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Sample records for step index fiber

  1. Optofluidic refractive-index sensor in step-index fiber with parallel hollow micro-channel.

    PubMed

    Lee, H W; Schmidt, M A; Uebel, P; Tyagi, H; Joly, N Y; Scharrer, M; Russell, P St J

    2011-04-25

    We present a simple refractive index sensor based on a step-index fiber with a hollow micro-channel running parallel to its core. This channel becomes waveguiding when filled with a liquid of index greater than silica, causing sharp dips to appear in the transmission spectrum at wavelengths where the glass-core mode phase-matches to a mode of the liquid-core. The sensitivity of the dip-wavelengths to changes in liquid refractive index is quantified and the results used to study the dynamic flow characteristics of fluids in narrow channels. Potential applications of this fiber microstructure include measuring the optical properties of liquids, refractive index sensing, biophotonics and studies of fluid dynamics on the nanoscale. PMID:21643070

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

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

  4. 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

  5. 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

  6. 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

  7. 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.

  8. Analysis of an upside-down taper lens end from a single-mode step-index fiber.

    PubMed

    Mondal, S K; Gangopadhyay, S; Sarkar, S

    1998-02-20

    We introduce and analyze the upside-down taper lens end drawn from step-index fibers. Also, we model the refractive-index distribution and present the ABCD transformation matrix of this fiber end under paraxial approximation. The analysis can be useful for designing micro-optic image systems and laser diodes to single-mode fiber coupling optics. PMID:18268676

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

    PubMed

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

    2014-07-28

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

  10. Demonstration of ultra-low NA rare-earth doped step index fiber for applications in high power fiber lasers.

    PubMed

    Jain, Deepak; Jung, Yongmin; Barua, Pranabesh; Alam, Shaiful; Sahu, Jayanta K

    2015-03-23

    In this paper, we report the mode area scaling of a rare-earth doped step index fiber by using low numerical aperture. Numerical simulations show the possibility of achieving an effective area of ~700 um² (including bend induced effective area reduction) at a bend diameter of 32 cm from a 35 μm core fiber with a numerical aperture of 0.038. An effective single mode operation is ensured following the criterion of the fundamental mode loss to be lower than 0.1 dB/m while ensuring the higher order modes loss to be higher than 10 dB/m at a wavelength of 1060 nm. Our optimized modified chemical vapor deposition process in conjunction with solution doping process allows fabrication of an Yb-doped step index fiber having an ultra-low numerical aperture of ~0.038. Experimental results confirm a Gaussian output beam from a 35 μm core fiber validating our simulation results. Fiber shows an excellent laser efficiency of ~81%and aM² less than 1.1. PMID:25837082

  11. 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.

  12. Octave-spanning supercontinuum generation in hybrid silver metaphosphate/silica step-index fibers.

    PubMed

    Chemnitz, Mario; Wei, Jingxuan; Jain, Chhavi; Rodrigues, Bruno P; Wieduwilt, Torsten; Kobelke, Jens; Wondraczek, Lothar; Schmidt, Markus A

    2016-08-01

    We reveal the potential of step-index fibers consisting of a metaphosphate glass core and a silica cladding as an ultrafast octave-spanning supercontinuum source. The hybrid waveguide was fabricated by pressure-assisted melt filling and possesses a sophisticated dispersion behavior with two zero-dispersion points in the proximity of the Erbium laser bands. The fiber generates an octave-spanning supercontinuum from 0.7 to 2.4 μm if pumped at 1.56 μm with 30 fs pulses and energies as low as 300 pJ. Numerical simulations reveal soliton fission and double dispersive wave generation as the dominant broadening effect. This study highlights phosphate glasses as a promising new candidate for the next generation of broadband photonic devices, as they allow for high rare earth-doping levels and dispersion posttuning via plasmonic nanoparticle growth. PMID:27472608

  13. 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

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

    DOEpatents

    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.

  15. 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.

  16. Mid-infrared supercontinuum generation up to 4.6 µm using step-index indium fluoride fiber pumped by a femtosecond fiber laser near 2 µm

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    We report mid-infrared supercontinuum (SC) generation in a dispersion-engineered step-index indium fluoride fiber pumped by a femtosecond fiber laser near 2 μm. The SC spans 1.8 octaves from 1.25 μm to 4.6 μm with an average output power of 270 mW. The pump source is an all-fiber femtosecond laser that generates sub-100 fs pulses at 50 MHz repetition rate with 570 mW average power. The indium fluoride fiber used for SC generation is designed to have a zerodispersion wavelength close to 1.9 μm. Two fiber lengths of 30 cm and 55 cm are selected for the SC generation experiments based on the numerical modelling results. The measured spectra and the numerical modelling results are presented showing good agreement for both lengths. The femtosecond pumping regime is a key requirement for generating a coherent SC. We show by modelling that the SC is coherent for a pump with the same pulse width and energy as our fiber laser and added quantum-limited noise. The results are promising for the realization of coherent and high-repetition-rate SC sources, two conditions that are critical for spectroscopy applications using FTIR spectrometers. Additionally, the entire SC system is built using optical fibers with similar core diameters, which enables integration into a compact platform.

  17. 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.

  18. Bragg gratings inscription in step-index PMMA optical fiber by femtosecond laser pulses at 400 nm

    NASA Astrophysics Data System (ADS)

    Hu, X.; Kinet, D.; Chah, K.; Mégret, P.; Caucheteur, C.

    2016-05-01

    In this paper, we report photo-inscription of uniform Bragg gratings in trans-4-stilbenemethanol-doped photosensitive step-index polymer optical fiber. Gratings were produced at ~1575 nm by the phase mask technique with a femtosecond laser emitting at 400 nm with different average optical powers (8 mW, 13 mW and 20 mW). The grating growth dynamics in transmission were monitored during the manufacturing process, showing that the grating grows faster with higher power. Using 20 mW laser beam power, the reflectivity reaches 94 % (8 dB transmission loss) in 70 seconds. Finally, the gratings were characterized in temperature in the range 20 - 45 °C. The thermal sensitivity has been computed equal to - 86.6 pm/°C.

  19. 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.

  20. 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

  1. 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.

  2. Fiber optic refractive index monitor

    DOEpatents

    Weiss, Jonathan David

    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.

  3. 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.

  4. 0.6-3.2 μm supercontinuum generation in a step-index germania-core fiber using a 4.4 kW peak-power pump laser.

    PubMed

    Yang, Linyong; Zhang, Bin; Yin, Ke; Yao, Jinmei; Liu, Guangchen; Hou, Jing

    2016-06-13

    An ultra-broadband supercontinuum was generated in a short piece of step-index germania-core fiber using a fiber laser with a peak power of 4.4 kW. The pure germania core made this fiber capable of propagating light towards the desirable mid-infrared region. The spectral broadening characteristics towards the mid-infrared region under different lengths of germania-core fiber were investigated using pump pulses of 4.4 kW and 1.1 ns at 1550 nm. The large nonlinear refractive index of germania and the small core size of germania-core fiber produced a nonlinear coefficient as high as 11.8 (W km)-1 at 1550 nm, which was beneficial for supercontinuum generation. The pump wavelength was located in the anomalous dispersion regime and close to the zero dispersion wavelength of this germania-core fiber, 1.426 μm. Eventually, an ultra-broadband supercontinuum source with a spectrum spanning from 0.6 to 3.2 μm was obtained and had a total output power of 350 mW at an optimized germania-core fiber length of 0.8 m. This work is the first demonstration, to the best of our knowledge, of a germania-core fiber-based ultra-broadband supercontinuum source that spans from the visible region to the mid-infrared region. PMID:27410281

  5. 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.

  6. Mid-infrared supercontinuum generation in step-index As2S3 fibers pumped by a nanosecond shortwave-infrared supercontinuum pump source.

    PubMed

    Yao, Jinmei; Zhang, Bin; Yin, Ke; Yang, Linyong; Hou, Jing; Lu, Qisheng

    2016-06-27

    A supercontinuum (SC) source spanning from 2 to 4 μm is demonstrated in As2S3-chalcogenide fibers pumped by a nanosecond supercontinuum pump source in the normal dispersion region. In this experiment, two pieces of 3-m-long step-index As2S3 fiber with different core diameters of 7 μm and 9 μm are pumped by a 1.9-2.5 μm nanosecond supercontinuum source. The zero dispersion wavelengths are both beyond 6.6 μm, thus cascaded stimulated Raman scattering is believed to be the dominant mechanism responsible for spectral broadening. With a low peak pump power of ~2.9 kW, both of the output spectra have extended to 4 μm with enhanced power distribution in the MIR region. The maximum output power of the mid-infrared supercontinua is ~140 mW. To the best of our knowledge, it is the first supercontinuum extenting to 4 μm in an As2S3 fiber pumped by shortwave-infrared SC pluses in the normal dispersion region. PMID:27410660

  7. Uncladded sensing fiber for refractive index measurement

    NASA Astrophysics Data System (ADS)

    Bhardwaj, V.; Gangwar, R. K.; Pathak, A. K.; Singh, V. K.

    2016-05-01

    The formation of chemically etched optical fiber for use in refractive index sensor is addressed. This presented design of a refractive index (RI) sensor is based on recording the power loss exhibited by radiation propagating through an etched multimode fiber (MMF) immersed in the liquid under study. The decreasing diameters of fibers are found to be strongly dependent on the temperature and etchant composition. This experiment was performed for different unclad etched fibers for same sensing length and the RI changes from 1.33 RIU to 1.38 RIU. When the multimode fiber (MMF) is etched for 12 hours the sensitivity of the sensor is approximately 204.25dBm/RIU, which is larger than without etched fiber having sensitivity 127.2dBm/RIU.

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. Fiber Optic-Based Refractive Index Sensing at INESC Porto

    PubMed Central

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

    2012-01-01

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

  13. 3D refractive index measurements of special optical fibers

    NASA Astrophysics Data System (ADS)

    Yan, Cheng; Huang, Su-Juan; Miao, Zhuang; Chang, Zheng; Zeng, Jun-Zhang; Wang, Ting-Yun

    2016-09-01

    A digital holographic microscopic chromatography-based approach with considerably improved accuracy, simplified configuration and performance stability is proposed to measure three dimensional refractive index of special optical fibers. Based on the approach, a measurement system is established incorporating a modified Mach-Zehnder interferometer and lab-developed supporting software for data processing. In the system, a phase projection distribution of an optical fiber is utilized to obtain an optimal digital hologram recorded by a CCD, and then an angular spectrum theory-based algorithm is adopted to extract the phase distribution information of an object wave. The rotation of the optic fiber enables the experimental measurements of multi-angle phase information. Based on the filtered back projection algorithm, a 3D refraction index of the optical fiber is thus obtained at high accuracy. To evaluate the proposed approach, both PANDA fibers and special elliptical optical fiber are considered in the system. The results measured in PANDA fibers agree well with those measured using S14 Refractive Index Profiler, which is, however, not suitable for measuring the property of a special elliptical fiber.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Two-dimensional refractive index profiling of optical fibers by modified refractive near-field technique

    NASA Astrophysics Data System (ADS)

    El Sayed, A.; Pilz, Soenke; Ryser, Manuel; Romano, Valerio

    2016-02-01

    The refractive index distribution in the core-cladding region of an optical fiber plays an important role in determining the transmission and dispersion properties of the waveguide. The refracted near-field technique (RNF) is among the most widespread techniques used for measuring the refractive index profile of optical fibers and is based on illuminating the end-facet of a fiber with a focused beam whose vertex angle greatly exceeds the acceptance angle of the fiber, which is immersed in an index matching liquid. What one observes are then the refracted unguided rays rather than the guided rays. Nevertheless, the standard refracted near-field technique cannot be applied to a wide range of optical fibers e.g. if their shapes are not axially symmetric. In this work we demonstrate a modified method which allows 2-D imaging of the refractive index profile and thereby overcoming the axial symmetric limitation of the standard RNF. The new system is operating at 630 nm and based on the same principle of the RNF, but the optical path is reversed so that the light at the fiber end-facet is collected by an objective lens and detected by a CCD camera. The method does not require scanning over the fiber end-facet. Thus the system is faster and less sensitive to vibrations and external conditions compared to the standard RNF, furthermore it allows averaging to improve the signal to noise ratio. The spatial resolution of the system is determined by the numerical aperture of the objective and by the resolution of the CCD camera. To calibrate the setup, a reference multi-step index fiber provided by National Physical Laboratory was used.

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. One-step electrospinning of cross-linked chitosan fibers.

    PubMed

    Schiffman, Jessica D; Schauer, Caroline L

    2007-09-01

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

  6. 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.

  7. 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.

  8. 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.

