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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

Equivalent step-index model of multifilament core fibers  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

3

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

4

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

5

Bent induced refractive index profile variation and mode field distribution of step-index multimode optical fiber  

NASA Astrophysics Data System (ADS)

The effect of bending of step-index optical fiber on its refractive index profile and the mode field distribution were investigated. An enhanced slab model is suggested in this investigation. A qualitative study has been done on a bent step-index optical fiber. A very small radius of bending curvature (R) has been reached, practically R is 9.25 mm. In this case a dramatic change of the refractive index profile has been observed with an induced birefringence. The refractive index profile is recovered from the interferograms which were generated by Mach-Zehnder interferometer. The interferogram has been analyzed using advanced image analyses software. We have proposed another approach to calculate the refractive index profile of bent optical fiber. In this approach the fiber is divided into layers and slabs, simultaneously. The induced refractive index profile variation of the bent optical fiber, for parallel and perpendicular components of the light beam, is calculated considering the refraction of the light beam traversing the fiber. The mode field distribution and mode numbers in these two directions of polarizations are determined for both straight and bent fibers.

Sokkar, T. Z. N.; Ramadan, W. A.; Shams El-Din, M. A.; Wahba, H. H.; Aboleneen, S. S.

2014-02-01

6

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

7

Fabrication and amplification of Rhodamine B-doped step-index polymer optical fiber  

Microsoft Academic Search

A step-index polymer optical fiber (SI POF) containing Rhodamine B in poly(methyl methacrylate) (PMMA) has been fabricated by a preform technique. Fluo- rescence of different fiber lengths were observed and dis- cussed. A high gain (23 dB) for a SI POF with 60-cm length, 400-m diameter was obtained. The Rhodamine B content of the doped SI POF is 5 ppm-wt.

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

2004-01-01

8

Channel capacity of step-index Polymer Optical Fibers: Experiments and simulation with realistic parameters  

Microsoft Academic Search

Step-index Polymer Optical Fibers (SI-POF) are candidates for broadband in-house networks. For the first time, we give a comprehensive overview over the real channel capacity of POF links up to 100 m, based on experimental investigations and complex system simulations. More than 2 Gbit\\/s can be transmitted at very low BER with existing components. Improved devices will give place for

Roman Kruglov; Sven Loquai; Olaf Zieman; Juri Vinogradov; Christian Bunge

2010-01-01

9

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

PubMed

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

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

2014-07-28

10

Fabrication and amplified spontaneous emission of Eu(DBM) 3 Phen doped step-index polymer optical fiber  

Microsoft Academic Search

A step-index polymer optical fiber (SI POF) with a core of poly(methyl methacrylate) (PMMA) containing Eu(DBM)3Phen has been fabricated by a preform technique. Fluorescence analysis showed that there is not obvious change in the local environment around Eu3+with the increase of Eu(DBM)3Phen doping concentration. Amplified spontaneous emission (ASE) phenomenon of the doped SI POF by end-pumping with an Ar+-laser of

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

2004-01-01

11

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

12

Splicing Hollow-Core Photonic Bandgap Fibers to Step-Index Fibers Using an Arc Fusion Splicer  

E-print Network

FiberSMF Fiber Fiber Splicer Electrodes Gap Optical Power Meter Axis 1550 nm Diode Laser PBG FiberSMF Fiber Fiber Splicer Electrodes Gap Optical Power Meter Axis 1550 nm Diode Laser Fig. 1. (a) Experimental). During the splice program the two fibers were briefly butt-coupled (touch point) and then a gap of +10 µm

Washburn, Brian

13

1.9 octave supercontinuum generation in a As2S3 step-index fiber driven by mid-IR OPCPA.  

PubMed

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

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

2014-10-01

14

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

NASA Astrophysics Data System (ADS)

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

Stepniak, G.; Siuzdak, J.

2014-08-01

15

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

16

Amplified spontaneous emission of Eu(DBM)3Phen doped step-index polymer optical fiber by end-pumping with a YAG  

Microsoft Academic Search

Eu(DBM)3Phen doped poly(methyl methac- rylate) core step-index polymer optical fiber (SI POF) has been fabricated and related properties of the doping mate- rial were discussed. Amplified spontaneous emission (ASE) at 613 nm of a SI POF with 40 cm length has been observed at ambient temperature by end-pumping with a YAG at 355

Hao Liang; Biao Chen; Qijin Zhang; Zhiqiang Zheng; Hai Ming; Fuquan Guo

2005-01-01

17

A Media Converter Prototype for 10Mb\\/s Ethernet Transmission Over 425 m of Large-Core Step-Index Polymer Optical Fiber  

Microsoft Academic Search

A prototype media converter for transmitting 10-Mb\\/s Ethernet\\/IEEE 802.3 data over a large-core (1 mm) step-index polymer optical fiber (SI-POF) is presented. The system is demonstrated over a record maximum distance of 425 m, which greatly outperforms, in terms of reach, previously published results and commercially available systems, which are usually limited to approximately 100 m. This extended reach allows

Daniel Cárdenas; Antonino Nespola; Pietro Spalla; Silvio Abrate; Roberto Gaudino

2006-01-01

18

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

Microsoft Academic Search

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

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

2009-01-01

19

Fiber optic refractive index monitor  

DOEpatents

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

Weiss, Jonathan David (Albuquerque, NM)

2002-01-01

20

High-bandwidth graded-index polymer optical fiber  

Microsoft Academic Search

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

Yasuhiro Koike; Takaaki Ishigure; E. Nihei

1995-01-01

21

Multimode interference refractive index sensor based on coreless fiber  

NASA Astrophysics Data System (ADS)

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

Li, Yang; Liu, Zhibo; Jian, Shuisheng

2014-03-01

22

Index-matching elastomers for fiber optics  

Microsoft Academic Search

Silicone elastomers prepared to match the index of refraction of the core of an optical fiber are discussed. The system is composed of a vinyl-terminated dimethyldiphenylsiloxane copolymer crosslinked with tri- or tetrafunctional silanes in the presence of a chloroplatinic acid catalyst. The refractive index of the copolymer was determined as a function of diphenyl content and temperature. By measuring the

R. W. Filas; B. H. Johnson; C. P. Wong

1989-01-01

23

Observation of images in graded-index multimode fiber  

E-print Network

of a multimode fiber. . . . . . . . . . 6 Optical spectrum of lasertmn laser Circuit diagram of temperature controller. . . . . Connection between temperature contmller and lasertron laser . Refractive index profile of a graded-index multimode.... The reason for this performance of the graded-index fiber can be explained referring to Fig. l. There are three propagation paths to be considered in a graded-index fiber. The center of the fiber with a high refractive index is surrounded by a steadily...

Begum, Sultana

2012-06-07

24

Analytical Expression for Measurement of Intrinsic Coupling Loss in Multistep Index Optical Fibers  

NASA Astrophysics Data System (ADS)

The aim of this paper is to obtain an analytical expression for intrinsic coupling losses in multistep index (MSI) fibers. For this purpose, a uniform power distribution is assumed. In order to validate the theoretical expression, the obtained results were compared with computer simulations using the ray-tracing method as well as with results obtained using existing models for step index (SI) and clad power-law profile graded index (GI) fibers. This analytical expression will provide fiber manufacturers with a very valuable tool for the assessment of fiber quality in terms of waveguide tolerances.

Aldabaldetreku, G.; Durana, G.; Zubia, J.; Arrue, J.

2006-03-01

25

Materials technology for perfluorinated graded-index polymer optical fibers  

Microsoft Academic Search

Advances in polymer materials technology have allowed the development of perfluorinated graded-index polymer optical fibers that have loss and bandwidth performance competitive with multimode silica optical fibers, but with greatly simplified interconnection.

L. L. Blyler; W. R. White; R. Ratnagiri

2001-01-01

26

Refractive index sensor based on terahertz multimode interference fiber device  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

27

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

28

Weakly guiding analysis of elliptical core step index waveguides based on the characteristic numbers of Mathieu's equation  

Microsoft Academic Search

A new weak guidance analysis for step index elliptical core optical fibers is developed. The method shows that weakly guiding, or linearly polarized (LP), modes are determined by and correspond uniquely to the characteristic numbers of Mathieu's equation. This is the first analysis of elliptical core weakly guiding modes which determines propagation constants and indexes modes by directly solving the

J. K. Shaw; W. M. Henry; W. R. Winfrey

1995-01-01

29

Polymer microstructured fibers by one-step extrusion  

NASA Astrophysics Data System (ADS)

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

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

2007-05-01

30

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

31

Temperature dependence of the refractive index of optical fibers  

NASA Astrophysics Data System (ADS)

Many experimental investigations on the temperature dependence of the refractive index of optical fibers have been reported previously, however a satisfying theoretical explanation for it is still absent. In this paper, a theoretical model about the temperature dependence of the refractive index of optical fibers is presented and it is in agreement with the previous experimental results. This work is a significant reference for the research and development of temperature sensors based on optical fiber delay lines.

Wang, Zhi-Yong; Qiu, Qi; Shi, Shuang-Jin

2014-03-01

32

Fiber Optic-Based Refractive Index Sensing at INESC Porto  

PubMed Central

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

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

2012-01-01

33

Refractive index fiber sensor based on Brillouin fast light  

NASA Astrophysics Data System (ADS)

A new type of refractive index fiber sensor was invented by combining the evanescent-field scattering sensing mechanism with the Brillouin fast light scheme. Superluminal light was realized using Brillouin lasing oscillation in a fiber ring cavity. The refractive index of the solution around the microfiber within the cavity is related to the group velocity of the fast light. This fast light refractive index sensor offers an alternative for high-accuracy sensing applications.

Chen, Jiali; Gan, Jiulin; Zhang, Zhishen; Yang, Tong; Deng, Huaqiu; Yang, Zhongmin

2014-01-01

34

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

NASA Astrophysics Data System (ADS)

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

Ivanov, Oleg V.; Zlodeev, Ivan V.

2014-01-01

35

Graded Index Microstructured Polymer Optical Fibers for Terahertz Applications  

E-print Network

Graded index microstructured polymer optical fiber incorporating a specially designed air-hole array featuring variable air-hole diameters and inter-hole separation is proposed, fabricated and characterized in view of the fiber potential applications in low-loss, low-dispersion terahertz guidance. The proposed fiber features simultaneously low chromatic and intermodal dispersions, as well as low loss in the terahertz spectral range. We then experimentally demonstrate that proposed fibers exhibit smaller pulse distortion, larger bandwidth and more reliable excitation when compared to the porous fibers of comparable geometry.

Ma, Tian; Wang, Lili; Skorobogatiy, Maksim

2014-01-01

36

Fabrication process and optical properties of perdeuterated graded-index polymer optical fiber  

Microsoft Academic Search

We proposed a graded-index polymer optical fiber (GI-POF) enabling greater-than-gigabit data transmission in a short reach network by applying a two-step interfacial-gel polymerization process to a perdeuterated polymer material. Using this process, it is possible to fabricate a nearly optimum refractive-index profile with good reproducibility. In this paper, the preparation of a perdeuterated polymethyl methacrylate (PMMA-d8)-based GI-POF utilizing a PMMA

Atsushi Kondo; Takaaki Ishigure; Yasuhiro Koike

2005-01-01

37

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

NASA Technical Reports Server (NTRS)

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

Kawalko, Stephen F.

1990-01-01

38

Fiber in-line Michelson Interferometer for refractive index sensing  

NASA Astrophysics Data System (ADS)

A fiber in-line Michelson interferometer based on open micro-cavity is demonstrated, which is fabricated by femtosecond laser micromachining and thin film coating technique. In refractive index sensing, this interferometer operates in a reflection mode of detection, exhibits compact sensor head, good mechanical reliability, wide operation range and high sensitivity of 975nm/RIU (refractive index unit) at the refractive index value of 1.484.

Liao, C. R.; Wang, D. N.; Wang, Min; Yang, Minghong; Wang, Yiping

2013-09-01

39

Reconstruction of 3D refractive index profiles of PM PANDA optical fiber using digital holographic method  

NASA Astrophysics Data System (ADS)

In this paper, the refractive indices distributions on the two birefringent axes of polarization maintaining (PM) PANDA type optical fiber are reconstructed. The local refraction of the incident rays crossing the PM optical fiber is considered. Off-axis digital holographic interferometric phase shifting arrangement is employed in this investigation. The recorded mutual phase shifted holograms, starts with 0° with steps of ?/4, are combined and numerically reconstructed in the image plane to obtain the optical interference phase map. Consequently, the optical phase differences due to the PM optical fiber are extracted after unwrapping and background subtraction of the enhanced optical interference phase map. The birefringence and the beat length in the two directions, fast and slow axes of PM optical fiber, of polarizations in the core region are calculated. This holographic technique and the advanced analysis of the phase shifting permit the calculation of the 3D refractive index distributions for PM PANDA optical fiber.

Wahba, H. H.

2014-10-01

40

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

41

Side polished fiber Bragg grating sensor for simultaneous measurement of refractive index and temperature  

Microsoft Academic Search

A fiber sensor to achieve simultaneous measurement of refractive index and temperature is proposed by using a side polished fiber Bragg grating. The reflective wavelength of side polished fiber Bragg grating shifts with the ambient refractive index and local temperature. By overlaying half of the polished surface of fiber Bragg grating with liquid material, simultaneous discrimination of liquid refractive index

Zhe Chen; Jieyuan Tang; Ruoyan Fan; Yongchun Zhong; Jun Zhang; Siben Li

2011-01-01

42

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

43

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

44

Mode field diameters of index-guided microstructured optical fibers  

NASA Astrophysics Data System (ADS)

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

Sharma, Dinesh Kumar; Sharma, Anurag

2013-06-01

45

Refractive index sensor based on a polymer fiber directional coupler for low index sensing.  

PubMed

We propose, numerically analyze and experimentally demonstrate a novel refractive index sensor specialized for low index sensing. The device is based on a directional coupler architecture implemented in a single microstructured polymer optical fiber incorporating two waveguides within it: a single-mode core and a satellite waveguide consisting of a hollow high-index ring. This hollow channel is filled with fluid and the refractive index of the fluid is detected through changes to the wavelength at which resonant coupling occurs between the two waveguides. The sensor design was optimized for both higher sensitivity and lower detection limit, with simulations and experiments demonstrating a sensitivity exceeding 1.4 × 10(3) nm per refractive index unit. Simulations indicate a detection limit of ~2 × 10(-6) refractive index units is achievable. We also numerically investigate the performance for refractive index changes localized at the surface of the holes, a case of particular importance for biosensing. PMID:25090565

Lee, Kwang Jo; Liu, Xiaoqi; Vuillemin, Nelly; Lwin, Richard; Leon-Saval, Sergio G; Argyros, Alexander; Kuhlmey, Boris T

2014-07-14

46

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

47

Tunable third-harmonic generation in a chalcogenide-tellurite hybrid optical fiber with high refractive index difference.  

PubMed

A chalcogenide-tellurite hybrid optical fiber with a step-index structure is fabricated by the rod-in-tube drawing technique. The core is made of 15Ge-3Ga-12Sb-70S (mol. %) glass, and the cladding is made of 78TeO?-5ZnO-12Li?O-5Bi?O? (mol. %) glass. The refractive index difference ?n=0.24. Tunable third-harmonic generation from 568 to 869 nm is observed when the optical fiber is pumped by an optical parametric oscillator with the pump wavelength changing from 1700 to 2600 nm. PMID:24562263

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

2014-02-15

48

Reflectance Imaging by Graded-Index Short Multimode Fiber  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

49

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

E-print Network

using surface plas- mon resonance [28,29] and in-fiber Bragg grating (FBG) [30,31] have been usedSensors and Actuators B 123 (2007) 594­605 Fiber optic sensing of liquid refractive index Argha of the fiber. The sensitivity of the sensor to refractive index change is dependent on cladding thickness

50

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

51

Analysis of graded-index polymer optical fiber link performance under fiber bending  

Microsoft Academic Search

Bending effects on bandwidth and loss of a graded-index polymer optical fiber (GI POF) were investigated, and those influences on the optical link performance were discussed simultaneously for the first time. The numerical apertures (NAs) of the GI POFs were deliberately varied from 0.154 to 0.292. A bending radius larger than 10 mm induced little mode coupling and little change

Kenji Makino; Takuhiro Nakamura; Takaaki Ishigure; Yasuhiro Koike

2005-01-01

52

Phase stepping methods based on PTDC for Fiber-Optic Projected-Fringe Digital Interferometry  

NASA Astrophysics Data System (ADS)

Active homodyne control can be used to stabilize; ?/2-rad phase steps in a Fiber-Optic Projected-Fringe Digital Interferometry. Two beams emitted from a fiber-optic coupler are combined to form an interference fringe pattern on a diffusely reflecting object. Fresnel reflections from the distal fiber ends undergo a double pass in the fibers and interference at the fourth port of the coupler which formed a Michelson interferometer. We suggested a method of PTDC (DC phase tracking) to maintain the interference intensity at quadrature by feedback control. Stepping between quadrature positions force a ?/2-rad phase step. A method based on the ratio of harmonic of the interference signal is proposed to estimate phase step accuracy .A root-mean-square phase stability of 2 mrad and phase step accuracy of 13.8 mrad were measured with PTDC for the Fiber-Optic Projected-Fringe Digital Interferometry. It worked well in 2 h without resetting the integrator.

Chao, Zhang; Fa-Jie, Duan

2012-06-01

53

Effect of dip in refractive index profile on fiber Raman gain amplifier performance  

NASA Astrophysics Data System (ADS)

We have studied and reported the effect of practically possible linear dips in the inner core of a coaxial fiber Raman gain amplifier having step index inner and outer cores in the structure on the amplifier performance. In this work, we have used single pump wavelength of 1.465 ?m. A variation of dip depth beyond 0.25% of maximum refractive index and that of dip width beyond 25% of the inner core radius deteriorate the gain performance of characteristics of this amplifier significantly along with an appreciable shift of phase matching wavelength. Within these limits, the amplifier resembles closely the behavior of an ideal one. These prescribed limits of dip depth and dip width are also valid limits above which there will be valid ground in their effect to modulate Raman gain performance and dispersion. The present study should find wide attention of system designers.

Pramanik, Sanchita; Sarkar, Somenath

2014-10-01

54

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

55

Measurement of effective refractive-index differences in a few-mode fiber by axial fiber stretching.  

PubMed

A method for measuring the effective refractive-index differences in a few-mode fiber by applying axial fiber stretching is described. This method represents a straightforward technique for characterization of few-mode fibers. Interference between LP01 and LP11 and in some cases also between LP11 and LP21 are observed in a fiber designed for support of LP01 and LP11. The relative strength of the coupled modes depends on specific splicing characteristics, and in some cases only two modes are seen. The results agree well with theoretical predictions for the fiber under investigation. PMID:23038505

Savolainen, Juha-Matti; Grüner-Nielsen, Lars; Kristensen, Poul; Balling, Peter

2012-08-13

56

Measurement of index of refraction of unknown solution using a microstructure fiber Bragg grating  

NASA Astrophysics Data System (ADS)

We demonstrate an application of fiber Bragg grating to measure the index of refraction of an unknown liquid by using a cladding depleted FBG. The measurements of the index of refraction were calibrated by the index oil with known index of refraction. Samples of liquid with difference percentage of sugar content were prepared and measured the index of refraction using this method. It shows that accuracy of index of refraction measurement as high as 0.01 can be achieved.

Kang, C. J.; Chen, Z. C.; Shih, M. C.

2013-06-01

57

Highly sensitive fiber Bragg grating refractive index sensors Wei Liang, Yanyi Huang,a  

E-print Network

Highly sensitive fiber Bragg grating refractive index sensors Wei Liang, Yanyi Huang,a Yong Xu We combine fiber Bragg grating FBG technology with a wet chemical etch-erosion procedure American Institute of Physics. DOI: 10.1063/1.1904716 Since the early 1990s, fiber Bragg grating FBG

Huang, Yanyi

58

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

E-print Network

based on perfluorinated polymer were prepared for use as UV-curable optical cladding for silica fibers polymer into Defensa. Both formulations were used as primary coatings on dual coated silica optical fibersMechanical behavior of silica optical fibers coated with low index, low surface energy

Matthewson, M. John

59

Modeling of two core photonic crystal fiber modal interferometer for refractive index measurement by equalization wavelength  

NASA Astrophysics Data System (ADS)

We propose a modification structure model of in-fiber sensor based on intermodal interference in two core photonic crystal fiber for external refractive index measuring. Essential characteristics and influences of the structure are investigated. Formation of an extreme (equalization wavelength) in phase constant spectral dependence is presented and its using for simple external refractive index determination.

Tatar, Peter; Kacik, Daniel

2013-08-01

60

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

Microsoft Academic Search

Bandwidth characteristics and refractive index profile formation of the low-loss graded-index polymer optical fiber were described. Low material dispersion of the perfluorinated polymer base GI POF provides higher bandwidth than the conventional silica base GI multimode fiber in visible to near infrared region

T. Ishigure; E. Nihei; Y. Koike

1998-01-01

61

High-bandwidth, high-numerical aperture graded-index polymer optical fiber  

Microsoft Academic Search

A new large core (0.5-1.0 mm) graded-index polymer optical fiber was proposed to solve the connection problem of the single-mode silica fiber indoor use for high speed multimedia network. The bending loss for 10-mm bending diameter was dramatically decreased from 20 dB to less than 1 dB by preparing the high numerical aperture graded-index polymer optical fiber. The bandwidth was

Takaaki Ishigure; Akihiro Horibe; Eisuke Nihei; Yasuhiro Koike

1995-01-01

62

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...

63

Single-step fabrication of ceramic hollow fibers for oxygen permeation  

Microsoft Academic Search

A gas-tight LSCF hollow fiber membrane that possesses an asymmetric structure has been prepared in a single-step using an immersion induced phase inversion technique. The results obtained from oxygen permeation experiments show that the porous inner surface of the prepared LSCF hollow fiber membrane is favorable for oxygen permeation when the feed air is introduced in the dense outer surfaces

K. Li; Xiaoyao Tan; Yutie Liu

2006-01-01

64

Formation of the refractive index profile in the graded index polymer optical fiber for gigabit data transmission  

Microsoft Academic Search

Bandwidth characteristics of the large core graded index polymer optical fiber (GI-POF) are theoretically and experimentally clarified. The refractive index profile of the GI-POF was controlled by interfacial-gel polymerization to investigate the relation between the index profile and the bandwidth characteristics. It was experimentally confirmed that the maximum bandwidth of the poly methyl methacrylate (PMMA) base GI-POF is at most

Takaaki Ishigure; Masataka Satoh; Osamu Takanashi; Eisuke Nihei; Takayuki Nyu; Shuntaro Yamazaki; Yasuhiro Koike

1997-01-01

65

Refractive index insensitive temperature sensor based on coaxial waveguide fiber modal interferometer  

NASA Astrophysics Data System (ADS)

A refractive index insensitive temperature sensor based on coaxial dual-waveguide optical fiber was proposed and demonstrated. The coaxial fiber contains a central core along the fiber axis and an annular core between the inner/outer claddings. By inserting the coaxial fiber in between two single mode fibers through core-offset splicing, cladding modes are excited at the splice point and therefore a modal Mach-Zehnder interferometer is achieved. The effective refractive index of the inner cladding mode is independent of the external refractive index due to the existence of the annular core. Owing to the large thermo-optic coefficient difference between the coaxial fiber's core and cladding, the modal interferometer has high temperature sensitivity. Such an interferometer is extremely suitable for temperature measurement in wet or liquid environment.

