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
Sensors play an important role in shaping and monitoring human health.Exploration of methods to use Fiber Bragg Grating(FBG)with enhanced sensitivity has attracted great interest in the field of medical research.In th...Sensors play an important role in shaping and monitoring human health.Exploration of methods to use Fiber Bragg Grating(FBG)with enhanced sensitivity has attracted great interest in the field of medical research.In this paper,a novel apodization function is proposed and performance evaluation and optimization of the same have been made.A comparison was conducted between various existing apodization functions and the proposed one based on optical characteristics and sensor parameters.The results evince the implementation of the proposed apodization function for vital sign measurement.The optical characteristics considered for evaluation are Peak Resonance Reflectivity level,Side Lobes Reflectivity level and FullWidth HalfMaximum(FWHM).The proposed novel apodization novel function has better FWHM,which is narrower than the FWHM of uniform FBG.Sensor characteristics like a quality parameter,detection accuracy and sensitivity also show improvement.The proposed novel apodization function is demonstrated to have a better shift in wavelength in terms of temperature and pulse measurement than the existing functions.The sensitivity of the proposed apodized function is enhanced with a Poly-dimethylsiloxane coating of varying thickness,which is 6 times and 5.14 times greater than uniform Fiber Bragg grating and FBG with the proposed novel apodization function,respectively,enhancing its utilization in the field of medicine.展开更多
Optical chaos has attracted widespread attention owing to its complex dynamic behaviors.However,the time delay signature(TDS)caused by the external cavity mode reduces the complexity of optical chaos.We propose and nu...Optical chaos has attracted widespread attention owing to its complex dynamic behaviors.However,the time delay signature(TDS)caused by the external cavity mode reduces the complexity of optical chaos.We propose and numerically demonstrate the critical dispersion of chirped fiber Bragg grating(CFBG)for eliminating the TDS of laser chaos in this work.The critical dispersion,as a function of relaxation frequency and bandwidth of the optical spectrum,is found through extensive dynamics simulations.It is shown that the TDS can be eliminated when the dispersion of CFBG is above this critical dispersion.In addition,the influence of dispersive feedback light and output light from a laser is investigated.These results provide important quantitative guidance for designing chaotic semiconductor lasers without TDS.展开更多
Optical fibers are typically used in telecommunications services for data transmission,where the use of fiber tags is essential to distinguish between the different transmission fibers or channels and thus ensure the ...Optical fibers are typically used in telecommunications services for data transmission,where the use of fiber tags is essential to distinguish between the different transmission fibers or channels and thus ensure the working functionality of the communication system.Traditional physical entity marking methods for fiber labeling are bulky,easily confused,and,most importantly,the label information can be accessed easily by all potential users.This work proposes an encrypted optical fiber tag based on an encoded fiber Bragg grating(FBG)array that is fabricated using a point-by-point femtosecond laser pulse chain inscription method.Gratings with different resonant wavelengths and reflectivities are realized by adjusting the grating period and the refractive index modulations.It is demonstrated that a binary data sequence carried by a fiber tag can be inscribed into the fiber core in the form of an FBG array,and the tag data can be encrypted through appropriate design of the spatial distributions of the FBGs with various reflection wavelengths and reflectivities.The proposed fiber tag technology can be used for applications in port identification,encrypted data storage,and transmission in fiber networks.展开更多
Fiber Bragg grating(FBG)sensors are often used in monitoring activities and to ensure that environmental parameters satisfy industrial requirements.They offer crucial safety measures in the early detection of hazards ...Fiber Bragg grating(FBG)sensors are often used in monitoring activities and to ensure that environmental parameters satisfy industrial requirements.They offer crucial safety measures in the early detection of hazards due to their greatly reduced size,low weight,flexibility,and immunity to electromagnetic interference.These characteristics make FBGs suitable also for use in relation to the human body for in vivo measurements and long-term monitoring.In this study,recent developments are presented with regard to the utilization of these sensors to measure the so-called post-mortem interval(PMI).Such developments rely on numerical simulations based on the Matlab software and monitoring of the rectal temperature,which is one of the main parameters for estimating the PMI.First,the Matlab software is used to solve the Henssge equation for different ambient temperatures and for different body masses;then a Bragg grating sensors is used for post-mortem dating.The results and their accuracy are discussed.展开更多
