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Sample records for grating strain sensors

  1. 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.

  2. Fiber Bragg grating sensors for strain monitoring of steelwork

    NASA Astrophysics Data System (ADS)

    Wang, Tao; He, Dawei; Yang, Fan; Wang, Yongsheng

    2009-11-01

    Over the last few years, fiber Bragg grating (FBG) sensors have attracted a lot of interest and they are being used in various applications. This paper describes the FBG sensors used for strain monitoring of bogie and other steelworks. FBG sensors and resistance strain gauges are set on different position of steel girder, and weight is loaded on the steel girder. Strain value of the steel girder can be caught by two kinds of sensors when weight loaded is changed. Result of experiment shows that strain value obtained by resistance strain gauges and FBG sensor is coinciding. There is a linear correlation between value of strain and the weight loaded on the steel girder. FBG sensors with different encapsulations are set on bogie by acrylic plastic materials in order to monitor its dynamic strains. When sinusoidal load with its frequency from 0.15Hz to 2Hz was set on the bogie, FBG sensor system with data sampling rate of 20Hz were used to monitoring the dynamic strains. Strain data caught by FBG sensor system can offer accurate description of dynamic strain, and value of strain provided by FBG sensor suits theoretical values well. The experimental observations show that FBG sensors can be set on steelworks easily, and can monitor both static strain and dynamic strains well.

  3. 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.

  4. 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.

  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. 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.

  7. The influence of adhesive on fiber Bragg grating strain sensor

    NASA Astrophysics Data System (ADS)

    Chen, Jixuan; Gong, Huaping; Jin, Shangzhong; Li, Shuhua

    2009-08-01

    A fiber Bragg grating (FBG) sensor was fixed on the uniform strength beam with three adhesives, which were modified acrylate, glass glue and epoxy resin. The influence of adhesive on FBG strain sensor was investigated. The strain of FBG sensor was varied by loading weight to the uniform strength beam. The wavelength shift of the FBG sensor fixed by the three kinds of adhesive were measured with different weight at the temperatures 0°C, 10°C, 20°C, 30°C, 40°C. The linearity, sensitivity and their stability at different temperature of FBG sensor which fixed by every kind of adhesives were analyzed. The results show that, the FBG sensor fixed by the modified acrylate has a high linearity, and the linear correlation coefficient is 0.9996. It also has a high sensitivity which is 0.251nm/kg. The linearity and the sensitivity of the FBG sensor have a high stability at different temperatures. The FBG sensor fixed by the glass glue also has a high linearity, and the linear correlation coefficient is 0.9986, but it has a low sensitivity which is only 0.041nm/kg. The linearity and the sensitivity of the FBG sensor fixed by the glass glue have a high stability at different temperatures. When the FBG sensor is fixed by epoxy resin, the sensitivity and linearity is affected significantly by the temperature. When the temperature changes from 0°C to 40°C, the sensitivity decreases from 0.302nm/kg to 0.058nm/kg, and the linear correlation coefficient decreases from 0.9999 to 0.9961.

  8. 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.

  9. On the use of optical fiber Bragg grating (FBG) sensor technology for strain modal analysis

    NASA Astrophysics Data System (ADS)

    Peeters, Bart; dos Santos, Fábio Luis Marques; Pereira, Andreia; Araujo, Francisco

    2014-05-01

    This paper discusses the use of optical fiber Bragg grating (FBG) strain sensors for structural dynamics measurements. For certain industrial applications, there is an interest to use strain sensors rather than or in combination with accelerometers for experimental modal analysis. Classical electrical strain gauges can be used hereto, but optical strain sensors are an interesting alternative with some very specific advantages. This paper gives an overview of dynamic strain measurements in industrial applications, discusses the benefits of FBG sensors and reviews their measurement principle. Finally, the concept of strain modal analysis is introduced and a helicopter main rotor blade vibration testing and analysis case study is presented.

  10. 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

  11. Sensitive strain sensor based on regenerated microfiber Bragg grating for high temperature environment

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    In this paper, an abnormal grating evolution was recorded during microfiber Bragg grating (mFBG) inscription under 193nm excimer laser. Within 20 minutes exposing, a Type IIa FBG could be obtained with above 20dB strength in 8.5 μm microfiber. This regenerated mFBG had good survival ability against high temperature up to 800 °C. Moreover, the strain response of the regenerated grating was enlarged by the microfiber structure. Thus, highly sensitive strain sensor with considerable temperature resistance could be obtained, which had potential applications in gas/oil and aerospace territory.

  12. Dynamic strain detection using a fiber Bragg grating sensor array for geotechnical applications

    NASA Astrophysics Data System (ADS)

    Schmidt-Hattenberger, Cornelia; Naumann, M.; Borm, Gunter

    2003-03-01

    In recent years fiber Bragg gratings have been successfully introduced as sensors for strain, temperature and pressure variations. Their performance and reliability has been proven in many practical applications including strain monitoring in civil engineering and tunneling, downhole monitoring in oil reservoirs and flow assurance monitoring in pipelines. The gratings have great potential to at as true structurally integrated sensor elements. They can be embedded in typical structural or reinforcing elements of civil and geotechnical buildings. Several methods of interrogation schemes are established depending on the desired accuracy and resolution of the measurement. The most important methods are the linear discriminator, the tunable Fbry-Perot filter technique, and several interferometer setups.

  13. FIBER BRAGG GRATING SENSORS FOR LOCALIZED STRAIN MEASUREMENTS AT LOW TEMPERATURE AND IN HIGH MAGNETIC FIELD

    SciTech Connect

    Ramalingam, Rajinikumar

    2010-04-09

    Study of magnetostrictive effects in the bulk superconductors is very essential and can give more knowledge about the effects like namely, flux pinning induced strain, pincushion distortions in the magnets and so on. Currently used electro mechanical sensors are magnetic field dependent and can only give the global stress/strain information but not the local stress/strains. But the information like radius position dependent strain and characterisation of shape distortion in non cylindrical magnets are interesting. Wavelength encoded multiplexed fiber Bragg Grating sensors inscribed in one fiber gives the possibility to measure magentostrictive effects spatially resolved in low temperature and high magnetic field. This paper specifies the design and technology requirements to adapt FBG sensors for such an application. Also reports the experiments demonstrate the properties of glass FBG at low temperature (4.2 K) and the results of strain measurement at 4.2 K/8 T. The sensor exhibits a linear wavelength change for the strain change.

  14. Fiber Bragg grating sensors for use in pavement structural strain-temperature monitoring

    NASA Astrophysics Data System (ADS)

    Wang, Jian-Neng; Tang, Jaw-Luen; Chang, Hsiang-Ping

    2006-03-01

    In this paper, we describe the development and realization of a newly high-resolution temperature and strain sensor with fiber Bragg grating (FBG) technology. The FBG sensor consists of a reference fiber grating and a grating pair scheme that could offer the potential of simultaneous measurement of strain and temperature for monitoring pavement structures. Experimental results showed that measurement errors of 6 μɛ and 0.13 °C for strain and temperature could be achieved, respectively. The reliability and long-term stability for temperature measurement with this type of sensor were examined by mounting sensors on the surface of asphalt and concrete specimens. Small root mean square temperature variations (better than 1 °C) and excellent long-term stability (within 2%) were obtained. The maximum variations in temperature for 48 hours were only 1.94% and 2.32% for asphalt and concrete specimens, respectively. The feasibility of strain measurement for pavement structures was conducted by mounting the packaged sensor on the surface of an asphalt specimen under the indirect tensile loading condition. The measured strains from the packaged FBG sensor agreed linearly with applied loads. A finite-element model (FEM) was conducted to verify the strains obtained from the sensors. In comparison with experimental data and numerical results, the numerical values were all located within FBG measurement error ranges. The strain differences between measurements from the FBG sensor and FEM predictions were between 5% and 7%. This type of simple and low-cost FBG sensor is expected to benefit the developments and applications of pavement structures or transportation infrastructure.

  15. Fiber Bragg Grating Sensors for Measuring Temperature and Strain Simultaneously at Cryogenic Temperature

    NASA Astrophysics Data System (ADS)

    Rajinikumar, R.; Suesser, M.; Narayankhedkar, K. G.; Krieg, G.; Atrey, M. D.

    2008-03-01

    Feasibility of employing Fiber Bragg Gratings (FBG) for measuring thermodynamic parameters of superconducting (SC) coils has been studied. The distribution of mechanical stress and temperature inside the coil are important for an optimized magnet design. Standard sensors with electrical connections like resistance thermometer and strain gauges cannot be placed inside the coil. So it is impossible to access local stress and temperature data. The superimposed dual wavelength bi—metallic recoated Bragg gratings, fabricated in one fiber at same location are better suited for this purpose. Coil temperature and stress will vary the gratings periods which can be read out with a tuneable laser. The spectral position of the reflections may be correlated with the spatial position of the gratings. The shift of the gratings' maximum reflection indicates the change of the gratings' period. This, in turn, measures temperature and stress. The simultaneous temperature and strain measurement response of an aluminium—indium bi—metal coated FBG sensor is reported in this paper.

  16. Split-mode fiber Bragg grating sensor for high-resolution static strain measurements.

    PubMed

    Malara, P; Mastronardi, L; Campanella, C E; Giorgini, A; Avino, S; Passaro, V M N; Gagliardi, G

    2014-12-15

    We demonstrate a strain sensor with very high sensitivity in the static and low frequency regime based on a fiber ring cavity that includes a π phase-shifted fiber Bragg grating. The grating acts as a partial reflector that couples the two counter-propagating cavity modes, generating a splitting of the resonant frequencies. The presence of a sharp transition within the π phase-shifted fiber Bragg grating's spectral transmittance makes this frequency splitting extremely sensitive to length, temperature, and the refractive index of the fiber in the region where the grating is written. The splitting variations caused by small mechanical deformations of the grating are tracked in real time by interrogating a cavity resonance with a locked-carrier scanning-sideband technique. The measurable strain range and bandwidth are characterized, and a resolution of 320  pϵ/Hz(1/2) at 0 Hz is experimentally demonstrated, the highest achieved to date with a fiber Bragg grating sensor. PMID:25503025

  17. Ultrasonic Sensitivity of Strain-Insensitive Fiber Bragg Grating Sensors and Evaluation of Ultrasound-Induced Strain

    PubMed Central

    Tsuda, Hiroshi; Kumakura, Kenji; Ogihara, Shinji

    2010-01-01

    In conventional ultrasound detection in structures, a fiber Bragg grating (FBG) is glued on or embedded in the structure. However, application of strain to the structure can influence the sensitivity of the FBG toward ultrasound and can prevent its effective detection. An FBG can work as a strain-insensitive ultrasound sensor when it is not directly glued to the monitored structure, but is instead applied to a small thin plate to form a mobile sensor. Another possible configuration is to affix an FBG-inscribed optical fiber without the grating section attached to the monitored structure. In the present study, sensitivity to ultrasound propagated through an aluminum plate was compared for a strain-insensitive FBG sensor and an FBG sensor installed in a conventional manner. Strains induced by ultrasound from a piezoelectric transducer and by quasi-acoustic emission of a pencil lead break were also quantitatively evaluated from the response amplitude of the FBG sensor. Experimental results showed that the reduction in the signal-to-noise ratio for ultrasound detection with strain-insensitive FBG sensors, relative to traditionally-installed FBG sensors, was only 6 dB, and the ultrasound-induced strain varied within a range of sub-micron strains. PMID:22163523

  18. Flat-Cladding Fiber Bragg Grating Sensors for Large Strain Amplitude Fatigue Tests

    PubMed Central

    Feng, Aihen; Chen, Daolun; Li, Cheng; Gu, Xijia

    2010-01-01

    We have successfully developed a flat-cladding fiber Bragg grating sensor for large cyclic strain amplitude tests of up to ±8,000 με. The increased contact area between the flat-cladding fiber and substrate, together with the application of a new bonding process, has significantly increased the bonding strength. In the push-pull fatigue tests of an aluminum alloy, the plastic strain amplitudes measured by three optical fiber sensors differ only by 0.43% at a cyclic strain amplitude of ±7,000 με and 1.9% at a cyclic strain amplitude of ±8,000 με. We also applied the sensor on an extruded magnesium alloy for evaluating the peculiar asymmetric hysteresis loops. The results obtained were in good agreement with those measured from the extensometer, a further validation of the sensor. PMID:22163621

  19. Fiber Bragg grating dynamic strain sensor using an adaptive reflective semiconductor optical amplifier source.

    PubMed

    Wei, Heming; Tao, Chuanyi; Zhu, Yinian; Krishnaswamy, Sridhar

    2016-04-01

    In this paper, a reflective semiconductor optical amplifier (RSOA) is configured to demodulate dynamic spectral shifts of a fiber Bragg grating (FBG) dynamic strain sensor. The FBG sensor and the RSOA source form an adaptive fiber cavity laser. As the reflective spectrum of the FBG sensor changes due to dynamic strains, the wavelength of the laser output shifts accordingly, which is subsequently converted into a corresponding phase shift and demodulated by an unbalanced Michelson interferometer. Due to the short transition time of the RSOA, the RSOA-FBG cavity can respond to dynamic strains at high frequencies extending to megahertz. A demodulator using a PID controller is used to compensate for low-frequency drifts induced by temperature and large quasi-static strains. As the sensitivity of the demodulator is a function of the optical path difference and the FBG spectral width, optimal parameters to obtain high sensitivity are presented. Multiplexing to demodulate multiple FBG sensors is also discussed. PMID:27139682

  20. Experimental study of steel welded joints localization with using fiber Bragg grating strain sensor

    NASA Astrophysics Data System (ADS)

    Harasim, Damian

    2015-12-01

    Optical sensing systems has a not weakening research and development in recent years. Because of its unique properties of being unsusceptible to electromagnetic interference, having wide range of operational temperature and having extreme small physical dimensions, optical fiber sensors has increasing acceptance. Fiber Bragg Gratings (FBG) is the most frequently used type of optical sensor types because of its huge multiplexing potential and potentiality of being embedded into composite material (e.g. in structural health monitoring) or attached into measured structure. Embedding or attaching FBG into an inhomogeneous environment, spectral characteristic of the sensing grating do not retain full symmetry, which is due to related differences in the distribution of the axial stress of the grating. When periodicity of the grating is constant, the peak of FBG reflection spectrum should be narrow and sharp. An inhomogeneous axial strain distribution will cause a distorsion in measured transmission or reflection spectrum. This paper shows an distorsions in FBG reflection spectrum measured from sensor attached on surface with welded joint. The sensor strain-to-wavelength shift processing characteristics obtained for homogeneous and welded steel samples were compared.

  1. Simultaneous, inherently temperature and strain insensitive bio-sensors based on dual-resonance long-period gratings

    NASA Astrophysics Data System (ADS)

    Mani Tripathi, Saurabh; Verma, Deep Shikha; Bock, Wojtek J.; Mikulic, Predrag

    2016-05-01

    Addressing temperature and strain induced cross-talks simultaneously, we propose an inherently strain and temperature insensitive fiber-optic bio-sensor. The insensitivity has been achieved by properly adjusting the dopants and their concentrations, and by optimizing the grating period and the strength of concatenated dual-resonance long-period-gratings.

  2. Error Analysis and Measurement Uncertainty for a Fiber Grating Strain-Temperature Sensor

    PubMed Central

    Tang, Jaw-Luen; Wang, Jian-Neng

    2010-01-01

    A fiber grating sensor capable of distinguishing between temperature and strain, using a reference and a dual-wavelength fiber Bragg grating, is presented. Error analysis and measurement uncertainty for this sensor are studied theoretically and experimentally. The measured root mean squared errors for temperature T and strain ε were estimated to be 0.13 °C and 6 με, respectively. The maximum errors for temperature and strain were calculated as 0.00155 T + 2.90 × 10−6 ε and 3.59 × 10−5 ε + 0.01887 T, respectively. Using the estimation of expanded uncertainty at 95% confidence level with a coverage factor of k = 2.205, temperature and strain measurement uncertainties were evaluated as 2.60 °C and 32.05 με, respectively. For the first time, to our knowledge, we have demonstrated the feasibility of estimating the measurement uncertainty for simultaneous strain-temperature sensing with such a fiber grating sensor. PMID:22163567

  3. Application of fiber Bragg grating sensors to real-time strain measurement of cryogenic tanks

    NASA Astrophysics Data System (ADS)

    Takeda, Nobuo; Mizutani, Tadahito; Hayashi, Kentaro; Okabe, Yoji

    2003-08-01

    Although many researches of strain measurement using fiber Bragg grating (FBG) sensors were conducted, there were few applications of FBG sensors to spacecraft in operation. It is very significant to develop an onboard system for the real-time strain measurement during the flight operation. In the present research, the real-time strain measurement of a composite liquid hydrogen (LH2) tank, which consisted of CFRP and aluminum liner, was attempted. Adhesive property of the FBG sensors was investigated first of all. As a result, UV coated FBG sensors and polyurethane adhesive were adopted. Then, reflection spectra from FBG sensors were measured through the tensile test at liquid helium (LHe) temperature. Since the center wavelength shifted in proportion to the applied strain, the FBG sensor was suitable as a precise strain sensor even at LHe temperature. Next, the development of an onboard FBG demodulator was discussed. This onboard demodulator was designed for weight saving to be mounted on a reusable rocket vehicle test (RVT) operated by the Institute of Space and Astronautical Science (ISAS). FBG sensors were bonded on the surface of the composite LH2 tank for the RVT. Then, strain measurement using the onboard demodulator was conducted through the cryogenic pressure test of the tank and compared with the result measured using the optical spectrum analyzer (OSA).

  4. Modeling, design, fabrication, and testing of a fiber Bragg grating strain sensor array

    NASA Astrophysics Data System (ADS)

    Abdi, Abdeq M.; Suzuki, Shigeru; Schülzgen, Axel; Kost, Alan R.

    2007-05-01

    The modeling, design, simulation, fabrication, calibration, and testing of a three-element, 15.3 cm fiber Bragg grating strain sensor array with the coherent optical frequency domain reflectometry (C-OFDR) interrogation technique are demonstrated. The fiber Bragg grating array (FBGA) is initially simulated using in-house software that incorporates transfer matrices. Compared to the previous techniques used, the transfer matrix method allows a systemwide approach to modeling the FBGA-C-OFDR system. Once designed and simulated, the FBGA system design is then imprinted into the core of a boron-germanium codoped photosensitive fiber using the phase mask technique. A fiber optic Fabry-Perot interferometric (FPI) strain gauge calibrator is then used to determine the strain gauge factor of a single fiber Bragg grating (FBG), and the results are used on the FBGA. The FPI strain gauge calibrator offers nondestructive testing of the FBG. To test the system, the FBGA is then attached to a 75 cm cantilever beam and interrogated using an incremental tunable laser. Electric strain gauges (ESGs) are then used to independently verify the strain measurements with the FBGA at various displacements of the cantilever beam. The results show that the peak strain error is 18% with respect to ESG results. In addition, good agreement is shown between the simulation and the experimental results.

  5. Temperature-compensated strain measurement using fiber Bragg grating sensors embedded in composite laminates

    NASA Astrophysics Data System (ADS)

    Tanaka, Nobuhira; Okabe, Yoji; Takeda, Nobuo

    2003-12-01

    For accurate strain measurement by fiber Bragg grating (FBG) sensors, it is necessary to compensate the influence of temperature change. In this study two devices using FBG sensors have been developed for temperature-compensated strain measurement. They are named 'hybrid sensor' and 'laminate sensor', respectively. The former consists of two different materials connected in series: carbon fiber reinforced plastic (CFRP) and glass fiber reinforced plastic. Each material contains an FBG sensor with a different Bragg wavelength, and both ends of the device are glued to a structure. Using the difference of their Young's moduli and coefficients of thermal expansion, both strain and temperature can be measured. The latter sensor is a laminate of two 90° plies of CFRP and an epoxy plate, and an FBG sensor is embedded in the epoxy plate. When the temperature changes, the cross section of the optical fiber is deformed by the thermal residual stress. The deformation of the fiber causes the birefringence and widens the reflection spectrum. Since the temperature can be calculated from the spectrum width, which changes in proportion to the temperature, the accuracy of the strain measurement is improved. The usefulness of these sensors was experimentally confirmed.

  6. Performance evaluation of fiber Bragg grating sensors by digital holographic technique, strain gauge measurement

    NASA Astrophysics Data System (ADS)

    Di Maio, A.; Rocco, A.; Ferraro, P.; De Rosa, M.; De Natale, P.; De Nicola, S.; Finizio, A.; Pierattini, G.; Coppola, G.; Iodice, M.; Striano, V.

    2007-03-01

    In view of the growing interest for non-destructive tests of materials, geodynamical monitoring and in general remote sensing, there is a great effort to bring practical optical sensors from research labs to industrial and environmental applications. In this paper, we employ digital holographic technique as an efficient tool for evaluating the strain measurement capability of fiber Bragg gratings (FBG). A cantilever beam has been employed as a test structure under loading test. The strain measurements results obtained by fiber-based sensors have been compared to those obtained by using full-field digital holographic technique and point-wise strain gauge sensors glued on the same cantilever beam. A simple theoretical model is also presented to interpret and compare the experimental results coming from different techniques.

