action potentials in short rabbit Purkinje fibers with sodium currents measured with a two-microelecrrode voltage clamp. The number of sodium channels available to open during a sudden depolarization was varied either by blockade with tetrodotoxin or by inactivation with steady depolarizations. In both cases, the maximal upstroke velocity was found to be

Charles J. Cohen; Bruce P. Bean; Richard W. Tsien

340

Resonant THz sensor for paper quality monitoring using THz fiber Bragg gratings.  

PubMed

We report fabrication of THz fiber Bragg gratings (TFBG) using CO(2) laser inscription on subwavelength step-index polymer fibers. A fiber Bragg grating with 48 periods features a ~4 GHz-wide stop band and ~15 dB transmission loss in the middle of a stop band. The potential of such gratings in the design of resonant sensors for the monitoring of paper quality is demonstrated. Experimental spectral sensitivity of the TFBG-based paper thickness sensor was found to be ~-0.67 GHz/10 ?m. A 3D electromagnetic model of a Bragg grating was used to explain experimental findings. PMID:23811876

Yan, Guofeng; Markov, Andrey; Chinifooroshan, Yasser; Tripathi, Saurabh M; Bock, Wojtek J; Skorobogatiy, Maksim

2013-07-01

341

Theory of fiber-optic, evanescent-wave spectroscopy and sensors  

NASA Astrophysics Data System (ADS)

A general theory for fiber-optic, evanescent-wave spectroscopy and sensors is presented for straight, uncladded, step-index, multimode fibers. A three-dimensional model is formulated within the framework of geometric optics. The model includes various launching conditions, input and output end-face Fresnel transmission losses, multiple Fresnel reflections, bulk absorption, and evanescent-wave absorption. An evanescent-wave sensor response is analyzed as a function of externally controlled parameters such as coupling angle, f number, fiber length, and diameter. Conclusions are drawn for several experimental apparatuses.

Messica, A.; Greenstein, A.; Katzir, A.

1996-05-01

342

M2-characterization of beams emerging from LMA fibers by means of modal decomposition  

NASA Astrophysics Data System (ADS)

We report on a fast measurement procedure for the widespread beam propagation ratio of light emerging from LMA fibers. The investigated beam is decomposed into its eigenmodes using a computer generated holographic filter. The modally resolved measurement of amplitudes and phases enables the reconstruction of the optical field. With the full field information, the propagation of the beam through free space is simulated and a virtual caustic measurement is realized. After comparing the presented method with ISO-standard measurements it is applied to conventional step-index fibers as well as to a multicore fiber.

Flamm, Daniel; Schulze, Christian; Schmidt, Oliver A.; Schröter, Siegmund; Duparré, Michael

2011-02-01

343

Development of the multiwavelength monolithic integrated fiber optics terminal  

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

344

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.

2007-06-01

345

Study of lanthanum aluminum silicate glasses for passive and active optical fibers  

NASA Astrophysics Data System (ADS)

We report on SiO2-Al2O3-La2O3 glasses - with and without Yb2O3 - suitable for nonlinear and fiber laser applications. We also present successful supercontinuum generation and fiber laser operation around 1060 nm in step-index fibers. We have optimized the glass compositions in terms of thermal and optical requirements for both a high La2O3 (24 mol%) and Yb2O3(6 mol%) concentration. The aluminum concentration was adjusted to about 21 mol% Al2O3 to increase the solubility of lanthanum and ytterbium in the glass beyond possible MCVD based techniques. The glasses have been characterized by dilatometrical methods to find transition temperatures from 860 to 880°C and thermal expansion coefficients between 4.1 and 7.0 × 10-6 K-1. Structured step index fibers with a SiO2-Al2O3-La2O3 core and silica cladding have been realized showing a fiber loss minimum of about 500 dB/km at 1200 nm wavelength. The chromatic dispersion could be adjusted to shift the zero dispersion wavelength (ZDW) close to the pump wavelength of 1550 nm in a supercontinuum generation setup. First fiber laser experiments show an efficiency of about 41 % with a remarkably reduced photodarkening compared to MCVD based fibers.

Schuster, K.; Litzkendorf, D.; Grimm, S.; Kobelke, J.; Schwuchow, A.; Ludwig, A.; Leich, M.; Jetschke, S.; Dellith, J.; Auguste, J.-L.; Leparmentier, S.; Humbert, G.; Werner, G.

2013-03-01

346

Nonsilica glasses for holey fibers  

Microsoft Academic Search

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

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

2005-01-01

347

4.7 Gbit\\/s transmission over 50m long 1mm diameter multi-core plastic optical fiber  

Microsoft Academic Search

We report, for the first time, 4.7 Gbit\\/s transmission over 50 m long 1 mm diameter multi-core step-index plastic optical fiber, employing discrete multitone techniques and low-cost optical transceiver. A spectral efficiency of 13 bit\\/s\\/Hz is demonstrated.

H. Yang; E. Tangdiongga; SCJ Lee; CM Okonkwo; Boom van den HPA; S. Randel; AMJ Koonen

2010-01-01

348

Step Into Cyberspace  

NSDL National Science Digital Library

In this activity, learners discover that they can modify a regular piece of paper so that it's large enough for them to walk through! Learners follow a cutting pattern on the printout, unfold it, and step through the paper. This activity may be extended with the challenge to recreate this cutting pattern on an index card.

Wnet.org

2006-01-01

349

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

350

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

351

Cellulosic Fibers: Effect of Processing on Fiber Bundle Strength  

Microsoft Academic Search

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

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

2011-01-01

352

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

353

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

NASA Astrophysics Data System (ADS)

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

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

2006-03-01

354

Single-mode chirally-coupled-core fibers with larger than 50µm diameter cores.  

