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Sample records for bragg gratings photosensitivity

  1. Thermal Stability of Photosensitive Bragg Gratings in Sputter-Deposited Germanosilicate Glass

    SciTech Connect

    POTTER JR.,BARRETT G.; POTTER,KELLY SIMMONS; DUNBAR,TIMOTHY D.

    2000-07-24

    The thermal stability of photo-imprinted Bragg gratings formed in reactive-atmosphere, RF-magnetron sputtered germanosilicate thin films was evaluated in terms of point defect modifications observed during isochronal annealing. Optical and magnetic spectroscopes were utilized to evaluate structural relaxation in these sputtered glasses on both a local and medium-range size scale. Depending upon the substrate temperature used during deposition, significant structural rearrangement was found to occur with increasing post-deposition anneal temperature to 600 C. This resulted in changes in the photobleaching response of the material itself as the identity of optically active structural defects evolved. Based on a color center model for photosensitivity in these materials and measured changes in optical absorption with annealing, the thermal stability of a photo-imprinted Bragg grating was modeled. Good qualitative agreement with experiment was observed.

  2. Apodized Volume Bragg Gratings

    NASA Astrophysics Data System (ADS)

    Mokhov, Sergiy

    2015-03-01

    Reflective and transmissive volume Bragg grating (VBGs) are widely used in high power laser applications because of their large operational aperture and robustness. They are fabricated in photosensitive material through holographic recording of uniform interference pattern of two overlapping coherent waves obtained by splitting a flat-top shaped laser beam. The following thermal treatment produces permanent refractive index modulation (RIM). Reflective VBGs have fringes parallel to operational anti-reflective coated surfaces and they demonstrate narrow reflection bandwidth. Transmissive VBGs are cut with fringes perpendicular to surfaces and they are characterized by narrow angular selectivity. Uniform RIM causes secondary lobes in corresponding reflection and transmission spectra due to sharp boundary conditions for volume Bragg diffraction. We propose to create apodization of RIM by recording two interference patterns with slightly different parameters in the same volume which would create slow varying moire envelope of amplitude of RIM. Cutting the specimen at zeros of moire envelope with one sine semi-period thickness will produce VBGs apodized at sides which will reduce parasitic secondary lobes in spectra. In reflection geometry, two patterns of the same orientation with slightly different periods are required for apodization along Bragg wave vector. In transmission case, recording of the same interference patterns with small mutual rotation angle provides apodization in direction perpendicular to Bragg wave vector. Modeling results show significant improvement in selective properties of VBGs with such moire apodization.

  3. Type IIa Bragg gratings formed in microfibers.

    PubMed

    Ran, Yang; Jin, Long; Gao, Shuai; Sun, Li-Peng; Huang, Yun-Yun; Li, Jie; Guan, Bai-Ou

    2015-08-15

    In this Letter, Type IIa Bragg gratings are inscribed into microfibers. The large germanium-doped core region of the multimode fiber provides the necessary photosensitivity to form a Type IIa grating when it is drawn down to the microscale. Reducing the diameter of the microfiber due to lower saturate modulation and the amplified tension-strain transformation effect can accelerate the formation of a Type IIa grating. This provides an efficient method for the fabrication of fiber gratings with 800°C temperature resistance. PMID:26274664

  4. Planar Bragg grating in bulk polymethylmethacrylate.

    PubMed

    Rosenberger, M; Koller, G; Belle, S; Schmauss, B; Hellmann, R

    2012-12-01

    We report on a one-step writing process of a planar waveguide including a Bragg grating structure in bulk Polymethylmethacrylate (PMMA). A KrF excimer laser and a phase mask covered by an amplitude mask were used to locally increase the refractive index in PMMA and thereby generate simultaneously the planar waveguide and the Bragg grating. Our results show a reflected wavelength of the Bragg grating of about 1558.5 nm in accordance to the phase mask period. The reflectivity of the grating is about 80%. Initial characteristics of the Bragg grating structure towards humidity are investigated.

  5. Advanced Fibre Bragg Grating and Microfibre Bragg Grating Fabrication Techniques

    NASA Astrophysics Data System (ADS)

    Chung, Kit Man

    Fibre Bragg gratings (FBGs) have become a very important technology for communication systems and fibre optic sensing. Typically, FBGs are less than 10-mm long and are fabricated using fused silica uniform phase masks which become more expensive for longer length or non-uniform pitch. Generally, interference UV laser beams are employed to make long or complex FBGs, and this technique introduces critical precision and control issues. In this work, we demonstrate an advanced FBG fabrication system that enables the writing of long and complex gratings in optical fibres with virtually any apodisation profile, local phase and Bragg wavelength using a novel optical design in which the incident angles of two UV beams onto an optical fibre can be adjusted simultaneously by moving just one optical component, instead of two optics employed in earlier configurations, to vary the grating pitch. The key advantage of the grating fabrication system is that complex gratings can be fabricated by controlling the linear movements of two translation stages. In addition to the study of advanced grating fabrication technique, we also focus on the inscription of FBGs written in optical fibres with a cladding diameter of several ten's of microns. Fabrication of microfibres was investigated using a sophisticated tapering method. We also proposed a simple but practical technique to filter out the higher order modes reflected from the FBG written in microfibres via a linear taper region while the fundamental mode re-couples to the core. By using this technique, reflection from the microfibre Bragg grating (MFBG) can be effectively single mode, simplifying the demultiplexing and demodulation processes. MFBG exhibits high sensitivity to contact force and an MFBG-based force sensor was also constructed and tested to investigate their suitability for use as an invasive surgery device. Performance of the contact force sensor packaged in a conforming elastomer material compares favourably to one

  6. Fabrication and Characterization of Tilted Fiber Optic Bragg Grating Filters over Various Wavelengths

    NASA Technical Reports Server (NTRS)

    Grant, Joseph; Jackson, Kurt V.; Wang, Y.; Sharma, A.; Burdine, Robert V. (Technical Monitor)

    2002-01-01

    Fiber Optic Bragg Grating taps are fabricated and characterized at various wavelengths using a modified Talbot interferometric technique. Gratings are fabricated by tilting the photosensitive fiber to angles up to 45 degrees w.r.t. the writing angle. Diffraction characteristics of the tilted grating is monitored in first and second orders.

  7. Cross-fiber Bragg grating transducer

    NASA Technical Reports Server (NTRS)

    Albin, Sacharia (Inventor); Zheng, Jianli (Inventor); Lavarias, Arnel (Inventor)

    2000-01-01

    A transducer has been invented that uses specially-oriented gratings in waveguide a manner that allows the simultaneous measurement of physical phenomena (such as shear force, strain and temperature) in a single sensing element. The invention has a highly sensitive, linear response and also has directional sensitivity with regard to strain. The transducer has a waveguide with a longitudinal axis as well as two Bragg gratings. The transducer has a first Bragg grating associated with the waveguide that has an angular orientation .theta..sub.a relative to a perpendicular to the longitudinal axis such that 0.degree.<.theta..sub.a <.theta..sub.max. The second Bragg grating is associated with the waveguide in such a way that the angular orientation .theta..sub.b of the grating relative to a perpendicular to the longitudinal axis is (360.degree.-.theta..sub.max)<.theta..sub.b <360.degree.. The first Bragg grating can have a periodicity .LAMBDA..sub.a and the second Bragg grating can have a periodicity .LAMBDA..sub.b such that the periodicity .LAMBDA..sub.a of the first Bragg grating does not equal the periodicity .LAMBDA..sub.b of the second Bragg grating. The angle of the gratings can be such that .theta..sub.a =360.degree.-.theta..sub.b. The waveguide can assume a variety of configurations, including an optical fiber, a rectangular waveguide and a planar waveguide. The waveguide can be fabricated of a variety of materials, including silica and polymer material.

  8. Direct infrared femtosecond laser inscription of chirped fiber Bragg gratings.

    PubMed

    Antipov, Sergei; Ams, Martin; Williams, Robert J; Magi, Eric; Withford, Michael J; Fuerbach, Alexander

    2016-01-11

    We compare and contrast novel techniques for the fabrication of chirped broadband fiber Bragg gratings by ultrafast laser inscription. These methods enable the inscription of gratings with flexible period profiles and thus tailored reflection and dispersion characteristics in non-photosensitive optical fibers. Up to 19.5 cm long chirped gratings with a spectral bandwidth of up to 30 nm were fabricated and the grating dispersion was characterized. A maximum group delay of almost 2 ns was obtained for linearly chirped gratings with either normal or anomalous group velocity dispersion, demonstrating the potential for using these gratings for dispersion compensation. Coupling to cladding modes was reduced by careful design of the inscribed modification features. PMID:26832235

  9. Thermally triggered fiber lasers based on secondary-type-In Bragg gratings.

    PubMed

    Feng, Fu-Rong; Ran, Yang; Liang, Yi-Zhi; Gao, Shuai; Feng, Yuan-Hua; Jin, Long; Guan, Bai-Ou

    2016-06-01

    The secondary-type-In grating formed in a small-core photosensitivity active fiber is discovered and investigated. Due to the different grating types, the transmission dip of a secondary grating structure chases and integrates with the type-In grating structure as the temperature increases, which strengthens the reflectivity of the grating. By use of these secondary-type-In gratings as Bragg reflectors, a thermally activated distributed Bragg reflector (DBR) fiber laser is proposed, which can be potentially used in high-temperature alarms and sensors. PMID:27244391

  10. Fibre Bragg grating for flood embankment monitoring

    NASA Astrophysics Data System (ADS)

    Markowski, Konrad; Nevar, Stanislau; Dworzanski, Adam; Hackiewicz, Krzysztof; Jedrzejewski, Kazimierz

    2014-11-01

    In this article we present the preliminary studies for the flood embankment monitoring system based on the fibre Bragg gratings. The idea of the system is presented. The Bragg resonance shift is transformed to the change of the power detected by the standard InGaAs photodiode. The discrimination of the received power was executed by another fibre Bragg grating with different parameters. The project of the fully functional system is presented as well.

  11. Birefringence Bragg Binary (3B) grating, quasi-Bragg grating and immersion gratings

    NASA Astrophysics Data System (ADS)

    Ebizuka, Noboru; Morita, Shin-ya; Yamagata, Yutaka; Sasaki, Minoru; Bianco, Andorea; Tanabe, Ayano; Hashimoto, Nobuyuki; Hirahara, Yasuhiro; Aoki, Wako

    2014-07-01

    A volume phase holographic (VPH) grating achieves high angular dispersion and very high diffraction efficiency for the first diffraction order and for S or P polarization. However the VPH grating could not achieve high diffraction efficiency for non-polarized light at a large diffraction angle because properties of diffraction efficiencies for S and P polarizations are different. Furthermore diffraction efficiency of the VPH grating extinguishes toward a higher diffraction order. A birefringence binary Bragg (3B) grating is a thick transmission grating with optically anisotropic material such as lithium niobate or liquid crystal. The 3B grating achieves diffraction efficiency up to 100% for non-polarized light by tuning of refractive indices for S and P polarizations, even in higher diffraction orders. We fabricated 3B grating with liquid crystal and evaluated the performance of the liquid crystal grating. A quasi-Bragg (QB) grating, which consists long rectangle mirrors aligned in parallel precisely such as a window shade, also achieves high diffraction efficiency toward higher orders. We fabricated QB grating by laminating of silica glass substrates and glued by pressure fusion of gold films. A quasi-Bragg immersion (QBI) grating has smooth mirror hypotenuse and reflector array inside the hypotenuse, instead of step-like grooves of a conventional immersion grating. An incident beam of the QBI grating reflects obliquely at a reflector, then reflects vertically at the mirror surface and reflects again at the same reflector. We are going to fabricate QBI gratings by laminating of mirror plates as similar to fabrication of the QB grating. We will also fabricate silicon and germanium immersion gratings with conventional step-like grooves by means of the latest diamond machining methods. We introduce characteristics and performance of these gratings.

  12. Polymer planar Bragg grating for sensing applications

    NASA Astrophysics Data System (ADS)

    Rosenberger, M.; Hartlaub, N.; Koller, G.; Belle, S.; Schmauss, B.; Hellmann, R.

    2013-05-01

    Bragg gratings have become indispensable as optical sensing elements and are already used for a variety of technical applications. Mainly silica fiber Bragg gratings (FBGs) have been extensively studied over the last decades and are nowadays commercially available. Bragg grating sensors consisting of other materials like polymers, however, have only recently come into the focus of fundamental and applied research. Polymers exhibit significantly different properties advantageous for many sensing applications and therefore provide a good alternative to silica based devices. In addition, polymer materials are inexpensive, simple to handle as well as available in various forms like liquid resists or bulk material. Accordingly, polymer integrated optics attract increasing interest and can serve as a substitute for optical fibers. We report on the fabrication of a planar Bragg grating sensor in bulk Polymethylmethacrylate (PMMA). The sensor consists of an optical waveguide and a Bragg grating, both written simultaneously into a PMMA chip by a single writing step, for which a phase mask covered by an amplitude mask is placed on top of the PMMA and exposed to the UV radiation of a KrF excimer laser. Depending on the phase mask period, different Bragg gratings reflecting in the telecommunication wavelength range are fabricated and characterized. Reflection and transmission measurements show a narrow reflection band and a high reflectivity of the polymer planar Bragg grating (PPBG). After connecting to a single mode fiber, the portable PPBG based sensor was evaluated for different measurands like humidity and strain. The sensor performance was compared to already existing sensing systems. Due to the obtained results as well as the rapid and cheap fabrication of the sensor chip, the PPBG qualifies for a low cost sensing element.

  13. Strongly Dispersive Transient Bragg Grating for High Harmonics

    SciTech Connect

    Farrell, J.; Spector, L.S.; Gaarde, M.B.; McFarland, B.K.; Bucksbaum, P.H.; Guhr, Markus; /SLAC, PULSE /Stanford U., Phys. Dept. /Stanford U., Appl. Phys. Dept.

    2010-06-04

    We create a transient Bragg grating in a high harmonic generation medium using two counterpropagating pulses. The Bragg grating disperses the harmonics in angle and can diffract a large bandwidth with temporal resolution limited only by the source size.

  14. Fiber Bragg Grating Filter High Temperature Sensors

    NASA Technical Reports Server (NTRS)

    Lyons, Donald R.; Brass, Eric D.; Pencil, Eric (Technical Monitor)

    2001-01-01

    We present a scaled-down method for determining high temperatures using fiber-based Bragg gratings. Bragg gratings are distributed along the length of the optical fiber, and have high reflectivities whenever the optical wavelength is twice the grating spacing. These spatially distinct Bragg regions (located in the core of a fiber) are sensitive to local temperature changes. Since these fibers are silica-based they are easily affected by localized changes in temperature, which results in changes to both the grating spacing and the wavelength reflectivity. We exploit the shift in wavelength reflectivity to measure the change in the local temperature. Note that the Bragg region (sensing area) is some distance away from where the temperature is being measured. This is done so that we can measure temperatures that are much higher than the damage threshold of the fiber. We do this by affixing the fiber with the Bragg sensor to a material with a well-known coefficient of thermal expansion, and model the heat gradient from the region of interest to the actual sensor. The research described in this paper will culminate in a working device as well as be the second portion of a publication pending submission to Optics Letters.

  15. Second-order Bragg gratings in single-mode chalcogenide fibres

    SciTech Connect

    Bernier, M; Asatryan, K E; Vallee, R; Galstian, T M; Vasil'ev, Sergei A; Medvedkov, O I; Plotnichenko, V G; Gnusin, P I; Dianov, Evgenii M

    2011-05-31

    Bragg gratings with a second-order resonance wavelength in the near-IR spectral region have been inscribed into single-mode chalcogenide (As{sub 2}S{sub 3}) glass fibre by a He - Ne laser beam using a configuration typical of Bragg grating fabrication in germanosilicate fibre, with the use of a phase mask that ensures effective diffraction of the writing light into the +1 and -1 orders. The spectra of the inscribed gratings show no resonances due to cladding mode excitation because the cladding material is photosensitive. (fibre optics)

  16. Top-hat random fiber Bragg grating.

    PubMed

    Yin, Hongwei; Gbadebo, Adenowo; Turitsyna, Elena G

    2015-08-01

    We examined the possibility of using noise or pseudo-random variations of the refractive index in the design of fiber Bragg gratings (FBGs). We demonstrated theoretically and experimentally that top-hat FBGs may be designed and fabricated using this approach. The reflectivity of the fabricated top-hat FBG matches quite well with that of the designed one. PMID:26258365

  17. Thermal annealing of tilted fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    González-Vila, Á.; Rodríguez-Cobo, L.; Mégret, P.; Caucheteur, C.; López-Higuera, J. M.

    2016-05-01

    We report a practical study of the thermal decay of cladding mode resonances in tilted fiber Bragg gratings, establishing an analogy with the "power law" evolution previously observed on uniform gratings. We examine how this process contributes to a great thermal stability, even improving it by means of a second cycle slightly increasing the annealing temperature. In addition, we show an improvement of the grating spectrum after annealing, with respect to the one just after inscription, which suggests the application of this method to be employed to improve saturation issues during the photo-inscription process.

  18. Fiber Bragg Grating Sensors for Harsh Environments

    PubMed Central

    Mihailov, Stephen J.

    2012-01-01

    Because of their small size, passive nature, immunity to electromagnetic interference, and capability to directly measure physical parameters such as temperature and strain, fiber Bragg grating sensors have developed beyond a laboratory curiosity and are becoming a mainstream sensing technology. Recently, high temperature stable gratings based on regeneration techniques and femtosecond infrared laser processing have shown promise for use in extreme environments such as high temperature, pressure or ionizing radiation. Such gratings are ideally suited for energy production applications where there is a requirement for advanced energy system instrumentation and controls that are operable in harsh environments. This paper will present a review of some of the more recent developments. PMID:22438744

  19. An optical fiber Bragg grating tactile sensor

    NASA Astrophysics Data System (ADS)

    Cowie, Barbara; Allsop, Thomas; Williams, John; Webb, David; Bennion, Ian; Fisher, Matthew

    2007-05-01

    Tactile sensors are needed for many emerging robotic and telepresence applications such as keyhole surgery and robot operation in unstructured environments. We have proposed and demonstrated a tactile sensor consisting of a fibre Bragg grating embedded in a polymer "finger". When the sensor is placed in contact with a surface and translated tangentially across it measurements on the changes in the reflectivity spectrum of the grating provide a measurement of the spatial distribution of forces perpendicular to the surface and thus, through the elasticity of the polymer material, to the surface roughness. Using a sensor fabricated from a Poly Siloxane polymer (Methyl Vinyl Silicone rubber) spherical cap 50 mm in diameter, 6 mm deep with an embedded 10 mm long Bragg grating we have characterised the first and second moment of the grating spectral response when scanned across triangular and semicircular periodic structures both with a modulation depth of 1 mm and a period of 2 mm. The results clearly distinguish the periodicity of the surface structure and the differences between the two different surface profiles. For the triangular structure a central wavelength modulation of 4 pm is observed and includes a fourth harmonic component, the spectral width is modulated by 25 pm. Although crude in comparison to human senses these results clearly shown the potential of such a sensor for tactile imaging and we expect that with further development in optimising both the grating and polymer "finger" properties a much increased sensitivity and spatial resolution is achievable.

  20. Fiber Bragg grating cryogenic temperature sensors

    NASA Astrophysics Data System (ADS)

    Gupta, Sanjay; Mizunami, Toru; Yamao, Takashi; Shimomura, Teruo

    1996-09-01

    Temperature sensing to as low as 80 K was demonstrated with 1.55- mu m fiber Bragg gratings. The gratings were bonded on substrates to increase sensitivity, and a shift of the reflection wavelength was measured. The temperature sensitivity was 0.02 nm/K at 100 K when an aluminum substrate was used and 0.04 nm/K at 100 K when a poly(methyl methacrylate) substrate was used. These values are smaller than those at room temperature because of the nonlinearity of both the thermal expansion and the thermo-optic effect. Extension to the liquid helium temperature is also discussed.

  1. Cross-slot waveguide Bragg grating

    NASA Astrophysics Data System (ADS)

    Roussey, Matthieu; Stenberg, Petri; Bera, Arijit; Paul, Somnath; Tervo, Jani; Kuittinen, Markku; Honkanen, Seppo

    2015-02-01

    A polarization independent band-pass filter is created by combining a silicon cross-slot waveguide and a Bragg grating cavity. By theoretically investigating different types of cavities we show how the sensitivity to polarization of the device can vary, and how we can strongly confine light in a two-dimensional slot waveguide. This kind of structure, where a slot waveguide, a photonic crystal and a nanowire waveguide are merged together, may find applications in the field of sensing. Indeed, a slight variation in the surrounding refractive index breaks the device symmetry. One polarization can thus be used to monitor the fluctuation of the other one. We describe here the principle of a Bragg grating merged with a cross slot waveguide in which a cavity is placed. We discuss the advantage of using different geometries of cavity and how this choice may affect the response of the device.

  2. Fiber Bragg grating based tunable sensitivity goniometer

    NASA Astrophysics Data System (ADS)

    Padma, Srivani; Umesh, Sharath; Pant, Shweta; Srinivas, Talabattula; Asokan, Sundarrajan

    2016-03-01

    Goniometer has found extensive usage in diverse applications, primary being medical field in which it is employed for obtaining the range of motion of joints during physical therapy. It is imperative to have a dynamic system to measure the range of motion which will aid for a progressive therapeutic treatment. Hence in the present study, a novel goniometer for real time dynamic angle measurement between two surfaces with the aid of a Fiber Bragg Grating sensor is proposed. The angular rotation between the two surfaces will be identified by the two arms of the Fiber Bragg Grating Goniometer (FBGG), which is translated to the rotation of the shaft which holds these arms together. A cantilever beam is fixed onto the base plate whose free end is connected to the rotating shaft. The rotating shaft will actuate a mechanism which will pull the free end of the cantilever resulting in strain variation over the cantilever beam. The strain variation on the cantilever beam is measured by the Fiber Bragg Grating sensor bonded over it. Further, the proposed FBGG facilitates tunable sensitivity by the discs of varying diameters on the rotating shaft. Tunable sensitivity of the FBGG is realised by the movement of these discs by varying circumferential arc lengths for the same angular movement, which will actuate the pull on the cantilever beam. As per the requirement of the application in terms of resolution and range of angular measurement, individual mode of sensitivity may be selected.

  3. High efficiency holographic Bragg grating with optically prolonged memory

    PubMed Central

    Khoo, Iam Choon; Chen, Chun-Wei; Ho, Tsung-Jui

    2016-01-01

    In this paper, we show that photosensitive azo-dye doped Blue-phase liquid crystals (BPLC) formed by natural molecular self-assembly are capable of high diffraction efficiency holographic recording with memory that can be prolonged from few seconds to several minutes by uniform illumination with the reference beam. Operating in the Bragg regime, we have observed 50 times improvement in the grating diffraction efficiency and shorter recording time compared to previous investigations. The enabling mechanism is BPLC’s lattice distortion and index modulation caused by the action of light on the azo-dopant; upon photo-excitation, the azo-molecules undergo transformation from the oblong-shaped Trans-state to the bent-shaped Cis-state, imparting disorder and also cause the surrounding BPLC molecules to undergo coupled flow & reorientation leading to lattice distortion and index modulation. We also showed that the same mechanism at work here that facilitates lattice distortion can be used to frustrate free relaxation of the lattice distortion, thereby prolonging the lifetime of the written grating, provided the reference beam is kept on after recording. Due to the ease in BPLC fabrication and the availability of azo-dopants with photosensitivity throughout the entire visible spectrum, one can optimize the controlling material and optical parameters to obtain even better performance. PMID:27782197

  4. Fiber optic security seal including plural Bragg gratings

    DOEpatents

    Forman, Peter R.

    1994-01-01

    An optical security system enables the integrity of a container seal to be remotely interrogated. A plurality of Bragg gratings is written holographically into the core of at least one optical fiber placed about the container seal, where each Bragg grating has a predetermined location and a known frequency for reflecting incident light. A time domain reflectometer is provided with a variable frequency light output that corresponds to the reflecting frequencies of the Bragg gratings to output a signal that is functionally related to the location and reflecting frequency of each of the Bragg gratings.

  5. Fiber optic security seal including plural Bragg gratings

    DOEpatents

    Forman, P.R.

    1994-09-27

    An optical security system enables the integrity of a container seal to be remotely interrogated. A plurality of Bragg gratings is written holographically into the core of at least one optical fiber placed about the container seal, where each Bragg grating has a predetermined location and a known frequency for reflecting incident light. A time domain reflectometer is provided with a variable frequency light output that corresponds to the reflecting frequencies of the Bragg gratings to output a signal that is functionally related to the location and reflecting frequency of each of the Bragg gratings. 2 figs.

  6. Optically tunable chirped fiber Bragg grating.

    PubMed

    Li, Zhen; Chen, Zhe; Hsiao, V K S; Tang, Jie-Yuan; Zhao, Fuli; Jiang, Shao-Ji

    2012-05-01

    This work presents an optically tunable chirped fiber Bragg grating (CFBG). The CFBG is obtained by a side-polished fiber Bragg grating (SPFBG) whose thickness of the residual cladding layer in the polished area (D(RC)) varies with position along the length of the grating, which is coated with a photoresponsive liquid crystal (LC) overlay. The reflection spectrum of the CFBG is tuned by refractive index (RI) modulation, which comes from the phase transition of the overlaid photoresponsive LC under ultraviolet (UV) light irradiation. The broadening in the reflection spectrum and corresponding shift in the central wavelength are observed with UV light irradiation density of 0.64mW/mm. During the phase transition of the photoresponsive LC, the RI increase of the overlaid LC leads to the change of the CFBG reflection spectrum and the change is reversible and repeatable. The optically tunable CFBGs have potential use in optical DWDM system and an all-fiber telecommunication system. PMID:22565706

  7. Composite cure monitoring with Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Slattery, Kerry T.; Corona-Bittick, Kelli; Dorr, Donald J.

    1998-03-01

    Residual stress is induced in fiber composite materials during the cure process because the thermal expansion coefficient of the fiber is generally much lower than that of the polymer matrix. The two materials are 'locked' together at the cure temperature. Then, as they cool, the matrix attempts to contract more than the fiber leading to tension in the matrix and compression in the fiber. This can lead to the formation of microcracks parallel to the fibers in thick composite piles or yarns. The magnitude of residual stress can be reduced by modifying the cure cycle; however, optimizing the cure cycle requires a complete understanding of the state of cure throughout the composite. This is a complex problem -- especially in thick composites. Pilot studies have been performed placing Bragg gratin sensors in glass fabric preforms and monitoring the response of the grating during resin infusion and cure. The typical response shows the initial thermal expansion of the Bragg grating, a rapid contraction of the grating as the resin gels, slower contraction during cure, and thermal contraction at the composite thermal expansion coefficient during cool down. This data is then sued with micromechanical models of the fiber/matrix interaction during cure to establish material parameters for cure simulation. Once verified, these cure simulation methods will be used to optimize tooling design and cure cycles in composite components.

  8. Measuring Bragg gratings in multimode optical fibers.

    PubMed

    Schmid, Markus J; Müller, Mathias S

    2015-03-23

    Fiber Bragg gratings (FBG) in multimode optical fibers provide a means for cost-effictive devices resulting in simplified and robust optic sensor systems. Parasitic mode effects in optical components of the entire measurement system strongly influence the measured multi-resonance reflection spectrum. Using a mode transfer matrix formalism we can describe these complex mode coupling effects in multimode optical systems in more detail. We demonstrate the accordance of the theory by two experiments. With this formalism it is possible to understand and optimize mode effects in multimode fiber optic systems. PMID:25837146

  9. Longitudinal coupling effect in microfiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Zhao, Ping; Zhang, Jihua; Wang, Guanghui; Jiang, Meng; Ping Shum, Perry; Zhang, Xinliang

    2012-10-01

    We theoretically present longitudinal coupling effect (LCE) in air-cladding microfiber Bragg gratings (MFBGs). Distinct from conventional weakly-guiding optical fibers, large longitudinal electric field (Ez) exists in wavelength-scale microfibers. Due to LCE, MFBG reflectivity can be reduced by more than 30% within the band-gap and the full width at half maximum (FWHM) is obviously narrowed. This theoretical analytical work is instructive to precisely design and fabricate MFBGs that are promising in the areas of optical sensing and nanophotonics.

  10. Theory of Fiber Optical Bragg Grating: Revisited

    NASA Technical Reports Server (NTRS)

    Tai, H.

    2003-01-01

    The reflected signature of an optical fiber Bragg grating is analyzed using the transfer function method. This approach is capable to cast all relevant quantities into proper places and provides a better physical understanding. The relationship between reflected signal, number of periods, index of refraction, and reflected wave phase is elucidated. The condition for which the maximum reflectivity is achieved is fully examined. We also have derived an expression to predict the reflectivity minima accurately when the reflected wave is detuned. Furthermore, using the segmented potential approach, this model can handle arbitrary index of refraction profiles and compare the strength of optical reflectivity of different profiles. The condition of a non-uniform grating is also addressed.

  11. Design and fabrication of polymeric waveguide Bragg grating devices

    NASA Astrophysics Data System (ADS)

    Huang, Cheng-Sheng

    The subject of this dissertation is a feasibility study of a flexible polymeric microfabricated waveguide Bragg grating (WBG) for potential sensing application. First, the optical design of the proposed device will be analyzed by examining the wave propagation and optical response of the Bragg grating inside the polymeric rib waveguide structure. The optical response is approximated using a coupled mode theory based on the slab waveguide model. Second, fabrication procedures on waveguide and Bragg grating design will be discussed. Third, preliminary results on the optical performance of the waveguide and grating responses using the proposed device will be presented. Finally, proposed future work on enhancing the design of the device will be addressed.

  12. First order Bragg grating filters in silicon on insulator waveguides

    NASA Astrophysics Data System (ADS)

    Waugh, Peter Michael

    2008-08-01

    The subject of this project is the design; analysis, fabrication and characterisation of first order Bragg Grating optical filters in Silicon-on-Insulator (SOI) planar waveguides. It is envisaged that this work will result in the possibility of Bragg Grating filters for use in Silicon Photonics. It is the purpose of the work to create as far as is possible flat surface waveguides so as to facilitate Thermo-Optic tuning and also the incorporation into rib-waveguide Silicon Photonics. The spectral response of the shallow Bragg Gratings was modelled using Coupled Mode Theory (CMT) by way of RSoft Gratingmod TM. Also the effect of having a Bragg Grating with alternate layers of refractive index of 1.5 and 3.5 was simulated in order to verify that Silica and Silicon layered Bragg Gratings could be viable. A series of Bragg Gratings were patterned on 1.5 micron SOI at Philips in Eindhoven, Holland to investigate the variation of grating parameters with a) the period of the gratings b) the mark to space ratio of the gratings and c) the length of the region converted to Bragg Gratings (i.e. the number of grating period repetitions). One set of gratings were thermally oxidised at Philips in Eindhoven and another set were ion implanted with Oxygen ions at the Ion Beam Facility, University of Surrey, England. The gratings were tested and found to give transmission minima at approximately 1540 nanometres and both methods of creating flat surfaces were found to give similar minima. Atomic Force Microscopy was applied to the grating area of the as-implanted samples in the Advanced Technology Institute, University of Surrey, which were found to have surface undulations in the order of 60 nanometres.

  13. Tailored draw tower fiber Bragg gratings for various sensing applications

    NASA Astrophysics Data System (ADS)

    Lindner, Eric; Mörbitz, Julia; Chojetzki, Christoph; Becker, Martin; Brückner, Sven; Schuster, Kay; Rothhardt, Manfred; Willsch, Reinhardt; Bartelt, H.

    2012-02-01

    The idea of fabricating fiber Bragg gratings during the drawing process of an optical fiber dates back almost 20 years. The application of a transverse holographic writing method on a fiber draw tower offers a promising solution for a highly effective Bragg grating production. Because of the high technology requirements it took more than 10 years to develop the method into a reliable process. The improvements in the technical development during the last five years enable today a cost efficient industrial production of draw tower grating (DTG®) arrays. In this paper we report about new possibilities of the improved process with respect to the grating type (type I gratings, type II gratings), the coating type (2ORMOCER®, metals) and the fiber diameter (125μm, 80μm and below). Furthermore, we present an example for the application of draw tower fiber Bragg gratings in sensing technologies for medical applications.

  14. Periodic waves in fiber Bragg gratings

    SciTech Connect

    Chow, K. W.; Merhasin, Ilya M.; Malomed, Boris A.; Nakkeeran, K.; Senthilnathan, K.; Wai, P. K. A.

    2008-02-15

    We construct two families of exact periodic solutions to the standard model of fiber Bragg grating (FBG) with Kerr nonlinearity. The solutions are named ''sn'' and ''cn'' waves, according to the elliptic functions used in their analytical representation. The sn wave exists only inside the FBG's spectral bandgap, while waves of the cn type may only exist at negative frequencies ({omega}<0), both inside and outside the bandgap. In the long-wave limit, the sn and cn families recover, respectively, the ordinary gap solitons, and (unstable) antidark and dark solitons. Stability of the periodic solutions is checked by direct numerical simulations and, in the case of the sn family, also through the calculation of instability growth rates for small perturbations. Although, rigorously speaking, all periodic solutions are unstable, a subfamily of practically stable sn waves, with a sufficiently large spatial period and {omega}>0, is identified. However, the sn waves with {omega}<0, as well as all cn solutions, are strongly unstable.

  15. A High Resolution Fiber Bragg Grating Resonator Strain Sensing System

    NASA Astrophysics Data System (ADS)

    Allsop, T.; Sugden, K.; Bennion, I.; Neal, R.; Malvern, A.

    A strain sensing system is demonstrated, consisting of a fiber Bragg grating resonator as the strain-sensing element. Signal encoding and decoding is achieved by a synthetic heterodyne technique. A strain accuracy of ±0.426 μɛwas attained; a value comparable to that of the classical fiber Fabry Perot (FFP) sensor and higher than conventional Bragg grating strain sensing schemes. This sensing element does not suffer from fabrication problems like the FFP sensor and the interrogation problems of the conventional Bragg grating sensor.

  16. Writing Bragg Gratings in Multicore Fibers.

    PubMed

    Lindley, Emma Y; Min, Seong-Sik; Leon-Saval, Sergio G; Cvetojevic, Nick; Lawrence, Jon; Ellis, Simon C; Bland-Hawthorn, Joss

    2016-01-01

    Fiber Bragg gratings in multicore fibers can be used as compact and robust filters in astronomical and other research and commercial applications. Strong suppression at a single wavelength requires that all cores have matching transmission profiles. These gratings cannot be inscribed using the same method as for single-core fibers because the curved surface of the cladding acts as a lens, focusing the incoming UV laser beam and causing variations in exposure between cores. Therefore we use an additional optical element to ensure that the beam shape does not change while passing through the cross-section of the multicore fiber. This consists of a glass capillary tube which has been polished flat on one side, which is then placed over the section of the fiber to be inscribed. The laser beam enters the fiber through the flat surface of the capillary tube and hence maintains its original dimensions. This paper demonstrates the improvements in core-to-core uniformity for a 7-core fiber using this method. The technique can be generalized to larger multicore fibers. PMID:27167576

  17. Fiber optical Bragg grating sensors embedded in CFRP wires

    NASA Astrophysics Data System (ADS)

    Nellen, Philipp M.; Frank, Andreas; Broennimann, Rolf; Meier, Urs; Sennhauser, Urs J.

    1999-05-01

    Based on the example application of Emmenbridge, a newly built steel-concrete-composite bridge in Switzerland with 47 m long built-in carbon fiber reinforced polymer (CFRP) prestressing cables, we will present and analyze the process chain leading to a reliable surveillance of modern civil engineering structures with embedded fiber optical Bragg gratings. This consists first in the embedding of optical fibers and in-fiber Bragg gratings in long CFRP wires in an industrial environment, including fiber optical monitoring of the curing process. Then, various qualifying tests were done: annealing experiments for determining optical lifetime of the Bragg gratings used, dynamic and static tensile tests for estimating their mechanical lifetime under operation, push-out experiments to check adhesion of fiber/coating/matrix interfaces, and performance tests to determine strain and temperature sensitivity of the embedded Bragg gratings. Finally, the prestressing cables were equipped with the CFRP sensor wires and built into the bridge.

  18. Response of fiber Bragg gratings to longitudinal ultrasonic waves.

    PubMed

    Minardo, Aldo; Cusano, Andrea; Bernini, Romeo; Zeni, Luigi; Giordano, Michele

    2005-02-01

    In the last years, fiber optic sensors have been widely exploited for several sensing applications, including static and dynamic strain measurements up to acoustic detection. Among these, fiber Bragg grating sensors have been indicated as the ideal candidate for practical structural health monitoring in light of their unique advantages over conventional sensing devices. Although this class of sensors has been successfully tested for static and low-frequency measurements, the identification of sensor performances for high-frequency detection, including acoustic emission and ultrasonic investigations, is required. To this aim, the analysis of feasibilty on the use of fiber Bragg grating sensors as ultrasonic detectors has been carried out. In particular, the response of fiber Bragg gratings subjected to the longitudinal ultrasonic (US) field has been theoretically and numerically investigated. Ultrasonic field interaction has been modeled, taking into account the direct deformation of the grating pitch combined with changes in local refractive index due to the elasto-optic effect. Numerical results, obtained for both uniform and Gaussian-apodized fiber Bragg gratings, show that the grating spectrum is strongly influenced by the US field in terms of shape and central wavelength. In particular, a key parameter affecting the grating response is the ratio between the US wavelength and the grating length. Normal operation characterized by changes in wavelength of undistorted Bragg peak is possible only for US wavelengths longer than the grating length. For US wavelengths approaching the grating length, the wavelength change is accompanied by subpeaks formation and main peak amplitude modulation. This effect can be attributed to the nonuniformity of the US perturbation along the grating length. At very high US frequencies, the grating is not sensitive any longer. The results of this analysis provide useful tools for the design of grating-based ultrasound sensors for

  19. Research of fiber Bragg grating geophone based on cantilever beam

    NASA Astrophysics Data System (ADS)

    Wang, Liang; Chen, Shao-hua; Tao, Guo; Lu, Gui-wu; Zhao, Kun

    2009-07-01

    Along with the development of seismic exploration, the demand of frequency, dynamic range, precision and resolution ration is increased. However, the traditional geophone has disadvantages of narrower bandwidth, lower dynamic range and resolution, and cannot meet the new needs of seismic exploration. Geophone technology is a choke point, which constrains the development of petroleum prospecting in recent years. Fiber Bragg Grating seism demodulation technology is the newest kind of seism demodulation technology. The sensing probe of the Fiber Bragg Grating geophone is made up of Fiber Bragg Gating. The information which it collects is embodied by wavelength. The modulation-demodulation is accomplished by Fiber Bragg Gating geophone directly. In this paper, we design different size Fiber Bragg Grating geophones based on the transmission properties of Fiber Bragg Grating and cantilever beam method. Beryllium bronze and stainless steel are chosen as the elastic beam and shell materials, respectively. The parameters such as response function and sensitivity are given theoretically. In addition, we have simulated the transmission characteristics of Fiber Bragg Grating geophone by virtue of finite element analysis. The influences of wavelength, mass block, fiber length on the characteristics of geophones are discussed in detail, and finally the appropriate structural parameters are presented.

  20. Dynamic fiber Bragg grating sensing method

    NASA Astrophysics Data System (ADS)

    Ho, Siu Chun Michael; Ren, Liang; Li, Hongnan; Song, Gangbing

    2016-02-01

    The measurement of high frequency vibrations is important in many scientific and engineering problems. This paper presents a novel, cost effective method using fiber optic fiber Bragg gratings (FBGs) for the measurement of high frequency vibrations. The method uses wavelength matched FBG sensors, with the first sensor acting as a transmission filter and the second sensor acting as the sensing portion. Energy fluctuations in the reflection spectrum of the second FBG due to wavelength mismatch between the sensors are captured by a photodiode. An in-depth analysis of the optical circuit is provided to predict the behavior of the method as well as identify ways to optimize the method. Simple demonstrations of the method were performed with the FBG sensing system installed on a piezoelectric transducer and on a wind turbine blade. Vibrations were measured with sampling frequencies up to 1 MHz for demonstrative purposes. The sensing method can be multiplexed for use with multiple sensors, and with care, can be retrofitted to work with FBG sensors already installed on a structure.

  1. Electrostriction mechanism of Bragg grating formation in germanosilicate fibres

    SciTech Connect

    Neustruev, V B

    2001-11-30

    An electrostriction model is proposed for the photorefractive effect observed during the writing of Bragg gratings in germanosilicate fibres. Electrostriction is caused by a spatial charge grating formed upon the exposure to UV radiation. According to our estimate, the contribution of electrostriction to the photorefractive effect under real writing conditions is comparable with the contribution from colour centres and exceeds the contribution from the electrooptical effect by more than an order of magnitude. The electrostriction model explains the production of the IIA type Bragg grating in fibres with a high content of germanium in the core, as well as a number of effects that could not be explained earlier. (optical fibres)

  2. Fiber-bragg grating-loop ringdown method and apparatus

    DOEpatents

    Wang, Chuji

    2008-01-29

    A device comprising a fiber grating loop ringdown (FGLRD) system of analysis is disclosed. A fiber Bragg grating (FBG) or Long-Period grating (LPG) written in a section of single mode fused silica fiber is incorporated into a fiber loop. By utilizing the wing areas of the gratings' bandwidth as a wavelength dependent attenuator of the light transmission, a fiber grating loop ringdown concept is formed. One aspect of the present invention is temperature sensing, which has been demonstrated using the disclosed device. Temperature measurements in the areas of accuracy, stability, high temperature, and dynamic range are also described.

  3. Amplitude-squeezed fiber-Bragg-grating solitons

    SciTech Connect

    Lee, R.-K.; Lai Yinchieh

    2004-02-01

    Quantum fluctuations of optical fiber-Bragg-grating solitons are investigated numerically by the back-propagation method. It is found that the band-gap effects of the grating act as a nonlinear filter and cause the soliton to be amplitude squeezed. The squeezing ratio saturates after a certain grating length and the optimal squeezing ratio occurs when the pulse energy is slightly above the fundamental soliton energy.

  4. Damage behaviors of fiber Bragg grating sensor in fabrication

    NASA Astrophysics Data System (ADS)

    Tang, Liqun; Sang, Dengfeng; Chen, Jinming; Yang, Bao; Liu, Yiping

    2008-11-01

    It is has been noted that for fiber Bragg grating sensor (FBGS), the tensile strengths of fiber Bragg grating sensors (FBGSs) were decreased after the gratings were written, which may reduce the sensor's measurement range obviously. In this paper, we focused on the damage behaviours of FBGS after fabrication experimentally. Firstly, the tensile tests were carried to measure the tensile strengths of naked optical fiber, decoated optical fiber and optical fiber with Bragg gratings to learn deduction of the tensile strength of optical fiber in the cases respectively. Further, the microscope photography was used to observe the surfaces of optical fiber with or without exposure of excimer laser. The main conclusion is that the UV pulse is the main contribution to reduce the strength remarkably, and the mechanical decoating method also can induce the surface damage on the optical fiber.

  5. Trends and future of fiber Bragg grating sensing technologies: tailored draw tower gratings (DTGs)

    NASA Astrophysics Data System (ADS)

    Lindner, E.; Hartung, A.; Hoh, D.; Chojetzki, C.; Schuster, K.; Bierlich, J.; Rothhardt, M.

    2014-05-01

    Today fiber Bragg gratings are commonly used in sensing technology as well as in telecommunications. Numerous requirements must be satisfied for their application as a sensor such as the number of sensors per system, the measurement resolution and repeatability, the sensor reusability as well as the sensor costs. In addition current challenges need to be met in the near future for sensing fibers to keep and extend their marketability such as the suitability for sterilization, hydrogen darkening or the separation of strain and temperature (or pressure and temperature). In this contribution we will give an outlook about trends and future of the fiber Bragg gratings in sensing technologies. Specifically, we will discuss how the use of draw tower grating technology enables the production of tailored Bragg grating sensing fibers, and we will present a method of separating strain and temperature by the use of a single Bragg grating only, avoiding the need for additional sensors to realize the commonly applied temperature compensation.

  6. Fabrication of Fiber-Optic Tilted Bragg Grating Filter in 40 nm Range with A Single Phase Mask

    NASA Technical Reports Server (NTRS)

    Grant, Joseph; Wang, Y.; Sharma, A.; Burdine, Robert V. (Technical Monitor)

    2002-01-01

    Fiber-optic Bragg grating filters are fabricated with a range of Bragg wavelength between 1296 and 1336 nm, using a single phase mask. 30 mW of continuous-wave light at 244 nm is used from a frequency-doubled argon-ion laser having an intracavity etalon. Gratings are fabricated by tilting the photosensitive fiber with respect to the phase mask up to an angle of 15 degrees. The variation of Bragg wavelength with the fiber-tilt is explained with a simple formula. High spatial coherence of 244 nm light makes it possible to displace the fiber as much as 6 mm in front of the phase mask and tilt the fiber by as much as 15 degrees. This results in nearly constant band-width and near 100% reflectively for all gratings throughout the 40 nm range.

  7. Applications of distributed fiber Bragg grating sensors in civil engineering

    NASA Astrophysics Data System (ADS)

    Nellen, Philipp M.; Broennimann, Rolf; Sennhauser, Urs J.; Askins, Charles G.; Putnam, Martin A.

    1995-09-01

    We report on civil engineering applications of wavelength multiplexed optical-fiber Bragg grating arrays produced directly on the draw tower for testing and surveying advanced structures and material like carbon fiber reinforced concrete elements and prestressing tendons. We equipped a 6 m X 0.9 m X 0.5 m concrete cantilever beam reinforced with carbon fiber lamellas with fiber Bragg grating sensors. Static and dynamic strain levels up to 1500 micrometers /m were measured with a Michelson interferometer used as Fourier spectrometer with resolutions of about 10 micrometers /m for all sensors. Comparative measurements with electrical resistance strain gauges were in good agreement with the fiber optic results. We used the fiber sensors in two different arrangements: some Bragg grating array elements measured the local strain while others were configured in an extensometric way to measure moderate strain over 0.1-1 m.

  8. Diffraction of Gaussian beams on intracavity Bragg gratings

    NASA Astrophysics Data System (ADS)

    Bitauld, David; Menez, Ludivine; Zaquine, Isabelle; Maruani, Alain; Frey, Robert

    2005-06-01

    The diffraction of Gaussian beams on intracavity Bragg gratings is analyzed theoretically. For reasonable waists the associated beam divergence does not significantly influence the diffraction efficiency of such devices. Nevertheless, the tilt angle of the incident beam, imposed by the Bragg resonance condition, strongly reduces the diffraction efficiency at short grating periods. However, the angular selectivity can be maintained if the Fabry-Perot cavity is tuned to the incident beam direction, which allows the use of small-volume holograms together with a dense angular multiplex. This theoretical analysis can be applied to the optimization of the diffraction properties of Gaussian beams on any intracavity Bragg grating, which could then be used for free-space parallel signal processing.

  9. Technical textiles with embedded fibre Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Bilro, L.; Cunha, H.; Pinto, J. L.; Nogueira, R. N.

    2009-10-01

    The characterization of fiber Bragg grating (FBG) sensors integrated on 2D and 3D mesh structures is presented. Several materials and configurations were tested, namely cork, foams, PVC, hexagonal 3D. Sensors were embedded between two substrates using textile lamination technique. Every sample was subjected to temperature variations and mechanical deformations. Through Bragg wavelength monitoring, thermal, deformation and pressure performance were evaluated. These results provide significant information to the conception of smart textiles.

  10. Security System Responsive to Optical Fiber Having Bragg Grating

    NASA Technical Reports Server (NTRS)

    Gary, Charles K. (Inventor); Ozcan, Meric (Inventor)

    1997-01-01

    An optically responsive electronic lock is disclosed comprising an optical fiber serving as a key and having Bragg gratings placed therein. Further, an identification system is disclosed which has the optical fiber serving as means for tagging and identifying an object. The key or tagged object is inserted into a respective receptacle and the Bragg gratings cause the optical fiber to reflect a predetermined frequency spectra pattern of incident light which is detected by a decoder and compared against a predetermined spectrum to determine if an electrical signal is generated to either operate the lock or light a display of an authentication panel.

  11. Demodulation System for Fiber Optic Bragg Grating Dynamic Pressure Sensing

    NASA Technical Reports Server (NTRS)

    Lekki, John D.; Adamovsky, Grigory; Floyd, Bertram

    2001-01-01

    Fiber optic Bragg gratings have been used for years to measure quasi-static phenomena. In aircraft engine applications there is a need to measure dynamic signals such as variable pressures. In order to monitor these pressures a detection system with broad dynamic range is needed. This paper describes an interferometric demodulator that was developed and optimized for this particular application. The signal to noise ratio was maximized through temporal coherence analysis. The demodulator was incorporated in a laboratory system that simulates conditions to be measured. Several pressure sensor configurations incorporating a fiber optic Bragg grating were also explored. The results of the experiments are reported in this paper.

  12. Performance Evaluation of Fiber Bragg Gratings at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Juergens, Jeffrey; Adamovsky, Grigory; Floyd, Bertram

    2004-01-01

    The development of integrated fiber optic sensors for smart propulsion systems demands that the sensors be able to perform in extreme environments. In order to use fiber optic sensors effectively in an extreme environment one must have a thorough understanding of the sensor s limits and how it responds under various environmental conditions. The sensor evaluation currently involves examining the performance of fiber Bragg gratings at elevated temperatures. Fiber Bragg gratings (FBG) are periodic variations of the refractive index of an optical fiber. These periodic variations allow the FBG to act as an embedded optical filter passing the majority of light propagating through a fiber while reflecting back a narrow band of the incident light. The peak reflected wavelength of the FBG is known as the Bragg wavelength. Since the period and width of the refractive index variation in the fiber determines the wavelengths that are transmitted and reflected by the grating, any force acting on the fiber that alters the physical structure of the grating will change what wavelengths are transmitted and what wavelengths are reflected by the grating. Both thermal and mechanical forces acting on the grating will alter its physical characteristics allowing the FBG sensor to detect both temperature variations and physical stresses, strain, placed upon it. This ability to sense multiple physical forces makes the FBG a versatile sensor. This paper reports on test results of the performance of FBGs at elevated temperatures. The gratings looked at thus far have been either embedded in polymer matrix materials or freestanding with the primary focus of this paper being on the freestanding FBGs. Throughout the evaluation process, various parameters of the FBGs performance were monitored and recorded. These parameters include the peak Bragg wavelength, the power of the Bragg wavelength, and total power returned by the FBG. Several test samples were subjected to identical test conditions to

  13. Hybrid Oxygen-Responsive Reflective Bragg Grating Platforms

    PubMed Central

    Yung, Ka Yi; Xu, Huina; Liu, Ke; Martinez, Greggory J.; Bright, Frank V.; Detty, Michael R.; Cartwright, Alexander N.

    2014-01-01

    Oxygen responsive sensor platforms were fabricated by pin printing tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) ([Ru(dpp)3]2+) doped sols onto wavelength tuned reflective Bragg gratings. In an epi-luminescence configuration, these Bragg gratings (Gr) were designed to reflect selectively the O2 responsive [Ru(dpp)3]2+ emission toward the detector to enhance the detected signal magnitude. The xerogel based sensors were formed onto: (i) glass (XGl), (ii) directly on top of the grating (XGrGl), or (iii) on the glass substrate opposite the grating (XGlGr). The results show that all sensors exhibit linear, statistically equivalent O2 sensitivities and the XGrGl platform yields up to an 8 fold increase in relative detected analytical signal (RDAS) in comparison to the control (XGl) platform. PMID:22191377

  14. Creation of a microstructured polymer optical fiber with UV Bragg grating inscription for the detection of extensions at temperatures up to 125°C

    NASA Astrophysics Data System (ADS)

    Fasano, Andrea; Woyessa, Getinet; Stajanca, Pavol; Markos, Christos; Stefani, Alessio; Nielsen, Kristian; Rasmussen, Henrik K.; Krebber, Katerina; Bang, Ole

    2016-04-01

    We describe the fabrication of a polycarbonate (PC) micro-structured polymer optical fiber (mPOF) and the writing of fiber Bragg gratings (FBGs) in it to enable strain and temperature measurements. We demonstrate the photosensitivity of a dopant-free PC fiber by grating inscription using a UV laser. We further show that PC Bragg gratings can be extended up to at least 3% without affecting the initial functionality of the micro-structured fiber. The response of PC FBGs to temperature up to 125°C is also investigated. Polycarbonate has good mechanical properties and its high temperature resistance might extend the range of application of polymeric FBGs.

  15. Bragg-selectivity of a volume gain grating

    NASA Astrophysics Data System (ADS)

    Damzen, M. J.; Matsumoto, Y.; Crofts, G. J.; Green, R. P. M.

    1996-02-01

    We adapt the theory of volume grating holography to model analytically the diffraction efficiency of a volume gain grating and its variation due to deviation from Bragg-matching. We present modelling of the case when the gain grating is optically-written in a saturable laser amplifier by spatial hole burning, under both steady-state and transient conditions. We perform an experimental measurement of the angular-sensitivity of a volume transmission gain grating optically-written in a Nd:YAG amplifier rod. It is shown that the amplification of the writing beams needs to be considered since this leads to a spatial variation of the grating modulation depth and thereby to the reduction of its angular sensitivity compared to the uniform grating case.

  16. Experimental demonstration of a fiber Bragg grating accelerometer

    SciTech Connect

    Berkoff, T.A.; Kersey, A.D.

    1996-12-01

    The authors report a fiber Bragg grating transducer for the measurement of acceleration. Results obtained using interferometric wavelength-shift detection demonstrate a demodulated signal output range of 50-g rms with a minimum detectable signal of {approximately}1 mg/{radical}Hz.

  17. Bragg grating extensometer rods (BGX) for geotechnical strain measurements

    NASA Astrophysics Data System (ADS)

    Schmidt-Hattenberger, Cornelia; Borm, Gunter

    1998-06-01

    We report on a new type of optical extensometer for strain measurement in geotechnical and civil engineering applications. The system key elements are fiber Bragg gratings embedded in glass fiber reinforced polymer rockbolts. In order to monitor rock deformations in tunnels, a prototype sensor rockbolt was designed. First measurements have been made to demonstrate the characteristics of the sensor system.

  18. Monolithic integrated optic fiber Bragg grating sensor interrogator

    NASA Astrophysics Data System (ADS)

    Mendoza, Edgar A.; Esterkin, Yan; Kempen, Cornelia; Sun, Songjian

    2010-04-01

    Fiber Bragg gratings (FBGs) are a mature sensing technology that has gained rapid acceptance in civil, aerospace, chemical and petrochemical, medicine, aviation and automotive industries. Fiber Bragg grating sensors can be use for a variety of measurements including strain, stress, vibration, acoustics, acceleration, pressure, temperature, moisture, and corrosion distributed at multiple locations within the structure using a single fiber element. The most prominent advantages of FBGs are: small size and light weight, multiple FBG transducers on a single fiber, and immunity to radio frequency interference. A major disadvantage of FBG technology is that conventional state-of-the-art fiber Bragg grating interrogation systems are typically bulky, heavy, and costly bench top instruments that are assembled from off-the-shelf fiber optic and optical components integrated with a signal electronics board into an instrument console. Based on the need for a compact FBG interrogation system, this paper describes recent progress towards the development of a miniature fiber Bragg grating sensor interrogator (FBG-TransceiverTM) system based on multi-channel monolithic integrated optic sensor microchip technology. The integrated optic microchip technology enables the monolithic integration of all of the functionalities, both passive and active, of conventional bench top FBG sensor interrogators systems, packaged in a miniaturized, low power operation, 2-cm x 5-cm small form factor (SFF) package suitable for the long-term structural health monitoring in applications where size, weight, and power are critical for operation.

  19. Visible wavelength fiber Bragg gratings: thermal and strain sensitivities

    NASA Astrophysics Data System (ADS)

    Loren Inácio, Patrícia; Chiamenti, Ismael; Sualehe, Ivenso d. S. V.; Oliveira, Valmir; Kalinowski, Hypolito J.

    2016-05-01

    The thermal and deformation properties of fiber Bragg gratings (FBG) in the visible range were characterized for the first time in our knowledge. The FBG were written in silica single mode (cutoff in the visible and infrared range) and multimode fibers, using a phase-mask (460 nm period) illuminated by a 248 nm femtosecond laser.

  20. High Speed Measurements using Fiber-optic Bragg Grating Sensors

    SciTech Connect

    Benterou, J J; May, C A; Udd, E; Mihailov, S J; Lu, P

    2011-03-26

    Fiber grating sensors may be used to monitor high-speed events that include catastrophic failure of structures, ultrasonic testing and detonations. This paper provides insights into the utility of fiber grating sensors to measure structural changes under extreme conditions. An emphasis is placed on situations where there is a structural discontinuity. Embedded chirped fiber Bragg grating (CFBG) sensors can track the very high-speed progress of detonation waves (6-9 km/sec) inside energetic materials. This paper discusses diagnostic instrumentation and analysis techniques used to measure these high-speed events.

  1. Ultrafast laser inscribed fiber Bragg gratings for sensing applications

    NASA Astrophysics Data System (ADS)

    Mihailov, Stephen J.

    2016-05-01

    Because of their small size, passive nature, immunity to electromagnetic interference, and capability to directly measure physical parameters such as temperature and strain, fiber Bragg grating sensors have developed beyond a laboratory curiosity and are becoming a mainstream sensing technology. Recently, high temperature stable gratings based on femtosecond infrared laser-material processing have shown promise for use in extreme environments such as high temperature, pressure or ionizing radiation. Such gratings are ideally suited for energy production applications where there is a requirement for advanced energy system instrumentation and controls that are operable in harsh environments. This tutorial paper will present a review of some of the more recent developments.

  2. Silicon waveguide polarization rotation Bragg grating with phase shift section and sampled grating scheme

    NASA Astrophysics Data System (ADS)

    Okayama, Hideaki; Onawa, Yosuke; Shimura, Daisuke; Yaegashi, Hiroki; Sasaki, Hironori

    2016-08-01

    We describe a Bragg grating with a phase shift section and a sampled grating scheme that converts input polarization to orthogonal polarization. A very narrow polarization-independent wavelength peak can be generated by phase shift structures and polarization-independent multiple diffraction peaks by sampled gratings. The characteristics of the device were examined by transfer matrix and finite-difference time-domain methods.

  3. 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.

  4. Time-dependent variation of fiber Bragg grating reflectivity in PMMA-based polymer optical fibers.

    PubMed

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

    2015-04-01

    In this Letter, we investigate the effects of viscoelasticity on both the strength and resonance wavelength of two fiber Bragg gratings (FBGs) inscribed in microstructured polymer optical fiber (mPOF) made of undoped PMMA. Both FBGs were inscribed under a strain of 1% in order to increase the material photosensitivity. After the inscription, the strain was released, and the FBGs spectra were monitored. We initially observed a decrease of the reflection down to zero after which it began to increase. After that, strain tests were carried out to confirm the results, and finally the gratings were monitored for a further 120 days, with a stable reflection response being observed beyond 50 days. PMID:25831363

  5. Round Robin for Optical Fiber Bragg Grating Metrology

    PubMed Central

    Rose, A. H.; Wang, C.-M.; Dyer, S. D.

    2000-01-01

    NIST has administered the first round robin of measurements for optical fiber Bragg gratings. We compared the measurement of center wavelength, bandwidth, isolation, minimum relative transmittance, and relative group delay among several grating types in two industry groups, telecommunications and sensors. We found that the state of fiber Bragg grating metrology needs improvement in most areas. Specifically, when tunable lasers are used a filter is needed to remove broadband emissions from the laser. The linear slope of relative group delay measurements is sensitive to drift and systematic bias in the rf-modulation technique. The center wavelength measurement had a range of about 27 pm in the sensors group and is not adequate to support long-term structural monitoring applications. PMID:27551640

  6. Reannealed Fiber Bragg Gratings Demonstrated High Repeatability in Temperature Measurements

    NASA Technical Reports Server (NTRS)

    Adamovsky, Grigory; Juergens, Jeffrey R.