The combination of Radio Frequency and Optical Fiber has resulted high capacity transmission at lower costs components and makes Radio over Fiber as a current trend of large broadband communication. In Fiber optics fi...The combination of Radio Frequency and Optical Fiber has resulted high capacity transmission at lower costs components and makes Radio over Fiber as a current trend of large broadband communication. In Fiber optics field, the use of Fiber Bragg Grating (FBG) was been proposed in recent research with different purpose of uses. However, the compensation of dispersion method of Fiber Bragg Grating (FBG) can boost significantly the system performance. This paper investigates the performance capacity improvement of adaptive Radio over Fiber system. The system design was performed using OptiSystem 7.0 software, which 10 Gb/s Non Return to Zero (NRZ) signal was launched into 50 Km Universal Mode Fiber and Fiber Bragg Grating was used as a compensator of dispersion before frequency up conversion. Therefore, the system performances were investigated by comparing the Bit Error Rate (BER) and Q-factors of Positive Intrinsic Negative (PIN) and Ultrafast Avalanche Photodiode (APD) as optical receivers. The Eye diagram analyzer showed acceptable improvement due to use of Fiber Bragg Grating as a compensator of dispersion.展开更多
A perimeter security system based on ultra-weak fiber Bragg grating high-speed wavelength demodulation was proposed. The demodulation system for signal acquisition and high-speed wavelength calculation was designed ba...A perimeter security system based on ultra-weak fiber Bragg grating high-speed wavelength demodulation was proposed. The demodulation system for signal acquisition and high-speed wavelength calculation was designed based on field programmable gate array (FPGA) platform. The principle of ultra-weak fiber Bragg grating high-speed demodulation and signal recognition method were analyzed theoretically, and the Support Vector Machine model was introduced to optimize the event recognition accuracy of the system. A perimeter security experimental system containing 1000 ultra-weak fiber Bragg gratings, ultra-weak fiber Bragg grating sense optical cables with a diameter of 2.0 mm and a reflectivity of 0.01%, steel space frames and demodulation equipments was built to recognize four typical events such as knocking, shaking, wind blowing and rainfall. The experimental resulted show that the system has a spatial resolution of 1m and an acquisition frequency of 200 Hz. The joint time-frequency domain detection method is used to achieve 99.2% alarm accuracy, and 98% recognition accuracy of two intrusion events, which has good anti-interference performance.展开更多
The grating ends bonding fiber Bragg grating(FBG)sensor has been widely used in sensor packages such as substrate type and clamp type for health monitoring of large structures.However,owing to the shear deformation of...The grating ends bonding fiber Bragg grating(FBG)sensor has been widely used in sensor packages such as substrate type and clamp type for health monitoring of large structures.However,owing to the shear deformation of the adhesive layer of FBG,the strain measured by FBG is often different from the strain of actual matrix,which causes strain measurement errors.This investigation aims at improving the measurement accuracy of strain for the grating ends surface-bonded FBG.To fulfill this objective,a strain transfer equation of the grating ends bonding FBG is derived,and a theoretical model of the average strain transfer from the matrix to the optical fiber is developed.Moreover,parameters that influence the average strain transfer rate from the matrix to the optical fiber are analyzed.A selection scheme of bonding parameters by numerical simulation is provided,which is significantly advantageous over that of the grating bonding FBG.The theoretical equation is verified by finite element method(FEM).Compared with the existing model,the proposed model has higher measurement accuracy.Experimental tests are performed to validate the effectiveness of the proposed model on the equalintensity cantilever beam,whose surface is attached to the bare FBG with grating ends bonding and strain gauge by using epoxy glue.The results show that there is a great agreement between the outcome of the bare FBG and that of the strain gauge,and the corrected strain is closer to the true strain.The proposed model provides a theoretical basis for the design of the grating ends surface-bonded FBG strain sensor for health monitoring of large structures.展开更多
Centrifugal model testsare playing an increasingly importantrolein investigating slope characteristics under rainfall conditions. However, conventional electronic transducers usually fail during centrifugal model test...Centrifugal model testsare playing an increasingly importantrolein investigating slope characteristics under rainfall conditions. However, conventional electronic transducers usually fail during centrifugal model tests because of the impacts of limitedtest space, high centrifugal force, and presence of water, with the result that limited valid data is obtained. In this study, Fiber Bragg Grating(FBG) sensing technology is employed in the design and development of displacement gauge, an anchor force gauge and an anti-slide pile moment gauge for use on centrifugal model slopes with and without a retaining structure. The two model slopes were installed and monitored at a centrifugal acceleration of 100 g. The test results show that the sensors developed succeed in capturing the deformation and retaining structure mechanical response of the model slopes during and after rainfall. The deformation curvefor the slope without retaining structure shows a steepresponse that turns gradualfor the slope with retaining structure. Importantly, for the slope with the retaining structure, results suggest that more attention be paid to increase of anchor force and antislide pile moment during rainfall. This study verifies the effectiveness of FBG sensing technology in centrifuge research and presents a new and innovative method for slope model testing under rainfall conditions.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