PubMed

In this paper, we report an advance in increasing core size of effective single-mode chirally-coupled-core (CCC) Ge-doped and Yb-doped double-clad fibers into 55µm to 60µm range, and experimentally demonstrate their robust single-mode performance. Theoretical and numerical description of CCC fibers structures with multiple side cores and polygon-shaped central core is consistent with experimental results. Detailed experimental characterization of 55µm-core CCC fibers based on spatially and spectrally resolved broadband measurements (S2 technique) shows that modal performance of these large core fibers well exceeds that of standard 20?m core step-index large mode area fibers. PMID:24787810

Ma, Xiuquan; Zhu, Cheng; Hu, I-Ning; Kaplan, Alex; Galvanauskas, Almantas

2014-04-21

355

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

356

Optical fibers for 355nm pulsed lasers and high-power broadband light sources  

NASA Astrophysics Data System (ADS)

In the past, the spectral stability of multimode UV-fibers has been mainly characterized using deuterium lamps with a broadband spectrum in the DUV. In meantime, new UV light-sources with higher powers are available. For example, improved pulsed Nd:YAG lasers with higher harmonics or high-power broadband plasma lamps are interesting candidates for new systems and applications. Because of better beam quality, multimode all-silica fibers with core diameter smaller than 100 ?m can be recommended. A new step-index fiber with a large cladding-to-core ratio will be introduced. Using the new light-sources, the degradation during UV-light delivery will be described in detail, comparing the hydrogen-loaded and non-loaded version of this fiber. These results of UV-induced damage will be compared to a commercially available improved 100 ?m UV-fiber damaged with deuterium lamp.

Heimann, Jan; Klein, Karl-Friedrich; Gonschior, Cornell P.; Klein, Moritz; Hillrichs, Georg

2013-03-01

357

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

358

Microchannels in conventional single-mode fibers  

NASA Astrophysics Data System (ADS)

Microchannels are fabricated into conventional single-mode fibers by femtosecond laser processing and chemical etching. Fabrication limitations imposed by the fiber geometry are highlighted and resolved through a simple technique without compromising fabrication flexibility. A microfluidic fiber device consisting of a 4 ?m wide microchannel that intersects the fiber core for refractive index sensing is further demonstrated.

Lai, Y.; Zhou, K.; Zhang, L.; Bennion, I.

2006-09-01

359

Microchannels in conventional single-mode fibers  

Microsoft Academic Search

Microchannels are fabricated into conventional single-mode fibers by femtosecond laser processing and chemical etching. Fabrication limitations imposed by the fiber geometry are highlighted and resolved through a simple technique without compromising fabrication flexibility. A microfluidic fiber device consisting of a 4 mum wide microchannel that intersects the fiber core for refractive index sensing is further demonstrated.

Y. Lai; K. Zhou; L. Zhang; I. Bennion

2006-01-01

360

Microchannels in conventional single-mode fibers.  

PubMed

Microchannels are fabricated into conventional single-mode fibers by femtosecond laser processing and chemical etching. Fabrication limitations imposed by the fiber geometry are highlighted and resolved through a simple technique without compromising fabrication flexibility. A microfluidic fiber device consisting of a 4 microm wide microchannel that intersects the fiber core for refractive index sensing is further demonstrated. PMID:16902618

Lai, Y; Zhou, K; Zhang, L; Bennion, I

2006-09-01

361

Imaging local index variations in an optical waveguide using a tapping-mode near-field scanning optical microscope  

NASA Astrophysics Data System (ADS)

Imaging local index variations by using a form of modulated near-field scanning optical microscopy is suggested. To test these ideas, we have probed two different optical structures, one a well-characterized BK-7 glass prism in the total internal reflection configuration, and the other a side-polished optical fiber waveguide with a step index of refraction of 4.5×10-3. Using a recently developed tapping-mode tuning-fork near-field scanning optical microscope, we have obtained images showing distinct local index variations. This method may have applicability to the characterization of a wide variety of optical waveguide structures.

Tsai, Din Ping; Yang, Chi Wen; Lo, Shu-Zee; Jackson, Howard E.

1999-08-01

362

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

363

Mode couplings and elasto-optic effects study in a proposed mechanical microperturbed multimode optical fiber sensor.  

PubMed

A step index multimode optical fiber with a perturbation on a micrometer scale, inducing a periodic deformation of the fiber section along its propagation axis, is theoretically investigated. The studied microperturbation is mechanically achieved using two microstructured jaws squeezing the straight fiber. As opposed to optical fiber microbend sensors, the optical axis of the proposed transducer is not bended; only the optical fiber section is deformed. Further, the strain applied on the fiber produces a periodical elliptical modification of the core and a modulation of the index of refraction. As a consequence of the micrometer scale perturbation period, the resulting mode coupling occurs directly between guided and radiated modes. To simulate the transmission induced by these kinds of perturbations, simplified models considering only total mode couplings are often used. In order to investigate the range of validity of this approximation, results are compared to the electromagnetic mode couplings rigorously computed for the first time, to our knowledge, with a large multimode fiber (more than 6000 linear polarized modes) using the Marcuse model. In addition, in order to have a more complete modeling of the proposed transducer, the anisotropic elasto-optic effects in the stressed multimode fiber are considered. In this way, the transmission of the microperturbed optical fiber transmission and, therefore, the behavior of the transducer are physically explained and its applications as a future stretching sensor are discussed. PMID:23201801

Bichler, Anthony; Lecler, Sylvain; Serio, Bruno; Fischer, Sylvain; Pfeiffer, Pierre

2012-11-01

364

Indexing Images.  

ERIC Educational Resources Information Center

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

Rasmussen, Edie M.

1997-01-01

365

Optical fiber sensor for temperature measuring  

Microsoft Academic Search

Simple fiber-optic sensor for temperature measuring, based upon the temperature-dependent bend losses in plastic clad silica optical fibers, is being proposed. The quantity of light energy transmitted along the fiber depends on the numerical aperture of the fiber, i.e. the refractive index difference between the silica core (n1) and the plastic cladding (n0). On the one hand, the refractive index

Markijan Baran

1996-01-01

366

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

367

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

368

Mode evolution in long tapered fibers with high tapering ratio.  

PubMed

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

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

2012-11-01

369

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

370

In-Line Optical Fiber Polarizer.  

National Technical Information Service (NTIS)

Document describes a method and means for forming an in-line integrated optical fiber polarizer comprising the steps of providing a length of highly birefringent optical fiber, and thermal tapering one or more separated but approximately adjacent small se...