  7. Demodulation of a fiber Bragg grating strain sensor by a multiwavelength fiber laser

    NASA Astrophysics Data System (ADS)

    Cong, Shan; Sun, Yunxu; Zhao, Yuxi; Pan, Lifeng

    2012-04-01

    A fiber Bragg grating (FBG) sensors system utilizing a multi-wavelength erbium-doped fiber lasers (EDFL) with frequency shifter is proposed. The system is one fiber laser cavity with two FBG sensors as its filters. One is for strain sensing, and the other one is for temperature compensation. A frequency shifter is used to suppress the mode competition to lase two wavelengths that correspond with FBGs. The wavelength shift of the EDFL represents the sensing quantity, which is demodulated by Fiber Fabry-Perot (FFP) filter. The sensor's response to strain is measured by experiment. Because of exploiting the dual-wavelength fiber laser with a frequency shifter forming the feedback as the light source, many advantages of this system are achieved, especially high signal-to-noise ratio, high detected power, and low power consuming comparing with conventional FBG sensor system utilizing broadband light as the light source. What's more, this structure is also easy to combine with FBG array.

  8. Demodulation of a fiber Bragg grating strain sensor by a multiwavelength fiber laser

    NASA Astrophysics Data System (ADS)

    Cong, Shan; Sun, Yunxu; Zhao, Yuxi; Pan, Lifeng

    2011-11-01

    A fiber Bragg grating (FBG) sensors system utilizing a multi-wavelength erbium-doped fiber lasers (EDFL) with frequency shifter is proposed. The system is one fiber laser cavity with two FBG sensors as its filters. One is for strain sensing, and the other one is for temperature compensation. A frequency shifter is used to suppress the mode competition to lase two wavelengths that correspond with FBGs. The wavelength shift of the EDFL represents the sensing quantity, which is demodulated by Fiber Fabry-Perot (FFP) filter. The sensor's response to strain is measured by experiment. Because of exploiting the dual-wavelength fiber laser with a frequency shifter forming the feedback as the light source, many advantages of this system are achieved, especially high signal-to-noise ratio, high detected power, and low power consuming comparing with conventional FBG sensor system utilizing broadband light as the light source. What's more, this structure is also easy to combine with FBG array.

  9. Packaging and testing of fiber Bragg gratings for use as strain sensor in rock specimens

    NASA Astrophysics Data System (ADS)

    Castro-Caicedo, Alvaro; Torres, Pedro; Lain, Ricardo

    2013-11-01

    This paper reports a packaging and calibration procedure for surface mounting of fiber Bragg grating (FBG) sensors to measure strain in rocks. The packaging of FBG sensors is performed with glass fiber and polyester resin, and then subjected to tensile loads in order to obtain strength and deformability parameters, necessaries to assess the mechanical performance of the sensor packaging. For a specific package, an optimal curing condition has been found, showing good repeatability and adaptability for non-planar surfaces, such as occurs in rock engineering. The successfully packaged sensors and electrical strain gages were attached to standard rock specimens of gabbro. Longitudinal and transversal strains under compression loads were measured with both techniques, showing that response of FBG sensors is linear and reliable. An analytical model is used to characterize the influences of rock substrate and FBG packaging in strain transmission. As a result, we obtained a sensor packaging for non-planar and complex natural material under acceptable sensitivity suitable for very small strains as occurs in hard rocks.

  10. 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.

  11. Strain fiber sensor based on beat frequency with chirped fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Wang, Xu; Zhang, Haojie; Wen, Quan; Chen, Longfei; Wang, Fang; Liu, Yufang; Yu, Kun

    2016-07-01

    We propose a strain fiber sensor that is interrogated via longitudinal mode beat frequency with a linear chirped fiber Bragg grating (CFBG). Unlike conventional sensors, in the proposed sensor, the CFBG is used to convert wavelength changes into resonant cavity length changes. Further, the beat frequency stability of the fiber laser is fully utilized to significantly improve measurement accuracy. Consequently, because cavity changes account for 5.1% of the total cavity length, the measurement accuracy can be as large as 7.06×10-7 ɛ-i.e., approximately five times greater than the accuracy obtained by stretching the resonant cavity fiber. The maximum experimental strain error range is ±14.5 μɛ.

  12. Fiber Optic Sensors for Health Monitoring of Morphing Airframes. Part 1; Bragg Grating Strain and Temperature Sensor

    NASA Technical Reports Server (NTRS)

    Wood, Karen; Brown, Timothy; Rogowski, Robert; Jensen, Brian

    2000-01-01

    Fiber optic sensors are being developed for health monitoring of future aircraft. Aircraft health monitoring involves the use of strain, temperature, vibration and chemical sensors to infer integrity of the aircraft structure. Part 1 of this two part series describes sensors that will measure load and temperature signatures of these structures. In some cases a single fiber may be used for measuring these parameters. Part 2 will describe techniques for using optical fibers to monitor composite cure in real time during manufacture and to monitor in-service integrity of composite structures using a single fiber optic sensor capable of measuring multiple chemical and physical parameters. The facilities for fabricating optical fiber and associated sensors and the methods of demodulating Bragg gratings for strain measurement will be described.

  13. 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.

  14. Fiber Bragg grating strain sensors to monitor and study active volcanoes

    NASA Astrophysics Data System (ADS)

    Sorrentino, Fiodor; Beverini, Nicolò; Carbone, Daniele; Carelli, Giorgio; Francesconi, Francesco; Gambino, Salvo; Giacomelli, Umberto; Grassi, Renzo; Maccioni, Enrico; Morganti, Mauro

    2016-04-01

    Stress and strain changes are among the best indicators of impending volcanic activity. In volcano geodesy, borehole volumetric strain-meters are mostly utilized. However, they are not easy to install and involve high implementation costs. Advancements in opto-electronics have allowed the development of low-cost sensors, reliable, rugged and compact, thus particularly suitable for field application. In the framework of the EC FP7 MED-SUV project, we have developed strain sensors based on the fiber Bragg grating (FBG) technology. In comparison with previous implementation of the FBG technology to study rock deformations, we have designed a system that is expected to offer a significantly higher resolution and accuracy in static measurements and a smooth dynamic response up to 100 Hz, implying the possibility to observe seismic waves. The system performances are tailored to suit the requirements of volcano monitoring, with special attention to power consumption and to the trade-off between performance and cost. Preliminary field campaigns were carried out on Mt. Etna (Italy) using a prototypal single-axis FBG strain sensor, to check the system performances in out-of-the-lab conditions and in the harsh volcanic environment (lack of mains electricity for power, strong diurnal temperature changes, strong wind, erosive ash, snow and ice during the winter time). We also designed and built a FBG strain sensor featuring a multi-axial configuration which was tested and calibrated in the laboratory. This instrument is suitable for borehole installation and will be tested on Etna soon.

  15. Interrogation of a wavelength tunable fiber Bragg grating sensor based ring laser for dynamic strain monitoring

    NASA Astrophysics Data System (ADS)

    Balogun, Oluwaseyi; Zhu, Yinian; Krishnaswamy, Sridhar

    2010-03-01

    Fiber Bragg gratings (FBGs) are wavelength selective optical reflectors with excellent strain sensitivity and small sensing footprint, which makes them suitable as diagnostic sensors for structural health monitoring applications. In this work, we explore the narrowband wavelength selectivity of FBGs for optical feedback in a tunable fiber ring laser. The fiber ring laser consists of an erbium doped fiber laser that is pumped with a Raman laser (980 nm) to produce population inversion and amplified spontaneous emission (ASE) in the C-band. The ASE light is used to illuminate a FBG sensor connected to the ring, and the reflected light from the sensor is fed back into the laser cavity to produce stimulated emission at the instantaneous center wavelength of the sensor. As the wavelength of the sensor shifts due mechanical or thermal strains, the wavelength of the optical output from the ring laser shifts accordingly. By combining the ring laser with a dynamic spectral demodulator for optical readout, the instantaneous wavelength of the ring laser is tracked with high temporal resolution. The fiber ring laser system offers several potential advantages in the diagnostic sensing of mechanical strains for SHM applications including, fully integrated laser and sensor system, high source power levels at the sensor wavelength, narrow spectral line-width, coherent spectral demodulation, and low system costs. In this work, we present experimental results that detail the feasibility of dynamic spectral tuning of the fiber ring laser at frequencies up to hundreds of kilohertz using a single FBG sensing element. Using multiple sensing elements, the fiber ring laser system would allow for active monitoring of dynamic strains in a multi-point sensor array configuration, which is particularly suitable for the localization of high frequency mechanical strains produced by impact loading and cracking events in structures.

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

    NASA Astrophysics Data System (ADS)

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

    2008-03-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

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

  18. Adaptive two-wave mixing wavelength demodulation of fiber Bragg grating sensor for monitoring dynamic strains

    NASA Astrophysics Data System (ADS)

    Qiao, Yi; Zhou, Yi; Krishnaswamy, Sridhar

    2005-05-01

    A two-wave mixing (TWM) wavelength demodulator using InP:Fe photorefractive crystal (PRC) in the C-band (1530-1570nm) is demonstrated. The system can be used as a wavelength demodulator for use with Fiber Bragg Grating (FBG) sensors to monitor dynamic strains. In this configuration, the FBG is illuminated with a broadband source, and any strain in the FBG is encoded as a wavelength shift of the light reflected by the FBG. The reflected light from the FBG is spilt into two unbalanced paths and both beams (pump and signal) mix in the PRC. Any wavelength shift of the reflected light results in an equivalent phase shift between the pump and signal beams as they travel unbalanced path lengths. Since TWM is an adaptive process, the two interfering beams are naturally in quadrature and remain in quadrature even in the presence of large quasi-static strains. We demonstrate that FBG demodulation using TWM has the ability to selectively monitor dynamic strains without the need for active compensation of large quasi-static strains that otherwise would cause the FBG sensor to drift. As TWM interferometers can be readily multiplexed at relatively low cost; the proposed technique can be used to demodulate signals from a network of FBG sensors for use in structural health monitoring.

  19. Analysis of the performance of temperature compensation for fiber Bragg grating strain sensor

    NASA Astrophysics Data System (ADS)

    Meng, Fanyong; Jia, Limin

    2015-07-01

    FBG(fiber Bragg grating) strain sensor are widely applied in structure health monitoring, the temperature compensation problem is a key issue that impact the performance of the strain sensor, many kinds of temperature compensation method also have been put forward, but the compensation result get from these method can't meet the engineering requirements very well, especially when the ambient temperature changes rapidly due to the sunshine, the wind, the rain or other factors, and these impact can't avoid when monitoring an open-air structure project. Through engineering case and experiments test found that, the inaccurate compensation temperature is the key reason lead to test result error, and closer analysis could found that the temperature from strain sensitive FBG and temperature sensitive FBG have non synchronous phenomenon, and the error could be reach 1 degrees Celsius, so use the temperature from the same moment to compensate the strain calculation also can't get accurate results. The author thinks that the temperature non synchronous phenomenon may be caused by the temperature sensitive FBG and strain sensitive FBG have different package structure or package material, also may be installed on different positions, because all of these factors may lead to inconsistent temperature response speed between the two FBG when the ambient temperature changed rapidly. In order to confirm this conclusion, designed a FBG strain sensor package structure, the temperature sensitive FBG and strain sensitive FBG are packaged in one and the same structure with special stress isolation mechanism. Through temperature chamber test and engineering simulation experiment verified that the compensation temperature error could be reduced to 0.1 degrees Celsius, this will greatly improve the accuracy of temperature compensation for the FBG strain sensor.

  20. Dynamic Strain Sensing in a Long-Span Suspension Bridge Using Fiber Bragg Grating Sensors

    NASA Astrophysics Data System (ADS)

    Zhu, Yinian; Zhu, Yan-Jin; Balogun, Oluwaseyi; Zhu, Songye; Xu, You-Lin; Krishnaswamy, Sridhar

    2011-06-01

    Optical fiber sensors are ideal for monitoring continuous deterioration conditions of civil infrastructure, especially of long-span bridges. Typically, a network of sensors is used to measure the strains or low frequency vibrational response of the structure. In this work, we demonstrate dynamic spectral demodulation of fiber Bragg grating (FBG) sensor responses with a stabilized Michelson interferometer for monitoring mechanical strains in a model of long-span bridge. A series of experiments has been performed, including the measurements of the natural resonant modes of the model bridge, impact response of a bridge member and acoustic emissions in a fractured aluminum bar. The experimental results not only reveal that dynamic spectral demodulation of FBG strain responses at frequencies extending up to about 3.5 MHz is possible, but also suggest that the method may be suitable for monitoring high frequency mechanical strains in civil structures that result from cracking or impact loading, thus providing a tool for local detection of structural damage.

  1. Interrogation of fiber-Bragg-grating temperature and strain sensors with a temperature-stabilized VCSEL

    NASA Astrophysics Data System (ADS)

    Mizunami, Toru; Yamada, Taichi; Tsuchiya, Satoshi

    2016-07-01

    The interrogation of fiber-Bragg-grating (FBG) sensors using a vertical-cavity surface-emitting laser (VCSEL) is discussed. A long-wavelength (1.54 μm) VCSEL was used as a wavelength-tunable source by variation in the current. Temperature stabilization was performed with a thermoelectric device. Characteristics of temperature and strain sensing were investigated. FBGs with different reflectivities were compared. For temperature sensing, the root-mean-square error in the measurement was reduced to 1/3 that without temperature stabilization. The dependence of the measurement error on the reflectivities of the FBGs was investigated. The measurement error was larger for FBGs with lower reflectivities in both temperature and strain sensing. Improvement on the sensing with low-reflectivity FBGs is discussed.

  2. Continuous monitoring of mining induced strain in a road pavement using fiber Bragg grating sensors

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

    This paper describes the application of fiber 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-fiber 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.

  3. High-precision thermal strain measurements using surface-mounted fiber Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Mueller, Uwe C.; Both, Jan; Roths, Johannes; Baier, Horst

    2010-03-01

    Thermal strain measurements by fiber Bragg grating (FBG) sensors mounted onto different host materials are demonstrated for low coefficients of thermal expansion (CTE). Such low CTEs are typically found in carbon fiber reinforced plastics (CFRP). This work has application potential for FBG sensor networks in the highprecision control of thermal deformations in structures or in curing monitoring. For this purpose, a thermal error model of the FBG sensor, which accounts for the thermo-optic coefficient and the thermal expansion of the FBG, was characterized experimentally. The error-model characterization method is based on reference measurements of FBGs bonded to ZERODUR ceramics. Using this error model, thermal strain can be measured by surface-mounted FBGs on any given host structure using an external temperature reference and the FBG's wavelength shift. This method is demonstrated successfully for unidirectional layers of CFRP with a CTE of -0.4 . 10-6 1/K in fiber direction and for steel (316 Ti), which is commonly used in cryogenic applications. Measurements are performed for temperatures from 100K to 320K and the results are verified by high-precision dilatometer measurements. Accuracy limits of the FBG-based thermal strain measurements are discussed, as well as the minimization of errors induced by the FBG's structural interface. Further, the reduction of errors in the adhesive bonding is discussed. This work expands the understanding of the separation of thermal and mechanical effects in the signals obtained by FBGs.

  4. 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.

  5. Strain monitoring of dual-room box-girder during prestressing tension based on fiber Bragg grating sensor

    NASA Astrophysics Data System (ADS)

    Wang, Dansheng; Jin, Tao; Zhu, Hongping; He, Weiping; Li, Ming

    2011-11-01

    Monitoring techniques based on fiber Bragg grating sensor have proved to exhibit meaningful benefits when compared with the current solutions of an electric nature in recent years. In this study, several fiber Bragg grating (FBG) strain sensors were embedded into a prestressed concrete dual-room box-girder when construction at a prefabrication workshop to monitor strain of concrete girder during prestressing tension. All FBG sensors are alive during monitoring, which shows the advantages of robust surviving capability and long-term on-line monitoring performance. From the monitoring results it is found that the variances in strain at the measurement sites are small and almost is linear with time in certain one tension process, and the strain at the measurement sites almost synchronously and linearly change with the increase of the prestress. It is also found that the changes in strain at the measurement sites during the final tension are larger than that during the early tension.

  6. Strain monitoring of dual-room box-girder during prestressing tension based on fiber Bragg grating sensor

    NASA Astrophysics Data System (ADS)

    Wang, Dansheng; Jin, Tao; Zhu, Hongping; He, Weiping; Li, Ming

    2012-04-01

    Monitoring techniques based on fiber Bragg grating sensor have proved to exhibit meaningful benefits when compared with the current solutions of an electric nature in recent years. In this study, several fiber Bragg grating (FBG) strain sensors were embedded into a prestressed concrete dual-room box-girder when construction at a prefabrication workshop to monitor strain of concrete girder during prestressing tension. All FBG sensors are alive during monitoring, which shows the advantages of robust surviving capability and long-term on-line monitoring performance. From the monitoring results it is found that the variances in strain at the measurement sites are small and almost is linear with time in certain one tension process, and the strain at the measurement sites almost synchronously and linearly change with the increase of the prestress. It is also found that the changes in strain at the measurement sites during the final tension are larger than that during the early tension.

  7. Dynamic fiber Bragg grating strain sensor using a wavelength-locked tunable fiber ring laser

    NASA Astrophysics Data System (ADS)

    Zhu, Yinian; Krishnaswamy, Sridhar

    2012-04-01

    The interrogation systems based on fiber-optic sensors are very attractive for the practical applications in structural health monitoring owing to a number of advantages of optical fiber elements over their electronic counterparts. Among the fiber-optic sensors, the fiber Bragg gratings (FBGs) have their own unique features to be widely used for detection of acoustic emission. We have developed a dynamic strain sensing system by using a tunable single longitudinal mode Erbium-doped fiber ring laser to be locked to the middle-reflection wavelength of the FBG as the demodulation technique. A proportional-integral-derivative device continuously controls the laser wavelength that is kept at the FBG middle-reflection wavelength, thus stabilizing the operating point against quasi-static perturbation, while the high frequency dynamic strain shifts the FBG reflection profile. The reflected power varies in proportion to the applied strain which can be derived directly from AC photocurrent of the reflected signal. We have designed and assembled a fourchannel demodulator system for simultaneous high frequency dynamic strain sensing.

  8. High temperature strain sensor based on a fiber Bragg grating and rhombus metal structure.

    PubMed

    Zhang, Liang; Liu, Yueming; Gao, Xiaoliang; Xia, Zhongcheng

    2015-10-01

    In this paper, a novel high temperature strain sensor based on a polyimide-coated fiber Bragg grating (FBG) and a rhombus metal structure is presented and experimentally demonstrated. By heating low softening point glass via a micro torch, the polyimide-coated FBG could be fixed into the rhombus metal structure. Consequently, when the rhombus structure is stretched and compressed, respectively, then the FBG will be subjected to a reverse state. Moreover, the strain sensitivity is controllable and enhanced by adjusting the dimension of the rhombus metal structure appropriately. The experiment was then carried out by using an equi-intensity cantilever beam and high temperature chamber, and the result showed that the proposed high temperature strain sensor could be used at the high temperature of 300°C. A resolution of ∼10  με has been experimentally achieved. The average wavelength strain sensitivity at 300°C is 1.821 and 1.814 pm/με, for the compressed and stretched states, respectively. PMID:26479639

  9. A packaged, low-cost, robust optical fiber strain sensor based on small cladding fiber sandwiched within periodic polymer grating.

    PubMed

    Chiang, Chia-Chin; Li, Chein-Hsing

    2014-06-01

    In the present study, a novel packaged long-period fiber grating (PLPFG) strain sensor is first presented. The MEMS process was utilized to fabricate the packaged optical fiber strain sensor. The sensor structure consisted of etched optical fiber sandwiched between two layers of thick photoresist SU-8 3050 and then packaged with poly (dimethylsiloxane) (PDMS) polymer material to construct the PLPFG strain sensor. The PDMS packaging material was used to prevent the glue effect, wherein glue flows into the LPFG structure and reduces coupling strength, in the surface bonding process. Because the fiber grating was packaged with PDMS material, it was effectively protected and made robust. The resonance attenuation dip of PLPFG grows when it is loading. This study explored the size effect of the grating period and fiber diameter of PLPFG via tensile testing. The experimental results found that the best strain sensitivity of the PLPFG strain sensor was -0.0342 dB/με, and that an R2 value of 0.963 was reached. PMID:24921583

  10. Health monitoring of an Oregon historical bridge with fiber grating strain sensors

    NASA Astrophysics Data System (ADS)

    Seim, John M.; Udd, Eric; Schulz, Whitten L.; Laylor, Harold M.

    1999-05-01

    Twenty-eight fiber-grating sensors were used to instrument two reinforced concrete beams that were externally strengthened with composites on the historic Horsetail Falls Bridge in the Columbia River Gorge. Sensor assemblies were placed in the beams and mounted on the outside of the composite to provide performance data.

  11. Photosensitivity of Germanium-Doped Silica Fibers, Mask Fabrication of Fiber Bragg Gratings, and Their Application as a Strain Sensor.

    NASA Astrophysics Data System (ADS)

    Prohaska, John Dennis

    This thesis addresses issues related to the formation and application of fiber Bragg gratings. A description of existing methods of grating formation is reviewed. Also, mechanisms for photo-induced refractive index changes in germanium doped silica fibers are examined. A new method of fiber Bragg grating formation is proposed and experimentally verified using diffraction masks. The near field diffraction theory of Fresnel images is described in relation to this new method. Bragg reflectors have been experimentally produced in germanium doped silica optical fibers through the use of a surface relief phase mask. By the addition of an optical system the period of the produced grating may be changed. The wavelength of a fiber Bragg grating has been experimentally tuned using wave front shaping optics. The application of fiber Bragg grating as a strain sensor is examined in the context of a civil engineering environment. The issues and advantages of fiber Bragg gratings as devices for distributed strain measurements in large scale concrete structures are experimentally evaluated.

