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Sample records for fibre bragg grating

  1. 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.

  2. 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

  3. 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)

  4. 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)

  5. 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)

  6. 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)

  7. Distributive tactile sensing using fibre Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Cowie, Barbara M.; Webb, David J.; Tam, Betty; Slack, Paul; Brett, Peter N.

    2006-04-01

    Two distributive tactile sensing systems are presented, based on fibre Bragg grating sensors. The first is a onedimensional metal strip with an array of 4 sensors, which is capable of detecting the magnitude and position of a contacting load. This system is compared experimentally with a similar system using resistive strain gauges. The second is a two-dimensional steel plate with 9 sensors which is able to distinguish the position and shape of a contacting load. This system is compared with a similar system using 16 infrared displacement sensors. Each system uses neural networks to process the sensor data to give information concerning the type of contact.

  8. Weldable fibre Bragg grating sensors for steel bridge monitoring

    NASA Astrophysics Data System (ADS)

    Barbosa, C.; Costa, N.; Ferreira, L. A.; Araújo, F. M.; Varum, H.; Costa, A.; Fernandes, C.; Rodrigues, H.

    2008-12-01

    For applications related to the structural health monitoring of steel bridges, novel weldable strain and temperature sensors based on fibre Bragg gratings were developed. These sensors, which can be directly welded to metallic structures, reveal linear responses over typical required measurement ranges and stability over thousands of load and temperature cycles. Proper installation procedures and in-field mechanical protection were also developed and implemented. The significance of the developed sensors was demonstrated through the installation of a complete sensing network on a new circular pedestrian bridge in Aveiro, Portugal, where it was used for loading tests, and also for in-service monitoring of its structural health.

  9. Vibration measurement of electrical machines using integrated fibre Bragg gratings

    NASA Astrophysics Data System (ADS)

    Fabian, M.; Borg Bartolo, J.; Ams, M.; Gerada, C.; Sun, T.; Grattan, K. T. V.

    2015-09-01

    In this paper a method to track the rotating force vector set up within the air-gap of radial flux rotating electrical machines using fibre Bragg gratings is reported. The proposed technique offers the potential for simultaneous rotor speed and position monitoring. This specific sensor design, together with other FBG-based multi-parameter measurements, is aimed to create an all-optical sensor solution for electrical machines, reducing the component count of existing systems and addressing noise issues traditionally associated with electrical sensors used. In this work, an optical fibre sensor system has been successfully integrated into an off-the-shelf four-pole 11kW induction motor.

  10. A fibre Bragg grating stress cell for geotechnical engineering applications

    NASA Astrophysics Data System (ADS)

    Legge, T. Francis H.; Swart, Pieter L.; van Zyl, Gideon; Chtcherbakov, Anatoli A.

    2006-05-01

    Existing technology used to measure stress in granular materials is susceptible to water ingress and resulting damage to the electrical components, which limits this technology's use in long-term monitoring of soil structures. The connections of these instruments to readout or recording devices are also fragile and easily damaged. In order to explore the efficacy of fibre optic technology not just as a replacement component, but rather as a material of robust elastic properties, a series of experiments was devised to test the possibility of applying a transverse lateral stress to the fibre and measuring its transformed longitudinal strain. The fibre was inscribed with a 5 mm long Bragg grating and encapsulated in a softer material of high Poisson's ratio in an attempt to enhance the longitudinal strain developed in the fibre. This encapsulated device was then subjected to one-dimensional stress in a standard sand, and the strain in the fibre measured. The experiment showed that satisfactory correlation exists between the measured strain output when converted to an applied stress and the mathematically (and numerically) derived stresses. The fibre/silicone bonding was also modelled and results showed that slippage on that interface could be considered insignificant. In both theoretical and practical applications, this experiment can be regarded as successfully validating the principle of deriving stress from a longitudinal elastic strain measured normal to the applied stress. Hence, development can move towards both miniaturization (for research) and more robust construction (to withstand field conditions). Further research will encompass investigating the response of the cell to water and saturated soil conditions, particularly the device sensitivity to transient stress conditions. In addition, development of the sensor to read the complete three-dimensional state of stress in a soil remains the ultimate goal. South African Provisional Patent Application no 2005/06016.

  11. Fibre Bragg grating based accelerometer with extended bandwidth

    NASA Astrophysics Data System (ADS)

    Basumallick, Nandini; Biswas, Palas; Chakraborty, Rajib; Chakraborty, Sushanta; Dasgupta, Kamal; Bandyopadhyay, Somnath

    2016-03-01

    We have shown experimentally that the operable bandwidth of a fibre Bragg grating (FBG) based accelerometer can be extended significantly, without compromising its sensitivity, using a post-signal processing technique which involves frequency domain weighting. It has been demonstrated that using the above technique acceleration can be correctly interpreted even when the operating frequency encroaches on the region where the frequency response of the sensor is non-uniform. Two different excitation signals, which we often encounter in structural health monitoring applications, e.g. (i) a signal composed of multi-frequency components and (ii) a sinusoidal excitation with a frequency sweep, have been considered in our experiment. The results obtained have been compared with a piezo accelerometer.

  12. Anomalously high noise levels in a fibre Bragg grating semiconductor laser

    SciTech Connect

    Kurnosov, V D; Kurnosov, K V

    2015-01-31

    Taking into account gain nonlinearity allows one to obtain anomalously high noise levels in a fibre Bragg grating laser diode. This paper examines the effect of the gain nonlinearity due to spectral hole burning on noise characteristics. (lasers)

  13. 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)

  14. Temperature-Insensitive Fibre-Optic Acceleration Sensor Based on Intensity-Referenced Fibre Bragg Gratings

    NASA Astrophysics Data System (ADS)

    Sun, Li-Qun; Dong, Bo; Wang, Yong-Xin; Evan, LALLY; Wang, An-Bo

    2008-10-01

    A temperature-insensitive acceleration sensor using two fibre Bragg gratings (FBGs), based on reflection spectrum intensity modulation and optical power detection, is proposed and demonstrated. A cantilever beam is used to generate acceleration-induced axial strain along two sensing gratings, which are glued on the two opposite surfaces of the beam. Because the two gratings operate within the linear spectral range of a light source, formed by a thermally-tunable extrinsic Fabry-Perot optical filter, the intensity difference of the two reflections from the gratings is proportional to the acceleration applied. This eliminates the need for sophisticated wavelength interrogation of the gratings, and it also endows the sensor with immunity to temperature variation. Compared with a commercial micromachined accelerometer, the sensor is proven to be capable of accurately detecting acceleration.

  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. REVIEW ARTICLE: Modulational instability in a fibre and a fibre Bragg grating

    NASA Astrophysics Data System (ADS)

    Ganapathy, R.; Senthilnathan, K.; Porsezian, K.

    2004-05-01

    In this review article, we study the influence of cross-phase modulation, higher order nonlinear effects such as self-steepening, self-induced Raman scattering and higher order dispersion effects such as third and fourth order dispersion on cross-phase modulational instability for a highly elliptical birefringent optical fibre, and obtain the conditions for the occurrence of cross-phase modulational instability in the normal dispersion regime. In addition, we also consider the pulse propagation through a fibre Bragg grating structure where we investigate the occurrence of modulational instability at the two edges of the photonic bandgap as well as on the upper and lower branches of the dispersion curves.

  17. Fibre Bragg grating sensors for distributive tactile sensing

    NASA Astrophysics Data System (ADS)

    Cowie, Barbara M.; Webb, David J.; Tam, Betty; Slack, Paul; Brett, Peter N.

    2007-01-01

    Distributive tactile sensing is a method of tactile sensing in which a small number of sensors monitors the behaviour of a flexible substrate which is in contact with the object being sensed. This paper describes the first use of fibre Bragg grating sensors in such a system. Two systems are presented: the first is a one-dimensional metal strip with an array of four sensors, which is capable of detecting the magnitude and position of a contacting load. This system is favourably compared experimentally with a similar system using resistive strain gauges. The second system is a two-dimensional steel plate with nine sensors which is able to distinguish the position and shape of a contacting load, or the positions of two loads simultaneously. This system is compared with a similar system using 16 infrared displacement sensors. Each system uses neural networks to process the sensor data to give information concerning the type of contact. Issues and limitations of the systems are discussed, along with proposed solutions to some of the difficulties.

  18. 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.

  19. Gauge factors of fibre Bragg grating strain sensors in different types of optical fibres

    NASA Astrophysics Data System (ADS)

    Jülich, Florian; Aulbach, Laura; Wilfert, Andre; Kratzer, Peter; Kuttler, Rolf; Roths, Johannes

    2013-09-01

    Gauge factors of fibre Bragg grating (FBG)-based strain sensors that had been inscribed into three different types of optical fibres, which differ in core diameters and doping concentrations, were determined at room temperature with high accuracy. Repeated measurements were carried out with several samples of each type of fibre to allow statistical evaluations. For each type, the gauge factors were measured in two configurations: when the bare fibres were glued on a specimen at the location of the FBG and when they were vertically suspended and not bonded to any structure at the location of the FBG. By combining the results of both configurations, the strain transfer ratio of the gluing process and the strain-optic coefficient, peff, of the different types of fibres were determined. The strain-optic coefficient was found to vary up to 1.5% for the different types of optical fibres. The strain transfer ratio was obtained to be close to unity (>99%), showing the high quality of the gluing technique employed. The investigations demonstrate that highly accurate strain sensing is possible with fibre-optic strain sensors. The results are important for the development of accurate and reliable attaching techniques for coated sensor fibres and fibre-optic sensor patches.

  20. Development of a Fibre Bragg Grating Sensor for Rock Deformation Monitoring

    NASA Astrophysics Data System (ADS)

    Kanopoulos, Patrick Paskalis

    This thesis examines the theoretical and experimental performance of a fibre Bragg grating sensor for static and dynamic strain measurement in hard rock. A literature review focuses on the fundamental theory of fibre Bragg gratings, various physical demodulation schemes used to interrogate Bragg sensors with an emphasis on charge coupled device spectrometry, as well as the aliasing behaviour of Bragg gratings as sensors. A coupled numerical-analytical analysis is conducted on various sensor configurations designed for borehole deployment in order to establish the response of the strain sensors under various strain conditions. The findings of an experimental investigation of two sensors subjected to uniaxial strain within a grout and a rock specimen are presented. The experimental data confirm the feasibility of using the proposed sensor as a part of an integrated optical strain sensing network.

  1. 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.

  2. 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.

  3. In-situ measurements with fibre Bragg gratings embedded in stainless steel

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    Metal clad single mode optical fibres containing high reflectivity Bragg gratings are successfully embedded into stainless steel components using bespoke laser based additive manufacturing technology. Temperature cycling of the embedded sensor demonstrates the ability of gratings to survive the embedding process, and act as temperature or strain sensors. At extreme temperatures up to 500 °C, discontinuities in the gratings response are observed and these have been attributed to possible delamination issues at the interface between glass fiber and the surrounding metal.

  4. 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)

  5. 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.

  6. Photochemical changes in hydrogen-loaded optical fibres with application to Bragg grating formation

    NASA Astrophysics Data System (ADS)

    Nguty, T. A.; Potton, R. J.

    1997-10-01

    The sensitization to UV-induced refractive-index changes, by hydrogen, of germanosilicate glass is important in the production of in-fibre Bragg gratings. During grating formation fluorescence from germanium lone-pair centres is excited in the core of the fibre by the UV exposure. This fluorescence has been used to monitor photochemical reduction of substituted tetravalent germanium atoms by hydrogen. The photoreduced atoms occupy 0957-0233/8/10/004/img1 sites and absorb fluorescent radiation. Together with 0957-0233/8/10/004/img2 ions they are responsible for the refractive-index changes exploited in the holographic formation of Bragg gratings in hydrogen-loaded, germanium-doped fibres.

  7. Bragg grating inscription in CYTOP polymer optical fibre using a femtosecond laser

    NASA Astrophysics Data System (ADS)

    Lacraz, A.; Polis, M.; Theodosiou, A.; Koutsides, C.; Kalli, K.

    2015-05-01

    We report on the inscription of fibre Bragg gratings (FBGs) in CYTOP (cyclic transparent optical polymer) optical fibres. A femtosecond laser beam, operating in the visible wavelength range, is focussed into the core of the fibre for direct inscription of FBGs. The fibre is moved under the focussed beam by a nanometre-resolution air-bearing stage for maximal inscription precision. The grating plane dimensions (measured with bright field microscopy) are typically 30μm × 30μm × 1μm (line by line grating) or 10μm×1μm×1μm (point by point grating) and centred in the core of the fibre for optimal grating efficiency. The FBGs have a typical reflectivity of 70%, a bandwidth of 0.25nm and an index change of ~10-4. The FBG operate in the C-band, where CYTOP offers key advantages over poly (methyl methacrylate) optical fibres, having a significantly lower optical loss in the important near infra-red (NIR) optical communications window, with a theoretical loss of ~0.3dB/km at 1550nm. Additionally, CYTOP has a far lower affinity for water absorption and a core mode refractive index that coincides with the aqueous index regime. These properties offer several unique opportunities for polymer optical fibre sensing at NIR wavelengths, such as compatibility with existing optical networks, the potential for optical fibre sensor multiplexing and suitability for bio-sensing. We have investigated the temperature response of the grating: a linear positive shift of ~ +40pm/K has been measured with little difference between the heating and cooling response. The strain response of the FBG has also been studied with a linear shift of ~ +1.3pm/μɛ measured over a few hundreds of μɛ. We also demonstrated compatibility with a commercial Bragg grating demodulator.

  8. 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

  9. Strain measurements of composite laminates with embedded fibre bragg gratings: criticism and opportunities for research.

    PubMed

    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

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Temperature and strain effects discrimination inside composite materials with embedded weakly tilted fibre Bragg grating

    NASA Astrophysics Data System (ADS)

    Kinet, D.; Garray, D.; Mégret, P.; Caucheteur, C.

    2013-05-01

    Fibre Bragg gratings (FBGs) are strain sensors that can be embedded into composite materials, without affecting their mechanical performances. In this study, we report the use of a short and weakly tilted FBG inscribed in a single mode highly germanium doped photosensitive optical fibre to discriminate, with a good spatial resolution, strain and temperature effects for structural health monitoring (SHM) application. The transmission spectrum of a weakly tilted FBG (TFBG) presents three regions of interest: the Bragg resonance, the ghost mode resonance and all other cladding mode resonances that are not exploited in this work. We make use of the differential temperature sensitivity of the Bragg mode and the ghost mode to discriminate between temperature and strain effects inside composite materials.

  15. 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.

  16. 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)

  17. 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.

  18. 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.

  19. 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.

  20. Fibre Bragg grating sensing and finite element analysis of the biomechanics of the mandible

    NASA Astrophysics Data System (ADS)

    Silva, J. C. C.; Ramos, A.; Carvalho, L.; Nogueira, R. N.; Ballu, A.; Mesnard, M.; Pinto, J. L.; Kalinowski, Hypolito J.; Simoes, J. A.

    2005-05-01

    This paper describes the application of fibre Bragg grating (FBG) sensors to measure strains at the outer surface of a mandible. The strains were correlated to identical ones obtained with a numerical finite element model. For this purpose, a synthetic mandible was used and 4 Bragg sensors were glued to the mandible. Strain patterns were assessed for different load configurations which included the forces of the masseter and temporal muscles and occlusion loads on different tooth (incisor, canine and molar). Overall the strains obtained using different measuring methods were identical, namely for the case of symmetric loading. When loading was non-symmetric, strain differences were observed at one sensor.