W. K. Burns C. A. Villarruel

1983-01-01

371

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

372

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

373

High-OH fibers with higher stability in the UV-region  

NASA Astrophysics Data System (ADS)

For medical and analytical applications, step-index fibers based on synthetic silica are widely used. For special applications, high-OH all-silica fibers with excellent UV-transmission are commercially available, even at 180 nm. E'-centers with an absorption band around 215 nm, generated by the UV-light transported in these fibers, have to be taken into account. In addition to stable E'-centers, transient defects exist at room temperature, as well; therefore, the transmission at 215 nm wavelength depends on the operational conditions. The newly developed fibers with different diameters (from 100 ?m to 600 ?m core) will have a reduced defect concentration at 215 nm. In addition, the transient defect concentration has been reduced, too. The variation between the two power levels (dark, light) depends on the fiber diameter: the value is less than 0.3 dB/2m or 30 mAU/2m for large core fibers, one magnitude of order better than the comparable UVM-fiber described above. The hydrogen-content of the new fibers is negligible; therefore, the long-term behavior of these fibers, from 100 ?m to 600 ?m core diameter, is significantly better. In addition to low-power deuterium-lamps, the UV-damage of these fibers has been studied with high-power pulsed UV-lasers at 193 nm wavelength. Using the standard high-OH UV-fibers and UVM-fibers for comparison, the damage results will be discussed in detail. In addition, the established system for quality control of these UV-fibers will be described.

Khalilov, Valery Kh.; Klein, Karl-Friedrich; Belmahdi, Jalal; Timmerman, Rick; Nelson, Gary

2006-03-01

374

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

Microsoft Academic Search

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

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

2011-01-01

375

Automatic indexing  

SciTech Connect

Automatic indexing has been a critical technology as more full-text data becomes available online. The paper discusses issues for automatic indexing of different types of full-text and also presents a survey of much of the current research into new techniques for automatic indexing.

Harman, D.

1992-09-01

376

Congenital fiber type disproportion myopathy caused by LMNA mutations.  

PubMed

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

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

2014-05-15

377

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

378

GaAs VCSEL's at ?=780 and 835 nm for short-distance 2.5Gb\\/s plastic optical fiber data links  

Microsoft Academic Search

Selectively oxidized GaAs vertical-cavity surface-emitting lasers for ?=780- and 835-nm emission wavelength and 120-?m-core diameter step index plastic optical fiber (POF) are investigated for short distance interconnects. 2.5-Gb\\/s pseudorandom data transmission over up to 2.5 m of plastic fiber is demonstrated with a bit-error rate (BER) of better than 10-11. Furthermore, bias-free data transmission at 2.5 Gb\\/s over 1-m fiber

P. Schnitzer; M. Grabherr; R. Jager; F. Mederer; R. Michalzik; D. Wiedenmann; K. J. Ebeling

1999-01-01

379

Fiber optic sensor for the measurement of concentration of silica in water with dual wavelength probing  

NASA Astrophysics Data System (ADS)

The design, development, and characterization of a fiber optic evanescent wave based sensor with selectivity suitable for concentration measurement are presented. The sensor that is made up of a step index plastic multimode fiber can be used for the measurement of silica in water. Generally evanescent wave fiber optic sensors employ a single source and detector that show change in output optical power irrespective of the interacting species, i.e., they lack selectivity. This design employing two sources provides excellent selectivity, and the differential arrangement further enhances sensitivity and repeatability. Advantages of this design include the use of inexpensive and easily available light-emitting diode sources that match the analytical wavelength of the samples. The use of dual wavelength probing topology enhances the selectivity, sensitivity, and repeatability, which cannot be achieved by single source evanescent wave fiber optic sensors.

Varghese P, Benjamin; John, Satish; Madhusoodanan, K. N.

2010-03-01

380

Beam Quality Factor of Single-Mode Gain-Guided Fiber Lasers  

Microsoft Academic Search

The beam quality factor M^2 for the fundamental LP01 mode of a step-index\\u000afiber is calculated in the presence of gain, in a closed form, as a function of\\u000athe complex generalized V-number. It is shown that the M^2 value of a\\u000asingle-mode gain-guided fiber laser can be arbitrary large. The results are\\u000aimportant for the interpretation of the beam

Krishna Mohan Gundu; Parisa Gandomkar Yarandi; Arash Mafi

2010-01-01

381

Dispersion tailoring in single mode optical fiber by doping silver nanoparticle  

NASA Astrophysics Data System (ADS)

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

Chattopadhyay, Rik; Bhadra, Shyamal K.

2013-05-01

382

Harnessing the fiber fuse for sensing applications.  

PubMed

A simple refractive index sensor based on a small section of fiber damaged by the fiber fuse is proposed and demonstrated with a sensitivity of 350.58 nm/refractive index unit (RIU). For comparison, a hetero-core structure fiber sensor composed of a short no-core fiber (NCF) sandwiched between two pieces of single-mode fibers is demonstrated with a sensitivity of 157.29 nm/RIU. The fiber fuse technique can allow mass production of sensors by incorporating small sections of the damaged fiber of any type into each device. We believe this is the first application of the periodic damage tracks in optical fibers formed by the fiber fuse. PMID:24787785

Lin, Guei-Ru; Baiad, Mohamad Diaa; Gagne, Mathieu; Liu, Wen-Fung; Kashyap, Raman

2014-04-21

383

Analysis and Design of Broadband Single-Mode Multi - Fibers.  

NASA Astrophysics Data System (ADS)

In the last several years, considerable attention has been paid to the study of dispersion-flattened single -mode fibers which offer a high transmission capacity with low losses through a wide range of wavelengths. However, the existing designs are sensitive to bending and manufacturing tolerances, and are not truly single-mode at most wavelengths of interest. To remedy these problems a new series of broadband dispersion-flattened truly single-mode fiber designs are proposed. These fibers have both dispersion-shifted and dispersion-flattened features with low splice and bend losses. Results demonstrating a total dispersion of +/-0.97 ps/km-nm over the entire spectral range between 1.31 mu m to 1.66 mu m are presented. Such dispersion-flattening is achieved while simultaneously maintaining a mode-field radius of 3 mu m to 5 mu m in the dispersion-flattened wavelength range. The most significant achievement is that the proposed multi -clad fiber design is strictly single-mode and splice and bend losses are smaller than those of double-clad, triple -clad, and quadruple-clad fibers with the same value of dispersion. Ultralow dispersion fibers, whose chromatic dispersion and the first and second-order derivatives of the chromatic dispersion are zero at 1.5 mu m or 1.55 mu m, are described. This effectively increases the laser emission tolerance. Ultralow dispersion fibers open the way to wavelength multiplexing with currently available inexpensive multifrequency lasers, either in local or long distance networks. These fibers also have low splice and bend losses compared to double-clad, triple -clad, and quadruple-clad fibers. An inverse waveguide synthesis program, which can trace multiple objective functions and optimize multiple parameters simultaneously, is developed. An objective function is applied, for the first time, to optimize the dispersion-flattened single-mode fiber index profile with respect to: (1) minimum dispersion, (2) the wavelengths of zero-dispersion, (3) maximum width of dispersion-flattened window, (4) maximum layer index difference less than 0.8%, and (5) layer thickness larger than 3.5 mu m. The accuracy of chromatic dispersion calculations in dispersion-flattened fibers is evaluated. It has been shown that the accuracy of approximate methods is influenced not only by the index differences, but also by their derivatives with respect to wavelength. The matrix method and direct numerical integration of the wave equation are used to compute the mode propagation constants, cutoff frequencies, field distributions, mode -field radius, and splice loss, and carry out production tolerance analysis for multi-clad step-index fibers and graded-index fibers, respectively. Detailed analysis and optimized fiber data are presented.