  12. Design and application of a fiber Bragg grating strain sensor with enhanced sensitivity in the small-scale dam model

    NASA Astrophysics Data System (ADS)

    Ren, Liang; Chen, Jianyun; Li, Hong-Nan; Song, Gangbing; Ji, Xueheng

    2009-03-01

    Accurate measurement of strain variation and effective prediction of failure within models have been major objectives for strain sensors in dam model tests. In this paper, a fiber Bragg grating (FBG) strain sensor with enhanced strain sensitivity that is packaged by two gripper tubes is presented and applied in the seismic tests of a small-scale dam model. This paper discusses the principle of enhanced sensitivity of the FBG strain sensor. Calibration experiments and reliability tests were conducted to evaluate the sensor's strain transferring characteristics on plates of different material. This paper also investigates the applicability of the FBG strain sensors in seismic tests of a dam model by conducting a comparison between the test measurements of FBG sensors and analytical predictions, monitoring the failure progress and predicting the cracking inside the dam model. Results of the dam model tests prove that the FBG strain sensor has the advantages of small size, high precision, and embeddability. It has a promising potential in the cracking and failure monitoring and identification of the dam model.

  13. Sensitivity-Improved Strain Sensor over a Large Range of Temperatures Using an Etched and Regenerated Fiber Bragg Grating

    PubMed Central

    Wang, Yupeng; Qiao, Xueguang; Yang, Hangzhou; Su, Dan; Li, Ling; Guo, Tuan

    2014-01-01

    A sensitivity-improved fiber-optic strain sensor using an etched and regenerated fiber Bragg grating (ER-FBG) suitable for a large range of temperature measurements has been proposed and experimentally demonstrated. The process of chemical etching (from 125 μm to 60 μm) provides regenerated gratings (at a temperature of 680 °C) with a stronger reflective intensity (from 43.7% to 69.8%), together with an improved and linear strain sensitivity (from 0.9 pm/με to 4.5 pm/με) over a large temperature range (from room temperature to 800 °C), making it a useful strain sensor for high temperature environments. PMID:25299954

  14. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

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

  16. Hybrid Raman/fiber Bragg grating sensor for distributed temperature and discrete dynamic strain measurements.

    PubMed

    Toccafondo, Iacopo; Taki, Mohammad; Signorini, Alessandro; Zaidi, Farhan; Nannipieri, Tiziano; Faralli, Stefano; Di Pasquale, Fabrizio

    2012-11-01

    We propose and experimentally demonstrate a hybrid fiber optic sensing technique that effectively combines Raman optical time domain reflectometry and in-line time-division-multiplexing for fiber Bragg grating (FBG) dynamic interrogation. The highly integrated proposed scheme employs broadband apodized low reflectivity FBGs with a single narrowband optical source and a shared receiver block, allowing for simultaneous measurements of distributed static temperature and discrete dynamic strain, over the same sensing fiber. PMID:23114320

  17. Application of fiber-Bragg-grating-based strain sensors for civil infrastructure health monitoring

    NASA Astrophysics Data System (ADS)

    Tjin, Swee C.; Rupali, S.; Moyo, Pilate; Brownjohn, James M. W.; Ngo, Nam Quoc

    2003-10-01

    Over past few years, the concept of structural health monitoring has been emerging as a new area of research. Fiber Bragg grating (FBG) based sensor offers a new sensing approach with a number of advantages over conventional sensors. This new sensing technology is suitable for the harsh environment of construction industry due to its robustness, ruggedness and ease of installation. Two unique advantages of FBG based sensors are immunity to electromagnetic interference and multiplexing capability. This paper reports some of the results of a multi-disciplinary program on the FBG based sensors involving the School of Electrical and Electronic Engineering and the School of Civil and Environment Engineering at Nanyang Technological University, Singapore.

  18. Dynamic measurement of inside strain distributions in adhesively bonded joints by embedded fiber Bragg grating sensor

    NASA Astrophysics Data System (ADS)

    Murayama, Hideaki; Ning, Xiaoguang; Kageyama, Kazuro; Wada, Daichi; Igawa, Hirotaka

    2014-05-01

    Long-length fiber Bragg grating (FBG) with the length of about 100 mm was embedded onto the surface of a carbon fiber reinforced plastics (CFRP) substrate and two CFRP adherends were joined by adhesive to form an adhesive bonded single-lap joint. The joint was subjected to 0.5 Hz cyclic tensile load and longitudinal strain distributions along FBG were measured at 5 Hz by the fiber-optic distributed sensing system based on optical frequency domain reflectometry (OFDR). We could successfully monitor the strain distributions accurately with high spatial resolution of around 1 mm.

  19. Compact fiber Bragg grating dynamic strain sensor cum broadband thermometer for thermally unstable ambience

    NASA Astrophysics Data System (ADS)

    Sreekumar, K.; Asokan, S.

    2010-01-01

    An instrument for simultaneous measurement of dynamic strain and temperature in a thermally unstable ambience has been proposed, based on fiber Bragg grating technology. The instrument can function as a compact and stand-alone broadband thermometer and a dynamic strain gauge. It employs a source wavelength tracking procedure for linear dependence of the output on the measurand, offering high dynamic range. Two schemes have been demonstrated with their relative merits. As a thermometer, the present instrumental configuration can offer a linear response in excess of 500 °C that can be easily extended by adding a suitable grating and source without any alteration in the procedure. Temperature sensitivity is about 0.06 °C for a bandwidth of 1 Hz. For the current grating, the upper limit of strain measurement is about 150 µɛ with a sensitivity of about 80 nɛ Hz-1/2. The major source of uncertainty associated with dynamic strain measurement is the laser source intensity noise, which is of broad spectral band. A low noise source device or the use of optical power regulators can offer improved performance. The total harmonic distortion is less than 0.5% up to about 50 µɛ,1.2% at 100 µɛ and about 2.3% at 150 µɛ. Calibrated results of temperature and strain measurement with the instrument have been presented. Traces of ultrasound signals recorded by the system at 200 kHz, in an ambience of 100-200 °C temperature fluctuation, have been included. Also, the vibration spectrum and engine temperature of a running internal combustion engine has been recorded as a realistic application of the system.

  20. Optical fiber strain sensor based on sandwiched long-period fiber gratings with a surface bonding layer

    NASA Astrophysics Data System (ADS)

    Chiang, Chia-Chin; Li, Chien-Hsing

    2014-10-01

    An optical fiber strain sensor based on sandwiched long-period fiber gratings (OFSS-SLPFG) with a surface bonding layer is proposed. The proposed OFSS-SLPFG is an etched optical fiber that is sandwiched between two thick photoresists with a periodic structure. To prevent the glue effect in the surface bonding process, where glue flows into the SLPFG structure, reducing the coupling strength, a surface bonding layer (thickness: 16 μm) is used as the base layer on the bottom of the OFSS-SLPFG. The OFSS-SLPFG is, therefore, more effective for use as a strain sensor. When external strain loading is applied, the resonant dip loss of the OFSS-SLPFG is reflected linearly. A bending strain calibration experiment is demonstrated by the four-point bending test. The results show an average linearity (R2) of 0.980, with a sensitivity of 0.00788 dB/με. This phenomenon suggests that the OFSS-SLPFG can be utilized as a sensitive strain transducer.

  1. Streicker Bridge: a comparison between Bragg-grating long-gauge strain and temperature sensors and Brillouin scattering-based distributed strain and temperature sensors

    NASA Astrophysics Data System (ADS)

    Glisic, Branko; Chen, Jeremy; Hubbell, David

    2011-04-01

    The Streicker Bridge at Princeton University campus has been equipped with two fiber-optic sensing technologies: discrete long-gauge sensing, based on Fiber Bragg-Gratings (FBG), and truly-distributed sensing, based on Brillouin Optical Time Domain Analysis (BOTDA). The sensors were embedded in concrete during the construction. The early age measurements, including hydration swelling and contraction, and post-tensioning of concrete were registered by both systems and placed side by side in order to compare their performances. Aside from the usual behavior, an unusual increase in strain was detected by several sensors in various cross-sections. The nature of this event is still under investigation, but preliminary study indicates early-age cracking as the cause. The comparison between the two monitoring systems shows good agreement in the areas where no unusual behavior was detected, but some discrepancies are noticed at locations where unusual behavior occurred and during the early age of concrete. These discrepancies are attributed to the spatial resolution of the distributed monitoring system and the temperature influences at early age. In this paper, general information concerning the Streicker Bridge project is given. The monitoring systems and their specifications are briefly presented. The monitoring data are analyzed and a comparison between the two systems is performed.

  2. 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.

  3. 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.

  4. 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

  5. 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

  6. Metal embedded Fiber Brag Grating Sensors

    NASA Astrophysics Data System (ADS)

    Khanal, Chooda; Vargas, Garman; Balani, Kantesh; Keshri, Anup; Barbosa, Carmen; Agarwal, Arvind; Panepucci, Roberto

    2009-03-01

    A novel method of embedding optical fibers and optical fiber sensors, inside metallic structures will be discussed. We specifically report results for embedding fiber bragg grating sensors in an aluminum coating onto a steel plate. Characterization of an embedded FBG sensor and its effects on the sensor operation are also presented. Temperature sensitivity and the strain sensitivity will be discussed. The novel high throughput deposition method show the potential of embedding optical sensors onto metallic structures which make it suitable for many engineering applications in biomedical, civil, mechanical and aeronautical, among other fields.

  7. In Search of Multi-Peaked Reflective Spectrum with Optic Fiber Bragg Grating Sensor for Dynamic Strain Measurement

    NASA Technical Reports Server (NTRS)

    Tai, Hsiang

    2006-01-01

    In a typical optic fiber Bragg grating (FBG) strain measurement, unless in an ideal static laboratory environment, the presence of vibration or often disturbance always exists, which often creates spurious multiple peaks in the reflected spectrum, resulting in a non-unique determination of strain value. In this report we attempt to investigate the origin of this phenomenon by physical arguments and simple numerical simulation. We postulate that the fiber gratings execute small amplitude transverse vibrations changing the optical path in which the reflected light traverses slightly and non-uniformly. Ultimately, this causes the multi-peak reflected spectrum.

  8. Intrinsic Fabry-Perot interferometric fiber sensor based on ultra-short Bragg gratings for quasi-distributed strain and temperature measurements

    NASA Astrophysics Data System (ADS)

    Wang, Zhuang

    The health monitoring of smart structures in civil engineering is becoming more and more important as in-situ structural monitoring would greatly reduce structure life-cycle costs and improve reliability. The distributed strain and temperature sensing is highly desired in large structures where strain and temperature at over thousand points need to be measured simultaneously. It is difficult to carry out this task using conventional electrical strain sensors. Fiber optic sensors provide an excellent opportunity to fulfill this need due to their capability to multiplex many sensors along a single fiber cable. Numerous research studies have been conducted in past decades to increase the number of sensors to be multiplexed in a distributed sensor network. This dissertation presents detailed research work on the analysis, design, fabrication, testing, and evaluation of an intrinsic Fabry-Perot fiber optic sensor for quasi-distributed strain and temperature measurements. The sensor is based on two ultra-short and broadband reflection fiber Bragg gratings. One distinct feature of this sensor is its ultra low optical insertion loss, which allows a significant increase in the sensor multiplexing capability. Using a simple integrated sensor interrogation unit and an optical spectrum based signal processing algorithm, many sensors can be interrogated along a single optical fiber with high accuracy, high resolution and large dynamic range. Based on the experimental results and theoretical analysis, it is expected that more than 500 sensors can be multiplexed with little crosstalk using a frequency-division multiplexing technology. With this research, it is possible to build an easy fabrication, robust, high sensitivity and quasi-distributed fiber optic sensor network that can be operated reliably even in harsh environments or extended structures. This research was supported in part by U.S. National Science Foundation under grant CMS-0427951.

  9. Performance of low-cost few-mode fiber Bragg grating sensor systems: polarization sensitivity and linearity of temperature and strain response.

    PubMed

    Ganziy, D; Rose, B; Bang, O

    2016-08-10

    We evaluate whether 850 nm fiber Bragg grating (FBG) sensor systems can use low-cost 1550 nm telecom fibers; in other words, how detrimental the influence of higher-order modes is to the polarization stability and linearity of the strain and temperature response. We do this by comparing polarization sensitivity of a few-mode 850 nm FBG sensor to a strictly single-mode 850 nm FBG sensor system using 850 nm single-mode fibers. We also compare the performance of the FBGs in strain and temperature tests. Our results show that the polarization stability and the linearity of the response degrade due to the presence of the higher-order modes. We demonstrate that, by using simple coiling of the 1550 nm fiber, one can regain the performance of the few-mode system and make it usable for high precision measurements. PMID:27534455

  10. Dynamic Strain Measurements on Automotive and Aeronautic Composite Components by Means of Embedded Fiber Bragg Grating Sensors

    PubMed Central

    Lamberti, Alfredo; Chiesura, Gabriele; Luyckx, Geert; Degrieck, Joris; Kaufmann, Markus; Vanlanduit, Steve

    2015-01-01

    The measurement of the internal deformations occurring in real-life composite components is a very challenging task, especially for those components that are rather difficult to access. Optical fiber sensors can overcome such a problem, since they can be embedded in the composite materials and serve as in situ sensors. In this article, embedded optical fiber Bragg grating (FBG) sensors are used to analyze the vibration characteristics of two real-life composite components. The first component is a carbon fiber-reinforced polymer automotive control arm; the second is a glass fiber-reinforced polymer aeronautic hinge arm. The modal parameters of both components were estimated by processing the FBG signals with two interrogation techniques: the maximum detection and fast phase correlation algorithms were employed for the demodulation of the FBG signals; the Peak-Picking and PolyMax techniques were instead used for the parameter estimation. To validate the FBG outcomes, reference measurements were performed by means of a laser Doppler vibrometer. The analysis of the results showed that the FBG sensing capabilities were enhanced when the recently-introduced fast phase correlation algorithm was combined with the state-of-the-art PolyMax estimator curve fitting method. In this case, the FBGs provided the most accurate results, i.e., it was possible to fully characterize the vibration behavior of both composite components. When using more traditional interrogation algorithms (maximum detection) and modal parameter estimation techniques (Peak-Picking), some of the modes were not successfully identified. PMID:26516854

  11. High speed demodulation systems for fiber optic grating sensors

    NASA Technical Reports Server (NTRS)

    Udd, Eric (Inventor); Weisshaar, Andreas (Inventor)

    2002-01-01

    Fiber optic grating sensor demodulation systems are described that offer high speed and multiplexing options for both single and multiple parameter fiber optic grating sensors. To attain very high speeds for single parameter fiber grating sensors ratio techniques are used that allow a series of sensors to be placed in a single fiber while retaining high speed capability. These methods can be extended to multiparameter fiber grating sensors. Optimization of speeds can be obtained by minimizing the number of spectral peaks that must be processed and it is shown that two or three spectral peak measurements may in specific multiparameter applications offer comparable or better performance than processing four spectral peaks. Combining the ratio methods with minimization of peak measurements allows very high speed measurement of such important environmental effects as transverse strain and pressure.

  12. Dynamic Strain Measurements on Automotive and Aeronautic Composite Components by Means of Embedded Fiber Bragg Grating Sensors.

    PubMed

    Lamberti, Alfredo; Chiesura, Gabriele; Luyckx, Geert; Degrieck, Joris; Kaufmann, Markus; Vanlanduit, Steve

    2015-01-01

    The measurement of the internal deformations occurring in real-life composite components is a very challenging task, especially for those components that are rather difficult to access. Optical fiber sensors can overcome such a problem, since they can be embedded in the composite materials and serve as in situ sensors. In this article, embedded optical fiber Bragg grating (FBG) sensors are used to analyze the vibration characteristics of two real-life composite components. The first component is a carbon fiber-reinforced polymer automotive control arm; the second is a glass fiber-reinforced polymer aeronautic hinge arm. The modal parameters of both components were estimated by processing the FBG signals with two interrogation techniques: the maximum detection and fast phase correlation algorithms were employed for the demodulation of the FBG signals; the Peak-Picking and PolyMax techniques were instead used for the parameter estimation. To validate the FBG outcomes, reference measurements were performed by means of a laser Doppler vibrometer. Sensors 2015, 15 27175 The analysis of the results showed that the FBG sensing capabilities were enhanced when the recently-introduced fast phase correlation algorithm was combined with the state-of-the-art PolyMax estimator curve fitting method. In this case, the FBGs provided the most accurate results, i.e. it was possible to fully characterize the vibration behavior of both composite components. When using more traditional interrogation algorithms (maximum detection) and modal parameter estimation techniques (Peak-Picking), some of the modes were not successfully identified. PMID:26516854

  13. Fiber grating systems used to measure strain in cylindrical structures

    NASA Astrophysics Data System (ADS)

    Udd, Eric; Corona-Bittick, Kelli; Slattery, Kerry T.; Dorr, Donald J.; Crowe, C. Robert; Vandiver, Terry L.; Evans, Robert N.

    1997-07-01

    Fiber optic grating systems are described that have been used to measure strain in cylindrical structures. The applications of these systems to a composite utility pole and to a composite missile body are described. Composite utility poles have significant advantages with respect to wooden utility poles that include superior strength and uniformity; light weight for ease of deployment; the ability to be recycled, reducing hazardous waste associated with chemically treated wooden poles; and compatibility with embedded fiber optic sensors, allowing structural loads to be monitored. Tests conducted of fiber optic grating sensors in combination with an overcoupled coupler demodulation system to support structural testing of a 22-ft composite pole are reported. Monitoring strain in composite missile bodies has the potential to improve the quality of manufactured parts, support performance testing, and enhance safety during long periods of storage. Strain measurements made with fiber optic grating and electrical strain gauges are described.

  14. Fiber Bragg grating sensors for strain changes measurements at volcanic sites (MED-SUV project; WP 2; Sub-Task 2.2.2)

    NASA Astrophysics Data System (ADS)

    Sorrentino, Fiodor; Beverini, Nicolò; Calamai, Massimo; Carbone, Daniele; Fotino, Nicoletta; Francesconi, Francesco; Gambino, Salvatore; Grassi, Renzo; Messin, Alfio Alex; Maccioni, Enrico; Morganti, Mauro

    2015-04-01

    Stress and strain changes at volcanic areas are recognized among the best indicators of changes in the activity of the system, and its possible evolution towards critical stages. Depending on their time evolution, stress and strain changes have been the focus of either geodetic (static changes) or seismological (dynamical changes) studies. In volcano geodesy, encouraging results have been obtained though borehole strain-meters. However, they are not easy to install and involve high costs. Therefore, the near future of strain observations at volcanoes depends on the development of broad-band sensors which are low-cost and easy to install, even in the form of dense arrays. Advancements in opto-electronics have allowed the development of low-cost sensors, reliable, rugged and compact, which are particularly suitable for on-field application. In the framework of WP 2 (New monitoring and Observing systems) of the MED-SUV project, the sub-task 2.2 involves the development of strain sensors based on the fiber Bragg grating (FBG) technology. In comparison with previous implementation of the FBG technology to study rock deformations, the system that is being developed within MED-SUV is expected to offer a significantly higher resolution and accuracy in static measurements. Moreover, a careful study is being carried out in order to obtain a smooth dynamic response up to 100 Hz, thus allowing the observation of seismic waves. Finally, the system under development will allow multi-axial strain sensing. The system performances are tailored to suit the requirements of volcano monitoring, with special attention to the trade-off between resolution and cost, and with special care to power consumption. Here we present the results of a field campaign with a preliminary, single-axis FBG strain sensor prototype on Etna, which was carried out in order to check the system performances in out-of-the-lab conditions and in the hostile volcanic environment (lack of mains electricity for

  15. Study on the fiber grating sensors in concrete safety monitoring

    NASA Astrophysics Data System (ADS)

    Liu, Hang; Li, Yang; Zhang, Yu-hong

    2014-09-01

    The concrete may be damaged because there are freeze-thaw cycles between winter and summer in cold regions. Strain is an alternative parameter which can be used to describe deformation. In this paper, the fiber bragg gratings(FBG) were used to concrete safety monitoring. The strain and temperature sensing properties have been studied. The fiber reinforced polymers (FRP) were used for the packaged techniques of FBG sensors. The neural network was applied to temperature compensation for FBG sensors.

  16. Long distance fiber Bragg grating strain sensor interrogation using a high speed Raman-based Fourier domain mode-locked fiber laser with recycled residual Raman pump.

    PubMed

    Kim, Sunduck; Kwon, Oh-Jang; Lee, Hyeong-Seok; Kim, Chang-Seok; Han, Young-Geun

    2013-06-01

    We propose a novel fiber Bragg grating (FBG) sensor interrogation using a Raman-based Fourier-domain mode locking (FDML) fiber laser for a high speed and long distance measurement. A residual Raman pump after the generation of the Raman-based FDML fiber laser is recycled for secondary signal amplification in a 2-m erbium-doped fiber (EDF) to further enhance the output power. The chromatic dispersion is precisely controlled to suppress the phase noise in the FDML laser cavity, resulting in the improvement of an R-number of 1.43 mm/dB. After recycling residual pump, we achieve the 40-km round trip transmission of the sensing probe signal with a high scan rate of 30.8 kHz. With 205-mW residual pump power, the bandwidth and the maximum gain are measured to be more than 50 nm, 10.3 dB at 1550 nm, respectively. The sensitivity of the proposed Raman-based FDML fiber laser to strain is also measured, which are 0.81 pm/μstrain in the spectral domain and 0.19 ns/μstrain in the time domain, respectively. PMID:23736592

  17. 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.

