Aiming at the requirement for high-precision tilt monitoring in the field of structural health monitoring(SHM),this paper proposes a sensitivity-enhanced tilt sensor based on a femtosecond fiber Bragg grating(FBG).Fir...Aiming at the requirement for high-precision tilt monitoring in the field of structural health monitoring(SHM),this paper proposes a sensitivity-enhanced tilt sensor based on a femtosecond fiber Bragg grating(FBG).Firstly,structural design of the tilt sensor was conducted based on static mechanics principles.By positioning the FBG away from the beam’s neutral axis,linear strain enhancement in the FBG was achieved,thereby improving sensor sensitivity.The relationship between FBG strain,applied force,and the offset distance from the neutral axis was established,determining the optimal distance corresponding to maximum strain.Based on this optimization scheme,a prototype of the tilt sensor was designed,fabricated,and experimentally tested.Experimental results show that the FBG offset distance yielding maximum sensitivity is 4.4 mm.Within a tilt angle range of−30°to 30°,the sensor achieved a sensitivity of 129.95 pm/°and a linearity of 0.9997.Compared to conventional FBG-based tilt sensors,both sensitivity and linearity were significantly improved.Furthermore,the sensor demonstrated excellent repeatability(error<0.94%),creep resistance(error<0.30%),and temperature stability(error<0.90%).These results demonstrate the sensor’s excellent potential for SHM applications.The sensor has been successfully deployed in an underground pipeline project,conducting long-term monitoring of tilt and deformation in the steel support structures,further proving its value for engineering safety monitoring.展开更多
A compact and highly sensitive gas pressure and temperature sensor based on Fabry-Pérot interferometer(FPI)and fiber Bragg grating(FBG)is proposed and demonstrated experimentally in this paper.The theoretical mod...A compact and highly sensitive gas pressure and temperature sensor based on Fabry-Pérot interferometer(FPI)and fiber Bragg grating(FBG)is proposed and demonstrated experimentally in this paper.The theoretical model for pressure and temperature sensing is established.Building on this foundation,a novel micro silicon cavity sensor structure sensitive to pressure is devised downstream of an FBG.The concept of separate measurement and the mechanisms enhancing pressure sensitivity are meticulously analyzed,and the corresponding samples are fabricated.The experimental results indicate that the pressure sensitivity of the sensor is-747.849 nm/MPa in 0—100 k Pa and its linearity is 99.7%and it maintains good stability in 150 min.The sensor offers the advantages of compact size,robust construction,easy fabrication,and high sensitivity,making it potentially valuable for micro-pressure application.展开更多
Purpose–To address the encapsulation challenge of fiber Bragg grating(FBG)sensors in complex railway environments,this paper designs a clip-on composite sensor enabling installation-friendly deployment and long-term ...Purpose–To address the encapsulation challenge of fiber Bragg grating(FBG)sensors in complex railway environments,this paper designs a clip-on composite sensor enabling installation-friendly deployment and long-term axle counting system monitoring.Design/methodology/approach–Wheel–rail mechanical behavior was simulated via finite element analysis(FEA)to determine optimal sensor placement.A clip-on composite sensor was subsequently engineered.Stress transduction efficacy was validated through FEA quantification of stress responses at the axle counter location.Findings–The proposed FBG axle counter integrates temperature compensation and anti-detachment monitoring as well as advantages such as simplified installation with minimal maintenance and sustained operational reliability.It effectively transmits stress,yielding a measured strain of 39μe under static loading conditions without sensitivity-enhancing elements.Originality/value–This study performs FEA of wheel-rail stress distribution and engineers the dual-slot composite sensor,FEAwas conducted to quantify the stress magnitude at the axle sensor position of the dual-slot composite sensor.Additionally,FEA was performed on sensors with different structural configurations,including adjustments to the axle sensor position,number of slots and axle position.The results confirmed that the designed composite sensor exhibits superior stress transfer characteristics.展开更多
