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Sample records for step index fiber

  1. Step-Index Optical Fiber Made of Biocompatible Hydrogels.

    PubMed

    Choi, Myunghwan; Humar, Matjaž; Kim, Seonghoon; Yun, Seok-Hyun

    2015-07-15

    A biocompatible step-index optical fiber made of poly(ethylene glycol) and alginate hydrogels is demonstrated. The fabricated fiber exhibits excellent light-guiding efficiency in biological tissues. Moreover, the core of hydrogel fibers can be easily doped with functional molecules and nanoparticles for localized light emission, sensing, and therapy. PMID:26045317

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

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

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

  3. Single mode step-index polymer optical fiber for humidity insensitive high temperature fiber Bragg grating sensors.

    PubMed

    Woyessa, Getinet; Fasano, Andrea; Stefani, Alessio; Markos, Christos; Nielsen, Kristian; Rasmussen, Henrik K; Bang, Ole

    2016-01-25

    We have fabricated the first single-mode step-index and humidity insensitive polymer optical fiber operating in the 850 nm wavelength ranges. The step-index preform is fabricated using injection molding, which is an efficient method for cost effective, flexible and fast preparation of the fiber preform. The fabricated single-mode step-index (SI) polymer optical fiber (POF) has a 4.8µm core made from TOPAS grade 5013S-04 with a glass transition temperature of 134°C and a 150 µm cladding made from ZEONEX grade 480R with a glass transition temperature of 138°C. The key advantages of the proposed SIPOF are low water absorption, high operating temperature and chemical inertness to acids and bases and many polar solvents as compared to the conventional poly-methyl-methacrylate (PMMA) and polystyrene based POFs. In addition, the fiber Bragg grating writing time is short compared to microstructured POFs. PMID:26832507

  4. Statistical analysis of intrinsic and extrinsic coupling losses for step-index polymer optical fibers.

    PubMed

    Werzinger, Stefan; Bunge, Christian-Alexander

    2015-08-24

    The intrinsic and extrinsic coupling losses of step-index polymer optical fibers are statistically examined by Monte Carlo simulations. In contrast to most existing models that linearly scale individual losses, a comprehensive analytic coupling loss model is used that also considers the interdependencies between mismatches in numerical aperture and core diameter, as well as radial and longitudinal offsets. As a typical example, the coupling losses of A4a.2 step-index multimode fibers are analyzed for an equilibrium mode distribution. The results show considerably less conservative coupling loss estimations than with traditional models, improving link power budgeting. PMID:26368203

  5. Comparison of numerical methods for light propagating in fibers with high steps of refractive index

    NASA Astrophysics Data System (ADS)

    Zegadło, K. B.; Karpierz, M. A.

    2011-10-01

    Fast development of complex structures like microstructural fibers, photonic nanowires or slot waveguides requires numerical tools to predict a light propagation. There are many works concerning weakly guided case, but the microstructural fibers need algorithm for a high step of the refractive index. In this paper, three approximate methods are compared. The comparison concerns a structure consisting of circular cores surrounded by cladding for different values of the refractive index steps. Application of these methods in chromatic dispersion case is also presented. It is shown that certain conditions prefer two dimensional scalar algorithms (based on approximated methods) than three dimensional ones. This allows us to implement more efficient and less complicated methods.

  6. Comparison of numerical methods for light propagating in fibers with high steps of refractive index

    NASA Astrophysics Data System (ADS)

    Zegadło, K.; Karpierz, M.

    2012-03-01

    Fast development of complex structures like microstructural fibers, photonic nanowires or slot waveguides requires numerical tools to predict a light propagation. There are many works concerning weakly guided case, but the microstructural fibers need algorithm for a high step of the refractive index. In this paper, three approximate methods are compared. The comparison concerns a structure consisting of circular cores surrounded by cladding for different values of the refractive index steps. Application of these methods in chromatic dispersion case is also presented. It is shown that certain conditions prefer two dimensional scalar algorithms (based on approximated methods) than three dimensional ones. This allows us to implement more efficient and less complicated methods.

  7. Broadband azimuthal polarization conversion using gold nanowire enhanced step-index fiber.

    PubMed

    Tuniz, Alessandro; Jain, Chhavi; Weidlich, Stefan; Schmidt, Markus A

    2016-02-01

    We show broadband azimuthal polarization state conversion using an entirely connectorized step-index fiber with a central gold nanowire. This device provides broadband polarization discrimination of the low-loss TE01 fiber mode with respect to all other modes, and converts light into the azimuthal polarization state, resulting in a high beam quality and an azimuthal conversion efficiency of 37%. The device is monolithically integrated into fiber circuitry, representing a new platform for plasmonics and fiber optics and enabling important applications in super-resolution microscopy, laser tweezing, and plasmonic superfocussing. PMID:26907394

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

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

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

  9. Efficiency of various modulation types in Step Index Polymer Optical Fiber

    NASA Astrophysics Data System (ADS)

    Siuzdak, Jerzy; Stepniak, Grzegorz

    2014-11-01

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

  10. Equilibrium modal power distribution measurement of step-index hard plastic cladding and graded-index silica multimode fibers

    NASA Astrophysics Data System (ADS)

    Tao, Ruichen; Hayashi, Takehiro; Kagami, Manabu; Kobayashi, Shigeru; Yasukawa, Manabu; Yang, Hui; Robinson, David; Baghsiahi, Hadi; Fernández, F. Aníbal; Selviah, David R.

    2015-03-01

    A stable reproducible optical standard source for measuring multimode optical fiber attenuation is required as recent round robin measurements of such fibers at several international companies and national standards organizations showed significant variation when using a source having only the encircled flux in the near field emerging from it defined. The paper presents and compares the far field modal power distributions for (i) 2 km and 3 km step-index multimode Hard Plastic Cladding Fibers, HPCF, (SI-MMF) with 200 μm silica core diameter, 0.37 numerical aperture (NA) and polymer cladding, (ii) a 10 m silica graded-index multimode fiber (GI-MMF) with 50 μm core diameter and 0.2 NA, and (ii) a near field Encircled Flux Mode Convertor or "modcon". A free space method for measuring the far field using a Lightemitting diode (LED) centered at 850 nm wavelength with 40 nm 10 dB-bandwidth and a charge-coupled device (CCD) camera is compared with a f-theta multi-element lens based far field pattern (FFP) system. Mandrels of different diameter and different numbers of turns of the fiber around them were used to achieve an equilibrium mode distribution (EMD) for the GI-MMF. The paper defines encircled angular flux (EAF) as the fraction of the total optical power radiating from a multimode optical fiber core within a certain solid angle in the far field. The paper calculates the EAF when the solid angle increases from the far field centroid.

  11. Mid-infrared supercontinuum generation spanning 1.8 octaves using step-index indium fluoride fiber pumped by a femtosecond fiber laser near 2 µm.

    PubMed

    Salem, Reza; Jiang, Zack; Liu, Dongfeng; Pafchek, Robert; Gardner, David; Foy, Paul; Saad, Mohammed; Jenkins, Doug; Cable, Alex; Fendel, Peter

    2015-11-30

    A nearly two-octave wide coherent mid-infrared supercontinuum is demonstrated in a dispersion-engineered step-index indium fluoride fiber pumped near 2 µm. The pump source is an all-fiber femtosecond laser with 100 fs pulse width, 570 mW average power and 50 MHz repetition rate. The supercontinuum spectrum spans from 1.25 µm to 4.6 µm. Numerical modelling of the supercontinuum spectra show good agreement with the measurements. The coherence of the supercontinuum is calculated using a numerical model and shows a high degree of coherence across the generated bandwidth allowing it to be used for frequency comb applications. PMID:26698692

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

    SciTech Connect

    Yalin, Azer P; Joshi, Sachin

    2014-06-03

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

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

    NASA Astrophysics Data System (ADS)

    Stepniak, G.; Siuzdak, J.

    2014-08-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    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.

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

    PubMed

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

    2011-05-23

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

  16. Simplified study of guided modes in plasma cladded step-index optical fiber

    NASA Astrophysics Data System (ADS)

    Mishra, A. K.; Singh, O. N.

    2015-06-01

    In this paper, the effect of plasma cladding on the modal dispersion characteristics of guided modes is explored. The dispersion relation of guided modes which is derived employing the usual boundary conditions, show a strong dependency on the operating frequency. The numerical aperture of plasma cladded light guide decreases on increasing the operating frequency which is quite contrary to conventional dielectric optical fibers. Our study further revealed that this decrease in numerical aperture is more prompt at lower frequency and hence, an unusual dispersion characteristic is displayed by hybrid modes. The transverse modes display the usual dispersion characteristics with only exceptions that these modes occur in pairs with approximately equal cutoff frequency. We hope that the study will be quite useful to investigate the behavior of high power laser beam propagating through air core or hollow fibers.

  17. One step method to attach gold nanoparticles onto the surface of an optical fiber used for refractive index sensing

    NASA Astrophysics Data System (ADS)

    García, J. A.; Monzón-Hernández, D.; Manríquez, J.; Bustos, E.

    2016-01-01

    Localized surface plasmon resonance (LSPR) has recently emerged as an efficient and powerful tool for bio-photonic applications due to its high sensitivity to refractive index changes. One technique to excite LSP is by the interaction of the evanescent wave of the light guided by an optical fiber with metallic nanoparticles deposited over the surface of the fiber. This paper proposes a novel, simple, and fast method to attach gold nanoparticles to the optical fiber surface, which can be used to construct highly sensitive refractive index sensors based on localized surface plasmon resonance. A hetero-core structured fiber, composed by a small section of single-mode fiber inserted in a multimode fiber, was coated with nanoparticles using the method proposed here. A sensor sensitivity and resolution of 765 nm/RIU and ∼1 × 10-4 RIU, respectively, were estimated over a refractive index range of 1.333-1.365. This coating method is appealing to construct optical fiber refractive index sensors since it is very simple and low cost.

  18. Mid-infrared supercontinuum generation spanning 2.0 to 15.1  μm in a chalcogenide step-index fiber.

    PubMed

    Cheng, Tonglei; Nagasaka, Kenshiro; Tuan, Tong Hoang; Xue, Xiaojie; Matsumoto, Morio; Tezuka, Hiroshige; Suzuki, Takenobu; Ohishi, Yasutake

    2016-05-01

    We experimentally demonstrate mid-infrared (MIR) supercontinuum (SC) generation spanning ∼2.0 to 15.1 μm in a 3 cm-long chalcogenide step-index fiber. The pump source is generated by the difference frequency generation with a pulse width of ∼170  fs, a repetition rate of ∼1000  Hz, and a wavelength range tunable from 2.4 to 11 μm. To the best of our knowledge, this is the broadest MIR SC generation observed so far in optical fibers. It facilitates fiber-based applications in sensing, medical, and biological imaging areas. PMID:27128088

  19. Third-harmonic generation with a more than 500 nm tunable spectral range in a step-index tellurite fiber

    NASA Astrophysics Data System (ADS)

    Gao, Weiqing; Cheng, Tonglei; Deng, Dinghuan; Xue, Xiaojie; Suzuki, Takenobu; Ohishi, Yasutake

    2014-09-01

    We demonstrate third-harmonic generation (THG) with a tunable spectral range of more than 500 nm in a step-index tellurite fiber. Third-harmonic (TH) signals with a peak wavelength from 524 to 1043 nm are obtained in a 3 cm-long fiber when the fundamental wavelength shifts from 1560 to 3100 nm. To our knowledge, the tunable spectral range covering almost one octave is the widest tunable range of THG in fibers so far. The far-field patterns of the TH signals by 1560 nm to 2100 nm pumping are recorded by a charge coupled device camera, which are close to the fundamental mode profile. The THG in such a wide tunable range is attributable to the high nonlinearity of the tellurite fiber and the high pump peak power of the pump pulse.

  20. Ince-gauss based multiple intermodal phase-matched third-harmonic generations in a step-index silica optical fiber

    NASA Astrophysics Data System (ADS)

    Borne, Adrien; Katsura, Tomotaka; Félix, Corinne; Doppagne, Benjamin; Segonds, Patricia; Bencheikh, Kamel; Levenson, Juan Ariel; Boulanger, Benoit

    2016-01-01

    Several third-harmonic generation processes were performed in a single step-index germanium-doped silica optical fiber under intermodal phase-matching conditions. The nanosecond fundamental beam range between 1400 and 1600 nm. The transverse distributions of the energy were successfully modeled in the form of Ince-Gauss modes, pointing out some ellipticity of fiber core. From these experiments and theoretical calculations, we discuss the implementation of frequency degenerated triple photon generation that shares the same phase-matching condition as third-harmonic generation, which is its reverse process.

  1. Fiber optic refractive index monitor

    DOEpatents

    Weiss, Jonathan David (Albuquerque, NM)

    2002-01-01

    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.

  2. Near-Diffraction-Limited Operation of Step-Index Large-Mode-Area Fiber Lasers Via Gain Filtering

    SciTech Connect

    Marciante, J.R.; Roides, R.G.; Shkunov, V.V.; Rockwell, D.A.

    2010-06-04

    We present, for the first time to our knowledge, an explicit experimental comparison of beam quality in conventional and confined-gain multimode fiber lasers. In the conventional fiber laser, beam quality degrades with increasing output power. In the confined-gain fiber laser, the beam quality is good and does not degrade with output power. Gain filtering of higher-order modes in 28 μm diameter core fiber lasers is demonstrated with a beam quality of M^2 = 1.3 at all pumping levels. Theoretical modeling is shown to agree well with experimentally observed trends.

  3. Characterization of splice loss as a function of wavelength in step-index, single-mode, optical waveguide fibers

    NASA Astrophysics Data System (ADS)

    Dreyer, D. R.; Emig, K. A.; Minthorn, A. R.

    1986-11-01

    One of the significant contributors to a single-mode optical fiber system's overall power budget is the cumulative loss incurred when splicing cable sections together. Considerable theoretical work has been completed relating splice loss to the respective mode field diameters of the fibers being spliced, the lateral offset of their mode fields, and to the general wavelength dependent nature of mode field diameter. Therefore, the theoretical dependence of splice loss on wavelength can be determined. This paper describes the experimental results of a study conducted to measure the splice loss dependency of wavelength in single-mode fiber.

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

    PubMed

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

    2010-05-15

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

  5. Analysis of refractive index single mode optical fiber for fiber-to-the-home application

    NASA Astrophysics Data System (ADS)

    Palodiya, Vikram; Raghuwanshi, Sanjeev K.

    2015-07-01

    A Comparative study of step-index and trench-assisted single mode fiber in terms of bending losses and mode field diameter is carried out. Trench- index fiber proved to be a potential candidate for fiber-to-the-home application.

  6. High power gain guided index antiguided fiber lasers and amplifiers

    NASA Astrophysics Data System (ADS)

    Gandomkar Yarandi, Parisa

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

  7. Radial image transfer by cylindrical, step-index optical waveguides

    NASA Technical Reports Server (NTRS)

    Heacox, William D.

    1987-01-01

    The theoretical extent of image transfer by perfect, cylindrical, step-index optical waveguides is examined. Azimuthal image structure is essentially removed by such waveguides, while substantial radial image structure is transmitted. The consequences of this behavior for optical-fiber image scramblers are discussed; such devices may be unsuitable for simple photometric applications but appear to be potentially useful in reducing zonal errors in slit spectroscopy.

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

    NASA Astrophysics Data System (ADS)

    Murshid, Syed H.; Chakravarty, Abhijit

    2011-06-01

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

  9. Pixelated high-index ring Bragg fibers.

    PubMed

    Baz, Assaad; Bouwmans, Graud; Bigot, Laurent; Quiquempois, Yves

    2012-08-13

    A new type of Anti Resonant Reflecting Optical Waveguide (ARROW) fiber with a low refractive index contrast is reported. This waveguide is similar to a Bragg fiber for which the high index rings are replaced by discontinuous rings made of circular High Index Inclusions (HII). As compared to conventional Bragg fibers, such a new structure enables true Photonic BandGap (PBG) guidance and limits the number of cladding modes located within the high index regions, thus enhancing the guiding properties. A Mode Field Diameter (MFD) of 26 ?m is reported at a wavelength of 1400 nm. Single Mode (SM) behavior is also observed beyond 1400 nm for a 1 m-long fiber. PMID:23038519

  10. Fiber optic liquid refractive index sensor

    NASA Astrophysics Data System (ADS)

    Bhardwaj, Vanita; Gangwar, Rahul Kumar; Singh, Vinod Kumar

    2015-08-01

    In this present work we report fabrication of fiber optic liquid refractive index (RI) measurement sensor based on Michelson Interferometer method. This sensor was assembled by using graded index multimode (MM) fiber with core diameter 50 µm and the cladding of fiber was removed by simple chemical method. To perform this experiment a 2×2 3dB coupler is used. The fiber ends are then immersed in solvent and solution to provide reference and refractive index measurements, respectively. This method was successfully used to measure refractive index of Sodium Chloride (NaCl)-Water solution at different concentrations. The fringe contrast sensitivity of device is 92.90 dB/RIU measured in the RI range from 1.34 to 1.42 which is better than Mach-Zehnder Interferometer sensor [1] and Fabry perot based sensor [2]. The fabrication of sensor is simple, low cost and highly sensitive.

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

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

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

  12. Speckle interferometry using fiber optic phase stepping

    NASA Technical Reports Server (NTRS)

    Mercer, Carolyn R.; Beheim, Glenn

    1989-01-01

    A system employing closed-loop phase-stepping is used to measure the out-of-plane deformation of a diffusely reflecting object. Optical fibers are used to provide reference and object beam illumination for a standard two-beam speckle interferometer, providing set-up flexibility and ease of alignment. Piezoelectric fiber-stretchers and a phase-measurement/servo system are used to provide highly accurate phase steps. Intensity data is captured with a charge-injection-device camera, and is converted into a phase map using a desktop computer. The closed-loop phase-stepping system provides 90 deg phase steps which are accurate to 0.02 deg, greatly improving this system relative to open-loop interferometers. The system is demonstrated on a speckle interferometer, measuring the rigid-body translation of a diffusely reflecting object with an accuracy + or - 10 deg, or roughly + or - 15 nanometers. This accuracy is achieved without the use of a pneumatically mounted optics table.

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

    SciTech Connect

    Raju, Thokala Soloman; Panigrahi, Prasanta K.

    2011-09-15

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

  14. Biocompatible silk step-index optical waveguides

    PubMed Central

    Applegate, Matthew B.; Perotto, Giovanni; Kaplan, David L.; Omenetto, Fiorenzo G.

    2015-01-01

    Biocompatible optical waveguides were constructed entirely of silk fibroin. A silk film (n=1.54) was encapsulated within a silk hydrogel (n=1.34) to form a robust and biocompatible waveguide. Such waveguides were made using only biologically and environmentally friendly materials without the use of harsh solvents. Light was coupled into the silk waveguides by direct incorporation of a glass optical fiber. These waveguides are extremely flexible, and strong enough to survive handling and manipulation. Cutback measurements showed propagation losses of approximately 2 dB/cm. The silk waveguides were found to be capable of guiding light through biological tissue. PMID:26600988

  15. Biocompatible silk step-index optical waveguides.

    PubMed

    Applegate, Matthew B; Perotto, Giovanni; Kaplan, David L; Omenetto, Fiorenzo G

    2015-11-01

    Biocompatible optical waveguides were constructed entirely of silk fibroin. A silk film (n=1.54) was encapsulated within a silk hydrogel (n=1.34) to form a robust and biocompatible waveguide. Such waveguides were made using only biologically and environmentally friendly materials without the use of harsh solvents. Light was coupled into the silk waveguides by direct incorporation of a glass optical fiber. These waveguides are extremely flexible, and strong enough to survive handling and manipulation. Cutback measurements showed propagation losses of approximately 2 dB/cm. The silk waveguides were found to be capable of guiding light through biological tissue. PMID:26600988

  16. Improved analytical model for the field of index-guiding microstructured optical fibers

    NASA Astrophysics Data System (ADS)

    Sharma, Dinesh Kumar; Sharma, Anurag

    2016-05-01

    We present an improved version of our earlier developed analytical field model for the fundamental mode of index-guiding microstructured optical fibers (MOFs), to obtain better accuracy in the simulated results. Using this improved field model, we have studied the splice losses between an MOF and a traditional step-index single-mode fiber (SMF). Comparisons with available experimental and numerical simulation results have also been included.

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

    PubMed Central

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

    2012-01-01

    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.

  18. Temperature dependence of the refractive index of optical fibers

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    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.

  19. High-precision confocal reflection measurement for two dimensional refractive index mapping of optical fibers

    NASA Astrophysics Data System (ADS)

    Raisin, Philippe; Scheuner, Jonas; Romano, Valerio; Ryser, Manuel

    2015-05-01

    We introduce a new fiber-optical approach for reflection based refractive index mapping. Our approach leads to improved stability and reliability over existing free-space confocal instruments and significantly cuts alignment efforts and reduces the number of components needed. Other than properly cleaved fiber end-faces, this setup requires no additional sample preparation. The instrument is calibrated by means of a set of samples with known refractive indices. The index steps of commercially available fibers are measured accurately down to < 10-3. The precision limit of the instrument is currently of the order of 10-4.

  20. Characterization of graded index optical fibers by digital holographic interferometry.

    PubMed

    Wahba, Hamdy H; Kreis, Thomas

    2009-03-10

    For the first time to our knowledge, digital holography is used to determine the distribution of parabolic or nonparabolic refractive index fields in graded index optical fibers. The fiber is embedded in an index matching fluid whose refractive index can be varied to a matching and mismatching index with respect to that of the cladding. In experiments for both cases high precision phase-shifting digital holographic interferometry is applied with numerical evaluation employing the multilayer model for recognition of the refraction. Due to the higher redundancy in the multiple phase-shifted holograms better accuracy can be obtained compared to classical two-beam interferometry. Therefore the holographic method is recommended as a nondestructive and noncontacting method for characterizing graded index optical fibers. PMID:19277091

  1. Dispersion flattening by optimization of fiber index profile

    NASA Astrophysics Data System (ADS)

    Santitissadeekorn, Naratip

    The advent of wavelength division multiplexing (WDM) and the development of AllWaveRTM fiber, which has low attenuation over the bandwidth of 1.30 through 1.60 mum, offers the potential for ultra high capacity optical communication systems. What remains to be solved is manageable dispersion over this bandwidth. This requirement demands the design of non-zero dispersion-flattened fibers. This novel type of optical fiber is usually composed of multiple claddings and requires numerical modeling for its design. Thus, the subject matter of the design is to develop a fast, simple and reliable numerical technique that can simulate dispersion characteristics of optical fibers featuring arbitrary refractive index profiles. In this thesis a numerical tool using the pseudospectral method based on Chebyshev interpolation is developed. Using this tool is possible to determine the refractive index profiles of optical fibers to achieve fibers with low dispersion over a broad spectral bandwidth.

  2. All-fiber mode-group-selective photonic lantern using graded-index multimode fibers.

    PubMed

    Huang, Bin; Fontaine, Nicolas K; Ryf, Roland; Guan, Binbin; Leon-Saval, Sergio G; Shubochkin, R; Sun, Y; Lingle, R; Li, Guifang

    2015-01-12

    We demonstrate the first all-fiber mode-group-selective photonic lantern using multimode graded-index fibers. Mode selectivity for mode groups LP(01), LP(11) and LP(21)+LP(02) is 20-dB, 10-dB and 7-dB respectively. The insertion loss when butt coupled to multimode graded-index fiber is below 0.6-dB. The use of the multimode graded-index fibers in the taper can significantly reduce the adiabaticity requirement. PMID:25835669

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

    NASA Technical Reports Server (NTRS)

    Kawalko, Stephen F.

    1990-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2007-05-01

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

  5. Adiabatic tapered optical fiber fabrication in two step etching

    NASA Astrophysics Data System (ADS)

    Chenari, Z.; Latifi, H.; Ghamari, S.; Hashemi, R. S.; Doroodmand, F.

    2016-01-01

    A two-step etching method using HF acid and Buffered HF is proposed to fabricate adiabatic biconical optical fiber tapers. Due to the fact that the etching rate in second step is almost 3 times slower than the previous droplet etching method, terminating the fabrication process is controllable enough to achieve a desirable fiber diameter. By monitoring transmitted spectrum, final diameter and adiabaticity of tapers are deduced. Tapers with losses about 0.3 dB in air and 4.2 dB in water are produced. The biconical fiber taper fabricated using this method is used to excite whispering gallery modes (WGMs) on a microsphere surface in an aquatic environment. So that they are suitable to be used in applications like WGM biosensors.

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

    NASA Astrophysics Data System (ADS)

    Wahba, H. H.

    2014-10-01

    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 π/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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    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.

  8. Spectral characteristics of draw-tower step-chirped fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Idrisov, Ravil F.; Varzhel, Sergey V.; Kulikov, Andrey V.; Meshkovskiy, Igor K.; Rothhardt, Manfred; Becker, Martin; Schuster, Kay; Bartelt, Hartmut

    2016-06-01

    This paper presents research results on the spectral properties of step-chirped fiber Bragg grating arrays written during the fiber drawing process into a birefringent optical fiber with an elliptical stress cladding. The dependences of resonance shift of the step-chirped fiber Bragg grating on bending, on applied tensile stress and on temperature have been investigated. A usage of such step-chirped fiber Bragg gratings in fiber-optic sensing elements creation has been considered.

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

    SciTech Connect

    Raju, Thokala Soloman; Panigrahi, Prasanta K.

    2010-04-15

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

  10. Phase stepping optical profilometry using fiber optic Lloyd's mirrors.

    PubMed

    Kösoğlu, Gülşen; Yüksel, Heba; Inci, Mehmet Naci

    2016-02-01

    A three-step phase stepping profilometry based on a fiber optic Lloyd's mirror assembly is employed in the optical profilometry for the first time to measure the shapes of 3D objects. Required π/2 phase shifts for interference fringe pattern are obtained by mechanically sliding the Lloyd assembly via an ordinary micrometer stage. The experimental setup is simple and low cost to construct, and is insensitive to the ambient temperature fluctuations and environmental vibrations that cause unwanted effects on the projected fringe pattern. Consecutive interferograms are captured by a CCD camera and are processed with an algorithm to accomplish 3D topographies. PMID:26836090

  11. Constant Refractive Index Multi-Core Fiber Laser

    SciTech Connect

    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

    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.

  12. Graded-index optical fiber tweezers with long manipulation length.

    PubMed

    Gong, Yuan; Huang, Wei; Liu, Qun-Feng; Wu, Yu; Rao, Yunjiang; Peng, Gang-Ding; Lang, Jinyi; Zhang, Ke

    2014-10-20

    Long manipulation length is critical for optical fiber tweezers to enhance the flexibility of non-contact trapping. In this paper a long manipulation distance of more than 40 μm is demonstrated experimentally by the graded-index fiber (GIF) tweezers, which is fabricated by chemically etching a GIF taper with a large cone angle of 58°. The long manipulation distance is obtained by introducing an air cavity between the lead-in single mode fiber and the GIF as well as by adjusting the laser power in the existence of a constant background flow. The influence of the cavity length and the GIF length on the light distribution and the focusing length of the GIF taper is investigated numerically, which is helpful for optimizing the parameters to perform stable optical trapping. This kind of optical fiber tweezers has advantages including low-cost, easy-to-fabricate and easy-to-use. PMID:25401560

  13. Photonic crystal fiber tip interferometer for refractive index sensing.

    PubMed

    Mileńko, Karolina; Hu, Dora Juan Juan; Shum, Perry Ping; Zhang, Taishi; Lim, Jun Long; Wang, Yixin; Woliński, Tomasz R; Wei, Huifeng; Tong, Weijun

    2012-04-15

    In this paper we present an interferometer based on photonic crystal fiber (PCF) tip ended with a solid silica-sphere for refractive index sensing. The sensor is fabricated by splicing one end of the holey PCF to a single mode fiber (SMF) and applying arc at the other end to form a solid sphere. The sensor has been experimentally tested for refractive index and temperature sensing by monitoring its wavelength shift. Measurement results show that the sensor has the resolution of the order of 8.7×10(-4) over the refractive index range of 1.33-1.40, and temperature sensitivity of the order of 10 pm/°C in the range of 20-100 °C. PMID:22513690

  14. Single Step Sintered Calcium Phosphate Fibers from Avian EGG Shell

    NASA Astrophysics Data System (ADS)

    Dadhich, Prabhash; Das, Bodhisatwa; Dhara, Santanu

    2013-11-01

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

  15. Analysis of dual-end-pumped Nd3+-doped index-crossover gain guided-index antiguided fiber laser

    NASA Astrophysics Data System (ADS)

    Shen, Xiao; Wei, Wei; Zou, Hui; Zhang, Liaolin

    2016-05-01

    A dual-end pumped Nd3+-doped index-crossover gain guided-index antiguided (IGG-IAG) fiber laser is analyzed in theory. Pump light propagation and output laser characteristics are both explored by solving the related rate equations. Simulation results show that pump power confined in the IGG-IAG fiber core is larger and more uniform than that of the gain-guided and index-antiguided(GG-IAG) fiber, and the optimum fiber length and the output power of the IGG-IAG fiber laser are both larger than that of GG-IAG fiber laser. The relationship between threshold pump power and doped concentration, fiber length, fiber radius is researched respectively. The analysis results give out a method for the optimal design of the IGG-IAG fiber laser.

  16. Refractive index measurement based on fiber Bragg grating connected with a multimode fiber core

    NASA Astrophysics Data System (ADS)

    Shao, Min; Qiao, Xueguang; Jiasurname, Zhenan; Fusurname, Haiwei; Liu, Yinggang; Li, Huidong; Zhao, Xue

    2015-09-01

    A novel fiber refractive index sensor based on a fiber-Bragg grating (FBG) connected with a section of multimode fiber core (MMFC) is proposed and demonstrated. The MMFC excites high-order modes to form modal interference, and the core mode reflected by the FBG is sensitive to the surrounding refractive index (SRI) for the power of the core mode within MMFC is dependent on SRI. Measuring the reflective power variation of the core mode could realize the refractive index (RI) detection. Experimental results show that the core mode of FBG has a linear response to RI with enhanced sensitivity of 193.55 dB/RIU in the RI range of 1.3350-1.4042 RIU. The temperature effect of the sensor is also discussed.

  17. Improved fully vectorial effective index method in photonic crystal fiber.

    PubMed

    Zhao, Xingtao; Hou, Lantian; Liu, Zhaolun; Wang, Wei; Zhou, Guiyao; Hou, Zhiyun

    2007-07-01

    In the simulation of photonic crystal fibers, the fixed value of the normalized equivalent core radius (p/Lambda) in the fully vectorial effective index method is inaccurate. For what is believed to be the first time, the relation of p/Lambda with normalized frequency (Lambda/lambda) and hole-to-pitch ratio (d/Lambda) is obtained. The improved fully vectorial effective index method (IFVEIM) is proposed. The modal properties computed with the IFVEIM, such as the effective index and the total dispersion, are closely matched to those of the multipole method as well as to experimental values, and the errors of the effective index have been reduced by 2 to 3 orders of magnitude. PMID:17571146

  18. Multi-point fiber-optic refractive index sensor by using coreless fibers

    NASA Astrophysics Data System (ADS)

    Liu, Xiuxin; Zhang, Xinpu; Liu, Yun; Liu, Zigeng; Peng, Wei

    2016-04-01

    We present a novel multi-point fiber-optic refractive index (RI) sensor based on two different length coreless fibers spliced between single mode fibers (SMFs). The sensing probe operated based on multimode interference. A multi-point interferometer with 25 mm and 30 mm coreless fiber is fabricated and the measurement of RI is realized by measuring the wavelength shift of resonance dips in the transmission spectrum of the multi-point interferometer. Experimental characterization for a multi-point refractometer is presented. In the RI range of 1.3288-1.3666, the corresponding RI sensitivities are 148.60 nm/RIU and 119.27 nm/RIU for each point, respectively. We demonstrate that this multi-point fiber optic interferometer can be used as a simple transducer for RI sensing with comparable sensitivity.

  19. Templated growth of II-VI semiconductor optical fiber devices and steps towards infrared fiber lasers

    NASA Astrophysics Data System (ADS)

    Sazio, Pier J. A.; Sparks, Justin R.; He, Rongrui; Krishnamurthi, Mahesh; Fitzgibbons, Thomas C.; Chaudhuri, Subhasis; Baril, Neil F.; Peacock, Anna C.; Healy, Noel; Gopalan, Venkatraman; Badding, John V.

    2015-02-01

    ZnSe and other zinc chalcogenide semiconductor materials can be doped with divalent transition metal ions to create a mid-IR laser gain medium with active function in the wavelength range 2 - 5 microns and potentially beyond using frequency conversion. As a step towards fiberized laser devices, we have manufactured ZnSe semiconductor fiber waveguides with low (less than 1dB/cm at 1550nm) optical losses, as well as more complex ternary alloys with ZnSxSe(1-x) stoichiometry to potentially allow for annular heterostructures with effective and low order mode corecladding waveguiding.

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

    PubMed

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

    2014-06-15

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

  1. Reflectance Imaging by Graded-Index Short Multimode Fiber

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

    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.

  2. Refractive index sensitivity of long-period fiber gratings written in thinned cladding fiber by CO2 laser

    NASA Astrophysics Data System (ADS)

    Zhao, Yunhe; Liu, Yunqi; Guo, Qiang; Wang, Tingyun

    2014-05-01

    We demonstrate the fabrication of the long-period fiber gratings (LPFGs) in the thinned cladding fiber (TCF) using CO2 laser. The sensing response of the gratings to surrounding refractive index has been investigated experimentally. The LPFGs written in the TCF could be used as the high sensitive refractive index sensors.

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Knudsen, Sverre; Bløtekjær, Kjell

    1995-06-01

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

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

    NASA Astrophysics Data System (ADS)

    Spitzberg, Joshua David

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

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

    PubMed Central

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

    2013-01-01

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

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

    SciTech Connect

    Chen Jihuan; Zhao Jiarong; Huang Xuguang; Huang Zhenjian

    2010-10-10

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

  8. Graded index porous optical fibers – dispersion management in terahertz range.

    PubMed

    Ma, Tian; Markov, Andrey; Wang, Lili; Skorobogatiy, Maksim

    2015-03-23

    A graded index porous optical fiber incorporating an air-hole array featuring variable air-hole diameters and inter-hole separations is proposed, fabricated, and characterized in a view of the fiber potential applications in low-loss, low-dispersion terahertz guidance. The proposed fiber features simultaneously low modal and intermodal dispersions, as well as low loss in the terahertz spectral range. We experimentally demonstrate that graded index porous fibers exhibit smaller pulse distortion, larger bandwidth, and higher excitation efficiency when compared to fibers with uniform porosity. PMID:25837124

  9. Design of fiber metamaterials with negative refractive index in the infrared.

    PubMed

    Townsend, Scott; Zhou, Shiwei; Li, Qing

    2015-07-13

    Metamaterials possess intricate, sub-wavelength microstructures, making scalability a salient concern in regard to their practicality. Fiber-drawing offers a route to producing large quantities of material at relatively low cost, though to our knowledge, a fiber-based design capable of negative refractive index behaviour has not yet been proposed. We submit that the electric and magnetic dipole resonance modes of the fiber can be enhanced by including in the fiber aligned metallic inclusions. Addition of a solid metallic core can effect a synchronisation of these modes, allowing a collection of the fibers to possess negative refractive index. PMID:26191880

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

    NASA Astrophysics Data System (ADS)

    Hebenstreit, Florian

    2011-07-01

    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 fiber-based devices, and the characterization of CO2-laser-induced LPFGs are identified and discussed.

