Comparing distributed acoustic sensing data with hydrophone recordings

Abstract

Distributed acoustic sensing (DAS) is a technology that transforms telecommunication fiber optic cables into dense sensor arrays by continuously transmitting pulses of light down the cable and measuring backscattering from natural inhomogeneities within the fiber cable. The technology can densely sample the acoustic field over long ranges (up to 100 km), providing a means for large scale passive acoustic monitoring. To evaluate the capabilities of DAS, it is necessary to benchmark and calibrate the technology relative to traditional hydrophone data. The DAS Calibration Experiment 2022 (DASCAL22) recorded 9 days of both DAS and hydrophone data in Puget Sound, WA in October 2022. The DAS data were recorded with a sample rate of 2 kHz, and the cable extended 3.5 km on the seafloor between two islands, reaching depths of 100 m, and the hydrophones were moored adjacent to the DAS cable at 5 m and 25 m from the seafloor. The recordings include impulses from an active source at 1 m, 5 m, and 10 m depths, and an abundance of passive acoustic data corresponding to ship traffic, wind, and rain. This work aims to draw comparisons between the hydrophone and DAS recordings to evaluate the capability of DAS at detecting sounds at frequencies as high as 1 kHz.