Submarine communications cable

A submarine communications cable is a cable laid on the seabed between land-based stations to carry telecommunication signals across stretches of ocean and sea.

The first submarine communications cables were laid beginning in the 1850s and carried telegraphy traffic, establishing the first instant telecommunications links between continents, such as the first transatlantic telegraph cable which became operational on 16 August 1858. By 1872 all the continents with the exception of Antarctica had been linked by submarine telecommunications cables. Although plans have been made to construct one, as of February 2026, Antarctica remains without a submarine cable link to the other continents.

Subsequent generations of cables carried telephone traffic, then data communications traffic. These early cables used copper wires in their cores, but modern cables use optical fiber technology to carry digital data, which includes telephone, internet and private data traffic. Modern cables are typically about 25 mm (1 in) in diameter and weigh around 1.4 tonnes per kilometre (2.5 short tons per mile; 2.2 long tons per mile) for the deep-sea sections which comprise the majority of the run, although larger and heavier cables are used for shallow-water sections near shore.