We proposed and experimentally demonstrated a cascaded tilted fiber Bragg grating(TFBG) for enhanced refractive index sensing. The TFBG is UV-inscribed in series in ordinary single-mode fiber(SMF) and reduced-diameter...We proposed and experimentally demonstrated a cascaded tilted fiber Bragg grating(TFBG) for enhanced refractive index sensing. The TFBG is UV-inscribed in series in ordinary single-mode fiber(SMF) and reduced-diameter SMF with the same tilt angle, and then excites two sets of superposed spectral combs of cladding modes. The cascaded TFBG with total length of 18 mm has a much wider wavelength range over 100 nm and narrower wavelength separation than that of a TFBG only in the SMF, enabling an enlarged range and a higher accuracy of refractive index measurement. The fabricated TFBG with the merits of enhanced sensing capability and temperature self-calibration presents great potentials in the biochemical sensing applications.展开更多
Running composite insulators are prone to failure due to their harsh surrounding work environment, which directly affects the safe operation of transmission lines. This paper puts forward the method of using fiber Bra...Running composite insulators are prone to failure due to their harsh surrounding work environment, which directly affects the safe operation of transmission lines. This paper puts forward the method of using fiber Bragg grating(FBG) as the monitors to parameters correlated with thermal and stress of the composite insulators in transmission lines at working status. Firstly, monitoring points are found out by the mechanical test on composite insulator samples. Secondly, based on the monitoring theory, this paper introduces the feasibility design frame of the composite insulator with FBG implanted in the rod and the online monitor system. At last, it describes applications of this monitor system in the field of transmission lines.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
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
Thermo-poro-mechanical responses along sliding zone/surface have been extensively studied.However,it has not been recognized that the potential contribution of other crucial engineering geological interfaces beyond th...Thermo-poro-mechanical responses along sliding zone/surface have been extensively studied.However,it has not been recognized that the potential contribution of other crucial engineering geological interfaces beyond the slip surface to progressive failure.Here,we aim to investigate the subsurface multiphysics of reservoir landslides under two extreme hydrologic conditions(i.e.wet and dry),particularly within sliding masses.Based on ultra-weak fiber Bragg grating(UWFBG)technology,we employ specialpurpose fiber optic sensing cables that can be implanted into boreholes as“nerves of the Earth”to collect data on soil temperature,water content,pore water pressure,and strain.The Xinpu landslide in the middle reach of the Three Gorges Reservoir Area in China was selected as a case study to establish a paradigm for in situ thermo-hydro-poro-mechanical monitoring.These UWFBG-based sensing cables were vertically buried in a 31 m-deep borehole at the foot of the landslide,with a resolution of 1 m except for the pressure sensor.We reported field measurements covering the period 2021 and 2022 and produced the spatiotemporal profiles throughout the borehole.Results show that wet years are more likely to motivate landslide motions than dry years.The annual thermally active layer of the landslide has a critical depth of roughly 9 m and might move downward in warmer years.The dynamic groundwater table is located at depths of 9e15 m,where the peaked strain undergoes a periodical response of leap and withdrawal to annual hydrometeorological cycles.These interface behaviors may support the interpretation of the contribution of reservoir regulation to slope stability,allowing us to correlate them to local damage events and potential global destabilization.This paper also offers a natural framework for interpreting thermo-hydro-poro-mechanical signatures from creeping reservoir bank slopes,which may form the basis for a landslide monitoring and early warning system.展开更多
This paper focused on high-precision demodulation of wavelength shift of FBG sensor. Fiber tunable F-P filer was used as a demodulation method. 32-bit embedded processor ARM9-S3C2440 chip was used as the main controll...This paper focused on high-precision demodulation of wavelength shift of FBG sensor. Fiber tunable F-P filer was used as a demodulation method. 32-bit embedded processor ARM9-S3C2440 chip was used as the main controller and simulated annealing algorithm was realized on ARM to demodulate wavelength signal. Simulation results show that the simulated annealing algorithm is reliable to process analog signals on ARM chip and significant performance is achieved such as saving bandwidth,increasing the amounts of reusable fiber grating sensors in sensor system and speeding up data processing.展开更多