  1. 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.

  2. Embedded Fibre Bragg Grating Sensor Response Model: Crack Growing Detection in Fibre Reinforced Plastic Materials

    NASA Astrophysics Data System (ADS)

    Pereira, G.; Mikkelsen, L. P.; McGugan, M.

    2015-07-01

    This article presents a novel method to simulate the sensor output response of a Fibre Bragg Grating (FBG) sensor when embedded in a host material (Composite material or adhesive), during a crack growing/damage event. A finite element model of the crack growth mechanisms was developed, and different fracture modes were addressed. Then an output algorithm was developed to predict the sensor spectrum change during the different stages of the crack growing. Thus, it is possible to identify specific phenomenon that will only happen within the proximity of a crack, as compression field ahead the crack or non-uniform strain, and then identify the presence of such damage in the structure. Experimental tests were conducted in order to validate this concept and support the model. The FBG sensor response model was applied in a delamination of a Wind Turbine trailing edge, to demonstrate the applicability of this technique to more complicated structures, and to be used as a structural health monitoring design tool.

  3. 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.

  4. 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

  5. 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)

  6. A flexible, highly sensitive catheter for high resolution manometry based on in-fibre Bragg gratings

    NASA Astrophysics Data System (ADS)

    Bueley, Christopher; Wild, Peter M.

    2013-09-01

    This work presents a fibre optic-based flexible catheter for high resolution manometry (HRM), with sensing pods located at a pitch of 10 mm and an overall diameter of 2.8 mm. In-fibre Bragg gratings act as the sensing elements within these sensing pods. Hydrodynamic pressure resolution of 0.2 mmHg is demonstrated in conjunction with insensitivity to occlusion pressure. This result is significant in the context of HRM where independent measurement of hydrodynamic pressure is clinically relevant. The sensing system is compact, robust and flexible. Crosstalk between individual sensors is characterized and a compensation scheme is developed and validated.

  7. Evaluation of a 1540nm VCSEL for fibre Bragg gratings interrogation in dynamic measurement applications

    NASA Astrophysics Data System (ADS)

    Garcia-Souto, J. A.; Martin-Mateos, P.; Posada, J. E.; Acedo, P.; Jackson, D. A.

    2014-05-01

    The performance of a 1540 nm pigtailed VCSEL has been characterized in terms of output power, frequency range and rate of wavelength sweeping for its application in fibre Bragg grating interrogation. Results are presented for the laser operating under optimized control when used to illuminate a single FBG mounted under tension between a fixed plane and a loud speaker cone subject to a range of frequencies at arbitrary amplitudes and transients. The ultimate objective is to extend the set-up to a parallel fibre topology supporting 8 FBGs with equal wavelengths.

  8. 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.

  9. Exploring the dark continent with fibre Bragg gratings

    NASA Astrophysics Data System (ADS)

    Arkwright, John W.; Wang, David Hsiao-Chuan; Maunder, Simon A.; Blenman, Neil G.; Underhill, Ian; Patton, Vicki; Dinning, Phil G.

    2014-05-01

    The lower gastrointestinal tract has been referred to as the `Dark Continent' of the human body because it is so hard to access without resorting to a surgeon's blade. In response to an unmet clinical need we have developed a fibre optic manometry catheter that is now in clinical use across Australia and New Zealand. The unparalleled detail of colonic activity that these devices provide is being hailed as ground breaking by global experts. In this paper we present the design and clinical application of the catheters, and also some of the (sometimes surprising) requirements of our clinical colleagues.

  10. Fibre Bragg Grating sensor for shock wave diagnostics

    NASA Astrophysics Data System (ADS)

    Ravid, A.; Shafir, E.; Zilberman, S.; Berkovic, G.; Glam, B.; Appelbaum, G.; Fedotov Gefen, A.

    2014-05-01

    We measured the response of short FBGs to a weak planar shock wave. The combined effect of the Photo-Elastic effect and the FBG strain was estimated theoretically depending on its orientation with respect to shock front (for 1550 nm FBG, parallel: 0.9 nm/kbar, perpendicular: -1.4 nm/kbar). The experimental results imply that the FBG/fibre survives for more than 1 μs at 5 kbar shock stress, and that our assumptions about the FBG behaviour under dynamic loading are valid, though more work is needed to fully quantify the effect.

  11. 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.

  12. Shape memory polymeric composites sensing by optic fibre Bragg gratings: A very first approach

    NASA Astrophysics Data System (ADS)

    Quadrini, Fabrizio; Santo, Loredana; Ciminello, Monica; Concilio, Antonio; Volponi, Ruggero; Spena, Paola

    2016-05-01

    Shape memory polymer composites (SMPCs) have the potential for many applications in aerospace, spanning from self-repairing of structures to self-deploying of antennas, solar sails, or functional devices (e.g. for grabbing small space debris). In all these cases, it may be essential to have information about their configuration at different stages of shape recovery. In this study, the strain history of a prepreg carbon fibre system, cured with a shape memory polymer (SMP) interlayer, is monitored through a Fibre Bragg Grating (FBG), a fibre optic sensor device. SMPC has been manufactured by using traditional technologies for aerospace. After manufacturing cylindrical shape samples, an external fibre optic system is added to the composite structure; this system is especially suited for high temperatures which are necessary for SMP recovery and composite softening. Sensor functionality is checked before and after each strain history path. Optic fibre arrangement is optimized to avoid unwanted breakings whereas strains are limited by fibre collapsing, i.e. within nominal 2% of deformation. Dynamic information about shape recovery gives fundamental insights about strain evolution during time as well as its spatial distribution.

  13. PRAXIS: a low background NIR spectrograph for fibre Bragg grating OH suppression

    NASA Astrophysics Data System (ADS)

    Horton, Anthony; Ellis, Simon; Lawrence, Jon; Bland-Hawthorn, Joss

    2012-09-01

    Fibre Bragg grating (FBG) OH suppression is capable of greatly reducing the bright sky background seen by near infrared spectrographs. By filtering out the airglow emission lines at high resolution before the light enters the spectrograph this technique prevents scattering from the emission lines into interline regions, thereby reducing the background at all wavelengths. In order to take full advantage of this sky background reduction the spectrograph must have very low instrumental backgrounds so that it remains sky noise limited. Both simulations and real world experience with the prototype GNOSIS system show that existing spectrographs, designed for higher sky background levels, will be unable to fully exploit the sky background reduction. We therefore propose PRAXIS, a spectrograph optimised specifically for this purpose. The PRAXIS concept is a fibre fed, fully cryogenic, fixed format spectrograph for the J and H-bands. Dark current will be minimised by using the best of the latest generation of NIR detectors while thermal backgrounds will be reduced by the use of a cryogenic fibre slit. Optimised spectral formats and the use of high throughput volume phase holographic gratings will further enhance sensitivity. Our proposal is for a modular system, incorporating exchangeable fore-optics units, integral field units and OH suppression units, to allow PRAXIS to operate as a visitor instrument on any large telescope and enable new developments in FBG OH suppression to be incorporated as they become available. As a high performance fibre fed spectrograph PRAXIS could also serve as a testbed for other astrophotonic technologies.

  14. 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)

  15. Crack Detection in Fibre Reinforced Plastic Structures Using Embedded Fibre Bragg Grating Sensors: Theory, Model Development and Experimental Validation.

    PubMed

    Pereira, G F; Mikkelsen, L P; McGugan, M

    2015-01-01

    In a fibre-reinforced polymer (FRP) structure designed using the emerging damage tolerance and structural health monitoring philosophy, sensors and models that describe crack propagation will enable a structure to operate despite the presence of damage by fully exploiting the material's mechanical properties. When applying this concept to different structures, sensor systems and damage types, a combination of damage mechanics, monitoring technology, and modelling is required. The primary objective of this article is to demonstrate such a combination. This article is divided in three main topics: the damage mechanism (delamination of FRP), the structural health monitoring technology (fibre Bragg gratings to detect delamination), and the finite element method model of the structure that incorporates these concepts into a final and integrated damage-monitoring concept. A novel method for assessing a crack growth/damage event in fibre-reinforced polymer or structural adhesive-bonded structures using embedded fibre Bragg grating (FBG) sensors is presented by combining conventional measured parameters, such as wavelength shift, with parameters associated with measurement errors, typically ignored by the end-user. Conjointly, a novel model for sensor output prediction (virtual sensor) was developed using this FBG sensor crack monitoring concept and implemented in a finite element method code. The monitoring method was demonstrated and validated using glass fibre double cantilever beam specimens instrumented with an array of FBG sensors embedded in the material and tested using an experimental fracture procedure. The digital image correlation technique was used to validate the model prediction by correlating the specific sensor response caused by the crack with the developed model. PMID:26513653

  16. Crack Detection in Fibre Reinforced Plastic Structures Using Embedded Fibre Bragg Grating Sensors: Theory, Model Development and Experimental Validation

    PubMed Central

    Pereira, G. F.; Mikkelsen, L. P.; McGugan, M.

    2015-01-01

    In a fibre-reinforced polymer (FRP) structure designed using the emerging damage tolerance and structural health monitoring philosophy, sensors and models that describe crack propagation will enable a structure to operate despite the presence of damage by fully exploiting the material’s mechanical properties. When applying this concept to different structures, sensor systems and damage types, a combination of damage mechanics, monitoring technology, and modelling is required. The primary objective of this article is to demonstrate such a combination. This article is divided in three main topics: the damage mechanism (delamination of FRP), the structural health monitoring technology (fibre Bragg gratings to detect delamination), and the finite element method model of the structure that incorporates these concepts into a final and integrated damage-monitoring concept. A novel method for assessing a crack growth/damage event in fibre-reinforced polymer or structural adhesive-bonded structures using embedded fibre Bragg grating (FBG) sensors is presented by combining conventional measured parameters, such as wavelength shift, with parameters associated with measurement errors, typically ignored by the end-user. Conjointly, a novel model for sensor output prediction (virtual sensor) was developed using this FBG sensor crack monitoring concept and implemented in a finite element method code. The monitoring method was demonstrated and validated using glass fibre double cantilever beam specimens instrumented with an array of FBG sensors embedded in the material and tested using an experimental fracture procedure. The digital image correlation technique was used to validate the model prediction by correlating the specific sensor response caused by the crack with the developed model. PMID:26513653

  17. Code generator using distributed phase shifts applied on a chirped fibre Bragg grating in a semiconductor fibre ring laser

    NASA Astrophysics Data System (ADS)

    D. Simard, Alexandre; LaRochelle, Sophie

    2009-06-01

    As data traffic increases on telecommunication networks, optical communication systems must adapt to deal with this increasing bursty traffic. Packet switched networks are considered a good solution to provide efficient bandwidth management. We recently proposed the use of spectra amplitude codes (SAC) to implement all-optical label processing for packet switching and routing. The implementation of this approach requires agile photonic components including filters and lasers. In this paper, we propose a reconfigurable source able to generate the routing codes, which are composed of two wavelengths on a 25 GHz grid. Our solution is to use a cascade of two chirped fibre Bragg gratings (CFBG) in a semiconductor fibre ring laser. The wavelength selection process comes from distributed phase shifts applied on the CFBG that is used in transmission. Those phase shifts are obtained via local thermal perturbations created by resistive chrome lines deposited on a glass plate. The filter resonances are influenced by four parameters: the chrome line positions, the temperature profile along the fibre, the neighbouring heater state (ON/OFF) and the grating itself. Through numerical modeling, these parameters are optimized to design the appropriate chrome line pattern. With this device, we demonstrate successful generation of reconfigurable SAC codes.

  18. 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.

  19. Fibre Bragg gratings sensor for monitoring distance changes between structural elements inside a building

    NASA Astrophysics Data System (ADS)

    Smeu, E.; Gnewuch, H.; Jackson, D. A.; Podoleanu, A.

    2006-03-01

    The distance changes between structural elements inside a building (e.g. walls, pillars, stairs, etc.) ought to be monitored, especially in seismic-prone areas, in order to assess its stability. Fibre Bragg grating (FBG) sensors are now the most interesting choice for this purpose, since several gratings can be included in the fibre, resulting in a quasi-distributed sensor, which can be illuminated using a single light source and interrogated simply by a single optical spectrum analyzer (USA), using wavelength multiplexing. The paper deals with such a sensor, which was installed for monitoring the distance changes in a construction joint between two building blocks inside the University "Politehnica" of Bucharest. Since this city is placed in a seismic-prone area, we use a fast scanning USA, so that the dynamic behavior of the monitored construction joint is expected to be captured during future earthquakes. Slow drifts of the construction joint width will be also monitored. The paper describes the sensor structure and working principle, the experimental tests and main parameters evaluation. The reported sensor is temperature compensated. It has an estimated distance resolution better or equal to 10 μm, and a linearity of +0.2%...-0.35% for displacements up to 0.55 mm. Simulated dynamic tests are also reported.

  20. High dynamic range temperature-compensated fibre Bragg gratings sensor for structural monitoring of buildings

    NASA Astrophysics Data System (ADS)

    Smeu, E.; Gnewuch, H.; Jackson, D. A.; Podoleanu, A.

    2006-06-01

    The distance changes between structural elements inside a building (e.g. walls, pillars, stairs, etc.) ought to be monitored, especially in seismic-prone areas, in order to assess its stability. Fibre Bragg grating (FBG) sensors are now the most interesting choice for this purpose, since several gratings can be included in the fibre, resulting in a quasi-distributed sensor, which can be illuminated using a single light source and interrogated simply by a single optical spectrum analyzer (OSA), using wavelength multiplexing. The paper deals with such a sensor, which was installed for monitoring the distance changes in a construction joint between two building blocks inside the University "Politehnica" of Bucharest. Since this city is placed in a seismic-prone area, we use a fast scanning OSA, so that the dynamic behavior of the monitored construction joint is expected to be captured during future earthquakes. Slow drifts of the construction joint width will be also monitored. The paper describes the sensor structure and working principle, the experimental tests and main parameters evaluation. The reported sensor is temperature compensated. It has an estimated distance resolution better or equal to 10 μm, and a linearity of +0.2%...-0.35% for displacements up to 0.55 mm. Simulated dynamic tests are also reported.

  1. Online Monitoring Research of Composite Insulator Based on Fibre Bragg Grating Sensor

    NASA Astrophysics Data System (ADS)

    Yuan, Duanlei; Chen, Yanhui; Shi, Hongwei; Song, XiaoGuang; Ji, Yundong

    Composite insulator has good insulation properties and mechanical properties. But under long-term electrical load and exposed to the sun and rain, its organic materials have aging problem, it is essential to test its operational state online. In this paper, the operational state of composite insulator were online detected by Fibre Bragg Grating (FBG) Sensor.During the process of making composite insulator, FBG sensor was embedded in this study. Firstly, composite insulators with FBG sensor exposed to accelerated aging, then artificial flashover imposed on composite insulator, the temperature of composite insulator were detected by FBG sensor, and the temperature field of pollution flashover was drawn. Test results indicate that the area where the flashover occured had high temperature, the silicone rubber surface significantly become black and hard, and had many small cracks, the hydrophobic of composite insulator basically loss. Studies show that FBG sensor has broad application prospects on online detection of composite insulator.

  2. 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

  3. 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.