Lu, Liang-Ju.

384

High sensitivity evanescent field fiber Bragg grating sensor  

Microsoft Academic Search

The paper summarizes on the development of a fiber Bragg grating sensor for the detection of small changes of index of refraction of the medium surrounding the fiber. The etched fiber Bragg grating sensor can detect changes of the index of refraction of a liquid as small as a few parts in 10-5.

A. N. Chryssis; S. M. Lee; M. Dagenais

2004-01-01

385

Nanocomposite Fibers.  

National Technical Information Service (NTIS)

Nanocomposite fibers involve the concept of integrally dispensing nanosized particles of the second phase inorganic material into fiber forming polymers such as nylon or polyester. The material goal involves obtaining bi- phasic fibers with high mechanica...

Y. K. Kim A. F. Lewis P. K. Patra S. B. Warner S. K. Mhetrev

2003-01-01

386

High power pulsed fiber lasers at near-IR optical wavelengths  

NASA Astrophysics Data System (ADS)

Among fiber-based lasers, the availability of high energy and high peak-power pulsed sources is of critical importance for a variety of application ranging from remote sensing, material processing to laser-plasma EUV generation. For most of the applications, high average-power is required in preferably diffraction-limited beams. In this dissertation, we demonstrate usage of very large-mode-area (LMA) fibers to significantly exceed fundamental pulse energy and peak-power limitations of standard single-mode fibers and explore the limit of core size scaling in LMA fibers. We show systematic studies in both theoretical modeling and experimental characterization of beam quality control in extremely large core LMA fibers, including coiling induced higher-order-mode filtering effect in low numerical aperture (NA) Yb-doped fiber amplifiers and fundamental mode excitation in high NA Er-doped fiber amplifiers. We report achieving good beam qualities (M2˜1.3) in 80-mum Yb-doped and 70-mum Er-doped fiber amplifiers, corresponding to the largest mode diameters of conventional step-index LMA fibers with nearly diffraction-limited output for applications at ˜1-mum and ˜1.55mum wavelengths, respectively. Large core size ensures higher energy extraction and increases thresholds for the onset of optical damage and detrimental nonlinear effects. We demonstrate in this work that millijoule energies and megawatt peak-powers in nanosecond pulses can be achieved in nearly diffraction-limited beam using 80-mum core Yb-doped fiber amplifier, and also show the average-power scalability of this pulsed fiber laser up to 85-W. Comparable pulse energies and peak-powers are believed to be achievable in 70-mum core Er-doped fiber amplifier for applications at ˜1.55-mum wavelength. Here, we report demonstration of average-power scaling of nanosecond and ultrashort pulsed fiber lasers using 25-mum core Er/Yb co-doped fiber amplifier. In particular, high average-power (˜28-W) ultrashort (˜1.4-ps) pulsed fiber laser was realized in fiber-based chirped pulse amplification (FCPA) system using novel chirped volume Bragg grating (CVBG) pulse stretchers/compressors. These results indicate that fiber laser technology has significant potential of replacing conventional pulsed solid-state lasers and is a better alternative for applications that require high average-powers.

Cheng, Ming-Yuan

387

Following autophagy step by step  

PubMed Central

Autophagy is an evolutionarily conserved lysosomal degradation route for soluble components of the cytosol and organelles. There is great interest in identifying compounds that modulate autophagy because they may have applications in the treatment of major diseases including cancer and neurodegenerative disease. Hundeshagen and colleagues describe this month in BMC Biology a screening assay based on flow cytometry that makes it possible to track distinct steps in the autophagic process and thereby identify novel modulators of autophagy. See research article: http://www.biomedcentral.com/1741-7007/9/38

2011-01-01

388

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

389

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

390

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.

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

2012-01-01

391

Fabrication of polymer waveguides and spot size converters by UV induced refractive index modification  

NASA Astrophysics Data System (ADS)

Generalization of optical communication promotes fabrication of low cost integrated waveguide components. Polymer waveguides are attractive because they are very simple to process and are promising for low cost devices. Up to date, several methods are used to make single mode guides in polymer films. Traditionally, they require multi-step processes involving photolithography, etching and annealing. The UV induced modification of the dielectrics property of polymers is a useful technique for low cost realization of integrated optical circuits and can enable a direct writing process. This paper reports a demonstration of photo-printed waveguides in an intrinsically photosensitive polymer film. In this polymer (PVCi: PolyVinylCinnamate), local UV irradiation yields a lowering of refractive index even at telecom wavelengths (1300 and 1550 nm). We show significant achievement concerning the index contrasts up to 3x10-2 at 1550 nm. The more the refractive index contrast between the core and cladding increases, the more the guide size and curvature can be reduced, allowing the manufacture of smaller photonic devices. However miniaturization of optical planar waveguides in integrated devices increases the coupling losses from and to single-mode optical fibers. Simulations and experimental demonstrations with PVCi photosensitive waveguides also show the potential of photo-printing process to make efficient index mode converters between small planar waveguides and single-mode fibers. The process uses the post-irradiation of the guide by an UV source to gradually decrease the refractive index from the guide to the fibre.

