Distributed optical fiber hydrophone based on Φ-OTDR and its field test

TLDR

The study demonstrates and field‑tests a distributed optical fiber hydrophone based on Φ‑OTDR. The system employs a sensitized optical cable with −146 dB rad/µPa/m sensitivity, a Φ‑OTDR heterodyne coherent detection setup, and an array signal‑processing model to enable spatial spectrum estimation, beamforming, and motion tracking over a 104‑m cable. This first field trial shows the DOFH’s ability for high‑accuracy acoustic imaging and indicates it could provide kilometer‑scale array coverage with meter‑level element spacing, offering broad prospects for marine acoustic detection.

Abstract

In this letter, a distributed optical fiber hydrophone (DOFH) based on Φ-OTDR is demonstrated and tested in the field. The specially designed sensitized optical cable with sensitivity up to −146 dB rad/µPa/m is introduced, and an array signal processing model for DOFH is constructed to analyze the equivalence and specificity of the distributed array of acoustic sensors. In the field test, a 104-meter-long optical cable and a Φ-OTDR system based on heterodyne coherent detection (Het Φ-OTDR) is utilized, and underwater acoustic signal spatial spectrum estimation, beamforming and motion trajectory tracking with high accuracy can be realized. As far as we know, this is the first report on the field trial of DOFH based on Φ-OTDR. The DOFH has the potential to achieve an array range of tens of kilometers, with elements spaced up to the meter level and flexible configuration, which has a broad application prospect for marine acoustic detection.