Research On High Speed Fiber Bragg Grating Demodulation Based On FPGA And Sawtooth Spectral Filter

As the optical information science and technology developing in recent years, many researches focus on optical fiber sensing technology at home and abroad. Fiber Bragg grating is important in the field of fiber sensing device and widely used in aerospace, shipping, Bridges, tunnels construction, petroleum chemical industry, medicine and electromagnetic interference. The wavelength demodulation technology is the key in fiber sensing system.In this paper, starting from the concept of FBG sensing theory, we analyze and research FBG wavelength demodulation scheme and put forward a high speed demodulation system. The system’s core optical filter is based on VIPA and using FPGA as data acquisition and signal processing.The main work of this paper is as follows:(1) Based on fiber Bragg grating sensing applications, we introduce the development of high speed demodulation system. The current advantages of FBG sensing technology in practical application and the problems need to be solved are analyzed. Based on the existing FBG demodulation method, comparing the advantages and disadvantages of the principle of different demodulation schemes.(2) Study the basic theory of VIPA and optimize the sawtooth spectral filter based on VIPA with numerical analysis. The modified structure of the JAWS filter improves the linearity and duty ratio. The structure is simpler and the entire optical path length is reduced to10cm. The loss is reduced to3dB with transmission working mode.(3) The principle of FPGA, development process and hardware descriptive language are introduced in detail. The high speed demodulation system is based on FPGA and sawtooth spectral filter. The system adopts differential detection structure, which improves the system anti-interference ability. Design the FPGA modules with Verilog programming language. Simulate and verify all modules with ISE development platform. Build the test environment to verify the function of high speed fiber Bragg grating demodulation system based on FPGA and sawtooth spectral filter.