    2004-01-01

    Fiber Bragg gratings (FBGs) are formed by periodic variations of the refractive index of an optical fiber. These periodic variations allow an FBG to act as an embedded optical filter, passing the majority of light propagating through a fiber while reflecting back a narrow band of the incident light. The peak reflected wavelength of the FBG is known as the Bragg wavelength. Since the period and width of the refractive index variation in the fiber determines the wavelengths that are transmitted and reflected by the grating, any force acting on the fiber that alters the physical structure of the grating will change the wavelengths that are transmitted and reflected by it. Both thermal and mechanical forces acting on the grating will alter its physical characteristics, allowing the FBG sensor to detect both the temperature variations and the physical stresses and strains placed upon it. This ability to sense multiple physical forces makes the FBG a versatile sensor. To assess the feasibility of using Bragg gratings as temperature sensors for propulsion applications, researchers at the NASA Glenn Research Center evaluated the performance of Bragg gratings at elevated temperatures for up to 300 C. For these purposes, commercially available polyimide-coated high-temperature gratings were used that were annealed by the manufacturer to 300 C. To assure the most thermally stable gratings at the operating temperatures, we reannealed the gratings to 400 C at a very slow rate for 12 to 24 hr until their reflected optical powers were stabilized. The reannealed gratings were then subjected to periodic thermal cycling from room temperature to 300 C, and their peak reflected wavelengths were monitored. The setup shown is used for reannealing and thermal cycling the FBGs. Signals from the photodetectors and the spectrum analyzer were fed into a computer equipped with LabVIEW software. The software synchronously monitored the oven/furnace temperature and the optical spectrum analyzer

  7. A highly sensitive fiber Bragg grating diaphragm pressure transducer

    NASA Astrophysics Data System (ADS)

    Allwood, Gary; Wild, Graham; Lubansky, Alex; Hinckley, Steven

    2015-10-01

    In this work, a novel diaphragm based pressure transducer with high sensitivity is described, including the physical design structure, in-depth analysis of optical response to changes in pressure, and a discussion of practical implementation and limitations. A flat circular rubber membrane bonded to a cylinder forms the body of the transducer. A fiber Bragg grating bonded to the center of the diaphragm structure enables the fractional change in pressure to be determined by analyzing the change in Bragg wavelength of the reflected spectra. Extensive evaluation of the physical properties and optical characteristics of the transducer has been performed through experimentation, and modeling using small deformation theory. The results show the transducer has a sensitivity of 0.116 nm/kPa, across a range of 15 kPa. Ultra-low cost interrogation of the optical signal was achieved through the use of an optically mismatched Bragg grating acting as an edge filter to convert the spectral change into an intensity change. A numerical model of the intensity based interrogation was implemented in order to validate the experimental results. Utilizing this interrogation technique and housing both the sensing and reference Bragg gratings within the main body of the transducer means it is effectively temperature insensitive and easily connected to electronic systems.

  8. High frequency strain measurements with fiber Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Koch, J.; Angelmahr, M.; Schade, W.

    2015-05-01

    In recent years fiber Bragg grating sensors gained interest in structural health monitoring and concepts for smart structures. They are small, lightweight, and immune to electromagnetic interference. Using multiplexing techniques, several sensors can be addressed by a single fiber. Therefore, well-established structures and materials in industrial applications can be easily equipped with fiber optical sensors with marginal influence on their mechanical properties. In return, critical components can be monitored in real-time, leading to reduced maintenance intervals and a great reduction of costs. Beside of generally condition monitoring, the localization of failures in a structure is a desired feature of the condition monitoring system. Detecting the acoustic emission of a sudden event, its place of origin can be determined by analyzing the delay time of distributed sensor signals. To achieve high localization accuracies for the detection of cracks, breaks, and impacts high sampling rates combined with the simultaneous interrogation of several fiber Bragg grating sensors are required. In this article a fiber Bragg grating interrogator for high frequency measurements up to the megahertz range is presented. The interrogator is based on a passive wavelength to intensity conversion applying arrayed waveguide gratings. Light power fluctuations are suppressed by a differential data evaluation, leading to a reduced signal-to-noise ratio and a low strain detection limit. The measurement system is used to detect, inter alia, wire breaks in steel wire ropes for dockside cranes.

  9. Graphene-controlled fiber Bragg grating and enabled optical bistability.

    PubMed

    Gan, Xuetao; Wang, Yadong; Zhang, Fanlu; Zhao, Chenyang; Jiang, Biqiang; Fang, Liang; Li, Dongying; Wu, Hao; Ren, Zhaoyu; Zhao, Jianlin

    2016-02-01

    We report a graphene-assisted all-optical control of a fiber Bragg grating (FBG), which enables in-fiber optical bistability and switching. With an optical pump, a micro-FBG wrapped by graphene evolves into chirped and phase-shifted FBGs, whose characteristic wavelengths and bandwidths could be controlled by the pump power. Optical bistability and multistability are achieved in the controlled FBG based on a shifted Bragg reflection or Fabry-Perot-type resonance, which allow the implementation of optical switching with an extinction ratio exceeding 20 dB and a response time in tens of milliseconds. PMID:26907434

  10. Modeling of spectral changes in bent fiber Bragg gratings.

    PubMed

    Zhang, Wei; Lei, Xiaohua; Chen, Weimin; Xu, Hengyi; Wang, Anbo

    2015-07-15

    To better apply fiber Bragg gratings (FBGs) to various bending required situations, good understanding of their bending characteristics is crucial. In this Letter, a theoretical model to describe the changes of spectral properties of an FBG against the bending radius is proposed. This model shows that all the bend-induced spectral changes, the shift of center wavelength, decrease of reflectivity, and reduction of bandwidth, may be explained by the decrease of the effective "dc" refractive index change spatially averaged over one grating period. Experimental results are in agreement with theoretical predictions and confirm the effectiveness of the proposed model. PMID:26176444

  11. Magneto-Optic Field Coupling in Optical Fiber Bragg Gratings

    NASA Technical Reports Server (NTRS)

    Carman, Gregory P. (Inventor); Mohanchandra, Panduranga K. (Inventor); Emmons, Michael C. (Inventor); Richards, William Lance (Inventor)

    2016-01-01

    The invention is a magneto-optic coupled magnetic sensor that comprises a standard optical fiber Bragg grating system. The system includes an optical fiber with at least one Bragg grating therein. The optical fiber has at least an inner core and a cladding that surrounds the inner core. The optical fiber is part of an optical system that includes an interrogation device that provides a light wave through the optical fiber and a system to determine the change in the index of refraction of the optical fiber. The cladding of the optical fiber comprises at least a portion of which is made up of ferromagnetic particles so that the ferromagnetic particles are subject to the light wave provided by the interrogation system. When a magnetic field is present, the ferromagnetic particles change the optical properties of the sensor directly.

  12. Fiber optic Bragg grating sensors embedded in GFRP rockbolts

    NASA Astrophysics Data System (ADS)

    Frank, Andreas; Nellen, Philipp M.; Broennimann, Rolf; Sennhauser, Urs J.

    1999-05-01

    Rockbolt anchors for tunnel or mine roofs are key elements during construction and operation. We report on the fabrication of glass fiber reinforced polymer (GFRP) rockbolts with embedded fiber optical Bragg grating sensors and their first field application in a test tunnel. Optical fibers and in-fiber Bragg grating sensors were embedded in GFRP rockbolts during a continuously ongoing pultrusion process on an industrial production machine. Depending on their outer diameter the rods equipped with fiber sensors serve as measuring rockbolts or as extensometric sensors for the motion of boulders in the tunnel roof. The adhesion and force transfer of different fiber coatings were tested by push-out experiments. By temperature and strain cycle tests the performance of the rockbolt sensors was evaluated. We will present these results and the measurements made during a first installation of fiber optical rockbolt sensors in a tunnel.

  13. Fiber Bragg gratings for low-temperature measurement.

    PubMed

    Filho, Elton Soares de Lima; Baiad, Mohamad Diaa; Gagné, Mathieu; Kashyap, Raman

    2014-11-01

    We demonstrate the use of fiber Bragg gratings (FBGs) as a monolithic temperature sensor from ambient to liquid nitrogen temperatures, without the use of any auxiliary embedding structure. The Bragg gratings, fabricated in three different types of fibers and characterized with a high density of points, confirm a nonlinear thermal sensitivity of the fibers. With a conventional interrogation scheme it is possible to have a resolution of 0.5 K for weak pure-silica-core FBGs and 0.25 K using both boron-doped and germanium-doped standard fibers at 77 K. We quantitatively show for the first time that the nonlinear thermal sensitivity of the FBG arises from the nonlinearity of both thermo-optic and thermal expansion coefficients, allowing consistent modeling of FBGs at low temperatures. PMID:25401912

  14. Temperature effects in concrete structures measured with fibre Bragg grating

    NASA Astrophysics Data System (ADS)

    Silva, Jean C.; Martelli, Cicero; Penner, Elisabeth; Kalinowski, Hypolito J.

    2004-06-01

    We analyze the action of fire, causing degradation in a concrete cantilever beam using dynamic testing. The structure is instrumented with two fiber Bragg gratings (FBG) sensors. One of them is used to measure vibration and another one is used to measure temperature inside of the cantilever beam, while the beam is exposed to fire. The temperature in the cantilever beam increased until 150°C and a reduction in the strength of concrete can be observed through the modal analysis. A fiber Bragg grating interrogation system, based on tunable filter method, is used for the static and dynamic measurements during the experiments. That system has low cost and it is easy to assemble and maintain when compared to other available instruments.

  15. Processing of Signals from Fiber Bragg Gratings Using Unbalanced Interferometers

    NASA Technical Reports Server (NTRS)

    Adamovsky, Grigory; Juergens, Jeff; Floyd, Bertram

    2005-01-01

    Fiber Bragg gratings (FBG) have become preferred sensory structures in fiber optic sensing system. High sensitivity, embedability, and multiplexing capabilities make FBGs superior to other sensor configurations. The main feature of FBGs is that they respond in the wavelength domain with the wavelength of the returned signal as the indicator of the measured parameter. The wavelength is then converted to optical intensity by a photodetector to detect corresponding changes in intensity. This wavelength-to-intensity conversion is a crucial part in any FBG-based sensing system. Among the various types of wavelength-to-intensity converters, unbalanced interferometers are especially attractive because of their small weight and volume, lack of moving parts, easy integration, and good stability. In this paper we investigate the applicability of unbalanced interferometers to analyze signals reflected from Bragg gratings. Analytical and experimental data are presented.

  16. Cryogenic Fiber Optic Sensors Based on Fiber Bragg Gratings

    NASA Astrophysics Data System (ADS)

    Swinehart, P. R.; Maklad, M.; Courts, S. S.

    2008-03-01

    Fiber optic sensing has many favorable characteristics—a single fiber can be used to multiplex multiple sensors along the length of the fiber, fiber optic sensing is immune to electromagnetic noise and is inherently safe for combustible liquids and atmospheres. Previously, fiber optic sensors based on fiber Bragg gratings (FBGs) have been demonstrated for cryogenic use for both temperature and strain sensing, but often little data is supplied as to the reproducibility or unit-to-unit uniformity of these sensors. Lake Shore Cryotronics has manufactured fiber optic cryogenic temperature sensors based on Bragg gratings using novel packaging techniques. The temperature response and reproducibility is reported from 80K to 480K for glass-packaged sensors, and a calibration for a high sensitivity, wide range zinc-packaged sensor is reported.

  17. Pressure Effects on the Temperature Sensitivity of Fiber Bragg Gratings

    NASA Technical Reports Server (NTRS)

    Wu, Meng-Chou

    2012-01-01

    A 3-dimensional physical model was developed to relate the wavelength shifts resulting from temperature changes of fiber Bragg gratings (FBGs) to the thermal expansion coefficients, Young s moduli of optical fibers, and thicknesses of coating polymers. Using this model the Bragg wavelength shifts were calculated and compared with the measured wavelength shifts of FBGs with various coating thickness for a finite temperature range. There was a discrepancy between the calculated and measured wavelength shifts. This was attributed to the refractive index change of the fiber core by the thermally induced radial pressure. To further investigate the pressure effects, a small diametric load was applied to a FBG and Bragg wavelength shifts were measured over a temperature range of 4.2 to 300K.

  18. Trial analysis of swine's periodontal ligament with Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Menegotto, G. F.; Grabarski, L.; Kalinowski, H. J.; Simões, J. A.

    2009-10-01

    In this work it is reported the measurement of the differential strain between the dental and bone tissues under effect of an applied load. Slices of swine mandible, containing the premolar tooth, are cut and measured in fresh condition. The strain is measured using fibre Bragg grating sensors glued to both tissues. In the measured range the results show a linear behaviour and confirm the importance of the periodontal ligament in the load transfer mechanism.

  19. Highly reproducible Bragg grating acousto-ultrasonic contact transducers

    NASA Astrophysics Data System (ADS)

    Saxena, Indu Fiesler; Guzman, Narciso; Lieberman, Robert A.

    2014-09-01

    Fiber optic acousto-ultrasonic transducers offer numerous applications as embedded sensors for impact and damage detection in industrial and aerospace applications as well as non-destructive evaluation. Superficial contact transducers with a sheet of fiber optic Bragg gratings has been demonstrated for guided wave ultrasound based measurements. It is reported here that this method of measurement provides highly reproducible guided ultrasound data of the test composite component, despite the optical fiber transducers not being permanently embedded in it.

  20. Applications of compound fiber Bragg grating structures in lightwave communications

    NASA Astrophysics Data System (ADS)

    Chen, Lawrence R.

    Photonic networks have been identified as one solution that can satisfy the growing demand for bandwidth due to increased Internet traffic and the information superhighway. New enabling photonic technologies will be required in order to successfully implement, operate, and manage these all-photonic networks. In this thesis, we develop fiber Bragg grating technology for realizing photonic components that can perform a wide variety of optical signal processing functions for aggressive network management and performance requirements. First, we show how to tailor the spectral response of chirped moiré fiber Bragg gratings so that they can be used as transmission passband filters. We have fabricated filters having near ideal filter response which will be useful for providing wavelength selectivity in wavelength-division-multiplexed and wavelength routing networks. Second, we demonstrate the first hybrid wavelength- encodingt/time-spreading optical code-division multiple- access system using chirped moiré fiber Bragg gratings for encoding/decoding. Limitations imposed by the electronic bottleneck due to optical-to-electrical and electrical-to-optical conversions are overcome since all encoding/decoding operations are performed all- optically. Third, we realize a simple and cost-effective means using serial fiber Bragg grating arrays for performing power equalization among different wavelength channels in an erbium-doped fiber amplifier module. Such a module will be critical for compensating the deleterious effects of gain nonuniformity and transients in wavelength-division- multiplexed or wavelength routing networks. Finally, we demonstrate two different actively mode- locked erbium-doped fiber lasers that simultaneously emit two wavelengths with stable room-temperature operation. Wavelength spacings of 1.8 nm and 0.7 nm have been achieved-the closest reported to date. These lasers will find applications in high-performance transmission systems seeking to exploit

  1. Distributed fiber Bragg grating sensors information fusion and decoupling

    NASA Astrophysics Data System (ADS)

    Chen, Xiyuan

    2005-02-01

    Optical fiber sensors can be used to measure many different parameters including strain, temperature, pressure, displacement, electrical field, refractive index, rotation, position and vibrations. Among a variety of fiber sensors, fiber Bragg grating (FBG) has numerous advantages over other optical fiber sensors. One of the major advantages of this type of sensors is attributed to wavelength-encoded information given by the Bragg grating. Since the wavelength is an absolute parameter, signal from FBG may be processed such that its information remains immune to power fluctuations along the optical path. This inherent characteristic makes the FBG sensors very attractive for application in harsh environment, and on-site measurements. But FBG sensors can measure temperature and strain simultaneously; it is necessary to decouple measurement information. In the present paper, A distributed fiber Bragg grating sensors measurement system that measures global deformations of large surface online-based FBG sensors is introduced. Short overview of the measurement principle and the signal processing realized and fusion method as well as the application of the sensor in the field of large surface will be presented. A new fusion method based on the federal Kalman filter to decouple information of the temperature and strain is proposed. The algorithm of optimum estimation fusion for distributed FBG systems based on the model of deformation of beam is studied. Simulation results and experimental results show algorithm of fusion and decoupling is an efficient method for improving performance of distributed FBG sensors system.

  2. Split step solution in the iteration of the beam propagation method for analyzing Bragg gratings.

    PubMed

    Shu, Hong

    2009-08-20

    The split step method is applied to the iteration of the beam propagation method for analyzing the reflection of a laser beam by a volume Bragg grating. The application of the split step method is made possible by a way to properly treat the grating coupling terms in the paraxial wave equations. This method is demonstrated to be accurate in addition to efficient and robust. After this modification, the iteration of the beam propagation method is suitable for analyzing finite beams in volume Bragg gratings, for which the grating strength might be large. It is also suitable for analyzing Bragg gratings with nonuniform grating structures.

  3. Simulations of waveguide Bragg grating filters based on subwavelength grating waveguide

    NASA Astrophysics Data System (ADS)

    Čtyroký, Jiří; Kwiecien, Pavel; Wang, Junjia; Richter, Ivan; Glesk, Ivan; Chen, Lawrence

    2015-05-01

    Subwavelength grating waveguides represent a flexible and perspective alternative to standard silicon-on-insulator nanophotonic waveguides. In such structures, waves propagate in the form of Bloch modes, in contrast to standard longitudinally uniform waveguides. Tunability of parameters of subwavelength grating structures possesses a great advantage of a broad variability of the (effective) refractive index and its dispersion, without significantly increasing fabrication complexity. A subwavelength grating structure is based on a (quasi)-periodic arrangement of two different materials, i.e. rectangular nanoblocks of silicon, embedded into a lower-index superstrate, with a period (much) smaller than the operational wavelength of the optical radiation. Clearly, by changing the filling factor, i.e., the duty-cycle of the subwavelength grating structure, its effective refractive index can be varied essentially between that of the superstrate and that of silicon. Our contribution is devoted to a detailed numerical analysis of Bloch modes in subwavelength grating waveguides and Bragg gratings based on subwavelength grating waveguides. Two independent versions of 3D Fourier modal methods developed within last years in our laboratories are used as our standard numerical tools. By comparison with results obtained with a 2D FDTD commercially available method we show that for reliable design of subwavelength grating waveguide devices of this kind, full-vector 3D methods have to be used. It is especially the case of Bragg gratings based on subwavelength grating waveguides, as analyzed in this paper. We discuss two options of a subwavelength grating modulation - designed by changing the subwavelength grating duty cycle, and by misplacement of Si blocks, and compare their properties from the point of view of fabrication feasibility.

  4. Tunable optical delay line in SOI implemented with step chirped Bragg gratings and serial grating arrays

    NASA Astrophysics Data System (ADS)

    Spasojevic, Mina; Chen, Lawrence R.

    2013-10-01

    Tunable optical delay devices have numerous applications in optical communications [1] and have been successfully implemented using slow light elements and fiber or waveguide gratings. There has been considerable interest in siliconon- insulator (SOI) as a technology platform for compact integration of optical signal processing systems. SOI-based delay lines have been realized using coupled ring resonators [2], photonic crystals [3], and various Bragg grating-based configurations including single or coupled chirped sidewall gratings [4,5] as well as tapered rib waveguide gratings [6]. By linearly chirping the period in sidewall gratings, relatively small delays (a few ps) over a bandwidth of tens of nm were demonstrated [4]; with tapered waveguides, significantly larger delays (300-500 ps) were obtained, albeit over a narrower bandwidth (< 2 nm) [6]. On the other hand, some signal processing applications may require large delays (e.g., tens to hundreds of ps) over large bandwidths (several to tens of nm). Several designs have been proposed to meet these requirements, e.g., a step-chirped rib waveguide grating providing 50 ps delay over 15 nm [7] or complementary apodized sidewall gratings providing up to 275 ps over 3 nm [8], however, they have not been realized experimentally. In this paper, we demonstrate discretely tunable optical delay lines that provide tens of ps delay (up to 65 ps) in steps of 15-32 ps over bandwidths of several tens of nm (35-70 nm). The devices are fabricated on SOI using electron beam lithography and implemented through two different approaches: serial sidewall Bragg grating arrays and the step-chirped sidewall Bragg gratings.

  5. Improved Phase-Mask Fabrication of Fiber Bragg Gratings

    NASA Technical Reports Server (NTRS)

    Grant, Joseph; Wang, Ying; Sharma, Anup

    2004-01-01

    An improved method of fabrication of Bragg gratings in optical fibers combines the best features of two prior methods: one that involves the use of a phase mask and one that involves interference between the two coherent laser beams. The improved method affords flexibility for tailoring Bragg wavelengths and bandwidths over wide ranges. A Bragg grating in an optical fiber is a periodic longitudinal variation in the index of refraction of the fiber core. The spatial period (Bragg wavelength) is chosen to obtain enhanced reflection of light of a given wavelength that would otherwise propagate relatively unimpeded along the core. Optionally, the spatial period of the index modulation can be made to vary gradually along the grating (such a grating is said to be chirped ) in order to obtain enhanced reflection across a wavelength band, the width of which is determined by the difference between the maximum and minimum Bragg wavelengths. In the present method as in both prior methods, a Bragg grating is formed by exposing an optical fiber to an ultraviolet-light interference field. The Bragg grating coincides with the pattern of exposure of the fiber core to ultraviolet light; in other words, the Bragg grating coincides with the interference fringes. Hence, the problem of tailoring the Bragg wavelength and bandwidth is largely one of tailoring the interference pattern and the placement of the fiber in the interference pattern. In the prior two-beam interferometric method, a single laser beam is split into two beams, which are subsequently recombined to produce an interference pattern at the location of an optical fiber. In the prior phase-mask method, a phase mask is used to diffract a laser beam mainly into two first orders, the interference between which creates the pattern to which an optical fiber is exposed. The prior two-beam interferometric method offers the advantage that the period of the interference pattern can be adjusted to produce gratings over a wide range

  6. 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.

  7. Simultaneous interrogation of interferometric and Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Brady, G.; Kalli, K.; Webb, D. J.; Jackson, D. A.; Reekie, L.; Archambault, J. L.

    1995-06-01

    We propose a new method for the simultaneous interrogation of conventional two-beam interferometers and Bragg grating sensors. The technique employs an unbalanced Mach-Zehnder interferometer illuminated by a single low-coherence source, which acts as a wavelength-tunable source for the grating and as a path-matched filter for the Fizeau interferometer, thus providing a high phase resolution output for each sensor. The grating sensor demonstrates a dynamic strain resolution of \\similar 0.05 mu 3 / \\radical Hz \\end-radical at 20 Hz, while the interferometric phase resolution is better than 1mrad/ \\radical Hz \\end-radical at 20 Hz, corresponding to an rms mirror displacement of 0.08 nm.

  8. Fiber Bragg Grating Temperature Sensor for Defence and Industrial Applications

    NASA Astrophysics Data System (ADS)

    Gebru, Haftay Abadi; Padhy, B. B.

    2011-10-01

    This paper presents the design and development of fiber Bragg grating (FBG) temperature sensor suitable for naval applications like temperature monitoring of onboard ships. The Bragg gratings used here have a reflection Bragg wavelength of 1550 nm and are inscribed by phase mask technique using ultraviolet (UV) laser beam at 255.3 nm. The high-resolution temperature sensor has been designed and developed based on the principle of converting the strain to temperature. This is achieved by using bimetallic configuration. Here lead and tungsten metals are used. The expansion of lead is concentrated on the Bragg grating, thus imparting strain on it. The wavelength shift with change of temperature is recorded with optical spectrum analyzer. The minimum temperature that could be measured accurately by the sensor with repeatability is of the order of 10-2. We have achieved thermal sensitivity of 46 pm/°C and 72 pm/°C for sensor lengths (length of the metallic strips) of 60 mm and 100 mm respectively. The thermal sensitivity achieved is approximately 3.5 times and 5.5 times that of bare FBG with thermal sensitivity of 13 pm/°C for the respective sensor lengths. This type of sensor can play vital role in defence and industrial applications like monitoring fresh water/lubricating oil temperatures of machinery in onboard ships, temperature monitoring of airframe of the aircraft, aircraft engine control system sensors, temperature measurement of hot gases from propellant combustion to protect the rocket motor casing, monitoring and control of temperature of copper bars of the power generators etc.

  9. Optomechanical behavior of embedded fiber Bragg grating strain sensors

    NASA Astrophysics Data System (ADS)

    Mastro, Stephen A.

    2005-11-01

    Fiber Bragg gratings (FBGs) can provide extremely sensitive strain measurements for various materials and structures. The main functionality of the Bragg grating is along the fiber's main axis, where changes in the grating's spacing can be converted into strain measurements. Previous work from a number of researchers has identified bifurcation and broadening of the Bragg signal under transverse loading. The work presented in this thesis highlights efforts to relate transverse loading to changes in index of refraction in the fiber core cross section, and then ultimately to predicted changes in Bragg signals. The background of FBGs, their application, manufacturing, and operation is outlined. In addition, background on the general concept of photoelasticity, the relationship of stress and index of refraction, in glass materials is presented. A theoretical analysis was performed for uncoated silica fiber to calculate the stresses within an optical fiber core under transverse loading. The transverse loading profile ranged from pure diametric point loading to a more distributed profile. The stresses calculated were translated into changes of index of refraction and FBG signal values. The analysis was then simulated utilizing a numerical model, calculating stress, change of index of refraction, and change in FBG signal with various transverse loading profiles. In addition to an uncoated fiber, a polymer coated fiber system was analyzed. The model was verified by performing a laboratory experiment where FBGs were loaded transversely and their signal monitored. A special loading rig was designed and fabricated to impart transverse loading to the fiber while monitoring the compression load and deflection of the loading plates. The laboratory experienced showed reasonable agreement with the numerical model. The data show that side loading of the FBG caused a bifurcation of the signal, and that this effect can be predicted by the theoretical model. The modeling work completed

  10. Cladding-mode obtained by core-offset structure and applied in fiber Bragg grating sensor

    NASA Astrophysics Data System (ADS)

    Zhang, Xinpu; Peng, Wei; Liu, Yun; Li, Hong; Jing, Zhenguo; Yu, Qi; Zhou, Xinlei; Yao, Wenjuan; Wang, Yanjie; Liang, Yuzhang

    2011-12-01

    Comparing to core-modes of optical fibers, some cladding-modes are more sensitive to the surroundings which are very valuable to sensing application; recently, a novel type of FBG sensor with core-offset structure attracts more and more interests. Normally, the forward core-mode is not only reflected and coupled to the backward core mode by the Fiber Bragg Grating in the step-type photosensitive single mode fiber, but also coupled to the backward cladding-modes and the radiation modes, eventually they will leak or be absorbed by the high refraction index coating layer. These backward cladding-modes can also be used for sensing analysis. In this paper, we propose and develop a core-offset structure to obtain the backward core-mode and backward cladding-modes by using the wavelength shift of the backward core-mode and the power of the backward cladding-modes in Fiber Bragg Grating sensor, and the power of the backward cladding-modes are independent from temperature variation. We develop a mode coupling sensor model between the forward core-mode and the backward cladding-modes, and demonstrate two coupling methods in the core-offset structure experimentally. The sensor is fabricated and demonstrated for refractive index monitoring. Some specific works are under investigation now, more analysis and fabrication will be done to improve this cladding-mode based sensor design for applicable sensing technology.

  11. Fiber laser source/analyzer for Bragg grating sensor array interrogation

    SciTech Connect

    Ball, G.A.; Morey, W.W.; Cheo, P.K.

    1994-04-01

    This paper reports on the application of a calibrated, narrow-linewidth, single-frequency, continuously wavelength-tunable erbium fiber laser to the interrogation of a multipoint Bragg grating temperature sensor. The fiber laser was wavelength-tuned, through an array of three fiber Bragg grating sensors, to determine the temperature of each individual grating. The temperatures of the three gratings were measured as a function of grating Bragg wavelength. The minimum wavelength resolution, due to electro-mechanical repeatability, of the fiber laser source/analyzer was determined to be approximately 2.3 picometers. This corresponds to a frequency resolution of approximately 300 MHz. 10 refs.

  12. Self-heated fiber Bragg grating sensors for cryogenic environments

    NASA Astrophysics Data System (ADS)

    Chen, Tong; Swinehart, Philip R.; Maklad, Mokhtar S.; Buric, Michael P.; Chen, Kevin P.

    2010-04-01

    Cryogenic fuels are often considered as major energy alternatives to coal and petroleum based fuels. Safe and reliable sensor networks are required for on-demand, real-time fuel management in cryogenic environments. In this paper, a new sensor design is described that enhances the low-temperature performance of fiber sensors. FBGs inscribed in high attenuation fiber (HAF) are used to absorb in-fiber power light to raise the local sensor temperature in the cryogenic environment. When in-fiber power light is turned off, FBG sensors can serve as passive sensors to gauge temperature and stress in the cryogenic system. When the in-fiber power light is turned on, the heated sensors can be used to rapidly gauge fuel level and fuel leaks. In one example, a hydrogen gas sensor is demonstrated with a palladium-coated fiber Bragg grating (FBG). The low-temperature performance of the sensor was improved by heating the gratings as much as 200 K above the ambient temperature, and hydrogen concentration well below the 4% explosion limit was measured at 123K. In a second example, an array of four aluminum coated fiber Bragg gratings was used to measure liquid level in a cryogenic environment.

  13. Optical high temperature sensor based on fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Zhang, Bowei

    The aim of this thesis is to fabricate a fiber Bragg grating (FBG) temperature sensor that is capable to measure temperatures in excess of 1100°C. For this purpose, two topics have been studied and investigated during this project. One of them is the development of a high temperature resistant molecular-water induced FBGs; and the other is to investigate the effect of microwave-irradiation on the hydrogen-loaded FBG. The molecular-water induced FBGs are different from the other types of FBG. In these devices the refractive index is modulated by the periodic changes of molecular-water concentration within the grating. The device was developed using thermal annealing technology based on hydrogen-load FBG. Thermal stability of these devices was studied by measuring the grating reflectivity from room temperature to 1000°C. The stability of the device was tested by examining the FBG reflectivity for a period of time at certain temperatures. The results show that these devices are extremely stable at temperatures in excess of 1000°C. The hydroxyl concentration in the grating has been also investigated during this thesis. Based on the knowledge of hydroxyl groups inside FBG, a microwave treatment was designed to increase the hydroxyl concentration in the FBG area. The results show that the molecular-water induced grating, which was fabricated using microwave radiated hydrogen-loaded FBI, are stable at temperatures above 1100°C.

  14. Discretely tunable single-frequency fibre Bragg grating diode laser

    SciTech Connect

    Duraev, V P; Lutts, G B; Nedelin, E T; Sumarokov, M A; Medvedkov, O I; Vasil'ev, S A

    2007-12-31

    The results of the development of discretely tunable single-frequency semiconductor lasers with the external cavity based on fibre Bragg gratings (FBGs) written in a single-mode fibre are presented. It is shown, in particular, that, by using an external cavity semiconductor laser with the output mirror representing a superposition of several FBGs with different resonance wavelengths, it is possible to obtain lasing at one or several wavelengths simultaneously by varying the injection current and (or) the temperature of the active area of the laser diode. (lasers)

  15. Dynamic gate algorithm for multimode fiber Bragg grating sensor systems.

    PubMed

    Ganziy, D; Jespersen, O; Woyessa, G; Rose, B; Bang, O

    2015-06-20

    We propose a novel dynamic gate algorithm (DGA) for precise and accurate peak detection. The algorithm uses a threshold-determined detection window and center of gravity algorithm with bias compensation. We analyze the wavelength fit resolution of the DGA for different values of the signal-to-noise ratio and different peak shapes. Our simulations and experiments demonstrate that the DGA method is fast and robust with better stability and accuracy than conventional algorithms. This makes it very attractive for future implementation in sensing systems, especially based on multimode fiber Bragg gratings. PMID:26193010

  16. Fiber Bragg Gratings for High-Temperature Thermal Characterization

    SciTech Connect

    Stinson-Bagby, Kelly L.; Fielder, Robert S.

    2004-07-01

    Fiber Bragg grating (FBG) sensors were used as a characterization tool to study the SAFE-100 thermal simulator at the Nasa Marshal Space Flight Center. The motivation for this work was to support Nasa space nuclear power initiatives through the development of advanced fiber optic sensors for space-based nuclear power applications. Distributed high temperature measurements, up to 1150 deg. C, were made with FBG temperature sensors. Additionally, FBG strain measurements were taken at elevated temperatures to provide a strain profile of the core during operation. This paper will discuss the contribution of these measurements to meet the goals of Nasa Marshall Space Flight Center's Propulsion Research Center. (authors)

  17. Development of pulse laser processing for mounting fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Nishimura, Aikihko; Shimada, Yukihiro; Yonemoto, Yukihiro; Suzuki, Hirokazu; Ishibashi, Hisayoshi

    2012-07-01

    Pulse laser processing has been developed for the application of industrial plants in monitoring and maintenance. Surface cleaning by nano-second laser ablation was demonstrated for decontamination of oxide layers of Cr contained steel. Direct writing by femtosecond processing induced a Bragg grating in optical fiber to make it a seismic sensor for structural health monitoring. Adhesive cement was used to fix the seismic sensor on the surface of reactor coolant pipe material. Pulse laser processing and its related technologies were presented to overcome the severe accidents of nuclear power plants.

  18. Development of pulse laser processing for mounting fiber Bragg grating

    SciTech Connect

    Nishimura, Aikihko; Shimada, Yukihiro; Yonemoto, Yukihiro; Suzuki, Hirokazu; Ishibashi, Hisayoshi

    2012-07-11

    Pulse laser processing has been developed for the application of industrial plants in monitoring and maintenance. Surface cleaning by nano-second laser ablation was demonstrated for decontamination of oxide layers of Cr contained steel. Direct writing by femtosecond processing induced a Bragg grating in optical fiber to make it a seismic sensor for structural health monitoring. Adhesive cement was used to fix the seismic sensor on the surface of reactor coolant pipe material. Pulse laser processing and its related technologies were presented to overcome the severe accidents of nuclear power plants.

  19. Three-port binary reflective grating with high efficiency under second Bragg angle incidence

    NASA Astrophysics Data System (ADS)

    Li, Hongtao; Wang, Bo

    2016-10-01

    A binary three-port reflective grating under second Bragg angle incidence is designed in this paper. Under second Bragg angle incidence, the grating can separate nearly 33% light wave energy into the 2nd order, the 1st order and the 0th diffractive orders, respectively. Rigorous coupled-wave analysis can give numerical calculation to optimize the three-port grating depths and periods. For the optimized reflective three-port grating, TE polarization and TM polarization can have different values of grating depth and period. Compared with the reported three-port binary grating under Bragg angle incidence, the diffraction efficiencies can be improved. Moreover, the modal method is applied to explain the propagating mechanism. The highly efficient three-port binary reflective grating under second Bragg angle incidence would be manufactured in the emerging industry for its novel performance.

  20. Simultaneous demodulation of polarization mode coupling and fiber Bragg grating within a polarization maintaining fiber

    NASA Astrophysics Data System (ADS)

    Zhao, Yanshuang; Liu, Yanlei; Zhang, Jianzhong; Yang, Jun; Canning, John; Peng, G. D.; Chen, Yujin; Yuan, Libo

    2015-09-01

    We propose a simultaneous demodulation scheme of polarization mode coupling and fiber Bragg grating in a polarization maintaining fiber based on a white light interferometer. A polarization maintaining fiber with two inscribed fiber Bragg gratings is used to demonstrate the feasibility.

  1. Strain sensitivity control of fiber Bragg grating structures with fused tapers.

    PubMed

    Frazão, Orlando; Silva, Susana F O; Guerreiro, Ariel; Santos, José L; Ferreira, Luis A; Araújo, Francisco M

    2007-12-20

    We report on the analysis and experimental validation of the strain sensitivity dependences of a fiber Bragg grating written in standard optical fiber when combined with fused tapers. By controlling the difference between the cross sections of the fused taper and the Bragg grating, the strain sensitivity of the Bragg wavelength can be changed by acting on the gauge length. The strain sensing characteristics of an interferometric structure formed by fabricating a fused taper in the middle of a fiber Bragg grating are also reported. PMID:18091967

  2. Arrayed waveguide grating interrogator for fiber Bragg grating sensors: measurement and simulation.

    PubMed

    Koch, Jan; Angelmahr, Martin; Schade, Wolfgang

    2012-11-01

    A fiber Bragg grating (FBG) interrogation system based on an intensity demodulation and demultiplexing of an arrayed waveguide grating (AWG) module is examined in detail. The influence of the spectral line shape of the FBG on the signal obtained from the AWG device is discussed by accomplishing the measurement and simulation of the system. The simulation of the system helps to create quickly and precisely calibration functions for nonsymmetric, tilted, or nonapodized FBGs. Experiments show that even small sidebands of nonapodized FBGs have strong influences on the signal resulted by an AWG device with a Gaussian profile. PMID:23128724

  3. Arrayed waveguide grating interrogator for fiber Bragg grating sensors: measurement and simulation.

    PubMed

    Koch, Jan; Angelmahr, Martin; Schade, Wolfgang

    2012-11-01

    A fiber Bragg grating (FBG) interrogation system based on an intensity demodulation and demultiplexing of an arrayed waveguide grating (AWG) module is examined in detail. The influence of the spectral line shape of the FBG on the signal obtained from the AWG device is discussed by accomplishing the measurement and simulation of the system. The simulation of the system helps to create quickly and precisely calibration functions for nonsymmetric, tilted, or nonapodized FBGs. Experiments show that even small sidebands of nonapodized FBGs have strong influences on the signal resulted by an AWG device with a Gaussian profile.

  4. Reflectivity of linear and nonlinear gamma radiated apodized chirped Bragg grating under ocean

    SciTech Connect

    Hamdalla, Taymour A.

    2012-09-06

    In this paper, the effect Co{sup 60} gamma radiation is investigated on the effective refractive index of apodized chirped Bragg grating. Nine apodization profiles are considered. Comparison between the reflectivity of the gamma radiated and non radiated fiber Bragg grating has been carried out. The electric field of signals propagating through the apodized chirped fiber Bragg grating (ACFBG) is first calculated from which, new values for the refractive index are determined. The nonlinear effects appear on the ACFBG reflectivity. The effect of nonlinearity and undersea temperature and pressure on the grating is also studied.

  5. Superposition of fiber Bragg and LPG gratings for embedded strain measurement

    NASA Astrophysics Data System (ADS)

    Guyard, Romain; Leduc, Dominique; Lecieux, Yann; Lupi, Cyril

    2016-11-01

    When a fiber Bragg grating strain sensor is embedded inside a structure, the interaction of the sensor with the host material can lead to spurious results if the radial strain is neglected. In this article, we use numerical simulations to show that the axial and radial strains can be simultaneously measured with a single fiber in which a Bragg grating and a long-period grating are superimposed. Moreover, we present an optimal architecture of the sensor. xml:lang="fr"

  6. Interrogating adhesion using fiber Bragg grating sensing technology

    NASA Astrophysics Data System (ADS)

    Rasberry, Roger D.; Rohr, Garth D.; Miller, William K.; Udd, Eric; Blach, Noah T.; Davis, Ryan A.; Olson, Walter R.; Calkins, David; Roach, Allen R.; Walsh, David S.; McElhanon, James R.

    2015-05-01

    The assurance of the integrity of adhesive bonding at substrate interfaces is paramount to the longevity and sustainability of encapsulated components. Unfortunately, it is often difficult to non-destructively evaluate these materials to determine the adequacy of bonding after manufacturing and then later in service. A particularly difficult problem in this regard is the reliable detection/monitoring of regions of weak bonding that may result from poor adhesion or poor cohesive strength, or degradation in service. One promising and perhaps less explored avenue we have recently begun to investigate for this purpose centers on the use of (chirped) fiber Bragg grating sensing technology. In this scenario, a grating is patterned into a fiber optic such that a (broadband) spectral reflectance is observed. The sensor is highly sensitive to local and uniform changes across the length of the grating. Initial efforts to evaluate this approach for measuring adhesive bonding defects at substrate interfaces are discussed. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  7. Detuning in apodized point-by-point fiber Bragg gratings: insights into the grating morphology.

    PubMed

    Williams, Robert J; Krämer, Ria G; Nolte, Stefan; Withford, Michael J; Steel, M J

    2013-11-01

    Point-by-point (PbP) inscription of fiber Bragg gratings using femtosecond laser pulses is a versatile technique that is currently experiencing significant research interest for fiber laser and sensing applications. The recent demonstration of apodized gratings using this technique provides a new avenue of investigation into the nature of the refractive index perturbation induced by the PbP modifications, as apodized gratings are sensitive to variation in the average background index along the grating. In this work we compare experimental results for Gaussian- and sinc-apodized PbP gratings to a coupled-mode theory model, demonstrating that the refractive index perturbation induced by the PbP modifications has a negative contribution to the average background index which is small, despite the presence of strong reflective coupling. By employing Fourier analysis to a simplified model of an individual modification, we show that the presence of a densified shell around a central void can produce strong reflective coupling with near-zero change in the average background index. This result has important implications for the experimental implementation of apodized PbP gratings, which are of interest for a range of fiber laser and fiber sensing technologies. PMID:24216907

  8. Draw tower fiber Bragg gratings and their use in sensing technology

    NASA Astrophysics Data System (ADS)

    Lindner, E.; Mörbitz, J.; Chojetzki, C.; Becker, M.; Brückner, S.; Schuster, K.; Rothhardt, M.; Bartelt, H.

    2011-06-01

    The idea of fabricating fiber Bragg gratings already during the drawing of a fiber dates back almost 20 years. The application of a transverse holographic writing method on a draw tower offers a promising solution for a highly effective Bragg grating production. Because of the high technology requirements it took more than 10 years to develop the method into a reliable process. During the last five years the improvements in the technical development enables cost effective industrial production of draw tower gratings (1DTG®). In this paper we report about new possibilities of the improved process with respect to the grating type (type I gratings, type II gratings), the coating type (2ORMOCER®, metals) and the fiber type and diameter (125μm, 80μm and below). Furthermore, we present examples for the application of draw tower fiber Bragg gratings in sensing technologies for medical applications.

  9. System Construction for the Measurement of Bragg Grating Characteristics in Optical Fibers

    NASA Technical Reports Server (NTRS)

    West, Douglas P.

    1995-01-01

    Bragg gratings are used to measure strain in optical fibers. To measure strain they are sometimes used as a smart structure. They must be characterized after they are written to determine their spectral response. This paper deals with the test setup to characterize Bragg grating spectral responses.Bragg gratings are a photo-induced phenomena in optical fibers. The gratings can be used to measure strain by measuring the shift in wavelength. They placed the fibers into a smart structure to measure the stress and strain produced on support columns placed in bridges. As the cable is subjected to strain the grating causes a shift to a longer wavelength if the fiber is stretched and a shift to a shorter wavelength shift if the fiber is compacted. Our applications involve using the fibers to measure stress and strain on airborne systems. There are many ways to write Bragg gratings into optical fibers. Our focus is on side writing the grating. Our capabilities are limited in the production rate of the gratings. The Bragg grating is written into a fiber and becomes a permanent fixture. We are writing the grating to be centered at 1300 nm because that is the standard phase mask wavelength.

  10. Polarization Dependent Azimuthal Scattering From Tilted Fibre Bragg Gratings

    NASA Astrophysics Data System (ADS)

    Walker, Robert Bruce

    Polarization sensitive mode coupling characteristics of tilted fibre Bragg gratings (FBGs) have been exploited to develop a number of useful devices including fibre polarimeters, gain flattening filters, spectrum analyzers, polarization dependent loss (PDL) compensators, reconfigurable optical add / drop multiplexers (ROADM), as well as interferometric, and surface plasmon based sensors. Recently it was demonstrated that a single grating structure could couple the light guided in a fibre to two azimuthally separated, polarization independent, radiated beams. However the reasons for such behaviour had not been fully explained, precluding the complete understanding, exploitation and optimization of this phenomenon. This thesis explains the mechanisms underlying such behaviour through a thorough analytical examination of an existing equation formulated with the Volume Current Method (VCM), quantifying the degree to which a tilted FBG's radiation field is directionally dependent on the phase matching characteristics of a grating's three-dimensional structure as well as the polarization dependent dipole response of the medium itself. Examination of the equation's parameter space, revealed the possibility of three-beam azimuthal responses as well, and resulted in some guidelines for the design and optimization of these devices. Experimental measurements of the out-tapped field are also provided, clearly confirming these theoretical findings and reporting the fabrication of a three-beam azimuthal response grating for the first time. Drawing upon these advances, an improved polarimeter design is proposed that samples more than four detected beams with only two tilted FBGs, theoretically resulting in average Stokes vector error reductions of roughly 20%, facilitating monitoring at lower signal to noise ratios (SNRs). Finally, this thesis undertakes an analysis and re-derivation of the VCM formulation itself, designed to expand its applicability to FBGs written with

  11. Direct UV-written planar Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Holmes, Christopher; Gates, James C.; Carpenter, Lewis G.; Rogers, Helen L.; Parker, Richard M.; Cooper, Peter A.; Chaotan, Sima; Mahamd Adikan, Faisal R.; Gawith, Corin B. E.; Smith, Peter G. R.

    2015-11-01

    Integrated photonics is a proven platform for physical and chemical sensing. It offers miniaturised solutions that are suited for use in extreme environments, including strong EM-fields, EM-pulses and contact with flammable materials, often far exceeding electronic sensors in this regard. This review looks into direct UV-written planar Bragg grating technology and its application to integrated photonic sensors. The platform has been demonstrated widely for measurement of physical properties such as temperature, pressure and strain. In addition, by using an evanescent interaction, refractive index can be measured allowing for chemical and biochemical detection. Further to this, the platform has recently been utilised in quantum information processing, where quantum gate operations and single photon detection has been shown.

  12. Remote (250 km) Fiber Bragg Grating Multiplexing System

    PubMed Central

    Fernandez-Vallejo, Montserrat; Rota-Rodrigo, Sergio; Lopez-Amo, Manuel

    2011-01-01

    We propose and demonstrate two ultra-long range fiber Bragg grating (FBG) sensor interrogation systems. In the first approach four FBGs are located 200 km from the monitoring station and a signal to noise ratio of 20 dB is obtained. The second improved version is able to detect the four multiplexed FBGs placed 250 km away, offering a signal to noise ratio of 6–8 dB. Consequently, this last system represents the longest range FBG sensor system reported so far that includes fiber sensor multiplexing capability. Both simple systems are based on a wavelength swept laser to scan the reflection spectra of the FBGs, and they are composed by two identical-lengths optical paths: the first one intended to launch the amplified laser signal by means of Raman amplification and the other one is employed to guide the reflection signal to the reception system. PMID:22164101

  13. Femtosecond soliton diode on heterojunction Bragg-grating structure

    NASA Astrophysics Data System (ADS)

    Deng, Zhigui; Lin, Haolin; Li, Hongji; Fu, Shenhe; Liu, Yikun; Xiang, Ying; Li, Yongyao

    2016-09-01

    We numerically propose a scheme for realizing an all-optical femtosecond soliton diode based on a tailored heterojunction Bragg grating, which is designed by two spatially asymmetric chirped cholesteric liquid crystals. Our simulations demonstrate that with the consideration of optical nonlinearity, not only the femtosecond diode effect with nonreciprocal transmission ratio up to 120 can be achieved but also the optical pulse evolving into soliton which maintains its shape during propagation through the sample is observed. Further, the influence of pulse width and the carrier wavelength to the femtosecond diode effect is also discussed in detail. Our demonstrations might suggest a direction for experimentally realizing the femtosecond soliton diode based on the cholesteric liquid crystals.

  14. Remote (250 km) fiber Bragg grating multiplexing system.

    PubMed

    Fernandez-Vallejo, Montserrat; Rota-Rodrigo, Sergio; Lopez-Amo, Manuel

    2011-01-01

    We propose and demonstrate two ultra-long range fiber Bragg grating (FBG) sensor interrogation systems. In the first approach four FBGs are located 200 km from the monitoring station and a signal to noise ratio of 20 dB is obtained. The second improved version is able to detect the four multiplexed FBGs placed 250 km away, offering a signal to noise ratio of 6-8 dB. Consequently, this last system represents the longest range FBG sensor system reported so far that includes fiber sensor multiplexing capability. Both simple systems are based on a wavelength swept laser to scan the reflection spectra of the FBGs, and they are composed by two identical-lengths optical paths: the first one intended to launch the amplified laser signal by means of Raman amplification and the other one is employed to guide the reflection signal to the reception system. PMID:22164101

  15. Open pit slope deformation monitoring by fiber Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Xu, Guoquan; Xiong, Daiyu; Duan, Yun; Cao, Xiaoshuang

    2015-01-01

    With microstrain resolution and the capability to sample at rates of 2000 Hz or higher, fiber Bragg grating (FBG) strain sensor offers exciting new possibilities for in situ deformation monitoring induced by blasting load in an open pit slope. Here, we are developing a new technology for measuring deformation in real time on the microstrain in an open pit slope during the blasting. A fiber optically instrumented rock mass strain sensor measured strain at 100-cm intervals along a two anchor rock bolt grouted in the slope intact rock mass. In field testing, a number of transient signals have been observed, which in some cases were large enough to trigger rapid sampling. The combination of short- and long-term observation offers new insight into the slope stability and blasting cumulative effects. Therefore, FBG sensors are a useful tool for measuring in situ strain in intact rock masses.

  16. A film pressure sensor based on optical fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Zhang, Zhichun; Deng, Gang; Dai, Yongbo; Liu, Yanju; Leng, Jinsong

    2010-03-01

    The measurement of pressure is essential for the design and flying controlling of aircraft. In order to measure the surface pressures of the aircraft, the common pressure tube method and Pressure sensitive paint measurement method have their own disadvantages, and are not applicable to all aircraft structures and real time pressure monitoring. In this paper, a novel thin film pressure sensor based on Fiber Bragg Grating (FBG) is proposed, using FBG measuring the tangential strain of the disk sensing film. Theoretical circle strain of the disk sensing film of the pressure sensor under pressure and temperature variation are analyzed, and the linear relationship between FBG center wavelength shift and pressure, temperature variation is gotten. The pressure and temperature calibration experiments prove the theoretical analysis. But the calibration sensing parameters are small than the calculating ones, which is caused by the constraint of optical fibre to the thin sensing film.

  17. Strain Measurement Validation of Embedded Fiber Bragg Gratings

    NASA Astrophysics Data System (ADS)

    Emmons, Michael C.; Karnani, Sunny; Trono, Stefano; Mohanchandra, Kotekar P.; Richards, W. Lance; Carman, Gregory P.

    2010-03-01

    This study investigates the influence of strain state distribution on the accuracy of embedded optical fiber Bragg gratings (FBGs) used as strain sensors. An optical fiber embedded parallel to adjacent structural fibers in a graphite epoxy quasi-isotropic [(90/ ±45/0)S]3 lay-up is evaluated with mechanical loading parallel to the fiber optic direction. Finite element analysis (FEA) is used to evaluate the fiber optic sensors' responses both in the far field and near field regions of the mechanical grips. Comparison between experimental fiber optic strains, strain gauges, and FEA provides good correlation in the far field with differences of less than 1%. However, in the near field region, some discrepancies are found and attributed to birefringence arising from complex strain states.

  18. Dynamic and static strain gauge using superimposed fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Ma, Y. C.; Yang, Y. H.; Li, J. M.; Yang, M. W.; Tang, J.; Liang, T.

    2012-10-01

    This paper demonstrates a simple and fast interrogation method for the dynamic and/or static strain gauge using a reflection spectrum from two superimposed fiber Bragg gratings (FBGs). The superimposed FBGs are designed to decrease nonequidistant space of generated a sensing pulse train in a time domain during dynamic strain gauge. By combining centroid finding with smooth filtering methods, both the interrogation speed and accuracy are improved. A four times increase in the interrogation speed of dynamic strain, by generating a 2 kHz optical sensing pulse train from a 500 Hz scanning frequency, is demonstrated experimentally. The interrogation uncertainty and total harmonic distortion characterization of superimposed FBGs are tested and less than 4 pm standard deviation is obtained.

  19. A Magnetostrictive Composite-Fiber Bragg Grating Sensor

    PubMed Central

    Quintero, Sully M. M.; Braga, Arthur M. B.; Weber, Hans I.; Bruno, Antonio C.; Araújo, Jefferson F. D. F.

    2010-01-01

    This paper presents a light and compact optical fiber Bragg Grating sensor for DC and AC magnetic field measurements. The fiber is coated by a thick layer of a magnetostrictive composite consisting of particles of Terfenol-D dispersed in a polymeric matrix. Among the different compositions for the coating that were tested, the best magnetostrictive response was obtained using an epoxy resin as binder and a 30% volume fraction of Terfenol-D particles with sizes ranging from 212 to 300 μm. The effect of a compressive preload in the sensor was also investigated. The achieved resolution was 0.4 mT without a preload or 0.3 mT with a compressive pre-stress of 8.6 MPa. The sensor was tested at magnetic fields of up to 750 mT under static conditions. Dynamic measurements were conducted with a magnetic unbalanced four-pole rotor. PMID:22163644

  20. CCD fiber Bragg grating sensor demodulation system based on FPGA

    NASA Astrophysics Data System (ADS)

    Zhou, Q.; Ning, T. G.; Pei, L.; Li, J.; Wen, X. D.; Li, Z. X.

    2010-11-01

    A CCD fiber Bragg grating sensor demodulation system based on FPGA is proposed. The system is divided into three units: spectral imaging unit, signal detection unit and signal acquisition and processing unit. The spectral imaging unit uses reflective imaging system, which has few aberration, small size, simple structure and low cost. In the signal detection unit, information of spectrum are accessed by CCD detector, the measurement of spectral line is converted into the measurement of the pixel position of spot, multi point can be simultaneously measured, so the system's reusability, stability and reliability are improved. In the signal acquisition and processing unit, drive circuit and signal acquisition and processing circuit are designed by programmable logic device FPGA, fully use of programmable and high real-time features, simplified system design, improved the system's real-time monitoring capabilities and demodulation speed.

  1. All-optical low noise fiber Bragg grating microphone.

    PubMed

    Bandutunga, Chathura P; Fleddermann, Roland; Gray, Malcolm B; Close, John D; Chow, Jong H

    2016-07-20

    We present an all-fiber design for a microphone using a fiber Bragg grating Fabry-Perot resonator attached to a diaphragm transducer. We analytically model and verify the fiber-diaphragm mechanical interaction, using the Hänsch-Couillaud readout technique to provide necessary sensitivity. We achieved a noise-equivalent strain sensitivity of 7.1×10-12  ϵ/Hz, which corresponds to a sound pressure of 74  μPa/Hz at 1 kHz limited by laser frequency noise and yielding a signal-to-noise ratio of 47±2  dB with a 1 Pa drive at 1 kHz, in close agreement with modeled results. PMID:27463906

  2. Precise adaptive photonic rf filters realized with adaptive Bragg gratings

    NASA Astrophysics Data System (ADS)

    Wickham, Michael G.; Upton, Eric L.

    2000-09-01

    The demand for higher data capacity and reduced levels of interference in the communications arena are driving dtat links toward high carrier frequencies and wider modulation bandwidths. Circuitry for performing intermediate frequency processing over these more demanding ranges is needed to provide complex signal processing. We have demonstrated photonics technologies utilizing Bragg Grating Signal Processing (BGSP), which can be used to perform a variety of RF filter functions. The desirable benefits of multiple-tap adaptive finite impulse response (FIR) filters, infinite impulse response (IIR) filters, and equalizers are well known; however, they are usually the province of digital signal processing and demand preprocessor sample rates that require high system power consumption. BGSPs provide these functions with discrete optical taps and digital controls while only requiring bandwidths easily provided by conventional RF circuitry. This is because the actual signal processing of the large information bandwidths is performed in the optical regime, while control functions are performed at RF frequencies compatible with integrated circuit technologies. To realize the performance benefits of photonic processing, the Bragg grating reflectors must be stabilized against environmental without unduly taxing the RF control circuitry. We have implemented a orthogonally coded tap modulation technique which stabilizes the transfer function of the signal processor and enables significant adaptive IF signal processing to be obtained with very low size, weight, and power. Our demonstration of a photonic proof-of-concept architecture is a reconfigurable, multiple-tap FIR filter that is dynamically controlled to implement low-pass, high-pass, band-pass, band-stop, and tunable filters operating over bandwidths of 3 Ghz.

  3. Planar waveguide Bragg grating sensors for composite monitoring

    NASA Astrophysics Data System (ADS)

    Teigell Benéitez, Nuria; Missinne, Jeroen; Chiesura, Gabriele; Luyckx, Geert; Degrieck, Joris; Van Steenberge, Geert

    2016-04-01

    Composite materials are extensively used in a wide array of application markets by virtue of their strength, stiffness and lightness. Many composite structures are replaced today not only after failure but also before, for precautionary reasons. Adding optical sensing intelligence to these structures not only prolongs their lifetime but also significantly reduces the use of raw materials and energy. The use of optical based sensors offer numerous advantages i.e. integrability, high sensitivity, compactness and electromagnetic immunity. Most sensors integrated in composites are based on silica fibers with Bragg gratings. However, polymers are an interesting alternative because they present several advantages. They have high values in the opticalconstants involved in sensing, are cost-effective and allow larger elongations than silica. Moreover, planar optical waveguides represent an interesting approach to be further integrated e.g. in circuits. We present a comparison between Ormocer®-based and epoxy-based polymer waveguide Bragg grating sensors. Both polymers were screened for their compatibility with composite production processes and for their sensitivity to measure temperature and stress. Ormocer®-based sensors were found to exhibit a very high sensitivity (-250 pm/°C) for temperature sensing, while the epoxy-based sensors, although less sensitive (-90 pm/°C) were more compatible with the epoxy-based composite production process. In terms of sensitivity to measure stress, both materials were found to be analogous with measured values of (2.98 pm/μepsilon) for the epoxy-based and (3.00 pm/μepsilon) for Ormocer®-based sensors.

  4. Microfiber Bragg grating hydrogen sensor base on co-sputtered Pd/Ni composite film

    NASA Astrophysics Data System (ADS)

    Wang, Gaopeng; Yang, Minghong; Dai, Jixiang; Cheng, Cheng; Yuan, Yinqian

    2015-07-01

    A novel hydrogen sensor based on Pd/Ni co-sputtered coating on micro fiber Bragg grating (MFBG) is proposed and experimentally demonstrated. The microfiber is stretched uniformly and the Bragg grating is directly inscribed on the microfiber without hydrogen loading using 193 nm ArF excimer laser and a phase mask. Palladium and nickel coatings are co-sputtered on the micro fiber Bragg grating for hydrogen sensing. The MFBG hydrogen sensors are characterized concerning their response to the hydrogen, ambient temperature and ambient refractive index, respectively. The performance of the proposed MFBG hydrogen sensor is obviously enhanced, especially when compared to standard FBG hydrogen sensors.

  5. Compressive and tensile strain sensing using a polymer planar Bragg grating.

    PubMed

    Rosenberger, M; Hessler, S; Belle, S; Schmauss, B; Hellmann, R

    2014-03-10

    A polymer planar Bragg grating sensor is used for measuring both mechanical compressive and tensile strain. The planar waveguide with integrated Bragg grating is fabricated in bulk Polymethylmethacrylate in a single writing step using combined amplitude and phase mask technique. After butt coupling of a single-mode optical fiber the planar structure can be applied for measuring both mechanical tensile and compressive strain alongside the integrated waveguide without the need of further modifications. In this respect, we particularly report for the first time compressive strain measurements using a polymer Bragg grating. Furthermore, the sensitivity of the sensor against tensile and compressive strain, its reproducibility and hysteresis are investigated and discussed.

  6. Implementation of interrogation systems for fiber Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Varghese P, Benjamin; Kumar R, Dinesh; Raju, Mittu; Madhusoodanan, K. N.