  18. Review of High-Speed Fiber Optic Grating Sensors Systems

    SciTech Connect

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

    2010-03-24

    Fiber grating sensors can be used to support a wide variety of high speed measurement applications. This includes measurements of vibrations on bridges, traffic monitoring on freeways, ultrasonic detection to support non-destructive tests on metal plates and providing details of detonation events. This paper provides a brief overview of some of the techniques that have been used to support high speed measurements using fiber grating sensors over frequency ranges from 10s of kHz, to MHZ and finally toward frequencies approaching the GHz regime. Very early in the development of fiber grating sensor systems it was realized that a high speed fiber grating sensor system could be realized by placing an optical filter that might be a fiber grating in front of a detector so that spectral changes in the reflection from a fiber grating were amplitude modulated. In principal the only limitation on this type of system involved the speed of the output detector which with the development of high speed communication links moved from the regime of 10s of MHz toward 10s of GHz. The earliest deployed systems involved civil structures including measurements of the strain fields on composite utility poles and missile bodies during break tests, bridges and freeways. This was followed by a series of developments that included high speed fiber grating sensors to support nondestructive testing via ultrasonic wave detection, high speed machining and monitoring ship hulls. Each of these applications involved monitoring mechanical motion of structures and thus interest was in speeds up to a few 10s of MHz. Most recently there has been interest in using fiber grating to monitor the very high speed events such as detonations and this has led to utilization of fiber gratings that are consumed during an event that may require detection speeds of hundreds of MHz and in the future multiple GHz.

  19. 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.

  20. 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.

  1. Vectorial strain gauge method using single flexible orthogonal polydimethylsiloxane gratings.

    PubMed

    Guo, Hao; Tang, Jun; Qian, Kun; Tsoukalas, Dimitris; Zhao, Miaomiao; Yang, Jiangtao; Zhang, Binzhen; Chou, Xiujian; Liu, Jun; Xue, Chenyang; Zhang, Wendong

    2016-01-01

    A vectorial strain gauge method using a single sensing element is reported based on the double-sided polydimethylsiloxane (PDMS) Fraunhofer diffraction gratings structures. Using O2 plasma treatment steps, orthogonal wrinkled gratings were fabricated on both sides of a pre-strained PDMS film. Diffracted laser spots from this structure have been used to experimentally demonstrate, that any applied strain can be quantitatively characterized in both the x and y directions with an error of less than 0.6% and with a gauge factor of approximately 10. This simple and low cost technology which is completely different from the traditional vectorial strain gauge method, can be applied to surface vectorial strain measurement and multi-axis integrated mechanical sensors. PMID:27005493

  2. Vectorial strain gauge method using single flexible orthogonal polydimethylsiloxane gratings

    PubMed Central

    Guo, Hao; Tang, Jun; Qian, Kun; Tsoukalas, Dimitris; Zhao, Miaomiao; Yang, Jiangtao; Zhang, Binzhen; Chou, Xiujian; Liu, Jun; Xue, Chenyang; Zhang, Wendong

    2016-01-01

    A vectorial strain gauge method using a single sensing element is reported based on the double-sided polydimethylsiloxane (PDMS) Fraunhofer diffraction gratings structures. Using O2 plasma treatment steps, orthogonal wrinkled gratings were fabricated on both sides of a pre-strained PDMS film. Diffracted laser spots from this structure have been used to experimentally demonstrate, that any applied strain can be quantitatively characterized in both the x and y directions with an error of less than 0.6% and with a gauge factor of approximately 10. This simple and low cost technology which is completely different from the traditional vectorial strain gauge method, can be applied to surface vectorial strain measurement and multi-axis integrated mechanical sensors. PMID:27005493

  3. Vectorial strain gauge method using single flexible orthogonal polydimethylsiloxane gratings

    NASA Astrophysics Data System (ADS)

    Guo, Hao; Tang, Jun; Qian, Kun; Tsoukalas, Dimitris; Zhao, Miaomiao; Yang, Jiangtao; Zhang, Binzhen; Chou, Xiujian; Liu, Jun; Xue, Chenyang; Zhang, Wendong

    2016-03-01

    A vectorial strain gauge method using a single sensing element is reported based on the double-sided polydimethylsiloxane (PDMS) Fraunhofer diffraction gratings structures. Using O2 plasma treatment steps, orthogonal wrinkled gratings were fabricated on both sides of a pre-strained PDMS film. Diffracted laser spots from this structure have been used to experimentally demonstrate, that any applied strain can be quantitatively characterized in both the x and y directions with an error of less than 0.6% and with a gauge factor of approximately 10. This simple and low cost technology which is completely different from the traditional vectorial strain gauge method, can be applied to surface vectorial strain measurement and multi-axis integrated mechanical sensors.

  4. 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.

  5. 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.

  6. 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.

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

    PubMed Central

    Wang, Jian-Neng; Tang, Jaw-Luen

    2010-01-01

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

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. Self-referenced waveguide grating sensor.

    PubMed

    Kehl, Florian; Follonier, Stephane

    2016-04-01

    Like any other sensor system, performances of waveguide grating couplers are affected by adverse effects such as noise and drift, mainly limiting the devices' resolution and long-term stability. It is therefore often required to reference the measurement with a secondary, parallel sensor to decrease these undesired influences. Here we present a simple but effective method to self-reference a label-free waveguide grating coupler by partially coating and thereby passivating the sensitive area with an inert layer. The presented waveguide grating chip design offers the advantage of internal self-referencing for adverse effects, such as inherent system instabilities, mechanical disturbance, or temperature drift, without the need of a sacrificial reference channel. PMID:27192258

  14. 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

  15. High-speed fiber grating pressure sensors

    NASA Astrophysics Data System (ADS)

    Udd, Eric; Rodriguez, George; Sandberg, Richard L.

    2014-06-01

    Fiber grating pressure sensors have been used to support pressure measurements associated with burn, deflagration and detonation of energetic materials. This paper provides an overview of this technology and serves as a companion paper to the application of this technology to measuring pressure during high speed impacts.

  16. 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.

  17. Use of 3000 Bragg Grating Strain Sensors Distributed on Four Eight-meter Optical Fibers During Static Load Tests of a Composite Structure

    NASA Technical Reports Server (NTRS)

    Childers, Brooks A.; Froggatt, Mark E.; Allison, Sidney G.; Moore, Thomas C., Sr.; Hare, David A.; Batten, Christopher F.; Jegley, Dawn C.

    2001-01-01

    This paper describes the use of a fiber optic system to measure strain at thousands of locations along optical fibers where weakly reflecting Bragg gratings have been photoetched. The optical fibers were applied to an advanced composite transport wing along with conventional foil strain gages. A comparison of the fiber optic and foil gage systems used for this test will be presented including: a brief description of both strain data systems; a discussion of the process used for installation of the optical fiber; comparative data from the composite wing test; the processes used for the location and display of the high density fiber optic data. Calibration data demonstrating the potential accuracy of the fiber optic system will also be presented. The opportunities for industrial and commercial applications will be discussed. The fiber optic technique is shown to be a valuable augmentation to foil strain gages providing insight to structural behavior previously requiring reliance on modeling.

  18. 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.

  19. Simultaneous multipoint strain measurement using cascaded long period fiber gratings

    NASA Astrophysics Data System (ADS)

    Tanaka, Satoshi; Tsukida, Osamu; Ngo, Tang T.; Wada, Atsushi; Takahashi, Nobuaki

    2015-09-01

    A fiber-optic strain sensor array using long period fiber gratings (LPGs) is proposed and demonstrated, in which cascaded LPGs (C-LPGs) are employed as the sensing elements and a Fourier transform technique is applied to their periodic channeled spectra for the interrogation scheme. In this technique, strain-induced shift of the channeled spectrum of C-LPG can be determined precisely from the cross-spectrum (i.e. Fourier transform of cross-correlation) between the original and shifted channeled spectra and multiplexing operation of C-LPG sensor array can be achieved by using the different C-LPGs having the channeled spectra with various periods. In the experiment, several kinds of CLPGs are fabricated by UV-irradiation technique and simultaneous multipoint strain measurements are successfully demonstrated.

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

    NASA Astrophysics Data System (ADS)

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

    2001-06-01

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

  1. 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.

  2. Safety monitoring of rail transit by fiber grating sensors

    NASA Astrophysics Data System (ADS)

    Xu, Xiaomei; Li, Xuejin; Deng, Yuanlong; Liu, Xiaoqing; Yu, Yongqin; Zhou, Huasheng

    2013-12-01

    The subway is a representative form of the rail transit, and its catenary suspension system is a very important aspect to the safety of the whole system. The safety monitoring of the subway catenary suspension system is studied in this paper. A demonstrate model is set up in the laboratory, and some fiber Bragg grating (FBG) sensors including strain sensors and displacement sensors were utilized in the demonstrate system. It is shown that the used sensors could indicate the safety information of the system effectively. Especially, the designed displacement sensor that is packaged by athermal technique can abandon the influence of the environment temperature in a certain degree. Its engineering applicability is greatly improved.

  3. 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.

  4. 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.

  5. 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.

  6. Intracore fiber bragg gratings for strain measurement in embedded composite structures.

    PubMed

    Murukeshan, V M; Chan, P Y; Ong, L S; Asundi, A

    2001-01-01

    An intracore Bragg grating written on a photosensitive fiber core is used for strain measurement in composite specimens under load. The strain information is directly related to the absolute change in the Bragg-reflected wavelength. Fiber Bragg grating (FBG) sensors (fibers with intracore gratings) are thus sensitive to strain that is caused by changes in temperature as well as to load-induced changes. Thus these sensors can be made to be independent of source intensity variations and losses. FBG sensors used for load-induced strain sensing in composite structures and the effects of temperature on them are discussed. A detailed account of the use of such embedded structures as self-monitoring nondestructive testing devices is given. PMID:18356985

  7. MEMS Graphene Strain Sensor

    NASA Astrophysics Data System (ADS)

    Young, Clinton Wen-Chieh

    Graphene is a two dimensional honeycomb structure of sp2 hybridized carbon atoms that has possibilities in many applications due to its excellent mechanical and electrical properties. One application for Graphene is in the field of sensors. Graphene's electronic properties do not degrade when it undergoes mechanical strain which is advantageous for strain sensors. In this thesis, certain properties, such as the piezo-resistivity and flexibility, of graphene will be explored to show how they can be utilized to make a strain sensing device. Our original fabrication process of patterning graphene and the transfer process of graphene onto a flexible substrate will be discussed. The development of a stretchable and flexible graphene based rosette strain sensor will also be detailed. Developing a novel, reliable patterning process for the graphene is the first step to manufacture a stretchable graphene based sensor. The graphene was patterned using a photolithography and etching process that was developed by our research team, then it was transferred to a flexible polymer substrate with the use of a combination of soft lithography and wet etching of the Ni foil with ferric chloride solution. Graphene patterning is an essential step in fabricating reliable and sensitive sensors. With this process, graphene can be consistently patterned into different shapes and sizes. To utilize the graphene as the sensing material it also needs to be transferred onto a flexible substrate. The innovative transfer process developed by our research team consistently adheres graphene to a flexible PDMS substrate while removing the original nickel substrate. In the end, the graphene was transferred from the metal substrate to the desired flexible substrate. This process was repeated multiple times to create a stack and multilayer device. While many graphene-based strain sensors have been developed, they are uni-directional and can only measure the strain applied on the sensor in a principle

  8. 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.

  9. 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.

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

    NASA Astrophysics Data System (ADS)

    Deng, Fodan; Huang, Ying; Azarmi, Fardad

    2016-04-01

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

  11. 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.

  12. 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

  13. Development of sensors based on the fiber Bragg grating technology to measure strain changes at volcanoes (MED-SUV project; WP 2; Sub-Task 2.2.2)

    NASA Astrophysics Data System (ADS)

    Beverini, Nicolò; Calamai, Massimo; Carbone, Daniele; Francesconi, Francesco; Gambino, Salvo; Grassi, Renzo; Messina, Alfio Alex; Maccioni, Enrico; Morganti, Mauro; Sorrentino, Fiodor

    2014-05-01

    Stress and strain changes at volcanic areas are recognized among the best indicators of changes in the activity of the system, and its possible evolution towards critical stages. Depending on their time evolution, stress and strain changes have been the focus of either geodetic (static changes) or seismological (dynamical changes) studies. In volcano geodesy, encouraging results have been obtained though borehole strain-meters. However, they are not easy to install and involve high costs. Therefore, the near future of strain observations at volcanoes depends on the development of broad-band sensors which are low-cost and easy to install, even in the form of dense arrays. Advancements in opto-electronics have allowed the development of low-cost sensors, reliable, rugged and compact, which are particularly suitable for on-field application. In the framework of WP 2 (New monitoring and Observing systems) of the MED-SUV project, the sub-task 2.2 involves the development of strain sensors based on the fiber Bragg grating (FBG) technology. In comparison with previous implementation of the FBG technology to study rock deformations, the system that is being developed within MED-SUV is expected to offer a significantly higher resolution and accuracy in static measurements. Moreover, a careful study will be carried out in order to obtain a smooth dynamic response up to 100 Hz, thus allowing the observation of seismic waves. Finally, strategies to implement a tri-axial configuration will be studied. The performances of the proposed systems will be tailored to suit the requirements of volcano monitoring, with special attention to the trade-off between resolution and cost. Here we present an overview of FBG technology applied to strain measurement, the main objectives of our sub-task in the framework of MED-SUV and some preliminary data from a test installation on Etna.

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

    NASA Astrophysics Data System (ADS)

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

    1994-05-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

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

  16. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    Results of experiments performed using germanium-doped, elliptical core, two-mode optical fibers whose sensitivity to strain was spatially varied through the use of chirped, refractive-index gratings permanently induced into the core using Argon-ion laser light are presented. This type of distributed sensor falls into the class of eighted-fiber sensors which, through a variety of means, weight the strain sensitivity of a fiber according to a specified spatial profile. We describe results of a weighted-fiber vibration mode filter which successfully enhances the particular vibration mode whose spatial profile corresponds to the profile of the grating chirp. We report on the high temperature survivability of such grating-based sensors and discuss the possibility of multiplexing more than one sensor within a single fiber.

  18. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  20. 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.

  1. 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

  2. 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

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

    PubMed

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

    2015-12-28

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

  4. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

  6. 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.

  7. 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.

  8. Dynamic Landslide Deformation Monitoring with Fiber Bragg Grating Sensors

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

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

  9. Fiber Bragg grating sensors for steel wire monitoring in real-time

    NASA Astrophysics Data System (ADS)

    Koch, Jan; Angelmahr, Martin; Schade, Wolfgang

    2014-05-01

    Steel wires are widely applied in industrial applications - in most cases as critical components fulfilling high safety requirements in harsh environments (e.g. dockside cranes). In this paper a technique for real-time monitoring of steel ropes applying optical strain sensors based on fiber Bragg gratings is presented. The optical sensors are integrated within the wire strand and replace the core. The strain transmission from the outer wires to the sensors is assured by the mechanical coupling between the optical fiber and the strand. The actual strain load and rope vibrations in the kilohertz range can be determined in real-time.

  10. Fiber Bragg grating sensors: a market overview

    NASA Astrophysics Data System (ADS)

    Méndez, A.

    2007-07-01

    Over the last few years, optical fiber sensors have seen increased acceptance and widespread use. Among the multitude of sensor types, FBG based sensors, more than any other particular sensor type, have become widely known and popular. Given their intrinsic capability to measure a multitude of parameters such as strain, temperature, pressure, chemical and biological agents - and many others - coupled with their flexibility of design to be used as single point or multi-point sensing arrays and their relative low cost, make of FBGs ideal devices to be adopted for a multitude of different sensing applications and implemented in different fields and industries. However, some technical hurdles and market barriers need to be overcome in order for this technology - and fiber sensors in general - to gain more commercial momentum and achieve faster market growth such as the need for industry standards on FBGs and FBG-based sensors, adequate packaging designs, as well as training and education of prospective customers and end-users.

  11. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

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

  13. Demountable connection for polymer optical fiber grating sensors

    NASA Astrophysics Data System (ADS)

    Abang, Ada; Webb, David J.

    2012-08-01

    The authors fabricated a demountable Ferrule connector/Physical contact connection between silica fiber and a polymer optical fiber (POF) containing a fiber Bragg grating. The use of a connector for POF grating sensors eliminates the limitations of ultraviolet glued connections and increases the ease with which the devices can be applied to real-world measurement tasks.

  14. 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.

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

    NASA Technical Reports Server (NTRS)

    Wu, Meng-Chou; Prosser, William H.

    2003-01-01

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

  16. 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.

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

    NASA Astrophysics Data System (ADS)

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

    1995-12-01

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

  18. Novel fiber Bragg grating sensor for temperature-insensitive displacement measurement

    NASA Astrophysics Data System (ADS)

    Dong, Xinyong; Shum, Ping; Ngo, Nam Quoc; Chan, Chi Chiu; Tan, Khay M.

    2004-12-01

    We report the design and development of a novel optical fiber Bragg grating based displacement sensor. A fiber Bragg grating is glued at a slant orientation onto the lateral side of a specially designed cantilever beam. It is found that the bandwidth of the FBG-based sensor changes linearly with the variation of displacement at the free end of the beam due to the displacement-induced strain gradient. Displacement sensing is realized by measuring the reflected optical power of the signal from the grating with a photodetector. A linear response of 37.9 mV/mm was obtained within a displacement range of 9.0 mm. This sensor is also cost effective due to the use of a simple demodulation method and is inherently temperature-insensitive; eliminating the need for temperature compensation.

  19. TECHNICAL NOTE: A novel temperature-insensitive fiber Bragg grating sensor for displacement measurement

    NASA Astrophysics Data System (ADS)

    Dong, Xinyong; Yang, Xiufeng; Zhao, Chun-Liu; Ding, Lei; Shum, P.; Ngo, N. Q.

    2005-04-01

    This paper presents the design and development of an optical fiber Bragg grating based displacement sensor. A fiber Bragg grating is glued at a slant orientation onto the lateral side of a specially designed cantilever beam. It is found that the bandwidth of the FBG based sensor changes linearly with the variation of the displacement at the free end of the beam due to the displacement-induced strain gradient. Displacement sensing is realized by measuring the reflected optical power of the signal from the grating with a photodetector. A linear response of 37.9 mV mm-1 was obtained within a displacement range of 9.0 mm. This sensor is also cost-effective due to the use of a simple demodulation method and is inherently temperature insensitive, eliminating the need for temperature compensation.

  20. Fiber-optical grating sensors for wind turbine blades: a review

    NASA Astrophysics Data System (ADS)

    Glavind, Lars; Olesen, Ib Svend; Skipper, Bjarne Funch; Kristensen, Martin

    2013-03-01

    With the rapid growth of wind turbines and focus on maintenance costs structural measurements are becoming essential. Fiber-optical sensors have physical properties that make them suitable for embedding in wind turbine blades, such as small size and immunity to electrical interferences. Fiber-optical grating sensors can be utilized to provide important information regarding strain, temperature, and curvature of the blades, which can be applied in condition-monitoring to detect fatigue failure and furthermore for optimization of the production from the wind turbine. We provide an overview of the current status and a discussion on research and implementation of fiber Bragg gratings and long-period gratings in wind turbine blade sensors.

  1. 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.

  2. 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.

  3. Using Custom Fiber Bragg Grating-Based Sensors to Monitor Artificial Landslides.

    PubMed

    Zhang, Qinghua; Wang, Yuan; Sun, Yangyang; Gao, Lei; Zhang, Zhenglin; Zhang, Wenyuan; Zhao, Pengchong; Yue, Yin

    2016-01-01

    Four custom fiber Bragg grating (FBG)-based sensors are developed to monitor an artificial landslide located in Nanjing, China. The sensors are composed of a rod and two FBGs. Based on the strength of the rods, two sensors are referred to as "hard sensors" (Sensor 1 and Sensor 2), the other two are referred to as "soft sensors" (Sensor 3 and Sensor 4). The two FBGs are fixed on each sensor rod at distances of 50 cm and 100 cm from the top of the rod (an upper FBG and a lower FBG). In the experiment presented in this paper, the sensors are installed on a slope on which an artificial landslide is generated through both machine-based and manual excavation. The fiber sensing system consists of the four custom FBG-based sensors, optical fiber, a static fiber grating demodulation instrument (SM125), and a PC with the necessary software. Experimental data was collected in the presence of an artificial landslide, and the results show that the lower FBGs are more sensitive than the upper FBGs for all four of the custom sensors. It was also found that Sensor 2 and Sensor 4 are more capable of monitoring small-scale landslides than Sensor 1 and Sensor 3, and this is mainly due to their placement location with respect to the landslide. The stronger rods used in the hard sensors make them more adaptable to the harsh environments of large landslides. Thus, hard sensors should be fixed near the landslide, while soft sensors should be placed farther away from the landslide. In addition, a clear tendency of strain variation can be detected by the soft sensors, which can be used to predict landslides and raise a hazard alarm. PMID:27598163

  4. Comparison of strain sensitivity of bare and structure-integrated fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Lebid, Solomija Y.; Hofmann, Detlef; Basedau, Frank; Daum, Werner

    2003-07-01

    For the last decade sensor architectures with embedded fibers found their application in large structure monitoring and proved their capability to replace existing techniques for monitoring of linear strain, temporary or permanent none-uniform strain and load, temperature, vibrations, bending, or complex strain-temperature, vibrations-temperature influences, etc. Such sensor architectures, called smart structures, use different sensing mechanisms, in one of which - fiber Bragg grating (FBG) - is applied as a sensitive element. Because of high sensitivity, absolute measurement ability, possibility to work reliable in adverse environment, such as electromagnetic fields, radiation, extreme temperature, and quick response time, FBGs are object of numerous research of leading laboratories worldwide. Some problems are still remaining in this field, although there have been some ways found to solve part of them. This paper discusses some aspects of different fixing mechanisms of FBG and provides evaluation and comparison of methods of FBG integration in sensor housing or in sensor architecture.