Hardy, Isabelle; Grosso, Philippe; Bosc, Dominique

2005-06-01

392

Numerical analysis and experimental study of fiber bundles and multi-core photonic crystal fibers for use in endoscopes  

NASA Astrophysics Data System (ADS)

Flexible endoscopes for confocal and multiphoton imaging have the potential to revolutionize the medical field by obviating the need for invasive biopsies; however, these high expectations can be achieved only by reducing endoscope size and by improving image resolution. In this dissertation, methods for enhancing the performance of current endoscopes are explored by studying the properties of multi-core fibers using numerical modeling and experimental analysis. Numerical simulation tools are based on the normal mode expansion of the fields, coupled mode theory, and the multipole method. Image fibers (multi-core step-index fibers commonly used in fiber endoscopes) have small, closely spaced cores that are predicted through basic theoretical analysis to be strongly coupled. These image fibers are explained to successfully transmit images because of nonuniformities in their cross-section that reduce inter-core coupling. The wavelength, average core size, and degree of variation in core size determine the strength of coupling between adjacent cores, such that fibers with smaller cores at longer wavelengths require more nonuniformity in order for reliable image transmission. Guidelines are given for assessing the performance of image fibers in a particular system. In addition, due to the random nature of this effect, strong core coupling can be observed experimentally, demonstrating that the quality of images from current endoscopes is still compromised by crosstalk. Multi-core photonic crystal fibers (PCFs) are a potential alternative for use in flexible endoscopes. PCFs achieve tighter mode confinement than image fibers and are therefore predicted to allow higher core densities with less crosstalk and, ultimately, improved image contrast and resolution. The fabrication of these fibers, however, typically introduces nonuniformities into the photonic crystal cladding. Random nonuniformities in the air hole size and location are shown to reduce the coupling length and the coupling efficiency. When the air holes are large, variations in the lattice of less than 1% are sufficient to cause essentially independent core propagation. Nonuniformities are also shown to increase the core birefringence although the dispersion and loss of PCFs are rather robust to variations. Understanding the characteristics of core coupling is a first step towards improving the design of current endoscopes.

Reichenbach, Kristen Paulene Lantz

393

Studies on the combined effect of injection temperature and fiber content on the properties of polypropylene-glass fiber composites  

Microsoft Academic Search

This paper focuses on correlations between physical and mechanical properties of polypropylene (PP) and PP\\/glass fiber composites molded at different injection temperatures and fiber weight fractions (20% and 30% w\\/w). Density, melt flow index (MFI), thermal stability, crystallinity and tensile and impact properties have been evaluated. The MFI of the composites was dependent on fiber content, fiber length distributions, a

W. N. Ota; S. C. Amico; K. G. Satyanarayana

2005-01-01

394

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

395

Al/Ge co-doped large mode area fiber with high SBS threshold.  

PubMed

We propose a novel approach of making large effective area laser fiber with higher threshold for the stimulated Brillouin scattering (SBS) using Al/Ge co-doping in the fiber core. The increased SBS threshold is achieved by reducing the acoustic-optic overlap integral while keeping the optical refractive index profile with a step structure. The manipulation of the overlap integral is done by adjusting the relative doping level between Al(2)O(3) and GeO(2) in the core. The mechanism is validated by detailed examples of numerical modeling. An Yb-doped double clad fiber with the core co-doped with Al(2)O(3) and GeO(2) was fabricated by the OVD process. Measured acoustic velocity profile using a scanning acoustic microscope verified that the acoustic velocity in the fiber core changes with the design. An amplifier utilizing the fiber demonstrated that the proposed fiber yielded 6 dB higher SBS threshold than a fiber without using the co-doping scheme. PMID:19547158

Li, Ming-Jun; Chen, Xin; Wang, Ji; Gray, Stuart; Liu, Anping; Demeritt, Jeffrey A; Ruffin, A B; Crowley, Alana M; Walton, Donnell T; Zenteno, Luis A

2007-06-25

396

Selected Bibliography on Fiber-Reinforced Cement and Concrete.  

National Technical Information Service (NTIS)

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

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

1976-01-01

397

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

398

Tunable random fiber laser  

SciTech Connect

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

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

2011-08-15

399

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

SciTech Connect

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

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

2000-04-18

400

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.

White, William M.; Department Of Earth And Atmospheric Sciences, Cornell U.

401

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

402

High birefringence photonic crystal fiber with a complex unit cell of asymmetric elliptical air hole cladding  

NASA Astrophysics Data System (ADS)

High birefringence induced by elliptical air hole photonic crystal fibers (EHPCFs) is analyzed numerically using the finite-element method. Statistical correlations between the birefringence and the various parameters are obtained. We found that the complex elliptical air hole is better than that of a circular one to obtain high birefringence in photonic crystal fibers. Our suggested structures can considerably enhance the birefringence in EHPCFs and show that the birefringence can be as high as 1.1294×10-2, which is higher than the birefringence obtained from conventional step-index fiber (5 × 10-4), circular air holes PCF (3.7×10-3), and elliptical hollow PCF (2.35 × 10-3).

Sun, Yuh-Sien; Chau, Yuan-Fong; Yeh, Han-Hsuan; Shen, Lin-Fang; Yang, Tzong-Jer; Tsai, Din Ping

2007-08-01

403

A reliable, sensitive and fast optical fiber hydrogen sensor based on surface plasmon resonance.  

PubMed

We report for the first time on the experimental response of a Surface Plasmon Resonance fiber optic sensor based on wavelength modulation for hydrogen sensing. This approach of measuring the hydrogen concentration makes the sensor insensitive to intensity fluctuations. The intrinsic fiber sensor developed provides remote sensing and enables the possibility of multi-points sensing. The sensor consists of a multilayer of 35 nm Au/180 nm SiO2/Pd deposited on a step- index multimode fiber core. The sensitivity and selectivity of the sensor are optimal at a Pd thickness of 3.75 nm. The sensor is sensitive to a hydrogen concentration ranging between 0.5 and 4% H2 in Ar, with a response time less than 15 s. PMID:23388931

Perrotton, Cédric; Westerwaal, Ruud J; Javahiraly, Nicolas; Slaman, Martin; Schreuders, Herman; Dam, Bernard; Meyrueis, Patrick

2013-01-14

404

Fibrillation of aramid fiber using a vibrating ball mill and evaluation of the degree of fibrillation  

Microsoft Academic Search

Methods of fibrillation of aramid fiber for a fiber-dispersion type of composite and evaluation of the degree of fibrillation were investigated. Continuous fibrillation of aramid fiber was carried out using a vibrating ball mill. The morphology of the fiber surface was controlled by adjusting the processing time of the fiber in the mill. An index based on image analysis was

A. Hashimoto; M. Satoh; T. Iwasaki; M. Morita

2002-01-01

405

Characterization of coated optical fibers by Fourier-domain optical coherence tomography  

Microsoft Academic Search

Fourier-domain optical coherence tomography is used to image the cross sections of coated optical fibers. A standard single-mode fiber with a dual coating and a hard-clad silica fiber with a single thin low-index coating are studied. The individual coating dimensions, coated and uncoated fiber diameters, and the fiber coating's concentricity are retrieved from a single measurement.