    2013-09-01

    The development of two simple methods for wavelength-optical intensity modulation techniques for fiber Bragg grating (FBG) sensors is presented. The performance is evaluated by measuring the strain and temperature. The first method consists of a narrow band source, an optical circulator, an FBG, and a power meter. The source and Bragg reflected signal from the FBG need to be matched to get linear results with good power levels. The source spectral power levels are very critical in this study. The power reflected from a matched reference FBG is fed into the measuring FBG in the second method. Since the FBGs are matched, the entire power is reflected back initially. During the measurement, the change in the measurand causes the reflected power from the sensing FBG to vary. A costly high resolution spectrum analyzer is required only during the characterization of the FBG and source. The performances of two interrogators are compared by measuring the strain and temperature. In the second method, the strain measurements can be made insensitive to the temperature variation by selecting a source with a flat spectrum at the measurement range. Highlights of these methods are the portability, cost effectiveness and better resolution.

  7. Enhancement of detection accuracy of fiber Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Zeh, Thomas; Schweizer, Hans; Meixner, Andreas; Purde, Andreas; Koch, Alexander W.

    2004-06-01

    Over the course of the last few years, several readout techniques for fiber Bragg grating (FBG) sensors have been proposed. However, all of them suffer from specific restrictions concerning response speed, accuracy, sensor multiplexibility and cost. In the past, it was often assumed that diffraction grating spectrometers were suitable only for FBG applications with modest resolution. The achievable pixel resolution is nowadays in the range of several tens of pm. For FBG sensors with typical temperature coefficients of 5 pm/K and strain coefficients of 0.7 pm/μɛ this resolution is not sufficient for the majority of applications. We present a discussion on different methods for the subpixel registration of FBG spectra and we introduce a novel detection algorithm: the linear phase operator technique (LPO). Even under extreme noisy conditions LPO ensures a significant resolution enhancement by a factor of three compared to conventional algorithms and is shown to be very efficient in its implementation. The efficiencies of several conventional algorithms and LPO is compared by simulations and by means of a test bench. With slight efforts LPO is adaptable to further applications like spectrometer based Fabry-Perot sensors and other sensors with CCD detectors.

  8. Nonpigtail optical coupling to embedded fiber Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Qiu, Liang; Goossen, Keith W.; Heider, Dirk; O'Brien, Daniel J.; Wetzel, Eric D.

    2010-05-01

    In recent decades, optical fiber has proven useful for many sensor applications. Specifically, fiber Bragg grating (FBG) sensors have shown great utility for integrity management and environmental sensing of composite structures. One major drawback of FBG sensors, however, is the lack of a robust, nonpigtail technique for coupling to the embedded FBG sensor. In this paper, a novel method of free-space passive coupling of light into FBG sensors is described. An angled 45-deg mirror integrated directly into the fiber was used as an input coupling technique. We investigated the application of this approach to both single- and multimode glass fibers containing FBGs. For multimode FBGs, we studied the grating's uniformity across the fiber diameter and its effect on normal free-space coupling. In single-mode investigations, a novel method of coupling to the sensor via splicing a multimode fiber to a single-mode FBG (SMFBG) was developed. Finally, free-space coupling to an embedded SMFBG was employed to measure the tensile strain. Excellent agreement was found between the FBG and conventional electrical resistance strain gauges. We conclude that this coupling method might eliminate the need for pigtailing by providing a more robust coupling method for FBG sensors.

  9. Fiber optic hot-wire flowmeter based on a metallic coated hybrid long period grating/fiber Bragg grating structure.

    PubMed

    Caldas, Paulo; Jorge, Pedro A S; Rego, Gaspar; Frazão, Orlando; Santos, José Luís; Ferreira, Luís Alberto; Araújo, Francisco

    2011-06-10

    In this work an all-optical hot-wire flowmeter based on a silver coated fiber combining a long period grating and a fiber Bragg grating (FBG) structure is proposed. Light from a pump laser at 1480  nm propagating down the fiber is coupled by the long period grating into the fiber cladding and is absorbed by the silver coating deposited on the fiber surface over the Bragg grating structure. This absorption acts like a hot wire raising the fiber temperature locally, which is effectively detected by the FBG resonance shift. The temperature increase depends on the flow speed of the surrounding air, which has the effect of cooling the fiber. It is demonstrated that the Bragg wavelength shift can be related to the flow speed. A flow speed resolution of 0.08  m/s is achieved using this new configuration. PMID:21673779

  10. Femtosecond-laser-inscribed sampled fiber Bragg grating with ultrahigh thermal stability.

    PubMed

    Zhang, Congzhe; Yang, Yuanhong; Wang, Chao; Liao, Changrui; Wang, Yiping

    2016-02-22

    We have successfully fabricated a series of sampled fiber Bragg gratings with easily adjustable sampling periods and duty cycles using an 800 nm femtosecond laser point-by-point inscription. The thermal stability of the fabricated fiber gratings was investigated using isochronal annealing tests, which indicated that the fiber gratings are capable of maintaining high reflectivity at temperatures of up to 1000°C for 8 h. This demonstrates the potential of the developed sampled fiber Bragg gratings for use in multi-wavelength fiber lasers and a variety of high temperature applications. PMID:26907050

  11. Enhanced strain and temperature sensing by reduced graphene oxide coated etched fiber Bragg gratings.

    PubMed

    S, Sridevi; Vasu, K S; Asokan, S; Sood, A K

    2016-06-01

    This Letter reports on an etched fiber Bragg grating (eFBG) sensor coated with reduced graphene oxide (RGO) having enhanced sensitivity for physical parameters such as strain and temperature. The synergetic effect of the changes in grating pitch and refractive index of RGO with change in temperature or strain enhances the shift in Bragg wavelength (λB). The RGO-coated eFBG sensors exhibit a strain sensitivity of 5.5 pm/μϵ (∼5 times that of bare fiber Bragg gratings) and temperature sensitivity of 33 pm/°C (∼3 times that of bare fiber Bragg gratings). The resolutions of ∼1  μϵ and ∼0.3°C have been obtained for strain and temperature respectively, using RGO-coated eFBG sensors. PMID:27244425

  12. Enhanced strain and temperature sensing by reduced graphene oxide coated etched fiber Bragg gratings.

    PubMed

    S, Sridevi; Vasu, K S; Asokan, S; Sood, A K

    2016-06-01

    This Letter reports on an etched fiber Bragg grating (eFBG) sensor coated with reduced graphene oxide (RGO) having enhanced sensitivity for physical parameters such as strain and temperature. The synergetic effect of the changes in grating pitch and refractive index of RGO with change in temperature or strain enhances the shift in Bragg wavelength (λB). The RGO-coated eFBG sensors exhibit a strain sensitivity of 5.5 pm/μϵ (∼5 times that of bare fiber Bragg gratings) and temperature sensitivity of 33 pm/°C (∼3 times that of bare fiber Bragg gratings). The resolutions of ∼1  μϵ and ∼0.3°C have been obtained for strain and temperature respectively, using RGO-coated eFBG sensors.

  13. Excitation of surface electromagnetic waves in a graphene-based Bragg grating

    PubMed Central

    Sreekanth, Kandammathe Valiyaveedu; Zeng, Shuwen; Shang, Jingzhi; Yong, Ken-Tye; Yu, Ting

    2012-01-01

    Here, we report the fabrication of a graphene-based Bragg grating (one-dimensional photonic crystal) and experimentally demonstrate the excitation of surface electromagnetic waves in the periodic structure using prism coupling technique. Surface electromagnetic waves are non-radiative electromagnetic modes that appear on the surface of semi-infinite 1D photonic crystal. In order to fabricate the graphene-based Bragg grating, alternating layers of high (graphene) and low (PMMA) refractive index materials have been used. The reflectivity plot shows a deepest, narrow dip after total internal reflection angle corresponds to the surface electromagnetic mode propagating at the Bragg grating/air boundary. The proposed graphene based Bragg grating can find a variety of potential surface electromagnetic wave applications such as sensors, fluorescence emission enhancement, modulators, etc. PMID:23071901

  14. Fiber Bragg Grating (FBG) sensors as flatness and mechanical stretching sensors

    NASA Astrophysics Data System (ADS)

    Abbaneo, D.; Abbas, M.; Abbrescia, M.; Abdelalim, A. A.; Abi Akl, M.; Aboamer, O.; Acosta, D.; Ahmad, A.; Ahmed, W.; Ahmed, W.; Aleksandrov, A.; Aly, R.; Altieri, P.; Asawatangtrakuldee, C.; Aspell, P.; Assran, Y.; Awan, I.; Bally, S.; Ban, Y.; Banerjee, S.; Barashko, V.; Barria, P.; Bencze, G.; Beni, N.; Benussi, L.; Bhopatkar, V.; Bianco, S.; Bos, J.; Bouhali, O.; Braghieri, A.; Braibant, S.; Buontempo, S.; Calabria, C.; Caponero, M.; Caputo, C.; Cassese, F.; Castaneda, A.; Cauwenbergh, S.; Cavallo, F. R.; Celik, A.; Choi, M.; Choi, S.; Christiansen, J.; Cimmino, A.; Colafranceschi, S.; Colaleo, A.; Conde Garcia, A.; Czellar, S.; Dabrowski, M. M.; De Lentdecker, G.; De Oliveira, R.; De Robertis, G.; Dildick, S.; Dorney, B.; Elmetenawee, W.; Endroczi, G.; Errico, F.; Fenyvesi, A.; Ferry, S.; Furic, I.; Giacomelli, P.; Gilmore, J.; Golovtsov, V.; Guiducci, L.; Guilloux, F.; Gutierrez, A.; Hadjiiska, R. M.; Hassan, A.; Hauser, J.; Hoepfner, K.; Hohlmann, M.; Hoorani, H.; Iaydjiev, P.; Jeng, Y. G.; Kamon, T.; Karchin, P.; Korytov, A.; Krutelyov, S.; Kumar, A.; Kim, H.; Lee, J.; Lenzi, T.; Litov, L.; Loddo, F.; Madorsky, A.; Maerschalk, T.; Maggi, M.; Magnani, A.; Mal, P. K.; Mandal, K.; Marchioro, A.; Marinov, A.; Masod, R.; Majumdar, N.; Merlin, J. A.; Mitselmakher, G.; Mohanty, A. K.; Mohamed, S.; Mohapatra, A.; Molnar, J.; Muhammad, S.; Mukhopadhyay, S.; Naimuddin, M.; Nuzzo, S.; Oliveri, E.; Pant, L. M.; Paolucci, P.; Park, I.; Passeggio, G.; Passamonti, L.; Pavlov, B.; Philipps, B.; Piccolo, D.; Pierluigi, D.; Postema, H.; Puig Baranac, A.; Radi, A.; Radogna, R.; Raffone, G.; Ranieri, A.; Rashevski, G.; Riccardi, C.; Rodozov, M.; Rodrigues, A.; Ropelewski, L.; RoyChowdhury, S.; Russo, A.; Ryu, G.; Ryu, M. S.; Safonov, A.; Salva, S.; Saviano, G.; Sharma, A.; Sharma, A.; Sharma, R.; Shah, A. H.; Shopova, M.; Sturdy, J.; Sultanov, G.; Swain, S. K.; Szillasi, Z.; Talvitie, J.; Tatarinov, A.; Tuuva, T.; Tytgat, M.; Vai, I.; Van Stenis, M.; Venditti, R.; Verhagen, E.; Verwilligen, P.; Vitulo, P.; Volkov, S.; Vorobyev, A.; Wang, D.; Wang, M.; Yang, U.; Yang, Y.; Yonamine, R.; Zaganidis, N.; Zenoni, F.; Zhang, A.

    2016-07-01

    A novel approach which uses Fiber Bragg Grating (FBG) sensors has been utilized to assess and monitor the flatness of Gaseous Electron Multipliers (GEM) foils. The setup layout and preliminary results are presented.

  15. High-speed two-dimensional laser scanner based on Bragg gratings stored in photothermorefractive glass.

    PubMed

    Yaqoob, Zahid; Arain, Muzammil A; Riza, Nabeel A

    2003-09-10

    A high-speed free-space wavelength-multiplexed optical scanner with high-speed wavelength selection coupled with narrowband volume Bragg gratings stored in photothermorefractive (PTR) glass is reported. The proposed scanner with no moving parts has a modular design with a wide angular scan range, accurate beam pointing, low scanner insertion loss, and two-dimensional beam scan capabilities. We present a complete analysis and design procedure for storing multiple tilted Bragg-grating structures in a single PTR glass volume (for normal incidence) in an optimal fashion. Because the scanner design is modular, many PTR glass volumes (each having multiple tilted Bragg-grating structures) can be stacked together, providing an efficient throughput with operations in both the visible and the infrared (IR) regions. A proof-of-concept experimental study is conducted with four Bragg gratings in independent PTR glass plates, and both visible and IR region scanner operations are demonstrated.

  16. Excitation of surface electromagnetic waves in a graphene-based Bragg grating.

    PubMed

    Sreekanth, Kandammathe Valiyaveedu; Zeng, Shuwen; Shang, Jingzhi; Yong, Ken-Tye; Yu, Ting

    2012-01-01

    Here, we report the fabrication of a graphene-based Bragg grating (one-dimensional photonic crystal) and experimentally demonstrate the excitation of surface electromagnetic waves in the periodic structure using prism coupling technique. Surface electromagnetic waves are non-radiative electromagnetic modes that appear on the surface of semi-infinite 1D photonic crystal. In order to fabricate the graphene-based Bragg grating, alternating layers of high (graphene) and low (PMMA) refractive index materials have been used. The reflectivity plot shows a deepest, narrow dip after total internal reflection angle corresponds to the surface electromagnetic mode propagating at the Bragg grating/air boundary. The proposed graphene based Bragg grating can find a variety of potential surface electromagnetic wave applications such as sensors, fluorescence emission enhancement, modulators, etc. PMID:23071901

  17. High-speed two-dimensional laser scanner based on Bragg gratings stored in photothermorefractive glass.

    PubMed

    Yaqoob, Zahid; Arain, Muzammil A; Riza, Nabeel A

    2003-09-10

    A high-speed free-space wavelength-multiplexed optical scanner with high-speed wavelength selection coupled with narrowband volume Bragg gratings stored in photothermorefractive (PTR) glass is reported. The proposed scanner with no moving parts has a modular design with a wide angular scan range, accurate beam pointing, low scanner insertion loss, and two-dimensional beam scan capabilities. We present a complete analysis and design procedure for storing multiple tilted Bragg-grating structures in a single PTR glass volume (for normal incidence) in an optimal fashion. Because the scanner design is modular, many PTR glass volumes (each having multiple tilted Bragg-grating structures) can be stacked together, providing an efficient throughput with operations in both the visible and the infrared (IR) regions. A proof-of-concept experimental study is conducted with four Bragg gratings in independent PTR glass plates, and both visible and IR region scanner operations are demonstrated. PMID:14503693

  18. Excitation of surface electromagnetic waves in a graphene-based Bragg grating.

    PubMed

    Sreekanth, Kandammathe Valiyaveedu; Zeng, Shuwen; Shang, Jingzhi; Yong, Ken-Tye; Yu, Ting

    2012-01-01

    Here, we report the fabrication of a graphene-based Bragg grating (one-dimensional photonic crystal) and experimentally demonstrate the excitation of surface electromagnetic waves in the periodic structure using prism coupling technique. Surface electromagnetic waves are non-radiative electromagnetic modes that appear on the surface of semi-infinite 1D photonic crystal. In order to fabricate the graphene-based Bragg grating, alternating layers of high (graphene) and low (PMMA) refractive index materials have been used. The reflectivity plot shows a deepest, narrow dip after total internal reflection angle corresponds to the surface electromagnetic mode propagating at the Bragg grating/air boundary. The proposed graphene based Bragg grating can find a variety of potential surface electromagnetic wave applications such as sensors, fluorescence emission enhancement, modulators, etc.

  19. Wavelength interrogation of fiber Bragg grating sensors using tapered hollow Bragg waveguides.

    PubMed

    Potts, C; Allen, T W; Azar, A; Melnyk, A; Dennison, C R; DeCorby, R G

    2014-10-15

    We describe an integrated system for wavelength interrogation, which uses tapered hollow Bragg waveguides coupled to an image sensor. Spectral shifts are extracted from the wavelength dependence of the light radiated at mode cutoff. Wavelength shifts as small as ~10  pm were resolved by employing a simple peak detection algorithm. Si/SiO₂-based cladding mirrors enable a potential operational range of several hundred nanometers in the 1550 nm wavelength region for a taper length of ~1  mm. Interrogation of a strain-tuned grating was accomplished using a broadband amplified spontaneous emission (ASE) source, and potential for single-chip interrogation of multiplexed sensor arrays is demonstrated. PMID:25361125

  20. Wavelength interrogation of fiber Bragg grating sensors using tapered hollow Bragg waveguides.

    PubMed

    Potts, C; Allen, T W; Azar, A; Melnyk, A; Dennison, C R; DeCorby, R G

    2014-10-15

    We describe an integrated system for wavelength interrogation, which uses tapered hollow Bragg waveguides coupled to an image sensor. Spectral shifts are extracted from the wavelength dependence of the light radiated at mode cutoff. Wavelength shifts as small as ~10  pm were resolved by employing a simple peak detection algorithm. Si/SiO₂-based cladding mirrors enable a potential operational range of several hundred nanometers in the 1550 nm wavelength region for a taper length of ~1  mm. Interrogation of a strain-tuned grating was accomplished using a broadband amplified spontaneous emission (ASE) source, and potential for single-chip interrogation of multiplexed sensor arrays is demonstrated.

  1. Practical considerations for a four-channel multiplexed Bragg grating fiber sensor system

    NASA Astrophysics Data System (ADS)

    Alavie, A. Tino; Ohn, Myo M.; Glennie, Derek J.; Karr, Shawn E.; Maaskant, Robert; Fishbein, G.; Lee, R.; Huang, Shang Yuan; Measures, Raymond M.

    1994-02-01

    A multichannel Bragg grating fiber laser demodulation system capable of interrogating four or more Bragg grating sensors for strain and temperature monitoring has been designed and developed. System configuration and various practical considerations for a field deployable system are discussed. Preliminary data indicates a dynamic strain range in excess of 5000 (mu) (epsilon) at a resolution of 1 (mu) (epsilon) . Both the strain dynamic range and resolution are easily modified.

  2. Polarization mode coupling and related effects in fiber Bragg grating inscribed in polarization maintaining fiber.

    PubMed

    Zhao, Yanshuang; Sun, Bo; Liu, Yanlei; Ren, Jing; Zhang, Jianzhong; Yang, Jun; Canning, John; Peng, G D; Yuan, Libo

    2016-01-11

    Polarization mode coupling (PMC) and related effects from writing fiber Bragg gratings in polarization maintaining fiber (FBGs-in-PMF) are observed experimentally for the first time by optical fiber coherence domain polarimetry (OCDP) using a broadband light source. PMC is another useful aspect of FBG-in-PMF besides Bragg wavelength and its possible potential is evaluated and discussed. A localized and long range temperature measurement based on the PMC and Bragg wavelength is given as an example. PMID:26832291

  3. [Research on Temperature Detection System Based on Improved Fiber Bragg Grating].

    PubMed

    Yu, Li-xia; Qin, Li

    2016-01-01

    Traditional temperature detection system based on Fiber Bragg Grating is suitable for large-scale, real-time multi-point temperature detection field. But its stability of temperature response is poor, shift amount of Bragg grating center wavelength is poor linearity with temperature variation. In order to improve the stability for system and temperature detection accuracy of the system, an improved temperature detection system based on Fiber Bragg Grating was designed. The method of dual fiber parallel acquisition for temperature data was used on the same point, and then center wavelength data was differentially processed. It was realized that the random errors of the system were effectively real-time eliminated in the process temperature. The function relationships of center wavelength shift amount of Fiber Bragg Grating and temperature variation was derived in this mode, and the new structure of the probes for Fiber Bragg Grating was designed. In the experiments, measurement data of Improved temperature detection system based on Fiber Bragg Grating was compared with the data of traditional system. Experimental results show that temperature measurement accuracy of improved system was up to 0.5 degrees C, and its accuracy has been improved compared to conventional systems. Meanwhile, the measurement error was significantly better than traditional systems. It proved that the design can improve the stability of temperature detection for the system. PMID:27228783

  4. Fabrication of Extremely Short Length Fiber Bragg Gratings for Sensor Applications

    NASA Technical Reports Server (NTRS)

    Wu, Meng-Chou; Rogowski, Robert S.; Tedjojuwono, Ken K.

    2002-01-01

    A new technique and a physical model for writing extremely short length Bragg gratings in optical fibers have been developed. The model describes the effects of diffraction on the spatial spectra and therefore, the wavelength spectra of the Bragg gratings. Using an interferometric technique and a variable aperture, short gratings of various lengths and center wavelengths were written in optical fibers. By selecting the related parameters, the Bragg gratings with typical length of several hundred microns and bandwidth of several nanometers can be obtained. These short gratings can be apodized with selected diffraction patterns and hence their broadband spectra have a well-defined bell shape. They are suitable for use as miniaturized distributed strain sensors, which have broad applications to aerospace research and industry as well.

  5. Response of some pi-phase-shifted Bragg gratings to elevated pressure

    NASA Astrophysics Data System (ADS)

    Bal, Harpreet K.; Dragomir, Nicoleta M.; Sidiroglou, Fotios; Wade, Scott A.; Baxter, Greg W.; Collins, Stephen F.

    2011-05-01

    The effect of pressures up to 200 kPa on pi-phase-shifted Bragg gratings was investigated in several types of fibers placed in a pressure chamber. Standard and alternative types of pi-phase shifted gratings were studied, and changes in reflection spectra caused by pressure changes were monitored. The alternative pi-phase shifted grating was fabricated using a phase mask with 536-nm pitch exhibiting features at twice the Bragg wavelength near 1552 nm due to the interleaved refractive index modulations along the fiber core with the periodicity of the phase mask. The three gratings studied exhibited quite different variation in Bragg wavelength with increased pressure for the different fiber types, and the alternative pi-phase-shifted grating in Corning HI 1060 FLEX fiber also suffered a significant change in the shape of the peaks.

  6. All-Optical Micro Motors Based on Moving Gratings in Photosensitive Media

    NASA Technical Reports Server (NTRS)

    Curley, M.; Sarkisov, S. S.; Fields, A.; Smith, C.; Kukhtarev, N.; Kulishov, M. B.; Adamovsky, G. (Technical Monitor)

    2000-01-01

    An all-optical micro motor with a rotor driven by a traveling wave of surface deformation of a stator being in contact with the rotor is being studied. Instead of an ultrasonic wave produced by an electrically driven piezoelectric actuator as in ultrasonic motors, the wave is a result of a photo induced surface deformation of a photosensitive material produced by a traveling holographic grating. Two phase modulated coherent optical beams generate the grating. Several types of photosensitive materials are studied such as photorefractive crystals, photosensitive piezoelectric ceramics, and side-chain liquid crystalline polyesters. In order to be considered as a possible candidate for micro motors, the material should exhibit surface deformation produced by moving grating of the order of 10 micron. Deformations produced by static holographic gratings are studied in photorefractive crystals of LiNbO3 using high vertical resolution surface profilometer Dektak 3 and surface interferometer WYKO. An experimental set-up with moving grating has been developed. The set-up uses a two-beam interferometry configuration with one beam being reflected by a thin mirror mounted on a loud speaker. A ramp voltage signal generator drives the speaker. Changing voltage, polarity, and frequency of the signal can easily generate vibrating gratings or moving gratings in both directions. A vibrating grating has been applied to a photorefractive crystal of BSO controlled by an external electric field of the order of 104 V/cm. We have additionally studied effects of moving grating interaction with light absorbing fluids such as solutions of 2,9,16,23-Tetrakis(phenylthio)-29H, 31 Hphthalocyanine in chlorobenzene in capillary tubes. The purpose of using a liquid is to show that the moving gratings can force a liquid to shift. The interaction of a single low power focused laser beam at 633 nm with such fluid produced an intensive circular motion, which also might be applied to all-optical micro

  7. Thermal Evaluation of Fiber Bragg Gratings at Extreme Temperatures

    NASA Technical Reports Server (NTRS)

    Juergens, Jeffrey; Adamovsky, Grigory; Bhatt, Ramakrishna; Morscher, Gregory; Floyd, Bertram

    2005-01-01

    The development of integrated fiber optic sensors for use in aerospace health monitoring systems demands that the sensors be able to perform in extreme environments. In order to use fiber optic sensors effectively in an extreme environment one must have a thorough understanding of the sensor's capabilities, limitations, and performance under extreme environmental conditions. This paper reports on our current sensor evaluation examining the performance of freestanding fiber Bragg gratings (FBG) at extreme temperatures. While the ability of FBGs to survive at extreme temperatures has been established, their performance and long term survivability is not well documented. At extreme temperatures the grating structure would be expected to dissipate, degrading the sensors performance and eventually ceasing to return a detectable signal. The fiber jacket will dissipate leaving a brittle, unprotected fiber. For FBGs to be used in aerospace systems their performance and limitations need to be thoroughly understood at extreme temperatures. As the limits of the FBGs performance are pushed the long term survivability and performance of the sensor comes into question. We will not only examine the ability of FBGs to survive extreme temperatures but also look at their performance during many thermal cycles. This paper reports on test results of the performance of thermal cycling commercially available FBGs, at temperatures up to 1000 C, seen in aerospace applications. Additionally this paper will report on the performance of commercially available FBGs held at 1000 C for hundreds of hours. Throughout the evaluation process, various parameters of the FBGs performance were monitored and recorded. Several test samples were subjected to identical test conditions to allow for statistical analysis of the data. Test procedures, calibrations, referencing techniques, performance data, and interpretations and explanations of results are presented in the paper along with directions for

  8. Investigation of Structural Properties of Carbon-Epoxy Composites Using Fiber-Bragg Gratings

    NASA Technical Reports Server (NTRS)

    Grant, J.; Kaul, R.; Taylor, S.; Jackson, K.; Sharma, A.; Burdine, Robert V. (Technical Monitor)

    2002-01-01

    Fiber Bragg-gratings are embedded in carbon-epoxy laminates as well as bonded on the surface of cylindrical structures fabricated out of such composites. Structural properties of such composites is investigated. The measurements include stress-strain relation in laminates and Poisson's ratio in several specimens with varying orientation of the optical fiber Bragg-sensor with respect to the carbon fiber in an epoxy matrix. Additionally, Bragg gratings are bonded on the surface of cylinders fabricated out of carbon-epoxy composites and longitudinal and hoop strain on the surface is measured.

  9. Generation of High-Density Electrons Based on Plasma Grating Induced Bragg Diffraction in Air

    SciTech Connect

    Shi Liping; Li Wenxue; Wang Yongdong; Lu Xin; Ding Liang'en; Zeng Heping

    2011-08-26

    Efficient nonlinear Bragg diffraction was observed as an intense infrared femtosecond pulse was focused on a plasma grating induced by interference between two ultraviolet femtosecond laser pulses in air. The preformed electrons inside the plasma grating were accelerated by subsequent intense infrared laser pulses, inducing further collisional ionization and significantly enhancing the local electron density.

  10. Sensing delamination in epoxy encapsulant systems with fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Jones, Brad H.; Rohr, Garth D.; Kaczmarowski, Amy K.

    2016-05-01

    Fiber Bragg gratings (FBGs) are well-suited for embedded sensing of interfacial phenomena in materials systems, due to the sensitivity of their spectral response to locally non-uniform strain fields. Over the last 15 years, FBGs have been successfully employed to sense delamination at interfaces, with a clear emphasis on planar events induced by transverse cracks in fiber-reinforced plastic laminates. We have built upon this work by utilizing FBGs to detect circular delamination events at the interface between epoxy films and alumina substrates. Two different delamination processes are examined, based on stress relief induced by indentation of the epoxy film or by cooling to low temperature. We have characterized the spectral response pre- and post-delamination for both simple and chirped FBGs as a function of delamination size. We show that delamination is readily detected by the evolution of a non-uniform strain distribution along the fiber axis that persists after the stressing condition is removed. These residual strain distributions differ substantially between the delamination processes, with indentation and cooling producing predominantly tensile and compressive strain, respectively, that are well-captured by Gaussian profiles. More importantly, we observe a strong correlation between spectrally-derived measurements, such as spectral widths, and delamination size. Our results further highlight the unique capabilities of FBGs as diagnostic tools for sensing delamination in materials systems.

  11. WDM hybrid microoptical transceiver with Bragg volume grating

    NASA Astrophysics Data System (ADS)

    Jeřábek, Vitezslav; Armas, Julio; Mareš, David; Prajzler, Václav

    2012-02-01

    The paper presents the design, simulation and construction results of the wavelength division multiplex bidirectional transceiver module (WDM transceiver) for the passive optical network (PON) of a fiber to the home (FTTH) topology network. WDM transceiver uses a microoptical hybrid integration technology with volume holographic Bragg grating triplex filter -VHGT and a collimation lenses imagine system for wavelength multiplexing/ demultiplexing. This transmission type VHGT filter has high diffraction angle, very low insertion loses and optical crosstalk, which guide to very good technical parameters of transceiver module. WDM transceiver has been constructed using system of a four micromodules in the new circle topology. The optical micromodule with VHGT filter and collimation and decollimation lenses, two optoelectronics microwave receiver micromodules for receiving download information (internet and digital TV signals) and optoelectronic transmitter micromodule for transmitting upload information. In the paper is presented the optical analysis of the optical imagine system by ray-transfer matrix. We compute and measure VHGT characteristics such as diffraction angle, diffraction efficiency and diffraction crosstalk of the optical system for 1310, 1490 and 1550 nm wavelength radiation. For the design of optoelectronic receiver micromodule was used the low signal electrical equivalent circuit for the dynamic performance signal analysis. In the paper is presented the planar form WDM transceiver with polymer optical waveguides and two stage interference demultiplexing optical filter as well.

  12. WDM hybrid microoptical transceiver with Bragg volume grating

    NASA Astrophysics Data System (ADS)

    Jeřábek, Vitezslav; Armas, Julio; Mareš, David; Prajzler, Václav

    2011-09-01

    The paper presents the design, simulation and construction results of the wavelength division multiplex bidirectional transceiver module (WDM transceiver) for the passive optical network (PON) of a fiber to the home (FTTH) topology network. WDM transceiver uses a microoptical hybrid integration technology with volume holographic Bragg grating triplex filter -VHGT and a collimation lenses imagine system for wavelength multiplexing/ demultiplexing. This transmission type VHGT filter has high diffraction angle, very low insertion loses and optical crosstalk, which guide to very good technical parameters of transceiver module. WDM transceiver has been constructed using system of a four micromodules in the new circle topology. The optical micromodule with VHGT filter and collimation and decollimation lenses, two optoelectronics microwave receiver micromodules for receiving download information (internet and digital TV signals) and optoelectronic transmitter micromodule for transmitting upload information. In the paper is presented the optical analysis of the optical imagine system by ray-transfer matrix. We compute and measure VHGT characteristics such as diffraction angle, diffraction efficiency and diffraction crosstalk of the optical system for 1310, 1490 and 1550 nm wavelength radiation. For the design of optoelectronic receiver micromodule was used the low signal electrical equivalent circuit for the dynamic performance signal analysis. In the paper is presented the planar form WDM transceiver with polymer optical waveguides and two stage interference demultiplexing optical filter as well.

  13. Current developments in fiber Bragg grating sensors and their applications

    NASA Astrophysics Data System (ADS)

    Annamdas, Venu Gopal Madhav; Yang, Yaowen; Liu, Hui

    2008-03-01

    Whatever may be the material used to build the engineering structures, they are bound to undergo damage at some point in their lifetime. The damage could develop because of continuous usage, degradation, environmental factors, earthquakes or man-made disasters. Structural health monitoring (SHM) has emerged as an important area that has attracted intensive research attention in the recent time. Smart materials like piezoceramics (e.g. lead zirconate titanate or PZT) and fibre optical sensors (FOSs) based effective SHM tools are rapidly developing. Especially, the FOSs offer great potential as monitoring sensors due to their small size, immunity to electromagnetic interference, robustness and survivability in harsh environment. Conventional FOSs use phase modulation techniques for sensing. In spite of the above advantages, they are dependent heavily on source intensity fluctuations and coupling loses. However the fibre Bragg grating (FBG) sensors developed from FOSs are immune to source intensity fluctuations, thus addressing some potential problems of the conventional FOSs. This paper presents a review on the current development of FBG based monitoring techniques and their applications.

  14. Comparison of damage measures based on fiber Bragg grating spectra

    NASA Astrophysics Data System (ADS)

    Park, Chun; Peters, Kara

    2012-02-01

    We compare the performance of four different damage measures based on the full spectral response of fiber Bragg grating (FBG) sensors: spectral bandwidth, number of peaks, cross-correlation coefficient and fractal dimension. These damage measures provide a rapid indication of the extent of damage near the FBG sensor. Each damage measure is applied to data simulating the response of a FBG to a pure strain gradient and experimental data from FBG sensors embedded in a laminate subjected to multiple impacts. The cross-correlation coefficient and number of peaks did not perform well for the experimental data. The spectral bandwidth presented a low sensitivity to noise and a high sensitivity to rapidly increasing strain fields, whereas the fractal dimension was more sensitive to more gradually changing strain fields. Ultimately, the best strategy would be to fuse the results of the spectral bandwidth and fractal dimension damage measures to incorporate the strengths of each approach. At the same time, this study highlighted the challenges in using such spectral data from FBG sensors embedded in structural materials, primarily due to the variability in response between sensors exposed to the same damage states.

  15. Experiences with fiber optic Bragg grating sensors in civil engineering

    NASA Astrophysics Data System (ADS)

    Brownjohn, James M. W.; Moyo, Pilate; Wang, Yong; Tjin, Chuan S.; Lim, Tuan-Kay

    2001-06-01

    Initially developed for applications in the aerospace industry, fiber-optic Bragg grating sensors (FBG) have attracted attention in the civil engineering community. The interest in FBG sensors has been motivated by the potential advantages they can offer over existing sensing technologies. They are, immune to electromagnetic interference, small in size and can be easier to install than traditional electrical resistance strain gauges. They can also be multiplexed, that is, a single fiber may have more than one change. Although field test of FBG sensors have been reported in literature, there is a dearth of information on their installation procedures, their precision in quantifying strains of concrete structures, and robustness requirements for embedment in concrete structures. In particular the harsh environment during the construction of concrete structures is a great challenge in the installation of these fragile sensors. The paper reports on our experiences with FBG sensors in concrete structures. FBG sensor have been sued to quantify strain, temperature and to capture vibration signals. Th result of these studies indicate that, if properly installed, FBG sensors can survive the sever conditions associated with the embedment process and yield accurate measurements of strains and vibration response, so it is possible to benefit from their potential advantages.

  16. A Fiber Bragg Grating Sensing Based Triaxial Vibration Sensor.

    PubMed

    Li, Tianliang; Tan, Yuegang; Liu, Yi; Qu, Yongzhi; Liu, Mingyao; Zhou, Zude

    2015-01-01

    A fiber Bragg grating (FBG) sensing based triaxial vibration sensor has been presented in this paper. The optical fiber is directly employed as elastomer, and the triaxial vibration of a measured body can be obtained by two pairs of FBGs. A model of a triaxial vibration sensor as well as decoupling principles of triaxial vibration and experimental analyses are proposed. Experimental results show that: sensitivities of 86.9 pm/g, 971.8 pm/g and 154.7 pm/g for each orthogonal sensitive direction with linearity are separately 3.64%, 1.50% and 3.01%. The flat frequency ranges reside in 20-200 Hz, 3-20 Hz and 4-50 Hz, respectively; in addition, the resonant frequencies are separately 700 Hz, 40 Hz and 110 Hz in the x/y/z direction. When the sensor is excited in a single direction vibration, the outputs of sensor in the other two directions are consistent with the outputs in the non-working state. Therefore, it is effectively demonstrated that it can be used for three-dimensional vibration measurement. PMID:26393616

  17. A Fiber Bragg Grating Sensing Based Triaxial Vibration Sensor

    PubMed Central

    Li, Tianliang; Tan, Yuegang; Liu, Yi; Qu, Yongzhi; Liu, Mingyao; Zhou, Zude

    2015-01-01

    A fiber Bragg grating (FBG) sensing based triaxial vibration sensor has been presented in this paper. The optical fiber is directly employed as elastomer, and the triaxial vibration of a measured body can be obtained by two pairs of FBGs. A model of a triaxial vibration sensor as well as decoupling principles of triaxial vibration and experimental analyses are proposed. Experimental results show that: sensitivities of 86.9 pm/g, 971.8 pm/g and 154.7 pm/g for each orthogonal sensitive direction with linearity are separately 3.64%, 1.50% and 3.01%. The flat frequency ranges reside in 20–200 Hz, 3–20 Hz and 4–50 Hz, respectively; in addition, the resonant frequencies are separately 700 Hz, 40 Hz and 110 Hz in the x/y/z direction. When the sensor is excited in a single direction vibration, the outputs of sensor in the other two directions are consistent with the outputs in the non-working state. Therefore, it is effectively demonstrated that it can be used for three-dimensional vibration measurement. PMID:26393616

  18. Investigation on Thermal-Induced Decay of Fiber Bragg Grating

    NASA Astrophysics Data System (ADS)

    Zhang, Peng; Ding, Pinyi; Liu, Li

    2015-06-01

    A fiber Bragg grating (FBG), with advantages such as high anti-interference ability, a simple structure, and multiplexing, is widely used as a core component in numerous applications to monitor adverse environments of high temperature and air pressure. When FBGs are exposed to these extreme conditions, especially high temperature, performance decay may occur, bringing serious impact on the stability and reliability of the instruments. Therefore, it is necessary to make a detailed analysis on the mechanism of the thermal-induced decay of a FBG. One commonly used theory is proposed by Erdogn, which is based on a power function and aging curve method. However, these empirical equations are limited in application because only one single type of FBG can be analyzed this way. This paper focuses on the mechanism of a FBG, and presents a detailed analysis on the theory of the thermal-induced decay of a FBG using the electron dipole mode. Theoretical relationships between reflectivity and time or temperature were obtained, and a corresponding thermal-induced decay testing system was designed. The experimental and theoretical reflectivity decline under different temperatures of and are plotted, and the curves of reduction derived from the theoretical model fit the experimental data well. Thus, this model can be applied to predict the performance decay of FBGs at high temperature.

  19. Microstructured optical fiber Bragg grating sensor for DNA detection

    NASA Astrophysics Data System (ADS)

    Candiani, A.; Giannetti, S.; Sozzi, M.; Coscelli, E.; Poli, F.; Cucinotta, A.; Bertucci, A.; Corradini, R.; Konstantaki, M.; Margulis, W.; Pissadakis, S.; Selleri, S.

    2013-03-01

    In this work the inner surface of a microstructured optical fiber, where a Bragg grating was previously inscribed, has been functionalized using peptide nucleic acid probe targeting a DNA sequence of the cystic fibrosis disease. The solution of DNA molecules, matched with the PNA probes, has been infiltrated inside the fiber capillaries and hybridization has been realized according to the Watson - Crick Model. In order to achieve signal amplification, oligonucleotide-functionalized gold nanoparticles were then infiltrated and used to form a sandwich-like system. Experimental measurements show a clear wavelength shift of the reflected high order mode for a 100 nM DNA solution. Several experiments have been carried out on the same fiber using the identical concentration, showing the same modulation and proving a good reproducibility of the results, suggesting the possibility of the reuse of the sensor. Measurements have been also made using a 100 nM mis-matched DNA solution, containing a single nucleotide polymorphism, demonstrating the high selectivity of the sensor.

  20. A non-contact fiber Bragg grating vibration sensor.

    PubMed

    Li, Tianliang; Tan, Yuegang; Wei, Li; Zhou, Zude; Zheng, Kai; Guo, Yongxing

    2014-01-01

    A non-contact vibration sensor based on fiber Bragg grating (FBG) sensing has been proposed and studied in this paper. The principle of the sensor as well as simulation and experimental analyses are introduced. When the distance between the movable head and the measured shaft changed, the diaphragm deformed under magnetic coupling of the permanent magnet on the measured magnetic shaft. As a result, the center wavelength of the FBG connected to the diaphragm changed, based on which the vibration displacement of the rotating shaft could be obtained. Experimental results show that the resonant frequency of the sensor is about 1500 Hz and the working band ranges within 0-1300 Hz, which is consistent with the simulation analysis result; the sensitivity is -1.694 pm/μm and the linearity is 2.92% within a range of 2-2.4 mm. It can be used to conduct non-contact measurement on the vibration of the rotating shaft system.

  1. A Fiber Bragg Grating Sensing Based Triaxial Vibration Sensor.

    PubMed

    Li, Tianliang; Tan, Yuegang; Liu, Yi; Qu, Yongzhi; Liu, Mingyao; Zhou, Zude

    2015-09-18

    A fiber Bragg grating (FBG) sensing based triaxial vibration sensor has been presented in this paper. The optical fiber is directly employed as elastomer, and the triaxial vibration of a measured body can be obtained by two pairs of FBGs. A model of a triaxial vibration sensor as well as decoupling principles of triaxial vibration and experimental analyses are proposed. Experimental results show that: sensitivities of 86.9 pm/g, 971.8 pm/g and 154.7 pm/g for each orthogonal sensitive direction with linearity are separately 3.64%, 1.50% and 3.01%. The flat frequency ranges reside in 20-200 Hz, 3-20 Hz and 4-50 Hz, respectively; in addition, the resonant frequencies are separately 700 Hz, 40 Hz and 110 Hz in the x/y/z direction. When the sensor is excited in a single direction vibration, the outputs of sensor in the other two directions are consistent with the outputs in the non-working state. Therefore, it is effectively demonstrated that it can be used for three-dimensional vibration measurement.

  2. Microwave photonic integrator based on a multichannel fiber Bragg grating.

    PubMed

    Zhang, Jiejun; Yao, Jianping

    2016-01-15

    We propose and experimentally demonstrate a microwave photonic integrator based on a multichannel fiber Bragg grating (FBG) working in conjunction with a dispersion compensating fiber (DCF) to provide a step group delay response with no in-channel dispersion-related distortion. The multichannel FBG is designed based on the spectral Talbot effect, which provides a large group delay dispersion (GDD) within each channel. A step group delay response can then be achieved by cascading the multichannel FBG with a DCF having a GDD opposite the in-channel GDD. An optical comb, with each comb line located at the center of each channel of the FBG, is modulated by a microwave signal to be integrated. At the output of the DCF, multiple time-delayed replicas of the optical signal, with equal time delay spacing are obtained and are detected and summed at a photodetector (PD). The entire operation is equivalent to the integration of the input microwave signal. For a multichannel FBG with an in-channel GDD of 730 ps/nm and a DCF with an opposite GDD, an integrator with a bandwidth of 2.9 GHz and an integration time of 7 ns is demonstrated. PMID:26766692

  3. Opto-acoustic behavior of coated fiber Bragg gratings.

    PubMed

    Moccia, Massimo; Pisco, Marco; Cutolo, Antonello; Galdi, Vincenzo; Bevilacqua, Pierantonio; Cusano, Andrea

    2011-09-26

    In this paper, we present the study of the acousto-optic behavior of underwater-acoustic sensors constituted by fiber Bragg gratings (FBGs) coated by ring-shaped overlays. Via full-wave numerical simulations, we study the complex opto-acousto-mechanical interaction among an incident acoustic wave traveling in water, the optical fiber surrounded by the ring shaped coating, and the FBG inscribed the fiber, focusing on the frequency range 0.5-30 kHz of interest for SONAR applications. Our results fully characterize the mechanical behavior of an acoustically driven coated FBG, and highlight the key role played by the coating in enhancing significantly its sensitivity by comparison with a standard uncoated configuration. Furthermore, the hydrophone sensitivity spectrum exhibits characteristic resonances, which strongly improve the sensitivity with respect to its background (i.e., away from resonances) level. Via a three-dimensional modal analysis, we verify that the composite cylindrical structure of the sensor acts as an acoustic resonator tuned at the frequencies of its longitudinal vibration modes. In order to evaluate the sensor performance, we also carry out a comprehensive parametric analysis by varying the geometrical and mechanical properties of the coating, whose results also provide a useful design tool for performance optimization and/or tailoring for specific SONAR applications. Finally, a preliminary validation of the proposed numerical analysis has been carried out through experimental data obtained using polymeric coated FBGs sensors revealing a good agreement and prediction capability.

  4. Fiber Bragg gratings in the radiation environment: Change under the influence of radiolytic hydrogen

    SciTech Connect

    Butov, Oleg V. Golant, Konstantin M.; Shevtsov, Igor' A.; Fedorov, Artem N.

    2015-08-21

    The change of the transmission spectra of fiber Bragg gratings written in the optical fibers, whose silica cores are doped with either germanium or nitrogen, is studied experimentally under the influence of gamma-radiation. The transmission spectra in the neighborhood of the resonance (Bragg) wavelengths were regularly recorded “in-situ” in the course of irradiation during 24 days. For this purpose, uncoated gratings were placed in a pool near the spent fuel rods of a nuclear reactor. The fibers with the gratings written in them were in immediate contact with water. The estimated total absorbed radiation dose of the fibers is approximately 5 MGy. Molecular hydrogen, which is produced by radiolysis of water and penetrates into the core of silica fiber, is found to interact with the defects of Ge-doped silica induced by gamma-radiation, thereby causing a strong impact on the parameters of the spectrum of the Bragg gratings. On the contrary, in the case of gratings inscribed in N-doped silica fibers, the hydrogen molecules interact with defects induced in the course of laser UV exposure during the grating writing only. The possible subsequent formation of additional defects in N-doped silica under the influence of gamma-radiation has no substantial impact on the transmission spectra of Bragg gratings, which remained stable. The obtained results suggest that a small amount of molecular hydrogen resided in the fiber core is the main source of radiation instability of Ge-doped fiber Bragg grating sensors in radiation environments. These hydrogen molecules can remain in the Bragg gratings, in particular, after the inscription process in the hydrogen-loaded fibers.

  5. Fiber Bragg gratings in the radiation environment: Change under the influence of radiolytic hydrogen

    NASA Astrophysics Data System (ADS)

    Butov, Oleg V.; Golant, Konstantin M.; Shevtsov, Igor'A.; Fedorov, Artem N.

    2015-08-01

    The change of the transmission spectra of fiber Bragg gratings written in the optical fibers, whose silica cores are doped with either germanium or nitrogen, is studied experimentally under the influence of gamma-radiation. The transmission spectra in the neighborhood of the resonance (Bragg) wavelengths were regularly recorded "in-situ" in the course of irradiation during 24 days. For this purpose, uncoated gratings were placed in a pool near the spent fuel rods of a nuclear reactor. The fibers with the gratings written in them were in immediate contact with water. The estimated total absorbed radiation dose of the fibers is approximately 5 MGy. Molecular hydrogen, which is produced by radiolysis of water and penetrates into the core of silica fiber, is found to interact with the defects of Ge-doped silica induced by gamma-radiation, thereby causing a strong impact on the parameters of the spectrum of the Bragg gratings. On the contrary, in the case of gratings inscribed in N-doped silica fibers, the hydrogen molecules interact with defects induced in the course of laser UV exposure during the grating writing only. The possible subsequent formation of additional defects in N-doped silica under the influence of gamma-radiation has no substantial impact on the transmission spectra of Bragg gratings, which remained stable. The obtained results suggest that a small amount of molecular hydrogen resided in the fiber core is the main source of radiation instability of Ge-doped fiber Bragg grating sensors in radiation environments. These hydrogen molecules can remain in the Bragg gratings, in particular, after the inscription process in the hydrogen-loaded fibers.

  6. Tunable channel drop filters consisting of a tilted Bragg grating and a mode sorting polymer waveguide.

    PubMed

    Park, Tae-Hyun; Shin, Jin-Soo; Huang, Guanghao; Chu, Woo-Sung; Oh, Min-Cheol

    2016-03-21

    Optical wavelength filters with large tuning range and narrow bandwidth are crucial for enhancing the capability of WDM communication systems. A polymeric tunable filter for C-band, comprising a tilted Bragg grating and a mode sorting waveguide junction is proposed in this work. For dropping a certain wavelength signal, the tilted Bragg grating reflects an odd mode into an even mode and then the reflected even mode propagates towards an output port of the asymmetric Y-junction due to the mode sorting. Consequently, the output port is separated from the input port, which is not possible in an ordinary Bragg reflector. The tilted Bragg reflector with an odd-even mode coupling efficiency of 61% exhibited a maximum reflectivity of 95% for a grating of 6 mm. A linear wavelength tuning of over 10 nm was achieved for an applied thermal power of 312 mW.

  7. Variable wavefront tuning with a SLM for tailored femtosecond fiber Bragg grating inscription.

    PubMed

    Voigtländer, Christian; Krämer, Ria G; Goebel, Thorsten A; Richter, Daniel; Nolte, Stefan

    2016-01-01

    We report on the inscription of fiber Bragg gratings using femtosecond laser pulses and the phase-mask technique. The wavefront of the inscription laser is variably tuned with a spatial light modulator (SLM). By applying Fresnel lenses with different focal lengths, the period of the fiber Bragg gratings could be shifted. A linear change of the grating period for a FBG inscribed with a third-order deformed wavefront and a quadratic-period behavior for a fourth-order wavefront could be verified experimentally for the first time. PMID:26696147

  8. Type IIa Bragg grating based ultra-short DBR fiber laser with high temperature resistance.

    PubMed

    Ran, Yang; Feng, Fu-Rong; Liang, Yi-Zhi; Jin, Long; Guan, Bai-Ou

    2015-12-15

    We report on the fabrication of a thermally resistant ultra-short distributed Bragg reflector (DBR) fiber laser based on the photo inscription of two wavelength-matched type IIa gratings in a thin-core Er-doped fiber. With continuous UV exposure, each Bragg reflector initially grows as a type I grating, followed by decay in strength, and then re-grows as a type IIa grating with enhanced thermal resistance. The DBR laser, with an entire length of 13 mm, can stably operate at 600°C with single longitude mode, which provides potential applications in high temperature environments. PMID:26670491

  9. Thermal activation of regenerated fiber Bragg grating in few mode fibers

    NASA Astrophysics Data System (ADS)

    Lai, Man-Hong; Gunawardena, Dinusha S.; Lim, Kok-Sing; Machavaram, Venkata R.; Lee, Say-Hoe; Chong, Wu-Yi; Lee, Yen-Sian; Ahmad, Harith

    2016-03-01

    This work demonstrated for the first time, the thermal regeneration of two and four modes graded index fiber Bragg gratings using high temperature tube furnace. During the regeneration process, the seed grating is erased and a new grating with lower index contrast is formed. The thermal calibration shows that the temperature sensitivity of regenerated grating is slightly higher for fiber with larger core. On the other hand, the regeneration temperature is lower for fiber with smaller core. The temperature sustainability up to 900 °C is observed for the produced regenerated gratings in few mode fibers.

  10. Structurally embedded fiber Bragg gratings: civil engineering applications

    NASA Astrophysics Data System (ADS)

    Nellen, Philipp M.; Broennimann, Rolf; Frank, Andreas; Mauron, Pascal; Sennhauser, Urs J.

    1999-12-01

    In civil engineering it is of interest to monitor long-term performance of structures made of new lightweight materials like glass or carbon fiber reinforced polymers (GFRP/CFRP). In contrast to surface applied optical fiber sensors, embedded sensors are expected to be better protected against rough handling and harsh environmental conditions. We report on two recently done fiber optical sensor applications in civil engineering. Both include structurally embedded fiber Bragg grating (BG) arrays but have different demands with respect to their operation. For the first application fiber BGs were embedded in GFRP rockbolts of 3 - 5 m in length either of 3, 8, or 22 mm diameter. The sensor equipped rockbolts are made for distributed measurements of boulder motion during tunnel construction and operation and should withstand strain up to 1.6%. Rockbolt sensors were field tested in a tunnel near Sargans in Switzerland. For a second application fiber BGs were embedded in CFRP wires of 5 mm diameter used for the pre- stressing cables of a 56 m long bridge near Lucerne in Switzerland. The permanent load on the cable corresponds to 0.8% strain. Due to the embedded sensors, strain decay inside the cable anchoring heads could be measured for the first time during loading and operation of the cables. For both applications mechanical and thermal loading tests were performed to assess the function of these new elements. Also, temperature and strain sensitivity were calibrated. Reliability studies with respect to stress transfer, fiber mechanical failure, and wavelength shift caused by thermal BG decay as well as monitoring results of both applications are presented.

  11. 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

  12. Using Dual-wavelength Fiber Bragg Gratings for Temperature and Strain Sensing at Cryogenic Temperature

    NASA Technical Reports Server (NTRS)

    Wu, Meng-Chou; Prosser, William H.; Rogowski, Robert S.; DeHaven, Stanton L.

    2003-01-01

    By using dual-wavelength fiber-optic Bragg gratings, a new technique has been developed for sensing both temperature and strain simultaneously in cryogenic temperature range. Two Bragg gratings with different wavelengths were inscribed at the same location in an optical fiber to form a dual-wavelength sensor. By measuring the wavelength shifts that resulted from the fiber being subjected to different temperatures and strains, the wavelength-dependent thermo-optic coefficients and photoelastic coefficients of the fiber were determined. These coefficients were used to construct the elements of the K matrix, which enables to determine inversely the strain and temperature changes by measuring the wavelength shifts of the dual-wavelength Bragg grating. In this study, measurements were made over the temperature range from room temperature down to about 10 K, addressing much of the low temperature range of cryogenic tanks. A structure transition of the optical fiber during the temperature change was found from about 70 K to 140 K. This transition caused splitting of the waveforms characterizing the Bragg gratings, and the determination of wavelength shifts was consequently complicated. Several alternatives are proposed to resolve this problem. The effectiveness and sensitivities of these measurements in different temperature ranges are discussed. The separation of two wavelengths for the dual-wavelength Bragg grating has been widened to increase the sensitivities of measurement; however, this separation can still be covered in the scanning range from single scanning laser.

  13. Adaptive Integrated Optical Bragg Grating in Semiconductor Waveguide Suitable for Optical Signal Processing

    NASA Astrophysics Data System (ADS)

    Moniem, T. A.

    2016-05-01

    This article presents a methodology for an integrated Bragg grating using an alloy of GaAs, AlGaAs, and InGaAs with a controllable refractive index to obtain an adaptive Bragg grating suitable for many applications on optical processing and adaptive control systems, such as limitation and filtering. The refractive index of a Bragg grating is controlled by using an external electric field for controlling periodic modulation of the refractive index of the active waveguide region. The designed Bragg grating has refractive indices programmed by using that external electric field. This article presents two approaches for designing the controllable refractive indices active region of a Bragg grating. The first approach is based on the modification of a planar micro-strip structure of the iGaAs traveling wave as the active region, and the second is based on the modification of self-assembled InAs/GaAs quantum dots of an alloy from GaAs and InGaAs with a GaP traveling wave. The overall design and results are discussed through numerical simulation by using the finite-difference time-domain, plane wave expansion, and opto-wave simulation methods to confirm its operation and feasibility.

  14. Novel methods for simultaneous strain and temperature measurements with optical fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Frank, Andreas; Nellen, Philipp M.; Sennhauser, Urs J.

    1999-12-01

    We report on feasibility studies of two new approaches for simultaneous strain and temperature measurements with optical fiber Bragg gratings. In sensor applications fiber Bragg gratings cannot be thermally isolated. Therefore temperature has to be compensated or measured simultaneously with the measurand of interest. In strain sensing this is often done by measuring the wavelength response of a second Bragg grating attached to an unstrained sample specimen and comparing its response to response of the strained sample. This method is very accurate. However, often it is not possible or difficult to have unstrained samples, e.g., in rockbolt anchors with embedded fiber Bragg gratings. We propose two new simultaneous measurement concepts and compare them to known concepts. The first investigated method uses the different sensitivities to strain and temperature of the main peak of a Bragg grating in transmission compared to the back-reflected cladding modes. We will present first results of simultaneous strain and temperature measurements over a range from 2 degrees Celsius to 95 degrees Celsius up to 3500 micrometer/m in strain. This method leads to a combined resolution in temperature and strain of 4 degrees Celsius and 35 micrometer, respectively. The second method is based on two low reflectivity gratings. They are in close vicinity to each other in the fiber. Both have a small refractive index modulation of about 2 (DOT) 10-4, but one was homogeneously post-illuminated and has an increased mean refractive index. We will present first results indicating that the additional UV-illumination changes temperature- and strain-sensitivity of the post-illuminated Bragg grating slightly.

  15. Fused-silica sandwiched three-port grating under second Bragg angle incidence

    NASA Astrophysics Data System (ADS)

    Li, Hongtao; Wang, Bo; Pei, Hao; Chen, Li; Lei, Liang; Zhou, Jinyun

    2016-05-01

    The fused-silica sandwiched three-port grating under second Bragg angle incidence is presented with operation in transmission. To obtain a highly-efficient three-port grating for a working wavelength of 800 nm, the grating depth and period should be optimized by using rigorous coupled-wave analysis. With the optimized different three-port grating depths and periods, both TE-polarized and TM-polarized waves can be diffracted into three orders with nearly 33% efficiency for the given duty cycle of 0.6. Based on the grating parameters of numerical optimization, modal method may be employed to explain the physical mechanism of the beam propagation in the grating and analyze the splitting behavior. For the sandwiched three-port grating, it is feasible that the diffraction efficiencies can be enhanced for both TE and TM polarizations.

  16. Simultaneous Temperature and Strain Sensing for Cryogenic Applications Using Dual-Wavelength Fiber Bragg Gratings

    NASA Technical Reports Server (NTRS)

    Wu, Meng-Chou; Prosser, William H.

    2003-01-01

    A new technique has been developed for sensing both temperature and strain simultaneously by using dual-wavelength fiber-optic Bragg gratings. Two Bragg gratings with different wavelengths were inscribed at the same location in an optical fiber to form a sensor. By measuring the wavelength shifts that resulted from the fiber being subjected to different temperatures and strains, the wavelength-dependent thermo-optic coefficients and photoelastic coefficients of the fiber were determined. This enables the simultaneous measurement of temperature and strain. In this study, measurements were made over the temperature range from room temperature down to about 10 K, addressing much of the low temperature range of cryogenic tanks. A structure transition of the optical fiber during the temperature change was found. This transition caused splitting of the waveforms characterizing the Bragg gratings, and the determination of wavelength shifts was consequently complicated. The effectiveness and sensitivities of these measurements in different temperature ranges are also discussed.

  17. How reliable do fibre Bragg grating patches perform as strain sensors?

    NASA Astrophysics Data System (ADS)

    Schlüter, Vivien Gisela; Kusche, Nadine; Habel, Wolfgang R.

    2010-09-01

    In Germany, the first guideline for the use of fibre Bragg grating strain sensors, "Optical Strain Sensor based on Fibre Bragg Grating" [1], has been developed by the GESA guideline group of VDI "The Association of German Engineers" and published by Beuth Verlag. This guideline provides the basic specifications of these sensor types and the sensor characteristics which have to be known for a reliable sensor performance. In conformity to this guideline, experimental investigations on the strain transfer characteristics of fibre Bragg grating patches have been carried out. A comparison between patches and resistance strain gauges during tensile tests and combined temperature and tensile loading was carried out. The evaluated strain gauge factor and the temperature sensitivity of the strain gauge factor have been compared to the manufacturer's data. The overall performance of the patches has been evaluated. The experimental investigations showed that there are partial disagreements between the manufacturer's specifications and the observed characteristics.

  18. Twist effect and sensing of few mode polymer fibre Bragg gratings

    NASA Astrophysics Data System (ADS)

    Yan, Binbin; Luo, Yanhua; Bhowmik, Kishore; Rajan, Ginu; Ji, Minning; Wen, Jianxiang; Peng, Gang-Ding

    2016-01-01

    For the development of the twist sensor based on few mode polymer optical fibre (POF) gratings, we investigated the twist effect of few mode (FM) POF Bragg gratings with large twist, and found the twist effect on reflection is highly mode dependent-insignificant on the fundamental mode and considerable on higher order modes, which seems closely related to the symmetry of modal field. In addition, Bragg wavelengths of both the fundamental mode and higher modes red-shift with the twisting and blue-shift with the twist releasing, and they almost display the similar response trend without any mode dependence. Further analysis found that the red-shift of the Bragg wavelength should be attributed to the redistribution of the pre-strain applied upon the POF, activated by twist. Finally, based on the reflection response to the twist, one kind of twist sensing scheme with few mode POF gratings has been demonstrated, showing great potential as a twist sensor.

