Fiber Bragg grating(FBG)is the most widely used optical fiber sensor due to its compact size,high sensitivity,and easiness for multiplexing.Conventional FBGs fabricated by using an ultraviolet(UV)laser phase-mask meth...Fiber Bragg grating(FBG)is the most widely used optical fiber sensor due to its compact size,high sensitivity,and easiness for multiplexing.Conventional FBGs fabricated by using an ultraviolet(UV)laser phase-mask method require the sensitization of the optical fiber and could not be used at high temperatures.Recently,the fabrication of FBGs by using a femtosecond laser has attracted extensive interests due to its excellent flexibility in creating FBGs array or special FBGs with complex spectra.The femtosecond laser could also be used for inscribing various FBGs on almost all fiber types,even fibers without any photosensitivity.Such femtosecond-laser-induced FBGs exhibit excellent thermal stability,which is suitable for sensing in harsh environment.In this review,we present the historical developments and recent advances in the fabrication technologies and sensing applications of femtosecond-laser-inscribed FBGs.Firstly,the mechanism of femtosecond-laser-induced material modification is introduced.And then,three different fabrication tech no logies,i.e.,femtosecond laser phase mask technology,femtosecond laser holographic interferometry,and femtosecond laser direct writing technology,are discussed.Finally,the advances in high-temperature sensing applications and vector bending sensing applications of various femtosecond-laser-inscribed FBGs are summarized.Such femtosecond-laser-inscribed FBGs are promising in many industrial areas,such as aerospace vehicles,nuclear plants,oil and gas explorations,and advanced robotics in harsh environments.展开更多
Monitoring shear deformation of sliding zones is of great significance for understanding the landslide evolution mechanism,in which fiber optic strain sensing has shown great potential.However,the cor-relation between...Monitoring shear deformation of sliding zones is of great significance for understanding the landslide evolution mechanism,in which fiber optic strain sensing has shown great potential.However,the cor-relation between strain measurements of quasi-distributed fiber Bragg grating(FBG)sensing arrays and shear displacements of surrounding soil remains elusive.In this study,a direct shear model test was conducted to simulate the shear deformation of sliding zones,in which the soil internal deformation was captured using FBG strain sensors and the soil surface deformation was measured by particle image velocimetry(PIV).The test results show that there were two main slip surfaces and two secondary ones,developing a spindle-shaped shear band in the soil.The formation of the shear band was successfully captured by FBG sensors.A sinusoidal model was proposed to describe the fiber optic cable deformation behavior.On this basis,the shear displacements and shear band widths were calculated by using strain measurements.This work provides important insight into the deduction of soil shear deformation using soil-embedded FBG strain sensors.展开更多
We proposed a method for shape sensing using a few multicore fiber Bragg grating (FBG) sensors ina single-port continuum surgical robot (CSR). The traditional method of utilizing a forward kinematic model tocalculate t...We proposed a method for shape sensing using a few multicore fiber Bragg grating (FBG) sensors ina single-port continuum surgical robot (CSR). The traditional method of utilizing a forward kinematic model tocalculate the shape of a single-port CSR is limited by the accuracy of the model. If FBG sensors are used forshape sensing, their accuracy will be affected by their number, especially in long and flexible CSRs. A fusionmethod based on an extended Kalman filter (EKF) was proposed to solve this problem. Shape reconstructionwas performed using the CSR forward kinematic model and FBG sensors, and the two results were fused usingan EKF. The CSR reconstruction method adopted the incremental form of the forward kinematic model, whilethe FBG sensor method adopted the discrete arc-segment assumption method. The fusion method can eliminatethe inaccuracy of the kinematic model and obtain more accurate shape reconstruction results using only a smallnumber of FBG sensors. We validated our algorithm through experiments on multiple bending shapes underdifferent load conditions. The results show that our method significantly outperformed the traditional methodsin terms of robustness and effectiveness.展开更多
