Ultra-Thin Fiber Laser Hydrophone With Static Pressure Equalization and Improved Response

In this letter, we propose a new scheme that combines a capillary tube with an elastic cavity to develop a thin fiber laser hydrophone (FLH) with static pressure equalization, enhanced dynamic pressure sensitivity and broadband flat response. We demonstrate the improvement on the hydrophone response characteristics by introducing the compensation structure into a diaphragm-based FLH. A hydrophone prototype with a diameter of 7.2 mm was packaged and the hydrophone has a flat pressure sensitivity of 9×10 ^-3 pm/Pa (120 dB re Hz/Pa) over a bandwidth from 40 Hz to 4 kHz. The static pressure sensitivity is - 11×10 ^-6 pm/Pa in the measurement range of 0 to 3 MPa.