  9. High index contrast hole-free photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Lipovskii, Andrey; Anan'ev, Anatoly; Maksimov, Leonid; Polukhin, Vladimir; Tagantsev, Dmitry; Tatarintsev, Boris

    2007-05-01

    A couple of multicomponent glasses was used to produce solid hole-free photonic crystal fiber (PCF) with high contrast of index. These glasses were a high index barium-lanthanum flint-glass (n~1.8) and a low index cron-glass (n~1.5). The compositions of selected glasses provided the coincidence of their viscosities in the temperature range of drawing, close thermal expansion coefficients, and chemical compatibility. To produce the PCF densely packed bundles of glass rods (elements) of 1 mm diameter assembled in a given structures were multiply co-drawn down to 0.2-2.0 microns diameter of a single element. This procedure allowed scaling of initial structures and resulted in two PCF structures: axially symmetrical eight-period structure and five-period "birefringent" structure. Optical transmission of the resultant PCF demonstrates the existence of photonic band-gaps, and intensity distribution of propagating mode corresponds to the results of numerical simulation performed.

  10. 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

  11. 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.

  12. Detection of analyte refractive index and concentration using liquid-core photonic Bragg fibers

    NASA Astrophysics Data System (ADS)

    Li, Jingwen; Qu, Hang; Skorobogatiy, Maksim

    2016-03-01

    We demonstrate detection of liquid analyte refractive index by using a hollow-core photonic Bragg fiber. We apply this fiber sensor to monitor concentrations of commercial cooling oil. The sensor operates on a spectral modality. Variation in the analyte refractive index modifies the bandgap guidance of a fiber, leading to spectral shifts in the fiber transmission spectrum. The sensitivity of the sensor to changes in the analyte refractive index filling in the fiber core is found to be 1460nm/Refractive index unit (RIU). By using the spectral modality and effective medium theory, we determine the concentrations of commercial fluid from the measured refractive indices with an accuracy of ~0.42%. The presented fiber sensor can be used for on-line monitoring of concentration of many industrial fluids and dilutions with sub-1%v accuracy.

  13. [The refractive index sensing characteristics of polarization maintaining microstructured optical fiber chirped grating].

    PubMed

    Guo, Xuan; Bi, Wei-Hong; Liu, Feng

    2013-01-01

    The refractive index sensing characteristics of the polarization maintaining (PM) microstructured optical fiber (MOF) chirped grating was systematically investigated based on finite element method (FEM) and transfer matrix method (TMM). The chirp Bragg grating reflection spectrum was numerically analyzed with the fiber air holes injected with different refractive index medium, and the relation between the reflection spectrum area and the analyte refractive index is discussed here. The analysis results show that when the analyte refractive index increases, the reflection spectrum area will be reduced; and the detection demodulation is simplified with the light intensity demodulation. Moreover, the dependence of the reflection spectrum on the center big holes size, the chirp coefficient and the site function was studied. Since two polarization modes respond similarly to the outside perturbation, the fiber possesses high stability. The results provide the theoretical basis for the application of PM-MOF grating in the optical fiber refractive index sensor and the optical fiber label-free biosensing. PMID:23586270

  14. Augmenting data rate performance for higher order modulation in triangular index profile multicore fiber interconnect

    NASA Astrophysics Data System (ADS)

    Mishra, Jitendra K.; Priye, Vishnu; Rahman, B. M. A.

    2016-07-01

    A triangular profile multicore fiber (MCF) optical interconnect (OI) is investigated to augment performance that typically degrades at high data rates for higher order modulation in a short reach transmission system. Firstly, probability density functions (PDFs) variation with inter-core crosstalk is calculated for 8-core MCF OI with different index profile in the core and it was observed that the triangular profile MCF OI is the most crosstalk tolerant. Next, symbol error probability (SEP) for higher order quadrature phase shift keying (QPSK) modulated signal due to inter-core crosstalk is analytically obtained and their dependence on typical characteristic parameters are examined. Further, numerical simulations are carried out to compare the error performance of QPSK for step index and triangular index MCF OI by generating eye diagram at 40 Gbps per channel. Finally, it is shown that MCF OI with triangular index profile supporting QPSK has double spectral efficiency with tolerable trade off in SEP as compared with those of binary phase shift keying (BPSK) at high data rates which is scalable up to 5 Tbps.

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

    NASA Astrophysics Data System (ADS)

    Hutsel, Michael R.

    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

  16. 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...

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

    NASA Astrophysics Data System (ADS)

    Hutsel, Michael R.

    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

  18. Simultaneous measurement of strain, temperature and refractive index based on multimode interference, fiber tapering and fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Oliveira, Ricardo; Osório, Jonas H.; Aristilde, Stenio; Bilro, Lúcia; Nogueira, Rogerio N.; Cordeiro, Cristiano M. B.

    2016-07-01

    We report the development of an optical fiber sensor capable of simultaneously measuring strain, temperature and refractive index. The sensor is based on the combination of two fiber Bragg gratings written in a standard single-mode fiber, one in an untapered region and another in a tapered region, spliced to a no-core fiber. The possibility of simultaneously measuring three parameters relies on the different sensitivity responses of each part of the sensor. The results have shown the possibility of measuring three parameters simultaneously with a resolution of 3.77 με, 1.36 °C and 5  ×  10‑4, respectively for strain, temperature and refractive index. On top of the multiparameter ability, the simple production and combination of all the parts involved on this optical-fiber-based sensor is an attractive feature for several sensing applications.

  19. Arc-discharge effects on residual stress and refractive index in single-mode optical fibers.

    PubMed

    Wang, Pengfei; Jenkins, Micah H; Gaylord, Thomas K

    2016-03-20

    Arc-discharge effects on the residual stress and refractive index in single-mode optical fibers are investigated using a previously developed three-dimensional concurrent stress-index measurement method. Using commercial optical fibers and a commercial fusion splicer, the residual stress and refractive index perturbations caused by weak electrical arc discharges in single-mode fibers were measured. Refractive index changes greater than 10-4 and longitudinal perturbation lengths of less than 500 μm were shown to be possible. The subsequent prospects for arc-induced long-period fiber gratings are analyzed, and a typical transmission resonance is predicted to have a depth of 56 dB and a bandwidth of 0.08 nm at a wavelength of 1585 nm. The results of this investigation will be useful in modeling device performance and optimization of arc-induced long-period fiber grating fabrication. PMID:27140587

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

    PubMed

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

    2015-02-15

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

  1. 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

  2. Monolithically integrated asymmetric graded and step-index couplers for microphotonic waveguides

    NASA Astrophysics Data System (ADS)

    Delâge, A.; Janz, S.; Lamontagne, B.; Bogdanov, A.; Dalacu, D.; Xu, D.-X.; Yap, K. P.

    2006-01-01

    A monolithically integrated asymmetric graded index (GRIN) or step-index (GRIN) mode converters for microphotonic waveguides are proposed and described. The design parameters and tolerances are calculated for amorphous silicon (a-Si) couplers integrated with silicon-on-insulator waveguides. The GRIN and step-index couplers operate over a wide wavelength range with low polarization dependence, and the lithographic resolution needed is only +/-1 μm. Finally, experimental results are presented for a single layer 3 μm thick step-index a-Si coupler integrated on a 0.8 μm thick SOI waveguide. The measured variation of coupling efficiency with coupler length is in agreement with theory, with an optimal coupling length of 15 μm for this device.

  3. 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.

  4. 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).

  5. 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

  6. Step Counts and Body Mass Index Among 9-14 Years Old Greek Schoolchildren

    PubMed Central

    Michalopoulou, Maria; Gourgoulis, Vassilios; Kourtessis, Thomas; Kambas, Antonios; Dimitrou, Martina; Gretziou, Helen

    2011-01-01

    The main purpose of this study was the identification of the current pedometer determined physical activity levels of a large sample of 9 -14 years old Greek schoolchildren and the determination of the association between daily step counts and body mass index through the comparison of step counts among overweight, obese and normal-weight children. A total of 532 children (263 boys and 269 girls) were measured for height and weight. Their activity levels were analyzed using pedometers to measure mean steps for 7 consecutive days. Overweight and obese status was determined using the international reference standard (Cole et al., 2000). According to data analysis mean step counts ranged from 15371 to10539 for boys and from 11536 to 7893 for girls. Steps per day were significantly more for boys compared to girls. Children with normal weight performed significantly more steps per day compared to their overweight and obese classmates. Daily step counts reported in this study for 9 -14 year old schoolchildren were relatively low when compared to step counts from other European countries. Only 33.9% of the participants satisfied the body mass index referenced standards for recommended steps per day. Finally, the results of this study provide baseline information on youth pedometer determined physical activity and on youth body mass index levels. High prevalence of low daily step counts and BMI determined obesity was revealed prompting for further exploration of the relationship between objectively measured physical activity and adiposity in particular for children and adolescents that experience both health risk factors. Key points The mean steps/day taken by both boys and girls in Greece 9-14 years old were 13.446 and 10.656 respectively. Daily step counts tended to be leveled for ages 9-12 years and a significant drop in steps/day was apparent for children aged 13 -14 years. According to the IOTF criteria, 23% of the boys that participated in this study were overweight

  7. Tailored dispersion profile in controlling optical solitons in a tapered parabolic index fiber

    NASA Astrophysics Data System (ADS)

    Prakash, S. Arun; Malathi, V.; Mani Rajan, M. S.

    2016-03-01

    We investigate the soliton dynamics in tapered parabolic index fibers via symbolic computation for a variety of dispersion profiles to inspect how a specific dispersion profile controls the optical soliton. By means of AKNS procedure, Lax pair is constructed for nonlinear Schrödinger equation with variable coefficients. Using obtained Lax pair, multi-soliton solutions are generated via Darboux transformation technique. Using multi-soliton solutions, soliton dynamics in tapered parabolic index fiber with the hyperbolic, Gaussian, exponential, and linear profiles are discussed. Results obtained in this study will be of certain potential application on construction of the nonlinear optical devices by soliton control. Results obtained in this study will be of certain value to the studies on the propagation and application of the soliton in the tapered parabolic index fiber and dispersion-managed fiber system.

  8. Tapered-fiber-based refractive index sensor at an air/solution interface.

    PubMed

    Lu, Ping; Harris, Jeremie; Wang, Xiaozhen; Lin, Ganbin; Chen, Liang; Bao, Xiaoyi

    2012-10-20

    An approach to achieve refractive index sensing at an air and aqueous glycerol solution interface is proposed using a tapered-fiber-based microfiber Mach-Zehnder interferometer (MFMZI). Compared to a surrounding uniform medium of air or solutions, the spectral interference visibility of the MFMZI at the air/solution interface is significantly reduced due to a weak coupling between the fundamental cladding mode and high-order asymmetric cladding modes, which are extremely sensitive to the external refractive index. The MFMZI is experimentally demonstrated as an evanescent wave refractive index sensor to measure concentrations of glycerol solutions by monitoring average power attenuation of the tapered fiber. PMID:23089794

  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. 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

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

    NASA Astrophysics Data System (ADS)

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

    2008-03-01

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

  12. Optimized split-step method for modeling nonlinear pulse propagation in fiber Bragg gratings

    SciTech Connect

    Toroker, Zeev; Horowitz, Moshe

    2008-03-15

    We present an optimized split-step method for solving nonlinear coupled-mode equations that model wave propagation in nonlinear fiber Bragg gratings. By separately controlling the spatial and the temporal step size of the solution, we could significantly decrease the run time duration without significantly affecting the result accuracy. The accuracy of the method and the dependence of the error on the algorithm parameters are studied in several examples. Physical considerations are given to determine the required resolution.

  13. 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

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

    NASA Astrophysics Data System (ADS)

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

    2007-02-01

    We have numerically compared the performance of various designs for the core refractive-index (RI) and rare-earth-dopant distributions of large-mode-area fibers for use in bend-loss-filtered, high-power amplifiers. We first established quantitative targets for the key parameters that determine fiber-amplifier performance, including effective LP 01 modal area (A eff, both straight and coiled), bend sensitivity (for handling and packaging), high-order mode discrimination, mode-field displacement upon coiling, and index contrast (manufacturability). We compared design families based on various power-law and hybrid profiles for the RI and evaluated confined rare-earth doping for hybrid profiles. Step-index fibers with straight-fiber A eff values > 1000 μm2 exhibit large decreases in A eff and transverse mode-field displacements upon coiling, in agreement with recent calculations of Hadley et al. [Proc. of SPIE, Vol. 6102, 61021S (2006)] and Fini [Opt. Exp. 14, 69 (2006)]. Triangular-profile fibers substantially mitigate these effects, but suffer from excessive bend sensitivity at A eff values of interest. Square-law (parabolic) profile fibers are free of modal distortion but are hampered by high bend sensitivity (although to a lesser degree than triangular profiles) and exhibit the largest mode displacements. We find that hybrid (combined power-law) profiles provide some decoupling of these tradeoffs and allow all design goals to be achieved simultaneously. We present optimized fiber designs based on this analysis.