A kind of erbium doped photosensitive fiber(EDPF) was proposed and fabricated,whose core was made of double layers named photosensitive layer and erbium doped layer.The double-layer core de-sign can overcome difficult...A kind of erbium doped photosensitive fiber(EDPF) was proposed and fabricated,whose core was made of double layers named photosensitive layer and erbium doped layer.The double-layer core de-sign can overcome difficulties in fabrication of EDPF with single core design,i.e.the conflict between the high consistency rare earth doping and high consistency germanium doping.A sample was fabri-cated through the modified chemical vapor deposition method combined with solution doping tech-nique.The peak absorption coefficient was 48.80 dB/m at 1.53 μm,the background loss was lower than 0.1 dB/m,and the reflectivity of the fiber Brag gratings(FBG) written directly on the sample fiber was up to 97.3% by UV-writing technology.Moreover,a C band tunable fiber laser was fabricated using the sample fiber,in which a uniform FBG was written directly on EDPFs as a reflector.A single wavelength lasing with a maximum wavelength tuning range of 1555.2―1558.0 nm was achieved experimentally.Within this tuning range,the full-width at half maximum(FWHM) of the laser output was smaller than 0.015 nm and the side mode suppression ratio(SMSR) was better than 50 dB.展开更多
The three-layer structure model of the fiber Bragg grating is proposed in this paper. And through experimental study and reasoning calculation to verify the three layer structure of the optical waveguide model, so the...The three-layer structure model of the fiber Bragg grating is proposed in this paper. And through experimental study and reasoning calculation to verify the three layer structure of the optical waveguide model, so the sensitivity characteristic of the Bragg wavelength to the refractive index of chemical solution is obtained. And the relationships between the concentration and the shift of Bragg wavelength of sucrose, ethanol, and Nacl solution are achieved. Finally the shifts of the Bragg wavelength with the external concentration are obtained by experiments. A kind of simple structure, small size, good stability, high sensitivity chemical concentration sensor is obtained.展开更多
presented an application of using 3 D printing technique for the design and fabrication of a novel fiber Bragg grating( FBG)based sensing platform for foot planar pressure measurement.Pressure sensing unit was fabrica...presented an application of using 3 D printing technique for the design and fabrication of a novel fiber Bragg grating( FBG)based sensing platform for foot planar pressure measurement.Pressure sensing unit was fabricated using 3 D printing technique by layering of extruded polylactic acid( PLA) material and mounting FBG sensor at the center of each sensing unit for pressure measurement. Performance of the sensing system was validated by applying load step by step as well as cyclic load on FBG pressure sensors. A simulation study was carried out using the sensing platform to assess foot plantar pressure distribution arises from weight gaining and losing processes of pregnant woman. The monitored four different foot positions such as first metatarsus,second metatarsus,mid-foot and heel exhibited obvious differences during testing process. Foot plantar pressure of heel was 1. 7 times of the pressure occurred at the first and second metatarsus( fore-foot),while there was limited pressure occurred at the mid-foot position during weight gaining process of a female subject. The occurred pressures at the two metatarsus areas were around 90%( pressure ratio) of heel and decreased continuously as the increase of subject weight,but weight losing process had very limited influence on this pressure ratio. Center of gravity of pregnant woman was found to shift backward substantially during the weighting gaining process,leading to a significant rise of the heel pressure. Hence, the protection of the heel position for female is highly important during both pregnancy and after baby delivery.展开更多
An active temperature compensated fiber Bragg grating(FBG)vibration sensor with a constant section cantilever beam is proposed for the simultaneous measurement of temperature and vibration,and the sensor is verified b...An active temperature compensated fiber Bragg grating(FBG)vibration sensor with a constant section cantilever beam is proposed for the simultaneous measurement of temperature and vibration,and the sensor is verified by a temperature compensation feedback system.The high-temperature vibration sensor is composed of a quartz cantilever beam and a femtosecond Bragg grating.The feedback control demodulation system of active temperature compensation can adjust the laser wavelength to stabilize the grating offset point and realize simultaneous measurement of temperature and vibration.On this basis,the performance of the sensor is tested and analyzed within the range of 20-400℃by setting up a high-temperature vibration test system.The experimental results show that the sensitivity of the sensor is about 132.33 mV/g,and the nonlinearity is about 3.33%.The sensitivity between the laser wavelength and temperature is about 0.01307 nm/℃.In addition,the active temperature compensated fiber Bragg grating vibration sensor has the advantages of a simple structure,stable performance,easy demodulation and high sensitivity.Moreover,the sensor can achieve high temperature vibration signal monitoring and has good practical application value.展开更多