J. Jasapara; Stephan Wielandy

2005-01-01

406

Tunable highly birefringent photonic bandgap fibers.  

PubMed

A novel tunable highly birefringent photonic bandgap fiber (PBGF) is designed theoretically by filling its air holes with high-index material. The transmission band can be continuously tuned by changing the refractive index of the filling material. Accordingly, the tunable modal birefringence and polarization mode dispersion of the PBGFs are investigated by adjusting the refractive index of the filling material. Furthermore, we have also analyzed the effect of surface modes in the photonic bandgap on the characteristics of the tunable PBGFs. The simulation results show the feasibility of constructing birefringence-tunable photonic crystal fibers and related fiber devices in practical applications. PMID:16252747

Zhang, Chunshu; Kai, Guiyun; Wang, Zhi; Liu, Yange; Sun, Tingting; Yuan, Shuzhong; Dong, Xiaoyi

2005-10-15

407

Silica glass fiber photorefractometer.  

PubMed

We report a fiber-optic refractive-index sensor that is applicable to a long-distance measurement. The sensor consists of a silica glass fiber bent into a U shape with a bending radius of typically several hundred micrometers. The cladding at the tip of the sensor is stripped off. The sensing mechanism is based on the variation of the output intensity that is induced by radiation loss at the bend, which enables us to measure the refractive index of the outer medium. A fabrication method of fusing the sensor with a CO(2) laser and etching with HF is described. Multipoint measurements of optical-time-domain reflectometry are also described. PMID:20717369

Takeo, T; Hattori, H

1992-01-01

408

Investigations on birefringence effects in polymer optical fiber Bragg gratings  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

409

Fiber Optic Velocity Interferometry  

SciTech Connect

This paper explores the use of a new velocity measurement technique that has several advantages over existing techniques. It uses an optical fiber to carry coherent light to and from a moving target. A Fabry-Perot interferometer, formed by a gradient index lens and the moving target, produces fringes with a frequency proportional to the target velocity. This technique can measure velocities up to 10 km/s, is accurate, portable, and completely noninvasive.

Neyer, Barry T.

1988-04-01

410

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

411

Hollow fiber liquid phase microextraction as a preconcentration and clean-up step after pressurized hot water extraction for the determination of non-steroidal anti-inflammatory drugs in sewage sludge  

Microsoft Academic Search

A method for the quantitative determination of non-steroidal anti-inflammatory drugs (NSAIDs) in sewage sludge was developed and validated. The target compounds were extracted using pressurized hot water extraction (PHWE) and then purified and preconcentrated by three-phase hollow fiber liquid phase microextraction (HF-LPME) followed by LC–ESI-MS analysis. The PHWE was optimized with regard to the pH of solvent as well as

Abolfazl Saleh; Estelle Larsson; Yadollah Yamini; Jan Åke Jönsson

2011-01-01

412

Mutual diffusion process for continuous fabrication of graded-index plastic rod lenses  

NASA Astrophysics Data System (ADS)

We propose a new process for fabrication of plastic rod lenses based on the traditional method of fiber extrusion. The process consists of the following steps: multilayer conjugate extrusion, monomer diffusion between adjacent layers, and photopolymerization of an uncured strand fiber. We call this process a mutual diffusion process for continuous plastic rod lens fabrication. Characteristics of this process are as follows: fast production speed (~100 cm/min), precision control of refractive-index distribution, high angular aperture, and long-term reliability. The optical resolution of the rod-lens array is 300 dpi, which is high enough for application to G3 facsimiles with transmission time of less than 1 min and monochromatic scanners.

Uozu, Yoshihiro; Horie, Kazuyuki

2003-11-01

413

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

414

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

415

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

NASA Astrophysics Data System (ADS)

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

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

2011-07-01

416

Gap soliton propagation in optical fiber gratings  

NASA Astrophysics Data System (ADS)

Intense optical pulse propagation in a GeO2 -doped silica glass fiber grating results in nonlinear pulse propagation velocities and increased transmission at wavelengths where the grating reflects light in the linear limit. These nonlinear pulse propagation effects are predicted by numerical simulations of gap soliton propagation. The large linear refractive-index variations used for the fiber gratings in these experiments permit the propagation of gap solitons in short lengths of fiber.

Mohideen, U.; Slusher, R. E.; Mizrahi, V.; Erdogan, T.; Kuwata-Gonokami, M.; Lemaire, P. J.; Sipe, J. E.; Martijn de Sterke, C.; Broderick, Neil G. R.

1995-08-01

417

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

418

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

419

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

420

Fiber optic sensor system  

NASA Astrophysics Data System (ADS)

The design, development, and performance of a microbend fiber optical domain reflectometry (OTDR) based distributed strains sensor are described. A test bed has been developed to evaluate and compare this system to conventional discrete strain gauge sensors. The test bed consists of an aluminum cantilever beam to which have been attached several pairs of strain gauges (for reference) and several microbend transducers. A single standard multi-mode optical fiber is threaded through the microbend transducers. The fiber is pulse illuminated by a commercial OTDR instrument. The microbend losses are detected as step changes in the return OTDR signal waveform. The transducers consist of small pairs of opposing sets of teeth, one set mounted on the flexible beam test bed, the other machined into a small, rigid cantilever bar mounted to produce scissor action as the beam flexes. The transducers are biased to produce a step loss with the beam in its neural position. The direction of beam deformation is then determined by the increase or decrease of the step size.

Schoenwald, J. S.

1989-03-01

421

Comparative study of optical fiber cure-monitoring methods  

Microsoft Academic Search

This paper reports on a comparative study undertaken for different types of optical fiber sensor developed to monitor the cure of an epoxy resin system. The optical fiber sensors used to monitor the cure process were based on transmission spectroscopy, evanescent wave spectroscopy and refractive index monitoring. The transmission sensor was prepared by aligning two optical fibers within a specially

Peter A. Crosby; Graham R. Powell; Gerard F. Fernando; David N. Waters; Chris M. France; Ronald C. Spooncer

1997-01-01

422

Low-loss transmission through tightly bent standard telecommunication fibers  

NASA Astrophysics Data System (ADS)

This letter presents a principle of low-loss light transmission through tightly bent standard telecommunication optical fibers. The design is based on selective launching and filtering of the fundamental mode in standard graded index multimode fiber. The proposed system has demonstrated significantly better macrobend tolerance than commercially available bend resistant fibers.