There is limited amount of research on surface plasmon resonance(SPR)sensors with self-referencing capabilities which are based on dielectric gratings.In the short-wavelength range,a metal grating sensor is capable of...There is limited amount of research on surface plasmon resonance(SPR)sensors with self-referencing capabilities which are based on dielectric gratings.In the short-wavelength range,a metal grating sensor is capable of simultaneously measuring liquid refractive index under proposed temperature.A fabricated gold grating is placed on one side of a thin gold film for refractive index measurement,while the other with polydimethylsiloxane(PDMS)is deposited on the other side for temperature measurement.We use finite element analysis to research its sensing characteristics.Due to the high refractive index sensitivity of SPR sensors and thermo-optic coefficient of PDMS,we discovered the maximum spectral sensitivity of the sensor is 564 nm/RIU and-50 pm/℃when the liquid refractive index ranges from 1.30 to 1.40 with temperature ranging from 0℃ to 100℃.Numerical results indicate that there may not be mutual interference between two channels for measuring refractive index and temperature,which reduces the complexity of sensor measurements.展开更多
A grating eddy current displacement sensor(GECDS) can be used in a watertight electronic transducer to realize long range displacement or position measurement with high accuracy in difficult industry conditions.The pa...A grating eddy current displacement sensor(GECDS) can be used in a watertight electronic transducer to realize long range displacement or position measurement with high accuracy in difficult industry conditions.The parameters optimization of the sensor is essential for economic and efficient production.This paper proposes a method to combine an artificial neural network(ANN) and a genetic algorithm(GA) for the sensor parameters optimization.A neural network model is developed to map the complex relationship between design parameters and the nonlinearity error of the GECDS,and then a GA is used in the optimization process to determine the design parameter values,resulting in a desired minimal nonlinearity error of about 0.11%.The calculated nonlinearity error is 0.25%.These results show that the proposed method performs well for the parameters optimization of the GECDS.展开更多
Many theoretical studies have been developed to study the spectral response of a fiber Bragg grating (FBG) under non-uniform strain distribution along the length of FBG in recent years. However, almost no experiments ...Many theoretical studies have been developed to study the spectral response of a fiber Bragg grating (FBG) under non-uniform strain distribution along the length of FBG in recent years. However, almost no experiments were designed to obtain the evolution of the spectrum when a FBG is subjected to non-uniform strain. In this paper, the spectral responses of a FBG under non-uniform strain distributions are given and a numerical simulation based on the Runge-Kutta method is introduced to investigate the responses of the FBG under some typical non-uniform transverse strain fields, including both linear strain gradient and quadratic strain field. Experiment is carried out by using loads applied at different locations near the FBG. Good agreements between experimental results and numerical simulations are obtained.展开更多
A novel complementary grating structure is proposed for plasmonic refractive index sensing due to its strong resonance at near-infrared wavelength.The reflection spectra and the electric field distributions are obtain...A novel complementary grating structure is proposed for plasmonic refractive index sensing due to its strong resonance at near-infrared wavelength.The reflection spectra and the electric field distributions are obtained via the finite-difference time-domain method.Numerical simulation results show that multiple surface plasmon resonance modes can be excited in this novel structure.Subsequently,one of the resonance modes shows appreciable potential in refractive index sensing due to its wide range of action with the environment of the analyte.After optimizing the grating geometric variables of the structure,the designed structure shows the stable sensing performance with a high refractive index sensitivity of 1642 nm per refractive index unit(nm/RIU)and the figure of merit of 409 RIU^(-1).The promising simulation results indicate that such a sensor has a broad application prospect in biochemistry.展开更多
In this paper,we present a novel oil level monitoring sensor based on string tilted fiber Bragg grating(TFBG).The measurement range and sensitivity of oil level monitoring can be modulated via changing the length and ...In this paper,we present a novel oil level monitoring sensor based on string tilted fiber Bragg grating(TFBG).The measurement range and sensitivity of oil level monitoring can be modulated via changing the length and number of string tilted fiber gratings.The transmission spectrum of string TFBGs immersed in oil changes obviously with the oil level variation.Experiments are conducted on three 2 cm-length serial TFBGs with the same tilted angle of 10o.A sensitivity of 3.28 dB/cm in the string TFBG sensor is achieved with good linearity by means of TFBG spectrum characteristic with peak-low value.The cladding mode transmission power and the amplitude of high order cladding mode resonance are nearly linear to the oil level variation.This kind of sensor is insensitive to temperature and attributed to be employed in extremely harsh environment oil monitoring.展开更多