  11. Mechanical and optical behavior of index guiding photonic crystal fibers (PCF)

    NASA Astrophysics Data System (ADS)

    Kobelke, Jens; Gerth, Kirsten; Kirchhof, Johannes; Schuster, Kay; Moerl, Klaus; Aichele, Claudia

    2004-07-01

    The optical loss behavior of index guiding PC fibers made from high purity silica, was investigated with regard to the preform preparation steps and drawing procedure. Loss effects in the 1.4 μm region are caused mostly by incorporation of hydroxide groups during PC preform preparation. Typical sources are flame heat treatment procedures. However, hydroxide based absorption by water permeation into the holey structure was not observed, not even by storage in humid atmosphere over days. PCFs show additional NIR attenuation, possibly caused by drawing induced atomic defects in the pure silica material. By advanced PC preform preparation the minimum attentuation in the NIR range can be depressed down to 2.9 dB/km at 1.3 μm. PCFs have a reduced tensile strength in comparison with compact silica fibers. The mechanical stability increases with the cross section area of the solid outer cladding. This resembles the behavior of single capillary fibers without inner holey or cobweb structure. The tensile strength of PCFs decreases after a few days of hole contamination with condensed water.

  12. 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...

  13. D-shaped fiber grating refractive index sensor induced by an ultrashort pulse laser.

    PubMed

    Liao, Changrui; Wang, Qiao; Xu, Lei; Liu, Shen; He, Jun; Zhao, Jing; Li, Zhengyong; Wang, Yiping

    2016-03-01

    The fabrication of fiber Bragg gratings was here demonstrated using ultrashort pulse laser point-by-point inscription. This is a very convenient means of creating fiber Bragg gratings with different grating periods and works by changing the translation speed of the fiber. The laser energy was first optimized in order to improve the spectral properties of the fiber gratings. Then, fiber Bragg gratings were formed into D-shaped fibers for use as refractive index sensors. A nonlinear relationship was observed between the Bragg wavelength and liquid refractive index, and a sensitivity of ∼30  nm/RIU was observed at 1.450. This shows that D-shaped fiber Bragg gratings might be used to develop promising biochemical sensors. PMID:26974608

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

    PubMed

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

    2005-04-15

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

  15. Surface plasmon resonance sensor using an optical fiber with an inverted graded-index profile.

    PubMed

    Bardin, Fabrice; Ivan, Kasík; Trouillet, Alain; Matejec, Vlastimil; Gagnaire, Henri; Chomát, Mirek

    2002-05-01

    A new optical fiber sensor based on surface plasmon resonance is described. It uses an optical fiber with an inverted graded-index profile. A theoretical analysis of the optical propagation when a point light source was used and a computation of the optical power transmitted by the fiber were performed. Experiments were carried out to measure changes of the transmitted power caused by refractive-index variations of the surrounding dielectric medium. Both the simulation and experiments have shown that the sensor exhibits high sensitivity for changes of the surrounding medium in a refractive index range from 1.33 to 1.39. PMID:12009163

  16. High index contrast semiconductor ARROW and hybrid ARROW fibers.

    PubMed

    Healy, N; Sparks, J R; He, R R; Sazio, P J A; Badding, J V; Peacock, A C

    2011-05-23

    We investigate the guidance properties of two photonic crystal fibers that have been fabricated by filling the holes of a silica template with hydrogenated amorphous silicon inclusions. The first is an all-solid fiber that guides light via an antiresonant reflecting optical waveguiding mechanism and the second is only partially filled so that it guides light by a hybrid of modified total internal reflection and antiresonant reflecting optical waveguiding. It will be shown that, by selectively filling the silica template to leave an unfilled internal ring of holes, the fiber's confinement loss can be reduced significantly. This novel fiber design in which the light guided in the silica core can be modified by the semiconductor cladding provides a route to integrating functional semiconductor fibers with existing silica fiber infrastructures. PMID:21643359

  17. Reverse dispersion fiber with depressed core-index profile for dispersion-managed fiber pairs

    NASA Astrophysics Data System (ADS)

    Jiang, Xiaoqiang; Wang, Ruichun

    2005-11-01

    A reverse dispersion fiber (RDF) with depressed core-index profile has been developed successfully by using plasma chemical vapor deposition (PCVD) process. The fabricated RDF has a core-effective-area of 45 ?m2, a dispersion of -19.65 ps/nm/km and a dispersion slope of -0.132 ps/nm2/km while maintaining the low bending induced attenuation and low PMD value. The dispersion-managed pairs, which consisted of RDF and non-zero dispersion shifted fiber with ultra large effective core-area (ULAF), have the ultra low dispersion slope of less than 0.006 ps/nm2/km at the wavelength range of 1530-1625 nm, and the largest dispersion value is lower than 0.2 ps/nm/km. Moreover, the attenuation characteristic also shows a remarkable flatness over the broadband wavelength, the attenuation at 1550 nm is only 0.224 dB/km. The dispersion-managed pairs are suitable for large capacity, high bit-rate long-haul wavelength division multiplexing (WDM) transmission system without using dispersion compensation mode.

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

    PubMed

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

    2014-11-01

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

  19. Waveguide-loaded silica fibers for coupling to high-index micro-resonators

    NASA Astrophysics Data System (ADS)

    Latawiec, P.; Burek, M. J.; Venkataraman, V.; Lončar, M.

    2016-01-01

    Tapered silica fibers are often used to rapidly probe the optical properties of micro-resonators. However, their low refractive index precludes phase-matching when coupling to high-index micro-resonators, reducing efficiency. Here, we demonstrate efficient optical coupling from tapered fibers to high-index micro-resonators by loading the fibers with an ancillary adiabatic waveguide-coupler fabricated via angled-etching. We demonstrate greatly enhanced coupling to a silicon multimode micro-resonator when compared to coupling via the bare fiber only. Signatures of resonator optical bistability are observed at high powers. This scheme can be applied to resonators of any size and material, increasing the functional scope of fiber coupling.

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

    NASA Astrophysics Data System (ADS)

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

    2008-04-01

    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.

  1. Design of reflective optical fiber sensor for determining refractive index and sugar concentration of aqueous solutions

    NASA Astrophysics Data System (ADS)

    Marzuki, Ahmad; Wulan Sari, Nila; Riatun

    2016-02-01

    A reflective optical fiber sensor designed for measuring refractive index and sugar concentration of aqueous solutions is described. Two strains of parallel polymer optical fibers (POF) were wrapped in a bundle such that one of their fiber's end cross-sections had the same distance to the mirror surface. The light coming out from one strain of the fiber was reflected by the mirror to the second fiber. Sugar concentration of the aqueous solution filling the space between the fiber ends and the mirror was varied (1.0 M, 1.5 M, 2.0 M, 2.5 M, 3.0 M, 4.0 M, and 5.0 M). It was shown from the experiment that light intensity detected by photo-detector is linearly related to the percentage of the dissolved sugar in the solution as well as the variation of the sugar solution refractive index (R2 = 0.987).

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

    PubMed Central

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

    2013-01-01

    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

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

    PubMed

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

    2013-01-01

    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

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

    PubMed

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

    2010-12-20

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

  5. Unusual fault detection and loss analysis in optical fiber connections with refractive index matching material

    NASA Astrophysics Data System (ADS)

    Kihara, Mitsuru; Nagano, Ryuichiro; Izumita, Hisashi; Toyonaga, Masanobu

    2012-05-01

    We investigated and analyzed an unusual fault that occurs in optical access fiber networks, which is caused by a defective fiber connection. We developed a fault-detection system to locate such a fault by using both optical power level and optical pulse measurement methods. We investigated a defective mechanical splice in three laboratory tests: outward appearance, non-destructive, and dismantled. As a result, we confirmed that the defective mechanical splice had large gaps of more than 10 ?m. We also analyzed the unusual fault that occurs from such a defective mechanical splice in mechanically transferrable (MT) connector experiments. The experimental results revealed that the optical performance of fiber connections with a mixture of refractive index matching material and air-filled gaps was extremely unstable and varied widely. In the worst case, the insertion loss worsened to more than 30 dB. The case of the fault caused by a mixture of refractive index matching material and air-filled gaps between the ends of optical fibers is thought to occur independently of the sorts or structures of optical fiber connectors and could be a characteristic peculiar to optical fiber connections using refractive index matching material. These findings can be applied to optical fiber connections that use refractive index matching material, such as MT connectors in outside underground facilities, mechanical splices, or field assembly connectors at aerial and home sites in optical access networks. These findings also support the practical construction and operation of optical network systems.

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

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

    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.

  7. Low-loss coupling between two single-mode optical fibers with different mode-field diameters using a graded-index multimode optical fiber.

    PubMed

    Mafi, Arash; Hofmann, Peter; Salvin, Clémence Jollivet; Schülzgen, Axel

    2011-09-15

    We present a method for ultra-low-loss coupling between two single-mode optical fibers with different mode-field diameters using multimode interference in a graded-index multimode optical fiber. We perform a detailed analysis of the interference effects and show that the graded-index fiber can also be used as a beam expander or condenser. The results are important for devices in which optical fibers with different mode-field diameters are coupled in series, such as in ultra-short-pulse fiber ring lasers, or in optical fiber communication links. PMID:21931402

  8. Exploiting the image of the surface reflectivity to measure refractive index profiling for various optical fibers.

    PubMed

    Weng, Chun-Jen; Hsu, Ken-Yuh; Chen, Yung-Fu

    2015-05-01

    A direct image method of surface reflectivities on a cleaved fiber end with a filtered halogen lamp and a TE-cooled CCD with high dynamic range is proposed to measure the multi-wavelength refractive index profiling (RIP). A polished black glass is used to be a reference standard for measuring the absolute reflectivity of the fiber end. With the developed calibration procedures, both the spatially dependent sensitivity and spectral responsivity of the CCD pixels can be eliminated to achieve the high spatial accuracy. Tested fiber is connected with a fiber terminator to prevent errors from the backside return light. With the present method, the RIP can be precisely measured for not only multi-mode fibers but also single-mode fibers. PMID:25969266

  9. One-step Tape Casting of Composites via Slurry on Fiber

    NASA Technical Reports Server (NTRS)

    deGroh, Henry C., III

    2001-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  11. Spectral and spatial characterization of perfluorinated graded-index polymer optical fibers for the distribution of optical wireless communication cells.

    PubMed

    Hajjar, Hani Al; Montero, David S; Lallana, Pedro C; Vázquez, Carmen; Fracasso, Bruno

    2015-02-10

    In this paper, the characterization of a perfluorinated graded-index polymer optical fiber (PF-GIPOF) for a high-bitrate indoor optical wireless system is reported. PF-GIPOF is used here to interconnect different optical wireless access points that distribute optical free-space high-bitrate wireless communication cells. The PF-GIPOF channel is first studied in terms of transmission attenuation and frequency response and, in a second step, the spatial power profile distribution at the fiber output is analyzed. Both characterizations are performed under varying restricted mode launch conditions, enabling us to assess the transmission channel performance subject to potential connectorization errors within an environment where the end users may intervene by themselves on the home network infrastructure. PMID:25968032

  12. High-refractive-index transparent coatings enhance the optical fiber cladding modes refractometric sensitivity.

    PubMed

    Renoirt, Jean-Michel; Zhang, Chao; Debliquy, Marc; Olivier, Marie-Georges; Mégret, Patrice; Caucheteur, Christophe

    2013-11-18

    The high order cladding modes of standard single mode optical fiber appear in quasi-degenerate pairs corresponding to mostly radially or mostly azimuthally polarized light. In this work, we demonstrate that, in the presence of a high-refractive-index coating surrounding the fiber outer surface, the wavelength spacing between the orthogonally polarized cladding modes families can be drastically enhanced. This behavior can be advantageously exploited for refractometric sensing purposes. For this, we make use of tilted fiber Bragg gratings (TFBGs) as spectral combs to excite the orthogonally polarized cladding modes families separately. TFBGs were coated with a nanometer-scale transparent thin film characterized by a refractive index value close to 1.9, well higher than the one of pure silica. This coating brings two important assets: an ~8-fold increase in refractometric sensitivity is obtained in comparison to bare TFBGs while the sensitivity is extended to surrounding refractive index (SRI) values above 1.45. PMID:24514423

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

    SciTech Connect

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

    2003-07-24

    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.

  14. High power fiber delivery for laser ignition applications.

    PubMed

    Yalin, Azer P

    2013-11-01

    The present contribution provides a concise review of high power fiber delivery research for laser ignition applications. The fiber delivery requirements are discussed in terms of exit energy, intensity, and beam quality. Past research using hollow core fibers, solid step-index fibers, and photonic crystal and bandgap fibers is summarized. Recent demonstrations of spark delivery using large clad step-index fibers and Kagome photonic bandgap fibers are highlighted. PMID:24514929

  15. Refractive index sensing using V-shaped polymer optical fibers

    NASA Astrophysics Data System (ADS)

    Lee, Heeyoung; Hayashi, Neisei; Mizuno, Yosuke; Nakamura, Kentaro

    2015-11-01

    Although polymer optical fiber (POF) tapers with high flexibility have been used to measure the refractive indices (RIs) of liquids, their fabrication have caused some inconvenience including the need to use external heat sources or chemicals. Here, as an alternative, we develop a simple, secure, and low-cost method of measuring RIs of liquids using V-shaped bent POFs. When the bending angle is 120° (experimentally optimized), with increasing RI, the transmitted power increases almost linearly with a dependence coefficient of approximately 210 dB/RI unit.

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    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.

  17. Refraction index measurement using long period grating fabricated by symmetrical-hole fiber

    NASA Astrophysics Data System (ADS)

    Kang, Juan; Dong, Xinyong; Li, Mengchao; Zhang, Zaixuan; Jin, Shangzhong

    2010-12-01

    A Long-Period Fiber Grating (LPFG) fabricated by CO2 laser in a symmetrical two-hole single-mode fiber (STHSMF) for refraction index (RI) measurement is demonstrated. The solved sugar liquid of different concentration was filled into the holes by capillary force and its RI was experimentally measured. The results show that resonant peak shifts toward shorter wavelengths with its resonance peak intensity changes a little when the external refractive index increases. RI sensitivity of 141.67 nm/RIU have been achieved with R2 of 0.975.The temperature sensitivity of the STHSMF is also investigated.

  18. Refraction index measurement using long period grating fabricated by symmetrical-hole fiber

    NASA Astrophysics Data System (ADS)

    Kang, Juan; Dong, Xinyong; Li, Mengchao; Zhang, Zaixuan; Jin, Shangzhong

    2011-01-01

    A Long-Period Fiber Grating (LPFG) fabricated by CO2 laser in a symmetrical two-hole single-mode fiber (STHSMF) for refraction index (RI) measurement is demonstrated. The solved sugar liquid of different concentration was filled into the holes by capillary force and its RI was experimentally measured. The results show that resonant peak shifts toward shorter wavelengths with its resonance peak intensity changes a little when the external refractive index increases. RI sensitivity of 141.67 nm/RIU have been achieved with R2 of 0.975.The temperature sensitivity of the STHSMF is also investigated.

  19. Optical fiber Fabry-Perot refractive index sensor based on porous Al2O3 film

    NASA Astrophysics Data System (ADS)

    Huang, Chujia; Yang, Minghong; Xie, Weijing; Dai, Jixiang

    2015-08-01

    A fiber refractive index sensor based on porous alumina is fabricated by pasting porous alumina film with 42.36μm on single mode fiber tip using the UV-cured adhesive. Experimental results show that the proposed sensor has a very high correlation with glycerine concentration (0.0%~80.0%) with correlation coefficient of 99.771%. Its sensitivity and resolution was measure to be 99.771%, 154 nm/RIU and 1×10-4 respectively when the refractive index changes from 1.333 to 1.443.

  20. Diffusion tensor imaging fiber tracking with reliable tracking orientation and flexible step size☆

    PubMed Central

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

    2013-01-01

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

  1. Photonic crystal fibers confining light by both index-guiding and bandgap-guiding: hybrid PCFs.

    PubMed

    Xiao, Limin; Jin, Wei; Demokan, M S

    2007-11-26

    We propose two kinds of hybrid photonic crystal fiber (PCF) structures and investigate the properties of such PCFs in detail. The modal effective index, mode field area, confinement loss, group velocity dispersion, and birefringence are numerically simulated and compared with those of the corresponding index-guiding and bandgap PCFs, which allows for a deeper understanding of the guiding mechanism of the hybrid PCFs. The advantages of hybrid PCFs and potential applications are also discussed. PMID:19550851

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

    PubMed

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

    2009-11-15

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

  3. Wavelength dependence of stress-induced time of flight variations in graded-index multimode fibers

    NASA Astrophysics Data System (ADS)

    Kashima, N.; Kawashima, T.; Miyauchi, S.

    2015-10-01

    We investigate the wavelength dependence of stress-induced time of flight variations in graded-index multimode fibers (GI-MMFs) for wavelength λ = 1.26 μm ∼1.58 μm, theoretically and experimentally. Calculations were made based on simple equations using the refractive index of silica fibers. We measured the wavelength dependence of stress-induced time of flight variations by a newly proposed measurement method. We confirmed the similar wavelength dependence of GI-MMFs to that for standard single mode fibers (SSMF). However, the value of them is different. We compare the experimental and theoretical results for two types of fibers. The comparison indicates that the difference of stress-induced time of flight variations between two types of fibers is mainly due to the group velocity difference. We conclude that there is no significant difference of the photo-elastic constant between the measured SSMFs and GI-MMFs. Although many properties of GI-MMFs depended on the mode power distribution in general, we conclude the dependence of stress-induced time of flight variations on mode power distribution is small for the measured fibers.

  4. Low-cost refractive index and strain sensor based on tapered fibers

    NASA Astrophysics Data System (ADS)

    Mas, Sara; Martí, Javier; Monzón-Hernández, David; Palací, Jesús

    2016-02-01

    In this paper, biconical tapered fibers are used to carry out sensing in a simple and effective way by using an incoherent source and a power meter. This approach reduces the cost and complexity of traditional schemes based on tunable lasers while providing similar performance. Refractive index and strain sensing measurements are presented and their performance discussed.

  5. Thermal-induced transverse-mode evolution in thermally guiding index-antiguided-core fiber.

    PubMed

    Kong, Lingchao; Cao, Jianqiu; Guo, Shaofeng; Jiang, Zongfu; Lu, Qisheng

    2016-02-10

    The transverse-mode evolution in thermally guided (TG) index-antiguided-core (IAGc) fibers is numerically studied in this paper. With the finite-element method and thermal conduction equations, the fundamental mode evolution with a thermal load is investigated, and four evolution stages (i.e., the cladding-confined, quasi-cladding-confined, quasi-core-confined, and core-confined) are revealed. Thermal load thresholds corresponding to these stages are presented. Furthermore, the field evolutions of high-order modes also are investigated; the filling factors of these modes are discussed as well. The pertinent results can provide significant reference for designing TG IAGc fibers and understanding the thermal effect on the transverse mode of fibers involving the index-antiguided core. PMID:26906395

  6. Study of lateral-drilled DBR fiber laser and its responsivity to external refractive index.

    PubMed

    Li, Jie; Liu, Bo; Sun, Li-Peng; Liang, Yizhi; Li, Mengmeng; Guan, Bai-Ou

    2016-05-01

    We report a lateral-drilled DBR fiber laser which contains a defective parabola-like opening inside the cavity fabricated by the CO2-laser exposure and study the laser responsivity to external refractive index (RI). Surrounding materials can readily reach the vicinity of the fiber core via the opening and interact with the laser mode. Research shows that the laser emission power mainly relies on changes of external RI while the lasing wavelength on temperature. The effects of structural parameters, pump power, and external refractive index on the RI responsivity of the device are demonstrated. The lasing threshold condition is also concerned. This work provides an opportunity for controlling emission characteristics of the DBR fiber laser through modification of external RI value, of which the results are valuable for the potential applications in optical sensing, tunable lasing, and etc. PMID:27137561

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

    NASA Astrophysics Data System (ADS)

    Liu, Xue-Ming

    2006-04-01

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

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

    PubMed

    Liu, Xue-Ming

    2006-04-01

    An automatic step adjustment (ASA) method for average power analysis (APA) technique used in fiber amplifiers is proposed in this paper for the first time. In comparison with the traditional APA technique, the proposed method has suggested two unique merits such as a higher order accuracy and an ASA mechanism, so that it can significantly shorten the computing time and improve the solution accuracy. A test example demonstrates that, by comparing to the APA technique, the proposed method increases the computing speed by more than a hundredfold under the same errors. By computing the model equations of erbium-doped fiber amplifiers, the numerical results show that our method can improve the solution accuracy by over two orders of magnitude at the same amplifying section number. The proposed method has the capacity to rapidly and effectively compute the model equations of fiber Raman amplifiers and semiconductor lasers. PMID:19516389

  9. Optical properties of side-polished polarization maintaining fiber coupled with a high index planar waveguide

    NASA Astrophysics Data System (ADS)

    Kim, Kwang Taek; Yoon, Dae Sung; Kwoen, Gyeong-il

    2004-01-01

    We have investigated the behavior of an asymmetric directional coupler made of a side-polished polarization maintaining (PM) fiber covered with a high index planar waveguide (PWG). The effects of the modal birefringence of the side-polished PM fiber, the structural parameters of PWG and the deformation of the PM fiber on the transmission characteristics of the coupler has been measured and explained. Experimental results show that the coincidence of resonance wavelengths for transverse electric and transverse magnetic polarizations can be achieved through proper control of device parameters. Furthermore, the fabricated devices revealed a superior immunity to deformation of PM fibers. The device fabrication procedure, particularly, alignment of the birefringence axis with PWG is described in detail.

  10. Premenopausal dietary carbohydrate, glycemic index, glycemic load, and fiber in relation to risk of breast cancer.

    PubMed

    Cho, Eunyoung; Spiegelman, Donna; Hunter, David J; Chen, Wendy Y; Colditz, Graham A; Willett, Walter C

    2003-11-01

    Carbohydrate intake, glycemic index, and glycemic load have been hypothesized to increase risk of breast cancer by raising insulin levels, but these associations have not been studied extensively. The insulin response to dietary carbohydrate is substantially greater among overweight women than among leaner women. Although fiber intake has been hypothesized to reduce the risk of breast cancer, data from early adult life are lacking. We examined dietary carbohydrate, glycemic index, glycemic load, and fiber in relation to breast cancer risk among 90655 premenopausal women in the Nurses' Health Study II aged 26-46 years in 1991. Diet was assessed with a food frequency questionnaire in 1991 and 1995. During 8 years of follow-up, we documented 714 incident cases of invasive breast cancer. Dietary carbohydrate intake, glycemic load, and glycemic index were not related to breast cancer risk in the overall cohort. However, the associations differed by body mass index (BMI): among women with BMI < 25 kg/m(2), the multivariate relative risks for the increasing quintiles of carbohydrate intake were 1.00 (referent), 0.87, 0.77, 0.66, and 0.62 [95% confidence interval, 0.40-0.97; P, test for trend = 0.02]; and among women with BMI >or=25 kg/m(2), the corresponding relative risks were 1.00 (referent), 1.30, 1.35, 1.50, and 1.47 (95% confidence interval, 0.84-2.59; P, test for trend = 0.14; P, test for interaction = 0.02). Similar interaction with BMI was observed for glycemic load, but not for glycemic index. Intakes of total fiber and different types of fiber were not appreciably related to breast cancer risk. Our findings suggest that the associations between carbohydrate intake or glycemic load and breast cancer risk among young adult women differ by body weight. Our data do not support a strong association between fiber intake and breast cancer risk. PMID:14652274

  11. High sensitivity refractive index sensor based on adiabatic tapered optical fiber deposited with nanofilm by ALD.

    PubMed

    Zhu, Shan; Pang, Fufei; Huang, Sujuan; Zou, Fang; Dong, Yanhua; Wang, Tingyun

    2015-06-01

    Atomic layer deposition (ALD) technology is introduced to fabricate a high sensitivity refractive index sensor based on an adiabatic tapered optical fiber. Different thickness of Al2O3 nanofilm is coated around fiber taper precisely and uniformly under different deposition cycles. Attributed to the high refractive index of the Al2O3 nanofilm, an asymmetry Fabry-Perot like interferometer is constructed along the fiber taper. Based on the ray-optic analysis, total internal reflection happens on the nanofilm-surrounding interface. With the ambient refractive index changing, the phase delay induced by the Goos-Hänchen shift is changed. Correspondingly, the transmission resonant spectrum shifts, which can be utilized for realizing high sensitivity sensor. The high sensitivity sensor with 6008 nm/RIU is demonstrated by depositing 3000 layers Al2O3 nanofilm as the ambient refractive index is close to 1.33. This high sensitivity refractive index sensor is expected to have wide applications in biochemical sensors. PMID:26072758

  12. Characterization of refractive index change and fabrication of long period gratings in pure silica fiber by femtosecond laser radiation

    NASA Astrophysics Data System (ADS)

    Ahmed, Farid; Joe, Hang-Eun; Min, Byung-Kwon; Jun, Martin B. G.

    2015-11-01

    Ultrafast laser induced refractive index (RI) change in the core of a standard telecommunication fiber is quantified using the spectral shift of an in-fiber Bragg grating (FBG) based Fabry-Perot cavity. Measured RI change is used to design and then fabricate long period grating (LPG) in pure silica core single mode fiber (SMF) employing identical laser irradiation conditions used in core index characterization. A core length of 100 μm within the 10 mm long cavity structure is scanned with ultrafast laser pulses, and the corresponding spectral shift is used to calculate index modification. The index change of 0.000449 found in characterization process is used to simulate the LPG in pure silica fiber. Identical index modulation written in pure silica fiber by femtosecond laser radiation provides a rejection band that is in good agreement with the simulation results. The fabricated LPG sensors are also characterized for ambient temperature and RI.

  13. Surface Plasmon Scattering in Exposed Core Optical Fiber for Enhanced Resolution Refractive Index Sensing.

    PubMed

    Klantsataya, Elizaveta; François, Alexandre; Ebendorff-Heidepriem, Heike; Hoffmann, Peter; Monro, Tanya M

    2015-01-01

    Refractometric sensors based on optical excitation of surface plasmons on the side of an optical fiber is an established sensing architecture that has enabled laboratory demonstrations of cost effective portable devices for biological and chemical applications. Here we report a Surface Plasmon Resonance (SPR) configuration realized in an Exposed Core Microstructured Optical Fiber (ECF) capable of optimizing both sensitivity and resolution. To the best of our knowledge, this is the first demonstration of fabrication of a rough metal coating suitable for spectral interrogation of scattered plasmonic wave using chemical electroless plating technique on a 10 μm diameter exposed core of the ECF. Performance of the sensor in terms of its refractive index sensitivity and full width at half maximum (FWHM) of SPR response is compared to that achieved with an unstructured bare core fiber with 140 μm core diameter. The experimental improvement in FWHM, and therefore the detection limit, is found to be a factor of two (75 nm for ECF in comparison to 150 nm for the large core fiber). Refractive index sensitivity of 1800 nm/RIU was achieved for both fibers in the sensing range of aqueous environment (1.33-1.37) suitable for biosensing applications. PMID:26426022

  14. Surface Plasmon Scattering in Exposed Core Optical Fiber for Enhanced Resolution Refractive Index Sensing

    PubMed Central

    Klantsataya, Elizaveta; François, Alexandre; Ebendorff-Heidepriem, Heike; Hoffmann, Peter; Monro, Tanya M.

    2015-01-01

    Refractometric sensors based on optical excitation of surface plasmons on the side of an optical fiber is an established sensing architecture that has enabled laboratory demonstrations of cost effective portable devices for biological and chemical applications. Here we report a Surface Plasmon Resonance (SPR) configuration realized in an Exposed Core Microstructured Optical Fiber (ECF) capable of optimizing both sensitivity and resolution. To the best of our knowledge, this is the first demonstration of fabrication of a rough metal coating suitable for spectral interrogation of scattered plasmonic wave using chemical electroless plating technique on a 10 μm diameter exposed core of the ECF. Performance of the sensor in terms of its refractive index sensitivity and full width at half maximum (FWHM) of SPR response is compared to that achieved with an unstructured bare core fiber with 140 μm core diameter. The experimental improvement in FWHM, and therefore the detection limit, is found to be a factor of two (75 nm for ECF in comparison to 150 nm for the large core fiber). Refractive index sensitivity of 1800 nm/RIU was achieved for both fibers in the sensing range of aqueous environment (1.33–1.37) suitable for biosensing applications. PMID:26426022

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

    SciTech Connect

    Saito, T.T.

    2000-05-01

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

  16. A microdroplet-etched fiber Fabry-Perot resonator for the refractive index sensing

    NASA Astrophysics Data System (ADS)

    Liu, Bo; Li, Jie; Sun, Li-Peng; Geng, Mengmei; Huang, Yunyun; Jin, Long; Guan, Bai-Ou

    2015-07-01

    We realize a microdroplet-etched fiber Fabry-Perot resonator. Strong polarization discrimination is achieved due to the asymmetric fiber cross section in the cavity, which should be useful for improving the measurement precision in the refractive index (RI) sensing application. The measured RI sensitivities are ~133.8 nm/RI-unit for the x polarization and 117.1 nm/RI-unit for the y polarizations, respectively. Simultaneously, the temperature effect can be eliminated by monitoring the peak difference of the two polarizations, which have the similar temperature coefficient but different RI responses.

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

    PubMed Central

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

    2013-01-01

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

  18. Glycemic index and microstructure analysis of a newly developed fiber enriched cookie.

    PubMed

    Schuchardt, Jan Philipp; Wonik, Jasmin; Bindrich, Ute; Heinemann, Michaela; Kohrs, Heike; Schneider, Inga; Möller, Katharina; Hahn, Andreas

    2016-01-20

    A diet with a high glycemic index (GI) is associated with an elevated risk for obesity or type 2 diabetes. We investigated the GI of a newly-developed fiber enriched cookie and characterized the microstructure of ingredients used. In a study with 26 non-diabetic healthy volunteers it was shown that the fiber enriched cookie has a GI of 58.9 in relation to white bread as reference. Using a conversion factor of 1.4, the GI of the fiber enriched cookie in relation to a glucose-solution is 42.0 and can be classified as a low-GI food. Postprandial insulin concentration was significantly lower after consumption of fiber enriched cookies compared to white bread. Glucose release after in vitro digestion was significantly lower from fiber enriched cookies compared to other cookies tested. In addition to its high percentage of fiber, the cookies' low GI can be attributed to the limited gelatinization potential of the starch granules found in the ingredients used. Using confocal laser scanning microscopy it is shown that starch granule surface area of whole grain barley flour, spelt flour and oat flakes bears cluster-shaped protein-NSPS complexes that preferentially absorb water in conditions of water shortage and thereby prevent starch gelatinization. PMID:26514289

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

    ERIC Educational Resources Information Center

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

    2011-01-01

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

  20. Kinetics of UV-induced blue luminescence linked with the observation of the local mean index in fiber Bragg gratings.

    PubMed

    Paccou, L; Lancry, M; Douay, M

    2005-09-19

    We exposed H2-loaded optical fibers to cw UV light and simultaneously measured the intensity of the blue luminescence from the fiber core. The UV-induced blue luminescence experiences a non monotonous evolution and thus cannot be correlated to the refractive index changes. However, a quasi-linear relationship has been found between the increase of the blue luminescence and the refractive index changes in the range 5 10-4 < Deltan mean (or Deltan mod) < 2.5 10-3. Using this property, we analyze a fiber Bragg grating by focusing a UV beam probe onto the fiber core and we record the UV-induced blue luminescence at the end of the fiber. By scanning the UV beam along the fiber, we measure thus the axial profile of the refractive index changes with a spatial resolution of 1 mum. PMID:19498757

  1. Is a step in the primordial spectral index favoured by CMB data?

    SciTech Connect

    Joy, Minu; Shafieloo, Arman; Sahni, Varun; Starobinsky, Alexei A. E-mail: a.shafieloo1@physics.ox.ac.uk E-mail: alstar@landau.ac.ru

    2009-06-01

    A sudden small change in the second derivative of the inflaton potential can result in a universal local feature in the spectrum of primordial perturbations generated during inflation. The exact solution describing this feature \\cite(minu) is characterized by a step in the spectral index modulated by characteristic oscillations and results in a large running of the spectral index localized over a few e-folds of scale. In this paper we confront this step-like feature with the 5 year WMAP results and demonstrate that it provides a better fit to this data than a featureless initial spectrum. If such a feature exists at all, then it should lie at sufficiently large scales k{sub 0} ∼< 0.003 Mpc{sup −1} corresponding to l ∼< 40. The sign of the effect is shown to correspond to the negative running of n{sub s} localized near this scale. This feature could arise as a result of a 'mini-waterfall'-type fast second order phase transition experienced by an auxiliary heavy field during inflation, in a model similar to hybrid inflation (though for a different choice of parameters). If this is the case, then the auxiliary field should be positively coupled to the inflaton.

  2. Fiber optic based multiparametric spectroscopy in vivo: Toward a new quantitative tissue vitality index

    NASA Astrophysics Data System (ADS)

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

    2006-02-01

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

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

    NASA Astrophysics Data System (ADS)

    Saito, T. T.

    2000-05-01

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

  4. Refractive index sensors based on the fused tapered special multi-mode fiber

    NASA Astrophysics Data System (ADS)

    Fu, Xing-hu; Xiu, Yan-li; Liu, Qin; Xie, Hai-yang; Yang, Chuan-qing; Zhang, Shun-yang; Fu, Guang-wei; Bi, Wei-hong

    2016-01-01

    In this paper, a novel refractive index (RI) sensor is proposed based on the fused tapered special multi-mode fiber (SMMF). Firstly, a section of SMMF is spliced between two single-mode fibers (SMFs). Then, the SMMF is processed by a fused tapering machine, and a tapered fiber structure is fabricated. Finally, a fused tapered SMMF sensor is obtained for measuring external RI. The RI sensing mechanism of tapered SMMF sensor is analyzed in detail. For different fused tapering lengths, the experimental results show that the RI sensitivity can be up to 444.517 81 nm/RIU in the RI range of 1.334 9—1.347 0. The RI sensitivity is increased with the increase of fused tapering length. Moreover, it has many advantages, including high sensitivity, compact structure, fast response and wide application range. So it can be used to measure the solution concentration in the fields of biochemistry, health care and food processing.

  5. Femtosecond laser fabrication of long period fiber gratings and applications in refractive index sensing

    NASA Astrophysics Data System (ADS)

    Li, Benye; Jiang, Lan; Wang, Sumei; Tsai, Hai-Lung; Xiao, Hai

    2011-11-01

    An improved point-by-point inscription method is proposed to fabricate long period fiber gratings (LPFGs) by using a laser operating at 800 nm with 35 fs duration pulses. The sensitivity to misalignment between the core and the focus is reduced by scanning a rectangular part on the fiber. LPFGs with an attenuation depth of 20 dB are achieved within the wavelength range of 1465-1575 nm. Characterization of the temperature sensitivity and thermal stability of the LPFGs is presented. A 5.6 nm wavelength shift and a 1.2 dB decrease in the attenuation peak are observed following heat treatment at 600 °C for 4 h. The fabricated LPFGs are used as refractive index sensors. The effect of heat treatment on the response of the LPFGs to refractive index changes is also studied.

  6. Bend and refractive index sensing based on the tuning fork fiber

    NASA Astrophysics Data System (ADS)

    Sun, Bo; Li, Xuyou; Yu, Yingying; He, Kunpeng

    2015-08-01

    A fiber-optic based on the tuning fork structure is investigated for bend and refractive index (RI). The new bend/RI sensor based on the tuning fork structure is ease of fabrication, low cost, and simple signal acquisition. The operation principle relies on the power coupling of two cores inputted into light simultaneously. The beam-propagation method (BPM) is employed for modeling the propagation of light along the optical fiber sensing device proposed. The simulation results show that it exhibits very high sensitivity, accuracy and wide dynamic range in making curvature and RI measurements. The bending sensitivity is about 0.01184 W/m-1 at curvatures ranging from 0 to 50 m-1, the RI sensitivity is about -1.5557, -22.3031 and -102.44878 W/RIU at refractive indexes ranging from 1.33-1.418, 1.418-1.45 and 1.45-1.456, respectively.