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

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  6. Fiber Bragg grating displacement sensor for movement measurement of tendons and ligaments

    NASA Astrophysics Data System (ADS)

    Ren, Liang; Song, Gangbing; Conditt, Michael; Noble, Philip C.; Li, Hongnan

    2007-10-01

    Biomechanical studies often involve measurements of the strains developed in tendons or ligaments in posture or locomotion. Fiber-optic sensors present an attractive option for the measurement of strains in tendons and ligaments because of their low cost, ease of implementation, and increased accuracy compared with other implantable transducers. A new displacement sensor based on a fiber Bragg grating and shape memory alloy technology is proposed for the monitoring of tendon and ligament strains in different postures and in locomotion. After sensor calibration in the laboratory, a comparison of the fiber sensors and traditional camera displacement sensors was carried out to evaluate the performance of the fiber sensor during the application of tension to the Achilles tendon. Additional experiments were performed in cadaver knees to assess the suitability of these fiber sensors to measure ligament deformation in a variety of simulated postures. The results demonstrate that the proposed fiber Bragg grating sensor is a highly accurate, easily implantable, and minimally invasive method of measuring tendon and ligament displacement.

  7. Fourier optics analysis of grating sensors with tilt errors.

    PubMed

    Ferhanoglu, Onur; Toy, M Fatih; Urey, Hakan

    2011-06-15

    Dynamic diffraction gratings can be microfabricated with precision and offer extremely sensitive displacement measurements and light intensity modulation. The effect of pure translation of the moving part of the grating on diffracted order intensities is well known. This study focuses on the parameters that limit the intensity and the contrast of the interference. The effects of grating duty cycle, mirror reflectivities, sensor tilt and detector size are investigated using Fourier optics theory and Gaussian beam optics. Analytical findings reveal that fringe visibility becomes <0.3 when the optical path variation exceeds half the wavelength within the grating interferometer. The fringe visibility can be compensated by monitoring the interfering portion of the diffracted order light only through detector size reduction in the expense of optical power. Experiments were conducted with a grating interferometer that resulted in an eightfold increase in fringe visibility with reduced detector size, which is in agreement with theory. Findings show that diffraction grating readout principle is not limited to translating sensors but also can be used for sensors with tilt or other deflection modes. PMID:21685984

  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. 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.

  11. Strain monitoring of drilling riser in deepwater based on fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Jiang, Yajun; Yang, Dexing; Wang, Jun; Xu, Jian; Qin, Chuan; Liao, Wei; Zhao, Jianlin; Wang, Haiyan; Jiang, Shiquan

    2011-11-01

    It is very important to monitor the lateral and axial strains of drilling riser for evaluation its health in deepwater. An optical fiber strain sensing system based on optical fiber Bragg gratings (FBGs) used for monitoring the strain of drilling riser is presented. The optical fiber strain sensors are made by embedding FBGs into thin columned fiber reinforced polymer which protect FBGs from seawater corrosion. Four optical fiber strain sensors are installed parallel to the riser axis and arranged at 90° angles around the riser by a home-made metal belt, at the same time, twelve resistance strain gauges are pasted near the sensors around the drilling riser at 30° angles as reference sensors. A scaled drilling riser about 1 meter long and 0.245m diameter is pressed in the lateral and axial direction in the range of 0-400KN, the experimental results show that the relative error between optical fiber strain sensors and resistance strain gauges is less than 6%.

  12. Strain monitoring of composite pressure vessel with thin metal liner using fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Zhao, Jun-qing; Wang, Rong-guo; He, Xiao-dong; Liu, Wen-bo

    2009-07-01

    Composite pressure vessel with thin metal liner has the advantage of both composite and metal. Due to the difference of elastic strain limits of composite and metal, there is problem of the compatibility of deformation. Nine fiber Bragg gratings were bonded to the surface of longitudinal and hoop directions of pressure vessel to monitor the strain status during 4.5MPa service pressure condition. The measured strain by the Bragg sensor is perfectly linear with the applied force. However, the hoop strain decreased as loading process and increased as unloading process, it is also negative value on middle part of the dome. The phenomena had been discussed in this investigation. As a smart structure Bragg sensor can detect the real strain state of composite pressure vessel and is suitable for damage monitoring in service. Analyzing result shows the pressure vessel can work safely with the applied hydrostatic pressure.

  13. Utilization of fiber optic Bragg grating sensors in concrete columns confined with glass-fiber-reinforced plastic (GFRP) laminate under uniaxial compression test

    NASA Astrophysics Data System (ADS)

    Chan, Peter K. C.; Lau, Alan K.; Jin, Wei; Zhou, Limin

    1999-01-01

    In this paper we report of experimental studies on strain monitoring by using fiber Bragg grating sensors in concrete structures. The strain variation of the specimen under different loading conditions were monitored by the Fiber- optic Bragg grating (FBG) sensors. The FBG sensors have been pre-installed in the structure by embedding either inside the concrete specimen or at the interface between the concrete and the composites. The strain reading from the fiber grating sensor compares favorably with that obtained from the conventional strain gauge in uni-axial compression testing. The test result generally indicated that the concrete structures can be strengthened significantly by wrapping with glassfiber composites. The sensor embedded at the notch tip provides a very good indication of the health condition of the strengthened structure, especially in high stress concentration area. The strain sensitivity by using FBG sensor is 67 (mu) (epsilon) .

  14. Development and Experimental Validation of a Numerical Tool for Structural Health and Usage Monitoring Systems Based on Chirped Grating Sensors

    PubMed Central

    Bettini, Paolo; Guerreschi, Erika; Sala, Giuseppe

    2015-01-01

    The interest of the aerospace industries in structural health and usage monitoring systems is continuously increasing. Among the techniques available in literature those based on Fibre Bragg Grating sensors are much promising thanks to their peculiarities. Different Chirped Bragg Grating sensor configurations have been investigated in this paper. Starting from a numerical model capable of simulating the spectral response of a grating subjected to a generic strain profile (direct problem), a new code has been developed, allowing strain reconstruction from the experimental validation of the program, carried out through different loading cases applied on a chirped grating. The wavelength of the reflection spectrum for a chirped FBG has a one-to-one correspondence to the position along the gauge section, thus allowing strain reconstruction over the entire sensor length. Tests conducted on chirped FBGs also evidenced their potential for SHM applications, if coupled with appropriate numerical strain reconstructions tools. Finally, a new class of sensors—Draw Tower Grating arrays—has been studied. These sensors are applicable to distributed sensing and load reconstruction over large structures, thanks to their greater length. Three configurations have been evaluated, having different spatial and spectral characteristics, in order to explore possible applications of such sensors to SHM systems. PMID:25587979

  15. Elastomeric Polymer Resonant Waveguide Grating based Pressure Sensor

    PubMed Central

    Song, Fuchuan; Xie, Antonio Jou; Seo, Sang-Woo

    2014-01-01

    In this paper, we demonstrate an elastomeric polymer resonant waveguide grating structure to be used as a pressure sensor. The applied pressure is measured by optical resonance spectrum peak shift. The sensitivity - as high as 86.74pm/psi or 12.58pm/kPa - has been experimentally obtained from a fabricated sensor. Potentially, the sensitivity of the demonstrated sensor can be tuned to different pressure ranges by the choices of elastic properties and layer thicknesses of the waveguide and cladding layers. The simulation results agree well with experimental results and indicate that the dominant effect on the sensor is the change of grating period when external pressure is applied. Based on the two-dimensional planar structure, the demonstrated sensor can be used to measure applied surface pressure optically, which has potential applications for optical ultrasound imaging and pressure wave detection/mapping. PMID:25419447

  16. 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.

  17. Fiber Bragg grating sensor as valuable technological platform for new generation of superconducting magnets

    NASA Astrophysics Data System (ADS)

    Chiuchiolo, A.; Bajko, M.; Perez, J. C.; Bajas, H.; Viret, P.; Consales, M.; Giordano, M.; Breglio, G.; Cusano, A.

    2014-05-01

    New generation of superconducting magnets for high energy applications designed, manufactured and tested at the European Organization for Nuclear Research (CERN) require the implementation of reliable sensors able to monitor the mechanical stresses affecting the winding from fabrication to operation in magnetic field of 13 T. This work deals with the embedding of Fiber Bragg Grating sensors in a short model Nb3Sn dipole magnet in order to monitor the strain developed in the coil during the cool down to 1.9 K, the powering up to 15.8 kA and the warm up, offering perspectives for the replacement of standard strain gauges.

  18. Strain sensors for high field pulse magnets

    SciTech Connect

    Martinez, Christian; Zheng, Yan; Easton, Daniel; Farinholt, Kevin M; Park, Gyuhae

    2009-01-01

    In this paper we present an investigation into several strain sensing technologies that are being considered to monitor mechanical deformation within the steel reinforcement shells used in high field pulsed magnets. Such systems generally operate at cryogenic temperatures to mitigate heating issues that are inherent in the coils of nondestructive, high field pulsed magnets. The objective of this preliminary study is to characterize the performance of various strain sensing technologies at liquid nitrogen temperatures (-196 C). Four sensor types are considered in this investigation: fiber Bragg gratings (FBG), resistive foil strain gauges (RFSG), piezoelectric polymers (PVDF), and piezoceramics (PZT). Three operational conditions are considered for each sensor: bond integrity, sensitivity as a function of temperature, and thermal cycling effects. Several experiments were conducted as part of this study, investigating adhesion with various substrate materials (stainless steel, aluminum, and carbon fiber), sensitivity to static (FBG and RFSG) and dynamic (RFSG, PVDF and PZT) load conditions, and sensor diagnostics using PZT sensors. This work has been conducted in collaboration with the National High Magnetic Field Laboratory (NHMFL), and the results of this study will be used to identify the set of sensing technologies that would be best suited for integration within high field pulsed magnets at the NHMFL facility.

  19. The Fiber Grating Sensors Applied in the Deformation Measurement of Shipborne Antenna Basement

    NASA Astrophysics Data System (ADS)

    Liu, Yong; Chen, Jiahong; Zhao, Wenhua

    2016-02-01

    The optical fiber grating sensor is a novel fibre-optical passive device, its reflecting optical spectrum is linearly related with strain. It is broadly applied in the structural monitoring industry. Shipborne antenna basement is the basic supporting structure for the radar tracking movement. The bending deformation of the basement caused by ship attitude changing influences the antenna tracking precision, According to the structure of shipborne antenna basement, a distributed strain testing method based on the fibre grating sensor is approved to measure the bending deformation under the bending force. The strain-angle model is built. The regularity of the strain distribution is obtained. The finite element method is used to analyze the deformation of the antenna basement. The measuring experiment on the contractible basement mould is carried out to verify the availability of the method. The result of the experiment proves that the model is effective to apply in the deformation measurement. It provides an optimized method for the distribution of the fiber grating sensor in the actual measuring process.

  20. A personal review of 25 years of fiber grating sensor development

    NASA Astrophysics Data System (ADS)

    Udd, Eric

    2013-06-01

    Early efforts developing smart structures started with strain sensors based on interferometeric techniques. It immediately became apparent that structural engineers were used to dealing with conventional electrical strain gages and thermocouples with much shorter gage lengths. The fiber grating offered a competitive solution for the measurement of strain and temperature with the advantages of electrical isolation and improved ruggedness. The principal draw back was cost. So early applications involved high value projects where the unique capabilities of the technology offered superior performance. One area of particular interest involved the usage of fiber gratings to sensor more than one parameter simultaneously. Multi-dimensional strain and the measurement of pressure and temperature were two key examples of multi-parameter sensing. In parallel efforts were conducted to operate at high speed. Early examples in aerospace and civil structures were at speeds in the range of 10 kHz. Ballistic work later dictated increasing speeds to 5 MHz. Much more recent work with burn, deflagration and detonation has involved measurements from more than 100 MHz to multiple GHz. This paper provides a personal history of some of these developments and how fiber grating sensor technology is moving into the future.

  1. Low-cost fiber Bragg grating vibroacoustic sensor for voice and heartbeat detection.

    PubMed

    Tosi, Daniele; Olivero, Massimo; Perrone, Guido

    2008-10-01

    A fiber Bragg grating (FBG) vibroacoustic sensor exploiting an intensity-based interrogation principle is presented. The optical system is complemented by signal processing techniques that allow disturbances to be mitigated and improve the spectral estimation. The sensor is capable of performing frequency analysis of sounds up to 3 kHz, with top sensitivity in the 100-500 Hz frequency range, and of dynamically tracking pulsed phenomena that induce a strain to the FBG. The sensor has been applied to the detection of voice, showing a great intelligibility of the speech despite the low-quality environment, and to the monitoring of the heartbeat rate from the wrist. PMID:18830301

  2. Optical fiber sensors for measurement strain and vibration

    NASA Astrophysics Data System (ADS)

    Mikel, Bretislav; Helan, Radek; Buchta, Zdenek; Holík, Milan; Jelinek, Michal; Cip, Ondrej

    2015-01-01

    We present optical fiber sensors to measurement strain and vibration. The sensors are based on fiber Bragg gratings (FBG). We prepared construction of strain sensors with respect to its implementation on the outer surface of concrete structures and with compensation of potential temperature drifts. These sensors are projected with look forward to maximal elongation and strength which can be applied to the sensor. Each sensor contains two optical fibers with FBGs. One FBG is glued into the sensor in points of fixation which are in the line with mounting holes. This FBG is prestressed to half of measurement range, than the stretching and pressing can be measured simultaneously by one FBG. The second FBG is placed inside the sensor without fixation to measure temperature drifts. The sensor can be used to structure health monitoring. The sensors to measurement vibration are based on tilted fiber Bragg grating (TFBG) with fiber taper. The sensor uses the TFBG as a cladding modes reflector and fiber taper as a bend-sensitive recoupling member. The lower cladding modes (ghost), reflected from TFBG, is recoupled back into the fiber core via tapered fiber section. We focused on optimization of TFBG tilt angle to reach maximum reflection of the ghost and taper parameters. In this article we present complete set-up, optical and mechanical parameters of both types of sensors.

  3. A MEMS torsion magnetic sensor with reflective blazed grating integration

    NASA Astrophysics Data System (ADS)

    Long, Liang; Zhong, Shaolong

    2016-07-01

    A novel magnetic sensor based on a permanent magnet and blazed grating is presented in this paper. The magnetic field is detected by measuring the diffracted wavelength of the blazed grating which is changed by the torsion motion of a torsion sensitive micro-electromechanical system (MEMS) structure with a permanent magnet attached. A V-shape grating structure is obtained by wet etching on a (1 0 0) SOI substrate. When the magnet is magnetized in different directions, the in-plane or out-of-plane magnetic field is detected by a sensor. The MEMS magnetic sensor with a permanent magnet is fabricated after analytical design and bulk micromachining processes. The magnetic-sensing capability of the sensor is tested by fiber-optic detection system. The result shows the sensitivities of the in-plane and out-of-plane magnetic fields are 3.6 pm μT‑1 and 5.7 pm μT‑1, respectively. Due to utilization of the permanent magnet and fiber-optic detection, the sensor shows excellent capability of covering the high-resolution detection of low-frequency signals. In addition, the sensitive direction of the magnetic sensor can be easily switched by varying the magnetized direction of the permanent magnet, which offers a simple way to achieve tri-axis magnetic sensor application.

  4. Internal strain monitoring in composite materials with embedded photonic crystal fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Geernaert, Thomas; Sulejmani, Sanne; Sonnenfeld, Camille; Chah, Karima; Luyckx, Geert; Lammens, Nicolas; Voet, Eli; Becker, Martin; Thienpont, Hugo; Berghmans, Francis

    2014-09-01

    The possibility of embedding optical fiber sensors inside carbon fiber reinforced polymer (CFRP) for structural health monitoring purposes has already been demonstrated previously. So far however, these sensors only allowed axial strain measurements because of their low sensitivity for strain in the direction perpendicular to the optical fiber's axis. The design flexibility provided by novel photonic crystal fiber (PCF) technology now allows developing dedicated fibers with substantially enhanced sensitivity to such transverse loads. We exploited that flexibility and we developed a PCF that, when equipped with a fiber Bragg grating (FBG), leads to a sensor that allows measuring transverse strains in reinforced composite materials, with an order of magnitude increase of the sensitivity over the state-of-the-art. In addition it allows shear strain sensing in adhesive bonds, which are used in composite repair patches. This is confirmed both with experiments and finite element simulations on such fibers embedded in CFRP coupons and adhesive bonds. Our sensor brings the achievable transverse strain measurement resolution close to a target value of 1 μstrain and could therefore play an important role for multi-dimensional strain sensing, not only in the domain of structural health monitoring, but also in the field of composite material production monitoring. Our results thereby illustrate the added value that PCFs have to offer for internal strain measurements inside composite materials and structures.

  5. 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.

  6. Apparatus and Method for Measuring Strain in Bragg Gratings

    NASA Technical Reports Server (NTRS)

    Froggatt, Mark E. (Inventor)

    1998-01-01

    An apparatus and method for measuring strain of gratings written into an optical fiber is disclosed. Optical radiation is transmitted over a plurality of contiguous predetermined wavelength ranges into a reference optical fiber network and an optical fiber network under test to produce a plurality of reference interference fringes and measurement interference fringes. respectively. The reference and measurement fringes are detected and sampled such that each sampled value of the reference and measurement fringes is associated with a corresponding sample number. The wavelength change of the reference optical fiber, for each sample number, due to the wavelength of the optical radiation is determined. Each determined wavelength change is matched with a corresponding sampled value of each measurement fringe. Each sampled measurement fringe of each wavelength sweep is transformed into a spatial domain waveform. The spatial domain waveforms are summed to form a summation spatial domain waveform that is used to determine location of each grating with respect to a reference reflector. A portion of each spatial domain waveform that corresponds to a particular grating is determined and transformed into a corresponding frequency spectrum representation. The strain on the grating at each wavelength of optical radiation is determined by determining the difference between the current wavelength and an earlier, zero-strain wavelength measurement.

  7. Free water in fuel sensor using fiber long period grating

    NASA Astrophysics Data System (ADS)

    Zhang, W.; Grice, S.; Sugden, K.; Bennion, I.

    2011-05-01

    A fiber optic free water in fuel (WIF) sensor is proposed by utilizing a long period fiber grating (LPFG). The existence of free water in fuel is indicated by the appearance of a characteristic loss band. The free water level in fuel can be determined by measuring the transmissions of two characteristic loss bands.

  8. 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.

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

    PubMed

    Pacheco, Clara J; Bruno, Antonio C

    2013-01-01

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

  10. 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.

  11. Intensity-modulated and temperature-insensitive fiber Bragg grating vibration sensor

    NASA Astrophysics Data System (ADS)

    Li, Lan; Dong, Xinying; Zhang, Shuqin; Zhao, Chunliu; Sun, Yiling

    2010-10-01

    An intensity-modulated, fiber Bragg grating (FBG) vibration sensor is proposed and experimentally demonstrated. The sensing mechanism is based on the measurement of optical power of a strain-chirped FBG. An initially-uniform FBG is glued with a slanted direction onto the lateral surface of a simply-supported beam (SSB). A mass is fixed in the middle of the beam, which can transfer the vertical vibration to the deflection of the beam. Therefore, deflection induced nouniform strain is applied along the sensing FBG and makes it chirped. The reflected optical power from the FBG is measured with a photodetector (PD) and an oscilloscope. The experimental results are compared with the measurement results of a resistance strain sensor, and good agreement is achieved. Furthermore, this sensor is cost-effective and inherently insensitive to temperature.

  12. Three intelligentization methods for time grating displacement sensor

    NASA Astrophysics Data System (ADS)

    Liu, Xiaokang; Peng, Donglin; Fei, Yetai; Zeng, Yudan

    2008-12-01

    To improve the precision of time grating displacement sensor and enhance its performance by software, three intelligentization methods are studied. A self-compensation method is proposed based on digital closed-loop control technology that eliminates the influences of these factors such as working condition, circuitry parameters and so on. A self-calibration method for time grating is presented that eliminates zero drift and gain drift without external high-precision reference signals. Then an error self-correction method is proposed. Experiment results conform that high stability is obtained by using self-compensation and self-calibration technology, and high precision is achieved by using self-correction technology.