This paper reports a fiber Bragg grating(FBG)as a biosensor.The FBGs were etched using a chemical agent,namely,hydrofluoric acid(HF).This implies the removal of some part of the cladding layer.Consequently,the evanesc...This paper reports a fiber Bragg grating(FBG)as a biosensor.The FBGs were etched using a chemical agent,namely,hydrofluoric acid(HF).This implies the removal of some part of the cladding layer.Consequently,the evanescent field propagating out of the core will be closer to the environment and become more sensitive to the change in the surrounding.The proposed FBG sensor was utilized to detect toxic heavy metal ions aqueous medium namely,copper ions(Cu^(2+)).Two FBG sensors were etched with 20 and 40μm diameters and fabricated.The sensors were studied towards Cu^(2+)with different concentrations using wavelength shift as a result of the interaction between the evanescent field and copper ions.The FBG sensors showed a good response in terms of significant wavelength shift in corresponding to varying Cu2+concentrations when immersed in aqueous mediums.The sensors exhibited excellent repeatability towards Cu ions.The results demonstrate that the smaller FBG etching diameter,the better optical response in terms of wavelength and linearity.展开更多
Aiming for suppressing side-mode and spectrum broadening,a slit beam-shaping method and super-Gaussian apodization processing for femtosecond laser point-by-point(PbP)inscription technology of fiber Bragg gratings(FBG...Aiming for suppressing side-mode and spectrum broadening,a slit beam-shaping method and super-Gaussian apodization processing for femtosecond laser point-by-point(PbP)inscription technology of fiber Bragg gratings(FBGs)are reported here.High-quality FBGs,featuring narrow bandwidth of less than 0.3 nm,high reflectivity above 85%,low insertion loss(0.21 dB),and low cladding loss(0.82 dB),were obtained successfully.By a semi-automatic PbP inscription process,an array consisting of six FBGs,exhibiting almost no side-mode peaks with high suppression ability and narrow bandwidth,was fabricated along three independently developed single-mode fibers with an interval of 20 mm.展开更多
Hong Kong has a long history of applying masonry retaining walls to provide horizontal platforms and stabilize man-made slopes.Due to the sub-tropical climate,some masonry retaining walls are colonized by trees.Extrem...Hong Kong has a long history of applying masonry retaining walls to provide horizontal platforms and stabilize man-made slopes.Due to the sub-tropical climate,some masonry retaining walls are colonized by trees.Extreme weather,such as typhoons and heavy rains,may cause rupture or root failure of those trees,thus resulting in instability of the retaining walls.A monitoring and warning system for the movement of masonry retaining walls and sway of trees has been designed with the application of fiber Bragg grating(FBG)sensing technology.The monitoring system is also equipped with a solar power system and 4G data transmission devices.The key functions of the proposed monitoring system include remote sensing and data access,early warning,and real-time data visualization.The setups and working principles of the monitoring systems and related transducers are introduced.The feasibility,accuracy,serviceability and reliability of this monitoring system have been checked by in-site calibration tests and four-month monitoring.Besides,a two-level interface has been developed for data visualization.The monitoring results show that the monitored masonry retaining wall had a reversible movement up to 2.5 mm during the monitoring period.Besides,it is found that the locations of the maximum strain on trees depend on the crown spread of trees.展开更多
A simple quasi-distributed fiber sensing interrogation system based on random speckles is proposed for weak fiber Bragg gratings(WFBGs) in this work. Without using tunable lasers or spectrometers, a piece of multimode...A simple quasi-distributed fiber sensing interrogation system based on random speckles is proposed for weak fiber Bragg gratings(WFBGs) in this work. Without using tunable lasers or spectrometers, a piece of multimode fiber is applied to interrogate the WFBGs relying on the wavelength sensitivity of speckles. Instead of the CCD sensor, an InGaAs quadrant detector serves as the receiver to capture the fast-changing speckle patterns. A supervised deep learning algorithm of the multilayer perceptron architecture is implemented to process speckle data and to interrogate temperature changes or dynamic strains. The proposed demodulation system is experimentally demonstrated for WFBGs with 0.1% reflectivity.The experimental results demonstrate that the new system is capable of measuring temperature change with an accuracy of 1℃ and achieving dynamic frequency of 100 Hz. This speckle-based interrogation system paves a new way for distributed WFBGs sensing with a simple design.展开更多
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supported in part by Universiti Malaya,and ACU UK under Project No.IF063-2021.
