Design Of Phase Sensitive Vibration Sensing System Based On FPGA

With the rapid growth of China's economy and the deepening of informatization,the requirements of sensors and sensing systems in various industries have gradually increased.Distributed optical fiber sensing technology takes optical fiber as sensing medium and integrates sensing and transmission.It has the advantages of long detection distance,high accuracy,intrinsic safety,antiinterference and corrosion resistance.It plays an increasingly important role in large-scale engineering,aerospace,shipping industry,power industry and other fields.Phase sensitive optical time domain reflectometer is one of distributed optical fiber sensing technologies The single-time measurement can acquire the vibration information in the entire fiber region,and distinguish the multiple characteristics of the vibration event.Therefore,it has unique advantages in vibration detection.However,with the increase of the sensing distance,the improvement of the detection performance brings about the problems of huge vibration data and limitation of processing speed,which restricts the further development of the phase sensitive optical time domain reflectometer technology.To solve the above problems,a phase-sensitive vibration sensing system based on FPGA is proposed.Through the advantages of FPGA architecture,the functions of parallel execution,high flexibility and fast processing speed can be used to significantly improve the phase sensitive vibration sensing system.The vibration data is demodulated in real time to locate the position of the vibration source.The paper mainly studies from the following aspects:(1)The mechanism of optical time domain reflection is analyzed theoretically,and the related principles of demodulation of vibration information are expounded.Based on this,a phase sensitive vibration sensing system is designed and built.At the same time,the key performance parameters of the system are analyzed.(2)The data characteristics of vibration sensing signal are analyzed,and the implementation scheme of hardware circuit of FPGA is determined.Synchronous Triggering waveform acquisition scheme is proposed to ensure the stable acquisition of detection waveform.Pipeline Design signal processing scheme is proposed to realize real-time processing of sensing signal.Universal Serial Bus data transmission scheme is proposed to complete high-speed transmission of vibration data.(3)The monitoring software based on MFC is designed and developed.The operation control and data analysis of the sensor system are realized.The data cloud storage function is designed to improve data security.In addition,a graphical interactive interface is compiled,and the performance of the software is optimized.Reliability design is carried out to ensure the long-term and stable execution of the software.(4)Based on the above work,the system performance test and analysis are completed.The sensing distance,spatial resolution,positioning error and frequency response of the system are measured by experiments.The integrated design of the system was carried out,and the engineering prototype was built.The prototype was sent to the coal bed methane pipeline for field test.Through the above research,the phase-sensitive vibration sensing system based on FPGA can detect the vibration status in the whole sensing link in real time,realize the identification and early warning of disturbance behavior,and provide a new solution for real-time detection of vibration signals in long sensing distance and large detection range.