In Science magazine (19 May 2022, Volume 376, Issue 6595, Pages, 874-879), researchers described their work on using a transoceanic submarine cable to create an optical interferometry-based array of seafloor environmental sensors.

The researchers were able to isolate individual segments of a 5800-kilometer-long cable for seafloor monitoring. Because undersea cables have repeaters every 90 kilometers or so, these segments could each be used as vibrational sensors when coupled with a laser source. This approach allowed the authors to better constrain the location of an earthquake through triangulation, thus offering a method for much better spatial resolution for undersea monitoring.

Optical fiber-based sensing technology can drastically improve Earth observations by enabling the use of existing submarine communication cables as seafloor sensors. Previous interferometric and polarization-based techniques demonstrated environmental sensing over cable lengths up to 10,500 kilometers. However, measurements were limited to the integrated changes over the entire length of the cable. The researchers demonstrate the detection of earthquakes and ocean signals on individual spans between repeaters of the cable rather than the whole cable. By applying this technique to the existing undersea communication cables, the largely unmonitored ocean floor could be instrumented with thousands of permanent real-time environmental sensors without changes to the underwater infrastructure, according to the authors.