  4. Lamb wave detection in prepreg composite materials with fibre Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Miesen, Nick; Mizutani, Yoshihiro; Groves, Roger M.; Sinke, Jos; Benedictus, Rinze

    2011-04-01

    This paper demonstrates that existing Structural Health Monitoring (SHM) techniques have potential during the production phase in addition to their application for maintenance and for in-flight monitoring. Flaws occur during composite fabrication in industry, due to an imperfect process control and human errors. This decreases production efficiency and increases costs. In this paper, the monitoring of Lamb waves in unidirectional carbon fibre (UD-CFRP) prepreg material is demonstrated using both Fibre Bragg Gratings (FBG)s and piezolectric acoustic sensors, and that these SHM sensors may be used for flaw detection and production monitoring. The detection of Lamb waves in a one ply thick sheet of prepreg UD-CFRP material is demonstrated for an FBG sensor aligned with the carbon fibre orientation and bonded to the surface of the prepreg, Furthermore, the velocity of Lamb waves in prepreg UD-CFRP in different orientations is investigated. Finally the successful detection of a material crack in a prepreg UD-CFRP sheet using the Lamb wave detection method is demonstrated.

  5. Continuous monitoring of mining induced strain in a road pavement using fibre Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Whelan, B. E.; Brunton, M.; Nosenzo, Giorgio; Kay, Daryl; Buys, Henk

    2012-02-01

    This paper describes the application of Fibre Bragg Grating (FBG) based sensors for monitoring road pavement strains caused by mining induced ground subsidence as a result of underground longwall coal mining beneath a major highway in New South Wales, Australia. After a lengthy planning period, the risks to the highway pavement were successfully managed by the highway authority and the mining company through a technical committee. The technical committee comprised representatives of the mining company, the highway authority and specialists in the fields of pavement engineering, geotechnical engineering and subsidence. An important component of the management strategy is the installation of a total of 840 strain and temperature sensors in the highway pavement using FBG arrays encapsulated in glass-fibre composite cables. The sensors and associated demodulation equipment provide continuous strain measurements along the pavement, enabling on-going monitoring of the effects of mining subsidence on the pavement and timely implementation of planned mitigation and response measures to ensure the safety and serviceability of the highway throughout the mining period.

  6. Prediction of the reflected spectra from chirped fibre Bragg gratings embedded within cracked crossply laminates

    NASA Astrophysics Data System (ADS)

    Palaniappan, J.; Wang, H.; Ogin, S. L.; Thorne, A.; Reed, G. T.; Tjin, S. C.; McCartney, L. N.

    2006-06-01

    Matrix cracking damage is a generic type of damage that develops under load in the off-axis plies of laminated composites and is generally the precursor of more serious damage mechanisms, particularly delamination. Hence, it is important to identify and if possible locate this type of damage. Chirped fibre Bragg grating sensors have been embedded in a transparent glass fibre reinforced plastic crossply laminate and changes to the reflected spectra as a consequence of crack development have been studied. An approximately sinusoidal variation of the intensity of the reflected spectrum occurs at the position of the crack, enabling both crack development and crack position to be identified. A simulation of a reflected spectrum, incorporating a stress transfer model to predict the strains and an optical model to predict the reflected spectrum, is in reasonable agreement with the experimental results. This article was presented at the 13th International Conference on Sensors and Their Applications, held in Chatham, Kent, on 6-7 September 2005.

  7. Broad-area detection of structural irregularities in composites using fibre Bragg gratings

    NASA Astrophysics Data System (ADS)

    Davis, Claire E.; Norman, Patrick; Moss, Scott; Ratcliffe, Colin; Crane, Roger

    2010-04-01

    The Structural Irregularity and Damage Evaluation Routine (SIDER) is a broadband vibration-based technique that uses features in complex curvature operating shapes to locate damage and other areas with structural stiffness variations. It is designed for the inspection of large-scale composite structures not amenable to more conventional inspection methods. The current SIDER methodology relies on impact excitation at a series of grid points on the structure and records the response using a small number of accelerometers to determine the operational curvature shapes. This paper reports on a modification to the SIDER technique whereby the acceleration measurements are replaced with in-plane strain measurements using Fibre Bragg Gratings (FBGs). One of the major challenges associated with using Bragg gratings for this type of response measurement is that the strains induced by structural vibrations tend to be low, particularly at higher frequencies. This paper also reports on the development of an intensity-based, swept wavelength interrogation system to facilitate these measurements. The modified SIDER system was evaluated on an E-glass/vinyl ester composite test beam containing a machined notch. The measurements accurately detected the presence and location of the notch. The distributive capacity of FBGs means that these sensors have the potential to replace the excitation grid with a measurement grid, allowing for single point or environmental excitation. The spatially separated measurements of strain can be used to provide the curvature shapes directly. This change in approach could potentially transition SIDER from an interval-based, broad-area inspection tool to an in-service structural health monitoring system.

  8. Metal-packaged fibre Bragg grating strain sensors for surface-mounting onto spalled concrete wind turbine foundations

    NASA Astrophysics Data System (ADS)

    Perry, M.; Fusiek, G.; McKeeman, I.; Niewczas, P.; Saafi, M.

    2015-09-01

    In this work, we demonstrate preliminary results for a hermetically sealed, metal-packaged fibre Bragg grating strain sensor for monitoring existing concrete wind turbine foundations. As the sensor is bolted to the sub-surface of the concrete, it is suitable for mounting onto uneven, wet and degraded surfaces, which may be found in buried foundations. The sensor was able to provide reliable measurements of concrete beam strain during cyclic three- and four- point bend tests. The strain sensitivity of the prototype sensor is currently 10 % of that of commercial, epoxied fibre strain sensors.

  9. TECHNICAL NOTE: Metal coating for enhancing the sensitivity of fibre Bragg grating sensors at cryogenic temperature

    NASA Astrophysics Data System (ADS)

    Lupi, C.; Felli, F.; Ippoliti, L.; Caponero, M. A.; Ciotti, M.; Nardelli, V.; Paolozzi, A.

    2005-12-01

    Fibre Bragg grating (FBG) sensors that are immune to electromagnetic interference could advantageously perform cryogenic temperature monitoring in superconducting magnetic fields, but their intrinsic temperature sensitivity is quite poor and must be enhanced. In fact, the low thermal expansion coefficient of silica limits the temperature sensitivity of bare FBG sensors at cryogenic temperature. In this paper the possibility of improving the temperature sensitivity of FBG sensors by metal coating is investigated. Specifically, zinc and copper coating depositions are performed by the traditional electrowinning process, after aluminium pre-coating of the sensor. Coated FBG sensors are inspected by both optical and metallographic techniques. SEM metallographic investigations show that a homogeneous deposit is obtained, with good metal adhesion to the FBG sensor. Optical testing shows that the optical properties of the coated FBG sensors are slightly affected: aluminium pre-coating produces appreciable modification of the diffraction spectrum in both peak width and peak shift, while zinc coating produces a moderate peak shift and copper coating just enlarges the peak width. Results presented in this paper show that both metals appreciably increase the temperature sensitivity of the FBG sensors. Zinc coating provides the highest sensitivity and high-resolution temperature measurements are possible at temperatures as low as 15 K.

  10. Numerical modelling of interrogation systems for optical fibre Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Oswald, Daniel; Richardson, Steven; Wild, Graham

    2011-12-01

    There are a number of interrogation methods that can be used in optical Fibre Bragg Grating (FBG) sensing system. For very high frequency signals interrogating the sensor signal from an FBG is limited to two intensiometric methods, edge filter detection and power detection. In edge filter detection, a broadband light source illuminates an FBG, the reflected spectrum is then passed through a spectral filter. In power detection, a narrowband light source with a wavelength corresponding to the 3dB point of the FBG is filtered by the FBG itself. Both methods convert the spectral shift of the FBG into intensity signals. These two categories each have a number of variations, all with different performance characteristics. In this work we present a numerical model for all of these interrogation systems. The numerical model is based on previous analytical modelling, which could only be utilised for perfect Gaussian profiles. However, interrogation systems can make use of non Gaussian shaped filters, or sources. The numerical modelling enables the different variations to be compared using identical component performance, showing the relative strengths and weakness of the systems in terms of useful parameters, including, signal-to-noise ratio, sensitivity, and dynamic resolution. The two different detection methods can also be compared side-by-side using the same FBG. Since the model is numerical, it enables real spectral data to be used for the various components (FBG, light source, filters). This has the added advantage of increasing the accuracy and usefulness of the model, over previous analytical work.

  11. Temperature sensitivity of Bragg gratings in PMMA and TOPAS microstructured polymer optical fibres

    NASA Astrophysics Data System (ADS)

    Webb, David J.; Kalli, Kyriacos; Zhang, Chi; Komodromos, Michael; Argyros, Alexander; Large, Maryanne; Emiliyanov, Grigoriy; Bang, Ole; Kjaer, Erik

    2008-04-01

    We report on the temperature response of FBGs recorded in pure PMMA and TOPAS holey fibres. The gratings are fabricated for operational use at near IR wavelengths, using a phase mask and a CW He-Cd laser operating at 325nm. The room temperature grating response is non-linear and characterized by quadratic behaviour for temperatures from room temperature to the glass transition temperature, and this permanent change is affected by the thermal history of the gratings. We also report the first FBG inscription in microstructured polymer optical fibres fabricated from TOPAS. This material is fully polymerized and has very low moisture absorption, leading to very good fibre drawing properties. Furthermore, although TOPAS is chemically inert and bio-molecules do not readily bind to its surface, treatment with Antraquinon and subsequent UV activation allows sensing molecules to be deposited in well defined spatial locations. When combined with grating technology this provides considerable potential for label-free bio-sensing.

  12. Optimization of the accelerated curing process of concrete using a fibre Bragg grating-based control system and microwave technology

    NASA Astrophysics Data System (ADS)

    Fabian, Matthias; Jia, Yaodong; Shi, Shi; McCague, Colum; Bai, Yun; Sun, Tong; Grattan, Kenneth T. V.

    2016-05-01

    In this paper, an investigation into the suitability of using fibre Bragg gratings (FBGs) for monitoring the accelerated curing process of concrete in a microwave heating environment is presented. In this approach, the temperature data provided by the FBGs are used to regulate automatically the microwave power so that a pre-defined temperature profile is maintained to optimize the curing process, achieving early strength values comparable to those of conventional heat-curing techniques but with significantly reduced energy consumption. The immunity of the FBGs to interference from the microwave radiation used ensures stable readings in the targeted environment, unlike conventional electronic sensor probes.

  13. Recent progress in polymer optical fibre gratings

    NASA Astrophysics Data System (ADS)

    Zhang, C.; Carroll, K.; Webb, D. J.; Bennion, I.; Kalli, K.; Emiliyanov, G.; Bang, O.; Kjær, E.; Peng, G. D.

    2008-04-01

    We describe our recent progress in polymer fibre Bragg grating technology, including the writing of the first FBGs in TOPAS cyclic olefin copolymer, enhancements to photosensitivity brought about by dopants and studies on grating annealing.

  14. How to reliably measure composite-embedded fibre Bragg grating sensors influenced by transverse and point-wise deformations?

    NASA Astrophysics Data System (ADS)

    Lebid, S.; Habel, W.; Daum, W.

    2004-08-01

    Embedded conventional fibre Bragg grating (FBG) sensors with acrylate coating have been chosen for monitoring novel textile-reinforced composite materials with a complicated wavy structure as a result of reinforcing textures. Problems of monitoring this type of material occur due to the harsh fabrication technology of the composite and its complicated structure. Embedded fibre sensors are exposed to the influence of transverse and point-wise deformations. To what extent will these effects influence the measurement signal of a sensor? Temperature cycles, tension and vibration tests were carried out to answer this question. Transverse and point-wise deformation and micromechanical indentation tests on non-embedded FBG sensors were carried out to clarify the reliability of recorded signals.

  15. In-situ temperature calibration procedure for temperature and strain fibre Bragg grating sensors for monitoring pre-stressing strands

    NASA Astrophysics Data System (ADS)

    Mckeeman, I.; Fusiek, G.; Perry, M.; Niewczas, P.; Johnston, M.

    2015-09-01

    In this work, we demonstrate active and passive methods for in-situ temperature calibration of fibre Bragg grating strain and temperature sensors. The method is suitable for characterising sensors which are already attached to the steel reinforcements of civil structures. The proposed method, which involves the use of active induction heating or passive room temperature fluctuations, can be implemented using portable equipment, is time efficient, and can be used to calibrate attached sensors on-site, rather than in lab conditions. Preliminary results of the induction heating calibration show good agreement with pre-calibrated temperature sensors. In-situ calibration of fibre strain sensors, attached to a prestressing strand is also successfully carried out.

  16. Study of local properties of fibre Bragg gratings by the method of optical space-domain reflectometry

    SciTech Connect

    Korolev, I G; Vasil'ev, Sergei A; Medvedkov, O I; Dianov, Evgenii M

    2003-08-31

    The method of optical space-domain reflectometry for measuring local spatial characteristics of fibre Bragg gratings (FBGs) is described in detail. It is demonstrated experimentally that, by using IR and UV radiation sources, this method provides good sensitivity ({approx}10{sup -4}) of measuring the modulation amplitude of the induced refractive index in the core of an optical fibre and a high spatial resolution ({approx}100 {mu}m and better). The factors affecting the accuracy of measurements as well as technical and methodological limitations of the method are considered. A comparative analysis of modern methods for studying the spatial properties of FBGs is performed and applications of these methods are considered. (special issue devoted to the memory of academician a m prokhorov)

  17. Suppression of side lobes in a spectrum of fibre Bragg gratings due to the transverse displacement of phase mask with respect to the optical fibre

    SciTech Connect

    Abdullina, S R; Nemov, I N; Babin, Sergei A

    2012-09-30

    The possibility of apodisation of fibre Bragg gratings (FBGs) recorded in the interference region of two Gaussian beams in the phase-mask scheme is considered. The FBG reflection spectra are numerically simulated for different values of recordingbeam parameters and the distance between the axes of interfering beams diffracted into different orders, which is varied by transverse displacement of the phase mask with respect to the optical fibre. Suppression of side lobes and smoothing out of the FBG spectrum with an increase in the transverse displacement of the phase mask is experimentally demonstrated. It is shown that this effect is caused by the equalisation of the mean induced refractive index in the FBG region. (optical fibres, lasers and amplifiers. properties and applications)

  18. 870nm Bragg grating in single mode TOPAS microstructured polymer optical fibre

    NASA Astrophysics Data System (ADS)

    Yuan, Wu; Webb, David J.; Kalli, Kyriacos; Nielsen, Kristian; Stefani, Alessio; Rasmussen, Henrik K.; Bang, Ole

    2011-05-01

    We report the fabrication and characterization of a fiber Bragg grating (FBG) with 870 nm resonance wavelength in a single-mode TOPAS microstructured polymer optical fiber (mPOF). The grating has been UV-written with the phasemask technique using a 325 nm HeCd laser. The static tensile strain sensitivity has been measured as 0.64 pm/μstrain, and the temperature sensitivity was -60 pm/°C. This is the first 870nm FBG and the first demonstration of a negative temperature response for the TOPAS FBG, for which earlier results have indicated a positive temperature response. The relatively low material loss of the fiber at this wavelength compared to that at longer wavelengths will considerably enhance the potential utility of the TOPAS FBG.

