Monitoring Ship Movements With Seafloor Optical-Fiber Distributed Acoustic Sensing

Abstract

Long-term passive acoustic ship surveillance is expensive and seldom undertaken. Distributed acoustic sensing (DAS) is an emerging technology whereby optical-fiber (OF) cables are used as dense acoustic sensor arrays, offering an alternative for marine monitoring. In this article, we describe DAS-based ship surveillance using a predeployed OF cable in shallow water, where ship-radiated noise was successfully detected when a tanker passed overhead. Typical spectral signatures of ship-radiated noise were observed, and the effective durations of detection were found to be influenced by DAS inherent angular sensitivity. The use of two adjacent cable segments of different orientation allowed precise estimation of ship azimuth, and ship velocity was estimated by DAS frequency–wave number spectrum analysis. Both estimated ship azimuth and velocity were consistent with Automatic Identification System data. Our results indicate the potential of seafloor OF-cable-based DAS in ship monitoring.