Editing Submarine communications cable

{{Short description|Transoceanic communication line placed on the seabed}}
{{use mdy dates|cs1-dates=ly|date=October 2022}}

[[File:Submarine cable cross-section 3D plain.svg|right|thumb|upright=1.35|A [[cross section (geometry)|cross section]] of the shore-end of a modern submarine communications cable.<br />
1 {{color box|#C0D483}} – [[Polyethylene]]<br />
2 {{color box|#A493DC}} – [[BoPET|Mylar]] tape<br />
3 {{color box|#89B0D1}} – Stranded [[wire rope|steel wires]]<br />
4 {{color box|#C9C9C9}} – Aluminium water barrier<br />
5 {{color box|#A6A6A6}} – [[Polycarbonate]]<br />
6 {{color box|#E5AA5A}} – Copper or aluminium tube<br />
7 {{color box|#E5D56D}} – [[Petroleum jelly]]<br />
8 {{color box|#EEEEFF}} – [[Optical fiber]]s]]
[[File:France Telecom Marine Rene Descartes p1150247.jpg|thumb|Submarine cables are laid using special [[cable layer]] ships, such as the modern ''{{ill|René Descartes (ship)|fr|René Descartes (câblier)|lt=René Descartes}}'', operated by [[Orange Marine]].]]

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.

Submarine cables first connected all the world's [[continent]]s (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.<ref>Anton A. Huurdeman, ''The Worldwide History of Telecommunications'', pp. 136–140, John Wiley & Sons, 2003 {{ISBN|0471205052}}.</ref>

Subsequent generations of cables carried telephone traffic, then [[data transmission|data communication]]s 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 {{convert|25|mm|in|0|abbr=on}} in diameter and weigh around {{convert|1.4|t/km|ST/mi LT/mi|abbr=off}} 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.<ref>[https://web.archive.org/web/20160526231647/http://www.techteledata.com/how-submarine-cables-are-made-laid-operated-and-repaired/ "How Submarine Cables are Made, Laid, Operated and Repaired"], TechTeleData</ref><ref>[http://image.guardian.co.uk/sys-images/Technology/Pix/pictures/2008/02/01/SeaCableHi.jpg "The internet's undersea world"] {{webarchive|url=https://web.archive.org/web/20101223170755/http://image.guardian.co.uk/sys-images/Technology/Pix/pictures/2008/02/01/SeaCableHi.jpg |date=2010-12-23 }}&nbsp;– annotated image, ''The Guardian''.</ref>

==Early history: telegraph and coaxial cables==
===First successful trials===
After [[William Fothergill Cooke|William Cooke]] and [[Charles Wheatstone]] had introduced their [[Cooke and Wheatstone telegraph|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.<ref>{{Cite journal |last=Abildgaard |first=M. S. |date=2022 |title=The question of Icebergs: a cryo-history of Arctic submarine cables |url=https://www.cambridge.org/core/journals/polar-record/article/question-of-icebergs-a-cryohistory-of-arctic-submarine-cables/451A8E2657363D298C58EA70D92F6FDB |journal=Polar Record |language=en |volume=58 |pages= |doi=10.1017/S0032247422000262 |bibcode=2022PoRec..58E..41A |issn=0032-2474}}</ref> [[Samuel Morse]] proclaimed his faith in it as early as 1840, and in 1842, he submerged a wire, insulated with tarred [[hemp]] and [[Natural rubber|India rubber]],<ref>{{cite web |title=[Heroes of the Telegraph&nbsp;– Chapter III.&nbsp;– Samuel Morse] |url=http://www.globusz.com/ebooks/Telegraph/00000013.htm |website=Globusz |access-date=2008-02-05 |url-status=dead |archive-date=2008-12-01 |archive-url=https://web.archive.org/web/20081201131615/http://www.globusz.com/ebooks/Telegraph/00000013.htm}}</ref><ref>{{cite web |url=http://inventors.about.com/library/inventors/bl_morse_timeline1.htm |archive-url=https://archive.today/20120709103139/http://inventors.about.com/library/inventors/bl_morse_timeline1.htm |url-status=dead |archive-date=July 9, 2012 |title=Timeline&nbsp;– Biography of Samuel Morse |publisher=Inventors.about.com |date=2009-10-30 |access-date=2010-04-25 }}</ref> 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 (electrical)|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. [[Natural rubber|India rubber]] had been tried by [[Moritz von Jacobi]], the [[Prussia]]n [[electrical engineering|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 [[East India Company|British East India Company]].<ref name=Haigh>{{cite book|last=Haigh |first=Kenneth Richardson |title= Cable Ships and Submarine Cables |year=1968 |publisher=[[Adlard Coles]] |location=London |isbn=9780229973637 }}</ref>{{rp|26–27}} 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]].<ref name="guarnieri 7-1">{{Cite journal| last= Guarnieri|first=M.|year=2014|title=The Conquest of the Atlantic|journal=IEEE Industrial Electronics Magazine| volume=8| issue=1 |pages= 53–56/67|doi=10.1109/MIE.2014.2299492|s2cid=41662509}}</ref> In 1847 [[Carl Wilhelm Siemens|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, Cologne|Deutz]] and [[Cologne]].<ref>{{cite journal |title=C William Siemens |journal=The Practical Magazine |date=1875 |volume=5 |issue=10 |page=219}}</ref> In 1849, [[Charles Vincent Walker]], electrician to the [[South Eastern Railway (UK)|South Eastern Railway]], submerged {{cvt|2|mi|0|disp=flip}} of wire coated with gutta-percha off the coast from [[Folkestone]], which was tested successfully.<ref name=Haigh/>{{rp|26–27}}

