信号混叠是基于光纤水听器的现代声纳系统走向应用必须解决的一个关键问题。初步的实验结果已经表明,声低通滤波光纤水听器是解决信号混叠问题的一种简单且行之有效的方案。基于电-声类比理论,建立了声低通滤波光纤水听器的低频集中参量模型,利用电路分析的方法对其频响特性进行了研究。结果表明,这种光纤水听器系统与典型的二阶低通滤波电路具有相似的频响特性。为了验证理论分析的正确性,设计制作了一个简单的声低通滤波光纤水听器,并在驻波罐中对其声压灵敏度频响特性进行了测试,实验结果与数值计算的结果基本吻合。该光纤水听器低频响应非常平坦,声压灵敏度约为-141 dB,测量共振频率为985 Hz,与理论值1270 Hz基本一致。共振频率处的声压灵敏度为-126.8 dB,衰减速率约为20 dB/倍频程,3000 Hz以后的灵敏度衰减幅度大于20 dB。

Signal aliasing is a key problem in applications of modern sonar systems based on fiber-optic hydrophones. Preliminary experimental results have shown that the acoustic low-pass filtering fiber-optic hydrophone is a simple and effective anti-aliasing scheme. We construct the low frequency lumped parameter model of acoustic low-pass filtering fiber-optic hydrophone based on the theories of electro-acoustic analogy. The frequency response of the fiber-optic hydrophone is estimated using the circuit analysis method. Theoretical results show that the fiber-optic hydrophone system has the similar response characteristics as a classical two-order low-pass filtering circuit. A simple low-pass filtering fiber-optic hydrophone is designed and manufactured to test the theory. And the acoustic sensitivity frequency response is measured in a standing-wave tube. Experimental results are, on the whole, in agreement with the numerical values. The low frequency acoustic sensitivity is about -141.5 dB. The measured resonant frequency is 985 Hz, which accords well with the theoretical value of 1270 Hz. The acoustic sensitivity at resonant frequency is -126.8 dB, and the attenuation rate is about 20 dB/octave. The attenuation beyond 3 kHz is bigger than 20 dB.