Zhou, Ai; Xu, Quan; Zheng, Tuo; Yang, Jun; Yang, Yuanyuan; Yuan, Libo

2013-09-01

66

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

NASA Astrophysics Data System (ADS)

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

Hebenstreit, Florian

67

Evanescent field fiber Bragg grating sensors for index of refraction sensing with applications to structural health monitoring  

Microsoft Academic Search

Fiber Bragg grating sensing is a relatively mature fiber optic sensor technology currently being used in structural health monitoring systems. Therefore, there are significant benefits to using this technology as a platform for other sensing modalities. In this work, a side polished fiber Bragg sensor is described for sensing refractive index changes. The effective refractive index of a fiber Bragg

C.-F. Chan; G. A. Ferrier; D. J. Thomson; T. Coroy; P. Lefebvre; A. Vincelette

2006-01-01

68

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

NASA Astrophysics Data System (ADS)

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

Xu, Linlin; Li, Ying; Li, Baojun

2012-10-01

69

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

70

A simple method for prediction of first-order modal field and cladding decay parameter in graded index fiber  

NASA Astrophysics Data System (ADS)

Based on a series expansion method involving the Chebyshev technique, we present analytical expressions for first higher order modal field as well as cladding decay parameter in case of graded index fiber. This method utilizes the formulation of a linear relation of the ratio of first- and zero-order modified Bessel functions, with reciprocal of Cladding decay parameterE This leads to the evaluation of the Cladding decay parameter from a simple equation involving a third-order determinant and the first higher order modal field is thereafter found from two simple equations. Thus the paper presents the technique of avoiding complicated calculations of Chebyshev coefficients and therefore, the present formalism will be extremely important for practical engineering problems. Taking step and parabolic index fibers as examples, we show that our estimations of the said propagation characteristics agree excellently with the available exact results. The concerned calculations involve very little computations.

Patra, P.; Gangopadhyay, S.; Goswami, K.

2008-04-01

71

Mode field expansion in index-guiding microstructured optical fibers  

NASA Astrophysics Data System (ADS)

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

Sharma, Dinesh Kumar; Sharma, Anurag

2013-05-01

72

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

73

Analysis of Graded-Index Polymer Optical Fiber Link Performance Under Fiber Bending  

NASA Astrophysics Data System (ADS)

Bending effects on bandwidth and loss of a graded-index polymer optical fiber (GI POF) were investigated, and those influences on the optical link performance were discussed simultaneously for the first time. The numerical apertures (NAs) of the GI POFs were deliberately varied from 0.154 to 0.292. A bending radius larger than 10 mm induced little mode coupling and little change in the bandwidth of the GI POF. A bending radius smaller than 10 mm caused degradation in the bandwidths of the higher NA GI POFs. On the other hand, in the lower NA GI POFs, even more severe bending could cause little change in their bandwidths. Thus, the lower NA GI POF seemed preferable in suppressing the bandwidth change. However, the higher NA GI POF exhibited the lower bending loss. The preferable NAs for both characteristics were completely opposite. Moreover, the bending loss under underfilled launch (UFL) could be lower than that under overfilled launch (OFL). On the other hand, the bending loss was equivalent to the bandwidth degradation in view of the link power penalty. Therefore, the bandwidth change and loss caused by the bending were the critical factors to optimize the optical link considering the link power budget. The high-NA GI POF with almost ideal refractive-index profile could provide stable high performance in overgigabit communication even under any bending conditions.

Makino, Kenji; Nakamura, Takuhiro; Ishigure, Takaaki; Koike, Yasuhiro

2005-06-01

74

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

PubMed Central

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

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

2013-01-01

75

Optical Refractive-Index Sensor Based on Dual Fiber-Bragg Gratings Interposed With a Multimode-Fiber Taper  

Microsoft Academic Search

A new type of optical refractive-index (RI) sensor is proposed and experimentally demonstrated by using a structure of two single-mode fiber (SMF) Bragg gratings with a multimode fiber (MMF) taper in-between. The loss induced by a mismatch of waveguide structure between SMFs and MMFs is amplified by a tapering process, and is utilized for RI sensing through evanescent field. Experimental

Li-Yang Shao; A. Ping Zhang; Wei-Sheng Liu; Hong-Yan Fu; Sailing He

2007-01-01

76

High refractive index without absorption in a rare-earth-ion-doped optical fiber  

NASA Astrophysics Data System (ADS)

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

Wang, Zhiping; Yu, Benli

2012-11-01

77

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

NASA Astrophysics Data System (ADS)

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

Chen, Xiaogang; Hu, Xizhen; Huang, Dexiu

2014-09-01

78

Parameters affecting bending losses in graded-index polymer optical fibers  

Microsoft Academic Search

Radiation losses that occur when bending graded-index polymer optical fibers (POFs) are analyzed as a function of the profile exponent, the light wavelength, the fiber core radius, and the length of the bent section. For this purpose, a ray-tracing model is used, which combines both the generalized Fresnel power transmission coefficients for curved graded-index media and the differential equations that

J. Arrue; J. Zubia; G. Durana; J. Mateo

2001-01-01

79

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

80

Amplified spontaneous emission in graded-index polymer optical fibers: theory and experiment.  

PubMed

In this work we analyze experimentally and theoretically the properties of amplified spontaneous emission (ASE) in a rhodamine-6G-doped graded-index polymer optical fiber. A theoretical model based on the laser rate equations describes the ASE features successfully. The dependence of the ASE threshold and efficiency on fiber length is analyzed in detail. PMID:24104335

Illarramendi, M Asunción; Arrue, Jon; Ayesta, Igor; Jiménez, Felipe; Zubia, Joseba; Bikandi, Iñaki; Tagaya, Akihiro; Koike, Yasuhiro

2013-10-01

81

Measuring bacterial growth by refractive index tapered fiber optic biosensor  

Microsoft Academic Search

A single-mode tapered fiber optic biosensor was utilized for real-time monitoring of the Escherichia coli (E. coli K-12) growth in an aqueous medium. The applied fiber tapers were fabricated using heat-pulling method with waist diameter and length of 6–7?m and 3mm, respectively. The bacteria were immobilized on the tapered surface using Poly-l-Lysine. By providing the proper condition, bacterial population growth

Mohammad Ismail Zibaii; Alireza Kazemi; Hamid Latifi; Mahmoud Karimi Azar; Seyed Masoud Hosseini; Mohammad Hossein Ghezelaiagh

2010-01-01

82

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

NASA Astrophysics Data System (ADS)

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

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

2007-08-01

83

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

84

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

85

Single mode operation of elliptical gain guided and index antiguided fibers  

NASA Astrophysics Data System (ADS)

Elliptical gain guiding fibers in which gain guiding effects are dominant compared to conventional index guiding fiber is analyzed by solving Mathieu equations with complex-valued fiber parameters. The properties of mode propagation and single mode operation are evaluated in this elliptical gain guiding fiber with the assumption of a uniform gain distribution in the active core medium. Threshold for lossless mode propagation increases exponentially with the eccentricity of the elliptical cross section. Further, the difference in threshold between the lowest two order modes is constant for arbitrary eccentricity.

Wang, X.; Xiong, C.; Bass, M.

2012-02-01

86

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

87

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

88

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

E-print Network

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

Lindquist, Susan

89

Design of refractive-index and rare-earth-dopant distributions for large-mode-area fibers used in coiled high-power amplifiers  

NASA Astrophysics Data System (ADS)

We have numerically compared the performance of various designs for the core refractive-index (RI) and rare-earth-dopant distributions of large-mode-area fibers for use in bend-loss-filtered, high-power amplifiers. We first established quantitative targets for the key parameters that determine fiber-amplifier performance, including effective LP 01 modal area (A eff, both straight and coiled), bend sensitivity (for handling and packaging), high-order mode discrimination, mode-field displacement upon coiling, and index contrast (manufacturability). We compared design families based on various power-law and hybrid profiles for the RI and evaluated confined rare-earth doping for hybrid profiles. Step-index fibers with straight-fiber A eff values > 1000 ?m2 exhibit large decreases in A eff and transverse mode-field displacements upon coiling, in agreement with recent calculations of Hadley et al. [Proc. of SPIE, Vol. 6102, 61021S (2006)] and Fini [Opt. Exp. 14, 69 (2006)]. Triangular-profile fibers substantially mitigate these effects, but suffer from excessive bend sensitivity at A eff values of interest. Square-law (parabolic) profile fibers are free of modal distortion but are hampered by high bend sensitivity (although to a lesser degree than triangular profiles) and exhibit the largest mode displacements. We find that hybrid (combined power-law) profiles provide some decoupling of these tradeoffs and allow all design goals to be achieved simultaneously. We present optimized fiber designs based on this analysis.

Farrow, Roger L.; Hadley, G. Ronald; Kliner, Dahv A. V.; Koplow, Jeffrey P.

2007-02-01

90

Genomic prediction for Nordic Red Cattle using one-step and selection index blending.  

PubMed

This study investigated the accuracy of direct genomic breeding values (DGV) using a genomic BLUP model, genomic enhanced breeding values (GEBV) using a one-step blending approach, and GEBV using a selection index blending approach for 15 traits of Nordic Red Cattle. The data comprised 6,631 bulls of which 4,408 bulls were genotyped using Illumina Bovine SNP50 BeadChip (Illumina, San Diego, CA). To validate reliability of genomic predictions, about 20% of the youngest genotyped bulls were taken as test data set. Deregressed proofs (DRP) were used as response variables for genomic predictions. Reliabilities of genomic predictions in the validation analyses were measured as squared correlations between DRP and genomic predictions corrected for reliability of DRP, based on the bulls in the test data sets. A set of weighting (scaling) factors was used to construct the combined relationship matrix among genotyped and nongenotyped bulls for one-step blending, and to scale DGV and its expected reliability in the selection index blending. Weighting (scaling) factors had a small influence on reliabilities of GEBV, but a large influence on the variation of GEBV. Based on the validation analyses, averaged over the 15 traits, the reliability of DGV for bulls without daughter records was 11.0 percentage points higher than the reliability of conventional pedigree index. Further gain of 0.9 percentage points was achieved by combining information from conventional pedigree index using the selection index blending, and gain of 1.3 percentage points was achieved by combining information of genotyped and nongenotyped bulls simultaneously applying the one-step blending. These results indicate that genomic selection can greatly improve the accuracy of preselection for young bulls in Nordic Red population, and the one-step blending approach is a good alternative to predict GEBV in practical genetic evaluation program. PMID:22281355

Su, G; Madsen, P; Nielsen, U S; Mäntysaari, E A; Aamand, G P; Christensen, O F; Lund, M S

2012-02-01

91

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

92

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

93

Characterization of Fiber Distributed-Feedback Lasers with an Index-Perturbation Method  

Microsoft Academic Search

We demonstrate the characterization of fiber distributed-feedback lasers by scanning a heat-induced index perturbation along the cavity and by measuring the induced laser frequency shift. The measured shift is shown to be a good indicator for the intensity distribution in the cavity, and the experimental results reveal that the sensitivity of fiber distributed-feedback laser sensors with frequency readout is highly

Erlend Rønnekleiv; Morten Ibsen; Michael N. Zervas; Richard I. Laming

1999-01-01

94

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

PubMed

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

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

2013-09-01

95

Tunable fiber laser based on the refractive index characteristic of MMI effects  

NASA Astrophysics Data System (ADS)

A tunable erbium-doped all-fiber laser has been demonstrated. This tunable laser is based on a tunable fiber filter using the refractive index characteristics of multimode interference effects. A thinner no-core fiber with a diameter of 104 ?m is used to fabricate the tunable fiber filter. The joint point of the thinner no-core fiber with SMF is a taper, which improves its sensitivity for refractive index changes. The filter exhibits a very sensitive response to the change of the environmental refractive index, which is about 1000 nm/RIU in the RI range from 1.418 to 1.427. The tunable fiber laser based on the filter achieved a tunability of 32 nm, with the wavelength tuned from 1532 nm to 1564 nm covering the full C-band. The 3 dB bandwidth of the tunable laser is less than 0.02 nm with the signal-to-noise ratio of about 40 dB.

Ma, Lin; Qi, Yanhui; Kang, Zexin; Bai, Yunlong; Jian, Shuisheng

2014-04-01

96

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

97

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

NASA Astrophysics Data System (ADS)

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

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

2002-10-01

98

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

99

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

100

Refractive index and strain sensitivities of a long period fiber grating  

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

101

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

102

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

103

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

104

Modeling of gold circular sub-wavelength apertures on a fiber endface for refractive index sensing  

NASA Astrophysics Data System (ADS)

A finite-difference time-domain approach was used to investigate the excitation of surface plasmons of the circular sub-wavelength apertures on an optical fiber endface. This phenomenon provided the basis of a sensitive liquid refractive index sensor. The proposed sensor is compact and has the potential to be used in biomedical applications, having a sensitivity of (373 ± 16) nm per refractive index unit (RIU) as found through the variation of a reflection minimum with the wavelength.

Nguyen, Huy; Baxter, Gregory W.; Collins, Stephen F.; Sidiroglou, Fotios; Roberts, Ann; Davis, Timothy J.

2012-09-01

105

In situ measurement of refractive index changes induced by gamma radiation in germanosilicate fibers  

Microsoft Academic Search

We propose a technique to measure in situ the refractive index changes induced by ionizing radiation in single-mode optical fibers. This change can be derived from the channel drift appearing in narrow channel wavelength-division-multiplexing couplers exposed to gamma radiation. We measured a radiation-induced refractive index change of about 5 10-6\\/kGy[H2O] at low doses and 5 10-7\\/kGy[H2O] at higher doses. No

A. Fernandez Fernandez; B. Brichard; F. Berghmans

2003-01-01

106

Fabrication of a graded-index polymer optical fiber preform by using a centrifugal force  

Microsoft Academic Search

We have investigated a fabricating method for a graded index polymer optical fiber preform using a centrifugal force. When\\u000a two monomers with different densities and refractive indices are polymerized under a centrifugal force, a concentration gradient\\u000a is generated due to their density difference. Therefore, a graded refractive index can be obtained according to the concentration\\u000a gradient. When a monomer is

Sang Hyuk Im; Duck Jong Sun; Hansol Cho; Jin Sung Choi; Jae Keun Park; Jin Taek Hwang

2002-01-01

107

Mathematical modeling of a co-extrusion process for preparing gradient-index polymer optical fibers  

Microsoft Academic Search

The behavior of a closed co-extrusion process for the preparation of gradient-index polymer optical fibers is modeled theoretically. In particular, the effects of the essential parameters such as the volume ratios of the inner\\/outer layer, diffusivities of monomers, diffusion length, and monomer concentrations, on the distribution of refractive index (RI) are examined. The applicability of the model derived is justified

Bo-Tau Liu; Wen-Chang Chen; Jyh-Ping Hsu

1999-01-01

108

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

109

Graded-index polymer optical fiber with high temperature and high humidity stability  

Microsoft Academic Search

It was clarified for the first time that the slight attenuation increment observed in the previous poly methyl methacrylate (PMMA)-dopant system graded-index polymer optical fiber (GI POF) we reported originated in the excess scattering loss induced by the aggregation of absorbed water into the POF. Although the PMMA material generally absorbs two weight% of water at maximum, the low attenuation

Takaaki Ishigure; Masataka Sato; Atsushi Kondo; Yasuyuki Tsukimori; Yasuhiro Koike

2002-01-01

110

Analysis of Graded-Index Hollow Optical Fibers and Its Application to Atomic Waveguide Design  

Microsoft Academic Search

This paper presents a scalar analysis of hollow optical fiber (HOF) with a graded-index (GRIN) profile by using the modified Airy functions. A full-vectorial analysis based on finite element method is performed as well to confirm the validity of the scalar analysis results. Based on the results obtained, GRIN HOF is shown to offer a much steeper field gradient and

Joong-Ho Pi; Kyu-Tae Lee; Dongwook Park; Chang-Min Kim

2010-01-01

111

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

E-print Network

. Using a laser source, a power meter, and a thermo-couple we measured the amount of power recovered fromPartial power recovery of bend-induced loss using a hybrid index-guiding photonic crystal fiber fibers are typically all-silica optical fibers in which a pattern of air-holes running along their entire

Vlachos, Kyriakos G.

112

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

E-print Network

(LCI). The probes use novel fiber-optic gradient-index (GRIN) lenses fabricated by a recently developed preform was fabricated by use of modified chemi- cal-vapor deposition (MCVD), in which glass layers1794 OPTICS LETTERS / Vol. 27, No. 20 / October 15, 2002 Gradient-index fiber-optic microprobes

Schnitzer, Mark

113

Graded-index fiber lens proposed for ultrasmall probes used in biomedical imaging  

NASA Astrophysics Data System (ADS)

The quality and parameters of probing optical beams are extremely important in biomedical imaging systems both for image quality and light coupling efficiency considerations. For example, the shape, size, focal position, and focal range of such beams could have a great impact on the lateral resolution, penetration depth, and signal-to-noise ratio of the image in optical coherence tomography. We present a beam profile characterization of different variations of graded-index (GRIN) fiber lenses, which were recently proposed for biomedical imaging probes. Those GRIN lens modules are made of a single mode fiber and a GRIN fiber lens with or without a fiber spacer between them. We discuss theoretical analysis methods, fabrication techniques, and measured performance compared with theory.

Mao, Youxin; Chang, Shoude; Sherif, Sherif; Flueraru, Costel

2007-08-01

114

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

Microsoft Academic Search

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

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

2007-01-01

115

Core-offset-based fiber Bragg grating sensor for refractive index and temperature measurement  

NASA Astrophysics Data System (ADS)

We present a fiber-optic sensor based on a fiber Bragg grating (FBG) whose core has an offset to that of the lead-in fiber from splicing for simultaneous refractive index (RI) and temperature measurement. Due to the core offset, the core mode in the lead-in fiber is coupled to both the core mode and the cladding modes of the sensing fiber with the FBG. Then the two oppositely propagating code modes, the cladding modes, and the core modes are coupled by the FBG at particular wavelengths determined by the effective indices of the modes and the FBG structure, resulting in two peaks in the FBG reflection spectrum. The peak wavelength corresponding to the core-cladding mode coupling is sensitive to both RI and temperature, while the peak wavelength corresponding to the core-core mode coupling is only sensitive to temperature. Utilizing the difference of two reflection peaks of these coupling modes, both RI and temperature can be detected simultaneously. We fabricate and characterize a sensor. The preliminary experimental results show that it can detect the refractive index in a range of 1.33 to 1.4421, with a temperature sensitivity of 10 pm/°C.

Zhang, Xinpu; Peng, Wei; Liu, Yun; Yu, Qingxu

2013-02-01

116

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

117

Temperature insensitive refractive index sensor based on single-mode micro-fiber Sagnac loop interferometer  

NASA Astrophysics Data System (ADS)

A single-mode micro-fiber Sagnac loop interferometer (SMSLI) based on single-mode micro-fiber with a diameter of wavelength scale is demonstrated theoretically and experimentally. The influence of structure parameters in SMSLI on its transmission spectra has been investigated by both experimental and theoretical analysis. The sensor responses to the ambient refractive index (RI) and temperature are also investigated experimentally. Experimental results show that the proposed sensor exhibits quite high sensitivity to the ambient RI, which is found to be ˜12 500 nm/RIU. In addition, the sensitivity of SMSLI to ambient temperature is also demonstrated to be only ˜3 pm/ °C by experiments.

Chunyang, Han; Hui, Ding; Xianli, Li; Shaofei, Dong

2014-05-01

118

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

NASA Astrophysics Data System (ADS)

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

Pevec, Simon; Donlagic, Denis

2013-05-01

119

Single-mode operation regime for 12-fold index-guiding quasicrystal optical fibers  

NASA Astrophysics Data System (ADS)

We have studied the extent of the single-mode operation regime for high symmetric index-guiding quasicrystal fibers by analyzing the validity of the effective V parameter, which is used to determine the single-mode cutoff for photonic crystal fibers. We demonstrate that this parameter can also be applied, without any approximations, to a high symmetric 12-fold Stampfli quasicrystal made of silica. We explain this result in terms of both intrinsic-quasicrystal defect and photonic crystal constituent units. We also analyze the extent of the second-order mode operation to further confirm the cutoff between the single- and multimode operations.

Zhao, H.; Proietti Zaccaria, R.; Verma, P.; Song, J.; Sun, H.

2010-09-01

120

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

121

Determination of the refractive index profile of polymer optical fiber preform by the transverse ray tracing method  

Microsoft Academic Search

In graded-index polymer optical fiber (GI-POF), the refractive index profile is an important parameter in defining its bandwidth. However, direct determination of the refractive index profile of GI-POF is difficult due to its extreme thinness. In this study, the refractive index distribution of the GI-POF is indirectly determined by measuring the refractive index distribution of the GI-POF perform by applying

Eisuke Nihei; Shigehiro Shimizu

2007-01-01

122

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

123

Full vectorial BPM modeling of Index-Guiding Photonic Crystal Fibers and Couplers.  

PubMed

A 3D full-vectorial Beam Propagation Method is successfully applied to compute both the propagation constants and the modal profiles in high-contrast silica-air index-guiding Photonic Crystal Fibers. The approach is intrinsically suited to investigate longitudinally varying structures or propagation and polarization effects, which are of practical interest for advanced optical applications. As an example we model a dual-core coupler, showing that efficient polarization preserving coupling can be expected. PMID:19424330

Fogli, Fabrizio; Saccomandi, Luca; Bassi, Paolo; Bellanca, Gaetano; Trillo, Stefano

2002-01-14

124

Experimental and numerical study on stimulated Brillouin scattering in a graded-index multimode fiber.  

