A submarine communications cable is a cable laid on the sea bed between land-based stations to carry telecommunication signals across stretches of ocean and sea. The first submarine communications cables laid beginning in the 1850s 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. Subsequent generations of cables carried telephone traffic, then data communications traffic. Modern cables use optical fibre 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. Submarine cables first connected all the world's continents (except Antarctica) when Java was connected to Darwin, Northern Territory, Australia, in 1871 in anticipation of the completion of the Australian Overland Telegraph Line in 1872 connecting to Adelaide, South Australia and thence to the rest of Australia.

Cross-section of a modern submarine communications cable:

1. Polyethylene
2. Mylar tape
3. Stranded steel wires
4. Aluminium water barrier
5. Polycarbonate
6. Copper or aluminium tube
7. Petroleum jelly
8. Optical fibres

This article (https://www.computerworld.com/article...) indicates that Google laid 9000 km of cable for a total project cost of about $300 million. That would be about $10 per foot.

Visualization created by Tyler Morgan-Wall

More information:
  / tylermorganwall  
https://en.wikipedia.org/wiki/Submari...

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