A robust high temperature sensor probe based on a Ni-coated fiber Bragg grating（FBG） was fabricated by Ni electroplating of femtosecond laser written FBG. The probe can resist high temperature up to 800℃ with a hig...A robust high temperature sensor probe based on a Ni-coated fiber Bragg grating（FBG） was fabricated by Ni electroplating of femtosecond laser written FBG. The probe can resist high temperature up to 800℃ with a high sensitivity of 32.2 pm/℃. It also has a good mechanical strength even after high temperature annealing. The thermal strain of the probe was simulated by the finite element method（FEM）. The Bragg resonant wavelength shift with temperature and its sensitivity change with the thickness of the Ni-coated layer were also calculated.展开更多
To combine the technical functions and advantages of solid-core fiber Bragg gratings(FBGs) and hollow-core optical fibers(HCFs), the hollow and filled FBGs in nano-bore optical fibers(NBFs) with nano-bore in the GeO2-...To combine the technical functions and advantages of solid-core fiber Bragg gratings(FBGs) and hollow-core optical fibers(HCFs), the hollow and filled FBGs in nano-bore optical fibers(NBFs) with nano-bore in the GeO2-doped core are proposed.The fundamental mode field, effective mode index, and confinement loss of NBF with 50 nm–7 μm-diameter hollow and filled nano-bore are numerically investigated by the finite element method.The reflected spectra of FBGs in NBFs are obtained by the transmission matrix method.The hollow FBGs in NBFs can be acheived with ~5% power fraction in the bore and the ~0.9 reflectivity when bore diameter is less than 3 μm.The filled FBGs can be realized with^1% power fraction and 0.98 reflectivity with different fillings including o-xylene, trichloroethylene, and chloroform for 800-nm bore diameter.The feasibility of the index sensing by our proposed NBF FBG is also analyzed and discussed.The experimental fabrication of hollow and filled FBGs are discussed and can be achieved by current techniques.The aim of this work is to establish a principle prototype for investigating the HCFs and solid-core FBGs-based fiber-optic platforms,which are useful for applications such as the simultaneous chemical and physical sensing at the same position.展开更多
A novel multi-point sensing scheme to improve the signal-to-noise ratio(SNR),temperature measurement range of the fiber Bragg grating(FBG)sensors is proposed.The new sensing scheme adopted a composite coding technique...A novel multi-point sensing scheme to improve the signal-to-noise ratio(SNR),temperature measurement range of the fiber Bragg grating(FBG)sensors is proposed.The new sensing scheme adopted a composite coding technique based on Simplex codes and Golay codes and time division multiplexing technique to enhance the performance of the sensing system.Simulation results,in good agreement with the theory,confirmed that the maximum SNR enhancement of the sensor system employing composite coding based on 15-bit Simplex codes and 16-bit Golay codes was approximately 6.01 dB in comparison to the conventional single pulse case.展开更多
In this paper, the effects of three types of commonly used adhesives were studied via experiment and simulation. The results show that the strain sensitivity of fiber Bragg grating(FBG) sensor is about 1.201 pm/με a...In this paper, the effects of three types of commonly used adhesives were studied via experiment and simulation. The results show that the strain sensitivity of fiber Bragg grating(FBG) sensor is about 1.201 pm/με and the effects of three adhesives of epoxy resin, AB glue and 502 glue with the same thickness and length on sensitivity coefficients of FBG sensors are 99.20%, 93.80% and 96.50%, respectively. Finally, the sensitivity coefficient of the simulated FBG sensor is the same as the test result by ANSYS modeling.展开更多