A discrimination measurement method and demodulation technique for fiber Bragg grating (FBG) sensors were presented using digital filtering technique. The system can control a tunable fiber Fabry-Perot filter with saw...A discrimination measurement method and demodulation technique for fiber Bragg grating (FBG) sensors were presented using digital filtering technique. The system can control a tunable fiber Fabry-Perot filter with sawtooth wave voltage generated by digital clock to interrogate FBG sensors. Using the analogue digital converter (ADC), the reflected FBG signals were sampled with synchronous digital clock. With the aid of digital matched filtering technique, the sampled FBG signals were processed to obtain the maximum signal-to-noise ratio (SNR) and the Bragg wavelength shift from the FBG signals was recovered. The results demonstrate that this system has a scanning range of 1 520 nm-1 575 nm,and the wavelength detection accuracy is less than 2 pm with 1.5 Hz scanning frequency.展开更多
The phase diversity wavefront sensor is one of the tools used to estimate wavefront aberration, and it is often used as a wavefront sensor in adaptive optics systems. However, the performance of the traditional phase ...The phase diversity wavefront sensor is one of the tools used to estimate wavefront aberration, and it is often used as a wavefront sensor in adaptive optics systems. However, the performance of the traditional phase diversity wavefront sensor is limited by the accuracy and dynamic ranges of the intensity distribution at the focus and defocus positions of the CCD camera. In this paper, a modified phase diversity wavefront sensor based on a diffraction grating is proposed to improve the ability to measure the wavefront aberration with larger amplitude and higher spatial frequency. The basic principle and the optics construction of the proposed method are also described in detail. The noise propagation property of the proposed method is also analysed by using the numerical simulation method, and comparison between the diffraction grating phase diversity wavefront sensor and the traditional phase diversity wavefront sensor is also made. The simulation results show that the diffraction grating phase diversity wavefront sensor can obviously improve the ability to measure the wavefront aberration, especially the wavefront aberration with larger amplitude and higher spatial frequency.展开更多
In this article,we review recent advances in the technology of writing fiber Bragg gratings(FBGs)in selected cores of multicore fibers(MCFs)by using femtosecond laser pulses.The writing technology of such a key elemen...In this article,we review recent advances in the technology of writing fiber Bragg gratings(FBGs)in selected cores of multicore fibers(MCFs)by using femtosecond laser pulses.The writing technology of such a key element as the FBG opens up wide opportunities for the creation of next generation fiber lasers and sensors based on MCFs.The advantages of the technology are shown by using the examples of 3D shape sensors,acoustic emission sensors with spatially multiplexed channels,as well as multicore fiber Raman lasers.展开更多
The grating eddy current displacement sensor (GECDS) for distance or position measurement used in watertight electronic calipers was described. The sensor relies on repetitive variation of inductance against displacem...The grating eddy current displacement sensor (GECDS) for distance or position measurement used in watertight electronic calipers was described. The sensor relies on repetitive variation of inductance against displacement caused by the change of coupling areas between moving coils and static reflectors. The investigations focused on setting up and utilizing a computer model of the 3D eddy current fields and geometry to analyze causes of the production of measurement blind areas, and to investigate effects of the sensor parameters, such as axial gap between coils and reflectors, reflector length and reflector width on characteristics of the sensor. Simulation results indicated that the sensor has the smallest nonlinearity error of 0.15%, which agrees well with the experimental results.展开更多
A micro-displacement sensor based on fiber Bragg grating(FBG) is proposed. The device consists of a pair of FBGs with different central wavelengths fabricated by femtosecond laser phase mask method and a metal substra...A micro-displacement sensor based on fiber Bragg grating(FBG) is proposed. The device consists of a pair of FBGs with different central wavelengths fabricated by femtosecond laser phase mask method and a metal substrate with lever structure. The displacement is amplified by lever structure and it converts into axial tension of FBG, which has a high displacement sensitivity. The amplification factors obtained by theoretical analysis and finite element simulation are 2.67 and 2.50, respectively. The experimental results show that in the range of 0-50 μm the shift of FBG center wavelength is linearly related to the displacement of measured object and displacement sensitivity reaches 121 pm/μm. In addition, the cascaded FBG is used to compensate the temperature.展开更多