  13. Application of fiber Bragg grating sensors in light aircraft: ground and flight test

    NASA Astrophysics Data System (ADS)

    Kim, Jin-Hyuk; Shrestha, Pratik; Park, Yurim; Kim, Chun-Gon

    2014-05-01

    Fiber optic sensors are being spotlighted as the means to monitoring aircraft conditions due to their excellent characteristics. This paper presents an affordable structural health monitoring system based on a fiber Bragg grating sensor (FBG) for application in light aircrafts. A total of 24 FBG sensors were installed in the main wing of the test bed aircraft. In the ground test, the intactness of the installed sensors and device operability were confirmed. During the flight test, the strain and temperature responses of the wing structure were measured by the on-board low-speed FBG interrogator. The measured strains were successfully converted into the flight load history through the load calibration coefficient obtained from the ground calibration test.

  14. 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.

  15. Analytical Modeling for the Grating Eddy Current Displacement Sensors

    NASA Astrophysics Data System (ADS)

    Lv, Chunfeng; Tao, Wei; Lei, Huaming; Jiang, Yingying; Zhao, Hui

    2015-02-01

    As a new type of displacement sensor, grating eddy current displacement sensor (GECDS) combines traditional eddy current sensors and grating structure in one. The GECDS performs a wide range displacement measurement without precision reduction. This paper proposes an analytical modeling approach for the GECDS. The solution model is established in the Cartesian coordinate system, and the solving domain is limited to finite extents by using the truncated region eigenfunction expansion method. Based on the second order vector potential, expressions for the electromagnetic field as well as coil impedance related to the displacement can be expressed in closed-form. Theoretical results are then confirmed by experiments, which prove the suitability and effectiveness of the analytical modeling approach.

  16. TECHNICAL NOTE: Development of fiber Bragg grating sensor system using wavelength-swept fiber laser

    NASA Astrophysics Data System (ADS)

    Ryu, Chi-Young; Hong, Chang-Sun

    2002-06-01

    Fiber Bragg grating (FBG) sensors based on the wavelength division multiplexing technology are ideally suited for structural health monitoring. In many applications, it is desirable to form several arrays of optical fiber sensors to monitor the response of structures. In the present study, we constructed an improved FBG sensor system using a wavelength-swept fiber laser which exhibits high output power for several sensor arrays. A fiber cavity etalon was also fabricated for the calibration of the nonlinear output wavelength of a laser and for scaling the information in the wavelength domain for signal processing. The constructed FBG sensor system with the fiber cavity etalon and a reference FBG was applied for strain measurements of a laminated composite panel under axial compressive loading. In order to monitor the structural strain in real time, the signal-processing program was constructed using LabVIEW software for storing and visualizing data from the FBG sensors. Experiments showed that the constructed FBG sensor system and the real-time signal-processing program could successfully monitor the strain of composite laminates. This improved FBG sensor system could be useful for large structures which require a large number of sensor arrays.

  17. Simultaneous measurement of strain and temperature by two peanut tapers with embedded fiber Bragg grating.

    PubMed

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

    2015-12-20

    A compact optical fiber sensor for simultaneous measurement of strain and temperature is designed and experimentally investigated. The proposed sensor consists of a two-peanut-taper Mach-Zehnder interferometer (MZI) and in-line embedded fiber Bragg grating (FBG). The sensor at a length of 35 mm presents strain sensitivities 1.07  pm/με and 0.891  pm/με, the temperature sensitivities are 55.35  pm/°C and 10.85  pm/°C, for MZI and FBG, respectively. Through tapering the center of the sensor by a fusion splicer, the strain sensitivity of the MZI is improved to 1.93  pm/με. The resolutions for strain and temperature measurement are ±3.104  με and ±0.194°C with the wavelength resolution of 5 pm. The experimental results show that the sensor is able to simultaneously measure strain and temperature by sensitivity matrix with advantages such as simple structure, compact size, ease of fabrication, low cost, etc. PMID:26837035

  18. Mechanochromic polyurethane strain sensor

    NASA Astrophysics Data System (ADS)

    Cellini, F.; Khapli, S.; Peterson, S. D.; Porfiri, M.

    2014-08-01

    In this Letter, we study the mechanical and optical response of a thermoplastic polyurethane blended with 0.5 wt. % of bis(benzoxazolyl)stilbene dye. The mechanochromic behavior of the material is characterized in a uniaxial stress-relaxation test by simultaneously acquiring the applied force, mechanical deformation, and fluorescence emission. To offer insight into the stress-strain response of the polymer-dye blend, we adapt a classical nonlinear constitutive behavior for elastomeric materials that accounts for stress-induced softening. We correlate the fluorescent response with the mechanical strain to demonstrate the possibility of accurate strain sensing for a broad range of deformations during both loading and unloading.

  19. Optical Bragg grating sensor fibers for ultra-high temperature applications

    NASA Astrophysics Data System (ADS)

    Bartelt, Hartmut; Elsmann, Tino; Habisreuther, Tobias; Schuster, Kay; Rothhardt, Manfred

    2015-07-01

    Sapphire based optical fibers provide an attractive basis for ultra-high temperature stable optical sensor elements. Fiber Bragg gratings can be inscribed in such fibers by means of femtosecond-laser pulses with a wavelength of 400 nm in combination with a two-beam phase mask interferometer. We have investigated crystalline optical fibers as well as structured sapphire-derived all glass optical fibers with aluminum content in the core of up to 50 mol%. The reflection properties, the index modulation and the attenuation effects will be discussed. Results concerning the temperature and strain sensitivity for use as sensor elements at high temperatures will be presented.

  20. Fiber optic liquid level monitoring system using microstructured polymer fiber Bragg grating array sensors: performance analysis

    NASA Astrophysics Data System (ADS)

    Marques, C. A. F.; Pospori, A.; Sáez-Rodríguez, D.; Nielsen, K.; Bang, O.; Webb, D. J.

    2015-09-01

    A highly sensitive liquid level monitoring system based on microstructured polymer optical fiber Bragg grating (mPOFBG) array sensors is reported for the first time. The configuration is based on five mPOFBGs inscribed in the same fiber in the 850 nm spectral region, showing the potential to interrogate liquid level by measuring the strain induced in each mPOFBG embedded in a silicone rubber (SR) diaphragm, which deforms due to hydrostatic pressure variations. The sensor exhibits a highly linear response over the sensing range, a good repeatability, and a high resolution. The sensitivity of the sensor is found to be 98 pm/cm of water, enhanced by more than a factor of 9 when compared to an equivalent sensor based on a silica fiber around 1550 nm. The temperature sensitivity is studied and a multi-sensor arrangement proposed, which has the potential to provide level readings independent of temperature and the liquid density.

  1. Strain evaluation of strengthened concrete structures using FBG sensors

    NASA Astrophysics Data System (ADS)

    Lau, Kin-tak; Zhou, Li-min; Ye, Lin

    1999-12-01

    Fibre-optic Bragg Grating (FBG) sensor presents a great deal of potential in monitoring the internal status of the concrete structures after repairing or strengthening by an external adhered reinforcement. It can be used in a variety of configurations ranging from pointwise to multi-point strain measurement in order to investigate the strain distribution of the structures. In this paper, an experimental investigation on the rectangular notched-concrete beam, which was strengthened by glass fibre composites with the embedment of multiplexing FBG sensors is presented. Three point bending test was performed to investigate the strain profile of the specimen. Frequency modulated continuous wave (FMCW) technique was used to measure the strain variation of the fibre-grating regions. The results give a good agreement with the electrical resistance strain gauge in early loading condition. The difference of the strain-measuring results between the strain-gauge and FBG sensor was increased when further increasing the applied load. It was suspected that the micro/marco cracks occurred on the concrete surface and that the externally bonded strain-measuring device cannot be detected.

  2. Strain evaluation of strengthened concrete structures using FBG sensors

    SciTech Connect

    Lau Kintak; Zhou Limin; Ye Lin

    1999-12-02

    Fibre-optic Bragg Grating (FBG) sensor presents a great deal of potential in monitoring the internal status of the concrete structures after repairing or strengthening by an external adhered reinforcement. It can be used in a variety of configurations ranging from pointwise to multi-point strain measurement in order to investigate the strain distribution of the structures. In this paper, an experimental investigation on the rectangular notched-concrete beam, which was strengthened by glass fibre composites with the embedment of multiplexing FBG sensors is presented. Three point bending test was performed to investigate the strain profile of the specimen. Frequency modulated continuous wave (FMCW) technique was used to measure the strain variation of the fibre-grating regions. The results give a good agreement with the electrical resistance strain gauge in early loading condition. The difference of the strain-measuring results between the strain-gauge and FBG sensor was increased when further increasing the applied load. It was suspected that the micro/marco cracks occurred on the concrete surface and that the externally bonded strain-measuring device cannot be detected.

  3. Fiber Bragg Gratings, IT Techniques and Strain Gauge Validation for Strain Calculation on Aged Metal Specimens

    PubMed Central

    Montero, Ander; de Ocariz, Idurre Saez; Lopez, Ion; Venegas, Pablo; Gomez, Javier; Zubia, Joseba

    2011-01-01

    This paper studies the feasibility of calculating strains in aged F114 steel specimens with Fiber Bragg Grating (FBG) sensors and infrared thermography (IT) techniques. Two specimens have been conditioned under extreme temperature and relative humidity conditions making comparative tests of stress before and after aging using different adhesives. Moreover, a comparison has been made with IT techniques and conventional methods for calculating stresses in F114 steel. Implementation of Structural Health Monitoring techniques on real aircraft during their life cycle requires a study of the behaviour of FBG sensors and their wiring under real conditions, before using them for a long time. To simulate aging, specimens were stored in a climate chamber at 70 °C and 90% RH for 60 days. This study is framed within the Structural Health Monitoring (SHM) and Non Destructuve Evaluation (NDE) research lines, integrated into the avionics area maintained by the Aeronautical Technologies Centre (CTA) and the University of the Basque Country (UPV/EHU). PMID:22346619

  4. Fiber Bragg Gratings, IT techniques and strain gauge validation for strain calculation on aged metal specimens.

    PubMed

    Montero, Ander; de Ocariz, Idurre Saez; Lopez, Ion; Venegas, Pablo; Gomez, Javier; Zubia, Joseba

    2011-01-01

    This paper studies the feasibility of calculating strains in aged F114 steel specimens with Fiber Bragg Grating (FBG) sensors and infrared thermography (IT) techniques. Two specimens have been conditioned under extreme temperature and relative humidity conditions making comparative tests of stress before and after aging using different adhesives. Moreover, a comparison has been made with IT techniques and conventional methods for calculating stresses in F114 steel. Implementation of Structural Health Monitoring techniques on real aircraft during their life cycle requires a study of the behaviour of FBG sensors and their wiring under real conditions, before using them for a long time. To simulate aging, specimens were stored in a climate chamber at 70 °C and 90% RH for 60 days. This study is framed within the Structural Health Monitoring (SHM) and Non Destructuve Evaluation (NDE) research lines, integrated into the avionics area maintained by the Aeronautical Technologies Centre (CTA) and the University of the Basque Country (UPV/EHU). PMID:22346619

  5. 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.

  6. Research on a new type of fiber Bragg grating based corrosion sensor

    NASA Astrophysics Data System (ADS)

    Li, Peng; Song, Shide; Wang, Xiaona; Zhou, Weijie; Zhang, Zuocai

    2015-08-01

    Investigations of the corrosion of rebars in concrete structures are widely studied because of the serious damage to concrete caused by rebar corrosion. The rebar corrosion products in reinforced concrete take up 2~6 times the volume of the rebar. Based on this principle, a new type of fiber Bragg grating (FBG) corrosion sensor is proposed in this paper, which consists of two sensors, an FBG corrosion measurement sensor to measure the expansion strain caused by rebar corrosion, and a temperature compensation sensor to eliminate the cross-sensitivity of FBG corrosion sensor. The corrosion rate is derived by the wavelength shift of FBG corrosion sensor, so rebar corrosion can be monitored and assessed by the FBG wavelength shift. A customized rebar with epoxy fixing groove is designed to install a corrosion sensor on its surface and an embedded temperature compensation sensor. The corrosion sensor is embedded in cement mortar and subsequently casted in concrete. The performance of the corrosion sensor is studied in an accelerated electrochemical corrosion test. Experimental results show that the new type of corrosion sensor has advantage of relatively large measurement range of corrosion rate. The corrosion sensor is suitable to monitor slightly and moderately corroded rebars.

  7. Monitoring respiration and cardiac activity using fiber Bragg grating-based sensor.

    PubMed

    Dziuda, Lukasz; Skibniewski, Franciszek Wojciech; Krej, Mariusz; Lewandowski, Jaroslaw

    2012-07-01

    This paper shows the design of a fiber-based sensor for living activities in human body and the results of a laboratory evaluation carried out on it. The authors have developed a device that allows for monitoring the vibrations of human body evoked by living activities--breathing and cardiac rhythm. The device consists of a Bragg grating inscribed into a single mode optical fiber and operating on a wavelength of around 1550 nm. The fiber Bragg grating (FBG) is mounted inside a pneumatic cushion to be placed between the backrest of the seat and the back of the monitored person. Deformations of the cushion, involving deformations of the FBG, are proportional to the vibrations of the body leaning on the cushion. Laboratory studies have shown that the sensor allows for obtaining dynamic strains on the sensing FBG in the range of 50-124 μ strain caused by breathing and approximately 8.3 μstrain induced by heartbeat, which are fully measurable by today's FBG interrogation systems. The maximum relative measurement error of the presented sensor is 12%. The sensor's simple design enables it to be easily implemented in pilot's and driver's seats for monitoring the physiological condition of pilots and drivers. PMID:22514201

  8. [INVITED] Tilted fiber grating mechanical and biochemical sensors

    NASA Astrophysics Data System (ADS)

    Guo, Tuan; Liu, Fu; Guan, Bai-Ou; Albert, Jacques

    2016-04-01

    The tilted fiber Bragg grating (TFBG) is a new kind of fiber-optic sensor that possesses all the advantages of well-established Bragg grating technology in addition to being able to excite cladding modes resonantly. This device opens up a multitude of opportunities for single-point sensing in hard-to-reach spaces with very controllable cross-sensitivities, absolute and relative measurements of various parameters, and an extreme sensitivity to materials external to the fiber without requiring the fiber to be etched or tapered. Over the past five years, our research group has been developing multimodal fiber-optic sensors based on TFBG in various shapes and forms, always keeping the device itself simple to fabricate and compatible with low-cost manufacturing. This paper presents a brief review of the principle, fabrication, characterization, and implementation of TFBGs, followed by our progress in TFBG sensors for mechanical and biochemical applications, including one-dimensional TFBG vibroscopes, accelerometers and micro-displacement sensors; two-dimensional TFBG vector vibroscopes and vector rotation sensors; reflective TFBG refractometers with in-fiber and fiber-to-fiber configurations; polarimetric and plasmonic TFBG biochemical sensors for in-situ detection of cell, protein and glucose.

  9. 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.

  10. High speed fiber grating sensors for structural monitoring

    NASA Astrophysics Data System (ADS)

    Udd, Eric

    2014-06-01

    This paper provides an overview of selected applications of high speed structural monitoring using fiber grating sensors. Rapid and effective diagnostic capabilities are necessary to respond to changes in structural integrity that may affect safety. In the case of aerospace structures operating at high velocity rapid response has the potential to mitigate catastrophic failure. Similar safety issues apply to civil structures where timely decisions are critical to operations of bridges, dams and buildings. Rapid responses for oil and gas, medical and environmental monitoring applications are also highly important. A great deal of progress has been made in improving the quality and capabilities of high speed fiber grating sensor systems. Some of these systems will be discussed.

  11. Nano-imprint gold grating as refractive index sensor

    NASA Astrophysics Data System (ADS)

    Kumari, Sudha; Mohapatra, Saswat; Moirangthem, Rakesh S.

    2016-05-01

    Large scale of fabrication of plasmonic nanostructures has been a challenging task due to time consuming process and requirement of expensive nanofabrication tools such as electron beam lithography system, focused ion beam system, and extreme UV photolithography system. Here, we present a cost-effective fabrication technique so called soft nanoimprinting to fabricate nanostructures on the larger sample area. In our fabrication process, a commercially available optical DVD disc was used as a template which was imprinted on a polymer glass substrate to prepare 1D polymer nano-grating. A homemade nanoimprinting setup was used in this fabrication process. Further, a label-free refractive index sensor was developed by utilizing the properties of surface plasmon resonance (SPR) of a gold coated 1D polymer nano-grating. Refractive index sensing was tested by exposing different solutions of glycerol-water mixture on the surface of gold nano-grating. The calculated bulk refractive index sensitivity was found to be 751nm/RIU. We believed that our proposed SPR sensor could be a promising candidate for developing low-cost refractive index sensor with high sensitivity on a large scale.

  12. Micro-strain sensing using wrinkled stiff thin films on soft substrates as tunable optical grating.

    PubMed

    Ma, Teng; Liang, Hanshuang; Chen, George; Poon, Benny; Jiang, Hanqing; Yu, Hongbin

    2013-05-20

    We report a strain sensing approach that utilizes wrinkled patterns on poly (dimethylsiloxane) (PDMS) as an optical grating to measure thermally-induced strain of different materials. The mechanism for the strain sensing and the effect of PDMS grating on strain sensing are discussed. By bonding the PDMS grating onto a copper or silicon substrate, the coefficient of thermal expansion (CTE) of the substrates can be deduced by measuring the diffraction angle change due to the change in PDMS grating periodicity when thermal strain is introduced. The measured CTEs agree well with the known reference values. PMID:23736421

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

  14. Design, fabrication, and testing of fiber Bragg grating sensors for cryogenic long-range displacement measurement

    NASA Astrophysics Data System (ADS)

    Li, Jicheng; Neumann, H.; Ramalingam, R.

    2015-06-01

    It is essential to measure the shrinkage/expansion and positioning/aligning of magnets and to control valve displacement which plays a vital role in experiments like the Karlsruhe tritium neutrino experiment beam tube and Cryo pumps. Hence, a displacement sensor which, over a long working range, can be operated under extreme environmental conditions needs to be developed. Fiber Bragg gratings (FBG) have been considered to be excellent sensor elements useful for a variety of applications. This paper will discuss a long range displacement sensors based on fiber Bragg gratings for cryogenic temperature applications. The cryo pump inlet valve control requirements have been taken as example specifications for sensor design. To achieve the development goal, a proper signal transducer and sensor package were designed. A study of the strain transmission of surface-bonded FBG was conducted. The influence of bonding thickness and bonding length was reported. The design, fabrication, and performance were tested at low temperature of around 77 K. The sensor performance was found to be satisfactory at both room temperature and 77 K and linearly for long-range displacement of 550 mm with 14 pm/mm sensitivity and 0.142 mm accuracy.

  15. 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).

  16. 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.

  17. Smart sensing of aviation structures with fiber optic Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Trutzel, Michael N.; Wauer, Karsten; Betz, Daniel; Staudigel, Lothar; Krumpholz, Oskar; Muehlmann, Hans-Christian; Muellert, Thomas; Gleine, Wolfgang

    2000-06-01

    We developed a surface mounting technique where fiber-optic Bragg grating (FBG) sensors are glued to the surface of structures and tested the technique on the surface of a CFRP- wing at the DASA Airbus test center Hamburg for over one year. The FBG sensors were interrogated with a measurement system capable of determining the Bragg wavelength in a few seconds over a spectral range of 60 nm (around 1.53 μm) with an absolute accuracy better than 1 pm. A polarization scrambler was used to account for polarization effects. Excellent consistence between the values of electrical strain gauges and the FBG sensors were found during all measurements. However because this method shows drawbacks in a harsher environment such as a flight test, we are currently investigating the possibilities of integrating FBG sensors into the varnish of the structures. For reasons of their better mechanical performance we use FBG sensors produced on the fiber draw-tower with a special UV-curable coating. The sensors are integrated into an original Airbus varnish build- up. We observed linear strain sensitivities in a temperature range between -50 and +100 °C. Furthermore, at negative temperatures we found a vanish- induced polarization dependence which could be used to differentiate between strain and temperature effects.

  18. Development of viscosity sensor with long period fiber grating technology

    NASA Astrophysics Data System (ADS)

    Lin, Jyh-Dong; Wang, Jian-Neng; Chen, Shih-Huang; Wang, Juei-Mao

    2009-03-01

    In this paper, we describe the development of a viscosity sensing system using a simple and low-cost long-period fiber grating (LPFG) sensor. The LPFG sensor was extremely sensitive to the refractive index of the medium surrounding the cladding surface of the sensing grating, thus allowing it to be used as an ambient index sensor or chemical concentration indicator. Viscosity can be simply defined as resistance to flow of a liquid. We have measured asphalt binder, 100-190000 centistokes, in comparison with optical sensing results. The system sensing asphalt binders exhibited increase trend in the resonance wavelength shift when the refractive index of the medium changed. The prototype sensor consisted of a LPFG sensing component and a cone-shaped reservoir where gravitational force can cause asphalt binders flow through the capillary. Thus the measured time for a constant volume of asphalt binders can be converted into either absolute or kinematic viscosity. In addition, a rotational viscometer and a dynamic shear rheometer were also used to evaluate the viscosity of this liquid, the ratio between the applied shear stress and rate of shear, as well as the viscoelastic property including complex shear modulus and phase angle. The measured time could be converted into viscosity of asphalt binder based on calculation. This simple LPFG viscosity sensing system is hopefully expected to benefit the viscosity measurement for the field of civil, mechanical and aerospace engineering.