Structural health monitoring(SHM)in-service is very important for wind turbine system.Because the central wavelength of a fiber Bragg grating(FBG)sensor changes linearly with strain or temperature,FBG-based sensors ar...Structural health monitoring(SHM)in-service is very important for wind turbine system.Because the central wavelength of a fiber Bragg grating(FBG)sensor changes linearly with strain or temperature,FBG-based sensors are easily applied to structural tests.Therefore,the monitoring of wind turbine blades by FBG sensors is proposed.The method is experimentally proved to be feasible.Five FBG sensors were set along the blade length in order to measure distributed strain.However,environmental or measurement noise may cover the structural signals.Dual-tree complex wavelet transform(DT-CWT)is suggested to wipe off the noise.The experimental studies indicate that the tested strain fluctuate distinctly as one of the blades is broken.The rotation period is about 1 s at the given working condition.However,the period is about 0.3 s if all the wind blades are in good conditions.Therefore,strain monitoring by FBG sensors could predict damage of a wind turbine blade system.Moreover,the studies indicate that monitoring of one blade is adequate to diagnose the status of a wind generator.展开更多
Considering the spatial position and shape detection properties of the fiber Bragg grating(FBG)curve sensor used in the human body,the positioning accuracy of the FBG curve sensor plays a major role in the pre-diagnos...Considering the spatial position and shape detection properties of the fiber Bragg grating(FBG)curve sensor used in the human body,the positioning accuracy of the FBG curve sensor plays a major role in the pre-diagnosis and treatment of diseases.We present a new type of shape-sensing catheter(diameter of 2.0 mm and length of 810 mm)that is integrated with an array of four optical fibers,where each contains five nodes,to track the shape.Firstly,the distribution of the four orthogonal fiber gratings is wound around a nitinol wire using novel packaging technology,and the spatial curve shape is rebuilt based on the positioning of discrete points in space.An experimental platform is built,and then a reconstruction algorithm for coordinate point fitting of the Frenet frame is used to perform the reconstruction experiment on millimeter paper.The results show that,compared with those in previous studies,in 2D test,the maximum relative error for the end position is reduced to 2.74%,and in 3D reconstruction experiment,the maximum shape error is 3.43%,which verifies both the applicability of the sensor and the feasibility of the proposed method.The results reported here will provide an academic foundation and the key technologies required for navigation and positioning of noninvasive and minimally invasive surgical robots,intelligent structural health detection,and search and rescue operations in debris.展开更多
We present a new calorimetric method for measuring alternative current(AC)losses of high-temperature superconducting(HTS)tapes by optical fiber Bragg grating(FBG),which is particularly well suited for the AC loss meas...We present a new calorimetric method for measuring alternative current(AC)losses of high-temperature superconducting(HTS)tapes by optical fiber Bragg grating(FBG),which is particularly well suited for the AC loss measurement of Re BCO wires,so-called the second generation(2G)HTS wires.Compared with conventional calorimetric methods,the suggested method is both free of electromagnetic disturbance,magnetic field,and fast as well as simple.Self-field AC losses are measured by the optical FBG method and the conventional lock-in-amplifier(LIA)technique,respectively.The results show that the measured AC loss is in good agreement with those measured by the electric method,thus the presented calorimetric method would be available for measuring the AC loss of 2G wire and is expected to be generalized for the measurement of AC loss or thermal performances of HTS bulk.展开更多
This article focuses on health monitoring of structures using multiple smart materials.In this research,two fiber-optic sensors,namely fiber Bragg grating(FBG)and fiber-optic polarimetric sensor(FOPS),are investigated...This article focuses on health monitoring of structures using multiple smart materials.In this research,two fiber-optic sensors,namely fiber Bragg grating(FBG)and fiber-optic polarimetric sensor(FOPS),are investigated for damage detection in the beam specimen.FBG is used for local strain measurement while FOPS is used for global strain measurement.Both FBG and FOPS show significant changes in the strain due to damages in the specimen.Also,at the center of the specimen,piezoelectric wafer active sensor(PWAS)is attached.The electromechanical admittance(EMA)signature of the specimen beam is recorded by PWAS.The changes in the amplitudes of the peaks obtained at various frequencies in this EMA signature are analyzed,and it is shown that the peak amplitudes respond differently to damages and to change in loading.Thus,multiple smart materials(FBG,FOPS,and PWAS)are used to get improved information on the health of the beam.展开更多
基金supported by National Natural Science Foundation of China(NSFC)(Grant Nos.U1913212,61875128,and 61635007)Department of Science and Technology of Guangdong Province(Grant Nos.2019TQ05X113,2019A1515011393,2019B1515120042,and 2019A1515111114)Shenzhen Science and Technology Program(Grant Nos.RCYX20200714114538160 and JCYJ20180507182058432).