Donlagi?, Denis; Culshaw, Brian

2000-12-01

423

Power-referenced refractometer based on hybrid fiber grating  

NASA Astrophysics Data System (ADS)

A power-referenced fiber refractometer based on a hybrid fiber grating formed by a tilted-fiber Bragg grating (TFBG) cascading by a chirped-fiber Bragg grating (CFBG) is proposed and experimentally demonstrated. The optical signal reflected by the CFBG passes twice through the TFBG that enhances sensitivity of the refractometer. In addition, the optical signal is propagating all the way in the fiber core so that the extra insertion loss is low. Refractive index measurement with sensitivity up to 597.2 ?W/R.I.U. is achieved within the range from 1.333 to ~1.42. The maximum detectable refractive index is ~1.45.

Dong, Xinyong; Zheng, Jie; Shum, Perry Ping

2013-12-01

424

Supercontinuum Generation in Optical Fibers  

NASA Astrophysics Data System (ADS)

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

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

2010-04-01

425

Effective index model predicts modal frequencies of vertical-cavity lasers  

SciTech Connect

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

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

2000-04-18

426

Manual for Using Abuse and Neglect Indicators and Index.  

National Technical Information Service (NTIS)

This manual for using abuse and neglect indicators and abuse indices provides step - by - step information needed to understand, use, or adapt the protection indicators to measure the impact of child protective services on abuse situations. Each index -- ...

P. Coombes M. McCormack M. H. Chipley B. Archer J. C. Norman

1978-01-01

427

Engineering a resonant nanocoating for an optical refractive index sensor  

NASA Astrophysics Data System (ADS)

We proposing to boost the performance of refractive index sensors based on the tilted fiber Bragg grating (TFBG) structure by resonant coupling of small spherical nanoparticles to the TFBG resonances. The optimal choice of nanoparticle parameters is discussed.

Bialiayeu, A.; Ianoul, A.; Albert, J.

2014-03-01

428

Preparation of Fiber Optics for the Delivery of High-Energy High-Beam-Quality Nd:YAG Laser Pulses  

NASA Astrophysics Data System (ADS)

Recent improvements in design have made it possible to build Nd:YAG lasers with both high pulse energy and high beam quality. These lasers are particularly suited for percussion drilling of holes of as much as 1-mm diameter thick (a few millimeters) metal parts. An example application is the production of cooling holes in aeroengine components for which 1-ms duration, 30-J energy laser pulses produce holes of sufficient quality much more efficiently than with a laser trepanning process. Fiber optic delivery of the laser beam would be advantageous, particularly when one is processing complex three-dimensional structures. However, lasers for percussion drilling are available only with conventional bulk-optic beam delivery because of laser-induced damage problems with the small-diameter (approximately 200 400- m) fibers that would be required for preserving necessary beam quality. We report measurements of beam degradation in step-index optical fibers with an input beam quality corresponding to an M 2 of 22. We then show that the laser-induced damage threshold of 400- m core-diameter optical fibers can be increased significantly by a CO 2 laser treatment step following the mechanical polishing routine. This increase in laser-induced damage threshold is sufficient to propagate 25-J, 1-ms laser pulses with a 400- m core-diameter optical fiber and an output M 2 of 31.

Kuhn, Andreas; French, Paul; Hand, Duncan P.; Blewett, Ian J.; Richmond, Mark; Jones, Julian D. C.

2000-11-01

429

Refractive sensitivity of mechanical long-period fiber grating in side-hole fiber  

NASA Astrophysics Data System (ADS)

The refractive index sensor for use of mechanically induced long-period fiber grating (MLPG) in a side-hole singlemode fiber is proposed. The principle of operation is based on using of a long-period grating that is made by pressing a plate with periodic grooves against a short length of side-hole fiber. The strength of the resonant peak is tuned by adjusting the pressure applied on the side-hole SMF. The resonance wavelengths are shifted as the two side-holes of the fiber core were filled with the different the refractive index liquids. The resonant wavelength of 1588.6 nm has a total blue shift of approximately 12.2 nm for refractive index ranging from 1.35 to 1.43. The results show that it is more sensitive than that of the conventional SMF long-period fiber gratings.

Jin, Yongxing; Chan, Chi Chiu; Gong, Huaping; Dong, Xinyong

2009-11-01

430

Coating Carbon Fibers With Platinum  

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

431

Optic fiber sensors fabricated by laser-micromachining  

NASA Astrophysics Data System (ADS)

Recent progress in using excimer and femtosecond lasers to fabricate functional fiber-optic sensing devices is reviewed extensively in this paper. The application of femtosecond lasers is to fabricate fiber gratings and in-line fiber-optic interferometers for measurements of strain, temperature and refractive index. The application of 157 nm excimer lasers is to create fiber gratings and in-line fiber interferometers for measurements of strain, acceleration, pressure, temperature and refractive index. Compared with conventional optical fiber sensors, these novel micro optical fiber sensors fabricated by laser-micromachining have outstanding advantages, such as fast and direct formation, easy mass-production with ultralow-cost, good reproducibility, excellent optical performance, low temperature cross-sensitivity, etc., which pave a way to form a new generation of miniature fiber-optic sensors for many applications.

Rao, Yun-Jiang; Ran, Zeng-Ling

2013-12-01

432

Nanocomposite Fibers  

Microsoft Academic Search

The project is the development of biphasic fibers with properties that leapfrog those of the matrix polymers. For example, improved high temperature mechanical performance, useful optical properties, electrical, or barrier properties of these fibers will make a major impact in tire reinforcement, elecro-optical devices, and other applications. We are exploring the properties of novel biphasic fibrous materials in which the

Steven Warner; UMass Dartmouth; Armand Lewis; Malcolm Polk; Karl Jacob; Paul Calvert; Steve Fossey; Natick Army; Heidi Gibson; Labs Nylon; Praveen Singhal; Subbarao Kota

433

High-Bandwidth Plastic Optical Fiber for Fiber to the Display  

Microsoft Academic Search

Novel photonics polymer devices for broadband technologies are described, focusing on the high-bandwidth graded-index plastic optical fiber (GI POF). Based on these photonics polymer device technologies, the concept of \\

Yasuhiro Koike; Takaaki Ishigure

2006-01-01

434

Optical fiber design and the trapping of Cerenkov radiation.  