  19. Single-mode fibre optic Bragg grating sensing on the base of birefringence in surface-mounting and embedding applications

    NASA Astrophysics Data System (ADS)

    Lee, Jung-Ryul; Tsuda, Hiroshi; Koo, Bon-Yong

    2007-02-01

    Birefringence effects in the two typical installation techniques of fibre Bragg grating(FBG) sensor are investigated: surface-mounting and embedding configurations. When the FBG is bonded on a host material, the sensitivity loss in ultrasonic measurement caused by glue-induced low-birefringence is first reported. Next, the transverse stress-induced high birefringence when the FBG is embedded into a fabric composite laminate is measured as 3.6×10 -4. Such induced-birefringence effects are experimentally analysed in mechanical applications. Simple and effective solutions with respect to the respective installation configurations for removing the birefringence effect are proposed and the obtained zero-birefringence cases are compared with the birefringent cases.

  20. On-line monitoring of multi-component strain development in a tufting needle using optical fibre Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Chehura, Edmon; Dell'Anno, Giuseppe; Huet, Tristan; Staines, Stephen; James, Stephen W.; Partridge, Ivana K.; Tatam, Ralph P.

    2014-07-01

    Dynamic loadings induced on a tufting needle during the tufting of dry carbon fibre preform via a commercial robot-controlled tufting head were investigated in situ and in real-time using optical fibre Bragg grating (FBG) sensors bonded to the needle shaft. The sensors were configured such that the axial strain and bending moments experienced by the needle could be measured. A study of the influence of thread and thread type on the strain imparted to the needle revealed axial strain profiles which had equivalent trends but different magnitudes. The mean of the maximum axial compression strains measured during the tufting of a 4-ply quasi-isotropic carbon fibre dry preform were - 499 ± 79 μɛ, - 463 ± 51 μɛ and - 431 ± 59 μɛ for a needle without thread, with metal wire and with Kevlar® thread, respectively. The needle similarly exhibited bending moments of different magnitude when the different needle feeding configurations were used.

  1. Axle counter for high-speed railway based on fibre Bragg grating sensor and algorithm optimization for peak searching

    NASA Astrophysics Data System (ADS)

    Quan, Yu; He, Dawei; Wang, Yongsheng; Wang, Pengfei

    2014-08-01

    For the benefit of electrical isolation, corrosion resistance and quasi-distributed detecting, Fiber Bragg Grating Sensor has been studied for high-speed railway application progressively. Existing Axle counter system based on fiber Bragg grating sensor isn't appropriate for high-speed railway for the shortcoming of emplacement of fiber Bragg grating sensor, low Sampling rate and un-optimized algorithm for peak searching. We propose a new design for the Axle counter of high-speed railway based on high-speed fiber Bragg grating demodulating system. We also optimized algorithm for peak searching by synthesizing the three sensor data, bringing forward the time axle, Gaussian fitting and Finite Element Analysis. The feasibility was verified by field experiment.

  2. Pantograph-catenary monitoring by means of fibre Bragg grating sensors: Results from tests in an underground line

    NASA Astrophysics Data System (ADS)

    Bocciolone, Marco; Bucca, Giuseppe; Collina, Andrea; Comolli, Lorenzo

    2013-12-01

    One of the most common way to collect the traction current needed for the underground vehicle operation is by using the pantograph-overhead line system. The periodically check of pantographs and overhead lines is important to assure the correct interaction between the two systems in terms of good current collection quality. The main diagnostic tools are the monitoring of the vertical force between the overhead line and the pantograph head, and the vertical acceleration on the pantograph head. The pantograph system works under high voltage (1500 V, DC, in our tests) and high electromagnetic disturbances are present. For this reason, traditional electrical sensors can be used only with particular precautions that complicate the measurement set up; fibre optic sensors, and in particular fibre Bragg grating (FBG) sensors, are particularly suitable for this application. In this paper, the application of the FBG sensors on a pantograph for the monitoring of underground pantograph-catenary system is presented. FBG sensors are used to measure both the contact force and the vertical acceleration of the pantograph head. The same measurements are also gathered with a traditional electrical system, allowing a comparison. The result is a very good agreement between electrical and optical measurements, except in particular frequency ranges where the different positioning of the sensors influences the output, limiting the comparison. Moreover, some interesting results on the dynamic behaviour of the pantograph and its interaction with the overhead line are presented. Finally, a method to point out the main defects on the overhead line is shown.

  3. Detection of premature browning in ground beef with an integrated optical-fibre based sensor using reflection spectroscopy and fibre Bragg grating technology

    NASA Astrophysics Data System (ADS)

    O'Farrell, M.; Sheridan, C.; Lewis, E.; Zhao, W. Z.; Sun, T.; Grattan, K. T. V.; Kerry, J.; Jackman, N.

    2007-07-01

    This paper reports on an optical fibre based sensor system to detect the occurrence of premature browning in ground beef. Premature browning (PMB) occurs when, at a temperature below the pasteurisation temperature of 71°C, there are no traces of pink meat left in the patty. PMB is more frequent if poorer quality beef or beef that has been stored under imperfect conditions. The experimental work pertaining to this paper involved cooking fresh meat and meat that has been stored in a freezer for, 1 week, 1 month and 3 months and recording the reflected spectra and temperature at the core of the product, during the cooking process, in order to develop a classifier based on the spectral response and using a Self-Organising Map (SOM) to classify the patties into one of four categories, based on their colour. Further tests were also carried out on developing an all-optical fibre sensor for measuring both the temperature and colour in a single integrated probe. The integrated probe contains two different sensor concepts, one to monitor temperature, based on Fibre Bragg Grating (FBG) technology and a second for meat quality, based on reflection spectroscopy in the visible wavelength range.

  4. Damage Detection of CFRP Plates by Full-Spectral Analysis of a Fibre Bragg Grating Sensor Signal

    NASA Astrophysics Data System (ADS)

    Mizutani, Yoshihiro; Groves, Roger M.

    2010-05-01

    This paper describes the measurement of average strain, strain distribution and vibration of cantilever beam made of Carbon Fiber Reinforced Plastics (CFRP), using a single Fibre Bragg Grating (FBG) sensor mounted on the beam surface. Average strain is determined from the displacement of the peak wavelength of reflected light from the FBG sensor. Unstrained reference FBG sensors were used to compensate for temperature drift and the photoelastic coefficient (Pe), which was used to calculate the gauge factor. Measured strains agree with those measured by a resistance foil strain gauge attached to the sample. Stress distributions are measured by monitoring the variation in the full width half maximum (FWHM) values of the reflected spectrum, using a proposed optical analytical model, described in the paper. FWHM values were measured for both the cantilever test beam and a for a reference beam, loaded using a four-point bending rig. The trend of the stress distribution for the test beam matches with our analytical model, however with a relatively large noise present in the experimentally determined data. The vibration of cantilever beam was measured by temporal analysis of the peak reflection wavelength. This technique is very stable as measurements are not affected by variations in the signal amplitude. Finally an application of FBG sensors for damage detection of CFRP plates is demonstrated, by measuring the average strain and natural frequency. With small defects of different sizes applied to the CFRP plate, average strains were seen to increase with damage size and the natural frequency decreased with damage size.

  5. Damage Detection of CFRP Plates by Full-Spectral Analysis of a Fibre Bragg Grating Sensor Signal

    SciTech Connect

    Mizutani, Yoshihiro; Groves, Roger M.

    2010-05-28

    This paper describes the measurement of average strain, strain distribution and vibration of cantilever beam made of Carbon Fiber Reinforced Plastics (CFRP), using a single Fibre Bragg Grating (FBG) sensor mounted on the beam surface. Average strain is determined from the displacement of the peak wavelength of reflected light from the FBG sensor. Unstrained reference FBG sensors were used to compensate for temperature drift and the photoelastic coefficient (P{sub e}), which was used to calculate the gauge factor. Measured strains agree with those measured by a resistance foil strain gauge attached to the sample. Stress distributions are measured by monitoring the variation in the full width half maximum (FWHM) values of the reflected spectrum, using a proposed optical analytical model, described in the paper. FWHM values were measured for both the cantilever test beam and a for a reference beam, loaded using a four-point bending rig. The trend of the stress distribution for the test beam matches with our analytical model, however with a relatively large noise present in the experimentally determined data. The vibration of cantilever beam was measured by temporal analysis of the peak reflection wavelength. This technique is very stable as measurements are not affected by variations in the signal amplitude. Finally an application of FBG sensors for damage detection of CFRP plates is demonstrated, by measuring the average strain and natural frequency. With small defects of different sizes applied to the CFRP plate, average strains were seen to increase with damage size and the natural frequency decreased with damage size.

  6. NIR fibre Bragg grating as dynamic sensor: an application of 1D digital wavelet analysis for signal denoising

    NASA Astrophysics Data System (ADS)

    Hafizi, Z. M.; Kahandawa, G. C.; Epaarachchi, J.; Lau, K. T.; Canning, J.; Cook, K.

    2013-08-01

    During the past decade, many successful studies have evidently shown remarkable capability of Fiber Bragg Gratings (FBG) sensor for dynamic sensing. Most of the research works utilized the 1550 nm wavelength range of FBG sensors. However near infra-red (NIR) FBG sensors can offer the lower cost of Structural health Monitoring (SHM) systems which uses cheaper silicon sources and detectors. Unfortunately, the excessive noise levels that experienced in NIR wavelengths have caused the rejection of sensor that operating in this range of wavelengths for SHM systems. However, with the appropriate use of signal processing tools, these noisy signals can be easily `cleaned'. Wavelet analysis is one of the powerful signal processing tools nowadays, not only for time-frequency analysis but also for signal denoising. This present study revealed that the NIR FBG range gave good response to impact signals. Furthermore, these `noisy' signals' response were successfully filtered using one dimensional wavelet analysis.

  7. Temperature influence on the cladding mode distribution in highly localized point-by-point fibre Bragg gratings

    NASA Astrophysics Data System (ADS)

    Caucheteur, C.; Gonzalez-Vila, A.; Chikh-Bled, H.; Lasri, B.; Kinet, D.; Chah, K.

    2016-05-01

    An infrared femtosecond pulses laser is used to manufacture point-by-point gratings in telecommunication-grade optical fibres. The refractive index modulations are localized close to the core-cladding interface, yielding a strong coupling to cladding mode resonances together with an important photo-induced birefringence. Such gratings have been recently used for refractrometric measurements. In this work, their transmitted amplitude spectrum is measured with polarized light while they are exposed to temperature changes up to 900 °C. Despite an overall good thermal stability of the gratings that confirms their robustness for high-temperature refractometry, we report an interesting polarization effect depending on both the cladding mode resonance family (radially- and azimuthally-polarized modes) and mode order. While the birefringence of the core mode resonance decreases with the temperature, certain cladding mode resonances show an increase of the wavelength splitting between their orthogonally-polarized components. This differential behaviour can be of high interest to develop high-resolution multiparametric sensing platforms.

  8. Advances in Bio-Tactile Sensors for Minimally Invasive Surgery Using the Fibre Bragg Grating Force Sensor Technique:A Survey

    PubMed Central

    Abushagur, Abdulfatah A.G.; Arsad, Norhana; Ibne Reaz, Mamun; Ashrif, A.; Bakar, A.

    2014-01-01

    The large interest in utilising fibre Bragg grating (FBG) strain sensors for minimally invasive surgery (MIS) applications to replace conventional electrical tactile sensors has grown in the past few years. FBG strain sensors offer the advantages of optical fibre sensors, such as high sensitivity, immunity to electromagnetic noise, electrical passivity and chemical inertness, but are not limited by phase discontinuity or intensity fluctuations. FBG sensors feature a wavelength-encoding sensing signal that enables distributed sensing that utilises fewer connections. In addition, their flexibility and lightness allow easy insertion into needles and catheters, thus enabling localised measurements inside tissues and blood. Two types of FBG tactile sensors have been emphasised in the literature: single-point and array FBG tactile sensors. This paper describes the current design, development and research of the optical fibre tactile techniques that are based on FBGs to enhance the performance of MIS procedures in general. Providing MIS or microsurgery surgeons with accurate and precise measurements and control of the contact forces during tissues manipulation will benefit both surgeons and patients. PMID:24721774

  9. Fibre gratings and their applications

    SciTech Connect

    Vasil'ev, Sergei A; Medvedkov, O I; Korolev, I G; Bozhkov, A S; Kurkov, Andrei S; Dianov, Evgenii M

    2005-12-31

    A brief review is given of the state of the art in the research on the photosensitivity of fibres and photoinduced fibre gratings. The most important properties of fibre gratings are considered and the main methods of their production and their applications are discussed. The photosensitive compositions of silica glasses are presented and methods for increasing their photosensitivity are indicated. (review)

  10. 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.

  11. 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.

  12. 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.

  13. Multiplexing of fiber optic Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Chan, Kok Cheung Peter

    2000-11-01

    The main objective of this project was to develop a novel technique for multiplexing fiber Bragg grating sensors for strain measurements. Multiplexing is a very important issue for fiber Bragg grating sensors, as it allows them to be used for distributed sensing where their greatest impact is anticipated. Three types of multiplexed fiber Bragg grating sensor system prototypes were developed in this work. Most effort was devoted to a frequency-modulated continuous wave technique for multiplexing fiber Bragg grating sensors. A detailed mathematical analysis of the frequency-modulated continuous wave multiplexing technique was performed. It was identified that the technique can be used to multiplex up to 32 fiber Bragg grating sensors of the same nominal Bragg wavelength with a theoretical crosstalk performance of below -48 dB. This level of crosstalk corresponds to a wavelength detected error of well below 1 pm if fiber Bragg gratings having a bandwidth of around 0.2 nm are used. A few hundreds of sensors could be multiplexed by combining the frequency-modulated continuous wave technique with the well known wavelength-division-multiplexing technique. The practical factors which limit the performance, including the effect of biasing from the optimal working condition and the effect of non-ideal frequency sweeping intensity modulation, were investigated. The system performance, in terms of power budget and inter-sensor crosstalk for a serial and parallel architecture was also determined. A series of experiments were carried out to verify the principle of operation and to study the effects arising from the various practical performance limiting factors and from different network architectures. A three sensor system was experimentally demonstrated with -30 dB crosstalk level and with 2 μɛ resolution in terms of root-mean-square strain value. The system performance was found to be limited by the residual amplitude modulation due to the non-ideal frequency response of

  14. Interferometric fiber Bragg grating shift demodulation

    NASA Astrophysics Data System (ADS)

    Stepien, Karol; Jóźwik, Michalina; Nasilowski, Tomasz

    2015-09-01

    In this paper we present a fiber Bragg grating shift demodulator with changeable resolution based on an unbalanced fiber Mach-Zehnder interferometer. Preliminary research proves phase sensitivity to Bragg wavelength changes of 6,83 rad/mɛ. Phase sensitivity can be modified by changing the optical path difference witch is only limited by the coherence length of light reflected by the fiber Bragg grating. This solution can be used as a single sensor or as a part of a more complex system.

  15. 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.

  16. Evaluation of the optical switching characteristics of erbium-doped fibres for the development of a fibre Bragg grating sensor interrogator

    NASA Astrophysics Data System (ADS)

    Rigas, Evangelos; Correia, R.; Stathopoulos, N. A.; Savaidis, S. P.; James, S. W.; Bhattacharyya, D.; Kirby, P. B.; Tatam, R. P.

    2014-05-01

    A polling topology that employs optical switching based on the properties of erbium-doped fibres (EDFs) is used to interrogate an array of FBGs. The properties of the EDF are investigated in its pumped and un-pumped states and the EDFs' switching properties are evaluated by comparing them with a high performance electronically controlled MEM optical switch. Potential advantages of the proposed technique are discussed.

