A method to interrogate fiber Bragg grating vibration sensor by narrow line width light is demonstrated. The interrogation scheme takes advantage of the intensity modulation of narrow spectral bandwidth light, such as...A method to interrogate fiber Bragg grating vibration sensor by narrow line width light is demonstrated. The interrogation scheme takes advantage of the intensity modulation of narrow spectral bandwidth light, such as distributed feedback laser, when a reflection or transmission spectrum curve of an fiber Bragg grating （FBG） moves due to the strain which is applied on the sensor. The sensor＇s response to accelerating frequency and amplitude is measured by experiment. The factors which have impacts on the sensitivity of the interrogation system are also discussed.展开更多
This article presents a high-speed distributed vibration sensing based on Mach-Zehnder-OTDR （optical time-domain reflectometry）. Ultra-weak fiber Bragg gratings （UWFBG）, whose backward light intensity is 2-4 order...This article presents a high-speed distributed vibration sensing based on Mach-Zehnder-OTDR （optical time-domain reflectometry）. Ultra-weak fiber Bragg gratings （UWFBG）, whose backward light intensity is 2-4 orders of magnitude higher than that of Rayleigh scattering, are used as the reflection markers. A medium-coherence laser can substitute conventional narrow bandwidth source to achieve an excellent performance of distributed vibration sensing since our unbalanced interferometer matches the interval of UWFBGs. The 3 m of spatial resolution of coherent detection and multiple simultaneous vibration sources locating can be realized based on OTDR. The enhanced signal to noise ratio （SNR） enables fast detection of distributed vibration without averaging. The fastest vibration of 25 kHz and the slowest vibration of 10Hz can be detected with our system successfully, and the linearity is 0.9896 with a maximum deviation of 3.46nε.展开更多
One of the key technologies for optical fiber vibration pre-warning system （OFVWS） refers to identifying the vibration source accurately from the detected vibration signals. Because of many kinds of vibration source...One of the key technologies for optical fiber vibration pre-warning system （OFVWS） refers to identifying the vibration source accurately from the detected vibration signals. Because of many kinds of vibration sources and complex geological structures, the implement of identifying vibration sources presents some interesting challenges which need to be overcome in order to achieve acceptable performance. This paper mainly conducts on the time domain and frequency domain analysis of the vibration signals detected by the OFVWS and establishes attribute feature models including an energy information entropy model to identify raindrop vibration source and a fundamental frequency model to distinguish the construction machine and train or car passing by. Test results show that the design and selection of the feature model are reasonable, and the rate of identification is good.展开更多
Optical fiber vibration is detected by the coherent optical time domain reflection technique. In addition to the vibration signals, the reflected signals include clutters and noises, which lead to a high false alarm r...Optical fiber vibration is detected by the coherent optical time domain reflection technique. In addition to the vibration signals, the reflected signals include clutters and noises, which lead to a high false alarm rate. The ＂cell averaging＂ constant false alarm rate algorithm has a high computing speed, but its detection performance will be declined in nonhomogeneous environments such as multiple targets. The ＂order statistics＂ constant false alarm rate algorithm has a distinct advantage in multiple target environments, but it has a lower computing speed. An intelligent two-level detection algorithm is presented based on ＂cell averaging＂ constant false alarm rate and ＂order statistics＂ constant false alarm rate which work in serial way, and the detection speed of ＂cell averaging＂ constant false alarm rate and performance of ＂order statistics＂ constant false alarm rate are conserved, respectively. Through the adaptive selection, the ＂cell averaging＂ is applied in homogeneous environments, and the two-level detection algorithm is employed in nonhomogeneous environments. Our Monte Carlo simulation results demonstrate that considering different signal noise ratios, the proposed algorithm gives better detection probability than that of ＂order statistics＂.展开更多
A new type optical fiber sensor--Tip timing Sensor is introduced in this paper. It is mostly used in vibration measurement of turbine blade, which can realize real-time and non-contact measurement.
基金supported by the 11th Five Years Key Programs for Science and Technology Development of China under Grant No. 2006BAK04B02Natural Science Foundation of Shandong Province under Grant No. 2006ZRC01022.
文摘A method to interrogate fiber Bragg grating vibration sensor by narrow line width light is demonstrated. The interrogation scheme takes advantage of the intensity modulation of narrow spectral bandwidth light, such as distributed feedback laser, when a reflection or transmission spectrum curve of an fiber Bragg grating （FBG） moves due to the strain which is applied on the sensor. The sensor＇s response to accelerating frequency and amplitude is measured by experiment. The factors which have impacts on the sensitivity of the interrogation system are also discussed.
基金This work was supported in part by the National Natural Science Foundation of China （Gram No. 61735031）, Natural Science Foundation of Hubei Province of China （Grant No. 2018CFA056）, and the Excellent Dissertation Cultivation Funds of Wuhan University of Technology （Grant No. 2017-YS-057）.
文摘This article presents a high-speed distributed vibration sensing based on Mach-Zehnder-OTDR （optical time-domain reflectometry）. Ultra-weak fiber Bragg gratings （UWFBG）, whose backward light intensity is 2-4 orders of magnitude higher than that of Rayleigh scattering, are used as the reflection markers. A medium-coherence laser can substitute conventional narrow bandwidth source to achieve an excellent performance of distributed vibration sensing since our unbalanced interferometer matches the interval of UWFBGs. The 3 m of spatial resolution of coherent detection and multiple simultaneous vibration sources locating can be realized based on OTDR. The enhanced signal to noise ratio （SNR） enables fast detection of distributed vibration without averaging. The fastest vibration of 25 kHz and the slowest vibration of 10Hz can be detected with our system successfully, and the linearity is 0.9896 with a maximum deviation of 3.46nε.
文摘One of the key technologies for optical fiber vibration pre-warning system （OFVWS） refers to identifying the vibration source accurately from the detected vibration signals. Because of many kinds of vibration sources and complex geological structures, the implement of identifying vibration sources presents some interesting challenges which need to be overcome in order to achieve acceptable performance. This paper mainly conducts on the time domain and frequency domain analysis of the vibration signals detected by the OFVWS and establishes attribute feature models including an energy information entropy model to identify raindrop vibration source and a fundamental frequency model to distinguish the construction machine and train or car passing by. Test results show that the design and selection of the feature model are reasonable, and the rate of identification is good.
文摘Optical fiber vibration is detected by the coherent optical time domain reflection technique. In addition to the vibration signals, the reflected signals include clutters and noises, which lead to a high false alarm rate. The ＂cell averaging＂ constant false alarm rate algorithm has a high computing speed, but its detection performance will be declined in nonhomogeneous environments such as multiple targets. The ＂order statistics＂ constant false alarm rate algorithm has a distinct advantage in multiple target environments, but it has a lower computing speed. An intelligent two-level detection algorithm is presented based on ＂cell averaging＂ constant false alarm rate and ＂order statistics＂ constant false alarm rate which work in serial way, and the detection speed of ＂cell averaging＂ constant false alarm rate and performance of ＂order statistics＂ constant false alarm rate are conserved, respectively. Through the adaptive selection, the ＂cell averaging＂ is applied in homogeneous environments, and the two-level detection algorithm is employed in nonhomogeneous environments. Our Monte Carlo simulation results demonstrate that considering different signal noise ratios, the proposed algorithm gives better detection probability than that of ＂order statistics＂.
文摘A new type optical fiber sensor--Tip timing Sensor is introduced in this paper. It is mostly used in vibration measurement of turbine blade, which can realize real-time and non-contact measurement.
