Development Of Phase-Shifted Fiber Bragg Grating Resonance Peak Wavelength Demodulation Circuit Based On FPG

PS-FBG(Phase Shifted Fiber Bragg Grating)is a special type of fiber grating,which has important applications in high-frequency vibration and high-precision measurement.Because the linewidth of PS-FBG’s resonance peak is very narrow,usually on the order of pm traditionally.It is difficult to effectively demodulate the resonant peak wavelength with the proposed wavelength demodulation scheme,and a different wavelength demodulation scheme is urgently needed.Based on the overview of PS-FBG development history and resonant peak wavelength demodulation technology,this paper analyzes the advantages and disadvantages of different resonant peak wavelength demodulation,and proposes FPGA as the core device based on PDH(Pound-Drever-Hall)resonant peak wavelength demodulation scheme of frequency locking method,designed and built a PDH frequency locking demodulation system including tunable narrow linewidth fiber laser,polarization controller,analog mixer and digital-to-analog conversion control circuit,through tunable laser scanning the PS-FBG resonance peak obtains a stable error signal,and the wavelength demodulation signal is transmitted to the PC through the Gigabit Ethernet port for further analysis and processing.The feasibility of the frequency-locked demodulation scheme was verified,the PDH frequency-locked wavelength demodulation process was established,the accuracy of wavelength demodulation was analyzed,and on this basis,the function of mixing and low-pass filtering analog devices in the PDH frequency-locked demodulation circuit was digitized.The research to continue to improve the digitization and integration of the demodulation circuit.In summary,FPGA is the core digital-to-analog control tunable laser,combined with the mixing circuit can realize PDH frequency-locked wavelength demodulation,which provide the basis for further miniaturization and modularization of the PS-FBG resonant peak wavelength demodulation system.