  15. High refractive index Fresnel lens on a fiber fabricated by nanoimprint lithography for immersion applications

    NASA Astrophysics Data System (ADS)

    Koshelev, Alexander; Calafiore, Giuseppe; Piña-Hernandez, Carlos; Allen, Frances I.; Dhuey, Scott; Sassolini, Simone; Wong, Edward; Lum, Paul; Munechika, Keiko; Cabrini, Stefano

    2016-08-01

    In this Letter we present a Fresnel lens fabricated on the end of an optical fiber. The lens is fabricated using nanoimprint lithography of a functional high refractive index material, which is suitable for mass production. The main advantage of the presented Fresnel lens compared to a conventional fiber lens is its high refractive index (n=1.69), which enables efficient light focusing even inside other media such as water or adhesive. Measurement of the lens performance in an immersion liquid (n=1.51) shows a near diffraction limited focal spot of 810 nm in diameter at the 1/e2 intensity level for a wavelength of 660 nm. Applications of such fiber lenses include integrated optics, optical trapping and fiber probes.

  16. High refractive index Fresnel lens on a fiber fabricated by nanoimprint lithography for immersion applications.

    PubMed

    Koshelev, Alexander; Calafiore, Giuseppe; Piña-Hernandez, Carlos; Allen, Frances I; Dhuey, Scott; Sassolini, Simone; Wong, Edward; Lum, Paul; Munechika, Keiko; Cabrini, Stefano

    2016-08-01

    In this Letter, we present a Fresnel lens fabricated on the end of an optical fiber. The lens is fabricated using nanoimprint lithography of a functional high refractive index material, which is suitable for mass production. The main advantage of the presented Fresnel lens compared to a conventional fiber lens is its high refractive index (n=1.68), which enables efficient light focusing even inside other media, such as water or an adhesive. Measurement of the lens performance in an immersion liquid (n=1.51) shows a near diffraction limited focal spot of 810 nm in diameter at the 1/e2 intensity level for a wavelength of 660 nm. Applications of such fiber lenses include integrated optics, optical trapping, and fiber probes. PMID:27472584

  17. 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.

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

    PubMed Central

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

    2010-01-01

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

  19. 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.

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

    SciTech Connect

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

    2003-10-30

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

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

    PubMed Central

    Scheibel, Thomas; Bloom, Jesse; Lindquist, Susan L.

    2004-01-01

    A self-perpetuating change in the conformation of the translation termination factor Sup35p is the basis for the prion [PSI+], a protein-based genetic element of Saccharomyces cerevisiae. In a process closely allied to in vivo conversion, the purified soluble, prion-determining region of Sup35p (NM) converts to amyloid fibers by means of nucleated conformational conversion. First, oligomeric species convert to nuclei, and these nuclei then promote polymerization of soluble protein into amyloid fibers. To elucidate the nature of the polymerization step, we created single-cysteine substitution mutants at different positions in NM to provide unique attachment sites for various probes. In vivo, the mutants behaved like wild-type protein in both the [psi–] and [PSI+] states. In vitro, they assembled with wild-type kinetics and formed fibers with the same morphologies. When labeled with fluorescent probes, two mutants, NMT158C and NME167C, exhibited a change in fluorescence coincident with amyloid assembly. These mutants provided a sensitive measure for the kinetics of fiber elongation, and the lag phase in conversion. The cysteine in the mutant NMK184C remained exposed after assembly. When labeled with biotin and bound to streptavidin beads, it was used to capture radiolabeled soluble NM in the process of conversion. This process established the existence of a detergent-susceptible intermediate in fiber elongation. Thus, the second stage of nucleated conformational conversion, fiber elongation, itself contains at least two steps: the association of soluble protein with preformed fibers to form an assembly intermediate, followed by conformational conversion into amyloid. PMID:14983002

  2. Ultra-weak FBG and its refractive index distribution in the drawing optical fiber.

    PubMed

    Guo, Huiyong; Liu, Fang; Yuan, Yinquan; Yu, Haihu; Yang, Minghong

    2015-02-23

    For the online writing of ultra-weak fiber Bragg gratings (FBGs) in the drawing optical fibers, the effects of the intensity profile, pulse fluctuation and pulse width of the excimer laser, as well as the transverse and longitudinal vibrations of the optical fiber have been investigated. Firstly, using Lorentz-Loren equation, Gladstone-Dale mixing rule and continuity equation, we have derived the refractive index (RI) fluctuation along the optical fiber and the RI distribution in the FBG, they are linear with the gradient of longitudinal vibration velocity. Then, we have prepared huge amounts of ultra-weak FBGs in the non-moving optical fiber and obtained their reflection spectra, the measured reflection spectra shows that the intensity profile and pulse fluctuation of the excimer laser, as well as the transverse vibration of the optical fiber are little responsible for the inconsistency of ultra-weak FBGs. Finally, the effect of the longitudinal vibration of the optical fiber on the inconsistency of ultra-weak FBGs has been discussed, and the vibration equations of the drawing optical fiber are given in the appendix. PMID:25836517

  3. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  5. Silicate all-solid photonic crystal fibers with a glass high index contrast

    NASA Astrophysics Data System (ADS)

    Buczynski, Ryszard; Pysz, Dariusz; Kujawa, Ireneusz; Fita, Piotr; Pawlowska, Monika; Nowosielski, J.; Radzewicz, Czeslaw; Stepien, Ryszard

    2007-05-01

    An all-solid photonic crystal fiber can be developed using two thermally matched glasses with one glass forming the background, and the other the lattice of inclusions. Optical properties of all-solid holey fibers (SOHO) are sensitive to the photonic cladding configuration, much the same as PCFs with air holes, and strongly depend on dispersion properties of the materials used. When a high index contrast between the glasses is assured photonic crystal fiber can effectively guide light with photonic band gap mechanism. This can be easily achieved when multicomponent soft glass is used for fiber fabrication. We report on new developments of F2/NC-21 silicate all-glass PCFs. F2 is a commercially available glass (Schott Inc.) with a high concentration of lead-oxide (PbO=45.5%) and the refractive index n D=1.619. It can be used both as the background material and as a material for micro-rods (inclusions). A borosilicate glass (B IIO 3=26.0%) NC-21 glass has been synthesized in-house at IEMT. NC21 has the index n D=1.533 and was used as the material for micro-rods (inclusions) or as a background glass in the structures. The two selected glasses have a high index contrast equal to 0,084 at 1,55μm wavelength. In this report we present new results on optimization of the filling factor d/Λ and reduction of the lattice pitch Λ necessary to obtain efficient guidance at 1.55 μm. The numerical analysis of SOHO F2/NC21 fibers has been carried out using a full-vector mode solver based on the plane-wave expansion method. In our paper we report on photonic crystal fibers with two guiding mechanisms: an effective index with a high index core (low index inclusions made of NC21 glass and F2 used as a background glass) and a photonic band gap with a low index core (high index inclusions made of F2 glass and NC21 used as a background glass).

  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. Etching Bragg gratings in Panda fibers for the temperature-independent refractive index sensing.

    PubMed

    Li, Jie; Wang, Hao; Sun, Li-Peng; Huang, Yunyun; Jin, Long; Guan, Bai-Ou

    2014-12-29

    We demonstrate the evolution of the Bragg gratings inscribed in Panda fibers with chemical etching. The resonance wavelengths can blueshift with cladding reduction similar to the conventional counterparts. But the wavelength separation between the two polarizations is co-determined by the stress and the asymmetric shape effects. The fast and slow axes of the fiber can be reversed with each other and zero birefringence can be achieved by chemical etching the structure. When the stress-applying parts of the fiber are removed, the finalizing grating can be exploited for the temperature-independent refractive index sensing, since the modes corresponding to the two polarizations exhibit the dissimilar responses to the external refractive index change but the same response to temperature. Our device is featured with easy achievement, spectral controllability, and relative robustness. PMID:25607160

  8. 1×N optical fiber coupler based on a polyhedral gradient index lens

    NASA Astrophysics Data System (ADS)

    Yang, Yuanhong; Dai, Wen; Song, Kuiyan; Jin, Wei

    2014-05-01

    A method for building a 1×N fiber coupler based on a single polyhedral gradient-index lens (p-GRIN) is proposed. One end of the p-GRIN has polyhedral convex cone shape with N surfaces and is used as the light input port, while the other end is flat and used as the output port. When light from a single mode optical fiber illuminates the input end of the p- GRIN, N spatially separated light beams are generated at the output end and coupled respectively into N different output fibers. Results obtained from ray-tracing agree well with simulation results from the ZEMAX software. The output beam positions and light coupling efficiency to optical fibers could be optimized by adjusting the input cone angle and the distance between input fiber end and cone tip. This method may be adapted for any type of optical fibers and provide a practical solution for light coupling between single- and multi-core fibers.

  9. A reflective fiber-optic refractive index sensor based on multimode interference in a coreless silica fiber

    NASA Astrophysics Data System (ADS)

    Zhou, Xinlei; Chen, Ke; Mao, Xuefeng; peng, Wei; Yu, Qingxu

    2015-04-01

    A reflective fiber-optic refractive index (RI) sensor based on multimode interference (MMI) is presented and investigated in this paper. The sensor is made by splicing a small section of coreless silica fiber (CSF) to the standard single mode fiber (SMF). A wide-angle beam propagation method (WA-BPM) is employed for numerical simulation and design of the proposed RI sensor. Based on the simulation results, a RI sensor with a length of 1.7 cm of CSF is fabricated and experimentally studied. Experimental results show that the characteristic wavelength shift has an approximately linear relationship with the RI of the sample. A sensitivity of 141 nm/RIU (refractive index unit) and a resolution of 2.8×10-5 are obtained in the RI range from 1.33 to 1.38. As the RI value is higher than 1.38, the sensitivity of the sensor increase rapidly as the RI increase and a maximum sensitivity of 1561 nm/RIU can be achieved, corresponding to a resolution of 2.6×10-6. The experimental results fit well with the numerical simulation results.

  10. Fast response Fabry-Perot interferometer microfluidic refractive index fiber sensor based on concave-core photonic crystal fiber.

    PubMed

    Tian, Jiajun; Lu, Zejin; Quan, Mingran; Jiao, Yuzhu; Yao, Yong

    2016-09-01

    We report a fast response microfluidic Fabry-Perot (FP) interferometer refractive index (RI) fiber sensor based on a concave-core photonic crystal fiber (CPCF), which is formed by directly splicing a section CPCF with a section of single mode fiber. The CPCF is made by cleaving a section of multimode photonic crystal fiber with an axial tension. The shallow concave-core of CPCF naturally forms the FP cavity with a very short cavity length. The inherent large air holes in the cladding of CPCF are used as the open channels to let liquid sample come in and out of FP cavity. In order to shorten the liquid channel length and eliminate the harmful reflection from the outside end face of the CPCF, the CPCF is cleaved with a tilted tensile force. Due to the very small cavity capacity, the short length and the large sectional area of the microfluidic channels, the proposed sensor provides an easy-in and easy-out structure for liquids, leading to great decrement of the measuring time. The proposed sensor exhibits fast measuring speed, the measuring time is less than 359 and 23 ms for distilled water and pure ethanol, respectively. We also experimentally study and demonstrate the superior performances of the sensor in terms of high RI sensitivity, good linear response, low temperature cross-sensitivity and easy fabrication. PMID:27607621

  11. Single-mode D-shaped optical fiber sensor for the refractive index monitoring of liquid

    NASA Astrophysics Data System (ADS)

    Qazi, Hummad Habib; Mohammad, Abu Bakar bin; Ahmad, Harith; Zamani Zulkifli, Mohd; Wadi Harun, Sulaiman

    2016-04-01

    A new fabrication method is introduced for the production of D-shaped optical fiber. A mechanical end and edge polishing system with aluminum oxide polishing film is utilized to perform sequential polishing on one side (lengthwise) of single-mode optical fiber in order to obtain a D-shaped cross section. Adjusting specific mechanical parameters allows for control of the volume of the D-shaped zone, while the fiber surface smoothness is governed by selection of polishing film grit size. To meet the accuracy and repeatability requirements, optical power loss is monitored during the entire polishing process in situ and in real time. This proposed technique possesses advantages of rapidity, safety, simplicity, repeatability and stability with high precision in comparison with contemporary methods for production. Sensor performance tests on the fiber reveal a linear response with linearity up to R2 = 0.984 for surrounding refractive index in the range of 1.320-1.342 refractive index, which corresponds to different concentrations of the glucose solution test environment. The produced D-shaped optical fiber has potential sensing and monitoring applications in chemical, environmental, biological and biochemical fields.