  19. Temperature-independent accelerometer with a strain-chirped fiber Bragg grating

    NASA Astrophysics Data System (ADS)

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

    2009-11-01

    A novel fiber optic accelerometer is proposed and demonstrated. The sensing mechanism is based on the measurement of bandwidth and optical power of a strain-chirped fiber Bragg grating (FBG). An initially-uniform FBG is glued with a slanted direction onto the lateral surface of a simply-supported beam. Two masses are fixed on the top and bottom surfaces in the middle of the beam respectively, which can transfer the vertical acceleration to the deflection of the beam. Therefore, deflection induced nouniform strain is applied along the sensing FBG and makes it chirped. Experimental results show that 3-dB bandwidth and reflected optical power of the strain-chirped FBG responds to acceleration sensitively. The achieved sensitivities are up to 0.4 nm/g and 4.57 μW/g respectively in the linear range. Furthermore, this sensor is very cost-effective and inherently insensitive to temperature due to the simple demodulation method.

  20. Facile strain analysis of largely bending films by a surface-labelled grating method

    NASA Astrophysics Data System (ADS)

    Akamatsu, Norihisa; Tashiro, Wataru; Saito, Keisuke; Mamiya, Jun-Ichi; Kinoshita, Motoi; Ikeda, Tomiki; Takeya, Jun; Fujikawa, Shigenori; Priimagi, Arri; Shishido, Atsushi

    2014-06-01

    Mechanical properties of flexible films, for example surface strain of largely bending films, are key to design of stretchable electronic devices, wearable biointegrated devices, and soft microactuators/robots. However, existing methods are mainly based on strain-gauge measurements that require miniaturized array sensors, lead wires, and complicated calibrations. Here we introduce a facile method, based on surface-labelled gratings, for two-dimensional evaluation of surface strains in largely bending films. With this technique, we demonstrate that soft-matter mechanics can be distinct from the mechanics of hard materials. In particular, liquid-crystalline elastomers may undergo unconventional bending in three dimensions, in which both the inner and outer surfaces of the bending film are compressed. We also show that this method can be applied to amorphous elastomeric films, which highlights the general importance of this new mechanical evaluation tool in designing soft-matter-based electronic/photonic as well as biointegrated materials.

  1. 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.

  2. Facile strain analysis of largely bending films by a surface-labelled grating method

    PubMed Central

    Akamatsu, Norihisa; Tashiro, Wataru; Saito, Keisuke; Mamiya, Jun-ichi; Kinoshita, Motoi; Ikeda, Tomiki; Takeya, Jun; Fujikawa, Shigenori; Priimagi, Arri; Shishido, Atsushi

    2014-01-01

    Mechanical properties of flexible films, for example surface strain of largely bending films, are key to design of stretchable electronic devices, wearable biointegrated devices, and soft microactuators/robots. However, existing methods are mainly based on strain-gauge measurements that require miniaturized array sensors, lead wires, and complicated calibrations. Here we introduce a facile method, based on surface-labelled gratings, for two-dimensional evaluation of surface strains in largely bending films. With this technique, we demonstrate that soft-matter mechanics can be distinct from the mechanics of hard materials. In particular, liquid-crystalline elastomers may undergo unconventional bending in three dimensions, in which both the inner and outer surfaces of the bending film are compressed. We also show that this method can be applied to amorphous elastomeric films, which highlights the general importance of this new mechanical evaluation tool in designing soft-matter-based electronic/photonic as well as biointegrated materials. PMID:24948462

  3. 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

  4. 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.

  5. 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.

  6. Hydrogel-coated fiber Bragg grating sensor for pH monitoring

    NASA Astrophysics Data System (ADS)

    Pabbisetti, Vayu Nandana Kishore; Madhuvarasu, Sai Shankar

    2016-06-01

    We present a fiber-optic wavelength-modulated sensor for pH applications. Fiber Bragg grating (FBG) is functionalized with a stimulus-responsive hydrogel that induces a strain on FBG due to mechanical expansion of the gel in response to ambient pH changes. The gel is synthesized from the blends of poly (vinyl alcohol)/poly (acrylic acid). The induced strain results in a shift of FBG reflected peak that is monitored by an interrogator. The sensor system shows good linearity in the acidic pH range of 3 to 7 with a sensitivity of 12.16 pm/pH. In addition, it shows good repeatability and oscillator behavior, which proves it to be fit for pH sensing applications.

  7. Ground movement monitoring using an optic fiber Bragg grating sensored system

    NASA Astrophysics Data System (ADS)

    Ho, Yen-Te; Huang, An-Bin; Ma, Jiming; Zhang, Baishan

    2005-05-01

    The authors have developed a fiber optic ground movement monitoring system using the optic Fiber Bragg Grating (FBG). A series of FBG's are glued to the outside of flexible plastic elements. These flexible elements are connected together to form a single probe. When the flexible element is bent, the FBG's sense the flexural strain as a result of the bending. Twice integration of the strains along the longitudinal axis of the probe yields the distribution of the displacement of the monitoring probe associated with the bending. The sensitivity and range of allowable bending of the monitoring probe can be adjusted according to the need in the field. The FBG based monitoring system has been experimented to measure the displacement distribution of a laterally loaded pile in Yuin-Lin, Taiwan. This paper describes the principles of the FBG sensor monitoring probe system and presents a case of field application of the sensor system.

  8. Polymer optical fiber grating as water activity sensor

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Webb, David J.

    2014-05-01

    Controlling the water content within a product has long been required in the chemical processing, agriculture, food storage, paper manufacturing, semiconductor, pharmaceutical and fuel industries. The limitations of water content measurement as an indicator of safety and quality are attributed to differences in the strength with which water associates with other components in the product. Water activity indicates how tightly water is "bound," structurally or chemically, in products. Water absorption introduces changes in the volume and refractive index of poly(methyl methacrylate) PMMA. Therefore for a grating made in PMMA based optical fiber, its wavelength is an indicator of water absorption and PMMA thus can be used as a water activity sensor. In this work we have investigated the performance of a PMMA based optical fiber grating as a water activity sensor in sugar solution, saline solution and Jet A-1 aviation fuel. Samples of sugar solution with sugar concentration from 0 to 8%, saline solution with concentration from 0 to 22%, and dried (10ppm), ambient (39ppm) and wet (68ppm) aviation fuels were used in experiments. The corresponding water activities are measured as 1.0 to 0.99 for sugar solution, 1.0 to 0.86 for saline solution, and 0.15, 0.57 and 1.0 for the aviation fuel samples. The water content in the measured samples ranges from 100% (pure water) to 10 ppm (dried aviation fuel). The PMMA based optical fiber grating exhibits good sensitivity and consistent response, and Bragg wavelength shifts as large as 3.4 nm when the sensor is transferred from dry fuel to wet fuel.

  9. Shear stress sensing with Bragg grating-based sensors in microstructured optical fibers.

    PubMed

    Sulejmani, Sanne; Sonnenfeld, Camille; Geernaert, Thomas; Luyckx, Geert; Van Hemelrijck, Danny; Mergo, Pawel; Urbanczyk, Waclaw; Chah, Karima; Caucheteur, Christophe; Mégret, Patrice; Thienpont, Hugo; Berghmans, Francis

    2013-08-26

    We demonstrate shear stress sensing with a Bragg grating-based microstructured optical fiber sensor embedded in a single lap adhesive joint. We achieved an unprecedented shear stress sensitivity of 59.8 pm/MPa when the joint is loaded in tension. This corresponds to a shear strain sensitivity of 0.01 pm/µε. We verified these results with 2D and 3D finite element modeling. A comparative FEM study with conventional highly birefringent side-hole and bow-tie fibers shows that our dedicated fiber design yields a fourfold sensitivity improvement. PMID:24105585

  10. Design and performance of a fiber bragg grating displacement sensor for movement measurement of tendon and ligament

    NASA Astrophysics Data System (ADS)

    Ren, Liang; Song, Gangbing; Conditt, Michael; Noble, Philip C.; Li, Hongnan

    2007-04-01

    Biomechanical studies often involve measurements of the strains developed in tendons or ligaments in posture or locomotion. Fiber optic sensors present an attractive option for measurement of strains in tendons and ligaments due to their low cost, ease of implementation, and increased accuracy compared to other implantable transducers. A new displacement sensor based on fiber Bragg grating and shape memory alloy technology is proposed for the monitoring of tendon and ligament strains in different postures and in locomotion. After sensor calibration in the laboratory, a comparison test between the fiber sensors and traditional camera displacement sensors was carried out to evaluate the performance of the fiber sensor during application of tension to the Achilles tendon. Additional experiments were performed in cadaver knees to assess the suitability of these fiber sensors for measuring ligament deformation in a variety of simulated postures. The results demonstrate that the proposed fiber Bragg grating sensor is a high-accuracy, easily implantable, and minimally invasive method of measuring tendon and ligament displacement.

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

    SciTech Connect

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

    1994-04-01

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

  12. Measurement uncertainty sources analysis for parasitic time grating sensors

    NASA Astrophysics Data System (ADS)

    Yang, Hongtao; Zhou, Jiao; Fan, Bin; Fei, Yetai; Peng, Donglin; Wu, Tianfeng

    2016-01-01

    The signal quality of traveling wave and the measurement accuracy of parasitic time grating can be improved by optimiz ing its structure. This optimization process can be guided through building the electrical traveling wave equation with respect to the structure and the traveling wave signal generation principle. Based on Ansoft Maxwell simulation, the important electromagnetic parameters and the main uncertainty sources were analyzed and determined respectively. In the simulation parameters such as the excitation signal frequency, the gap width, the relative area of the probe, the coils number, the excitation signal amplitude and the core length were set to different values. It can be seen from the simulation results that excitation signal frequency, the gap width, the relative area between the probe and the rotor are the major factors to influence the angular measuring accuracy of parasitic time grating sensor. Meanwhile, the coils number, the excitation signal amplitude and the core length are the secondary factors. The analysis result can be utilized to optimize the structure of parasitic time grating and correct measurement error.

  13. 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.

  14. Design of a decoupled MRI-compatible force sensor using fiber bragg grating sensors for robot-assisted prostate interventions

    NASA Astrophysics Data System (ADS)

    Monfaredi, Reza; Seifabadi, Reza; Fichtinger, Gabor; Iordachita, Iulian

    2013-03-01

    During prostate needle insertion, the gland rotates and displaces resulting in needle placement inaccuracy. To compensate for this error, we proposed master-slave needle steering under real-time MRI in a previous study. For MRI-compatibility and accurate motion control, the master (and the slave) robot uses piezo actuators. These actuators however, are non-backdrivable. To cope with this issue, force sensor is required. Force sensor is also required at the slave side to reflect the insertion force to clinician's hand through the master robot. Currently, there is no MRI-compatible force sensor commercially available. In order to generate a combination of linear and rotary motions for needle steering, this study is seeking to develop a MRI-compatible 2 Degrees of Freedom (DOF) force/torque sensor. Fiber Brag Grating (FBG) strain measuring sensors which are proven to be MRI-compatible are used. The active element is made of phosphor-bronze and other parts are made of brass. The force and torque measurements are designed to be entirely decoupled. The sensor measures -20 to 20 N axial force with 0.1 N resolution, and -200 to 200 Nmm axial torque with 1 Nmm resolution. Analytical and Finite Element (FE) analyses are performed to ensure the strains are within the measurable range of the FBG sensors. The sensor is designed to be compact (diameter =15 mm, height =20 mm) and easy to handle and install. The proposed sensor is fabricated and calibrated using a commercial force/torque sensor.

  15. Note: strain sensitivity comparison between fiber Bragg gratings inscribed on 125 and 80 micron cladding diameter fibers, case study on the solidification monitoring of a photo-curable resin.

    PubMed

    Maccioni, E; Morganti, M; Brandi, F

    2015-02-01

    The influence of fiber Bragg grating diameter when measuring strain is investigated and quantified. Two fiber Bragg gratings with bare cladding diameter of 125 μm and 80 μm are produced by excimer laser irradiation through a phase mask, and are used to simultaneously monitor the Bragg wavelength shift due to the strain produced by the solidification of a photo-curable resin during light exposure. It is found that the ratio of the measured strains in the two fiber Bragg gratings is close to the inverse ratio of the fiber's cladding diameter. These results represent a direct simultaneous comparison between 125 μm and 80 μm diameter fiber Bragg grating strain sensors, and demonstrate the feasibility of strain measurements in photo-curable resins using bare 80 μm cladding diameter fiber Bragg gratings with an increased sensitivity and spatial resolution compared with standard 125 μm diameter fiber Bragg gratings. PMID:25725899

  16. Note: Strain sensitivity comparison between fiber Bragg gratings inscribed on 125 and 80 micron cladding diameter fibers, case study on the solidification monitoring of a photo-curable resin

    SciTech Connect

    Maccioni, E.; Morganti, M.; Brandi, F.

    2015-02-15

    The influence of fiber Bragg grating diameter when measuring strain is investigated and quantified. Two fiber Bragg gratings with bare cladding diameter of 125 μm and 80 μm are produced by excimer laser irradiation through a phase mask, and are used to simultaneously monitor the Bragg wavelength shift due to the strain produced by the solidification of a photo-curable resin during light exposure. It is found that the ratio of the measured strains in the two fiber Bragg gratings is close to the inverse ratio of the fiber’s cladding diameter. These results represent a direct simultaneous comparison between 125 μm and 80 μm diameter fiber Bragg grating strain sensors, and demonstrate the feasibility of strain measurements in photo-curable resins using bare 80 μm cladding diameter fiber Bragg gratings with an increased sensitivity and spatial resolution compared with standard 125 μm diameter fiber Bragg gratings.

  17. Distributed strain and temperature mapping in the Safe Affordable Fission Engine (SAFE-100) thermal simulator using fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

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

    2004-07-01

    The motivation for the reported research was to support NASA space nuclear power initiatives through the development of advanced fiber Bragg grating (FBG) sensors for the SAFE-100 non-nuclear core simulator. The purpose of the combined temperature and strain mapping was to obtain a correlation between power distribution and core shape within the simulator. In a nuclear reactor, core dimension affects local reactivity and therefore power distribution. 20 FBG temperature sensors were installed in the SAFE-100 thermal simulator at the NASA Marshal Space Flight Center in an interstitial location approximately 2.3mm in diameter. The simulator was heated during two separate experiments using graphite resistive heating elements. The first experiment reached a maximum temperature of approximately 800°C, while the second experiment reached 1150°C. A detailed profile of temperature vs. time and location within the simulator was generated. During a second test, highly distributed fiber Bragg grating strain sensors were arrayed about the circumference and along the length of the heated core region. The maximum temperature during this test was approximately 300°C. A radial and longitudinal strain distribution was obtained that correlated well with known power distribution. Work continues to increase the strain sensor operating temperature and sensor multiplexing to allow high-resolution mapping.

  18. Temperature-insensitive fiber Bragg grating displacement sensor based on a thin-wall ring

    NASA Astrophysics Data System (ADS)

    Tao, Sicong; Dong, Xiaopeng; Lai, Bowen

    2016-08-01

    The study on strain distribution of a thin-wall ring is presented and a bandwidth-demodulated displacement sensor based on a fiber Bragg grating (FBG) is proposed. The FBG is glued onto the inner surface of a spring steel ring, and it is found that its bandwidth is linearly changed with the displacement variation of the top point of the ring due to the ring-compression-induced gradient strain. The PD output responses of different grating lengths to the same dimension of the ring are investigated. Experimental results show that the high sensitivity and accuracy of 0.567 nm mm-1 and ±0.04 mm using 10 mm grating is achieved within a displacement range of 0-3.5 mm. The designed structure has a higher 3dB-bandwidth tuning ratio of 0.057 nm mm-2. A temperature stability better than ±0.02 mm over the temperature range from 0 to 60 °C is demonstrated.

  19. Nonlinearity error separation and self-correction methods for time grating displacement sensor

    NASA Astrophysics Data System (ADS)

    Liu, Xiaokang; Peng, Donglin; Wang, Xianquan; Yang, Wei

    2006-11-01

    A novel type of displacement sensor named time grating is introduced for measuring space with time. Multi-position probes measuring method is used to separate the non-linearity error of time grating, and Fourier series harmonic wave correction method is proposed to correct the error by software. Experiment results coming out from applications conform the remarkable effectiveness of these methods. A time grating displacement sensor with accuracy of +/-0.8" is developed. Test results show that high-precision measurement is achieved without high-precision manufacture. The realization of error self-correction endows time grating sensor with intelligence.

  20. Optical fiber long-period grating with solgel coating for gas sensor

    NASA Astrophysics Data System (ADS)

    Gu, Zhengtian; Xu, Yanping; Gao, Kan

    2006-08-01

    The novel long-period fiber grating (LPFG) film sensor is composed of the long-period grating coated with solgel-derived sensitive films. The characteristics of the transmissivity of the LPFG film sensor are studied. By analyzing the relation among the sensitivity Sn, the thin film optical parameters, and the fiber grating parameters, the optimal design parameters of the LPFG film sensor are obtained. Data simulation shows that the resolution of the refractive index of this LPFG film sensor is predicted to be 10-8. Experimentally, a LPFG film sensor for detection of C2H5OH was fabricated, and a preliminary gas-sensing test was performed.

  1. Fiber-coupled, Littrow-grating cavity displacement sensor.

    PubMed

    Allen, Graham; Sun, Ke-Xun; Byer, Robert

    2010-04-15

    We have demonstrated a compact, optical-fiber-fed, optical displacement sensor utilizing a Littrow-mounted diffraction grating to form a low-finesse Fabry-Perot cavity. Length changes of the cavity are read out via the Pound-Drever-Hall rf modulation technique at 925 MHz. The sensor has a nominal working distance of 2 cm and a total dynamic range of 160 nm. The displacement noise floor was less than 3x10(-10) m/sqrt[Hz] above 10(-2) Hz, limited by the frequency drift of the reference laser. A frequency-stabilized laser would reduce the noise floor to below 10(-12) m/sqrt[Hz]. The use of a 925 MHz modulation frequency demonstrates high-precision readout of a low-finesse compact resonant cavity. PMID:20410986

  2. Application of a Fiber Optic Distributed Strain Sensor System to Woven E-Glass Composite

    NASA Technical Reports Server (NTRS)

    Anastasi, Robert F.; Lopatin, Craig

    2001-01-01

    A distributed strain sensing system utilizing a series of identically written Bragg gratings along an optical fiber is examined for potential application to Composite Armored Vehicle health monitoring. A vacuum assisted resin transfer molding process was used to fabricate a woven fabric E-glass/composite panel with an embedded fiber optic strain sensor. Test samples machined from the panel were mechanically tested in 4-point bending. Experimental results are presented that show the mechanical strain from foil strain gages comparing well to optical strain from the embedded sensors. Also, it was found that the distributed strain along the sample length was consistent with the loading configuration.

  3. Improving the in-flight security by employing seat occupancy sensors based on Fiber Bragg grating technology

    NASA Astrophysics Data System (ADS)

    Zhang, Hongtao; Wang, Pengfei

    2012-06-01

    The current schemes of detecting the status of passengers in airplanes cannot satisfy the more strict regulations recently released by the United States Transportation Security Administration. In basis of investigation on the current seat occupancy sensors for vehicles, in this paper we present a novel scheme of seat occupancy sensors based on Fiber Bragg Grating technology to improve the in-flight security of airplanes. This seat occupancy sensor system can be used to detect the status of passengers and to trigger the airbags to control the inflation of air bags, which have been installed in the airplanes of some major airlines under the new law. This scheme utilizes our previous research results of Weight-In- Motion sensor system based on optical fiber Bragg grating. In contrast to the current seat occupancy sensors for vehicles, this new seat occupancy sensor has so many merits that it is very suitable to be applied in aerospace industry or high speed railway system. Moreover, combined with existing Fiber Bragg Grating strain or temperature sensor systems built in airplanes, this proposed method can construct a complete airline passenger management system.

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

    PubMed

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

    2015-01-01

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

  5. A Fiber Bragg Grating Sensing Based Triaxial Vibration Sensor

    PubMed Central

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

    2015-01-01

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

  6. Active resonant subwavelength grating for scannerless range imaging sensors.

    SciTech Connect

    Kemme, Shanalyn A.; Nellums, Robert O.; Boye, Robert R.; Peters, David William

    2006-11-01

    In this late-start LDRD, we will present a design for a wavelength-agile, high-speed modulator that enables a long-term vision for the THz Scannerless Range Imaging (SRI) sensor. It takes the place of the currently-utilized SRI micro-channel plate which is limited to photocathode sensitive wavelengths (primarily in the visible and near-IR regimes). Two of Sandia's successful technologies--subwavelength diffractive optics and THz sources and detectors--are poised to extend the capabilities of the SRI sensor. The goal is to drastically broaden the SRI's sensing waveband--all the way to the THz regime--so the sensor can see through image-obscuring, scattering environments like smoke and dust. Surface properties, such as reflectivity, emissivity, and scattering roughness, vary greatly with the illuminating wavelength. Thus, objects that are difficult to image at the SRI sensor's present near-IR wavelengths may be imaged more easily at the considerably longer THz wavelengths (0.1 to 1mm). The proposed component is an active Resonant Subwavelength Grating (RSG). Sandia invested considerable effort on a passive RSG two years ago, which resulted in a highly-efficient (reflectivity greater than gold), wavelength-specific reflector. For this late-start LDRD proposal, we will transform the passive RSG design into an active laser-line reflector.