文摘Sensors play an important role in shaping and monitoring human health.Exploration of methods to use Fiber Bragg Grating(FBG)with enhanced sensitivity has attracted great interest in the field of medical research.In this paper,a novel apodization function is proposed and performance evaluation and optimization of the same have been made.A comparison was conducted between various existing apodization functions and the proposed one based on optical characteristics and sensor parameters.The results evince the implementation of the proposed apodization function for vital sign measurement.The optical characteristics considered for evaluation are Peak Resonance Reflectivity level,Side Lobes Reflectivity level and FullWidth HalfMaximum(FWHM).The proposed novel apodization novel function has better FWHM,which is narrower than the FWHM of uniform FBG.Sensor characteristics like a quality parameter,detection accuracy and sensitivity also show improvement.The proposed novel apodization function is demonstrated to have a better shift in wavelength in terms of temperature and pulse measurement than the existing functions.The sensitivity of the proposed apodized function is enhanced with a Poly-dimethylsiloxane coating of varying thickness,which is 6 times and 5.14 times greater than uniform Fiber Bragg grating and FBG with the proposed novel apodization function,respectively,enhancing its utilization in the field of medicine.
基金the National Natural Science Foundation of China(Grant No.62105190)the Natural Science Foundation of Shanxi Province of China(Grant No.20210302124268)+1 种基金the Scientific and Technological Innovation Programs of Higher Education Institutions of Shanxi Province of China(Grant No.2021L285)the Youth Researchof Shanxi University of Finance and Economics(Grant No.QN-202015)。
文摘Optical chaos has attracted widespread attention owing to its complex dynamic behaviors.However,the time delay signature(TDS)caused by the external cavity mode reduces the complexity of optical chaos.We propose and numerically demonstrate the critical dispersion of chirped fiber Bragg grating(CFBG)for eliminating the TDS of laser chaos in this work.The critical dispersion,as a function of relaxation frequency and bandwidth of the optical spectrum,is found through extensive dynamics simulations.It is shown that the TDS can be eliminated when the dispersion of CFBG is above this critical dispersion.In addition,the influence of dispersive feedback light and output light from a laser is investigated.These results provide important quantitative guidance for designing chaotic semiconductor lasers without TDS.
基金supported by the National Natural Science Foundation of China(62122057,62075136,62105217,62205221,62205222)the Basic and Applied Basic Research Foundation of Guangdong Province(2022B1515120061)Shenzhen Science and Technology Program(Shenzhen Key Laboratory of Ultrafast Laser Micro/Nano Manufacturing ZDSYS20220606100405013,RCYX20200714114524139,JCYJ20200109114001806)。
文摘Optical fibers are typically used in telecommunications services for data transmission,where the use of fiber tags is essential to distinguish between the different transmission fibers or channels and thus ensure the working functionality of the communication system.Traditional physical entity marking methods for fiber labeling are bulky,easily confused,and,most importantly,the label information can be accessed easily by all potential users.This work proposes an encrypted optical fiber tag based on an encoded fiber Bragg grating(FBG)array that is fabricated using a point-by-point femtosecond laser pulse chain inscription method.Gratings with different resonant wavelengths and reflectivities are realized by adjusting the grating period and the refractive index modulations.It is demonstrated that a binary data sequence carried by a fiber tag can be inscribed into the fiber core in the form of an FBG array,and the tag data can be encrypted through appropriate design of the spatial distributions of the FBGs with various reflection wavelengths and reflectivities.The proposed fiber tag technology can be used for applications in port identification,encrypted data storage,and transmission in fiber networks.
文摘Fiber Bragg grating(FBG)sensors are often used in monitoring activities and to ensure that environmental parameters satisfy industrial requirements.They offer crucial safety measures in the early detection of hazards due to their greatly reduced size,low weight,flexibility,and immunity to electromagnetic interference.These characteristics make FBGs suitable also for use in relation to the human body for in vivo measurements and long-term monitoring.In this study,recent developments are presented with regard to the utilization of these sensors to measure the so-called post-mortem interval(PMI).Such developments rely on numerical simulations based on the Matlab software and monitoring of the rectal temperature,which is one of the main parameters for estimating the PMI.First,the Matlab software is used to solve the Henssge equation for different ambient temperatures and for different body masses;then a Bragg grating sensors is used for post-mortem dating.The results and their accuracy are discussed.
