含侧腔的机械抗混叠声低通滤波光纤水听器

报道了一种含侧腔的机械抗混叠声低通滤波光纤水听器.基于电-声类比理论建立了该光纤水听器的低频集中参量模型，画出了声学等效电路图，利用电路分析方法给出了声压传递函数表达式，并对其声学特性进行了理论分析.研究表明，该光纤水听器具有三个共振频率，由于侧腔的引入使得传递函数出现了一个零点，从而加快了第二个共振频率之后的衰减速度，可以获得更好的高频整体衰减特性.在充水驻波罐中对自行设计并制作的含侧腔的声低通滤波光纤水听器进行了测试.在50—7000 Hz频段上，该光纤水听器的声压灵敏度频响曲线与理论结果具有大致相同的变化形式，低频响应非常符合，声压灵敏度约为-140 dB（0 dB=1 rad/μPa），受低频模型精度的限制，高频响应差异较大.这为解决光纤水听器的高频混叠问题提供了一条简单可行的技术途径. 关键词： 光纤传感器 光纤水听器 声压灵敏度 低通滤波器

Mechanical anti-aliasing acoustic low-pass filtering fiber-optic hydrophones with side cavities

A novel mechanical anti-aliasing fiber-optic hydrophone with an acoustic low-pass filter of side cavities has been reported, to the best of our knowledge, for the first time. The low frequency lumped parameters model and the effective acoustic circuit of the hydrophone is constructed based on the theories of electro-acoustic analogy, and the acoustic performance is predicted by the circuit analysis methods. Theoretical results show that the hydrophone has three resonant frequencies and one inverse resonant frequency induced by the side cavities,and the hydrophone has good high frequency attenuation properties. A hydrophone with side cavities,designed and fabricated by us,is tested in a standing-wave tube filled with water. The measured frequency response curve,on the whole, has identical form as that predicted by theory, over the test frequency range of 50 to 7000 Hz. To be speaific.the low frequency responses are in good accordance,and the acoustic sensitivity is about - 140 dB re 1 rad/μPa. The high frequency responses have obvious difference, which is mainly induced by the operation limitation of the low frequency model. It is expected that this new type of fiber-optic hydrophone will work as an important class of sensors used to eliminate the aliasing in the future fiber-optic sonar systems.