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Detecting hydro-acoustic signals using Distributed Acoustics Sensing technology

Distributed Acoustic Sensing (DAS) is a relatively new technology that transforms fiber optic cables, typically used for telecommunications, into dense sensor arrays, capable of meter-scale recordings up to ∼100 km. The interest in these technologies for ocean exploration and monitoring has risen in recent years. These systems enable continuous and highly sensitive measurements of both temporal and spatial acoustic data. In this presentation, we use data recorded during a 4-day DAS experiment on the twin cables of the Ocean Observatories Initiative (OOI) Regional Cabled Array (RCA) extending off central Oregon. We demonstrate the capabilities of DAS in recording a wide range of acoustic signals including the 20-Hz call of fin whales, the 15-Hz calls and harmonics of the Northeast Pacific blue whale, and ship noises. We use beamforming and the time difference of arrival (TDOA) algorithm to find the bearing and the location of the signal of interest. We also explain the DAS array response and its sensitivity to paths arriving parallel or perpendicular to the cable and discuss the best practices to overcome the challenges in analyzing this large data set.