This paperdetails experimental work done to quantify stress measurements made optically utilizing ordinary single mode optical fibers. Strain-induced changes of birefringence for ordinary single mode optical fiber res...This paperdetails experimental work done to quantify stress measurements made optically utilizing ordinary single mode optical fibers. Strain-induced changes of birefringence for ordinary single mode optical fiber responses are characterized against standard stress measurements in a well understand configuration. The experimental scheme for this work and the results are presented in detaial. In this paper, POssible applications for this transverse stress character of single mode fibers are also proposed.展开更多
Aiming at some security problems in railway running and the application condition of existing technology, this paper studies some issues of using fiber optic sensing technology in railway security monitoring. Through ...Aiming at some security problems in railway running and the application condition of existing technology, this paper studies some issues of using fiber optic sensing technology in railway security monitoring. Through field experiment measuring the strain of the rail and analyzing the experiment data, the method of diagnosing the health condition of rail and wheel is investigated.展开更多
An intensity-modulated, fiber Bragg grating （FBG） sensor system based on radio-frequency （RF） signal measurement is presented. The RF signal is generated at a photodetector by two modulated optical signals reflect...An intensity-modulated, fiber Bragg grating （FBG） sensor system based on radio-frequency （RF） signal measurement is presented. The RF signal is generated at a photodetector by two modulated optical signals reflected from the sensing FBG and a reference one. Bragg wavelength shift of the sensing FBG changes intensity of the RF signal by changing phase difference between the two optical signals, with temperature effect being compensated automatically by the reference FBG, Strain measurement with a maximum sensitivity of -0.34 μV/με has been achieved.展开更多
Multicore fiber(MCF)which contains more than one core in a single fiber cladding has attracted ever increasing attention for application in optical sensing systems owing to its unique capability of independent light t...Multicore fiber(MCF)which contains more than one core in a single fiber cladding has attracted ever increasing attention for application in optical sensing systems owing to its unique capability of independent light transmission in multiple spatial channels.Different from the situation in standard single mode fiber(SMF),the fiber bending gives rise to tangential strain in off-center cores,and this unique feature has been employed for directional bending and shape sensing,where strain measurement is achieved by using either fiber Bragg gratings(FBGs),optical frequency-domain reflectometry(OFDR)or Brillouin distributed sensing technique.On the other hand,the parallel spatial cores enable space-division multiplexed(SDM)system configuration that allows for the multiplexing of multiple distributed sensing techniques.As a result,multi-parameter sensing or performance enhanced sensing can be achieved by using MCF.In this paper,we review the research progress in MCF based distributed fiber sensors.Brief introductions of MCF and the multiplexing/de-multiplexing methods are presented.The bending sensitivity of off-center cores is analyzed.Curvature and shape sensing,as well as various SDM distributed sensing using MCF are summarized,and the working principles of diverse MCF sensors are discussed.Finally,we present the challenges and prospects of MCF for distributed sensing applications.展开更多
a novel structure of the pure macro- bending sensor based on the tilted fiber Bragg grating （TFBG） is proposed. The TFBG located in the half circle with the different diameters is bent at a constant angle with respe...a novel structure of the pure macro- bending sensor based on the tilted fiber Bragg grating （TFBG） is proposed. The TFBG located in the half circle with the different diameters is bent at a constant angle with respect to the tilted grating planes. With the variations of the curvature, the core-mode resonance is unchanged and the transmission power of cladding modes detected by the photodiodes varies linearly with curvature, while the ghost mode changes by the form of two-order polynomial. So we can use the transmission power of ghost mode or other cladding modes to detect bending curvature as shape sensor. From a practical point of view, the sensor proposed here is simple, low cost and easy to implement. Moreover, it is possible to make a temperature-insensitive shape sensor due to the same temperature characteristic between the core mode and the cladding modes.展开更多
Optical fiber sensor network has attracted considerable research interests for geoscience applications.However,the sensor capacity and ultra-low frequency noise limits the sensing performance for geoscience data acqui...Optical fiber sensor network has attracted considerable research interests for geoscience applications.However,the sensor capacity and ultra-low frequency noise limits the sensing performance for geoscience data acquisition.To achieve a high-resolution and lager sensing capacity,a strain sensor network is proposed based on phase-sensitive op-tical time domain reflectometer(φ-OTDR)technology and special packaged fiber with scatter enhanced points(SEPs)ar-ray.Specifically,an extra identical fiber with SEPs array which is free of strain is used as the reference fiber,for com-pensating the ultra-low frequency noise in theφ-OTDR system induced by laser source frequency shift and environment temperature change.Moreover,a hysteresis operator based least square support vector machine(LS-SVM)model is in-troduced to reduce the compensation residual error generated from the thermal hysteresis nonlinearity between the sensing fiber and reference fiber.In the experiment,the strain sensor network possesses a sensing capacity with 55 sensor elements.The phase bias drift with frequency below 0.1 Hz is effectively compensated by LS-SVM based hyster-esis model,and the signal to noise ratio(SNR)of a strain vibration at 0.01 Hz greatly increases by 24 dB compared to that of the sensing fiber for direct compensation.The proposed strain sensor network proves a high dynamic resolution of 10.5 pε·Hz-1/2 above 10 Hz,and ultra-low frequency sensing resolution of 166 pεat 0.001 Hz.It is the first reported a large sensing capacity strain sensor network with sub-nεsensing resolution in mHz frequency range,to the best of our knowledge.展开更多
文摘This paperdetails experimental work done to quantify stress measurements made optically utilizing ordinary single mode optical fibers. Strain-induced changes of birefringence for ordinary single mode optical fiber responses are characterized against standard stress measurements in a well understand configuration. The experimental scheme for this work and the results are presented in detaial. In this paper, POssible applications for this transverse stress character of single mode fibers are also proposed.