  19. Q-switched all-fiber laser based on magnetostriction modulation of a Bragg grating.

    PubMed

    Pérez-Millán, P; Díez, A; Andrés, M; Zalvidea, D; Duchowicz, R

    2005-06-27

    We report an actively Q-switched all-fiber laser based on magnetostriction modulation of a Bragg grating. The laser employs a pair of Bragg gratings as reflective mirrors, one of which is bonded to a magnetostrictive element. Lengthening of the magnetostrictive element when a magnetic field is applied shifts the Bragg wavelength of the grating, allowing control of the Q-factor of the cavity and, thus, performing active Q-switching. The magnetostrictive modulator is small, compact and requires less than 300 mW electrical drive power. Using erbium-doped fiber and a maximum pump power of 120 mW, Q-switch pulses of more than 1 W peak power were obtained, with a pulse repetition rate that can be continuously varied from 1 Hz to 125 kHz. PMID:19498492

  20. Development of In-Fiber Reflective Bragg Gratings as Shear Stress Monitors in Aerodynamic Facilities

    NASA Technical Reports Server (NTRS)

    Parmar, Devendra S.; Sprinkle, Danny R.; Singh, Jag J.

    1998-01-01

    Bragg gratings centered at nominal wavelengths of 1290 nm and 1300 run were inscribed in a 9/125 microns germano-silicate optical fiber, using continuous wave frequency doubled Ar+ laser radiation at 244 nm. Such gratings have been used extensively as temperature and strain monitors in smart structures. They have, however, never been used for measuring aerodynamic shear stresses. As a test of their sensitivity as shear stress monitors, a Bragg fiber attached to a metal plate was subjected to laminar flows in a glass pipe. An easily measurable large flow-induced wavelength shift (Delta Lambda(sub B)) was observed in the Bragg reflected wavelength. Thereafter, the grating was calibrated by making one time, simultaneous measurements of Delta Lambda(sub B) and the coefficient of skin friction (C(sub f)) with a skin friction balance, as a function of flow rates in a subsonic wind tunnel. Onset of fan-induced transition in the tunnel flow provided a unique flow rate for correlating Delta Lambda(sub B) and (C(sub f) values needed for computing effective modulus of rigidity (N(sub eff)) of the fiber attached to the metal plate. This value Of N(sub eff) is expected to remain constant throughout the elastic stress range expected during the Bragg grating aerodynamic tests. It has been used for calculating the value of Cf at various tunnel speeds, on the basis of measured values of Bragg wavelength shifts at those speeds.

  1. Bragg gratings in a few mode microstructured polymer optical fiber in less than 30 seconds.

    PubMed

    Oliveira, Ricardo; Bilro, Lúcia; Nogueira, Rogério

    2015-04-20

    We report the inscription of a Bragg grating in an undoped polymethylmethacrylate based microstructured fiber in a time record. The fiber has been irradiated with a 248 nm ultraviolet radiation, through the phase mask technique using low fluence and low repetition rate. The experimental conditions were chosen to modify the core refractive index of the fiber at the incubation regime and avoiding polymer ablation. The peak reflection of the Bragg grating was centered in the infrared region with 20 dB reflection and 0.16 nm bandwidth. These spectral properties are well attractive for sensors and communications applications. PMID:25969060

  2. Magnetic field sensor based on fiber Bragg grating with a spiral microgroove ablated by femtosecond laser.

    PubMed

    Dai, Yutang; Yang, Minghong; Xu, Gang; Yuan, Yinquan

    2013-07-15

    A novel magnetic field sensor based on Terfenol-D coated fiber Bragg grating with spiral microstructure was proposed and demonstrated. Through a specially-designed holder, the spiral microstructure was ablated into the fiber Bragg grating (FBG) cladding by femtosecond laser. Due to the spiral microstructure, the sensitivity of FBG coated with magnetostrictive film was enhanced greatly. When the spiral pitch is 50 μm and microgroove depth is 13.5 μm, the sensitivity of the magnetic field sensor is roughly 5 times higher than that of non-microstructured standard FBG. The response to magnetic field is reversible, and could be applicable for magnetic field detection.

  3. Proof of Concept of Impact Detection in Composites Using Fiber Bragg Grating Arrays

    PubMed Central

    Gomez, Javier; Jorge, Iagoba; Durana, Gaizka; Arrue, Jon; Zubia, Joseba; Aranguren, Gerardo; Montero, Ander; López, Ion

    2013-01-01

    Impact detection in aeronautical structures allows predicting their future reliability and performance. An impact can produce microscopic fissures that could evolve into fractures or even the total collapse of the structure, so it is important to know the location and severity of each impact. For this purpose, optical fibers with Bragg gratings are used to analyze each impact and the vibrations generated by them. In this paper it is proven that optical fibers with Bragg gratings can be used to detect impacts, and also that a high-frequency interrogator is necessary to collect valuable information about the impacts. The use of two interrogators constitutes the main novelty of this paper. PMID:24021969

  4. Direct UV written planar Bragg gratings that feature zero fluence induced birefringence

    NASA Astrophysics Data System (ADS)

    Holmes, Christopher; Cooper, Peter A.; Fernando, Harendra N. J.; Stroll, Andreas; Gates, James C.; Krishnan, Chirenjeevi; Haynes, Roger; Mennea, Paolo L.; Carpenter, Lewis G.; Gawith, Corin B. E.; Roth, Martin M.; Charlton, Martin D.; Smith, Peter G. R.

    2015-12-01

    Direct UV writing is a planar fabrication process capable of simultaneously defining waveguides and Bragg gratings. The technique is fully computer controlled and uniquely uses a small focused spot ~7 μm in diameter for direct writing exposure. This work investigates its use to achieve phase trimming and Bragg grating definition in silica-on-silicon lithographic waveguides. It is observed that birefringence control using direct UV writing can be made independent of exposure fluence with this technique through tailoring substrate stress. The result is demonstrated experimentally and supported theoretically using finite element analysis.

  5. Automation for the manufacturing of fiber Bragg grating arrays enables new applications

    NASA Astrophysics Data System (ADS)

    Lefebvre, P.; Vincelette, A.; Beaulieu, C.; Ficocelli, P.

    2005-11-01

    The manufacturing process has a huge impact on the characteristics of the all optical fiber sensors array. By automating the manufacturing of fiber Bragg gratings, FBG arrays with much larger count of sensing points, stronger mechanical strength, tighter optical parameters tolerances and enhanced reliability are produced in a cost effective manner. Such fiber Bragg grating arrays are now commercially available with both acrylate or polyimide coating widening the range of applications for FBG sensors to larger scale of services for strain and temperature in a distributed configuration.

  6. Dynamic Landslide Deformation Monitoring with Fiber Bragg Grating Sensors

    NASA Astrophysics Data System (ADS)

    Moore, J. R.; Gischig, V.; Button, E.; Loew, S.

    2009-12-01

    Fiber optic (FO) strain sensors are a promising new technology for in-situ landslide monitoring. General performance advantages include high resolution, fast sampling rate, and insensitivity to electrical disturbances. Here we describe a new FO monitoring system based on long-gage fiber Bragg grating sensors installed at the Randa Rockslide Laboratory in southern Switzerland. We highlight the advantages and disadvantages of the system, describe relevant first results, and compare FO data to that from traditional instruments already installed on site. The Randa rock slope has been the subject of intensive research since its failure in 1991. Around 5 million cubic meters of rock remains unstable today, moving at rates up to 20 mm / year. Traditional in-situ monitoring techniques have been employed to understand the mechanics and driving forces of the currently unstable rock mass, however these investigations are limited by the resolution and low sampling rate of the sensors. The new FO monitoring system has micro-strain resolution and offers the capability to detect sub-micrometer scale deformations in both triggered-dynamic and continuous measurements. Two types of sensors have been installed: fully-embedded borehole sensors encased in grout at depths of 38, 40, and 68 m, and surface extensometers spanning active tension cracks. Dynamic measurements are triggered by sensor deformation and recorded at 100 Hz, while continuous measurements are logged every 5 minutes. Since installation in August 2008, the FO monitoring system has been operational 90% of the time. Time series deformation data show movement rates consistent with previous borehole extensometer surveys. Accelerated displacements following installation are likely related to long-term curing and dewatering of the grout. A number of interesting transients have been recorded, which in some cases were large enough to trigger rapid sampling. The combination of short- and long-term observation offers new

  7. Feasibility of Fiber Bragg Grating and Long-Period Fiber Grating Sensors under Different Environmental Conditions

    PubMed Central

    Wang, Jian-Neng; Tang, Jaw-Luen

    2010-01-01

    This paper presents the feasibility of utilizing fiber Bragg grating (FBG) and long-period fiber grating (LPFG) sensors for nondestructive evaluation (NDE) of infrastructures using Portland cement concretes and asphalt mixtures for temperature, strain, and liquid-level monitoring. The use of hybrid FBG and LPFG sensors is aimed at utilizing the advantages of two kinds of fiber grating to implement NDE for monitoring strains or displacements, temperatures, and water-levels of infrastructures such as bridges, pavements, or reservoirs for under different environmental conditions. Temperature fluctuation and stability tests were examined using FBG and LPFG sensors bonded on the surface of asphalt and concrete specimens. Random walk coefficient (RWC) and bias stability (BS) were used for the first time to indicate the stability performance of fiber grating sensors. The random walk coefficients of temperature variations between FBG (or LPFG) sensor and a thermocouple were found in the range of −0.7499 °C/ h to −1.3548 °C/ h. In addition, the bias stability for temperature variations, during the fluctuation and stability tests with FBG (or LPFG) sensors were within the range of 0.01 °C/h with a 15–18 h time cluster to 0.09 °C/h with a 3–4 h time cluster. This shows that the performance of FBG or LPFG sensors is comparable with that of conventional high-resolution thermocouple sensors under rugged conditions. The strain measurement for infrastructure materials was conducted using a packaged FBG sensor bonded on the surface of an asphalt specimen under indirect tensile loading conditions. A finite element modeling (FEM) was applied to compare experimental results of indirect tensile FBG strain measurements. For a comparative analysis between experiment and simulation, the FEM numerical results agreed with those from FBG strain measurements. The results of the liquid-level sensing tests show the LPFG-based sensor could discriminate five stationary liquid

  8. Simulation and experiment of packaging of the fibre Bragg grating sensors using brazing/soldering methods

    NASA Astrophysics Data System (ADS)

    Wen, Changjin; Li, Yulong; Hu, Ronghua; Xu, Jianning

    2016-08-01

    To manufacture fibre Bragg grating (FBG) transducer, finite element model simulation and experimental verification of packaging of the FBG by brazing/soldering were investigated. The packaging processes and their impacts on the wavelength change of FBG were analysed. Simulation results showed that the Bragg wavelength of packaged FBG shifted down a level of ~10 nm. For experimental verification, temperature sensitivity of the packaged FBG was enhanced about twice of the bare FBG, while its spectrum was well preserved. The Bragg wavelength was shifted down a level of ~10 nm which was in accordance with the simulation.

  9. Dynamic interrogator for elastic wave sensing using Fabry Perot filters based on fiber Bragg gratings.

    PubMed

    Harish, Achar V; Varghese, Bibin; Rao, Babu; Balasubramaniam, Krishnan; Srinivasan, Balaji

    2015-07-01

    Use of in-fiber Fabry-Perot (FP) filters based on fiber Bragg gratings as both sensor as well as an interrogator for enhancing the detection limit of elastic wave sensing is investigated in this paper. The sensitivity of such a demodulation scheme depends on the spectral discrimination of the sensor and interrogator gratings. Simulations have shown that the use of in-fiber FP filters with high finesse provide better performance in terms of sensitivity compared to the demodulation using fiber Bragg gratings. Based on these results, a dynamic interrogator capable of sensing acoustic waves with amplitude of less than 1 micro-strain over frequencies of 10 kHz to several 100 kHz has been implemented. Frequency response of the fiber Bragg gratings in the given experimental setup has been compared to that of the conventional piezo sensors demonstrating that fiber Bragg gratings can be used over a relatively broad frequency range. Dynamic interrogator has been packaged in a compact box without any degradation in its performance.

  10. Dynamic interrogator for elastic wave sensing using Fabry Perot filters based on fiber Bragg gratings.

    PubMed

    Harish, Achar V; Varghese, Bibin; Rao, Babu; Balasubramaniam, Krishnan; Srinivasan, Balaji

    2015-07-01

    Use of in-fiber Fabry-Perot (FP) filters based on fiber Bragg gratings as both sensor as well as an interrogator for enhancing the detection limit of elastic wave sensing is investigated in this paper. The sensitivity of such a demodulation scheme depends on the spectral discrimination of the sensor and interrogator gratings. Simulations have shown that the use of in-fiber FP filters with high finesse provide better performance in terms of sensitivity compared to the demodulation using fiber Bragg gratings. Based on these results, a dynamic interrogator capable of sensing acoustic waves with amplitude of less than 1 micro-strain over frequencies of 10 kHz to several 100 kHz has been implemented. Frequency response of the fiber Bragg gratings in the given experimental setup has been compared to that of the conventional piezo sensors demonstrating that fiber Bragg gratings can be used over a relatively broad frequency range. Dynamic interrogator has been packaged in a compact box without any degradation in its performance. PMID:25783780

  11. Supermode Bragg grating combined Mach-Zehnder interferometer for temperature-strain discrimination.

    PubMed

    Wu, Zhifang; Zhang, Hailiang; Shum, Perry Ping; Shao, Xuguang; Huang, Tianye; Seow, Ying Ming; Liu, Yan-ge; Wei, Huifeng; Wang, Zhi

    2015-12-28

    We report on a compact sensor by integrating a Mach-Zehnder interference and a cladding Bragg grating in a same section of all-solid photonic bandgap fiber. Theoretical investigation reveals that the Bragg grating resonance stems from the coupling of counter-propagating cladding LP01-like supermodes and the Mach-Zehnder interference works between a LP01-like supermode and LP01 core mode. Compared with the interference fringe, such supermode grating dip responses to axial strain in a more sensitive and opposite-direction manner. Whereas, the interference fringe shows a higher temperature sensitivity than the supermode grating dip. By means of these different responses, this device finds a useful application in the discrimination of temperature and axial strain. PMID:26831968

  12. Discrete nonplanar reflections from an ultrashort pulse written volume Bragg grating.

    PubMed

    Richter, Daniel; Voigtländer, Christian; Krämer, Ria G; Thomas, Jens U; Tünnermann, Andreas; Nolte, Stefan

    2015-06-15

    In this Letter, we present a direct writing technique for two-dimensional periodic volume Bragg gratings (VBGs) in fused silica based on the phase mask technology, ultrashort laser pulses, and three-beam interference. An algorithm to predict the grating pattern and its diffraction behavior under collimated, spectral broad illumination is developed. The predicted data are in good agreement with the measurements. PMID:26076257

  13. Dynamic index modulation mechanism in polarization-maintained fiber Bragg gratings induced by transverse acoustic waves.

    PubMed

    Miao, Ren; Zhang, Wei; Feng, Xue; Zhao, Jianhui; Liu, Xiaoming

    2009-08-20

    A novel index modulation mechanism of polarization-maintained fiber Bragg gratings based on the microbend of stress members induced by a transverse acoustic wave is proposed and investigated experimentally. The index modulation leads to a series of ghost gratings with specific polarization, whose wavelengths can be tuned by the acoustic wave frequency and whose intensities depend on the vibration direction of the transverse acoustic wave. Our method provides a novel way to achieve polarization-dependent narrowband acousto-optic tunable filters.

  14. Prediction of Composite Pressure Vessel Failure Location using Fiber Bragg Grating Sensors

    NASA Technical Reports Server (NTRS)

    Kreger, Steven T.; Taylor, F. Tad; Ortyl, Nicholas E.; Grant, Joseph

    2006-01-01

    Ten composite pressure vessels were instrumented with fiber Bragg grating sensors in order to assess the strain levels of the vessel under various loading conditions. This paper and presentation will discuss the testing methodology, the test results, compare the testing results to the analytical model, and present a possible methodology for predicting the failure location and strain level of composite pressure vessels.

  15. Angle dependent Fiber Bragg grating inscription in microstructured polymer optical fibers.

    PubMed

    Bundalo, Ivan-Lazar; Nielsen, Kristian; Bang, Ole

    2015-02-01

    We report on an incidence angle influence on inscription of the Fiber Bragg Gratings in Polymethyl methacrylate (PMMA) microstructured polymer optical fibers. We have shown experimentally that there is a strong preference of certain angles, labeled ГK, over the other ones. Angles close to ГK showed fast start of inscription, rapid inscription and stronger gratings. We have also shown that gratings can be obtained at almost any angle but their quality will be lower if they are not around ГK angle. Our experimental results verify earlier numerical and experimental predictions of Marshall et al. PMID:25836222

  16. Orientation-Dependent Displacement Sensor Using an Inner Cladding Fiber Bragg Grating.

    PubMed

    Yang, Tingting; Qiao, Xueguang; Rong, Qiangzhou; Bao, Weijia

    2016-01-01

    An orientation-dependent displacement sensor based on grating inscription over a fiber core and inner cladding has been demonstrated. The device comprises a short piece of multi-cladding fiber sandwiched between two standard single-mode fibers (SMFs). The grating structure is fabricated by a femtosecond laser side-illumination technique. Two well-defined resonances are achieved by the downstream both core and cladding fiber Bragg gratings (FBGs). The cladding resonance presents fiber bending dependence, together with a strong orientation dependence because of asymmetrical distribution of the "cladding" FBG along the fiber cross-section. PMID:27626427

  17. Orientation-Dependent Displacement Sensor Using an Inner Cladding Fiber Bragg Grating

    PubMed Central

    Yang, Tingting; Qiao, Xueguang; Rong, Qiangzhou; Bao, Weijia

    2016-01-01

    An orientation-dependent displacement sensor based on grating inscription over a fiber core and inner cladding has been demonstrated. The device comprises a short piece of multi-cladding fiber sandwiched between two standard single-mode fibers (SMFs). The grating structure is fabricated by a femtosecond laser side-illumination technique. Two well-defined resonances are achieved by the downstream both core and cladding fiber Bragg gratings (FBGs). The cladding resonance presents fiber bending dependence, together with a strong orientation dependence because of asymmetrical distribution of the “cladding” FBG along the fiber cross-section. PMID:27626427

  18. Characterization and reduction of spectral distortions in silicon-on-insulator integrated Bragg gratings.

    PubMed

    Simard, Alexandre D; Beaudin, Guillaume; Aimez, Vincent; Painchaud, Yves; Larochelle, Sophie

    2013-10-01

    A major issue in the fabrication of integrated Bragg grating filters in highly confined waveguides is the average effective index fluctuations caused by waveguide dimension variations. Lateral variations are caused by the sidewall roughness created during the etching process while vertical variations are coming from the wafer silicon layer thickness non-uniformity. Grating spectral distortions are known to result solely from the low spatial frequency components of these variations. As a result, in this work, we present an experimental method to quantify such relevant spatial components by stitching a hundred high-resolution scanning electron microscope images. Additionally, we propose two techniques to reduce, in the design, the phase noise impact on integrated Bragg gratings without relying on fabrication process improvements. More specifically, we show that the use of hybrid multimode/singlemode waveguides reduce by more than one order of magnitude the effect of sidewall roughness on integrated Bragg gratings while we show that the fabrication of ultra-compact gratings in spiral waveguides mitigate the impact of the silicon layer thickness variations. PMID:24104229

  19. Optical refractive index biosensor using evanescently coupled lateral Bragg gratings on silicon-on-insulator

    NASA Astrophysics Data System (ADS)

    Mendez-Astudillo, Manuel; Takahisa, Hiroki; Okayama, Hideaki; Nakajima, Hirochika

    2016-08-01

    In this paper, we present a compact silicon-on-insulator optical biosensor based on lateral Bragg gratings evanescently coupled to a waveguide. The device is fabricated by electron-beam lithography and dry-etched in a single step with inductive coupled plasma reactive ion etching (ICP-RIE). Fully etched grating couplers are used to couple the light in and out of the chip, while lateral Bragg gratings are used as the sensing element of the device. A sensitivity of 22 nm/RIU is obtained by exposing the device to deionized water with different NaCl concentrations with a footprint area of 15 × 4 µm2 that allows for densely multiplexed solutions.

  20. Design and analysis of metal/multi-insulator/metal waveguide plasmonic Bragg grating.

    PubMed

    Chang, Yin-Jung

    2010-06-01

    A metal/multi-insulator/metal waveguide plasmonic Bragg grating with a large dynamic range of index modulation is investigated analytically and numerically. Theoretical formalism of the dispersion relation for the present and general one-dimensional gratings is developed for TMwaves in the vicinity of each stop band.Wide-band and narrow-band designs with their respective FWHM bandwidths of 173.4 nm and < 3.4 nm in the 1550 nm band using a grating length of <16.0 microm are numerically demonstrated. Time-average power vortexes near the silica-silicon interfaces are revealed in the stop band and are attributed to the contra-flow interaction and simultaneous satisfactions of the Bragg condition for the incident and backward-diffracted waves. An enhanced forward-propagating power is thus shown to occur over certain sections within one period due to the power coupling from the backward-diffracted waves. PMID:20588455

  1. Reversible changes in the reflectivity of different types of fibre Bragg gratings

    SciTech Connect

    Gnusin, P I; Vasil'ev, Sergei A; Medvedkov, O I; Dianov, Evgenii M

    2010-12-09

    We have studied strain- and temperature-induced reversible changes in the reflectivity of different types of fibre Bragg gratings. The results demonstrate that the strain sensitivity of the reflectivity of type I and IIa Bragg gratings is mainly due to the photoinduced reduction in the elasto-optic coefficient p{sub 12} of the core glass and that its temperature sensitivity results from the increase in the thermo-optic coefficient of the glass. UV exposure of fibres loaded with molecular hydrogen has an insignificant effect on these material coefficients. We also analyse the effects of UV fluence and germanium concentration in the fibre core on the reversible changes in the reflectivity of the grating. (optical fibres)

  2. Theoretical and experimental investigation of fiber Bragg gratings with different lengths for ultrasonic detection

    NASA Astrophysics Data System (ADS)

    Yu, Zhouzhou; Jiang, Qi; Zhang, Hao; Wang, Junjie

    2016-06-01

    In this paper, the response of fiber Bragg gratings (FBGs) subjected to the ultrasonic wave has been theoretically and experimentally investigated. Although FBG sensors have been widely used in the ultrasonic detection for practical structural health monitoring, the relationship between the grating length and ultrasonic frequency is not yet to be obtained. To address this problem, an ultrasound detection system based on FBGs is designed and the response sensitivity of different lengths gratings are detected. Experimental results indicate that the grating with 3 mm length has a higher sensitivity when detecting high frequency ultrasonic wave, and the amplitude can be up to 0.6 mV. The 10 mm length grating has better detection sensitivity for low frequency ultrasonic wave and the amplitude is 0.8 mV. The results of this analysis provide useful tools for high sensitivity ultrasound detection in damage detection systems.

  3. Photorefractive Bragg gratings in nematic liquid crystals aligned by a magnetic field

    SciTech Connect

    Wiederrecht, G.P.; Wasielewski, M.R. |

    1999-06-01

    Photorefractive Bragg gratings are observed in low-molar-mass nematic liquid crystals doped with electron donor and acceptor molecules. This is accomplished by alignment of the nematic liquid crystals in a 0.3 T magnetic field, which produces thicker homeotropic aligned samples than traditional surfactant techniques. Grating fringe spacings as low as 3.7 {mu}m are achieved with 176-{mu}m-thick samples, producing grating {ital Q} values of 33. Up to this point, low molar mass nematic liquid crystals have exhibited photorefractive gratings with Q{le}1. Asymmetric two-beam coupling and photoconductivity experiments are performed to verify the photorefractive origin of the gratings. {copyright} {ital 1999 American Institute of Physics.}

  4. Optical generation of tunable microwave and millimeter waves by using asymmetric fiber Bragg grating Fabry-Perot cavity fiber laser

    NASA Astrophysics Data System (ADS)

    Chen, Cong; Wang, Meng; Li, Qi; Huang, Kaiqiang; Chen, Haiyan

    2014-10-01

    In this presentation, we propose and experimentally demonstrate a novel optical generation of microwave and millimeter wave signals by using asymmetric fiber Bragg grating Fabry-Perot cavity fiber laser, dual-wavelength emission can be achieved with wavelength separation of 0.68nm corresponding to the millimeter wave signal at 85GHz. By appropriately adjusting the operation temperature of intracavity fiber Bragg grating, the frequency of millimeter wave signal generated can be tunable. Our experimental results demonstrate the new concept of optical generation of microwave and millimeter wave signals by using asymmetric fiber Bragg grating Fabry-Perot cavity dual-wavelength fiber laser and the technical feasibility.

  5. High-sensitivity cryogenic temperature sensors using pressurized fiber Bragg gratings

    NASA Technical Reports Server (NTRS)

    Wu, Meng-Chou; DeHaven, Stanton L.

    2006-01-01

    Cryogenic temperature sensing was studied using a pressurized fiber Bragg grating (PFBG). The PFBG was obtained by simply applying a small diametric load to a regular fiber Bragg grating (FBG), which was coated with polyimide of a thickness of 11 micrometers. The Bragg wavelength of the PFBG was measured at temperatures from 295 to 4.2 K. A pressure-induced transition occurred at 200 K during the cooling cycle. As a result the temperature sensitivity of the PFBG was found to be nonlinear but reach 24 pm/K below 200 K, more than three times the regular FBG. For the temperature change from 80 K to 10 K, the PFBG has a total Bragg wavelength shift of about 470 pm, 10 times more than the regular FBG. From room temperature to liquid helium temperature the PFBG gives a total wavelength shift of 3.78 nm, compared to the FBG of 1.51 nm. The effect of the coating thickness on the temperature sensitivity of the gratings is also discussed.

  6. High-sensitivity Cryogenic Temperature Sensors using Pressurized Fiber Bragg Gratings

    NASA Technical Reports Server (NTRS)

    Wu, Meng-Chou; DeHaven, Stanton L.

    2006-01-01

    Cryogenic temperature sensing was studied using a pressurized fiber Bragg grating (PFBG). The PFBG was obtained by simply applying a small diametric load to a regular fiber Bragg grating (FBG), which was coated with polyimide of a thickness of 11 micrometers. The Bragg wavelength of the PFBG was measured at temperatures from 295 to 4.2 K. A pressure-induced transition occurred at 200 K during the cooling cycle. As a result the temperature sensitivity of the PFBG was found to be nonlinear but reach 24 pm/K below 200 K, more than three times the regular FBG. For the temperature change from 80 K to 10 K, the PFBG has a total Bragg wavelength shift of about 470 pm, 10 times more than the regular FBG. From room temperature to liquid helium temperature the PFBG gives a total wavelength shift of 3.78 nm, compared to the FBG of 1.51 nm. The effect of the coating thickness on the temperature sensitivity of the gratings is also discussed.

  7. Development of Interpretation Algorithm for Optical Fiber Bragg Grating Sensors for Composite Structures

    NASA Astrophysics Data System (ADS)

    Peters, Kara

    2002-12-01

    Increasingly, optical fiber sensors, and in particular Bragg grating sensors, are being used in aerospace structures due to their immunity to electrical noise and the ability to multiplex hundreds of sensors into a single optical fiber. This significantly reduces the cost per sensor as the number of fiber connections and demodulation systems required is also reduced. The primary objective of this project is to study the effects of mounting issues such as adhesion, surface roughness, and high strain gradients on the interpretation of the measured strain. This is performed through comparison with electrical strain gage benchmark data. The long-term goal is to integrate such optical fiber Bragg grating sensors into a structural integrity monitoring system for the 2nd Generation Reusable Launch Vehicle. Previously, researchers at NASA Langley instrumented a composite wingbox with both optical fiber Bragg grating sensors and electrical strain gages during laboratory load-to-failure testing. A considerable amount of data was collected during these tests. For this project, data from two of the sensing optical fibers (each containing 800 Bragg grating sensors) were analyzed in detail. The first fiber studied was mounted in a straight line on the upper surface of the wingbox far from any structural irregularities. The results from these sensors showed a relatively large amount of noise compared to the electrical strain gages, but measured the same averaged strain curve. It was shown that the noise could be varied through the choice of input parameters in the data interpretation algorithm. Based upon the assumption that the strain remains constant along the gage length (a valid assumption for this fiber as confirmed by the measured grating spectra) this noise was significantly reduced. The second fiber was mounted on the lower surface of the wingbox in a pattern that circled surface cutouts and ran close to sites of impact damage, induced before the loading tests. As

  8. Effects of Coating and Diametric Load on Fiber Bragg Gratings as Cryogenic Temperature Sensors

    NASA Technical Reports Server (NTRS)

    Wu, meng-Chou; Pater, Ruth H.; DeHaven, Stanton L.

    2008-01-01

    Cryogenic temperature sensing was demonstrated using pressurized fiber Bragg gratings (PFBGs) with polymer coating of various thicknesses. The PFBG was obtained by applying a small diametric load to a regular fiber Bragg grating (FBG). The Bragg wavelengths of FBGs and PFBG were measured at temperatures from 295 K to 4.2 K. The temperature sensitivities of the FBGs were increased by the polymer coating. A physical model was developed to relate the Bragg wavelength shifts to the thermal expansion coefficients, Young's moduli, and thicknesses of the coating polymers. When a diametric load of no more than 15 N was applied to a FBG, a pressure-induced transition occurred at 200 K during the cooling cycle. The pressure induced transition yielded PFBG temperature sensitivities three times greater than conventional FBGs for temperatures ranging from 80 to 200 K, and ten times greater than conventional fibers for temperatures below 80 K. PFBGs were found to produce an increased Bragg wavelength shift of 2.2 nm compared to conventional FBGs over the temperature range of 4.2 to 300 K. This effect was independent of coating thickness and attributed to the change of the fiber thermo-optic coefficient.

  9. Single-pulse coherent anti-Stokes Raman spectroscopy via fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Oh, Seung Ryeol; Park, Joo Hyun; Kwon, Won Sik; Kim, Jin Hwan; Kim, Kyung-Soo; Lee, Jae Yong; Kim, Soohyun

    2016-03-01

    Fiber Bragg grating is used in a variety of applications. In this study, we suggest compact, cost-effective coherent anti- Stokes Raman spectroscopy which is based on the pulse shaping methods via commercialized fiber Bragg grating. The experiment is performed incorporating a commercialized femtosecond pulse laser system (MICRA, Coherent) with a 100 mm length of 780-HP fiber which is inscribed 50 mm of Bragg grating. The pump laser for coherent anti-Stokes Raman spectroscopy has a bandwidth of 90 nm and central wavelength of 815 nm with a notch shaped at 785 nm. The positive chirped pulse is compensated by chirped mirror set. We compensate almost 14000 fs2 of positive group delay dispersion for the transform-limited pulse at the sample position. The pulse duration was 15 fs with average power of 50 mW, and showed an adequate notch shape. Finally, coherent anti-Stokes Raman signals are observed using a spectrometer (Jobin Yvon Triax320 and TE-cooled Andor Newton EMCCD). We obtained coherent anti-Stokes Raman signal of acetone sample which have Raman peak at the spectral finger-print region. In conclusion, the proposed method is more simple and cost-effective than the methods of previous research which use grating pairs and resonant photonic crystal slab. Furthermore, the proposed method can be used as endoscope application.

  10. Hydrostatic pressure sensor based on fiber Bragg grating written in single-ring suspended fiber

    NASA Astrophysics Data System (ADS)

    Htein, Lin; Liu, Zhengyong; Tam, Hwa-Yaw

    2016-05-01

    We present a novel optical fiber consisting of a suspended-fiber with core and cladding diameter of ~ 5 and 30 μm and a supporting ring with thickness of ~ 9 μm. The outer diameter of the fiber was 125 μm and a fiber Bragg grating (FBG) with a length of 1-mm was inscribed on it. Hydrostatic pressure was measured by monitoring the Bragg wavelength shifts of 9-mm long single-ring suspended fiber. Pressure sensitivity was measured to be -18.92 pm/MPa, which is about five times higher than FBG on standard single-mode fiber.

  11. Monitoring of ultraviolet pulse rate dependent photomechanical actuation in carbon nanotubes using fiber Bragg gratings

    SciTech Connect

    Shivananju, B. N.; Suri, Ashish; Asokan, S.; Misra, Abha

    2014-01-06

    In this Letter, we present a non-contact method of controlling and monitoring photomechanical actuation in carbon nanotubes (CNT) by exposing it to ultra-violet radiation at different pulse rates (10 to 200 Hz). This is accomplished by imparting a reversible photo induced strain (5–330 με) on CNT coated fibre Bragg gratings; CNT undergoes an internal reversible structural change due to cyclic photon absorption that leads to the development of mechanical strain, which in turn allows reversible switching of the Bragg wavelength. The results also reveal an interesting pulse rate dependent rise and fall times of photomechanical actuation in CNT.

  12. Polymer optical fiber Bragg grating acting as an intrinsic biochemical concentration sensor.

    PubMed

    Zhang, Wei; Webb, David; Peng, Gangding

    2012-04-15

    We demonstrate an intrinsic biochemical concentration sensor based on a polymer optical fiber Bragg grating. The water content absorbed by the polymer fiber from a surrounding solution depends on the concentration of the solution because of the osmotic effect. The variation of water content in the fiber causes a change in the fiber dimensions and a variation in refractive index and, therefore, a shift in the Bragg wavelength. Saline solutions with concentration from 0% to 22% were used to demonstrate the sensing principle, resulting in a total wavelength shift of 0.9 nm, allowing high-resolution concentration measurements to be realized.

  13. Vibration sensor based on highly birefringent Bragg gratings written in standard optical fiber by a femtosecond laser

    NASA Astrophysics Data System (ADS)

    Chah, Karima; Bueno, Antonio; Kinet, Damien; Caucheteur, Christophe; Chluda, Cédric; Mégret, Patrice; Wuilpart, Marc

    2014-05-01

    We present a vibration sensor based on highly birefringent fiber Bragg gratings written in standard single mode optical fiber and realized with UV femtosecond pulses. This vibration sensor takes advantage of the stress-induced phase shift between the two orthogonally polarized fiber eigenmodes which induces intensity distribution changes in the two fiber Bragg grating reflection modes. The gratings are inscribed with the femtosecond line by line technique and have a birefringence value of 6 10-4. We demonstrate that theses gratings are temperature birefringence insensitive and ideal for vibration measurements.

  14. Multiplexed Volume Bragg Gratings in Narrowand Broad-band Spectral Systems: Analysis and Application

    NASA Astrophysics Data System (ADS)

    Ingersoll, Gregory B.

    Volume Bragg gratings (VBGs) are important holographic optical elements in many spectral systems. Using multiple volume gratings, whether multiplexed or arranged sequentially, provides advantages to many types of systems in overall efficiency, dispersion performance, flexibility of design, etc. However, the use of multiple gratings---particularly when the gratings are multiplexed in a single holographic optical element (HOE)---is subject to inter-grating coupling effects that ultimately limit system performance. Analyzing these coupling effects requires a more complex mathematical model than the straightforward analysis of a single volume grating. We present a matrix-based algorithm for determining diffraction efficiencies of significant coupled waves in these multiplexed grating holographic optical elements (HOEs). Several carefully constructed experiments with spectrally multiplexed gratings in dichromated gelatin verify our conclusions. Applications of this theory to broad- and narrow-band systems are explored in detailed simulations. Broadband systems include spectrum splitters for diverse-bandgap photovoltaic (PV) cells. Volume Bragg gratings can serve as effective spectrum splitters, but the inherent dispersion of a VBG can be detrimental given a broad-spectrum input. The performance of a holographic spectrum splitter element can be improved by utilizing multiple volume gratings, each operating in a slightly different spectral band. However, care must be taken to avoid inter-grating coupling effects that limit ultimate performance. We explore broadband multi-grating holographic optical elements (HOEs) in sandwiched arrangements where individual single-grating HOEs are placed in series, and in multiplexed arrangements where multiple gratings are recorded in a single HOE. Particle swarm optimization (PSO) is used to tailor these systems to the solar spectrum taking into account both efficiency and dispersion. Both multiplexed and sandwiched two-grating systems

  15. Highly efficient cladding-pumped fibre laser based on an ytterbium-doped optical fibre and a fibre Bragg grating

    SciTech Connect

    Kurkov, Andrei S; Karpov, V I; Medvedkov, O I; Dianov, Evgenii M; Vasil'ev, Sergei A; Paramonov, Vladimir M; Protopopov, V N; Laptev, A Yu; Gur'yanov, A N; Umnikov, A A; Vechkanov, N I; Artyushenko, V G; Frahm, J

    1999-06-30

    Ytterbium-ion-doped double-clad optical fibres were developed. The differential quantum efficiency of a diode-pumped fibre laser, fabricated on the basis of such optical fibres with a fibre Bragg grating, was 90%. (lasers)

  16. Metal-coated second-order fibre Bragg gratings produced by infrared femtosecond radiation for dual temperature and strain sensing

    NASA Astrophysics Data System (ADS)

    Chah, K.; Kinet, D.; Caucheteur, C.

    2016-05-01

    We report highly localized second-order fibre Bragg gratings at 1585 nm inscribed by point-by-point focused infrared femtosecond pulses. A thin gold coating deposited on the fibre outer surface at the grating location allows shielding the cladding mode resonances from the outer medium, so that they remain present in the transmitted amplitude spectrum. The Bragg resonance of the second-order grating is surrounded by high-order cladding mode resonances of the first-order grating. These cladding modes exhibit the same temperature sensitivity as the Bragg resonance (10.6 pm/°C) but high differential strain sensitivity (-0.55 pm/μepsilon versus 1.20 pm/μepsilon for the Bragg mode). Therefore, the conditioning of the matrix inversion as demodulation method is fully satisfied, yielding a new design of fibre sensor able to discriminate between temperature and strain, with an unprecedented sensitivity.

  17. ASE Suppression in a Diode-Pumped Nd:YLF Regenerative Amplifier Using a Volume Bragg Grating

    SciTech Connect

    Okishev, A.V.; Dorrer, C.; Smirnov, V.I.; Glebov, L.B.; Zuegel, J.D.

    2007-10-11

    Instrument-limited suppression of out-of-band amplified spontaneous emission (ASE) is demonstrated for the first time in a Nd:YLF diode-pumped regenerative amplifier using a volume Bragg grating (VBG) as a cavity mirror.

  18. Comparison of recoated fiber Bragg grating sensors under tension on a steel coupon

    NASA Astrophysics Data System (ADS)

    Rivera, E.; Thomson, D. J.; Mufti, A. A.

    2005-05-01

    One of the key elements in a structural health monitoring system is the sensing element and data acquisition system. One type of fiber optic sensor used to measure strain is the fiber Bragg grating. Bragg gratings are fabricated using different methods. One method involves placing a mask pattern over the optical fiber and projecting UV light through it to change the refractive index of the core. However, before the grating is written into the core of the fibre, the outer fibre coatings must be stripped away either mechanically or chemically. Fibre Bragg gratings are then recoated after the grating has been written to maintain the strength and flexibility of the fibre by protecting the exposed glass from damage. Acrylate and polyimide are two types of recoat material typically used on fibre Bragg grating sensors. This work is a controlled comparison of polyimide and acrylate recoated fibres for Bragg grating strain sensors. The comparison was carried out using a tension test coupon with recoated FBG and electrical strain gauges bonded to its surface. The tension test specimen was made of cold rolled steel and was designed according to ASTM A30-97a standard. The dimensions were chosen such that three fibre optic sensors and a strain gauge can be attached on each side. The load was applied in 40 μɛ steps until the strain reached approximately 200 ´ɛ. The load was then incrementally decreased back to zero. FBG sensors from 2 manufacturers were compared. For the first manufacturer the Acrylate coated sensors required a gauge factor is 0.75 in order for electrical and FBG strain readings to agree. For Polyimide coated sensors, the appropriate gauge factor was very close to the theoretically predicted value of 0.8. Using these gauge factors, the error between the first manufacturers sensor readings and the strain gauges was well within +/-5´ɛ. On the other hand, the second manufacturers sensors did not perform nearly as well. Their readings were substantially lower

  19. Analysis of transmission mode of a matched fiber Bragg grating interrogation scheme.

    PubMed

    Wade, Scott A; Attard, Daniel P; Stoddart, Paul R

    2010-08-20

    A detailed investigation has been undertaken into the transmission mode of the matched fiber Bragg grating interrogation scheme with respect to its use in optical fiber sensor applications. Analytical and numerical models of the scheme have been developed. Experimental studies presented include the effect of the spectral characteristics of the gratings on system performance, results of strain and compression calibrations, a scheme to correct for intensity fluctuations, and the correction of temperature-induced shifts by collocating sensor and reference gratings. The results are in good agreement with a simplified model of the transmission mode. The analysis provides quantitative relationships between key sensor design parameters, such as sensitivity and measurement range as a function of grating bandwidth. PMID:20733619

  20. Development of Bragg Gratings as Shear Stress Monitors in Aerodynamic >Facilities

    NASA Astrophysics Data System (ADS)

    Parmar, Devandra S.

    1998-04-01

    Two Bragg gratings centered at 1289.565 nm and 1299.432 nm were co-written in the core of a 9/125 telecommunications fiber doped with 10 weight percent germanium. The fiber was mounted in a 126 deep groove, with a 127 diameter semicircular bottom, etched in a flat metal plate used as the test model. A 1 thick epoxy layer bonded the fiber to the metal plate. A thermocouple was also attached to the metal plate in the vicinity of the Bragg fiber. The metal plate was next mounted in the test section of a subsonic wind tunnel. A skin friction balance was also mounted on the wall of the test section. As the wind speed in the tunnel was increased from 0 to 90 m/sec, reflected Bragg wavelengths and the fiber temperatures were recorded continuously. At a windspeed of 38.89 m/sec, the tunnel flow experienced a fan-induced turbulence registered by the skin friction balance as well as the Bragg signals. This commonality of the turbulence signal registration provided a unique calibration datum for the modulus of rigidity of the Bragg fiber assembly. This value of h has been used to calculate the values of shear stress at various tunnel speeds on the basis of Bragg wavelength changes at those speeds.

  1. Strain measurement during stress rupture of composite over-wrapped pressure vessel with fiber Bragg gratings sensors

    NASA Astrophysics Data System (ADS)

    Banks, Curtis E.; Grant, Joseph; Russell, Sam; Arnett, Shawn

    2008-03-01

    Fiber optic Bragg gratings were used to measure strain fields during Stress Rupture (SSM) test of Kevlar Composite Over-Wrapped Pressure Vessels (COPVs). The sensors were embedded under the over-wrapped attached to the liner released from the Kevlar and attached to the Kevlar released from the liner. Additional sensors (foil gages and fiber bragg gratings) were surface mounted on the COPV liner.

  2. Strain Measurement during Stress Rupture of Composite Over-Wrapped Pressure Vessel with Fiber Bragg Gratings Sensors

    NASA Technical Reports Server (NTRS)

    Banks, Curtis E.; Grant, Joseph; Russell, Sam; Arnett, Shawn

    2008-01-01

    Fiber optic Bragg gratings were used to measure strain fields during Stress Rupture (SSM) test of Kevlar Composite Over-Wrapped Pressure Vessels (COPV). The sensors were embedded under the over-wrapped attached to the liner released from the Kevlar and attached to the Kevlar released from the liner. Additional sensors (foil gages and fiber bragg gratings) were surface mounted on the COPY liner.

  3. High-power soliton fiber laser based on pulse width control with chirped fiber Bragg gratings

    SciTech Connect

    Fermann, M.E.; Sugden, K.; Bennion, I.

    1995-01-15

    Chirped fiber Bragg gratings control the pulse width and energy in Kerr mode-locked erbium fiber soliton lasers. We create high-energy pulses by providing large amounts of excessive negative dispersion, which increases the pulse width while keeping the nonlinearity of the cavity constant. With a chirped fiber grating of 3.4-ps{sup 2} dispersion, 3-ps pulses with an energy content higher than 1 nJ are generated at a repetition rate of 27 MHz. By controlling the polarization state in the cavity, we obtain a tuning range from 1.550 to 1.562 {mu}m.

  4. Wavelength switchable graphene Q-switched fiber laser with cascaded fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Wu, Man; Chen, Shuqing; Chen, Yu; Li, Ying

    2016-06-01

    We have demonstrated a wavelength switchable graphene Q-switched fiber laser with two cascaded fiber Bragg gratings. Stable Q-switching operation with central wavelength 1542.9 nm (1543.7 nm), repetition rate 28.4 kHz (22.58 kHz), and pulse duration 2.16 μs (2.65 μs) can be obtained by adjusting the intra-cavity birefringence. Moreover, stable dual-wavelength operation with wavelength spacing 0.8 nm can also be observed. The cascaded fiber gratings combined with the graphene saturable absorber provide a simple and feasible way to get versatile pulsed fiber laser.

  5. Photonic crystals and Bragg gratings for the mid-IR and terahertz spectral ranges

    SciTech Connect

    Usikova, A. A. Il’inskaya, N. D.; Matveev, B. A.; Shubina, T. V.; Kop’ev, P. S.

    2013-12-15

    A method for the fabrication of 2D periodic structures by contact optical photolithography with image inversion is reported. The optical properties of photonic crystals and Bragg gratings for mid-IR and terahertz emitters are considered. The possibility of raising the integral emission intensity of light-emitting diodes for the mid-IR spectral range is demonstrated. The requirements to gratings for the output of terahertz emission generated by surface plasmons excited in layers of narrow-gap degenerate semiconductors with an accumulation layer are determined.

  6. Temperature-compensated fibre Bragg grating -based sensor with variable sensitivity

    NASA Astrophysics Data System (ADS)

    Di Sante, Raffaella; Bastianini, Filippo

    2015-12-01

    In this paper a Fibre Bragg Grating (FBG)-based sensor device for strain measurement with adjustable full-scale sensitivity is proposed. Installation flanges of the sensor can be moved with respect to the internal fixed FBG sensing length in order to adjust the overall strain sensitivity and the full scale measurement range of the device. Thermal drift is compensated using a technique based on the thermal expansion of a solid block connected to the fibre, in the pre-stressed region outside the grating. Typical calibration curves are reported to illustrate the sensor sensitivity variation with the layout and temperature.

  7. Gamma radiation-induced blue shift of resonance peaks of Bragg gratings in pure silica fibres

    NASA Astrophysics Data System (ADS)

    Faustov, A. V.; Gusarov, A. I.; Mégret, P.; Wuilpart, M.; Kinet, D.; Zhukov, A. V.; Novikov, S. G.; Svetukhin, V. V.; Fotiadi, A. A.

    2016-02-01

    We report the first observation of a significant gamma radiation-induced blue shift of the reflection/transmission peak of fibre Bragg gratings inscribed into pure-silica core fibres via multiphoton absorption of femtosecond pulses. At a total dose of ~100 kGy, the shift is ~20 pm. The observed effect is attributable to the ionising radiation-induced decrease in the density of the silica glass when the rate of colour centre formation is slow. We present results of experimental measurements that provide the key parameters of the dynamics of the gratings for remote dosimetry and temperature sensing.

  8. Wavelength-division and spatial multiplexing using tandem interferometers for Bragg grating sensor networks

    NASA Astrophysics Data System (ADS)

    Kalli, K.; Brady, G. P.; Webb, D. J.; Jackson, D. A.; Zhang, L.; Bennion, I.

    1995-12-01

    We present a new method for the interrogation of large arrays of Bragg grating sensors. Eight gratings operating between the wavelengths of 1533 and 1555 nm have been demultiplexed. An unbalanced Mach-Zehnder interferometer illuminated by a single low-coherence source provides a high-phase-resolution output for each sensor, the outputs of which are sequentially selected in wavelength by a tunable Fabry-Perot interferometer. The minimum detectable strain measured was 90 n 3 / \\radical Hz \\end-radical at 7 Hz for a wavelength of 1535 nm.

  9. Accuracy improvement in peak positioning of spectrally distorted fiber Bragg grating sensors by Gaussian curve fitting

    SciTech Connect

    Lee, Hyun-Wook; Park, Hyoung-Jun; Lee, June-Ho; Song, Minho

    2007-04-20

    To improve measurement accuracy of spectrally distorted fiber Bragg grating temperature sensors, reflection profiles were curve fitted to Gaussian shapes, of which center positions were transformed into temperature information.By applying the Gaussian curve-fitting algorithm in a tunable bandpass filter demodulation scheme,{approx}0.3 deg. C temperature resolution was obtained with a severely distorted grating sensor, which was much better than that obtained using the highest peak search algorithm. A binary search was also used to retrieve the optimal fitting curves with the least amount of processing time.

  10. Deformation monitoring in prestressing tendons using fibre Bragg gratings encapsulated in metallic packages

    NASA Astrophysics Data System (ADS)

    Fusiek, Grzegorz; Perry, Marcus; Niewczas, Pawel; Johnston, Michael

    2014-05-01

    An investigation into the capability of deformation monitoring using fibre Bragg gratings encapsulated in metallic packages is presented in the paper. The proposed approach relies on a grating inscription into a metal coated fibre and brazing the fibre into a metal capillary using induction heating. A metal rod instrumented with encapsulated FBG strain and temperature sensors is placed in an electromechanical tester and stressed up 80 % of its ultimate tensile strength. It is demonstrated through a 60 h experiment that the sensors are capable of real-time deformation monitoring.

  11. Femtosecond direct-writing of low-loss fiber Bragg gratings using a continuous core-scanning technique.

    PubMed

    Williams, Robert J; Krämer, Ria G; Nolte, Stefan; Withford, Michael J

    2013-06-01

    We report the inscription of low-loss fiber Bragg gratings using focused femtosecond (fs) pulses and a continuous core-scanning technique. This direct-write technique produces high-fidelity Type I-IR gratings that share the inherent advantages of other direct-write methods, such as the point-by-point (PbP) method, for which the grating period is a free parameter. However, here we demonstrate an order of magnitude improvement in scattering loss compared to PbP gratings, to a level comparable with that of phase-mask-based fs inscription. A first-order grating was inscribed in standard telecommunications fiber with -49 dB transmission at the Bragg wavelength and 0.1 dB broadband scattering loss. Potential application of these gratings to large-mode-area fibers and chirped grating fabrication are highlighted.

  12. Enhanced spectral response of π-phase shifted fiber Bragg gratings in closed-loop configuration.

    PubMed

    Malara, P; Campanella, C E; De Leonardis, F; Giorgini, A; Avino, S; Passaro, V M N; Gagliardi, G

    2015-05-01

    The transmission spectrum of a ring resonator enclosing a π-phase shifted fiber Bragg grating (π-FBG) shows a spectral feature at the Bragg wavelength that is much sharper than resonance of the π-FBG alone, and that can be detected with a simple integrated cavity output technique. Hence, the resolution of any sensor based on the fitting of the π-FBG spectral profile can be largely improved by the proposed configuration at no additional fabrication costs and without altering the sensor robustness. A theoretical model shows that the resolution enhancement attainable in the proposed closed-loop geometry depends on the quality factor of the ring resonator. With a commercial grating in a medium-finesse ring, a spectral feature 12 times sharper than the π-FBG resonance is experimentally demonstrated. A larger enhancement is expected in a low-loss, polarization maintaining setup. PMID:25927801

  13. Highly birefringent phase-shifted fiber Bragg gratings inscribed with femtosecond laser.

    PubMed

    He, Jun; Wang, Yiping; Liao, Changrui; Wang, Qiaoni; Yang, Kaiming; Sun, Bing; Yin, Guolu; Liu, Shen; Zhou, Jiangtao; Zhao, Jing

    2015-05-01

    We demonstrate a highly birefringent phase-shifted fiber Bragg grating (PS-FBG) inscribed in H2-free fiber with a near-infrared femtosecond Gaussian laser beam and uniform phase mask. The PS-FBG was fabricated from an ordinary fiber Bragg grating (FBG) in a case in which overexposure was applied. The spectral evolution from FBG to FS-FBG was observed experimentally with a decrease in transmission loss at dip wavelength, blueshift of the dip wavelength, decrease in the cladding mode loss, and an increase in the insertion loss. A high birefringence was demonstrated experimentally with the existence of PS-FBG only in TM polarization. The formation of the PS-FBG may be due to a negative index change induced by the higher intensity in the center of the Gaussian laser beam. PMID:25927770

  14. Damage evaluation and analysis of composite pressure vessels using fiber Bragg gratings to determine structural health

    NASA Astrophysics Data System (ADS)

    Kunzler, Marley; Udd, Eric; Kreger, Stephen; Johnson, Mont; Henrie, Vaughn

    2005-05-01

    With the augmented use of high performance composite materials in critical structures, it has become increasingly important for 'smart' systems to monitor these materials and provide rapid evaluation. Using fiber Bragg gratings embedded into the weave structure of carbon fiber epoxy composites allow the capability to monitor these composites during manufacture, cure, general aging, and damage. Fiber optic sensors allow greater insight into damage progression and can be used to verify analytical models. This paper emphasizes the results of recent work in which multiple arrays of Bragg gratings were wound into composite vessels and monitored while the part was damaged. Based on the response of these sensors, algorithms were developed to identify the location of damage impacts. Results were verified against eddy current and ultrasonic NDE methods.

  15. Fiber optic anemometer based on metal infiltrated microstructured optical fiber inscribed with Bragg grating

    NASA Astrophysics Data System (ADS)

    Wang, Jie; Gao, Shaorui; Liu, Zhengyong; Zhang, A. Ping; Shen, Yonghang; Tam, Hwayaw

    2015-09-01

    An all-fiber optical anemometer with high light-heat conversion efficiency by using an in-house microstructured optical fiber Bragg grating (MOFBG) is presented. Low-molten-temperature BiSnIn alloy was successfully infiltrated into 11- cm length of a six-hole microstructured optical fiber which was inscribed with a fibre Bragg grating (FBG) centered at ~848 nm. Light launched into the MOFBG was strongly absorbed by the metal to generate heat, while the FBG was utilized to monitor temperature change due to surrounding wind speed. The sensitivity of the laser-heated MOFBG anemometer was measured to be ~0.1 nm/(m/s) for wind speed ranged from 0.5 m/s to 2 m/s. The efficiency of the anemometer, defined as effective sensitivity per pump power, is 8.7 nm/(m/s*W).

  16. Power-compensated displacement sensing based on single mode-multimode fiber Bragg grating structure

    NASA Astrophysics Data System (ADS)

    Sun, An; Wu, Zhishen; Huang, Huang

    2013-01-01

    In this paper, power-compensated displacement sensing is proposed and investigated experimentally based on single mode-multimode fiber Bragg grating (FBG) structure, which is fabricated by a single mode fiber and an FBG written on 105/125 μm graded-index multimode fiber (MMF). Experimental results verify that the reflected peak power of multiple wavelengths in single mode-multimode fiber Bragg grating structure shows different response to displacement induced bending of transmitting multimode fiber as the result of multimode interference (MMI). By employing different bending responses between multiple wavelengths of multimode FBG, ratiometric detection based high sensitive displacement measurement can be achieved, which provides a simple and practical method for displacement sensing and meanwhile a potential solution for multi-parameter measurement.

  17. Soil water evaporation measurement of lysimeter based on fiber Bragg grating sensor

    NASA Astrophysics Data System (ADS)

    Yan, Kejun; Liu, Jun; Miao, Liping; Bai, Li; Zhong, Wenting

    2013-10-01

    A lysimeter weighing system based on fiber Bragg grating (FBG) sensor for measuring the soil water evaporation was presented in this paper. By the use of three mechanical levers and balance weight, the weight loaded on the FBG sensor was reduced K times (here, K was the ratio of levers). So the amount of water change in the soil container of tons can be weighted. A two-hole cantilever was selected as the elastomer structure of FBG weighing sensor, and an optimum design was carried on using the finite element method to meet the small-scaled design requirements. Using the matching fiber Bragg grating demodulation method based on LabVIEW, the demodulation system was easy to be implemented. Then the FBG center wavelength drift was converted into a time interval, and the weight can be obtained automatically through measuring the interval by computer. Preliminary experiment showed that this weighing system has the ability of measuring soil water evaporation accurately.

  18. Spectral interference fringes in chirped large-mode-area fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Poozesh, Reza; Madanipour, Khosro; Vatani, Vahid

    2016-09-01

    Spectral interference fringes were experimentally observed in chirped large mode area fiber Bragg grating (CFBG) in the overlapping region of the reflected spectrum of fiber modes by a high resolution spectrometer. It was demonstrated that the interference is due to optical path difference of the reflected modes in slight chirped FBGs. By assuming chirped fiber Bragg gratings as a Fabry-Perot (FP) cavity, free spectral range (FSR) of FP was calculated 0.08 nm which is matched with measurement very well. Furthermore, the experiments show that axial tension and temperature changes of the CFBG do not have observable effects on the magnitude of FSR, however coiling of the fiber deceases spectral interference fringe amplitude without sensible effect on FSR magnitude. The results of this work can be utilized in bending sensors.

  19. Dynamic analysis and temperature measurements of concrete cantilever beam using fibre Bragg gratings

    NASA Astrophysics Data System (ADS)

    da Silva, Jean Carlos Cardozo; Martelli, Cicero; Kalinowski, Hypolito José; Penner, Elisabeth; Canning, John; Groothoff, Nathaniel

    2007-01-01

    We analyzed the action of fire, causing degradation in a concrete cantilever beam using dynamic testing. The structure was fitted with two fibre Bragg gratings (FBG) sensors. One of them measured vibration and the other measured the temperature inside of the cantilever beam, while the beam was exposed to fire. A high-temperature probe based on a simple packaging system, which isolates the sensing FBG from any mechanical action, was developed. A low-cost fibre Bragg grating interrogation system, including easy assembly and maintenance, was used for the measurements. The temperature in the cantilever beam increased until 150 °C and a reduction in the strength of concrete was observed through modal analysis. Results reveal a considerable reduction in strength occurs even with exposures to moderate temperatures (less than 90 °C).

  20. Measurement of mandibular movements in parafunctional patient using occlusal splint with Bragg gratings: pilot study

    NASA Astrophysics Data System (ADS)

    Franco, Ana Paula G. O.; Gebert, Andréa. O.; Souza, Mauren A.; Jeranoski, Lorena; Kalinowski, Hypolito J.; Abe, Ilda

    2016-05-01

    The aim of the study is to demonstrate the potential of the fibre Braggs grating (FBG) in the measurement of different jaw movements that are performed for patients with occlusal parafunction using occlusal splints. Two silicon plates each 2mm are used, the fibre optic sensor is positioned in the maxillary left first molar region above the point of contact with opposing tooth after pressing the first plate on the model. Then the second silicon plate is pressed. The device has a final thickness of 2 mm. The occlusal splint is installed in the mouth of the patient who underwent different movements on occlusal splint. The maximum frequency bite is monitored. The results demonstrate that the bite shows a difference between grinding and clenching movements. The curves behaviour patterns are presented in order to show these different comparisons. Therefore, it is concluded that the fibre Braggs grating consists in an efficient method for monitoring the mechanical behaviour bite of patients with occlusal splints.

  1. Strain Sharing Assessment in Woven Fiber Reinforced Concrete Beams Using Fiber Bragg Grating Sensors.

    PubMed

    Montanini, Roberto; Recupero, Antonino; De Domenico, Fabrizio; Freni, Fabrizio

    2016-09-22

    Embedded fiber Bragg grating sensors have been extensively used worldwide for health monitoring of smart structures. In civil engineering, they provide a powerful method for monitoring the performance of composite reinforcements used for concrete structure rehabilitation and retrofitting. This paper discusses the problem of investigating the strain transfer mechanism in composite strengthened concrete beams subjected to three-point bending tests. Fiber Bragg grating sensors were embedded both in the concrete tensioned surface and in the woven fiber reinforcement. It has been shown that, if interface decoupling occurs, strain in the concrete can be up to 3.8 times higher than that developed in the reinforcement. A zero friction slipping model was developed which fitted very well the experimental data.