===First commercial cables===
[[File:British & Irish Magnetic Telegraph Co. Limited 3 shilling stamp c. 1862 remaindered without control number.jpg|thumbnail|right|A [[telegraph stamp]] of the British & Irish Magnetic Telegraph Co. Limited (c. 1862).]]

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.<ref name=Haigh/>{{rp|192–193}}<ref>The company is referred to as the English Channel Submarine Telegraph Company</ref> 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 (ship type)|hulk]], ''Blazer'', which was towed across the Channel.<ref name=Haigh/>{{rp|192–193}}<ref name=Brett>{{cite journal|last=Brett|first=John Watkins|title=On the Submarine Telegraph|journal=Royal Institution of Great Britain: Proceedings: Vol. II, 1854–1858|date=March 18, 1857 |url=http://www.atlantic-cable.com/Article/Brett/index.htm|access-date=17 May 2013|type=transcript|url-status=dead|archive-url=https://web.archive.org/web/20130517155316/http://www.atlantic-cable.com/Article/Brett/index.htm |archive-date=17 May 2013}}</ref><ref name="guarnieri 7-1"/>

In 1853, more successful cables were laid, linking Great Britain with Ireland, [[Belgium]], and the [[Netherlands]], and crossing [[The Belts]] in Denmark.<ref name=Haigh/>{{rp|361}} The [[British & Irish Magnetic Telegraph Company]] completed the first successful Irish link on May 23 between [[Portpatrick]] and [[Donaghadee]] using the [[collier (ship)|collier]] ''William Hutt''.<ref name=Haigh/>{{rp|34–36}} The same ship was used for the link from Dover to [[Ostend]] in Belgium, by the Submarine Telegraph Company.<ref name=Haigh/>{{rp|192–193}} 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 ''Monarch'', a [[paddle steamer]] which later became the first vessel with permanent cable-laying equipment.<ref name=Haigh/>{{rp|195}}

In 1858, the steamship ''Elba'' was used to lay a telegraph cable from [[Jersey]] to [[Guernsey]], on to [[Alderney]] and then to [[Weymouth, Dorset|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.<ref>{{cite book |title= Minutes of Proceedings of the Institution of Civil Engineers |issue=Volume 20 |page=26}}</ref>

=== 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.<ref>{{cite book | author1=Christopher Andrew |title=The Secret World: A History of Intelligence |publisher=Penguin Books Limited |year=2018 |page=ccxiii |isbn=9780241305225 }}</ref>

===Transatlantic telegraph cable===
{{Main|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.<ref name="guarnieri 7-1"/> 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|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 reaching to India from Aden, Yemen, in 1870.

===British dominance of early cable===
[[File:Telegraph QE3 19.jpg|thumb|upright=1.15|Operators in the submarine telegraph cable room at the [[General Post Office|GPO]]'s Central Telegraph Office in London c. 1898]]

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, [[British Empire|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 news about them of interest to the general public in the home country.