PubMed

Numerical and experimental results on stimulated Brillouin scattering (SBS) in a graded-index multimode silica fiber are reported. The Brillouin Gain Spectrum (BGS) is shown to strongly depend on the pump and probe modal content. By use of a numerical model, the BGS at varying launching conditions of both pump and probe beams is computed. Numerical results show that intramodal and intermodal SBS contribute to the overall BGS. Experiments confirm the numerical predictions. PMID:25090563

Minardo, Aldo; Bernini, Romeo; Zeni, Luigi

2014-07-14

125

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

126

A Fast Way to Fabricate Polymethyl Methacrylate for Graded-Index Polymer Optical Fibers  

Microsoft Academic Search

The coextrusion process was considered to be a main approach to prepare graded-index polymer optical fibers (GI-POFs) and the primary polymer to fabricate that is poly-methyl methacrylate (PMMA). The current process to polymerize methyl methacrylate (MMA) requires long hours. In this article, the heat transfer in the bulk polymerization was analyzed and calculated, according to which polymerization speed could enhance

Sude Ma; Lisheng Zhong; Pengguo Wang; Chuanxiang Xu; Xiaoyan Li

2006-01-01

127

Thermally stable high-bandwidth graded-index polymer optical fiber  

Microsoft Academic Search

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

Masataka Sato; Takaaki Ishigure; Yasuhiro Koike

2000-01-01

128

High-bandwidth graded-index polymer optical fiber with high-temperature stability  

Microsoft Academic Search

A newly developed graded-index polymer optical fiber (GI-POF) with high-temperature and high-humidity stability was proposed. As it was found that the high numerical aperture and high glass transition temperature (Tg) at the core center of the GI-POF were key issues to achieve both high-temperature and humidity stability, a partially fluorinated polymer material was adopted to obtain both characteristics in the

Takaaki Ishigure; Masataka Sato; Atsushi Kondo; Yasuhiro Koike

2002-01-01

129

Graded-Index Polymer Optical Fiber with High Thermal Stability of Bandwidth  

Microsoft Academic Search

The development of the perfluorinated (PF) polymer based graded-index polymer optical fiber (GI POF) for high-speed data communication is described. It was experimentally confirmed that gigabit data transmission for 500 1000 m at 1.3 µm wavelength was achieved by the low-loss PF polymer based GI POF. The thermal stability of poly (methyl methacrylate) PMMA based GI POF is discussed. We

Takaaki Ishigure; Masataka Sato; Eisuke Nihei; Yasuhiro Koike

1998-01-01

130

Absorption detection of cobalt(II) ions in an index-guiding microstructured optical fiber  

Microsoft Academic Search

We reported the absorption detection of cobalt(II) ions (Co2+) in aqueous solutions which is filled into the air-holes of a pure-silica microstructured optical fiber (MOF). The evanescent field in MOF which changes with solution of absorbing species is numerically investigated with respect to the change of refractive index, wavelength as well as the microstructure pattern in a systematic manner. Good

X. Yu; Y. C. Kwok; N. Amirah Khairudin; P. Shum

2009-01-01

131

Understanding differences between OTDR and cut-back attenuation measurements in multimode graded index fiber  

Microsoft Academic Search

In measuring the attenuation of multimode graded index fiber, differences have been noted between the results of the cut-back method and the optical time domain reflectometry (OTDR) method. Under certain conditions, the OTDR results can be higher by 0.1 to 0.3 dB\\/km than the cut-back results. In attempting to understand the origin of these differences, we have characterized the attenuation

M. Smith; D. Roland

1996-01-01

132

Kinesin-12 Kif15 Targets Kinetochore Fibers through an Intrinsic Two-Step Mechanism.  

PubMed

Proteins that recognize and act on specific subsets of microtubules (MTs) enable the varied functions of the MT cytoskeleton. We recently discovered that Kif15 localizes exclusively to kinetochore fibers (K-fibers) [1, 2] or bundles of kinetochore-MTs within the mitotic spindle. It is currently speculated that the MT-associated protein TPX2 loads Kif15 onto spindle MTs [3-5], but this model has not been rigorously tested. Here, we show that Kif15 accumulates on MT bundles as a consequence of two inherent biochemical properties. First, Kif15 is self-repressed by its C terminus. Second, Kif15 harbors a nonmotor MT-binding site, enabling dimeric Kif15 to crosslink and slide MTs. Two-MT binding activates Kif15, resulting in its accumulation on and motility within MT bundles but not on individual MTs. We propose that Kif15 targets K-fibers via an intrinsic two-step mechanism involving molecular unfolding and two-MT binding. This work challenges the current model of Kif15 regulation and provides the first account of a kinesin that specifically recognizes a higher-order MT array. PMID:25264249

Sturgill, Emma G; Das, Dibyendu Kumar; Takizawa, Yoshimasa; Shin, Yongdae; Collier, Scott E; Ohi, Melanie D; Hwang, Wonmuk; Lang, Matthew J; Ohi, Ryoma

2014-10-01

133

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

134

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

NASA Astrophysics Data System (ADS)

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

Zhang, Yao; Lei, Hongxiang; Li, Baojun

2013-07-01

135

Highly Sensitive Monolithic Silicon Photonic Crystal Fiber Tip Sensor for Simultaneous Measurement of Refractive Index and Temperature  

Microsoft Academic Search

Fiber optic sensors have applications in the measure- ment of a wide range of physical properties such as temperature, pressure, and refractive index. These sensors are immune to elec- tromagnetic interference, made of high temperature dielectric ma- terials and hence can be deployed in harsh environments where conventional electronics would fail. Photonic crystal (PC) fiber tip sensors are highly sensitive

Il Woong Jung; Bryan Park; J. Provine; Roger T. Howe; Olav Solgaard

2011-01-01

136

Fluorescence characterization and gain studies on a dye-doped graded index polymer optical-fiber preform  

Microsoft Academic Search

Preparation of an appropriate optical-fiber preform is vital for the fabrication of graded-index polymer optical fibers (GIPOF), which are considered to be a good choice for providing inexpensive high bandwidth data links, for local area networks and telecommunication applications. Recent development of the interfacial gel polymerization technique has caused a dramatic reduction in the total attenuation in GIPOF, and this

M. Kailasnath; T. S. Sreejaya; Rajesh Kumar; C. P. G. Vallabhan; V. P. N. Nampoori; P. Radhakrishnan

2008-01-01

137

A simplified technique for efficient fiber-polymer-waveguide power coupling using a customized cladding with tunable index of refraction  

Microsoft Academic Search

A novel technique to minimize the mode mismatch between the fiber and waveguide modes in integrating optical fiber to polymer waveguides is presented. The mode fields at the facets of the waveguides were tailored, optimizing the waveguide geometry as well as tuning the index of refraction of the lower cladding near the facets, by chemical composition. No additional processes were

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

2006-01-01

138

Closed-loop phase stabilizing and phase stepping methods for fiber-optic projected-fringe digital interferometry  

NASA Astrophysics Data System (ADS)

Closed-loop active homodyne control can be used to make an interferometer steady against phase fluctuating followed by, for example, temperature gradients. This technology is introduced to stabilize ?/2 -rad phase steps in a full-field interferometer. Two beams emitted from a fiber-optic coupler are combined to form an interference fringe pattern on a diffusely reflecting object. Fresnel reflections from the distal fiber ends undergo a double pass in the fibers and interference at the fourth port of the coupler which formed a Michelson interferometer. We suggested two means of ac phase tracking (PTAC) and dc phase tracking (PTDC) to maintain the interference intensity at quadrature by feedback control. Stepping between quadrature positions forces a ?/2 -rad phase step. A method based on the ratio of harmonic of the interference signal was proposed to estimate phase step accuracy. A root-mean-square phase stability of 1.5 mrad and phase step accuracy of 2.6 mrad were measured with PTAC and a root-mean-square phase stability of 2 mrad and phase step accuracy of 13.8 mrad were measured with PTDC for the fiber-optic projected-fringe digital interferometry following the same condition. It worked well in two hours without resetting the integrator.

Chao, Zhang; Fa-Jie, Duan

2011-11-01

139

Closed-loop phase stabilizing and phase stepping methods for fiber-optic projected-fringe digital interferometry.  

PubMed

Closed-loop active homodyne control can be used to make an interferometer steady against phase fluctuating followed by, for example, temperature gradients. This technology is introduced to stabilize ?/2 -rad phase steps in a full-field interferometer. Two beams emitted from a fiber-optic coupler are combined to form an interference fringe pattern on a diffusely reflecting object. Fresnel reflections from the distal fiber ends undergo a double pass in the fibers and interference at the fourth port of the coupler which formed a Michelson interferometer. We suggested two means of ac phase tracking (PTAC) and dc phase tracking (PTDC) to maintain the interference intensity at quadrature by feedback control. Stepping between quadrature positions forces a ?/2 -rad phase step. A method based on the ratio of harmonic of the interference signal was proposed to estimate phase step accuracy. A root-mean-square phase stability of 1.5 mrad and phase step accuracy of 2.6 mrad were measured with PTAC and a root-mean-square phase stability of 2 mrad and phase step accuracy of 13.8 mrad were measured with PTDC for the fiber-optic projected-fringe digital interferometry following the same condition. It worked well in two hours without resetting the integrator. PMID:22128964

Chao, Zhang; Fa-Jie, Duan

2011-11-01

140

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

PubMed

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

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

2011-11-01

141

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

142

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

143

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

144

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

145

Temperature insensitive refractive index sensor based on concatenated long period fiber gratings  

NASA Astrophysics Data System (ADS)

We propose and demonstrate a temperature immune biosensor based on two concatenated LPGs incorporating a suitable inter-grating-space (IGS). Compensating the thermal induced phase changes in the grating region by use of an appropriate length of the IGS the temperature insensitivity has been achieved. Using standard telecommunication grade single-mode fibers we show that a length ratio of ~8.2 is sufficient to realize the proposed temperature insensitivity. The resulting sensor shows a refractive index sensitivity of 423.28 nm/RIU displaying the capability of detecting an index variation of 2.36 × 10-6 RIU in the bio-samples. The sensor can also be applied as a temperature insensitive WMD channel isolation filter in the optical communication systems, removing the necessity of any external thermal insulation packaging.

Tripathi, Saurabh M.; Bock, Wojtek J.; Mikulic, Predrag

2013-10-01

146

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

Microsoft Academic Search

In this paper we theoretically analysed the influence of the number of QWs in the active region and the cladding layer width on the confinement factor, near field patterns and far field patterns. A comparison between the conventional step separate confinement heterostructure (SCH) and a graded-index separate structure (GRIN-SCH) is done regarding these parameters. We found that in the case

Juan A. Martín; M. Sánchez

2005-01-01

147

High-sensitivity fiber-optic refractive index sensor based on multimode interference using small-core single-mode fiber for biosensing  

NASA Astrophysics Data System (ADS)

A fiber-optic refractive index (RI) sensor using multimode interference (MMI) composed of an unclad multimode fiber (MMF) sandwiched by small-core single-mode fibers (SMFs) has been proposed and demonstrated. The small-core SMF at the input port enhances the diffraction of the light outputted to the MMF, and that at the output port provides a steep coupling characteristic of interfered light at the end of the MMF, resulting in the generation of a sharp signal. This leads to high sensitivity to small RI changes. A very high sensitivity of less than 6 × 10-6 at an RI of more than 1.35 has been realized.

Fukano, Hideki; Aiga, Tomohiro; Taue, Shuji

2014-01-01

148

[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

149

Imaging of rat brain using short graded-index multimode fiber  

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

150

Design and analysis of a refractive index sensor based on dual-core large-mode-area fiber  

NASA Astrophysics Data System (ADS)

We present a novel co-axial dual core large-mode-area (LMA) fiber design for refractive index sensing. In a dual-core fiber there is resonant coupling between the two cores, which is strongly affected by the refractive index (RI) of the outermost region. The transmittance of the fiber, therefore, varies sharply with the refractive index of surrounding medium. This characteristic of the proposed structure has been utilized to design a RI sensor. We have analyzed the structure by using the transfer matrix method. Our numerical results show that the proposed sensor is highly sensitive with the resolution of 2.0 × 10-6 around nex = 1.44376. Effect of design parameters on sensitivity of the proposed sensor has also been investigated.

Kamakshi, Koppole; Rastogi, Vipul; Kumar, Ajeet

2013-08-01

151

Tapered Mach-Zehnder interferometer based on two mechanically induced long-period fiber gratings as refractive index sensor  

NASA Astrophysics Data System (ADS)

A Mach-Zehnder interferometer formed in single mode fiber is implemented. The interferometer is built by two mechanically-induced long-period gratings. In addition, a fiber taper in the middle section is inserted. The spectral properties of the whole system are analyzed. Visibility of the interference fringes up to 0.80 (the higher ever reported using mechanically-induced long-period gratings) with fringe spacing in the 4.1 to 0.86 nm range are experimentally demonstrated. The proposed device allows reducing the fiber diameter of the section between gratings with a minimal effect in the interference fringe spacing. The sensitivity of the interferometer to external refractive index changes was also studied. It is experimentally shown that, due to the nature of the cladding mode excited, it is necessary to taper the fiber to improve the system sensitivity to external refractive index. Fiber tapers with different diameter, inserted between the long-period gratings pair were fabricated and tested for measuring external refractive index changes. A maximum resolution of 2.3×10-4 RIU in a refractive index range from 1.36 to 1.402 is achieved.

Cárdenas-Sevilla, G. A.; Monzón-Hernández, D.; Torres-Gómez, I.; Martínez-Ríos, A.

2012-07-01

152

High-sensitivity fiber refractive index sensor formed by sandwiching a thinned taper between two abrupt tapers  

NASA Astrophysics Data System (ADS)

A fiber refractive index (RI) sensor based on a Mach-Zehnder interferometer (MZI) formed by sandwiching a thinned taper between two abrupt tapers. The abrupt tapers and the thinned taper are easily fabricated by a commercial fiber fusion splicer and a homemade tapering machine, respectively. The sensor has been experimentally demonstrated for RI sensing by monitoring its spectral shifts. The experimental results show that the sensor with a thinner taper has higher sensitivity due to the strong evanescent field interaction. A sensitivity of 3808.4 nm/RIU (refractive index unit) is obtained, which is about 100 times higher than that of the conventional taper-based MZI sensors.

Chen, Jinping; Zhou, Jun; Shu, Lei; Ma, Yanan; Zhang, Haopeng

2013-12-01

153

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

NASA Astrophysics Data System (ADS)

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

Bhatia, Priya; Gupta, , Banshi D.

2013-01-01

154

Interrogation of in-series double cladding fiber sensor for simultaneous refractive index and temperature measurement  

NASA Astrophysics Data System (ADS)

An interrogation scheme for an in-series double cladding fiber (DCF) sensor is proposed and demonstrated, which can be used for simultaneous refractive index (RI) and temperature measurement. It utilizes two commercial distributed feedback lasers to match two cascade DCF sensors which have two band-rejected filtering spectra at different wavelengths. The two lasers were intensity modulated by different frequencies and demodulated by a lock-in amplifier. Experimental results indicated that a resolution of +/-2×10-5 in RI and +/-1.2°Cin temperature were achieved. Based on the simple and low cost interrogation scheme, the dual parameters sensor system will find potential applications in chemical sensors and biosensors.

Qi, Bo; Pang, Fufei; Wang, Tingyun; Chen, Na; Huang, Sujuan; Chen, Zhenyi

2012-06-01

155

S-tapered photonic crystal fiber interferometers for refractive index sensing  

NASA Astrophysics Data System (ADS)

An experimental investigation on an S-tapered photonic crystal fiber interferometer is presented. The whole fabrication process was carried out using a standard splicing machine. The interferometer shows a compact and stable structure with a waist diameter of 110 ?m, taper length of 280 ?m, and axial offset of 40 ?m. The transmission spectra indicated that it is highly sensitive to the surrounding refractive index (RI) and insensitive to temperature. Resolutions of 3.3×10-4 and 8.0×10-5 RI units were achieved in the 1.33 to 1.38 and 1.38 to 1.44 range, respectively. Furthermore, its temperature dependence was only 4 pm/°C.

Shi, Feifei; Wu, Yun; Wang, Jinzhong; Zhao, Liancheng; Shi, Huizhong

2013-03-01

156

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

E-print Network

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

Perez, Raul Castillo; Torba, Sergii M

2014-01-01

157

In-line fiber Fabry-Perot refractive index tip sensor based on photonic crystal fiber and spectrum differential integration method  

NASA Astrophysics Data System (ADS)

A novel and simple refractive index tip sensor based on filling-free Fabry-Perot interferometer is realized by simply splicing a section of endlessly single-mode photonic crystal fiber to a conventional single-mode fiber. The temperature and refractive index characteristics of the proposed device are investigated. Experimental results show that the device can provide temperature-independent measurement of refractive index with a fringe-contrast-sensitivity of ~52.4 dB/RIU. Meanwhile, it can also be used as a temperature sensor with a wavelength-temperature-sensitivity of ~7 pm/°C. In addition, we also propose that using a spectrum differential integration method to improve the performance of the device as compared to the method of measuring the fringe contrast.

Wu, Di; Huang, Wei; Wang, Guo-Yin; Fu, Jian-Yu; Chen, Yong-Yuan

2014-02-01

158

Photonic Crystal Fiber Mach-Zehnder Interferometer for Refractive Index Sensing  

PubMed Central

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

Wang, Jian-Neng; Tang, Jaw-Luen

2012-01-01

159

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. PMID:22344393

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

2011-01-01

160

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

PubMed

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

Wang, Jian-Neng; Tang, Jaw-Luen

2012-01-01

161

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

162

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

NASA Astrophysics Data System (ADS)

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 applications. However, the efficient of the sampled FBGs of which the index modulation is obtained by the simple inverse Fourier transformation is very slow. To get a high efficient, a particle swarm optimization algorithm is applied to design the phase of the target spectrum. Combing the two methods together, a high efficient multi-level phase sampled FBG that each channel is suppressed or not at will, can be obtained. We also use the particle swarms optimizations (PSO) algorithm to optimize the pure phase sampling profiles of the sampled FGB. Results showed that a much high efficient of the FBG can be obtained compared with that obtained from the simple inverse Fourier transformation technology. If appropriate grating period chirp and sampled period chirp is applied to such a grating, a novel FBGs based OADM or interleaver devices with dispersion or dispersion slope compensation can be designed.

Liu, Yumin; Yu, Zhongyuan; Yang, Hongbo; Zhang, Na

2004-10-01

163

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

PubMed Central

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

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

2012-01-01

164

Highly Sensitive Refractive Index Sensor Based on a Cladding-Etched Thin-Core Fiber Sandwiched between Two Single-Mode Fibers  

NASA Astrophysics Data System (ADS)

A refractive index (RI) sensor based on a cladding-etched thin-core single-mode fiber (TCSMF) sandwiched between two single-mode fibers is demonstrated. The experimental results show that the sensitivity, within the RI range of 1.333-1.340, is enhanced at least 6 times by etching. It increases with the surrounding RI and reaches 857.5 nm/RIU at RI of 1.3684, and it can be expected to be higher with the decrease of the cladding diameter of the TCSMF.

Xu, Ben; Li, Yi; Dong, Xin-Yong; Jin, Shang-Zhong; Zhang, Zai-Xuan

2012-09-01

165

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

Microsoft Academic Search

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

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

2007-01-01

166

11 Gb\\/sec data transmission through 100 m of perfluorinated graded-index polymer optical fiber  

Microsoft Academic Search

We report for the first time data transmission at 11 Gb\\/sec through 100 m of low loss (33 dB\\/km) perfluorinated graded index plastic optical fiber using inexpensive, uncooled, unisolated, Fabry Perot lasers at 1.3 ?m and a simple InGaAs pin photodetector

G. Giaretta; M. Wegmueller; R. V. Yelamarty

1999-01-01

167

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

E-print Network

resins with respect to the raw bagasse fiber and alkali-extracted bagasse fiber. On the other hand, the sugar industry generates over 4.5 million tons of dry fibrous materials (i.e., sugar- cane bagasse) per contains relatively low sucrose.2 Sugarcane bagasse (or bagasse) is the fibrous resid- ual material

168

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

169

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

PubMed Central

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

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

2013-01-01

170

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

E-print Network

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

Tsigaridas, G; Persephonis, P

2014-01-01

171

Single-mode fiber refractive index sensor with large lateral offset fusion splicing between two abrupt tapers  

NASA Astrophysics Data System (ADS)

We propose a novel refractive index (RI) sensor based on a fiber Mach-Zehnder interferometer formed by large lateral offset fusion splicing between two abrupt tapers. The cladding modes are efficiently excited by transmitted light in the large misalignment junctions. The RI sensitivity of the sensor to surrounding RI change is measured, and the sensitivity of 100 nm/RIU is obtained, which is three to six times higher than that of fiber structures with only a pair of tapers or two offset junctions. Moreover, the sensor is made by a low-cost fabrication method. Thus, the proposed structure is beneficial to the RI sensing applications.

Zhang, Qi; Zhou, Jun; Chen, Jinping; Tan, Xiaoling

2012-09-01

172

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

173

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

E-print Network

, actuation, and displays into clothing and surface coverings. With the performance and interconnection from a viable e-textile technology; fiber transistors will enable cloth-based large-area circuits-textile interconnection/integration. 250 µm and 500 µm diameter Al wires were used as gate lines. These may be directly

California at Irvine, University of

174

Determination of refractive index dispersion using fiber-optic low-coherence Fabry-Perot interferometer: implementation and validation  

NASA Astrophysics Data System (ADS)

We present the implementation and validation of low-coherence Fabry-Perot interferometer for refractive index dispersion measurements of liquids. A measurement system has been created with the use of four superluminescent diodes with different optical parameters, a fiber-optic coupler and an optical spectrum analyzer. The Fabry-Perot interferometer cavity has been formed by the fiber-optic end and mirror surfaces mounted on a micromechanical stage. The positive result of the validation procedure has been determined through statistical analysis. All obtained results were 99.999% statistically significant and were characterized by a strong positive correlation (r>0.98). The accuracy of the measured result of implemented low-coherence Fabry-Perot interferometer sensor is from 83% to 94%, which proves that the sensor can be used in the measurement of refractive index dispersion of liquids.

Karpienko, Katarzyna; Wróbel, Maciej S.; J?drzejewska-Szczerska, Ma?gorzata

2014-07-01

175

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

Microsoft Academic Search

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

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

2005-01-01

176

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

Microsoft Academic Search

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

Takaaki Ishigure; Yasuhiro Koike; James W. Fleming

2000-01-01

177

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

178

Theoretical investigation on the dispersion of graded-index polymer optical fibers  

Microsoft Academic Search

Various experiments on polymer optical fibers (POF's) suggest that they present a large transmission capacity, but this is not confirmed by the standard theory. In this paper we present a full dispersion model based on evaluating the frequency response of the fiber instead of the direct calculation of the pulse broadening from the moments of the impulse response. The mathematical

Gnitabour Yabre

2000-01-01

179

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

NASA Astrophysics Data System (ADS)

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

Martín, Juan A.; Sánchez, M.

2005-03-01

180

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

181

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

182

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

183

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

184

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

PubMed

Zirconium-doped ceria (Ce(1-x)Zr(x)O2) 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 Ce(1-x)Zr(x)O2 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 Ce(1-x)Zr(x)O2 (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

185

High Sensitive Temperature Sensor Using a Liquid-core Optical Fiber with Small Refractive Index Difference Between Core and Cladding Materials  

PubMed Central

An intensive temperature sensor based on a liquid-core optical fiber has been demonstrated for the measuring the temperature of the environment. The core of fiber is filled with a mixture of toluene and chloroform in order to make the refractive index of the liquid-core and the cladding of the fiber close. The experiment shows that a temperature sensitivity of about 5 dB/K and a tunable temperature range (from 20 °C to 60 °C) can be achieved. Based on the dielectric-clad liquid core fiber model, a simulation was carried out and the calculated results were in good accord with the experimental measurement.