  2. Sensitivity of Bragg gratings in birefringent optical fiber to transverse compression between conforming materials.

    PubMed

    Dennison, Christopher R; Wild, Peter M

    2010-04-20

    A theoretical and experimental investigation of the transverse load sensitivity of Bragg gratings in birefringent fibers to conforming contact is presented. A plane elasticity model is used to predict the contact dimensions between a conforming material and optical fiber and the principal stresses, indicating birefringence, created as a result of this contact. The transverse load sensitivity of commercially available birefringent fiber is experimentally measured for two cases of conforming contact. Theoretical and experimental results show that birefringent optical fiber can be used to make modulus-independent measurements of contact load. Therefore, Bragg gratings could be applied to conforming contact load measurements while avoiding some of the complications associated with existing contact sensors: specifically, the necessity to precalibrate by using materials with mechanical properties identical to those found in situ.

  3. Strain Sharing Assessment in Woven Fiber Reinforced Concrete Beams Using Fiber Bragg Grating Sensors.

    PubMed

    Montanini, Roberto; Recupero, Antonino; De Domenico, Fabrizio; Freni, Fabrizio

    2016-01-01

    Embedded fiber Bragg grating sensors have been extensively used worldwide for health monitoring of smart structures. In civil engineering, they provide a powerful method for monitoring the performance of composite reinforcements used for concrete structure rehabilitation and retrofitting. This paper discusses the problem of investigating the strain transfer mechanism in composite strengthened concrete beams subjected to three-point bending tests. Fiber Bragg grating sensors were embedded both in the concrete tensioned surface and in the woven fiber reinforcement. It has been shown that, if interface decoupling occurs, strain in the concrete can be up to 3.8 times higher than that developed in the reinforcement. A zero friction slipping model was developed which fitted very well the experimental data. PMID:27669251

  4. Bragg fibre grating semiconductor lasers with the narrow emission spectrum in the 1530 - 1560-nm region

    SciTech Connect

    Duraev, V P; Nedelin, E T; Nedobyvailo, T P; Sumarokov, M A; Klimov, K I

    2001-06-30

    The design of a cw single-frequency semiconductor laser with a Bragg fibre grating in a composite resonator emitting at a wavelength of 1553.6 nm and intended for fibre-optic communication systems with wavelength-division multiplexing is descried and its main parameters are presented. It is shown that the suppression of longitudinal eigenmodes of the laser diode caused by the antireflection coating deposited on the internal face of the crystal leads to lasing on a single longitudinal mode of the composite resonator. The lasing line half-width is no more than 0.1 nm and the lasing wavelength, which corresponds to the Bragg wavelength of a fibre grating, remains stable in the dynamic mode. (lasers, active media)

  5. Bayfol HX photopolymer for full-color transmission volume Bragg gratings

    NASA Astrophysics Data System (ADS)

    Berneth, Horst; Bruder, Friedrich-Karl; Fäcke, Thomas; Jurbergs, David; Hagen, Rainer; Hönel, Dennis; Rölle, Thomas; Walze, Günther

    2014-02-01

    Manipulating light with optical gratings based on volume Holographic Optical Elements (vHOEs), also known as volume Bragg gratings, has the advantage to reconstruct only the first diffraction order and hence provide high diffraction efficiencies and angular selectivity. In addition, they offer the further benefit to be fully transparent in the off- Bragg condition like it is required in optical combiners. We present the latest status of our instant-developing photopolymer film technology (Bayfol® HX) and show beneficial recording parameters - specifically we discuss the challenges to record transmission vHOEs and how to overcome them. Experimental results on color transmission recordings are shown and it is demonstrated that those match perfectly to Kogelniks coupled wave theory. It is recommended to adopt the dynamic range of the recording media by proper choice of recording dosage, recording power, beam ratio and photopolymer film type to the desired transmission vHOE design.

  6. Laser formation of Bragg gratings in polymer nanocomposite materials

    NASA Astrophysics Data System (ADS)

    Nazarov, M. M.; Khaydukov, K. V.; Sokolov, V. I.; Khaydukov, E. V.

    2016-01-01

    The method investigated in this work is based on the laser-induced, spatially inhomogeneous polymerisation of nanocomposite materials and allows control over the motion and structuring of nanoparticles. The mechanisms of nanoparticle concentration redistribution in the process of radical photopolymerisation are studied. It is shown that under the condition of spatially inhomogeneous illumination of a nanocomposite material, nanoparticles are diffused from the illuminated areas into the dark fields. Diffraction gratings with a thickness of 8 μm and a refractive index modulation of 1 × 10-2 are written in an OCM-2 monomer impregnated by silicon nanoparticles. The gratings may be used in the development of narrowband filters, in holographic information recording and as dispersion elements in integrated optical devices.

  7. 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.

  8. Imaging of various optical fiber Bragg gratings using differential interference contrast microscopy: analysis and comparison.

    PubMed

    Rollinson, Claire M; Wade, Scott A; Baxter, Greg W; Collins, Stephen F

    2016-02-01

    Differential interference contrast images of various optical fibers and optical fiber Bragg gratings (FBGs), written with the phase mask technique, are presented to provide information about the resultant refractive index variations present in each case. Use of different fiber types using two distinct phase masks producing four Type I FBGs and a Type In FBG allowed similarities and differences in these FBG images due to variations in the Talbot diffraction patterns produced to be studied. PMID:26836080

  9. 3D printed sensing patches with embedded polymer optical fibre Bragg gratings

    NASA Astrophysics Data System (ADS)

    Zubel, Michal G.; Sugden, Kate; Saez-Rodriguez, D.; Nielsen, K.; Bang, O.

    2016-05-01

    The first demonstration of a polymer optical fibre Bragg grating (POFBG) embedded in a 3-D printed structure is reported. Its cyclic strain performance and temperature characteristics are examined and discussed. The sensing patch has a repeatable strain sensitivity of 0.38 pm/μepsilon. Its temperature behaviour is unstable, with temperature sensitivity values varying between 30-40 pm/°C.

  10. Measurement of high-birefringent spun fiber parameters using short-length fiber Bragg gratings.

    PubMed

    Vasiliev, S A; Przhiyalkovsky, Ya V; Gnusin, P I; Medvedkov, O I; Dianov, E M

    2016-05-30

    Spectral polarization characteristics of short-length fiber Bragg gratings UV-written in a highly-birefringent spun-fiber have been investigated. Based on the analysis of the characteristics the technique for measuring the built-in linear phase birefringence as well as the spin period in this fiber type has been suggested. In this method the birefringence dispersion is excluded and therefore the built-in linear phase birefringence can be measured with an improved accuracy. PMID:27410060

  11. Ytterbium-doped fibre laser with a Bragg grating reflector written in a multimode fibre

    SciTech Connect

    Kurkov, Andrei S; Grukh, Dmitrii A; Medvedkov, O I; Paramonov, Vladimir M; Dianov, Evgenii M

    2005-04-30

    An efficient cladding-pumped Yb-doped fibre laser with a Bragg grating written in a multimode graded-index fibre is fabricated for the first time. The laser emits one transverse mode with a slope efficiency of 60%. The resonator design proposed in the paper can be used for the development of high-power fibre lasers with an increased fibre core diameter. (lasers)

  12. Photonic Bloch oscillations and Wannier-Stark ladders in exponentially chirped Bragg gratings.

    PubMed

    Wilkinson, P B

    2002-05-01

    The formation of photonic Bloch oscillations and Wannier-Stark ladders is demonstrated in an exponentially chirped one-dimensional Bragg grating. The photonic Bloch oscillations are investigated using Hamiltonian optics, and direct analogies are made with electron dynamics in periodic potentials. The results of transfer matrix calculations are presented, which show the existence of a photonic Wannier-Stark ladder that should be detectable in experiments.

  13. Compact fibre Bragg grating-based thermometer for on-line temperature monitoring of drill bits

    NASA Astrophysics Data System (ADS)

    Hey Tow, Kenny; Llera, Miguel; Le Floch, Sébastien; Salvadé, Yves; Thévenaz, Luc

    2016-05-01

    In this communication, a novel compact fibre Bragg grating-based thermometer for on-line temperature monitoring of drill bits is reported. Our proposed technique can potentially be used to optimize any drilling process, requiring the use of small drill bits, through direct temperature measurement at the drill bit instead of relying on indirect parameters (speed of rotation, applied force) in order to avoid an overheating as it is currently done nowadays.

  14. Sensitivity of contact-free fiber Bragg grating sensor to ultrasonic Lamb wave

    NASA Astrophysics Data System (ADS)

    Wee, Junghyun; Hackney, Drew; Peters, Kara; Wells, Brian; Bradford, Philip

    2016-04-01

    Networks of fiber Bragg grating (FBG) sensors can serve as structural health monitoring (SHM) systems for large-scale structures based on the collection of ultrasonic waves. The demodulation of structural Lamb waves requires a high signal-to-noise ratio because Lamb waves have a low amplitude. This paper investigates the signal transfer between Lamb waves propagating in an aluminum plate collected by an optical fiber containing a FBG. The fiber is bonded to the plate at locations away from the FBG. The Lamb waves are converted into longitudinal and flexural traveling waves propagating along the optical fiber, which are then transmitted to the Bragg grating. The signal wave amplitude is measured for different distances between the bond location and the Bragg grating. Bonding the optical fiber away from the FBG location and closer to the signal source produces a significant increase in signal amplitude, here measured to be 5.1 times that of bonding the Bragg grating itself. The arrival time of the different measured wave coupling paths are also calculated theoretically, verifying the source of the measured signals. The effect of the bond length to Lamb wavelength ratio is investigated, showing a peak response as the bond length is reduced compared to the wavelength. This study demonstrates that coupling Lamb waves into guided traveling waves in an optical fiber away from the FBG increases the signal-to-noise ratio of Lamb wave detection, as compared to direct transfer of the Lamb wave to the optical fiber at the location of the FBG.

  15. An experimental study of low-frequency amplitude noise in a fibre Bragg grating laser diode

    SciTech Connect

    Zholnerov, V S; Ivanov, A V; Kurnosov, V D; Kurnosov, K V; Romantsevich, V I; Chernov, R V

    2013-09-30

    We have studied the amplitude noise in a fibre Bragg grating laser diode. It has been shown that discontinuities in noise characteristics correlate with those in the power – current and spectral characteristics of the laser diode, whereas the noise characteristics of the pump source have no such discontinuities. The highest noise level has been observed at pump currents corresponding to concurrent generation of two longitudinal modes. (lasers)

  16. A Bragg grating tunable filter based on temperature control system to demodulate a voltage sensor

    NASA Astrophysics Data System (ADS)

    Ribeiro, Bessie A.; Werneck, Marcelo M.; de Nazaré, Fabio B. V.; Gonçalves, Marceli N.

    2015-09-01

    This work presents an innovative automated Fiber Bragg Grating (FBG) based tunable optical filter (TOF) controlled by temperature to be used in temperature compensating schemes in FBG sensing set-ups. Mechanical and electronic aspects are discussed, and the implemented FBG-TOF viability and reliability in sensing systems are showed. The system was employed to demodulate a high voltage AC signal applied to a FBG-PZT sensor, showing good linearity and sensitivity.

  17. Real time interrogation technique for fiber Bragg grating enhanced fiber loop ringdown sensors array.

    PubMed

    Zhang, Yunlong; Li, Ruoming; Shi, Yuechun; Zhang, Jintao; Chen, Xiangfei; Liu, Shengchun

    2015-06-01

    A novel fiber Bragg grating aided fiber loop ringdown (FLRD) sensor array and the wavelength-time multiplexing based interrogation technique for the FLRD sensors array are proposed. The interrogation frequency of the system is formulated and the interrelationships among the parameters of the system are analyzed. To validate the performance of the proposed system, a five elements array is experimentally demonstrated, and the system shows the capability of real time monitoring every FLRD element with interrogation frequency of 125.5 Hz.

  18. High-strain fiber bragg gratings for structural fatigue testing of military aircraft

    NASA Astrophysics Data System (ADS)

    Davis, Claire; Tejedor, Silvia; Grabovac, Ivan; Kopczyk, James; Nuyens, Travis

    2012-09-01

    This paper reports on an experimental program of work which investigates the reliability, durability, and packaging of fiber Bragg gratings (FBGs) for application as distributed strain sensors during structural fatigue testing of military platforms. The influence of the FBG fabrication process on sensor reliability is investigated. In addition, methodologies for broad-area packaging and surface-mounting of FBG sensing arrays to defense platforms are developed and tested.

  19. Railway track component condition monitoring using optical fibre Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Buggy, S. J.; James, S. W.; Staines, S.; Carroll, R.; Kitson, P.; Farrington, D.; Drewett, L.; Jaiswal, J.; Tatam, R. P.

    2016-05-01

    The use of optical fibre Bragg grating (FBG) strain sensors to monitor the condition of safety critical rail components is investigated. Fishplates, switchblades and stretcher bars on the Stagecoach Supertram tramway in Sheffield in the UK have been instrumented with arrays of FBG sensors. The dynamic strain signatures induced by the passage of a tram over the instrumented components have been analysed to identify features indicative of changes in the condition of the components.

  20. The biosensor based on fiber Bragg grating to determine the composition of the fuel and biofuel

    NASA Astrophysics Data System (ADS)

    Sadykov, I. R.; Morozov, O. G.; Sadeev, T. S.

    2011-12-01

    The aim of this paper is to examine the refractometric method of determining the octane number of gasoline and the presence of organic compounds in biological fuels. A feature of this method is p-shifted etched fiber Bragg grating as the sensing element utilization, which is characterized by a narrow bandwidth. The advantage of this method is the detection of changes in the refractive index at the level of 1,3×10-5.

  1. The biosensor based on fiber Bragg grating to determine the composition of the fuel and biofuel

    NASA Astrophysics Data System (ADS)

    Sadykov, I. R.; Morozov, O. G.; Sadeev, T. S.

    2012-01-01

    The aim of this paper is to examine the refractometric method of determining the octane number of gasoline and the presence of organic compounds in biological fuels. A feature of this method is p-shifted etched fiber Bragg grating as the sensing element utilization, which is characterized by a narrow bandwidth. The advantage of this method is the detection of changes in the refractive index at the level of 1,3×10-5.

  2. Fiber optic Bragg grating sensor network installed in a concrete road bridge

    NASA Astrophysics Data System (ADS)

    Maaskant, Robert; Alavie, A. Tino; Measures, Raymond M.; Ohn, Myo M.; Karr, Shawn E.; Glennie, Derek J.; Wade, C.; Tadros, Gamil; Rizkalla, Sami

    1994-05-01

    The installation of a fiber optic Bragg grating strain sensor network in a new road bridge is described. These sensors are attached to prestressing tendons embedded in prefabricated concrete girders. Three types of prestressing tendons are being monitored: conventional steel strand and two types of carbon fibers reinforced plastic tendons. Sensor durability issues are reviewed and the installation is described. Initial measurements indicate that the sensors are operational and provide some early comparison of tendon performance.

  3. Simplified sensor design for temperature-strain discrimination using fiber Bragg gratings embedded in laminated composites

    NASA Astrophysics Data System (ADS)

    Rodriguez-Cobo, L.; Marques, A. T.; Lopez-Higuera, J. M.; Santos, J. L.; Frazão, O.

    2013-05-01

    Several easy-to-manufacture designs based on a pair of Fiber Bragg Gratings structure embedded in Carbon Fiber Reinforced Plastic (CFRP) have been explored. These smart composites can be used for strain and temperature discrimination. A Finite Elements Analysis and Matlab software were used to study the mechanical responses and its optical behaviors. The results exhibited different sensitivity and using a matrix method it is possible to compensate the thermal drift in a real application keeping a simple manufacture process.

  4. Time division multiplexing of 106 weak fiber Bragg gratings using a ring cavity configuration

    NASA Astrophysics Data System (ADS)

    Wang, Zhi; Wen, Hongqiao; Luo, Zhihui; Dai, Yutang

    2016-06-01

    A time division multiplexing of 106 weak fibers Bragg gratings (FBGs) based on a ring resonant-cavity is demonstrated. A semiconductor optical amplifier is connected in the cavity to function as an amplifier as well as a switch. The 106 weak FBGs are written along a SMF-28 fiber in serial with peak reflectivity of about -30 dB and equal separations of 5 m. The crosstalk and spectral distortion are investigated through both theoretical analysis and experiments.

  5. In-line fiber Bragg grating sensors for steel corrosion detection

    NASA Astrophysics Data System (ADS)

    Deng, Fodan; Huang, Ying; Azarmi, Fardad

    2016-04-01

    A corrosion monitoring system for steel using Fiber Bragg grating (FBG) sensors is proposed. FBG sensors were protected by hypodermic tubes and a layer of adhesive. The increase in volume caused by the presence of corrosion product introduces strain that can be monitored by FBG sensors. Experimental results showed a positive correlation between the strain and corrosion product, and the change in central wavelength has the potential to serve as an indicator for material weight loss due to corrosion.

  6. Interrogation system for a fiber-Bragg-grating strain sensor for automotive applications

    NASA Astrophysics Data System (ADS)

    Falciai, Riccardo; Vannini, Andrea

    2001-09-01

    In this paper a derivative spectrometer, utilizing an FFP tunable filter for the wavelength shift detection and an electronic device for the signal processing, was realized and tested for data acquisition and elaboration from a fiber-Bragg-grating strain sensor system for automotive applications. The result of measurements carried out both under static and dynamic conditions have been compared with those performed with a strain gauge.

  7. Measuring residual stresses in metallic components manufactured with fibre Bragg gratings embedded by selective laser melting

    NASA Astrophysics Data System (ADS)

    Havermann, Dirk; Mathew, Jinesh; MacPherson, William N.; Hand, Duncan P.; Maier, Robert R. J.

    2015-09-01

    Metal clad single mode optical fibres containing Fibre Bragg Gratings are embedded in stainless steel components using bespoke laser based Selective Laser Melting technology (SLM). Significant residual stresses can be created in SLM manufactured components through the strong thermal gradients during the build process. We demonstrate the ability to monitor these internal stresses through embedded optical fibres with FBGs on a layer to layer basis, confirming estimates from models for residual stresses in additive manufactured components.

  8. Temperature field acquisition during gas metal arc welding using thermocouples, thermography and fibre Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Moreira, P. M. G. P.; Frazão, O.; Tavares, S. M. O.; de Figueiredo, M. A. V.; Restivo, M. T.; Santos, J. L.; de Castro, P. M. S. T.

    2007-03-01

    The paper presents the application of temperature acquisition systems integrating thermocouples, a thermographic camera and fibre Bragg grating (FBG) sensors in gas metal arc welding (GMAW) process, MIG (metal inert gas) welding type. Efficient procedures to use FBG sensors and thermocouples were developed. The paper presents and compares measurements made in welded plates of aluminium alloy 6082-T6. Tests were performed in both plate surfaces and good agreement between the three techniques was found.

  9. Highly polarized all-fiber thulium laser with femtosecond-laser-written fiber Bragg gratings.

    PubMed

    Willis, Christina C C; McKee, Erik; Böswetter, Pascal; Sincore, Alex; Thomas, Jens; Voigtländer, Christian; Krämer, Ria G; Bradford, Joshua D; Shah, Lawrence; Nolte, Stefan; Tünnermann, Andreas; Richardson, Martin

    2013-05-01

    We demonstrate and characterize a highly linearly polarized (18.8 dB) narrow spectral emission (<80 pm) from an all-fiber Tm laser utilizing femtosecond-laser-written fiber Bragg gratings. Thermally-dependent anisotropic birefringence is observed in the FBG transmission, the effects of which enable both the generation and elimination of highly linearly polarized output. To our knowledge, this is the first detailed study of such thermal anisotropic birefringence in femtosecond-written FBGs.

  10. Spectral narrowing and stabilization of interband cascade laser by volume Bragg grating.

    PubMed

    Venus, George; Smirnov, Vadim; Mokhun, Oleksiy; Bewley, William W; Merritt, Charles D; Canedy, Chadwick L; Kim, Chul Soo; Kim, Mijin; Vurgaftman, Igor; Meyer, Jerry; Vodopyanov, Konstantin; Glebov, Leonid

    2016-01-01

    A volume Bragg grating recorded in photo-thermo-refractive glass was used to spectrally lock the emission from an 18-μm-wide interband cascade laser ridge to a wavelength of 3.12 μm. The spectral width of emission into the resonant mode is narrowed by more than 300 times, and the thermal wavelength shift is reduced by 60 times. While the power loss penalty is about 30%, the spectral brightness increases by 200 times.

  11. Bent tilted fiber Bragg gratings for temperature-independent vibration sensing in vehicles

    NASA Astrophysics Data System (ADS)

    Ivanov, Alexei; Albert, Jacques

    2007-09-01

    Fiber grating based techniques have proven themselves as low cost, small size and low weight solutions for sensing strain and/or temperature in various applications, including structural health monitoring of aircrafts, ships and other man-made structures. However, normal fiber gratings are sensitive to both strain and temperature in a manner that is impossible to distinguish from the sensor response. Methods devised to circumvent this problem rely on combinations of gratings with different sensitivity to these two perturbations. Simultaneous measurements on two gratings then provide the necessary information to decode strain and temperature values but this requires special grating configurations and packaging to maximize the differential sensitivity. We will present experimental results of an alternative approach where we use a single very weakly tilted fiber Bragg grating (TFBG), to achieve the same effect. The grating couples light from the fundamental mode guided in the core to a large number of cladding modes, depending on the wavelength of interrogation. We propose and demonstrate a novel configuration in which many high order cladding mode resonances are removed by bonding the TFBG in a pre-bent state on a metal plate. After bonding, only a few low order mode resonances are left and occupy less than 5 nm of bandwidth (thereby allowing multiplexing). These resonances all have the same temperature sensitivity but very different behavior when the plate vibrates, bends or stretches statically. Differential measurements of the resonance power levels and shifts then provide valuable information about the mechanical state of the sensor.

  12. Efficient interpretation algorithm for embedded Bragg gratings for damage detection in composites

    NASA Astrophysics Data System (ADS)

    Prabhugoud, Mohanraj; Peters, Kara J.

    2003-07-01

    The goal of a structural health monitoring system is to detect, locate, and identify damages in a structure during its lifetime. The concept of structural health monitoring is particularly important for fiber reinforced composites due to the complexity of the possible failure mechanisms. The goal of this work is to simulate the response of optical fiber Bragg grating sensors to multi-component loading for their implementation in structural health monitoring algorithms for composites. A simulation method is presented to determine the effects of axial, bending and shear loading on an embedded optical fiber Bragg grating sensor. The effect of fiber bending on the Bragg grating sensor is experimentally verified by embedding the sensor in a solid cone, clamped at the base and subjected to a point load at the apex. Next, a numerically efficient method to calculate the response of sensors embedded in a unidirectional composite is developed using both finite element analysis and optimal shear-lag theory and taking into account the above effects. The limitations of the optimal shear-lag theory are derived through comparison with the finite element results. The application of this method is demonstrated through a numerical example, simulating the response of sensors embedded in one fiber layer to a transverse crack.

  13. Strain measurements on concrete beam and carbon fiber cable with distributed optical fiber Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Nellen, Philipp M.; Bronnimann, Rolf; Sennhauser, Urs J.; Askins, Charles G.; Putnam, Martin A.

    1996-09-01

    We report on civil engineering applications of wavelength multiplexed optical fiber Bragg grating arrays directly produced on the draw tower for testing and surveying advanced structures and materials such as carbon fiber reinforced concrete elements and prestressing cables. We equipped a 6 by 0.9 by 0.5 m concrete beam, which was reinforced with carbon fiber reinforced epoxy laminates, and a 7-m long prestressing carbon fiber cable made of seven twisted strands, with optical fiber Bragg grating sensors. Static strains up to 8000 micrometers/m and dynamic strains up to 1200 micrometers/m were measured with a Michelson interferometer used as Fourier spectrometer with a resolution of about 10 micrometers/m for all sensors. Comparative measurements with electrical resistance strain gauges were in good agreement with the fiber optical results. We installed the fiber sensors in two different arrangements: some Bragg grating array elements measured local strain while others were applied in an extensometric configuration to measure moderate strain over a base length of 0.1 to 1 m.

  14. Strain Measurements of Composite Laminates with Embedded Fibre Bragg Gratings: Criticism and Opportunities for Research

    PubMed Central

    Luyckx, Geert; Voet, Eli; Lammens, Nicolas; Degrieck, Joris

    2011-01-01

    Embedded optical fibre sensors are considered for structural health monitoring purposes in numerous applications. In fibre reinforced plastics, embedded fibre Bragg gratings are found to be one of the most popular and reliable solutions for strain monitoring. Despite of their growing popularity, users should keep in mind their shortcomings, many of which are associated with the embedding process. This review paper starts with an overview of some of the technical issues to be considered when embedding fibre optics in fibrous composite materials. Next, a monitoring scheme is introduced which shows the different steps necessary to relate the output of an embedded FBG to the strain of the structure in which it is embedded. Each step of the process has already been addressed separately in literature without considering the complete cycle, from embedding of the sensor to the internal strain measurement of the structure. This review paper summarizes the work reported in literature and tries to fit it into the big picture of internal strain measurements with embedded fibre Bragg gratings. The last part of the paper focuses on temperature compensation methods which should not be ignored in terms of in-situ measurement of strains with fibre Bragg gratings. Throughout the paper criticism is given where appropriate, which should be regarded as opportunities for future research. PMID:22346583

  15. Identification of structural damage using multifunctional Bragg grating sensors: I. Theory and implementation

    NASA Astrophysics Data System (ADS)

    Betz, Daniel C.; Thursby, Graham; Culshaw, Brian; Staszewski, Wieslaw J.

    2006-10-01

    Structural health monitoring has become a respected and established discipline in engineering. Health monitoring involves the development of autonomous systems for continuous monitoring, inspection and damage detection of structures with minimum involvement of labour. The ultimate goal of structural health monitoring is to increase reliability, improve safety, enable light-weight design and reduce maintenance costs for all kinds of structures. The identification of structural damage is therefore a key issue in structural health monitoring. The scope of this paper is to present the results of testing a system for the identification of structural damage based on fibre Bragg grating sensors. The basic idea is to use fibre Bragg gratings as acoustic receivers of ultrasonic Lamb waves. The layout of such a damage identification system is introduced and its theoretical limits are studied numerically and experimentally. The set-up for damage identification experiments is described and the results of initial experiments introducing damage detection based on the analysis of Lamb wave signals are presented. The results for the Bragg grating sensors are then compared to the results of established technology for Lamb wave detection using piezoceramic transducers.

  16. Distributed Sensing of Carbon-Epoxy Composites and Filament Wound Pressure Vessels Using Fiber-Bragg Gratings

    NASA Technical Reports Server (NTRS)

    Grant, J.; Kaul, R.; Taylor, S.; Myer, G.; Jackson, K.; Osei, A.; Sharma, A.

    2003-01-01

    Multiple Fiber Bragg-gratings are embedded in carbon-epoxy laminates as well as in composite wound pressure vessel. Structural properties of such composites are investigated. The measurements include stress-strain relation in laminates and Poisson's ratio in several specimens with varying orientation of the optical fiber Bragg-sensor with respect to the carbon fiber in an epoxy matrix. Additionally, fiber Bragg gratings are bonded on the surface of these laminates and cylinders fabricated out of carbon-epoxy composites and multiple points are monitored and compared for strain measurements at several locations.

  17. Single-polarization, switchable dual-wavelength erbium-doped fiber laser with two polarization-maintaining fiber Bragg gratings.

    PubMed

    Feng, Suchun; Xu, Ou; Lu, Shaohua; Mao, Xiangqiao; Ning, Tigang; Jian, Shuisheng

    2008-08-01

    An improved erbium-doped fiber laser configuration for achieving single-polarization, switchable dual-wavelength of orthogonal polarizations oscillations at room temperature is proposed. For the first time, two fiber Bragg gratings (FBGs) directly written in a polarization-maintaining (PM) and photosensitive erbium-doped fiber (PMPEDF) as the wavelength-selective component are used in a linear laser cavity. Due to the polarization hole burning (PHB) enhanced by the polarization-maintaining FBG (PMFBG), the laser can be designed to operate in stable dual-wavelength or wavelength-switching modes with a wavelength spacing of 0.336 nm at room temperature by adjusting a polarization controller (PC). Each lasing line shows a single polarization with a polarization extinction ratio of >25 dB under different pump levels. The optical signal-to-noise ratio (OSNR) is greater than 50 dB. The amplitude variation with 16 times scans in nearly one and half an hour is less than 0.5 dB at both operating wavelength.

  18. Single- and two-phase flow characterization using optical fiber bragg gratings.

    PubMed

    Baroncini, Virgínia H V; Martelli, Cicero; da Silva, Marco José; Morales, Rigoberto E M

    2015-01-01

    Single- and two-phase flow characterization using optical fiber Bragg gratings (FBGs) is presented. The sensor unit consists of the optical fiber Bragg grating positioned transversely to the flow and fixed in the pipe walls. The hydrodynamic pressure applied by the liquid or air/liquid flow to the optical fiber induces deformation that can be detected by the FBG. Given that the applied pressure is directly related to the mass flow, it is possible to establish a relationship using the grating resonance wavelength shift to determine the mass flow when the flow velocity is well known. For two phase flows of air and liquid, there is a significant change in the force applied to the fiber that accounts for the very distinct densities of these substances. As a consequence, the optical fiber deformation and the correspondent grating wavelength shift as a function of the flow will be very different for an air bubble or a liquid slug, allowing their detection as they flow through the pipe. A quasi-distributed sensing tool with 18 sensors evenly spread along the pipe is developed and characterized, making possible the characterization of the flow, as well as the tracking of the bubbles over a large section of the test bed. Results show good agreement with standard measurement methods and open up plenty of opportunities to both laboratory measurement tools and field applications. PMID:25789494

  19. Recovering strain readings from chirping fiber Bragg gratings in composite overwrapped pressure vessels

    NASA Astrophysics Data System (ADS)

    Strutner, Scott M.; Pena, Frank; Piazza, Anthony; Parker, Allen R.; Richards, W. Lance; Carman, Gregory P.

    2014-04-01

    This study reports on signal recovery of optical fiber Bragg gratings embedded in a carbon fiber composite overwrapped pressure vessel's (COPV) structure which have become chirped due to microcracks. COPVs are commonly used for the storage of high pressure liquids and gases. They utilize a thin metal liner to seal in contents, with a composite overwrap to strengthen the vessel with minimal additional mass. A COPV was instrumented with an array of surface mounted and embedded fiber Bragg gratings (FBGs) for structural health monitoring (SHM) via strain sensing of the material. FBGs have been studied as strain sensors for the last couple decades. Many of the embedded FBGs reflected a multi-peak, chirped response which was not able to be interpreted well by the current monitoring algorithm. Literature and this study found that the chirping correlated with microcracks. As loading increases, so does the number of chirped FBGs and microcracks. This study uses optical frequency domain reflectometry (OFDR) to demultiplex the array of FBGs, and then sub- divide individual FBGs. When a FBG is sub-divided using OFDR, the gratings' strain along its length is recovered. The sub-divided chirped FBGs have strain gradients along their length from microcracks. Applying this to all chirped gratings, nearly the entirety of the embedded sensors' readings can be recovered into a series of single peak responses, which show very large local strains throughout the structure. This study reports on this success in recovering embedded FBGs signal, and the strain gradient from microcracks.

  20. Single- and Two-Phase Flow Characterization Using Optical Fiber Bragg Gratings

    PubMed Central

    Baroncini, Virgínia H.V.; Martelli, Cicero; da Silva, Marco José; Morales, Rigoberto E.M.

    2015-01-01

    Single- and two-phase flow characterization using optical fiber Bragg gratings (FBGs) is presented. The sensor unit consists of the optical fiber Bragg grating positioned transversely to the flow and fixed in the pipe walls. The hydrodynamic pressure applied by the liquid or air/liquid flow to the optical fiber induces deformation that can be detected by the FBG. Given that the applied pressure is directly related to the mass flow, it is possible to establish a relationship using the grating resonance wavelength shift to determine the mass flow when the flow velocity is well known. For two phase flows of air and liquid, there is a significant change in the force applied to the fiber that accounts for the very distinct densities of these substances. As a consequence, the optical fiber deformation and the correspondent grating wavelength shift as a function of the flow will be very different for an air bubble or a liquid slug, allowing their detection as they flow through the pipe. A quasi-distributed sensing tool with 18 sensors evenly spread along the pipe is developed and characterized, making possible the characterization of the flow, as well as the tracking of the bubbles over a large section of the test bed. Results show good agreement with standard measurement methods and open up plenty of opportunities to both laboratory measurement tools and field applications. PMID:25789494

  1. Embedding silica and polymer fibre Bragg gratings (FBG) in plastic 3D-printed sensing patches

    NASA Astrophysics Data System (ADS)

    Zubel, Michal G.; Sugden, Kate; Webb, David J.; Sáez-Rodríguez, David; Nielsen, Kristian; Bang, Ole

    2016-04-01

    This paper reports the first demonstration of a silica fibre Bragg grating (SOFBG) embedded in an FDM 3-D printed housing to yield a dual grating temperature-compensated strain sensor. We also report the first ever integration of polymer fibre Bragg grating (POFBG) within a 3-D printed sensing patch for strain or temperature sensing. The cyclic strain performance and temperature characteristics of both devices are examined and discussed. The strain sensitivities of the sensing patches were 0.40 and 0.95 pm/μɛ for SOFBG embedded in ABS, 0.38 pm/μɛ for POFBG in PLA, and 0.15 pm/μɛ for POFBG in ABS. The strain response was linear above a threshold and repeatable. The temperature sensitivity of the SOFBG sensing patch was found to be up to 169 pm/°C, which was up to 17 times higher than for an unembedded silica grating. Unstable temperature response POFBG embedded in PLA was reported, with temperature sensitivity values varying between 30 and 40 pm/°C.

  2. In-Situ Continuous Detonation Velocity Measurements Using Fiber-optic Bragg Grating Sensors

    SciTech Connect

    Benterou, J; Udd, E; Wilkins, P; Roeske, F; Roos, E; Jackson, D

    2007-07-25

    In order to fully calibrate hydrocodes and dynamic chemistry burn models, initiation and detonation research requires continuous measurement of low order detonation velocities as the detonation runs up to full order detonation for a given density and initiation pressure pulse. A novel detector of detonation velocity is presented using a 125 micron diameter optical fiber with an integral chirped fiber Bragg grating as an intrinsic sensor. This fiber is embedded in the explosive under study and interrogated during detonation as the fiber Bragg grating scatters light back along the fiber to a photodiode, producing a return signal dependant on the convolution integral of the grating reflection bandpass, the ASE intensity profile and the photodetector response curve. Detonation velocity is measured as the decrease in reflected light exiting the fiber as the grating is consumed when the detonation reaction zone proceeds along the fiber sensor axis. This small fiber probe causes minimal perturbation to the detonation wave and can measure detonation velocities along path lengths tens of millimeters long. Experimental details of the associated equipment and preliminary data in the form of continuous detonation velocity records within nitromethane and PBX-9502 are presented.

  3. Reconfigurable optical-force-drive chirp and delay line in micro- or nanofiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Luo, Wei; Xu, Fei; Lu, Yan-qing

    2015-05-01

    The emergence of optical micro- or nanofibers (MNFs) with subwavelength diameter, which have ultralight mass and an intense light field, provides an opportunity for developing fiber-based optomechanical systems. In this study we show theoretically an optomechanical effect in silica MNF Bragg gratings (MNFBGs). The light-induced mechanical effect results in continuously distributed strain along the grating and the power-related strain introduces an optically reconfigurable chirp in the grating period. We develop optomechanical coupled-mode equations and analyze theoretically the influence of the optical-force-induced nonlinearity and chirp on the grating performance. Compared with the weak Kerr effect, the optomechanical effect dominates in the properties' evolution of MNFBGs. Significant group-velocity reduction and switching effect have been demonstrated theoretically at medium power level. This kind of optomechanical MNFBG with optically reconfigurable chirp may offer a path toward an all-optical tunable bandwidth of Bragg resonance and may lead to useful applications such as all-optical switching, optically controlled dispersion, and slow or fast light.

  4. Tapered and linearly chirped fiber Bragg gratings with co-directional and counter-directional resultant chirps

    NASA Astrophysics Data System (ADS)

    Osuch, Tomasz

    2016-05-01

    A method of spectral width tailoring of tapered fiber Bragg gratings is theoretically analyzed and experimentally verified. This concept is based on inscription grating structures in which synthesis of chirps comes from both taper profile and a linearly chirped phase mask used for grating inscription. It is shown that under UV exposure and depending on the orientation of the optical fiber taper relative to the variable-pitch phase mask, tapered and linearly chirped fiber Bragg gratings (TCFBG) with resultant co-directional or counter-directional chirps are achieved. Thus, both effects, those of reduction and enhancement of the grating chirp, as well as their influence on the grating spectral response, are presented. In particular, using the above approach TCFBG with significantly narrowed spectral width are shown. Moreover, fused tapered chirped FBG with relatively large waist diameter are shown having broad spectrum, something that prior to now was not attainable using previously developed techniques.

  5. Influence of photo-inscription conditions on the radiation-response of fiber Bragg gratings.

    PubMed

    Morana, Adriana; Girard, Sylvain; Marin, Emmanuel; Lancry, Matthieu; Marcandella, Claude; Paillet, Philippe; Lablonde, Laurent; Robin, Thierry; Williams, Robert J; Withford, Michael J; Boukenter, Aziz; Ouerdane, Youcef

    2015-04-01

    We compared the sensitivity to X-rays of several fiber Bragg gratings (FBGs) written in the standard telecommunication fiber Corning SMF28 with different techniques. Standard gratings were manufactured with phase-mask and UV lasers, continuum wave (cw) at 244 nm or pulsed in the nanosecond domain at 248 nm, in a pre-hydrogenated fiber. Others gratings were written by exposures to a femtosecond IR-laser (800 nm), with both phase-mask and point by point techniques. The response of these FBGs was studied under X-rays at room temperature and 100°C, by highlighting their similarities and differences. Independently of the inscription technique, the two types of fs-FBGs have showed no big difference up to 1 MGy(SiO(2)) dose. A discussion on the causes of the radiation-induced peak change is also reported. PMID:25968704

  6. Stimulated Brillouin scattering in ultra-long distributed feedback Bragg gratings in standard optical fiber.

    PubMed

    Loranger, Sébastien; Lambin-Iezzi, Victor; Wahbeh, Mamoun; Kashyap, Raman

    2016-04-15

    Distributed feedback (DFB) fiber Bragg gratings (FBG) are widely used as narrow-band filters and single-mode cavities for lasers. Recently, a nonlinear generation has been shown in 10-20 cm DFB gratings in a highly nonlinear fiber. First, we show in this Letter a novel fabrication technique of ultra-long DFBs in a standard fiber (SMF-28). Second, we demonstrate nonlinear generation in such gratings. A particular inscription technique was used to fabricate all-in-phase ultra-long FBG and to implement reproducible phase shift to form a DFB mode. We demonstrate stimulated Brillouin scattering (SBS) emission from this DFB mode and characterize the resulting laser. It seems that such a SBS based DFB laser stabilizes a pump's jittering and reduces its linewidth. PMID:27082348

  7. Fiber optic hydrogen sensor based on an etched Bragg grating coated with palladium.

    PubMed

    Coelho, L; de Almeida, J M M M; Santos, J L; Viegas, D

    2015-12-10

    A study of a sensor for hydrogen (H2) detection based on fiber Bragg gratings coated with palladium (Pd) with self-temperature compensation is presented. The cladding around the gratings was reduced down to 50 μm diameter by a chemical etching process. One of the gratings was left uncoated, and the other was coated with 150 nm of Pd. It was observed that palladium hydride has unstable behavior in environments with high humidity level. A simple solution to overcome this problem based on a Teflon tape is presented. The sensing device studied was able to respond to H2 concentrations in the range 0%-1% v/v at room temperature and atmospheric pressure, achieving sensitivities larger than 20 pm/% v/v. Considering H2 concentrations in nitrogen up to 1%, the performance of the sensing head was characterized for different thicknesses of Pd coating ranging from 50 to 200 nm.

  8. Fiber optic hydrogen sensor based on an etched Bragg grating coated with palladium.

    PubMed

    Coelho, L; de Almeida, J M M M; Santos, J L; Viegas, D

    2015-12-10

    A study of a sensor for hydrogen (H2) detection based on fiber Bragg gratings coated with palladium (Pd) with self-temperature compensation is presented. The cladding around the gratings was reduced down to 50 μm diameter by a chemical etching process. One of the gratings was left uncoated, and the other was coated with 150 nm of Pd. It was observed that palladium hydride has unstable behavior in environments with high humidity level. A simple solution to overcome this problem based on a Teflon tape is presented. The sensing device studied was able to respond to H2 concentrations in the range 0%-1% v/v at room temperature and atmospheric pressure, achieving sensitivities larger than 20 pm/% v/v. Considering H2 concentrations in nitrogen up to 1%, the performance of the sensing head was characterized for different thicknesses of Pd coating ranging from 50 to 200 nm. PMID:26836856

  9. Research and theoretical analysis of new fiber Bragg grating sensor demodulation system

    NASA Astrophysics Data System (ADS)

    Li, Yaocheng; Wang, Hai-tong; Wang, Ping

    2015-02-01

    In order to measure high-precision and large scale sensing signal and solve two-values question in signal detecting of strain sensor, we design a new kind of FBG matching demodulation system based on fiber Bragg grating matching demodulation principle. Through paralleling connection two groups of grating-matching whose center wavelength equal to sensing grating's, and then analyzing reflectance spectrum, we could get the relationship of strain and optical power detected by photoelectric detector. Then we can set up the theoretical model and complete system simulation. The simulation results show that the scheme is feasible. The scheme not only can solve the problem of double values and can simultaneously detect the positive and negative strain. The sensor measurement range can be up to952ue.

  10. Detection, Evaluation, and Optimization of Optical Signals Generated by Fiber Optic Bragg Gratings Under Dynamic Excitations

    NASA Technical Reports Server (NTRS)

    Adamovsky, Grigory; Lekki, John; Lock, James A.

    2002-01-01

    The dynamic response of a fiber optic Bragg grating to mechanical vibrations is examined both theoretically and experimentally. The theoretical expressions describing the consequences of changes in the grating's reflection spectrum are derived for partially coherent beams in an interferometer. The analysis is given in terms of the dominant wavelength, optical bandwidth, and optical path difference of the interfering signals. Changes in the reflection spectrum caused by a periodic stretching and compression of the grating were experimentally measured using an unbalanced Michelson interferometer, a Michelson interferometer with a non-zero optical path difference. The interferometer's sensitivity to changes in dominant wavelength of the interfering beams was measured as a function of interferometer unbalance and was compared to theoretical predictions. The theoretical analysis enables the user to determine the optimum performance for an unbalanced interferometer.

  11. Pipeline corrosion assessment using embedded Fiber Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Liang, Xiao; Huang, Ying; Galedari, Sahar Abuali; Azarmi, Fardad

    2015-04-01

    Corrosion is a leading cause of failure in metallic transmission pipelines. It significantly impacts the reliability and safety of metallic pipelines. An accurate assessment of corrosion status of the pipelines would contribute to timely pipeline maintenance and repair and extend the service life of the associated pipelines. To assess pipeline corrosion, various technologies have been investigated and the pipe-to-soil voltage potential measurement was commonly applied. However, remote and real-time corrosion assessment approaches are in urgent needs but yet achieved. Fiber optic sensors, especially, fiber Bragg gating (FBG) sensors, with unique advantages of real-time sensing, compactness, immune to EMI and moisture, capability of quasi-distributed sensing, and long life cycle, will be a perfect candidate for longterm pipeline corrosion assessment. In this study, FBG sensors are embedded inside pipeline external coating for corrosion monitoring of on-shore buried metallic transmission pipelines. Detail sensing principle, sensor calibration and embedment are introduced in this paper together with experimental corrosion evaluation testing ongoing. Upon validation, the developed sensing system could serve the purpose of corrosion monitoring to the numerous metallic pipelines across nation and would possibly reduce the pipeline corrosion induced tragedies.

  12. Characteristic analysis of two-mode fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Yan, Li; Hu, Guijun; Xiao, Jian; Chang, Yuxin; Bai, Song; Wang, Haiyan

    2014-12-01

    In this paper, the two-mode FBG is intensively studied in simulation and experiment. From the perspective of mode coupling, the coupling wavelength of the two-mode FBG is analyzed theoretically and the Bragg wavelength is calculated in simulation. Meanwhile, the variation of the two-mode FBG's reflection spectrum is simulated in different power ratios of the LP11 and LP01 modes. Then, a two-mode FBG is written on SMF-28e fiber by using the phase-mask technique and the two-mode FBG's reflection spectrum has been experimentally measured by adjusting the core-offset distance between the broadband light source's pigtail and the two-mode fiber which changes the power ratio of LP11 and LP01 modes. Eventually and most importantly, the mode characteristic of the two-mode FBG is studied, and the LP11 mode is successfully obtained by using an experimental system of a two-mode FBG combined with an optical circulator. The results show that the two-mode FBG has a good prospect for obtaining high-order mode and for application in mode division multiplexing/demultiplexing.

  13. Femtosecond inscription of phase-shifted gratings by overlaid fiber Bragg gratings.

    PubMed

    Shamir, Avishay; Ishaaya, Amiel A

    2016-05-01

    Two slightly shifted gratings are inscribed, one over the other, in an SMF fiber with a femtosecond laser and a phase mask. The transmission spectrum of the complex structure is similar to that of a phase-shifted grating; yet, the fabrication process is fast and simple compared to standard methods. High-quality semi-phase-shifted gratings with -24  dB transmission loss and <100  pm transmission bandwidth are presented. Their application as highly narrow micro-resonators and notch filters seems feasible. PMID:27128063

  14. Propagation of quasisolitons in a fiber Bragg grating written in a slow saturable fiber amplifier

    SciTech Connect

    Shapira, Yuval P.; Horowitz, Moshe

    2011-05-15

    We show, by using numerical simulations, that quasisolitons can propagate over a long distance in a fiber Bragg grating that is written in a slow saturable fiber amplifier, such as an erbium-doped fiber amplifier. During the pulse propagation, the front end of the pulse experiences a net gain while the rear end of pulse is attenuated due to the combination of gain saturation and loss. However, the pulse profile almost does not change after propagating over a length of 5 m that is approximately 2500 times larger than the spatial pulse width. The pulse amplitude has an approximately hyperbolic secant profile. We develop a reduced model by using a multiscale analysis to study solitary-wave propagation when nonlinearity and gain are small. When gain saturation also becomes small we find analytically a new family of solitary-wave hyperbolic-secant solutions that approximately solve the reduced model. The solitary waves propagate slightly faster than Bragg solitons that propagate in fiber Bragg gratings without gain and loss.

  15. Investigation of Carbon-Polymer Structures with Embedded Fiber-Optic Bragg Gratings

    NASA Technical Reports Server (NTRS)

    Grant, Joseph; Kaul, R.; Taylor, S.; Myers, G.; Sharma, A.

    2003-01-01

    Several Bragg-grating sensors fabricated within the same optical fiber are buried within multiple-ply carbon-epoxy planar and cylindrical structures. Effect of different orientation of fiber-sensors with respect to carbon fibers in the composite structure is investigated. This is done for both fabric and uni-tape material samples. Response of planar structures to axial and transverse strain up to 1 millistrain is investigated with distributed Bragg-grating sensors. Material properties like Young's Modulus and Poisson ratio is measured. A comparison is made between response measured by sensors in different ply-layers and those bonded on the surface. The results from buried fiber- sensors do not completely agree with surface bonded conventional strain gauges. A plausible explanation is given for observed differences. The planar structures are subjected to impacts with energies up to 10 ft-lb. Effect of this impact on the material stiffness is also investigated with buried fiber-optic Bragg sensors. The strain response of such optical sensors is also measured for cylindrical carbon-epoxy composite structures. The sensors are buried within the walls of the cylinder as well as surface bonded in both the axial as well as hoop directions. The response of these fiber-optic sensors is investigated by pressurizing the cylinder up to its burst pressure of around 1500 psi. This is done at both room temperature as well as cryogenic temperatures. The recorded response is compared with that from a conventional strain gauge.

  16. Low-cost interrogator for fiber-optic interferometers and fiber Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Gong, Jianmin; Li, Zhengying; Wang, Anbo

    2010-11-01

    We report a low-cost interrogator for fiber-optic interferometric and Bragg grating sensors. The interrogator is based on a compact optical path scanner which is made by splicing a hollow fiber to a single mode fiber and by sealing a segment of air and a segment of thermally expanded liquid inside the hollow fiber. The facets between the fiber-air interface and the air-liquid interface reflect the light from the single mode fiber back, and the optical path difference between the two facets can be controlled by changing the temperature of the liquid. When the compact optical path scanner is place inside a white light interferometer together with a sensing fiber-optic Fabry-Perot interferometer, the optical path difference of the sensing interferometer can be decoded as the optical path difference of the scanner when the interference signal gets maximum. The decoding accuracy of such an interferometer interrogation system was measured to be 14 nm over a range of 40 μm. The compact optical path scanner can also be used to form a wavelength meter, which can be applied to decode the Bragg wavelength of a fiber Bragg grating sensor. A decoding accuracy of 3.5 pm was obtained.

  17. Bragg-grating air-slot optical waveguide for label-free sensing

    NASA Astrophysics Data System (ADS)

    Jugessur, A. S.; Yagnyukova, M.; Dou, J.; Aitchison, J. S.

    2012-03-01

    The development of miniature and label-free optical sensors is very critical for applications in a wide range of areas such as medicine, environment, forensic and food quality control. In this report, a Bragg-grating air-slot waveguide is designed (using Finite Domain Time Difference modeling (FDTD)) and fabricated (using Electron beam lithography and Reactive ion etching) on a silicon-on-insulator substrate to develop a label-free optical sensor. The Bragg gratings constitute of recesses in the 140 nm wide air-slot waveguide. The grating structures generate a band-gap for certain frequencies and the spectral shift of the lower band-edge is used as the mechanism to sense fluids or bio-molecules in the air-slot. Based on the 3-D FDTD and experimental results, the sensitivity of the device is 620 nm/RIU, which is higher than other recently reported sensors. Due to the high electric field intensity in the air slot, this area becomes very sensitive to index variations caused by bio-molecules or fluids in the air-slot.

  18. Research on pressure tactile sensing technology based on fiber Bragg grating array

    NASA Astrophysics Data System (ADS)

    Song, Jinxue; Jiang, Qi; Huang, Yuanyang; Li, Yibin; Jia, Yuxi; Rong, Xuewen; Song, Rui; Liu, Hongbin

    2015-09-01

    A pressure tactile sensor based on the fiber Bragg grating (FBG) array is introduced in this paper, and the numerical simulation of its elastic body was implemented by finite element software (ANSYS). On the basis of simulation, fiber Bragg grating strings were implanted in flexible silicone to realize the sensor fabrication process, and a testing system was built. A series of calibration tests were done via the high precision universal press machine. The tactile sensor array perceived external pressure, which is demodulated by the fiber grating demodulation instrument, and three-dimension pictures were programmed to display visually the position and size. At the same time, a dynamic contact experiment of the sensor was conducted for simulating robot encountering other objects in the unknown environment. The experimental results show that the sensor has good linearity, repeatability, and has the good effect of dynamic response, and its pressure sensitivity was 0.03 nm/N. In addition, the sensor also has advantages of anti-electromagnetic interference, good flexibility, simple structure, low cost and so on, which is expected to be used in the wearable artificial skin in the future.

  19. Femtosecond laser writing of Bragg grating waveguide bundles in bulk glass.

    PubMed

    Thiel, Markus; Flachenecker, Günter; Schade, Wolfgang

    2015-04-01

    Waveguide bundles in bulk glass materials, consisting of several parallel scans of refractive index modifications, have been generated with a low-repetition femtosecond laser. Additionally, Bragg grating (BG) structures for 840 and 1550 nm have been introduced by segmentation of the central scan. A spectral loss in the transmission signal of >36  dB was achieved at 1550 nm with a second-order Bragg grating waveguide (BGW) in fused silica, which corresponds to an intrinsic grating efficiency of >16  dB/cm. This is to our knowledge the strongest BG structure realized in glass with a femtosecond laser. The BGW were proven to be stable up to a temperature of 250°C in fused silica. The diameter of the waveguide bundles can be adapted very easily for a broad range of wavelengths and have been demonstrated for diameters between 1 and 50 μm. The transmission properties of the waveguide bundles are affected minorly by the insertion of BG structures, which opens the ability for adjusting the BGW for a broad range of wavelength in single-mode or multimode optical circuits. BGW have been realized successfully in fused silica, borosilicate glass (BOROFLOAT 33), and AF 32 eco Thin Glass from Schott.

  20. Fiber Bragg grating sensing of detonation and shock experiments at Los Alamos National Laboratory

    NASA Astrophysics Data System (ADS)

    Rodriguez, G.; Sandberg, R. L.; Jackson, S. I.; Dattelbaum, D. M.; Vincent, S. W.; McCulloch, Q.; Martinez, R. M.; Gilbertson, S. M.; Udd, E.

    2013-05-01

    An all optical-fiber-based approach to measuring high explosive detonation front position and velocity is described. By measuring total light return using an incoherent light source reflected from a fiber Bragg grating sensor in contact with the explosive, dynamic mapping of the detonation front position and velocity versus time is obtained. We demonstrate two calibration procedures and provide several examples of detonation front measurements: PBX 9502 cylindrical rate stick, radial detonation front in PBX 9501, and PBX 9501 detonation along a curved meridian line. In the cylindrical rate stick measurement, excellent agreement with complementary diagnostics (electrical pins and streak camera imaging) is achieved, demonstrating accuracy in the detonation front velocity to below the 0.3% level when compared to the results from the pin data. In a similar approach, we use embedded fiber grating sensors for dynamic pressure measurements to test the feasibility of these sensors for high pressure shock wave research in gas gun driven flyer plate impact experiments. By applying well-controlled steady shock wave pressure profiles to soft materials such as PMMA, we study the dynamic pressure response of embedded fiber Bragg gratings to extract pressure amplitude of the shock wave. Comparison of the fiber sensor results is then made with traditional methods (velocimetry and electro-magnetic particle velocity gauges) to gauge the accuracy of the approach.

  1. pH induced switching in hydrogel coated fiber Bragg grating sensor

    NASA Astrophysics Data System (ADS)

    Shivananju, B. N.; Priydarshi, Manish K.; Roy Mahapatra, D.; Hegde, G. M.; Asokan, S.

    In this paper we report a novel hydrogel functionalized optical Fiber Bragg Grating (FBG) sensor based on chemo-mechanical- optical sensing, and demonstrate its specific application in pH activated process monitoring. The sensing mechanism is based on the stress due to ion diffusion and polymer phase transition which produce strain in the FBG. This results in shift in the Bragg wavelength which is detected by an interrogator system. A simple dip coating method to coat a thin layer of hydrogel on the FBG has been established. The gel consists of sodium alginate and calcium chloride. Gel formation is observed in real-time by continuously monitoring the Bragg wavelength shift. We have demonstrated pH sensing in the range of pH of 2 to 10. Another interesting phenomenon is observed by swelling and deswelling of FBG functionalized with hydrogel by a sequence of alternate dipping between acidic and base solutions. It is observed that the Bragg wavelength undergoes reversible and repeatable pH dependent switching.

  2. Fiber Bragg grating sensor for fault detection in high voltage overhead transmission lines

    NASA Astrophysics Data System (ADS)

    Moghadas, Amin

    2011-12-01

    A fiber optic based sensor capable of fault detection in both radial and network overhead transmission power line systems is investigated. Bragg wavelength shift is used to measure the fault current and detect fault in power systems. Magnetic fields generated by currents in the overhead transmission lines cause a strain in magnetostrictive material which is then detected by fiber Bragg grating (FBG) sensors. The Fiber Bragg interrogator senses the reflected FBG signals, and the Bragg wavelength shift is calculated and the signals are processed. A broadband light source in the control room scans the shift in the reflected signals. Any surge in the magnetic field relates to an increased fault current at a certain location. Also, fault location can be precisely defined with an artificial neural network (ANN) algorithm. This algorithm can be easily coordinated with other protective devices. It is shown that the faults in the overhead transmission line cause a detectable wavelength shift on the reflected signal of FBG sensors and can be used to detect and classify different kind of faults. The proposed method has been extensively tested by simulation and results confirm that the proposed scheme is able to detect different kinds of fault in both radial and network system.

  3. Fiber Bragg Grating Sensor for Fault Detection in Radial and Network Transmission Lines

    PubMed Central

    Moghadas, Amin A.; Shadaram, Mehdi

    2010-01-01

    In this paper, a fiber optic based sensor capable of fault detection in both radial and network overhead transmission power line systems is investigated. Bragg wavelength shift is used to measure the fault current and detect fault in power systems. Magnetic fields generated by currents in the overhead transmission lines cause a strain in magnetostrictive material which is then detected by Fiber Bragg Grating (FBG). The Fiber Bragg interrogator senses the reflected FBG signals, and the Bragg wavelength shift is calculated and the signals are processed. A broadband light source in the control room scans the shift in the reflected signal. Any surge in the magnetic field relates to an increased fault current at a certain location. Also, fault location can be precisely defined with an artificial neural network (ANN) algorithm. This algorithm can be easily coordinated with other protective devices. It is shown that the faults in the overhead transmission line cause a detectable wavelength shift on the reflected signal of FBG and can be used to detect and classify different kind of faults. The proposed method has been extensively tested by simulation and results confirm that the proposed scheme is able to detect different kinds of fault in both radial and network system. PMID:22163416

  4. Refractometer probe based on a reflective carbon nanotube-modified microfiber Bragg grating.

    PubMed

    Jiang, Biqiang; Xue, Meng; Zhao, Chenyang; Mao, Dong; Zhou, Kaiming; Zhang, Lin; Zhao, Jianlin

    2016-09-01

    A carbon nanotube (CNT)-modified microfiber Bragg grating (MFBG) is proposed to measure the refractive index with a strong enhancement of the sensitivity in the low refractive index region. The introduction of the CNT layer influences the evanescent field of the MFBG and causes modification of the reflection spectrum. With the increase of the surrounding refractive index (SRI), we observe significant attenuation to the peak of the Bragg resonance, while its wavelength remains almost unchanged. Our detailed experimental results disclose that the CNT-MFBG demonstrates strong sensitivity in the low refractive index range of 1.333-1.435, with peak intensity up to -53.4  dBm/refractive index unit, which is 15-folds higher than that of the uncoated MFBG. Therefore, taking advantage of the CNT-induced evanescent field enhancement, the reflective MFBG probe presents strong sensing capability in biochemical fields. PMID:27607280

  5. Fiber optic relative humidity sensor based on the tilted fiber Bragg grating coated with graphene oxide

    NASA Astrophysics Data System (ADS)

    Wang, Youqing; Shen, Changyu; Lou, Weimin; Shentu, Fengying; Zhong, Chuan; Dong, Xinyong; Tong, Limin

    2016-07-01

    A fiber optic relative humidity (RH) sensor based on the tilted fiber Bragg grating (TFBG) coated with graphene oxide (GO) film was presented. Amplitudes of the cladding mode resonances of the TFGB varies with the water sorption and desorption processes of the GO film, because of the strong interactions between the excited backward propagating cladding modes and the GO film. By detecting the transmission intensity changes of the cladding mode resonant dips at the wavelength of 1557 nm, the maximum sensitivity of 0.129 dB/%RH with a linear correlation coefficient of 99% under the RH range of 10-80% was obtained. The Bragg mode of TFBG can be used as power or wavelength references, since it is inherently insensitive to RH changes. In addition, the proposed humidity sensor shows a good performance in repeatability and stability.

  6. Toward the implementation of flexible sensing sheet with fibre Bragg grating sensing elements

    NASA Astrophysics Data System (ADS)

    Yan, Chunxiao; Ferraris, Eleonora; Reynaerts, Dominiek

    2012-04-01

    Optical sensing sheets, based on Fibre Bragg Grating (FBG) sensing elements embedded in exible polydimethyl- siloxane (PDMS), are produced and tested. The device shows promise in pressure mapping and tactile applications, in fields such as robotics and rehabilitation. FBGs inscribed in highly-birefringent photonic crystal fibres, reflecting two Bragg peaks, are used, and the potential to discriminate pressure and temperature is explored. The prototypes were produced by moulding technology and PDMS was cured at room temperature. One sample with FBGs embedded in the middle layer of a 2 mm thick PDMS sheet exhibited a linear pressure sensitivity of about 2:6 pm/kPa over the range of 0 - 250 kPa. Another sample was proposed and tested for temperature insensitive measurements, by realising local stress concentration at FBG sections of the embedded fibre.