British officials believed that depending on telegraph lines that passed through non-British territory posed a security risk, as lines could be cut and messages could be 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 to quickly interrupt enemy communications.<ref name="kennedy197110">{{cite journal | jstor= 563928 | title=Imperial Cable Communications and Strategy, 1870–1914 | url= https://archive.org/details/sim_english-historical-review_1971-10_86_341/page/728 | author=Kennedy, P. M. | journal= The English Historical Review |date=October 1971 | volume=86 | issue=341 | pages=728–752 | doi=10.1093/ehr/lxxxvi.cccxli.728}}</ref> Britain's very first action after declaring war on Germany in World War I was to have the [[CS Alert (1890)|cable ship ''Alert'']] (not the CS ''[[Telconia]]'' as frequently reported)<ref>Rhodri Jeffreys-Jones, ''In Spies We Trust: The Story of Western Intelligence'', page 43, Oxford University Press, 2013 {{ISBN|0199580979}}.</ref> cut the five cables linking Germany with France, Spain and the Azores, and through them, North America.<ref>Jonathan Reed Winkler, ''Nexus: Strategic Communications and American Security in World War I'', pages 5–6, 289, Harvard University Press, 2008 {{ISBN|0674033906}}.</ref> 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 when they reached their destination and give directions as to where to go next to pick up cargo 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, which reduced 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.<ref>Headrick, D.R., & Griset, P. (2001). "Submarine Telegraph Cables: Business and Politics, 1838–1939". ''The Business History Review'', 75(3), 543–578.</ref> During [[World War I]], Britain's telegraph communications were almost completely uninterrupted, while it was able to quickly cut Germany's cables worldwide.{{r|kennedy197110}}

===Cable to India, Singapore, East Asia and Australia===
[[File:1901 Eastern Telegraph cables.png|thumb|upright=1.15|Eastern Telegraph Company network in 1901. Dotted lines across the Pacific indicate planned cables laid in 1902–03.]]

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]].<ref>{{cite news |url=http://www.telegraphindia.com/1080203/jsp/frontpage/story_8856997.jsp |title=The Telegraph&nbsp;– Calcutta (Kolkata) &#124; Frontpage &#124; Third cable cut, but India's safe |publisher=Telegraphindia.com |date=2008-02-03 |access-date=2010-04-25 |url-status=live |archive-url=https://web.archive.org/web/20100903041957/http://www.telegraphindia.com/1080203/jsp/frontpage/story_8856997.jsp |archive-date=2010-09-03 }}</ref> In 1870, Bombay was linked to London via submarine cable in a combined operation by four cable companies, at the behest of the British Government. In 1872, these four companies were combined to form the mammoth globe-spanning [[Cable & Wireless plc|Eastern Telegraph Company]], owned by [[John Pender]]. A spin-off from Eastern Telegraph Company was a second sister company, the Eastern Extension, China and Australasia Telegraph Company, commonly known simply as "the Extension." In 1872, Australia was linked by cable to Bombay via Singapore and China and in 1876, the cable linked the British Empire from London to New Zealand.<ref>"Landing the New Zealand cable", pg 3, ''[[The Nelson Mail|The Colonist]]'', 19 February 1876</ref>

===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.<ref>{{cite web|url=http://www.brainyhistory.com/events/1903/july_4_1903_69271.html |title=Pacific Cable (SF, Hawaii, Guam, Phil) opens, President TR sends message July 4 in History |publisher=Brainyhistory.com |date=1903-07-04 |access-date=2010-04-25}}</ref> Canada, Australia, New Zealand and Fiji were also linked in 1902 with the trans-Pacific segment of the [[All Red Line]].<ref>{{cite web |url= http://www.canadainternational.gc.ca/australia-australie/bilateral_relations_bilaterales/history-histoire.aspx?lang=eng |title= History of Canada-Australia Relations |publisher= Government of Canada |access-date= 2014-07-28 |url-status= dead |archive-url= https://web.archive.org/web/20140720185110/http://www.canadainternational.gc.ca/australia-australie/bilateral_relations_bilaterales/history-histoire.aspx?lang=eng |archive-date= 2014-07-20 }}</ref> 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.<ref>{{cite web |title=The Commercial Pacific Cable Company |url=http://atlantic-cable.com/CableCos/ComPacCable |publisher=Atlantic Cable |work= atlantic-cable.com |access-date=September 24, 2016 |url-status=live |archive-url = https://web.archive.org/web/20160927110415/http://atlantic-cable.com/CableCos/ComPacCable |archive-date=September 27, 2016 }}</ref>

