Research On Location And Reconstruction Of Vibration Signal Based On ?-OTDR Optical Fiber System

The phase-sensitive optical time domain reflectometer(?-OTDR)uses optical fiber as a transmission and sensing medium to monitor vibration events along the sensing fiber and can be applied to long-distance health monitoring of large infrastructure such as bridges,tunnels and locations of monitored facilities.Since mechanical failure is generally accompanied by changes in vibration,the detection system is required to accurately locate the vibration and obtain accurate information of the vibration signal to distinguish the type of failure.Due to the influence of the external environment and the system's own noise,the reliability and accuracy of the monitoring system for complex vibration signal positioning is low,while the Rayleigh backscattering signal is weak,resulting in low system signal-to-noise,which further makes the vibration signal reconstruction difficult.Based on in depth analysis and research of noise and related signal processing methods of ?-OTDR system,this paper proposes a optical fiber vibration signal extraction and processing technology based on higher-order cumulants algorithm,through the statistical characteristics of the vibration signals to be measured from the background noise.The main contents of the paper are as follows:1.Outline the basic working principle,development process and research status of?-OTDR system,discuss and analyze the mechanism and key technical indicators of the system when detecting external vibration,and lay the foundation for the subsequent research on signal processing methods.2.A signal processing technique based on higher-order cumulants algorithm for?-OTDR system is proposed.In-depth study of the cumulants application characteristics of different orders,and the use of third-order cumulant to detect the vibration along the fiber.The system is built.In the laboratory environment,the piezoelectric ceramic tube is used to simulate the vibration signal,and the vibration condition at various positions along the sensing fiber is converted into the corresponding higher-order cumulants value,which improves the system positioning reliability and the vibration center positioning accuracy.The experiment uses 100ns pulsed light to detect.The results show that the higher-order cumulants signal-to-noise ratio of the vibration position is 16.7dB and the spatial resolution is about 5m.3.The method of reconstruction of vibration signal is studied and analyzed.The same sensing position of multiple acquisition order and related operations are processed,and the vibration signal is reconstructed by iterative method.