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.Anton A. Huurdeman, The Worldwide History of Telecommunications, pp. 136–140, John Wiley & Sons, 2003 .
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 in diameter and weigh around 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."The internet's undersea world" – annotated image, The Guardian.
Early history: telegraph and coaxial cables First successful trials After William Cooke and Charles Wheatstone had introduced their working telegraph in 1839, the idea of a submarine line across the Atlantic Ocean began to be thought of as a possible triumph of the future. Samuel Morse proclaimed his faith in it as early as 1840, and in 1842 he submerged a wire, insulated with tarred hemp and India rubber, in the water of New York Harbor, and telegraphed through it. The following autumn, Wheatstone performed a similar experiment in Swansea Bay. A good insulator to cover the wire and prevent the electric current from leaking into the water was necessary for the success of a long submarine line. India rubber had been tried by Moritz von Jacobi, the Prussian electrical engineer, as far back as the early 19th century.
Another insulating gum which could be melted by heat and readily applied to wire made its appearance in 1842. Gutta-percha, the adhesive juice of the Palaquium gutta tree, was introduced to Europe by William Montgomerie, a Scottish surgeon in the service of the British East India Company. Twenty years earlier, Montgomerie had seen whips made of gutta-percha in Singapore, and he believed that it would be useful in the fabrication of surgical apparatus. Michael Faraday and Wheatstone soon discovered the merits of gutta-percha as an insulator, and in 1845 the latter suggested that it should be employed to cover the wire which was proposed to be laid from Dover to Calais. In 1847 William Siemens, then an officer in the army of Prussia, laid the first successful underwater cable using gutta-percha insulation across the Rhine between Deutz and Cologne. In 1849 Charles Vincent Walker, electrician to the South Eastern Railway, submerged of wire coated with gutta-percha off the coast from Folkestone, which was tested successfully.
First commercial cables
In August 1850, having earlier obtained a concession from the French government, John Watkins Brett's English Channel Submarine Telegraph Company laid the first line across the English Channel using the converted tugboat Goliath. It was simply a copper wire coated with gutta-percha, without any other protection, and was not successful.The company is referred to as the English Channel Submarine Telegraph Company However, the experiment served to secure renewal of the concession, and in September 1851 a protected core, or true, cable was laid by the reconstituted Submarine Telegraph Company from a government hulk, Blazer, which was towed across the Channel.
In 1853 more successful cables were laid, linking Great Britain with Ireland, Belgium, and the Netherlands, and crossing The Belts in Denmark. The British & Irish Magnetic Telegraph Company completed the first successful Irish link on May 23 between Portpatrick and Donaghadee using the collier William Hutt. The same ship was used for the link from Dover to Ostend in Belgium by the Submarine Telegraph Company. Meanwhile the Electric & International Telegraph Company completed two cables across the North Sea from Orford Ness to Scheveningen, the Netherlands. These cables were laid by the Monarch, a paddle steamer which later became the first vessel with permanent cable-laying equipment.
In 1858 the steamship Elba was used to lay a telegraph cable from Jersey to Guernsey, on to Alderney, and then to Weymouth, the cable being completed successfully in September of that year. Problems soon developed with eleven breaks occurring by 1860 due to storms, tidal and sand movements, and wear on rocks. A report to the Institution of Civil Engineers in 1860 set out the problems to assist in future cable-laying operations.
Crimean War (1853–1856) In the Crimean War various forms of telegraphy played a major role; this was a first. At the start of the campaign there was a telegraph link at Bucharest connected to London. In the winter of 1854 the French extended the telegraph link to the Black Sea coast. In April 1855 the British laid an underwater cable from Varna to the Crimean peninsula so that news of the Crimean War could reach London in a handful of hours.
Transatlantic telegraph cable
The first attempt at laying a transatlantic telegraph cable was promoted by Cyrus West Field, who persuaded British industrialists to fund and lay one in 1858. However, the technology of the day was not capable of supporting the project; it was plagued with problems from the outset and was in operation for only a month. Subsequent attempts in 1865 and 1866 with the world's largest steamship, the SS Great Eastern, used a more advanced technology and produced the first successful transatlantic cable. Great Eastern later went on to lay the first cable to reach India from Aden, Yemen, in 1870.