Xu, Yonghao; Chen, Xianfeng; Zhu, Yu

2008-01-01

186

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

187

Sensitivity enhancement of surface plasmon resonance based fiber optic refractive index sensor using an additional layer of zinc oxide  

NASA Astrophysics Data System (ADS)

We have experimentally demonstrated the role of the high index dielectric layer of zinc oxide over the metal layer on the performance of the surface plasmon resonance based fiber optic refractive index sensor. The configuration contains copper as a SPR active metallic layer covered by dielectric layer. The configuration of Cu/ZnO shows high sensitivity. Further increase in the thickness of ZnO layer increases the sensitivity of the sensor. A good agreement between experimental results and the simulated ones based on multilayer two dimensional approach is obtained. The additional advantages of ZnO layer, apart from sensitivity enhancement, are protection of metallic layer from oxidation, tunability of the resonance wavelength region, biocompatibility and capability of gas sensing.

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

2013-05-01

188

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

NASA Astrophysics Data System (ADS)

A direct one-step and low temperature micro-fabrication process, enabling to realize large area totally inorganic TiO2 micro-patterns from a spin-on resist, is presented. High refractive index structures (up to 2 at 632 nm) without the need for transfer processes have been obtained by mask assisted UV lithography, exploiting photocatalytic titania properties. A distinctive feature not shared by any of the known available resists and boosting the material versatility, is that the system behaves either as a positive or as negative tone resist, depending on the process parameters and on the development chemistry. In order to explain the resist double tone behavior, deep comprehension of the lithographic process parameters optimization and of the resist chemistry and structure evolution during the lithographic process, generally uncommon in literature, is reported. Another striking property of the presented resist is that the negative tone shows a high contrast up to 19, allowing to obtain structures resolution down to 2 ?m wide. The presented process and material permit to directly fabricate different titania geometries of great importance for solar cells, photo-catalysis, and photonic crystals applications.

Zanchetta, E.; Della Giustina, G.; Brusatin, G.

2014-09-01

189

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

SciTech Connect

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

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

2006-05-15

190

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

191

ORIGINAL ARTICLES: DIETARY FIBRE Glycaemic Index of Fenugreek Recipes and Its Relation to Dietary Fiber  

Microsoft Academic Search

Background: Fenugreek seeds, a commonly used condiment, are a rich source of dietary fiber and have been shown to be beneficial in the management of diabetes. However, b itterness has limited its long-term use. Methods: Common recipes, containing fenugreek seeds in which the bitterness could be masked with other ingredients were formulated. Organoleptic evaluation revealed that 12 p reparations were

T. C. Raghuram; R. D. Sharma; S. Pasricha; K. K. Menon; G. Radhaiah

192

Reflection-type optical fiber refractive-index sensor using a multimode interference structure with high sensitivity  

NASA Astrophysics Data System (ADS)

A high-sensitivity reflection-type refractive-index (RI) sensor using a multimode interference structure has been fabricated by forming a gold mirror at the end of a sensor fiber. The sensor part is composed of single-mode fibers (SMFs) attached to a multimode fiber (MMF) with an end-face mirror. This structure has the same function as an MMF sandwiched by SMFs, which is called a multimode interference (MMI) structure. The fabricated sensor shows a sensitivity as high as 6.8 × 10-6 (at 1 pm wavelength resolution), which is estimated from the relationship between the change in RI and the shift in wavelength in a wide RI range, and 1.0 × 10-5 (at 0.01 dB power resolution), which is estimated from the relationship between the change in RI and the variation of interference power at a fixed wavelength, despite the sensor having only half the length of a conventional two-port multimode interference RI sensor.

Fukano, Hideki; Hashimoto, Takuya; Taue, Shuji

2014-01-01

193

High sensitivity refractive index sensing of Mach-Zehnder interferometer based on multimode fiber core sandwiched between two waist-enlarged fiber tapers  

NASA Astrophysics Data System (ADS)

A taper based Mach-Zehnder interferometer (MZI) for high sensitivity refractive index (RI) measurement is investigated. The sensor head consists of two waist-enlarged tapers, in which a section of multimode fiber core (MMFC) is sandwiched to improve the sensitivity of the MZI. Theoretical analysis shows that the RI sensitivity could be enhanced by reducing the MMFC diameter, which is verified in the experiments. A high RI sensitivity of 430.94 nm/RIU and resolution of 4.64×10-5 are achieved in the RI range of 1.33-1.39 for the MZI with MMFC core diameter of 68.5 um. The temperature response of the MZI is also demonstrated.

Shao, Min; Qiao, Xueguang; Fu, Haiwei; Liu, Yinggang; Zhao, Xue; Yao, Ni

2013-01-01

194

Liquid refractive index sensor with three-cascaded microchannels in single-mode fiber fabricated by femtosecond laser-induced water breakdown  

NASA Astrophysics Data System (ADS)

Liquid refractive index sensor with three-cascaded microchannels in single-mode fiber was fabricated by femtosecond laser-induced water breakdown. When the liquid is filled in three microchannels across the fiber core, the transmission spectrum of the sensor shows interference peaks. The refractive index of liquid can be sensed accurately based on both the wavelength shift and loss change of interference peaks. The refractive index sensitivities of wavelength shift and loss change reach to as high as -2,406.1 nm/RIU and -156.8 dB/RIU, respectively. The sensor is insensitive to the refractive index change of liquid caused by environmental temperature. It can be used for liquid refractive index sensing with high sensitivity, especially for water pollution monitoring.

Liu, Yi; Qu, Shiliang; Li, Yan

2013-03-01

195

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

Microsoft Academic Search

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

Giorgio Giaretta; Whitney White; Mark Wegmuller; Tsuyoshi Onishi

2000-01-01

196

A Reliable Split-Step Fourier Method for the Propagation Equation of Ultra-Fast Pulses in Single-Mode Optical Fibers  

SciTech Connect

The extension to the split-step Fourier method (SSFM) for Schrodinger-type pulse propagation equations that we propose in this article is designed with the accurate simulation of pulses in the femto-second regime in single-mode communication fibers in mind. We show that via an appropriate operator splitting scheme, Kerr nonlinearity and the self-steepening and stimulated Raman scattering terms can be combined into a single sub-step consisting of an inhomogeneous quasilinear first-order hyperbolic system for the real-valued quantities intensity and phase. First- and second-order accurate shock-capturing upwind schemes have been developed specifically for this nonlinear sub-step, which enables the accurate and oscillation-free simulation of signals under the influence of Raman scattering and extreme self-steepening with the SSFM. Benchmark computations of ultra-fast Gaussian pulses in fibers with strong nonlinearity demonstrate the superior approximation properties of the proposed approach.

Deiterding, Ralf [ORNL; Glowinski, R. [University of Houston, Houston; Oliver, Hilde [ORNL; Poole, Stephen W [ORNL

2013-01-01

197

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

198

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

E-print Network

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

Glebov, Leon

199

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. PMID:22319368

Wang, Ke; Pickrell, Gary

2011-01-01

200

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

201

Radiation damage in optical fibers  

SciTech Connect

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

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

1983-01-01

202

Biconical tapered optical fiber biosensor for measuring refractive index of a-amino acids in aqueous D-glucose and sucrose solution  

Microsoft Academic Search

A single-mode biconical tapered optical fiber (BTOF) sensor was utilized for sensing the variation of refractive index (RI) with concentration of D-glucose in double distilled deionized water and measuring of RI of amino acids (AAs) in carbohydrate solutions. This method showed a rewarding ability in understanding the basis of biomolecular interactions in biological systems. The BTOF is fabricated by heat

M. I. Zibaii; H. Latifi; M. Karami; M. Gholami; S. M. Hosseini; M. H. Ghezelayagh

2010-01-01

203

Launch device using endlessly single-mode PCF for ultra-wideband WDM transmission in graded-index multi-mode fiber.  

PubMed

We demonstrated ultra-wideband wavelength division multiplexing (WDM) transmission from 850 to 1550 nm in graded-index multi-mode fiber (GI-MMF) using endlessly single-mode photonic crystal fiber (ESM-PCF) as a launch device. Effective single-mode guidance is obtained in multi-mode fiber at all wavelengths by splicing cm-order length ESM-PCF to the transmission fiber. We achieved 3 × 10 Gbit/s WDM transmission in a 1 km-long 50-?m-core GI-MMF. We also realized penalty free 10 Gbit/s data transmission at a wavelength of 850 nm by optimizing the PCF structure. This method has the potential to achieve greater total transmission capacity for MMF systems by the addition of more wavelength channels. PMID:23187257

Ma, Lin; Hanzawa, Nobutomo; Tsujikawa, Kyozo; Azuma, Yuji

2012-10-22

204

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

205

Integrated and compact fiber-coupled single-photon system based on nitrogen-vacancy centers and gradient-index lenses.  

PubMed

A fiber-coupled single-photon system is presented. Gradient-index lenses are utilized for single-photon collection and fiber coupling of a nitrogen-vacancy defect center in a nanodiamond. Integrated filter technology separates excitation and laser light. Therefore, the system is ultracompact with 120 mm(3) in dimension as no bulky free beam optics are used. The commercial availability of all components and their simple assembly allows the implementation of a low-cost single-photon system, possibly approaching single-photon count rates of 500 kcts/s. PMID:22825172

Schröder, Tim; Engel, Philip; Schmidt, Eberhard; Benson, Oliver

2012-07-15

206

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

207

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

NASA Astrophysics Data System (ADS)

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

Oguama, Ferdinand Anayo

208

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

209

Numerical analysis of GeO2-concentration effects in arc-induced long-period fiber gratings under external refractive-index changes  

NASA Astrophysics Data System (ADS)

We present a numerical analysis of the response of arc-induced long-period fiber gratings (LPFGs) under ambient refractive-index changes using standard fibers with SiO2 as cladding material and different GeO2 concentration in the SiO2-GeO2 doped core. We obtain that the LPFG-sensitivity is increased using lower GeO2 concentrations and it follows a parabolic behavior. Also, we identify two linear regimes using an external index of 1.37: for GeO2 concentrations between 2 and 3.5 mol %, the LPFG-sensitivity changes with a rate of 3.614 nm per mole fraction of GeO2, while for higher concentrations the sensitivity changes with a rate of 1.39 nm/mol %. Additionally, for fibers with 2 mol% of GeO2, the sensitivity calculated is comparable to this obtained in previous works using corrugated and tapered LPFGs in SMF28 fibers. These results are of interest for the design of improved LPFG-sensors.

Guzman-Ramos, Valentin; Ceballos-Herrera, Daniel E.; Selvas-Aguilar, Romeo

2014-03-01

210

Making Optical-Fiber Chemical Detectors More Sensitive  

NASA Technical Reports Server (NTRS)

Calculations based on exact theory of optical fiber shown how to increase optical efficiency and sensitivity of active-cladding step-index-profile optical-fiber fluorosensor using evanescent wave coupling. Optical-fiber fluorosensor contains molecules fluorescing when illuminated by suitable light in presence of analyte. Fluorescence coupled into and launched along core by evanescent-wave interaction. Efficiency increases with difference in refractive indices.

Rogowski, Robert S.; Egalon, Claudio O.

1993-01-01

211

Axial strain insensitivity of weakly guiding optical fibers  

NASA Technical Reports Server (NTRS)

A numerical model has been developed to calculate the modal phase shift of circular step index profile weakly guiding fibers under axial strain. Whenever an optical fiber is under stress, the optical path length, the index of refraction, and the propagation constants of each mode change. In consequence, the phase of each mode is also modified. A relationship for the modal phase shift is presented. This relation is applied to both single mode and two-mode fibers in order to determine the sensitivity characteristics of strained fibers. It was found that the phase shift is strongly dependent on the core refractive index, n(co). It was also found that it is possible to design fibers which are insensitive to axial strain. Practical applications of strain insensitive fibers are discussed.

Egalon, Claudio O.; Rogowski, Robert S.

1993-01-01

212

Fabrication of a graded-index polymer optical fiber preform without a cavity by inclusion of an additional monomer under a centrifugal force field.  

PubMed

When two or more monomers with different densities and refractive indices are polymerized under a centrifugal force field, a radially varying refractive index is generated owing to the difference in density of the monomers. After the polymerization is completed, a cavity is generated about the rotational axis as a result of inherent volume shrinkage during bulk radical polymerization. Therefore it is necessary to feed an additional monomer into the cavity to compensate for the undesirable volume shrinkage. We have successfully fabricated a preform with graded indices for polymer optical fiber without a cavity by adding another monomer during rotation of the reactor. One can control the overall refractive-index profile by changing the rotation speed. Furthermore, the refractive-index profile can be predicted as a function of rotating speed by use of a simple mathematical model. PMID:11936782

Im, Sang Hyuk; Suh, Duck Jong; Park, O Ok; Cho, Hansol; Choi, Jin Sung; Park, Jae Keun; Hwang, Jin Taek

2002-04-01

213

Optical fiber devices: Novel fiber lasers and image amplifier  

NASA Astrophysics Data System (ADS)

Three fiber based optical devices: all phosphate glass fiber laser, single hybrid mode fiber laser, and fiber image amplifier, were investigated in this dissertation. Phosphate fiber Bragg grating (FBG) is desired to improve performance of recently developed high power single frequency lasers that were based on highly rare earth ion doped phosphate fibers because these lasers were fabricated with silica FBGs that have incompatible properties with standard phosphate glasses. Since standard phosphate glasses are not photosensitive, Ge-doped phosphate glasses were fabricated and their UV-photosensitivity was examined. A phosphate fiber that has Ge-doped core showed UV index changes more than ˜1.1 x 10-3. An all-phosphate fiber laser was also demonstrated with the Ge-doped phosphate FBG. Single hybrid mode fiber laser that involves a large area mode in cavity formation was demonstrated. The fiber laser consists of an Er-doped active fiber and two FBGs. One FBG was a core-cladding mode converter, and the other FBG was a narrowband high reflector that selects the lasing wavelength and mode. This approach for designing a laser cavity provides a much larger mode area than conventional large-mode-area step-index fibers, and is supposed to suitable for a high power fiber laser. Also this configuration allows us to make novel ring-like cavities and sensor devices that consist of higher mode of optical fibers. Image amplifier based on a highly rare earth ion doped phosphate fiber is a unique approach to overcome weakness of widely used image intensifiers that lose a lot of information in the image, such as spectral distribution, polarization, and phase. Image amplification with a 19-pixel optical image amplifier array based on high gain per unit length Yb3+-doped phosphate glass optical fiber was demonstrated. A 10-cm of the 19-pixel fiber image amplifier provides spatially uniform image amplification with gain of 30 dB/pixel or more. This image amplifier responds quickly to changes in the image position---with potential for GHz-level or higher frame rates. This unique approach for image amplification offers low noise, high gain, and wide field of view in a compact fiber-based device.

Suzuki, Shigeru

214

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

PubMed

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

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

2009-10-26

215

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

216

A new Mach-Zehnder interferometer in a thinned-cladding fiber fabricated by electric arc for high sensitivity refractive index sensing  

NASA Astrophysics Data System (ADS)

This study proposes an inline electric-arc induced Mach-Zehnder interferometer (MZI) in a thinned cladding fiber. The proposed MZI is used for refractive index (RI) sensing. At the diameter of 56 ?m and the length of 18 mm, in the RI of 1.3348-1.3558, the sensitivity is ˜580 nm/RIU, that is about 20 times greater than those of taper-based MZI sensors. Temperature characteristics of the MZI are investigated in 50-800 °C. It is demonstrated that the proposed MZI is a good choice for high-temperature harsh environment sensing.

Li, Benye; Jiang, Lan; Wang, Sumei; Mengmeng Wang, Qianghua Chen; Yang, Jinpeng

2012-06-01

217

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

218

Fiber optic radiation dosimetry for medical applications  

NASA Astrophysics Data System (ADS)

The dosimetry with glass fibers perrilits for the first time the dose to be determined in the immediate vicinity of the tumour. A fiberoptic dosimeter can either be introduced during an operation or else inserted via a cannula into the vicinity of the tumour to be irradiated. The dosimeter should remain in the patient's body until radiation therapy has been completed. The basic principle of the fiberoptic dosimeter is to measure the additional attenuation generated in the fiber by irradiation. A lead-glass fiber with 60 weight - % PbO was used as a particular radiationsensitive fiber. This is a step-index fiber with a core diameter of 100 pm and a total diameter of 110 pm. Measurements of the spectral distribution of the induced loss result in a detection sensitivity of smaller than 0.1 Gy for the lead-glass fiber at a local resolution of about 2 cm. This satisfies the demands of radiotherapy.

Bueker, Harald; Haesing, Friedrich W.; Nicolai, S.; Wolters, B.

1990-07-01

219

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

220

Dietary Fiber/Carnitine, Diacylglycerol, and Low Glycemic Index Starch Effects on Obesity and Triglyceride Rich Lipoprotein Metabolsim in Dogs  

E-print Network

. They administered a restricted amount of food to adult dogs (approx. 50 ? BW0.75) containing 3.1-23.7 g/1000 kJ dietary fiber, and then provided commercially available foods 3 h afterwards using whose intake and energy consumed as a marker of satiety. They found.... They administered a restricted amount of food to adult dogs (approx. 50 ? BW0.75) containing 3.1-23.7 g/1000 kJ dietary fiber, and then provided commercially available foods 3 h afterwards using whose intake and energy consumed as a marker of satiety. They found...

Mitsuhashi, Yuka

2011-02-22

221

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

222

Improved thermal and strain performance of annealed polymer optical fiber Bragg gratings  

Microsoft Academic Search

We report on a detailed study of the inscription and characterization of fiber Bragg gratings (FBGs) in commercial step index polymer optical fibers (POFs). Through the growth dynamics of the gratings, we identify the effect of UV-induced heating during the grating inscription. We found that FBGs in annealed commercial POFs can offer more stable short-term performance at both higher temperature

Wu Yuan; Alessio Stefani; Morten Bache; Torben Jacobsen; Bjarke Rose; Nicolai Herholdt-Rasmussen; Finn Kryger Nielsen; Søren Andresen; Ole Brøsted Sørensen; Knud Styhr Hansen; Ole Bang

2011-01-01

223

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

NASA Astrophysics Data System (ADS)

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

He, Zonghu

224

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

225

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

226

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

Microsoft Academic Search

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

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

2007-01-01

227

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

228

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

229

Peak-power limits on fiber amplifiers imposed by self-focusing  

Microsoft Academic Search

We have numerically investigated the behavior of the fundamental mode of a step-index, multimode (MM) fiber as the optical power approaches the self-focusing limit Pcrit. The analysis includes the effects of gain and bending (applicable to coiled fiber amplifiers). We find power-dependent, stationary solutions that propagate essentially without change at beam powers approaching Pcrit in straight and bent fibers. We

Roger L. Farrow; Dahv A. V. Kliner; G. Ronald Hadley; Arlee V. Smith

2006-01-01

230

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

PubMed

We present numerical modeling of mid-infrared (MIR) supercontinuum generation (SCG) in dispersion-optimized chalcogenide (CHALC) step-index fibres (SIFs) with exceptionally high numerical aperture (NA) around one, pumped with mode-locked praseodymium-doped (Pr3+) chalcogenide fibre lasers. The 4.5um laser is assumed to have a repetition rate of 4MHz with 50ps long pulses having a peak power of 4.7kW. A thorough fibre design optimisation was conducted using measured material dispersion (As-Se/Ge-As-Se) and measured fibre loss obtained in fabricated fibre of the same materials. The loss was below 2.5dB/m in the 3.3-9.4?m region. Fibres with 8 and 10?m core diameters generated an SC out to 12.5 and 10.7?m in less than 2m of fibre when pumped with 0.75 and 1kW, respectively. Larger core fibres with 20?m core diameters for potential higher power handling generated an SC out to 10.6?m for the highest NA considered but required pumping at 4.7kW as well as up to 3m of fibre to compensate for the lower nonlinearities. The amount of power converted into the 8-10?m band was 7.5 and 8.8mW for the 8 and 10?m fibres, respectively. For the 20?m core fibres up to 46mW was converted. PMID:25321003

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

2014-08-11

231

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

232

Fiber Mach-Zehnder interferometer based on concatenated down- and up-tapers for refractive index sensing applications  

NASA Astrophysics Data System (ADS)

We report a novel fiber Mach-Zehnder interferometer based on concatenated down- and up-tapers simply fabricated by arc discharging and fusion splicing. High-quality interference spectra with a maximum attenuation peak depth beyond 20 dB were obtained. Experimental results show that the RI sensitivity of the MZI with a length of 52 mm reaches -82.8 nm/RIU for a RI range of 1.333-1.3869, which is nearly 5 times higher than that of the conventional MZI based on two down-tapers, and 12 times higher than that of MZI based on two up-tapers. The temperature cross sensitivity is discussed and the influence can be eliminated by simultaneous measurement of RI and temperature using different sensitivities of different attenuation wavelength peaks. Such MZIs with low-cost and ease of fabrication will find various sensing applications.

Zhang, Shanshan; Zhang, Weigang; Geng, Pengcheng; Gao, Shecheng

2013-02-01

233

Sol-gel-based doped granulated silica for the rapid production of optical fibers  

NASA Astrophysics Data System (ADS)

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

Romano, Valerio; Pilz, Soenke; Etissa, Dereje

2014-03-01

234

EE160: Fiber-Optic Communication Systems University of California, Riverside Bourns College of Engineering, University of California, Riverside  

E-print Network

laser, erbium doped fiber amplifier, and high-speed optical receiver. Each lab will be approximately 3/5 Single Mode Propagation in Step-Index Fiber 2.1-2.2 Hw-1 4/7 Optical Fiber Loss and Dispersion 2.3, 2.5 4/12 Dispersion-Induced System Limitations 2.4 4/14 Optical Processes in Semiconductors 3.1 Read Ch. 3 4/15 Lab 1

235

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

236

Eyewear-style three-dimensional endoscope derived from microstructured polymer fiber with the function of image transmission  

NASA Astrophysics Data System (ADS)

A method of fabricating multi-core polymer image fiber is proposed. Image fiber preform is fabricated by stacking thousands of polymer fibers each with a 0.25-mm diameter orderly in a die by only one step. The preform is heated and stretched into image fiber with an outer diameter of 2 mm. Then a portable eyewear-style three-dimensional (3D) endoscope system is designed, fabricated, and characterized. This endoscopic system is composed of two graded index lenses, two pieces of 0.35-m length image guide fibers, and a pair of oculars. It shows good flexibility and portability, and can provide the depth information accordingly.

Kong, De-Peng; Wang, Li-Li; He, Zheng-Quan; Chu, Jiu-Rong; Ma, Tian

2013-02-01

237

Fiber optics in the BNL booster radiation environment  

SciTech Connect

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

Beadle, E.R.

