Development Of High Performance Distributed Optical Fiber Vibration Sensing System Based On ?-OTDR

The distributed optical fiber vibration sensing system based on the ?-OTDR has the performance of long distance,anti-interference,continuous perception of external information,monitoring and identification of intrusion,etc.So it can be widely used in perimeter security,large facility health monitoring,pipeline protection and cable safety monitoring,etc.This paper is based on the work accumulation of the distributed optical fiber vibration sensor system of the research group,and carries out the development of the high-performance distributed optical fiber vibration sensing system for engineering application.Firstly,this paper presents a distributed optical fiber vibration sensing system overall scheme and signal processing subsystem architecture,and designs a signal processing subsystem hardware upgrade scheme aiming at the signal sampling,processing and transmission with high speed requirements.Aiming at the influence of optical pulse on location accuracy,resolution,sensitivity and other indicators,a method for improving the performance of system by time-sharing controling optical pulse width is put forward.Aiming at the demand of long-distance and continuous sensing,this paper presents a scheme to adjust the Raman amplification and signal adaptive gain equalization.Aiming at the influence of wind and rain and other bad factors,a vibration point localization algorithm based on disturbance signal feature extraction is proposed.Then,the hardware circuit of the signal processing subsystem is designed,including light sending and receiving module and FPGA signal processing module.And the chip selection of each module and the schematic diagram design are analysised and determined.A high-stability and high-sensitivity optical transceiver module is developed,and the sensitivity is about-50 dbm.The FPGA signal acquisition and processing module is customized.And the module has four ADC and DAC ports,GPIO interfaces and a PCIe x4 Gen2.0 interface.The main frequency is 250 MHz,and the transmission rate of PCIe can reach 2000MB/s.The performance meets the requirements.The third generation system is further developed.Further,functional test and performance analysis are carried out on each module,and the work of each module is normal.Then the system test and analysis is carried out.Using the time-sharing optical pulse width control method to calculate the positioning accuracy is better than the case of a single pulse width,and the method can compensate for the defects of low sensitivity and weak signal strength at long distance.Using signal adaptive gain equalization adjustment method,the whole trace line is almost flattened,and the signal at long distance is amplified.Therefor the large dynamic range sensing is realized without saturation.For the positioning algorithm based on the disturbance signal feature extraction,this paper collects data for the simulation calculation under the heavy rain.The result can accurately alarm the intruding events.The missing report rate is 0,and the false alarm rate is less than 2%,and the positioning accuracy is 20 m,which proves that the algorithm can effectively filter the ambient noise and reduce the false alarm rate.In the end,this paper introduces a set of high performance distributed optical fiber vibration sensing engineering demonstration system based on the ?-OTDR in the perimeter of a Yuhua start-up park in Nanjing.Firstly,the scene and demand of the engineering site are analyzed,and the design scheme of the demonstration system is given.Then,the system's fiber optic cable layout and terminal installation are completed.Finally,the functions of the system are tested,and the experimental results are analyzed.