  7. Refractive index sensitivity enhancement of optical fiber cladding mode by depositing nanofilm via ALD technology.

    PubMed

    Zhao, Ying; Pang, Fufei; Dong, Yanhua; Wen, Jianxiang; Chen, Zhenyi; Wang, Tingyun

    2013-11-01

    The atomic layer deposition (ALD) technology is introduced to enhance the sensitivity of optical fiber cladding mode to surrounding refractive index (SRI) variation. The highly uniform Al2O nanofilm was deposited around the double cladding fiber (DCF) which presents cladding mode resonant feature. With the high refractive index coating, the cladding mode resonant spectrum was tuned. And the sensitivity enhancement for SRI sensor was demonstrated. Through adjusting the deposition cycles, a maximum sensitivity of 723 nm/RIU was demonstrated in the DCF with 2500 deposition cycles at the SRI of 1.34. Based on the analysis of cladding modes reorganization, the cladding modes transition of the coated DCF was investigated theoretically. With the high performance nanofilm coating, the proposed SRI sensor is expected to have wide applications in chemical sensors and biosensors. PMID:24216837

  8. Fabricating Continuous Supercapacitor Fibers with High Performances by Integrating All Building Materials and Steps into One Process.

    PubMed

    Wang, Bingjie; Fang, Xin; Sun, Hao; He, Sisi; Ren, Jing; Zhang, Ye; Peng, Huisheng

    2015-12-01

    Supercapacitor fibers are rapidly produced in minutes by an integrated one-step fabrication process. This method is simple and efficient for large production. A variety of pseudocapacitive active materials including graphene oxide, metal oxide, and conducting polymers can be incorporated. The resulting all-solid-state supercapacitor fibers show remarkable energy-storage capabilities with both high power and energy densities. PMID:26488334

  9. Simultaneous measurement of strain and temperature using a reverse index fiber Bragg grating sensor

    NASA Astrophysics Data System (ADS)

    Park, S. O.; Jang, B. W.; Lee, Y. G.; Kim, C. G.; Park, C. Y.

    2010-03-01

    The simultaneous measurement of strain and temperature is necessary for structural health monitoring of composite structures under diverse temperature environments. The FBG (fiber Bragg grating) sensor head is formed by two FBGs, normal and reverse index FBGs, fabricated by different procedures. The FBG sensor head offers the possibility of multiplexing and embedment, a straightforward measurement system and greater reliability due to the absence of a splicing operation. We evaluated the sensor head analytically and experimentally.

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

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Zhang, Yao; Lei, Hongxiang; Li, Baojun

    2013-07-01

    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.

  12. Humidity insensitive step-index polymer optical fibre Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Woyessa, G.; Fasano, A.; Stefani, A.; Markos, C.; Nielsen, K.; Rasmussen, H. K.; Bang, O.

    2015-09-01

    We have fabricated and characterised a humidity insensitive step index(SI) polymer optical fibre(POF) Bragg grating sensors. The fibre was made based on the injection molding technique, which is an efficient method for fast, flexible and cost effective preparation of the fibre preform. The fabricated SIPOF has a core made from TOPAS with a glass transition temperature of 134°C and a cladding from ZEONEX with a glass transition temperature of 138°C. The main advantages of the proposed SIPOF are the low water absorption and good chemical resistance compared to the conventional poly-methyl-methacrylate (PMMA) based SIPOFs. The fibre has a minimum loss of ~6dB/m at 770nm.

  13. Single tapered fiber tip for simultaneous measurements of thickness, refractive index and distance to a sample.

    PubMed

    Moreno-Hernández, Carlos; Monzón-Hernández, David; Hernández-Romano, Iván; Villatoro, Joel

    2015-08-24

    We demonstrate the capability of an air cavity Fabry-Perot interferometer (FPI), built with a tapered lead-in fiber tip, to measure three parameters simultaneously, distance, group refractive index and thickness of transparent samples introduced in the cavity. Tapering the lead-in fiber enhances the light coupling back efficiency, therefore is possible to enlarge the air cavity without a significant deterioration of the fringe visibility. Fourier transformation, used to analyze the reflected optical spectrum of our FPI, simplify the calculus to determine the position, thickness and refractive index. Samples made of 7 different glasses; fused silica, BK7, BalF5, SF2, BaF51, SF15, and glass slides were used to test our FPI. Each sample was measured nine times and the results for position, thickness and refractive index showed differences of ± 0.7%, ± 0.1%, and ± 0.16% respectively. The evolution of thickness and refractive index of a block of polydimethylsiloxane (PDMS) elastomer due to temperature changes in the range of 25°C to 90°C were also measured. The coefficients of the thermal expansion and thermo-optic estimated were α = 4.71x10(-4)/°C and dn/dT = -4.66 x10(-4) RIU/°C, respectively. PMID:26368188

  14. Highly sensitive refractive index fiber inline Mach-Zehnder interferometer fabricated by femtosecond laser micromachining and chemical etching

    NASA Astrophysics Data System (ADS)

    Sun, Xiao-Yan; Chu, Dong-Kai; Dong, Xin-Ran; Zhou, Chu; Li, Hai-Tao; Luo-Zhi; Hu, You-Wang; Zhou, Jian-Ying; Cong-Wang; Duan, Ji-An

    2016-03-01

    A High sensitive refractive index (RI) sensor based on Mach-Zehnder interferometer (MZI) in a conventional single-mode optical fiber is proposed, which is fabricated by femtosecond laser transversal-scanning inscription method and chemical etching. A rectangular cavity structure is formed in part of fiber core and cladding interface. The MZI sensor shows excellent refractive index sensitivity and linearity, which exhibits an extremely high RI sensitivity of -17197 nm/RIU (refractive index unit) with the linearity of 0.9996 within the refractive index range of 1.3371-1.3407. The experimental results are consistent with theoretical analysis.

  15. An optical fiber multiplexing interferometric system for measuring remote and high precision step height

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

    In this paper, an optical fiber multiplexing interferometric system including a Fizeau interferometer and a Michelson interferometer is designed for remote and high precision step height measurement. The Fizeau interferometer which is inserted in the remote sensing field is used for sensing the measurand, while the Michelson interferometer which is stabilized by a feedback loop works in both modes of low coherence interferometry and high coherence interferometry to demodulate the measurand. The range of the step height is determined by the low coherence interferometry and the value of it is measured precisely by the high coherence interferometry. High precision has been obtained by using the symmetrical peak-searching method to address the peak of the low coherence interferogram precisely and stabilizing the Michelson interferometer with a feedback loop. The maximum step height that could be measured is 6 mm while the measurement resolution is less than 1 nm. The standard deviation of 10 times measurement results of a step height of 1 mm configurated with two gauge blocks is 0.5 nm.

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

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

    SciTech Connect

    Smelser, Christopher W.; Mihailov, Stephen J.; Grobnic, Dan

    2008-05-15

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

  18. Cladded self-written multimode step-index waveguides using a one-polymer approach.

    PubMed

    Günther, Axel; Petermann, Ann Britt; Gleissner, Uwe; Hanemann, Thomas; Reithmeier, Eduard; Rahlves, Maik; Meinhardt-Wollweber, Merve; Morgner, Uwe; Roth, Bernhard

    2015-04-15

    Low-loss optical-coupling structures are highly relevant for applications in fields as diverse as information and communication technologies, integrated circuits, or flexible and highly-functional polymer sensor networks. For this suitable and reliable production methods are crucial. Self-written waveguides are an interesting solution. In this work, we present a simple and efficient one-polymer approach for self-written optical connections between light-guiding structures such as single-mode and multi-mode optical fibers or waveguides that relies on self focusing of the light inside a photopolymerizing mixture. The optical connections are produced in a two-step process by writing into monomer resin using cw laser light in the blue wavelength range and subsequent UV curing. Since only one photopolymerizing resin is required, we reduced the fabrication complexity compared to previous approaches to obtain a waveguide embedded in a rigid cladding material. We discuss the production method, the results obtained as function of relevant process parameters such as writing speed or curing time, and evaluate optical properties and coupling efficiencies. PMID:25872085

  19. Putty Index: An Important Aid for the Direct Fabrication of Fiber Reinforced Composite Resin FPD.

    PubMed

    Gupta, Nidhi; Singh, Kunwarjeet

    2014-12-01

    Fiber reinforced composite resin fixed partial dentures (FRCFPD) with composite resin, PFM or all ceramic pontic can be used as a short term or long term alternative to conventional fixed partial dentures or implant supported crown in young patients where conventional FPD is contraindicated (large pulp chambers) or in patient's unwilling to invasive implant placement surgical procedure and those who do not want to allow preparation of natural sound abutments for placement of retainers for FPD. FRCFPD can be successfully used for replacing missing anterior tooth (Turker and Sener, J Prosthet Dent 100:254-258, 2008), in conditions which allows minimum occlusal loading of pontic, over jet and overbite not greater than 3 mm (Ricketts, Provocations and perceptions in craniofacial orthopedics: dental science and facial art/parts 1 and 2. Rocky Mountain Orthodontics, Denver, p 7023, 1990) and structurally sound and intact abutments for the fiber reinforced matrix (Rose et al., Quintessence Int 33:579-583, 2002). The successful esthetic and functional rehabilitation of missing tooth with fiber reinforced composite resin FPD depends on accurate positioning of pontic in patient's mouth. It is difficult to hold the pontic in proper position with instrument or fingers while direct fabrication in mouth. For accurate positioning, stabilization of pontic is very important which can be achieved with putty index. Putty index maintain pontic in accurate mesiodistal, labiolingual and cervicoincisal position while fabricating FRCFPD directly. PMID:26199513

  20. Fabry-Perot interferometer based on etched side-hole fiber for microfluidic refractive index sensing

    NASA Astrophysics Data System (ADS)

    Wu, Shengnan; Yan, Guofeng; Zhou, Bin; He, Sailing

    2015-08-01

    In this paper, we present a novel fiber-optic open-cavity Fabry-Perot interferometer (FPI), which is specially designed for microfluidic refractive index (RI) sensing. An etching Side-hole fiber (SHF) was sandwiched between in two single-mode-fibers (SMF) and then a cavity was opened up by chemical etching method in the SHF. The minute order of the etching process endow such FPIs with low cost and ease of fabrication. For further microfluidic sensing test, the FPI was integrated with a cross microfluidic slit that was fabricated through photolithography. The refractive index response of the FPI was characterized using sodium hydroxide solution with RI range from 1.3400 to 1.3470. Experimental results show that FPIs with different length of open-cavity have the similar liner RI response with different RI sensitivities. The optimal RI sensitivity of more than 1138 nm/RI can be achieved with open-cavity length of 56 μm. The temperature response was also investigated, which shows that FPIs exhibit a very low temperature cross-sensitivities of 4.00 pm/ °C and 1.95 pm/ °C corresponding FPIs with cavity length of 123 μm and 56 μm, respectively. Such good performance renders the FPI a promising in-line microfluidic sensor for temperature-insensitive RI sensing.

  1. TCF-MMF-TCF fiber structure based interferometer for refractive index sensing

    NASA Astrophysics Data System (ADS)

    Fu, Haiwei; Li, Huidong; Shao, Min; Zhao, Na; Liu, Yinggang; Li, Yan; Yan, Xu; Liu, Qinpeng

    2015-06-01

    A liquid refractive index (RI) sensor based on in-fiber Mach-Zehnder interferometer (MZI) by sandwiching multi-mode fiber (MMF) between two short sections of thinned core fiber (TCF) is proposed in this paper. The first section of TCF excites the high-order modes and the second section TCF couples the core mode and high-order modes into lead-out SMF to form intermodal interference. The sensor with MMF length of 20 mm and TCFs length of 1 mm was fabricated. The transmission spectrum variation of the sensor with respect to surrounding refractive index (SRI) has been studied by experiment. The results show that the central wavelength of dips/peaks shifting had a good linearity with SRI. The RI sensitivity of the sensor is 130.00 nm/RIU over the RI range of 1.3333-1.4182. The RI sensitivity increase to 433.60 nm/RIU after etching the MMF cladding of the sensor. The sensor keeps low dependence on temperature before and after etching.

  2. Cladding modes in photonic crystal fiber: characteristics and sensitivity to surrounding refractive index

    NASA Astrophysics Data System (ADS)

    Jiang, Xiuli; Gu, Zhengtian; Zheng, Li

    2016-01-01

    Characteristics of cladding modes in a photonic crystal fiber (PCF) with triangular air-hole lattice in the cladding are numerically analyzed using a finite element method. The transition for LP11 cladding mode to core mode with variation of the normalized wavelength has been shown. The transition of the LP01 cladding mode to the outer silica mode and reorganization of the LP0m cladding modes caused by varying the fiber radius has been investigated. By choosing the optimized fiber radius, which is located in the cladding modes' reorganization region, the sensitivity of the coupled wavelength between the core mode LP01 and cladding mode LP03 to surrounding refractive index is increased by a factor of five and reaches to 2660 nm/refractive index unit over the range of 1.40 to 1.42. The sensitivity is competitive with that of long-period grating in PCF in response to changes in refractive indices of the medium contained in the cladding air channels.

  3. Graphene-deposited photonic crystal fibers for continuous refractive index sensing applications.

    PubMed

    Tan, Y C; Tou, Z Q; Chow, K K; Chan, C C

    2015-11-30

    We present a pilot demonstration of an optical fiber based refractive index (RI) sensor involving the deposition of graphene onto the surface of a segment of a photonic crystal fiber (PCF) in a fiber-based Mach-Zehnder Interferometer (MZI). The fabrication process is relatively simple and only involves the fusion splicing of a PCF between two single mode fibers. The deposition process relies only on the cold transfer of graphene onto the PCF segment, without the need for further physical or chemical treatment. The graphene overlay modified the sensing scheme of the MZI RI sensor, allowing the sensor to overcome limitations to its detectable RI range due to free spectral range issues. This modification also allows for continuous measurements to be obtained without the need for reference values for the range of RIs studied and brings to light the potential for simultaneous dual parameter sensing. The sensor was able to achieve a RI sensitivity of 9.4 dB/RIU for the RIs of 1.33-1.38 and a sensitivity of 17.5 dB/RIU for the RIs of 1.38-1.43. It also displayed good repeatability and the results obtained were consistent with the modeling. PMID:26698755

  4. The role of highly non-linear index change mechanism during femtosecond grating writing in microstructured optical fibers

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    New methods for fiber Bragg grating inscription in optical fibers use femtosecond laser sources, which can induce refractive index changes even in non-photosensitive fibers and which allow achieving gratings that remain stable at high temperatures. The index change takes place as a result of a highly non-linear multi-photon absorption process. Although such gratings were successfully inscribed in conventional fibers, there are still challenges involved when attempting to fabricate femtosecond gratings in microstructured optical fibers (MOFs). The air holes are usually impeding the delivery of optical power to the core region, which results in a lower grating writing efficiency. In this paper we report on our numerical computations that aim to estimate the influence of the MOF's holey cladding on the induced index change during interferometric grating inscription with an infrared (IR) femtosecond laser source. For high power femtosecond laser pulses at 800 nm the refractive index change in silica stems from a highly non-linear five photon absorption process. Using empirical data on refractive index changes from literature and intensity distribution data from our transverse coupling simulations we propose an approach to reconstruct the non-linear refractive index modification in the MOF core region. We then study the influence of the MOF angular orientation on the induced index change and we model the impact of MOF tapering as a possible way to increase the grating writing efficiency.

  5. Fiber refractive index sensor based on dual polarized Mach-Zehnder interference caused by a single-mode fiber loop.

    PubMed

    Chen, Lei; Zhang, Wei-Gang; Wang, Li; Zhou, Quan; Sieg, Jonathan; Zhao, De-Long; Wang, Biao; Yan, Tie-Yi; Wang, Song

    2016-01-01

    A novel refractive index (RI) sensor head is proposed and experimentally demonstrated in this paper. The proposed sensor head is composed of a segment of bared single-mode fiber and a fiber holder that is fabricated by a 3D printer. The mechanism of the sensor head is based on dual polarized Mach-Zehnder interference. According to the aforementioned mechanism, we derived that the RI responses of the resonance dips possess an exponential functional manner when the E field is along the fast or slow axes. In addition, based on the finite element method, we found that the resonance dips wavelength responses are more sensitive when the input E field is along the fast axis. A confirmation experiment was performed, and the results confirmed our hypothesis. The maximum arithmetic mean value of RI response is about 657.895  nm/RIU for the proposed sensor head when the ambient RI changes from 1.3350 to 1.4110. Moreover, in the case of the proposed liquid RI sensor head, aligning the E field along the fast axis is the potentially needed condition for polarization. PMID:26835622

  6. Monitoring of high refractive index edible oils using coated long period fiber grating sensors

    NASA Astrophysics Data System (ADS)

    Coelho, Luís.; Viegas, Diana; Santos, José Luís.; de Almeida, Jose Manuel M. M.

    2015-05-01

    Monitoring the quality of high refractive index edible oils is of great importance for the human health. Uncooked edible oils in general are healthy foodstuff, olive oil in particular, however, they are frequently used for baking and cooking. High quality edible oils are made from seeds, nuts or fruits by mechanical processes. Nevertheless, once the mechanical extraction is complete, up to 15% of the oil remains in oil pomace and in the mill wastewater, which can be extracted using organic solvents, often hexane. Optical fiber sensors based on long period fiber gratings (LPFG) have very low wavelength sensitivity when the surround refractive index is higher than the refractive index of the cladding. Titanium dioxide (TiO2) coated LPFG could lead to the realization of high sensitivity chemical sensor for the food industry. In this work LPFG coated with a TiO2 thin film were successfully used for to detect small levels of hexane diluted in edible oils and for real time monitoring the thermal deterioration of edible oils. For a TiO2 coating of 30 nm a wavelength sensitivity of 1361.7 nm/RIU (or 0.97 nm / % V/V) in the 1.4610-1.4670 refractive index range was achieved, corresponding to 0 to 12 % V/V of hexane in olive oil. A sensitivity higher than 638 nm/RIU at 225 ºC was calculated, in the 1.4670-1.4735 refractive index range with a detection limit of thermal deterioration of about 1 minute.

  7. High-sensitivity refractive index sensors based on fused tapered photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Fu, Xing-hu; Xie, Hai-yang; Yang, Chuan-qing; Qu, Yu-wei; Zhang, Shun-yang; Fu, Guang-wei; Guo, Xuan; Bi, Wei-hong

    2016-05-01

    In this paper, a novel liquid refractive index (RI) sensor based on fused tapered photonic crystal fiber (PCF) is proposed. It is fabricated by fusing and tapering a section of PCF which is spliced with two single-mode fibers (SMFs). Due to the fused biconical taper method, the sensor becomes longer and thinner, to make the change of the outside RI has more direct effects on the internal optical field of the PCF, which finally enhances the sensitivity of this sensor. Experimental results show that the transmission spectra of the sensor are red-shifted obviously with the increase of RI. The longer the tapered region of the sensor, the higher the sensitivity is. This sensor has the advantages of simple structure, easy fabrication, high performance and so on, so it has potential applications in RI measurement.

  8. Optofluidic tunable manipulation of microparticles by integrating graded-index fiber taper with a microcavity.

    PubMed

    Gong, Yuan; Zhang, Chenlin; Liu, Qun-Feng; Wu, Yu; Wu, Huijuan; Rao, Yunjiang; Peng, Gang-Ding

    2015-02-01

    We propose and demonstrate optofluidic tunable manipulation of polystyrene microparticles based on the combination of a graded-index fiber (GIF) taper and a microcavity. The tunability on the manipulation length is experimentally explored by changing the balance between the optical force and the microfluidic flow force, as well as by tuning the focus of light emitting from the GIF taper via adjusting the length of an air microcavity. By optimizing the geometric shape of the GIF taper, as well as the flow rate and laser power, a manipulation length of 177 μm is achieved, more than 4 times longer than the state-of-the-art optical fiber tweezers. This method has advantages of high flexibility, ease of fabrication and use, integration with microfluidics and has the potential for optofluidic sensing applications. PMID:25836228

  9. Trench-embedding fiber taper sensor fabricated by a femtosecond laser for gas refractive index sensing.

    PubMed

    Cao, Zhitao; Jiang, Lan; Wang, Sumei; Wang, Peng; Zhang, Fei; Lu, Yongfeng

    2014-02-20

    A fiber in-line, multimode coupling interferometer with a trench-embedding, fiber taper probe is proposed and fabricated by femtosecond-laser-induced water breakdown. The reflection-type taper probe is used for gas refractive index (RI) detection from 1.0001143 to 1.0002187 and temperature sensing from 50°C to 500°C. The largest RI sensitivity of the taper probe embedded with a trench at a width of 18.4 μm is 669.502  nm/RIU for hybrid nitrogen and helium. Temperature sensitivity is 9.97  pm/°C and it shows good linearity through the whole testing range. The new-type multimode interferometer is appropriate for high-accuracy gas RI detection of micrometer-scale spaces and wide-range temperature compensation can be realized. PMID:24663297

  10. Label free detection of DNA hybridization by refractive index tapered fiber biosensor

    NASA Astrophysics Data System (ADS)

    Zibaii, M. I.; Latifi, H.; Ghanati, E.; Gholami, M.; Hosseini, S. M.

    2010-04-01

    We demonstrate a simple refractive index sensor (RI) sensing system based on a biconical tapered optical fiber (BTOF), which is fabricated by heat pulling method, utilizing a CO2 laser. In this work we explore the application of these sensors for the detection of label free single stranded DNA (ssDNA) in real time. During the experiment, the target ssDNA did not need to be labeled with a fluorescent tag, which is expensive and complicated. The change in output optical transmission of the tapered fiber was recorded for Poly-L-Lysine (PLL) coating, ssDNA probe immobilization and hybridization. The result indicated that due to the hybridization with the complementary target ssDNA on the tapered surface, the RI of surrounding medium changes which leads to changes in the characteristics of the tapered region and change in the output power of the sensor.

  11. Effect of lower and upper parabolic dips in refractive index profile on performance of coaxial fiber Raman gain amplifier

    NASA Astrophysics Data System (ADS)

    Karak, Anup; Pramanik, Sanchita; Sarkar, Somenath

    2016-03-01

    An investigation on the effect of practically possible upper and lower parabolic dips in the refractive index profile of the inner core of the coaxial fiber Raman gain amplifier is reported using matrix method for single pump. It is seen that for lower parabolic dip, the tolerable limits of dip parameters correspond to dip depth of 0.25% and dip width of 25% of the respective parameters for ideal step index profile case and agree with the earlier predicted linear dip. However, for upper parabolic dip, one gets higher gain and better flatness at these limits. Even up to 1% of the dip depth for 25% of dip width or 75% of dip width for 0.25% of the dip depth or 0.5% of dip depth and 50% of dip width, one can expect performance as good as that of the ideal one. However, since system designers will be aimed to produce ideal profile, our recommendation is to keep tolerable limits within 0.25% of dip depth and 25% of dip width of respective parameters. But one can accept profile with upper parabolic dip if there is deviation within the above relaxation limits for such dip.

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

    PubMed

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

    2011-11-01

    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

  13. Changes in Gait Variability From First Steps to Adulthood: Normative Data for the Gait Variability Index.

    PubMed

    Gouelle, Arnaud; Leroux, Julien; Bredin, Jonathan; Mégrot, Fabrice

    2016-01-01

    The process of learning to walk is ongoing throughout childhood. The Gait Variability Index (GVI; A. Gouelle et al., 2013) has been proposed to quantify the variability of spatiotemporal parameters (STP) during gait. The authors' aim was to evaluate the GVI and STP of healthy children and teenagers to (a) determine changes in the GVI with age and to derive normal values in children and (b) to evaluate the influence of STP on the GVI. A total of 140 typically developing children from 1 to 17 years old were categorized into 7 groups of 20 based on age. Spatiotemporal gait parameters were recorded using an electronic walkway. GVI increased and STP changed with age. In the children-teenagers group, the GVI was positively related to step length, speed, and negatively to cadence. Following normalization by lower limb length, correlations were no longer significant. In contrast, raw base of support was not correlated with the GVI but normalized base of support was. A multiple linear regression showed that only age had a direct impact on the GVI, indicating that gait continues to change after 6-7 years. These changes were only demonstrated by the GVI, highlighting its usefulness for the evaluation of gait in young populations. PMID:26392028

  14. Use of optical fibers in spectrophotometry

    NASA Technical Reports Server (NTRS)

    Ramsey, Lawrence W.

    1988-01-01

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

  15. Ray and wave instabilities in twisted graded-index optical fibers.

    PubMed

    Longhi, S; Della Valle, G; Janner, D

    2004-05-01

    We study ray and wave propagation in an elliptical graded-index optical fiber or lens with a twisted axis and show analytically the existence of an instability for both ray trajectories and beam moments in a finite range of axis twist rate embedded within the spatial frequencies of periodically focused rays for the untwisted fiber. By considering the paraxial ray equations and the paraxial wave dynamics in a rotating frame that follows the fiber axis twist, we reduce the dynamical problem of ray trajectories to the classical Blackburn's pendulum, which shows a dynamical instability, corresponding to classical diverging trajectories, due to the competing effects of confining potential, Coriolis force, and centrifugal force. A closed set of linear evolution equations for generalized beam moments are also derived from the paraxial wave equation in the rotating reference frame, revealing the existence of a dynamical moment instability in addition to the trajectory instability. A detailed analysis of beam propagation is presented in case of a Gaussian beam, and different dynamical regimes are discussed. PMID:15244964

  16. Sex, body mass index, and dietary fiber intake influence the human gut microbiome.

    PubMed

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

    2015-01-01

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

  17. Imaging of rat brain using short graded-index multimode fiber

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    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 140μm and length of 5mm. SMMF (core diameter, 100μm) 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 4.4μm 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 4-5μm 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.

  18. Photonic crystal fiber refractive-index sensor based on multimode interferometry

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

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

    PubMed Central

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

    2015-01-01

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

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

    SciTech Connect

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

    2015-01-14

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

  1. Optical sensing of rainbow for non-contact gauging of diameter and refractive index of an axisymmetric transparent fiber

    NASA Astrophysics Data System (ADS)

    Świrniak, Grzegorz

    2015-05-01

    In the present paper an optical technique is described to measure non-invasively the diameter and refractive index of a transparent (glass or polymer) fiber that possess a circular cross-section. The method is based on an inverse analysis of the rainbow, which is formed by light scattering of low temporal coherency. This enables to achieve unambiguous mathematical relationships between fringe structure of the rainbow and the fiber.

  2. Step angles to reduce the north-finding error caused by rate random walk with fiber optic gyroscope.

    PubMed

    Wang, Qin; Xie, Jun; Yang, Chuanchuan; He, Changhong; Wang, Xinyue; Wang, Ziyu

    2015-10-20

    We study the relationship between the step angles and the accuracy of north finding with fiber optic gyroscopes. A north-finding method with optimized step angles is proposed to reduce the errors caused by rate random walk (RRW). Based on this method, the errors caused by both angle random walk and RRW are reduced by increasing the number of positions. For when the number of positions is even, we proposed a north-finding method with symmetric step angles that can reduce the error caused by RRW and is not affected by the azimuth angles. Experimental results show that, compared with the traditional north-finding method, the proposed methods with the optimized step angles and the symmetric step angles can reduce the north-finding errors by 67.5% and 62.5%, respectively. The method with symmetric step angles is not affected by the azimuth angles and can offer consistent high accuracy for any azimuth angles. PMID:26560383

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

    PubMed

    Kowalczyk, Maciej; Haberko, Jakub; Wasylczyk, Piotr

    2014-05-19

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

  4. Ultra-thin silver-coated tilted fiber grating for surface and bulk refractive index measurement

    NASA Astrophysics Data System (ADS)

    Qiu, Xuhui; Guo, Tuan; Liu, Fu; Guan, Bai-Ou; Tam, Hwa-Yaw; Albert, Jacques

    2015-09-01

    An ultra-thin silver-coated tilted fiber Bragg grating (TFBG) sensor with clear surface plasmon resonance (SPR) together with strong evanescent wave in transmission for "surface" and "bulk" surrounding refractive index (SRI) measurement is proposed and experimentally demonstrated. The thickness of the silver coating over the fiber surface is precisely controlled at 12~16 nm (much thinner than 40~50 nm for traditional SPR excitation). The transmission spectrum of the sensor provides a fine comb of narrowband resonances that overlap with the broader absorption of the surface plasmon and thus provide a unique tool to measure small shifts of the plasmon and identify the "surface" SRI changes with high accuracy. Meanwhile, the ultra-thin nanometric-coating permits part of high-order cladding modes to become leaky modes which have a large sensitivity to variations in the background solution for "bulk" SRI measurement. Experimental results show that above two resonances have an inverse amplitude responses to the SRI changing. Biological solutions (urine of rats with different concentration of Aquaporin) with different RI ranging from 1.3400 to 1.3408 were clearly discriminated in-situ by using the differential amplitude monitoring between "cut-off" cladding resonance and plasmonic resonance, with an amplitude variation sensitivity of ~8100 dB/RIU and a limit of detection of ~10-5 RIU.

  5. Sensor based on macrobent fiber Bragg grating structure for simultaneous measurement of refractive index and temperature.

    PubMed

    Liu, Tiegen; Chen, Yaofei; Han, Qun; Liu, Fangchao; Yao, Yunzhi

    2016-02-01

    A novel and compact all-fiber sensor based on a macrobent fiber Bragg grating (FBG) structure for simultaneous measurement of refractive index (RI) and temperature is proposed and experimentally investigated. The sensor can be easily fabricated by properly bending an FBG. The bending causes interference between the core mode and the whispering gallery mode, which induces another kind of dip in the transmission spectra of the sensor besides the sharp one of the FBG. Because the two kinds of dips respond differently to the surrounding RI and temperature, these two parameters can be unambiguously measured by the sensor. A sample sensor was fabricated and experimentally investigated, and RI sensitivity of 165.9276 nm/RIU in the range from 1.3330 to 1.3785 and temperature sensitivity of 31.7 pm/°C were achieved. This sensor provides a convenient and economical way for applications where temperature and RI have to be simultaneously measured. PMID:26836081

  6. [The experiment research on solution refractive index sensor based on tilted fiber Bragg grating].

    PubMed

    Jiang, Qi; Lü, Dan-Dan; Yu, Ming-Hao; Kang, Li-Min; Ouyang, Jun

    2013-12-01

    The present paper analyzes the sensor's basic principle of the bare tilted fiber Bragg grating (TFBG) and surface plasmon resonance sensor (SPR) that deposited nanoscale gold-coating on the surface of the cladding. We simulated the transmission spectrums and some order cladding mode of TFBG in different concentration solutions by Integration and optical fiber grating software OptiGrating. So by the graphic observation and data analysis, a preliminary conclusion was got that in a certain sensing scope, the cladding modes of TFBG shift slightly to right with the increasing the solution refractive index(SRI),and the relation between resonance peak caused by the coupling of core mode and a certain cladding mode and the SRI was linear. Then the 45 nm thick gold coating was deposited on the surface of the TFBG cladding in a small-scale sputtering chamber KYKY SBC-12, and thermal field scanning electron microscopy presents that the effect of gold-coating was satisfactory to a certain extent in terms of microscopic level. The refractive index(RI) sensing experiments of different concentration solutions of NaCI, MgCI2, CaCI2 were carried out using bare and gold deposited TFBG. The RI sensing characteristics of both bare and gold deposited TFBGs respectively were studied by experiments. Meanwhile, it proved the conclusion that the cladding modes of TFBG drifted to right gradually when the SRI was increasing and the relations between resonance peak caused by the coupling of core mode and a certain cladding mode and the SRI were linear. And by quantitative analysis, we know that SPR sensor with the deposited namoscale gold layer on the surface of cladding enhanced the RI sensitivity dramatically by 2 to 500 nm RIU-1 which is 200 to 300 times larger than that of the bare tilted fiber Bragg grating approximately. The degrees of linear fittings of resonance peak caused by the coupling of core mode and a certain cladding mode and SRI of bare and gold-coating deposited SPR sensor are very good and both of them reach up to more than 0. 99. PMID:24611416

  7. A proposal of T-structure fiber-optic refractive index sensor based on surface plasmon resonance

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Ming; Zhao, Chun-Liu; Wang, Yan-Ru; Jin, Shangzhong

    2016-06-01

    We present a compact and novel "T" structure optical fiber refractive index sensor proposal based on surface plasmon resonance. "T" structure sensing head consists of a single mode fiber (SMF) with a plasmonic facet and a cladding partly removed single mode fiber (CPR-SMF) with a gap. The gold film is deposited on the end of SMF instead of the side of the CPR-SMF. The simulation results show that the SPR based on the "T" structure can be excited effectively. The SPR transmission spectrum shifts towards longer wavelength with the sensing sample refractive index increasing largely. When we divide the refractive index range of the sensing sample to two parts, the linear relationships between the SPR wavelength and the refractive index can be used. The resolutions can be highly up to 7.115×10-6 RIU and 3.525×10-6 RIU for the refractive index ranges of 1.3333-1.36 and 1.37-1.4, respectively. The proposed "T" structure sensor works well for achieving the refractive index measurement with high sensitivity and wide range for samples with a tiny amount.

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

    PubMed

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

    2012-01-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    1995-03-01

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

  10. Gain guided and index alternate-guided fibers designed for large-mode-area and single-mode laser with higher output power and slope efficiency.

    PubMed

    Shen, Xiao; Wei, Wei

    2016-01-25

    A gain guided and index alternate-guided fiber (GGIA-GF) is proposed and numerically demonstrated. The conditions of single mode oscillation are analyzed based on the fiber laser parameters. The output laser power and slope efficiency of the GGIA-GF laser are derived from the improved rate equations. The results show that the output characteristics of the laser based on GGIA-GF can be greatly improved than that of the gain guided and index anti-guided fiber laser through the optimal design of the fiber laser parameters. GGIA-GF would be better applied in the field of large mode area and single mode fiber lasers. PMID:26832493

  11. Refractive index sensing characteristic of single-mode-multimode-single-mode fiber structure based on self-imaging effect

    NASA Astrophysics Data System (ADS)

    Bai, Xuekun; Wang, Haotian; Wang, Shaofei; Pu, Shengli; Zeng, Xianglong

    2015-10-01

    We research the refractive index (RI) sensing characteristic based on the bandpass spectrum caused by the self-imaging effect in the single-mode-multimode-single-mode (SMS) fiber structure theoretically and experimentally. A new selectable parameter, i.e., no-core fiber (NCF) length, is investigated for improving the sensitivity of the sensor. The results show that the sensor's sensitivity will be enhanced by shortening the NCF length when the self-imaging number remains constant. Experimentally, a maximum sensitivity of 1923 nm/RIU (RI unit) has been achieved when the RI ranges from 1.334 to 1.434. This work demonstrates a method to improve the sensitivity of SMS-fiber-structure-based RI sensors featuring a low cost, compact size, low insert loss, and high sensitivity optical fiber RI sensor.

  12. Enhancement of chemical sensing capability in a photonic crystal fiber with a hollow high index ring defect at the center.