  12. 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

  13. 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

  14. Investigation of refractive index sensing based on Fano resonance in fiber Bragg grating ring resonators.

    PubMed

    Campanella, Carlo Edoardo; De Leonardis, Francesco; Mastronardi, Lorenzo; Malara, Pietro; Gagliardi, Gianluca; Passaro, Vittorio M N

    2015-06-01

    In this paper we theoretically investigate a ring resonant cavity obtained by closing on itself a π-shifted fiber Bragg grating, to be used for refractive index sensing applications. Differently from a conventional π-shifted fiber Bragg grating, the spectral structure of this cavity is characterized by an asymmetric splitting doublet composed by a right side resonance having an asymmetric Fano profile and a left side resonance having a symmetric Lorentzian profile. The right side resonance shows a narrower and sharper peak than all the other kinds of resonance achievable with both conventional ring resonators and π-shifted fiber Bragg gratings. A reduction of the resonant linewidth with respect to a conventional π-shifted Fiber Bragg grating and a fiber ring resonator, having the same physical parameters, is theoretically proved, achieving up to five orders of magnitude improvement with respect to the usual ring resonator. Due to these resonance features, the π-shifted Bragg grating ring resonator results suitable for RI sensing applications requiring extremely narrow resonances for high resolution measurements. In particular, by assuming a refractive index sensing to detect the presence of sugar in water, the sensor can show a theoretical resolution better than 10-9 RIU. PMID:26072795

  15. 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…

  16. 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.

  17. 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.

  18. Kerr self-cleaning of femtosecond-pulsed beams in graded-index multimode fiber.

    PubMed

    Liu, Zhanwei; Wright, Logan G; Christodoulides, Demetrios N; Wise, Frank W

    2016-08-15

    We observe a nonlinear spatial self-cleaning process for femtosecond pulses in graded-index (GRIN) multimode fiber (MMF). Pulses with ∼80 fs duration at 1030 nm are launched into GRIN MMF with 62.5 μm core. The near-field beam profile at the output end of the fiber evolves from a speckled pattern to a centered, bell-shaped transverse structure with increasing pulse energy. The experimental observations agree well with numerical simulations, which show that the Kerr nonlinearity underlies the process. This self-cleaning process may find applications in ultrafast pulse generation and beam-combining. PMID:27519060

  19. 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 μm, 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 μm, 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

  20. 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

    2016-01-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    2011-05-01

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

  2. Contactless optical fiber refractive index sensor for liquid and solid samples

    NASA Astrophysics Data System (ADS)

    Moreno-Hernández, Carlos; Monzón-Hernández, D.; Villatoro, Joel

    2016-05-01

    We report on a contactless optical fiber refractive index (RI) sensor that can be used to measure the RI of solid or liquid samples. The sensor is simple to construct and consists of a Fabry-Perot interferometer (FPI) with long cavity. The cavity of our FPI consists of a tapered optical fiber tip and an external flat mirror. The output beam of the fiber tip is partially reflected from different interfaces of the sample present in the interferometer cavity. Each of such reflections interferes with the beam internally reflected by the fiber tip. Thus, a multiple-beam FPI is formed whose reflection spectrum is composed by the superposition of several two-beam interferences. The analysis of the multiple interference spectra was carried out in the Fourier domain. Several glass samples, water-sucrose and water-glycerol solutions were prepared and tested. Since the fiber tip is not in direct contact with the sample under test the measurement is simple and immediate. To our-knowledge, this is the first time that a fiber optic sensor can be used to measure the RI of solid and liquid samples without any modification.

  3. Design of photonic crystal fiber long-period grating refractive index sensor

    NASA Astrophysics Data System (ADS)

    Kanka, Jiri; Zhu, Yinian; He, Zonghu; Du, Henry

    2009-05-01

    Numerical optimization of photonic crystal fiber (PCF) structures for refractive index sensors based on long period gratings inscribed in PCFs has been performed. The optimization procedure employs the Nelder-Mead downhill simplex algorithm. This direct-search method attempts to minimize a scalar-valued nonlinear function of N real variables (called the objective function) using only function values, without any derivative information. An inverse design approach utilizes the objective function constructed using desired sensing characteristics. For the modal analysis of the PCF structure a fully-vectorial solver based on the finite element method is called by the objective function. The dispersion optimization of PCFs is aimed at achieving a high sensitivity of measurement of refractive index of analytes infiltrated into the air holes for the refractive index and probe wavelength ranges of interest. We have restricted our work to the index-guiding solid-core PCF structures with hexagonally arrayed air holes.

  4. 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).

  5. 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.

  6. Visible supercontinuum generation in a graded index multimode fiber pumped at 1064  nm.

    PubMed

    Lopez-Galmiche, G; Sanjabi Eznaveh, Z; Eftekhar, M A; Antonio Lopez, J; Wright, L G; Wise, F; Christodoulides, D; Amezcua Correa, R

    2016-06-01

    We observe efficient supercontinuum generation that extends into the visible spectral range by pumping a low differential mode group delay graded index multimode fiber in the normal dispersion regime. For a 28.5 m long fiber, the generated spectrum spans more than two octaves, starting from below 450 nm and extending beyond 2400 nm. The main nonlinear mechanisms contributing to the visible spectrum generation are attributed to multipath four-wave mixing processes and periodic spatio-temporal breathing dynamics. Moreover, by exploiting the highly multimodal nature of this system, we demonstrate versatile generation of visible spectral peaks in shorter fiber spans by altering the launching conditions. A nonlinearly induced mode cleanup was also observed at the pump wavelength. Our results could pave the way for high brightness, high power, and compact, multi-octave continuum sources. PMID:27244412

  7. 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.

  8. In-series double cladding fibers for simultaneous refractive index and temperature measurement.

    PubMed

    Liu, Huanhuan; Pang, Fufei; Guo, Hairui; Cao, Wenxin; Liu, Yunqi; Chen, Na; Chen, Zhenyi; Wang, Tingyun

    2010-06-01

    A fiber-optic sensor for simultaneous measurement of refractive index (RI) and temperature was proposed and demonstrated. It was fabricated by cascading two sections of specialty double cladding (DC) fibers which presented a pair of well-separated resonant spectra dips. The sensing properties of temperature and ambient RI were investigated theoretically based on the coupled mode theory. Experimental results indicated that these two resonant spectra shifts were linearly dependent on the variation of the RI in the range of 1.3333 approximately 1.4118 and on the temperature in the range of -10 degrees C approximately + 80 degrees C. Such a fiber-optic sensor is simple and easy for mass production and has potential applications for biosensors or chemical sensors. PMID:20588437

  9. 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.

  10. 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.

  11. Study of the sensitivity of gas sensing by use of index-guiding photonic crystal fibers.

    PubMed

    Li, Shu-Guang; Liu, Si-Ying; Song, Zhao-Yuan; Han, Yin; Cheng, Tong-Lei; Zhou, Gui-Yao; Hou, Lan-Tian

    2007-08-01

    We demonstrate an absorption transmission spectrum of CH(4) in a 16.9 cm long index-guiding photonic crystal fiber (PCF) fabricated in our laboratory. One of the main factors to improve the sensitivity is to increase the fraction of power in PCF cladding air holes. We study the fraction of power in PCF cladding air holes as a function of the index-guiding PCF parameters. We found that a PCF with small spacing and a large air-filling ratio has a higher fraction of power in its cladding air holes. At the same time the mode area in this PCF is small and would generate strong nonlinear effects in the fiber. If we use a PCF in which the core is formed by missing seven air holes, it is immediately obvious that the PCF used as a sensor has higher sensitivity and a larger mode area. PMID:17676130

  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. 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.

  14. 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.

  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. 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

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

    PubMed

    Chen, Nan-Kuang; Jian, Lian-Jiun

    2012-08-01

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

  20. Hybrid optical fiber Fabry-Perot interferometer for simultaneous measurement of gas refractive index and temperature.

    PubMed

    Wang, Ruohui; Qiao, Xueguang

    2014-11-10

    We present a hybrid miniature optical fiber Fabry-Perot interferometer for simultaneous measurement of gas refractive index and temperature. The interferometer is fabricated by cascading two short sections of capillary tubes with different inner diameters. One extrinsic interferometer is based on the air gap cavity formed by the capillary tube with large diameter. Another section of capillary tube with small inner diameter performs as an intrinsic interferometer and also provides a channel enabling gas to enter and leave the extrinsic cavity freely. The experiment shows that the different dips or peaks in fringe exhibit different responses to the changes in gas refractive index and temperature. Owing to this feature, simultaneous measurement of the gas refractive index and temperature can be realized. PMID:25402996

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. 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.

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

    NASA Astrophysics Data System (ADS)

    Sohn, In-Sung

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

  8. 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

  9. Investigation of refractive index distribution in different photonic crystal fiber elements

    NASA Astrophysics Data System (ADS)

    Jaroszewicz, Leszek R.; Kujawińska, Małgorzata; Stasiewicz, Karol; Marć, Paweł; Nasiłowski, Tomasz; Murawski, Michał; Szymański, Michał; Siwicki, Bartłomiej; Krauze, Wojciech

    2011-09-01

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

  10. 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

  11. 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.

  12. 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.

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

    PubMed

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

    2012-07-10

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

  14. 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.

  15. Hollow fiber surface plasmon resonance sensor for the detection of liquid with high refractive index.

    PubMed

    Liu, Bing-Hong; Jiang, Yong-Xiang; Zhu, Xiao-Song; Tang, Xiao-Li; Shi, Yi-Wei

    2013-12-30

    A new kind of surface plasmon resonance (SPR) sensor based on silver-coated hollow fiber (HF) structure for the detection of liquids with high refractive index (RI) is presented. Liquid sensed medium with high RI is filled in the hollow core of the HF and its RI can be detected by measuring the transmission spectra of the HF SPR sensor. The designed sensors with different silver thicknesses are fabricated and the transmission spectra for filled liquids with different RI are measured to investigate the performances of the sensors. Theoretical analysis is also carried out to evaluate the performance. The simulation results agree well with the experimental results. Factors that might affect sensitivity and detection accuracy of the sensor are discussed. The highest sensitivity achieved is 6,607 nm/RIU, which is comparable to the sensitivities of the other reported fiber SPR sensors. PMID:24514827

  16. Two-photon-induced excited-state absorption in high-index fibers

    NASA Astrophysics Data System (ADS)

    Shensky, William M., III; Cohanoschi, Ion; Sevian, Armen; Hagan, David J.; Van Stryland, Eric W.

    2004-06-01

    We have studied the nonlinear optical properties of a high-index (n = 1.82) glass that is used as the core material in a commercially available fiber optic inverter, which is a coherent fiber bundle twisted 180 degrees to produce an inverted image. We have determined through open aperture Z-scan the two-photon absorption coefficient of the glass to be 0.8 cm/GW using 23 ps pulses (FWHM) at 532 nm, far from the linear absorption edge of 320 nm. For 5 ns (FWHM) pulses the nonlinear absorption is much larger, and is dominated by two-photon induced excited-state absorption. These effects contribute to the nanosecond optical limiting response that we have observed for the inverter using an F/5 focusing geometry.

  17. 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

  18. 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

  19. Single mode tapered fiber-optic interferometer based refractive index sensor and its application to protein sensing.

    PubMed

    Yadav, T K; Narayanaswamy, R; Abu Bakar, M H; Kamil, Y Mustapha; Mahdi, M A

    2014-09-22

    We demonstrate refractive index sensors based on single mode tapered fiber and its application as a biosensor. We utilize this tapered fiber optic biosensor, operating at 1550 nm, for the detection of protein (gelatin) concentration in water. The sensor is based on the spectroscopy of mode coupling based on core modes-fiber cladding modes excited by the fundamental core mode of an optical fiber when it transitions into tapered regions from untapered regions. The changes are determined from the wavelength shift of the transmission spectrum. The proposed fiber sensor has sensitivity of refractive index around 1500 nm/RIU and for protein concentration detection, its highest sensitivity is 2.42141 nm/%W/V. PMID:25321749

  20. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

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

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

    PubMed

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

    2012-09-24

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

  3. Intrinsic Fabry-Pérot cavity sensor based on chemical etching of a multimode graded index fiber spliced to a single mode fiber

    NASA Astrophysics Data System (ADS)

    Tafulo, Paula A. R.; Frazão, O.; Jorge, P. A. S.; Araújo, F. M.

    2010-09-01

    An intrinsic Fabry-Pérot cavity for high temperature and strain measurement is presented. The in-fibre cavity is formed by a chemical etched graded index optical fiber spliced to a single mode fiber. The intrinsic sensor obtained shows high sensitivity to strain (6.2 pm/μɛ) and rather low sensitivity to temperature (0.9 pm/°C), being suitable for applications as a strain gauge at high temperature.

  4. In-fiber Mach-Zehnder interferometer for gas refractive index measurements based on a hollow-core photonic crystal fiber.