British dominance of early cable
From the 1850s until 1911, British submarine cable systems dominated the most important market, the North Atlantic Ocean. The British had both supply-side and demand-side advantages. In terms of supply, Britain had entrepreneurs willing to put forth enormous amounts of capital necessary to build, lay, and maintain these cables. In terms of demand, Britain's vast colonial empire led to business for the cable companies from news agencies, trading and shipping companies, and the British government. Many of Britain's colonies had significant populations of European settlers, making their news of interest to the general public in the home country.
British officials believed that dependence on telegraph lines passing through non-British territory posed a security risk, as lines could be cut and messages interrupted during wartime. They sought the creation of a worldwide network within the empire, which became known as the All Red Line, and conversely prepared strategies for quickly interrupting enemy communications. Britain's very first action after declaring war on Germany in World War I was to have the cable ship Alert (not the CS Telconia as frequently reported)Rhodri Jeffreys-Jones, In Spies We Trust: The Story of Western Intelligence, page 43, Oxford University Press, 2013 . cut the five cables linking Germany with France, Spain, and the Azores, and through them, North America.Jonathan Reed Winkler, Nexus: Strategic Communications and American Security in World War I, pages 5–6, 289, Harvard University Press, 2008 . Thereafter, the only way Germany could communicate was by wireless, and that meant that Room 40 could listen in.
The submarine cables were an economic benefit to trading companies because owners of ships could communicate with captains upon reaching their destinations and give directions as to where to pick up cargo next based on reported pricing and supply information. The British government had obvious uses for the cables in maintaining administrative communications with governors throughout its empire, as well as in engaging other nations diplomatically and communicating with its military units in wartime. The geographic location of British territory was also an advantage, as it included both Ireland on the east side of the Atlantic Ocean and Newfoundland in North America on the west side, making for the shortest route across the ocean and reducing costs significantly.
A few facts put this dominance of the industry in perspective. In 1896 there were 30 cable-laying ships in the world, 24 of which were owned by British companies. In 1892 British companies owned and operated two-thirds of the world's cables, and by 1923 their share was still 42.7 percent.Headrick, D.R., & Griset, P. (2001). "Submarine Telegraph Cables: Business and Politics, 1838–1939". The Business History Review, 75(3), 543–578. During World War I, Britain's telegraph communications were almost completely uninterrupted, while it was able to quickly cut Germany's cables worldwide.
Cable to India, Singapore, East Asia and Australia
Throughout the 1860s and 1870s, British cable expanded eastward into the Mediterranean Sea and the Indian Ocean. An 1863 cable to Bombay (now Mumbai), India, provided a crucial link to Saudi Arabia. At the behest of the British Government in 1870, Bombay was linked to London via submarine cable in a combined operation by four cable companies. In 1872 these four companies were combined to form the mammoth, globe-spanning Eastern Telegraph Company, owned by John Pender. A spin-off sister company became the Eastern Extension, China and Australasia Telegraph Company, commonly known simply as "the Extension". That same year, Australia was linked by cable to Bombay via Singapore and China, and by 1876 the cable linked the British Empire from London to New Zealand."Landing the New Zealand cable", pg 3, The Colonist, 19 February 1876
Submarine cables across the Pacific, 1902–1991 The first trans-Pacific cables providing telegraph service were completed in 1902 and 1903, linking the US mainland to Hawaii in 1902 and Guam to the Philippines in 1903. Canada, Australia, New Zealand and Fiji were also linked in 1902 with the trans-Pacific segment of the All Red Line. Japan was connected into the system in 1906. Service beyond Midway Atoll was abandoned in 1941 due to World War II, but the remainder stayed in operation until 1951 when the FCC gave permission to cease operations.
The first trans-Pacific telephone cable was laid from Hawaii to Japan in 1964, with an extension from Guam to The Philippines. Also in 1964, the Commonwealth Pacific Cable System (COMPAC), with 80 telephone channel capacity, opened for traffic from Sydney to Vancouver, and in 1967, the South East Asia Commonwealth (SEACOM) system, with 160 telephone channel capacity, opened for traffic. This system used microwave radio from Sydney to Cairns (Queensland), cable running from Cairns to Madang (Papua New Guinea), Guam, Hong Kong, Kota Kinabalu (capital of Sabah, Malaysia), Singapore, then overland by microwave radio to Kuala Lumpur. In 1991, the North Pacific Cable system was the first regenerative system (i.e., with repeaters) to completely cross the Pacific from the US mainland to Japan. The US portion of NPC was manufactured in Portland, Oregon, from 1989 to 1991 at STC Submarine Systems, and later Alcatel Submarine Networks. The system was laid by Cable & Wireless Marine on the CS Cable Venture.
Construction, 19–20th century