文摘The combination of Radio Frequency and Optical Fiber has resulted high capacity transmission at lower costs components and makes Radio over Fiber as a current trend of large broadband communication. In Fiber optics field, the use of Fiber Bragg Grating (FBG) was been proposed in recent research with different purpose of uses. However, the compensation of dispersion method of Fiber Bragg Grating (FBG) can boost significantly the system performance. This paper investigates the performance capacity improvement of adaptive Radio over Fiber system. The system design was performed using OptiSystem 7.0 software, which 10 Gb/s Non Return to Zero (NRZ) signal was launched into 50 Km Universal Mode Fiber and Fiber Bragg Grating was used as a compensator of dispersion before frequency up conversion. Therefore, the system performances were investigated by comparing the Bit Error Rate (BER) and Q-factors of Positive Intrinsic Negative (PIN) and Ultrafast Avalanche Photodiode (APD) as optical receivers. The Eye diagram analyzer showed acceptable improvement due to use of Fiber Bragg Grating as a compensator of dispersion.
文摘A perimeter security system based on ultra-weak fiber Bragg grating high-speed wavelength demodulation was proposed. The demodulation system for signal acquisition and high-speed wavelength calculation was designed based on field programmable gate array (FPGA) platform. The principle of ultra-weak fiber Bragg grating high-speed demodulation and signal recognition method were analyzed theoretically, and the Support Vector Machine model was introduced to optimize the event recognition accuracy of the system. A perimeter security experimental system containing 1000 ultra-weak fiber Bragg gratings, ultra-weak fiber Bragg grating sense optical cables with a diameter of 2.0 mm and a reflectivity of 0.01%, steel space frames and demodulation equipments was built to recognize four typical events such as knocking, shaking, wind blowing and rainfall. The experimental resulted show that the system has a spatial resolution of 1m and an acquisition frequency of 200 Hz. The joint time-frequency domain detection method is used to achieve 99.2% alarm accuracy, and 98% recognition accuracy of two intrusion events, which has good anti-interference performance.
文摘The grating ends bonding fiber Bragg grating(FBG)sensor has been widely used in sensor packages such as substrate type and clamp type for health monitoring of large structures.However,owing to the shear deformation of the adhesive layer of FBG,the strain measured by FBG is often different from the strain of actual matrix,which causes strain measurement errors.This investigation aims at improving the measurement accuracy of strain for the grating ends surface-bonded FBG.To fulfill this objective,a strain transfer equation of the grating ends bonding FBG is derived,and a theoretical model of the average strain transfer from the matrix to the optical fiber is developed.Moreover,parameters that influence the average strain transfer rate from the matrix to the optical fiber are analyzed.A selection scheme of bonding parameters by numerical simulation is provided,which is significantly advantageous over that of the grating bonding FBG.The theoretical equation is verified by finite element method(FEM).Compared with the existing model,the proposed model has higher measurement accuracy.Experimental tests are performed to validate the effectiveness of the proposed model on the equalintensity cantilever beam,whose surface is attached to the bare FBG with grating ends bonding and strain gauge by using epoxy glue.The results show that there is a great agreement between the outcome of the bare FBG and that of the strain gauge,and the corrected strain is closer to the true strain.The proposed model provides a theoretical basis for the design of the grating ends surface-bonded FBG strain sensor for health monitoring of large structures.
基金supported by the National Natural Science Foundation of China (Grant Nos.41502299,41372306)Research Planning of Sichuan Education Department, China (Grant No.16ZB0105)State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Independent Research Project (SKLGP2016Z007)
文摘Centrifugal model testsare playing an increasingly importantrolein investigating slope characteristics under rainfall conditions. However, conventional electronic transducers usually fail during centrifugal model tests because of the impacts of limitedtest space, high centrifugal force, and presence of water, with the result that limited valid data is obtained. In this study, Fiber Bragg Grating(FBG) sensing technology is employed in the design and development of displacement gauge, an anchor force gauge and an anti-slide pile moment gauge for use on centrifugal model slopes with and without a retaining structure. The two model slopes were installed and monitored at a centrifugal acceleration of 100 g. The test results show that the sensors developed succeed in capturing the deformation and retaining structure mechanical response of the model slopes during and after rainfall. The deformation curvefor the slope without retaining structure shows a steepresponse that turns gradualfor the slope with retaining structure. Importantly, for the slope with the retaining structure, results suggest that more attention be paid to increase of anchor force and antislide pile moment during rainfall. This study verifies the effectiveness of FBG sensing technology in centrifuge research and presents a new and innovative method for slope model testing under rainfall conditions.