    PubMed

    Andrews, Nicholas L P; Ross, Rachel; Munzke, Dorit; van Hoorn, Camiel; Brzezinski, Andrew; Barnes, Jack A; Reich, Oliver; Loock, Hans-Peter

    2016-06-27

    We describe an in-fiber interferometer based on a gas-filled hollow-core photonic crystal fiber. Expressions for the sensitivity, figure of merit and refractive index resolution are derived, and values are experimentally measured and theoretically validated using mode field calculations. The refractive indices of nine monoatomic and molecular gases are measured with a resolution of δns < 10-6. PMID:27410569

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

    PubMed

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

    2012-01-01

    Cortical folding (gyrification) is determined during the first months of life, so that adverse events occurring during this period leave traces that will be identifiable at any age. As recently reviewed by Mangin and colleagues(2), several methods exist to quantify different characteristics of gyrification. For instance, sulcal morphometry can be used to measure shape descriptors such as the depth, length or indices of inter-hemispheric asymmetry(3). These geometrical properties have the advantage of being easy to interpret. However, sulcal morphometry tightly relies on the accurate identification of a given set of sulci and hence provides a fragmented description of gyrification. A more fine-grained quantification of gyrification can be achieved with curvature-based measurements, where smoothed absolute mean curvature is typically computed at thousands of points over the cortical surface(4). The curvature is however not straightforward to comprehend, as it remains unclear if there is any direct relationship between the curvedness and a biologically meaningful correlate such as cortical volume or surface. To address the diverse issues raised by the measurement of cortical folding, we previously developed an algorithm to quantify local gyrification with an exquisite spatial resolution and of simple interpretation. Our method is inspired of the Gyrification Index(5), a method originally used in comparative neuroanatomy to evaluate the cortical folding differences across species. In our implementation, which we name local Gyrification Index (lGI(1)), we measure the amount of cortex buried within the sulcal folds as compared with the amount of visible cortex in circular regions of interest. Given that the cortex grows primarily through radial expansion(6), our method was specifically designed to identify early defects of cortical development. In this article, we detail the computation of local Gyrification Index, which is now freely distributed as a part of the Free

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

    PubMed

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

    2008-02-01

    A refractive index sensor based on the thinned and microstructure fiber Bragg grating (ThMs-FBG) was proposed and realized as a chemical sensing. The numerical simulation for the reflectance spectrum of the ThMs-FBG was calculated and the phase shift down-peak could be observed from the reflectance spectrum. Many factors influencing the reflectance spectrum were considered in detail for simulation, including the etched depth, length, and position. The sandwich-solution etching method was utilized to realize the microstructure of the ThMs-FBG, and the photographs of the microstructure were obtained. Experimental results demonstrated that the reflectance spectrum, phase shift down-peak wavelength, and reflected optical intensity of the ThMs-FBG all depended on the surrounding refractive index. However, only the down-peak wavelength of the ThMs-FBG changed with the surrounding temperature. Under the condition that the length and cladding diameter of the ThMs-FBG microstructure were 800 and 14 mum, respectively, and the position of the microstructure of the ThMs-FBG is in the middle of grating region, the refractive index sensitivity of the ThMs-FBG was 0.79 nm/refractive index unit with the wide range of 1.33-1.457 and a high resolution of 1.2 x 10(-3). The temperature sensitivity was 0.0103 nm/ degrees C, which was approximately equal to that of common FBG. PMID:18239709

  7. Characteristics of a long-period fiber grating with reduced cladding for refractive index sensing

    NASA Astrophysics Data System (ADS)

    Chen, Haiyun; Gu, Zhengtian

    2011-10-01

    The sensitivity to surrounding refractive index (SRI) of a long-period fiber grating (LPFG) can be effectively improved by decreasing the cladding radius. When the cladding is reduced, a three-layer model is necessary to evaluate the effective refractive index (ERI) of the core mode. A variation of SRI can induce a greater resonant wavelength shift when the core mode is coupled to a higher-order cladding mode. However, as the cladding is reduced further, the highest-order cladding mode would be cut off, i.e. the number of cladding modes that a given fiber structure can support would be less; thus, the higher-order cladding modes that can be used for higher sensitivity are limited. Hence, the implementation of high sensitivity for SRI sensing with cladding-reduced LPFGs is dependent on the proper combination of cladding radius and cladding mode order. Based on the vector coupled-mode theory, the transmission spectrum and sensitivity are numerically analyzed with respect to the cladding radius, which shows that the SRI sensitivity of the HE12 mode with cladding radius a 2 = 20 µm is 32 times as high as that with a 2 = 62.5 µm and the SRI resolution is available to the order of 10-7.

  8. 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.

  9. 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

  10. 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.

  11. 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.

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

    PubMed

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

    2011-07-01

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

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

    SciTech Connect

    Pekukhova, I.; Fotiadi, A. A.; Shubin, A. V.; Tomashuk, A. L.; Novikov, S. G.; Zolotovskiy, I. O.; Antipov, O. L.; Panajotov, K.; Thienpont, H.; Megret, P.

    2011-07-01

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

  14. Influence of the cladding diameter of optical fiber on the simultaneous measurement of the refractive index and temperature of liquids using tilted fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Kameyama, Akihiro; Katto, Masahito; Yokotani, Atsushi

    2016-06-01

    We considered the influence of the core and cladding diameters on the simultaneous measurement of the refractive index and temperature of liquids using a tilted fiber Bragg grating (TFBG). When the cladding diameter of a TFBG was only reduced from 125 to 123 µm, the calculated refractive index differed by 0.0068 from the expected value. When the core diameter was reduced from 9.6 to 7.8 µm, the change was less than 0.0005. We found that equalization of cladding diameter is required to improve the precision of the simultaneous measurement of the refractive index and temperature of liquids.

  15. SMS fiber structure with a multimode fiber graded index type for a temperature measurement using an intensity-based interrogation system

    NASA Astrophysics Data System (ADS)

    Mufarrikha, Ainun; Hatta, Agus M.; Koentjoro, Sekartedjo

    2015-01-01

    Temperature sensing based on a singlemode-multimode-singlemode (SMS) fiber structure with a graded index multimode fiber (GI-MMF) type using an intensity-based interrogation has been investigated numerically and experimentally. The effect of temperature on the SMS fiber structure with the MMF-GI type was modeled using a modal propagation analysis (MPA). The SMS fiber structures for temperature sensor was fabricated and tested with the MMF length of 57 mm. It is demonstrated experimentally, and supported with numerical results, that the sensor showed a sensitivity of 0.063 dB/°C with a temperature measurement range of 175-325°C. This sensor offers simple configuration and low cost of fabrication for the temperature measurement applications.

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

  17. Photonic Crystal Fiber Mach-Zehnder Interferometer for Refractive Index Sensing

    PubMed Central

    Wang, Jian-Neng; Tang, Jaw-Luen

    2012-01-01

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

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

    PubMed

    Wang, Jian-Neng; Tang, Jaw-Luen

    2012-01-01

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

  19. 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

  20. Gain-guided index-antiguided fiber with a Fabry-Perot layer for large mode area laser amplifiers.

    PubMed

    Lai, Chih-Hsien; Chen, Hsuan-Yu; Du, Cheng-Han; Chiou, Yih-Peng

    2015-02-23

    We propose a modified gain-guided index-antiguided (GGIAG) fiber structure for large mode area laser amplifiers, in which a thin dielectric layer is placed between the low-index core and the high-index cladding. The introduced dielectric layer functions as a Fabry-Perot etalon. By letting the resonant wavelength of the Fabry-Perot layer coincide with the signal wavelength, the signal is gain-guided in the fiber core. Moreover, the pump is confined in the low-index core owing to the antiresonant reflection originated from the Fabry-Perot layer. Numerical results indicate that the leakage loss of the pump can be minified over two orders of magnitude in the proposed structure, and thus the end-pumping efficiency could be enhanced significantly. PMID:25836427

  1. Optical characterization of radiation-resistant fibers

    SciTech Connect

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

    1984-01-01

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

  2. [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

  3. 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.

  4. Simultaneous monitoring the real and imaginary parts of the analyte refractive index using liquid-core photonic bandgap Bragg fibers.

    PubMed

    Li, Jingwen; Qu, Hang; Skorobogatiy, Maksim

    2015-09-01

    We demonstrate simultaneous monitoring of the real and imaginary parts of the liquid analyte refractive index by using a hollow-core Bragg fiber. We apply this two-channel fiber sensor to monitor concentrations of various commercial cooling oils. The sensor operates using spectral monitoring of the fiber bandgap center wavelength, as well as monitoring of the fiber transmission amplitude at mid-bandgap position. The sensitivity of the fiber sensor to changes in the real part of the core refractive index is found to be 1460nm/Refractive index unit (RIU). By using spectral modality and effective medium theory, we determine the concentrations of the two commercial fluids from the measured refractive indices with an accuracy of ~0.57% for both low- and high-loss oils. Moreover, using an amplitude-based detection modality allows determination of the oil concentration with accuracy of ~1.64% for low-loss oils and ~2.81% for the high-loss oils. PMID:26368402

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

    PubMed Central

    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

  6. Approximate solution for optical measurements of the diameter and refractive index of a small and transparent fiber.

    PubMed

    Świrniak, Grzegorz; Mroczka, Janusz

    2016-04-01

    When a plane electromagnetic wave is scattered by an optically transparent object, whose size is much larger than the wavelength, a series of bright and dark fringes forms the primary rainbow, which is one of the most splendid phenomena in nature. In this work, an optical technique is discussed for simultaneous measurement of the diameter and refractive index of an axisymmetric and dielectric fiber by studying some rainbow features. This noncontact optical technique uses a beam of light exhibiting low temporal coherence, which enabled us to reduce the detrimental sensitivity of the rainbow features to variations of the fiber properties, thus allowing for high-precision estimates. Approximate mathematical formulas for the diameter and refractive index measurements were derived from the lowest-order complex angular momentum correction to Airy theory of rainbow. Furthermore, sensitivity of the measurement data to small deformation of the fiber's cross section into an ellipse was discussed. Preliminary empirical results provide a qualitative verification. PMID:27140778

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

    NASA Astrophysics Data System (ADS)

    He, Jun-Rong; Yi, Lin

    2014-06-01

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

  8. 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

  9. 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.

  10. Theoretical investigation of core geometry variation influence on a few-mode optical signal distortion during propagation over silica graded-index multimode fiber with low DMD

    NASA Astrophysics Data System (ADS)

    Bourdine, Anton V.

    2012-01-01

    In recent works an alternative method for design of silica GeO2-doped graded-index multimode optical fibers 50/125 with low differential mode delay (DMD) was introduced. It is based on synthesis of special refractive index profile, providing the equalization of guided mode group velocities. A theoretical approbation of introduced fibers under the modeling of fiber optic link showed good results for a few-mode regime of high-speed laser-based serial data transmission. However on practice a different distributed core geometry parameter variation occurs in real optical fibers due to techniques features of preform manufacturing and fiber drawing. Here results of fiber optic link modeling with proposed multimode fibers 50/125 with low DMD under core diameter variation and refractive index profile deviation from the optimal form, and estimation of their influence on a few-mode optical signal distortion are represented.

  11. Theoretical investigation of core geometry variation influence on a few-mode optical signal distortion during propagation over silica graded-index multimode fiber with low DMD

    NASA Astrophysics Data System (ADS)

    Bourdine, Anton V.

    2011-12-01

    In recent works an alternative method for design of silica GeO2-doped graded-index multimode optical fibers 50/125 with low differential mode delay (DMD) was introduced. It is based on synthesis of special refractive index profile, providing the equalization of guided mode group velocities. A theoretical approbation of introduced fibers under the modeling of fiber optic link showed good results for a few-mode regime of high-speed laser-based serial data transmission. However on practice a different distributed core geometry parameter variation occurs in real optical fibers due to techniques features of preform manufacturing and fiber drawing. Here results of fiber optic link modeling with proposed multimode fibers 50/125 with low DMD under core diameter variation and refractive index profile deviation from the optimal form, and estimation of their influence on a few-mode optical signal distortion are represented.