  17. 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

  18. 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.

  19. 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.

  20. 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

  1. 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.

  2. 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

  3. Bragg wavelength shift for irradiated polymer fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Hamdalla, Taymour A.; Nafee, Sherif S.

    2015-11-01

    The effect of neutron-irradiation from a 5 Ci Am-241/Be-9 neutron source on the characteristics of Polymer Fiber Bragg Grating (PFBG) has been studied in the present work. The PFBG has been irradiated using fast neutrons with different doses range from 24 up to 720 Gy. The transmittance and reflectance of the PFBG have been recorded and interpreted before and after the irradiation. Results in this study showed that the neutron irradiation might cause a structural degradation of the polymer's main chain, which led to a shift in the Central Bragg Wavelength (CBW). In addition, the CBW increased from 4 pm to 14 pm when the neutron dose increased from 24 to 720 Gy. Moreover, no saturation has been observed in the CBW under the effect of the applied doses. Therefore, the PFBG of high Bragg wavelength is a suitable candidate for the use in the dosimetry systems.

  4. Polymer PCF Bragg grating sensors based on poly(methyl methacrylate) and TOPAS cyclic olefin copolymer

    NASA Astrophysics Data System (ADS)

    Johnson, Ian. P.; Webb, David J.; Kalli, Kyriacos; Yuan, Wu; Stefani, Alessio; Nielsen, Kristian; Rasmussen, Henrik K.; Bang, Ole

    2011-05-01

    Fibre Bragg grating (FBG) sensors have been fabricated in polymer photonic crystal fibre (PCF). Results are presented using two different types of polymer optical fibre (POF); first multimode PCF with a core diameter of 50μm based on poly(methyl methacrylate) (PMMA) and second, endlessly single mode PCF with a core diameter of 6μm based on TOPAS cyclic olefin copolymer. Bragg grating inscription was achieved using a 30mW continuous wave 325nm helium cadmium laser. Both TOPAS and PMMA fibre have a large attenuation of around 1dB/cm in the 1550nm spectral region, limiting fibre lengths to no longer than 10cm. However, both have improved attenuation of under 10dB/m in the 800nm spectral region, thus allowing for fibre lengths to be much longer. The focus of current research is to utilise the increased fibre length, widening the range of sensor applications. The Bragg wavelength shift of a grating fabricated in PMMA fibre at 827nm has been monitored whilst the POF is thermally annealed at 80°C for 7 hours. The large length of POF enables real time monitoring of the grating, which demonstrates a permanent negative Bragg wavelength shift of 24nm during the 7 hours. This creates the possibility to manufacture multiplexed Bragg sensors in POF using a single phase mask in the UV inscription manufacturing. TOPAS holds certain advantages over PMMA including a much lower affinity for water, this should allow for the elimination of cross-sensitivity to humidity when monitoring temperature changes or axial strain, which is a significant concern when using PMMA fibre.

  5. 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.

  6. 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.

  7. 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.

  8. Combining regenerated gratings and optical fibre Fabry-Pérot cavities for dual sensing of ultra-high temperature and strain

    NASA Astrophysics Data System (ADS)

    Cook, Kevin; Ran, Zengling; Gong, Yuan; Rao, Yunjiang; Canning, John

    2015-07-01

    The successful regeneration of fibre Bragg gratings (FBGs) inscribed in an inline fibre etalon is demonstrated. The etalon is formed by UV-micromaching of the fibre end-face to form a cylindrical hole, the fibre is then fusion spliced to seal the cavity. Such a fibre device has excellent potential for the simultaneous measurement of ultra-high temperatures and strain.

  9. Post-exposed fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Miller, Gary A.

    This thesis explains the development and characterization of a novel technique to fabricate weak fiber Bragg gratings for highly specific multi-element sensor arrays. This method, termed the "rescan technique," involves re-exposing a local region of a grating to fringeless ultraviolet light to "trim" unwanted portions of the reflection spectrum. The spectral effects that result from a rescan can only be adequately described by inventing the concept of a three-dimensional index growth surface, where induced index is a function of both the writing intensity and the exposure time. Using this information, it is possible to predict the spectral response of a rescanned grating using a numerical model. For our model, we have modified the piecewise-uniform approach to include coefficients within the coupled-mode formulism that imitate the same scattering properties as the actual grating. By taking high accuracy measurements of the refractive index change in germanosilicate fiber, we have created the necessary 3D map of photoinduced index to accurately model gratings and their post-exposure spectra. We will also demonstrate that optical fiber exhibits what we call "exposure history"; the final index change in a region depends on the previous exposures conditions.

  10. 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

  11. Novel technique for distributed fibre sensing based on faint long gratings (FLOGs)

    NASA Astrophysics Data System (ADS)

    Thévenaz, Luc; Chin, Sanghoon; Sancho, Juan; Sales, Salvador

    2014-05-01

    A novel approach for fibre distributed sensing is proposed, conceived to match as closely as possible to an ideally responding distributed sensor. It is demonstrated that it can be actually realized using fibre Bragg gratings of extremely low index contrast and continuously printed over the entire fibre length. The concept is experimentally validated over a restricted distance range that proves the huge potentialities of the technique in terms of response and precision.

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. Fiber Bragg gratings for microwave photonics subsystems.

    PubMed

    Wang, Chao; Yao, Jianping

    2013-09-23

    Microwave photonics (MWP) is an emerging filed in which photonic technologies are employed to enable and enhance functionalities in microwave systems which are usually very challenging to fulfill directly in the microwave domain. Various photonic devices have been used to achieve the functions. A fiber Bragg grating (FBG) is one of the key components in microwave photonics systems due to its unique features such as flexible spectral characteristics, low loss, light weight, compact footprint, and inherent compatibility with other fiber-optic devices. In this paper, we discuss the recent development in employing FBGs for various microwave photonics subsystems, with an emphasis on subsystems for microwave photonic signal processing and microwave arbitrary waveform generation. The limitations and potential solutions are also discussed. PMID:24104174

  18. 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.

  19. 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

  20. Modified femtosecond laser inscription method for tailored grating sensors in encapsulated silica and low-loss polymer optical fibres

    NASA Astrophysics Data System (ADS)

    Kalli, Kyriacos; Lacraz, Amedee; Theodosiou, Andreas; Kofinas, Marios

    2016-05-01

    There is great interest in the development of flexible wavelength filters and optical fibre sensors, such as Bragg and superstructure gratings, grating arrays and chirped gratings in glass and polymer optical fibres. A major hurdle is the development of an inscription method that should offer flexibility and reliability and be generally applicable to all optical fibre types. With this in mind we have developed a novel femtosecond laser inscription method; plane-by-plane inscription, whereby a 3D-index change of controlled length across the fibre core, width along the fibre axis and depth is written into the optical fibre. We apply this method for the inscription of various grating types in coated silica and low- loss CYTOP polymer optical fibres. The plane-by-plane method allows for multiple and overlapping gratings in the fibre core. Moreover, we demonstrate that this novel fibre Bragg grating inscription technique can be used to modify and add versatility to an existing, encapsulated optical fibre pressure sensor. The femtosecond laser is operated in the green or the near infra-red, based on the material properties under laser modification.

  1. 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.

  2. Fiber Bragg grating sensors for monitoring of wind turbine blades

    NASA Astrophysics Data System (ADS)

    Krebber, K.; Habel, W.; Gutmann, T.; Schram, C.

    2005-05-01

    Fiber Bragg grating sensor arrays can be used to monitor the mechanical behavior of rotor blades of wind turbines. In order to investigate how stable and reliably work such sensors, different fiber Bragg gratings were embedded into textilereinforced composite. Long-term temperature and tensile (fatigue) tests have been carried out with composite structure specimens. This paper reports on selected results of the tests and discusses important reliability aspects with regard to the fiber design and the fiber material.

  3. Composite scarf repair monitoring using fiber Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Li, Henry C. H.; Herszberg, Israel; Davis, Claire E.; Stoddart, Paul R.

    2007-04-01

    Structural health monitoring (SHM) technology may be applied to composite bonded repairs to enable the continuous through-life assessment of the repair efficacy. This paper describes an SHM technique for the detection of debonding in composite scarf repairs using fibre optic Bragg grating strain sensors. A typical composite sandwich structure with a scarf repair on one surface is examined in this paper. A finite element study was conducted which showed that the strain in the debonded region changed significantly compared to the undamaged state. A differential strain approach was used to facilitate the detection of debonds, where two sensors were strategically positioned so that their strain differential increased as the damage propagated. With the use of matching gratings, this technique greatly reduced the support equipment requirement by converting the spectral information into an intensity-modulated signal, thus allowing a compact photodetector to be used for sensor interrogation. An experimental investigation was conducted to validate the theoretically predicted results. The experimental measurements agreed well with the numerical findings qualitatively, indicating that the proposed scheme has great potential as a simple and effective monitoring technique for composite scarf repairs.

  4. Signal-to-noise ratio evaluation with draw tower fibre Bragg gratings (DTGs) for dynamic strain sensing at elevated temperatures and corrosive environment

    NASA Astrophysics Data System (ADS)

    De Pauw, B.; Lamberti, A.; Vanlanduit, S.; Van Tichelen, K.; Geernaert, T.; Berghmans, F.

    2014-05-01

    Measuring strain at the surface of a structure can help to estimate the dynamical properties of the structure under test. Such a structure can be a fuel assembly of a nuclear reactor consisting of fuel pins. In this paper we demonstrate a method to integrate draw tower gratings (DTGs) in a fuel pin and we subject this pin to conditions close to those encountered in a heavy liquid metal (HLM) reactor. More specifically, we report on the performance of DTGs used as a strain sensor when immersed in HLM during thermal cycles (up to 300_C) for up to 700 hours.

  5. Optical-Based Sensors for Monitoring Corrosion of Reinforcement Rebar via an Etched Cladding Bragg Grating

    PubMed Central

    Hassan, Muhammad Rosdi Abu; Bakar, Muhammad Hafiz Abu; Dambul, Katrina; Adikan, Faisal Rafiq Mahamd

    2012-01-01

    In this paper, we present the development and testing of an optical-based sensor for monitoring the corrosion of reinforcement rebar. The testing was carried out using an 80% etched-cladding Fibre Bragg grating sensor to monitor the production of corrosion waste in a localized region of the rebar. Progression of corrosion can be sensed by observing the reflected wavelength shift of the FBG sensor. With the presence of corrosion, the etched-FBG reflected spectrum was shifted by 1.0 nm. In addition, with an increase in fringe pattern and continuously, step-like drop in power of the Bragg reflected spectrum was also displayed. PMID:23202233

  6. 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.

  7. Strain gradient chirp of uniform fiber Bragg grating without shift of central Bragg wavelength

    NASA Astrophysics Data System (ADS)

    Dong, Xinyong; Guan, Bai-Ou; Yuan, Shuzhong; Dong, Xiaoyi; Tam, Hwa-Yaw

    2002-02-01

    A novel technique to introduce large linear chirp to an uniform fiber Bragg grating (FBG) is realized by gluing the grating in a slanted direction onto the side face of a simple supported beam. Strain gradient is formed along the length of the grating when the beam is bent, and produces a linear variation in the grating pitch. This permits a tunable chirp without central wavelength shift. The maximum bandwidth of the chirped FBG produced was 11.32 nm.

  8. Thermally tunable integrated planar Bragg-grating stabilized diode laser

    NASA Astrophysics Data System (ADS)

    Lynch, S. G.; Gates, J. C.; Berry, S. A.; Holmes, C.; Smith, P. G. R.

    2015-03-01

    A pair of external cavity diode lasers are fabricated using an integrated planar Bragg grating. The planar waveguide and Bragg reflector is UV-written within a glass-on-silicon chip. Intensity isolated, continuous wavelength tuning at > 1kHz modulation rate is acheived using micro-heating elements fabricated directly over the Bragg grating. Low RIN (<140dB) and low linewidth (δν ~ 200 kHz) operation is found using a heterodyne measurement. We demonstrate the lasers operating in phase-locked loop configuration where one laser is frequency-offset locked to the other.

  9. Linearized Bragg grating assisted electro-optic modulator.

    PubMed

    Khurgin, Jacob B; Morton, Paul A

    2014-12-15

    We propose a new linearized electro-optic modulator in which linearization is achieved by modulating the index of a Bragg grating reflector placed in the arm(s) of a Michelson Interferometer. This grating-assisted Michelson (GAMI) modulator can operate as either an intensity or amplitude modulator, and is shown to significantly improve the linearity of microwave photonics links. PMID:25503037

  10. Vibration sensing with fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Takahashi, Nobuaki; Yoshimura, Kazuto; Takahashi, Sumio

    2001-08-01

    The intensity of laser light is modulated when reflecting back from a fiber Bragg grating (FBG) which is glued onto a PZT vibrator and expands/contracts as the vibrator vibrates. The wavelength of the laser light is tuned to the slope of the FBG reflectance curve as a function of optical wavelength. Measuring the modulation component of the detected signal, we can directly observe mechanical vibration of the vibrator. The output of the sensor is stable and the involved harmonic component is below the system noise level. It is then believed that the sensor operation is linear. The sensitivity depends on the slope of the FBG reflection spectrum curve at the operating wavelength and is higher for the larger slope. The minimum amplitude of the vibrator measured in the experiment is 4.5 nm, which corresponds to the strain of 2.14 μstrain. Since not only an FBG has little influence on the object under measurement because of its small size and light weight but also its frequency characteristics are thought to be better than a PZT vibration sensor, i.e., the sensor can be used in a wide range of vibration frequency, an FBG is expected to provide us with an important tool of practicality for measuring mechanical vibration.

  11. 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.

  12. Multipoint sensor based on fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Méndez-Zepeda, O.; Muñoz-Aguirre, S.; Beltrán-Pérez, G.; Castillo-Mixcóatl, J.

    2011-01-01

    In some control and industrial measurement systems of physical variables (pressure, temperature, flow, etc) it is necessary one system and one sensor to control each process. On the other hand, there are systems such as PLC (Programmable Logic Control), which can process several signals simultaneously. However it is still necessary to use one sensor for each variable. Therefore, in the present work the use of a multipoint sensor to solve such problem has been proposed. The sensor consists of an optical fiber laser with two Fabry-Perot cavities constructed using fiber Bragg gratings (FBG). In the same system is possible to measure changes in two variables by detecting the intermodal separation frequency of each cavity and evaluate their amplitudes. The intermodal separation frequency depends on each cavity length. The sensor signals are monitored through an oscilloscope or a PCI card and after that acquired by PC, where they are analyzed and displayed. Results of the evaluation of the intermodal frequency separation peak amplitude behavior with FBG stretching are presented.

  13. 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.

  14. 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.