A fiber Bragg grating strain sensor,whose reflection bandwidth is insensitive to temperature,is presented.The cross-sec-tional area is designed to change linearly.Under axial stress,there is a linear relationship betw...A fiber Bragg grating strain sensor,whose reflection bandwidth is insensitive to temperature,is presented.The cross-sec-tional area is designed to change linearly.Under axial stress,there is a linear relationship between stress and average strain.Experimental results show that when temperature increases,reflection center wavelength shifts to longer wavelength,and there is a good linear relationship between center wavelength and temperature.When stress increases,reflection center wavelength shifts to longer wavelength,and reflection bandwidth increases.There are good linear relationships between reflection center wavelength and stress as well as reflection bandwidth and stress.展开更多
A twist sensor with hybrid few-mode tilted fiber Bragg grating(FM-TFBG) and few-mode long period grating(FM-LPG) in fiber laser cavity is demonstrated. The FM-LPG is utilized to excite LP11 core mode. The FM-TFBG is u...A twist sensor with hybrid few-mode tilted fiber Bragg grating(FM-TFBG) and few-mode long period grating(FM-LPG) in fiber laser cavity is demonstrated. The FM-LPG is utilized to excite LP11 core mode. The FM-TFBG is used for sensing. The transverse modes at 1 553.9 nm and 1 550.5 nm are LP01 and LP21 core modes, respectively, which are coupled from forward-propagating LP11 core mode. These two excitation wavelengths have opposite variation tendencies, which participate in sensing. The twist sensitivity of 0.16 dB/° from-40° to 40° is achieved. The proposed sensor has potentially used for structure monitoring in many areas.展开更多
Aiming at the requirements of installation and work environment of metal-based fiber Bragg grating(FBG)sensor,a resistance spot welding method is presented.Firstly,the effect of welding parameters on welding quality i...Aiming at the requirements of installation and work environment of metal-based fiber Bragg grating(FBG)sensor,a resistance spot welding method is presented.Firstly,the effect of welding parameters on welding quality is discussed theoretically,and a suitable resistance spot welding method for the metal-based FBG sensor is proposed for the first time.Then through serial resistance spot welding tests,the feasibility and practicability of the method are verified,and optimal welding parameters for two different tested metals are obtained.Fatigue performance test validates FBG sensors installed by the proposed method with good fatigue properties and long-term stable measurement performance.The research results can provide technical guidance for engineering structure long-term safety monitoring.展开更多
In this paper,we propose the novel system of multipoint measurement.The sensors of measurements are chirped Bragg grating and the interrogation of sensors is sub-carrier phase.The wavelength division multiplexing tech...In this paper,we propose the novel system of multipoint measurement.The sensors of measurements are chirped Bragg grating and the interrogation of sensors is sub-carrier phase.The wavelength division multiplexing technique is used for addressing a network of FBG sensors and the time-division multiplexing technique is used for multipoint measurements.In the system,the modulation frequency of 200 MHz is adopted.The range of dectetion is from 0 to 900μεand the resolution is 12με. The time of the sensor response is about 1ns.展开更多
On the basis of existing techniques,a compact micro-displacement sensor of phase grating interference(PGI)is described,which adopts cylindrical hologram diffraction grating as the calibration standard.The optical prin...On the basis of existing techniques,a compact micro-displacement sensor of phase grating interference(PGI)is described,which adopts cylindrical hologram diffraction grating as the calibration standard.The optical principle of the sensor is explained,and the relation between the grating motion displacement and the phase shift of interference stripes is deduced.The improvement of the integral structure and the method of photoelectric signal processing are described in detail.With the software system based on the virtual instrument development platform Labwindows/CVI and other hardwares such as the precision displacement worktable,the surfaces of typical parts are measured and the characterization results are given.The sensor has wide measuring range and high resolution,its sensitivity and resolution being independent of the wavelength of the incident light.The vertical measuring range is 0-6 mm,and the vertical resolution is 0.005μm.The experimental results show that the sensor can be used to measure and characterize the surface topography parameters of the plane and curved surface.展开更多