  7. Experimental researches of fiber Bragg gratings operating in a few-mode regime

    NASA Astrophysics Data System (ADS)

    Kafarova, Anastasia M.; Faskhutdinov, Lenar M.; Kuznetzov, Artem A.; Minaeva, Alina Y.; Sevruk, Nikita L.; Nureev, Ilnur I.; Vasilets, Alexander A.; Bourdine, Anton V.; Morozov, Oleg G.; Burdin, Vladimir A.

    2016-03-01

    This work presents results of experimental researches of fiber Bragg gratings (FBG) operating in a few-mode regime. We tested FBGs written on silica graded-index multimode fibers 50/125 Cat. OM2+/OM3 with Bragg wavelength 1550 nm by using them in a set of developed experimental schemes based on excitation of multimode fibers by corresponding laser sources. The researches were focused on analysis of both spectral and pulse responses under changing of selected mode mixing and power diffusion processes due to tension and/or stress local and distributed action to FBG or sensor fiber. Results of spectral and pulse response measurements at the output of schemes with installed described FBGs are represented.

  8. Ultrasonic imaging of seismic physical models using a phase-shifted fiber Bragg grating.

    PubMed

    Guo, Jingjing; Xue, Shigui; Zhao, Qun; Yang, Changxi

    2014-08-11

    We report what is to our knowledge the first ultrasonic imaging of seismic physical models by using a phase-shifted fiber Bragg grating (PS-FBG). Seismic models, which consist of multiple layer structures, were immersed in water. Piezoelectric (PZT) transducer was used to generate ultrasonic waves and a PS-FBG as a receiver. Two-dimensional (2D) ultrasonic images were reconstructed by scanning the PS-FBG with a high-precision position scanning device. In order to suppress the low-frequency drift of the Bragg wavelength during scanning, a tight wavelength tracking method was employed to lock the laser to the PS-FBG resonance in its reflection bandgap. The ultrasonic images captured by the PS-FBG have been compared with the images obtained by the geophysical imaging system, Sinopec, demonstrating the feasibility of our PS-FBG based imaging system in seismic modeling studies. PMID:25321040

  9. Ultrasonic imaging of seismic physical models using a phase-shifted fiber Bragg grating.

    PubMed

    Guo, Jingjing; Xue, Shigui; Zhao, Qun; Yang, Changxi

    2014-08-11

    We report what is to our knowledge the first ultrasonic imaging of seismic physical models by using a phase-shifted fiber Bragg grating (PS-FBG). Seismic models, which consist of multiple layer structures, were immersed in water. Piezoelectric (PZT) transducer was used to generate ultrasonic waves and a PS-FBG as a receiver. Two-dimensional (2D) ultrasonic images were reconstructed by scanning the PS-FBG with a high-precision position scanning device. In order to suppress the low-frequency drift of the Bragg wavelength during scanning, a tight wavelength tracking method was employed to lock the laser to the PS-FBG resonance in its reflection bandgap. The ultrasonic images captured by the PS-FBG have been compared with the images obtained by the geophysical imaging system, Sinopec, demonstrating the feasibility of our PS-FBG based imaging system in seismic modeling studies.

  10. 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.

  11. Dental composite resins: measuring the polymerization shrinkage using optical fiber Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Ottevaere, H.; Tabak, M.; Chah, K.; Mégret, P.; Thienpont, H.

    2012-04-01

    Polymerization shrinkage of dental composite materials is recognized as one of the main reasons for the development of marginal leakage between a tooth and filling material. As an alternative to conventional measurement methods, we propose optical fiber Bragg grating (FBG) based sensors to perform real-time strain and shrinkage measurements during the curing process of dental resin cements. We introduce a fully automated set-up to measure the Bragg wavelength shift of the FBG strain sensors and to accurately monitor the linear strain and shrinkage of dental resins during curing. Three different dental resin materials were studied in this work: matrix-filled BisGMA-based resins, glass ionomers and organic modified ceramics.

  12. A Noncontact Force Sensor Based on a Fiber Bragg Grating and Its Application for Corrosion Measurement

    PubMed Central

    Pacheco, Clara J.; Bruno, Antonio C.

    2013-01-01

    A simple noncontact force sensor based on an optical fiber Bragg grating attached to a small magnet has been proposed and built. The sensor measures the force between the magnet and any ferromagnetic material placed within a few millimeters of the sensor. Maintaining the sensor at a constant standoff distance, material loss due to corrosion increases the distance between the magnet and the corroded surface, which decreases the magnetic force. This will decrease the strain in the optical fiber shifting the reflected Bragg wavelength. The measured shift for the optical fiber used was 1.36 nm per Newton. Models were developed to optimize the magnet geometry for a specific sensor standoff distance and for particular corrosion pit depths. The sensor was able to detect corrosion pits on a fuel storage tank bottom with depths in the sub-millimeter range. PMID:23995095

  13. A noncontact force sensor based on a fiber Bragg grating and its application for corrosion measurement.

    PubMed

    Pacheco, Clara J; Bruno, Antonio C

    2013-01-01

    A simple noncontact force sensor based on an optical fiber Bragg grating attached to a small magnet has been proposed and built. The sensor measures the force between the magnet and any ferromagnetic material placed within a few millimeters of the sensor. Maintaining the sensor at a constant standoff distance, material loss due to corrosion increases the distance between the magnet and the corroded surface, which decreases the magnetic force. This will decrease the strain in the optical fiber shifting the reflected Bragg wavelength. The measured shift for the optical fiber used was 1.36 nm per Newton. Models were developed to optimize the magnet geometry for a specific sensor standoff distance and for particular corrosion pit depths. The sensor was able to detect corrosion pits on a fuel storage tank bottom with depths in the sub-millimeter range. PMID:23995095

  14. Characteristics of Plasmonic Bragg Reflectors with Graphene-Based Silicon Grating

    NASA Astrophysics Data System (ADS)

    Song, Ci; Xia, Xiushan; Hu, Zheng-Da; Liang, Youjian; Wang, Jicheng

    2016-09-01

    We propose a plasmonic Bragg reflector (PBR) composed of a single-layer graphene-based silicon grating and numerically study its performance. An external voltage gating has been applied to graphene to tune its optical conductivity. It is demonstrated that SPP modes on graphene exhibit a stopband around the Bragg wavelengths. By introducing a nano-cavity into the PBR, a defect resonance mode is formed inside the stopband. We further design multi-defect PBR to adjust the characteristics of transmission spectrum. In addition, through patterning the PBR unit into multi-step structure, we lower the insertion loss and suppress the rippling in transmission spectra. The finite element method (FEM) has been utilized to perform the simulation work.

  15. Characteristics of Plasmonic Bragg Reflectors with Graphene-Based Silicon Grating.

    PubMed

    Song, Ci; Xia, Xiushan; Hu, Zheng-Da; Liang, Youjian; Wang, Jicheng

    2016-12-01

    We propose a plasmonic Bragg reflector (PBR) composed of a single-layer graphene-based silicon grating and numerically study its performance. An external voltage gating has been applied to graphene to tune its optical conductivity. It is demonstrated that SPP modes on graphene exhibit a stopband around the Bragg wavelengths. By introducing a nano-cavity into the PBR, a defect resonance mode is formed inside the stopband. We further design multi-defect PBR to adjust the characteristics of transmission spectrum. In addition, through patterning the PBR unit into multi-step structure, we lower the insertion loss and suppress the rippling in transmission spectra. The finite element method (FEM) has been utilized to perform the simulation work. PMID:27654279

  16. Novel polyimide coated fiber Bragg grating sensing network for relative humidity measurements.

    PubMed

    Bai, Wei; Yang, Minghong; Dai, Jixiang; Yu, Haihu; Wang, Gaopeng; Qi, Chongjie

    2016-02-22

    A novel relative humidity (RH) sensing network based on ultra-weak fiber Bragg gratings (FBGs) is proposed and demonstrated. Experiment is demonstrated on a 5 serial ultra-weak FBGs sensing network chopped from a fiber array with 1124 FBGs. Experimental results show that the corresponding RH sensitivity varies from 1.134 to 1.832 pm/%RH when ambient environmental RH changes from 23.8%RH to 83.4%RH. The low-reflectance FBGs and time-division multiplexing (TDM) technology makes it possible to multiplex thousands of RH sensors in single optical fiber. PMID:26906986

  17. Waveform reconstruction for an ultrasonic fiber Bragg grating sensor demodulated by an erbium fiber laser.

    PubMed

    Wu, Qi; Okabe, Yoji

    2015-02-01

    Fiber Bragg grating (FBG) demodulated by an erbium fiber laser (EFL) has been used for ultrasonic detection recently. However, due to the inherent relaxation oscillation (RO) of the EFL, the detected ultrasonic signals have large deformations, especially in the low-frequency range. We proposed a novel data processing method to reconstruct an actual ultrasonic waveform. The noise spectrum was smoothed first; the actual ultrasonic spectrum was then obtained by deconvolution in order to mitigate the influence of the RO of the EFL. We proved by experiment that this waveform reconstruction method has high precision, and demonstrated that the FBG sensor demodulated by the EFL will have large practical applications in nondestructive testing.

  18. Non-intrusive measurement of internal pressure and flow in pipelines using fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Salgado, Pedro; Filograno, Massimo L.; Senent, Fernando D.; Corredera, Pedro

    2013-10-01

    In this paper we propose and demonstrate a non-intrusive measurement method for internal pressure and water flow in hydraulic pipeline systems. Fiber Bragg Gratings are used to measure deformations in the external side of pipes under different working conditions for two different experiments. In the first experiment a PVC sewerage pipeline with a diameter of 90 mm was subjected to a variable air pressures up to 4 bars; in the second a PVC sewerage pipeline with a diameter of 32 mm was subjected to a water flow between 10 and 35 liters per minute.

  19. Thinned fibre Bragg grating as a fuel adulteration sensor: simulation and experimental study

    NASA Astrophysics Data System (ADS)

    Agarwal, S.; Prajapati, Y. K.; Mishra, V.

    2015-12-01

    This paper presents the implementation of a thinned fibre Bragg grating as a fuel adulteration sensor for volatile organic compounds. The proposed sensor can detect upto 10% adulteration of benzene, toluene and xylene: hydrocarbons precisely, whereas traditional methods can detect only upto 20% adulteration. The results obtained from the experiments are verified using Finite Difference Time Domain method. It is found that experimental results have very less deviation from simulation results. The proposed sensor provides us with the new possibility that may have commercial application, as well.

  20. Novel polyimide coated fiber Bragg grating sensing network for relative humidity measurements.

    PubMed

    Bai, Wei; Yang, Minghong; Dai, Jixiang; Yu, Haihu; Wang, Gaopeng; Qi, Chongjie

    2016-02-22

    A novel relative humidity (RH) sensing network based on ultra-weak fiber Bragg gratings (FBGs) is proposed and demonstrated. Experiment is demonstrated on a 5 serial ultra-weak FBGs sensing network chopped from a fiber array with 1124 FBGs. Experimental results show that the corresponding RH sensitivity varies from 1.134 to 1.832 pm/%RH when ambient environmental RH changes from 23.8%RH to 83.4%RH. The low-reflectance FBGs and time-division multiplexing (TDM) technology makes it possible to multiplex thousands of RH sensors in single optical fiber.

  1. Simulation of path delay multiplexing-based Fourier transform spectrometer for fiber Bragg grating interrogation.

    PubMed

    Chelliah, Pandian; Sahoo, Trilochan; Singh, Sheela; Sujatha, Annie

    2015-10-20

    A Fourier transform spectrometer (FTS) used for interrogating a fiber Bragg grating (FBG) consists of a scanning-type interferometer. The FTS has a broad wavelength range of operation and good multiplexing capability. However, it has poor wavelength resolution and interrogation speed. We propose a modification to the FTS using path delay multiplexing to improve the same. Using this method, spatial resolution and interrogation time can be improved by n times by using n path delays. In this paper, simulation results for n=2, 5 are shown.

  2. Birefringence properties of a polarization maintaining Panda fibre during Bragg grating regeneration

    NASA Astrophysics Data System (ADS)

    Polz, Leonhard; Jarsen, Andreas; Bartelt, Hartmut; Roths, Johannes

    2015-09-01

    Regeneration of fibre Bragg gratings under application of a high temperature annealing process in a high birefringent polarisation maintaining fibre of type Panda was investigated. During the annealing process, a distinct nonlinearity and hysteresis of the birefringence with temperature was observed. After the temperature process, the birefringence between slow and fast axis at room temperature was nearly doubled, which is in agreement with observations of other researchers. The hysteresis in birefringence might be explained by the crossing of the transition temperature of the stress applying parts and the relief of in-frozen mechanical and thermal stresses.

  3. Performance characterization of fiber Bragg grating thermal response in space vacuum thermal environment

    NASA Astrophysics Data System (ADS)

    Jiang, Junfeng; Song, Luyao; Liu, Tiegen; Zhang, Jingchuan; Liu, Kun; Wang, Shuang; Yin, Jinde; Zhao, Peng; Xie, Jihui; Wu, Fan; Zhang, Xuezhi

    2013-12-01

    We investigated the fiber Bragg grating (FBG) thermal response in space vacuum thermal environment. The FBGs were packaged with 6061-T6 aluminum. The liquid nitrogen immersion experiment results show that its wavelength shift standard deviation is 0.76 pm for 217 h. The combination effect of vacuum and cryogenic temperature was studied by thermal cycling process in space environment simulator. The FBG sensors show accuracy better than 2% full scale, and the hysteresis errors are below 1%. It proves that these metal packaged FBG sensors can survive and meet the requirement of space measurement.

  4. Smoothing of the spectrum of fibre Bragg gratings in the Lloyd-interferometer recording scheme

    SciTech Connect

    Abdullina, S R; Vlasov, Aleksandr A; Babin, Sergei A

    2010-05-26

    The possibility of apodization of fibre Bragg gratings (FBGs) recorded in the region of interference of the two parts of a Gaussian beam in a Lloyd interferometer is considered. The reflection spectra of FBGs are numerically simulated for different parameters of the recording beam and its displacement with respect to the dividing axis in the interferometer. Aconsiderable suppression of sidelobe resonances in the FBG spectrum during the displacement of the beam centre with respect to the dividing axis by half the beam radius is predicted and experimentally demonstrated. It is shown that this is caused by the equating of the mean value of the refractive index in the FBG region. (fibres)

  5. Design of a Pressure Sensor Based on Optical Fiber Bragg Grating Lateral Deformation

    PubMed Central

    Urban, Frantisek; Kadlec, Jaroslav; Vlach, Radek; Kuchta, Radek

    2010-01-01

    This paper describes steps involved in the design and realization of a new type of pressure sensor based on the optical fiber Bragg grating. A traditional pressure sensor has very limited usage in heavy industrial environments, particularly in explosive or electromagnetically noisy environments. Utilization of optics in these environments eliminates all surrounding influences. An initial motivation for our development was the research, experimental validation, and realization of a complex smart pressure sensor based on the optical principle. The main benefit of this solution consists of increasing sensitivity, resistance to electromagnetic interference, dimensions, and potential increased accuracy. PMID:22163521

  6. Intensity-modulated optical fiber sensors based on chirped-fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Dong, Xinyong

    2011-09-01

    Intensity-modulated fiber Bragg grating (FBG) sensors, compared with normal wavelength-encoding FBG sensors, can reduce the cost of sensor system significantly by using cost-efficient optical power detection devices, instead of expensive wavelength measurement instruments. Chirped-FBG (CFBG) based intensity-modulated sensors show potential applications in various sensing areas due to their many advantages, including inherent independence of temperature, high measurement speed, and low cost, in addition to the merits of all fiber-optic sensors. This paper theoretically studies the sensing principle of CFBG-based intensity-modulated sensors and briefly reviews their recent progress in measurement of displacement, acceleration, and tilt angle.

  7. Bidirectional Wavelength Reconfigurable Module Based on Tunable Fiber Bragg Grating and Remote Pump Amplifier

    NASA Astrophysics Data System (ADS)

    Yu, Yi-Lin; Liaw, Shien-Kuei; Skaljo, Edvin; Le Minh, Hoa; Ghassemlooy, Zabih

    2014-09-01

    This article presents a novel bidirectional wavelength reconfigurable optical network utilizing a remotely pumped erbium-doped fiber amplifier and tunable fiber Bragg gratings. The system is experimentally demonstrated at a 10-Gb/s per channel over 20-km fiber span that verifies the metro-network range system performance. The achieved power penalty is less than 1 dB when compared to the back-to-back transmission link. An example of practical application where the proposed module is used as an add/drop multiplexer and a remote node in the bidirectional wavelength division multiplexing passive optical network system is described.

  8. Monitoring of reinforced composites processed by microwave radiation using fiber-Bragg gratings

    NASA Astrophysics Data System (ADS)

    Barrera, David; Roig, Inma; Sales, Salvador; Emmerich, Rudolf

    2014-05-01

    The use of microwave radiation for curing carbon-fiber reinforced polymer materials (CFRP) can solve the nonhomogeneous heating problems when using conventional techniques based on the use of catalysts and can reduce the processing times. Optical fiber sensors have well-known advantages for Fiber Reinforced Composites (FRC) monitoring. In this paper fiber Bragg gratings (FBGs) are used for online monitoring of the residual stress and distortions produced during the microwave curing process. The CFRP samples are composed by layers of unidirectional carbon fibers and epoxy resin. The results show a very different behavior between the direction of carbon fibers and the perpendicular direction. Results are compared with the conventional processing technique.

  9. Multiple fiber Bragg grating sensor system using code-division multiple access.

    PubMed

    Lee, Hojoon

    2002-09-01

    We propose and demonstrate experimentally a multiple fiber Bragg grating sensor system that uses a LED as a light source and adapts the code-division multiple access method to separate individual sensor signals. We measured static and dynamic strains and cross-talk levels among sensor signals. With our proposed scheme, a low-cost sensor system can be designed with a fast response speed. Cross-talk levels between sensor signals are found to be below the -30-dB level.

  10. Stainless steel component with compressed fiber Bragg grating for high temperature sensing applications

    NASA Astrophysics Data System (ADS)

    Jinesh, Mathew; MacPherson, William N.; Hand, Duncan P.; Maier, Robert R. J.

    2016-05-01

    A smart metal component having the potential for high temperature strain sensing capability is reported. The stainless steel (SS316) structure is made by selective laser melting (SLM). A fiber Bragg grating (FBG) is embedded in to a 3D printed U-groove by high temperature brazing using a silver based alloy, achieving an axial FBG compression of 13 millistrain at room temperature. Initial results shows that the test component can be used for up to 700°C for sensing applications.

  11. Quasi-distributed fiber Bragg grating temperature sensors for stator bars monitoring of large electric generators

    NASA Astrophysics Data System (ADS)

    Dreyer, Uilian J.; da Silva, Erlon V.; Biffe Di Renzo, André; Martelli, Cicero; Cardozo da Silva, Jean Carlos

    2016-05-01

    This work presents the application of a sensor based on quasi-distributed Fiber Bragg Gratings to monitor stator bars temperature of large electric generators. The applied FBG packaging method follows industrial standard procedures, and resulted in a robust and reliable sensing method, facilitating the future installation in the power plant. Experimental results are acquired in laboratory using the expected range of temperature values in the real machine. The measurement errors in the recorded results are within the calculated uncertainties and the time constant is shorter than what is obtained with conventional RTD for the same application.

  12. Centre of mass determination based on an optical weighing machine using fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Oliveira, Rui; Roriz, Paulo; Marques, Manuel B.; Frazão, Orlando

    2015-09-01

    The purpose of the present work was to construct a weighing machine based on fiber Bragg gratings (FBGs) for the location of the 2D coordinates of the center of gravity (COG) of objects with complex geometry and density distribution. The apparatus consisted of a rigid equilateral triangular platform mounted on three supports at its vertices, two of them having cantilevers instrumented with FBGs. As an example, two femur bone models, one with and one without a hip stem prosthesis, are used to discuss the changing of the COM caused by the implementation of the prosthesis.

  13. Additive non-uniform random sampling in superimposed fiber Bragg grating strain gauge

    NASA Astrophysics Data System (ADS)

    Ma, Y. C.; Liu, H. Y.; Yan, S. B.; Yang, Y. H.; Yang, M. W.; Li, J. M.; Tang, J.

    2013-05-01

    This paper demonstrates an additive non-uniform random sampling and interrogation method for dynamic and/or static strain gauge using a reflection spectrum from two superimposed fiber Bragg gratings (FBGs). The superimposed FBGs are designed to generate non-equidistant space of a sensing pulse train in the time domain during dynamic strain gauge. By combining centroid finding with smooth filtering methods, both the interrogation speed and accuracy are improved. A 1.9 kHz dynamic strain is measured by generating an additive non-uniform randomly distributed 2 kHz optical sensing pulse train from a mean 500 Hz triangular periodically changing scanning frequency.

  14. On the use of optical fiber Bragg grating (FBG) sensor technology for strain modal analysis

    NASA Astrophysics Data System (ADS)

    Peeters, Bart; dos Santos, Fábio Luis Marques; Pereira, Andreia; Araujo, Francisco

    2014-05-01

    This paper discusses the use of optical fiber Bragg grating (FBG) strain sensors for structural dynamics measurements. For certain industrial applications, there is an interest to use strain sensors rather than or in combination with accelerometers for experimental modal analysis. Classical electrical strain gauges can be used hereto, but optical strain sensors are an interesting alternative with some very specific advantages. This paper gives an overview of dynamic strain measurements in industrial applications, discusses the benefits of FBG sensors and reviews their measurement principle. Finally, the concept of strain modal analysis is introduced and a helicopter main rotor blade vibration testing and analysis case study is presented.

  15. High resolution magnetostriction measurements in pulsed magnetic fields using fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Daou, Ramzy; Weickert, Franziska; Nicklas, Michael; Steglich, Frank; Haase, Ariane; Doerr, Mathias

    2010-03-01

    We report on a new high resolution apparatus for measuring magnetostriction suitable for use at cryogenic temperatures in pulsed high magnetic fields which we have developed at the Hochfeld-Magnetlabor Dresden. Optical fiber strain gauges based on fiber Bragg gratings are used to measure the strain in small (˜1 mm) samples. We describe the implementation of a fast measurement system capable of resolving strains in the order of 10-7 with a full bandwidth of 47 kHz, and demonstrate its use on single crystal samples of GdSb and GdSi.

  16. Rovibrational hybrid fs/ps CARS using a volume Bragg grating for N₂ thermometry.

    PubMed

    Scherman, M; Nafa, M; Schmid, T; Godard, A; Bresson, A; Attal-Tretout, B; Joubert, P

    2016-02-01

    Coherent anti-Stokes Raman scattering (CARS) spectra of N2 in the hybrid femtosecond/picosecond regime have been recorded with 0.7  cm(-1) resolution. The Q-branch rovibrational structure has been resolved, making it suitable for gas-phase simultaneous rotational and vibrational thermometry applications. Resolving this spectral structure requires synchronization of a narrowband picosecond probe pulse with a broadband femtosecond pair of pump and Stokes pulses. It is achieved using a single femtosecond ytterbium-laser source and a volume Bragg grating in a compact experimental arrangement.

  17. Fiber Bragg grating sensors for steel wire monitoring in real-time

    NASA Astrophysics Data System (ADS)

    Koch, Jan; Angelmahr, Martin; Schade, Wolfgang

    2014-05-01

    Steel wires are widely applied in industrial applications - in most cases as critical components fulfilling high safety requirements in harsh environments (e.g. dockside cranes). In this paper a technique for real-time monitoring of steel ropes applying optical strain sensors based on fiber Bragg gratings is presented. The optical sensors are integrated within the wire strand and replace the core. The strain transmission from the outer wires to the sensors is assured by the mechanical coupling between the optical fiber and the strand. The actual strain load and rope vibrations in the kilohertz range can be determined in real-time.

  18. A Fibre Bragg Grating Sensor as a Receiver for Acoustic Communications Signals

    PubMed Central

    Wild, Graham; Hinckley, Steven

    2011-01-01

    A Fibre Bragg Grating (FBG) acoustic sensor is used as a receiver for acoustic communications signals. Acoustic transmissions were generated in aluminium and Carbon Fibre Composite (CFC) panels. The FBG receiver was coupled to the bottom surface opposite a piezoelectric transmitter. For the CFC, a second FBG was embedded within the layup for comparison. We show the transfer function, frequency response, and transient response of the acoustic communications channels. In addition, the FBG receiver was used to detect Phase Shift Keying (PSK) communications signals, which was shown to be the most robust method in a highly resonant communications channel. PMID:22346585

  19. Low-cost vibration sensor based on dual fiber Bragg gratings and light intensity measurement.

    PubMed

    Gao, Xueqing; Wang, Yongjiao; Yuan, Bo; Yuan, Yinquan; Dai, Yawen; Xu, Gang

    2013-09-20

    A vibration monitoring system based on light intensity measurement has been constructed, and the designed accelerometer is based on steel cantilever frame and dual fiber Bragg gratings (FBGs). By using numerical simulations for the dual FBGs, the dependence relationship of the area of main lobes on the difference of initial central wavelengths is obtained and the most optimal choice for the initial value and the vibration amplitude of the difference of central wavelengths of two FBGs is suggested. The vibration monitoring experiments are finished, and the measured data are identical to the simulated results.

  20. Demodulation of fiber bragg grating sensors based on dynamic tuning of a multimode laser diode.

    PubMed

    Ferreira, L A; Diatzikis, E V; Santos, J L; Farahi, F

    1999-08-01

    Dither demodulation of fiber Bragg grating sensors illuminated with multimode light from laser diodes is theoretically and experimentally investigated. Quasi-static temperature and strain sensitivities of 0.09 degrees C/ radical Hz and 0.6 microepsilon/ radical Hz are obtained. We show that it is possible to measure small ac signals that lie outside the feedback loop bandwidth by using a synchronous detection referenced to twice the dither frequency. In this situation, dynamic strain sensitivity of 3.3 n(epsilon)/ radical Hz is achieved. PMID:18323963

  1. High resolution and wide scale fiber Bragg grating sensor interrogation system

    NASA Astrophysics Data System (ADS)

    Ma, Youchun; Wang, Changjiang; Yang, Yuanhong; Yan, Shubin; Li, Jinming

    2013-09-01

    This paper demonstrates a high resolution and wide scale fiber Bragg grating sensor interrogation system based on fiber Fabry-Perot tunable filter (FFP-TF) and Fabry-Perot ITU filter (FPIF). By automatic control of the driving voltage of the FFP-TF, the wavelength of the laser can be tracked to the -3dB reflectivity spectrum of the FBG. Using FPIF as the reference channel, the measurement resolution of the system is improved by wiping out the nonlinearity of the FFP-TF. A high resolution of better than 2pm within wide strain measurement range was verified by experiments.

  2. All-fiber amplifier similariton laser based on a fiber Bragg grating filter.

    PubMed

    Olivier, Michel; Gagnon, Mathieu; Duval, Simon; Bernier, Martin; Piché, Michel

    2015-12-01

    This article presents, for the first time to our knowledge, an all-fiber amplifier similariton laser based on a fiber Bragg grating filter. The laser emits 2.9 nJ pulses at a wavelength of 1554 nm with a repetition rate of 31 MHz. The dechirped pulses have a duration of 89 fs. The characteristic features of the pulse profile and spectrum along with the dynamics of the laser are highlighted in representative simulations. These simulations also address the effect of the filter shape and detuning with respect to the gain spectral peak. PMID:26625073

  3. Estimating needle-tissue interaction forces for hollow needles using fiber Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Kumar, Saurabh; Shrikanth, V.; Bharadwaj, Amrutur; Asokan, Sundarrajan; Bobji, M. S.

    2016-03-01

    Brachytherapy and neurological procedures can benefit from real-time estimation of needle-tissue interaction forces, specifically for robotic or robot-assisted procedures. Fiber Bragg Grating Sensors provide advantages of very small size and electromagnetic immunity for use in measurement of the forces directly at the needle tip. This has advantages compared to measurements at the needle shaft which require extensive models of the friction between needle and tissues with varying depth. This paper presents the measurement of tip forces for a hollow needle and compensation for bending when encountering regions of varying stiffness in phantoms with multiple layers prepared using Polydimethylsiloxane.

  4. Rovibrational hybrid fs/ps CARS using a volume Bragg grating for N₂ thermometry.

    PubMed

    Scherman, M; Nafa, M; Schmid, T; Godard, A; Bresson, A; Attal-Tretout, B; Joubert, P

    2016-02-01

    Coherent anti-Stokes Raman scattering (CARS) spectra of N2 in the hybrid femtosecond/picosecond regime have been recorded with 0.7  cm(-1) resolution. The Q-branch rovibrational structure has been resolved, making it suitable for gas-phase simultaneous rotational and vibrational thermometry applications. Resolving this spectral structure requires synchronization of a narrowband picosecond probe pulse with a broadband femtosecond pair of pump and Stokes pulses. It is achieved using a single femtosecond ytterbium-laser source and a volume Bragg grating in a compact experimental arrangement. PMID:26907404

  5. Fiber-optic spectroscopic rotational Raman lidar with visible wavelength fiber Bragg grating for atmospheric temperature measurement

    NASA Astrophysics Data System (ADS)

    Li, Shichun; Hua, Dengxin; Wang, Yufeng; Gao, Fei; Yan, Qing; Shi, Xiaojing

    2015-03-01

    A fiber-optic spectroscopic rotational Raman lidar is demonstrated with the visible wavelength fiber Bragg grating technique for profiling the atmospheric temperature. Two-channel pure rotational Raman optical signals are extracted from lidar echo signals by two sets of visible wavelength fiber Bragg gratings. The rejection-type of fiber Bragg grating in visible region is successfully fabricated through the zero-order nulled phase mask. Its most significant parameter, out-of-band rejection, for fiber-optic spectroscopic system is tested to ensure the spectral purity of rotational Raman channel. A temperature profile up to a 0.7-km height is obtained by pure rotational Raman lidar with 300-mJ laser pulse energy, and a 250-mm telescope. Preliminary results of observations show that this fiber-optic spectroscopic scheme with high mechanical stability has >70-dB suppression to elastic backscattering in lidar echo signals.

  6. Femtosecond laser-inscribed fiber Bragg gratings for strain monitoring in power cables of offshore wind turbines.

    PubMed

    Burgmeier, Jörg; Schippers, Wolfgang; Emde, Nico; Funken, Peter; Schade, Wolfgang

    2011-05-01

    A fiber Bragg grating sensor system used for monitoring the effects of strain on the power cable of an offshore wind turbine is presented. The Bragg grating structure was inscribed into coated nonphotosensitive standard telecommunication fibers using an IR femtosecond laser and the point-by-point writing technique. Because of the presence of the protective coating of the fiber, the mechanical stability of the resultant sensor device is better than that of a sensor consisting of a bare fiber. A system containing this sensing element was to our knowledge for the first time successfully installed and tested in an offshore wind turbine prototype (REpower 6M, REpower Systems, AG, Germany) in February 2010, near Ellhöft (Germany). The fabrication process of the fiber Bragg gratings, measurement results of the online monitoring, and a comparison between the sensor signal and commonly used sensing techniques are presented.

  7. Effect of femtosecond photo-treatment on inscription of fiber Bragg gratings.

    PubMed

    Shamir, Avishay; Ishaaya, Amiel A

    2016-02-15

    Pre- and post-treatment of optical fibers is typically used to improve the fiber Bragg grating (FBG) fabrication process. Here, we investigate experimentally the effects of femtosecond photo-treatment on the ability to inscribe and erase FBGs in standard, non-sensitized, silica SMF fibers. We observe "immunity" to inscription after applying a suitable pre-treatment to the fiber and full "erasure" of the FGB after applying a suitable post-treatment. We characterize the required photo-treatment parameters and compare to FBG inscription on an untreated fiber. We believe that pre/post-photo-treatment of the fibers with fs pulses may have practical advantages such as modifying standard grating structures or observing ultrafast transient effects more clearly. PMID:26872183

  8. Off-axis ultraviolet-written fiber Bragg gratings for directional bending measurements.

    PubMed

    Feng, Dingyi; Qiao, Xueguang; Albert, Jacques

    2016-03-15

    Off-axis fiber Bragg gratings are inscribed by ultraviolet irradiation limited to expose only a portion of the fiber core cross section. The coupling to cladding modes is significantly increased, and the amplitude of the cladding mode resonances becomes sensitive to bending in magnitude and direction. Sensitivities ranging from +1.17  dB/m(-1) to -1.25  dB/m(-1) were obtained for bending in different directions relative to the offset direction of the grating, for curvatures from 0 to 1.1  m(-1), a range ideal for the shape sensing of large structures. The bending sensor response is also shown to be independent of temperature and the surrounding refractive index. PMID:26977669

  9. Temporal thermal response of Type II-IR fiber Bragg gratings

    SciTech Connect

    Liao Changrui; Wang Dongning; Li Yuhua; Sun Tong; Grattan, Kenneth T. V.

    2009-06-01

    We use the phase mask method to investigate both experimentally and theoretically the temporal thermal response of Type II-IR fiber Bragg gratings inscribed by a femtosecond laser. A fast testing system is developed to measure the thermal response time by means of periodic CO2 laser irradiation, which creates a rapid temperature change environment. The temporal thermal response is found to be independent of the heat power and the heat direction, although the grating produced destroys the axial symmetry of the fiber. The measured values of the temporal thermal response are {approx}230 ms for heating and {approx}275 ms for cooling, which different from the simulation results obtained from a lumped system equation. The causes of such differences are investigated in detail.

  10. Behavior of femtosecond laser-induced eccentric fiber Bragg gratings at very high temperatures.

    PubMed

    Chikh-Bled, Hicham; Chah, Karima; González-Vila, Álvaro; Lasri, Boumediène; Caucheteur, Christophe

    2016-09-01

    In this work, eccentric Bragg gratings are photoinscribed in telecommunication-grade optical fibers. They are localized close to the core-cladding interface, yielding strong cladding mode resonance couplings and high photoinduced birefringence. Their transmitted amplitude spectrum is measured with polarized light while they are exposed to temperature changes up to 900°C. Despite the gratings' overall good thermal stability that confirms their robustness for high-temperature refractometry, we report an interesting polarization effect depending on both the cladding mode resonance family and mode order. While the core mode birefringence decreases with growing temperatures, certain cladding mode resonances show an increase in wavelength splitting between their orthogonally polarized components. This differential behavior is of high interest in developing high-resolution, multiparametric sensing platforms. PMID:27607969

  11. Wavelength interrogation of fiber Bragg grating sensors based on crossed optical Gaussian filters.

    PubMed

    Cheng, Rui; Xia, Li; Zhou, Jiaao; Liu, Deming

    2015-04-15

    Conventional intensity-modulated measurements require to be operated in linear range of filter or interferometric response to ensure a linear detection. Here, we present a wavelength interrogation system for fiber Bragg grating sensors where the linear transition is achieved with crossed Gaussian transmissions. This unique filtering characteristic makes the responses of the two branch detections follow Gaussian functions with the same parameters except for a delay. The substraction of these two delayed Gaussian responses (in dB) ultimately leads to a linear behavior, which is exploited for the sensor wavelength determination. Beside its flexibility and inherently power insensitivity, the proposal also shows a potential of a much wider operational range. Interrogation of a strain-tuned grating was accomplished, with a wide sensitivity tuning range from 2.56 to 8.7 dB/nm achieved.

  12. Temperature insensitive hysteresis free highly sensitive polymer optical fiber Bragg grating humidity sensor.

    PubMed

    Woyessa, Getinet; Nielsen, Kristian; Stefani, Alessio; Markos, Christos; Bang, Ole

    2016-01-25

    The effect of humidity on annealing of poly (methyl methacrylate) (PMMA) based microstructured polymer optical fiber Bragg gratings (mPOFBGs) and the resulting humidity responsivity are investigated. Typically annealing of PMMA POFs is done in an oven without humidity control around 80°C and therefore at low humidity. We demonstrate that annealing at high humidity and high temperature improves the performances of mPOFBGs in terms of stability and sensitivity to humidity. PMMA POFBGs that are not annealed or annealed at low humidity level will have a low and highly temperature dependent sensitivity and a high hysteresis in the humidity response, in particular when operated at high temperature. PMMA mPOFBGs annealed at high humidity show higher and more linear humidity sensitivity with negligible hysteresis. We also report how annealing at high humidity can blue-shift the FBG wavelength more than 230 nm without loss in the grating strength. PMID:26832503

  13. Vibration measurement and mode analysis on concrete structures with embedded fiber Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Wang, Yong; Tjin, Chuan S.; Moyo, Pilate; Zheng, Xiahua; Brownjohn, James M. W.

    2001-08-01

    This paper reports our work on the applications of fiber Bragg grating-based strain sensors for the vibration tests and mode analysis on concrete structures. The arrayed fiber grating strain sensors, which were wavelength-division-multiplexed along the fibers, were attached onto the reinforced bars (rebars) before concrete was poured in to form a 5.5m long, 0.3m wide, 0.15m deep reinforced concrete beam. The embedded sensors will provide quasi-distributed real-time dynamic strain information along the length of the beam. For verification with the FBG strain sensors, some electrical accelerometers were also placed on the top surface of the concrete beam. All the data from FBG sensors and electrical accelerometers were recorded and analyzed by a computer. In the experiments, a hammer and an electrical shaker were used to excite the structure. The experimental results obtained with the FBG sensors show good consistency with the theoretical analysis.

  14. Arbitrary on-chip optical filter using complex waveguide Bragg gratings

    NASA Astrophysics Data System (ADS)

    Zhu, Tiecheng; Hu, Yiwen; Gatkine, Pradip; Veilleux, Sylvain; Bland-Hawthorn, Joss; Dagenais, Mario

    2016-03-01

    We demonstrate a Complex Waveguide Bragg Grating (CWBG) which can be designed to generate an arbitrary transmission spectrum. A comprehensive design method, based on the Layer Peeling/Adding algorithm, is developed to realize the grating on a silica-on-silicon platform. The CWBG has a simple one-layer waveguide structure for ease of fabrication. A spectral precision better than ±0.1 nm and a suppression ratio between 15 dB and 33 dB are achieved for a transmission spectrum consisting of 20 randomly distributed spectral notches with a 3 dB width of 0.3-0.4 nm. Among the CWBG's various potential applications, we highlight its use for eliminating OH emission lines from the Earth's atmosphere for ground-based astronomical observations.

  15. 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

  16. Post-Impact Fatigue Damage Monitoring Using Fiber Bragg Grating Sensors

    PubMed Central

    Shin, Chow-Shing; Liaw, Shien-Kuei; Yang, Shi-Wei

    2014-01-01

    It has been shown that impact damage to composite materials can be revealed by embedded Fiber Bragg Gratings (FBG) as a broadening and splitting of the latter's characteristic narrow peak reflected spectrum. The current work further subjected the impact damaged composite to cyclic loading and found that the FBG spectrum gradually submerged into a rise of background intensity as internal damages progressed. By skipping the impact, directing the impact to positions away from the FBG and examining the extracted fibers, we concluded that the above change is not a result of deterioration/damage of the sensor. It is caused solely by the damages initiated in the composite by the impact and aggravated by fatigue loading. Evolution of the grating spectrum may therefore be used to monitor qualitatively the development of the incurred damages. PMID:24594609

  17. Numerical analysis of double chirp effect in tapered and linearly chirped fiber Bragg gratings.

    PubMed

    Markowski, Konrad; Jedrzejewski, Kazimierz; Osuch, Tomasz

    2016-06-10

    In this paper, a theoretical analysis of recently developed tapered chirped fiber Bragg gratings (TCFBG) written in co-directional and counter-directional configurations is presented. In particular, the effects of the synthesis of chirps resulting from both a fused taper profile and a linearly chirped fringe pattern of the induced refractive index changes within the fiber core are extensively examined. For this purpose, a numerical model based on the transfer matrix method (TMM) and the coupled mode theory (CMT) was developed for such a grating. The impact of TCFBG parameters, such as grating length and steepness of the taper transition, as well as the effect of the fringe pattern chirp rate on the spectral properties of the resulting gratings, are presented. Results show that, by using the appropriate design process, TCFBGs with reduced or enhanced resulting chirp, and thus with widely tailored spectral responses, can be easily achieved. In turn, it reveals a great potential application of such structures. The presented numerical approach provides an excellent tool for TCFBG design. PMID:27409005

  18. Experimental study of steel welded joints localization with using fiber Bragg grating strain sensor

    NASA Astrophysics Data System (ADS)

    Harasim, Damian

    2015-12-01

    Optical sensing systems has a not weakening research and development in recent years. Because of its unique properties of being unsusceptible to electromagnetic interference, having wide range of operational temperature and having extreme small physical dimensions, optical fiber sensors has increasing acceptance. Fiber Bragg Gratings (FBG) is the most frequently used type of optical sensor types because of its huge multiplexing potential and potentiality of being embedded into composite material (e.g. in structural health monitoring) or attached into measured structure. Embedding or attaching FBG into an inhomogeneous environment, spectral characteristic of the sensing grating do not retain full symmetry, which is due to related differences in the distribution of the axial stress of the grating. When periodicity of the grating is constant, the peak of FBG reflection spectrum should be narrow and sharp. An inhomogeneous axial strain distribution will cause a distorsion in measured transmission or reflection spectrum. This paper shows an distorsions in FBG reflection spectrum measured from sensor attached on surface with welded joint. The sensor strain-to-wavelength shift processing characteristics obtained for homogeneous and welded steel samples were compared.

  19. Novel fiber Bragg grating fabrication method by high-precision shutter control

    NASA Astrophysics Data System (ADS)

    Liu, Yisi; Gu, Claire; Pan, J. J.; Dong, Liang; Zhou, Feng Q.

    2003-10-01

    Fiber Bragg grating (FBG) is an important element in many applications including filters and dispersion compensators in fiber communication systems. With recently developed inverse scattering algorithm, FBGs with desired reflection spectrum and/or dispersion properties can now be designed. However, most of these designs require arbitrary grating amplitude and phase control. Previously, fabrication of such FBGs relies on the accurate control of the temporal variation of the intensity pattern using a piezo electric translation stage. The precision of this fabrication method is limited by the noise in the control voltage, which is usually larger than 1%. The distortion in piezo response also affects the performance. In this paper, we develop and demonstrate a novel writing technique for arbitrary FBG fabrication. Our technique is based on a translate-and-write configuration. The incorporation of a precisely controlled shutter allows the apodization and phase of the FBG to be continuously changed at each grating line. The shutter error mainly results from the control signal's timing jitter, which is normally lower than 0.1%. Using this writing technique, we demonstrate a Hamming apodized grating with 20mm length, -22 dB minimum transmission, and < -25 dB reflection side lobe suppression. Furthermore, phase-shift in a grating can be fabricated by a simple delay in the control signal. We also demonstrate FBGs with π, π/2, 3π/2 phase-shifts, respectively. Our experimental results are in excellent agreement with theoretical predictions. To show the capability to fabricate a FBG with arbitrary structure, we demonstrate a 35 mm long zero dispersion grating.

  20. Enhancement of the sensitivity of a temperature sensor based on fiber Bragg gratings via weak value amplification.

    PubMed

    Salazar-Serrano, L J; Barrera, D; Amaya, W; Sales, S; Pruneri, V; Capmany, J; Torres, J P

    2015-09-01

    We present a proof-of-concept experiment aimed at increasing the sensitivity of Fiber-Bragg-gratings temperature sensors by making use of a weak-value-amplification scheme. The technique requires only linear optics elements for its implementation and appears as a promising method for increasing the sensitivity than state-of the-art sensors can currently provide. The device implemented here is able to generate a shift of the centroid of the spectrum of a pulse of ∼0.035  nm/°C, a nearly fourfold increase in sensitivity over the same fiber-Bragg-grating system interrogated using standard methods. PMID:26368687

  1. Electro-optical tunable waveguide embedded multiscan Bragg gratings in lithium niobate by direct femtosecond laser writing.

    PubMed

    Kroesen, Sebastian; Horn, Wolfgang; Imbrock, Jörg; Denz, Cornelia

    2014-09-22

    optical tunable Bragg gratings in lithium niobate fabricated by direct femtosecond laser writing. The hybrid design that consists of a circular type-II waveguide and a multiscan type-I Bragg grating exhibits low loss ordinary and extraordinary polarized guiding as well as narrowband reflections in the c-band of optical communications. High bandwidth tunability of more than a peak width and nearly preserved electro-optic coefficients of r(13) = 7.59 pm V(-1) and r(33) = 23.21 pm V(-1) are demonstrated.

  2. Wavelength-tunable, passively mode-locked fiber laser based on graphene and chirped fiber Bragg grating.

    PubMed

    He, Xiaoying; Liu, Zhi-bo; Wang, D N

    2012-06-15

    We demonstrate a wavelength-tunable, passively mode-locked erbium-doped fiber laser based on graphene and chirped fiber Bragg grating. The saturable absorber used to enable passive mode-locking in the fiber laser is a section of microfiber covered by graphene film, which allows light-graphene interaction via the evanescent field of the microfiber. The wavelength of the laser can be continuously tuned by adjusting the chirped fiber Bragg grating, while maintaining mode-locking stability. Such a system has high potential in tuning the mode-locked laser pulses across a wide wavelength range.

  3. A simultaneous interrogation system for intensity-type sensor/fiber Bragg grating/extrinsic Fabry-Perot interferometer

    NASA Astrophysics Data System (ADS)

    Jiang, Yi; Tang, Caijie

    2009-02-01

    A simultaneous interrogation system for an intensity-type sensor, fiber Bragg grating and an extrinsic Fabry-Perot interferometer is demonstrated. The three types of sensors occupy different wavelengths ranging from 1524 nm to 1563 nm, and all sensors are wavelength-division multiplexed and interrogated in one demodulation system. Experimental results show that a wavelength resolution of 2 pm for fiber Bragg grating, a loss resolution of 0.1 dB for an intensity-type sensor and a cavity-length resolution of 3.5 nm for an extrinsic Fabry-Perot interferometer are obtained. The cross-talk between the different sensors is also examined.

  4. Design and experimental research on cantilever accelerometer based on fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Xiang, Longhai; Jiang, Qi; Li, Yibin; Song, Rui

    2016-06-01

    Currently, an acceleration sensor based on fiber Bragg grating (FBG) has been widely used. A cantilever FBG accelerometer is designed. The simulation of this structure was implemented by finite element software (ANSYS) to analyze its sensing performance parameters. And then the optimized structure was produced and calibration experiments were conducted. On the basis of simulation, optical fiber is embedded in the inner tank of the vibrating mass, and Bragg grating is suspended above the cantilever structure, which can effectively avoid the phenomenon of center wavelength chirp or broadening, and greatly improve the sensitivity of the sensor. The experimental results show that the FBG accelerometer exhibits a sensitivity of 75 pm/(m/s2) (100 Hz) and dynamic range of 60 dB. Its linearity error is <2.31% and repeatability error is <2.76%. And the resonant frequency is ˜125 Hz. The simulation results match the experimental results to demonstrate the good performance of FBG accelerometer, which is expected to be used in the actual project.

  5. Health monitoring of the Saint-Jean bridge of Bordeaux, France using fiber Bragg grating extensometers

    NASA Astrophysics Data System (ADS)

    Magne, Sylvain; Boussoir, Jonathan; Rougeault, Stephane; Marty-Dewynter, Veronique; Ferdinand, Pierre; Bureau, Lionel

    2003-07-01

    Most civil engineering structures have been built in the 50's and 60's and reach similar level of degradation accelerated by loading conditions and corrosion. In Europe, National Authorities and the European Commission promote Health Monitoring concepts, instrumentation of existing structures and help in the design of new durable structures of higher performance. In this context, the CEA-List has achieved a non-exclusive industrial transfer of its Bragg grating sensing technology for civil engineering applications to Hydrolog (French SME), supported by the European Community and the french ministry of Industry. In order to check the reliability and user-friendliness of this instrumentation, eleven spectrally-multiplexed Bragg grating-based extensometers, four FBG temperature sensors and an acquisition unit have been installed into the Saint-Jean bridge in Bordeaux, France with the help of the Infrastructure Regional Direction (DRE-Aquitaine) and the Bordeaux Authority (Communaute Urbaine de Bordeaux). A standardized loading of the bridge has been performed on October 29, 1001, with the purpose of correlating its mechanical reaction to loading conditions. Moreover, the equipment has been operating for one year to take into account the winter-summer cycle.

  6. Remote picometer fiber Bragg grating demodulation using a dual-wavelength source.

    PubMed

    Clement, Juan; Torregrosa, Germán; Maestre, Haroldo; Fernández-Pousa, Carlos R

    2016-08-10

    We report on the self-referenced, intensity-based, remote and passive interrogation of a fiber Bragg grating (FBG) for point sensing, by use of a reconfigurable dual-wavelength source composed of a tunable wavelength and subsequent suppressed-carrier, electro-optic amplitude modulation. The demodulation procedure is based on the measurement of the reflected power at two different wavelengths within the FBG spectral response. The grating was interrogated by use of conventional spectral analysis, and also after 32.9 km of single-mode fiber using a dispersive incoherent optical Fourier-domain reflectometry technique. Both procedures provide picometer resolution in the determination of Bragg wavelength shifts at a comparatively similar scan time (∼1  s) and received power (-16  dBm). The main limitations in each interrogation scheme have been identified. These results show the feasibility of interrogation systems incorporating relatively simple frequency combs at a calibrated, and eventually reconfigurable, wavelength grid with an, at least, similar performance to that of commercial FBG interrogators. PMID:27534505

  7. Online diagnosis of the structural behavior of windmills by Bragg gratings and piezoelectrics

    NASA Astrophysics Data System (ADS)

    Diaz-Carrillo, Sebastian; Pardo, Carlos; Guemes, J. Alfredo

    1999-07-01

    Windmills are large composite structures, usually located at difficult-to-access sites, bearing strong dynamic loads in a harsh environment. In-service inspection involves dismounting the blades, a very costly process. Instead of inspecting the windmills regularly, they are usually overdesigned. Furthermore, the design of a windmill is based on estimated wind conditions, while the real wind is seldom measured. The main inconvenience for it are the characteristics of the conventional equipment needed to carry out the measurements. The substitution of traditional sensors for Bragg gratings and piezoelectronics to measure the strain field and vibrational frequencies adds the advantages of a smaller size, no drift, no EMI and the possibility of embedding them while manufacturing, so the windmill is fully equipped when installed. Long-term measurements are possible to check both the in-service conditions and the degradation of the structure. Two possibilities were tested: embedding of the sensors while manufacturing with low disturbance of the process and surface-bonding of the sensors. Windmill qualification test were carried out to check the survivability of the Bragg gratings and the piezoelectric sensors under extreme environment are presently running. Results are hopeful. The next step could be a permanent connection via modem to a remote controller that can use the acquired data to map the wind conditions and/or the structural health.

  8. Design and experimental research on cantilever accelerometer based on fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Xiang, Longhai; Jiang, Qi; Li, Yibin; Song, Rui

    2016-06-01

    Currently, an acceleration sensor based on fiber Bragg grating (FBG) has been widely used. A cantilever FBG accelerometer is designed. The simulation of this structure was implemented by finite element software (ANSYS) to analyze its sensing performance parameters. And then the optimized structure was produced and calibration experiments were conducted. On the basis of simulation, optical fiber is embedded in the inner tank of the vibrating mass, and Bragg grating is suspended above the cantilever structure, which can effectively avoid the phenomenon of center wavelength chirp or broadening, and greatly improve the sensitivity of the sensor. The experimental results show that the FBG accelerometer exhibits a sensitivity of 75 pm/(m/s2) (100 Hz) and dynamic range of 60 dB. Its linearity error is <2.31% and repeatability error is <2.76%. And the resonant frequency is ˜125 Hz. The simulation results match the experimental results to demonstrate the good performance of FBG accelerometer, which is expected to be used in the actual project.

  9. Multi-channel monolithic integrated optic fiber Bragg grating sensor interrogator

    NASA Astrophysics Data System (ADS)

    Mendoza, Edgar A.; Esterkin, Yan; Kempen, Cornelia; Sun, Zongjian

    2011-09-01

    Fiber Bragg grating (FBG) is a mature sensing technology for the measurement of strain, vibration, acoustics, acceleration, pressure, temperature, moisture, and corrosion. It has gained rapid acceptance in civil, aerospace, chemical and petrochemical, medicine, aviation and automotive industries. The most prominent advantages of FBG are: small size and light weight, distributed array of FBG transducers on a single fiber, and immunity to radio frequency interference. However, a major disadvantage of FBG technology is that conventional state-of-the-art FBG interrogation system is typically bulky, heavy, and costly bench top instruments that are typically assembled from off-the-shelf fiber optic and optical components integrated with a signal electronics board into an instrument console. Based on the industrial need for a compact FBG interrogation system, this paper describes recent progress towards the development of miniature fiber Bragg grating sensor interrogator (FBG-Transceiver™) system based on multi-channel monolithic integrated optic sensor microchip technology. The integrated optic microchip technology enables monolithic integration of all functionalities, both passive and active, of conventional bench top FBG sensor interrogator system, packaged in a miniaturized, low power operation, 2 cm×5 cm small form factor (SFF) package suitable for long-term structural health monitoring in applications where size, weight, and power are critical for operation.

  10. High resolution interrogation system for fiber Bragg grating (FBG) sensor application using radio frequency spectrum analyser

    NASA Astrophysics Data System (ADS)

    Muhammad, F. D.; Zulkifli, M. Z.; Harun, S. W.; Ahmad, H.

    2013-05-01

    In this paper, we propose a fiber Bragg grating (FBG) interrogation system for high resolution sensor application based on radio frequency (RF) generation technique by beating a single longitudinal mode (SLM) fiber ring laser with an external tunable laser source (TLS). The external TLS provides a constant wavelength (CW), functioning as the reference signal for the frequency beating technique. The TLS used has a constant output power and wavelength over time. The sensor signal is provided by the reflected wavelength of a typical fiber Bragg grating (FBG) in the SLM fiber ring laser, which consists of a 1 m long highly doped Erbium doped fiber as the gain medium. The key to ensure the SLM laser oscillation is the role of graphene as saturable absorber which is opposed to the commonly used unpumped erbiumdoped fiber and this consequently contributes to the simple and short cavity design of our proposed system. The signal from the SLM fiber ring laser, which is generated by the FBG in response to external changes, such as temperature, strain, air humidity and air movement, is heterodyned with the CW signal from the TLS at a 6 GHz photodetector using a 3-dB fused coupler to generate the frequency beating. This proposed system is experimentally demonstrated as a temperature sensor and the results shows that the frequency response of the system towards the changes in temperature is about 1.3 GHz/°C, taking into account the resolution bandwidth of 3 MHz of the radio frequency spectrum analyzer (RFSA).

  11. Bragg grating-based fiber laser vibration sensing system with novel phase detection

    NASA Astrophysics Data System (ADS)

    Yang, Xiufeng; Chen, Zhihao; Teo, Ju Teng; Ng, Soon Huat

    2014-01-01

    We characterized the dynamic response of a Bragg grating-based fiber laser sensing system. The sensing system comprises of a narrow line width fiber laser based on π-phase-shifted fiber Bragg grating formed in an active fiber, an unbalanced fiber Michelson interferometer (FMI), which performs wavelength-to-phase mapping, and a phase detection algorithm, which acquires the phase change from the interferometric output signal. The novel phase detection algorithm is developed based on the combination of the two traditional phase generated carrier algorithms: differential-cross-multiplying and arctangent algorithms, and possesses the advantages of the two algorithms. The modulation depth fluctuation of the carrier does not affect the performance of the sensing system. A relatively high side mode suppression ratio of above 50 dB has been achieved within a wide range of carrier amplitude from 1.6 to 5.0 V which correspond to the modulation depth from 1.314 to 4.106 rad. The linearity is 99.082% for the relationship between the power spectral density (dBm/Hz) of the detected signal and the amplitude (mv) of the test signal. The unbalanced FMI is used to eliminate the polarization effect.

  12. All-optical fiber anemometer based on laser heated fiber Bragg gratings.

    PubMed

    Gao, Shaorui; Zhang, A Ping; Tam, Hwa-Yaw; Cho, L H; Lu, Chao

    2011-05-23

    A fiber-optic anemometer based on fiber Bragg gratings (FBGs) is presented. A short section of cobalt-doped fiber was utilized to make a fiber-based "hot wire" for wind speed measurement. Fiber Bragg gratings (FBGs) were fabricated in the cobalt-doped fiber using 193 nm laser pulses to serve as localized temperature sensors. A miniature all-optical fiber anemometer is constructed by using two FBGs to determine the dynamic thermal equilibrium between the laser heating and air flow cooling through monitoring the FBGs' central wavelengths. It was demonstrated that the sensitivity of the sensor can be adjusted through the power of pump laser or the coating on the FBG. Experimental results reveal that the proposed FBG-based anemometer exhibits very good performance for wind speed measurement. The resolution of the FBG-based anemometer is about 0.012 m/s for wind speed range between 2.0 m/s and 8.0 m/s.

  13. Hybrid polymers processed by substrate conformal imprint lithography for the fabrication of planar Bragg gratings

    NASA Astrophysics Data System (ADS)

    Foerthner, M.; Rumler, M.; Stumpf, F.; Fader, R.; Rommel, M.; Frey, L.; Girschikofsky, M.; Belle, S.; Hellmann, R.; Klein, J. J.

    2016-03-01

    In this work, we present an approach to use UV-enhanced substrate conformal imprint lithography (UV-SCIL) as a soft imprint technique combined with excimer laser irradiation to manufacture Bragg gratings within planar waveguides on a full-wafer scale. For the first time, different hybrid polymers (OrmoComp®, OrmoStamp, OrmoCore, OrmoClad and OrmoClear) could be successfully patterned using UV-SCIL. For OrmoComp® (showing results very similar to OrmoStamp and OrmoClad), a complete imprint process could be realized. OrmoCore formed an inhibition layer in the presence of oxygen during the imprint, as could be observed for the use of OrmoClear as well. Processing options were elaborated to reduce the inhibition effect significantly, whereby the latter is mainly due to the atmospheric oxygen-containing PDMS layer of the UV-SCIL working stamp. Further on, the successful realization of a planar Bragg grating operating at the telecom wavelength is demonstrated by tuning the refractive index (RI) of OrmoComp® using a phase mask and an UV excimer laser. FTIR measurements show that the change in RI can be clearly correlated with a change in the chemical composition of the hybrid polymer during laser exposure.

  14. PARAFAC Decomposition for Ultrasonic Wave Sensing of Fiber Bragg Grating Sensors: Procedure and Evaluation

    PubMed Central

    Zheng, Rencheng; Nakano, Kimihiko; Ohashi, Rui; Okabe, Yoji; Shimazaki, Mamoru; Nakamura, Hiroki; Wu, Qi

    2015-01-01

    Ultrasonic wave-sensing technology has been applied for the health monitoring of composite structures, using normal fiber Bragg grating (FBG) sensors with a high-speed wavelength interrogation system of arrayed waveguide grating (AWG) filters; however, researchers are required to average thousands of repeated measurements to distinguish significant signals. To resolve this bottleneck problem, this study established a signal-processing strategy that improves the signal-to-noise ratio for the one-time measured signal of ultrasonic waves, by application of parallel factor analysis (PARAFAC) technology that produces unique multiway decomposition without additional orthogonal or independent constraints. Through bandpass processing of the AWG filter and complex wavelet transforms, ultrasonic wave signals are preprocessed as time, phase, and frequency profiles, and then decomposed into a series of conceptual three-way atoms by PARAFAC. While an ultrasonic wave results in a Bragg wavelength shift, antiphase fluctuations can be observed at two adjacent AWG ports. Thereby, concentrating on antiphase features among the three-way atoms, a fitting atom can be chosen and then restored to three-way profiles as a final result. An experimental study has revealed that the final result is consistent with the conventional 1024-data averaging signal, and relative error evaluation has indicated that the signal-to-noise ratio of ultrasonic waves can be significantly improved. PMID:26198232

  15. Behavior of Bragg gratings, written in germanosilicate fibers, against [gamma]-ray exposure at low dose rate

    SciTech Connect

    Niay, P.; Bernage, P.; Douay, M.; Fertein, E.; Lahoreau, F. . Lab. de Dynamique Moleculaire et Photonique); Bayon, J.F.; Georges, T.; Monerie, M. ); Ferdinand, P.; Rougeault, S.; Cetier, P. )

    1994-11-01

    Bragg gratings have been written within four germanosilicate fibers either by a pulsed or by a continuous-wave exposure of each fiber to a coherent UV two-beam interference pattern. These gratings have been exposed under steady state conditions to [gamma]-ray doses as high as 10[sup 4] Grays. The dose rates ranged between 10 Gy/h and 1.3 [times] 10[sup 2] Gy/h. The transmission spectra of the fibers have been recorded during and after the [sup 60]Co irradiation, near the grating Bragg wavelengths. Whereas the induced loss reached 600 dB/km near 1.3 [mu]m, no significant change in the spectral characteristics of the gratings could be detected within the experimental accuracy, enabling their future use in a nuclear environment.