  15. Simultaneous 2D Strain Sensing Using Polymer Planar Bragg Gratings

    PubMed Central

    Rosenberger, Manuel; Eisenbeil, Waltraud; Schmauss, Bernhard; Hellmann, Ralf

    2015-01-01

    We demonstrate the application of polymer planar Bragg gratings for multi-axial strain sensing and particularly highlight simultaneous 2D strain measurement. A polymer planar Bragg grating (PPBG) fabricated with a single writing step in bulk polymethylmethacrylate is used for measuring both tensile and compressive strain at various angles. It is shown that the sensitivity of the PPBG strongly depends on the angle between the optical waveguide into which the grating is inscribed and the direction along which the mechanical load is applied. Additionally, a 2D PPBG fabricated by writing two Bragg gratings angularly displaced from each other into a single polymer platelet is bonded to a stainless steel plate. The two reflected wavelengths exhibit different sensitivities while tested toward tensile and compressive strain. These characteristics make 2D PPBG suitable for measuring multi-axial tensile and compressive strain. PMID:25686313

  16. Simultaneous 2D strain sensing using polymer planar Bragg gratings.

    PubMed

    Rosenberger, Manuel; Eisenbeil, Waltraud; Schmauss, Bernhard; Hellmann, Ralf

    2015-01-01

    We demonstrate the application of polymer planar Bragg gratings for multi-axial strain sensing and particularly highlight simultaneous 2D strain measurement. A polymer planar Bragg grating (PPBG) fabricated with a single writing step in bulk polymethylmethacrylate is used for measuring both tensile and compressive strain at various angles. It is shown that the sensitivity of the PPBG strongly depends on the angle between the optical waveguide into which the grating is inscribed and the direction along which the mechanical load is applied. Additionally, a 2D PPBG fabricated by writing two Bragg gratings angularly displaced from each other into a single polymer platelet is bonded to a stainless steel plate. The two reflected wavelengths exhibit different sensitivities while tested toward tensile and compressive strain. These characteristics make 2D PPBG suitable for measuring multi-axial tensile and compressive strain. PMID:25686313

  17. 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.

  18. In situ health monitoring of bonded composite repairs using a novel fiber Bragg grating sensing arrangement

    NASA Astrophysics Data System (ADS)

    Davis, Claire; Baker, Wayne; Moss, Scott D.; Galea, Stephen C.; Jones, Rhys

    2002-11-01

    As the replacement costs of military aircraft escalate, there is an increasing trend to operate existing aircraft well beyond their original design life. As the fleet ages, structural problems such as airframe corrosion and cracking are becoming significant issues. In recent years, bonded composite patches or doublers have been developed to repair or reinforce defective regions of the airframe. However certification concerns have limited most application of these bonded composite repairs to secondary structures. In order to alleviate certification concerns, and thus facilitate the implementation of this repair technology to critical damage in primary structure, the 'smart patch' approach has been proposed. This approach involves incorporating sensors into the composite patch to self-monitor patch health. This paper describes the use of optical fibre Bragg gratings to measure the changes in thermal residual strain that occur when a composite patch starts to disbond from the parent structure. Conventionally, the Bragg sensing mechanism relies on a shift in reflected wavelength, which requires the use of costly optical measurement tools. A modified sensing arrangement is proposed, which incorporates two Bragg gratings, and a fibre optic coupler. The reflection from the first Bragg grating acts as a reference source for an active Bragg grating on the patch. This modified arrangement allows a relative wavelength shift to be translated into a change in the optical power, which can be measured easily using a low cost interrogation system. The modified sensing arrangement also allows us to more readily miniaturise the opto-electrical interrogation system, thus enabling these systems to be more easily implemented on operational aircraft.

  19. Compact and tunable silicon nitride Bragg grating filters in polymer

    NASA Astrophysics Data System (ADS)

    Zhang, Ziyang; Novo, Alejandro Maese; Liu, Dongliang; Keil, Norbert; Grote, Norbert

    2014-06-01

    A series of tunable filters based on silicon nitride waveguide Bragg gratings buried in polymer are studied, fabricated and analyzed. The gratings are etched completely through the waveguides to improve the peak reflectivity at short grating lengths. Reflectivity from 1% to 70% can be reached when the third-order grating length varies from 16 µm to 160 µm. The experimental results are in good agreement with numerical simulations. Due to its compact size and the thermal advantages of polymer, the filter can be tuned very efficiently by a micro heater buried beneath. A tuning range of 34.5 nm is demonstrated at a heat power of only 22 mW.

  20. 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.

  1. Photonic scanning receiver using an electrically tuned fiber Bragg grating.

    PubMed

    Rugeland, P; Yu, Z; Sterner, C; Tarasenko, O; Tengstrand, G; Margulis, W

    2009-12-15

    A 5-cm-long electrically tuned fiber Bragg grating is used to filter a microwave signal on an optical carrier at 1.55 mum. A chirped distributed-feedback structure is employed, with a transmission bandwidth of 54 MHz and relative optical carrier rejection of >30 dB for rf frequencies >2 GHz. The rapid monotonic sweep of the Bragg wavelength is translated into a fast-frequency sweep for rf analysis. PMID:20016616

  2. 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).

  3. Deformation monitoring of painted wood panels by fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Falciai, Riccardo; Trono, Cosimo; Lanterna, Giancarlo; Castelli, Ciro

    2003-11-01

    The conservation of painted panel supports is a fundamental aim of the whole restoration process. The measurement method up to now utilized by Opificio is based on the application on the panel of reference points, through which a centesimal gauge measures positive and negative movements. We propose a measurement method based on fiber Bragg grating (FBG) sensors. An array of Bragg gratings was glued on several crucial points of the wood structure, and the data were continuously collected. A set of measurements were performed in order to study the deformations of a painted wood panel, induced by relative humidity changes.

  4. Buffering and trapping ultrashort optical pulses in concatenated Bragg gratings.

    PubMed

    Fu, Shenhe; Liu, Yikun; Li, Yongyao; Song, Liyan; Li, Juntao; Malomed, Boris A; Zhou, Jianying

    2013-12-01

    Strong retardation of ultrashort optical pulses, including their deceleration and stoppage in the form of Bragg solitons in a cascaded Bragg grating (BG) structure, is proposed. The manipulations of the pulses are carried out, using nonlinear effects, in a chirped BG segment which is linked, via a defect, to a uniform grating. The storage of the ultrashort pulses is shown to be very robust with respect to variations of the input field intensity, suggesting the feasibility of storing ultrafast optical pulses in such a structure. Physical estimates are produced for the BGs written in silicon. PMID:24281506

  5. 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.

  6. 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.

  7. 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

  8. Solgel grating waveguides for distributed Bragg reflector lasers.

    PubMed

    Fardad, M A; Luo, H; Beregovski, Y; Fallahi, M

    1999-04-01

    Solgel grating waveguides and their application to the fabrication of external-cavity distributed Bragg reflector (DBR) lasers are demonstrated. A new composition of aluminosilicate material is developed for the fabrication of single-mode waveguides and Bragg reflectors. An average loss of <0.2 dB/cm is measured in the single-mode waveguides at 1550 nm. The reflectors show filtering greater than 97% near 1530 nm, with a bandwidth of ~0.6 nm . The Bragg reflectors are used as feedback resonators for DBR lasers. Single-mode lasing with a sidemode suppression of better than 25 dB is demonstrated. PMID:18071539

  9. 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

  10. Chirped pulse compression in nonuniform plasma Bragg gratings

    SciTech Connect

    Wu Huichun; Sheng Zhengming; Zhang Jie

    2005-11-14

    A nonuniform plasma Bragg grating with a monotonically increasing density-modulation profile can be naturally produced by two Gaussian laser pulses counterpropagating through a homogeneous plasma slab. Such a plasma grating exhibits a nonuniform photonic band gap with a monotonically increasing width. It can be used to compress a positively or negatively chirped pulse. Particle-in-cell simulations show that the compressed pulse has nearly no energy loss and the compression efficiency can exceed 90%.

  11. 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

  12. Refractive Index Sensitivity of Tilted Long Period Fibre Gratings Written in Thinned Cladding Fibre

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    We demonstrated the fabrication of tilted long period fibre gratings written in the thinned cladding fibre by CO2 laser. The refractive index characteristics of the gratings with different tilted angles were investigated experimentally. The experimental results show that the grating with larger tilted angle has higher sensitivity to the surrounding refractive index changes.

  13. 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.

  14. A fiber Bragg grating current sensor with temperature compensation

    NASA Astrophysics Data System (ADS)

    Tian, Fei-Fei; Cong, Jia-Wei; Yun, Bin-Feng; Cui, Yi-Ping

    2009-09-01

    A novel fiber Bragg grating (FBG) current sensor with temperature compensation has been proposed. The fiber Bragg grating is glued on the surface of an isosceles triangle cantilever beam, which has a step thickness along the beam axis. Due to the electromagnetic force created by a solenoid and a permanent magnet mounted on the top of the beam, a step strain is applied on the fiber Bragg grating. The change of the electric current in the solenoid makes the spectrum of the fiber Bragg grating split. By monitoring the shift difference of the two split center wavelengths, which is related to the electric current in the solenoid, a current sensor with temperature compensation is obtained. The test range of 0-400 mA is achieved. The experimental results also show that the relationship between the shift difference of the two split center wavelengths of the FBG and the electric current has a linearity of 0.9937, and the sensitivity is about 2.64 nm/A; the test results are independent of the temperature, so the cross sensitive problem is solved.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Flexible nanofiber-coupled hybrid plasmonic Bragg grating.

    PubMed

    Liu, Sheng; Zhou, Linjie; Xu, Jian; Wang, Xinyi; Chen, Jianping

    2016-05-01

    We report a hybrid plasmonic Bragg grating composed of a nanofiber coupled with orthogonally oriented metal strips. Numerical simulations are performed to study the transmission and reflection spectra of the grating. It shows that the TM polarization has much stronger Bragg reflection due to the excitation of hybrid plasmonic modes. The dependence of reflection peaks on several key device parameters is analyzed. Light propagation simulation further reveals that both fundamental and first-order TM modes are excited upon Bragg reflection, leading to two separate peaks in the spectrum. We implement the prototype device by attaching a nanofiber onto the surface of an array of sub-micrometer-wide metal strips. The main reflection peak is measured to have a 3-dB bandwidth of 15 nm and out-of-band rejection of more than 30 dB. The effects of nanofiber radius, alignment angle and coupling length on the device performance are also experimentally investigated. PMID:27137547

  1. 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

  2. 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

  3. 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.

  4. Spectrometer with CMOS demodulation of fiber optic Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Christiansen, Martin Brokner

    A CMOS imager based spectrometer is developed to interrogate a network containing a large number of Bragg grating sensors. The spectrometer uses a Prism-Grating- Prism (PGP) to spectrally separate serially multiplexed Bragg reflections on a single fiber. As a result, each Bragg grating produces a discrete spot on the CMOS imager that shifts horizontally as the Bragg grating experiences changes in strain or temperature. The reflected wavelength of the spot can be determined by finding the center of the spot produced. The use of a randomly addressable CMOS imager enables a flexible sampling rate. Some fibers can be interrogated at a high sampling rate while others can be interrogated at a low sampling rate. However, the use of a CMOS imager leads to several unique problems in terms of signal processing. These include a logarithmic pixel response, a low signal-to-noise ratio, a long pixel time constant, and software issues. The expected capabilities of the CMOS imager based spectrometer are determined with a theoretical model. The theoretical model tests three algorithms for determining the center of the spot: single row centroid, single row parabolic fit, and entire spot centroid. The theoretical results are compared to laboratory test data and field test data. The CMOS based spectrometer is capable of interrogating many optical fibers, and in the configuration tested, the fiber bundle consisted of 23 fibers. Using this system, a single fiber can be interrogated from 778 nm to 852 nm at 2100 Hz or multiple fibers can be interrogated over the same wavelength so that the total number of fiber interrogations is up to 2100 per second. The reflected Bragg wavelength can be determined within +/-3pm, corresponding to a +/-3μɛ uncertainty.

  5. 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.

  6. 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

  7. Simultaneous strain and temperature measurement system with fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Zhu, Dandan; Li, Zhiquan; Sun, Fu; Tian, Xiuxian; Wang, Haifang

    2007-01-01

    Simultaneous strain and temperature measurement system with fiber Bragg grating was presented in this paper. The light from broadband source (BBS) was coupled into sensing probe through 3dB coupler1. Reflective light of two FBGs was split through coupler2 and went into chirped gratings with different pass-band. Demodulation method adopted chirped grating and long period grating edge linear filtering technology. It can send each reflected spectrum to different edge filter. It makes every FBG's reflective spectrum was demodulate. The central reflected wavelength of two FBGs was 1546.15nm and 1554.17nm respectively. Through simulation experiment, we can get that (formula available in manuscript). Strain measurement ranged from 0 to 2000 με. Temperature measurement ranged from 0 to 200°C.

  8. 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

  9. 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

  10. 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.

  11. 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.

  12. 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.

  13. Respiratory monitoring using fibre long period grating sensors

    NASA Astrophysics Data System (ADS)

    Allsop, T.; Reeves, R.; Webb, D. J.; Bennion, I.; Earthrowl, T.; Jones, B.; Miller, M.

    2005-08-01

    We demonstrate the use of a series of in-line fibre long period grating curvature sensors on a garment, used to monitor the thoracic and abdominal volumetric tidal movements of a human subject. These results are used to obtain volumetric tidal changes of the human torso showing reasonable agreement with a spirometer used simultaneously to record the volume at the mouth during breathing. The curvature sensors are based upon long period gratings written in a progressive three layered fibre that are insensitive to refractive index changes. The sensor platform consists of the long period grating laid upon a carbon fibre ribbon, which is encapsulated in a low temperature curing silicone rubber.

  14. 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.

  15. Investigations on birefringence effects in polymer optical fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Hu, X.; Sáez-Rodríguez, D.; Bang, O.; Webb, D. J.; Caucheteur, C.

    2014-05-01

    Step-index polymer optical fiber Bragg gratings (POFBGs) and microstructured polymer optical fiber Bragg gratings (mPOFBGs) present several attractive features, especially for sensing purposes. In comparison to FBGs written in silica fibers, they are more sensitive to temperature and pressure because of the larger thermo-optic coefficient and smaller Young's modulus of polymer materials. (M)POFBGs are most often photowritten in poly(methylmethacrylate) (PMMA) materials using a continuous-wave 325 nm HeCd laser. For the first time to the best of our knowledge, we study photoinduced birefringence effects in (m)POFBGs. To achieve this, highly reflective gratings were inscribed with the phase mask technique. They were then monitored in transmission with polarized light. For this, (m)POF sections a few cm in length containing the gratings were glued to angled silica fibers. Polarization dependent loss (PDL) and differential group delay (DGD) were computed from the Jones matrix eigenanalysis using an optical vector analyser. Maximum values exceeding several dB and a few picoseconds were obtained for the PDL and DGD, respectively. The response to lateral force was finally investigated. As it induces birefringence in addition to the photo-induced one, an increase of the PDL and DGD values were noticed.

  16. 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

  17. Plasma Bragg density gratings produced by optical-field ionization

    SciTech Connect

    Yu Lule; Sheng Zhengming; Zhang Jie

    2009-11-15

    Plasma Bragg density gratings produced by optical-field ionization in underdense gas under the irradiation of two counterpropagating laser pulses at laser intensities around 10{sup 13} W/cm{sup 2} are investigated by particle-in-cell simulation. The grating is composed of interlacing layers of neutral gas and plasma (or partially ionized gas) with its density and period controlled by the initial gas density, laser wavelengths, and intersecting angles of the two laser pulses. The study shows that such gratings have a longer lifetime, about nanoseconds, as compared with those driven by the laser ponderomotive force at higher laser intensities around 10{sup 15} W/cm{sup 2}. They may be used for phase-matched high-harmonic generation, laser self-guiding, laser pulse compression and stretching, etc.

  18. 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.