文摘Fiber Bragg grating(FBG)is the most widely used optical fiber sensor due to its compact size,high sensitivity,and easiness for multiplexing.Conventional FBGs fabricated by using an ultraviolet(UV)laser phase-mask method require the sensitization of the optical fiber and could not be used at high temperatures.Recently,the fabrication of FBGs by using a femtosecond laser has attracted extensive interests due to its excellent flexibility in creating FBGs array or special FBGs with complex spectra.The femtosecond laser could also be used for inscribing various FBGs on almost all fiber types,even fibers without any photosensitivity.Such femtosecond-laser-induced FBGs exhibit excellent thermal stability,which is suitable for sensing in harsh environment.In this review,we present the historical developments and recent advances in the fabrication technologies and sensing applications of femtosecond-laser-inscribed FBGs.Firstly,the mechanism of femtosecond-laser-induced material modification is introduced.And then,three different fabrication tech no logies,i.e.,femtosecond laser phase mask technology,femtosecond laser holographic interferometry,and femtosecond laser direct writing technology,are discussed.Finally,the advances in high-temperature sensing applications and vector bending sensing applications of various femtosecond-laser-inscribed FBGs are summarized.Such femtosecond-laser-inscribed FBGs are promising in many industrial areas,such as aerospace vehicles,nuclear plants,oil and gas explorations,and advanced robotics in harsh environments.
基金This work was financially supported by the National Natural Science Foundation of China(Grant Nos.42225702 and 42077235)the Open Research Project Program of the State Key Laboratory of Internet of Things for Smart City(University of Macao)(Grant No.SKL-IoTSC(UM)-2021-2023/ORP/GA10/2022)。
文摘Monitoring shear deformation of sliding zones is of great significance for understanding the landslide evolution mechanism,in which fiber optic strain sensing has shown great potential.However,the cor-relation between strain measurements of quasi-distributed fiber Bragg grating(FBG)sensing arrays and shear displacements of surrounding soil remains elusive.In this study,a direct shear model test was conducted to simulate the shear deformation of sliding zones,in which the soil internal deformation was captured using FBG strain sensors and the soil surface deformation was measured by particle image velocimetry(PIV).The test results show that there were two main slip surfaces and two secondary ones,developing a spindle-shaped shear band in the soil.The formation of the shear band was successfully captured by FBG sensors.A sinusoidal model was proposed to describe the fiber optic cable deformation behavior.On this basis,the shear displacements and shear band widths were calculated by using strain measurements.This work provides important insight into the deduction of soil shear deformation using soil-embedded FBG strain sensors.
基金the National Natural Science Foundation of China(Nos.61873257 and U20A20195)the Project of Natural Science Foundation of Liaoning Province(No.2021-MS-033)the Foundation of Millions of Talents Project of the Department of Human Resources and Social Security of Liaoning Province(No.2021921037)。
文摘We proposed a method for shape sensing using a few multicore fiber Bragg grating (FBG) sensors ina single-port continuum surgical robot (CSR). The traditional method of utilizing a forward kinematic model tocalculate the shape of a single-port CSR is limited by the accuracy of the model. If FBG sensors are used forshape sensing, their accuracy will be affected by their number, especially in long and flexible CSRs. A fusionmethod based on an extended Kalman filter (EKF) was proposed to solve this problem. Shape reconstructionwas performed using the CSR forward kinematic model and FBG sensors, and the two results were fused usingan EKF. The CSR reconstruction method adopted the incremental form of the forward kinematic model, whilethe FBG sensor method adopted the discrete arc-segment assumption method. The fusion method can eliminatethe inaccuracy of the kinematic model and obtain more accurate shape reconstruction results using only a smallnumber of FBG sensors. We validated our algorithm through experiments on multiple bending shapes underdifferent load conditions. The results show that our method significantly outperformed the traditional methodsin terms of robustness and effectiveness.