The first trans-Pacific telephone cable was laid from Hawaii to Japan in 1964, with an extension from Guam to The Philippines.<ref>{{cite web |title=Milestones:TPC-1 Transpacific Cable System, 1964 |publisher=Engineering and Technology History WIKI |work=ethw.org |url=http://ethw.org/Milestones:TPC-1_Transpacific_Cable_System,_1964 |access-date=September 24, 2016 |url-status=dead |archive-url=https://web.archive.org/web/20160927020609/http://ethw.org/Milestones:TPC-1_Transpacific_Cable_System,_1964 |archive-date=September 27, 2016 }}</ref> 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 [[NPC (cable system)|North Pacific Cable system]] was the first regenerative system (i.e., with [[repeater]]s) 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 ''[[Cable Ship|CS]] Cable Venture''.{{citation needed|date=December 2024}}

===Construction, 19–20th century===
[[File:Bundesarchiv Bild 102-01035, New York, Verlegen von Unterseekabel.jpg|thumb|upright=1.15|right|Landing of an Italy-USA cable (4,704 nautical miles long), on [[Rockaway Beach, Queens]], New York, January 1925.]]
Transatlantic cables of the 19th century consisted of an outer layer of iron and later steel wire, wrapping India rubber, wrapping [[gutta-percha]], which surrounded a multi-stranded copper wire at the core. The portions closest to each shore landing had additional protective armour wires. Gutta-percha, a natural polymer similar to rubber, had nearly ideal properties for insulating submarine cables, with the exception of a rather high [[dielectric]] constant which made cable [[capacitance]] high. [[William Thomas Henley]] had developed a machine in 1837 for covering wires with silk or cotton thread that he developed into a wire wrapping capability for submarine cable with a factory in 1857 that became W.T. Henley's Telegraph Works Co., Ltd.<ref>{{cite web |title=Machine used for covering wires with silk and cotton, 1837 |publisher=The Science Museum Group |url=https://collection.sciencemuseumgroup.org.uk/objects/co44548 |access-date=24 January 2020}}</ref><ref name=Bright/> The [[India Rubber, Gutta Percha and Telegraph Works Company]], established by the Silver family and giving that [[Silvertown|name to a section of London]], furnished cores to Henley's as well as eventually making and laying finished cable.<ref name=Bright/> In 1870 [[William Hooper (chemist)|William Hooper]] established [[Hooper's Telegraph Works]] to manufacture his patented [[Vulcanization|vulcanized rubber]] core, at first to furnish other makers of finished cable, that began to compete with the gutta-percha cores. The company later expanded into complete cable manufacture and cable laying, including the building of the first cable ship specifically designed to lay transatlantic cables.<ref name=Bright>{{cite book |last=Bright |first=Charles |year=1898 |title=Submarine telegraphs: Their History, Construction, and Working |location=London |publisher=C. Lockwood and son |isbn= 9781108069489|lccn=08003683 |pages=125, 157–160, 337–339 |url=https://books.google.com/books?id=3DfeAgAAQBAJ&pg=PA157 |access-date=27 January 2020}}</ref><ref>{{cite web |last=Glover |first=Bill |title=History of the Atlantic Cable & Undersea Communications—CS Hooper/Silvertown |publisher=The Atlantic Cable |date=7 February 2019 |url=https://atlantic-cable.com/Cableships/Silvertown/index.htm |access-date=27 January 2020}}</ref><ref>{{cite web |last=Glover |first=Bill |title=History of the Atlantic Cable & Undersea Communications—British Submarine Cable Manufacturing Companies |publisher=The Atlantic Cable |date=22 December 2019 |url=https://atlantic-cable.com/CableCos/BritishMfrs/index.htm |access-date=27 January 2020}}</ref>

Gutta-percha and rubber were not replaced as a cable insulation until [[polyethylene]] was introduced in the 1930s. Even then, the material was only available to the military and the first submarine cable using it was not laid until 1945 during [[World War II]] across the [[English Channel]].<ref>Ash, Stewart, "The development of submarine cables", ch. 1 in, Burnett, Douglas R.; Beckman, Robert; Davenport, Tara M., ''Submarine Cables: The Handbook of Law and Policy'', Martinus Nijhoff Publishers, 2014 {{ISBN|9789004260320}}.</ref> In the 1920s, the American military experimented with rubber-insulated cables as an alternative to gutta-percha, since American interests controlled significant supplies of rubber but did not have easy access to gutta-percha manufacturers. The 1926 development by [[John T. Blake]] of deproteinized rubber improved the impermeability of cables to water.<ref>{{cite journal|last=Blake|first=J. T.|author2=Boggs, C. R.|title=The Absorption of Water by Rubber.|journal=Industrial & Engineering Chemistry |year=1926|volume=18|issue=3|pages=224–232|doi=10.1021/ie50195a002}}</ref>

