Optical Path And Algorithm Improvement Of Heterodyne Demodulation For Fiber-optic Hydrophone

With its superior performance,fiber optic hydrophones play an important role in modern anti-submarine operations and marine resource exploration.The research on optical fiber hydrophones has gradually matured after more than 40 years of development.However,there are still many areas to be improved in optical fiber hydrophones.This paper analyzes the basic original path of optical heterodyne detection and designs a fiber-optic hydrophone system based on the principle of heterodyne detection.It focuses on the analysis of several important parts of the demodulation optical path,the acousto-optic modulator and its driver are the premise to achieve the stable heterodyne frequency.And the extraction of the heterodyne reference signal is the most important to correctly demodulate the signal.The deficiencies of the existing demodulation algorithms are proposed and improved,so that the demodulation results are no longer affected by the light intensity disturbance,and then the feasibility and advantages of the new demodulation scheme are demonstrated using simulation analysis.Based on the demodulation optical path and demodulation algorithm,an experimental system was established.In the experiment,PZT controlled by a signal generator is used to simulate the optical fiber detection acoustic signal after the sensitization process.Using a signal generator to apply a sine wave signal with an amplitude of 100 m V and a frequency of1 k Hz,5k Hz,15 k Hz,and 30 k Hz to the PZT,the system can correctly demodulate the corresponding results;then ensure that the frequency of the signal is 5k Hz,and the amplitudes are 100 m V,200 m V and 500 m V sine wave signal.At this time,the system can also demodulate the correct result.Both theoretical analysis and experimental results demonstrate that the experimental system can demodulate signals with different frequencies and amplitudes.