| Since the fiber optic hydrophone came into being, it had turned from the laboratory state to the engineering application state for the reason of the huge value for the military affairs application and civil application. The study of this thesis was devoted to the practical design and research of fiber optic hydrophone.In this thesis, the modulation and detection theory of the interferometric optical fiber transducer were expounded first. Two kind of practical detections and demodulations plan were presented, namely the phase-generated carrier (PGC) technology and the multiphase detection technology, which bases on the 3×3 coupler. Then the sensitivity and the dynamic range were analysed in detail, which were the two important technical targets of the fiber optic hydrophone system. The meaning, difference and relation about the phase sensitivity and pressure sensitivity of the system were discussed. The upper limit and lower limit (background noise) of the dynamic range were presented, and the influencing factor of the dynamic range were analysised.In order to improve the overall performance of the fiber optic hydrophone system, this thesis thoroughly researches the frequency characteristics of the low-pass filter (LPF) of the system. Take the non-distorted transmission theory as the foundation, it analysed the amplitude-frequency and phase-frequency characteristics of the LPF, and drawn the conclusion. In order to guarantee the non-distortion output of the signal, require the steep cut-off characteristic and the linear phase for the LPF. If phase-frequency characteristics of the LPF is non-linear, then may change the frequency component and interference the spectrum analysis of the output signal of the system. According to the simulation result of the system, the thesis optimized establishment of the cut-off frequency of the LPF, it enhanced the upper limit of the dynamic range. These consequences can be significant references for further research. |
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