Submarine optical fiber communications are nowadays the most important infrastructure of international communications, carrying over 99% of the intercontinental data traffic. These critical infrastructures for communications also have a strong potential for geophysical monitoring in the bottom of the oceans. Here, we review our work on oceanographic monitoring using Distributed Acoustic Sensing (DAS) over submarine fiber cables. We show that these measurements can be used to obtain information of ocean dynamics, including accurate observations of surface waves, currents, and tides, and all the associated nonlinear phenomena driving water mixing, which have strong impact in climate change estimations. We show that internal waves, a large-scale phenomenon generated by the interaction of barotropic tides with bathymetric changes in the sea-bottom, can be very accurately observed using chirped-pulse DAS sensing technology over these cables.
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