Many early cables suffered from attack by sea life. The insulation could be eaten, for instance, by species of [[Teredo (bivalve)|''Teredo'']] (shipworm) and ''[[Xylophaga]]''. [[Hemp]] laid between the [[Steel wire armoured cable|steel wire armouring]] gave pests a route to eat their way in. Damaged armouring, which was not uncommon, also provided an entrance. Cases of sharks biting cables and attacks by [[sawfish]] have been recorded. In one case in 1873, a whale damaged the Persian Gulf Cable between [[Karachi]] and [[Gwadar]]. The whale was apparently attempting to use the cable to clean off [[barnacle]]s at a point where the cable descended over a steep drop. The unfortunate whale got its tail entangled in loops of cable and drowned. The cable repair ship ''Amber Witch'' was only able to winch up the cable with difficulty, weighed down as it was with the dead whale's body.<ref>[https://books.google.com/books?id=_hwAAAAAMAAJ&pg=PA311 "On Accidents to Submarine Cables"], ''Journal of the Society of Telegraph Engineers'', vol. 2, no. 5, pp. 311–313, 1873</ref>

===Bandwidth problems===
{{unreferenced section|date=December 2024}}
Early long-distance submarine telegraph cables exhibited formidable electrical problems. Unlike modern cables, the technology of the 19th century did not allow for in-line [[repeater]] [[amplifier]]s in the cable. Large [[voltage]]s were used to attempt to overcome the [[electrical resistance]] of their tremendous length but the cables' distributed [[capacitance]] and [[inductance]] combined to distort the telegraph pulses in the line, reducing the cable's [[Bandwidth (signal processing)|bandwidth]], severely limiting the [[Bit rate|data rate]] for telegraph operation to 10–12 [[words per minute]].

As early as 1816, [[Francis Ronalds]] had observed that electric signals were slowed in passing through an insulated wire or core laid underground, and outlined the cause to be induction, using the analogy of a long [[Leyden jar]].<ref>{{Cite book|title=Sir Francis Ronalds: Father of the Electric Telegraph|last=Ronalds|first=B.F.|publisher=Imperial College Press|year=2016|isbn=978-1-78326-917-4|location = London}}</ref><ref>{{Cite journal|last=Ronalds|first=B.F. |date=Feb 2016|title=The Bicentennial of Francis Ronalds's Electric Telegraph| journal=Physics Today|volume=69 |issue=2|pages=26–31 |doi= 10.1063/PT.3.3079|bibcode=2016PhT....69b..26R |doi-access=free}}</ref> The same effect was noticed by [[Latimer Clark]] (1853) on cores immersed in water, and particularly on the lengthy cable between England and The Hague. [[Michael Faraday]] showed that the effect was caused by capacitance between the wire and the [[ground (electricity)|earth]] (or water) surrounding it. Faraday had noticed that when a wire is charged from a battery (for example when pressing a telegraph key), the [[electric charge]] in the wire induces an opposite charge in the water as it travels along. In 1831, Faraday described this effect in what is now referred to as [[Faraday's law of induction]]. As the two charges attract each other, the exciting charge is retarded. The core acts as a [[capacitor]] distributed along the length of the cable which, coupled with the resistance and [[inductance]] of the cable, limits the speed at which a [[signal]] travels through the [[electrical conduction|conductor]] of the cable.

Early cable designs failed to analyse these effects correctly. Famously, [[E.O.W. Whitehouse]] had dismissed the problems and insisted that a transatlantic cable was feasible. When he subsequently became chief electrician of the [[Atlantic Telegraph Company]], he became involved in a public dispute with [[William Thomson, 1st Baron Kelvin|William Thomson]]. Whitehouse believed that, with enough voltage, any cable could be driven. Thomson believed that his [[law of squares]] showed that retardation could not be overcome by a higher voltage. His recommendation was a larger cable. Because of the excessive voltages recommended by Whitehouse, Cyrus West Field's first transatlantic cable never worked reliably, and eventually [[short circuit]]ed to the ocean when Whitehouse increased the voltage beyond the cable design limit.