    PubMed

    Park, Jiyoung; Lee, Sejin; Kim, Soan; Oh, Kyunghwan

    2011-01-31

    A new type of index-guided photonic crystal fiber is proposed to enhance chemical sensing capability by introducing a hollow high index ring defect that consists of the central air hole surrounded by a high index GeO2 doped SiO2 glass ring. Optical properties of the fundamental guided mode were numerically analyzed using the full-vector finite element method varying the design parameters of both the defects in the center and the hexagonal air-silica lattice in the cladding. Enhanced evanescent wave interaction in the holey region and lower confinement loss by an order of magnitude were achieved simultaneously, which shows a high potential in hyper sensitive fiber-optic chemical sensing applications. PMID:21369007

  13. Optical waveguide modeling of refractive index mediated pH responses in silica nanocomposite thin film based fiber optic sensors

    NASA Astrophysics Data System (ADS)

    Ohodnicki, P. R.; Wang, C.

    2016-02-01

    Recent experiments have demonstrated a pH-dependent optical transmission of silica based nanocomposite thin film enabled evanescent wave absorption spectroscopy based fiber optic sensors in aqueous solutions. Although the response was observed to linearly correlate with the pH-dependent surface charge density of the silica matrix, the responsible mechanism was not fully clarified. In this manuscript, an optical waveguide model is applied to describe observed responses through a modified effective refractive index of the silica matrix layer as a function of the solution phase pH. The refractive index dependence results from a surface charge dependent ionic adsorption, resulting in concentration of ionic species at charged surfaces. The resultant effective index modification to porous silica is estimated through effective medium theories and applied to an optical waveguide model of a multi-mode fiber optic based sensor response capable of reproducing all experimental observations reported to date.

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

    PubMed Central

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

    2013-01-01

    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

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

    USGS Publications Warehouse

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

    2007-01-01

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

  16. Ultra-high sensitivity Fabry-Perot interferometer gas refractive index fiber sensor based on photonic crystal fiber and Vernier effect.

    PubMed

    Quan, Mingran; Tian, Jiajun; Yao, Yong

    2015-11-01

    An ultra-high sensitivity open-cavity Fabry-Perot interferometer (FPI) gas refractive index (RI) sensor based on the photonic crystal fiber (PCF) and Vernier effect is proposed and demonstrated. The sensor is prepared by splicing a section of PCF to a section of fiber tube fused with a section of single mode fiber. The air holes running along the cladding of the PCF enable the gas to enter or leave the cavity freely. The reflection beam from the last end face of the PCF is used to generate the Vernier effect, which significantly improves the sensitivity of the sensor. Experimental results show that the proposed sensor can provide an ultra-high RI sensitivity of 30899 nm/RIU. This sensor has potential applications in fields such as gas concentration analyzing and humidity monitoring. PMID:26512476

  17. All-solid very large mode area ytterbium-doped silica microstructured fiber based on accurate control on cladding index.

    PubMed

    Wei, Huifeng; Chen, Kangkang; Yang, Yucheng; Li, Jinyan

    2016-04-18

    We have demonstrated a new approach for developing very large mode area silica-based microstructured Ytterbium (Yb)-doped fibers. The microstructured region acting as pump cladding around the core is composed by periodically arranged low-index Fluorine-doped silica inclusions with an extremely low filling ratio of 0.088. To the best of our knowledge, we achieved the most accurate controlling on cladding index by 1 × 10-5 via our passively doped cladding (PDC) method. Two fibers with 127μm and 50μm core diameter respectively were fabricated from the same final preform designed by this approach. It is verified that our 50μm core diameter fiber can maintain robust single mode behavior at 1064nm wavelength. The advantage of an all-solid structure along with a much simpler fabrication process makes our approach very suitable for realizing very large mode area fibers for high power fiber laser application. PMID:27137328

  18. Block Copolymer Nanocomposites with High Refractive Index Contrast for One-Step Photonics.

    PubMed

    Song, Dong-Po; Li, Cheng; Li, Wenhao; Watkins, James J

    2016-01-26

    Photonic crystals (PhCs) prepared using the self-assembly of block copolymers (BCPs) offer the potential for simple and rapid device fabrication but typically suffer from low refractive index contrast (Δn ≤ 0.1) between the phase-segregated domains. Here, we report the simple fabrication of BCP-based photonic nanocomposites with large differences in refractive index (Δn > 0.27). Zirconium oxide (ZrO2) nanoparticles coated with gallic acid are used to tune the optical constants of the target domains of self-assembled (polynorbornene-graft-poly(tert-butyl acrylate))-block-(polynorbornene-graft-poly(ethylene oxide)) (PtBA-b-PEO) brush block copolymers (BBCPs). Strong hydrogen-bonding interactions between the ligands on ZrO2 and PEO brushes of the BBCPs enable selective incorporation and high loading of up to 70 wt % (42 vol %) of the ZrO2 nanoparticles within the PEO domain, resulting in a significant increase of refractive index from 1.45 to up to 1.70. Consequently, greatly enhanced reflection at approximately 398 nm (increases of ∼250%) was observed for the photonic nanocomposites (domain spacing = 137 nm) relative to that of the unmodified BBCPs, which is consistent with numeric modeling results using transfer matrix methods. This work provides a simple strategy for a wide range tuning of optical constants of BCP domains, thereby enabling the design and creation of high-performance photonic coatings for various applications. The large refractive index contrast enables high reflectivity while simultaneously reducing the coating thickness necessary, compared to pure BCP systems. PMID:26713452

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

    NASA Astrophysics Data System (ADS)

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

    1994-06-01

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

  20. Impact of body mass index on neuronal fiber bundle lengths among healthy older adults

    PubMed Central

    Bolzenius, Jacob D.; Laidlaw, David H.; Cabeen, Ryan P.; Conturo, Thomas E.; McMichael, Amanda R.; Lane, Elizabeth M.; Heaps, Jodi M.; Salminen, Lauren E.; Baker, Laurie M.; Gunstad, John; Paul, Robert H.

    2013-01-01

    Increased body mass index (BMI) has been linked to various detrimental health outcomes, including cognitive dysfunction. Recent work investigating associations between obesity and the brain has revealed decreased white matter microstructural integrity in individuals with elevated BMI, independent of age or comorbid health conditions. However, the relationship between high BMI and white matter fiber bundle length (FBL), which represents a novel metric of microstructural brain integrity, remains unknown. The present study utilized quantitative tractography based on diffusion tensor imaging (DTI) to investigate the relationship between BMI and FBL in 72 otherwise healthy older adults (24 males, 48 females). All participants were between 51 and 85 years of age (M = 63.26, SD = 8.76). Results revealed that elevated BMI was associated with shorter FBL in the temporal lobe, independent of age (p < .01). In addition, increased age was associated with shorter frontal, temporal, and whole brain FBL (all p values < .01). These findings indicate that, while increased age is an important factor associated with reduced FBL, high BMI is uniquely associated with reduced FBL in the temporal lobe. These data offer evidence for additive adverse effects of high BMI on the brain, especially in areas already vulnerable to aging processes and age-related neurodegenerative diseases. Further research is necessary to determine the physiological mechanisms associated with the shortening of FBL in individuals with high BMI. PMID:23564371

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

    NASA Astrophysics Data System (ADS)

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

    2006-03-01

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

  2. Polarization-dependent refractive index fiber-optic sensor based on the core-offset with a taper

    NASA Astrophysics Data System (ADS)

    Wang, Youqing; Shen, Changyu; Lou, Weimin; Shentu, Fengying

    2016-01-01

    A polarization-dependent refractive index sensor based on the in-fiber Mach- Zehnder interferometer which is constructed by core-offset fusion splicing a tapered polarization maintaining fiber (PMF) with a length of 20 mm between the core-offset and the taper is proposed. Due to the introduced high environment-sensitivity of the two orthogonal polarization modes in the PMF and the enhancing effect of the tapered PMF, The sensitivity of the fast axis and the slow axis up to ∼-107.51 nm/RI and ∼-74.54 nm/RI in the RI range between 1.333 and 1.381 is obtained, respectively. Such kinds of low-cost and highly sensitive fiber-optic RI sensors would find applications in chemical or biochemical sensing fields.

  3. Simultaneous measurement of temperature and refractive index based on a Mach-Zehnder interferometer cascaded with a fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Cao, Ye; Liu, Huiying; Tong, Zhengrong; Yuan, Shuo; Su, Jun

    2015-05-01

    An all-fiber sensor for simultaneous measurement of temperature and refractive index (RI) is proposed and demonstrated. The sensor head is composed of a Mach-Zehnder interferometer (MZI) and a fiber Bragg grating (FBG). The MZI consists of a peanut-shape structure and a core-offset structure which are formed only by single mode fibers through different fusion technology. Experimental results show that the temperature sensitivities of the FBG (dip1) and the MZI (dip2) are 0.01228 nm/°C and 0.08329 nm/°C, respectively. Dip1 is insensitive to environmental RI, but dip2 is sensitive to environmental RI, and the sensitivity is -26.965 nm/RIU. Therefore the simultaneous measurement of the temperature and RI is demonstrated based on the sensitive matrix. The novel sensor processes low fabrication cost, simple configuration, high sensitivity etc. It will have attractive potential applications in chemical and biological sensing fields.

  4. Ultra-thin rigid endoscope: two-photon imaging through a graded-index multi-mode fiber

    NASA Astrophysics Data System (ADS)

    Sivankutty, Siddharth; Andresen, Esben Ravn; Cossart, Rosa; Bouwmans, Géraud; Monneret, Serge; Rigneault, Hervé

    2016-01-01

    Rigid endoscopes like graded-index (GRIN) lenses are known tools in biological imaging, but it is conceptually difficult to miniaturize them. In this letter, we demonstrate an ultra-thin rigid endoscope with a diameter of only 125 microns. In addition, we identify a domain where two-photon endoscopic imaging with fs-pulse excitation is possible. We validate the ultra-thin rigid endoscope consisting of a few cm of graded-index multi-mode fiber by using it to acquire optically sectioned two-photon fluorescence endoscopic images of three-dimensional samples.

  5. Ultra-thin rigid endoscope: two-photon imaging through a graded-index multi-mode fiber.

    PubMed

    Sivankutty, Siddharth; Andresen, Esben Ravn; Cossart, Rosa; Bouwmans, Géraud; Monneret, Serge; Rigneault, Hervé

    2016-01-25

    Rigid endoscopes like graded-index (GRIN) lenses are known tools in biological imaging, but it is conceptually difficult to miniaturize them. In this letter, we demonstrate an ultra-thin rigid endoscope with a diameter of only 125 μm. In addition, we identify a domain where two-photon endoscopic imaging with fs-pulse excitation is possible. We validate the ultra-thin rigid endoscope consisting of a few cm of graded-index multi-mode fiber by using it to acquire optically sectioned two-photon fluorescence endoscopic images of three-dimensional samples. PMID:26832466

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

    NASA Astrophysics Data System (ADS)

    Karpienko, Katarzyna; Wróbel, Maciej S.; Jędrzejewska-Szczerska, Małgorzata

    2014-07-01

    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.

  7. All fiber sensor based on Mach-Zehnder interferometer for simultaneous measurement of temperature and refractive index

    NASA Astrophysics Data System (ADS)

    Cao, Ye; Zhao, Chen; Tong, Zheng-rong

    2015-11-01

    In this paper, we propose and experimentally demonstrate a compact optical fiber sensor based on a Mach-Zehnder interferometer (MZI) cascaded with fiber Bragg grating (FBG) for simultaneous measurement of refractive index (RI) and temperature. In order to get a proper spectrum, we discuss the effects of different structure parameters of MZI. Using the resonant wavelength of the FBG (DipFBG) and the interference dip of the MZI (Dip1), the RI and temperature of the surrounding medium can be determined. The sensor has good operation linearity. The experimental results show that the distinctive spectral sensitivities are 0.071 75 nm/°C and -91.766 67 nm/RIU (refraction index unit) for Dip1 and 0.009 09 nm/°C for DipFBG.

  8. Multi-parameter sensor based on stimulated Brillouin scattering in inverse-parabolic graded-index fiber.

    PubMed

    Xu, Yanping; Ren, Meiqi; Lu, Yang; Lu, Ping; Lu, Ping; Bao, Xiaoyi; Wang, Lixian; Messaddeq, Younès; LaRochelle, Sophie

    2016-03-15

    We propose a unique multi-parameter optical fiber sensor based on intramodal stimulated Brillouin scattering of higher-order acoustic modes in inverse-parabolic graded-index fiber (IPGIF) without a mode converter. Both optical modes and acoustic modes guided in the IPGIF are characterized and demonstrated theoretically and experimentally. Simulation analysis shows that the multi-peak feature in the Brillouin gain spectrum of the IPGIF is attributed to the couplings between the guided optical mode and the higher-order acoustic modes. Thanks to the distinct acoustic properties of the peaks induced by the sharp refractive index profile of the IPGIF, the different temperature and strain dependences of the first three Brillouin peaks enable the discrimination of the temperature and strain at an accuracy of 0.85°C and 17.4 με. PMID:26977653

  9. Comparison of end-pumped and multi-point pumped Yb3+-doped gain guided and index antiguided fiber laser

    NASA Astrophysics Data System (ADS)

    Wu, Jingwei; Zhou, Enyu; Yan, Kunlun; Wei, Wei; Peng, Bo

    2012-11-01

    End-pumped and multi-point pumped Yb3+-doped gain guided and index antiguided (GG+IAG) fiber laser are analyzed by solving the rate equations and 3-D thermal conduction equations. Simulation results show that the multi-point pumped scheme can provide lower operating temperature and better temperature uniformity. Meanwhile, fabrication complexity, loss resulted from pump point should be taken into consideration in the practical design.

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

    EPA Science Inventory

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

  11. Fiber

    MedlinePlus

    Diet - fiber; Roughage; Bulk ... Dietary fiber adds bulk to your diet. Because it makes you feel full faster, it can help with weight control. Fiber aids digestion and helps prevent constipation . It is ...

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

    SciTech Connect

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

    1996-07-01

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

  13. Volatile profile of cashew apple juice fibers from different production steps.

    PubMed

    Nobre, Ana Carolina de Oliveira; de Almeida, Áfia Suely Santos da Silva; Lemos, Ana Paula Dajtenko; Magalhães, Hilton César Rodrigues; Garruti, Deborah dos Santos

    2015-01-01

    This study aimed to determine the volatile profile of cashew apple fibers to verify which compounds are still present after successive washings and thus might be responsible for the undesirable remaining cashew-like aroma present in this co-product, which is used to formulate food products like vegetarian burgers and cereal bars. Fibers were obtained from cashew apple juice processing and washed five times in an expeller press. Compounds were analyzed by the headspace solid-phase micro extraction technique (HS-SPME) and gas chromatography-mass spectrometry (GC-MS), using a DB-5 column. Sensory analysis was also performed to compare the intensity of the cashew-like aroma of the fibers with the original juice. Altogether, 80 compounds were detected, being esters and terpenes the major chemical classes. Among the identified substances, 14 were classified as odoriferous in the literature, constituting the matrix used in the Principal Component Analysis (PCA). Odoriferous esters were substantially reduced, but many compounds were extracted by the strength used in the expeller press and remained until the last wash. Among them are the odoriferous compounds ethyl octanoate, γ-dodecalactone, (E)-2-decenal, copaene, and caryophyllene that may contribute for the mild but still perceptible cashew apple aroma in the fibers that have been pressed and washed five times. Development of a deodorization process should include reduction of pressing force and stop at the second wash, to save water and energy, thus reducing operational costs and contributing to process sustainability. PMID:26023940

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

    NASA Astrophysics Data System (ADS)

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

    2005-03-01

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

  15. Coexistence of positive and negative refractive index sensitivity in the liquid-core photonic crystal fiber based plasmonic sensor.

    PubMed

    Shuai, Binbin; Xia, Li; Liu, Deming

    2012-11-01

    We present and numerically characterize a liquid-core photonic crystal fiber based plasmonic sensor. The coupling properties and sensing performance are investigated by the finite element method. It is found that not only the plasmonic mode dispersion relation but also the fundamental mode dispersion relation is rather sensitive to the analyte refractive index (RI). The positive and negative RI sensitivity coexist in the proposed design. It features a positive RI sensitivity when the increment of the SPP mode effective index is larger than that of the fundamental mode, but the sensor shows a negative RI sensitivity once the increment of the fundamental mode gets larger. A maximum negative RI sensitivity of -5500nm/RIU (Refractive Index Unit) is achieved in the sensing range of 1.50-1.53. The effects of the structural parameters on the plasmonic excitations are also studied, with a view of tuning and optimizing the resonant spectrum. PMID:23187403

  16. Surface-core fiber gratings

    NASA Astrophysics Data System (ADS)

    Osório, Jonas H.; Oliveira, Ricardo; Mosquera, L.; Franco, Marcos A. R.; Heidarialamdarloo, Jamshid; Bilro, Lúcia; Nogueira, Rogério N.; Cordeiro, Cristiano M. B.

    2015-09-01

    In this paper, we report, to our knowledge, the first demonstration of the induction of long-period and Bragg gratings on surface-core optical fibers. Surface-core fibers described herein were fabricated from commercial silica tubes and germanium-doped silica rods by employing a very simple procedure. Being the core on the fiber surface, it can be sensitive to refractive index variations in the environment in which the fiber is immersed. Thus, results concerning the sensitivity of these gratings to environmental refractive index variations are presented. Besides, simulation data are presented for comparison to the experimental behavior and for projecting future steps in this research.

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

    PubMed Central

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

    2011-01-01

    During new fiber sensor development experiments, an easy-to-fabricate simple sensing structure with a trench and partially ablated fiber core is fabricated by using an 800 nm 35 fs 1 kHz laser. It is demonstrated that the structure forms a Mach-Zehnder interferometer (MZI) with the interference between the laser light passing through the air in the trench cavity and that in the remained fiber core. The fringe visibilities are all more than 25 dB. The transmission spectra vary with the femtosecond (fs) laser ablation scanning cycle. The free spectral range (FSR) decreases as the trench length increases. The MZI structure is of very high fabrication and sensing repeatability. The sensing mechanism is theoretically discussed, which is in agreement with experiments. The test sensitivity for acetone vapor is about 104 nm/RIU, and the temperature sensitivity is 51.5 pm/°C at 200 ∼ 875 °C with a step of 25 °C. PMID:22346567

  18. Improved effective-index method for analysis of photonic crystal fibers.

    PubMed

    Park, Kwang N; Lee, Kyung S

    2005-05-01

    We propose, for the first time to our knowledge, an improved effective-index method (IEIM) that has the advantage of high speed and much better accuracy than the conventional effective-index method. The modal properties computed with the IEIM, such as effective index and dispersion, are closely matched to those of the multipole method as well as to experimental values. PMID:15906969

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  20. Miniature ⊓-shaped polymer fiber tip for simultaneous measurement of the liquid refractive index and temperature with high sensitivities

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

    A miniature fiber sensor tip with both high refractive index (RI) and temperature sensitivities was proposed for measuring the temperature and liquid RI simultaneously. A two-photon polymerization technique was used to fabricate a ⊓-shaped polymer micro-structure on the end-face of an optical fiber. A three-wave Fabry-Pérot interferometer was formed. The size of the proposed FPI can be precisely controlled and the total height is less than 30 μm. Temperature and RI variations can be detected simultaneously using the sensitivity matrix method. The sensor tip can be used in harsh environments, as cross-linking SU-8 has moderate acid and alkali resistance and good mechanical strength.

  1. Simultaneous measurement of refractive index and temperature with micro silica sphere cavity hybrid Fabry Perot optical fiber sensor

    NASA Astrophysics Data System (ADS)

    Ranjbar Naeini, O. R.; Latifi, H.; Zibaii, M. I.

    2015-09-01

    In this article, a novel Micro Silica Sphere Cavity Hybrid Fabry Perot optical fiber sensor is reported where refractive index (RI) and temperature can be simultaneously measured. The sensor is based on Micro Silica Sphere that was fabricated using a capillary tube. The micro silica sphere and optical fiber form a Hybrid Fabry Perot cavity. The temperature cross sensitivity of this sensor is small enough to be used for accurate RI measurement. The temperature sensitivity and RI sensitivity are -0.0028 dBm/ºC, -0.0044 dBm/ºC , -24.09 dBm/RIU and -20.6 dBm/RIU respectively, using two selected resonances.

  2. Improved Optical Fiber Chemical Sensors

    NASA Technical Reports Server (NTRS)

    Egalon, Claudio O.; Rogowski, Robert S.

    1994-01-01

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

  3. High efficient coupling between wedged-shaped fiber and planar lightwave circuit chip using gradient refractive-index media

    NASA Astrophysics Data System (ADS)

    Liu, Xu; Qu, Shuting; Xiao, Jinbiao; Sun, Xiaohan

    2006-10-01

    Planar lightwave circuit (PLC) chips based on III-V semiconductor MQW rib waveguide promise to be not only a solution to information access, but also direct the issues of bandwidth, pin count, reliability and complexity. Nanopositioning and precision alignment addresses vital importance in high-efficient connectivity between PLC chips and fiber arrays. Refractive-index mismatching between fused silica and III-V compound is one of the most serious problem which remains unsolved on one hand as well as mode field mismatching which can be mitigated in other hand through gradient geometry structure such as tapered spot size converter (SSC) and specialty fibers such as wedge-shaped fiber (WSF). Spherical gradient refractive-index (SGRIN) media intervened between WSF and MQW rib waveguide is put forward. The GRIN media virtually eliminates the reflection losses associated with the fused silica-air interface and III-V semiconductor-air interface. The beam spot emitted from WSF are observed by digital camera and the fundamental mode of MQW rib waveguide was calculated out. Lightwave propagation and mode field evolution in the WSF-SGRIN-PLC system is simulated by FDTD method with the coupling loss of 8.54dB at a wavelength of 1.55μm. An LED signal is injected into WSF, transmitted along GRIN media and PLC waveguide and output through single mode fiber (SMF). Optical power meter-based measurement verifies the whole system coupling loss to be consistent with the numeric estimation. The approach provides an experimental prototype for coupling and packaging technique of integrated photonic devices, hence supplying foundation for photonic network.

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

    PubMed

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

    2005-09-10

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

  5. Theoretical analysis of novel fiber grating pair

    NASA Astrophysics Data System (ADS)

    Wang, Liao; Jia, Hongzhi; Fang, Liang; You, Bei

    2016-04-01

    A novel fiber grating pair that consists of a conventional long-period fiber grating and a fiber Bragg cladding grating (FBCG) is proposed. The FBCG is a new type of fiber grating in which refractive index modulation is formed in the cladding. Through the coupled-mode theory, we accurately calculate the coupling coefficients between modes supported in the fibers. And some other mode coupling features in the fiber cladding gratings are analyzed in detail. The calculation of the modes involved in this paper is based on a model of three-layer step-index fiber geometry. Then, we have investigated the sensitivity characteristics for variation of the modulation strengths of the fiber Bragg cladding gratings' resonance peaks and the long-period cladding gratings' (LPCGs) dual resonant peaks. Finally, the modulation strength sensitivity of the grating pair's three resonant peaks is demonstrated, and the results indicate that these grating pairs may find potential applications in optical fiber sensing.

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

    PubMed

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

    2014-01-13

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

  7. Propagation characteristics of optical fiber structures with arbitrary shape and index variation

    NASA Technical Reports Server (NTRS)

    Manshadi, F.

    1990-01-01

    The application of the scalar wave-fast Fourier transform (SW-FFT) technique to the computation of the propagation characteristics of some complex optical fiber structures is presented. The SW-FFT technique is based on the numerical solution of the scalar wave equation by a forward-marching fast Fourier transform method. This solution yields the spatial configuration of the fields as well as its modal characteristics in and around the guiding structure. The following are treated by the SW-FFT method: analysis of coupled optical fibers and computation of their odd and even modes and coupling length; the solution of tapered optical waveguides (transitions) and the study of the effect of the slope of the taper on mode conversion; and the analysis of branching optical fibers and demonstration of their mode-filtering and/or power-dividing properties.

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

    PubMed

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

    2014-07-21

    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

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

    SciTech Connect

    Santos, J.S. dos; Ono, E.; Suzuki, C.K.

    2006-05-15

    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.

  10. Dietary fiber, whole grains, carbohydrate, glycemic index, and glycemic load in relation to risk of prostate cancer

    PubMed Central

    Wang, Rong-jiang; Tang, Jian-er; Chen, Yu; Gao, Jian-guo

    2015-01-01

    Background The relationships between dietary fiber, whole grains, carbohydrate, glycemic index (GI), glycemic load (GL), and prostate cancer risk are unclear. We conducted a systematic review and meta-analysis to investigate these associations. Methods Relevant studies were identified by a search of PubMed database and EMBASE database up to April 2015. A random effects model was used to calculate the summary relative risks (RRs) and their corresponding 95% confidence intervals (CIs). Results Twenty-seven epidemiological studies (18 casecontrol studies and nine cohort studies) were included in the final analysis. The pooled RRs of prostate cancer were 0.94 (95% CI 0.851.05, P=0.285), 1.13 (95% CI 0.981.30, P=0.095), 0.96 (95% CI 0.811.14, P=0.672), 1.06 (95% CI 0.961.18, P=0.254), and 1.04 (95% CI 0.911.18, P=0.590) for dietary fiber, whole grains, carbohydrate, GI, and GL, respectively. There was no evidence of significant publication bias based on the Beggs test and Eggers test. Conclusion The findings of this meta-analysis indicate that, based on available information, dietary fiber, whole grains, carbohydrate, GI, and GL are not associated with the risk of prostate cancer. PMID:26366096

  11. High-directionality fiber-chip grating coupler with interleaved trenches and subwavelength index-matching structure.

    PubMed

    Benedikovic, Daniel; Alonso-Ramos, Carlos; Cheben, Pavel; Schmid, Jens H; Wang, Shurui; Xu, Dan-Xia; Lapointe, Jean; Janz, Siegfried; Halir, Robert; Ortega-Moñux, Alejandro; Wangüemert-Pérez, J Gonzalo; Molina-Fernández, Iñigo; Fédéli, Jean-Marc; Vivien, Laurent; Dado, Milan

    2015-09-15

    We present the first experimental demonstration of a new fiber-chip grating coupler concept that exploits the blazing effect by interleaving the standard full (220 nm) and shallow etch (70 nm) trenches in a 220 nm thick silicon layer. The high directionality is obtained by controlling the separation between the deep and shallow trenches to achieve constructive interference in the upward direction and destructive interference toward the silicon substrate. Utilizing this concept, the grating directionality can be maximized independent of the bottom oxide thickness. The coupler also includes a subwavelength-engineered index-matching region, designed to reduce the reflectivity at the interface between the injection waveguide and the grating. We report a measured fiber-chip coupling efficiency of -1.3  dB, the highest coupling efficiency achieved to date for a surface grating coupler in a 220 nm silicon-on-insulator platform fabricated in a conventional dual-etch process without high-index overlays or bottom mirrors. PMID:26371893

  12. High power fiber optic laser beam delivery.

    SciTech Connect

    Leong, K. H.; Hunter, B. V.; Technology Development

    1996-05-01

    Fiber-optic beam delivery is commonly used on industrial laser systems. This article examines the conditions for the optimal propagation of high power beams through optical fibers. Beam quality effects by step and gradient index fibers of different lengths are considered. The differences between the diverging beam from a fiber and the beam at focus and on the fiber face are illustrated. Estimates are provided of the worst-case beam quality to be expected from fibers. Guidelines are also provided for the selection of beam delivery components based on the limitations of the optical system and the tasks to be performed.

  13. Modal power decomposition of light propagating through multimode optical fiber

    NASA Astrophysics Data System (ADS)

    Bolshakov, Maxim V.; Kundikova, Natalia D.; Vlazneva, Marianna A.

    2016-04-01

    The structure of the light field propagating through multimode fibers is of great interest for creating fiber sensors and other applications. Here, using only one linear polarized component of spatial-intensity profiles in near- and far-field regions of a beam emitted from the fiber, we propose a method for the modal power decomposition. As a simple example, modal power decomposition has been done for optical fibers with a step-like index profile. Experiments have been carried out for the fiber with V=54. The method can be used for fibers with any known refractive index profile, core diameter, indices of the core and cladding.

  14. Bending effect on modal interference in a fiber taper and sensitivity enhancement for refractive index measurement.

    PubMed

    Sun, Li-Peng; Li, Jie; Tan, Yanzhen; Gao, Shuai; Jin, Long; Guan, Bai-Ou

    2013-11-01

    We demonstrate the bending effect of microfiber on interference fringes in a compact taper-based modal interferometer and sensitivity for refractive index (RI) measurement. For the bend curvature ranging from 0 to 0.283 mm(-1), the measured RI sensitivity distinctively increases from 342.5 nm/RIU (refractive-index unit) to 1192.7 nm/RIU around RI = 1.333 and from 3847.1 nm/RIU to 11006.0 nm/RIU around RI = 1.430, respectively. Theoretical analysis reveals that such enhancement is determined by the dispersion property of the intermodal index rather than other parameters, such as the variation of the straightforward evanescent field. The magnitude of sensitivity varies as a function of the microfiber bend curvature. Approaching a critical curvature (the intermodal-index dispersion factor approaches zero), the sensitivity is significantly enhanced, exhibiting great potential in RI sensing areas. PMID:24216892

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

    SciTech Connect

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

    2014-09-14

    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 μm 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.

  16. Healthy Eating Index-2010 and food groups consumed by US adults who meet or exceed fiber intake recommendations NHANES 2001–2010

    PubMed Central

    McGill, Carla R.; Birkett, Anne; Fulgonii III, Victor L.

    2016-01-01

    Background The proportion of the US adult population who meet fiber intake recommendations is very low. Information about food groups consumed and diet quality for the adults who consume recommended amounts of fiber are scarce. Objective To examine food groups consumed and Healthy Eating Index (HEI-2010) scores for US adults meeting the fiber adequate intake (AI) based on National Health and Nutrition Examination Survey (NHANES) data 2001–2010. Design A secondary analysis of NHANES data from 2001 to 2010. Participants included adults aged 19 and older (n=24,807) with complete day 1 dietary records. Variables measured were food group sources of fiber and HEI-2010 scores. Sample-weighted data were used to calculate least square means (LSM)±standard error of the mean (SEM) by fiber intake quartile along with HEI-2010 scores. Significance was set at P<0.05. Results Major fiber food sources for US adults meeting the AI were grain products, vegetables, legumes, and fruits. The top grain products consumed were grain mixtures, ready-to-eat (RTE) cereals, and breads/rolls. The mean HEI-2010 score for adults meeting the AI for fiber was significantly (P<0.001) higher compared with all adult participants. The mean HEI-2010 score increased with increasing fiber intake in both groups. Conclusions Adults who meet the AI for fiber have a higher quality diet. Fiber may be an important dietary component that predicts diet quality. PMID:27098562

  17. Holographic Control Of Radial Distribution Of Myelinized Nervous Fiber Refractive Index In Vitality State

    NASA Astrophysics Data System (ADS)

    Antonov I., P.; Goroshkov A., V.; Kalyunov V., N.; Markhvida I., V.; Rubanov A., S.; Tanin L., V.

    1983-12-01

    The role of investigation of peripheral vervous fibers in bitality state is of great importance when elucidating the mechanism of a stimulant low-energy laser radiation influence which is widely applicable, for example, in practice for curing lumbar osteochondros-is (1), trigeminal verve radiculitis, and in developing the processes of transmission and processing of the information required for sustaining organism homeostasis. Using both electrophysiologic and holographic methods simultaneously can increase total information and authenticity of these investigations.

  18. Signals of an intermodal fiber interferometer induced by laser frequency modulation

    NASA Astrophysics Data System (ADS)

    Kotov, O. I.; Chapalo, I. E.; Petrov, A. V.

    2016-01-01

    Signals of an intermodal fiber interferometer induced by laser optical frequency modulation are studied. Dependences of signal amplitudes and spectra on the laser frequency deviation are examined theoretically and experimentally for various optical fibers. It is established that the sensitivity of the intermodal fiber interferometer to the laser frequency variation essentially depends on the fiber refractive index profile. The minimal sensitivity corresponds to graded-index (α ≈ 2) multimode optical fibers. Step-index optical fibers (α = ∞) are more sensitive to the laser frequency variation by more than a factor of 100.

  19. Thermo-optical behavior of rare-earth-doped low-NA fibers in high power operation.

    PubMed

    Hädrich, S; Schreiber, T; Pertsch, T; Limpert, J; Peschel, T; Eberhardt, R; Tünnermann, A

    2006-06-26

    The influence of the internal temperature gradient in rare-earth-doped low-numerical-aperture fibers on modal properties is analyzed for step-index and photonic crystal fibers. We provide guidelines when a single-mode fiber turns into a multimode fiber and how the mode-field-diameter is affected. PMID:19516781

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

    PubMed

    Liu, Yi; Qu, Shiliang

    2014-01-20

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

  1. Fabry-Perot based strain insensitive photonic crystal fiber modal interferometer for inline sensing of refractive index and temperature.

    PubMed

    Dash, Jitendra Narayan; Jha, Rajan

    2015-12-10

    We report a highly stable, compact, strain insensitive inline microcavity-based solid-core photonic crystal fiber (SCPCF) modal interferometer for the determination of the refractive index (RI) of an analyte and its temperature. The interferometer is fabricated by splicing one end of SCPCF with single-mode fiber (SMF) and the other end with hollow-core PCF. This is followed by cleaving the part of the solid glass portion possibly present after the microcavity. The formation of the cavities at the end faces of the SCPCF results in reduction of the period of the interference pattern that helps in achieving distinctiveness in the measurement. Three sensor heads have been fabricated, and each has a different length of the collapsed region formed by splicing SMF with SCPCF. The response of the sensors is found to be sensitive to the length of this collapsed region between SMF and SCPCF with a sensitivity of 53 nm/RI unit (RIU) and resolution of 1.8×10-4 RIU. The temperature response of the sensor is found to be linear, having a temperature sensitivity of 12 pm/°C. In addition to these findings, the effect of strain on the proposed structure is analyzed in both wavelength and intensity interrogation. PMID:26836874

  2. Fiber optics: A brief introduction

    SciTech Connect

    Gruchalla, M.E.

    1989-01-01

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

  3. Numerical modeling method for the dispersion characteristics of single-mode and multimode weakly-guiding optical fibers with arbitrary radial refractive index profiles

    NASA Astrophysics Data System (ADS)

    Mussina, Raushan; Selviah, David R.; Fernández, F. Aníbal; Tijhuis, Anton G.; de Hon, Bastiaan P.

    2013-03-01

    Accurate, reliable and fast numerical modeling methods are required to design the optimum radial refractive index profile for single and multimode fibers to give specific dispersion characteristics prior to or even obviating costly experimental work. Such profiles include graded index and multiple concentric cladding layers. In this paper, a new numerical method is introduced which enables the derivatives of the propagation coefficient to be calculated analytically up to the third order of a single mode or multimode weakly guiding optical fiber with an arbitrary radial refractive index profile. These quantities are required to determine the group delay, τg, chromatic dispersion, D, and dispersion slope of the fiber. The expansion of the modal fields in terms of Laguerre-Gauss polynomials in the Galerkin method offers certain benefits. In particular, due to simplicity of the basis functions it is possible to carry out further analytical work on the results such as repeated differentiation of the matrix equation resulting from the Galerkin method to define up to the third-order derivatives of the propagation coefficients with respect to wavelength. This avoids approximation errors inherent in numerical differentiation, giving better accuracy and, at the same time, significantly reduces the computation time. A computer program was developed to demonstrate the proposed method for single and multimode fibers with radially arbitrary refractive index profiles. The paper provides simulation results to validate the approach.

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

    PubMed Central

    Xu, Yonghao; Chen, Xianfeng; Zhu, Yu

    2008-01-01

    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.