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.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61775182 and 61505165)Marie Sktodowska-Curie Individual Fellowships in the European Union’s Horizon 2020 Research and Innovation Programme(Grant No.660648)
文摘We proposed and experimentally demonstrated a cascaded tilted fiber Bragg grating(TFBG) for enhanced refractive index sensing. The TFBG is UV-inscribed in series in ordinary single-mode fiber(SMF) and reduced-diameter SMF with the same tilt angle, and then excites two sets of superposed spectral combs of cladding modes. The cascaded TFBG with total length of 18 mm has a much wider wavelength range over 100 nm and narrower wavelength separation than that of a TFBG only in the SMF, enabling an enlarged range and a higher accuracy of refractive index measurement. The fabricated TFBG with the merits of enhanced sensing capability and temperature self-calibration presents great potentials in the biochemical sensing applications.
基金supported by National High-tech Research and Development Program of China (863 Program) (2013AA030701)Science and Technology Project of the State Grid Xinjiang Electric Power Corporation (5230DK15009L)
文摘Running composite insulators are prone to failure due to their harsh surrounding work environment, which directly affects the safe operation of transmission lines. This paper puts forward the method of using fiber Bragg grating(FBG) as the monitors to parameters correlated with thermal and stress of the composite insulators in transmission lines at working status. Firstly, monitoring points are found out by the mechanical test on composite insulator samples. Secondly, based on the monitoring theory, this paper introduces the feasibility design frame of the composite insulator with FBG implanted in the rod and the online monitor system. At last, it describes applications of this monitor system in the field of transmission lines.
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We acknowledge the funding support from the National Science Fund for Distinguished Young Scholars of National Natural Science Foundation of China(Grant No.42225702)the National Natural Science Foundation of China(Grant No.42077235).
文摘Thermo-poro-mechanical responses along sliding zone/surface have been extensively studied.However,it has not been recognized that the potential contribution of other crucial engineering geological interfaces beyond the slip surface to progressive failure.Here,we aim to investigate the subsurface multiphysics of reservoir landslides under two extreme hydrologic conditions(i.e.wet and dry),particularly within sliding masses.Based on ultra-weak fiber Bragg grating(UWFBG)technology,we employ specialpurpose fiber optic sensing cables that can be implanted into boreholes as“nerves of the Earth”to collect data on soil temperature,water content,pore water pressure,and strain.The Xinpu landslide in the middle reach of the Three Gorges Reservoir Area in China was selected as a case study to establish a paradigm for in situ thermo-hydro-poro-mechanical monitoring.These UWFBG-based sensing cables were vertically buried in a 31 m-deep borehole at the foot of the landslide,with a resolution of 1 m except for the pressure sensor.We reported field measurements covering the period 2021 and 2022 and produced the spatiotemporal profiles throughout the borehole.Results show that wet years are more likely to motivate landslide motions than dry years.The annual thermally active layer of the landslide has a critical depth of roughly 9 m and might move downward in warmer years.The dynamic groundwater table is located at depths of 9e15 m,where the peaked strain undergoes a periodical response of leap and withdrawal to annual hydrometeorological cycles.These interface behaviors may support the interpretation of the contribution of reservoir regulation to slope stability,allowing us to correlate them to local damage events and potential global destabilization.This paper also offers a natural framework for interpreting thermo-hydro-poro-mechanical signatures from creeping reservoir bank slopes,which may form the basis for a landslide monitoring and early warning system.
基金Sponsored by the Heilongjiang Department of Education Project(Grant No.11541308)
文摘This paper focused on high-precision demodulation of wavelength shift of FBG sensor. Fiber tunable F-P filer was used as a demodulation method. 32-bit embedded processor ARM9-S3C2440 chip was used as the main controller and simulated annealing algorithm was realized on ARM to demodulate wavelength signal. Simulation results show that the simulated annealing algorithm is reliable to process analog signals on ARM chip and significant performance is achieved such as saving bandwidth,increasing the amounts of reusable fiber grating sensors in sensor system and speeding up data processing.