In this paper, the effects of packaging material and structure of fiber Bragg grating sensor performance are investigated. The effects of thermal expansion coefficient of different embedding materials on the temperatu...In this paper, the effects of packaging material and structure of fiber Bragg grating sensor performance are investigated. The effects of thermal expansion coefficient of different embedding materials on the temperature sensitivities of the FBG sensors are studied both theoretically and experimentally with good agreement, which provides a means for selection of FBG packaging material to achieve desired temperature sensitivity. We also demonstrate a 4-point bending structured FBG lateral force sensor that measures up to 242N force with well-preserved reflection spectrum, whereas for 3-point bending structure, multiple-peaks start to occur when applied force reaches 72N.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
文摘Aiming at the requirement for high-precision tilt monitoring in the field of structural health monitoring(SHM),this paper proposes a sensitivity-enhanced tilt sensor based on a femtosecond fiber Bragg grating(FBG).Firstly,structural design of the tilt sensor was conducted based on static mechanics principles.By positioning the FBG away from the beam’s neutral axis,linear strain enhancement in the FBG was achieved,thereby improving sensor sensitivity.The relationship between FBG strain,applied force,and the offset distance from the neutral axis was established,determining the optimal distance corresponding to maximum strain.Based on this optimization scheme,a prototype of the tilt sensor was designed,fabricated,and experimentally tested.Experimental results show that the FBG offset distance yielding maximum sensitivity is 4.4 mm.Within a tilt angle range of−30°to 30°,the sensor achieved a sensitivity of 129.95 pm/°and a linearity of 0.9997.Compared to conventional FBG-based tilt sensors,both sensitivity and linearity were significantly improved.Furthermore,the sensor demonstrated excellent repeatability(error<0.94%),creep resistance(error<0.30%),and temperature stability(error<0.90%).These results demonstrate the sensor’s excellent potential for SHM applications.The sensor has been successfully deployed in an underground pipeline project,conducting long-term monitoring of tilt and deformation in the steel support structures,further proving its value for engineering safety monitoring.
基金supported in part by the National Natural Science Foundation of China(Nos.61735014 and 61927812)the Shaanxi Provincial Education Department(No.18JS093)+2 种基金the Natural Science Basic Research Program of Shaanxi Province(No.2024JC-YBMS-530)the Operation Fund of Logging Key Laboratory of Group Company(No.2021DQ0107-11)the Graduate Student Innovation Fund of Xi’an Shiyou University(No.YCS23213193)。
文摘A compact and highly sensitive gas pressure and temperature sensor based on Fabry-Pérot interferometer(FPI)and fiber Bragg grating(FBG)is proposed and demonstrated experimentally in this paper.The theoretical model for pressure and temperature sensing is established.Building on this foundation,a novel micro silicon cavity sensor structure sensitive to pressure is devised downstream of an FBG.The concept of separate measurement and the mechanisms enhancing pressure sensitivity are meticulously analyzed,and the corresponding samples are fabricated.The experimental results indicate that the pressure sensitivity of the sensor is-747.849 nm/MPa in 0—100 k Pa and its linearity is 99.7%and it maintains good stability in 150 min.The sensor offers the advantages of compact size,robust construction,easy fabrication,and high sensitivity,making it potentially valuable for micro-pressure application.
文摘Purpose–To address the encapsulation challenge of fiber Bragg grating(FBG)sensors in complex railway environments,this paper designs a clip-on composite sensor enabling installation-friendly deployment and long-term axle counting system monitoring.Design/methodology/approach–Wheel–rail mechanical behavior was simulated via finite element analysis(FEA)to determine optimal sensor placement.A clip-on composite sensor was subsequently engineered.Stress transduction efficacy was validated through FEA quantification of stress responses at the axle counter location.Findings–The proposed FBG axle counter integrates temperature compensation and anti-detachment monitoring as well as advantages such as simplified installation with minimal maintenance and sustained operational reliability.It effectively transmits stress,yielding a measured strain of 39μe under static loading conditions without sensitivity-enhancing elements.Originality/value–This study performs FEA of wheel-rail stress distribution and engineers the dual-slot composite sensor,FEAwas conducted to quantify the stress magnitude at the axle sensor position of the dual-slot composite sensor.Additionally,FEA was performed on sensors with different structural configurations,including adjustments to the axle sensor position,number of slots and axle position.The results confirmed that the designed composite sensor exhibits superior stress transfer characteristics.