  7. Highly stretchable miniature strain sensor for large dynamic strain measurement

    DOE PAGESBeta

    Song, Bo; Yao, Shurong; Nie, Xu; Yu, Xun; Blecke, Jill

    2016-01-01

    In this paper, a new type of highly stretchable strain sensor was developed to measure large strains. The sensor was based on the piezo-resistive response of carbon nanotube (CNT)/polydimethylsiloxane (PDMS) composite thin films. The piezo-resistive response of CNT composite gives accurate strain measurement with high frequency response, while the ultra-soft PDMS matrix provides high flexibility and ductility for large strain measurement. Experimental results show that the CNT/PDMS sensor measures large strains (up to 8 %) with an excellent linearity and a fast frequency response. The new miniature strain sensor also exhibits much higher sensitivities than the conventional foil strain gages,more » as its gauge factor is 500 times of that of the conventional foil strain gages.« less

  8. Highly stretchable miniature strain sensor for large dynamic strain measurement

    SciTech Connect

    Song, Bo; Yao, Shurong; Nie, Xu; Yu, Xun; Blecke, Jill

    2016-01-01

    In this paper, a new type of highly stretchable strain sensor was developed to measure large strains. The sensor was based on the piezo-resistive response of carbon nanotube (CNT)/polydimethylsiloxane (PDMS) composite thin films. The piezo-resistive response of CNT composite gives accurate strain measurement with high frequency response, while the ultra-soft PDMS matrix provides high flexibility and ductility for large strain measurement. Experimental results show that the CNT/PDMS sensor measures large strains (up to 8 %) with an excellent linearity and a fast frequency response. The new miniature strain sensor also exhibits much higher sensitivities than the conventional foil strain gages, as its gauge factor is 500 times of that of the conventional foil strain gages.

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  10. Multi-channel monolithic integrated optic fiber Bragg grating sensor interrogator

    NASA Astrophysics Data System (ADS)

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

    2011-09-01

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

  11. High resolution interrogation system for fiber Bragg grating (FBG) sensor application using radio frequency spectrum analyser

    NASA Astrophysics Data System (ADS)

    Muhammad, F. D.; Zulkifli, M. Z.; Harun, S. W.; Ahmad, H.

    2013-05-01

    In this paper, we propose a fiber Bragg grating (FBG) interrogation system for high resolution sensor application based on radio frequency (RF) generation technique by beating a single longitudinal mode (SLM) fiber ring laser with an external tunable laser source (TLS). The external TLS provides a constant wavelength (CW), functioning as the reference signal for the frequency beating technique. The TLS used has a constant output power and wavelength over time. The sensor signal is provided by the reflected wavelength of a typical fiber Bragg grating (FBG) in the SLM fiber ring laser, which consists of a 1 m long highly doped Erbium doped fiber as the gain medium. The key to ensure the SLM laser oscillation is the role of graphene as saturable absorber which is opposed to the commonly used unpumped erbiumdoped fiber and this consequently contributes to the simple and short cavity design of our proposed system. The signal from the SLM fiber ring laser, which is generated by the FBG in response to external changes, such as temperature, strain, air humidity and air movement, is heterodyned with the CW signal from the TLS at a 6 GHz photodetector using a 3-dB fused coupler to generate the frequency beating. This proposed system is experimentally demonstrated as a temperature sensor and the results shows that the frequency response of the system towards the changes in temperature is about 1.3 GHz/°C, taking into account the resolution bandwidth of 3 MHz of the radio frequency spectrum analyzer (RFSA).

  12. High Neutron Fluence Survivability Testing of Advanced Fiber Bragg Grating Sensors

    NASA Astrophysics Data System (ADS)

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

    2004-02-01

    The motivation for the reported research was to support NASA space nuclear power initiatives through the development of advanced fiber optic sensors for space-based nuclear power applications. The purpose of the high-neutron fluence testing was to demonstrate the survivability of fiber Bragg grating (FBG) sensors in a fission reactor environment. 520 FBGs were installed in the Ford reactor at the University of Michigan. The reactor was operated for 1012 effective full power hours resulting in a maximum neutron fluence of approximately 5×1019 n/cm2, and a maximum gamma dose of 2×103 MGy gamma. This work is significant in that, to the knowledge of the authors, the exposure levels obtained are approximately 1000 times higher than for any previously published experiment. Four different fiber compositions were evaluated. An 87% survival rate was observed for fiber Bragg gratings located at the fuel centerline. Optical Frequency Domain Reflectometry (OFDR), originally developed at the NASA Langley Research Center, can be used to interrogate several thousand low-reflectivity FBG strain and/or temperature sensors along a single optical fiber. A key advantage of the OFDR sensor technology for space nuclear power is the extremely low mass of the sensor, which consists of only a silica fiber 125μm in diameter. The sensors produced using this technology will fill applications in nuclear power for current reactor plants, emerging Generation-IV reactors, and for space nuclear power. The reported research was conducted by Luna Innovations and was funded through a Small Business Innovative Research (SBIR) contract with the NASA Glenn Research Center.

  13. High Neutron Fluence Survivability Testing of Advanced Fiber Bragg Grating Sensors

    SciTech Connect

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

    2004-02-04

    The motivation for the reported research was to support NASA space nuclear power initiatives through the development of advanced fiber optic sensors for space-based nuclear power applications. The purpose of the high-neutron fluence testing was to demonstrate the survivability of fiber Bragg grating (FBG) sensors in a fission reactor environment. 520 FBGs were installed in the Ford reactor at the University of Michigan. The reactor was operated for 1012 effective full power hours resulting in a maximum neutron fluence of approximately 5x1019 n/cm2, and a maximum gamma dose of 2x103 MGy gamma. This work is significant in that, to the knowledge of the authors, the exposure levels obtained are approximately 1000 times higher than for any previously published experiment. Four different fiber compositions were evaluated. An 87% survival rate was observed for fiber Bragg gratings located at the fuel centerline. Optical Frequency Domain Reflectometry (OFDR), originally developed at the NASA Langley Research Center, can be used to interrogate several thousand low-reflectivity FBG strain and/or temperature sensors along a single optical fiber. A key advantage of the OFDR sensor technology for space nuclear power is the extremely low mass of the sensor, which consists of only a silica fiber 125{mu}m in diameter. The sensors produced using this technology will fill applications in nuclear power for current reactor plants, emerging Generation-IV reactors, and for space nuclear power. The reported research was conducted by Luna Innovations and was funded through a Small Business Innovative Research (SBIR) contract with the NASA Glenn Research Center.

  14. A study on intermediate buffer layer of coated Fiber Bragg Grating cryogenic temperature sensors

    NASA Astrophysics Data System (ADS)

    Freitas, R.; Araujo, F.; Araujo, J.; Neumann, H.; Ramalingam, R.

    2015-12-01

    The sensor characteristics of a coated Fiber Bragg grating (FBG) thermal sensor for cryogenic temperatures depends mainly on the coating materials. The sensitivity of the coated FBG can be improved by enhancing the effective thermal strain transfer between the different layers and the bare FBG. The dual coated FBG's has a primary layer and the secondary layer. The primary coating acts as an intermediate buffer between the secondary coating and the bare FBG. The outer secondary coating is normally made of metals with high thermal expansion coefficient. In this work, a detailed study is carried out on chromium and titanium intermediate buffer layers with various coating thicknesses and combinations. To improve the sensitivity, the secondary coating layer was tested with Indium, Lead and Tin. The sensors were then calibrated in a cryogenic temperature calibration facility at Institute of Technical Physics (ITEP), Karlsruhe Institute of Technology. The sensors were subjected to several thermal cycles between 4.2 and 80 K to study the sensor performance and its thermal characteristics. The sensor exhibits a Bragg wavelength shift of 13pm at 20K. The commercially available detection equipment with a resolution of 1pm can result in a temperature resolution of 0.076 K at 20K.

  15. Instrumentation of integrally stiffened composite panel with fiber Bragg grating sensors for vibration measurements

    NASA Astrophysics Data System (ADS)

    Oman, Kyle; Van Hoe, Bram; Aly, Karim; Peters, Kara; Van Steenberge, Geert; Stan, Nikola; Schultz, Stephen

    2015-08-01

    We evaluate the performance of fiber Bragg grating (FBG) sensors for the measurement of dynamic strains in complex composite structures. The particular structure used in this study is an integrally stiffened composite panel for which the stiffeners and skin are fabricated in a single layup and cure process. Surface-mounted FBG sensors are bonded to the panels after curing, whereas embedded FBG sensors are successfully incorporated during the fabrication process. A finite element model was also constructed of the stiffened panel. The panels were subjected to repeated impacts and the post-impact vibration response of the panel was measured through the FBG sensor responses. Little change to the global response of the panel was observed after the repeated impacts, through the dynamic response of the surface-mounted FBGs. Pulsed phase thermography and micro-computer-tomography imaging of the panel confirmed that the damage was localized near the impact locations, producing negligible changes to the global response of the panel. All of the embedded FBG sensors survived the fabrication and multiple impacts; however, as these were embedded close to the neutral axis of the panel, they were not very sensitive to the vibration modes. Excitation of the panel near the first natural frequency did produce a measurable response in the FBG sensors, confirming their functionality.

  16. Evanescent-field-coupled guided-mode sensor based on a waveguide grating.

    PubMed

    Nesterenko, Dmitry V; Hayashi, Shinji; Sekkat, Zouheir

    2015-05-20

    A guided-mode (GM) sensor with a dielectric waveguide grating formed on a thin reflective film using Kretschmann configuration is proposed. Numerical results based on a finite-element method approach indicate a significant resolution improvement due to the excitation of a GM supported by the waveguide grating-sensing media system. The applicability of the waveguide theory to the design of waveguide gratings is validated by a comparison to the exact electromagnetic theory. Strong localization of an electromagnetic field in the sensing media within the grating with intensity enhancement up to two orders of magnitude is demonstrated. The sensor has potential for biological sensing and imaging applications. PMID:26192528

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

    PubMed

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

    2014-01-01

    A non-contact vibration sensor based on fiber Bragg grating (FBG) sensing has been proposed and studied in this paper. The principle of the sensor as well as simulation and experimental analyses are introduced. When the distance between the movable head and the measured shaft changed, the diaphragm deformed under magnetic coupling of the permanent magnet on the measured magnetic shaft. As a result, the center wavelength of the FBG connected to the diaphragm changed, based on which the vibration displacement of the rotating shaft could be obtained. Experimental results show that the resonant frequency of the sensor is about 1500 Hz and the working band ranges within 0-1300 Hz, which is consistent with the simulation analysis result; the sensitivity is -1.694 pm/μm and the linearity is 2.92% within a range of 2-2.4 mm. It can be used to conduct non-contact measurement on the vibration of the rotating shaft system. PMID:24517801

  18. 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.

  19. An Intrusion Detection System for the Protection of Railway Assets Using Fiber Bragg Grating Sensors

    PubMed Central

    Catalano, Angelo; Bruno, Francesco Antonio; Pisco, Marco; Cutolo, Antonello; Cusano, Andrea

    2014-01-01

    We demonstrate the ability of Fiber Bragg Gratings (FBGs) sensors to protect large areas from unauthorized activities in railway scenarios such as stations or tunnels. We report on the technological strategy adopted to protect a specific depot, representative of a common scenario for security applications in the railway environment. One of the concerns in the protection of a railway area centers on the presence of rail-tracks, which cannot be obstructed with physical barriers. We propose an integrated optical fiber system composed of FBG strain sensors that can detect human intrusion for protection of the perimeter combined with FBG accelerometer sensors for protection of rail-track access. Several trials were carried out in indoor and outdoor environments. The results demonstrate that FBG strain sensors bonded under a ribbed rubber mat enable the detection of intruder break-in via the pressure induced on the mat, whereas the FBG accelerometers installed under the rails enable the detection of intruders walking close to the railroad tracks via the acoustic surface waves generated by footsteps. Based on a single enabling technology, this integrated system represents a valuable intrusion detection system for railway security and could be integrated with other sensing functionalities in the railway field using fiber optic technology. PMID:25268920

  20. An intrusion detection system for the protection of railway assets using Fiber Bragg Grating sensors.

    PubMed

    Catalano, Angelo; Bruno, Francesco Antonio; Pisco, Marco; Cutolo, Antonello; Cusano, Andrea

    2014-01-01

    We demonstrate the ability of Fiber Bragg Gratings (FBGs) sensors to protect large areas from unauthorized activities in railway scenarios such as stations or tunnels. We report on the technological strategy adopted to protect a specific depot, representative of a common scenario for security applications in the railway environment. One of the concerns in the protection of a railway area centers on the presence of rail-tracks, which cannot be obstructed with physical barriers. We propose an integrated optical fiber system composed of FBG strain sensors that can detect human intrusion for protection of the perimeter combined with FBG accelerometer sensors for protection of rail-track access. Several trials were carried out in indoor and outdoor environments. The results demonstrate that FBG strain sensors bonded under a ribbed rubber mat enable the detection of intruder break-in via the pressure induced on the mat, whereas the FBG accelerometers installed under the rails enable the detection of intruders walking close to the railroad tracks via the acoustic surface waves generated by footsteps. Based on a single enabling technology, this integrated system represents a valuable intrusion detection system for railway security and could be integrated with other sensing functionalities in the railway field using fiber optic technology. PMID:25268920

  1. Design of an enhanced sensitivity FBG strain sensor and application in highway bridge engineering

    NASA Astrophysics Data System (ADS)

    Li, Litong; Zhang, Dongsheng; Liu, Hui; Guo, Yongxing; Zhu, Fangdong

    2014-06-01

    The theoretical design method of enhanced sensitivity fiber grating (FBG) strain sensors was given, and moreover high qualified strain sensors were developed and fabricated, whose sensing properties were good for practical applications. The strain sensor with cylindrical shell encapsulation contained three tubular structures, due to the uneven surface structure, in the area of the strain concentration, improving the sensitivity. It could achieve the embedment strain measurement and surface measurement and had the advantages of the easy installation. The good agreement was obtained between the measurements and theoretical simulation results. After each calibration test, twenty-four FBG strain sensors and six FBG temperature compensation sensors have been installed on the undersurface of the box girder of Diaoshuiyan bridge in Yongtaiwen highway. Finally, we built up a long-term structure health system for the highway bridge.

  2. Numerical demonstration of MEMS strain sensor

    NASA Astrophysics Data System (ADS)

    Saboonchi, Hossain; Ozevin, Didem

    2012-04-01

    Silicon has piezoresistive property that allows designing strain sensor with higher gauge factor compared to conventional metal foil gauges. The sensing element can be micro-scale using MEMS, which minimizes the effect of strain gradient on measurement at stress concentration regions such as crack tips. The challenge of MEMS based strain sensor design is to decouple the sensing element from substrate for true strain measurement and to compensate the temperature effect on the piezoresistive coefficients of silicon. In this paper, a family of MEMS strain sensors with different geometric designs is introduced. Each strain sensor is made of single crystal silicon and manufactured using deposition/ etching/oxidation steps on a n- doped silicon wafer in (100) plane. The geometries include sensing element connected to the free heads of U shape substrate, a set of two or more sensing elements in an array in order to capture strain gradients and two directional sensors. The response function and the gauge factor of the strain sensors are identified using multi-physics models that combine structural and electrical behaviors of sensors mounted on a strained structure. The relationship between surface strain and strain at microstructure is identified numerically in order to include the relationship in the response function calculation.

  3. Sensor for Measuring Strain in Textile

    PubMed Central

    Mattmann, Corinne; Clemens, Frank; Tröster, Gerhard

    2008-01-01

    In this paper a stain sensor to measure large strain (80%) in textiles is presented. It consists of a mixture of 50wt-% thermoplastic elastomer (TPE) and 50wt-% carbon black particles and is fiber-shaped with a diameter of 0.315mm. The attachment of the sensor to the textile is realized using a silicone film. This sensor configuration was characterized using a strain tester and measuring the resistance (extension-retraction cycles): It showed a linear resistance response to strain, a small hysteresis, no ageing effects and a small dependance on the strain velocity. The total mean error caused by all these effects was ±5.5% in strain. Washing several times in a conventional washing machine did not influence the sensor properties. The paper finishes by showing an example application where 21 strain sensors were integrated into a catsuit. With this garment, 27 upper body postures could be recognized with an accuracy of 97%.

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

    PubMed

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

    2016-03-01

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

  5. Nickel plating of FBG strain sensors for nuclear applications

    NASA Astrophysics Data System (ADS)

    Perry, Marcus; Niewczas, Pawel; Johnston, Michael; Mackersie, John

    2011-05-01

    We present a method for plating FBG strain sensors with a strongly-bonded, hermetic nickel layer, without exposure of the fiber to corrosive environments. A 1μm thick, highly adhesive chrome layer is deposited onto bare fibers via evaporation. Addition of an inert and electrically conductive gold layer then allows the fiber to be electroplated with a 50-100μm nickel layer. Finite element models have confirmed that nickel plated FBG sensors can be brazed into steel structures and used to monitor local strain and temperature. Embedding gratings that are temperature and radiation resistant will be particularly applicable to the structural health monitoring of steel prestressing tendons used in the concrete containments of nuclear power plants and other safety-significant structures.

  6. Thick film wireless and powerless strain sensor

    NASA Astrophysics Data System (ADS)

    Jia, Yi; Sun, Ke

    2006-03-01

    The development of an innovative wireless strain sensing technology has a great potential to extend its applications in manufacturing, civil engineering and aerospace industry. This paper presents a novel wireless and powerless strain sensor with a multi-layer thick film structure. The sensor employs a planar inductor (L) and capacitive transducer (C) resonant tank sensing circuit, and a strain sensitive material of a polarized polyvinylidene fluoride (PVDF) piezoelectric thick film to realize the wireless strain sensing by strain to frequency conversion and to receive radio frequency electromagnetic energy for powering the sensor. The prototype sensor was designed and fabricated. The results of calibration on a strain constant cantilever beam show a great linearity and sensitivity about 0.0013 in a strain range of 0-0.018.

  7. Noncontact respiration-monitoring system using fiber grating sensor

    NASA Astrophysics Data System (ADS)

    Sato, Isao; Nakajima, Masato

    2004-10-01

    In this research, the new non-contact breathing motion monitoring system using Fiber Grating 3-dimension Sensor is used to measure the respiratory movement of the chest and the abdomen and the shape of the human body simultaneously. Respiratory trouble during sleep brings about various kinds of diseases. Particularly, Sleep Apnea Syndrome (SAS), which restricts respiration during sleep, has been in the spotlight in recent years. However, present equipment for analyzing the blessing motion requires attaching various sensors on the patient's body. This system adopted two CCD cameras to measure the movements of projected infrared bright spots on the patient's body which measure the body form, breathing motion of the chest and breathing motion of the abdomen in detail. Since the equipment does not contact the patient's body, the patient feels incompatibility, and there is no necessity to worry about the equipment coming off. Sleep Apnea Syndrome is classified into three types by their respiratory pattern-Obstructive, Central and Mixed SAS based on the characteristic. This paper reports the method of diagnosing SAS automatically. It is thought that this method will be helpful not only for the diagnosis of SAS but also for the diagnosis of other kinds of complicated respiratory disease.

  8. Microstructured optical fiber Bragg grating sensor for DNA detection

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

  9. Strain calibration of optical FBG-based strain sensors

    NASA Astrophysics Data System (ADS)

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

    2010-09-01

    A facility for strain sensitivity calibration of optical FBG-based strain sensors according to the German VDI/VDE 2660 guideline was established and characterized. Statistical analysis of several calibration measurement series performed with one single type of FBG strain sensor and application technique showed a reproducibility of 0.15%. Strain sensitivities for FBGs inscribed in two different types of optical fibres (GF1B and PR2008) showed significantly different strain sensitivities of k = 0.7885+/-0.0026 and k = 0.7758+/-0.0024, respectively.

  10. Calibration of a needle tracking device with fiber Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    K. Mandal, Koushik; Parent, Francois; Martel, Sylvain; Kashyap, Raman; Kadoury, Samuel

    2015-03-01

    Accurate needle placement is essential in percutaneous procedures such as radiofrequency ablation (RFA) of liver tumors. Use of real-time navigation of an interventional needle can improve targeting accuracy and yield precise measurements of the needle tip inside the body. An emerging technology based on Fiber Bragg Grating (FBG) sensors has demonstrated the potential of estimating shapes at high frequencies (up to 20 kHz), fast enough for real-time applications. In this paper, we present a calibration procedure for this novel needle tracking technology using strain measurements obtained from fiber Bragg gratings (FBGs). Three glass fibers equipped with two FBGs each were incorporated into a 19G needle. The 3D needle shape is reconstructed based on a polynomial fitting of strain measurements obtained from the fibers. The real-time information provided by the needle tip position and shape allows tracking of the needle deflections during tissue insertion. An experimental setup was designed to yield a calibration that is insensitive to ambient temperature fluctuations and robust to slight external disturbances. We compare the shape of the 3D reconstructed needle to measurements obtained from camera images, as well as assess needle tip tracking accuracy on a ground-truth phantom. Initial results show that the tracking errors for the needle tip are under 1mm, while 3D shape deflections are minimal near the needle tip. The accuracy is appropriate for applications such as RFA of liver tumors.