Research On Four-channel Fiber Optic Sensor Digital PGC Demodulation Technology

With the development of optical fiber sensing technology,Interferometric fiber optic sensors are widely used in the field of military,eavesdropping,underwater monitoring and so on due to its high resolution,high sensitivity,corrosion resistance,low cost and resisting electromagnetic interference.The demodulation method of interferometric fiber optic sensor directly influences the dynamic range,detection accuracy and other important parameters of optical fiber sensor system demodulation.Phase generated carrier(PGC)demodulation technology is the most widely used in the interferometric fiber sensor demodulation method.However,the traditional PGC-DCM demodulation algorithm is susceptible to the laser intensity disturbance.And the traditional PGC-Arctan demodulation algorithm is dependent on the modulation depth and the algorithm is limited by modulation depth.To solve these problems,we propose four-channel fiber-optic sensor digital PGC demodulation scheme based on PGCArctan and ellipse fitting algorithm which are proposed by Yang Jun and complete the hardware implementations of the PGC demodulation system.This scheme overcomes the dependence of the PGC-Arctan demodulation algorithm on the modulation depth,suppresses the harmonic distortion and expands the dynamic range of PGC demodulation system.The main works of the paper are as follows:Firstly,we describe the background and significance of the paper,introduce the current situation and the development trend of optical fiber sensor PGC demodulation algorithm and research the interference structure and the related theory,including: the sensing principle of optical fiber sensors,the principle of phase generated carrier modulation and demodulation and technical index analysis.And several improved PGC demodulation algorithms are compared and analyzed.Secondly,in order to make up for the shortcomings of the traditional PGC demodulation algorithm,we propose four-channel fiber-optic sensor digital PGC demodulation scheme and the system design indicators.The algorithm overcomes the dependence on the modulation depth,suppresses the influence of the laser intensity disturbance and non-linear error and expands the dynamic range of the modulation system.Then,we use Verilog HDL and C language to complete the design and implementation of each module of the four-channel fiber-optic sensor digital PGC demodulation algorithm in Vivado and Linux after we use Matlab for theoretical verification.Combined with Xilinx IP core,the calculation step of the tangent segmentation algorithm is optimized,the operation frequency is reduced and the hardware resource is reduced.Using Vivado HLS,the structure of elliptical fitting algorithm is improved and the system delay is reduced.Finally,we complete the design of the data acquisition board,and the system test platform is set up to perform functional verification and performance testing of the four-channel fiberoptic sensor digital PGC demodulation system.The test result shows that the design of the fourchannel fiber-optic sensor digital PGC demodulation system is correct and effective,and the four-channel fiber-optic sensor digital PGC demodulation system has a certain value in engineering.