  16. All-fiber 10 MHz acousto-optic modulator of a fiber Bragg grating at 1060 nm wavelength.

    PubMed

    Silva, Ricardo E; Tiess, Tobias; Becker, Martin; Eschrich, Tina; Rothhardt, Manfred; Jäger, Matthias; Pohl, Alexandre A P; Bartelt, Hartmut

    2015-10-01

    Acousto-optic modulation of a 1 cm fiber Bragg grating at 10.9 MHz frequency and 1065 nm wavelength is demonstrated for the first time. A special modulator design is employed to acoustically induce a dynamic radial long period grating which couples power of the fundamental mode to the higher-order modes supported by the Bragg grating. A modulated reflection band with a depth of 16 dB and 320 pm bandwidth has been achieved. The results indicate a higher modulation frequency compared to previous studies using flexural acoustic waves. In addition, the reduction of the grating length and the modulator size points to compact and faster acousto-optic modulators. PMID:26480112

  17. Narrow band SWIR hyperspectral imaging: a new approach based on volume Bragg grating

    NASA Astrophysics Data System (ADS)

    Verhaegen, M.; Lessard, S.; Blais-Ouellette, S.

    2012-06-01

    Volume Bragg grating technology has enabled the development of a new type of staring hyperspectral camera. Based on Bragg Tunable filters, these hyperspectral cameras have both high spectral and spatial resolution, and significantly higher sensitivity than competing technologies like push broom spectrometer, liquid crystal tunable filters, or acousto-optic tunable filters. They are minimally sensitive to polarization and their spectral isolation can reach 106. Here we thus present an innovative tool to collect SWIR hyperspectral data with high spectral and spatial resolution. This new instrument is based on a 3nm bandwidth Bragg Tunable Filter, continuously tunable from 1.0um and 2.5um. Because high spectral resolution also means less light per channel, a low noise custom HgCdTe (MCT) camera was also developed to meet the requirement of the filter. The high speed capability of more than 300 fps and the low operating temperature of 200K (deep cooled option to 77K) allow full frame 500 spectral channel datacube acquisitions in minimal time. Basic principle of this imaging filter will be reviewed as well as the custom MCT camera performances. High resolution hyperspectral measurements will be demonstrated between 1.0um and 2.5um on different objects.

  18. CO2 sensing at room temperature using carbon nanotubes coated core fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Shivananju, B. N.; Yamdagni, S.; Fazuldeen, R.; Sarin Kumar, A. K.; Hegde, G. M.; Varma, M. M.; Asokan, S.

    2013-06-01

    The sensing of carbon dioxide (CO2) at room temperature, which has potential applications in environmental monitoring, healthcare, mining, biotechnology, food industry, etc., is a challenge for the scientific community due to the relative inertness of CO2. Here, we propose a novel gas sensor based on clad-etched Fiber Bragg Grating (FBG) with polyallylamine-amino-carbon nanotube coated on the surface of the core for detecting the concentrations of CO2 gas at room temperature, in ppm levels over a wide range (1000 ppm-4000 ppm). The limit of detection observed in polyallylamine-amino-carbon nanotube coated core-FBG has been found to be about 75 ppm. In this approach, when CO2 gas molecules interact with the polyallylamine-amino-carbon nanotube coated FBG, the effective refractive index of the fiber core changes, resulting in a shift in Bragg wavelength. The experimental data show a linear response of Bragg wavelength shift for increase in concentration of CO2 gas. Besides being reproducible and repeatable, the technique is fast, compact, and highly sensitive.

  19. A technique for mitigating the effect of the writing-beam profile on fibre Bragg grating fabrication.

    PubMed

    Turitsyna, Elena G; Gbadebo, Adenowo; Williams, John A R

    2015-05-18

    We propose and demonstrate a pre-compensation mechanism to account for the writing-beam profile which when applied to the design of advanced fibre Bragg gratings helps to achieve a desired design spectral response. We use the example of a complex multi-channel grating as an example to demonstrate the improvement achievable using the pre-compensation and find good agreement between experimental results and numerical calculations.

  20. 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.

  1. Temperature-insensitive fiber Bragg grating displacement sensor based on a thin-wall ring

    NASA Astrophysics Data System (ADS)

    Tao, Sicong; Dong, Xiaopeng; Lai, Bowen

    2016-08-01

    The study on strain distribution of a thin-wall ring is presented and a bandwidth-demodulated displacement sensor based on a fiber Bragg grating (FBG) is proposed. The FBG is glued onto the inner surface of a spring steel ring, and it is found that its bandwidth is linearly changed with the displacement variation of the top point of the ring due to the ring-compression-induced gradient strain. The PD output responses of different grating lengths to the same dimension of the ring are investigated. Experimental results show that the high sensitivity and accuracy of 0.567 nm mm-1 and ±0.04 mm using 10 mm grating is achieved within a displacement range of 0-3.5 mm. The designed structure has a higher 3dB-bandwidth tuning ratio of 0.057 nm mm-2. A temperature stability better than ±0.02 mm over the temperature range from 0 to 60 °C is demonstrated.

  2. Micro-structured fiber Bragg gratings: optimization of the fabrication process.

    PubMed

    Iadicicco, A; Campopiano, S; Paladino, D; Cutolo, A; Cusano, A

    2007-11-12

    This work has been devoted to present and demonstrate a novel approach for the fabrication of micro-structured fiber Bragg gratings (MSFBGs) with enhanced control of the geometric features and thus of the spectral properties of the final device. The investigated structure relies on the localized stripping of the cladding layer in a well defined region in the middle of the grating structure leading to the formation of a defect state in the spectral response. In order to fully explore the versatility of MSFBGs for sensing and communications applications, a technological assessment of the fabrication process aimed to provide high control of the geometrical features is required. To this aim, here, we demonstrate that the optimization of this device is possible by adopting a fabrication process based on polymeric coatings patterned by high resolution UV laser micromachining tools. The function of the polymeric coating is to act as mask for the HF based chemical etching process responsible for the cladding stripping. Whereas, UV laser micromachining provides a valuable method to accurately pattern the polymeric coating and thus obtain a selective stripping along the grating structure. Here, we experimentally demonstrate the potentiality of the proposed approach to realize reliable and cost efficient MSFBGs enabling the prototyping of advanced photonics devices based on this technology.

  3. Efficient frequency doubling of a pulsed laser diode by use of a periodically poled KTP waveguide crystal with Bragg gratings

    NASA Astrophysics Data System (ADS)

    Rafailov, E. U.; Birkin, D. J. L.; Sibbett, W.; Battle, P.; Fry, T.; Mohatt, D.

    2001-12-01

    Blue light with an average power of as much as 7.5 mW in picosecond pulses has been generated at 486, 488, and 491 nm from a frequency-doubled, nonresonant injection seeded, gain-switched InGaAs/GaAs diode laser by use of a periodically poled KTP waveguide crystal that incorporates a Bragg grating section.

  4. Efficient frequency doubling of a pulsed laser diode by use of a periodically poled KTP waveguide crystal with Bragg gratings.

    PubMed

    Rafailov, E U; Birkin, D J; Sibbett, W; Battle, P; Fry, T; Mohatt, D

    2001-12-15

    Blue light with an average power of as much as 7.5 mW in picosecond pulses has been generated at 486, 488, and 491 nm from a frequency-doubled, nonresonant injection seeded, gain-switched InGaAs/GaAs diode laser by use of a periodically poled KTP waveguide crystal that incorporates a Bragg grating section. PMID:18059745

  5. Fiber Bragg Grating Sensor/Systems for In-Flight Wing Shape Monitoring of Unmanned Aerial Vehicles (UAVs)

    NASA Technical Reports Server (NTRS)

    Parker, Allen; Richards, Lance; Ko, William; Piazza, Anthony; Tran, Van

    2006-01-01

    A viewgraph presentation describing an in-flight wing shape measurement system based on fiber bragg grating sensors for use in Unmanned Aerial Vehicles (UAV) is shown. The topics include: 1) MOtivation; 2) Objective; 3) Background; 4) System Design; 5) Ground Testing; 6) Future Work; and 7) Conclusions

  6. Simultaneous high bit-rate format and mode conversion with a single tilted apodized few-mode fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Gao, Ya; Sun, Junqiang; Sima, Chaotan

    2016-10-01

    We propose an all-optical approach for simultaneous high bit-rate return-to-zero (RZ) to non-return-to-zero (NRZ) format and LP01 to LP11 mode conversion using a weakly tilted apodized few-mode fiber Bragg grating (TA-FM-FBG) with specific linear spectral response. The grating apodization profile is designed by utilizing an efficient inverse scattering algorithm and the maximum refractive index modulation is adjusted based on the grating tilt angle, according to Coupled-Mode Theory. The temporal performance and operation bandwidth of the converter are discussed. The approach provides potential favorable device for the connection of various communication systems.

  7. Multi-Stress Monitoring System with Fiber-Optic Mandrels and Fiber Bragg Grating Sensors in a Sagnac Loop.

    PubMed

    Kim, Hyunjin; Sampath, Umesh; Song, Minho

    2015-07-29

    Fiber Bragg grating sensors are placed in a fiber-optic Sagnac loop to combine the grating temperature sensors and the fiber-optic mandrel acoustic emission sensors in single optical circuit. A wavelength-scanning fiber-optic laser is used as a common light source for both sensors. A fiber-optic attenuator is placed at a specific position in the Sagnac loop in order to separate buried Bragg wavelengths from the Sagnac interferometer output. The Bragg wavelength shifts are measured with scanning band-pass filter demodulation and the mandrel output is analyzed by applying a fast Fourier transform to the interference signal. This hybrid-scheme could greatly reduce the size and the complexity of optical circuitry and signal processing unit, making it suitable for low cost multi-stress monitoring of large scale power systems.

  8. Fiber Optic Fabry-Perot Current Sensor Integrated with Magnetic Fluid Using a Fiber Bragg Grating Demodulation.

    PubMed

    Xia, Ji; Wang, Qi; Liu, Xu; Luo, Hong

    2015-07-09

    An optical fiber current sensor based on Fabry-Perot interferometer using a fiber Bragg grating demodulation is proposed. Magnetic fluid is used as a sensitive medium in fiber optical Fabry-Perot (F-P) cavity for the optical characteristic of magnetic-controlled refractive index. A Fiber Bragg grating (FBG) is connected after the F-P interferometer which is used to reflect the optical power at the Bragg wavelength of the interference transmission spectrum. The corresponding reflective power of the FBG will change with different external current intensity, due to the shift on the interference spectrum of the F-P interferometer. The sensing probe has the advantages of convenient measurement for its demodulation, low cost and high current measurement accuracy on account of its sensing structure. Experimental results show that an optimal sensitivity of 0.8522 nw/A and measurement resolution of 0.001 A is obtained with a FBG at 1550 nm with 99% reflectivity.

  9. Multi-Stress Monitoring System with Fiber-Optic Mandrels and Fiber Bragg Grating Sensors in a Sagnac Loop

    PubMed Central

    Kim, Hyunjin; Sampath, Umesh; Song, Minho

    2015-01-01

    Fiber Bragg grating sensors are placed in a fiber-optic Sagnac loop to combine the grating temperature sensors and the fiber-optic mandrel acoustic emission sensors in single optical circuit. A wavelength-scanning fiber-optic laser is used as a common light source for both sensors. A fiber-optic attenuator is placed at a specific position in the Sagnac loop in order to separate buried Bragg wavelengths from the Sagnac interferometer output. The Bragg wavelength shifts are measured with scanning band-pass filter demodulation and the mandrel output is analyzed by applying a fast Fourier transform to the interference signal. This hybrid-scheme could greatly reduce the size and the complexity of optical circuitry and signal processing unit, making it suitable for low cost multi-stress monitoring of large scale power systems. PMID:26230700

  10. Residual stress and debonding analysis using a fiber Bragg grating in a model composite specimen

    NASA Astrophysics Data System (ADS)

    Colpo, F.; Dunkel, G.; Humbert, L.; Botsis, J.

    2005-05-01

    Optical Fibre Bragg Grating (FBG) sensors are excellent non-destructive tools for internal strain characterization of composite materials and structures. They can be embedded at selected locations during material preparation to provide accurate in-situ measurements. In this study, long-gauge-FBGs are introduced in cylindrical specimens of epoxy. This configuration is particularly attractive because it simplifies the study of some relevant phenomena in micromechanics of composites, for instance residual stresses and fracture of the fibre-matrix interface. Because the matrix epoxy shrinks during the polymerisation process, the optical sensor undergoes substantial non-uniform strain along the fibre. The response of a FBG to a non-uniform strain distribution is investigated using a new Optical Low-Coherence Reflectometry (OLCR) technique developed at EPFL. This method provides a direct reconstruction of the optical period and the corresponding strain distribution along the grating without any a priori assumption about the strain field. Considering the non-uniform residual strain as a reference state, new Bragg wavelength distributions are obtained for two configurations. First, a new Bragg wavelength distribution is measured as a function of the depth of circular cracks machined in the radial direction. These measurements lead to the knowledge of (a) the zone of perturbation of the reinforcing fibre on the residual stresses and (b) the effect of the presence of the mechanically induced crack on the residual stress state in the specimen. A finite element modelling of the residual stress field based on an equivalent thermo-elastic approach is also proposed, showing a very good agreement with experimental data. Second, an interface crack (debonding) between the epoxy and the fibre is introduced by fatigue and monitored using a specifically designed video acquisition system. The induced variations in the FBG response are measured when the fibre is unloaded and then

  11. Design of a compact and high sensitive refractive index sensor base on metal-insulator-metal plasmonic Bragg grating.

    PubMed

    Binfeng, Yun; Guohua, Hu; Ruohu, Zhang; Yiping, Cui

    2014-11-17

    A nanometric and high sensitive refractive index sensor based on the metal-insulator-metal plasmonic Bragg grating is proposed. The wavelength encoded sensing characteristics of the refractive index sensor were investigated by analyzing its transmission spectrum. The numerical results show that a good linear relationship between the Bragg wavelength and the refractive index of the sensing material can be obtained, which is in accordance with the analytical results very well. A high refractive index sensitivity of 1,488 nm/RIU around Bragg resonance wavelength of 1,550 nm was obtained. Besides, the simulation results show that the sensitivity is depended on the Bragg resonance wavelength and the longer the Bragg resonance wavelength, the higher sensitivity can be obtained. Furthermore, the figure of merit of the refractive index sensor can be greatly increased by introducing a nano-cavity in the proposed plasmonic Bragg grating structure. This work pave the way for high sensitive nanometric refractive index sensor design and application.

  12. Design of a compact and high sensitive refractive index sensor base on metal-insulator-metal plasmonic Bragg grating.

    PubMed

    Binfeng, Yun; Guohua, Hu; Ruohu, Zhang; Yiping, Cui

    2014-11-17

    A nanometric and high sensitive refractive index sensor based on the metal-insulator-metal plasmonic Bragg grating is proposed. The wavelength encoded sensing characteristics of the refractive index sensor were investigated by analyzing its transmission spectrum. The numerical results show that a good linear relationship between the Bragg wavelength and the refractive index of the sensing material can be obtained, which is in accordance with the analytical results very well. A high refractive index sensitivity of 1,488 nm/RIU around Bragg resonance wavelength of 1,550 nm was obtained. Besides, the simulation results show that the sensitivity is depended on the Bragg resonance wavelength and the longer the Bragg resonance wavelength, the higher sensitivity can be obtained. Furthermore, the figure of merit of the refractive index sensor can be greatly increased by introducing a nano-cavity in the proposed plasmonic Bragg grating structure. This work pave the way for high sensitive nanometric refractive index sensor design and application. PMID:25402107

  13. Software Development to Assist in the Processing and Analysis of Data Obtained Using Fiber Bragg Grating Interrogation Systems

    NASA Technical Reports Server (NTRS)

    Hicks, Rebecca

    2009-01-01

    A fiber Bragg grating is a portion of a core of a fiber optic strand that has been treated to affect the way light travels through the strand. Light within a certain narrow range of wavelengths will be reflected along the fiber by the grating, while light outside that range will pass through the grating mostly undisturbed. Since the range of wavelengths that can penetrate the grating depends on the grating itself as well as temperature and mechanical strain, fiber Bragg gratings can be used as temperature and strain sensors. This capability, along with the light-weight nature of the fiber optic strands in which the gratings reside, make fiber optic sensors an ideal candidate for flight testing and monitoring in which temperature and wing strain are factors. The purpose of this project is to research the availability of software capable of processing massive amounts of data in both real-time and post-flight settings, and to produce software segments that can be integrated to assist in the task as well.

  14. Application of fiber Bragg grating sensing technology in long-distance detection of temperature in weapon depots

    NASA Astrophysics Data System (ADS)

    Xu, Jianguo; Zhang, ZhiLi; Zhao, Bing; Fu, Zhulin

    2010-10-01

    Incessantly long-term real-time detection of temperature is demanded in weapon depots, where the weapon equipment is stored in, to realize the self-regulation of temperature. Long-Distance intellectualized control can be actualized by setting sensor-net which is composed by several temperature sensors to simultaneously detect multi-point and multi- parameter. The temperature sensors based on Fiber Bragg Grating Technology are more suitable for long-term detection for their preponderance in high sensitivity, small volume, anti-jamming and so on. The temperature sensing system, which is composed by several Fiber Bragg Grating sensors in one light-cable, can accomplish Quasi-Distributed measurement and is suitable for multi-point and multi- parameter detection. Basal principle of Fiber Bragg Grating sensing technology is expounded in the article, with a sensing system applied to the long-distance detection of temperature in the depots is designed based on F-P Scanning Method. Besides, DSP and FPGA are adopted pre-treat the transformed data from AD such as filter and determine threshold. The main modules of this demodulation system such as 1550nm exact photoelectric detection module and trigonal wave voltage scan module are designed in this paper to realize demodulation. Proved by the analysis of the testing data, the Fiber Bragg Grating temperature sensing system, whose testing precision achieved the design purpose, has advantages of real-time measure and long-term stability. The system, which provides guarantee to realize the auto-control of temperature, can be generalized and will provide favorable foundation for the broad using of Fiber Bragg Grating sensing technology in the army.

  15. Switchable multiwavelength erbium doped fiber laser based on a nonlinear optical loop mirror incorporating multiple fiber Bragg gratings.

    PubMed

    Tran, Thi Van Anh; Lee, Kwanil; Lee, Sang Bae; Han, Young-Geun

    2008-02-01

    We propose and experimentally demonstrate a switchable multiwavelength erbium doped fiber laser based on a highly nonlinear dispersion shifted fiber and multiple fiber Bragg gratings. A nonlinear optical loop mirror based on a highly nonlinear dispersion shifted fiber is implemented in the ring laser cavity to stabilize the multiwavelength output at room temperature. Multiple fiber Bragg gratings with the wavelength spacing of 0.8 nm are connected with an arrayed waveguide grating to establish a multichannel filter. The high quality of the multiwavelength output with a high extinction ratio of ~60 dB and high output flatness of ~0.5 dB is realized. The nonlinear polarization rotation based on the nonlinear optical loop mirror can provide the switching performance of the proposed multiwavelength fiber laser. The lasing wavelength can be switched individually by controlling the polarization controller and the cavity loss.

  16. Mathematical model of optimized design of multi-point sensoric measurement with Bragg gratings using wavelength divison multiplex

    NASA Astrophysics Data System (ADS)

    Fajkus, Marcel; Nedoma, Jan; Kepak, Stanislav; Rapant, Lukas; Martinek, Radek; Bednarek, Lukas; Novak, Martin; Vasinek, Vladimir

    2016-04-01

    Fiber Bragg gratings (FBGs) belongs to the single-point optical sensors used in many fields and applications where they often replace a standard sensors. They are easy to multiplex and the wavelength division multiplex is the most widely used method. FBGs in sensory branch are designed for a different Bragg wavelength which gives different measure and sensitivity coefficients. Existing algorithm is based on the determination of left and right boundaries of the measuring channel and the central Bragg wavelength. In this paper is presented the new mathematical model for calculation of Bragg wavelength, sensitivity coefficient and channel width of any FBG in the single step. The model takes into account the following input parameters: wavelength of the optical source, source bandwidth, the type of measured quantity, measuring ranges, width of the FBG reflected spectrum and the guard band between adjacent channels. The mathematical model is verified by using a simulation in software OptiSystem.

  17. [Spectral analysis of fiber bragg grating modulated by double long period grating and its application in smart structure monitoring].

    PubMed

    Lu, Ji-Yun; Liang, Da-Kai; Zhang, Xiao-Li; Zhu, Zhu

    2009-12-01

    Spectrum of fiber bragg grating (FBG) sensor modulated by double long period grating (LPFG) is proposed in the paper. Double LPFG consists of two LPFGS whose center wavelengths are the same and reflection spectrum of FBG sensor is located in linear range of double LPFG transmission spectrum. Based on spectral analysis of FBG and double LPFG, reflection spectrum of FBG modulated by double LPFG is obtained and studied by use of band-hider filter characteristics for double LPFG. An FBG sensor is attached on the surface of thin steel beam, which is strained by bending, and the center wavelength of FBG sensor will shift. The spectral peak of FBG sensor modulated by double LPFG is changed correspondingly, and the spectral change will lead to variation in exit light intensity from double LPFG. Experiment demonstrates that the relation of filtering light intensity from double LPFG monitored by optical power meter to center wavelength change of FBG sensor is linear and the minimum strain of material (steel beam) detected by the modulation and demodulation system is 1.05 microepsilon. This solution is used in impact monitoring of optical fibre smart structure, and FBG sensor is applied for impulse response signal monitoring induced by low-velocity impact, when impact pendulum is loaded to carbon fiber-reinforced plastics (CFP). The acquired impact response signal and fast Fourier transform of the signal detected by FBG sensor agree with the measurement results of eddy current displacement meter attached to the FBG sensor. From the results, the present method using FBG sensor is found to be effective for monitoring the impact. The research provides a practical reference in dynamic monitoring of optical fiber smart structure field. PMID:20210187

  18. A wide range tunable fiber Bragg grating using fast changeable electromagnetic force

    NASA Astrophysics Data System (ADS)

    Fayed, Heba A.; Mahmoud, Mohamed; Aboul Seoud, A. K.; Aly, Moustafa H.

    2010-06-01

    We demonstrate a silica-based tunable fiber Bragg grating (TFBG) filter with a wavelength tuning range over 60 nm. A magnetically TFBG package is employed to obtain a wide wavelength tuning range from 1540 to 1602 nm which covers the entire C band and most of the L-band. TFBG is achieved by varying an input current to a solenoid, resulting in an electromagnetic force, used as a strain (tension and compression) on the FBG. This approach is fast, has a broad band of tuning wavelengths and achieves a power reduction as no continuous supply of power is needed to maintain the set shift, due to the latch system used. This novel TFBG device can have a variety of applications in optical fiber communication systems such as programmable optical add/drop multiplexers (OADMs), dispersion compensators and tunable lasers.

  19. Environmentally stable high-power soliton fiber lasers that use chirped fiber Bragg gratings

    SciTech Connect

    Fermann, M.E.; Sugden, K.; Bennion, I.

    1995-08-01

    Environmentally stable high-power erbium fiber soliton lasers are constructed by Kerr or carrier-type mode locking. We obtain high-energy pulses by using relatively short fiber lengths and providing large amounts of negative dispersion with chirped fiber Bragg gratings. The pulse energies and widths generated with both types of soliton laser are found to scale with the square root of the cavity dispersion. Kerr mode locking requires pulses with an approximately three times higher nonlinear phase shift in the cavity than carrier mode locking, which leads to the generation of slightly shorter pulses with as much as seven times higher pulse energies at the mode-locking threshold. {copyright} {ital 1995} {ital Optical} {ital Society} {ital of} {ital America}.

  20. Simulation of a high-speed superimposed fiber Bragg gratings interrogation system.

    PubMed

    Ma, Youchun; Mills, James K; Xiong, Jijun; Zhang, Wendong; Tan, Qiuling

    2015-09-01

    This paper presents a simulation of high-speed nonuniform random sampling in a superimposed fiber Bragg gratings (SFBGs) interrogation system. The simulated Gauss SFBGs are used to generate a nonuniform sensing pulse train during each scanning cycle. Six different conditions that can cause nonuniform sampling are simulated, and a random sine-wave driving method to improve the driving speed is proposed. An 11.8 kHz dynamic strain is measured by generating an additive nonuniform randomly distributed 12 kHz optical sensing pulse train from a mean 2 kHz sinusoidal periodically changing scanning frequency and three SFBGs. Four conditions that can improve the sampling results are also simulated. PMID:26368898

  1. Enhancing the sensitivity of poly(methyl methacrylate) based optical fiber Bragg grating temperature sensors.

    PubMed

    Zhang, Wei; Webb, David J; Peng, Gang-Ding

    2015-09-01

    In poly(methyl methacrylate) (PMMA)-based optical fiber gratings (POFBGs), the temperature response is determined by thermal expansion and the thermo-optic effect of the fiber. Because thermal expansion introduces a positive change and the thermo-optic effect introduces a negative change in the Bragg wavelength of the POFBG, they cancel out each other to some extent, leading to reduced and varying temperature sensitivity. By pre-straining a POFBG, the contribution of thermal expansion can be removed, and, consequently, the temperature sensitivity of POFBG can be greatly enhanced. Theoretical analysis also indicates a reduced thermo-optic coefficient of POFBG due to restrained linear expansion that matches experimental results. PMID:26368708

  2. Dependence of the spectral parameters of a Raman fibre laser on the Bragg grating temperature

    SciTech Connect

    Babin, S A; Potapov, V V; Churkin, D V; Kurkov, Andrei S

    2003-12-31

    Changes in the output power and emission spectrum of a two-stage Raman phosphosilicate fibre laser are measured during the temperature tuning of fibre Bragg gratings (FBGs) forming enclosed resonators (1.26/1.52 {mu}m). The output emission spectrum of the dense resonator (1.26 {mu}m) is split into two components, whose relative amplitudes change during the temperature tuning of FBGs. A simple analytic model is constructed which describes the broadening and splitting of the spectrum as well as the appearance of its asymmetry upon the relative detuning of FBGs. It is shown that these effects result in the increase in the effective transmission coefficient of the dense resonator at least by an order of magnitude, which affects the output power of the Raman laser. (control of laser radiation parameters)

  3. All optical mode controllable Er-doped random fiber laser with distributed Bragg gratings.

    PubMed

    Zhang, W L; Ma, R; Tang, C H; Rao, Y J; Zeng, X P; Yang, Z J; Wang, Z N; Gong, Y; Wang, Y S

    2015-07-01

    An all-optical method to control the lasing modes of Er-doped random fiber lasers (RFLs) is proposed and demonstrated. In the RFL, an Er-doped fiber (EDF) recoded with randomly separated fiber Bragg gratings (FBG) is used as the gain medium and randomly distributed reflectors, as well as the controllable element. By combining random feedback of the FBG array and Fresnel feedback of a cleaved fiber end, multi-mode coherent random lasing is obtained with a threshold of 14 mW and power efficiency of 14.4%. Moreover, a laterally-injected control light is used to induce local gain perturbation, providing additional gain for certain random resonance modes. As a result, active mode selection of the RFL is realized by changing locations of the laser cavity that is exposed to the control light. PMID:26125397

  4. Distributed OTDR-interferometric sensing network with identical ultra-weak fiber Bragg gratings.

    PubMed

    Wang, Chen; Shang, Ying; Liu, Xiao-Hui; Wang, Chang; Yu, Hai-Hu; Jiang, De-Sheng; Peng, Gang-Ding

    2015-11-01

    We demonstrate a distributed sensing network with 500 identical ultra-weak fiber Bragg gratings (uwFBGs) in an equal separation of 2m using balanced Michelson interferometer of the phase sensitive optical time domain reflectometry (φ-OTDR) for acoustic measurement. Phase, amplitude, frequency response and location information can be directly obtained at the same time by using the passive 3 × 3 coupler demodulation. Lab experiments on detecting sound waves in water tank are carried out. The results show that this system can well demodulate distributed acoustic signal with the pressure detection limit of 0.122Pa and achieve an acoustic phase sensitivity of around -158dB (re rad/μPa) with a relatively flat frequency response between 450Hz to 600Hz. PMID:26561173

  5. Fibre-Bragg-grating writing in single-mode optical fibres by UV femtosecond pulses

    SciTech Connect

    Zagorul'ko, K A; Kryukov, P G; Dianov, Evgenii M; Dragomir, A; Nikogosyan, D N

    2003-08-31

    Fibre-Bragg-grating writing in single-mode optical fibres by the phase-mask method using 220-fs, 264-nm UV pulses of intensity 31 - 77 GW cm{sup -2} is reported for the first time. The achieved degree of modulation of the photoinduced refractive index was 1.9 x 10{sup -3} in an H{sub 2}-loaded SMF-28 telecommunication fibre and 1.1 x 10{sup -3} in a H{sub 2}-free Nufern GF1 fibre. The dependence of the induced refractive index on the intensity for the same irradiation fluences in the case of the H{sub 2}-loaded SMF-28 fibre shows that the refractive index is induced due to nonlinear absorption. (letters)

  6. kW-level narrow linewidth fiber amplifier seeded by a fiber Bragg grating based oscillator.

    PubMed

    Hao, Jinping; Zhao, Hong; Zhang, Dayong; Zhang, Liming; Zhang, Kun

    2015-05-20

    This paper demonstrates an all-fiber narrow linewidth amplifier with a seed based on narrow linewidth fiber Bragg gratings (FBGs). The fiber amplifier achieves a narrow bandwidth output of 823 W, with an opto-optic efficiency of 84.5%. The pair of FBGs in the seed configuration helps to assure a narrow linewidth of the laser as 0.08 nm. In the laser profile, we introduce a cladding stripper with a sectional structure, which realizes high pump power leakage with high efficiency. The paper also discusses the impact of seed linewidth and fiber length on the SBS threshold in a narrow bandwidth laser. Based on this analysis, we discovered ways to inhibit SBS onset and scale power output. PMID:26192524

  7. Highly sensitive liquid level monitoring system utilizing polymer fiber Bragg gratings.

    PubMed

    Marques, Carlos A F; Peng, Gang-Ding; Webb, David J

    2015-03-01

    A novel and highly sensitive liquid level sensor based on a polymer optical fiber Bragg grating (POFBG) is experimentally demonstrated. Two different configurations are studied and both configurations show the potential to interrogate liquid level by measuring the strain induced in a POFBG embedded in a silicone rubber diaphragm, which deforms due to hydrostatic pressure variations. The sensor exhibits a highly linear response over the sensing range and a good repeatability. For comparison, a similar sensor using a FBG inscribed in silica fiber is fabricated, which displays a sensitivity that is a factor of 5 smaller than the POFBG. The temperature sensitivity is studied and a novel multi-sensor arrangement proposed which has the potential to provide level readings independent of temperature and the liquid density. PMID:25836830

  8. Experimental investigation of a fiber Bragg grating integrated optical limiting amplifier with high dynamic range

    NASA Astrophysics Data System (ADS)

    Liaw, Shien Kuei; Chi, Sien

    1998-07-01

    By inserting a bidirectional erbium-doped fiber amplifier (EDFA) in between an optical circulator and a fiber Bragg grating (FBG), we realize an FBG-integrated optical limiting amplifier (OLA) with high dynamic range. The dual-pass OLA has a wide dynamic range of over 40 dB and a saturation signal output power of about 13.0 dBm. The performance of dual-pass OLA has no obvious degradation due to back reflection of the amplified signal. A negligible power penalty of about 0.3 dB is observed when compared with other conventional configurations. The FBG-integrated OLA configuration has potential application in wavelength division multiplexing systems where high saturated power is needed for multichannel transmission.

  9. Application of fiber Bragg grating sensors in light aircraft: ground and flight test

    NASA Astrophysics Data System (ADS)

    Kim, Jin-Hyuk; Shrestha, Pratik; Park, Yurim; Kim, Chun-Gon

    2014-05-01

    Fiber optic sensors are being spotlighted as the means to monitoring aircraft conditions due to their excellent characteristics. This paper presents an affordable structural health monitoring system based on a fiber Bragg grating sensor (FBG) for application in light aircrafts. A total of 24 FBG sensors were installed in the main wing of the test bed aircraft. In the ground test, the intactness of the installed sensors and device operability were confirmed. During the flight test, the strain and temperature responses of the wing structure were measured by the on-board low-speed FBG interrogator. The measured strains were successfully converted into the flight load history through the load calibration coefficient obtained from the ground calibration test.

  10. Fiber Bragg Grating Array as a Quasi Distributed Temperature Sensor for Furnace Boiler Applications

    NASA Astrophysics Data System (ADS)

    Reddy, P. Saidi; Prasad, R. L. N. Sai; Sengupta, D.; Shankar, M. Sai; Srimannarayana, K.; Kishore, P.; Rao, P. Vengal

    2011-10-01

    This paper presents the experimental work on distributed temperature sensing making use of Fiber Bragg grating (FBG) array sensor for possible applications in the monitoring of temperature profile in high temperature boilers. A special sensor has been designed for this purpose which consists of four FBGs (of wavelengths λB1 = 1547.28 nm, λB2 = 1555.72 nm, λB3 = 1550.84 nm, λB4 = 1545.92 nm) written in hydrogen loaded fiber in line with a spacing of 15 cm between them. All the FBGs are encapsulated inside a stainless steel tube for avoiding micro cracks using rigid probe technique. The spatial distribution of temperature profile inside a prototype boiler has been measured experimentally both in horizontal and vertical directions employing the above sensor and the results are presented.

  11. Ultrasonic sensor employing two cascaded phase-shifted fiber Bragg gratings suitable for multiplexing.

    PubMed

    Wu, Qi; Okabe, Yoji

    2012-08-15

    An ultrasonic sensor based on two cascaded phase-shifted fiber Bragg gratings (PS-FBGs) is proposed and demonstrated. In place of an external cavity laser, a broadband amplified spontaneous emission light source is used to demonstrate multiplexing ability suitable for sensor networks. The system has a high sensitivity to ultrasonic waves generated by a PZT actuator placed 7.5 cm away from the PS-FBG, because of the steep slope in the center of the PS-FBG spectrum. A second advantage of the phase shift is to reduce the effective sensor length, leading to the achievement of broadband characteristics. A pencil lead break test was performed and all results are compared to a traditional PZT sensor.

  12. Wide band fiber Bragg grating accelerometer for rotating AC machinery condition monitoring

    NASA Astrophysics Data System (ADS)

    Vilchis-Rodriguez, Damian S.; Djurovic, Sinisa; Kung, Peter; Comanici, Maria I.; Scepanovic, S.; Tshiloz, Kavul; Smith, Alexander C.

    2014-09-01

    This paper investigates the use of fiber Bragg grating (FBG) accelerometers for wide band vibration monitoring in a wound rotor induction generator. The sensor performance is assessed in a series of experiments on a laboratory test rig comprising a 30kW induction machine operating under steady state and variable speed regimes. Vibration measurements are investigated in the frequency domain for generator fault specific electromagnetically induced vibration components. The fiber optic sensor effectiveness in detection of wide band spectral effects (<1kHz) in the vibration signal is compared with that of a commercial piezoelectric based solution. The potential and limitations of the prototype wide band FBG accelerometer are evaluated for use in vibration monitoring applications.

  13. Detuned Plasmonic Bragg Grating Sensor Based on a Defect Metal-Insulator-Metal Waveguide

    PubMed Central

    Qu, Shinian; Song, Ci; Xia, Xiushan; Liang, Xiuye; Tang, Baojie; Hu, Zheng-Da; Wang, Jicheng

    2016-01-01

    A nanoscale Bragg grating reflector based on the defect metal-insulator-metal (MIM) waveguide is developed and numerically simulated by using the finite element method (FEM). The MIM-based structure promises a highly tunable broad stop-band in transmission spectra. The narrow transmission window is shown to appear in the previous stop-band by changing the certain geometrical parameters. The central wavelengths can be controlled easily by altering the geographical parameters. The development of surface plasmon polarition (SPP) technology in metallic waveguide structures leads to more possibilities of controlling light at deep sub-wavelengths. Its attractive ability of breaking the diffraction limit contributes to the design of optical sensors. PMID:27240381

  14. Rebar corrosion monitoring in concrete structure under salt water enviroment using fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Pan, Yuheng; Liu, Tiegen; Jiang, Junfeng; Liu, Kun; Wang, Shuang; He, Pan; Yan, Jinlin

    2015-08-01

    Monitoring corrosion of steel reinforcing bars is critical for the durability and safety of reinforced concrete structures. Corrosion sensors based on fiber optic have proved to exhibit meaningful benefits compared with the conventional electric ones. In recent years, Fiber Bragg Grating (FBG) has been used as a new kind of sensing element in an attempt to directly monitor the corrosion in concrete structure due to its remarkable advantages. In this paper, we present a novel kind of FBG based rebar corrosion monitoring sensor. The rebar corrosion is detected by volume expansion of the corroded rebar by transferring it to the axial strain of FBG when concrete structure is soaked in salt water. An accelerated salt water corrosion test was performed. The experiment results showed the corrosion can be monitored effectively and the corrosion rate is obtained by volume loss rate of rebar.

  15. Compact bending sensor based on a fiber Bragg grating in an abrupt biconical taper.

    PubMed

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

    2015-05-01

    We propose and experimentally demonstrate a compact bending sensor. The head of the sensor is only 0.8 mm in length, and consists of an abrupt biconical fiber taper formed using a conventional fusion splicer, in which a fiber Bragg grating (FBG) is inscribed using a femtosecond laser. The biconical taper incorporating the FBG can couple light from the cladding to the backward-propagating core mode, which realizes an interferometer in reflection-mode. Bending of the structure can be detected from the contrast change of interference fringes. A configuration to measure curvature is investigated to demonstrate the sensing characteristics. The temperature cross-sensitivity of the sensor is studied, and the results demonstrate that it is insensitive to temperature. PMID:25969198

  16. Fiber Bragg gratings sensing network with a bus chain typology structure

    NASA Astrophysics Data System (ADS)

    Wen, Xiaoyan; Shuai, Huang; Zhu, Fangdong; Zhang, Dongsheng

    2016-06-01

    A fiber Bragg grating (FBG) sensing network with a bus chain typology structure based on time-division multiplexing (TDM) technology has been developed. Each FBG sensor was placed in an isolated branching circuit separated by an optical splitter. By doing this, multiple reflection and spectrum shadow, which are common in a traditional TDM network, were eliminated since incident light reflected by each sensor did not go through the other sensors. Interference among different FBGs was also avoided. The system was experimentally verified by constructing such a network with 17 FBGs involved. Wavelength and position interrogation were successfully realized. Temperature experiment was carried out on four of the FBGs and the sensitivity was 9.87, 9.92, 9.91, and 9.97 pm/°C, respectively. The durability, reliability, and measuring accuracy of the sensing network were effectively improved due to the bus chain typology structure.

  17. Split Hopkinson bar measurement using high-speed full-spectrum fiber Bragg grating interrogation.

    PubMed

    Seng, Frederick; Hackney, Drew; Goode, Tyler; Shumway, LeGrand; Hammond, Alec; Shoemaker, George; Pankow, Mark; Peters, Kara; Schultz, Stephen

    2016-09-01

    The development and validation of a high-speed, full-spectrum measurement technique is described for fiber Bragg grating (FBG) sensors. A FBG is surface-mounted to a split-Hopkinson tensile bar specimen to induce high strain rates. The high strain gradients and large strains that indicate material failure are analyzed under high strain rates up to 500  s-1. The FBG is interrogated using a high-speed full-spectrum solid-state interrogator with a repetition rate of 100 kHz. The captured deformed spectra are analyzed for strain gradients using a default interior point algorithm in combination with the modified transfer matrix approach. This paper shows that by using high-speed full-spectrum interrogation of an FBG and the modified transfer matrix method, highly localized strain gradients and discontinuities can be measured without a direct line of sight.

  18. Simulation of a high-speed superimposed fiber Bragg gratings interrogation system.

    PubMed

    Ma, Youchun; Mills, James K; Xiong, Jijun; Zhang, Wendong; Tan, Qiuling

    2015-09-01

    This paper presents a simulation of high-speed nonuniform random sampling in a superimposed fiber Bragg gratings (SFBGs) interrogation system. The simulated Gauss SFBGs are used to generate a nonuniform sensing pulse train during each scanning cycle. Six different conditions that can cause nonuniform sampling are simulated, and a random sine-wave driving method to improve the driving speed is proposed. An 11.8 kHz dynamic strain is measured by generating an additive nonuniform randomly distributed 12 kHz optical sensing pulse train from a mean 2 kHz sinusoidal periodically changing scanning frequency and three SFBGs. Four conditions that can improve the sampling results are also simulated.

  19. Optical computation of the Laplace operator using phase-shifted Bragg grating.

    PubMed

    Bykov, Dmitry A; Doskolovich, Leonid L; Bezus, Evgeni A; Soifer, Victor A

    2014-10-20

    Diffraction of a 3D optical beam on a multilayer phase-shifted Bragg grating (PSBG) is considered. It is shown that the PSBG enables optical computation of the spatial Laplace operator of the electromagnetic field components of the incident beam. The computation of the Laplacian is performed in reflection at normal incidence. As a special case, the parameters of the PSBG transforming the incident Gaussian beam into a Laguerre-Gaussian mode of order (1,0) are obtained. Presented numerical results demonstrate high quality of the Laplace operator computation and confirm the possibility of the formation of Laguerre-Gaussian mode. We expect the proposed applications to be useful for all-optical data processing.

  20. Note: A concrete erosion sensor based on a chirped fibre optic Bragg grating

    NASA Astrophysics Data System (ADS)

    Kanopoulos, Patrick; Xia, Kaiwen; Gu, Xijia; Amirchoupani, Ardavan; Yao, Wei

    2015-12-01

    Erosion of concrete surfaces in major civil structures is a common problem, which in certain circumstances can undermine the structural and operational integrities of the structure. The manual monitoring of the erosion process can be difficult and dangerous under certain circumstances (such as within hydrotunnels and spillways of dams). This paper describes a concrete erosion sensor based on a chirped fibre Bragg grating (FBG) which is able to monitor the extent of concrete erosion at a single point to sub-millimetre accuracy. The chirped FBG length embedded below the concrete surface decreases as a result of concrete erosion and consequently the reflected light spectrum bandwidth narrows. A simple procedure is presented to determine the extent of erosion, and this procedure is applied to an experimental demonstration of the sensing device.

  1. Spectra power and bandwidth of fiber Bragg grating under influence of gradient strain

    NASA Astrophysics Data System (ADS)

    Liu, Qinpeng; Qiao, Xueguang; Jia, Zhen'an; Fu, Haiwei

    2016-09-01

    The reflective spectrum power and the bandwidth of the fiber Bragg grating (FBG) under gradient strain are researched and experimentally demonstrated. The gradient strain is applied on the FBG, which can induce FBG bandwidth broadening, resulting in the variation of reflective power. Based on the coupled-mode theory and transfer matrix method, the segmental linear relationship between the gradient strain, the reflective power, and the bandwidth is simulated and analyzed, and the influence of the FBG length on the reflective spectrum is analyzed. In the experiment, the strict gradient stain device is designed; the experimental results indicate that the reflective optic power and the bandwidth of the FBG under gradient stain are concerned with the length of the FBG. Experimental results are well consistent with the theoretical analysis, which have important guiding significance in the FBG dynamic sensing.

  2. Application of fiber-Bragg-grating-based strain sensors for civil infrastructure health monitoring

    NASA Astrophysics Data System (ADS)

    Tjin, Swee C.; Rupali, S.; Moyo, Pilate; Brownjohn, James M. W.; Ngo, Nam Quoc

    2003-10-01

    Over past few years, the concept of structural health monitoring has been emerging as a new area of research. Fiber Bragg grating (FBG) based sensor offers a new sensing approach with a number of advantages over conventional sensors. This new sensing technology is suitable for the harsh environment of construction industry due to its robustness, ruggedness and ease of installation. Two unique advantages of FBG based sensors are immunity to electromagnetic interference and multiplexing capability. This paper reports some of the results of a multi-disciplinary program on the FBG based sensors involving the School of Electrical and Electronic Engineering and the School of Civil and Environment Engineering at Nanyang Technological University, Singapore.

  3. Interrogation of fiber-Bragg-grating temperature and strain sensors with a temperature-stabilized VCSEL

    NASA Astrophysics Data System (ADS)

    Mizunami, Toru; Yamada, Taichi; Tsuchiya, Satoshi

    2016-10-01

    The interrogation of fiber-Bragg-grating (FBG) sensors using a vertical-cavity surface-emitting laser (VCSEL) is discussed. A long-wavelength (1.54 μm) VCSEL was used as a wavelength-tunable source by variation in the current. Temperature stabilization was performed with a thermoelectric device. Characteristics of temperature and strain sensing were investigated. FBGs with different reflectivities were compared. For temperature sensing, the root-mean-square error in the measurement was reduced to 1/3 that without temperature stabilization. The dependence of the measurement error on the reflectivities of the FBGs was investigated. The measurement error was larger for FBGs with lower reflectivities in both temperature and strain sensing. Improvement on the sensing with low-reflectivity FBGs is discussed.

  4. Functionalized planar Bragg grating sensor for the detection of BTX in solvent vapor

    NASA Astrophysics Data System (ADS)

    Girschikofsky, M.; Rosenberger, M.; Belle, S.; Brutschy, M.; Waldvogel, S. R.; Hellmann, R.

    2012-04-01

    We report on an optical planar Bragg grating evanescent wave refractive index sensor functionalized by a simple method against aromatic hydrocarbons such as benzene, toluene and xylene (BTX) in solvent vapor. To functionalize the sensor against BTX, substituted cyclodextrins are applied to the sensor surface using dip coating. Cyclodextrins have a hydrophobic cavity, which favors the accommodation of an organic molecule of appropriate dimensions leading to a non-covalent inclusion complex. The temporal sensor response reveals a multi-exponential rise towards an equilibrium state, whose level is found to be linearly related to the exposed analyte concentration. Taking into account the spectral resolution of the interrogation system we find a minimum concentration threshold of 200 ppm for benzene, 70 ppm for toluene and 20 ppm for m-xylene, respectively.

  5. Note: Dissolved hydrogen detection in power transformer oil based on chemically etched fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Jiang, Jun; Ma, Guo-ming; Song, Hong-tu; Zhou, Hong-yang; Li, Cheng-rong; Luo, Ying-ting; Wang, Hong-bin

    2015-10-01

    A fiber Bragg grating (FBG) sensor based on chemically etched cladding to detect dissolved hydrogen is proposed and studied in this paper. Low hydrogen concentration tests have been carried out in mixed gases and transformer oil to investigate the repeatability and sensitivity. Moreover, to estimate the influence of etched cladding thickness, a physical model of FBG-based hydrogen sensor is analyzed. Experimental results prove that thin cladding chemically etched by HF acid solution improves the response to hydrogen detection in oil effectively. At last, the sensitivity of FBG sensor chemically etched 16 μm could be as high as 0.060 pm/(μl/l), increased by more than 30% in comparison to un-etched FBG.

  6. 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.

  7. Gas refractometer based on an S-taper fiber tailored fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Shao, Zhihua; Bao, Weijia; Qiao, Xueguang; Rong, Qiangzhou

    2015-09-01

    A fiber Bragg grating (FBG)-based gas refractometer is proposed and demonstrated experimentally. The configuration consists of a short section of S-type taper followed with a FBG. The S-taper is capable to couple the core mode to cladding modes into the downstream SMF, and the low-order cladding modes can be reflected back to the fiber core via the FBG, in which the recoupling efficiency is highly dependent on surrounding refractive index (RI) of liquid and gas. Experimental results show that some recoupled cladding modes show high sensitivities to surround RI. This power-referenced RI measurement and wavelength-referenced temperature measurement have been achieved via selective cladding modes monitoring.

  8. Fiber Bragg grating Fabry-Perot cavity sensor based on pulse laser demodulation technique

    NASA Astrophysics Data System (ADS)

    Gao, Fangfang; Chen, Jianfeng; Liu, Yunqi; Wang, Tingyun

    2011-12-01

    We demonstrate a fiber laser sensing technique based on fiber Bragg grating Fabry-Perot (FBG-FP) cavity interrogated by pulsed laser, where short pulses generated from active mode-locked erbium-doped fiber ring laser and current modulated DFB laser are adopted. The modulated laser pulses launched into the FBG-FP cavity produce a group of reflected pulses. The optical loss in the cavity can be determined from the power ratio of the first two pulses reflected from the cavity. This technique does not require high reflectivity FBGs and is immune to the power fluctuation of the light source. Two short pulse laser sources were compared experimentally with each other on pulse width, pulse stability, pulse chirp and sensing efficiency.

  9. A Fiber Bragg grating based tilt sensor suitable for constant temperature room

    NASA Astrophysics Data System (ADS)

    Tang, Guoyu; Wei, Jue; Zhou, Wei; Wu, Mingyu; Yang, Meichao; Xie, Ruijun; Xu, Xiaofeng

    2015-07-01

    Constant-temperature rooms have been widely used in industrial production, quality testing, and research laboratories. This paper proposes a high-precision tilt sensor suitable for a constant- temperature room, which has achieved a wide-range power change while the fiber Bragg grating (FBG) reflection peak wavelength shifted very little, thereby demonstrating a novel method for obtaining a high-precision tilt sensor. This paper also studies the effect of the reflection peak on measurement precision. The proposed sensor can distinguish the direction of tilt with an excellent sensitivity of 403 dBm/° and a highest achievable resolution of 2.481 × 10-5 ° (that is, 0.08% of the measuring range).

  10. Mode-splitting cloning in birefringent fiber Bragg grating ring resonators.

    PubMed

    Campanella, C E; Malara, P; Campanella, C M; Giove, F; Dunai, M; Passaro, V M N; Gagliardi, G

    2016-06-15

    In this Letter, we report the theoretical model and the experimental evidence of a mode-splitting cloning effect due to the resonant coupling between modes having different polarizations in weakly birefringent fiber Bragg grating (FBG) ring resonators. This modal coupling depends on the fiber birefringence and the FBG reflectivity. In the ideal case of the absence of birefringence, a single split-mode resonant structure can be observed in the resonator transmission spectrum due to the degeneracy removal of the two counter-propagating modes. In the presence of FBG birefringence, a secondary split doublet resulting in a clone of the initial one is generated. The described effect can be exploited for spectroscopic-sensing applications based on more complex split-mode dynamics. PMID:27304260

  11. FIBER BRAGG GRATING SENSORS FOR LOCALIZED STRAIN MEASUREMENTS AT LOW TEMPERATURE AND IN HIGH MAGNETIC FIELD

    SciTech Connect

    Ramalingam, Rajinikumar

    2010-04-09

    Study of magnetostrictive effects in the bulk superconductors is very essential and can give more knowledge about the effects like namely, flux pinning induced strain, pincushion distortions in the magnets and so on. Currently used electro mechanical sensors are magnetic field dependent and can only give the global stress/strain information but not the local stress/strains. But the information like radius position dependent strain and characterisation of shape distortion in non cylindrical magnets are interesting. Wavelength encoded multiplexed fiber Bragg Grating sensors inscribed in one fiber gives the possibility to measure magentostrictive effects spatially resolved in low temperature and high magnetic field. This paper specifies the design and technology requirements to adapt FBG sensors for such an application. Also reports the experiments demonstrate the properties of glass FBG at low temperature (4.2 K) and the results of strain measurement at 4.2 K/8 T. The sensor exhibits a linear wavelength change for the strain change.

  12. Fiber Bragg grating laser sensor with direct radio-frequency readout.

    PubMed

    Malara, P; Campanella, C E; Giorgini, A; Avino, S; Gagliardi, G

    2016-04-01

    A fiber Bragg grating (FBG)-coupled ring laser sensor is demonstrated. In the proposed configuration the interrogating source, the sensing head and the readout instrument are integrated in a single fiber-optic device. An FBG inserted within a bidirectional fiber ring couples the two counterpropagating modes of the cavity, generating a splitting of the resonant wavelengths proportional to the FBG reflectivity. When the cavity gain is brought beyond threshold, the two peaks of the split resonances simultaneously lase, leading to a beat note in the emission spectrum whose frequency tracks any small shift of the FBG reflectivity spectrum. Such a beat note can be simply monitored by a frequency counter, without the need for an optical spectrometer, allowing to significantly reduce size and costs of the sensor setup. The sensing performance compares well to the state-of-the-art thermo-mechanical fiber sensors. PMID:27192251

  13. Strain fiber sensor based on beat frequency with chirped fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Wang, Xu; Zhang, Haojie; Wen, Quan; Chen, Longfei; Wang, Fang; Liu, Yufang; Yu, Kun

    2016-07-01

    We propose a strain fiber sensor that is interrogated via longitudinal mode beat frequency with a linear chirped fiber Bragg grating (CFBG). Unlike conventional sensors, in the proposed sensor, the CFBG is used to convert wavelength changes into resonant cavity length changes. Further, the beat frequency stability of the fiber laser is fully utilized to significantly improve measurement accuracy. Consequently, because cavity changes account for 5.1% of the total cavity length, the measurement accuracy can be as large as 7.06×10-7 ɛ-i.e., approximately five times greater than the accuracy obtained by stretching the resonant cavity fiber. The maximum experimental strain error range is ±14.5 μɛ.

  14. Interrogation of fiber-Bragg-grating temperature and strain sensors with a temperature-stabilized VCSEL

    NASA Astrophysics Data System (ADS)

    Mizunami, Toru; Yamada, Taichi; Tsuchiya, Satoshi

    2016-07-01

    The interrogation of fiber-Bragg-grating (FBG) sensors using a vertical-cavity surface-emitting laser (VCSEL) is discussed. A long-wavelength (1.54 μm) VCSEL was used as a wavelength-tunable source by variation in the current. Temperature stabilization was performed with a thermoelectric device. Characteristics of temperature and strain sensing were investigated. FBGs with different reflectivities were compared. For temperature sensing, the root-mean-square error in the measurement was reduced to 1/3 that without temperature stabilization. The dependence of the measurement error on the reflectivities of the FBGs was investigated. The measurement error was larger for FBGs with lower reflectivities in both temperature and strain sensing. Improvement on the sensing with low-reflectivity FBGs is discussed.

  15. High-resolution fiber Bragg grating based transverse load sensor using microwave photonics filtering technique.

    PubMed

    Wang, Yiping; Wang, Ming; Xia, Wei; Ni, Xiaoqi

    2016-08-01

    In this paper, a new fiber Bragg grating (FBG) sensor exploiting microwave photonics filter technique for transverse load sensing is firstly proposed and experimentally demonstrated. A two-tap incoherent notch microwave photonics filter (MPF) based on a transverse loaded FBG, a polarization beam splitter (PBS), a tunable delay line (TDL) and a length of dispersion compensating fiber (DCF) is demonstrated. The frequency response of the filter with respect to the transverse load is studied. By detecting the resonance frequency shifts of the notch MPF, the transverse load can be determined. The theoretical and experimental results show that the proposed FBG sensor has a higher resolution than traditional methods based on optical spectrum analysis. The sensitivity of the sensor is measured to be as high as 2.5 MHz/N for a sensing fiber with a length of 18mm. Moreover, the sensitivity can be easily adjusted. PMID:27505763

  16. Fiber Bragg grating dynamic strain sensor using an adaptive reflective semiconductor optical amplifier source.

    PubMed

    Wei, Heming; Tao, Chuanyi; Zhu, Yinian; Krishnaswamy, Sridhar

    2016-04-01

    In this paper, a reflective semiconductor optical amplifier (RSOA) is configured to demodulate dynamic spectral shifts of a fiber Bragg grating (FBG) dynamic strain sensor. The FBG sensor and the RSOA source form an adaptive fiber cavity laser. As the reflective spectrum of the FBG sensor changes due to dynamic strains, the wavelength of the laser output shifts accordingly, which is subsequently converted into a corresponding phase shift and demodulated by an unbalanced Michelson interferometer. Due to the short transition time of the RSOA, the RSOA-FBG cavity can respond to dynamic strains at high frequencies extending to megahertz. A demodulator using a PID controller is used to compensate for low-frequency drifts induced by temperature and large quasi-static strains. As the sensitivity of the demodulator is a function of the optical path difference and the FBG spectral width, optimal parameters to obtain high sensitivity are presented. Multiplexing to demodulate multiple FBG sensors is also discussed. PMID:27139682

  17. Dynamic strain measurement system with fiber Bragg gratings and noise mitigation techniques

    NASA Astrophysics Data System (ADS)

    Tosi, D.; Olivero, M.; Perrone, G.

    2009-06-01

    A low-cost fiber Bragg grating (FBG) vibrometer specifically suited for structural monitoring and aimed at the detection of low-amplitude vibrations is presented. The optical system exploits an intensity modulation principle of operation, while signal processing techniques are used to complement the transducer to improve the performances: a recursive least-squares adaptive filter improves the noise power mitigation by 14 dB, and an efficient spectral estimator permits operating spectral analysis even under high noise conditions. With these methods, a strain sensitivity of 5.6 nɛ has been achieved in the ±60 µɛ range. Experimental assessment tests carried out in typical structural monitoring contexts have demonstrated that the developed sensor is well suited to measure mechanical perturbations of different structures.

  18. Fiber Bragg grating microphone system for condition-based maintenance of industrial facilities

    NASA Astrophysics Data System (ADS)

    Tosi, D.; Olivero, M.; Perrone, G.; Vallan, A.

    2011-05-01

    This paper presents a multipoint fiber Bragg grating (FBG) sensing system operating as a precision microphone. This instrument aims to become the best performing technology for condition-based maintenance (CBM) of critical elements, like ball bearings and cogwheels, embedded in industrial manufacturing machineries. The system architecture is based on the simple matched-laser principle, leading to a low-cost and high-sensitivity system, operating in time and wavelength multiplexing mode. Then, heavy signal processing is applied, providing an outstanding performance improvement of 59 dB in terms of signal-to-noise ratio. A demonstration of condition-based maintenance operation has been performed using standard models of ball bearing sound spectra. Compared to traditional microphones applied to CBM, the signal processing-powered FBG system provides remarkable advantages in terms of sensitivity and rejection of environment noise, providing an improvement of cost-effectiveness of CBM.

  19. Temperature sensing of micron scale polymer fibers using fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Zhou, J.; Zhang, Y.; Mulle, M.; Lubineau, G.

    2015-08-01

    Highly conductive polymer fibers are key components in the design of multifunctional textiles. Measuring the voltage/temperature relationships of these fibers is very challenging due to their very small diameters, making it impossible to rely on classical temperature sensing techniques. These fibers are also so fragile that they cannot withstand any perturbation from external measurement systems. We propose here, a non-contact temperature measurement technique based on fiber Bragg gratings (FBGs). The heat exchange is carefully controlled between the probed fibers and the sensing FBG by promoting radiation and convective heat transfer rather than conduction, which is known to be poorly controlled. We demonstrate our technique on a highly conductive Poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS)-based fiber. A non-phenomenological model of the sensing system based on meaningful physical parameters is validated towards experimental observations. The technique reliably measures the temperature of the polymer fibers when subjected to electrical loading.

