Hardware Design And Implementation Of Fiber Disturbance Detection System Based On FPGA

Since the advent of low-loss single-mode optical fiber,distributed optical fiber sensing technology has developed rapidly in the field of sensing technology relying on its unique advantages.As the carrier of light and the sensitive element of sensor,optical fiber can make the continuous measurement of dynamic events possible along the optical fiber.When the disturbance is caused by the change of the environment,the location of the disturbance point can be located quickly.This technology is widely used in the fields of dynamic detection of communication optical fibers,perimeter security and intrusion detection.Disturbance refers to the transient deformation of optical fibers under external force,which is a dynamic process.Disturbance detection includes capture of perturbation events and location of perturbation positions.In this paper,a fiber disturbance detection system based on FPGA and embedded Linux is designed for the dynamic detection of communication optical fibers.The system can capture and locate the disturbance events.This paper mainly completes the following work:1)Based on the optical scattering mechanism,an improved Sagnac optical fiber sensing technology is proposed by using distributed sensing technology,combining Sagnac interference and ?-OTDR technology.This technology solves the problems of local signal demodulation and location in Sagnac interferometry,and has the advantages of high detection sensitivity and low false alarm rate.2)The hardware system of optical fiber disturbance detection based on FPGA and embedded Linux is developed,and it includes that the control part is based on embedded Linux system board,as well as laser module,state detection and indication module;the optical signal acquisition and processing part is based on FPGA,as well as detector module,ADC sampling circuit and Gigabit network circuit;and the power part converts AC to DC power.It supplies power for each module and the optical part of the improved Sagnac fiber ring.3)By using the simulation software to analyze the signal characteristics and simulate the algorithm of optical fiber disturbance events,the accumulative average and edge detection method are used to capture and locate the dynamic events of optical fibers.While ensuring positioning accuracy and system sensitivity,the real-time performance of disturbance detection is greatly improved.The transplantation of FPGA algorithm and other functional programming are completed.It can realize the functions of acquisition of ADC digital signal,processing of ADC digital signal by accumulative average and edge detection algorithm,sending of location result by serial port logic and sending of original data by UDP logic.4)The application software based on Linux system is developed,which can detect the status of each module in the whole device and communicate with the host computer in real time.The main functions are as follows: creating service terminal to provide communication and service interface for PC,setting laser working parameters,managing laser state,setting communication parameters and algorithm parameters in FPGA logic,monitoring temperature of each module,controlling cooling fan,detecting detector overload signal and controlling indicator lights.5)The system hardware and embedded software are tested.Firstly,the functions of each module are tested,and the functions of laser control,state management,parameter setting,host computer communication,data acquisition and transmission are verified respectively.Then the performance of the system for disturbance capture and location is tested.The test results show that all the indicators of the system meet the requirements of the project,which lays a good foundation for the application of the system in the field of optical fiber dynamic detection.