Membrane-based fibre Fabry-Perot cavity hydrophone with high sensitivity

In this paper, a high-sensitivity fibre Fabry Perot (FP) cavity hydrophone is investigated, which uses a metal film as the sensitive acoustic wave element. The end face of the optical fibre is coated with a high refractive index dielectric film to form an interference structure of the FP cavity. And water is used to fill the FP cavity to balance the pressure difference between the inside and outside of the cavity. The sensitivity, frequency response, and hydrostatic pressure resistance of fibre FP cavity hydrophones are characterized with self-built setup. The membrane-based fibre FP cavity hydrophone showed a high sensitivity of -137 dB re 1V/μPa@100 Hz, and can withstand hydrostatic pressure up to 120 Mpa, which is a depth of 12000 m water.