  19. Research of embedded fiber Bragg grating temperature sensor system

    NASA Astrophysics Data System (ADS)

    Hu, Ji; Wan, Shengpeng; Xie, Changlin; Zhang, Zhimin; Luo, Ningning; He, Shuai

    2010-10-01

    In this article, an embedded fiber Bragg grating temperature sensor system is proposed and researched. The demodulating system controls a Piezoelectric Ceramic (PZT) with sawteeth wave to scan the matching grating, then do photoelectric conversion using a detector, and use Digital Signal Processor (DSP) to find the max intensity. Meanwhile, use PZT drive voltage to control the central wavelength of sensor grating to demodulate. Then use the USB interface chip to realize the communication between DSP and the host computer, and send the collected data to the host computer. Finally, the real time temperature can be inquired and stored through the inquiring interface programmed by computer. The result demonstrates that this experimental system has the wave addressing range from 1540 to 1565 nm and the temperature resolution of 0.1°C.

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Optical code division multiplexed fiber Bragg grating sensing networks

    NASA Astrophysics Data System (ADS)

    Triana, Cristian; Varón, Margarita; Pastor, Daniel

    2015-09-01

    We present the application of Optical Code Division Multiplexing (OCDM) techniques in order to enhance the spectral operation and detection capability of fiber Bragg grating (FBG) sensors networks even under overlapping conditions. In this paper, Optical Orthogonal Codes (OOC) are used to design FBG sensors composed of more than one reflection band. Simulation of the interaction between the encoded Gaussian-shaped sensors is presented. Signal decoding is performed in the electrical domain without requiring additional optical components by means of the autocorrelation product between the reflected spectrum and each sensor-codeword. Results illustrate the accuracy and distinction capability of the method.

  7. Underwater acoustic sensors based on fiber bragg gratings.

    PubMed

    Campopiano, Stefania; Cutolo, Antonello; Cusano, Andrea; Giordano, Michele; Parente, Giuseppe; Lanza, Giuseppe; Laudati, Armando

    2009-01-01

    We report on recent results obtained with a fiber optic hydrophone based on the intensity modulation of the laser light in a FBG (Fiber Bragg Grating) under the influence of the sound pressure. In order to control the behavior of the hydrophone in terms of sensitivity and bandwidth, FBGs have been coated with proper materials, characterized by different elastic modulus and shapes. In particular, new experiments have been carried out using a cylindrical geometry with two different coating, showing that the sensitivity is not influenced by the shape but by the transversal dimension and the material characteristics of the coating. PMID:22408534

  8. 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.

  9. Biofuncationalized microfiber Bragg grating for acid-based sensing

    NASA Astrophysics Data System (ADS)

    Ran, Yang; Huang, Yunyun; Shen, Xiang; Sun, Dandan; Wang, Xiuxin; Jin, Long; Li, Jie; Guan, Baiou

    2014-05-01

    We demonstrate an acid-based sensor from the biofuncationalized microfiber Bragg grating. By electrostatic selfassembly layer-by-layer technique, the film consisting of sodium alginate which has hygroscopic response to the potential of hydrogen is coated on the fiber surface. Consequently, the refractive index variation of the sensing film caused by water absorption can be measured by mFBG's higher order mode peak which can be translated into pH value information. The sensitivity of the sensor is received as high as 265pm/pH.

  10. Microfiber-Based Bragg Gratings for Sensing Applications: A Review

    PubMed Central

    Kou, Jun-Long; Ding, Ming; Feng, Jing; Lu, Yan-Qing; Xu, Fei; Brambilla, Gilberto

    2012-01-01

    Microfiber-based Bragg gratings (MFBGs) are an emerging concept in ultra-small optical fiber sensors. They have attracted great attention among researchers in the fiber sensing area because of their large evanescent field and compactness. In this review, the basic techniques for the fabrication of MFBGs are introduced first. Then, the sensing properties and applications of MFBGs are discussed, including measurement of refractive index (RI), temperature, and strain/force. Finally a summary of selected MFBG sensing elements from previous literature are tabulated. PMID:23012522

  11. Pressure mapping at orthopaedic joint interfaces with fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Mohanty, Lipi; Tjin, Swee Chuan

    2006-02-01

    We present the concept of a fiber-optic sensor that can be used for pressure mapping at the prosthetic knee joint, in vitro and in vivo. An embedded array of fiber Bragg gratings is used to measure the load on the tibial spacer. The sensor gives the magnitude and the location of the applied load. The effect of material properties on the sensitivity of each subgrating is presented. The wavelength-shift maps show the malalignment of implants and demonstrate the potential of this sensor for use during total knee arthroplasty.

  12. Fiber Bragg Grating sensor for shock wave diagnostics

    NASA Astrophysics Data System (ADS)

    Ravid, Avi; Shafir, Ehud; Zilberman, Shlomi; Berkovic, Garry; Glam, Benny; Appelbaum, Gabriel

    2013-06-01

    Fiber Bragg Grating (FBG) sensor response was studied in gas-gun shock wave experiments. The sensors were embedded in PMMA target subjected to planar shock waves under 1 GPa. Two orientations of the FBG sensor with respect to the shock plane were examined: parallel and perpendicular. The shift of the reflected wavelength was measured with a system based on commonly available communication grade add-drop filters that covered the maximal expected wavelength swing. The FBG sensors survived the shock and their strain-to-wavelength response was determined by comparison to the calculated strain based on the known PMMA EOS and VISAR measurements.

  13. 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.

  14. Spectral compression of femtosecond pulses using chirped volume Bragg gratings.

    PubMed

    Nejbauer, Michał; Kardaś, Tomasz M; Stepanenko, Yuriy; Radzewicz, Czesław

    2016-06-01

    In this Letter, we demonstrate a 360 fold spectral bandwidth reduction of femtosecond laser pulses using the method of sum frequency generation of pulses with opposite chirps. The reduction has been achieved in a compact setup in which a single chirped volume Bragg grating replaces conventional stretcher and compressor units. Starting with 180 fs pulses, we have obtained, with a 30% overall efficiency, pulses longer than 100 ps with the spectral bandwidth of 0.23  cm-1 (7 GHz). We also discuss our method on theoretical grounds. PMID:27244372

  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. Absolute strain measurements made with fiber Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Song, In C.; Lee, Sun K.; Jeong, Sung H.; Lee, Byeong H.

    2004-02-01

    A strain sensor system based on optical fiber Bragg gratings (FBGs) is proposed with a new matched-filter design. The strain variation on the sensor FBG is continuously followed and matched by a filter FBG by use of a feedback control loop that produces an identical strain condition on the filter FBG. The matched strain on the filter FBG is then determined from the resonance vibration of the fiber piece embedding the filter FBG. The implementation and the performance of the proposed system are described. It is demonstrated that the proposed system can distinguish strain variation on the sensor FBG with resolution of one microstrain.

  17. 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)

  18. Hydrogen sensing array based on weak fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Bai, Wei; Yang, Minghong; Hu, Chenyuan; Dai, Jixiang; Li, Zhi; Yu, Haihu

    2015-09-01

    Optical fiber hydrogen sensing system based on weak fiber Bragg grating (WFBG) array deposited with palladium (Pd) film is proposed and experimentally demonstrated. For multi-point measurement, three hydrogen WFBG sensors array are weld in a single optical fiber. A time-division multiplexing (TDM) interrogation system is employed to demodulate the sensing array. Sensing experiments to different hydrogen concentrations ranging from 0 to 3.6% are conducted, and the results show good agreement with standard FBG technology. Due to its strong multiplexing capability of weak FBG, the system is possible to integrate thousands of WFBG hydrogen sensors in a single optical fiber.

  19. Modeling of bend effects on fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Cadusch, Peter J.; Thompson, Alexander C.; Stoddart, Paul R.; Wade, Scott A.

    2012-02-01

    Sensing and telecommunication applications requiring the bending of optical fibers to small diameters are on the increase. Recent work has shown that the centre wavelength of fiber Bragg gratings has a bend dependence the magnitude of which varies with the type of fiber in which the grating is written. In this work the basis of the centre wavelength shift is investigated by modeling the effects of several potential causes for standard and depressed cladding fiber designs. The majority of the expected affects, including bend induced stress and mode field deformation, were found to result in small wavelength shifts in the opposite direction to those observed experimentally. However, a new account of the shift, based on simplistic geometrical optics, does show wavelength changes in the observed direction, of up to -0.15 nm, which is in the range of the experimentally measured shifts.

  20. 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

  1. Fiber Bragg grating sensors for dynamic machining applications

    NASA Astrophysics Data System (ADS)

    Bartow, Matthew J.; Calvert, Sean G.; Bayly, Philip V.

    2003-11-01

    Fiber Bragg grating sensors have attracted considerable attention for measurement applications due to their greatly reduced size, low weight, and immunity to electromagnetic interference in comparison with traditional sensing methods. Dynamic measurement of industrial machine tools is useful for gauging surface accuracy, monitoring tool condition, and predicting process stability, but requires a robust sensing scheme. The small size and high natural frequencies of micro machining tools coupled with a harsh manufacturing environment can render traditional sensors ineffective. This work presents a new method for measuring tool motion with fiber Bragg grating strain sensors. The feasibility of the sensing scheme is first demonstrated with a simple bench-top cantilever beam experiment. Then, a method for potting the sensors in the through coolant holes of a 1/8" carbide end mill with a high-viscosity gap-filling cyanoacrylate is demonstrated. Comparative structural analysis tests demonstrate the effectiveness of the sensors. Measurements of tool motion during cutting are presented. Finally, methods of noise reduction and improving signal accuracy are discussed.

  2. Strain transferring of embedded fiber Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Li, Dong-Sheng; Li, Hong-Nan

    2005-05-01

    The relationship between the strains measured by a fiber Bragg grating sensor and the actual structural strains is deduced, then the average strain transfer rate computed by the formulation developed in this paper is compared with available experimental data. The critical adherence length of an optical fiber sensor is determined by a strain lag parameter, which contains both the effects of the geometry and the relative stiffness of the structural components. The analyses shows that the critical adherence length of a fiber sensing segment is the minimum length with which the fiber has to be tightly glued to a structure for adequate sensing. The strain transfer rate of an optical fiber sensor embedded in a multi-layered structure is developed in a similar way, and the factors that influence the efficiency of optical fiber sensor strain transferring are discussed. It is concluded that the strains, sensed by a fiber Bragg grating, have to be magnified by a factor (strain transfer rate) to equal exactly to the actual structural strains.

  3. 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.

  4. 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.

  5. Optical coupling between a long-period fiber grating and a parallel tilted fiber Bragg grating.

    PubMed

    Liu, Yunqi; Liu, Qing; Chiang, Kin Seng

    2009-06-01

    We experimentally demonstrate the contradirectional optical coupling between two parallel fibers that contain a long-period fiber grating and a tilted fiber Bragg grating, respectively. Strong coupling occurs between the cladding modes of the same order over the overlapped resonance bands of the two gratings. By optimizing the coupling conditions, we achieve a peak coupling efficiency of approximately 80% at approximately 1,534 nm with a 3 dB bandwidth of approximately 0.12 nm and a side-mode suppression ratio of approximately 16 dB, regardless of which fiber light is launched into. This coupler configuration can be explored for the development of narrow-band all-fiber optical components. PMID:19488162

  6. 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

  7. Fiber Bragg grating strain sensors for in situ analysis and monitoring of fiber-reinforced historical civil structures

    NASA Astrophysics Data System (ADS)

    Rossi, G. L.; Speranzini, E.

    2008-06-01

    The aim of this work is to develop and validate a measurement technique for investigating and analysing stress and strain on civil structures reinforced with carbon fibre composites. The proposed sensing elements are Bragg's fibre grating strain sensors. In order to verify the performances of the proposed method, a comparison was made with the results obtained using a laser Doppler vibrometer. The measurement technique was used to study two historical buildings still in use. The vault of the "Elmi - Pandolfi" building in Foligno, and the wooden floor of the "Siaz Building" in Trevi, both located in the province of Perugia, Italy. Both buildings were reinforced with Carbon Fibre Reinforced Plastic (CFRP) after an earthquake.

  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. 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.

  10. 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.

  11. Organic and hybrid tunable bragg gratings for photonic devices

    NASA Astrophysics Data System (ADS)

    Abbate, G.; Marino, A.; Tkachenko, V.; Vita, F.

    2007-05-01

    We present a survey on organic composite and hybrid materials suitable for a new family of optical devices like thermo- and electro-tunable multilayer mirrors, microcavities and optical filters. The main component is a tunable and/or switchable Bragg grating. Two different classes of materials have been realized, characterized, and designed in form of prototype devices, namely a) polymer-liquid crystal composite and b) liquid crystal infiltrated porous silicon. Different geometries and patterns can be envisaged, leading to different physical properties and a large number of device potentialities, most of them yet unexplored. Obtained results look promising for both material families, especially for the porous silicon one, which includes an inherent immediate integration with the electronic fabric technology.

  12. Temperature-independent fiber Bragg grating acceleration sensor

    NASA Astrophysics Data System (ADS)

    Li, Lan; Dong, Xinyong; Zhou, Wenjun; Jin, Yongxing; Sun, Yiling

    2009-08-01

    An acceleration sensor based on measurement of the reflection bandwidth of a single fiber Bragg grating (FBG) is presented. The FBG is glued in a slanted direction onto the lateral surface at the center of the beam. Two weights were fixed respectively on the upper and lower surfaces in the middle of the beam to sense the variation of the acceleration in the vertical direction. Preliminary experimental results indicate that when the acceleration was increased, the 3-dB bandwidth of the FBG responded linearly from zero to 8 g, with very low temperature dependence. The measurement sensitivity and resolution are 0.4 nm/g and 0.05 g, respectively.

  13. Fiber Bragg grating (FBG) sensors used in coal mines

    NASA Astrophysics Data System (ADS)

    Wang, Jinyu; Liu, Tongyu; Song, Guangdong; Xie, Hongjing; Li, Lianqing; Deng, Xiaolin; Gong, Zhijie

    2014-06-01

    The fiber Bragg grating (FBG) strain sensors were used for on-line monitoring of the stress variation of the lined wall in the gateway retained along the goaf of No. 3203 coal mining face in Dongtan Mine. The results showed that the FBG strain sensor with the wide measuring range could measure the stress variation accurately during the support process of the gateway retained along the goaf and could provide the basis to further optimize the support structure and to determine the support plan of the gateway retained along the goaf. The FBG micro-seismic sensors were used in Xinglong Mine to detect the micro-seismic signal. The signals were well received and analyzed to determine the location and energy level of the source of the micro-seismic event warning. The FBG sensors and detecting system show a significant potential for micro-seismic detection and geological disasters detection.

  14. Fiber Bragg grating strain sensor for hard rocks

    NASA Astrophysics Data System (ADS)

    Castro-Caicedo, Alvaro; Nieto-Callejas, María. J.; Torres, Pedro

    2015-09-01

    Strain is an important property to be measured in rock structures such as tunnels, slopes, dams, and mining. However, commercial surface mountable fiber Bragg grating (FBG) strain sensors are packaged in planar configuration, which is not appropriate for the irregular surface of the rocks since an unacceptable bonding layer fails to transfer the strain from the rock to the FBG. As a first approach to this problem, in this work we analyze packaged FBG sensors for cylindrical samples of hard rocks. A calibration process was carried out to evaluate the performance of the packaging and bonding layer as compared to electrical resistance strain gage methods. We show the importance of both packaging and bonding layer in FBG sensor technology for measuring strain in hard rocks.

