Development Of Fiber Grating Dynamic Demodulation System Based On FPGA

With the development of optical fiber sensing technology,there are more and more kinds of fiber grating sensors whose field of application is more and more extensive.The development of fiber grating sensor has greatly promoted the development of fiber grating demodulation system.The demodulation systems based on different demodulation principles have been developed one after another.However,for some special dynamic measurement signals,the performance of existing demodulation system is not good.Therefore,it is of great significance to develop a demodulation equipment with high accuracy,wide range and high frequency of demodulation.Due to the development of semiconductor lasers,it has become a research hotspot that bases fiber grating demodulation system on tunable semiconductor lasers in recent years.It is analyzed that different demodulation systems have advantages and disadvantages in this paper by investigating the existing demodulation methods.In order to meet the demodulation requirements of fiber grating sensor,a design scheme is proposed that bases fiber grating demodulation system based on tunable laser,whose core control chip is FPGA.In this paper,the main research contents include:the design and construction of the optical system,the design and implementation of the hardware circuit and the programming of the upper computer software of demodulation system.Firstly,it is analyzed that bases the principle of fiber grating sensor demodulation on tunable sensor,and the whole demodulation system is designed.The optical system of demodulation system is realized.and the four-channel simultaneous demodulation index of the demodulation system is realized by the 1×4 coupler module.Secondly,the hardware circuit of the demodulation system is designed and implemented.including design of power module,FPGA controller module design,tunable laser input current circuit,tunable laser temperature control circuit,serial port and network card communication circuit design and photoelectric conversion circuit.In order to improve the demodulation frequency of demodulation system as much as possible.high-speed components are selected for electronic devices.In software aspect,for hardware circuit module,the control program based on Verilog language is compiled to realize the normal operation of each hardware circuit module and the overall demodulation function.At the same time,the upper computer software of demodulation system based on C++ is designed to realize the functions of displaying demodulation data and storing demodulation dataFinally,for the developed demodulation system,relevant performance test experiments are carried out,including verifying range of demodulation,accuracy of demodulation,stability of demodulation and frequency of demodulation.The experimental results show that the demodulation system has excellent performance.The range of demodulation is 1525nm-1565nm.The accuracy of demodulation is less than±3pm.The stability of demodulation is less than±1pm and the speed of demodulation is able to reach 1kHzIn summary,the situation of fiber grating sensor and fiber grating demodulation system is studied in this paper at home and abroad.It is developed that bases a fiber grating demodulation system on tunable semiconductor laser.The design of optical path,hardware circuit,software and host computer program of the demodulation system are completed.The demodulation system has a relatively ideal demodulation performance after the relevant performance test and verification.