基金Supported by the National High Technology Research and Development Program of China (863 Project) (Grant No. 2007AA01Z258)the National Natural Science Foundation of China (Grant No. 60771008)+2 种基金Program for New Century Excellent Talents in University (Grant No. NCET-06-0076)Beijing Natural Science Founda-tion (Grant No. 4052023)the Beijing Jiaotong University Foundation (Grant No. 2006XM003)
文摘A kind of erbium doped photosensitive fiber(EDPF) was proposed and fabricated,whose core was made of double layers named photosensitive layer and erbium doped layer.The double-layer core de-sign can overcome difficulties in fabrication of EDPF with single core design,i.e.the conflict between the high consistency rare earth doping and high consistency germanium doping.A sample was fabri-cated through the modified chemical vapor deposition method combined with solution doping tech-nique.The peak absorption coefficient was 48.80 dB/m at 1.53 μm,the background loss was lower than 0.1 dB/m,and the reflectivity of the fiber Brag gratings(FBG) written directly on the sample fiber was up to 97.3% by UV-writing technology.Moreover,a C band tunable fiber laser was fabricated using the sample fiber,in which a uniform FBG was written directly on EDPFs as a reflector.A single wavelength lasing with a maximum wavelength tuning range of 1555.2―1558.0 nm was achieved experimentally.Within this tuning range,the full-width at half maximum(FWHM) of the laser output was smaller than 0.015 nm and the side mode suppression ratio(SMSR) was better than 50 dB.
文摘The three-layer structure model of the fiber Bragg grating is proposed in this paper. And through experimental study and reasoning calculation to verify the three layer structure of the optical waveguide model, so the sensitivity characteristic of the Bragg wavelength to the refractive index of chemical solution is obtained. And the relationships between the concentration and the shift of Bragg wavelength of sucrose, ethanol, and Nacl solution are achieved. Finally the shifts of the Bragg wavelength with the external concentration are obtained by experiments. A kind of simple structure, small size, good stability, high sensitivity chemical concentration sensor is obtained.
基金Fundamental Research Funds for the Central Universities,China(No.17D110116)Henan Key Laboratory of Textile Materials,ChinaNational Natural Science Foundation of China(No.41602352)
文摘presented an application of using 3 D printing technique for the design and fabrication of a novel fiber Bragg grating( FBG)based sensing platform for foot planar pressure measurement.Pressure sensing unit was fabricated using 3 D printing technique by layering of extruded polylactic acid( PLA) material and mounting FBG sensor at the center of each sensing unit for pressure measurement. Performance of the sensing system was validated by applying load step by step as well as cyclic load on FBG pressure sensors. A simulation study was carried out using the sensing platform to assess foot plantar pressure distribution arises from weight gaining and losing processes of pregnant woman. The monitored four different foot positions such as first metatarsus,second metatarsus,mid-foot and heel exhibited obvious differences during testing process. Foot plantar pressure of heel was 1. 7 times of the pressure occurred at the first and second metatarsus( fore-foot),while there was limited pressure occurred at the mid-foot position during weight gaining process of a female subject. The occurred pressures at the two metatarsus areas were around 90%( pressure ratio) of heel and decreased continuously as the increase of subject weight,but weight losing process had very limited influence on this pressure ratio. Center of gravity of pregnant woman was found to shift backward substantially during the weighting gaining process,leading to a significant rise of the heel pressure. Hence, the protection of the heel position for female is highly important during both pregnancy and after baby delivery.