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  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. Monitoring of gamma-irradiated Yb-doped optical fibers through pump induced refractive index changes effect

    NASA Astrophysics Data System (ADS)

    Fotiadi, Andrei A.; Petukhova, Irina; Mégret, Patrice; Shubin, Alexey V.; Tomashuk, Alexander L.; Novikov, Sergey G.; Borisova, Christina V.; Zolotovskiy, Igor O.; Antipov, Oleg L.; Panajotov, Krassimir; Thienpont, Hugo

    2012-04-01

    We discuss a radioactivity sensing based on monitoring of color centers formation in Yb-doped fiber under gamma irradiation. New method exploits the dynamic effect of refractive index changes (RIC) induced by laser pumping into the fiber absorption band. In our experiment four identical samples of the single-mode aluminum silicate Yb-doped optical fiber have been γ-irradiated with different doses from a 60Co source. All fibers passed the test in the intereferometric setup for the purpose of the pump induced RIC effect. During the test the phase shifts induced in the fiber by 1-mssquare pump pulses at 980 nm were recorded with a probe signal at eleven different wavelengths ranging from ~1.46 to ~1.61 μm. The phase traces have been normalized to their maximum values and averaged over 100 traces for each probe wavelength and also over all probe wavelengths. The averaged phase traces highlight the differences in their growing and decaying parts in respect to the case of non-irradiated fibers. These differences are found to be in correlation with the fiber irradiation dose. For non-irradiated fibers decay parts are perfectly fitted by one exponential function with the relaxation time constant equal to the Yb-ion excited state life-time ~750 μs, to be the same for all fiber samples. However, for irradiated fibers the similar fitting gives a triple exponential decay with time constants estimated as ~750, ~500 and 40μs. For higher irradiation dose the difference with one exponential fitting is more pronounced. Having in mind that the obtained difference in phase shift dynamics could be associated with excitation of some color centers induced in the fiber matrix by gamma irradiation, we represent the normalized phase shifts as a superposition of two contributions. The first contribution is due to excitation of Yb-ion, the same for all fiber samples. The second is due to excitation of color centers. The amplitude of the second part highlights a degree of fiber

  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. A novel method to generate a self-accelerating Bessel-like beam based on graded index multimode optical fiber

    NASA Astrophysics Data System (ADS)

    Zhang, Yaxun; Liu, Chunlan; Yu, Zhang; Liu, Zhihai; Zhao, Enming; Yang, Jun; Yuan, Libo

    2015-09-01

    We propose and demonstrate a transverse self-accelerating Bessel-like beam generator based on a graded index multimode optical fiber(GIF). The single-mode fiber and the graded-index multimode fiber are spliced with a defined offset. The offset Δx and the GIF length L affect the final properties of the Bessel-like beam, here we choose the offset Δx=20μm and the GIF length L=430μm to be optimal. The beam accelerates along the designed parabolic path up to 250μm in z direction and 40μm in x direction, the curvature of bending is 16% (40μm/250μm, x/z). This transverse self-accelerating Bessel-like beam generator based on the graded index multimode optical fiber constitutes a new development for high-precision micro particles experiments and manipulations because of its simple structure, high integration and small size.

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. 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

  5. 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.

  6. Fiber

    MedlinePlus

    ... it can help with weight control. Fiber aids digestion and helps prevent constipation . It is sometimes used ... fiber attracts water and turns to gel during digestion. This slows digestion. Soluble fiber is found in ...

  7. 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

  8. Dietary Fiber, Carbohydrates, Glycemic Index and Glycemic Load in Relation to Breast Cancer Prognosis in the HEAL Cohort

    PubMed Central

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

    2011-01-01

    Background Dietary intake of fiber, carbohydrate, glycemic index (GI), and glycemic load (GL) may influence breast cancer survival, but consistent and convincing evidence is lacking. Methods We investigated associations of dietary fiber, carbohydrates, GI, and GL with breast cancer prognosis among n=688 stage 0 to IIIA breast cancer survivors in the Health, Eating, Activity, and Lifestyle (HEAL) study. Pre- and postmenopausal women from Western Washington State, Los Angeles County, and New Mexico participated. Usual diet was assessed with a food frequency questionnaire. Total mortality, breast cancer mortality, non-fatal recurrence and second occurrence data were obtained from SEER registries and medical records. Cox proportional hazards regression estimated multivariate-adjusted hazard ratios and 95% CIs. Results During a median of 6.7 years follow-up after diagnosis, n= 106 total deaths, n=83 breast cancer-specific deaths and n=82 non-fatal recurrences were confirmed. We observed an inverse association between fiber intake and mortality. Multivariate-adjusted HRRs comparing high to low intake were 0.53 (95% CI 0.23-1.23) and 0.75 (95% CI 0.43-1.31). A threshold effect was observed whereby no additional benefit was observed for intakes >9 g/day. Fiber intake was suggestively inversely associated with breast-cancer specific mortality (HRR=0.68, 95% CI 0.27-1.70) and risk of non-fatal recurrence or second occurrence (HRR=0.68, 95% CI 0.27-1.70), but results were not statistically significant. Conclusion Dietary fiber was associated with a non-significant inverse association with breast cancer events and total mortality. Further studies to assess and confirm this relationship are needed in order to offer effective dietary strategies for breast cancer patients. Impact Increasing dietary fiber may an effective lifestyle modification strategy for breast cancer survivors. PMID:21430298

  9. 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.

  10. Reflective long-period fiber grating-based sensor with Sagnac fiber loop mirror for simultaneous measurement of refractive index and temperature.

    PubMed

    Yuan, Jianying; Zhao, Chun-Liu; Zhou, Yumeng; Yu, Xiangdong; Kang, Juan; Wang, Jianfeng; Jin, Shangzhong

    2014-10-10

    In this paper, we propose a reflective long-period grating-based sensor with a Sagnac fiber loop mirror (SFLM) for simultaneous measurement of refractive index (RI) and temperature. By cascading the SFLM to the end of a long-period fiber grating (LPFG), the LPFG works as a reflection operation, which is convenient in some applications. Further, the SFLM and the LPFG have different sensitivities to RI and temperature. As a result, RI and temperature measurement can be simultaneously achieved by monitoring the wavelength shifts of the LPFG and the SFLM's dips in the reflection spectrum. Experimental results show that the temperature sensitivity can reach 1.533 nm/°C, and the RI sensitivity is from 16.864 nm/RIU (refractive index unit) to 113.142 nm/RIU when the RI range is from 1.333 to 1.430. The application for 40 km long-distance RI and temperature measurement shows that the sensor has potential application in long-distance sensing. PMID:25322436

  11. 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.

  12. Fiber-optic temperature sensor based on interaction of temperature-dependent refractive index and absorption of germanium film.

    PubMed

    Li, Min; Li, Yulin

    2011-01-10

    The interaction of a large temperature-dependent refractive index and a temperature-dependent absorption of semiconductor materials at 1550 nm can be used to build a very sensitive, film coated fiber-optic temperature probe. We developed a sensor model for the optical fiber-germanium film sensor. A temperature sensitivity of reflectivity change of 0.0012/°C, corresponding to 0.1°C considering a moderate signal processing system, over 100°C within the temperature regime of -20°C to 120°C, has been demonstrated by experimental tests of the novel sensor. The potential sensitivity and further applications of the sensor are discussed. PMID:21221150

  13. 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.

  14. Theoretical analysis of novel fiber grating pair

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    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.

  15. The influence of temperature to a refractive index sensor based on a macro-bending tapered plastic optical fiber

    NASA Astrophysics Data System (ADS)

    Teng, Chuan-xin; Yu, Fang-da; Jing, Ning; Zheng, Jie

    2016-09-01

    The temperature influence to a refractive index (RI) sensor based on a macro-bending tapered plastic optical fiber (POF) was investigated experimentally. The total temperature dependence loss (TDLtotal) and total temperature dependence RI deviation (TDRtotal) were measured at different temperature (10-60 °C) over an RI range of 1.33-1.41. The temperature dependence RI deviation of the sensor itself was obtained by subtracting the temperature dependence RI of measured liquid from TDRtotal. Therefore, the influence of temperature variation to the sensor was characterized and corrected.

  16. Numerical and experimental investigation of long-period gratings in photonic crystal fiber for refractive index sensing of gas media.

    PubMed

    Tian, Fei; He, Zonghu; Du, Henry

    2012-02-01

    We have used the finite-difference frequency-domain (FDFD) method to simulate the core mode to cladding mode couplings in long-period gratings (LPGs) in photonic crystal fiber (PCF). Four sets of LPG-PCF have been fabricated with respective periodicities of 590, 540, 515, and 490 μm, resulting in corresponding resonance wavelengths (RWs) of 1241, 1399, 1494, and 1579 nm. We show both theoretically and experimentally that the longer the RW, the more sensitive the LPG-PCF is to the index change in Ar. We demonstrate a robust sensitivity of 517 nm per refractive index unit using the LPG-PCF at 1579 nm RW. PMID:22297359

  17. Dual-Charged Hollow Fiber Membranes for Low-Pressure Nanofiltration Based on Polyelectrolyte Complexes: One-Step Fabrication with Tailored Functionalities.

    PubMed

    Gherasim, Cristina Veronica; Luelf, Tobias; Roth, Hannah; Wessling, Matthias

    2016-07-27

    A new nanofiltration (NF) hollow fiber membrane is developed by using two oppositely charged polyelectrolytes coagulating into a polyelectrolyte complex (PEC) onto polyether sulfone base polymer. The particular membrane architecture emerges during a single-step procedure, allowing setting both the porous negatively charged support of the hollow fiber and the separation layer containing also the positive polyelectrolyte (PEI/PDADMAC) through a single layer dry-jet wet spinning process. The novelty is two-pronged: the composition of the hollow fiber membrane itself and its fabrication procedure (one-step fabrication of membranes employing polyelectrolytes). These result in highly permeable hollow fiber membranes with a stable separation layer and performance at par with the membranes reported in literature obtained by multistep processes. More importantly, the membranes are obtained through a simple, very fast (one-step), and less expensive procedure. The best performance among these newly obtained hollow-fiber membranes is achieved by PD5% hollow fiber (MWCO of 300 Da), which showed 7.6 L/m(2)·h·bar permeability and ∼90% rejection of MgCl2, MgSO4, and Na2SO4 at 2 bar pressure. Thus, the resulting membranes not only have the advantages of the hollow-fiber configuration, but perform very well at extremely low pressures (the lowest reported in the literature). The broad impact of the results presented in this Article lies in the potential to dramatically reduce both the fabrication (duration and complexity) and the price and desalination costs of highly performing NF hollow fiber membranes. These might result in interesting potential applications and open new directions toward designing efficient functional NF hollow fibers for water desalination. PMID:27406046

  18. Development of dual-wavelength fiber ring laser and its application to step-height measurement using self-mixing interferometry.

    PubMed

    Ma, S; Xie, F; Chen, L; Wang, Y Z; Dong, L L; Zhao, K Q

    2016-03-21

    A dual-wavelength erbium-doped fiber (EDF) ring laser was developed and its application to step-height measurement using two-wavelength self-mixing interferometry (SMI) was demonstrated. The fiber laser can emit two different wavelengths without any laser mode competition. It is composed of two EDF laser cavities and employs fiber Bragg gratings to determine which wavelengths are emitted. The step heights can be measured using SMI of the two wavelengths, and the maximum height that can be measured is half the synthetic wavelength of the two wavelengths. A step height of 1mm was constructed using two gauge blocks and then measured using the laser. The measurement was repeated ten times, and the standard deviation of the measurements was 2.4nm. PMID:27136766

  19. Single-step optical realization of bio-inspired dual-periodic motheye and gradient-index-array photonic structures.

    PubMed

    Behera, Saraswati; Joseph, Joby

    2016-08-01

    This Letter demonstrates a single-step optical realization method for hexagonal and square lattice-based dual periodic motheye and gradient-index-array photonic structures over large areas. Computed phase mask of gradient interference patterns are used as inputs to a phase-only spatial light modulator (SLM), and the first-order diffracting beams are coherently superposed with the help of a 2f-2f Fourier filtering setup to avoid complex optical geometry for generation and control of individual beams. The simulated interference patterns are verified experimentally through a CMOS camera. The fabricated micro-structures on a positive photoresist are shown to have a major periodicity of 638 μm and minor periodicity of 25.2 μm, with the air hole diameter varying from 22.7 to 6.9 μm along the X and Y axes. The depth of the fabricated structure gradually varies from 4.203 μm at the center to 1.818 μm at the corner. These structures may be scaled down to submicron features that can show improved anti-reflection properties for solar energy harvesting and GRIN lens for optical wavelength region. PMID:27472623

  20. 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.

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

    NASA Astrophysics Data System (ADS)

    Kanka, Jiri

    2011-05-01

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

  2. 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

  3. 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.