  15. [INVITED] New advances in polymer fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Nogueira, Rogério; Oliveira, Ricardo; Bilro, Lúcia; Heidarialamdarloo, Jamshid

    2016-04-01

    During the last years, fiber Bragg gratings (FBGs) written in polymer optical fibers (POFs) have been pointed as an interesting alternative to silica FBGs for applications in sensors and in optical access networks. In order to use such components in real applications, the manipulation of POFs, as well as the increase of quality in the production of FBGs has to be achieved. In this article some of the recent advances regarding these two aspects are reported and include recent developments to produce smooth POFs end face with high quality, benefiting the current splicing process and the inscription of high quality FBGs in a few seconds. Furthermore, additional characterizations to strain, temperature, pressure, and humidity are also shown.

  16. 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.

  17. 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.

  18. 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

  19. 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.

  20. Humidity insensitive TOPAS polymer fiber Bragg grating sensor.

    PubMed

    Yuan, Wu; Khan, Lutful; Webb, David J; Kalli, Kyriacos; Rasmussen, Henrik K; Stefani, Alessio; Bang, Ole

    2011-09-26

    We report the first experimental demonstration of a humidity insensitive polymer optical fiber Bragg grating (FBG), as well as the first FBG recorded in a TOPAS polymer optical fiber in the important low loss 850 nm spectral region. For the demonstration we have fabricated FBGs with resonance wavelength around 850 nm and 1550 nm in single-mode microstructured polymer optical fibers made of TOPAS and the conventional poly (methyl methacrylate) (PMMA). Characterization of the FBGs shows that the TOPAS FBG is more than 50 times less sensitive to humidity than the conventional PMMA FBG in both wavelength regimes. This makes the TOPAS FBG very appealing for sensing applications as it appears to solve the humidity sensitivity problem suffered by the PMMA FBG. PMID:21996915

  1. Fiber Bragg grating demodulation through innovative numerical procedures

    NASA Astrophysics Data System (ADS)

    Dinardo, Giuseppe; Vacca, Gaetano

    2016-01-01

    The aim of this article is to introduce an innovative algorithm for the calculation of the shift of the maximum reflectivity wavelength of a Fiber Bragg Grating experiencing an applied strain. An accurate and precise evaluation of the FBG spectrum displacement is crucial for determining the amount of the physical quantity inducing such perturbations. The proposed method is based on the Fast Fourier Transform based Cross Correlation function. Such method is compared to Least Squares Fitting (LSF) and the centroid algorithms, pointing out remarkable improvements in accuracy, precision, and time consumption performance. In addition, a further improvement of the proposed algorithm is introduced. It consists in an iteratively performed Cross Correlation algorithm. It has been proved that such improvement leads to estimations characterized by better accuracy and precision, thanks also to a considerable reduction of the peak-locking effect due to the FBG spectral resolution.

  2. Wavefront distortion optimized with volume Bragg gratings in photothermorefractive glass.

    PubMed

    Gao, Fan; Zhang, Xiang; Sun, Xiaojie; Yuan, Xiao

    2016-03-15

    The wavefront characteristics in 2D angular filtering on the basis of two orthogonal transmitting volume Bragg gratings (VBGs) is presented. The experimental results show that middle-high frequency wavefront distortions are efficiently suppressed with VBGs. The peak-valley value of the beam at a wavelength of 1053 nm reduces from 2.075λ to 0.209λ, and the root mean square value reduces from 0.207λ to 0.041λ. The wavefront power spectrum density shows that the wavefront distribution of the beam in medium and high frequencies is corrected by the VBGs. Additionally, the far-field distribution and focusing properties of the beam are improved. The beam Strehl ratio increases from 0.43 to 0.96, and the encircled energy improves from 95% energy at 4.01 mrad to 95% energy at 1.26 mrad. PMID:26977639

  3. 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

  4. Volume Bragg grating stabilized spectrally narrow Tm fiber laser.

    PubMed

    McComb, Timothy; Sudesh, Vikas; Richardson, Martin

    2008-04-15

    A Tm-doped large mode area (LMA) silica fiber laser has been locked to a stable wavelength of 2,053.9 nm using a volume Bragg grating (VBG). The measured spectral width of the laser output was <300 pm, limited by the spectrometer resolution. Although this laser had modest output (approximately 5W) and slope efficiency (41%), this new approach to spectrally limiting the output of LMA fiber lasers is inherently extendable to kilowatt powers, opening up several applications including high-power pulsed fiber lasers and spectral beam combining. Performance characteristics of the laser compared to one using a dielectric mirror as a high reflector are described, and the results imply low VBG losses. PMID:18414564

  5. 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

  6. Miniature fiber Bragg grating sensor interrogator (FBG-Transceiver) system

    NASA Astrophysics Data System (ADS)

    Mendoza, Edgar A.; Kempen, Cornelia; Lopatin, Craig

    2007-04-01

    This paper describes recent progress conducted towards the development of a miniature fiber Bragg grating sensor interrogator (FBG-Transceiver TM) system based on multi-channel integrated optic sensor (InOSense TM) microchip technology. The hybrid InOSense TM microchip technology enables the integration of all of the functionalities, both passive and active, of conventional bench top FBG sensor interrogator systems, packaged in a miniaturized, low power operation, 2-cm x 5-cm package suitable for the long-term structural health monitoring in applications where size, weight, and power are critical for operation. The FBG-Transceiver system uses active optoelectronic components monolithically integrated to the InOSense TM microchip, a microprocessor controlled signal processing electronics board capable of processing the FBG sensors signals related to stress-strain and temperature as well as vibration and acoustics. The FBG-Transceiver TM system represents a new, reliable, highly robust technology that can be used to accurately monitor the status of an array of distributed fiber optic Bragg grating sensors installed in critical infrastructures. Its miniature package, low power operation, and state-of-the-art data communications architecture, all at a very affordable price makes it a very attractive solution for a large number of SHM/NDI applications in aerospace, naval and maritime industry, civil structures like bridges, buildings and dams, the oil and chemical industry, and for homeland security applications. The miniature, cost-efficient FBG-Transceiver TM system is poised to revolutionize the field of structural health monitoring and nondestructive inspection market. The sponsor of this program is NAVAIR under a DOD SBIR contract.

  7. 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.

  8. Measurement of the thermal expansion of melt-textured YBCO using optical fibre grating sensors

    NASA Astrophysics Data System (ADS)

    Zeisberger, M.; Latka, I.; Ecke, W.; Habisreuther, T.; Litzkendorf, D.; Gawalek, W.

    2005-02-01

    In this paper we present measurements of the thermal expansion of melt-textured YBaCuO in the temperature range 30-300 K by means of optical fibre sensors. The sample, which had a size of 38 × 38 × 18 mm3, was prepared by our standard melt-texturing process using SmBaCuO seeds. One fibre containing three Bragg gratings which act as strain sensors was glued to the sample surface with two sensors parallel to the ab-plane and one sensor parallel to the c-axis. The sample was cooled down to a minimum temperature of 30 K in a vacuum chamber using a closed cycle refrigerator. In the temperature range we used, the thermal expansion coefficients are in the range of (3-9) × 10-6 K-1 (ab-direction) and (5-13) × 10-6 K-1 (c-direction).

  9. Bragg grating fabrication on tapered fiber tips based on focused ion beam milling

    NASA Astrophysics Data System (ADS)

    André, Ricardo M.; Becker, Martin; Dellith, Jan; Rothhardt, Manfred; Zibaii, M. I.; Latifi, H.; Marques, Manuel B.; Bartelt, Hartmut; Frazão, Orlando

    2015-09-01

    Focused ion beam milling is used on chemically etched tapered fiber tips to create fiber Bragg gratings. These fiber Bragg gratings are based on a modulation of silica and external medium. This leads to a wide and structured spectrum obtained due to imperfections and the inherent structure of the tip. The fiber Bragg gratings presented are very short and have a length of 27 μm and 43 μm and are milled on the tapered fiber tip. They are characterized in the high temperature range 350-850ºC and a sensitivity of 14.4 pm/K is determined.

  10. 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.

  11. Strain distribution and sensitivity in fiber Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Dadpay, C.; Sivakumar, N. R.; Mrad, N.

    2008-06-01

    Optical Fiber Bragg Gratings (FBG) sensors have seen significant development in recent years. Such sensor technology developed initially for the civil infrastructure is currently attracting the aerospace industry due to the potential versatility of this technology and its measurement capability. The structural health monitoring and the diagnostics and prognostics health management communities are excited about such development and ready to embrace such capability. Sensors reliability and accuracy, however, continue to be two parameters critical to the eventual implementation of the technology in high value targets. Such parameters can be improved by different manufacturing techniques as well as optimum grating's coating selection. This paper presents an evaluation of the mechanical behavior of the FBG strain sensors. A simulated analysis, using finite element modeling, revealed the impact of coating material selection, coating thickness selection, and bonding effect on the strain transfer loss. Results illustrate that metallic fiber coatings are more suitable for improved strain transfer than their polymeric counterparts and acrylic coatings are least effective with adhesive layer as small as possible.

  12. Integrated waveguide Bragg gratings for microwave photonics signal processing.

    PubMed

    Burla, Maurizio; Cortés, Luis Romero; Li, Ming; Wang, Xu; Chrostowski, Lukas; Azaña, José

    2013-10-21

    Integrated Microwave photonics (IMWP) signal processing using Photonic Integrated Circuits (PICs) has attracted a great deal of attention in recent years as an enabling technology for a number of functionalities not attainable by purely microwave solutions. In this context, integrated waveguide Bragg grating (WBG) devices constitute a particularly attractive approach thanks to their compactness and flexibility in producing arbitrarily defined amplitude and phase responses, by directly acting on coupling coefficient and perturbations of the grating profile. In this article, we review recent advances in the field of integrated WBGs applied to MWP, analyzing the advantages leveraged by an integrated realization. We provide a perspective on the exciting possibilities offered by the silicon photonics platform in the field of MWP, potentially enabling integration of highly-complex active and passive functionalities with high yield on a single chip, with a particular focus on the use of WBGs as basic building blocks for linear filtering operations. We demonstrate the versatility of WBG-based devices by proposing and experimentally demonstrating a novel, continuously-tunable, integrated true-time-delay (TTD) line based on a very simple dual phase-shifted WBG (DPS-WBG). PMID:24150355

  13. 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.

  14. Tunable phase-shifted fiber Bragg grating based on femtosecond laser fabricated in-grating bubble.

    PubMed

    Liao, Changrui; Xu, Lei; Wang, Chao; Wang, D N; Wang, Yiping; Wang, Qiao; Yang, Kaiming; Li, Zhengyong; Zhong, Xiaoyong; Zhou, Jiangtao; Liu, Yingjie

    2013-11-01

    We present a type of phase-shifted fiber Bragg gratings based on an in-grating bubble fabricated by femtosecond (fs) laser ablation together with a fusion-splicing technique. A microchannel vertically crossing the bubble is drilled by fs laser to allow liquid to flow in or out. By filling different refractive index (RI) liquid into the bubble, the phase-shift peak is found to experience a linear red shift with the increase of RI, while little contribution to the change of phase shift comes from the temperature and axial strain. Therefore, such a PS-FBG could be used to develop a promising tunable optical filter and sensor. PMID:24177122

  15. 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

  16. Fiber Bragg grating sensing in smart composite patch repairs for aging aircraft

    NASA Astrophysics Data System (ADS)

    Botsev, Y.; Gorbatov, Nahum; Tur, Moshe; Ben-Simon, U.; Kressel, I.; Green, A. K.; Ghilai, G.; Gali, S.

    2004-06-01

    A Fiber-Bragg-Grating based, advanced co-cured smart composite patch for the repair of metallic structures is proposed and demonstrated. Advantages include real time cure monitoring and long-term in-service structural integrity evaluation.

  17. 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

  18. 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

  19. 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.

  20. 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

  1. Solid-state laser spectral narrowing using a volumetric photothermal refractive Bragg grating cavity mirror

    NASA Astrophysics Data System (ADS)

    Chung, Te-Yuan; Rapaport, Alexandra; Smirnov, Vadim; Glebov, Leonid B.; Richardson, Martin C.; Bass, Michael

    2006-01-01

    Dramatic spectral narrowing of two normally broadband lasers, Ti:sapphire and Cr:LiSAF, was achieved by simply replacing the output mirror with a reflective, volumetric Bragg grating recorded in photothermal refractive glass. The output power of each laser was unchanged from that obtained using dielectric coated output mirrors with the same output coupling as the Bragg grating while spectral brightness increased by 3 orders of magnitude.

  2. Fibre optic grating sensors for biofuels

    NASA Astrophysics Data System (ADS)

    Muller, M.; Fabris, J. L.; Kalinowski, H. J.

    2010-09-01

    Biofuels will have more intense impact on the energetic grid of the planet, because known fossil fuels reserves are being exhausted. The biofuel production relies on the transformation process of some organic material in the desired hydrocarbon product. Because of the natural characteristics of the related processes, fibre optic sensors appear to be adequate candidates to be used.

  3. BOR-FDTD analysis of nonlinear Fiber Bragg grating and distributed Bragg resonator

    NASA Astrophysics Data System (ADS)

    EL Mashade, Mohamed B.; Nady, M.

    2011-10-01

    Recently, nonlinear materials have attracted a great deal of attention because of their importance in designing new devices to meet a need range of optical systems. An intense investigation of the possibility of using these materials for all optical ultrafast applications is achieved by allowing their dielectric characteristics to be varied in such a way that a periodic perturbation of their refractive index along the length of the waveguide will be formed. The Finite-Difference Time-Domain (FDTD) method, on the other hand, has been proven to be one of the most powerful numerical techniques that are usefully applied to a wide range of optical devices. In this paper, a FDTD technique, developed for nonlinear structures, is used to analyze a nonlinear waveguide and periodic nonlinear structures that exhibit attractive properties that make them suitable for novel devices with wavelength tunable characteristics. More specifically, the Bodies of Revolution (BOR) FDTD numerical simulation method will be used to model the fiber Bragg Grating (FBG) and the direct integration method will be employed to include the effect of Self Phase Modulation (SPM) in this model. The combination of these techniques will result in a model that is used to analyze two different types of periodic nonlinear structure, FBG and Distributed Bragg Resonator (DBR). The nonlinear effect provides the designer an added degree of design flexibility for devices with wavelength tunable characteristics, for example, in the design of tunable filters, WDM systems and optical sensors.

  4. 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

  5. [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

  6. 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.

  7. Characterization of sidewall Bragg gratings using optical low-coherence interferometry with a broadband source

    NASA Astrophysics Data System (ADS)

    Zhang, Chen; Wang, Xin; Madsen, Christi K.

    2015-02-01

    In this work, we present fabrication and measurement of sidewall Bragg gratings in chalcogenide arsenic tri-sulfide (As2S3) on titanium-diffused lithium niobate (Ti:LiNbO3) channel waveguides. The transfer matrix method was used to analyze the temporal and spectral response of the sidewall gratings in the mid-infrared. The waveguide sidewall Bragg gratings were fabricated by electron-beam lithography (EBL), metal liftoff and subsequent reactive-ion etching (RIE). Insertion loss of the mid-infrared Ti:LiNbO3 optical waveguides were measured at ~2 dB and the propagation loss was estimated to be 0.45 dB/cm. Configuration of an optical low-coherence interferometer that is capable of characterizing the mid-infrared sidewall grating-based devices was experimentally implemented and preliminary results from fiber Bragg gratings are presented.

  8. 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

  9. [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

  10. 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.