Submarine Cable-Based Distributed Acoustic Sensing for Tide Monitoring

Tide monitoring is essential for coastal management and protection. In this study, a commercial submarine cable was used to measure the vibration signals induced by the tide edge on the coast. An intensity-based distributed acoustic sensing (DAS) interrogator was used to acquire the vibration datasets along the submarine cable up to the first repeater. The preliminary results demonstrated that the DAS system and the existing submarine cable can achieve sea level and shoreline wave-induced vibration strength monitoring in the manner of online and distributed measurement. The vibration strength experienced by the submarine cable in the land section and the sea section induced by the tide edge are different, forming a clear boundary that can be analyzed further for coastal structure monitoring. Experimental results indicate the potential of DAS for effective tide-level monitoring, revealing the standard deviations of 0.221 m and a mean difference of 0.004 m in tide-level variation and the standard deviation of 0.120 m/h and a mean speed difference of 0.003 m/h in the rate of tide-level fluctuations. This study foresees the potential for developing a submarine sensor network using DAS technology, coupled with the existing or customized fiber optic submarine cables to monitor coastal structures and enhance coastal protection capabilities in coastal cities.