1991-01-01

238

Biconical tapered optical fiber biosensor for measuring refractive index of a-amino acids in aqueous D-glucose and sucrose solution  

NASA Astrophysics Data System (ADS)

A single-mode biconical tapered optical fiber (BTOF) sensor was utilized for sensing the variation of refractive index (RI) with concentration of D-glucose in double distilled deionized water and measuring of RI of amino acids (AAs) in carbohydrate solutions. This method showed a rewarding ability in understanding the basis of biomolecular interactions in biological systems. The BTOF is fabricated by heat pulling method, utilizing a CO2 laser. The detection limit of the BTOF was 50 ppb for the D-glucose concentration ranging from 0 to 80 ppm, and RI detection limit corresponding to these concentrations in the range at 1.3333 to 1.3404 was 5.4×10-6 as a refractometer sensor. The response of the BTOF shows that the different kinds of interactions of various groups of AAs such as L-alanine, L-leucine, and L-cystein with D-glucose, sucrose and water molecules depend on functional groups in AAs such as OH, SH;CH2;NH3+ ,COO-. These results can be interpreted in terms of solute-solute and solute-solvent interactions and structure making/breaking ability of solutes in the given solution.

Zibaii, M. I.; Latifi, H.; Karami, M.; Gholami, M.; Hosseini, S. M.; Ghezelayagh, M. H.

2010-04-01

239

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

240

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

241

Title Code Step/Grade Title Code Step/Grade  

E-print Network

Title Code Step/Grade Salary / to Title Code Step/Grade Salary / to Dist% TEMPORARY INTERCAMPUS) Code (ex: BYA, by-agreement: REG, regular pay etc) SD Fund Source to be charged (Index, Fund & Location

Tsien, Roger Y.

242

Application of asymptotic expressions for numerical simulation of fiber optic output radiation  

NASA Astrophysics Data System (ADS)

The procedure of numerical simulation of near and far fields of diffraction of optical fibers using asymptotic expressions for eigenvalues and eigenfunctions of waveguide modes is considered. The asymptotic expressions suitable for dispersion and polarization effects calculating in step index profiel optical fibers are obatined. The output intensity light profiles are simulated, the statistical properties of distributions are defined and the comparison with experiment is carried out.

Kiesewetter, Dmitry

2003-10-01

243

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

Microsoft Academic Search

A preform technique is used to prepare a step-index (SI) polymer optical fiber (POF) doped with Eu(DBM)3Phen. The gain (5.7 dB) at 613 nm of the doped SI POF with Eu3+ content of 4000 in 10 6 wt., 0.4-mm core diameter, and 30-cm fiber length is observed at ambient temperature by end pumping with a YAG at 355 nm. The

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

2004-01-01

244

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

245

Asymptotic expressions for calculation of length of decay of linear-polarized groups in optical fibers  

NASA Astrophysics Data System (ADS)

The asymptotic expressions for the difference of axial propagation constants of waveguide modes inside one linear-polarized modal group and length of decay of polarization in step index profile optical fibers are submitted. The estimation of accuracy of the obtained formulas is executed.

Kiesewetter, Dmitry

2005-02-01

246

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

247

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

248

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

Microsoft Academic Search

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

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

249

Simulating Optical Fibers.  

ERIC Educational Resources Information Center

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

Edgar, Dale

1988-01-01

250

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

E-print Network

We report fabrication of THz fiber Bragg gratings (TFBG) using CO2 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 design of resonant sensor for monitoring of paper quality is demonstrated. Experimental spectral sensitivity of the TFBG-based paper thickness sensor was found to be ~ -0.67 GHz / 10 um. A 3D electromagnetic model of a Bragg grating was used to explain experimental findings.

Yan, Guofeng; Mikulic, Predrag; Bock, Wojtek J; Skorobogatiy, Maksim

2013-01-01

251

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

252

The tellurite highly nonlinear microstructured fibers for THG and SC generations  

NASA Astrophysics Data System (ADS)

Tellurite highly nonlinear microstructured fibers were fabricated by pumping a positive pressure of nitrogen gas into the holes of cane in the fiber drawing process. By adjusting the pump pressure to inflate the holes of the fiber, the microstructures were reshaped, and the chromatic dispersions were tailored. Two kinds of fiber were fabricated. One is an air-clad fiber with a 1 ?m hexagonal core, which is the smallest core in this shape for the air-clad fiber. By changing the inflation pressure, the diameter ratio of holey region to core (DRHC) was changed in the range of 1-20. Fibers with DRHC of 3.5, 10, 20 were demonstrated. By increasing the DRHC, the zero dispersion wavelengths were shifted to the short wavelength and the confinement loss were decreased. Another is a complex microstructure fiber with a 1.8 ?m core surrounded by four ring holes. The shape of the microstructure was reshaped so heavily by the inflation pressure that it is obviously different from the original shape in the cane. The correlations among pump pressure, hole size, surface tension and temperature gradient were investigated. The temperature gradient at the bottom of the preform's neck region was evaluated quantitatively. The chromatic dispersion of this fiber was compared with that of a step-index air-clad fiber. It was found that this fiber had a much more flattened chromatic dispersion. Supercontinuum generations were investigated by the pump of a 1557 nm femtosecond fiber laser. Intense third harmonic generations were obtained from the 1?m haxgonal core fiber. Broad and flattened spectrum was obtained from the complex microstructure fiber. This investigations show that, by using a positive pressure to reshape the microstructure and by controlling the fabrication conditions exactly, highly nonlinear soft glass fibers with desirable chromatic dispersion can be fabricated, and such fibers have interesting applications in highly nonlinear field such as THG and SC generation.

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

2010-04-01

253

Applicability of classical optical fiber theories to holey fibers  

Microsoft Academic Search

We discuss the applicability of well-established classical optical fiber theories to holey fibers. By appropriately defining the V parameter, we can easily estimate the fundamental properties of holey fibers, such as effective index, group-velocity dispersion, mode field diameter, beam divergence, and splice loss, through simple empirical expressions without the need for heavy numerical computations. We confirm the validity of the

Masanori Koshiba; Kunimasa Saitoh

2004-01-01

254

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

255

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

NASA Astrophysics Data System (ADS)

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

Matjasec, Ziga; Donlagic, Denis

2014-05-01

256

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.

257

Aerogel-clad optical fiber  

DOEpatents

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

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

1997-11-04

258

Aerogel-clad optical fiber  

DOEpatents

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

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

1997-01-01

259

Microstructured fibers for sensing applications  

Microsoft Academic Search

Microstructured fibers (MOFs) are among the most innovative developments in optical fiber technology in recent years. These fibers contain arrays of tiny air holes that run along their length and define the waveguiding properties. Optical confinement and guidance in MOFs can be obtained either through modified total internal reflection, or photonic bandgap effects; correspondingly, they are classified into index-guiding Holey

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

2005-01-01

260

High index contrast platform for silicon photonics  

E-print Network

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

Akiyama, Shoji, 1972-

2004-01-01

261

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

Microsoft Academic Search

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

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

2008-01-01

262

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

263

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

PubMed

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

Sakoda, Tatsuya; Sonoda, Yoshito

2006-04-01

264

ALPD (Axial Lateral Plasma Deposition) - A new process for the production of high quality optical fibers  

NASA Astrophysics Data System (ADS)

A quasi-continuous process is presented for the production of large core low-mass step index all-silica fibers which uses a combination of axial plasma deposition and lateral plasma deposition. This process, called the Axial Lateral Plasma Deposition technique, is shown to allow the industrial production of 2 db/km fibers (0.85 micron) which is almost equivalent to the loss limit of silica fibers estimated from the characteristics of intrinsic infrared absorption and Rayleigh Scattering losses. It is demonstrated that these fibers possess an excellent radiation hardness and high power throughput capability due to their pure fused silica core. It is concluded that these fibers are perfectly suited for long distance, low bit rate applications (computer, video links) for military, space, and nuclear environment, as well as for medicine, instrumentation, and robotics.

Boucher, D.; Wurier, B.; Aldebert, P.; Neuman, V.; Ripoche, P.

265

The influence of the drawing process on the intrinsic stress in optical fibers and the arising possibility to optimize the birefringence of PM fibers  

NASA Astrophysics Data System (ADS)

The properties of optical fibers can significantly be influenced by intrinsic stress. It is well known that these stresses are caused by various reasons, e.g. the variations in the thermal expansion coecient of the differently doped regions in the fiber. The so called thermal stresses are only dependent on the composition of the fiber and not on its preparation history. Another main reason for stress in the final fiber is the mechanical force that is applied during the fiber drawing process. It generates so called mechanical stress that depends on the composition of the fiber and the thermal history of the fiber fabrication process. Using a non-destructive polarimetric system, we are able to measure the intrinsic stress state in optical fibers as well as in their preforms. Knowing on the one hand the thermal induced stresses in the preform of a fiber and on the other hand the final stress state in the fiber itself, we are able to differentiate between the two kinds of stress. In this paper we present results of stress measurements on optical ber preforms and fibers. We show, that the measured stress profile in the preform matches the theoretically assumed stress profile for thermal stress very well. Moreover we used this preform to draw fibers under different drawing conditions represented in a large difference in the applied force during the fiber drawing. We present the stress results for these differently fabricated fibers and show how huge the effect of the drawing tension can be. We find that for high drawing forces, the stress state can be reversed in comparison to the thermal stresses that are induced by the material composition. Due to the fact that stress on the one hand has a strong effect on the mechanical properties of glass and modifies the refractive index, this can lead to signicant effects on the fiber stability and modal behaviour. Finally, we present a way to compensate the additionally induced mechanical stress, which is for example a very good possibility to increase the stress birefringence in polarization maintaining (PM) fibers with panda structure. We compare the mechanical stress states of such Panda Fibers after their fabrication with the state after an additional high temperature step. We clearly find that it is possible to improve the birefringence of these fibers using appropriate preparation steps.

Just, Florian; Jäger, Matthias; Bartelt, Hartmut

2012-04-01

266

Fabrication of a graded-index polymer optical fiber preform without a cavity by inclusion of an additional monomer under a centrifugal force field  

Microsoft Academic Search

When two or more monomers with different densities and refractive indices are polymerized under a centrifugal force field, a radially varying refractive index is generated owing to the difference in density of the monomers. After the polymerization is completed, a cavity is generated about the rotational axis as a result of inherent volume shrinkage during bulk radical polymerization. Therefore it

Sang Hyuk Im; Duck Jong Suh; Hansol Cho; Jin Sung Choi; Jae Keun Park; Jin Taek Hwang

2002-01-01

267

Polarimetric optical fiber refractometer.  

PubMed

An optical fiber refractometer based on a photometric return-path birefringence sensor is proposed. For measuring the refractive index, the phase shift between polarization components on total internal reflection inside a refractometric prism is used. Several kinds of refractometric prism are described. It is shown that a refractive-index sensitivity of 0.0001 and higher for a wide range of index values is attainable. PMID:18357282

Shribak, M

2001-06-01

268

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

269

High-power tandem pumped fiber amplifier with an output power of 2.9 kW.  

PubMed

We report on a high power fiber amplifier tandem pumped by an industrial style thin-disk laser. An output power of 1 kW and a very good slope efficiency of 73% have been obtained for a state-of-the-art photonic crystal fiber originally designed for short-pulse amplification. We also compare this result to an experiment, where a power of 2.9 kW could be obtained from a step-index large-mode-area fiber with the same slope efficiency. PMID:21847160

Wirth, Christian; Schmidt, Oliver; Kliner, Andrea; Schreiber, Thomas; Eberhardt, Ramona; Tünnermann, Andreas

2011-08-15

270

All-fiber Bessel beam generator based on M-type optical fiber  

NASA Astrophysics Data System (ADS)

We propose and demonstrate an all-fiber Bessel beam generator based on M-type optical fiber and graded-index optical fiber. We show that the output optical beam from the graded-index optical fiber end-face is a Bessel-like beam, which is generated by Fourier transform of a ring light that is generated by M-type optical fiber using graded-index optical fiber lens. We also study wave propagation in this generator using beam propagation method. The simulated results show that the output beam from this generator is rather like an ideal Bessel-Gaussian beam.

Deng, Hongchang; Yuan, Libo

2013-09-01

271

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

272

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

273

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

274

Three-hole microstructured optical fiber for efficient Fiber Bragg Grating refractometer  

E-print Network

the refractive index sensitivity of a standard Fiber Bragg Grating (FBG) sensor photowritten in the suspended Ge1 Three-hole microstructured optical fiber for efficient Fiber Bragg Grating refractometer Minh Ch) as sensing platform [4,5]. In a previous study, we had photowritten fiber Bragg gratings in a six

Paris-Sud XI, Université de

275

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

276

The optimal fiber volume fraction and fiber-matrix property compatibility in fiber reinforced composites  

NASA Technical Reports Server (NTRS)

Although the question of minimum or critical fiber volume fraction beyond which a composite can then be strengthened due to addition of fibers has been dealt with by several investigators for both continuous and short fiber composites, a study of maximum or optimal fiber volume fraction at which the composite reaches its highest strength has not been reported yet. The present analysis has investigated this issue for short fiber case based on the well-known shear lag (the elastic stress transfer) theory as the first step. Using the relationships obtained, the minimum spacing between fibers is determined upon which the maximum fiber volume fraction can be calculated, depending on the fiber packing forms within the composites. The effects on the value of this maximum fiber volume fraction due to such factors as fiber and matrix properties, fiber aspect ratio and fiber packing forms are discussed. Furthermore, combined with the previous analysis on the minimum fiber volume fraction, this maximum fiber volume fraction can be used to examine the property compatibility of fiber and matrix in forming a composite. This is deemed to be useful for composite design. Finally some examples are provided to illustrate the results.

Pan, Ning

1992-01-01

277

Band-rejection fiber filter and fiber sensor based on a Bragg fiber of transversal resonant structure.  

PubMed

We propose a novel band-rejection fiber filter based on a Bragg fiber of transversal resonant structure, which can also be used as a fiber sensor. Defect layers are introduced in the periodic high/low index structure in the cladding of the Bragg fiber. Coupling between the core mode and the defect mode results in large confinement loss for some resonant wavelengths inside the band gap of the Bragg fiber. A segment of the Bragg fiber of transversal resonant structure can be used as a band-rejection fiber filter, whose characteristics are mainly determined by the defect layer. The loss peak wavelength of the Bragg fiber is dependent on the refractive index and the thickness of the defect layer which indicates its applications of refractive index and strain sensing. PMID:18852756

Chen, Daru; Yang, Tzong-Jer; Wu, Jin-Jei; Shen, Linfang; Liao, Kun-Lin; He, Sailing

2008-10-13

278

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

279

Fiber lasers: materials, structures and technologies  

NASA Astrophysics Data System (ADS)

Rare earth doped silica based fiber lasers and amplifiers have been shown to be suitable for a variety of applications in industry, science and medicine. They can yield very high power output both in the pulsed and cw regime with high efficiency, reliability and beam quality. Great progress was possible by new design concepts as non-symmetric double clads and large mode area guiding structures and by carefully tailoring the material properties. Extreme power load and complicated fiber structures make high demands on the preparation technology. Special aspects of material and technology development will be discussed in the following. Basic requirement for a successful production of defined fiber core compositions is the knowledge of the incorporation mechanism of the rare earths into the high silica matrix. Diffusion processes during the preparation steps determine refractive index distribution, geometry and numerical aperture. Strong concentration dependences of codopants and the interaction between codopants and active components must be taken into account. The optical properties of rare earths ions can be tailored by defined codopant relations according to the intended application. Some unusual basic loss contributions of certain rare earths have to be considered and controlled in order to get high laser performance. Loss effects by UV radiation play a role if UV cured coatings are used or if the fibers are provided with Bragg gratings as laser mirrors.

Kirchhof, Johannes; Unger, Sonja; Schwuchow, Anka

2003-07-01

280

Advanced components for multi-kW fiber lasers  

NASA Astrophysics Data System (ADS)

We report on the development and performance of a key components that enable the construction of multi-kW fiber amplifiers for government and industrial applications that are both reliable and highly affordable. The usefulness of these components span the range from single frequency near diffraction limited kW class fiber lasers to multimode wide linewidth fiber lasers for welding and cutting applications. The key components for these amplifiers are 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 20/440 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 500 ?m 0.55 NA core of the PCF fiber with a measured pump combining efficiency of 92% with zero 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 90% while maintaining polarization with a measured PER of 20 dB. We report the signal coupling efficiency and power handling capability as well.

Sipes, Donald L., Jr.; Tafoya, Jason D.; Schulz, Daniel S.; Ward, Benjamin G.; Carlson, Chad G.

2012-02-01

281

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

PubMed Central

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

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

2011-01-01

282

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

283

Low scattering loss fiber with segmented-core and depressed inner cladding structure  

NASA Astrophysics Data System (ADS)

In this paper, using the FEM method new low-loss fiber is proposed to minimize Rayleigh scattering with a segmented-core and depressed inner-cladding. The optical loss of the designed fiber is calculated based on Rayleigh scattering losses. Rayleigh scattering loss (RSL) has been estimated by Rayleigh scattering coefficient (RSC) and power distribution in the fiber. We have shown loss of less than 0.3 dB/km at 1310 nm, 0.18 dB/km at 1550 nm for step-index fibers which consist of conventional glass compositions such as SiO2, GeO2-SiO2, F-SiO2 while satisfying all of ITU-G.652.D attributes.

Pournoury, Marzieh; Moon, Dae Seung; Nazari, Tavakol; Kassani, Sahar Hosseinzadeh; Do, Mun-Hyun; Lee, Yeong Seop; Oh, Kyunghwan

2014-04-01

284

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

NASA Astrophysics Data System (ADS)

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

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

2010-06-01

285

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

286

Optical fibers for communication.  

PubMed

The transparency of glass fibers in the visible and near infrared-improved beyond all expectations by recent breakthroughs-seems now sufficient to transmit optical signals unprocessed over miles. No wonder that efforts have intensified all over the world to utilize fibers in future communication systems. Materials research and fabrication are the fields where present progress is most rapid. New ways of preform preparation by deposition, doping, or diffusion are being studied and found to offer improvements and versatility. As far as materials are concerned, fused silica has shown the lowest bulk losses and hence receives the most interest, but many glasses are being studied as well. As new processes become available and record lows in fiber loss are being reached, propagation theory is finding new challenges as well. On the one hand, multimode fibers seem desirable with respect to transmitter compatibility, splicing, and fabrication tolerances. On the other hand, the signal distortion caused by mode delay differences in multimode fibers can be considerable and requires equalization-inherent in the fiber or at the fiber end. Beyond that, the wavelength dependence of the refractive index produces dispersion effects serious enough to be of importance. Thinking ahead, one is confronted with the question of fiber handling, strength, and life. The technology of making cables and splices from a brittle material like glass is in its infancy, and we can only indicate the extent of these difficult problems ahead. PMID:20125968

Gloge, D

1974-02-01

287

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

288

Effects of Accelerated Aging on Fiber Damage Thresholds  

SciTech Connect

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

Setchell, R.E.

1999-02-15

289

Bivariate step processes and random evolutions  

Microsoft Academic Search

A random evolution process constructed from regular step processes with a common state space and indexed on an evolution rule space is shown to be a regular step process on the product space. Conversely, it is shown that under mild conditions, any regular step process on a product space is equivalent to a random evolution process. Conditions are given on

Kyle Siegrist

1984-01-01

290

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

291

End-face preparation methods for high-intensity fiber applications  

SciTech Connect

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

Setchell, R.E.

1997-10-01

292

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

Microsoft Academic Search

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

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

2011-01-01

293

Stepped nozzle  

SciTech Connect

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

294

A New Type of Motor: Pneumatic Step Motor.  

PubMed

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

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

2007-02-01

295

A New Type of Motor: Pneumatic Step Motor  

PubMed Central

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

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

2011-01-01

296

Distributed fiber Bragg grating sensors information fusion and decoupling  

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 grating (FBG) has 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

Xiyuan Chen

2005-01-01

297

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

298

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

299

Nonlinear analysis of nano-cluster doped fiber  

Microsoft Academic Search

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

Gang Liu; Ru Zhang

2007-01-01

300

Immigration Index  

NSDL National Science Digital Library

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

301

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

NASA Astrophysics Data System (ADS)

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

Javahiraly, Nicolas; Chakari, Ayoub

2013-05-01

302

An SMS fiber structure based on chalcogenide multimode fiber  

NASA Astrophysics Data System (ADS)

We theoretically and experimentally investigate a singlemode-multimode-singlemode (SMS) structure based on chalcogenide (As2S3) multimode fiber and conventional silica singlemode fibers. The experimental results show a general agreement with the numerical simulation results based on a wide angle-beam propagation method (WA-BPM). The chalcogenide fiber and silica fibers were mechanically spliced and packaged using a UV cured polymer with a low refractive index on a microscope slide. Multimode interference variation was observed by photo-induced refractive index changes resulting from both a localized laser irradiation at a wavelength of 405 nm and a UV lamp. Our result provides a platform for the development of compact, high-optical-quality, and robust photonic nonlinear devices.

Wang, Pengfei; Brambilla, Gilberto; Ding, Ming; Zhang, Xueliang; Semenova, Yuliya; Wu, Qiang; Farrell, Gerald

2012-06-01

303

Fiber-optic sensors based on fluctuation oscillations of waveguide micro-optomechanical resonance structures  

NASA Astrophysics Data System (ADS)

The characteristics of fiber-optic oscillation frequency sensors of deformation and temperature that employ the thermal fluctuation resonant oscillations in the SMS(M) fiber structures (sensitive elements that represent oscillation systems with distributed parameters based on series-connected single- and multimode step-index fibers) are developed and studied. The measurements of the fluctuation oscillations are based on the amplitude-phase modulation of the optical wave in the multimode oscillating section due to variations in the path-length difference and tunneling of interfering beams. Accuracies of temperature and relative deformation measurements of ±2°C and ±10-5, respectively, are demonstrated. The estimation of the ultimate measurement sensitivity of the resonance frequency is based on the approximate calculation of the Allan variance that shows a possibility of the above sensors with temperature and deformation threshold sensitivities of 0.001°C and 10-8, respectively.

Egorov, F. A.

2013-11-01

304

Observations of fiber orientation in suspensions subjected to planar extensional flows  

Microsoft Academic Search

Fibers in a planar extensional flow tend to align parallel to the axis of extension, with a small orientational dispersion resulting from hydrodynamic, fiber–fiber interactions. We have visualized the orientation of an opaque, tracer fiber in the midst of an index of refraction and density matched fiber suspension in a four-roll mill and determined the mean squares of the components

Mani Rahnama; Donald L. Koch; Claude Cohen

1995-01-01

305

Technology of high-birefringent photonic crystal fibers for sensing applications  

Microsoft Academic Search

Paper described fabrication methods of high birefringence index guided holey fibers made from silica and high silica glasses. Several kinds of high birefringence holey fibers are described in the point of view their fabrication technology and basic characterization. There are: triple defect fiber with shape induced birefringence, two kinds of fibers with filling factor asymmetry induced birefringence, fibers with filling

Jan Wójcik; Pawel Mergo; Krzysztof Skorupski; Krzysztof Poturaj; Waclaw Urbanczyk; Marcin Szpulak; Tadeusz Martynkien; Hugo Thienpont; Tomasz Nasilowski; Francis Berghmans

2006-01-01

306

Fiber refractometer based on a fiber Bragg grating and single-mode-multimode-single-mode fiber structure.  