基金National Natural Science Foundation of China(No.51935011)Natural Science Foundation of Shanxi Province of China(No.201901D111160)Innovative Research Group Project of National Science Foundation of China(No.51821003)。
文摘An active temperature compensated fiber Bragg grating(FBG)vibration sensor with a constant section cantilever beam is proposed for the simultaneous measurement of temperature and vibration,and the sensor is verified by a temperature compensation feedback system.The high-temperature vibration sensor is composed of a quartz cantilever beam and a femtosecond Bragg grating.The feedback control demodulation system of active temperature compensation can adjust the laser wavelength to stabilize the grating offset point and realize simultaneous measurement of temperature and vibration.On this basis,the performance of the sensor is tested and analyzed within the range of 20-400℃by setting up a high-temperature vibration test system.The experimental results show that the sensitivity of the sensor is about 132.33 mV/g,and the nonlinearity is about 3.33%.The sensitivity between the laser wavelength and temperature is about 0.01307 nm/℃.In addition,the active temperature compensated fiber Bragg grating vibration sensor has the advantages of a simple structure,stable performance,easy demodulation and high sensitivity.Moreover,the sensor can achieve high temperature vibration signal monitoring and has good practical application value.
基金the National Natural Science Foundation of China
文摘A robust high temperature sensor probe based on a Ni-coated fiber Bragg grating（FBG） was fabricated by Ni electroplating of femtosecond laser written FBG. The probe can resist high temperature up to 800℃ with a high sensitivity of 32.2 pm/℃. It also has a good mechanical strength even after high temperature annealing. The thermal strain of the probe was simulated by the finite element method（FEM）. The Bragg resonant wavelength shift with temperature and its sensitivity change with the thickness of the Ni-coated layer were also calculated.
基金Project supported by the Beijing Natural Science Foundation,China(Grant No.4192047)the Fundamental Research Funds for the Central Universities,China(Grant Nos.2018JBM070 and 2018JBM065)the National Natural Science Foundation of China(Grant No.61675019)
文摘To combine the technical functions and advantages of solid-core fiber Bragg gratings(FBGs) and hollow-core optical fibers(HCFs), the hollow and filled FBGs in nano-bore optical fibers(NBFs) with nano-bore in the GeO2-doped core are proposed.The fundamental mode field, effective mode index, and confinement loss of NBF with 50 nm–7 μm-diameter hollow and filled nano-bore are numerically investigated by the finite element method.The reflected spectra of FBGs in NBFs are obtained by the transmission matrix method.The hollow FBGs in NBFs can be acheived with ~5% power fraction in the bore and the ~0.9 reflectivity when bore diameter is less than 3 μm.The filled FBGs can be realized with^1% power fraction and 0.98 reflectivity with different fillings including o-xylene, trichloroethylene, and chloroform for 800-nm bore diameter.The feasibility of the index sensing by our proposed NBF FBG is also analyzed and discussed.The experimental fabrication of hollow and filled FBGs are discussed and can be achieved by current techniques.The aim of this work is to establish a principle prototype for investigating the HCFs and solid-core FBGs-based fiber-optic platforms,which are useful for applications such as the simultaneous chemical and physical sensing at the same position.
基金Graduate Project Foundation of Shanghai Polytechnic University,China(No.A01GY18F022)
文摘A novel multi-point sensing scheme to improve the signal-to-noise ratio(SNR),temperature measurement range of the fiber Bragg grating(FBG)sensors is proposed.The new sensing scheme adopted a composite coding technique based on Simplex codes and Golay codes and time division multiplexing technique to enhance the performance of the sensing system.Simulation results,in good agreement with the theory,confirmed that the maximum SNR enhancement of the sensor system employing composite coding based on 15-bit Simplex codes and 16-bit Golay codes was approximately 6.01 dB in comparison to the conventional single pulse case.
基金supported by the Scientific Research Project of Hefei Normal University(No.2017QN14)the National Innovation Training Program of Hefei Normal University in 2018(No.201814098045)
文摘In this paper, the effects of three types of commonly used adhesives were studied via experiment and simulation. The results show that the strain sensitivity of fiber Bragg grating(FBG) sensor is about 1.201 pm/με and the effects of three adhesives of epoxy resin, AB glue and 502 glue with the same thickness and length on sensitivity coefficients of FBG sensors are 99.20%, 93.80% and 96.50%, respectively. Finally, the sensitivity coefficient of the simulated FBG sensor is the same as the test result by ANSYS modeling.
