Research And Implementation Of Multi-longitudinal Mode Laser Beat Frequency Demodulation Technology Based On FPGA

In recent years,with the rapid development of optical fiber communication industry and technological breakthroughs,optical fiber laser sensors have been widely used in the fields of underwater acoustic,pressure and acceleration measurement by virtue of their advantages of high signal-to-noise ratio,high sensitivity and narrow linewidth.In order to solve the problems of high cost and slow speed of traditional fiber laser sensing demodulation system,this dissertation starts from the theory and application of fiber laser sensing technology,combines the longitudinal mode frequency demodulation and digital signal processing technology,proposes an all-electronic and high speed digital demodulation scheme design based on FPGA.The multi-longitudinal mode fiber laser sensing of annular resonator and the automatic temperature control platform were built for stress sensing testing,to verify the sensing characteristics of beat signal and clarify the principle of selecting the best beat frequency.By limiting the bandwidth of the fiber grating,the SNR of the beat frequency signal is further improved and the utilization rate of the pump light source is improved.In order to reduce the sampling rate of the stringent requirements and demodulation difficulty,select the appropriate beat frequency sense signal,based on the FPGA hardware platform,adopt a noncoherent demodulation method based on the bandpass sampling digital frequency discrimination,combined with the spectrum analyzer,oscilloscope,such as equipment for hardware debugging result verification,implements sinusoid vibration signals quickly and accurately demodulation,and it further promotes the digital transmission process of fiber laser sensing.