  20. Split Hopkinson bar measurement using high-speed full-spectrum fiber Bragg grating interrogation.

    PubMed

    Seng, Frederick; Hackney, Drew; Goode, Tyler; Shumway, LeGrand; Hammond, Alec; Shoemaker, George; Pankow, Mark; Peters, Kara; Schultz, Stephen

    2016-09-01

    The development and validation of a high-speed, full-spectrum measurement technique is described for fiber Bragg grating (FBG) sensors. A FBG is surface-mounted to a split-Hopkinson tensile bar specimen to induce high strain rates. The high strain gradients and large strains that indicate material failure are analyzed under high strain rates up to 500  s-1. The FBG is interrogated using a high-speed full-spectrum solid-state interrogator with a repetition rate of 100 kHz. The captured deformed spectra are analyzed for strain gradients using a default interior point algorithm in combination with the modified transfer matrix approach. This paper shows that by using high-speed full-spectrum interrogation of an FBG and the modified transfer matrix method, highly localized strain gradients and discontinuities can be measured without a direct line of sight. PMID:27607299

  1. Research on the fiber Bragg grating sensor for the shock stress measurement

    PubMed Central

    Deng, Xiangyang; Chen, Guanghua; Peng, Qixian; Li, Zeren; Meng, Jianhua; Liu, Jun

    2011-01-01

    A fiber Bragg grating (FBG) sensor with an unbalanced Mach-Zehnder fiber interferometer for the shock stress measurement is proposed and demonstrated. An analysis relationship between the shock stress and the central reflection wavelength shift of the FBG is firstly derived. In this sensor, the optical path difference of the unbalanced Mach-Zehnder fiber interferometer is ∼3.1 mm and the length of the FBG is 2 mm. An arctangent function reduction method, which can avoid sine function's insensitive zone where the shock stress measurement has a reduced accuracy, is presented. A shock stress measurement of water driven by one stage gun (up to 1.4 GPa), with good theoretical accuracy (∼10%), is launched. PMID:22047282

  2. Residual internal stress optimization for EPON 828/DEA thermoset resin using fiber Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Rohr, Garth D.; Rasberry, Roger D.; Kaczmarowski, Amy K.; Stavig, Mark E.; Gibson, Cory S.; Udd, Eric; Roach, Allen R.; Nation, Brendan

    2015-05-01

    Internal residual stresses and overall mechanical properties of thermoset resins are largely dictated by the curing process. It is well understood that fiber Bragg grating (FBG) sensors can be used to evaluate temperature and cure induced strain while embedded during curing. Herein, is an extension of this work whereby we use FBGs as a probe for minimizing the internal residual stress of an unfilled and filled Epon 828/DEA resin. Variables affecting stress including cure cycle, mold (release), and adhesion promoting additives will be discussed and stress measurements from a strain gauge pop-off test will be used as comparison. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  3. Stationary light pulses in cold atomic media and without Bragg gratings.

    PubMed

    Lin, Yen-Wei; Liao, Wen-Te; Peters, Thorsten; Chou, Hung-Chih; Wang, Jian-Siung; Cho, Hung-Wen; Kuan, Pei-Chen; Yu, Ite A

    2009-05-29

    We study the creation of stationary light pulses (SLPs), i.e., light pulses without motion, based on the effect of electromagnetically induced transparency with two counterpropagating coupling fields in cold atoms. We show that the Raman excitations created by counterpropagating probe and coupling fields prohibit the formation of SLPs in media of cold and stationary atoms such as laser-cooled atom clouds, Bose condensates or color-center crystals. A method is experimentally demonstrated to suppress these Raman excitations and SLPs are realized in laser-cooled atoms. Furthermore, we report the first experimental observation of a bichromatic SLP at wavelengths for which no Bragg grating can be established. Our work advances the understanding of SLPs and opens a new avenue to SLP studies for few-photon nonlinear interactions.

  4. Pulse transit time differential measurement by fiber Bragg grating pulse recorder.

    PubMed

    Umesh, Sharath; Padma, Srivani; Ambastha, Shikha; Kalegowda, Anand; Asokan, Sundarrajan

    2015-05-01

    The present study reports a noninvasive technique for the measurement of the pulse transit time differential (PTTD) from the pulse pressure waveforms obtained at the carotid artery and radial artery using fiber Bragg grating pulse recorders (FBGPR). PTTD is defined as the time difference between the arrivals of a pulse pressure waveform at the carotid and radial arterial sites. The PTTD is investigated as an indicator of variation in the systolic blood pressure. The results are validated against blood pressure variation obtained from a Mindray Patient Monitor. Furthermore, the pulse wave velocity computed from the obtained PTTD is compared with the pulse wave velocity obtained from the color Doppler ultrasound system and is found to be in good agreement. The major advantage of the PTTD measurement via FBGPRs is that the data acquisition system employed can simultaneously acquire pulse pressure waveforms from both FBGPRs placed at carotid and radial arterial sites with a single time scale, which eliminates time synchronization complexity. PMID:26021719

  5. Flat-Cladding Fiber Bragg Grating Sensors for Large Strain Amplitude Fatigue Tests

    PubMed Central

    Feng, Aihen; Chen, Daolun; Li, Cheng; Gu, Xijia

    2010-01-01

    We have successfully developed a flat-cladding fiber Bragg grating sensor for large cyclic strain amplitude tests of up to ±8,000 με. The increased contact area between the flat-cladding fiber and substrate, together with the application of a new bonding process, has significantly increased the bonding strength. In the push-pull fatigue tests of an aluminum alloy, the plastic strain amplitudes measured by three optical fiber sensors differ only by 0.43% at a cyclic strain amplitude of ±7,000 με and 1.9% at a cyclic strain amplitude of ±8,000 με. We also applied the sensor on an extruded magnesium alloy for evaluating the peculiar asymmetric hysteresis loops. The results obtained were in good agreement with those measured from the extensometer, a further validation of the sensor. PMID:22163621

  6. Comparison of strain sensitivity of bare and structure-integrated fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Lebid, Solomija Y.; Hofmann, Detlef; Basedau, Frank; Daum, Werner

    2003-07-01

    For the last decade sensor architectures with embedded fibers found their application in large structure monitoring and proved their capability to replace existing techniques for monitoring of linear strain, temporary or permanent none-uniform strain and load, temperature, vibrations, bending, or complex strain-temperature, vibrations-temperature influences, etc. Such sensor architectures, called smart structures, use different sensing mechanisms, in one of which - fiber Bragg grating (FBG) - is applied as a sensitive element. Because of high sensitivity, absolute measurement ability, possibility to work reliable in adverse environment, such as electromagnetic fields, radiation, extreme temperature, and quick response time, FBGs are object of numerous research of leading laboratories worldwide. Some problems are still remaining in this field, although there have been some ways found to solve part of them. This paper discusses some aspects of different fixing mechanisms of FBG and provides evaluation and comparison of methods of FBG integration in sensor housing or in sensor architecture.

  7. Temperature-independent gas refractometer based on an S-taper fiber tailored fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Shao, Zhihua; Qiao, Xueguang; Bao, Weijia; Rong, Qiangzhou

    2016-09-01

    A fiber Bragg grating (FBG)-based gas refractometer is proposed and demonstrated experimentally. The configuration consists of a short section of S-type taper incorporated in the upstream of a FBG. The S-taper is capable to couple the core mode to cladding modes into the downstream single mode fiber (SMF), and the low-order cladding modes can be reflected back to the fiber core via the FBG. Because of the recoupling efficiency depending on surrounding refractive index (SRI), the reflection power of the device presents high response to gas RI change with the sensitivity of 172.7 dB/RIU. This power-referenced RI measurement and wavelength-referenced temperature measurement have been achieved via selective cladding modes monitoring.

  8. Fiber Bragg Gratings, IT techniques and strain gauge validation for strain calculation on aged metal specimens.

    PubMed

    Montero, Ander; de Ocariz, Idurre Saez; Lopez, Ion; Venegas, Pablo; Gomez, Javier; Zubia, Joseba

    2011-01-01

    This paper studies the feasibility of calculating strains in aged F114 steel specimens with Fiber Bragg Grating (FBG) sensors and infrared thermography (IT) techniques. Two specimens have been conditioned under extreme temperature and relative humidity conditions making comparative tests of stress before and after aging using different adhesives. Moreover, a comparison has been made with IT techniques and conventional methods for calculating stresses in F114 steel. Implementation of Structural Health Monitoring techniques on real aircraft during their life cycle requires a study of the behaviour of FBG sensors and their wiring under real conditions, before using them for a long time. To simulate aging, specimens were stored in a climate chamber at 70 °C and 90% RH for 60 days. This study is framed within the Structural Health Monitoring (SHM) and Non Destructuve Evaluation (NDE) research lines, integrated into the avionics area maintained by the Aeronautical Technologies Centre (CTA) and the University of the Basque Country (UPV/EHU).

  9. Waveform reconstruction for an ultrasonic fiber Bragg grating sensor demodulated by an erbium fiber laser.

    PubMed

    Wu, Qi; Okabe, Yoji

    2015-02-01

    Fiber Bragg grating (FBG) demodulated by an erbium fiber laser (EFL) has been used for ultrasonic detection recently. However, due to the inherent relaxation oscillation (RO) of the EFL, the detected ultrasonic signals have large deformations, especially in the low-frequency range. We proposed a novel data processing method to reconstruct an actual ultrasonic waveform. The noise spectrum was smoothed first; the actual ultrasonic spectrum was then obtained by deconvolution in order to mitigate the influence of the RO of the EFL. We proved by experiment that this waveform reconstruction method has high precision, and demonstrated that the FBG sensor demodulated by the EFL will have large practical applications in nondestructive testing. PMID:25967776

  10. Thermal Characterization of a Simulated Fission Engine via Distributed Fiber Bragg Gratings

    SciTech Connect

    Duncan, Roger G.; Fielder, Robert S.; Seeley, Ryan J.; Kozikowski, Carrie L.; Raum, Matthew T.

    2005-02-06

    We report the use of distributed fiber Bragg gratings to monitor thermal conditions within a simulated nuclear reactor core located at the Early Flight Fission Test Facility of the NASA Marshall Space Flight Center. Distributed fiber-optic temperature measurements promise to add significant capability and advance the state-of-the-art in high-temperature sensing. For the work reported herein, seven probes were constructed with ten sensors each for a total of 70 sensor locations throughout the core. These discrete temperature sensors were monitored over a nine hour period while the test article was heated to over 700 deg. C and cooled to ambient through two operational cycles. The sensor density available permits a significantly elevated understanding of thermal effects within the simulated reactor. Fiber-optic sensor performance is shown to compare very favorably with co-located thermocouples where such co-location was feasible.

  11. Acoustic Emission Measurement with Fiber Bragg Gratings for Structure Health Monitoring

    NASA Technical Reports Server (NTRS)

    Banks, Curtis E.; Walker, James L.; Russell, Sam; Roth, Don; Mabry, Nehemiah; Wilson, Melissa

    2010-01-01

    Structural Health monitoring (SHM) is a way of detecting and assessing damage to large scale structures. Sensors used in SHM for aerospace structures provide real time data on new and propagating damage. One type of sensor that is typically used is an acoustic emission (AE) sensor that detects the acoustic emissions given off from a material cracking or breaking. The use of fiber Bragg grating (FBG) sensors to provide acoustic emission data for damage detection is studied. In this research, FBG sensors are used to detect acoustic emissions of a material during a tensile test. FBG sensors were placed as a strain sensor (oriented parallel to applied force) and as an AE sensor (oriented perpendicular to applied force). A traditional AE transducer was used to collect AE data to compare with the FBG data. Preliminary results show that AE with FBGs can be a viable alternative to traditional AE sensors.

  12. High Purcell factor in fiber Bragg gratings utilizing the fundamental slow-light mode.

    PubMed

    Skolianos, George; Arora, Arushi; Bernier, Martin; Digonnet, Michel J F

    2015-08-01

    We demonstrate through numerical simulations that the slow-light resonances that exist in strong, apodized fiber Bragg gratings (FBGs) fabricated with femtosecond pulses in deuterium-loaded fibers can exhibit very large intensity enhancements and Purcell factors with the proper optimization of their length. This potential is illustrated with two saturated FBGs that are less than 5 mm long and have been annealed to reduce their internal loss. The first one exhibits the largest measured Purcell factor in an all-fiber device (38.7), and the second one exhibits the largest intensity enhancement (1525). These devices are anticipated to have significant applications in quantum-dot lasers, nonlinear fiber devices, and cavity quantum-electrodynamics experiments. PMID:26258327

  13. Analytical description of 3D optical pulse diffraction by a phase-shifted Bragg grating.

    PubMed

    Golovastikov, Nikita V; Bykov, Dmitry A; Doskolovich, Leonid L; Soifer, Victor A

    2016-08-22

    Diffraction of a three-dimensional (3D) spatiotemporal optical pulse by a phase-shifted Bragg grating (PSBG) is considered. The pulse diffraction is described in terms of signal transmission through a linear system with a transfer function determined by the reflection or transmission coefficient of the PSBG. Resonant approximations of the reflection and transmission coefficients of the PSBG as functions of the angular frequency and the in-plane component of the wave vector are obtained. Using these approximations, a hyperbolic partial differential equation (Klein-Gordon equation) describing a general class of transformations of the incident 3D pulse envelope is derived. A solution to this equation is found in the form of a convolution integral. The presented rigorous simulation results fully confirm the proposed theoretical description. The obtained results may find application in the design of new devices for spatiotemporal pulse shaping and for optical information processing and analog optical computing. PMID:27557167

  14. Silicon-based on-chip electrically tunable sidewall Bragg grating Fabry-Perot filter.

    PubMed

    Zhang, Weifeng; Ehteshami, Nasrin; Liu, Weilin; Yao, Jianping

    2015-07-01

    We report the design, fabrication, and testing of a silicon-based on-chip electrically tunable sidewall Bragg grating Fabry-Perot filter. Spectral measurement shows that the filter has a narrow notch in reflection of approximately 46 pm, a Q-factor of 33,500, and an extinction ratio of 16.4 dB. DC measurement shows that the average central wavelength shift rates with forward and reverse bias are -1.15  nm/V and 4.2  pm/V, respectively. Due to strong light confinement in the Fabry-Perot cavity, the electro-optic frequency response shows that the filter has a 3-dB modulation bandwidth of ∼5.6  GHz. The performance of using the filter to perform modulation of a 3.5  Gb/s2(7)-1 nonreturn-to-zero pseudorandom binary sequence is evaluated.

  15. Advanced Interrogation of Fiber-Optic Bragg Grating and Fabry-Perot Sensors with KLT Analysis.

    PubMed

    Tosi, Daniele

    2015-10-29

    The Karhunen-Loeve Transform (KLT) is applied to accurate detection of optical fiber sensors in the spectral domain. By processing an optical spectrum, although coarsely sampled, through the KLT, and subsequently processing the obtained eigenvalues, it is possible to decode a plurality of optical sensor results. The KLT returns higher accuracy than other demodulation techniques, despite coarse sampling, and exhibits higher resilience to noise. Three case studies of KLT-based processing are presented, representing most of the current challenges in optical fiber sensing: (1) demodulation of individual sensors, such as Fiber Bragg Gratings (FBGs) and Fabry-Perot Interferometers (FPIs); (2) demodulation of dual (FBG/FPI) sensors; (3) application of reverse KLT to isolate different sensors operating on the same spectrum. A simulative outline is provided to demonstrate the KLT operation and estimate performance; a brief experimental section is also provided to validate accurate FBG and FPI decoding.

  16. Determination of Terfenol-D magnetostriction characteristics for sensor application using fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    de Morais Sousa, Kleiton; Zandonay, Ricardo; Vagner da Silva, Erlon; Martelli, Cicero; Cardozo da Silva, Jean Carlos

    2014-08-01

    Electric current sensor based on magnetostriction phenomenon has been reported in several papers. In common these previous papers used a fiber Bragg grating (FBG) to determine the strain of the magnetostrictive material. However, magnetostriction sensors present few disadvantages often neglected, such as the temperature dependence of magnetostriction. In this paper a Terfenol-D rod (a giant magnetostrictive material-GMM) is used for tests. For simultaneous measurement of temperature and strain two multiplexed FBGs are used. The first test presents unipolar characteristics of Terfenol-D magnetostriction. Other test determines the Terfenol-D response for different temperatures. The Terfenol-D sensitivity increase when the temperature increases, however the saturation of the material occurs in small field values. The characteristics presented in this paper must be taken into account in the development of magnetostrictive sensors and its limitations.

  17. Sensitivity Distribution Properties of a Phase-Shifted Fiber Bragg Grating Sensor to Ultrasonic Waves

    PubMed Central

    Wu, Qi; Okabe, Yoji; Saito, Kazuya; Yu, Fengming

    2014-01-01

    In this research, the sensitivity distribution properties of a phase-shifted fiber Bragg grating (PS-FBG) to ultrasonic waves were investigated employing the surface attachment method. A careful consideration was taken and examined by experimental results to explain that the distances and angles between the sensor and ultrasonic source influence not only the amplitudes, but also the initial phases, waveforms, and spectra of detected signals. Furthermore, factors, including the attachment method and the material's geometric dimensions, were also discussed. Although these results were obtained based on PS-FBG, they are also applicable to a normal FBG sensor or even an optical fiber sensor, due to the identical physical changes induced by ultrasonic waves in all three. Thus, these results are useful for applications of optical fiber sensors in non-destructive testing and structural health monitoring. PMID:24412903

  18. Fiber optic sensors for health monitoring of morphing airframes: I. Bragg grating strain and temperature sensor

    NASA Astrophysics Data System (ADS)

    Wood, Karen; Brown, Timothy; Rogowski, Robert; Jensen, Brian

    2000-04-01

    Fiber optic sensors are being developed for health monitoring of future aircraft. Aircraft health monitoring involves the use of strain, temperature, vibration and chemical sensors to infer integrity of the aircraft structure. Part 1 of this two part series describes sensors that will measure load and temperature signatures of these structures. In some cases a single fiber may be used for measuring these parameters. Part 2 will describe techniques for using optical fibers to monitor composite cure in real time during manufacture and to monitor in-service integrity of composite structures using a single fiber optic sensor capable of measuring multiple chemical and physical parameters. The facilities for fabricating optical fiber and associated sensors and the methods of demodulating Bragg gratings for strain measurement will be described.

  19. 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.

  20. Fiber optic liquid level monitoring system using microstructured polymer fiber Bragg grating array sensors: performance analysis

    NASA Astrophysics Data System (ADS)

    Marques, C. A. F.; Pospori, A.; Sáez-Rodríguez, D.; Nielsen, K.; Bang, O.; Webb, D. J.

    2015-09-01

    A highly sensitive liquid level monitoring system based on microstructured polymer optical fiber Bragg grating (mPOFBG) array sensors is reported for the first time. The configuration is based on five mPOFBGs inscribed in the same fiber in the 850 nm spectral region, showing the potential to interrogate liquid level by measuring the strain induced in each mPOFBG embedded in a silicone rubber (SR) diaphragm, which deforms due to hydrostatic pressure variations. The sensor exhibits a highly linear response over the sensing range, a good repeatability, and a high resolution. The sensitivity of the sensor is found to be 98 pm/cm of water, enhanced by more than a factor of 9 when compared to an equivalent sensor based on a silica fiber around 1550 nm. The temperature sensitivity is studied and a multi-sensor arrangement proposed, which has the potential to provide level readings independent of temperature and the liquid density.

  1. Note: A concrete erosion sensor based on a chirped fibre optic Bragg grating.

    PubMed

    Kanopoulos, Patrick; Xia, Kaiwen; Gu, Xijia; Amirchoupani, Ardavan; Yao, Wei

    2015-12-01

    Erosion of concrete surfaces in major civil structures is a common problem, which in certain circumstances can undermine the structural and operational integrities of the structure. The manual monitoring of the erosion process can be difficult and dangerous under certain circumstances (such as within hydrotunnels and spillways of dams). This paper describes a concrete erosion sensor based on a chirped fibre Bragg grating (FBG) which is able to monitor the extent of concrete erosion at a single point to sub-millimetre accuracy. The chirped FBG length embedded below the concrete surface decreases as a result of concrete erosion and consequently the reflected light spectrum bandwidth narrows. A simple procedure is presented to determine the extent of erosion, and this procedure is applied to an experimental demonstration of the sensing device.

  2. Note: Dissolved hydrogen detection in power transformer oil based on chemically etched fiber Bragg grating.

    PubMed

    Jiang, Jun; Ma, Guo-ming; Song, Hong-tu; Zhou, Hong-yang; Li, Cheng-rong; Luo, Ying-ting; Wang, Hong-bin

    2015-10-01

    A fiber Bragg grating (FBG) sensor based on chemically etched cladding to detect dissolved hydrogen is proposed and studied in this paper. Low hydrogen concentration tests have been carried out in mixed gases and transformer oil to investigate the repeatability and sensitivity. Moreover, to estimate the influence of etched cladding thickness, a physical model of FBG-based hydrogen sensor is analyzed. Experimental results prove that thin cladding chemically etched by HF acid solution improves the response to hydrogen detection in oil effectively. At last, the sensitivity of FBG sensor chemically etched 16 μm could be as high as 0.060 pm/(μl/l), increased by more than 30% in comparison to un-etched FBG.

  3. Advanced Interrogation of Fiber-Optic Bragg Grating and Fabry-Perot Sensors with KLT Analysis

    PubMed Central

    Tosi, Daniele

    2015-01-01

    The Karhunen-Loeve Transform (KLT) is applied to accurate detection of optical fiber sensors in the spectral domain. By processing an optical spectrum, although coarsely sampled, through the KLT, and subsequently processing the obtained eigenvalues, it is possible to decode a plurality of optical sensor results. The KLT returns higher accuracy than other demodulation techniques, despite coarse sampling, and exhibits higher resilience to noise. Three case studies of KLT-based processing are presented, representing most of the current challenges in optical fiber sensing: (1) demodulation of individual sensors, such as Fiber Bragg Gratings (FBGs) and Fabry-Perot Interferometers (FPIs); (2) demodulation of dual (FBG/FPI) sensors; (3) application of reverse KLT to isolate different sensors operating on the same spectrum. A simulative outline is provided to demonstrate the KLT operation and estimate performance; a brief experimental section is also provided to validate accurate FBG and FPI decoding. PMID:26528975

  4. Fiber Bragg grating tether used to measure drag forces in neutral buoyancy flow tank tests.

    PubMed

    Wade, S A; Jolley, W; Fouras, A

    2008-06-01

    The drag exerted on neutrally buoyant tethered spheres in a flow tank was measured as a function of flow rate. A unique solution to the problem was achieved using an optical fiber including a Bragg grating sensor as part of the tether. Measurements of the strain on the tether taken at flow rates between 0.14 and 0.33 m/s, were used to determine drag forces for spheres with diameters ranging from 40 to 100 mm. Vortex-induced vibration was observed in tests performed at Reynolds numbers from 5 x 10(3) to 4.5 x 10(4). The drag coefficients for these tests were found to range from 0.51 to 0.77.

  5. Fabrication of fiber Bragg gratings in embedded-core hollow optical fiber

    NASA Astrophysics Data System (ADS)

    Mao, Guopei; Sun, Bo; Yuan, Tingting; Zhong, Xing; Shi, Jinhui; Guan, Chunying; Yuan, Libo

    2015-07-01

    A novel Bragg fiber grating (FBG) in an embedded-core hollow optical fiber (ECHOF) has been proposed and experimentally demonstrated. The high-quality FBG fabricated with phase-mask technique by using 248 nm ultraviolet laser, has a resonant wavelength of ~943.1 nm and a dip of ~24.2 dB. Subsequently, the dependences of the resonant peak on the temperature and the axial strain were studied. Experimental results show that the temperature and axial stain sensitivity are 6.5 pm/°С and 1.1 pm/μɛ, respectively. In addition, a 0.03 nm shift of the transmission dip can be obtained when the polarization state changes from X polarization to Y polarization.

  6. Femtosecond laser inscribed Bragg gratings in gold-coated fiber for space application

    NASA Astrophysics Data System (ADS)

    Wang, Qiaoni; Yang, Yuanhong; He, Jun; Wang, Yiping

    2015-09-01

    We reported a Bragg grating inscribed in gold-coated fiber (FBG) by NIR femtosecond laser (fs) for space application. Gold coating can shield the FBG from ultraviolet radiation and oxygen atom erosion. Cryogenic test, high temperature test, and gamma irradiation test were carried out. The reflectivity of the H2-free FBG remained stable at +/- 120 °C for 100 h or with 50.4 krad γ irradiation, and the central wavelength shifted within 5 pm and 1.6 pm respectively. Regeneration of the fs-FBG was observed in case the FBG was annealed at 800 °C for 5 h, and the remained 5% in reflectivity after 19 h. Such fs-FBGs inscribed in gold-coated fiber could be employed as high performance fiber sensors for space application.

  7. Transmission comb of a distributed Bragg reflector with two surface dielectric gratings

    PubMed Central

    Zhao, Xiaobo; Zhang, Yongyou; Zhang, Qingyun; Zou, Bingsuo; Schwingenschlogl, Udo

    2016-01-01

    The transmission behaviour of a distributed Bragg reector (DBR) with surface dielectric gratings on top and bottom is studied. The transmission shows a comb-like spectrum in the DBR band gap, which is explained in the Fano picture. The number density of the transmission peaks increases with increasing number of cells of the DBR, while the ratio of the average full width at half maximum to the corresponding average free spectral range, being only few percent for both transversal electric and magnetic waves, is almost invariant. The transmission peaks can be narrower than 0.1 nm and are fully separated from each other in certain wavebands. We further prove that the transmission combs are robust against randomness in the heights of the DBR layers. Therefore, the proposed structure is a candidate for an ultra-narrow-band multichannel filter or polarizer. PMID:26893069

  8. Distributed OTDR-interferometric sensing network with identical ultra-weak fiber Bragg gratings.

    PubMed

    Wang, Chen; Shang, Ying; Liu, Xiao-Hui; Wang, Chang; Yu, Hai-Hu; Jiang, De-Sheng; Peng, Gang-Ding

    2015-11-01

    We demonstrate a distributed sensing network with 500 identical ultra-weak fiber Bragg gratings (uwFBGs) in an equal separation of 2m using balanced Michelson interferometer of the phase sensitive optical time domain reflectometry (φ-OTDR) for acoustic measurement. Phase, amplitude, frequency response and location information can be directly obtained at the same time by using the passive 3 × 3 coupler demodulation. Lab experiments on detecting sound waves in water tank are carried out. The results show that this system can well demodulate distributed acoustic signal with the pressure detection limit of 0.122Pa and achieve an acoustic phase sensitivity of around -158dB (re rad/μPa) with a relatively flat frequency response between 450Hz to 600Hz.

  9. High Purcell factor in fiber Bragg gratings utilizing the fundamental slow-light mode.

    PubMed

    Skolianos, George; Arora, Arushi; Bernier, Martin; Digonnet, Michel J F

    2015-08-01

    We demonstrate through numerical simulations that the slow-light resonances that exist in strong, apodized fiber Bragg gratings (FBGs) fabricated with femtosecond pulses in deuterium-loaded fibers can exhibit very large intensity enhancements and Purcell factors with the proper optimization of their length. This potential is illustrated with two saturated FBGs that are less than 5 mm long and have been annealed to reduce their internal loss. The first one exhibits the largest measured Purcell factor in an all-fiber device (38.7), and the second one exhibits the largest intensity enhancement (1525). These devices are anticipated to have significant applications in quantum-dot lasers, nonlinear fiber devices, and cavity quantum-electrodynamics experiments.

  10. Cognitive fiber Bragg grating sensors system based on fiber Fabry-Perot tunable filter technology

    NASA Astrophysics Data System (ADS)

    Zhang, Hongtao; Wang, Pengfei; Zou, Jilin; Xie, Jing; Cui, Hong-Liang

    2011-05-01

    The wavelength demodulation based on a Fiber Fabry-Pérot Tunable Filter (FFP-TF) is a common method for multiplexing Fiber Bragg Grating (FBG) sensors. But this method cannot be used to detect high frequency signals due to the limitation by the highest scanning rate that the FFP-TF can achieve. To overcome this disadvantage, in this paper we present a scheme of cognitive sensors network based on FFP-TF technology. By perceiving the sensing environment, system can automatically switch into monitoring signals in two modes to obtain better measurement results: multi measurement points, low frequency (<1 KHz) signal, and few measurement points but high frequency (~50 KHz) signals. This cognitive sensors network can be realized in current technology and satisfy current most industrial requirements.

  11. Demodulation of a fiber Bragg grating strain sensor by a multiwavelength fiber laser

    NASA Astrophysics Data System (ADS)

    Cong, Shan; Sun, Yunxu; Zhao, Yuxi; Pan, Lifeng

    2012-04-01

    A fiber Bragg grating (FBG) sensors system utilizing a multi-wavelength erbium-doped fiber lasers (EDFL) with frequency shifter is proposed. The system is one fiber laser cavity with two FBG sensors as its filters. One is for strain sensing, and the other one is for temperature compensation. A frequency shifter is used to suppress the mode competition to lase two wavelengths that correspond with FBGs. The wavelength shift of the EDFL represents the sensing quantity, which is demodulated by Fiber Fabry-Perot (FFP) filter. The sensor's response to strain is measured by experiment. Because of exploiting the dual-wavelength fiber laser with a frequency shifter forming the feedback as the light source, many advantages of this system are achieved, especially high signal-to-noise ratio, high detected power, and low power consuming comparing with conventional FBG sensor system utilizing broadband light as the light source. What's more, this structure is also easy to combine with FBG array.

  12. Demodulation of a fiber Bragg grating strain sensor by a multiwavelength fiber laser

    NASA Astrophysics Data System (ADS)

    Cong, Shan; Sun, Yunxu; Zhao, Yuxi; Pan, Lifeng

    2011-11-01

    A fiber Bragg grating (FBG) sensors system utilizing a multi-wavelength erbium-doped fiber lasers (EDFL) with frequency shifter is proposed. The system is one fiber laser cavity with two FBG sensors as its filters. One is for strain sensing, and the other one is for temperature compensation. A frequency shifter is used to suppress the mode competition to lase two wavelengths that correspond with FBGs. The wavelength shift of the EDFL represents the sensing quantity, which is demodulated by Fiber Fabry-Perot (FFP) filter. The sensor's response to strain is measured by experiment. Because of exploiting the dual-wavelength fiber laser with a frequency shifter forming the feedback as the light source, many advantages of this system are achieved, especially high signal-to-noise ratio, high detected power, and low power consuming comparing with conventional FBG sensor system utilizing broadband light as the light source. What's more, this structure is also easy to combine with FBG array.

  13. Stabilized interrogation and multiplexing techniques for fibre Bragg grating vibration sensors

    NASA Astrophysics Data System (ADS)

    Bang, Hyung-Joon; Jun, Seung-Moon; Kim, Chun-Gon

    2005-03-01

    We demonstrated a simple interrogation system for multiplexed fibre Bragg grating (FBG) sensors in a high-frequency range. A tunable fibre Fabry-Perot (FFP) filter with narrow free spectral range (FSR) was used to simplify the multiplexing demodulator for FBG vibration sensors. A stabilization-controlling unit was also developed for the maintenance of maximum sensitivity of the sensors. In order to verify the performance of the stabilization control unit, we measured the sensitivity of the FBG sensor by changing environmental temperature, and the system showed an average sensitivity of 2.5 nɛRMS Hz-1/2 for a stabilization-controlled case. Finally, multi-point vibration tests using in-line FBG sensors were conducted to validate the multiplexing performance of the FBG system.

  14. Real-time transverse force sensing using fiber Bragg grating through direct Stokes parameters measurement.

    PubMed

    Su, Yang; Zhu, Yong; Zhang, Baofu; Zhou, Hua

    2015-12-14

    Characteristics of a fiber Bragg grating (FBG) transverse force sensor based on Stokes parameters are presented. Real-time force measurement is achieved through direct measurement of the Stokes parameters at single wavelength. A proportional relationship and linear fit are found between Stokes parameters and applied force. The sensitivity and dynamic range dependence on the state of polarization (SOP) of the incident light is investigated theoretically and experimentally. A maximum sensitivity of 0.037/N is experimentally achieved and it can be improved further by adjusting the incident SOP. This design significantly reduces system complexity and improves data processing speed, which has great practical value in real-time FBG sensing applications. PMID:26699020

  15. Note: A concrete erosion sensor based on a chirped fibre optic Bragg grating.

    PubMed

    Kanopoulos, Patrick; Xia, Kaiwen; Gu, Xijia; Amirchoupani, Ardavan; Yao, Wei

    2015-12-01

    Erosion of concrete surfaces in major civil structures is a common problem, which in certain circumstances can undermine the structural and operational integrities of the structure. The manual monitoring of the erosion process can be difficult and dangerous under certain circumstances (such as within hydrotunnels and spillways of dams). This paper describes a concrete erosion sensor based on a chirped fibre Bragg grating (FBG) which is able to monitor the extent of concrete erosion at a single point to sub-millimetre accuracy. The chirped FBG length embedded below the concrete surface decreases as a result of concrete erosion and consequently the reflected light spectrum bandwidth narrows. A simple procedure is presented to determine the extent of erosion, and this procedure is applied to an experimental demonstration of the sensing device. PMID:26724088

  16. Realization of nano static strain sensing with fiber Bragg gratings interrogated by narrow linewidth tunable lasers.

    PubMed

    Liu, Qingwen; Tokunaga, Tomochika; He, Zuyuan

    2011-10-10

    Aiming at realizing a static strain sensor of nano-strain resolution, which is required in most geophysical applications, this paper presents a thorough analysis on the strain resolution of a fiber Bragg grating (FBG) static strain sensor interrogated with a narrow linewidth tunable laser. The main noise sources of the sensor are discussed, and the strain resolution is deduced with a cross-correlation algorithm. The theoretical prediction agrees well with our experimental result, and the analysis is further validated by numerical simulations. Based on the analysis, the paper provides the guidelines for optimizing this type of sensor to realize ultra-high resolution. It is shown that with properly designed FBGs and interrogation systems, nano static strain resolution can be realized, as we recently demonstrated in experiment.

  17. Hydrogel-coated fiber Bragg grating sensor for pH monitoring

    NASA Astrophysics Data System (ADS)

    Pabbisetti, Vayu Nandana Kishore; Madhuvarasu, Sai Shankar

    2016-06-01

    We present a fiber-optic wavelength-modulated sensor for pH applications. Fiber Bragg grating (FBG) is functionalized with a stimulus-responsive hydrogel that induces a strain on FBG due to mechanical expansion of the gel in response to ambient pH changes. The gel is synthesized from the blends of poly (vinyl alcohol)/poly (acrylic acid). The induced strain results in a shift of FBG reflected peak that is monitored by an interrogator. The sensor system shows good linearity in the acidic pH range of 3 to 7 with a sensitivity of 12.16 pm/pH. In addition, it shows good repeatability and oscillator behavior, which proves it to be fit for pH sensing applications.

  18. Pulse transit time differential measurement by fiber Bragg grating pulse recorder

    NASA Astrophysics Data System (ADS)

    Umesh, Sharath; Padma, Srivani; Ambastha, Shikha; Kalegowda, Anand; Asokan, Sundarrajan

    2015-05-01

    The present study reports a noninvasive technique for the measurement of the pulse transit time differential (PTTD) from the pulse pressure waveforms obtained at the carotid artery and radial artery using fiber Bragg grating pulse recorders (FBGPR). PTTD is defined as the time difference between the arrivals of a pulse pressure waveform at the carotid and radial arterial sites. The PTTD is investigated as an indicator of variation in the systolic blood pressure. The results are validated against blood pressure variation obtained from a Mindray Patient Monitor. Furthermore, the pulse wave velocity computed from the obtained PTTD is compared with the pulse wave velocity obtained from the color Doppler ultrasound system and is found to be in good agreement. The major advantage of the PTTD measurement via FBGPRs is that the data acquisition system employed can simultaneously acquire pulse pressure waveforms from both FBGPRs placed at carotid and radial arterial sites with a single time scale, which eliminates time synchronization complexity.

  19. Fibre Bragg grating sensors for in-situ measurement of resin pressure in curing composites

    NASA Astrophysics Data System (ADS)

    Ganapathi, A. S.; Maheshwari, Muneesh; Joshi, Sunil C.; Chen, Zhong; Asundi, Anand; Tjin, Swee Chuan

    2015-03-01

    A fibre optic sensor was developed for in-situ pressure measurement based on the principle of differential pressure in liquids. This sensor system is very simple and consists of fibre Bragg grating (FBG) done on a fibre with core diameter of 9 μm. A calibration study was carried out with a water column and the pressure sensitivity was found to be 1.636 × 10-2MPa-1. The results show that response of FBG to the rise of water level is linear and agrees well with the theoretical results. The reliability of the sensors is confirmed by repeating the measurements for three times. The sensor is useful in applications that involve in-situ resin pressure measurement in manufacturing of laminated composite materials.

  20. Interrogation of fibre Bragg gratings through a fibre optic rotary joint on a geotechnical centrifuge

    NASA Astrophysics Data System (ADS)

    Correia, Ricardo; James, Stephen W.; Marshall, Alec; Heron, Charles; Korposh, Sergiy

    2016-05-01

    The monitoring of an array of fibre Bragg gratings (FBGs) strain sensors was performed through a single channel, single mode fibre optic rotary joint (FORJ) mounted on a geotechnical centrifuge. The array of three FBGs was attached to an aluminum plate that was anchored at the ends and placed on the model platform of the centrifuge. Acceleration forces of up to 50g were applied and the reflection signal of the monitored FBGs recorded dynamically using a 2.5kHz FBG interrogator placed outside the centrifuge. The use of a FORJ allowed the monitoring of the FBGs without submitting the FBG interrogator to the high g-forces experienced in the centrifuge.

  1. A novel fabrication of fiber Bragg grating in hollow-core fiber with HPDLCs

    NASA Astrophysics Data System (ADS)

    Hsu, Chih-Hao; Choi, Wing-Kit; Wang, Lon A.

    2015-02-01

    An electrically controllable fiber Bragg grating (FBG) for working in the communication band is demonstrated by utilizing holographic polymer-dispersed liquid crystal (HPDLCs). PDLC is infiltrated in hollow-core fibers which are about 2μm and 5μm by means of capillarity. For the purpose of periodically separating polymer and liquid crystal to form an FBG, a two-beam interference system based on an argon laser (wavelength: 364nm) is used. To reduce coupling loss, we directly connect single-mode fibers (SMFs) to input and output ports. A maximum transmission loss dip of approximately 5-dB band rejection is obtained. After the cladding diameter is etched by buffered oxide etchant (BOE) solution to 12μm and a 150V external voltage is applied, a dip shift by ~ 15nm is measured

  2. Holographic polymer-dispersed liquid crystal Bragg grating integrated inside a solid core photonic crystal fiber.

    PubMed

    Zito, Gianluigi; Pissadakis, Stavros

    2013-09-01

    A polymer/liquid crystal-based fiber Bragg grating (PLC-FBG) is fabricated with visible two-beam holography by photo-induced modulation of a prepolymer/liquid crystal solution infiltrated into the hollow channels of a solid core photonic crystal fiber (PCF). The fabrication process and effects related to the photonic bandgap guidance into the infiltrated PCF, and characterization of the PLC-FBG, are discussed. Experimental data presented here demonstrate that the liquid crystal inclusions of the PLC-FBG lead to high thermal and bending sensitivities. The microscopic behavior of the polymer/liquid crystal phase separation inside the PCF capillaries is examined using scanning electron microscopy, and is discussed further. PMID:23988927

  3. Advanced Interrogation of Fiber-Optic Bragg Grating and Fabry-Perot Sensors with KLT Analysis.

    PubMed

    Tosi, Daniele

    2015-01-01

    The Karhunen-Loeve Transform (KLT) is applied to accurate detection of optical fiber sensors in the spectral domain. By processing an optical spectrum, although coarsely sampled, through the KLT, and subsequently processing the obtained eigenvalues, it is possible to decode a plurality of optical sensor results. The KLT returns higher accuracy than other demodulation techniques, despite coarse sampling, and exhibits higher resilience to noise. Three case studies of KLT-based processing are presented, representing most of the current challenges in optical fiber sensing: (1) demodulation of individual sensors, such as Fiber Bragg Gratings (FBGs) and Fabry-Perot Interferometers (FPIs); (2) demodulation of dual (FBG/FPI) sensors; (3) application of reverse KLT to isolate different sensors operating on the same spectrum. A simulative outline is provided to demonstrate the KLT operation and estimate performance; a brief experimental section is also provided to validate accurate FBG and FPI decoding. PMID:26528975

  4. A Fiber Bragg Grating Temperature Sensor for 2-400 K

    SciTech Connect

    Zaynetdinov, Madrakhim; See, Erich M.; Geist, Brian; Ciovati, Gianluigi; Robinson, Hans D.; Kochergin, Vladimir

    2015-03-01

    We demonstrate fiber optic, multiplexible temperature sensing using a fiber Bragg grating (FBG) with an operational range of 2-400 K, and a temperature resolution better than 10 mK for temperatures < 12 K. This represents a significant reduction in the lowest usable temperature as well as a significant increase in sensitivity at cryogenic temperatures compared with previously reported multiplexible solutions. This is accomplished by mounting the section of the fiber with a FBG on a polytetrafluoroethylene coupon, which has a non-negligible coefficient of thermal expansion down to < 4 K. The sensors exhibit a good stability over multiple temperature cycles and acceptable sensor-to-sensor repeatability. Possible applications for this sensor include distributed temperature sensing across superconducting elements and cryogenic temperature measurements in environments where electrical measurements are impractical or unsafe.

  5. Dynamic assessment of women pelvic floor function by using a fiber Bragg grating sensor system

    NASA Astrophysics Data System (ADS)

    Ferreira, Luis A.; Araújo, Francisco M.; Mascarenhas, Teresa; Natal Jorge, Renato M.; Fernandes, António A.

    2006-02-01

    We present a novel sensing system consisting of an intravaginal probe and an optoelectronic measurement unit, which allows an easy, comfortable and quantitative dynamic evaluation of women pelvic floor muscle strength. The sensing probe is based on a silicone cylinder that transduces radial muscle pressure into axial load applied to a fiber Bragg grating strain sensor. The performance of a first sensor probe prototype with temperature referentiation and of the autonomous, portable optoelectronic measurement unit with data logging capabilities and graphical user interface is disclosed. The presented results refer to an ongoing collaboration work between researchers from the Medical, Optoelectronics and Mechanical areas, directed to the development of equipment that can assist in medical practice and help in the research of primary mechanisms responsible for several pelvic floor disorders, in particular urogenital prolapses.

  6. All-Optical Micro Motors Based on Moving Gratings in Photosensitive Media

    NASA Technical Reports Server (NTRS)

    Curley, M.; Sarkisov, S. S.; Fields, A.; Smith, C.; Kukhtarev, N.; Kulishov, M. B.; Adamovsky, Grigory

    2001-01-01

    An all-optical micromotor with a rotor driven by a traveling wave of surface deformation of a stator being in contact with the rotor is being studied. Instead of an ultrasonic wave produced by an electrically driven piezoelectric actuator as in ultrasonic motors, the wave is a result of a photo-induced surface deformation of a photosensitive material produced by an incident radiation. A thin piezoelectric polymer will deform more easily LiNbO3 or metal when irradiated with light. The type of photosensitive material studied are piezoelectric polymers with and without coatings for connecting electrodes. In order to be considered as a possible candidate for micromotors, the material should exhibit surface deformation produced by a laser beam of the order of 10 microns. This is compared to the deformations produced by static holographic gratings studied in photorefractive crystals of LiNbO3 using high vertical resolution surface profilometer Dektak 3 and surface interferometer WYKO. An experimental setup showing the oscillations has been developed. The setup uses a chopped beam from an Argon ion laser to produce the deformation while a probe beam is reflected by the thin film into a fiber which is then detected on an oscilloscope. A ramp voltage signal generator will drive the piezoelectric film in another experiment to determine the resonance of the film. A current is generated when light is incident upon the film and this current can be measured. The reverse process has already been demonstrated in other piezoelectric actuators. Changing voltage, polarity, and frequency of the signal can easily generate vibrations similar to those when light is incident on the film. This can be compared to the effects of laser interaction with light absorbing fluids such as solutions of 2,9,16,23-Tetrakis(phenylthio)-29H, 31 H-phthalocyanine in chlorobenzene in capillary tubes, The possibility of using a liquid with the piezoelectric film would be a novel idea for a micromotor since

  7. High Neutron Fluence Survivability Testing of Advanced Fiber Bragg Grating Sensors

    NASA Astrophysics Data System (ADS)

    Fielder, Robert S.; Klemer, Daniel; Stinson-Bagby, Kelly L.

    2004-02-01

    The motivation for the reported research was to support NASA space nuclear power initiatives through the development of advanced fiber optic sensors for space-based nuclear power applications. The purpose of the high-neutron fluence testing was to demonstrate the survivability of fiber Bragg grating (FBG) sensors in a fission reactor environment. 520 FBGs were installed in the Ford reactor at the University of Michigan. The reactor was operated for 1012 effective full power hours resulting in a maximum neutron fluence of approximately 5×1019 n/cm2, and a maximum gamma dose of 2×103 MGy gamma. This work is significant in that, to the knowledge of the authors, the exposure levels obtained are approximately 1000 times higher than for any previously published experiment. Four different fiber compositions were evaluated. An 87% survival rate was observed for fiber Bragg gratings located at the fuel centerline. Optical Frequency Domain Reflectometry (OFDR), originally developed at the NASA Langley Research Center, can be used to interrogate several thousand low-reflectivity FBG strain and/or temperature sensors along a single optical fiber. A key advantage of the OFDR sensor technology for space nuclear power is the extremely low mass of the sensor, which consists of only a silica fiber 125μm in diameter. The sensors produced using this technology will fill applications in nuclear power for current reactor plants, emerging Generation-IV reactors, and for space nuclear power. The reported research was conducted by Luna Innovations and was funded through a Small Business Innovative Research (SBIR) contract with the NASA Glenn Research Center.

  8. High Neutron Fluence Survivability Testing of Advanced Fiber Bragg Grating Sensors

    SciTech Connect

    Fielder, Robert S.; Klemer, Daniel; Stinson-Bagby, Kelly L.

    2004-02-04

    The motivation for the reported research was to support NASA space nuclear power initiatives through the development of advanced fiber optic sensors for space-based nuclear power applications. The purpose of the high-neutron fluence testing was to demonstrate the survivability of fiber Bragg grating (FBG) sensors in a fission reactor environment. 520 FBGs were installed in the Ford reactor at the University of Michigan. The reactor was operated for 1012 effective full power hours resulting in a maximum neutron fluence of approximately 5x1019 n/cm2, and a maximum gamma dose of 2x103 MGy gamma. This work is significant in that, to the knowledge of the authors, the exposure levels obtained are approximately 1000 times higher than for any previously published experiment. Four different fiber compositions were evaluated. An 87% survival rate was observed for fiber Bragg gratings located at the fuel centerline. Optical Frequency Domain Reflectometry (OFDR), originally developed at the NASA Langley Research Center, can be used to interrogate several thousand low-reflectivity FBG strain and/or temperature sensors along a single optical fiber. A key advantage of the OFDR sensor technology for space nuclear power is the extremely low mass of the sensor, which consists of only a silica fiber 125{mu}m in diameter. The sensors produced using this technology will fill applications in nuclear power for current reactor plants, emerging Generation-IV reactors, and for space nuclear power. The reported research was conducted by Luna Innovations and was funded through a Small Business Innovative Research (SBIR) contract with the NASA Glenn Research Center.

  9. The study of the thermal annealing of the Bragg gratings induced in the hydrogenated birefringent optical fiber with an elliptical stress cladding

    NASA Astrophysics Data System (ADS)

    Munko, A. S.; Varzhel', S. V.; Arkhipov, S. V.; Gribaev, A. I.; Konnov, K. A.; Belikin, M. N.

    2016-08-01

    In this work the comparative results on the dynamics of fiber Bragg gratings inscription in both the conventional and the subjected to hydrogenation birefringent optical fiber with elliptical stress cladding as well as in the same type of lightguide with the increased GeO2 concentration are presented. Also the research on the thermal impact on the fiber Bragg gratings written in the birefringent fiber with elliptical stress cladding has been carried out. The dependences of the fiber Bragg reflectance coefficient on the time of the thermal impact, obtained by annealing of the refractive index gratings, induced in the optical fibers with increased photorefractivity, are shown.

  10. Radiation tolerant fiber Bragg gratings for high temperature monitoring at MGy dose levels.

    PubMed

    Morana, A; Girard, S; Marin, E; Marcandella, C; Paillet, P; Périsse, J; Macé, J-R; Boukenter, A; Cannas, M; Ouerdane, Y

    2014-09-15

    We report a method for fabricating fiber Bragg gratings (FBG) resistant to very severe environments mixing high radiation doses (up to 3 MGy) and high temperatures (up to 230°C). Such FBGs have been written in two types of radiation resistant optical fibers (pure-silica and fluorine-doped cores) by exposures to a 800 nm femtosecond IR laser at power exceeding 500 mW and then subjected to a thermal annealing treatment of 15 min at 750°C. Under radiation, our study reveals that the radiation induced Bragg wavelength shift (BWS) at a 3 MGy dose is strongly reduced compared to responses of FBGs written with nonoptimized conditions. The BWS remains lower than 10 pm for temperatures of irradiation ranging from 25°C to 230°C without noticeable decrease of the FBG peak amplitude. For an applicative point of view, this radiation induced BWS corresponds to an additional error on the temperature measurements lower than 1.5°C, opening the way to the development of radiation-tolerant multi-point temperature sensors for nuclear industry. PMID:26466259

  11. Influence of Fiber Bragg Grating Spectrum Degradation on the Performance of Sensor Interrogation Algorithms

    PubMed Central

    Lamberti, Alfredo; Vanlanduit, Steve; De Pauw, Ben; Berghmans, Francis

    2014-01-01

    The working principle of fiber Bragg grating (FBG) sensors is mostly based on the tracking of the Bragg wavelength shift. To accomplish this task, different algorithms have been proposed, from conventional maximum and centroid detection algorithms to more recently-developed correlation-based techniques. Several studies regarding the performance of these algorithms have been conducted, but they did not take into account spectral distortions, which appear in many practical applications. This paper addresses this issue and analyzes the performance of four different wavelength tracking algorithms (maximum detection, centroid detection, cross-correlation and fast phase-correlation) when applied to distorted FBG spectra used for measuring dynamic loads. Both simulations and experiments are used for the analyses. The dynamic behavior of distorted FBG spectra is simulated using the transfer-matrix approach, and the amount of distortion of the spectra is quantified using dedicated distortion indices. The algorithms are compared in terms of achievable precision and accuracy. To corroborate the simulation results, experiments were conducted using three FBG sensors glued on a steel plate and subjected to a combination of transverse force and vibration loads. The analysis of the results showed that the fast phase-correlation algorithm guarantees the best combination of versatility, precision and accuracy. PMID:25521386

  12. Fiber Bragg gratings in heterogeneous multicore fiber for directional bending sensing

    NASA Astrophysics Data System (ADS)

    Zhang, Hailiang; Wu, Zhifang; Shum, Perry Ping; Wang, Ruoxu; Quyen Dinh, Xuan; Fu, Songnian; Tong, Weijun; Tang, Ming

    2016-08-01

    We present the fabrication of fiber Bragg gratings (FBGs) in a trench-assisted heterogeneous multicore fiber (MCF). Two obviously different Bragg reflection peaks are obtained due to the slight difference of refractive indices between the center core and the outer cores. To investigate the reflections of the two FBGs simultaneously, only a segment of multimode fiber is inserted between the lead-in single mode fiber and the MCF. The experimental results confirm that the curvature sensitivity of the FBG in the outer core is a sinusoidal function of the bending orientation angle. The maximum linear curvature sensitivity is about 0.128 nm/m‑1. The cross sensitivity to temperature or externally applied axial strain can be eliminated by discriminating the different responses of FBGs inscribed in outer cores and the center core. Thus this MCF with FBGs can be utilized as a directional bending sensor. Moreover, the proposed sensor offers several advantages, such as low cost and flexibility in fabrication.

  13. Engine test for wavelength-multiplexed fiber Bragg grating temperature sensor

    NASA Astrophysics Data System (ADS)

    Yu, Li; Wang, Dorothy Y.; Wang, Yunmiao; Collins, Christopher M.; Schneck, William C.; Bailey, Justin M.; O'Brien, Walter F.; Wang, Anbo

    2013-05-01

    A temperature sensor link based on wavelength-multiplexed fiber Bragg grating (FBG) was designed and fabricated for distributed temperature measurement in a jet engine nozzle under field conditions. Eight FBGs with different Bragg wavelengths ranging from 1520 nm to 1560 nm were fabricated along one single-mode fiber which was packaged inside a stainless steel tube. The reflected signal from the sensor link was simultaneously collected by an optical sensing interrogator and converted into temperature information. The steel tube was embedded in a steel flange assembly attached to a jet engine. Three engine cycles were performed from 55% (idle) to 80% of the engine's full power to test the sensor response under high temperature, vibration and strong exhaust flow conditions. Test results show good survivability of the sensor, and the temperature around the nozzle was measured up to 290 °C. The system has a temperature measurement range from 20 °C to 600 ° and the response time is less than 1 second.

  14. Study on the weighing system based on optical fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Wang, Xiaona; Yu, Qingxu; Li, Yefang

    2010-10-01

    The optical fiber sensor based on wavelength demodulation such as fiber Bragg grating(FBG), with merits of immunity to electromagnetic interference, low drift and high precision, has been widely used in many areas, such as structural health monitoring and smart materials, and the wavelength demodulation system was also studied widely. In the paper, a weighing system based on FBG was studied. The optical source is broadband Erbium-doped fiber ring laser with a spectral range of 1500~1600nm and optical power of 2mW; A Fabry-Perot Etalon with orientation precision of 1pm was adopted as real-time wavelength calibration for the swept laser; and multichannel high resolution simultaneous sampling card was used in the system to acquire sensing signals simultaneously, thus high-resolution and real-time calibration of sweep-wavelength can be achieved. The FBG was adhered to a cantilever beam and the Bragg wavelength was demodulated with the system. The weighing system was done after calibrated with standard weight. Experimental results show that the resolution of the weighing system is 0.5 g with a full scale of 2Kg.

  15. Sensitive detection of C-reactive protein using optical fiber Bragg gratings.

    PubMed

    Sridevi, S; Vasu, K S; Asokan, S; Sood, A K

    2015-03-15

    An accurate and highly sensitive sensor platform has been demonstrated for the detection of C-reactive protein (CRP) using optical fiber Bragg gratings (FBGs). The CRP detection has been carried out by monitoring the shift in Bragg wavelength (ΔλB) of an etched FBG (eFBG) coated with an anti-CRP antibody (aCRP)-graphene oxide (GO) complex. The complex is characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and atomic force microscopy. A limit of detection of 0.01mg/L has been achieved with a linear range of detection from 0.01mg/L to 100mg/L which includes clinical range of CRP. The eFBG sensor coated with only aCRP (without GO) show much less sensitivity than that of aCRP-GO complex coated eFBG. The eFBG sensors show high specificity to CRP even in the presence of other interfering factors such as urea, creatinine and glucose. The affinity constant of ∼1.1×10(10)M(-1) has been extracted from the data of normalized shift (ΔλB/λB) as a function of CRP concentration. PMID:25461166

  16. Fiber Bragg gratings in heterogeneous multicore fiber for directional bending sensing

    NASA Astrophysics Data System (ADS)

    Zhang, Hailiang; Wu, Zhifang; Shum, Perry Ping; Wang, Ruoxu; Quyen Dinh, Xuan; Fu, Songnian; Tong, Weijun; Tang, Ming

    2016-08-01

    We present the fabrication of fiber Bragg gratings (FBGs) in a trench-assisted heterogeneous multicore fiber (MCF). Two obviously different Bragg reflection peaks are obtained due to the slight difference of refractive indices between the center core and the outer cores. To investigate the reflections of the two FBGs simultaneously, only a segment of multimode fiber is inserted between the lead-in single mode fiber and the MCF. The experimental results confirm that the curvature sensitivity of the FBG in the outer core is a sinusoidal function of the bending orientation angle. The maximum linear curvature sensitivity is about 0.128 nm/m-1. The cross sensitivity to temperature or externally applied axial strain can be eliminated by discriminating the different responses of FBGs inscribed in outer cores and the center core. Thus this MCF with FBGs can be utilized as a directional bending sensor. Moreover, the proposed sensor offers several advantages, such as low cost and flexibility in fabrication.

  17. Measurements of endotracheal tube cuff contact pressure using fibre Bragg gratings

    NASA Astrophysics Data System (ADS)

    Hernandez, F. U.; Correia, R.; Korposh, S.; Morgan, S. P.; Hayes-Gill, B. R.; James, S. W.; Evans, D.; Norris, A.

    2015-09-01

    An optical fibre Bragg grating (FBG) was used to measure local strain (due to contact pressure) at the interface of a cuffed endotracheal tube (ETT) tested in a tracheal model. The tracheal model consisted of a corrugated tube. Two FBG sensors written in a single optical fibre were attached to the outside wall of the cuff of the ETT. Intracuff endotracheal pressure was measured using a digital manometer, while the contact pressure between the model trachea and the ETT was measured using Flexiforce sensors. Changes in the Bragg wavelengths in response to the inflation of the cuff of the ETT, and concomitant pressure increase, were observed to be dependent on the location of the FBGs at the corrugations, i.e., the annular peaks and troughs of the corrugated tube. The performance of both contact pressure sensors FBG and Flexiforce suggests that FBG technology is better suited to this application as it allows the measurement of contact pressures on non-uniform surfaces such as in the tracheal model.

  18. A new method for fiber Bragg grating wavelength demodulation with calibration

    NASA Astrophysics Data System (ADS)

    Fu, Jian-wei; Xiao, Li-zhi; Zhang, Yuan-zhong; Zhao, Xiao-liang; Chen, Hai-feng

    2006-01-01

    A wavelength calibration method is proposed to improve Fiber Bragg Grating (FBG) Wavelength detection precision. The reflected spectra of two reference FBG elements and a sensing FBG element are scanned by narrow band light from a fiber F-P tunable filter (FFP-TF) driven by triangular waveform voltage. Sequence numbers of FBG and peak position of spectra are identified with full spectrum analysis. Two reference FBG elements with fixed wavelength are used to monitor the transmission wavelength of filter and to construct the relationship between wavelength and the driving voltage, the driving voltage of the sensing FBG spectrum peak is scaled as the Bragg wavelength with the linear interpolation method. In the temperature experiment, three peak-seek methods such as centroid method, differential method and Gaussian-fit method are introduced and the temperature measurement precisions of +/-1C °,+/-0.5C ° and +/-0.3C ° are achieved respectively, corresponding to the wavelength error of +/-10pm, +/-5pm and +/-3pm. Finally, multipoint FBG sensing system is accomplished with calibration and wavelength measurement precisions of +/-10pm is obtained. The experimental results shows that the new method can reduce the wavelength measurement error caused by nonlinearity in piezoelectric transducer (PZT) response and wavelength drift due to PZT hysteresis.

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

  20. Enhancing the humidity response time of polymer optical fiber Bragg grating by using laser micromachining.

    PubMed

    Chen, Xianfeng; Zhang, Wei; Liu, Chen; Hong, Yanhua; Webb, David J

    2015-10-01

    The humidity sensors constructed from polymer optical fiber Bragg gratings (POFBG) respond to the water content change in the fiber induced by varying environmental condition. The water content change is a diffusion process. Therefore the response time of the POFBG sensor strongly depends on the geometry and size of the fiber. In this work we investigate the use of laser micromachining of D-shaped and slotted structures to improve the response time of polymer fiber grating based humidity sensors. A significant improvement in the response time has been achieved in laser micromachined D-shaped POFBG humidity sensors. The slotted geometry allows water rapid access to the core region but this does not of itself improve response time due to the slow expansion of the bulk of the cladding. We show that by straining the slotted sensor, the expansion component can be removed resulting in the response time being determined only by the more rapid, water induced change in core refractive index. In this way the response time is reduced by a factor of 2.5. PMID:26480109