Analyzing underwater radiated noise from ships using distributed acoustic sensing

Distributed Acoustic Sensing (DAS) technology enables continuous monitoring of acoustic vibrations along fiber-optic cables, providing high-resolution spatial and temporal data for marine acoustic applications. This study investigates DAS’s capability for analyzing underwater radiated noise from ships, leveraging 4 days of DAS data collected in November 2021 using two cables from the Ocean Observatories Initiative Regional Cabled Array, extending offshore central Oregon. Data were collected using OptaSense and Silixa interrogators with gauge lengths of either 30 or 50 m and sampling rates ranging from 200 to 1000 Hz. Ship signals were identified in DAS data using Automatic Identification System (AIS) information and analyzed across different fibers and interrogators to assess system performance. Our results demonstrate that large ships are clearly visible in the DAS data within the 10–90 Hz frequency band at ranges exceeding 10 km. Low-frequency filtering extends the detection range, enhancing the ability to monitor ship signals. DAS-derived ship signals are compared with hydrophone data and a propagation model to assess the DAS system's detection capabilities. This study highlights the potential of DAS technology for maritime acoustic monitoring and its complementary role to traditional hydrophone systems in capturing underwater radiated noise by ships.