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

    PubMed

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

    2011-08-25

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

  6. Nonlinear refractive index change and optical rectification in a GaN-based step quantum wells with strong built-in electric field

    NASA Astrophysics Data System (ADS)

    Zhang, Li

    2015-11-01

    Based on the compact density matrix approach, the linear and nonlinear refractive index change (RIC) and optical rectification (OR) coefficients in a GaN-based step QW with strong built-in electric field (BEF) have been theoretically deduced and investigated in detail. The analytical electronic state is derived by the two airy functions. And the band nonparabolicity is taken into account by using an energy dependence effective mass (EDEM) method. Numerical calculations on a four-layer AlN/GaN/AlxGa1-xN/AlN step QW are performed, and the curves for the geometric factors, the linear, the nonlinear, the total RICs and the OR coefficients as functions of the structural parameters of the step QW are discussed. The features for these curves were specified and reasons for the features were explained reasonably. It is found that the decreasing of well width Lw, and step barrier width Lb and the doped concentration x in step barrier will result in the significant enhancement of the RICs. With the decrease of Lw, Lb and x, the resonant photon energies of RIC and OR coefficients have obvious blue-shift. Moreover, the RIC and OR coefficients behave different dependence on the structural parameters of the GaN-based step QWs. The profound physical reasons are also analyzed.

  7. Distinct docking and stabilization steps of the pseudopilus conformational transition path suggest rotational assembly of type IV pilus-like fibers

    PubMed Central

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

    2014-01-01

    SUMMARY The closely related bacterial type II secretion (T2S) and type IV pilus (T4P) systems are sophisticated machines that assemble dynamic fibers promoting protein transport, motility or adhesion. Despite their essential role in virulence, the molecular mechanisms underlying helical fiber assembly remain unknown. Here we use electron microscopy and flexible modeling to study conformational changes of PulG pili assembled by the Klebsiella oxytoca T2SS. Neural network analysis of 3900 pilus models suggested a transition path towards low-energy conformations driven by progressive increase in fiber helical twist. Detailed predictions of inter-protomer contacts along this path were tested by site-directed mutagenesis, pilus assembly and protein secretion analyses. We demonstrate that electrostatic interactions between adjacent protomers (P-P+1) in the membrane drive pseudopilin docking, while P-P+3 and P-P+4 contacts determine downstream fiber stabilization steps. These results support a new model of a spool-like assembly mechanism for fibers of the T2SS-T4P superfamily. PMID:24685147

  8. Distinct docking and stabilization steps of the Pseudopilus conformational transition path suggest rotational assembly of type IV pilus-like fibers.

    PubMed

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

    2014-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

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

    PubMed

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

    2013-02-01

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

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

    PubMed

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

    2014-07-23

    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

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

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

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

  13. Four-week low-glycemic index breakfast with a modest amount of soluble fibers in type 2 diabetic men.

    PubMed

    Kabir, Morvarid; Oppert, Jean-Michel; Vidal, Hubert; Bruzzo, Francoise; Fiquet, Caroline; Wursch, Pierre; Slama, Gerard; Rizkalla, Salwa W

    2002-07-01

    Low-glycemic index diets are associated with a wide range of benefits when followed on a chronic basis. The chronic effects, however, of the substitution of 1 meal per day are not well known in diabetic subjects. Therefore, we aimed to evaluate whether the chronic use of a low-glycemic index breakfast (low-GIB) rich in low-GI carbohydrates and a modest amount of soluble fibers could have an effect on lipemia at a subsequent lunch, and improve glucose and lipid metabolism in men with type 2 diabetes. A total of 13 men with type 2 diabetes were randomly allocated in a double-blind cross-over design to a 4-week daily intake of a low-GI versus a high-GI breakfast separated by a 15-day washout interval. The low-GI breakfast was composed of whole grain bread and muesli containing 3 g beta-glucan from oats. Low-GIB induced lower postprandial plasma glucose peaks than the high-GIB at the beginning (baseline, P <.001) and after the 4-week intake (P <.001). The incremental area under the plasma glucose curve was also lower (P <.001, P <.01, baseline, and 4 weeks, respectively). There was no effect on fasting plasma glucose, insulin, fructosamine, or glycosylated hemoglobin (HbA(1c)). Fasting plasma cholesterol, as well as the incremental area under the cholesterol curve, were lower (P <.03, P <.02) after the 4-week low-GIB period than after the high-GIB period. Apolipoprotein B (apo B) was also decreased by the 4-week low-GIB. There was no effect of the low-GI breakfast on triacylglycerol excursions or glucose and insulin responses at the second meal. The high-GIB, however, tended to decrease the amount of mRNA of leptin in abdominal adipose tissue, but had no effect on peroxisome proliferator-activated receptor gamma (PPARgamma) and cholesterylester transfer protein (CETP) mRNA amounts. In conclusion, the intake of a low-GI breakfast containing a modest amount (3 g) of beta-glucan for 4 weeks allowed good glycemic control and induced low plasma cholesterol levels in men with type 2 diabetes. The decrease in plasma cholesterol associated with low-GI breakfast intake may reduce the risk of developing cardiovascular complications in subjects with type 2 diabetes. PMID:12077724

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

    NASA Astrophysics Data System (ADS)

    Chen, Yong; Zhao, Hui; Han, Bing

    2014-12-01

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

  15. Mode coupling in glass optical fibers and liquid-core optical fibers by three methods

    NASA Astrophysics Data System (ADS)

    Djordjevich, Alexandar; Savović, Svetislav

    2015-12-01

    We test Slemon and Wells's function and recently reported Hurand et al.'s (Appl. Opt., 50, 492-499, 2011) function for calculation of coupling characteristics in step-index optical fibers against experimental measurements and against calculations by a related method that is based on the power flow equation. Compared are the coupling length Lc (which is the fiber length where the equilibrium mode distribution is achieved) and length zs (where steady-state distribution is achieved) in three step index glass optical fibers as well as a liquid core optical fiber. The two functions, while simpler to apply being just algebraic formulas, are less accurate over a wide range of numerical apertures. It is also shown that fibers with same coupling coefficient can have much different coupling characteristics.

  16. Walking the Line: A Fibronectin Fiber-Guided Assay to Probe Early Steps of (Lymph)angiogenesis

    PubMed Central

    Mitsi, Maria; Schulz, Martin Michael Peter; Gousopoulos, Epameinondas; Ochsenbein, Alexandra Michaela; Detmar, Michael; Vogel, Viola

    2015-01-01

    Angiogenesis and lymphangiogenesis are highly complex morphogenetic processes, central to many physiological and pathological conditions, including development, cancer metastasis, inflammation and wound healing. While it is described that extracellular matrix (ECM) fibers are involved in the spatiotemporal regulation of angiogenesis, current angiogenesis assays are not specifically designed to dissect and quantify the underlying molecular mechanisms of how the fibrillar nature of ECM regulates vessel sprouting. Even less is known about the role of the fibrillar ECM during the early stages of lymphangiogenesis. To address such questions, we introduced here an in vitro (lymph)angiogenesis assay, where we used microbeads coated with endothelial cells as simple sprouting sources and deposited them on single Fn fibers used as substrates to mimic fibrillar ECM. The fibers were deposited on a transparent substrate, suitable for live microscopic observation of the ensuing cell outgrowth events at the single cell level. Our proof-of-concept studies revealed that fibrillar Fn, compared to Fn-coated surfaces, provides far stronger sprouting and guidance cues to endothelial cells, independent of the tested mechanical strains of the Fn fibers. Additionally, we found that VEGF-A, but not VEGF-C, stimulates the collective outgrowth of lymphatic endothelial cells (LEC), while the collective outgrowth of blood vascular endothelial cells (HUVEC) was prominent even in the absence of these angiogenic factors. In addition to the findings presented here, the modularity of our assay allows for the use of different ECM or synthetic fibers as substrates, as well as of other cell types, thus expanding the range of applications in vascular biology and beyond. PMID:26689200

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

    PubMed

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

    2014-09-22

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

  18. Comparison Of Mode Field Diameter Definitions For Various Single-Mode Fiber Structures

    NASA Astrophysics Data System (ADS)

    Auge, J. C.; Jeunhomme, L. B.

    1985-11-01

    The four most popular definitions of mode field diameter in single mode fibers are compared : Near-Field (or Far-Field) Gaussian fit ; Transverse Offset ; Variable Aperture Far Field ; Far-Field R MS width. We then use the values calculated for step-index matched-cladding, step-index depressed-cladding, and triangular-core dispersion-shifted fibers, for predicting the splicing losses between fibers. A classification of these various definitions is presented with respect to the exact splice loss computed for various fiber parameter mismatch and alignment errors, at 1300 nm and 1550 nm.

  19. Axial strain insensitivity of weakly guiding optical fibers

    NASA Technical Reports Server (NTRS)

    Egalon, Claudio O.; Rogowski, Robert S.

    1993-01-01

    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.

  20. Making Optical-Fiber Chemical Detectors More Sensitive

    NASA Technical Reports Server (NTRS)

    Rogowski, Robert S.; Egalon, Claudio O.

    1993-01-01

    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.

  1. Fiber-coupled ultraviolet planar laser-induced fluorescence for combustion diagnostics.

    PubMed

    Loccisano, Frank; Joshi, Sachin; Franka, Isaiah S; Yin, Zhiyao; Lempert, Walter R; Yalin, Azer P

    2012-09-20

    Multimode silica step-index optical fibers are examined for use in planar laser-induced fluorescence (PLIF) for combustion diagnostics using ultraviolet (UV) laser sources. The multimode step-index fibers are characterized at UV wavelengths by examining their energy damage thresholds and solarization performance. The beam quality achievable with large clad step-index multimode fibers is also studied. Emphasis is placed on simultaneously achieving high output energy and beam quality (low output M(2)). The use of multimode fibers to deliver UV pulses at 283 nm for PLIF measurements of OH radicals in a Hencken burner is demonstrated. The fiber delivery capability of UV light will benefit combustion diagnostics in hostile environments, such as augmentor and combustor rigs. PMID:23033042

  2. Migration of additive molecules in a polymer filament obtained by melt spinning: Influence of the fiber processing steps

    NASA Astrophysics Data System (ADS)

    Gesta, E.; Skovmand, O.; Espuche, E.; Fulchiron, R.

    2015-12-01

    The purpose of this study is to understand the influence of the yarn processing on the migration of additives molecules, especially insecticide, within polyethylene (PE) yarns. Yarns were manufactured in the laboratory focusing on three key-steps (spinning, post-stretching and heat-setting). Influence of each step on yarn properties was investigated using tensile tests, differential scanning calorimetry and wide-angle X-ray diffraction. The post-stretching step was proved to be critical in defining yarn mechanical and structural properties. Although a first orientation of polyethylene crystals was induced during spinning, the optimal orientation was only reached by post-stretching. The results also showed that the heat-setting did not significantly change these properties. The presence of additives crystals at the yarn surface was evidenced by scanning-electron microscopy. These studies performed at each yarn production step allowed a detailed analysis of the additives' ability to migrate. It is concluded that while post-stretching decreased the migration rate, heat-setting seems to boost this migration.

  3. Improve the flame retardancy of cellulose fibers by grafting zinc ion.

    PubMed

    Zhang, KeKe; Zong, Lu; Tan, Yeqiang; Ji, Quan; Yun, Weicai; Shi, Ran; Xia, Yanzhi

    2016-01-20

    Zinc ion as the only flame retardant of cellulose fibers was successfully grafted onto cellulose fibers. Grafting maleic anhydride onto cellulose fibers via homogeneous acylation reaction between N,N-dimethyl formamide (DMF) as the first step. Then, graft zinc ion onto the formed cellulose fibers was conducted with zinc carbonate. The resulting copolymers were characterized by FTIR. Flame retardancy and thermal degradation of zinc-ion-modified cellulose fibers (cellulose-Zn fibers) was investigated by limiting oxygen index (LOI), cone calorimeter (CONE), XRD, TG and SEM. Zinc ion could effectively improve flame retardancy and thermal degradation when its content increases up to 4.96 wt%. PMID:26572337

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

    PubMed

    Zhang, Yuzhen; Fu, Xiaoguo; Chen, Hongzhang

    2012-10-01

    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

  5. Advances in infrared fibers

    NASA Astrophysics Data System (ADS)

    Tao, Guangming; Abouraddy, Ayman F.

    2015-05-01

    Infrared (IR) fibers that transmit radiation at wavelengths from ~ 2 μm up to ~ 25 μm, a spectrum that extends across both the mid-IR (MIR) and far-IR (FIR), has gained extensive attention concomitant with the recent availability of MIR semiconductors sources and detectors. Chalcogenide glasses (ChGs) are a leading candidate for IR fibers by virtue of their wide optical transmission windows and high nonlinearity in the IR region. After extensive studies since the 1960s, the development and applications of ChG IR fibers are primarily hindered by their unfavorable mechanical properties. Here, we summarize our recent advances in low-cost, robust multimaterial ChG IR fibers with broad transmission windows and low optical losses, based on our multimaterial fiber preforms produced by several fabrication methodologies. Hundreds of meters of fibers are thermally drawn in an ambient atmosphere with desired step-index structure from a macroscopic multimaterial preform that contains few grams of ChG. These simple and efficient processes overcome many of the traditional obstacles, and therefore enable rapid production in an industrial setting.

  6. Building polymer fiber optic network

    NASA Astrophysics Data System (ADS)

    Bienias, P.; Bereś-Pawlik, E.

    2015-09-01

    The paper describes an investigation of transmission in LAN with using polymer optical fiber (POF). There were used two kinds of POF, step index plastic optical fiber (SI-POF) and graded index plastic optical fiber (GI-POF). Furthermore, the paper include a comparison between SI-POF and GI-POF and possibilities of using them. For the project's needs, new type of couplers has been designed and built, optimization has been performed to obtain the best parameters for designed couplers. Additionally, the coupler has been built from the same material, which GI-POF - PMMA is made of. Moreover, CWDM (Coarse Wavelength Division Multiplexing) transmissions is investigated to improve the network capacity.

  7. Investigations on beam-shape transformation by direct inscribing an index modulation pattern on optical fiber surface

    NASA Astrophysics Data System (ADS)

    Liao, Tongqing; Zhao, QiDa; Li, ShuHong

    2008-11-01

    End surface grating by direct inscribing an index modulation pattern on optical waveguide surface to control amplitude and direction of the diffracted light is fabricated. Direct inscribing an index modulation pattern by femto-laser is simple, agile and the pattern is steady and durable. We control power and direction of diffracting orders by inscribing different modulation patterns and the controllability may well offer opportunities for various kinds of applications such as beam splitter, beam deflector, and beam shape controller.

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

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

    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.

  9. 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)

    He, Zonghu

    2011-12-01

    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.

  10. Mid-infrared supercontinuum covering the 1.4-13.3 μm molecular fingerprint region using ultra-high NA chalcogenide step-index fibre

    NASA Astrophysics Data System (ADS)

    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

    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 μm or 6.3 μm into short pieces of ultra-high numerical-aperture step-index chalcogenide glass optical fibre generates a mid-infrared supercontinuum spanning 1.5 μm to 11.7 μm and 1.4 μm to 13.3 μm, 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.

  11. Humidity coefficient correction in the calculation equations of air refractive index by He-Ne laser based on phase step interferometry.

    PubMed

    Chen, Qianghua; Liu, Jinghai; He, Yongxi; Luo, Huifu; Luo, Jun; Wang, Feng

    2015-02-10

    The refractive index of air (RIA) is an important parameter in precision measurement. The revisions to Edlen's equations by Boensch and Potulski [Metrologia 35, 133 (1998)] are mostly used to calculate the RIA at present. Since the humidity correction coefficients in the formulas were performed with four wavelengths of a Cd(114) lamp (644.0, 508.7, 480.1, and 467.9 nm) and at the temperature range of 19.6C-20.1C, the application is restricted when an He-Ne laser is used as the light source, which is mostly applied in optical precision measurement, and the environmental temperature is far away from 20C as well. To solve this problem, a measurement system based on phase step interferometry for measuring the effect of the humidity to the RIA is presented, and a corresponding humidity correction equation is derived. The analysis and comparison results show that the uncertainty of the presented equation is better than that of Boensch and Potulski's. It is more suitable in present precision measurements by He-Ne laser, and the application temperature range extends to 14.6C-24.0C as well. PMID:25968028

  12. Estimation of probability distribution of reflection attenuation at optical fibers fusion splices

    NASA Astrophysics Data System (ADS)

    Burdin, Vladimir A.; Bourdine, Anton V.

    2001-10-01

    The results of investigations of reflection signals occurring at fusion splices on real cable sections of long- haul transmission lines are represented. Conditions of rising of reflection signals at fusion splices of the single mode step index optical fibers were experimentally investigated. Approximate solution to estimate probability of reflection at splice of single mode optical fibers is proposed. The results of probability calculations of reflection at splice of conventional single mode step index optical fibers are represented. Analysis of obtained data shows a good agreement between experimental and calculation results.

  13. High-angle light scattering to determine the optical fiber core

    NASA Astrophysics Data System (ADS)

    Świrniak, Grzegorz

    2015-06-01

    The aim of the paper is to discuss the possibility of non-invasive sizing of a step-index optical fiber with the use of a beam of light of low temporal coherence. For this purpose we examine the angular profile of light scattered from the fiber at a high angle. The scattered pattern comprises chiefly two coupled, twin rainbows and depends on the fiber physical characteristics, i.e. its dimensions, shape, and refractive index profile. In order to find a causal link between the scattering pattern and the fiber morphology, a spectral analysis (Fast Fourier Transform, FFT) is performed over the scattering intensity. From the spectral data, the core diameter of a step-index optical fiber is extracted inversely.

  14. The effect of ALD-grown Al2O3 on the refractive index sensitivity of CVD gold-coated optical fiber sensors

    NASA Astrophysics Data System (ADS)

    Mandia, David J.; Zhou, Wenjun; Ward, Matthew J.; Joress, Howie; Sims, Jeffrey J.; Giorgi, Javier B.; Albert, Jacques; Barry, Seán T.

    2015-10-01

    The combined effect of nanoscale dielectric and metallic layers prepared by atomic layer deposition (ALD) and chemical vapor deposition (CVD) on the refractometric properties of tilted optical fiber Bragg gratings (TFBG) is studied. A high index intermediate layer made up of either 50 nm or 100 nm layers of Al2O3 (refractive index near 1.62) was deposited by ALD and followed by thin gold layers (30-65 nm) deposited from a known single-source gold (I) iminopyrrolidinate CVD precursor. The fabricated devices were immersed in different surrounding refractive indices (SRI) and the spectral transmission response of the TFBGs was measured. Preliminary results indicate that the addition of the dielectric Al2O3 pre-coating enhances the SRI sensitivity by up to 75% but this enhancement is highly dependent on the polarization and dielectric thickness. In fact, the sensitivity decreases by up to 50% for certain cases. These effects are discussed with support from TFBG simulations and models, by quantifying the penetration of the evanescently coupled light out of the fiber through the various coating layers. Additional characterization studies have been carried out on these samples to further correlate the optical behaviour of the coated TFBGs with the physical properties of the gold and Al2O3 layers, using atomic force microscopy x-ray photoelectron spectroscopy and an ensemble of other optical and x-ray absorption spectroscopy techniques. The purity, roughness, and morphology of gold thin films deposited by CVD onto the dielectric-TFBG surface are also provided.

  15. Heterogeneous trench-assisted few-mode multi-core fiber with graded-index profile and square-lattice layout for low differential mode delay.

    PubMed

    Tu, Jiajing; Saitoh, Kunimasa; Amma, Yoshimichi; Takenaga, Katsuhiro; Matsuo, Shoichiro

    2015-07-13

    We propose a kind of heterogeneous trench-assisted graded-index few-mode multi-core fiber with square-lattice layout. For each core in the fiber, effective area (A(eff)) of LP(01) mode and LP(11) mode can achieve about 110 μm(2) and 220 μm(2). Absolute value of differential mode delay (|DMD|) is smaller than 100 ps/km over C + L bands, which can decrease the complexity of digital signal processing at the receiver end. Considering the upper limit of cladding diameter (D(cl)) and cable cutoff wavelength of LP(21) mode in the cores located at the inner layer, we set core pitch (Λ) as 43 μm. In this case, D(cl) is about 220.4 μm, inter-core crosstalk (XT) is lower than -40 dB/500 km and the relative core multiplicity factor (RCMF) reaches 15.93. PMID:26191840

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

    PubMed

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

    2011-11-21

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

  17. Analysis of cladded uniaxial single crystal fibers

    NASA Astrophysics Data System (ADS)

    Dai, J. D.; Jen, C. K.

    Integrated optics (IO) devices have become an essential part of the telecommunication industry as signal processing devices and are finding new applications in other areas such as sensors. Recently single crystal fibers are emerging as an attractive component in the area of optical second harmonic generation and fiber lasers due to their long length, small diameter, light weight and high mechanical flexibility. It is expected that single crystal cladded fibers (SCCFs) consisting of both core and cladding regions can be used as key IO components, especially since they can be easily integrated with fiber optic systems. In this article a complete analysis for a uniaxial core uniaxial cladding step-index fiber is presented. Numerical results of a few lowest order modes are presented for weakly guiding LiNbO3 single crystal cladded fibers. It was found that the fundamental mode in a uniaxial fiber is not linearly polarized (LP) but has significant orthogonal components even though the fiber is under weak guidance and has no birefringence. It is concluded that the large anisotropy can cause the invalidity of the linear polarization approximation in a uniaxial fiber, but birefringence are not necessarily involved. The electrical lines of the fundamental modes for a uniaxial fiber are also considerably different from those of an isotropic one but eigenvalues and fractions of power in the core are very similar.

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

    PubMed

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

    2013-02-22

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

  19. Flax Fiber - Interfacial Bonding

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  20. Low-loss hybrid fiber with zero dispersion wavelength shifted to 1 μm

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

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

    NASA Astrophysics Data System (ADS)

    Romano, Valerio; Pilz, Soenke; Etissa, Dereje

    2014-03-01

    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.

  2. Statistical modeling of splice nonhomogeneity of optical fibers in communication cables

    NASA Astrophysics Data System (ADS)

    Bourdine, Anton V.

    2001-10-01

    Approximation model, algorithm and results of statistical modeling of irregularity at fusion splice of conventional single-mode step index fibers are represented. Statistical characteristics have been obtained by the method of statistical modeling. At this step a probability distribution and its parameters were determined. An evaluation of probability of deviation from normative values based on investigation results was executed.

  3. High-brightness power delivery for fiber laser pumping: simulation and measurement of low-NA fiber guiding

    NASA Astrophysics Data System (ADS)

    Yanson, Dan; Levy, Moshe; Peleg, Ophir; Rappaport, Noam; Shamay, Moshe; Dahan, Nir; Klumel, Genady; Berk, Yuri; Baskin, Ilya

    2015-02-01

    Fiber laser manufacturers demand high-brightness laser diode pumps delivering optical pump energy in both a compact fiber core and narrow angular content. A pump delivery fiber of a 105 μm core and 0.22 numerical aperture (NA) is typically used, where the fiber NA is under-filled to ease the launch of laser diode emission into the fiber and make the fiber tolerant to bending. At SCD, we have developed multi-emitter fiber-coupled pump modules that deliver 50 W output from a 105 μm, 0.15 NA fiber at 915, 950 and 976 nm wavelengths enabling low-NA power delivery to a customer's fiber laser network. In this work, we address the challenges of coupling and propagating high optical powers from laser diode sources in weakly guiding step-index multimode fibers. We present simulations of light propagation inside the low-NA multimode fiber for different launch conditions and fiber bend diameters using a ray-racing tool and demonstrate how these affect the injection of light into cladding-bounded modes. The mode filling at launch and source NA directly limit the bend radius at which the fiber can be coiled. Experimentally, we measure the fiber bend loss using our 50 W fiber-coupled module and establish a critical bend diameter in agreement with our simulation results. We also employ thermal imaging to investigate fiber heating caused by macro-bends and angled cleaving. The low mode filling of the 0.15 NA fiber by our brightness-enhanced laser diodes allows it to be coiled with diameters down to 70 mm at full operating power despite the low NA and further eliminates the need for mode-stripping at fiber combiners and splices downstream from our pump modules.

  4. Specialty fibers for fiber optic sensor application

    NASA Astrophysics Data System (ADS)

    Bennett, K.; Koh, J.; Coon, J.; Chien, C. K.; Artuso, A.; Chen, X.; Nolan, D.; Li, M.-J.

    2007-09-01

    Over the last several years, Fiber Optic Sensor (FOS) applications have seen an increased acceptance in many areas including oil & gas production monitoring, gyroscopes, current sensors, structural sensing and monitoring, and aerospace applications. High level optical and mechanical reliability of optical fiber is necessary to guarantee reliable performance of FOS. In this paper, we review recent research and development activities on new specialty fibers. We discuss fiber design concepts and present both modeling and experimental results. The main approaches to enhancing fiber attributes include new index profile design and fiber coating modification.

  5. Imaging characteristics of an 8.8  mm long and 125  μm thick graded-index short multimode fiber probe.

    PubMed

    Sato, Manabu; Shouji, Kou; Saito, Daisuke; Nishidate, Izumi

    2016-04-20

    We demonstrated the feasibility of an ultrathin imaging probe with a 50-μm core diameter, a 125 μm total diameter, and an 8.8 mm length, which is a typical graded-index multimode fiber for optical communications. We used an ABCD matrix to analyze the imaging conditions and magnification, which corresponded closely to the measured results. The lateral resolution was calculated at 1.2 μm with a wavelength of 730 nm, which reflects the image test pattern where a period of 4.38 μm was measured with a wavelength of 730 nm. In the numerical aperture of the objective lens, we experimentally evaluated the tradeoff between the magnification and the coupling efficiency. At four wavelengths of 540 nm, 632 nm, 730 nm, and 852 nm, the contrast and signal intensity versus the wavelength were investigated to show that the contrast at 632 and 730 nm is relatively high. By using a thin random phase screen model, we explained that as the wavelength decreases the greater the decrease in the optical transfer function at higher spatial frequencies. Using a 635 nm LED light source, we imaged the surfaces of chicken tendons in contact and the surface roughness was visible. PMID:27140102

  6. Interlaboratory comparison of radiation-induced attenuation in optical fibers

    SciTech Connect

    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.; Los Alamos National Lab., NM; Harry Diamond Labs., Adelphi, MD; Fraunhofer-Institut fuer Naturwissenschaftlich-Technische Trendanalysen , Euskirchen; Direction des Recherches, Etudes et Techni

    1989-08-01

    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.

  7. Hybrid CATV/16-QAM-Digital CATV/16-QAM-OFDM in-building network over passive optical network and gradient index-plastic optical fiber/visible light communication transport

    NASA Astrophysics Data System (ADS)

    Li, Chung-Yi; Ying, Cheng-Ling; Lin, Chun-Yu

    2015-03-01

    We propose and experimentally demonstrate a hybrid CATV/16-QAM-Digital CATV/16-QAM-OFDM in-building network over a 40-km single-mode fiber and graded index-plastic optical fiber/10-m visible light communication. The application of external injection technology with the addition of an optoelectronic feedback that raises the resonance frequency of the laser diode results in increased system transmission capability. Good performances of carrier-to-noise ratio, composite second-order, and composite triple-beat are obtained for the CATV signal. A low bit-error-rate value is achieved for the 16-QAM-Digital CATV/16-QAM-OFDM signal.

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

    PubMed

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

    2013-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2009-02-01

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

  11. Chromatic dispersion behavior of Si-NC Er doped optical fiber

    NASA Astrophysics Data System (ADS)

    Salman Ogli, A.; Rostami, A.

    2008-09-01

    The chromatic dispersion for conventional and Er-doped fibers using the refractive index approximation is examined. A first, analytical method for investigation of dispersion in step index triple clad optical fiber is used. To design of zero-dispersion shifted fiber for optical communication purpose manipulation of the refractive index and radius of the core are considered. We show that in presence of the Si-NC-Er ions, zero-dispersion wavelength is displaced and the dispersion quantity is increased. In this work, we try to optimize system parameters to obtain minimum dispersion and dispersion shifted fiber with control of the doping levels of Er ions and Si-NC as well as doping profiles. For especial case, we assumed the Gaussian inhomogeneous core refractive index for zero-dispersion wavelength and dispersion managements.

  12. Improved deep UV fiber for medical and spectroscopy applications

    NASA Astrophysics Data System (ADS)

    Khalilov, Valery; Shannon, John; Timmerman, Richard; Geshell, Dale

    2015-03-01

    An effort to demonstrate long term transmission stability in a high -OH synthetic fused silica step index multimode optical fiber optimized for Deep-UV operation, designated as FDP, was successfully completed at Polymicro Technologies. The development achieved significant improvement in long term stability for the 214 and 265nm absorption bands typically associated with solarization effects in fused silica. The improvements were applied to fiber core sizes from 67 to 100µm, a common size range for bundle applications used in medical and spectroscopy. Results of UV degradation measurements for the fiber with minimum 70 hour exposures are presented along with a description of the test protocols.

  13. Source polarization effects in an optical fiber fluorosensor

    NASA Technical Reports Server (NTRS)

    Egalon, Claudio O.; Rogowski, Robert S.

    1992-01-01

    The exact field solution of a step-index profile fiber was used to determine the injection efficiency of a thin-film distribution of polarized sources located in the cladding of an optical fiber. Previous results for random source orientation were confirmed. The behavior of the power efficiency, P(eff), of a polarized distribution of sources was found to be similar to the behavior of a fiber with sources with random orientation. However, for sources polarized in either the x or y direction, P(eff) was found to be more efficient.

  14. Low-loss hybrid fiber with zero dispersion wavelength shifted to 1 µm.

    PubMed

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

    2013-10-01

    We proposed and investigated a novel type of all-glass hybrid fiber where light is confined in the low-index core due to both total internal reflection and coherent Fresnel reflection (a photonic bandgap mechanism). The hybrid mode has an anomalous dispersion of 13 ps/(nm km) at 1064 nm and low loss (~6 dB/km), and it can be easily excited by splicing with a single-mode step-index fiber. The compression of positively chirped 8 ps pulses down to 330 fs was demonstrated with the fabricated hybrid fiber. PMID:24104294

  15. Spectrally efficient polymer optical fiber transmission

    NASA Astrophysics Data System (ADS)

    Randel, Sebastian; Bunge, Christian-Alexander

    2011-01-01

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

  16. Multimode optical fiber

    DOEpatents

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

    2014-11-04

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

  17. The effect of partial extraction of troponin C on the elementary steps of the cross-bridge cycle in rabbit psoas muscle fibers.

    PubMed Central

    Zhao, Y; Swamy, P M; Humphries, K A; Kawai, M

    1996-01-01

    The elementary steps of the cross-bridge cycle in which troponin C (TnC) was partially extracted were investigated by sinusoidal analysis in rabbit psoas muscle fibers. The effects of MgATP and phosphate on the rate constants of exponential processes were studied at 200 mM ionic strength, pCa 4.20, pH 7.00, and at 20 degrees C. The results were analyzed with the following cross-bridge scheme: [formula: see text] where A is actin, M is myosin, S is MgATP, D is MgADP, and P is phosphate (Pi). When TnC was extracted so that the average remaining tension was 11% (range 8-15%), K1 (MgATP association constant) increased to 7x, k2 (rate constant of cross-bridge detachment) increased to 1.55x, k-2 (reversal of detachment) decreased to 0.27x, and K2 (= k2/k-2: equilibrium constant of cross-bridge detachment) increased to 6.6x, k4 (rate constant of force generation) decreased to 0.4x, k-4 (reversal of force generation) increased to 2x, K4 (= k4/k-4) decreased to 0.17x, and K5 (Pi association constant) did not change. The activation factor alpha, which represents the fraction of cross-bridges participating in the cycling, decreased from 1 to 0.14 with TnC extraction. The fact that K1 increased with TnC extraction implies that the condition of the thin filament modifies the contour of the substrate binding site on the myosin head and is consistent with the Fenn effect. The fact that alpha decreased to 0.14 is consistent with the steric blocking mechanism (recruitment hypothesis) and indicates that some of the cross-bridges disappear from the active cycling pool. The fact that the equilibrium constants changed is consistent with the cooperative activation mechanism (graded activation hypothesis) among thin-filament regulatory units that consist of troponin (TnC, Tnl, TnT), tropomyosin, and seven actin molecules, and possibly include cross-bridges. Images FIGURE 2 PMID:8913613

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

    NASA Technical Reports Server (NTRS)

    Heacox, W. D.

    1986-01-01

    Single, step-index optical fibers, when properly employed, can function as optically efficient image scramblers. Their use as optical feeds for astronomical slit spectrographs can reduce zonal error levels in those instruments by orders of magnitude. As a consequence, the application of optical-fiber couplers to new and existing spectrographs may greatly increase the wavelength metric quality of conventional astronomical spectroscopy. The optical efficiencies of fiber couplers of a few tens of meters in length can be comparable to those of typical coude mirror trains in the visible portions of the spectrum. Elements of the design of fiber couplers are illustrated by discussion of a currently operational instrument.

  19. Compound parabolic concentrator optical fiber tip for FRET-based fluorescent sensors

    NASA Astrophysics Data System (ADS)

    Ul Hassan, Hafeez; Nielsen, Kristian; Aasmul, Soren; Bang, Ole

    2015-09-01

    The Compound Parabolic Concentrator (CPC) optical fiber tip shape has been proposed for intensity based fluorescent sensors working on the principle of FRET (Förster Resonance Energy Transfer). A simple numerical Zemax model has been used to optimize the CPC tip geometry for a step-index multimode polymer optical fiber for an excitation and emission wavelength of 550 nm and 650nm, respectively. The model suggests an increase of a factor of 1.6 to 4 in the collected fluorescent power for an ideal CPC tip, as compared to the plane-cut fiber tip for fiber lengths between 5 and 45mm.

  20. Photosensitivity and Hydroxyl in Hydrogenated Silica Fibers

    NASA Astrophysics Data System (ADS)

    Tan, Gu; Lin, Xiang-zhi; Liu, Hong-du; Fu, Li-bin; E, Pun Y. B.; P, Chung S.

    1998-09-01

    Optical loss spectra and refractive index changes have been measured in the hydrogenated standard telecommunication fiber and photosensitive fiber. The index changes due to ultraviolet exposure were found to be closely related with the OH formation in both types of fibers. A direct photolytical model is proposed to explain the effect of hydrogen loading on the enhancement of the photosensitivity in silica fibers.

  1. Laser-direct writing of single mode and multi-mode polymer step index waveguide structures for optical backplanes and interconnection assemblies

    NASA Astrophysics Data System (ADS)

    Kruse, Kevin; Middlebrook, Christopher

    2015-01-01

    A laser direct writing (LDW) method is implemented as a cost efficient polymer waveguide (WG) fabrication method for prototyping large substrates for optical backplanes and optical interconnection assemblies. The LDW setup utilizes a 3-axis air-bearing motion platform to reduce WG fabrication error to within ±0.15 μm. A UV laser diode coupled single mode fiber with a focusing lens module is capable of LDW WGs at both multimode (50 μm) and single mode (6 μm) dimensions. Correlation between LDW parameters and fabricated WG dimensions using Dow Corning® OE-4140 UV-Cured Optical Elastomer (ncore = 1.5142, nclad = 1.5064) is discussed theoretically and confirmed experimentally for both applications. A theoretical model is developed and utilized for producing LDW multi-mode (0.04 dB/cm, λ = 850 nm) and single mode (0.55 dB/cm, λ = 1310 nm) WGs. Measured propagation losses of LDW WGs are comparable to losses of photolithographic multi-mode (0.04 dB/cm @ 850 nm) and single mode (0.59 dB/cm @ 1310 nm) WG builds. LDW multi-mode and single mode WG radial bend and crossing losses are evaluated for advanced optical communication channel routing capabilities and do not exhibit significant deviations from photolithographic-manufactured WG device loss.