基金supported by the National Natural Science Foundation of China(No.52276094)the Education Project of Hunan Provincial Department(Nos.20B602 and 22C0112)+2 种基金the Industry University Education Cooperation Project(No.230803117185211)the Research Project on Teaching Reform in Ordinary Undergraduate Universities in Hunan Province(No.202401000142)the Natural Science Foundation of Hunan Province(No.2020JJ4935)。
文摘There is limited amount of research on surface plasmon resonance(SPR)sensors with self-referencing capabilities which are based on dielectric gratings.In the short-wavelength range,a metal grating sensor is capable of simultaneously measuring liquid refractive index under proposed temperature.A fabricated gold grating is placed on one side of a thin gold film for refractive index measurement,while the other with polydimethylsiloxane(PDMS)is deposited on the other side for temperature measurement.We use finite element analysis to research its sensing characteristics.Due to the high refractive index sensitivity of SPR sensors and thermo-optic coefficient of PDMS,we discovered the maximum spectral sensitivity of the sensor is 564 nm/RIU and-50 pm/℃when the liquid refractive index ranges from 1.30 to 1.40 with temperature ranging from 0℃ to 100℃.Numerical results indicate that there may not be mutual interference between two channels for measuring refractive index and temperature,which reduces the complexity of sensor measurements.
文摘A grating eddy current displacement sensor(GECDS) can be used in a watertight electronic transducer to realize long range displacement or position measurement with high accuracy in difficult industry conditions.The parameters optimization of the sensor is essential for economic and efficient production.This paper proposes a method to combine an artificial neural network(ANN) and a genetic algorithm(GA) for the sensor parameters optimization.A neural network model is developed to map the complex relationship between design parameters and the nonlinearity error of the GECDS,and then a GA is used in the optimization process to determine the design parameter values,resulting in a desired minimal nonlinearity error of about 0.11%.The calculated nonlinearity error is 0.25%.These results show that the proposed method performs well for the parameters optimization of the GECDS.
基金supported by the National High Technology Research and Development Program of China (No.2007AA03Z117)the Key Program of National Natural Science Foundation of China (No.50830201)
文摘Many theoretical studies have been developed to study the spectral response of a fiber Bragg grating (FBG) under non-uniform strain distribution along the length of FBG in recent years. However, almost no experiments were designed to obtain the evolution of the spectrum when a FBG is subjected to non-uniform strain. In this paper, the spectral responses of a FBG under non-uniform strain distributions are given and a numerical simulation based on the Runge-Kutta method is introduced to investigate the responses of the FBG under some typical non-uniform transverse strain fields, including both linear strain gradient and quadratic strain field. Experiment is carried out by using loads applied at different locations near the FBG. Good agreements between experimental results and numerical simulations are obtained.
基金Project supported by the National Natural Science Foundation of China(Grant No.61865008)the Scientific Research Fund of Sichuan Provincial Science and Technology Department,China(Grant No.2020YJ0137)。
文摘A novel complementary grating structure is proposed for plasmonic refractive index sensing due to its strong resonance at near-infrared wavelength.The reflection spectra and the electric field distributions are obtained via the finite-difference time-domain method.Numerical simulation results show that multiple surface plasmon resonance modes can be excited in this novel structure.Subsequently,one of the resonance modes shows appreciable potential in refractive index sensing due to its wide range of action with the environment of the analyte.After optimizing the grating geometric variables of the structure,the designed structure shows the stable sensing performance with a high refractive index sensitivity of 1642 nm per refractive index unit(nm/RIU)and the figure of merit of 409 RIU^(-1).The promising simulation results indicate that such a sensor has a broad application prospect in biochemistry.
基金supported by the National Natural Science Foundation of China (No.51079080)
文摘In this paper,we present a novel oil level monitoring sensor based on string tilted fiber Bragg grating(TFBG).The measurement range and sensitivity of oil level monitoring can be modulated via changing the length and number of string tilted fiber gratings.The transmission spectrum of string TFBGs immersed in oil changes obviously with the oil level variation.Experiments are conducted on three 2 cm-length serial TFBGs with the same tilted angle of 10o.A sensitivity of 3.28 dB/cm in the string TFBG sensor is achieved with good linearity by means of TFBG spectrum characteristic with peak-low value.The cladding mode transmission power and the amplitude of high order cladding mode resonance are nearly linear to the oil level variation.This kind of sensor is insensitive to temperature and attributed to be employed in extremely harsh environment oil monitoring.
