[S-SS04] Seismological advances in the ocean

[SSS04-01] Trans-Oceanic Distributed Sensing of Tides over Telecommunication Cable Between Portugal and Brazil

★Invited Papers

*Meichen Liu¹, Luis Costa², Pierre Mertz³, Siddharth Varughese³, Sumudu Edirisinghe³, Valey Kamalov⁴, Zhongwen Zhan¹ (1.California Institute of Technology, 2.NASA Jet Propulsion Laboratory, 3.Infinera Corporation, 4.Valey Kamalov LLC)

Keywords:Submarine fiber optic sensing, Ocean tides, Trans-oceanic cables, Poisson effect, Ocean temperature

Geophysical sensing in the open ocean is both costly and technically challenging. Here we developed a novel distributed fiber optic sensing technique that employs microwave modulation for phase measurement in signals returned from submarine repeaters. We transformed a trans-Atlantic telecom cable into an 81-sensor array and measured sub-millihertz strains. The strains spatiotemporally correlate with ocean tide height variations in phase, suggesting a dominant factor of the cable’s Poisson’s effect. Large strains observed at fiber spans located in the shallow waters match the strong variations of simulated seafloor temperature. This study presents the first experimental confirmation of detecting sub-millihertz signals with trans-oceanic submarine cables at span-wise spatial resolution (~80km). Scaling this technique to operational submarine cables provides a cost-efficient, non-disruptive approach for tsunami early warning and long-term ocean temperature monitoring.