  2. Helvacioglu reproducibility index: a new algorithm to evaluate the effects of misalignments on the measurements of retinal nerve fiber layer by spectral-domain OCT

    PubMed Central

    Helvacioglu, Firat; Uyar, Osman Murat; Sencan, Sadik; Tunc, Zeki; Kapran, Ziya

    2015-01-01

    AIM To evaluate the effect of misalignment on the measurements of retinal nerve fiber layer (RNFL) by spectral-domain optical coherence tomography (OCT). METHODS A total of 42 eyes from 21 healthy young subjects underwent RNFL measurements with RTVue spectral-domain OCT (Optovue Inc., Fremont, California, USA). Two baseline measurements with perfectly aligned central circle to the borders of the optic nerve and four misaligned measurements which were misaligned towards to four quadrants were taken. The differences in RNFL between the baseline and misaligned measurements were analyzed with a new algorithm called Helvacioglu reproducibility index (HRI) which is designed to measure the reproducibility of the scans by evaluating the RNFL changes in the four main quadrants. RESULTS The average RNFL scores of the first two baseline measurements have good correlation (c=0.930) and good reproducibility scores (0.15±0.07). Superior misaligned measurements had significantly lower superior quadrant score and higher inferior quadrant score, similar nasal and little higher temporal scores (P1, P2<0.001, P3=0.553, P4=0.001). Inferior misaligned measurements had significantly higher superior quadrant score and lower inferior quadrant score with similar temporal and little lower nasal scores (P1, P2<0.001, P3=0.315, P4=0.016). Nasal misaligned measurements had significantly higher temporal quadrant score and lower nasal quadrant score with little lower superior and inferior scores (P1, P2, P4<0.001, P3=0.005). Temporal misaligned measurements had significantly higher nasal quadrant score and lower temporal quadrant score with similar superior and little higher inferior scores (P1, P2<0.001, P3=0.943, P4=0.001). CONCLUSION Good alignment of the central circle to the borders of optic nerve is crucial to have correct and repeatable RNFL measurements. Misalignment to a quadrant resulted in falsely low readings at that quadrant and falsely high readings at the opposite quadrant. PMID:26558218

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

  4. Security: Step by Step

    ERIC Educational Resources Information Center

    Svetcov, Eric

    2005-01-01

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

  5. Fiber propagation of vector modes.

    PubMed

    Ndagano, Bienvenu; Brüning, Robert; McLaren, Melanie; Duparré, Michael; Forbes, Andrew

    2015-06-29

    Here we employ both dynamic and geometric phase control of light to produce radially modulated vector-vortex modes, the natural modes of optical fibers. We then measure these modes using a vector modal decomposition set-up as well as a tomography measurement, the latter providing a degree of the non-separability of the vector states, akin to an entanglement measure for quantum states. We demonstrate the versatility of the approach by creating the natural modes of a step-index fiber, which are known to exhibit strong mode coupling, and measure the modal cross-talk and non-separability decay during propagation. Our approach will be useful in mode division multiplexing schemes for transport of classical and quantum states. PMID:26191742

  6. Development of on-fiber optical sensors utilizing chromogenic materials

    NASA Astrophysics Data System (ADS)

    Yuan, Jianming; El-Sherif, Mahmoud A.

    1999-01-01

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

  7. 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)

    Fang, Liang; Jia, Hongzhi

    2014-07-01

    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.

  8. Phase-matching of the HE11 and HE13 modes of highly doped GeO2-SiO2 fiber waveguides at 1596 nm and 532 nm, respectively, for triple-photon generation

    NASA Astrophysics Data System (ADS)

    Tsvetkov, S.; Katamadze, K.; Borshchevskaia, N.; Sysolyatin, A.; Fedorov, M.; Kulik, S.; Salganskii, M.; Belanov, A.

    2016-02-01

    We theoretically investigate a phase-matching (PM) between the HE11 and HE13 modes at wavelengths 1596 and 532 nm, respectively, of a real germania-silica fiber waveguide, whose preform was made by MCVD technology. For several measured refractive index profiles of the fiber preform, the corresponding waveguide diameters, providing homogeneous PM, both with modal dispersion and power characteristics, are calculated. The PM parameters obtained for the real fiber are compared to that calculated for a standard step-index fiber model.

  9. Fiber optic laser rod

    DOEpatents

    Erickson, G.F.

    1988-04-13

    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.

  10. Palladium particles embedded into silica optical fibers for hydrogen gas detection

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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.

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

    SciTech Connect

    Meyer, M.K.

    1991-12-20

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

  12. Simulating Optical Fibers.

    ERIC Educational Resources Information Center

    Edgar, Dale

    1988-01-01

    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)

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

    NASA Astrophysics Data System (ADS)

    Lee, Yin-Wen

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

  14. Next Step for STEP

    SciTech Connect

    Wood, Claire; Bremner, Brenda

    2013-08-09

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

  15. Development of the multiwavelength monolithic integrated fiber optics terminal

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

  16. Aerogel-clad optical fiber

    DOEpatents

    Sprehn, Gregory A.; Hrubesh, Lawrence W.; Poco, John F.; Sandler, Pamela H.

    1997-01-01

    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.

  17. Aerogel-clad optical fiber

    DOEpatents

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

    1997-11-04

    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.

  18. Delivery of ultrashort spatially focused pulses through a multimode fiber

    NASA Astrophysics Data System (ADS)

    Morales-Delgado, Edgar E.; Papadopoulos, Ioannis N.; Farahi, Salma; Psaltis, Demetri; Moser, Christophe

    2015-08-01

    Multimode optical fibers potentially allow the transmission of larger amounts of information than their single mode counterparts because of their high number of supported modes. However, propagation of a light pulse through a multimode fiber suffers from spatial distortions due to the superposition of the various exited modes and from time broadening due to modal dispersion. We present a method based on digital phase conjugation to selectively excite in a multimode fiber specific optical fiber modes that follow similar optical paths as they travel through the fiber. The excited modes interfere constructively at the fiber output generating an ultrashort spatially focused pulse. The excitation of a limited number of modes following similar optical paths limits modal dispersion, allowing the transmission of the ultrashort pulse. We have experimentally demonstrated the delivery of a focused spot of pulse width equal to 500 fs through a 30 cm, 200 micrometer core step index multimode fiber. The results of this study show that two-photon imaging capability can be added to ultra-thin lensless endoscopy using commercial multimode fibers.

  19. Numerical analysis of the harmonic components of the Bragg wavelength content in spectral responses of apodized fiber Bragg gratings written by means of a phase mask with a variable phase step height.

    PubMed

    Osuch, Tomasz

    2016-02-01

    The influence of the complex interference patterns created by a phase mask with variable diffraction efficiency in apodized fiber Bragg grating (FBGs) formation on their reflectance spectra is studied. The effect of the significant contributions of the zeroth and higher (m>±1) diffraction orders on the Bragg wavelength peak and its harmonic components is analyzed numerically. The results obtained for Gaussian and tanh apodization profiles are compared with similar data calculated for a uniform grating. It is demonstrated that when an apodized FBG is written using a phase mask with variable diffraction efficiency, significant enhancement of the harmonic components and a reduction of the Bragg wavelength peak in the grating spectral response are observed. This is particularly noticeable for the Gaussian apodization profile due to the substantial contributions of phase mask sections with relatively small phase steps in the FBG formation. PMID:26831768

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    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 3 400/440μm 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 μm 0.22 NA pump fibers to the 525 μm 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 μm intermediate core region in the combiner between the 20 μm core of the input fiber and the 40 μm 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.

  2. Fiber bundle phase conjugate mirror

    SciTech Connect

    Ward, Benjamin G.

    2012-05-01

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

  3. High resolution gamma ray telescope using scintillating fibers and position sensitive photomultipliers

    NASA Astrophysics Data System (ADS)

    Atac, Muzaffer; Cline, David B.; Chrisman, David; Kolonko, James J.; Park, June; Fenyves, Ervin J.; Chaney, Roy C.

    1989-08-01

    Recently high photon yielding and long attenuation length step index scintillating plastic fibers have been developed. Scintillating fibers of 1 mm diameter made of polystyrene doped with butyl-PBD and POPOP (λ = 420 nm), and clad with PMMA (poly-methylmetacrylate) have resulted attenuation lengths over 2 meters. Scintillating fibers stacked up into scintillating fiber planes U, V and W that are rotated by 60° angle relative to each other and coupled to position sensitive photomultipliers can be used as high resolution imaging gamma-ray detectors. We are presenting the design of a large area gamma-ray telescope with high angular and energy resolution for space based experiments, using scintillating fibers and recently developed position sensitive photomultiplier tubes.

  4. Micromachine Wedge Stepping Motor

    SciTech Connect

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

    1998-11-04

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

  5. Longitudinally Graded Optical Fibers

    NASA Astrophysics Data System (ADS)

    Evert, Alexander George

    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.

  6. Picosecond Yb-doped single-trench fiber amplifier with diffraction limited output

    NASA Astrophysics Data System (ADS)

    Jain, Deepak; Gorman, Philip; Codemard, Christophe; Jung, Yongmin; Zervas, Michalis N.; Sahu, Jayanta K.

    2015-03-01

    We propose a novel fiber design single-trench fiber (STF) for large mode area fiber laser and amplifier. Fiber offers cylindrical symmetry and also offer higher refractive index of core compared to cladding. This avoids the need of stack and draw process and refractive index compensation of core doped with index raising rare earth and co-dopants ions, which are an indispensable condition in most of other fiber designs. That is why, this fiber design can be fabricated with conventional modified chemical vapour deposition process in conjunction with solution doping process, which can dramatically reduce the fabrication cost, hence suitable for mass production. Fiber offers very high loss (>10dB/m) and low power fraction in core (<50%) to the higher order modes for low loss of fundamental mode (<0.1dB/m) and high power fraction in core (>80%) thanks to the resonant coupling between core and ring modes. We fabricated a preform for 30μm core STF using MCVD process in conjunction with solution doping process in a single step, without using any micro-structuration and pixilation of core. Experiments ensure the robust single mode behaviour irrespective of launching condition of input beam. Furthermore, this fiber used in three stages MOPA provides 80kW peak pulses with repetition rate of 500 kHz, average power up to 10W, with M2 ~ 1.14. Moreover, all solid structure ensures easy cleaving and splicing. In nutshell, an ultra-low cost, monolithic, compact, and an effective single mode fiber amplifier device can be achieved using single-trench fiber.

  7. Fiber optic testing laboratory

    NASA Astrophysics Data System (ADS)

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

    2001-08-01

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

  8. Robust fiber clustering of cerebral fiber bundles in white matter

    NASA Astrophysics Data System (ADS)

    Yao, Xufeng; Wang, Yongxiong; Zhuang, Songlin

    2014-11-01

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

  9. Tapered GRIN fiber microsensor.

    PubMed

    Beltrán-Mejía, Felipe; Biazoli, Claudecir R; Cordeiro, Cristiano M B

    2014-12-15

    The sensitivity of an optical fiber microsensor based on inter-modal interference can be considerably improved by tapering a short extension of the multimode fiber. In the case of Graded Index fibers with a parabolic refractive index profile, a meridional ray exhibits a sinusoidal path. When these fibers are tapered, the period of the propagated beam decrease down-taper and increase up-taper. We take advantage of this modulation -along with the enhanced overlap between the evanescent field and the external medium- to substantially increase the sensitivity of these devices by tuning the sensor's maximum sensitivity wavelength. Moreover, the extension of this device is reduced by one order of magnitude, making it more propitious for reduced space applications. Numerical and experimental results demonstrate the success and feasibility of this approach. PMID:25606989

  10. 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)

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

    2014-05-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Pan, Ning

    1992-01-01

    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.

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

    PubMed

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

    2013-02-11

    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

  13. Indexing Images.

    ERIC Educational Resources Information Center

    Rasmussen, Edie M.

    1997-01-01

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

  14. PHOEBE - step by step manual

    NASA Astrophysics Data System (ADS)

    Zasche, P.

    2016-03-01

    An easy step-by-step manual of PHOEBE is presented. It should serve as a starting point for the first time users of PHOEBE analyzing the eclipsing binary light curve. It is demonstrated on one particular detached system also with the downloadable data and the whole procedure is described easily till the final trustworthy fit is being reached.

  15. Dispersion Compensating Fibers

    NASA Astrophysics Data System (ADS)

    Grüner-Nielsen, Lars; Knudsen, Stig Nissen; Edvold, Bent; Veng, Torben; Magnussen, Dorte; Larsen, C. Christian; Damsgaard, Hans

    2000-04-01

    The basic principles for use of dispersion compensating fibers (DCF) are reviewed, including definition of figure of merit and condition for dispersion slope compensation. The main design features of a triple-cladding index profile design are examined theoretically and experimentally. Production results are presented for three types of DCF. It is shown that polarization-mode dispersion can be reduced by introducing oscillatory twist into the fiber. The splice loss between DCF and standard fibers is shown to be reducible by use of a special intermediate fiber. Two methods for measuring the nonlinear effective area of DCF are compared and good agreement is found. Measurement results for the nonlinear refractive index n2 are reported. The nonlinear coefficient n2/Aeff of DCF is found to be a factor of 5 higher than that on standard single-made fibers. The macrobending resistance of DCF is examined and found to be comparable with that of standard fibers. The microbending resistance of DCF is found to be better than that of standard fibers. Finally, positive results from a cabling experiment with DCF are reported.

  16. Step Pultrusion

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  17. Optical fiber tip templating using direct focused ion beam milling

    PubMed Central

    Micco, A.; Ricciardi, A.; Pisco, M.; La Ferrara, V.; Cusano, A.

    2015-01-01

    We report on a method for integrating sub-wavelength resonant structures on top of optical fiber tip. Our fabrication technique is based on direct milling of the glass on the fiber facet by means of focused ion beam. The patterned fiber tip acts as a structured template for successive depositions of any responsive or functional overlay. The proposed method is validated by depositing on the patterned fiber a high refractive index material layer, to obtain a ‘double-layer’ photonic crystal slab supporting guided resonances, appearing as peaks in the reflection spectrum. Morphological and optical characterizations are performed to investigate the effects of the fabrication process. Our results show how undesired effects, intrinsic to the fabrication procedure should be taken into account in order to guarantee a successful development of the device. Moreover, to demonstrate the flexibility of our approach and the possibility to engineering the resonances, a thin layer of gold is also deposited on the fiber tip, giving rise to a hybrid photonic-plasmonic structure with a complementary spectral response and different optical field distribution at the resonant wavelengths. Overall, this work represents a significant step forward the consolidation of Lab-on-Fiber Technology. PMID:26531887

  18. Optical fiber tip templating using direct focused ion beam milling

    NASA Astrophysics Data System (ADS)

    Micco, A.; Ricciardi, A.; Pisco, M.; La Ferrara, V.; Cusano, A.

    2015-11-01

    We report on a method for integrating sub-wavelength resonant structures on top of optical fiber tip. Our fabrication technique is based on direct milling of the glass on the fiber facet by means of focused ion beam. The patterned fiber tip acts as a structured template for successive depositions of any responsive or functional overlay. The proposed method is validated by depositing on the patterned fiber a high refractive index material layer, to obtain a double-layer photonic crystal slab supporting guided resonances, appearing as peaks in the reflection spectrum. Morphological and optical characterizations are performed to investigate the effects of the fabrication process. Our results show how undesired effects, intrinsic to the fabrication procedure should be taken into account in order to guarantee a successful development of the device. Moreover, to demonstrate the flexibility of our approach and the possibility to engineering the resonances, a thin layer of gold is also deposited on the fiber tip, giving rise to a hybrid photonic-plasmonic structure with a complementary spectral response and different optical field distribution at the resonant wavelengths. Overall, this work represents a significant step forward the consolidation of Lab-on-Fiber Technology.

  19. Optical fiber tip templating using direct focused ion beam milling.

    PubMed

    Micco, A; Ricciardi, A; Pisco, M; La Ferrara, V; Cusano, A

    2015-01-01

    We report on a method for integrating sub-wavelength resonant structures on top of optical fiber tip. Our fabrication technique is based on direct milling of the glass on the fiber facet by means of focused ion beam. The patterned fiber tip acts as a structured template for successive depositions of any responsive or functional overlay. The proposed method is validated by depositing on the patterned fiber a high refractive index material layer, to obtain a 'double-layer' photonic crystal slab supporting guided resonances, appearing as peaks in the reflection spectrum. Morphological and optical characterizations are performed to investigate the effects of the fabrication process. Our results show how undesired effects, intrinsic to the fabrication procedure should be taken into account in order to guarantee a successful development of the device. Moreover, to demonstrate the flexibility of our approach and the possibility to engineering the resonances, a thin layer of gold is also deposited on the fiber tip, giving rise to a hybrid photonic-plasmonic structure with a complementary spectral response and different optical field distribution at the resonant wavelengths. Overall, this work represents a significant step forward the consolidation of Lab-on-Fiber Technology. PMID:26531887

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

    DOEpatents

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

    2006-06-06

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

  1. Minimal dispersion refractive index profiles.

    PubMed

    Feit, M D

    1979-09-01

    The analogy between optics and quantum mechanics is exploited by considering a 2-D quantum system whose Schroedinger equation is closely related to the wave equation for light propagation in an optical fiber. From this viewpoint, Marcatili's condition for minimal-dispersion-refractive-index profiles, and the Olshansky- Keck formula for rms pulse spreading in an alpha-profile fiber may be derived without recourse to the WKB approximation. Besides affording physical insight into these results, the present approach points out a possible limitation in their application to real fibers. PMID:20212780

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

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

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

  3. Step cell

    SciTech Connect

    Epstein, J.; Marincic, N.

    1981-10-06

    A lithium/thionyl chloride electrochemical cell, particularly suitable for use in surgically implanted devices, is disclosed which exhibits a step change in its output voltage sufficiently prior to full cell discharge to enable the timely replacement of the cell under non-critical circumstances.

  4. Fiber biology

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cotton fiber cells arising from seed epidermis is the most important agricultural textile commodity in the world. To produce fully mature fibers, approximately two months of fiber developmental process are required. The timing of four distinctive fiber development stages consisting of initiation, ...

  5. Fiber optic flocculation sensor

    NASA Astrophysics Data System (ADS)

    Cheng, Lun K.; Stelwagen, Uilke

    1994-02-01

    A fiber optic flocculation sensor based on measuring the intensity of light reflected by solid particles in suspension (i.e. paper pulp) in a well defined measurement volume, was constructed. This sensor is designed for monitoring the flocculation state of paper pulp in the papermaking process. The flocculation determines to a great extent the quality of the final product, the paper. Tests with different types of pulp were performed in both a closed loop system and a small paper machine. In this investigation the flocculation state is expressed as a root mean square flocculation index. The flocculation index delivered by this fiber optic system shows a very high correlation with the flocculation index provided by a camera system `looking at' the same pulp, while the latter has a great resemblance with the human perception of the flocculation.

  6. Chiral fiber sensors

    NASA Astrophysics Data System (ADS)

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

    2010-04-01

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

  7. Material composition and structure design in PCVD silica-based single-mode fiber

    NASA Astrophysics Data System (ADS)

    Han, Qingrong; Zhao, Xiujian; Tu, Feng; Luo, Jie

    2006-09-01

    Single mode fiber (SMF) has been used widely in local and access network since the early 1980's. Fiber loss reduction will accelerate the construction of various transmission systems with longer repeater spacing. It has been reported that the transmission loss in SMF increases due to residual stress, which is caused by viscosity mismatch between the core and cladding material. The idea of viscosity matching is to match the viscosity of core and cladding doping to minimize the viscosity difference on the cross-section of the fiber or preform. The dopant concentrations can be chosen so that the viscosity of core and the cladding are equal in ideal step index fiber. However, all the reported viscosity-matching design is based on single dopant, for example, only GeO2 is doped in the central core and only F in the cladding. In this paper, optical loss reduction through viscosity-matched design for the SMF with GeO2-F codoped silica core and cladding is described. The impact of viscosity-matching on optical loss of silica-based single-mode fiber has been investigated in detail theoretically and experimentally based on PCVD fiber. For PCVD optical fiber, F is introduced in core is to reduce the water peak. Single mode optical fiber with low attenuation fabricated by PCVD process can be gotten through viscosity-matching design between core and cladding. Viscosity-matching can reduce the sensitivity of attenuation to drawing tension. The model for estimating the viscosity matching has been deduced, which can not only be used for conventional SMF but also for the fiber with arbitrary index profile.

  8. Activated carbon fibers and engineered forms from renewable resources

    DOEpatents

    Baker, Frederick S.

    2010-06-01

    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.

  9. Activated carbon fibers and engineered forms from renewable resources

    SciTech Connect

    Baker, Frederick S

    2013-02-19

    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.

  10. Novel OTDR effects in determining losses of single-mode fibers and splices

    NASA Astrophysics Data System (ADS)

    Kapron, Felix; Kozikowski, Carrie; Olson, Tom

    1986-11-01

    OTDR effects on fiber attenuation and splice loss are studied. Fiber group index or group delay is best determined by measurement, rather than from the refractive index. In this way, fiber and cable differences are accounted for. Cursor placement is important in length determination, and a fiber input pigtail and output reflection are desirable.

  11. Stepped nozzle

    DOEpatents

    Sutton, G.P.

    1998-07-14

    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.

  12. Stepped nozzle

    DOEpatents

    Sutton, George P.

    1998-01-01

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

  13. A magneto-optical fiber device based on magnetic fluid-filled photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Huang, Yi; Bai, Xuekun; Chai, Zhaopu; Pang, Fufei; Wen, Jianxiang; Wang, Tingyun

    2015-08-01

    Magneto-optical fiber plays an important role in magneto-optical devices. The fiber has larger Verdet constant will lead to a larger Faraday rotation per unit length fiber and applied field. In order to increase the magneto-optical characteristic, especially the Verdet constant of photonic crystal fiber, a magneto-optical fiber device based on combination of the magnetic fluid and the tunable photonic bandgap effect of photonic crystal fiber is proposed. The magnetic fluid is filled into the air holes of the cladding layer in the photonic crystal fiber using a new air pressure-filled method. Because the magnetic fluid prepared in this experiment has higher refractive index (>1.45), and is filled into the air-holes of photonic crystal fiber, as a result, the index guiding fiber is converted into photonic bandgap fiber. A magneto-optic system based on the Stokes polarization parameters method is designed which could analyze the Faraday effect. The corresponding Faraday rotation could be measured in the external magnetic field with different magnetic intensity by this magneto-optic system. The Faraday rotation of the photonic crystal fiber filled with magnetic fluid is approximately 5 times than that of the single mode optical fiber. The proposed magneto-optical fiber device takes full advantage of the ultrahigh sensitivity characteristic of photonic bandgap fiber and the large Verdet constant of magneto-optical fiber, can be used for high sensitive magnetic field sensor, magneto-optical switch, and magneto-optical modulator, etc.

  14. A New Type of Motor: Pneumatic Step Motor.

    PubMed

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

    2007-02-01

    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

  15. A New Type of Motor: Pneumatic Step Motor

    PubMed Central

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

    2011-01-01

    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

  16. Fiber Bragg grating inscription with UV femtosecond exposure and two beam interference for fiber laser applications

    NASA Astrophysics Data System (ADS)

    Becker, Martin; Brückner, Sven; Lindner, Eric; Rothhardt, Manfred; Unger, Sonja; Kobelke, Jens; Schuster, Kay; Bartelt, Hartmut

    2010-06-01

    Fiber Bragg grating based fiber lasers are promising for stable all fiber laser solutions. Standard methods for fiber Bragg gratings in fiber lasers apply germanium doped passive fibers which are connected to the amplifier section of the fiber laser with a splice. The connection is usually recoated using a low-index polymer coating to maintain guidance properties for the pump light. At high pump powers the spliced connections are affected by absorbed pump light and are prone to thermal degradation. Fiber Bragg gratings made with femtosecond laser exposure allow the direct inscription of resonator mirrors for fiber lasers into the amplifying section of the fiber laser. Such a technology has a number of advantages. The number of splices in the laser cavity is reduced. Fiber Bragg grating inscription does not relay on hydrogenation to increase the photosensitivity of the fiber. This is of special interest since hydrogen loading in large mode area fibers is a time consuming procedure due to the diffusion time of hydrogen in silica glass. Finally, one gets direct access to fiber Bragg gratings in air-clad fibers. In this paper we use a two beam interferometric inscription setup in combination with an frequency tripled femtosecond laser for grating inscription. It allows to write fiber Bragg gratings in rare earth doped fibers with a reflection wavelength span that covers the Ytterbium amplification band. Reflections with values higher than 90% have been realized.

  17. Delivery of an ultrashort spatially focused pulse to the other end of a multimode fiber using digital phase conjugation

    NASA Astrophysics Data System (ADS)

    Morales Delgado, Edgar E.; Papadopoulos, Ioannis N.; Farahi, Salma; Psaltis, Demetri; Moser, Christophe

    2015-03-01

    Multimode optical fibers potentially allow the transmission of larger amounts of information than their single mode counterparts because of their high number of supported modes. However, propagation of a light pulse through a multimode fiber suffers from spatial distortions due to the superposition of the various exited modes and from time broadening due to modal dispersion. We present a method based on digital phase conjugation to selectively excite in a multimode fiber specific optical fiber modes that follow similar optical paths as they travel through the fiber. The excited modes interfere constructively at the fiber output generating an ultrashort spatially focused pulse. The excitation of a limited number of modes following similar optical paths limits modal dispersion, allowing the transmission of the ultrashort pulse. We have experimentally demonstrated the delivery of a focused spot of pulse width equal to 500 fs through a 30 cm, 200 micrometer core step-index multimode fiber. The results of this study show that two-photon imaging capability can be added to ultra-thin lensless endoscopy using commercial multimode fibers.

  18. An SMS fiber structure based on chalcogenide multimode fiber

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

    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.

  19. Dietary Fiber

    MedlinePlus

    Fiber is a substance in plants. Dietary fiber is the kind you eat. It's a type of carbohydrate. You may also see it listed on a food label as soluble ... types have important health benefits. Good sources of dietary fiber include Whole grains Nuts and seeds Fruit and ...

  20. FLAX FIBERS

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  1. A transmission line model for propagation in elliptical core optical fibers

    NASA Astrophysics Data System (ADS)

    Georgantzos, E.; Papageorgiou, C.; Boucouvalas, A. C.

    2015-12-01

    The calculation of mode propagation constants of elliptical core fibers has been the purpose of extended research leading to many notable methods, with the classic step index solution based on Mathieu functions. This paper seeks to derive a new innovative method for the determination of mode propagation constants in single mode fibers with elliptic core by modeling the elliptical fiber as a series of connected coupled transmission line elements. We develop a matrix formulation of the transmission line and the resonance of the circuits is used to calculate the mode propagation constants. The technique, used with success in the case of cylindrical fibers, is now being extended for the case of fibers with elliptical cross section. The advantage of this approach is that it is very well suited to be able to calculate the mode dispersion of arbitrary refractive index profile elliptical waveguides. The analysis begins with the deployment Maxwell's equations adjusted for elliptical coordinates. Further algebraic analysis leads to a set of equations where we are faced with the appearance of harmonics. Taking into consideration predefined fixed number of harmonics simplifies the problem and enables the use of the resonant circuits approach. According to each case, programs have been created in Matlab, providing with a series of results (mode propagation constants) that are further compared with corresponding results from the ready known Mathieu functions method.

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

    NASA Astrophysics Data System (ADS)

    Javahiraly, Nicolas; Chakari, Ayoub

    2013-05-01

    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 μm rc (core radius) = 50 μm 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.

  3. Theory and modeling of photodarkening-induced quasi static degradation in fiber amplifiers.

    PubMed

    Ward, Benjamin

    2016-02-22

    A theory of photodarkening-induced quasi-static degradation in fiber amplifiers is presented. As the doped core of a fiber photodarkens and continues to absorb more power converting it to heat, the intensity grating created by higher order mode interference with the fundamental mode moves toward the input end. This creates a persistent absorption grating that remains phase-shifted from the modal interference pattern. This leads to power transfer from the fundamental mode to a higher order mode with a very small frequency offset that occurs on a time scale of minutes to hours. This process is modeled in large mode area step index and photonic crystal fibers and is found to produce reasonable threshold values. PMID:26907007

  4. Rib index.

    PubMed

    Grivas, Theodoros B

    2014-01-01

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

  5. [Carbohydrates and fiber].

    PubMed

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

    1988-09-01

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

  6. Carbon Fibers Conductivity Studies

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

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

  7. INDEXING MECHANISM

    DOEpatents

    Kock, L.J.

    1959-09-22

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

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

  9. Resonantly pumped amplification in a Tm-doped large mode-area photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Sincore, Alex; Shah, Lawrence; Wysmolek, Mateusz; Ryan, Robert; Abdulfattah, Ali; Richardson, Martin

    2015-03-01

    Ultra-large mode area thulium-doped photonic crystal fibers (Tm:PCF) have enabled the highest peak powers in 2 micron fiber laser systems to date. However, Tm:PCFs are limited by slope efficiencies of <50% when pumped with 790 nm laser diodes. A well-known alternative is pumping at 1550 nm with erbium/ytterbium-doped fiber (Er/Yb:fiber) lasers for efficiencies approaching ~70%. However, these 1550 nm pump lasers are also relatively inefficient themselves. A recently demonstrated and more attractive approach to enable slope efficiencies over 90% in thuliumdoped step-index fibers is resonant pumping (or in-band pumping). This utilizes a high power thulium fiber laser operating at a shorter wavelength as the pump. In this manuscript, we describe an initial demonstration of resonant pumping in Tm:PCF. While the extracted power was still in the exponential regime due to pump power limitations, slope efficiencies in excess of ~64 have been observed, and there is still room for improvement. These initial results show promise for applying resonant pumping in Tm:PCF to improve efficiencies and facilitate high power scaling in ultralarge mode area systems.

  10. Electrospinning of continuous aligned polymer fibers

    NASA Astrophysics Data System (ADS)

    Sundaray, Bibekananda; Subramanian, V.; Natarajan, T. S.; Xiang, Rong-Zheng; Chang, Chia-Cheng; Fann, Wun-Shain

    2004-02-01

    Electrospinning is a technique employed for preparing polymer fibers having diameters in the range of 10 μm-10 nm using high electrostatic field. In this letter, we report the formation of aligned polymer fibers, several centimeters in length, with separation between the fibers in the range of 5-100 μm. Achieving alignment is an important step toward the exploitation of these fibers in applications. We have employed about 4500 V and a separation distance of about 1-3 cm between the electrodes. Smaller distance between electrodes, we believe, provides better control on the formation of the fibers.

  11. Simple method of fabrication tapered fiber

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

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

  12. Thermal activation of regenerated fiber Bragg grating in few mode fibers

    NASA Astrophysics Data System (ADS)

    Lai, Man-Hong; Gunawardena, Dinusha S.; Lim, Kok-Sing; Machavaram, Venkata R.; Lee, Say-Hoe; Chong, Wu-Yi; Lee, Yen-Sian; Ahmad, Harith

    2016-03-01

    This work demonstrated for the first time, the thermal regeneration of two and four modes graded index fiber Bragg gratings using high temperature tube furnace. During the regeneration process, the seed grating is erased and a new grating with lower index contrast is formed. The thermal calibration shows that the temperature sensitivity of regenerated grating is slightly higher for fiber with larger core. On the other hand, the regeneration temperature is lower for fiber with smaller core. The temperature sustainability up to 900 °C is observed for the produced regenerated gratings in few mode fibers.

  13. Characterization of double-clad thulium-doped fiber with increased quantum conversion efficiency

    NASA Astrophysics Data System (ADS)

    Aubrecht, Jan; Cajzl, Jakub; Peterka, Pavel; Honztko, Pavel; Koka, Pavel; Baravets, Yauhen; Becker, Martin; Podrazk, Ond?ej; Todorov, Filip; Kak, Ivan

    2015-05-01

    In this paper we present experimental results of characterization of the experimentally prepared thulium-doped optical fibers in double-clad hexagonal fiber geometry for cladding optical pumping at a wavelength of 793 nanometers. The fiber was fabricated by the modified chemical vapor deposition and solution doping method and coated with polymer with lower refractive index than silica. The fiber was characterized in views of its refractive index profiles, thulium ions concentration, spectral absorptions, fluorescence lifetime, and performance in fiber laser.

  14. Multi-wavelength fiber laser based on a fiber Fabry-Perot interferometer

    NASA Astrophysics Data System (ADS)

    Estudillo-Ayala, J. M.; Jauregui-Vazquez, D.; Haus, J. W.; Perez-Maciel, M.; Sierra-Hernandez, J. M.; Avila-Garcia, M. S.; Rojas-Laguna, R.; Lopez-Dieguez, Y.; Hernandez-Garcia, J. C.

    2015-12-01

    In this work we report experimental studies of an erbium-doped fiber laser design that simultaneously emits up to three wavelengths. The laser cavity configuration has an all-fiber, Fabry-Perot interferometer, based on the insertion of air cavities in the fiber, near one end of a conventional single-mode fiber. The laser emissions have a side-mode suppression ratio over 25 dB, wavelength variations around 0.04 nm, and 2 dB power fluctuations. By using a simple, controlled fiber curvature technique cavity losses are varied over a section of convectional single-mode fiber and the laser output is switched between single-, dual-, and triple-wavelength emission. Moreover, by applying a refractive index change over the fiber filter the emission wavelengths are shifted. The fiber laser offers a compact, simple, and low-cost design for a multiple wavelength outputs that can be adopted in future applications.

  15. Multiplexed displacement fiber sensor using thin core fiber exciter.

    PubMed

    Chen, Zhen; Hefferman, Gerald; Wei, Tao

    2015-06-01

    This letter reports a multiplexed optical displacement sensor using a thin core fiber (TCF) exciter. The TCF exciter is followed by a stripped single mode optical fiber. A small section of buffer is used as the movable component along the single mode fiber. Ultra-weak cladding mode reflection (< - 75 dB) was employed to probe the refractive index discontinuity between the air and buffer coating boundary. The position change of the movable buffer segment results in a delay change of the cladding mode reflection. Thus, it is a measure of the displacement of the buffer segment with respect to the glass fiber. The insertion loss of one sensor was measured to be less than 3 dB. A linear relationship was evaluated between the measurement position and absolute position of the moving actuator. Multiplexed capability was demonstrated and no cross talk was found between the sensors. PMID:26133865

  16. Multiplexed displacement fiber sensor using thin core fiber exciter

    NASA Astrophysics Data System (ADS)

    Chen, Zhen; Hefferman, Gerald; Wei, Tao

    2015-06-01

    This letter reports a multiplexed optical displacement sensor using a thin core fiber (TCF) exciter. The TCF exciter is followed by a stripped single mode optical fiber. A small section of buffer is used as the movable component along the single mode fiber. Ultra-weak cladding mode reflection (< - 75 dB) was employed to probe the refractive index discontinuity between the air and buffer coating boundary. The position change of the movable buffer segment results in a delay change of the cladding mode reflection. Thus, it is a measure of the displacement of the buffer segment with respect to the glass fiber. The insertion loss of one sensor was measured to be less than 3 dB. A linear relationship was evaluated between the measurement position and absolute position of the moving actuator. Multiplexed capability was demonstrated and no cross talk was found between the sensors.

  17. Coating Carbon Fibers With Platinum

    NASA Technical Reports Server (NTRS)

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

    2007-01-01

    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.

  18. A Statistical Analysis of Cotton Fiber Properties

    NASA Astrophysics Data System (ADS)

    Ghosh, Anindya; Das, Subhasis; Majumder, Asha

    2016-04-01

    This paper reports a statistical analysis of different cotton fiber properties, such as strength, breaking elongation, upper half mean length, length uniformity index, short fiber index, micronaire, reflectance and yellowness measured from 1200 cotton bales. The uni-variate, bi-variate and multi-variate statistical analysis have been invoked to elicit interrelationship between above-mentioned properties taking them up singularly, pairwise and multiple way, respectively. In multi-variate analysis all cotton fiber properties are simultaneously considered for multi-dimensional techniques of principal factor analysis.