  4. Fabrication and characterization of metal-packaged fiber Bragg grating sensor by one-step ultrasonic welding

    NASA Astrophysics Data System (ADS)

    Zhang, Yumin; Zhu, Lianqing; Luo, Fei; Dong, Mingli; Ding, Xiangdong; He, Wei

    2016-06-01

    A metallic packaging technique of fiber Bragg grating (FBG) sensors is developed for measurement of strain and temperature, and it can be simply achieved via one-step ultrasonic welding. The average strain transfer rate of the metal-packaged sensor is theoretically evaluated by a proposed model aiming at surface-bonded metallic packaging FBG. According to analytical results, the metallic packaging shows higher average strain transfer rate compared with traditional adhesive packaging under the same packaging conditions. Strain tests are performed on an elaborate uniform strength beam for both tensile and compressive strains; strain sensitivities of approximately 1.16 and 1.30 pm/μɛ are obtained for the tensile and compressive situations, respectively. Temperature rising and cooling tests are also executed from 50°C to 200°C, and the sensitivity of temperature is 36.59 pm/°C. All the measurements of strain and temperature exhibit good linearity and stability. These results demonstrate that the metal-packaged sensors can be successfully fabricated by one-step welding technique and provide great promise for long-term and high-precision structural health monitoring.

  5. A fiber optic damage monitor

    NASA Astrophysics Data System (ADS)

    Jen, C. K.; Cielo, P.; Farnell, G. W.; Parker, M.

    A simplified fiber-optic damage monitoring system for on-line assessments of the condition of composite structural materials in F/A-18 fighters is described. Optical fibers are implanted into the composite mesh in a configuration with horizontal and vertical orientations. When light is pumped into the fibers, and failure of transmittance in either the x- or y-coordinates indicates the location of a defect at that coordinate, as revealed by the fiber damage. Attaching photodiodes to the optic fibers and connecting the entire system to a video camera and computer permits on-line monitoring of the mesh-holding panels. Sample results are provided from a system with multimode step index fibers, a VAX 11/780 computer and a video camera with a 488 x 380 cell photodiode array. Image subtraction is an effective means for fast determination of the identities of broken fibers by comparisons of images of arrays of original and damaged fibers.

  6. 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

  7. 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.

  8. Towards refractive index sensitivity of long-period gratings at level of tens of µm per refractive index unit: fiber cladding etching and nano-coating deposition.

    PubMed

    Śmietana, Mateusz; Koba, Marcin; Mikulic, Predrag; Bock, Wojtek J

    2016-05-30

    In this work we report experimental results on optimizing the refractive index (RI) sensitivity of long-period gratings (LPGs) by fiber cladding etching and thin aluminum oxide (Al2O3) overlay deposition. The presented LPG takes advantage of work in the dispersion turning point (DTP) regime as well as the mode transition (MT) effect for higher-order cladding modes (LP09 and LP010). The MT was obtained by depositing Al2O3 overlays with single-nanometer precision using the Atomic Layer Deposition method (ALD). Etching of both the overlay and the fiber cladding was performed using hydrofluoric acid (HF). For shallow etching of the cladding, i.e., DTP observed at next = 1.429 and 1.439 RIU for an LPG with no overlay, followed by deposition of an overlay of up to 167 nm in thickness, HF etching allowed for post-deposition fine-tuning of the overlay thickness resulting in a significant increase in RI sensitivity mainly at the DTP of the LP09 cladding mode. However, at an external RI (next) above 1.39 RIU, the DTP of LP010 was noticed, and its RI sensitivity exceeded 9,000 nm/RIU. Deeper etching of the cladding, i.e., DTP observed for next above 1.45 RIU, followed by the deposition of thicker overlays (up to 201 nm in thickness) allowed the sensitivity to reach values of over 40,000 nm/RIU in a narrow RI range. Sensitivity exceeding 20,000 nm/RIU was obtained in an RI range suitable for label-free biosensing applications. PMID:27410112

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

    NASA Astrophysics Data System (ADS)

    Pike, John N.; Matthews, Linn H.

    1997-10-01

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

  10. 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

  11. Effects of Carbohydrate and Dietary Fiber Intake, Glycemic Index and Glycemic Load on HDL Metabolism in Asian Populations

    PubMed Central

    Yanai, Hidekatsu; Katsuyama, Hisayuki; Hamasaki, Hidetaka; Abe, Shinichi; Tada, Norio; Sako, Akahito

    2014-01-01

    High-density lipoprotein (HDL) is a lipoprotein which has anti-atherogenic property by reverse cholesterol transport from the peripheral tissues to liver. Low HDL-cholesterol (HDL-C) levels are associated with the development of coronary artery diseases (CADs). Various epidemiological studies have suggested that the development of CAD increase in individuals with less than 40 mg/dL of HDL-C. In spite of accumulation of evidences which suggest a significant association between low HDL-C and cardiovascular diseases, effects of dietary factors on HDL metabolism remained largely unknown. There may be interracial differences in effects of dietary factors on HDL metabolism. Here we reviewed published articles about effects of carbohydrate and dietary fiber intake, glycemic index (GI) and glycemic load (GL), on HDL-C metabolism, regarding meta-analyses and clinical studies performed in Asian population as important articles. Low carbohydrate intake, GI and GL may be beneficially associated with HDL metabolism. Dietary fiber intake may be favorably associated with HDL metabolism in Asian populations. PMID:25110535

  12. A Highly Sensitive Fiber-Optic Fabry–Perot Interferometer Based on Internal Reflection Mirrors for Refractive Index Measurement

    PubMed Central

    Li, Xuefeng; Shao, Yujiao; Yu, Yuan; Zhang, Yin; Wei, Shaowen

    2016-01-01

    In this study, a new type of highly sensitive fiber-optic Fabry–Perot interferometer (FFPI) is proposed with a high sensitivity on a wide refractive index (RI) measurement range based on internal reflection mirrors of micro-cavity. The sensor head consists of a single-mode fiber (SMF) with an open micro-cavity. Since light reflections of gold thin films are not affected by the RI of different measuring mediums, the sensor is designed to improve the fringe visibility of optical interference through sputtering the gold films of various thicknesses on the inner surfaces of the micro-cavity, as a semi-transparent mirror (STM) and a total-reflection mirror (TRM). Experiments have been carried out to verify the feasibility of the sensor’s design. It is shown that the fabricated sensor has strong interference visibility exceeding 15 dB over a wide measurement range of RI, and the sensor sensitivity is higher than 1160 nm/RIU, and RI resolution is better than 1.0 × 10−6 RIU. PMID:27258273

  13. A Highly Sensitive Fiber-Optic Fabry-Perot Interferometer Based on Internal Reflection Mirrors for Refractive Index Measurement.

    PubMed

    Li, Xuefeng; Shao, Yujiao; Yu, Yuan; Zhang, Yin; Wei, Shaowen

    2016-01-01

    In this study, a new type of highly sensitive fiber-optic Fabry-Perot interferometer (FFPI) is proposed with a high sensitivity on a wide refractive index (RI) measurement range based on internal reflection mirrors of micro-cavity. The sensor head consists of a single-mode fiber (SMF) with an open micro-cavity. Since light reflections of gold thin films are not affected by the RI of different measuring mediums, the sensor is designed to improve the fringe visibility of optical interference through sputtering the gold films of various thicknesses on the inner surfaces of the micro-cavity, as a semi-transparent mirror (STM) and a total-reflection mirror (TRM). Experiments have been carried out to verify the feasibility of the sensor's design. It is shown that the fabricated sensor has strong interference visibility exceeding 15 dB over a wide measurement range of RI, and the sensor sensitivity is higher than 1160 nm/RIU, and RI resolution is better than 1.0 × 10(-6) RIU. PMID:27258273

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

    NASA Astrophysics Data System (ADS)

    Balac, Stéphane; Fernandez, Arnaud

    2014-10-01

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

  15. Fiber

    MedlinePlus

    ... broccoli, spinach, and artichokes legumes (split peas, soy, lentils, etc.) almonds Look for the fiber content of ... salsa, taco sauce, and cheese for dinner. Add lentils or whole-grain barley to your favorite soups. ...

  16. Fiber

    MedlinePlus

    ... short period of time can cause intestinal gas ( flatulence ), bloating , and abdominal cramps . This problem often goes ... 213. National Research Council. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and ...

  17. 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.

  18. Fabrication and characterization of a hybrid four-hole AsSe₂-As₂S₅ microstructured optical fiber with a large refractive index difference.

    PubMed

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

    2014-06-01

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

  19. 3D laser-written silica glass step-index high-contrast waveguides for the 3.5 μm mid-infrared range.

    PubMed

    Martínez, Javier; Ródenas, Airán; Fernandez, Toney; Vázquez de Aldana, Javier R; Thomson, Robert R; Aguiló, Magdalena; Kar, Ajoy K; Solis, Javier; Díaz, Francesc

    2015-12-15

    We report on the direct laser fabrication of step-index waveguides in fused silica substrates for operation in the 3.5 μm mid-infrared wavelength range. We demonstrate core-cladding index contrasts of 0.7% at 3.39 μm and propagation losses of 1.3 (6.5) dB/cm at 3.39 (3.68) μm, close to the intrinsic losses of the glass. We also report on the existence of three different laser modified SiO₂ glass volumes, their different micro-Raman spectra, and their different temperature-dependent populations of color centers, tentatively clarifying the SiO₂ lattice changes that are related to the large index changes. PMID:26670520

  20. 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.

  1. 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

  2. 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

  3. 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

  4. Simultaneous measurement of temperature and refractive index using focused ion beam milled Fabry-Perot cavities in optical fiber micro-tips.

    PubMed

    André, Ricardo M; Warren-Smith, Stephen C; Becker, Martin; Dellith, Jan; Rothhardt, Manfred; Zibaii, M I; Latifi, H; Marques, Manuel B; Bartelt, Hartmut; Frazão, Orlando

    2016-06-27

    Optical fiber micro-tips are promising devices for sensing applications in small volume and difficult to access locations, such as biological and biomedical settings. The tapered fiber tips are prepared by dynamic chemical etching, reducing the size from 125 μm to just a few μm. Focused ion beam milling is then used to create cavity structures on the tapered fiber tips. Two different Fabry-Perot micro-cavities have been prepared and characterized: a solid silica cavity created by milling two thin slots and a gap cavity. A third multi-cavity structure is fabricated by combining the concepts of solid silica cavity and gap cavity. This micro-tip structure is analyzed using a fast Fourier transform method to demultiplex the signals of each cavity. Simultaneous measurement of temperature and external refractive index is then demonstrated, presenting sensitivities of - 15.8 pm/K and -1316 nm/RIU, respectively. PMID:27410566

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

    NASA Astrophysics Data System (ADS)

    Gao, Peng; Chen, Xiuyan; Feng, Wenjiang

    2012-10-01

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

  6. Refractive index sensitivity of optical fiber lossy-mode resonance sensors based on atomic layer deposited TiOx thin overlay

    NASA Astrophysics Data System (ADS)

    Burnat, Dariusz; Koba, Marcin; Wachnicki, Łukasz; Gierałtowska, Sylwia; Godlewski, Marek; Śmietana, Mateusz

    2016-05-01

    This work presents an optical fiber refractive index sensors based on lossy-mode resonance (LMR) effect supported by titanium oxide (TiOx) thin overlay. The TiOx overlays of different thickness were deposited on core of polymer-clad silica (PCS) fibers using atomic layer deposition (ALD) method. Based on numerical simulations, a number of structures differing in the location of exposed core area and the thickness of TiOx coatings were designed. For fabricated structures the spectral response to external refractive index (next) was measured. The maximum sensitivity reaches 634.2 nm/RIU (next range: 1.357 - 1.402 RIU; TiOx coating thickness: 260.9 nm; investigated spectral range: 500-800 nm) and it highly depends on the thin-film thickness.

  7. Wavelength switching of picosecond pulses generated from a self-seeded Fabry-Perot laser diode with a tilted fiber Bragg grating formed in a graded-index multimode fiber.

    PubMed

    Liu, Yunqi; Chiang, Kin Seng

    2011-02-20

    We demonstrated the generation of wavelength-switchable picosecond pulses from a self-seeded Fabry-Perot laser diode that used a tilted fiber Bragg grating (FBG) formed in a graded-index multimode fiber as an external optical feedback element, where wavelength switching was achieved by controlling the modal distribution in the FBG. We measured the reflection spectra of multimode FBGs fabricated with different tilt angles and discussed the effects of the tilt angle on wavelength selection. By using a 20 mm long 1.65° tilted FBG and a fiber deformer to control the modal distribution in the FBG, we generated 2 GHz pulses with a wavelength switchable over 14 wavelengths at a spacing of ∼0.8 nm. PMID:21343961

  8. 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.