PubMed

A refractive index (RI) sensor based on a novel fiber structure that consists of a single-mode-multimode-single-mode (SMS) fiber structure followed by a fiber Bragg grating was demonstrated. The multimode fiber in the SMS structure excites cladding modes within output single-mode fiber (SMF) and recouple the reflected cladding Bragg wavelength to the input SMF core. By measuring the relative Bragg wavelength shift between core and cladding Bragg wavelengths, the RI can be determined. Experimentally we have achieved a maximum sensitivity of 7.33 nm/RIU (RI unit) at RI range from 1.324 to 1.439. PMID:21685965

Wu, Qiang; Semenova, Yuliya; Yan, Binbin; Ma, Youqiao; Wang, Pengfei; Yu, Chongxiu; Farrell, Gerald

2011-06-15

307

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

308

Physiologically responsive, mechanically adaptive polymer optical fibers for optogenetics.  

PubMed

The capability to deliver light to specific locations within the brain using optogenetic tools has opened up new possibilities in the field of neural interfacing. In this context, optical fibers are commonly inserted into the brain to activate or mute neurons using photosensitive proteins. While chronic optogenetic stimulation studies are just beginning to emerge, knowledge gathered in connection with electrophysiological implants suggests that the mechanical mismatch of conventional optical fibers and the cortical tissue may be a significant contributor to neuroinflammatory response. Here, we present the design and fabrication of physiologically responsive, mechanically adaptive optical fibers made of poly(vinyl alcohol) (PVA) that may mitigate this problem. Produced by a one-step wet-spinning process, the fibers display a tensile storage modulus E' of ?7000??MPa in the dry state at 25°C and can thus readily be inserted into cortical tissue. Exposure to water causes a drastic reduction of E' to ?35??MPa on account of modest swelling with the water. The optical properties at 470 and 590 were comparable with losses of 0.7±0.04??dB/cm at 470 nm and 0.6±0.1??dB/cm at 590 nm in the dry state and 1.1±0.1??dB/cm at 470 nm and 0.9±0.3??dB/cm at 590 nm in the wet state. The dry end of a partially switched fiber with a length of 10 cm was coupled with a light-emitting diode with an output of 10.1 mW to deliver light with a power density of >500??mW/cm2 from the wet end, which is more than sufficient to stimulate neurons in vivo. Thus, even without a low-refractive index cladding, the physiologically responsive, mechanically adaptive optical fibers presented here appear to be a very useful new tool for future optogenetic studies. PMID:24978225

Jorfi, Mehdi; Voirin, Guy; Foster, E Johan; Weder, Christoph

2014-05-15

309

Microstructured fibers for sensing applications  

NASA Astrophysics Data System (ADS)

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

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

2005-11-01

310

Design and fabrication of an asymmetric twin-core fiber directional coupler for gain-flattened EDFA  

NASA Astrophysics Data System (ADS)

Fiber directional couplers made of highly asymmetric twin-cores (ATC), one of which is doped with erbium, are designed to achieve an inherently gain flattened erbium doped fiber amplifier (EDFA). The refractive index profiles of the fibers as well as the spacing between the two cores were carefully designed to achieve a targeted gain with low gain excursions across the C-band. One of the designs yielded a theoretical median gain ~ 38 dB with an excursion within +/-1 dB. In order to suite fabrication of such an inherently gain flattened EDFA by the MCVD fiber preform fabrication process, the design had to be modified and a more modest target of about 20 dB was set with excursion below +/- 1.5 dB for metro-centric applications. It involved preparation of two independent preforms, which required selective polishing of the cladding from one side by a certain amount to meet the required nominal separation between the two cores set at the design stage of the fiber. Several intricate operations were required to implement the fiber drawing step from the two assembled preforms. Preliminary characterization of the fabricated fiber shows filtering of ASE peak through selective wavelength coupling from Er-doped core to un-doped core.

Nagaraju, B.; Ude, M.; Trzésien, S.; Dussardier, B.; Varshney, R. K.; Monnom, G.; Blanc, W.; Pal, B. P.

2011-12-01

311

THz porous fibers: design, fabrication and experimental characterization.  

PubMed

Porous fibers have been identified as a means of achieving low losses, low dispersion and high birefringence among THz polymer fibers. By exploiting optical fiber fabrication techniques, two types of THz polymer porous fibers--spider-web and rectangular porous fibers--with 57% and 65% porosity have been fabricated. The effective refractive index measured by terahertz time domain spectroscopy shows a good agreement between the theoretical and experimental results indicating a lower dispersion for THz porous fiber compared to THz microwires. A birefringence of 0.012 at 0.65 THz is also reported for rectangular porous fiber. PMID:19654813

Atakaramians, Shaghik; Afshar V, Shahraam; Ebendorff-Heidepriem, Heike; Nagel, Michael; Fischer, Bernd M; Abbott, Derek; Monro, Tanya M

2009-08-01

312

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

313

Regeneration of fiber Bragg gratings under strain.  

PubMed

The effect of strain on both the index modulation, ?n(mod), and average index, ?n, during grating regeneration within two types of fibers is studied. Significant tunability of the Bragg wavelength (?(B)>48 nm) is observed during postannealing at or above the strain temperature of the glass. The main reason for the grating wavelength shift during annealing with load is the elongation of the fiber. As well, the observed Moiré interference cycling through regeneration indicates the presence of two gratings. PMID:23545963

Wang, Tao; Shao, Li-Yang; Canning, John; Cook, Kevin

2013-04-01

314

"Photonic lantern" spectral filters in multi-core Fiber.  

PubMed

Fiber Bragg gratings are written across all 120 single-mode cores of a multi-core optical Fiber. The Fiber is interfaced to multimode ports by tapering it within a depressed-index glass jacket. The result is a compact multimode "photonic lantern" filter with astrophotonic applications. The tapered structure is also an effective mode scrambler. PMID:22714465

Birks, T A; Mangan, B J; Díez, A; Cruz, J L; Murphy, D F

2012-06-18

315

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

PubMed Central

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

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

2014-01-01

316

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

PubMed

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

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

2012-09-10

317

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

318

Dual-twist fiber long period gratings  

NASA Astrophysics Data System (ADS)

Long period fiber gratings couple core and co-propagating cladding modes to produce dips in the transmission spectrum and have been widely utilized as sensors and filters. We have recently developed a new approach to long period fiber gratings utilizing optical fibers, which are uniformly twisted at elevated temperatures to produce double or single helices. Because these fibers are not manufactured by exposing photosensitive glass to patterned UV illumination, as is the case for traditional fiber Bragg gratings (FBGs) or long period gratings (LPGs), they are more robust in harsh thermal and chemical environments. Double helix fibers are polarization sensitive and are fabricated by twisting fiber preforms with high-index noncircular cores while single helix gratings are polarization insensitive and are created by twisting standard optical fibers with cores that are not perfectly centered. Here, we present a new approach to single-helix chiral long-period gratings (CLPGs). The CLPG is created in a glassforming process in which two optical fibers are twisted together to form a helix in the signal fiber as the fibers pass through a miniature oven. "Dual-twist" CLPGs may be fabricated from any conventional or specialty fiber and provide reproducible spectra that may be tailored to specific applications.

Churikov, Victor M.; Kopp, Victor I.; Genack, A. Z.

2009-02-01

319

Magneto-optical fiber sensor based on bandgap effect of photonic crystal fiber infiltrated with magnetic fluid  

NASA Astrophysics Data System (ADS)

A magnetic field sensor based on combination of the magnetic fluid and the tunable photonic bandgap effect of photonic crystal fiber is proposed. The magnetic fluid with higher refractive index (>1.45) is prepared and filled into the air-holes of photonic crystal fiber to convert the index guiding fiber into photonic bandgap fiber. The proposed sensor takes full advantage of the ultrahigh sensitivity characteristic of photonic bandgap fiber and achieves a high sensitivity and resolution of 1.56 nm/Oe and 0.0064 Oe, respectively, which are 2-3 orders of magnitude better than other sensors based on magnetic fluid.

Zu, Peng; Chiu Chan, Chi; Gong, Tianxun; Jin, Yongxing; Chang Wong, Wei; Dong, Xinyong

2012-12-01

320

Programmable optic-fiber delay line  

E-print Network

& is the group refractive index of the fiber mode). In the illustration of Fig. 1(a), there are four 4-port switches and four delay lines, whose lengths are Lp, 2Lp, 4Lp and BLp respectively. By appropriately adjusting these 4 switches, we can get 16 different...B per switch). In Figure 2 is illustrated a design for an all-fiber switch made with two 50:50 single-mode directional couplers which form a Mach-Zender interferometer. A heater is provided for one of the two fiber arms to change the refractive index...

Fang, Shin-Puu

2012-06-07

321

Photosensitive indium-doped germano-silica fiber for strong FBGs with high temperature sustainability  

Microsoft Academic Search

A highly photosensitive indium-doped germano-silicate fiber (In-Ge fiber) has been developed for fiber Bragg grating (FBG) fabrication. Tests carried out on the photosensitivity of the fiber have shown that the grating written into this fiber may show a high refractive index modulation, of 3.2×10-4. Annealing experiments of the FBGs written into this fiber have shown that the FBGs can survive

Yonghang Shen; Jie Xia; Tong Sun; Kenneth T. V. Grattan

2004-01-01

322

Etched-Core Fiber Bragg Grating Sensors Integrated With Microfluidic Channels  

Microsoft Academic Search

In this paper, we demonstrate a fiber Bragg grating sensor for bio-chemical detection. In the sensor area, the fiber has been chemically etched to the core with a diameter of 7 $\\\\mu$ m. Due to increased index contrast, the etched-core fiber Bragg grating supports multiple guided modes which respond differently to the refractive index of the surrounding medium, temperature and

Sang-Mae Lee; Myung-Yung Jeong; Simarjeet S. Saini

2012-01-01

323

Integrated Optofluidic Multimaterial Fibers  

NASA Astrophysics Data System (ADS)

The creation of integrated microphotonic devices requires a challenging assembly of optically and electrically disparate materials into complex geometries with nanometer-scale precision. These challenges are typically addressed by mature wafer-based fabrication methods, which while versatile, are limited to low-aspect-ratio structures and by the inherent complexity of sequential processing steps. Multimaterial preform-to-fiber drawing methods on the other hand present unique opportunities for realizing optical and optoelectronic devices of extended length. Importantly, these methods allow for monolithic integration of all the constituent device components into complex architectures. My research has focused on addressing the challenges and opportunities associated with microfluidic multimaterial fiber structures and devices. Specifically: (1) A photonic bandgap (PBG) fiber is demonstrated for single mode transmission at 1.55 microm with 4 dB/m losses. This fiber transmits laser pulses with peak powers of 13.5 MW. (Chapter 2) (2) A microfluidic fiber laser, characterized by purely radia l emission is demonstrated. The laser cavity is formed by an axially invariant, 17-period annular PBG structure with a unit cell thickness of 160nm. This laser is distinct from traditional lasers with cylindrically symmetric emission, which rely almost exclusively on whispering gallery modes, characterized by tangential wavevectors. (Chapter 4) (3) An array of independently-controlled liquid-crystal microchannels flanked by viscous conductors is integrated in the fiber cladding and encircles the PBG laser cavity in (2). The interplay between the radially-emitting laser and these liquid-crystal modulators enables controlled directional emission around a full azimuthal angular range. (Chapter 4) (4) The electric potential profile along the length of the electrodes in (3) is characterized and found to depend on frequency. This frequency dependence presents a new means to tune the transversely-directed transmission at a given location along the fiber axis. (Chapter 5) (5) A chemical sensing system is created within a fiber. By integrating a chemiluminescent peroxide-sensing material into the hollow core of a PBG fiber, a limit-of-detection of 300 ppb for peroxide vapors is achieved. (Chapter 3)

Stolyarov, Alexander Mark

324

Index modulation type waveguides written by laser direct writing technology  

NASA Astrophysics Data System (ADS)

In this paper, we describe the cost-effective and simplified fabrication of an index modulation type buried waveguide using laser direct writing. Our studies have a potential of manufacturing waveguides on an uneven surface and a large area because there is no need for photo-mask, etching and development processes. We used organic-inorganic hybrid materials (HYBRIMER) for the fabrication of the waveguides, which have a high transparency from a visible region to an infrared region. We exposed the core layer (HYBRIMER) to a focused laser beam after a one-step spin coating process on a buffer layer. The silicon oxide was used as a buffer layer. The refractive index of the HYBRIMER film is increased by exposure from a laser beam. Therefore, the refractive index of the exposed region is higher than that of the unexposed region, which forms the index modulation type waveguide without an etching process. The fabricated waveguide channels were baked at 120°C during 3hrs for stabilization of the organic and inorganic networks. The laser direct writing apparatus was used to produce the pattern of waveguide channels. This system consists of a He-Cd laser radiating 325nm beam, high-resolution computer-controlled translation stages and a video camera that images the sample onto a monitor. The pattern of the waveguide channel was written using various writing speeds to optimize the writing condition. The core section of optimized waveguides was a rectangular shape and the core dimension was 7?m wide and 8?m high. The refractive index is increased from 1.495 to 1.5 after exposure. The difference of the refractive index between the core and cladding was approximately 0.33%. The insertion loss of the waveguides was measured by cut-back method using a single-mode fiber as an input tip, a multimode fiber (50 ?m GI) as an output tip, and a 1310nm wavelength laser light source. The insertion loss shows a linear relationship with the length of the waveguide. The propagation loss of the buried waveguide was approximately 0.3dB/cm at a wavelength of 1310nm.

Lee, Woo-Jin; Cho, In-Kui; Han, Sang-Pil; Kim, Woo-Soo; Bae, Byeong-Soo; Ahn, Seoung-Ho

2006-09-01

325

Course Selection Step by Step 1. Find the courses you would like to enroll in.  

E-print Network

Course Selection Step by Step 1. Find the courses you would like to enroll in. You can search for courses under http://nol2.aca.ntu.edu.tw/nol/guest/index.php Click on "English" for the English version of the website 2. For Englishtaught courses, click on the "Courses taught in English" section. #12;3. Browse

Wu, Yih-Min

326

Interferometric Fiber Optic Sensors  

PubMed Central

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

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

2012-01-01

327

Optical Fiber Protection  

NASA Technical Reports Server (NTRS)

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

1999-01-01

328

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

329

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

330

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

PubMed

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

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

2014-10-01

331

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

332

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

333

Fiber optic fluid detector  

DOEpatents

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

Angel, S.M.

1987-02-27

334

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

335

Pulsed radiation-induced attenuation in certain optical fibers  

Microsoft Academic Search

Using the X-ray pulse from the HERMES II simulation machine at Sandia National Laboratories, the pulsed radiation-induced attenuation was measured in two optical fibers considered to be 'nonrad-hard': the 50-micron-core, graded-index fiber from Corning and the plastic (PMMA) fiber from the Mitsubishi Rayon Company. These fibers were exposed to radiation up to doses of 19.5 and 28 krad(Si), respectively. In

Jonathan D. Weiss

1992-01-01

336

Pulsed radiation-induced attenuation in certain optical fibers  

Microsoft Academic Search

Using the X-ray pulse from the HERMES II simulation machine at Sandia National Laboratories, the author measured the pulsed radiation-induced attenuation in two optical fibers considered to be `non-rad-hard': the 50 ?m core graded-index fiber from Corning and the plastic (PMMA) fiber from the Mitsubishi Rayon Company. These fibers were exposed to radiation up to doses of 19.5 and 28

J. D. Weiss

1992-01-01

337

Design of the optical fibers for differential mode delay compensation  

NASA Astrophysics Data System (ADS)

We introduce a method for differential mode delay (DMD) compensation by using a special silica GeO2-doped graded-index multimode optical fiber, which provides a reverse reproducing of mode group velocity diagram of the target fiber, and algorithm for design it. Results of proposed method approbation for synthesis of DMD compensation fiber for OM2+/OM3 category target multimode fiber under both central and overfilled launch conditions are represented.

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

2012-01-01

338

Large effective-area fibers  

NASA Astrophysics Data System (ADS)

Refractive-index nonlinearities have negligible effect on the performance of short-haul fiber-optic communication links utilizing electronic repeaters. However, in long optical fiber links, nonlinearities can cause severe signal degradations. To mitigate nonlinear effects, new generation of fibers, referred to as large effective-area fibers, have been introduced in recent years. This paper reviews the latest research and development work on these fibers conducted by several research groups around the world. Attention is focused on a class of large effective-area fibers that are based on a depressed-core multiple-cladding design. Transmission properties, including dispersion, dispersion slope, effective area, mode-field diameter, bending loss, polarization-mode dispersion, and cutoff wavelength are discussed. Dispersion-shifted, non-zero dispersion-shifted, and dispersion-flattened designs are addressed. Design optimization, particularly with regard to effective area, bending loss, and polarization-mode dispersion, is elaborated upon. The trade-off between effective-area and bending loss is emphasized. Results for dispersion-shifted and non-zero dispersion-shifted large effective-area fibers with zero polarization-mode dispersion and low bending loss at 1.55 micrometer wavelength are presented.

Safaai-Jazi, Ahmad; Hattori, H. T.; Baghdadi, J. A.

1999-04-01

339

Page 1 of 1 "Aspheric nonimaging concentrators for multimode fiber coupling"  

E-print Network

coupling from laser-to-fiber and from fiber-to-detector is an important consideration for loss limitedPage 1 of 1 "Aspheric nonimaging concentrators for multimode fiber coupling" Robert P. Dahlgren cavity surface emitting lasers to high bandwidth multimode graded-index optical fiber made from

Miller, Ethan L.

340

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

341

Stepping motor controller  

DOEpatents

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

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

1984-01-01

342

Stepping motor controller  

DOEpatents

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

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

1982-07-02

343

Estimation of ovular fiber production in cotton  

DOEpatents

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

Van't Hof, Jack (Brookhaven, NY)

1998-09-01

344

Estimation of ovular fiber production in cotton  

DOEpatents

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

Van`t Hof, J.

1998-09-01

345

Refractive index profiling-state of the art  

Microsoft Academic Search

Problems associated with different calibration techniques and some instrumental effects that can determine instrumental accuracy are discussed. It is shown how transmission effects can be observed and used to generate a correction curve for refracted near-field instruments. High-quality fiber slices needed for axial interferometry were used to obtain refractive index differences on suitable fibers to ±1% with the measurements traceable

K. W. Raine; J. G. N. Baines; D. E. Putland

1989-01-01

346

Self-Organized Coherence In Fiber Laser Arrays  

Microsoft Academic Search

Self-organized coherence between fiber lasers has been reported both via all-fiber 2x2 directional coupler trees and in spatially multi-core fibers. We have taken this a major step forward, coupling together a number of independent fiber lasers to obtain a spatially and spectrally coherent far field, with no active length, polarization, or amplitude control. The near field output comes from a

M. L. Minden; Hans Bruesselbach; J. L. Rogers; G. J. Dunning; D. L. Hammon; A. J. Solis; L. Vaughan

347

Fiber quality parameters and within-boll yield components of Gossypium arboreum L. putative mutant lines  

E-print Network

mean fiber length (UBM), fiber bundle strength, micronaire, and uniformity index. Lint yield components, using the ontogenetic yield model proposed by Worley et al. included: lint percentage (LP), seeds per boll (S/BOLL), seed cotton per seed (SC...

Naivar, Kevin Scott

2012-06-07

348

Accelerating XPath location steps  

Microsoft Academic Search

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

Torsten Grust

2002-01-01

349

Soft capacitor fibers using conductive polymers for electronic textiles  

NASA Astrophysics Data System (ADS)

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

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

2010-11-01

350

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

NASA Astrophysics Data System (ADS)

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

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

2010-03-01

351

Concentric core optical fiber with multiple-mode signal transmission  

DOEpatents

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

Muhs, J.D.

1997-05-06

352

Concentric core optical fiber with multiple-mode signal transmission  

DOEpatents

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

Muhs, Jeffrey D. (Lenoir City, TN)

1997-01-01

353

Design and fabrication of erbium-doped fibers for optical amplifiers  

NASA Astrophysics Data System (ADS)

Erbium-doped optical fibers are designed using the refractive index difference, fiber core diameter and Er concentration as parameters in the numerical calculations. The fibers are fabricated with modified chemical vapor deposition and solution doping techniques, which are described in detail. Preform and fiber parameters also measured at several laboratories participating in the European Community's COST 217 project are given and compared with the fiber design values. The produced Er fiber is utilized in prototype fiber amplifiers. The differential efficiency of an Al-doped Er fiber is measured to be 77%.

Kiiveri, Pauli; Tammela, Simo K.

2000-07-01

354

Acta Clinica Croatica: progress of a journal step by step.  

PubMed

The journal Acta Clinica Croatica (ACC) was founded in 1962 under the title Anali Bolnice Dr. M. Stojanovi?. In 1995, the title of the journal was changed into its present form and ever since all papers have been published in English. In 2000, the electronic (online) edition of the ACC was released in addition to the print version. The paper presents development of the journal from 1962 to 2012 based on the analysis of the following SCOPUS citation index parameters: type and number of documents published in the journal; number of citations; and number of domestic and foreign authors. The studied period was analyzed in three time segments: the period from 1995 to 1999, the period from 2000 to 2006 and the period from 2007 to 2012. The same parameters were analyzed in the Web of Science/SCI-Expanded bibliographic and citation index for the 2007-2012 period. The increasing number of documents, authors (both domestic and foreign) and citations demonstrates gradual rise in the quality, visibility and impact of the journal. The fifty years of experience show that a goal, at first very distant and almost unachievable, may be reached by progressing step by step. PMID:24974665

Ramljak, Gordana

2014-03-01

355

Lightning Leader Stepping  

NASA Astrophysics Data System (ADS)

Recent measurements may help explain the uneven propagation, or stepping, of lightning leaders. Measurements of the electric vector vs. time near a negative lightning leader show that each step forward is accompanied by a wave that moves backward along the ionized channel. This backward-moving wave---which could be called a "step recoil wave"--- rapidly transfers charge and energy from the existing ionized channel to the channel segment created by the new step. The transfer of charge and energy from the existing channel into the new step implies a reduction of the channel potential energy. The potential energy of the new step is further reduced as it produces excited molecules and ion-electron pairs. Eventually the new step stops. A current from the original source of charge for the leader increases the potential energy of the channel until another step is initiated.

Winn, W. P.

2010-12-01

356

Solving Single Step Equations  

NSDL National Science Digital Library

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

Reddish, Ms.

2011-09-30

357

A Step Circuit Program.  

