The Research Of Fiber Grating Demodulation System Based On FPGA And Fabry-Perot Filter

With the continuous development of optical communication technology and the optical fiber technology in recent years,fiber bragg grating sensor is a new type of fiber optical sensors,leading a new research direction in the field of modern sensing.Compared with the electronic sensors,it has the advantage of high accuracy,small size,corrosion resistance,distributed sensing,etc.It has a broad prospect of application in aerospace,construction,petrochemical,transportation and power fileds.In the future war,precision guidance and defense in the space field are extremely important.In order to acquiring accurate positioning of the target objects in complex space environment,simulate the stress and strain distribution of the target location.The FBG sensor array is used to measure the strain at different positions of the target.and then determine the target position by algorithm.Demodulation technology is the key to the measurement accuracy and speed to achieve the demodulation of FBG sensor signal.This article designes a fiber grating demodulation system based on FPGA and fabry-perot filter,including the sensor module,real-time demodulation hardware module,FPGA logic module.Firstly,select the appropriate optical model of the light source,the tunable filter,and the etalometere;build up an optical testing system.Secondly,complete the design of hardware circuits based on high performance FPGA,including the design of optical signal I/V conversion and amplification circuit,data acquisition circuit and the drive circuit of F-P filter.And analyze the peak algorithm of grating reflection spectrum peak algorithm,comparing the demodulation accuracy,processing speed,and occupied internal resources of Gaussian polynomia and centroid algorithm,Finally we chose the centroid algorithm that is suitable for the system.According to the nonlinear characteristics of F-P filter,the linear compensation is carried out by using the direct frequency synthesis technique in FPGA.and the nonlinear effect of the PZT is greatly improved.To solve the problem of the light source power instability,a double overlap compensation algorithm is proposed to ensure that the optical signal is transmitted into the circuit with a good signal-to-noise ratio.Finally,it finishes the vertication of the demodulation system designed in this paper.Comparing the demodulation results with the data output from the spectrometer.The results show that the temperature measurement error of the grating sensor is within 0.32 degrees,which meets the requirements.