文摘This paper reports a fiber Bragg grating(FBG)as a biosensor.The FBGs were etched using a chemical agent,namely,hydrofluoric acid(HF).This implies the removal of some part of the cladding layer.Consequently,the evanescent field propagating out of the core will be closer to the environment and become more sensitive to the change in the surrounding.The proposed FBG sensor was utilized to detect toxic heavy metal ions aqueous medium namely,copper ions(Cu^(2+)).Two FBG sensors were etched with 20 and 40μm diameters and fabricated.The sensors were studied towards Cu^(2+)with different concentrations using wavelength shift as a result of the interaction between the evanescent field and copper ions.The FBG sensors showed a good response in terms of significant wavelength shift in corresponding to varying Cu2+concentrations when immersed in aqueous mediums.The sensors exhibited excellent repeatability towards Cu ions.The results demonstrate that the smaller FBG etching diameter,the better optical response in terms of wavelength and linearity.
基金supported by the Sichuan Provincial Natural Science Foundation(No.23NSFSC4751)。
文摘Aiming for suppressing side-mode and spectrum broadening,a slit beam-shaping method and super-Gaussian apodization processing for femtosecond laser point-by-point(PbP)inscription technology of fiber Bragg gratings(FBGs)are reported here.High-quality FBGs,featuring narrow bandwidth of less than 0.3 nm,high reflectivity above 85%,low insertion loss(0.21 dB),and low cladding loss(0.82 dB),were obtained successfully.By a semi-automatic PbP inscription process,an array consisting of six FBGs,exhibiting almost no side-mode peaks with high suppression ability and narrow bandwidth,was fabricated along three independently developed single-mode fibers with an interval of 20 mm.
基金supported by the Development Bureau of Hong Kong SAR Government,a Research Impact Fund(RIF)project(Grant No.R5037-18)a Theme-based Research Scheme Fund(TRS)project(Grant No.T22-502/18-R)a General Research Fund(GRF)projects(Grant No.PolyU 152130/19E)from Research Grants Council(RGC)of Hong Kong SAR.
文摘Hong Kong has a long history of applying masonry retaining walls to provide horizontal platforms and stabilize man-made slopes.Due to the sub-tropical climate,some masonry retaining walls are colonized by trees.Extreme weather,such as typhoons and heavy rains,may cause rupture or root failure of those trees,thus resulting in instability of the retaining walls.A monitoring and warning system for the movement of masonry retaining walls and sway of trees has been designed with the application of fiber Bragg grating(FBG)sensing technology.The monitoring system is also equipped with a solar power system and 4G data transmission devices.The key functions of the proposed monitoring system include remote sensing and data access,early warning,and real-time data visualization.The setups and working principles of the monitoring systems and related transducers are introduced.The feasibility,accuracy,serviceability and reliability of this monitoring system have been checked by in-site calibration tests and four-month monitoring.Besides,a two-level interface has been developed for data visualization.The monitoring results show that the monitored masonry retaining wall had a reversible movement up to 2.5 mm during the monitoring period.Besides,it is found that the locations of the maximum strain on trees depend on the crown spread of trees.
基金supported by the National Key Research and Development Program of China(No.2021YFC3340400)Key Laboratory of Medical Electronics and Digital Health of Zhejiang Province(No.MEDH202209)+1 种基金Natural Science Foundation of Zhejiang Province(No.LY22F050004)Zhejiang Xinmiao Talents Program(No.2022R409043).
文摘A simple quasi-distributed fiber sensing interrogation system based on random speckles is proposed for weak fiber Bragg gratings(WFBGs) in this work. Without using tunable lasers or spectrometers, a piece of multimode fiber is applied to interrogate the WFBGs relying on the wavelength sensitivity of speckles. Instead of the CCD sensor, an InGaAs quadrant detector serves as the receiver to capture the fast-changing speckle patterns. A supervised deep learning algorithm of the multilayer perceptron architecture is implemented to process speckle data and to interrogate temperature changes or dynamic strains. The proposed demodulation system is experimentally demonstrated for WFBGs with 0.1% reflectivity.The experimental results demonstrate that the new system is capable of measuring temperature change with an accuracy of 1℃ and achieving dynamic frequency of 100 Hz. This speckle-based interrogation system paves a new way for distributed WFBGs sensing with a simple design.