Laser interferometry, a technique initially developed for atomic physics and optical clocks, can be applied to underwater fibre-optic cables to detect geophysical signals and monitor the seafloor.
This has been demonstrated by a study carried out by scientists at the National Physical Laboratory (UK, coordinator) and published in the prestigious Science Magazine. The research also involved the Italian National Institute of Metrological Research (INRIM) and Google.
By launching high coherence laser light into a 5,860 km-long submarine optical fibre cable, which extends across the Atlantic Ocean between the UK and Canada, the researchers showed the detection of earthquakes and ocean signals, such as waves and currents.
The study has demonstrated that the existing submarine communications cables, used for internet traffic, could be used to monitor the seafloor and acquire data from the most remote areas of our planet, which are currently unmonitored due to the lack of suitable instrumentation. The research has demonstrated how the underwater telecoms infrastructure can be converted into a giant array of geophysical sensors.