基金supported by the National Natural Science Foundation of China(No.11402112)the National Key Technology Support Program (No.2012BAA01B02)。
文摘Structural health monitoring(SHM)in-service is very important for wind turbine system.Because the central wavelength of a fiber Bragg grating(FBG)sensor changes linearly with strain or temperature,FBG-based sensors are easily applied to structural tests.Therefore,the monitoring of wind turbine blades by FBG sensors is proposed.The method is experimentally proved to be feasible.Five FBG sensors were set along the blade length in order to measure distributed strain.However,environmental or measurement noise may cover the structural signals.Dual-tree complex wavelet transform(DT-CWT)is suggested to wipe off the noise.The experimental studies indicate that the tested strain fluctuate distinctly as one of the blades is broken.The rotation period is about 1 s at the given working condition.However,the period is about 0.3 s if all the wind blades are in good conditions.Therefore,strain monitoring by FBG sensors could predict damage of a wind turbine blade system.Moreover,the studies indicate that monitoring of one blade is adequate to diagnose the status of a wind generator.
基金This work was jointly supported by the National Nature Science Foundation of China(Grant No.51275282)Major Basic Projects of the Shanghai Science and Technology Commission(Grant No.18JC1410402).
文摘Considering the spatial position and shape detection properties of the fiber Bragg grating(FBG)curve sensor used in the human body,the positioning accuracy of the FBG curve sensor plays a major role in the pre-diagnosis and treatment of diseases.We present a new type of shape-sensing catheter(diameter of 2.0 mm and length of 810 mm)that is integrated with an array of four optical fibers,where each contains five nodes,to track the shape.Firstly,the distribution of the four orthogonal fiber gratings is wound around a nitinol wire using novel packaging technology,and the spatial curve shape is rebuilt based on the positioning of discrete points in space.An experimental platform is built,and then a reconstruction algorithm for coordinate point fitting of the Frenet frame is used to perform the reconstruction experiment on millimeter paper.The results show that,compared with those in previous studies,in 2D test,the maximum relative error for the end position is reduced to 2.74%,and in 3D reconstruction experiment,the maximum shape error is 3.43%,which verifies both the applicability of the sensor and the feasibility of the proposed method.The results reported here will provide an academic foundation and the key technologies required for navigation and positioning of noninvasive and minimally invasive surgical robots,intelligent structural health detection,and search and rescue operations in debris.
基金supported by the National Natural Science Foundation of China(Grant No.51477053)the Beijing Education Commissions(Grant No.GJ2013009)
文摘We present a new calorimetric method for measuring alternative current(AC)losses of high-temperature superconducting(HTS)tapes by optical fiber Bragg grating(FBG),which is particularly well suited for the AC loss measurement of Re BCO wires,so-called the second generation(2G)HTS wires.Compared with conventional calorimetric methods,the suggested method is both free of electromagnetic disturbance,magnetic field,and fast as well as simple.Self-field AC losses are measured by the optical FBG method and the conventional lock-in-amplifier(LIA)technique,respectively.The results show that the measured AC loss is in good agreement with those measured by the electric method,thus the presented calorimetric method would be available for measuring the AC loss of 2G wire and is expected to be generalized for the measurement of AC loss or thermal performances of HTS bulk.
基金The authors acknowledge the financial support from NTU,Singapore.
文摘This article focuses on health monitoring of structures using multiple smart materials.In this research,two fiber-optic sensors,namely fiber Bragg grating(FBG)and fiber-optic polarimetric sensor(FOPS),are investigated for damage detection in the beam specimen.FBG is used for local strain measurement while FOPS is used for global strain measurement.Both FBG and FOPS show significant changes in the strain due to damages in the specimen.Also,at the center of the specimen,piezoelectric wafer active sensor(PWAS)is attached.The electromechanical admittance(EMA)signature of the specimen beam is recorded by PWAS.The changes in the amplitudes of the peaks obtained at various frequencies in this EMA signature are analyzed,and it is shown that the peak amplitudes respond differently to damages and to change in loading.Thus,multiple smart materials(FBG,FOPS,and PWAS)are used to get improved information on the health of the beam.