  19. Two Fiber Optical Fiber Thermometry

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  20. Interferometric Fiber Optic Sensors

    PubMed Central

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

    2012-01-01

    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

  1. Optical Fiber Protection

    NASA Technical Reports Server (NTRS)

    1999-01-01

    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

  2. Optical Fibers

    NASA Astrophysics Data System (ADS)

    Ghatak, Ajoy; Thyagarajan, K.

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

  3. Benefits of glass fibers in solar fiber optic lighting systems.

    PubMed

    Volotinen, Tarja T; Lingfors, David H S

    2013-09-20

    The transmission properties and coupling of solar light have been studied for glass core multimode fibers in order to verify their benefits for a solar fiber optic lighting system. The light transportation distance can be extended from 20 m with plastic fibers to over 100 m with the kind of glass fibers studied here. A high luminous flux, full visible spectrum, as well as an outstanding color rendering index (98) and correlated color temperature similar to the direct sun light outside have been obtained. Thus the outstanding quality of solar light transmitted through these fibers would improve the visibility of all kinds of objects compared to fluorescent and other artificial lighting. Annual relative lighting energy savings of 36% in Uppsala, Sweden, and 76% in Dubai were estimated in an office environment. The absolute savings can be doubled by using glass optical fibers, and are estimated to be in the order of 550 kWh/year in Sweden and 1160 kWh/year in Dubai for one system of only 0.159 m(2) total light collecting area. The savings are dependent on the fiber length, the daily usage time of the interior, the type of artificial lighting substituted, the system light output flux, and the available time of sunny weather at the geographic location. PMID:24085167

  4. An Incorrect Index of Skewness.

    ERIC Educational Resources Information Center

    Pettibone, Timothy J.; Diamond, James J.

    Checking of parametric assumptions is an often ignored step in the inferential process. A misconception regarding symmetry (one aspect of "robustness") is prevalent: that in nonsymmetric distributions the mean and median are always non-coincidental. It is to this fallacious point that the discussion is directed. A generally accepted index of…

  5. Wetting morphologies on randomly oriented fibers.

    PubMed

    Sauret, Alban; Boulogne, Franois; Soh, Beatrice; Dressaire, Emilie; Stone, Howard A

    2015-06-01

    We characterize the different morphologies adopted by a drop of liquid placed on two randomly oriented fibers, which is a first step toward understanding the wetting of fibrous networks. The present work reviews previous modeling for parallel and touching crossed fibers and extends it to an arbitrary orientation of the fibers characterized by the tilting angle and the minimum spacing distance. Depending on the volume of liquid, the spacing distance between fibers and the angle between the fibers, we highlight that the liquid can adopt three different equilibrium morphologies: 1) a column morphology in which the liquid spreads between the fibers, 2) a mixed morphology where a drop grows at one end of the column or 3) a single drop located at the node. We capture the different morphologies observed using an analytical model that predicts the equilibrium configuration of the liquid based on the geometry of the fibers and the volume of liquid. PMID:26123768

  6. Fiber optic fluid detector

    DOEpatents

    Angel, S. Michael

    1989-01-01

    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.

  7. Fiber optic fluid detector

    DOEpatents

    Angel, S.M.

    1987-02-27

    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.

  8. Large effective-area fibers

    NASA Astrophysics Data System (ADS)

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

    1999-04-01

    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.

  9. Pragmatic Approach to Subject Indexing: A New Concept.

    ERIC Educational Resources Information Center

    Dutta, S.; Sinha, P. K.

    1984-01-01

    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…

  10. Fireblocking Fibers

    NASA Technical Reports Server (NTRS)

    1986-01-01

    PBI was originally developed for space suits. In 1980, the need for an alternative to asbestos and stricter government anti-pollution standards led to commercialization of the fire blocking fiber. PBI is used for auto racing driver suits and aircraft seat covers. The fiber does not burn in air, is durable and easily maintained. It has been specified by a number of airliners and is manufactured by Hoechst-Celanese Corporation.

  11. WANTED: Fully Automated Indexing.

    ERIC Educational Resources Information Center

    Purcell, Royal

    1991-01-01

    Discussion of indexing focuses on the possibilities of fully automated indexing. Topics discussed include controlled indexing languages such as subject heading lists and thesauri, free indexing languages, natural indexing languages, computer-aided indexing, expert systems, and the need for greater creativity to further advance automated indexing.…

  12. Registration of TTU-0782 upland cotton germplasm line with superior fiber quality

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A germplasm line of upland cotton (Gossypium hirsutum L.) designated as TTU 0782 with improved fiber quality was developed. It possesses longer fiber length, higher fiber bundle strength, high uniformity index, low short fiber content, high maturity ratio, and low nep counts. Spinning tests also ind...

  13. Beam Quality after Propagation of Nd:YAG Laser Light through Large-Core Optical Fibers

    NASA Astrophysics Data System (ADS)

    Kuhn, Andreas; Blewett, Ian J.; Hand, Duncan P.; Jones, Julian D. C.

    2000-12-01

    Laser beam characteristics are altered during propagation through large-core optical fibers. The distribution of modes excited by the input laser beam is modified by means of mode coupling on transmission through the fiber, leading to spatial dispersion of the profile and, ultimately and unavoidably, to degradation in the quality of the delivered beam unless the beam is spatially filtered with consequent power loss. Furthermore, a mismatch between the intensity profile of a typical focused high-power laser beam and the profile of the step-index fiber gives rise to additional beam-quality degradation. Modern materials processing applications demand ever higher delivered beam qualities (as measured by a parameter such as M 2 ) to achieve greater machining precision and efficiency, a demand that is currently in conflict with the desire to utilize the convenience and flexibility of large-core fiber-optic beam delivery. We present a detailed experimental investigation of the principal beam-quality degradation effects associated with fiber-optic beam delivery and use numerical modeling to aid an initial discussion of the causes of such degradation.

  14. A proteome quality index.

    PubMed

    Zaucha, Jan; Stahlhacke, Jonathan; Oates, Matt E; Thurlby, Natalie; Rackham, Owen J L; Fang, Hai; Smithers, Ben; Gough, Julian

    2015-01-01

    We present the Proteome Quality Index (PQI; http://pqi-list.org), a much-needed resource for users of bacterial and eukaryotic proteomes. Completely sequenced genomes for which there is an available set of protein sequences (the proteome) are given a one- to five-star rating supported by 11 different metrics of quality. The database indexes over 3000 proteomes at the time of writing and is provided via a website for browsing, filtering and downloading. Previous to this work, there was no systematic way to account for the large variability in quality of the thousands of proteomes, and this is likely to have profoundly influenced the outcome of many published studies, in particular large-scale comparative analyses. The lack of a measure of proteome quality is likely due to the difficulty in producing one, a problem that we have approached by integrating multiple metrics. The continued development and improvement of the index will require the contribution of additional metrics by us and by others; the PQI provides a useful point of reference for the scientific community, but it is only the first step towards a 'standard' for the field. PMID:25339269

  15. Effective index model predicts modal frequencies of vertical-cavity lasers

    SciTech Connect

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

    2000-04-18

    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.

  16. Automatic inference of indexing rules for MEDLINE

    PubMed Central

    Névéol, Aurélie; Shooshan, Sonya E; Claveau, Vincent

    2008-01-01

    Background: Indexing is a crucial step in any information retrieval system. In MEDLINE, a widely used database of the biomedical literature, the indexing process involves the selection of Medical Subject Headings in order to describe the subject matter of articles. The need for automatic tools to assist MEDLINE indexers in this task is growing with the increasing number of publications being added to MEDLINE. Methods: In this paper, we describe the use and the customization of Inductive Logic Programming (ILP) to infer indexing rules that may be used to produce automatic indexing recommendations for MEDLINE indexers. Results: Our results show that this original ILP-based approach outperforms manual rules when they exist. In addition, the use of ILP rules also improves the overall performance of the Medical Text Indexer (MTI), a system producing automatic indexing recommendations for MEDLINE. Conclusion: We expect the sets of ILP rules obtained in this experiment to be integrated into MTI. PMID:19025687

  17. Estimation of ovular fiber production in cotton

    DOEpatents

    Van`t Hof, J.

    1998-09-01

    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.

  18. Estimation of ovular fiber production in cotton

    DOEpatents

    Van't Hof, Jack

    1998-09-01

    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.

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

    PubMed Central

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

    2012-01-01

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

  20. Long period gratings coated with hafnium oxide by plasma-enhanced atomic layer deposition for refractive index measurements.

    PubMed

    Melo, Luis; Burton, Geoff; Kubik, Philip; Wild, Peter

    2016-04-01

    Long period gratings (LPGs) are coated with hafnium oxide using plasma-enhanced atomic layer deposition (PEALD) to increase the sensitivity of these devices to the refractive index of the surrounding medium. PEALD allows deposition at low temperatures which reduces thermal degradation of UV-written LPGs. Depositions targeting three different coating thicknesses are investigated: 30 nm, 50 nm and 70 nm. Coating thickness measurements taken by scanning electron microscopy of the optical fibers confirm deposition of uniform coatings. The performance of the coated LPGs shows that deposition of hafnium oxide on LPGs induces two-step transition behavior of the cladding modes. PMID:27137052

  1. Soft capacitor fibers using conductive polymers for electronic textiles

    NASA Astrophysics Data System (ADS)

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

    2010-11-01

    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 kΩ 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.

  2. Concentric core optical fiber with multiple-mode signal transmission

    DOEpatents

    Muhs, Jeffrey D.

    1997-01-01

    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. Concentric core optical fiber with multiple-mode signal transmission

    DOEpatents

    Muhs, J.D.

    1997-05-06

    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.

  4. Accurate loss analysis of single-mode fiber/D-fiber splice by vectorial finite-element method

    NASA Astrophysics Data System (ADS)

    Conese, Tiziana; Barbarossa, Giovanni; Armenise, Mario N.

    1995-05-01

    Fiber/D-fiber splice loss can be minimized by precise axial offsetting. We present an accurate loss analysis of single-mode fiber/D-fiber splice by using a combination of vectorial finite-element method and mode matching method. The splice between fiber and D-fiber with same or different refractive index difference is considered. Splice loss variation is investigated in terms of transverse offset between fiber axes and axial rotation, for various values of the D-fiber core-to-flat distance. It is found that optimum values of offset and rotation exist that minimize splice loss for a given D-fiber core-to-flat distance.

  5. Evanescently coupled optical fiber refractometer based a tilted fiber Bragg grating and a D-shaped fiber.

    PubMed

    Cai, Zhongyue; Liu, Fu; Guo, Tuan; Guan, Bai-Ou; Peng, Gang-Ding; Albert, Jacques

    2015-08-10

    A novel tip-reflective and power-referenced refractometer based on strong fiber-to-fiber optical coupling for a large range of surrounding refractive index (SRI) (from 1.33 to 1.45) is proposed and experimentally demonstrated. A short D-shaped fiber stub is placed in parallel and close contact to another standard circular fiber containing a weakly tilted Bragg grating (TFBG). The TFBG couples the light from the circular fiber's core into its cladding where it remains guided. Apart from the direct light coupling over the contact interface, the evanescent field from the guided cladding modes penetrates the surroundings and reaches the D-fiber core by tunneling across the medium into which the fiber pair is located. The amount of tunneling depends strongly on the SRI so that the total amount of light collected by the D-fiber provides a measure of the SRI. Sensitivities ranging from ~1000 to 13000 nW/RIU (Refractive Index Unit) have been obtained and the result is independent of temperature (within +/-10 nW of uncertainty). The measurement can be temperature-referenced through measurement of the TFBG spectrum if needed. PMID:26367949

  6. Novel optical fiber design for DTS measurement purposes

    NASA Astrophysics Data System (ADS)

    Siska, Petr; Hajek, Lukas; Vasinek, Vladimir; Koudelka, Petr; Latal, Jan

    2015-07-01

    This article is dealing with an optical fiber refractive index design optimized for utilization in DTS (Distributed Temperature Sensing) measurements. Presented optical fiber uses wavelength of 850 nm for communication purposes and 1060 nm for sensory operation. The aim of this work is to design an optical fiber with redistribution of the optical field at 850 nm similar to communication multi-mode optical fiber 50/125 μm and for wavelength of 1060 nm the redistribution of the optical field will be shifted closer to the core-cladding boundary to increase its sensitivity to temperature. Optical properties obtained from fiber design are compared with standard multi-mode optical fiber with graded refractive index to ensure that new optical fiber design has better sensing characteristics, but still keeps good enough communication properties at the same time.

  7. Soluble vs. insoluble fiber

    MedlinePlus

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

  8. Stepping motor controller

    DOEpatents

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

    1982-07-02

    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.

  9. Stepping motor controller

    DOEpatents

    Bourret, Steven C.; Swansen, James E.

    1984-01-01

    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.

  10. Step-Growth Polymerization.

    ERIC Educational Resources Information Center

    Stille, J. K.

    1981-01-01

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

  11. Coherence property of mid-infrared supercontinuum generation in tapered chalcogenide fibers with different structures

    NASA Astrophysics Data System (ADS)

    Liu, Lai; Nagasaka, Kenshiro; Qin, Guanshi; Suzuki, Takenobu; Ohishi, Yasutake

    2016-01-01

    We have numerically investigated the coherence property of mid-infrared supercontinuum generation in tapered step-index chalcogenide fibers with different structures. The pump source is a 4 μm laser with pulse width of 500 fs and peak power of 1 kW. The length ratio is the ratio of transition region length near the laser input to the other transition region length near the output. We calculate the bandwidth and the spectrally averaged coherence of the supercontinuum spectra generated in fibers with different length ratios under the same pumping condition. Numerical results show that as the length ratio increases, the bandwidth decreases from 4.84 μm to 4.11 μm while the spectrally averaged coherence increases from 0.53 to 0.9 and then jitters near the maximum. The length ratio within 1-1.5 is preferable to keep a balance between bandwidth and coherence.

  12. Optimization and Application of Reflective LSPR Optical Fiber Biosensors Based on Silver Nanoparticles

    PubMed Central

    Chen, Jiangping; Shi, Se; Su, Rongxin; Qi, Wei; Huang, Renliang; Wang, Mengfan; Wang, Libing; He, Zhimin

    2015-01-01

    In this study, we developed a reflective localized surface plasmon resonance (LSPR) optical fiber sensor, based on silver nanoparticles (Ag NPs). To enhance the sensitivity of the LSPR optical sensor, two key parameters were optimized, the length of the sensing area and the coating time of the Ag NPs. A sensing length of 1.5 cm and a 1-h coating time proved to be suitable conditions to produce highly sensitive sensors for biosensing. The optimized sensor has a high refractive index sensitivity of 387 nm/RIU, which is much higher than that of other reported individual silver nanoparticles in solutions. Moreover, the sensor was further modified with antigen to act as a biosensor. Distinctive wavelength shifts were found after each surface modification step. In addition, the reflective LSPR optical fiber sensor has high reproducibility and stability. PMID:26016910

  13. All-optical correlator based on modal dispersion in multimode fiber

    NASA Astrophysics Data System (ADS)

    Sun, Jian; Tan, Zhongwei; Li, Tangjun; Wang, Muguang

    2016-03-01

    We propose and demonstrate an all-optical correlator based on modal dispersion in a multimode fiber. Many of the modes can be excited in a large core high numerical aperture step-index multimode fiber under overfilled launching. The incident optical signal is copied into different modes and a time delay is introduced by the modal dispersion. We use a mask with slits as a space filter to select the modes needed. A correlator of the mask and input signal is achieved at the output end. Thanks to the use of modal dispersion, the correlator is nearly independent of the wavelength and bandwidth of the input signal. By adjusting the slits on the mask, the target patterns of the correlator can be changed easily. A radio frequency signal detection is also experimentally demonstrated with this construction.

  14. Simulation of the coherent MDM transmission using principal modes of the optical fiber as signal carriers

    NASA Astrophysics Data System (ADS)

    Lyubopytov, Vladimir S.; Zakirov, Robert A.; Vinogradova, Irina L.; Sultanov, Albert K.

    2015-03-01

    In this paper we demonstrate computer simulation results obtained for the coherent mode division multiplexed (MDM) 5x5 QPSK transmission using principal modes (PMs) of the stepped-index few-mode fiber (FMF) as a basis of independent signal carriers. The output signal recovering and the fiber propagation matrix determination are considered to be carried out in optical domain by means of reconfigurable multibranch diffractive optical elements (DOEs). Both the cases of Gaussian and Nyquist raised-cosine pulse shaping are considered for optical signal modulation. The simulation results show, that the transmission in the basis of PMs in strong coupling regime allows the reliability of the coherent MDM system to be fundamentally improved. As a result, utilization of the optical signal processing for MDM transmission could minimize substantially the DSP circuit complexity required for the real-time recovering of the transmitted signal.

  15. Coiled Fiber Pulsed Laser Simulator

    Energy Science and Technology Software Center (ESTSC)

    2009-01-29

    This suite of codes simulates the transient output pulse from an optically-pumped coiled fiber amplifier. The input pulse is assumed to have a Gaussian time dependence and a spatial dependence that may be Gaussian or an eigenmode of the straight of bent fiber computed using bend10 or bend20. Only one field component is used (semivectorial approximation). The fully-spatially-dependent fiber gain profile is specified is subroutines "inversion" and "interp_inversion" and is presently read from a datamore » file, although other means of specifying fiber gain could be reallized through modification of these subroutines. The input pulse is propagated through the fiber, including the following physical effects: spatial and temporal gain saturation, self-focusing, bend losses, and confinement from a user-defined fiber index profile. The user can follow the propagation progress with 3D graphics that show an intensity profile via user-modifiable cutting planes through the time space axes. A restart capability is also included. Approximate solutions in the frequency domain may be obtained much faster using the auxilliary codes bendbpm10 (full vector), bendbpm20 (semivectoral), and bendbpm21 (semivectoral with gain sheet spproximation for gain and self-focusing). These codes all include bend loss and spatial (but not temporal) gain saturation.« less

  16. Photovoltaic fibers

    NASA Astrophysics Data System (ADS)

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

    2006-08-01

    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.

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

    PubMed

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

    2014-01-15

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

  18. Fluoride glass fibers: applications and prospects

    NASA Astrophysics Data System (ADS)

    Poulain, Marcel

    1998-09-01

    Fluoride glass fibers have been intensively developed for the last 20 years. A major effort was devoted to the fabrication of low loss fibers for repeaterless long haul telecommunications. This step which ended in the late eighties provided the basic technology for the manufacturing of multimode and single mode fibers with minimum losses below 10 dB/km. Such fibers area now used for various passive applications requiring the handling of IR signal. In this respect, fluoride fibers are complementary to silica fibers when wavelength exceeds 2 micrometers . Some practical set ups are operating for IR imaging, remote spectroscopy and thermometry. Special fibers such as polarization maintaining fibers have been developed for interferometric astronomy, which could also apply to sensors. UV transmission has still to be developed. Laser power delivery is another field of application for these fibers. YAG:Er laser at 2.9 micrometers attracts a growing interest for medical applications, ophthalmology and dentistry, while prospects for CO laser are positive. Active fibers are based on rare earth doped single mode fibers. They lead to the definition of numerous new laser lines and emphasized the potential of up conversion for the generation of visible light using IR pumping laser diodes. High power output has been achieved in the blue and the red light, which open prospects for compact and all solid state fiber lasers for a wide range of applications, from displays to medical uses. Optical amplification makes another field of R and D centered on telecommunication needs. Pr3+ doped fluoride fibers have been used for the 1.3 micrometers band, and Er based fluoride fiber amplifiers exhibit wider and flatter gain than those made from silica. Optical amplification may be implemented at other wavelengths for more general purposes.

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

    NASA Astrophysics Data System (ADS)

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

    2008-09-01

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

  20. Fiber crops

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Much research continues to develop renewable, recyclable, sustainable, and bio-based products from agricultural feed stocks such as cotton and flax fiber. Primary requirements are sustainable production, low cost, and consistent and known quality. To better understand these products, research contin...

  1. Fabrication of helical long-period fiber gratings by use of a CO2 laser

    NASA Astrophysics Data System (ADS)

    Oh, Seungtae; Lee, Kyung Rok; Paek, Un-Chul; Chung, Youngjoo

    2004-07-01

    We present a method of helical long-period fiber grating (H-LPFG) fabrication by use of a CO2 laser for use as an optical torque sensor. A conventional optical fiber grating has periodic vertical index changes along its fiber axis, but a H-LPFG has a screw-type index modulation. The helical index modulation is obtained with the asymmetric index change caused by a single-side laser beam exposure. The H-LPFG shows peak shifts with codirectional or contradirectional torsion to the helix. Also, the polarization-dependent loss is measured to be relatively small compared with that of a conventional long-period fiber grating.

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

    DOEpatents

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

    2010-06-01

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

  3. Miniature fiber optic surface plasmon resonance biosensors

    NASA Astrophysics Data System (ADS)

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

    1999-01-01

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

  4. Exceptional stiffening in composite fiber networks

    NASA Astrophysics Data System (ADS)

    Shahsavari, A. S.; Picu, R. C.

    2015-07-01

    We study the small strain elastic behavior of composite athermal fiber networks constructed by adding stiffer fibers to a cross-linked base network. We observe that if the base network is in the affine deformation regime, the composite behaves similar to a fiber-reinforced continuum. When the base network is in the nonaffine deformation regime, the stiffness of the composite increases by orders of magnitude upon the addition of a small fraction of stiff fibers. The increase is not gradual, but rather occurs in two steps. Of these, one is associated with the stiffness percolation of the network of added fibers. The other, which occurs at very small fractions of stiff fibers, is due to the percolation of perturbation zones, or "interphases," induced in the base network by the stiff fibers, regions where the energy is stored mostly in the axial deformation mode. Their size controls the stiffening transition and depends on base network parameters and the length of added fibers. It is also shown that the perturbation field introduced in the base network by the presence of a stiff fiber is much longer ranged than in the case when the fiber is tied to a continuum of same modulus with the base network.

  5. Photonic lantern with cladding-removable fibers

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    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.

  6. Exposed-core chalcogenide microstructured optical fibers for chemical sensing

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

    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.

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

    ERIC Educational Resources Information Center

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

    2009-01-01

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

  8. Optimization of laser fibers for high pump light absorption

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    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.

  9. Fabrication of nonlinear plastic optical fiber (POF) and application

    NASA Astrophysics Data System (ADS)

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

    2007-04-01

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

  10. Intrinsic Fabry-Perot optical fiber sensors and their multiplexing

    DOEpatents

    Wang, Anbo

    2007-12-11

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

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

    NASA Astrophysics Data System (ADS)

    Joshi, Sachin

    2008-10-01

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

  12. A Step Circuit Program.

    ERIC Educational Resources Information Center

    Herman, Susan

    1995-01-01

    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,…

  13. Resonance optical activity in multihelicoidal optical fibers.

    PubMed

    Alexeyev, C N; Lapin, B P; Yavorsky, M A

    2016-03-01

    We have studied the effect of optical activity (OA) in optical fibers with multihelical distribution of refractive index profiles near the resonance wavelength, at which the conversion of an incident Gaussian beam into an optical vortex (and vice versa) takes place. We have shown that at such a wavelength the polarization vector of the input Gaussian beam rotates within the fiber at an average rate proportional to the difference in propagation constants of left- and right-circularly polarized optical vortices with the same topological charge. We also show that for certain fiber lengths the magnitude of OA can greatly exceed its average level and reach anomalously high values. PMID:26974091

  14. Regeneration of fiber Bragg gratings under strain.

    PubMed

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

    2013-04-01

    The effect of strain on both the index modulation, Δn(mod), and average index, Δn, during grating regeneration within two types of fibers is studied. Significant tunability of the Bragg wavelength (λ(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

  15. Comparison of different methods for rigorous modeling of photonic crystal fibers.

    PubMed

    Szpulak, Marcin; Urbanczyk, Waclaw; Serebryannikov, Evgenii; Zheltikov, Aleksei; Hochman, Amit; Leviatan, Yehuda; Kotynski, Rafal; Panajotov, Krassimir

    2006-06-12

    We present a summary of the simulation exercise carried out within the EC Cost Action P11 on the rigorous modeling of photonic crystal fiber (PCF) with an elliptically deformed core and noncircular air holes with a high fill factor. The aim of the exercise is to calculate using different numerical methods and to compare several fiber characteristics, such as the spectral dependence of the phase and the group effective indices, the birefringence, the group velocity dispersion and the confinement losses. The simulations are performed using four rigorous approaches: the finite element method (FEM), the source model technique (SMT), the plane wave method (PWM), and the localized function method (LFM). Furthermore, we consider a simplified equivalent fiber method (EFM), in which the real structure of the holey fiber is replaced by an equivalent step index waveguide composed of an elliptical glass core surrounded by air cladding. All these methods are shown to converge well and to provide highly consistent estimations of the PCF characteristics. Qualitative arguments based on the general properties of the wave equation are applied to explain the physical mechanisms one can utilize to tailor the propagation characteristics of nonlinear PCFs. PMID:19516739

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

    PubMed

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

    2013-08-10

    A 125 μm-diameter erbium-ytterbium-codoped single-mode fiber is reported. The utilization of depressed inner cladding guarantees the improvement of trade-off between the effective area and bending sensitivity compared to step-index profiles. Changes of cutoff wavelength, effective area, and macrobend loss under the influence of various structural parameters, and the balancing selection of core radius and subsidence layer width are investigated systematically. For the laboratory-made depressed inner cladding fiber, a macrobend loss of 0.06 dB/loop for a bending radius as tight as 10 mm was achieved, while maintaining an effective area of 164.22 μm² with intact single-mode properties at 1550 nm. The maximum small signal gain was achieved at 40.9 dB, and the gain fluctuation was less than 1 dB at the C-band. The fiber is suitable for high-power, small, portable, and handy optical fiber devices. PMID:23938442

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  18. Fibrin Fiber Stiffness Is Strongly Affected by Fiber Diameter, but Not by Fibrinogen Glycation.

    PubMed

    Li, Wei; Sigley, Justin; Pieters, Marlien; Helms, Christine Carlisle; Nagaswami, Chandrasekaran; Weisel, John W; Guthold, Martin

    2016-03-29

    The major structural component of a blood clot is a mesh of fibrin fibers. Our goal was to determine whether fibrinogen glycation and fibrin fiber diameter have an effect on the mechanical properties of single fibrin fibers. We used a combined atomic force microscopy/fluorescence microscopy technique to determine the mechanical properties of individual fibrin fibers formed from blood plasma. Blood samples were taken from uncontrolled diabetic patients as well as age-, gender-, and body-mass-index-matched healthy individuals. The patients then underwent treatment to control blood glucose levels before end blood samples were taken. The fibrinogen glycation of the diabetic patients was reduced from 8.8 to 5.0 mol glucose/mol fibrinogen, and the healthy individuals had a mean fibrinogen glycation of 4.0 mol glucose/mol fibrinogen. We found that fibrinogen glycation had no significant systematic effect on single-fiber modulus, extensibility, or stress relaxation times. However, we did find that the fiber modulus, Y, strongly decreases with increasing fiber diameter, D, as Y∝D(-1.6). Thin fibers can be 100 times stiffer than thick fibers. This is unusual because the modulus is a material constant and should not depend on the sample dimensions (diameter) for homogeneous materials. Our finding, therefore, implies that fibrin fibers do not have a homogeneous cross section of uniformly connected protofibrils, as is commonly thought. Instead, the density of protofibril connections, ρPb, strongly decreases with increasing diameter, as ρPb∝D(-1.6). Thin fibers are denser and/or have more strongly connected protofibrils than thick fibers. This implies that it is easier to dissolve clots that consist of fewer thick fibers than those that consist of many thin fibers, which is consistent with experimental and clinical observations. PMID:27028649

  19. Integrated fiber optic probe for dynamic light scattering

    NASA Technical Reports Server (NTRS)

    Dhadwal, Harbans S.; Khan, Romel R.; Suh, Kwang

    1993-01-01

    An integrated fiber optic probe, comprising a monomode optical fiber fusion spliced to a short length of a graded-index multimode fiber, is fabricated for use as a coherent receiver in dynamic light scattering. The multimode fiber is cleaved to provide a gradient-index fiber lens with a focal length of 125 microns and an f-number close to unity. An integrated fiber receiver is used to measure the intensity-intensity autocorrelation data from a 0.05 percent by weight concentration of an aqueous suspension of polystyrene latex spheres. Analysis of 100 independent data sets indicates that the particle size can be recovered with an accuracy of +/- 1 percent.

  20. Effect of adding the novel fiber, PGX®, to commonly consumed foods on glycemic response, glycemic index and GRIP: a simple and effective strategy for reducing post prandial blood glucose levels - a randomized, controlled trial

    PubMed Central

    2010-01-01

    Background Reductions in postprandial glycemia have been demonstrated previously with the addition of the novel viscous polysaccharide (NVP), PolyGlycopleX® (PGX®), to an OGTT or white bread. This study explores whether these reductions are sustained when NVP is added to a range of commonly consumed foods or incorporated into a breakfast cereal. Methods Ten healthy subjects (4M, 6F; age 37.3 ± 3.6 y; BMI 23.8 ± 1.3 kg/m2), participated in an acute, randomized controlled trial. The glycemic response to cornflakes, rice, yogurt, and a frozen dinner with and without 5 g of NVP sprinkled onto the food was determined. In addition, 3 granolas with different levels of NVP and 3 control white breads and one white bread and milk were also consumed. All meals contained 50 g of available carbohydrate. Capillary blood samples were taken fasting and at 15, 30, 45, 60, 90 and 120 min after the start of the meal. The glycemic index (GI) and the glycemic reduction index potential (GRIP) were calculated. The blood glucose concentrations at each time and the iAUC values were subjected to repeated-measures analysis of variance (ANOVA) examining for the effect of test meal. After demonstration of significant heterogeneity, differences between individual means was assessed using GLM ANOVA with Tukey test to adjust for multiple comparisons. Results Addition of NVP reduced blood glucose response irrespective of food or dose (p < 0.01). The GI of cornflakes, cornflakes+NVP, rice, rice+NVP, yogurt, yogurt+NVP, turkey dinner, and turkey dinner+NVP were 83 ± 8, 58 ± 7, 82 ± 8, 45 ± 4, 44 ± 4, 38 ± 3, 55 ± 5 and 41 ± 4, respectively. The GI of the control granola, and granolas with 2.5 and 5 g of NVP were 64 ± 6, 33 ± 5, and 22 ± 3 respectively. GRIP was 6.8 ± 0.9 units per/g of NVP. Conclusion Sprinkling or incorporation of NVP into a variety of different foods is highly effective in reducing postprandial glycemia and lowering the GI of a food. Clinical Trial registration NCT00935350. PMID:21092221

  1. DIDA: Distributed Indexing Dispatched Alignment.

    PubMed

    Mohamadi, Hamid; Vandervalk, Benjamin P; Raymond, Anthony; Jackman, Shaun D; Chu, Justin; Breshears, Clay P; Birol, Inanc

    2015-01-01

    One essential application in bioinformatics that is affected by the high-throughput sequencing data deluge is the sequence alignment problem, where nucleotide or amino acid sequences are queried against targets to find regions of close similarity. When queries are too many and/or targets are too large, the alignment process becomes computationally challenging. This is usually addressed by preprocessing techniques, where the queries and/or targets are indexed for easy access while searching for matches. When the target is static, such as in an established reference genome, the cost of indexing is amortized by reusing the generated index. However, when the targets are non-static, such as contigs in the intermediate steps of a de novo assembly process, a new index must be computed for each run. To address such scalability problems, we present DIDA, a novel framework that distributes the indexing and alignment tasks into smaller subtasks over a cluster of compute nodes. It provides a workflow beyond the common practice of embarrassingly parallel implementations. DIDA is a cost-effective, scalable and modular framework for the sequence alignment problem in terms of memory usage and runtime. It can be employed in large-scale alignments to draft genomes and intermediate stages of de novo assembly runs. The DIDA source code, sample files and user manual are available through http://www.bcgsc.ca/platform/bioinfo/software/dida. The software is released under the British Columbia Cancer Agency License (BCCA), and is free for academic use. PMID:25923767

  2. DIDA: Distributed Indexing Dispatched Alignment

    PubMed Central

    Mohamadi, Hamid; Vandervalk, Benjamin P; Raymond, Anthony; Jackman, Shaun D; Chu, Justin; Breshears, Clay P; Birol, Inanc

    2015-01-01

    One essential application in bioinformatics that is affected by the high-throughput sequencing data deluge is the sequence alignment problem, where nucleotide or amino acid sequences are queried against targets to find regions of close similarity. When queries are too many and/or targets are too large, the alignment process becomes computationally challenging. This is usually addressed by preprocessing techniques, where the queries and/or targets are indexed for easy access while searching for matches. When the target is static, such as in an established reference genome, the cost of indexing is amortized by reusing the generated index. However, when the targets are non-static, such as contigs in the intermediate steps of a de novo assembly process, a new index must be computed for each run. To address such scalability problems, we present DIDA, a novel framework that distributes the indexing and alignment tasks into smaller subtasks over a cluster of compute nodes. It provides a workflow beyond the common practice of embarrassingly parallel implementations. DIDA is a cost-effective, scalable and modular framework for the sequence alignment problem in terms of memory usage and runtime. It can be employed in large-scale alignments to draft genomes and intermediate stages of de novo assembly runs. The DIDA source code, sample files and user manual are available through http://www.bcgsc.ca/platform/bioinfo/software/dida. The software is released under the British Columbia Cancer Agency License (BCCA), and is free for academic use. PMID:25923767

  3. Carbon fiber manufacturing via plasma technology

    DOEpatents

    Paulauskas, Felix L.; Yarborough, Kenneth D.; Meek, Thomas T.

    2002-01-01

    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.

  4. Semiclassical model of triple photons generation in optical fibers.

    PubMed

    Richard, S; Bencheikh, K; Boulanger, B; Levenson, J A

    2011-08-01

    In this Letter we study spontaneous generation of triple photon states in optical fibers by third order spontaneous downconversion. Using a semiclassical approach we derive an explicit expression for the triple photons generation efficiency as a function of fiber parameters. We show that optical fibers with well suited index profiles and standard outer diameters could be the key component of future triple photons sources. PMID:21808385

  5. Continuous Fiber Ceramic Composites (CFCC)

    SciTech Connect

    R. A. Wagner

    2002-12-18

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  7. Temperature-independent polymer optical fiber evanescent wave sensor.