ERIC Educational Resources Information Center

Aerobics instructors can use step aerobics to motivate students. One creative method is to add the step to the circuit workout. By incorporating the step, aerobic instructors can accommodate various fitness levels. The article explains necessary equipment and procedures, describing sample stations for cardiorespiratory fitness, muscular strength,…

Herman, Susan

1995-01-01

358

Three-hole microstructured optical fiber for efficient fiber Bragg grating refractometer.  

PubMed

We present a photosensitive three-hole microstructured optical fiber specifically designed to improve the refractive index sensitivity of a standard fiber Bragg grating (FBG) sensor photowritten in the suspended Ge-doped silica core. We describe the specific photowriting procedure used to realize gratings in such a fiber. We then determine their spectral sensitivity to the refractive index changes of material filling the holes surrounding the core. The sensitivity is compared with that of standard FBGs photowritten in a six-hole fiber with a larger core diameter. We demonstrate an improvement in the sensitivity by two orders of magnitude and reach a resolution of 3 x 10(-5) and 6 x 10(-6) around mean refractive index values of 1.33 and 1.40, respectively. PMID:17700795

Phan Huy, Minh Châu; Laffont, Guillaume; Dewynter, Véronique; Ferdinand, Pierre; Roy, Philippe; Auguste, Jean-Louis; Pagnoux, Dominique; Blanc, Wilfried; Dussardier, Bernard

2007-08-15

359

Longitudinal strain sensing with photonic crystal fibers and fiber Bragg gratings  

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

360

Photovoltaic fibers  

NASA Astrophysics Data System (ADS)

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

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

2006-08-01

361

STEP: A Futurevision, Today  

NASA Technical Reports Server (NTRS)

STEP (STandard for the Exchange of Product Model Data) is an innovative software tool that allows the exchange of data between different programming systems to occur and helps speed up the designing in various process industries. This exchange occurs easily between those companies that have STEP, and many industries and government agencies are requiring that their vendors utilize STEP in their computer aided design projects, such as in the areas of mechanical, aeronautical, and electrical engineering. STEP allows the process of concurrent engineering to occur and increases the quality of the design product. One example of the STEP program is the Boeing 777, the first paperless airplane.

1994-01-01

362

Fibrillogenesis in Continuously Spun Synthetic Collagen Fiber  

PubMed Central

The universal structural role of collagen fiber networks has motivated the development of collagen gels, films, coatings, injectables, and other formulations. However, reported synthetic collagen fiber fabrication schemes have either culminated in short, discontinuous fiber segments at unsuitably low production rates, or have incompletely replicated the internal fibrillar structure that dictates fiber mechanical and biological properties. We report a continuous extrusion system with an off-line phosphate buffer incubation step for the manufacture of synthetic collagen fiber. Fiber with a cross-section of 53±14 by 21±3 µm and an ultimate tensile strength of 94±19 MPa was continuously produced at 60 m/hr from an ultrafiltered monomeric collagen solution. The effect of collagen solution concentration, flow rate, and spinneret size on fiber size was investigated. The fiber was further characterized by microdifferential scanning calorimetry, transmission electron microscopy (TEM), second harmonic generation (SHG) analysis, and in a subcutaneous murine implant model. Calorimetry demonstrated stabilization of the collagen triple helical structure, while TEM and SHG revealed a dense, axially aligned D-periodic fibril structure throughout the fiber cross-section. Implantation of glutaraldehyde crosslinked and non-crosslinked fiber in the subcutaneous tissue of mice demonstrated limited inflammatory response and biodegradation after a 6-week implant period. PMID:20024969

Caves, Jeffrey M.; Kumar, Vivek A.; Wen, Jing; Cui, Wanxing; Martinez, Adam; Apkarian, Robert; Coats, Julie E.; Berland, Keith; Chaikof, Elliot L.

2013-01-01

363

1804 JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 31, NO. 11, JUNE 1, 2013 Slow-Light Fiber-Bragg-Grating Strain Sensor  

E-print Network

, and Michel J. F. Digonnet Abstract--We report a fiber strain sensor based on a single fiber Bragg grating Society of America Index Terms--Fiber Bragg gratings, fiber optics sensors. I. INTRODUCTION STRAIN sensors1804 JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 31, NO. 11, JUNE 1, 2013 Slow-Light Fiber-Bragg-Grating

Fan, Shanhui

364

Multi-trench Fiber for high power laser applications Deepak Jain*, Timothy C. May-Smith, and Jayanta K. Sahu  

E-print Network

+ and Al3+ doped preform. (b) Measured slope efficiency of the fabricated fiber. Inset image shows index profile design in Fig. 1. [3]. This fiber design offers advantages of relatively easy fabrication of the proposed optical fiber. Fig. 2 Shows the refractive index profile of the fabricated MTF. Inset shows

Sóbester, András

365

Photonic lantern with cladding-removable fibers  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

366

Exposed-core chalcogenide microstructured optical fibers for chemical sensing  

NASA Astrophysics Data System (ADS)

Chemical bonds of most of the molecules vibrate at a frequency corresponding to the near or mid infrared field. It is thus of a great interest to develop sensitive and portable devices for the detection of specific chemicals and biomolecules for various applications in health, the environment, national security and so on. Optical fibers define practical sensing tools. Chalcogenide glasses are known for their transparency in the infrared optical range and their ability to be drawn as fibers. They are consequently good candidates to be used in biological/chemical sensing. For that matter, in the past decade, chalcogenide glass fibers have been successfully implemented in evanescent wave spectroscopy experiments, for the detection of bio-chemical species in various fields of applications including microbiology and medicine, water pollution and CO2 detection. Different types of fiber can be used: single index fibers or microstructured fibers. Besides, in recent years a new configuration of microstructured fibers has been developed: microstructured exposed-core fibers. This design consists of an optical fiber with a suspended micron-scale core that is partially exposed to the external environment. This configuration has been chosen to elaborate, using the molding method, a chalcogenide fiber for chemical species detection. The sensitivity of this fiber to detect molecules such as propan-2-ol and acetone has been compared with those of single index fibers. Although evanescent wave absorption is inversely proportional to the fiber diameter, the result shows that an exposed-core fiber is much more sensitive than a single index fiber having a twice smaller external diameter.

Troles, Johann; Toupin, Perrine; Brilland, Laurent; Boussard-Plédel, Catherine; Bureau, Bruno; Cui, Shuo; Mechin, David; Adam, Jean-Luc

2013-05-01

367

Fabrication of annular waveguide layer capillary optical fiber preform and temperature field distribution during fiber draw  

NASA Astrophysics Data System (ADS)

In this paper, we demonstrate a novel kind of annular waveguide layer capillary optical fiber perform which is composed of cladding, optical waveguide layer and central air hole. On the other hand, we fabricate a capillary optical fiber with an MCVD method using an advanced graphite furnace to heat and a specially made fiber drawing tower. The cross-section drawings of the optical fiber and the refractive index distribution are shown. Accordingly, we give cross section of capillary optical fiber and refractive index distribution profile. Moreover, by combining non-stable Fourier Heat-Conduction theory with fiber drawing technology, the simplified temperature field transmission model during capillary optical fiber preform drawing is established, and the temperature field distribution equation of the perform neck-down region is deduced. Meanwhile, we obtain the relationship between the temperature distribution of the neck-down region and the speed of preform feed and the furnace temperature through the numerical simulation. The conclusion shows that the high-qualified annular waveguide layer capillary optical fiber can be gotten when the temperature field distribution of the capillary optical fiber perform neck-down region is near to steady state, which well agrees with the experiment result.

Zhang, Minghui; Zhang, Tao; Liu, Guanyu; Fan, Zhaoceng

2011-11-01

368

Adaptive Indexing in Modern Database Kernels  

E-print Network

Physical design represents one of the hardest problems for database management systems. Without proper tuning, systems cannot achieve good performance. Offline indexing creates indexes a priori assuming good workload knowledge and idle time. More recently, online indexing monitors the workload trends and creates or drops indexes online. Adaptive indexing takes another step towards completely automating the tuning process of a database system, by enabling incremental and partial online indexing. The main idea is that physical design changes continuously, adaptively, partially, incrementally and on demand while processing queries as part of the execution operators. As such it brings a plethora of opportunities for rethinking and improving every single corner of database system design. We will analyze the indexing space between offline, online and adaptive indexing through several state of the art indexing techniques, e.g., what-if analysis and soft indexes. We will discuss in detail adaptive indexing techniques such as database cracking, adaptive merging, sideways cracking and various hybrids that try to balance the online tuning overhead with the convergence speed to optimal performance. In addition, we will discuss how various aspects of modern techniques for database architectures, such as vectorization, bulk processing, column-store execution and storage affect adaptive indexing. Finally, we will discuss several open research topics towards fully automomous database kernels. 1.

Stratos Idreos; Stefan Manegold; Goetz Graefe

369

Dietary Carbohydrates, Fiber, and Breast Cancer Risk  

Microsoft Academic Search

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

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

2004-01-01

370

Optimization of laser fibers for high pump light absorption  

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

371

The SAFOD Optical Fiber Strainmeter  

NASA Astrophysics Data System (ADS)

As part of the SAFOD project, we developed and deployed a unique optical fiber strainmeter. The instrument consists of a single mode optical fiber under tension attached to the outside of the inner well casing and extending in a loop to a depth of 782 meters. An optical interferometer tracks minute length changes in the fiber caused by vertical strain in the Earth. The sensor detects both teleseismic earthquakes and local events, along with coseismic strain steps consistent with theoretical dislocation models. For teleseismic events, we investigated the possibility of determining local Rayleigh-wave phase velocities beneath the borehole by comparing the ratio of vertical ground acceleration from a nearby seismometer to vertical strain. While similar studies have used horizontal components and rotations, this is the first such attempt utilizing vertical measurements. We show that at periods from around 16-40 seconds, we can recover general dispersion characteristics that are within a few percent of models of realistic local structure.

Zumberge, M. A.; Blum, J. A.

2010-12-01

372

Soft capacitor fibers using conductive polymers for electronic textiles  

E-print Network

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

Gu, Jian Feng; Skorobogatiy, Maksim

2010-01-01

373

Nonadiabatic tapered optical fiber for biosensor applications  

NASA Astrophysics Data System (ADS)

A brief review on biconical tapered fiber sensors for biosensing applications is presented. A variety of configurations and formats of this sensor have been devised for label free biosensing based on measuring small refractive index changes. The biconical nonadiabatic tapered optical fiber offers a number of favorable properties for optical sensing, which have been exploited in several biosensing applications, including cell, protein, and DNA sensors. The types of these sensors present a low-cost fiber biosensor featuring a miniature sensing probe, label-free direct detection, and high sensitivity.

Latifi, Hamid; Zibaii, Mohammad I.; Hosseini, Seyed M.; Jorge, Pedro

2012-12-01

374

External reflection from omnidirectional dielectric mirror fibers.  

PubMed

We report the design and fabrication of a multilayered macroscopic fiber preform and the subsequent drawing and optical characterization of extended lengths of omnidirectional dielectric mirror fibers with submicrometer layer thickness. A pair of glassy materials with substantially different indices of refraction, but with similar thermomechanical properties, was used to construct 21 layers of alternating refractive index surrounding a tough polymer core. Large directional photonic band gaps and high reflection efficiencies comparable to those of the best metallic reflectors were obtained. Potential applications of these fibers include woven fabrics for radiation barriers, spectral authentication of cloth, and filters for telecommunications. PMID:11964473

Hart, Shandon D; Maskaly, Garry R; Temelkuran, Burak; Prideaux, Peter H; Joannopoulos, John D; Fink, Yoel

2002-04-19

375

Fiber type, meal frequency and colonic cytokinetics  

E-print Network

of resected colon or rectal cancer were provided with wheat bran fiber (13. 5g/day for 8 weeks after 2 g/day for 1 month). Six out of the eight patients who initially had high labeling indexes in the rectal mucosa biopsy specimens showed a significant... of resected colon or rectal cancer were provided with wheat bran fiber (13. 5g/day for 8 weeks after 2 g/day for 1 month). Six out of the eight patients who initially had high labeling indexes in the rectal mucosa biopsy specimens showed a significant...

Zhang, Jianhu

2012-06-07

376

Optimization of fiber shapes in biocomposites  

NASA Astrophysics Data System (ADS)

Fibers can be used to improve the mechanical properties of acrylic bone cement. However, debonding of the fibers from the matrix due to the poor fiber/matrix interface is a major failure mechanism for such reinforcements. Optimization of the fiber shape can improve load transfer between the fibers and the matrix, thereby providing improved overall mechanical performance. The goals of this study include: (1) Develop an analytical model to evaluate the effects of fiber end geometry on the pullout load and stress distribution; (2) Determine the optimal fiber morphology for maximum stress transfer in composites using optimization and finite element modeling; (3) Fabricate the fibers with optimal morphology determined by the previous step; (4) Manufacture composites reinforced with the optimized fibers and demonstrate improved mechanical properties experimentally. Analytical solutions were derived to predict the effects of the enlarged end shape on the pullout load and stress distribution. It is shown that the shape of the enlarged end has a significant influence on the stress distribution of the short fiber. A procedure for structural shape optimization of short fibers was developed. The effects of the interfacial bond and fiber orientation were investigated to obtain the optimal fiber shape. The general optimal fiber shape is a variable diameter fiber (VDF). Due to the mechanical interlock, the VDF can both bridge matrix cracks effectively and improve the composite mechanical properties. Ceramic VDFs were successfully fabricated. Static and fatigue tests were carried out on the VDF reinforced composites. Conventional straight fiber (CSF) reinforced bone cement was also tested for comparison purposes. Results demonstrated that both the stiffness and the fatigue life of VDF reinforced bone cement are significantly improved compared with the unreinforced cement. Also, the fatigue life of VDF reinforced bone cement was significantly longer than that of CSF reinforced cement. This study shows the feasibility of a novel fiber (VDFs) technology for reinforced polymers. This fiber family significantly improves the fatigue life of bone cement at a very high level of reliability. VDFs could potentially avoid implant loosening due to the mantle fracture of bone cement and delay the need for revision surgery.

Zhou, Yan

377

Environmental stability of intercalated graphite fibers  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

378

Detecting Stepping Stones  

Microsoft Academic Search

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

Vern Paxson

379

Image transport using Anderson localized modes in disordered optical fibers  

NASA Astrophysics Data System (ADS)

An optical fiber with a transversely disordered yet longitudinally invariant refractive index profile can propagate a beam of light using transverse Anderson localization. A launched beam of light into the disordered optical fiber expands till it reaches its localization radius beyond which it propagates without further expansion. In contrast to a conventional single-core optical fiber in which a propagating beam of light can only couple to and propagate in the core, the beam of light can be coupled to any point at the tip of the disordered fiber. This property originated from the localized highly multimodal property of disordered optical fibers that can be used for high quality optical image transport. We experimentally compare the quality of the transported images in the disordered polymer optical fibers with those transported through the multicore imaging fibers, as well as conventional single core fibers. The impacts of source wavelength and refractive index difference between the disordered sites on the quality of the transported images in the disordered optical fibers is studied numerically. The role of randomness in improving the quality of transported images is investigated by comparing the full vectorial modes of a disordered fiber with those in a periodic multicore fiber.

Karbasi, Salman; Frazier, Ryan J.; Koch, Karl W.; Hawkins, Thomas; Ballato, John; Mafi, Arash

2014-03-01

380

Carbon fiber manufacturing via plasma technology  

DOEpatents

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

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

2002-01-01

381

Plane Wave: Step Scattering  

NSDL National Science Digital Library

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

Palop, Jose I.

2010-12-13

382

Investigations on mechanical properties of poly(propylene) and poly(lactic acid) reinforced by miscanthus fibers  

Microsoft Academic Search

Microscopic, nanoindentation and tensile tests were carried out to determine the mechanical behavior of PP and PLLA\\/reed fiber composites. As a first step, nanoindentation investigations were carried out to obtain longitudinal modulus and hardness of vegetal fibers. This study has allowed us to place the mechanical properties of reed fibers between those of sisal and hemp fibers.Optical microscopic observations have

Alain Bourmaud; Sylvie Pimbert

2008-01-01

383

Monolithic silicon photonic crystal slab fiber tip sensor  

Microsoft Academic Search

We demonstrate that monolithic photonic crystals (PCs) confined to the facet, or tip, of single-mode optical fibers can be designed as highly sensitive refractive index point sensors. Monolithic photonic-crystal slabs are fabricated on silicon wafers and subsequently released and micro-assembled on the tip of optical fibers. The PC slab's reflection spectrum is modulated by the refractive index of the environment

Il Woong Jung; Bryan Park; J. Provine; Roger T. Howe; Olav Solgaard

2009-01-01

384

Chemiluminescence detection in liquid-core microstructured optical fibers  

Microsoft Academic Search

We reported the first measurement of chemiluminescence photon emission in microstructured optical fibers (MOFs). The hollow-core of a polymer MOF was infiltrated with fluid to support an index-guiding mechanism. The selective filling method involved sealing the cladding air-holes during polishing, leaving the hollow core available for the chemiluminescence solution. Experimental results, compared with a solid-core index-guiding fiber, indicated that the

Xia Yu; Khoi Seng Lok; Yien Chian Kwok; Ying Zhang; Huifeng Wei; Weijun Tong

385

Transverse strain sensitivity of fiber Bragg grating sensors  

Microsoft Academic Search

This article presents an integrated formulation for the calculation of the spectral response of a fiber Bragg grating sensor embedded in a host material system, as a function of the loading applied to the host structure. In particular, the calculation of the transverse strain sensitivity of a fiber Bragg grating sensor through the calculation of the change in effective index

Mohanraj Prabhugoud; Kara Peters

2005-01-01

386

Etched core fiber Bragg grating sensor integrated with microfluidic channel  

Microsoft Academic Search

We demonstrate an etched-core fiber Bragg grating sensor for detection of bio-chemical agents. The fiber Bragg grating of the sensor is etched to a diameter of 7 mum. The transition between the etched and the unetched core consists of an asymmetric taper resulting in excitation of multiple modes. The different excited modes respond differently to change in refractive index, temperature

Sang-Mae Lee; Myung-Yung Jeong; Simarjeet S. Saini

2011-01-01

387

Finite element model for embedded fiber Bragg grating sensor  

Microsoft Academic Search

This paper presents an integrated formulation for the calculation of the spectral response of a fiber Bragg grating sensor embedded in a host material system, as a function of the loading applied to the host structure. In particular, the calculation of the transverse strain sensitivity of a fiber Bragg grating sensor through the calculation of the change in effective index

Mohanraj Prabhugoud; Kara Peters

2006-01-01

388

Dietary fiber from coconut flour: A functional food  

Microsoft Academic Search

To determine the effectiveness of dietary fiber present in coconut flour as a functional food, the following studies were conducted: (a) Dietary Fiber Composition and Fermentability of Coconut Flour; (b) The Effect of Coconut Flour on Mineral Availability from Coconut Flour Supplemented Foods; (c) Glycemic Index of Coconut Flour Supplemented Foods in Normal and Diabetic Subjects; and (d) The Cholesterol

Trinidad P. Trinidad; Aida C. Mallillin; Divinagracia H. Valdez; Anacleta S. Loyola; Faridah C. Askali-Mercado; Joan C. Castillo; Rosario R. Encabo; Dina B. Masa; Angelica S. Maglaya; Modesto T. Chua

2006-01-01

389

Direct functionalization of an optical fiber by a plasmonic nanosensor.  

PubMed

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

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

2011-08-01

390

Soft glasses for photonic crystal fibers and microstructured optical components  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

391

Effect of pulses from a high-power ytterbium fiber laser on a material with a nonuniform refractive index. II. Production and parameters of Nd:Y2O3 nanopowders  

NASA Astrophysics Data System (ADS)

The laser ablation of the Nd:Y2O3 target with substantially nonuniform refractive index leads to the formation of a needle-shaped surface with a needle height of 6-8 mm. An increase in the displacement velocity of the laser beam on the surface to 80 cm/s and an increase in the diameter of the laser spot at the central part of the beam waist to 430 ?m lead to a more uniform relief of the target surface and an increase in the nanopowder yield and production rate to 22% and 23 g/h, respectively. In addition, an excess of the mole content of the low-melting Nd2O3 in the powder decreases from 174 to 11% in comparison with the target. At an air pressure in the evaporation chamber of 0.8 bar, the mean sizes of nanoparticles (13-14 nm) are virtually independent of the displacement velocity of the beam on the surface (7-81 cm/s) and the rate of air flow above the target (13-70 m/s) in spite of significantly different nanopowder production rates.

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

2014-05-01

392

Computing discharge using the index velocity method  

USGS Publications Warehouse

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

Levesque, Victor A.; Oberg, Kevin A.

2012-01-01

393

Reflective fiber-optic refractometer based on a thin-core fiber tailored Bragg grating reflection.  

PubMed

A novel reflective refractometer based on a thin-core fiber (TCF) sandwiched between a leading single-mode fiber (SMF) and a fiber Bragg grating (FBG) imprinted SMF stub was demonstrated. The reflection from the fiber stub occurs in two well-defined wavelength bands, corresponding to the Bragg core mode and cladding modes. The TCF section functions as a tailorable bridge between the FBG core mode reflection and the surrounding refractive index (SRI). Linear response with enhanced sensitivity of 133.26 dB/refractive index unit for temperature-immune SRI measurement within the biologically desirable sensing range of 1.33-1.41 has been achieved via cost-effective power detection. PMID:22297340

Ma, Yue; Qiao, Xueguang; Guo, Tuan; Wang, Ruohui; Zhang, Jing; Weng, Yinyan; Rong, Qiangzhou; Hu, Manli; Feng, Zhongyao

2012-02-01

394

Tapered fiber tips for fiber optic biosensors  

NASA Astrophysics Data System (ADS)

Tapered fiber tips with different geometries are fabricated for developing a fiber optic biosensor. Fluorescence experiments are performed to compare the coupling efficiency of light for different fiber tip configurations. When light is generated in a `thick' layer (> 1 micrometers ) around a fiber core, the continuously tapered tip with the steepest taper collects light more efficiently than the longer combination tapered tip. To demonstrate the applicability of our results, we have successfully detected weak chemiluminescent signal collected by a bundle of fibers with the short continuously tapered tips using a cooled CCD array detector. The chemiluminescence reaction was catalyzed by alkaline phosphatase immobilized on the fiber tips by a sol-gel technique.

Gao, Harry H.; Chen, Zhongping; Kumar, Jayant; Tripathy, Sukant K.; Kaplan, David L.

1995-12-01

395

Nucleic acid indexing  

DOEpatents

A restriction site indexing method for selectively amplifying any fragment generated by a Class II restriction enzyme includes adaptors specific to fragment ends containing adaptor indexing sequences complementary to fragment indexing sequences near the termini of fragments generated by Class II enzyme cleavage. A method for combinatorial indexing facilitates amplification of restriction fragments whose sequence is not known.

Guilfoyle, Richard A. (Madison, WI); Guo, Zhen (Bellevue, WA)

2001-01-01

396

Nucleic acid indexing  

DOEpatents

A restriction site indexing method for selectively amplifying any fragment generated by a Class II restriction enzyme includes adaptors specific to fragment ends containing adaptor indexing sequences complementary to fragment indexing sequences near the termini of fragments generated by Class II enzyme cleavage. A method for combinatorial indexing facilitates amplification of restriction fragments whose sequence is not known.

