LAUSR

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. We demonstrate the detection of earthquakes and ocean signals on individual spans between repeaters of a 5860-kilometer-long transatlantic cable rather than the whole cable. By applying this technique to the existing undersea communication cables, which have a repeater-to-repeater span length of 45 to 90 kilometers, the largely unmonitored ocean floor could be instrumented with thousands of permanent real-time environmental sensors without changes to the underwater infrastructure. Description Relying on repeaters Underwater optical cables can be used to monitor seismic disturbances and ocean currents, but the signal tends to be integrated over the entire length of the cable, which can be thousands of kilometers long. Marra et al. were able to isolate individual segments of a 5800-kilometer-long cable for seafloor monitoring. Because undersea cables have repeaters every 90 kilometers, 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. —BG Individual repeaters on undersea cables can be used to better characterize seismic vibrations and ocean currents.