  9. Mode scalability in bent optical fibers.

    PubMed

    Schermer, Ross T

    2007-11-26

    This paper introduces a simple, analytical method for generalizing the behavior of bent, weakly-guided fibers and waveguides. It begins with a comprehensive study of the modes of the bent step-index fiber, which is later extended to encompass a wide range of more complicated waveguide geometries. The analysis is based on the introduction of a scaling parameter, analogous to the V-number for straight step-index fibers, for the bend radius. When this parameter remains constant, waveguides of different bend radii, numerical apertures and wavelengths will all propagate identical mode field distributions, except scaled in size. This allows the behavior of individual waveguides to be broadly extended, and is especially useful for generalizing the results of numerical simulations. The technique is applied to the bent step-index fiber in this paper to arrive at simple analytical formulae for the propagation constant and mode area, which are valid well beyond the transition to whispering-gallery modes. Animations illustrating mode deformation with respect to bending and curves describing polarization decoupling are also presented, which encompass the entire family of weakly-guided, step-index fibers. PMID:19550854

  10. 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

  11. Refractive index detection range adjustable liquid-core fiber optic sensor based on surface plasmon resonance and a nano-porous silica coating

    NASA Astrophysics Data System (ADS)

    Chen, Yuzhi; Li, Xuejin; Zhou, Huasheng; Hong, Xueming; Geng, Youfu

    2016-09-01

    A liquid-core fiber optic surface plasmon resonance sensor with an adjustable nano-porous silica coating is first presented in this paper. By adjusting the refractive index of the nano-porous silica coating, the sensor can be used in different refractive index detection ranges. A low refractive index interval of 1.33–1.34 and a high refractive index interval of 1.42–1.44 are taken as examples to be investigated. Results show that our sensor works well in these two intervals by using appropriate nano-porous silica coatings. The highest sensitivities of the low and high refractive index intervals are obtained to be 5840 nm/RIU and 5120 nm/RIU, respectively. In addition, the sensing performances and the working wavelengths can be adjusted to meet different working requirements by changing the refractive index of the nano-porous silica coating. We also take the single mode incidence cases to explain the effects of different single incident light modes on the sensing performances.

  12. Glycemic index, glycemic load, dietary carbohydrate, and dietary fiber intake and risk of liver and biliary tract cancers in Western Europeans

    PubMed Central

    Fedirko, V.; Lukanova, A.; Bamia, C.; Trichopolou, A.; Trepo, E.; Nöthlings, U.; Schlesinger, S.; Aleksandrova, K.; Boffetta, P.; Tjønneland, A.; Johnsen, N. F.; Overvad, K.; Fagherazzi, G.; Racine, A.; Boutron-Ruault, M. C.; Grote, V.; Kaaks, R.; Boeing, H.; Naska, A.; Adarakis, G.; Valanou, E.; Palli, D.; Sieri, S.; Tumino, R.; Vineis, P.; Panico, S.; Bueno-de-Mesquita, H. B(as).; Siersema, P. D.; Peeters, P. H.; Weiderpass, E.; Skeie, G.; Engeset, D.; Quirós, J. R.; Zamora-Ros, R.; Sánchez, M. J.; Amiano, P.; Huerta, J. M.; Barricarte, A.; Johansen, D.; Lindkvist, B.; Sund, M.; Werner, M.; Crowe, F.; Khaw, K. T.; Ferrari, P.; Romieu, I.; Chuang, S. C.; Riboli, E.; Jenab, M.

    2013-01-01

    Background The type and quantity of dietary carbohydrate as quantified by glycemic index (GI) and glycemic load (GL), and dietary fiber may influence the risk of liver and biliary tract cancers, but convincing evidence is lacking. Patients and methods The association between dietary GI/GL and carbohydrate intake with hepatocellular carcinoma (HCC; N = 191), intrahepatic bile duct (IBD; N = 66), and biliary tract (N = 236) cancer risk was investigated in 477 206 participants of the European Prospective Investigation into Cancer and Nutrition cohort. Dietary intake was assessed by country-specific, validated dietary questionnaires. Hazard ratios and 95% confidence intervals were estimated from proportional hazard models. HBV/HCV status was measured in a nested case–control subset. Results Higher dietary GI, GL, or increased intake of total carbohydrate was not associated with liver or biliary tract cancer risk. For HCC, divergent risk estimates were observed for total sugar = 1.43 (1.17–1.74) per 50 g/day, total starch = 0.70 (0.55–0.90) per 50 g/day, and total dietary fiber = 0.70 (0.52–0.93) per 10 g/day. The findings for dietary fiber were confirmed among HBV/HCV-free participants [0.48 (0.23–1.01)]. Similar associations were observed for IBD [dietary fiber = 0.59 (0.37–0.99) per 10 g/day], but not biliary tract cancer. Conclusions Findings suggest that higher consumption of dietary fiber and lower consumption of total sugars are associated with lower HCC risk. In addition, high dietary fiber intake could be associated with lower IBD cancer risk. PMID:23123507

  13. Optical communication technology. II - Properties of optical fibers

    NASA Astrophysics Data System (ADS)

    1980-07-01

    The pulse dispersion of short light impulses is examined with respect to mode, waveguides, and material and profile dispersion. Impulse expansions of up to 50 ns/km are measured and equations for calculating light impulses from fiber length and light speed in vacuum are presented, together with equations of refraction profiles and profile patterns. Attention is given to multimode-step index fibers, gradient fibers, and monomode fibers as well as to their differing properties. Diagrams of numerical aperture, light dispersion (of the above mentioned fiber types), and interference of two waveguides are given.

  14. Polymer Clad Silica Fibers for Tailoring Modal Area and Dispersion

    PubMed Central

    Rishøj, Lars; Jones, Maxwell; Demas, Jeffrey; Gregg, Patrick; Prabhakar, Gautam; Yan, Lu; Hawkins, Thomas; Ballato, John; Ramachandran, Siddharth

    2016-01-01

    We demonstrate higher-order-mode (Aeff up to ~2000 μm2) propagation in a 100 μm outer diameter pure-silica fiber with a low-index polymer jacket commonly used for fiber-laser pump-guidance. This simple structure obviates the need for complex designs deemed necessary for realizing large-mode-area fibers. Modes ranging from HE1,12 to HE1,22 were found to propagate stably over 15 m in this fiber. The index step is approximately 4 times larger than that obtained with fluorine down doping, thus the fiber supports even higher order modes, which may have implications for building rare earth doped fiber lasers or achieving enhanced dispersion tunability for high-energy fiber nonlinear phenomena. PMID:27472625

  15. Evaluation and optimization of a reusable hollow fiber ultrafilter as a first step in concentrating Cryptosporidium parvum oocysts from water.

    PubMed

    Kuhn, R C; Oshima, K H

    2001-08-01

    Experiments with a small-scale hollow fiber ultrafiltration system (50,000 MWCO) was used to characterize the filtration process and identify conditions that optimize the recovery of Cryptosporidium parvum oocysts from 2 L samples of water. Seeded experiments were conducted using deionized water as well as four environmental water sources (tap, ground, Arkansas river, and Rio Grande river; 0-30.9NTU). Optimal and consistent recovery of spiked oocysts was observed (68-81%), when the membrane was sanitized with a 10% sodium dodecyl sulfate (SDS) solution and then blocked with 5% fetal bovine serum (FBS). PMID:11456179

  16. Increased sensitivity of femtosecond laser micro-machined in-fiber Mach-Zehnder interferometer for small-scale refractive index sensing

    NASA Astrophysics Data System (ADS)

    Debowska, Anna K.; Koba, Marcin; Janik, Monika; Bock, Wojtek J.; Śmietana, Mateusz

    2016-05-01

    In this paper we focus on refractive index (RI) sensing properties of a micro-size In-fiber Mach-Zehnder Interferometer (μIMZI). The μIMZI structure was fabricated as a precisely controlled side opening of a single-mode fiber using a femtosecond laser. The sensitivity to RI change in the micro-cavity has been measured and two RI sensitivity regions have been found for RI 1.33-1.36 and 1.37-1.40 RIU. The sensitivity in the first region is over 12,000 nm/RIU, and in the higher RI region is close to 50% higher. The obtained structures are an excellent solution for RI sensing with negligible temperature cross-sensitivity, especially where small amounts of liquid are available, e.g. in lab-on-chip, microfluidics.

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

    SciTech Connect

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

    2015-12-17

    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.

  18. 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.

  19. Fiber based generation of azimuthally polarized light

    NASA Astrophysics Data System (ADS)

    Jocher, Christoph; Jauregui, Cesar; Voigtländer, Christian; Stutzki, Fabian; Nolte, Stefan; Limpert, Jens; Tünnermann, Andreas

    2012-02-01

    We report on a novel approach for the generation of radially and azimuthally polarized light employing a fiber mode filter. The mode filter consists of a Fiber Bragg Grating written in a strongly guiding fiber with lifted modal degeneracy. These kinds of fibers guide radially and azimuthally polarized modes with non-degenerated, i.e. distinct, effective refractive indexes. The Fiber Bragg Grating reflects light only if the Bragg condition is fulfilled. In case of strongly guiding fibers the radially and azimuthally polarized modes are guided with different effective refractive indices and, consequently, the Bragg condition is fulfilled at different wavelengths. If the reflection bandwidth of the Fiber Bragg Grating is narrow enough, the radially and azimuthally polarized modes are spectrally separated. Thus, with such a mode filter it is possible to filter the radially or azimuthally polarized mode. This filter is suitable for its integration in a resonator for stable, compact and high polarization purity azimuthally and radially polarized all-fiber oscillators. In a first experiment an azimuthally polarized mode filter consisting of a commercially available step index fiber and a femtosecond written Fiber Bragg Grating was fabricated. The experimental results are presented and discussed.

  20. Novel step-tunable wavelength-swept optical system based on a SSB modulator driven by a RF generator for fiber sensing networks

    NASA Astrophysics Data System (ADS)

    Yang, Tianxin; Qiu, Changren; Wang, Changle; Wang, Zhaoying; Ge, Chunfeng; Sang, Mei

    2012-03-01

    High resolution wavelength-tunable lasers are essential to sensing applications. For sensing applications, high resolution is needed to improve the spatial resolution and/or measurement accuracy, and fast tuning (sweeping) is required to enhance the measurement speed for dynamic sensing. However the demand of high resolution conflicts with the requirement of fast continuous wavelength tuning. The solution to this issue is tuning the wavelength of the output in a quasi-continuous way in which the length of each step is dependent on the frequency of a RF generator which is used to drive a single-sideband (SSB) modulator in the wavelength-swept optical system. In this paper, a principle of the step-tunable wavelength-swept optical system is proposed and demonstrated. The two optical features of narrow bandwidth and fairly high optical output power make the system unique for improving the accuracy of the measurement of the center-wavelength of a fiber Bragg grating (FBG) sensor. In addition, changing the tuning-step by adjusting the frequency of a RF generator electrically is user-friendly compared to the conventional wavelength swept systems by tuning optical elements mechanically.

  1. 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

  2. Numerical Investigation on Performance of In-Building Plastic Optical Fiber Transmission Systems and Role of Digital Television Broadcasting

    NASA Astrophysics Data System (ADS)

    Matera, Francesco; Tiano, Stefania; Settembre, Marina

    2012-07-01

    This article reports a numerical investigation on the transmission performance of multilevel systems operating in building links encompassing step-index plastic optical fibers. For such an aim, a simplified model for the multimode fiber propagation is introduced. A sub-carrier multiplexing technique is also simulated to demonstrate the distribution of broadcasting television channels by adopting such fibers. The reported results show that a unique building network based on step-index plastic optical fibers is suitable to carry both Ethernet and broadcast TV signals in all rooms.

  3. 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.

  4. 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.

  5. 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

  6. Confocal microscopy via multimode fibers: fluorescence bandwidth

    NASA Astrophysics Data System (ADS)

    Loterie, Damien; Psaltis, Demetri; Moser, Christophe

    2016-03-01

    We recently described a method for confocal reflection imaging through fibers, as a way to increase contrast when imaging unstained biological specimens. Using a transmission matrix, focused spots can be created at the distal end of a fiber. The backscattered field coming back from the sample can be filtered using optical correlation to obtain spatial selectivity in the detection. In this proceedings article, we briefly review the working principle of this method, and we discuss how the scheme could be adapted to confocal fluorescence imaging. In particular, we show simulations of the achievable detection bandwidth when using step-index multimode fibers as imaging devices.

  7. 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.

  8. 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 19.6°C-20.1°C, 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 20°C 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 14.6°C-24.0°C as well. PMID:25968028

  9. 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.

  10. Phase-shift formed in a long period fiber grating and its application to the measurements of temperature and refractive index.

    PubMed

    Hishiki, Keisuke; Li, Hongpu

    2013-05-20

    A novel approach to calibrate a phase-shift formed in a long-period fiber grating (LPG) is firstly proposed and numerically demonstrated, which is based on the use of either intensity- or wavelength-interrogation technique to the main loss-peak of the phase-shift LPG in the spectrum. Moreover, by using a CO2 laser with high-repetition-rate pulses emission, an equivalent phase-shift is successfully created at middle of the LPG. As an application of the proposed calibration scheme, measurement for the temperature and the refractive index of the ambient solution has been proposed and successfully demonstrated by using a phase-shifted LPG. PMID:23736412