    PubMed

    Zhong, Nianbing; Liao, Qiang; Zhu, Xun; Zhao, Mingfu; Huang, Yun; Chen, Rong

    2015-01-01

    Although the numerous advantages of polymer optical fibers have been exploited in the fields of sensors and telecommunications, such fibers still experience a critical problem: the temperature dependency. Therefore, we explored the temperature-independent operation of a polymer fiber-optic evanescent wave sensor immersed in distilled water. We investigated variations in the surface morphology, deformation trajectory, refractive index, and weight of the fiber-sensing region with varying water temperature. We also examined the spectral transmission and transmitted light intensity of fibers subjected to a heating-cooling treatment. We observed that the light-transmission modes and sensitivity of the sensor were affected by changes in the surface morphology, diameter, and refractive index of the sensing region caused by changes in temperature. The transmitted light intensity of the sensor was maintained at a constant level after five cycles of the heating-cooling treatment, after which the fibers exhibited a smooth surface, low refractive index, and large fiber diameter. Consequently, we utilized the heating-cooling-treated fiber to realize a temperature-independent, U-shaped polymer fiber-optic evanescent wave sensor. The temperature independence was evaluated using glucose solutions in the range of 10 to 70 °C. The fabricated sensor showed significant temperature independence and high degree of consistency in measuring solutions. PMID:26112908

  8. Temperature-independent polymer optical fiber evanescent wave sensor

    PubMed Central

    Zhong, Nianbing; Liao, Qiang; Zhu, Xun; Zhao, Mingfu; Huang, Yun; Chen, Rong

    2015-01-01

    Although the numerous advantages of polymer optical fibers have been exploited in the fields of sensors and telecommunications, such fibers still experience a critical problem: the temperature dependency. Therefore, we explored the temperature-independent operation of a polymer fiber-optic evanescent wave sensor immersed in distilled water. We investigated variations in the surface morphology, deformation trajectory, refractive index, and weight of the fiber-sensing region with varying water temperature. We also examined the spectral transmission and transmitted light intensity of fibers subjected to a heating-cooling treatment. We observed that the light-transmission modes and sensitivity of the sensor were affected by changes in the surface morphology, diameter, and refractive index of the sensing region caused by changes in temperature. The transmitted light intensity of the sensor was maintained at a constant level after five cycles of the heating-cooling treatment, after which the fibers exhibited a smooth surface, low refractive index, and large fiber diameter. Consequently, we utilized the heating-cooling-treated fiber to realize a temperature-independent, U-shaped polymer fiber-optic evanescent wave sensor. The temperature independence was evaluated using glucose solutions in the range of 10 to 70 °C. The fabricated sensor showed significant temperature independence and high degree of consistency in measuring solutions. PMID:26112908

  9. Temperature-independent polymer optical fiber evanescent wave sensor

    NASA Astrophysics Data System (ADS)

    Zhong, Nianbing; Liao, Qiang; Zhu, Xun; Zhao, Mingfu; Huang, Yun; Chen, Rong

    2015-06-01

    Although the numerous advantages of polymer optical fibers have been exploited in the fields of sensors and telecommunications, such fibers still experience a critical problem: the temperature dependency. Therefore, we explored the temperature-independent operation of a polymer fiber-optic evanescent wave sensor immersed in distilled water. We investigated variations in the surface morphology, deformation trajectory, refractive index, and weight of the fiber-sensing region with varying water temperature. We also examined the spectral transmission and transmitted light intensity of fibers subjected to a heating-cooling treatment. We observed that the light-transmission modes and sensitivity of the sensor were affected by changes in the surface morphology, diameter, and refractive index of the sensing region caused by changes in temperature. The transmitted light intensity of the sensor was maintained at a constant level after five cycles of the heating-cooling treatment, after which the fibers exhibited a smooth surface, low refractive index, and large fiber diameter. Consequently, we utilized the heating-cooling-treated fiber to realize a temperature-independent, U-shaped polymer fiber-optic evanescent wave sensor. The temperature independence was evaluated using glucose solutions in the range of 10 to 70 °C. The fabricated sensor showed significant temperature independence and high degree of consistency in measuring solutions.

  10. Lobby index in networks

    NASA Astrophysics Data System (ADS)

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

    2009-06-01

    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 α the distribution of the l-index has power tail with exponent α(α+1). Properties of the l-index and extensions are discussed.

  11. Nucleic acid indexing

    DOEpatents

    Guilfoyle, Richard A.; Guo, Zhen

    2001-01-01

    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.

  12. Nucleic acid indexing

    DOEpatents

    Guilfoyle, Richard A.; Guo, Zhen

    1999-01-01

    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.

  13. Microbend fiber-optic temperature sensor

    DOEpatents

    Weiss, J.D.

    1995-05-30

    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. 5 figs.

  14. Golgi-Cox Staining Step by Step

    PubMed Central

    Zaqout, Sami; Kaindl, Angela M.

    2016-01-01

    Golgi staining remains a key method to study neuronal morphology in vivo. Since most protocols delineating modifications of the original staining method lack details on critical steps, establishing this method in a laboratory can be time-consuming and frustrating. Here, we describe the Golgi-Cox staining in such detail that should turn the staining into an easily feasible method for all scientists working in the neuroscience field. PMID:27065817

  15. Golgi-Cox Staining Step by Step.

    PubMed

    Zaqout, Sami; Kaindl, Angela M

    2016-01-01

    Golgi staining remains a key method to study neuronal morphology in vivo. Since most protocols delineating modifications of the original staining method lack details on critical steps, establishing this method in a laboratory can be time-consuming and frustrating. Here, we describe the Golgi-Cox staining in such detail that should turn the staining into an easily feasible method for all scientists working in the neuroscience field. PMID:27065817

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

    PubMed

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

    2014-07-14

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

  17. Fiber distributed feedback laser

    NASA Technical Reports Server (NTRS)

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

    1976-01-01

    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.

  18. Silicone polymer waveguide bridge for Si to glass optical fibers

    NASA Astrophysics Data System (ADS)

    Kruse, Kevin L.; Riegel, Nicholas J.; Middlebrook, Christopher T.

    2015-03-01

    Multimode step index polymer waveguides achieve high-speed, (<10 Gb/s) low bit-error-rates for onboard and embedded circuit applications. Using several multimode waveguides in parallel enables overall capacity to reach beyond 100 Gb/s, but the intrinsic bandwidth limitations due to intermodal dispersion limit the data transmission rates within multimode waveguides. Single mode waveguides, where intermodal dispersion is not present, have the potential to further improve data transmission rates. Single mode waveguide size is significantly less than their multimode counterparts allowing for greater density of channels leading to higher bandwidth capacity per layer. Challenges in implementation of embedded single mode waveguides within printed circuit boards involves mass production fabrication techniques to create precision dimensional waveguides, precision alignment tolerances necessary to launch a mode, and effective coupling between adjoining waveguides and devices. An emerging need in which single mode waveguides can be utilized is providing low loss fan out techniques and coupling between on-chip transceiver devices containing Si waveguide structures to traditional single mode optical fiber. A polymer waveguide bridge for Si to glass optical fibers can be implemented using silicone polymers at 1310 nm. Fabricated and measured prototype devices with modeling and simulation analysis are reported for a 12 member 1-D tapered PWG. Recommendations and designs are generated with performance factors such as numerical aperture and alignment tolerances.

  19. Computing discharge using the index velocity method

    USGS Publications Warehouse

    Levesque, Victor A.; Oberg, Kevin A.

    2012-01-01

    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.

  20. Strong fibers

    SciTech Connect

    Li, Che-Yu.

    1991-03-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

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

  2. Bridge SHM system based on fiber optical sensing technology

    NASA Astrophysics Data System (ADS)

    Li, Sheng; Fan, Dian; Fu, Jiang-hua; Huang, Xing; Jiang, De-sheng

    2015-09-01

    The latest progress of our lab in recent 10 years on the area of bridge structural health monitoring (SHM) based on optical fiber sensing technology is introduced. Firstly, in the part of sensing technology, optical fiber force test-ring, optical fiber vibration sensor, optical fiber smart cable, optical fiber prestressing loss monitoring method and optical fiber continuous curve mode inspection system are developed, which not only rich the sensor types, but also provides new monitoring means that are needed for the bridge health monitoring system. Secondly, in the optical fiber sensing network and computer system platform, the monitoring system architecture model is designed to effectively meet the integration scale and effect requirement of engineering application, especially the bridge expert system proposed integration of sensing information and informatization manual inspection to realize the mode of multi index intelligence and practical monitoring, diagnosis and evaluation. Finally, the Jingyue bridge monitoring system as the representative, the research on the technology of engineering applications are given.

  3. What the Index Medicus indexes, and why.

    PubMed

    Truelson, S D

    1966-10-01

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

  4. The Twelve Steps Experientially.

    ERIC Educational Resources Information Center

    Horne, Lianne

    Experiential activities provide each participant with the ability to see, feel, and experience whatever therapeutic issue the facilitator is addressing, and usually much more. This paper presents experiential activities to address the 12 steps of recovery adopted from Alcoholics Anonymous. These 12 steps are used worldwide for many other recovery…

  5. Steps in Test Construction.

    ERIC Educational Resources Information Center

    Tanguma, Jesus

    This paper addresses four steps in test construction specification: (1) the purpose of the test; (2) the content of the test; (3) the format of the test; and (4) the pool of items. If followed, such steps not only will assist the test constructor but will also enhance the students' learning. Within the "Content of the Test" section, two examples…

  6. Slow light in fiber sensors

    NASA Astrophysics Data System (ADS)

    Digonnet, Michel J. F.; Wen, He; Terrel, Matthew A.; Fan, Shanhui

    2012-03-01

    This paper examines the sensitivity improvements that have been achieved by making use of slow light in a variety of fiber sensors. We show in particular that slow light can have dramatically different impacts depending on its nature (material or structural) and on the parameter that is being sensed. In a fiber optic gyroscope measuring an absolute rotation for example, structural slow light does not enhance the maximum sensitivity achievable for a given loss and sensing area compared to a non-resonant structure such as a Sagnac-based fiber optic gyroscope. However, it does reduce the length of fiber required to achieve this sensitivity. For fiber sensors relying on the measurement of absorption, such as gas detectors, structural slow light improves the sensitivity because it increases the effective path length through the absorber and therefore the level of absorption. Material slow light, on the other hand, has been measured to have no impact on the sensitivity. For many other parameters besides rotation and absorption, the sensitivity is expected to be enhanced by either type of slow light, by orders of magnitude with suitable configurations. We illustrate this enormous potential with two configurations of strain sensors utilizing a fiber Bragg grating (FBG) as the sensing and slow-light medium. In properly designed FBGs supporting light with a group index in the range of 50 to 130, we measured a maximum sensitivity of 1.7-3.14 105 strain-1 and a record minimum detectable strain of 820-880 fɛ/√Hz. This value is ~730 lower than the previous record using conventional light in a passive FBG sensor, in accord with predictions. Further enhancements are expected with straightforward improvements in FBG design.

  7. Fiber exposure reassessed with the new indices

    SciTech Connect

    Schneider, T.; Skotte, J. )

    1990-02-01

    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.

  8. Ribbon Fiber Laser-Theory and Experiment

    SciTech Connect

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

    2002-05-10

    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.

  9. STEP Experiment Requirements

    NASA Technical Reports Server (NTRS)

    Brumfield, M. L. (Compiler)

    1984-01-01

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

  10. All-fiber 7 × 1 signal combiner for high power fiber lasers.

    PubMed

    Zhou, Hang; Chen, Zilun; Zhou, Xuanfeng; Hou, Jing; Chen, Jinbao

    2015-04-10

    We present an all-fiber 7×1 signal combiner for high power fiber lasers. Through theoretical analysis, the fabrication method is confirmed and the taper length of the fiber bundle is chosen to be 1 cm to ensure a high transmission efficiency of the combiner. Based on the theoretical results, an all-fiber 7×1 signal combiner with high transmission efficiency is fabricated. A capillary with low refractive index is fused around the bundle of signal fibers to make an additional cladding layer. Then the fiber bundle is tapered to match the core of the output fiber and then spliced with the output fiber. The combiner is tested with a 500 W fiber laser and a temperature increase of 13°C/kW without any active cooling is observed in the combiner. The power transmission efficiency is measured to be close to 99% for each input port and the beam quality M2 is around 10. PMID:25967291

  11. Fiber-Coupled Acousto-Optical-Filter Spectrometer

    NASA Technical Reports Server (NTRS)

    Levin, Kenneth H.; Li, Frank Yanan

    1993-01-01

    Fiber-coupled acousto-optical-filter spectrometer steps rapidly through commanded sequence of wavelengths. Sample cell located remotely from monochromator and associated electronic circuitry, connected to them with optical fibers. Optical-fiber coupling makes possible to monitor samples in remote, hazardous, or confined locations. Advantages include compactness, speed, and no moving parts. Potential applications include control of chemical processes, medical diagnoses, spectral imaging, and sampling of atmospheres.

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

  13. Toxin detection using a fiber-optic-based biosensor

    NASA Astrophysics Data System (ADS)

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

    1993-05-01

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

  14. Axial contraction in etched optical fiber due to internal stress reduction.

    PubMed

    Lim, Kok-Sing; Yang, Hang-Zhou; Chong, Wu-Yi; Cheong, Yew-Ken; Lim, Chin-Hong; Ali, Norfizah M; Ahmad, Harith

    2013-02-11

    When an optical fiber is dipped in an etching solution, the internal stress profile in the fiber varies with the fiber diameter. We observed a physical contraction as much as 0.2% in the fiber axial dimension when the fiber was reduced from its original diameter to ~6 m through analysis using high resolution microscope images of the grating period of an etched FBG at different fiber diameters. This axial contraction is related to the varying axial stress profile in the fiber when the fiber diameter is reduced. On top of that, the refractive index of fiber core increases with reducing fiber diameter due to stress-optic effect. The calculated index increment is as much as 1.8 10(-3) at the center of fiber core after the diameter is reduced down to ~6 m. In comparison with the conventional model that assumes constant grating period and neglects the variation in stress-induced index change in fiber core, our proposed model indicates a discrepancy as much as 3nm in Bragg wavelength at a fiber diameter of ~6 m. PMID:23481713

  15. The index of human insecurity.

    PubMed

    Lonergan, S; Gustavson, K; Carter, B

    2000-01-01

    In the past, human security has been endangered not only by military threats, but also of resource scarcity, rapid population growth, human rights abuses, and outbreaks of infectious diseases, environmental degradation, pollution, and loss of biodiversity. As a result, the Index of Human Insecurity (IHI) was developed as a classification system that distinguishes the perception of vulnerability and insecurity of different countries. In calculating IHI, the following steps must be used: 1) establishment of complete time series for indicators and countries; 2) standardization of data; and 3) classification of data and calculation of indexes. Indicators used in IHI include the environment, economy, society, and institutions. Furthermore, the indicators used actually define the meaning of human security, compare the relative levels of insecurity, and exclude the vulnerability to natural hazards and income distribution. Comparing the efficacy of using the IHI with Human Development Index, it indicated the transparency of IHI in identifying variability in human security; stronger theoretical base of IHI to both human security and development; and the efficacy of IHI in addressing the issue of perception. To end, policy implications and future applications of IHI indicate that despite the need for constant evaluation of the index, it demonstrates a potential for measuring sustainability, development and human security. PMID:12295923

  16. Lawrence Berkeley Lab Indexing Toolbox

    Energy Science and Technology Software Center (ESTSC)

    2003-09-08

    The Lawrence Berkeley Lab Indexing Toolbox is intended to be used in the context of X-ray crystallography experiments involving biological macromolecules. Macromolecules such as proteins form 3-dimensional periodic arrays (crystal) which in turn lead to lattice-like diffraction patterns when the crystal sample is irradiated with collimated X-rays from a synchrotron or other X-ray source. Once the diffraction pattern is captured on an imaging device the next step is to deduce the periodic nature of themore » crystal sample, along with its internal symmetry. this analysis, known as "indexing" is a well-studied problem. However, there are no other implementations designed to operate in an automated setting, in which the human experimentalist is not prosent to manually verify the results of indexing. In particular LABELIT uses three novel algorithms to facilitate automation: a more robust way to verify the position of the incident X-ray beam on the image, a better way to verify that the deduced lattice is consistent with the observed crystal lattice, and new method to deduce the internal symmetry from measurements of the lattice. Moreover, the algorithms are implemented in a Python framework that permits indexing to fail (in rare cases) without crashing the program, thus allowing the software to be incorporated in robotic systems where unattended operation is expected. It will be especially useful for high throughput operations at snychrotron beamlines.« less

  17. Multimedia indexing over the Web

    NASA Astrophysics Data System (ADS)

    Agnew, Brent; Faloutsos, Christos; Wang, Zhenyu; Welch, Donald J.; Xue, Xiaogang

    1997-01-01

    There has been work on database systems that can retrieve multimedia objects by their content. We are extending this work by using the World Wide Web as source and storage for multimedia objects much like current text search engines do for textual information. A system that can access all types of multimedia objects by their content is a formidable task and improvements are constantly being made to indexing techniques. We have taken an important first step in demonstrating the viability of this technique while laying the groundwork for a larger, more capable system. We have implemented a simple indexing scheme while concentrating on building the infrastructure to support this system. Our system can retrieve references to images on the WWW, index those images, and store those images using spatial access methods. We then use query by example to find a set of images on the WWW that resemble our query image. Due to its design, it is easy to include additional context features, to substitute different indexing schemes, and add other types of multimedia to our system like time sequences, voice and video.

  18. Continuous, linearly intermixed fiber tows and composite molded article thereform

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  19. CENDI Indexing Workshop

    NASA Technical Reports Server (NTRS)

    1994-01-01

    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.

  20. Method of identifying features in indexed data

    DOEpatents

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

    2001-06-26

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

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

    PubMed

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

    2010-08-01

    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

  2. Does topology drive fiber polymerization?

    PubMed

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

    2014-12-16

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

  3. Tellurium halide IR fibers for remote spectroscopy

    NASA Astrophysics Data System (ADS)

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

    1994-07-01

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

  4. Pulse Shepherding in Nonlinear Fiber Optics

    NASA Technical Reports Server (NTRS)

    Yeh, C.; Bergman, L.

    1996-01-01

    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.

  5. Prediction of fiber composite mechanical behavior made simple

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.

    1980-01-01

    A convenient procedure is described for the determination of the mechanical behavior (elastic properties and failure stresses of angleplied fiber composite laminates using a pocket calculator. The procedure consists of simple equations and appropriate graphs of (plus or minus theta) ply combinations. The procedure can handle all types of fiber composites including hybrids. The versatility and generality of the procedure is illustrated using several step-by-step numerical examples.

  6. Silica Bottle Resonator Sensor for Refractive Index and Temperature Measurements.

    PubMed

    Nemova, Galina; Kashyap, Raman

    2016-01-01

    We propose and theoretically demonstrate a bottle resonator sensor with a nanoscale altitude and with alength several of hundreds of microns made on the top of the fiber with a radius of tens microns for refractive index and temperature sensor applications. The whispering gallery modes (WGMs) in the resonators can be excited with a taper fiber placed on the top of the resonator. These sensors can be considered as an alternative to fiber Bragg grating (FBG) sensors.The sensitivity of TM-polarized modes is higher than the sensitivity of the TE-polarized modes, but these values are comparable and both polarizations are suitable for sensor applications. The sensitivity ~150 (nm/RIU) can be reached with abottle resonator on the fiber with the radius 10 μm. It can be improved with theuse of a fiber with a smaller radius. The temperature sensitivity is found to be ~10 pm/K. The temperature sensitivity can decrease ~10% for a fiber with a radius r(co) = 10 μm instead of a fiber with a radius r(co) = 100 μm. These sensors have sensitivities comparable to FBG sensors. A bottle resonator sensor with a nanoscale altitude made on the top of the fiber can be easily integrated in any fiber scheme. PMID:26761011

  7. Silica Bottle Resonator Sensor for Refractive Index and Temperature Measurements

    PubMed Central

    Nemova, Galina; Kashyap, Raman

    2016-01-01

    We propose and theoretically demonstrate a bottle resonator sensor with a nanoscale altitude and with alength several of hundreds of microns made on the top of the fiber with a radius of tens microns for refractive index and temperature sensor applications. The whispering gallery modes (WGMs) in the resonators can be excited with a taper fiber placed on the top of the resonator. These sensors can be considered as an alternative to fiber Bragg grating (FBG) sensors.The sensitivity of TM-polarized modes is higher than the sensitivity of the TE-polarized modes, but these values are comparable and both polarizations are suitable for sensor applications. The sensitivity ~150 (nm/RIU) can be reached with abottle resonator on the fiber with the radius 10 μm. It can be improved with theuse of a fiber with a smaller radius. The temperature sensitivity is found to be ~10 pm/K. The temperature sensitivity can decrease ~10% for a fiber with a radius rco = 10 μm instead of a fiber with a radius rco = 100 μm. These sensors have sensitivities comparable to FBG sensors. A bottle resonator sensor with a nanoscale altitude made on the top of the fiber can be easily integrated in any fiber scheme. PMID:26761011

  8. Design Procedures for Fiber Composite Box Beams

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

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

  9. Designing the Structure of Carbon Fibers for Optimal Mechanical Properties

    SciTech Connect

    Ozcan, Soydan; Vautard, Frederic; Naskar, Amit K

    2014-01-01

    Carbon fiber manufacturing follows generic processing steps: formation of thermoplastic fibers, stabilization, and carbonization. The final structures and end properties of the carbon fiber can differ significantly depending on the precursor chemistry and the associated processing sciences. Polyacrylonitrile (PAN) and mesophase pitch are the predominant precursors used in the production of carbon fibers. PAN-based carbon fibers consist of nanocrystalline graphitic domains typically 1.5 5 nm in size surrounded by amorphous carbon; in contrast, pitch-based carbon fibers are 10 50 nm crystallites with the graphitic (002) planes mostly aligned parallel to the fiber axis. It has been seen that the skin core structure of PAN-based carbon fibers plays a significant role in their mechanical properties. Designing a more homogenous carbon fiber microstructure by controlling the starting polymer and process parameters results in a different set of tensile strengths and elastic moduli. In this study the microstructural defect distribution (0.1 200 nm), measured by small-angle X-ray scattering, was shown to be directly related to the tensile strength of the carbon fibers. Here the formation of carbon structures from various polymer precursors is reviewed. Such a comprehensive understanding offers the opportunity to design carbon fiber microstructures with improved properties and to ultimately create new types of carbon fibers from alternative precursors at reduced cost.

  10. Computer-aided fiber analysis for crime scene forensics

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

    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.

  11. Chemical Sensing Using Fiber Cavity Ring-Down Spectroscopy

    PubMed Central

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

    2010-01-01

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

  12. Improvement of the coupling efficiency between LEDs and optical fibers.

    PubMed

    Solomin, A Z; Alexopoulos, N G

    1979-06-15

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

  13. Sensing Features of Long Period Gratings in Hollow Core Fibers

    PubMed Central

    Iadicicco, Agostino; Campopiano, Stefania

    2015-01-01

    We report on the investigation of the sensing features of the Long-Period fiber Gratings (LPGs) fabricated in hollow core photonic crystal fibers (HC-PCFs) by the pressure assisted Electric Arc Discharge (EAD) technique. In particular, the characterization of the LPG in terms of shift in resonant wavelengths and changes in attenuation band depth to the environmental parameters: strain, temperature, curvature, refractive index and pressure is presented. The achieved results show that LPGs in HC-PCFs represent a novel high performance sensing platform for measurements of different physical parameters including strain, temperature and, especially, for measurements of environmental pressure. The pressure sensitivity enhancement is about four times greater if we compare LPGs in HC and standard fibers. Moreover, differently from LPGs in standard fibers, these LPGs realized in innovative fibers, i.e., the HC-PCFs, are not sensitive to surrounding refractive index. PMID:25855037

  14. Photonic crystal fiber half-taper probe based refractometer.

    PubMed

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

    2014-04-01

    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 μm 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

  15. Sensing features of long period gratings in hollow core fibers.

    PubMed

    Iadicicco, Agostino; Campopiano, Stefania

    2015-01-01

    We report on the investigation of the sensing features of the Long-Period fiber Gratings (LPGs) fabricated in hollow core photonic crystal fibers (HC-PCFs) by the pressure assisted Electric Arc Discharge (EAD) technique. In particular, the characterization of the LPG in terms of shift in resonant wavelengths and changes in attenuation band depth to the environmental parameters: strain, temperature, curvature, refractive index and pressure is presented. The achieved results show that LPGs in HC-PCFs represent a novel high performance sensing platform for measurements of different physical parameters including strain, temperature and, especially, for measurements of environmental pressure. The pressure sensitivity enhancement is about four times greater if we compare LPGs in HC and standard fibers. Moreover, differently from LPGs in standard fibers, these LPGs realized in innovative fibers, i.e., the HC-PCFs, are not sensitive to surrounding refractive index. PMID:25855037

  16. Fiber optic connector

    DOEpatents

    Rajic, Slobodan; Muhs, Jeffrey D.

    1996-01-01

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

  17. Fiber optic temperature sensor

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

    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.

  18. Fiber optic temperature sensor

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

    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.

  19. ISMI: a classification index for high angular resolution diffusion imaging

    NASA Astrophysics Data System (ADS)

    Röttger, D.; Dudai, D.; Merhof, D.; Müller, S.

    2012-02-01

    Magnetic resonance diffusion imaging provides a unique insight into the white matter architecture of the brain in vivo. Applications include neurosurgical planning and fundamental neuroscience. Contrary to diffusion tensor imaging (DTI), high angular resolution diffusion imaging (HARDI) is able to characterize complex intra-voxel diffusion distributions and hence provides more accurate information about the true diffusion profile. Anisotropy indices aim to reduce the information of the diffusion probability function to a meaningful scalar representation that classifies the underlying diffusion and thereby the neuronal fiber configuration within a voxel. These indices can be used to answer clinical questions such as the integrity of certain neuronal pathways. Information about the underlying fiber distribution can be beneficial in tractography approaches, reconstructing neuronal pathways using local diffusion orientations. Therefore, an accurate classification of diffusion profiles is of great interest. However, the differentiation between multiple fiber orientations and isotropic diffusion is still a challenging task. In this work, we introduce ISMI, an index which successfully differentiates isotropic diffusion and single and multiple fiber populations. The classifier is based on the orientation distribution function (ODF) resulting from Q-ball imaging. We compare our results with the well-known general fractional anisotropy (GFA) index using a fiber phantom comprising challenging diffusion profiles such as crossing, fanning and kissing fiber configurations and a human brain dataset considering the centrum semiovale. Additionally, we visualize the results directly on the fibers represented by streamtubes using a heat color map.

  20. Graphical Drop Caps Indexing

    NASA Astrophysics Data System (ADS)

    Chouaib, Hassan; Cloppet, Florence; Vincent, Nicole

    This paper presents a method for graphical drop caps indexing. Drop caps are extracted from old books. Finding a method classifying them according to styles defined by the historian is of considerable interest. The developed method is a statistical approach, where all possible patterns included in a pixel mask are processed in order to extract indexes that characterize the image. Then these indexes are used to classify a query drop cap by searching its most similar drop caps in the indexed base.

  1. Coatings for graphite fibers

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

    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.

  2. Microbend fiber-optic temperature sensor

    DOEpatents

    Weiss, Jonathan D.

    1995-01-01

    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.

  3. Dietary fiber and the glycemic response.

    PubMed

    Jenkins, D J; Jenkins, A L

    1985-12-01

    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

  4. Gene-rich islands for fiber development in the cotton genome

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  5. The Europe 2020 Index

    ERIC Educational Resources Information Center

    Pasimeni, Paolo

    2013-01-01

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

  6. Machine-Aided Indexing.

    ERIC Educational Resources Information Center

    Jacobs, Charles R.

    Progress is reported at the 1,000,000 word level on the development of a partial syntatic analysis technique for indexing text. A new indexing subroutine for hyphens is provided. New grammars written and programmed for Machine Aided Indexing (MAI) are discussed. (ED 069 290 is a related document) (Author)

  7. Numerical simulation of fiber interaction in short-fiber injection-molded composite using different cavity geometries

    NASA Astrophysics Data System (ADS)

    Thi, Thanh Binh Nguyen; Yokoyama, Atsushi; Hamanaka, Senji; Yamashita, Katsuhisa; Nonomura, Chisato

    2016-03-01

    The theoretical fiber-interaction model for calculating the fiber orientation in the injection molded short fiber/thermoplastic composite parts was proposed. The proposed model included the fiber dynamics simulation in order to obtain an equation of the global interaction coefficient and accurate estimate of the fiber interacts at all orientation states. The steps to derive the equation for this coefficient in short fiber suspension as a function of the fiber aspect ratio, volume fraction and general shear rate are delineated. Simultaneously, the high-resolution 3D X-ray computed tomography system XVA-160α was used to observe fiber distribution of short-glass-fiber-reinforced polyamide specimens using different cavity geometries. The fiber orientation tensor components are then calculated. Experimental orientation measurements of short-glass-fiber-reinforced polyamide is used to check the ability of present theory for predicting orientation. The experiments and predictions show a quantitative agreement and confirm the basic understanding of fiber orientation in injection-molded composites.

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

    PubMed

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

    2006-09-01

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

  9. Detailed numerical investigation of the interaction of longitudinal acoustic waves with fiber Bragg gratings in suspended-core fibers

    NASA Astrophysics Data System (ADS)

    Silva, Ricardo E.; Hartung, Alexander; Rothhardt, Manfred; Pohl, Alexandre A. P.; Bartelt, Hartmut

    2015-06-01

    The interaction between longitudinal acoustic waves and fiber Bragg gratings in suspended-core optical fibers is numerically investigated. The fiber core size and the air hole size are varied, and the mechanical and grating properties are simulated by means of the finite element method and the transfer matrix method, respectively. Changes of the effective index, confinement factor, silica area, strain and wavelength shift induced by the acoustic wave are evaluated, and the resultant side lobe reflectivity is estimated. A side lobe reflectivity increase of 66% compared to standard fibers is estimated, which allows reducing the modulation index or the grating length in as much as 75%. Besides, the larger reduction of the required acoustic power for achieving the acousto-optic modulation points out to more efficient modulator devices in suspended-core fibers.

  10. Fiber optic monitoring device

    DOEpatents

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

    1993-01-01

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

  11. Alumina fiber strength improvement

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

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

    PubMed Central

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

    2011-01-01

    We demonstrate generation of Cerenkov radiation at 850 nm in a higher-order-mode (HOM) fiber. The LP02 mode in this solid, silica-based fiber has anomalous dispersion from 690 nm to 810 nm. Cerenkov radiation with 3 nJ pulse energy is generated in this module, exhibiting 60% energy conversion efficiency from the input. The HOM fiber provides a valuable fiber platform for nonlinear wavelength conversion with pulse energies in-between index-guided silica-core photonic crystal fibers and air-core photonic bandgap fibers. PMID:21643129

  13. A birefringence study of changes in myosin orientation during relaxation of skinned muscle fibers induced by photolytic ATP release.

    PubMed Central

    Peckham, M; Ferenczi, M A; Irving, M

    1994-01-01

    The birefringence of isolated skinned fibers from rabbit psoas muscle was measured continuously during relaxation from rigor produced by photolysis of caged ATP at sarcomere length 2.8-2.9 microns, ionic strength 0.1 M, 15 degrees C. Birefringence, the difference in refractive index between light components polarized parallel and perpendicular to the fiber axis, depends on the average degree of alignment of the myosin head domain with the fiber axis. After ATP release birefringence increased by 5.8 +/- 0.7% (mean +/- SE, n = 6) with two temporal components. A small fast component had an amplitude of 0.9 +/- 0.2% and rate constant of 63 s-1. By the completion of this component, the instantaneous stiffness had decreased to about half the rigor value, and the force response to a step stretch showed a rapid (approximately 1000 s-1) recovery phase. Subsequently a large slow birefringence component with rate constant 5.1 s-1 accompanied isometric force relaxation. Inorganic phosphate (10 mM) did not affect the fast birefringence component but accelerated the slow component and force relaxation. The fast birefringence component was probably caused by formation of myosin.ATP or myosin.ADP.Pi states that are weakly bound to actin. The average myosin head orientation at the end of this component is slightly more parallel to the fiber axis than in rigor. PMID:7811926

  14. Apparatus for Teaching Physics: Optical Fiber Communications.

    ERIC Educational Resources Information Center

    Throckmorton, Carl; Dey, Joe

    1988-01-01

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

  15. Method of forming composite fiber blends

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

    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.

  16. Development of optical fiber biosensors with long period gratings

    NASA Astrophysics Data System (ADS)

    Zhang, Zheng

    2000-07-01

    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.

  17. Toughness of fiber reinforced shotcrete

    SciTech Connect

    Morgan, D.R.; Chen, L.; Beaupre, D.

    1995-12-31

    Fibers are added to shotcrete to improve energy absorption and impact resistance, to provide crack resistance and crack control, and to provide apparent ductility, i.e., an ability to continue to carry load after the shotcrete matrix has cracked. In order to be able to quantify the benefits of fiber addition, a variety of different toughness measuring systems have been developed in different countries. Most commonly used are flexural toughness systems which determine load vs. deflection responses and relate the area under the curve to some absolute or dimensionless index energy parameter. In North America the ASTM C1018 test method is most commonly used. In Japan the JSCE-SF4 test procedure is used. A variety of procedures have been used in Europe, but the template approach of the Norwegian Guidelines NBP No. 7, seems to be finding favor. This paper briefly assesses the relative advantages and disadvantages of the various methods of characterizing toughness. It then provides recommendations for a new procedure which uses the ASTM C1018 test method for generating the flexural load vs. deflection curve, but analyzes the data using a modified version of the Norwegian template approach. The load vs. deflection curve is directly compared against four residual strength curves and the fiber reinforced shotcrete assigned one of four toughness performance levels. It is believed that this new procedure should provide suitable within and between laboratory reproducibility and be more suitable for purposes of differentiating between different fiber types and addition rates and specifying toughness for fiber reinforced shotcrete products than any of the existing methods.

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

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.

    1980-01-01

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

  19. Structural diagnostics using optical fiber sensors

    NASA Astrophysics Data System (ADS)

    Surace, Giuseppe; Chiaradia, Agostino

    1997-11-01

    After establishing the basis for assessing the structural implications of introducing a widespread sensor architecture in laminated composite materials in order to precisely identify and locate damage, the paper addresses the problem of structural diagnostics with a discussion of the development of several optical sensors. The research project will first investigate a passive optical fiber impact sensor to be implemented in the matrix of a composite material used in aeronautic and automotive applications. The senor's operating principle is based on the changes in propagation conditions occurring in a fiber subjected to transverse compression: under these circumstances, structural microdistortions produce local energy losses and hence a reduction in the optical power which propagates in the fiber and can be measured at its opposite end. As optical power losses also take place as a result of micro-bending of the optical fiber's longitudinal axis, a preliminary feasibility study will measure power attenuation versus fiber curve radius as the first step in the development of an optical fiber delamination sensor which locates separations between the layers of a composite material, i.e. debonding of sandwich panel core faces. Finally, an active impact sensor will be developed which uses optical fiber's sensitivity to pressure changes to detect the pressure gradient caused by an approaching vehicle or obstacle. The automotive industry will be able to make strategic use of these sensors, for example by installing them on vehicle sides to active the side airbag in the event of impact or collision.

  20. High-Power Laser Beam Transfer through Optical Relay Fibers for a Laser Guide Adaptive Optics System

    NASA Astrophysics Data System (ADS)

    Ito, Meguru; Hayano, Yutaka; Saito, Yoshihiko; Takami, Hideki; Saito, Norihito; Akagawa, Kazuyuki; Takazawa, Akira; Ito, Mayumi; Wada, Satoshi; Iye, Masanori

    2009-08-01

    We are developing a laser guide star adaptive optics (LGSAO) system for the Subaru Telescope on Mauna Kea, Hawaii. The AO188 system will dramatically increase the observable sky area. This system differs from systems used at other large telescopes in that it utilizes the combination of an all-solid-state mode-locked sum-frequency generation (SFG) laser as a light source and single-mode optical fiber for beam transference. Optical fibers transfer laser light from the source, located at the Nasmyth platform, to the laser launching telescope more flexibly and more easily than do mirror relay optics. However, optical fibers induce nonlinear scattering effects, such as stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS), beyond certain threshold levels in high-power lasers. We measured the laser transmission characteristics of a photonic crystal fiber (PCF) whose mode field diameter (MFD) was 11μm, and a step index fiber (SIF) cable whose MFD was 4.2μm to evaluate the threshold levels for non-linear effects. We observed SRS in the 200-m-long SIF when we input 1.3W. However, SRS and SBS were not induced in the 200-m-long PCF, even for an input power of 5.3W. As a result, we estimated the threshold of SRS to be 33W for the 35-m-long PCF designed for the Subaru LGSAO system. Given that the fiber will carry a laser beam of about 30W with a pulse width of less than 1ns, we conclude that nonlinear scattering will pose no problems for this application.