Fiber Bragg Grating Hydrophone Based on Helical Tube Equilibrium Static Pressure

Abstract

The invention relates to an optical fiber hydrophone, and particularly discloses an optical fiber grating hydrophone based on a spiral tube balanced static pressure. The fiber grating hydrophone includes a cylindrical rigid tube with an open end, and is characterized in that: the opening end of the rigid tube is equipped with a sound-sensitive diaphragm and an end cover is connected to the port, and a sound-transmitting tube is opened on the side wall of the end cover. The inner wall of the rigid cylinder is equipped with an elastic compensator close to the sound-sensitive diaphragm; the inner axis of the rigid cylinder is installed with a fiber grating, one end of the fiber grating is connected to the sound-sensitive diaphragm, and the other end is connected to the closed end of the rigid cylinder There is a communication hole on the side wall of the rigid cylinder, the spiral tube is installed in the rigid cylinder, one end of which is opened to connect to the outside of the rigid cylinder through the communication hole, and one end is opened in the rigid cylinder. The invention realizes high dynamic sensitivity and static pressure balance in a small volume; increases the length of the tube in an effective space, reduces the high-pass cut-off frequency, expands the low-frequency bandwidth, and greatly improves reliability.

Description

[0001] (1) Technical field [0002] The invention relates to an optical fiber hydrophone, in particular to an optical fiber grating hydrophone based on a spiral tube balancing static pressure. [0003] (2) Background technology [0004] Optical fiber hydrophone is an instrument that detects sound in water by using the light transmission characteristics of optical fiber and the modulation effect generated by the sound pressure of the surrounding environment. Compared with traditional electromagnetic hydrophones, optical fiber hydrophones have the following advantages: high sound pressure sensitivity, no electromagnetic interference, small size, waterproof and corrosion resistance, and both sensing and transmission. It has good application prospects in resource exploration, underwater navigation, marine defense and other fields. [0005] At present, the main technical solutions of fiber optic hydrophones include intensity modulation type, interference type, fiber grating type, e...

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Problems solved by technology

[0012] (1) Complex structure, bulky volume, limited working water depth, and low reliability. For example, in the scheme proposed by Steven Goodman, the volume of the airbag is large, which is not conducive to the miniaturization of the hydrophone structure and affects practicality; the volume of the airbag is the cavity of the hydrophone When the volume is 5 times, the theoretical maximum water depth is only 50m; the airbag is large and easily damaged;

[0013] (2) The contradiction between balancing static pressure and maintaining high dynamic sensitivity, such as the scheme proposed by Zhang Wentao et al. When the hydrostatic pressure is large enough to completely fill the cavity with water, due to the incompressibility of water, the piston will It is difficult to deform under the action, and the sensitivity and amplitude-frequency characteristics will deteriorate; there are long holes in the side wall of the hydrophone support tube, and the fiber grating is exposed to the external fluid and is easily damaged;

[0014] (3) Low-frequency characteristics. The hydrophone’s balanced static pressure is characterized by high-pass filtering in terms of response characteristics. Therefore, the sensitivity is reduced in the frequency band below the high-pass cut-off frequency. The detection ability of extremely low-frequency underwater acoustic signals and infrasound signals is insufficient. How to reduce High-pass cut-off frequency, to extend the low-frequency frequency range, is a technical problem that needs to be solved

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