基金Doctoral Foundation of Ministry of Education of China (No. 20040056008)
文摘A discrimination measurement method and demodulation technique for fiber Bragg grating (FBG) sensors were presented using digital filtering technique. The system can control a tunable fiber Fabry-Perot filter with sawtooth wave voltage generated by digital clock to interrogate FBG sensors. Using the analogue digital converter (ADC), the reflected FBG signals were sampled with synchronous digital clock. With the aid of digital matched filtering technique, the sampled FBG signals were processed to obtain the maximum signal-to-noise ratio (SNR) and the Bragg wavelength shift from the FBG signals was recovered. The results demonstrate that this system has a scanning range of 1 520 nm-1 575 nm,and the wavelength detection accuracy is less than 2 pm with 1.5 Hz scanning frequency.
文摘The phase diversity wavefront sensor is one of the tools used to estimate wavefront aberration, and it is often used as a wavefront sensor in adaptive optics systems. However, the performance of the traditional phase diversity wavefront sensor is limited by the accuracy and dynamic ranges of the intensity distribution at the focus and defocus positions of the CCD camera. In this paper, a modified phase diversity wavefront sensor based on a diffraction grating is proposed to improve the ability to measure the wavefront aberration with larger amplitude and higher spatial frequency. The basic principle and the optics construction of the proposed method are also described in detail. The noise propagation property of the proposed method is also analysed by using the numerical simulation method, and comparison between the diffraction grating phase diversity wavefront sensor and the traditional phase diversity wavefront sensor is also made. The simulation results show that the diffraction grating phase diversity wavefront sensor can obviously improve the ability to measure the wavefront aberration, especially the wavefront aberration with larger amplitude and higher spatial frequency.
基金supported by the Russian Ministry of Science and Higher Education (14.Y26.31.0017)Russian Foundation for Basic Research(18-52-7822)the work concerning MCF fiber Raman lasers was supported by Russian Science Foundation (21-72-30024)
文摘In this article,we review recent advances in the technology of writing fiber Bragg gratings(FBGs)in selected cores of multicore fibers(MCFs)by using femtosecond laser pulses.The writing technology of such a key element as the FBG opens up wide opportunities for the creation of next generation fiber lasers and sensors based on MCFs.The advantages of the technology are shown by using the examples of 3D shape sensors,acoustic emission sensors with spatially multiplexed channels,as well as multicore fiber Raman lasers.
文摘The grating eddy current displacement sensor (GECDS) for distance or position measurement used in watertight electronic calipers was described. The sensor relies on repetitive variation of inductance against displacement caused by the change of coupling areas between moving coils and static reflectors. The investigations focused on setting up and utilizing a computer model of the 3D eddy current fields and geometry to analyze causes of the production of measurement blind areas, and to investigate effects of the sensor parameters, such as axial gap between coils and reflectors, reflector length and reflector width on characteristics of the sensor. Simulation results indicated that the sensor has the smallest nonlinearity error of 0.15%, which agrees well with the experimental results.
基金Projects(51875585, 51875584, 51935013) supported by the National Natural Science Foundation of ChinaProject(2020JJ4247) supported by the Natural Science Foundation of Hunan Province,ChinaProject(ZHD202001) supported by the Opening Project of Science and Technology on Reliability Physics and Application Technology of Electronic Component Laboratory,China。
文摘A micro-displacement sensor based on fiber Bragg grating(FBG) is proposed. The device consists of a pair of FBGs with different central wavelengths fabricated by femtosecond laser phase mask method and a metal substrate with lever structure. The displacement is amplified by lever structure and it converts into axial tension of FBG, which has a high displacement sensitivity. The amplification factors obtained by theoretical analysis and finite element simulation are 2.67 and 2.50, respectively. The experimental results show that in the range of 0-50 μm the shift of FBG center wavelength is linearly related to the displacement of measured object and displacement sensitivity reaches 121 pm/μm. In addition, the cascaded FBG is used to compensate the temperature.