文摘Aiming at some security problems in railway running and the application condition of existing technology, this paper studies some issues of using fiber optic sensing technology in railway security monitoring. Through field experiment measuring the strain of the rail and analyzing the experiment data, the method of diagnosing the health condition of rail and wheel is investigated.
基金supported by the National Natural Science Foundation of China under Grant No. 60807021.
文摘An intensity-modulated, fiber Bragg grating （FBG） sensor system based on radio-frequency （RF） signal measurement is presented. The RF signal is generated at a photodetector by two modulated optical signals reflected from the sensing FBG and a reference one. Bragg wavelength shift of the sensing FBG changes intensity of the RF signal by changing phase difference between the two optical signals, with temperature effect being compensated automatically by the reference FBG, Strain measurement with a maximum sensitivity of -0.34 μV/με has been achieved.
文摘Multicore fiber(MCF)which contains more than one core in a single fiber cladding has attracted ever increasing attention for application in optical sensing systems owing to its unique capability of independent light transmission in multiple spatial channels.Different from the situation in standard single mode fiber(SMF),the fiber bending gives rise to tangential strain in off-center cores,and this unique feature has been employed for directional bending and shape sensing,where strain measurement is achieved by using either fiber Bragg gratings(FBGs),optical frequency-domain reflectometry(OFDR)or Brillouin distributed sensing technique.On the other hand,the parallel spatial cores enable space-division multiplexed(SDM)system configuration that allows for the multiplexing of multiple distributed sensing techniques.As a result,multi-parameter sensing or performance enhanced sensing can be achieved by using MCF.In this paper,we review the research progress in MCF based distributed fiber sensors.Brief introductions of MCF and the multiplexing/de-multiplexing methods are presented.The bending sensitivity of off-center cores is analyzed.Curvature and shape sensing,as well as various SDM distributed sensing using MCF are summarized,and the working principles of diverse MCF sensors are discussed.Finally,we present the challenges and prospects of MCF for distributed sensing applications.
基金supported by the National 863 Program under Grant No. 2006AA01Z217the National Natural Science Foundation of China under Grant No. 60736039 and 60572018the Technological Tackle Key Problem Project of Tianjin under Grant No. 07ZCKFGX00200.
文摘a novel structure of the pure macro- bending sensor based on the tilted fiber Bragg grating （TFBG） is proposed. The TFBG located in the half circle with the different diameters is bent at a constant angle with respect to the tilted grating planes. With the variations of the curvature, the core-mode resonance is unchanged and the transmission power of cladding modes detected by the photodiodes varies linearly with curvature, while the ghost mode changes by the form of two-order polynomial. So we can use the transmission power of ghost mode or other cladding modes to detect bending curvature as shape sensor. From a practical point of view, the sensor proposed here is simple, low cost and easy to implement. Moreover, it is possible to make a temperature-insensitive shape sensor due to the same temperature characteristic between the core mode and the cladding modes.
基金financial supports from the National Natural Science Foundation of China(NSFC)(No.61922033&61775072)Major Technology Innovation of Hubei Province(2019AAA053)+1 种基金Foundation for Innovative Research Groups of Hubei Province of China(2018CFA004)Innovation Fund of WNLO。
文摘Optical fiber sensor network has attracted considerable research interests for geoscience applications.However,the sensor capacity and ultra-low frequency noise limits the sensing performance for geoscience data acquisition.To achieve a high-resolution and lager sensing capacity,a strain sensor network is proposed based on phase-sensitive op-tical time domain reflectometer(φ-OTDR)technology and special packaged fiber with scatter enhanced points(SEPs)ar-ray.Specifically,an extra identical fiber with SEPs array which is free of strain is used as the reference fiber,for com-pensating the ultra-low frequency noise in theφ-OTDR system induced by laser source frequency shift and environment temperature change.Moreover,a hysteresis operator based least square support vector machine(LS-SVM)model is in-troduced to reduce the compensation residual error generated from the thermal hysteresis nonlinearity between the sensing fiber and reference fiber.In the experiment,the strain sensor network possesses a sensing capacity with 55 sensor elements.The phase bias drift with frequency below 0.1 Hz is effectively compensated by LS-SVM based hyster-esis model,and the signal to noise ratio(SNR)of a strain vibration at 0.01 Hz greatly increases by 24 dB compared to that of the sensing fiber for direct compensation.The proposed strain sensor network proves a high dynamic resolution of 10.5 pε·Hz-1/2 above 10 Hz,and ultra-low frequency sensing resolution of 166 pεat 0.001 Hz.It is the first reported a large sensing capacity strain sensor network with sub-nεsensing resolution in mHz frequency range,to the best of our knowledge.