PubMed

Cerenkov radiation is generated in optical fibers immersed in radiation fields and can interfere with signal transmission. We develop a theory for predicting the intensity of Cerenkov radiation generated within the core of a multimode optical fiber by using a ray optic approach and use it to make predictions of the intensity of radiation transmitted down the fiber in propagating modes. The intensity transmitted down the fiber is found to be dominated by bound rays with a contribution from tunneling rays. It is confirmed that for relativistic particles the intensity of the radiation that is transmitted along the fiber is a function of the angle between the particle beam and the fiber axis. The angle of peak intensity is found to be a function of the fiber refractive index difference as well as the core refractive index, with larger refractive index differences shifting the peak significantly toward lower angles. The angular range of the distribution is also significantly increased in both directions by increasing the fiber refractive index difference. The intensity of the radiation is found to be proportional to the cube of the fiber core radius in addition to its dependence on refractive index difference. As the particle energy is reduced into the nonrelativistic range the entire distribution is shifted toward lower angles. Recommendations on minimizing the quantity of Cerenkov light transmitted in the fiber optic system in a radiation field are given. PMID:17151754

Law, S H; Fleming, S C; Suchowerska, N; McKenzie, D R

2006-12-20

435

Optical fiber design and the trapping of Cerenkov radiation  

NASA Astrophysics Data System (ADS)

Cerenkov radiation is generated in optical fibers immersed in radiation fields and can interfere with signal transmission. We develop a theory for predicting the intensity of Cerenkov radiation generated within the core of a multimode optical fiber by using a ray optic approach and use it to make predictions of the intensity of radiation transmitted down the fiber in propagating modes. The intensity transmitted down the fiber is found to be dominated by bound rays with a contribution from tunneling rays. It is confirmed that for relativistic particles the intensity of the radiation that is transmitted along the fiber is a function of the angle between the particle beam and the fiber axis. The angle of peak intensity is found to be a function of the fiber refractive index difference as well as the core refractive index, with larger refractive index differences shifting the peak significantly toward lower angles. The angular range of the distribution is also significantly increased in both directions by increasing the fiber refractive index difference. The intensity of the radiation is found to be proportional to the cube of the fiber core radius in addition to its dependence on refractive index difference. As the particle energy is reduced into the nonrelativistic range the entire distribution is shifted toward lower angles. Recommendations on minimizing the quantity of Cerenkov light transmitted in the fiber optic system in a radiation field are given.

Law, S. H.; Fleming, S. C.; Suchowerska, N.; McKenzie, D. R.

2006-12-01

436

Beam quality after propagation of Nd:YAG laser light through large-core optical fibers.  

PubMed

Laser beam characteristics are altered during propagation through large-core optical fibers. The distribution of modes excited by the input laser beam is modified by means of mode coupling on transmission through the fiber, leading to spatial dispersion of the profile and, ultimately and unavoidably, to degradation in the quality of the delivered beam unless the beam is spatially filtered with consequent power loss. Furthermore, a mismatch between the intensity profile of a typical focused high-power laser beam and the profile of the step-index fiber gives rise to additional beam-quality degradation. Modern materials processing applications demand ever higher delivered beam qualities (as measured by a parameter such as M(2)) to achieve greater machining precision and efficiency, a demand that is currently in conflict with the desire to utilize the convenience and flexibility of large-core fiber-optic beam delivery. We present a detailed experimental investigation of the principal beam-quality degradation effects associated with fiber-optic beam delivery and use numerical modeling to aid an initial discussion of the causes of such degradation. PMID:18354689

Kuhn, A; Blewett, I J; Hand, D P; Jones, J D

2000-12-20

437

Amphibole Fiber Concentration Determination for a Series of Community Air Samples: Use of X-Ray Diffraction to Supplement Electron Microscope Analysis.  

National Technical Information Service (NTIS)

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. ...

P. M. Cook P. L. Smith D. G. Wilson

1978-01-01

438

Interferometric Fiber Optic Sensors  

PubMed Central

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

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

2012-01-01

439

Interferometric fiber optic sensors.  

PubMed

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

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

2012-01-01

440

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

441

An experimental study on the relationships between the speckle noise and the deformation of optical fiber  

Microsoft Academic Search

In order to apply a speckle noise in optical fiber to sensor, the relationship between speckle noise pattern and deformation of the optical fiber was investigated. In the experiment. the He-Ne gas laser as light source, and the multi-mode and graded index optical fiber (quartz) were used. The image through the optical fiber was observed with respect to the movement

M. Taniguchi; M. Hasegawa; T. Takagi

2002-01-01

442

On the possible use of optical fiber Bragg gratings as strain sensors for geodynamical monitoring  

Microsoft Academic Search

Optical fiber sensors can be used to measure many different parameters including strain, temperature, pressure, displacement, electrical field, refractive index, rotation, position and vibrations. Among a variety of fiber sensors, fiber Bragg gratings (FBG) have numerous advantages over other optical fiber sensors. One of the major advantages of this type of sensors is attributed to wavelength-encoded information given by the

Pietro Ferraro; Giuseppe De Natale

2002-01-01

443

A new optical fiber sensor with improved strain sensitivity based on distributed optical fiber sensing technique  

Microsoft Academic Search

In general, macro-strain is an effective index for health monitoring of civil infrastructures, which can reveal the unforeseen damage accumulation. However, it is difficult to acquire precise strain distribution with existing fully-distributed optical fiber sensing techniques. Based on the distributed optical fiber strain sensing technique of pulse-prepump Brillouin Optical Time Domain Analysis (PPP-BOTDA), a new optical fiber sensor with improved

Sheng Shen; Zhisheng Wu; Caiqian Yang; Yongsheng Tang; Gang Wu; Wan Hong

2009-01-01

444

Inverse Variation: Step By Step Lesson  

NSDL National Science Digital Library

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

2012-01-01

445

Introduction to Step Dynamics and Step Instabilities  

Microsoft Academic Search

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

Joachim Krug

2004-01-01

446

Fiber optic fluid detector  

DOEpatents

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

Angel, S. Michael (Livermore, CA)

1989-01-01

447