A high-sensitivity and low-noise fiber-optic EFPI hydrophone array for underwater acoustic detection

A time-division multiplexed (TDM) array system based on extrinsic Fabry-Perot interferometer (EFPI) hydrophones is presented. To achieve high-precision, low-noise underwater acoustic detection, a miniaturized probe design and a wavelength diversity averaging demodulation scheme are employed. The EFPI hydrophone structure and packaging process have been optimized to ensure high sensitivity and uniformity across the array. The fabricated device exhibits a sensitivity of –160 dB re 1 rad/ μ Pa, with fluctuation within ± 2 dB, while its dimensions are reduced to ϕ 6 × 8 mm. By adopting the wavelength diversity averaging demodulation scheme, array noise is significantly reduced and crosstalk is effectively suppressed. All array elements show noise levels below –97.27 dB at 1 kHz, and a flat noise floor is maintained across the frequency range of 1–2000 Hz. A four-element fiber-optic EFPI hydrophone TDM array is constructed and evaluated under both laboratory and lake conditions. Stable frequency response and omnidirectional directivity are confirmed, along with excellent linearity. Field tests demonstrate correlation coefficients exceeding 0.9796 when compared with a standard piezoelectric hydrophone. Line spectrum signals emitted from an active vessel are successfully detected, demonstrating the capability for underwater target identification. The proposed system offers outstanding acoustic sensing performance, characterized by compact size, high sensitivity, and low noise. Considerable application potential in marine exploration, unmanned platforms, and environmental monitoring is indicated.