基金supported by the National Natural Science Foundation of China(Nos.60837002and61177069)the Ph.D.Programs Foundation of Ministry of Education of China(No.20090009110003)the Fundamental Research Funds for the Central Universities(No.2011YJS214)
文摘A fiber Bragg grating strain sensor,whose reflection bandwidth is insensitive to temperature,is presented.The cross-sec-tional area is designed to change linearly.Under axial stress,there is a linear relationship between stress and average strain.Experimental results show that when temperature increases,reflection center wavelength shifts to longer wavelength,and there is a good linear relationship between center wavelength and temperature.When stress increases,reflection center wavelength shifts to longer wavelength,and reflection bandwidth increases.There are good linear relationships between reflection center wavelength and stress as well as reflection bandwidth and stress.
基金supported by the National Natural Science Foundation of China(Nos.11674177,61775107,61835006 and 11704283)the Natural Science Foundation of Tianjin in China(No.16JCZDJC31000)the Scientific Research Planning and Development Project of Handan in China(No.1621203035)
文摘A twist sensor with hybrid few-mode tilted fiber Bragg grating(FM-TFBG) and few-mode long period grating(FM-LPG) in fiber laser cavity is demonstrated. The FM-LPG is utilized to excite LP11 core mode. The FM-TFBG is used for sensing. The transverse modes at 1 553.9 nm and 1 550.5 nm are LP01 and LP21 core modes, respectively, which are coupled from forward-propagating LP11 core mode. These two excitation wavelengths have opposite variation tendencies, which participate in sensing. The twist sensitivity of 0.16 dB/° from-40° to 40° is achieved. The proposed sensor has potentially used for structure monitoring in many areas.
文摘Aiming at the requirements of installation and work environment of metal-based fiber Bragg grating(FBG)sensor,a resistance spot welding method is presented.Firstly,the effect of welding parameters on welding quality is discussed theoretically,and a suitable resistance spot welding method for the metal-based FBG sensor is proposed for the first time.Then through serial resistance spot welding tests,the feasibility and practicability of the method are verified,and optimal welding parameters for two different tested metals are obtained.Fatigue performance test validates FBG sensors installed by the proposed method with good fatigue properties and long-term stable measurement performance.The research results can provide technical guidance for engineering structure long-term safety monitoring.
文摘In this paper,we propose the novel system of multipoint measurement.The sensors of measurements are chirped Bragg grating and the interrogation of sensors is sub-carrier phase.The wavelength division multiplexing technique is used for addressing a network of FBG sensors and the time-division multiplexing technique is used for multipoint measurements.In the system,the modulation frequency of 200 MHz is adopted.The range of dectetion is from 0 to 900μεand the resolution is 12με. The time of the sensor response is about 1ns.
基金This project is supported by National Natural Sciences Foundation of China(No.50175037).
文摘On the basis of existing techniques,a compact micro-displacement sensor of phase grating interference(PGI)is described,which adopts cylindrical hologram diffraction grating as the calibration standard.The optical principle of the sensor is explained,and the relation between the grating motion displacement and the phase shift of interference stripes is deduced.The improvement of the integral structure and the method of photoelectric signal processing are described in detail.With the software system based on the virtual instrument development platform Labwindows/CVI and other hardwares such as the precision displacement worktable,the surfaces of typical parts are measured and the characterization results are given.The sensor has wide measuring range and high resolution,its sensitivity and resolution being independent of the wavelength of the incident light.The vertical measuring range is 0-6 mm,and the vertical resolution is 0.005μm.The experimental results show that the sensor can be used to measure and characterize the surface topography parameters of the plane and curved surface.
基金Supported by Science & Engineering Research Council of Singapore (052 118 0052)
文摘In this paper, the effects of packaging material and structure of fiber Bragg grating sensor performance are investigated. The effects of thermal expansion coefficient of different embedding materials on the temperature sensitivities of the FBG sensors are studied both theoretically and experimentally with good agreement, which provides a means for selection of FBG packaging material to achieve desired temperature sensitivity. We also demonstrate a 4-point bending structured FBG lateral force sensor that measures up to 242N force with well-preserved reflection spectrum, whereas for 3-point bending structure, multiple-peaks start to occur when applied force reaches 72N.
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.
