Submarine communications cable

Article By:

Finn, Bernard Electricity Collections, National Museum of American History, Smithsonian Institution, Washington, DC.

Last reviewed:January 2021

DOI:https://doi.org/10.1036/1097-8542.664200

A cable laid on the ocean floor to transmit signals. The challenge for submarine cables has been to convey signals long distances under water where there is no opportunity for easy access at intervening points. In the 1850s these were direct-current telegraph signals, and the principal difficulties to be overcome were quality control in manufacture of the cable, laying the cable, and devising instruments that could sense feeble attenuated pulses. One hundred years later a major advance was made when small reliable amplifiers, first using vacuum tubes and then transistors, were submerged with the cable. The message capacity was increased by some three orders of magnitude. And in the 1980s the modern era began when a series of problems were solved in the science and technology of fiber optics so that signals could be both conveyed and amplified using beams of light through strands of glass, increasing the message capacity by an astonishing five orders of magnitude. The purpose of this article is to describe the science and technology behind these fiber-optic cables. Some is completely new, but much is a modification of techniques that were learned in the development of the earlier cable forms.

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