Guilfoyle, Richard A. (Madison, WI); Guo, Zhen (Bellevue, WA)

1999-01-01

397

Lobby index in networks  

NASA Astrophysics Data System (ADS)

We propose a new node centrality measure in networks, the lobby index, which is inspired by Hirsch’s h-index. It is shown that in scale-free networks with exponent ? the distribution of the l-index has power tail with exponent ?(?+1). Properties of the l-index and extensions are discussed.

Korn, A.; Schubert, A.; Telcs, A.

2009-06-01

398

KSC Construction Cost Index  

NASA Technical Reports Server (NTRS)

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

Brown, J. A.

1983-01-01

399

Multimaterial acoustic fibers  

E-print Network

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

Chocat, Noémie

2012-01-01

400

Photoluminescence mapping of oxygen-defect emission for nanoscale spatial characterization of fiber Bragg gratings  

E-print Network

.1063/1.2746819 Highly sensitive fiber Bragg grating refractive index sensors Appl. Phys. Lett. 86, 151122 (2005); 10 on the temperature sensitivity of fiber Bragg gratings AIP Conf. Proc. 1511, 1570 (2013); 10.1063/1.4789229 Bragg.1063/1.1904716 Evanescent field imaging of an optical fiber Bragg grating Appl. Phys. Lett. 75, 4058 (1999); 10

401

IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 17, NO. 6, JUNE 2005 1253 High Sensitivity Evanescent Field Fiber  

E-print Network

Fiber Bragg Grating Sensor Athanasios N. Chryssis, Sang M. Lee, Sang B. Lee, Simarjeet S. Saini, Member--Biological sensor, chemical sensor, evanescent field, fiber Bragg grating (FBG). I. INTRODUCTION MONITORING index is shown by etching the core of a fiber Bragg grating. A maximum sensitivity of 1394 nm

Dagenais, Mario

402

Side-polished and tilted fiber Bragg grating sensors for structural health monitoring applications  

Microsoft Academic Search

Fiber Bragg gratings (FBG) are one of several fiber optic sensor technologies currently being used in structural health monitoring systems. When the effective refractive index of a fiber Bragg grating is changed by external environmental variations (e.g. temperature, pH), the wavelength at which incident light experiences a maximum reflection from the grating will correspondingly shift. To detect small environmental variations

C.-F. Chan; G. A. Ferrier; D. J. Thomson; C. Chen; J. Albert; A. Vincelette; P. Lefebvre

2007-01-01

403

Optical fiber delivery of intense ultrashort laser for endoscopic medical applications  

Microsoft Academic Search

This paper reports on the delivery of intense ultrashort pulse through graded index (GI) fibers. Numerical simulation of dispersion management during passing through the optical fibers is also described. In addition, the feasibility of endoscopic cancer treatment by use of fiber delivery of intense femtosecond laser is also explained.

L. Kamino; M. Kanai; M. Obara

2003-01-01

404

Observation of type I and type II gratings behavior in polymer optical fiber  

Microsoft Academic Search

We report the first observation of type I and type II fiber grating behaviors in making polymer optical fiber Bragg gratings. Our observation reveals that there are two distinctive stages in the fabrication of polymer optical fiber Bragg gratings. Notably the two stages of grating formation correspond to low and high-index modulation gratings, which match well with those in silica

H. Y Liu; H. B Liu; G. D Peng; P. L Chu

2003-01-01

405

TESLA Report No. 2000-26 September 2000 Fiber Optic Radiation Sensing Systems  

E-print Network

TESLA Report No. 2000-26 September 2000 Fiber Optic Radiation Sensing Systems for TESLA by H, Germany F. Wulf Hahn-Meitner-Institut HMI, Germany #12;Fiber Optic Radiation Sensing Systems for TESLA of refractive index at high radiation doses 4 3. Fiber optic dosimeter types for different TESLA sections 4 3

406

Detecting hybridization of DNA by highly sensitive evanescent field etched core fiber Bragg grating sensors  

Microsoft Academic Search

Highly sensitive fiber Bragg grating sensors were developed by etching away the cladding and part of the core of the fiber and detecting the change of Bragg wavelength due to the change of index of the surrounding medium. A sensitivity of 1394 nm\\/riu was achieved when the diameter of the grating core was 3.4 ?m and the index of the

Athanasios N. Chryssis; Simarjeet S. Saini; Sang M. Lee; Hyunmin Yi; William E. Bentley; Mario Dagenais

2005-01-01

407

Step Barrier Scattering Model  

NSDL National Science Digital Library

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

Christian, Wolfgang

2008-10-09

408

Selective mode excitation by non-axial evanescent coupling for bandwidth enhancement of multimode fiber links  

NASA Astrophysics Data System (ADS)

We present an analysis of conditioned launch in a gradient-index multimode fiber (MMF). Selective mode excitation is obtained by nonaxial evanescent coupling between two highly asymmetric side-polished fibers: a single-mode fiber and an MMF with an exposed core. An index-matching slab improves the coupling efficiency and selectivity. The simulation shows that about 40% of modes, only high-order modes, are excited in the MMF. When compared to an overfilled launch, the bandwidth of a perturbed index fiber is enhanced more than twofold for large parameter variations.

Vaissie, Laurent; Johnson, Eric G.

2002-08-01

409

Fiber distributed feedback laser  

NASA Technical Reports Server (NTRS)

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

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

1976-01-01

410

Fiber-optic oxygen sensor using molybdenum chloride cluster luminescence  

E-print Network

Fiber-optic oxygen sensor using molybdenum chloride cluster luminescence Ruby N. Ghosh,a) Gregory L on a reflection-mode fiber-optic oxygen sensor based on the 3 O2 quenching of the red emission from hexanuclear steps in the sensor response for changes of 0.1% absolute oxygen concentration in the 0%­1.0% range

Ghosh, Ruby N.

411

Strong fibers  

SciTech Connect

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

Li, Che-Yu.

1991-03-01

412

Development of an ingredient containing apple peel, as a source of polyphenols and dietary fiber.  

PubMed

Apple peel is a waste product from dried apple manufacture. The content of phenolic compounds, dietary fiber, and mineral are higher in apple peel, compared to other edible parts of this fruits. The objective of this study was to develop an ingredient from Granny Smith apple peel, using a pilot scale double drum-dryer, as drying technology. The control of all steps to maximize the retention of phenolic compounds and dietary fiber was considered. Operational conditions, such as drying temperature and time were determined, as well as important preprocessing steps like grinding and PPO inhibition. In addition, the physical-chemical characteristics, mineral and sugar content, and technological functional properties such as water retention capacity, solubility index, and dispersability among others, were analyzed. A simple, economical, and suitable pilot scale process, to produce a powder ingredient from apple peel by-product, was obtained. The drying process includes the application of ascorbic acid at 0.5% in the fresh apple peel slurry, drum-dryer operational conditions were 110 degrees C, 0.15 rpm and 0.2 mm drum clearance. The ingredient developed could be considered as a source of phenolic compounds (38.6 mg gallic acid equivalent/g dry base) and dietary fiber (39.7% dry base) in the formulation of foods. Practical Application: A method to develop an ingredient from Granny Smith apple peel using a pilot scale double drum-dryer as drying technology was developed. The method is simple, economical, feasible, and suitable and maximizes the retention of phenolic compounds and dietary fiber present in the raw matter. The ingredient could be used in the formulation of foods. PMID:20722929

Henríquez, Carolina; Speisky, Hernán; Chiffelle, Italo; Valenzuela, Tania; Araya, Manuel; Simpson, Ricardo; Almonacid, Sergio

2010-08-01

413

Fiber exposure reassessed with the new indices  

SciTech Connect

The concentration of airborne fibers longer than 5 microns, thinner than 3 microns, and with an aspect ratio exceeding 3 as counted by phase contrast optical microscopy is the most widely used fiber exposure index. Recently, more adequate, specific exposure indices for asbestosis, lung cancer, and mesothelioma risk have been suggested by Lippmann. The consequences of using these indices are examined on the basis of calculations for a broad range of theoretical and published size distributions. Optical microscopy appears to be a good predictor of the exposure indices for asbestosis and for lung cancer after scaling. Only fibers longer than about 3 microns need to be counted in a transmission electron microscope. The lung cancer index still cannot explain the large differences of risk among chrysotile exposures. Both the mesothelioma exposure index and the ratio mesothelioma to lung cancer index ranks in order of increasing risk: wollastonite, glass and mineral wool, amosite, glass microfibers, chrysotile, and crocidolite. Amosite is thus not ranked according to epidemiological evidence. Detailed size information should be made available so that the size criteria can be adjusted. It may still prove necessary to use fiber type specific concentration limits.

Schneider, T.; Skotte, J. (Danish National Institute of Occupational Health, Copenhagen (Netherland))

1990-02-01

414

Ribbon Fiber Laser-Theory and Experiment  

SciTech Connect

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

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

2002-05-10

415

Single-mode optical fiber goniometer  

NASA Astrophysics Data System (ADS)

A two-element single-mode optical fiber goniometer that uses graded-index microlens receivers is presented that measures the angular orientation of a remote laser. The goniometer exhibits a sensitivity of 1.0 V/mrad and a calculated shot-noise-limited angular resolution of 1.0 nrad/sq root Hz.

Mermelstein, M. D.; Blodgett, J. A.

1992-01-01

416

Fiber exposure reassessed with the new indices.  

PubMed

The concentration of airborne fibers longer than 5 microns, thinner than 3 microns, and with an aspect ratio exceeding 3 as counted by phase contrast optical microscopy is the most widely used fiber exposure index. Recently, more adequate, specific exposure indices for asbestosis, lung cancer, and mesothelioma risk have been suggested by Lippmann (1988, Environ. Res., 46, 86-106). The consequences of using these indices are examined on the basis of calculations for a broad range of theoretical and published size distributions. Optical microscopy appears to be a good predictor of the exposure indices for asbestosis and for lung cancer after scaling. Only fibers longer than about 3 microns need to be counted in a transmission electron microscope. The lung cancer index still cannot explain the large differences of risk among chrysotile exposures. Both the mesothelioma exposure index and the ratio mesothelioma to lung cancer index ranks in order of increasing risk: wollastonite, glass and mineral wool, amosite, glass microfibers, chrysotile, and crocidolite. Amosite is thus not ranked according to epidemiological evidence. Detailed size information should be made available so that the size criteria can be adjusted. It may still prove necessary to use fiber type specific concentration limits. PMID:2153537

Schneider, T; Skotte, J

1990-02-01

417

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

PubMed

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

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

2013-07-01

418

High gain ytterbium doped Ge pedestal large pitch fiber  

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

419

A new fiber optic accelerometer based on fiber Bragg grating  

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

420

A new fiber optic accelerometer based on fiber Bragg grating  

NASA Astrophysics Data System (ADS)

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

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

2012-01-01

421

Melt blown nanofibers: Fiber diameter distributions and onset of fiber breakup  

Microsoft Academic Search

Poly(butylene terephthalate), polypropylene, and polystyrene nanofibers with average diameters less than 500nm have been produced by a single orifice melt blowing apparatus using commercially viable processing conditions. This result is a major step towards closing the gap between melt blowing technology and electrospinning in terms of the ability to produce nano-scale fibers. Furthermore, analysis of fiber diameter distributions reveals they

Christopher J. Ellison; Alhad Phatak; David W. Giles; Christopher W. Macosko; Frank S. Bates

2007-01-01

422

Quantification of dislocations in hemp fibers using acid hydrolysis and fiber segment length distributions  

Microsoft Academic Search

Natural fibers such as flax or hemp may be used in composite materials. However, their use for this purpose is hampered by\\u000a the large natural variation in tensile strength and other quality parameters. The first step in managing these variations\\u000a is to develop methods for fast and reliable determination of relevant parameters. One quality parameter of the fibers is the

Lisbeth G. Thygesen

2008-01-01

423

The state of water in different forms of sulfo ion-exchange fiber  

NASA Astrophysics Data System (ADS)

The state of water in the copper, zinc, and cobalt forms of VION KS-3 ion-exchange fiber is investigated by derivatography. The presence of differently bound water is found. For each step of water removal, hydration numbers of the fiber are determined. It is shown that the amount of water in the fiber depends on its ionic form.

Astapov, A. V.; Peregudov, Yu. S.; Kopylova, V. D.

2011-07-01

424

Computer-aided fiber analysis for crime scene forensics  

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

425

Noise Performance Comparison of 1.5 um Correlated Photon Pair Generation in Different Fibers  

E-print Network

In this paper, the noise performances of 1.5 um correlated photon pair generations based on spontaneous four wave-mixing in three types of fibers, i.e., dispersion shifted fiber, highly nonlinear fiber, and highly nonlinear microstructure fiber are investigated experimentally. Result of the comparison shows that highly nonlinear microstructure fiber has the lowest Raman noise photon generation rate among the three types of fibers while correlated photon pair generation rate is the same. Theoretical analysis shows that the noise performance is determined by the nonlinear index and Raman response of the material in fiber core. The Raman response raises with increasing doping level, however, the nonlinear index is almost unchanged with it. As a result, highly nonlinear microstructure fiber with pure silica core has the best noise performance and has great potential in practical sources of correlated photon pairs and heralded single photons.

Qiang Zhou; Wei Zhang; Jie-rong Cheng; Yi-dong Huang; Jiang-de Peng

2010-06-10

426

CENDI Indexing Workshop  

NASA Technical Reports Server (NTRS)

The CENDI Indexing Workshop held at NASA Headquarters, Two Independence Square, 300 E Street, Washington, DC, on September 21-22, 1994 focused on the following topics: machine aided indexing, indexing quality, an indexing pilot project, the MedIndEx Prototype, Department of Energy/Office of Scientific and Technical Information indexing activities, high-tech coding structures, category indexing schemes, and the Government Information Locator Service. This publication consists mostly of viewgraphs related to the above noted topics. In an appendix is a description of the Government Information Locator Service.

1994-01-01

427

Pulse Shepherding in Nonlinear Fiber Optics  

NASA Technical Reports Server (NTRS)

In a wavelength division multiplexed fiber system, where pulses on different wavelength beams may co-propagate in a single mode fiber, the cross-phase-modulation (CPM) effects caused by the nonlinearity of the optical fiber are unavoidable. In other words, pulses on different wavelength beams can interact with and affect each other through the intensity dependence of the refractive index of the fiber. Although CPM will not cause energy to be exchanged among the beams, the pulse shapes and locations on these beams can be altered significantly. This phenomenon makes possible the manipulation and control of pulses co-propagating on different wavelength beams through the introduction of a shepherd pulse at a separate wavelength. How this can be accomplished is demonstrated in this paper.

Yeh, C.; Bergman, L.

1996-01-01

428

FOA Lecture 22: Mode Power Distribution in Multimode Fibers  

NSDL National Science Digital Library

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

2013-06-20

429

Photonic crystal fiber half-taper probe based refractometer.  

PubMed

A compact single-mode photonic crystal fiber single-mode fiber tip (SPST) refractive index sensor is demonstrated in this Letter. A CO2 laser cleaving technique is utilized to provide a clean-cut fiber tip, which is then coated by a layer of gold to increase reflection. An average sensitivity of 39.1 nm/RIU and a resolvable index change of 2.56×10(-4) are obtained experimentally with a ?3.2 ?m diameter SPST. The temperature dependence of this fiber-optic sensor probe is presented. The proposed SPST refractometer is also significantly less sensitive to temperature and an experimental demonstration of this reduced sensitivity is presented in the Letter. Because of its compactness, ease of fabrication, linear response, low temperature dependency, easy connectivity to other fiberized optical components and low cost, this refractometer could find various applications in chemical and biological sensing. PMID:24686678

Wang, Pengfei; Ding, Ming; Bo, Lin; Guan, Chunying; Semenova, Yuliya; Sun, Weimin; Yuan, Libo; Brambilla, Gilberto; Farrell, Gerald

2014-04-01

430

Derivation of a planetary ionospheric storm index  

Microsoft Academic Search

The planetary ionospheric storm index, Wp, is deduced from the numerical global ionospheric GPS-IONEX maps of the vertical total electron content, TEC, for more than half a solar cycle, 1999-2008. The TEC values are extracted from the 600 grid points of the map at latitudes 60° N to 60° S with a step of 5° and longitudes 0° to 345°

T. L. Gulyaeva; I. Stanislawska

2008-01-01

431

Method of forming composite fiber blends  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

432

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

Microsoft Academic Search

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

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

2009-01-01

433

Optical fiber production  

NASA Astrophysics Data System (ADS)

A report of the U.N. Industrial Development Organization on Optical fiber production includes the following topics: Basics of optical communication; Technology trends; Classification of fibers - fiber standards; Production of optical fibers; Production of optical cables; Testing and quality control; Requirements; Capital investment; Economics of production; Potential suppliers of equipment and technology; Fiberoptics markets - characteristics and trends; Position of developing countries; and recommendations.

Bonek, E.; Furch, B.; Otruba, H.

1985-07-01

434

Fiber Sensor Technology Today  

Microsoft Academic Search

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

Kazuo Hotate

2006-01-01

435

Microstructured Polymer Optical Fibers  

Microsoft Academic Search

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

Alexander Argyros

2009-01-01

436

Fabrication and characterization of special microstructured fibers  

NASA Astrophysics Data System (ADS)

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

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

2011-05-01

437

Dietary fiber and the glycemic response.  

PubMed

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

Jenkins, D J; Jenkins, A L

1985-12-01

438

Microbend fiber-optic temperature sensor  

DOEpatents

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

Weiss, Jonathan D. (Albuquerque, NM)

1995-01-01

439

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

440

Fiber optic temperature sensor  

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

441

In-line microfluidic refractometer based on C-shaped fiber assisted photonic crystal fiber Sagnac interferometer.  

PubMed

We propose and demonstrate a highly sensitive in-line photonic crystal fiber (PCF) microfluidic refractometer. Ultrathin C-shaped fibers are spliced in-between the PCF and standard single-mode fibers. The C-shaped fibers provide openings for liquid to flow in and out of the PCF. Based on a Sagnac interferometer, the refractive index (RI) response of the device is investigated theoretically and experimentally. A high sensitivity of 6621 nm/RIU for liquid RI from 1.330 to 1.333 is achieved in the experiment, which agrees well with the theoretical analysis. PMID:23988935

Wu, Chuang; Tse, Ming-Leung Vincent; Liu, Zhengyong; Guan, Bai-Ou; Lu, Chao; Tam, Hwa-Yaw

2013-09-01

442

Baby Steps: How \\  

Microsoft Academic Search

We present an empirical study of two very simple approaches to unsupervised grammar induction. Both are based on Klein and Manning's Dependency Model with Valence. The first, Baby Steps, requires no initialization and bootstraps itself via iterated learning of increasingly longer sentences. This method substantially exceeds Klein and Manning's published numbers and achieves39.4% accuracy on Section 23 of the Wall

Valentin I. Spitkovsky; Hiyan Alshawi; Daniel Jurafsky

443

Steps toward Successful Dictation.  

ERIC Educational Resources Information Center

Relates a technique that helps students learn dictation while enjoying the topic. Provides six steps: (1) send students to the blackboard to take dictation; (2) have students listen first; (3) ask students to isolate melody from rhythm; (4) have all students sing using solfege syllables; (5) provide feedback; and (6) accommodate varying abilities.…

Liebhaber, Barbara

2001-01-01

444

Stepped inlet optical panel  

DOEpatents

An optical panel includes stacked optical waveguides having stepped inlet facets collectively defining an inlet face for receiving image light, and having beveled outlet faces collectively defining a display screen for displaying the image light channeled through the waveguides by internal reflection.

Veligdan, James T. (6 Stephanie La., Manorville, NY 11949)

2001-01-01

445

Coatings for graphite fibers  

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

446

Development of optical fiber biosensors with long period gratings  

NASA Astrophysics Data System (ADS)

This dissertation successfully developed a new sensitive optical fiber biosensor with Long Period Gratings (LPG), using the self-fabricated LPG and self-built demodulation system. The LPG biosensor is a in-fiber sensor which is especially suitable for sensing in remote and hostile environments. The biosensor is also unique in that it is a label-free sensor with the ability of real-time detection and the potential for multiplexing. We began the research with detailed computer simulations, using a new simplified three-layer model for a cylindrical waveguide with doubly-cladded step-index profile. The simulation results showed the nonlinear relationship between the LPG spectral sensitivity and the ambient refractive index. It was also shown that, at the same ambient refractive index, higher LPG modes resulted in higher sensitivity. Simulations of biolayer formation on the LPG surface showed a linear relationship between the LPG spectral shift and the biolayer thickness and a linear relationship between the LPG spectral shift and the biolayer refractive index. In the case of antibody detection, the simulation results for the LPG biosensor suggested an estimated minimum detectable human Immuno- Globin G (hIgG) concentration of ~1.0 picomole/mL. By immobilizing Goat anti-human IgG (antibody) on the LPG surface, a LPG biosensor (immunosensor) was successfully developed for the sensitive detection of a specific antigen (human IgG). The binding of non-labeled hIgGs on the LPG surface was investigated by experiments in real time. It was observed that both the maximum output signal and the calculated initial signal slope were concentration dependent over a range of 2-100 ?g/mL of homogeneous hIgG solutions in PBS. If applying initial signal slope determination, the target antigen hIgG concentration or the final signal level could be determined in approximately 10 minutes after the target solution was introduced into the flow chamber of the LPG immunosensor. Also, the dissertation found that the minimum detectable hIgG concentration for the LPG immunosensor was about 6.7 picomole/mL, which was pretty close to the estimated sensitivity of ~1.0 picomole/mL based on the computer simulations. Finally, the specificity of the LPG immunosensor was positively verified, and the biosensor regeneration and re-treatment were successfully tested.

Zhang, Zheng

2000-07-01

447

Thermally induced mode distortion and its limit to power scaling of fiber lasers.  

PubMed

A general model is proposed to describe thermal-induced mode distortion in the step-index fiber (SIF) high power lasers. Two normalized parameters in the model are able to determine the mode characteristic in the heated SIFs completely. Shrinking of the mode fields and excitation of the high-order modes by the thermal-optic effect are investigated. A simplified power amplification model is used to describe the output power redistribution under various guiding modes. The results suggest that fiber with large mode area is more sensitive on the thermally induced mode distortion and hence is disadvantaged in keeping the beam quality in high power operation. The model is further applied to improve the power scaling analysis of Yb-doped fiber lasers. Here the thermal effect is considered to couple with the optical damage and the stimulated Raman scattering dynamically, whereas direct constraint from the thermal lens is relaxed. The resulting maximal output power is from 67kW to 97kW, depending on power fraction of the fundamental mode. PMID:23787616

Ke, Wei-Wei; Wang, Xiao-Jun; Bao, Xian-Feng; Shu, Xiao-Jian

2013-06-17