Undersea cables could be used as a vast network of environmental sensors

3 Jun 2022

Image: © Christoph Burgstedt/Stock.adobe.com

Researchers say splitting subsea cables into a sensor array ‘has the potential to transform our understanding of both shallow and deep processes inside the Earth’.

A group of researchers from the US, UK and Italy have come up with a new approach to detecting activity on our ocean floors using subsea cables.

Their method builds on previous research that demonstrated how optical fibre-based infrastructure could double as seafloor sensing technology.

These undersea cables, which stretch across the Earth to connect people through telecoms, can be made to detect seismic vibrations and ocean currents with greater precision.

Previous research demonstrating that existing underwater optical communication cables can be used as seafloor sensors utilised the entire cable as a single sensor. As one cable can span thousands of kilometres, this approach creates limitations in spatial resolution and sensitivity.

This latest research suggests a new approach that converts one long optical cable into many individual segments capable of detecting activity around them. This method means one undersea cable could become a vast network of seafloor environmental sensors without the need to change existing infrastructure.

This is because undersea cables typically have repeaters – which amplify an optical signal as it moves through a cable – placed every 45km to 90km along the length of cable. These segments could each be used as vibrational sensors when coupled with a laser source, according to research published in the journal Science.

The researchers tested their theory on a 5,860km long submarine optical fibre link between the UK and Canada, which contained repeaters approximately every 46km. Using the cable segments as an optical interferometry–based array of sensors, the team detected several earthquakes, weak seismic movements and ocean currents along the cable. They were also able to determine the epicentre of a distant earthquake by triangulating signals from different segments along the cable.

“By converting submarine cables into arrays of environmental sensors, a large network of hundreds or thousands of permanent and real-time seafloor sensors could be implemented without modification of the existing subsea infrastructure,” the research team wrote.

“This has the potential to transform our understanding of both shallow and deep processes inside the Earth.”

The research paper has 18 different authors. Lead author, Giuseppe Marra, is based out of the National Physical Laboratory (NPL) in the UK. Several of his co-authors are also from the NPL.

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Blathnaid O’Dea is Careers reporter at Silicon Republic