Thomson designed a complex electric-field generator that minimized current by [[resonance|resonating]] the cable, and a sensitive light-beam [[mirror galvanometer]] for detecting the faint telegraph signals. Thomson became wealthy on the royalties of these, and several related inventions. Thomson was elevated to [[Lord Kelvin]] for his contributions in this area, chiefly an accurate [[mathematical model]] of the cable, which permitted design of the equipment for accurate telegraphy. The effects of [[atmospheric electricity]] and the [[geomagnetic field]] on submarine cables also motivated many of the [[International Geophysical Year|early polar expeditions]].

Thomson had produced a mathematical analysis of propagation of electrical signals into telegraph cables based on their capacitance and resistance, but since long submarine cables operated at slow rates, he did not include the effects of inductance. By the 1890s, [[Oliver Heaviside]] had produced the modern general form of the [[telegrapher's equations]], which included the effects of inductance and which were essential to extending the theory of [[transmission line]]s to the higher [[frequencies]] required for high-speed data and voice.

===Transatlantic telephony===
[[File:Submarine Telephone Cables PICT8182 1.JPG|thumb|right|<!--Five is dubious, I count only three – but then again I might be blind...-->Submarine communication cables crossing the Scottish shore at Scad Head on [[Hoy, Orkney|Hoy]], Orkney.]]

While laying a transatlantic telephone cable was seriously considered from the 1920s, the technology required for economically feasible telecommunications was not developed until the 1940s. A first attempt to lay a "[[pupinize]]d" telephone cable—one with loading coils added at regular intervals—failed in the early 1930s due to the [[Great Depression]].

[[TAT-1]] (Transatlantic No. 1) was the first [[transatlantic telephone cable]] system. Between 1955 and 1956, cable was laid between Gallanach Bay, near [[Oban]], Scotland and [[Clarenville, Newfoundland and Labrador]], in Canada. It was inaugurated on September 25, 1956, initially carrying 36 telephone channels.

In the 1960s, transoceanic cables were [[coaxial cable]]s that transmitted [[frequency-division multiplexing|frequency-multiplexed voiceband signals]]. A high-voltage direct current on the inner conductor powered repeaters (two-way amplifiers placed at intervals along the cable). The first-generation repeaters remain among the most reliable [[vacuum tube]] amplifiers ever designed.<ref>{{cite web |url =http://www.iscpc.org/information/Timeline_History.htm |title =Learn About Submarine Cables |publisher =International Submarine Cable Protection Committee |url-status =dead |archive-url =https://web.archive.org/web/20071213042957/http://www.iscpc.org/information/Timeline_History.htm |archive-date =2007-12-13 |access-date =2007-12-30 }}. From this page: In 1966, after ten years of service, the 1,608 tubes in the repeaters had not suffered a single failure. In fact, after more than 100 million tube-hours over all, AT&T undersea repeaters were without failure.</ref> Later ones were transistorized. Many of these cables are still usable, but have been abandoned because their capacity is too small to be commercially viable. Some have been used as scientific instruments to measure earthquake waves and other geomagnetic events.<ref>{{cite web |url= http://www.whoi.edu/science/GG/DSO/H2O/EOSarticle/H2O_article_revised_9.pdf |title=The Hawaii-2 Observatory (H2O) |author=Butler, R. |author2 =A. D. Chave |author3= F. K. Duennebier |author4=D. R. Yoerger |author5=R. Petitt |author6=D. Harris |author7=F.B. Wooding |author8 =A. D. Bowen |author9=J. Bailey |author10=J. Jolly |author11=E. Hobart |author12=J. A. Hildebrand |author13=A. H. Dodeman |url-status= live |archive-url= https://web.archive.org/web/20080226234700/http://www.whoi.edu/science/GG/DSO/H2O/EOSarticle/H2O_article_revised_9.pdf |archive-date=2008-02-26}}</ref>

===Other uses===
In 1942, [[Siemens Brothers]] of [[New Charlton]], London, in conjunction with the United Kingdom [[National Physical Laboratory, UK|National Physical Laboratory]], adapted submarine communications cable technology to create the world's first submarine oil pipeline in [[Operation Pluto]] during [[World War II]].

Active fiber-optic cables may be useful in detecting seismic events which alter cable polarization.<ref>{{cite journal |last1=Zhan |first1=Zhongwen |title=Optical polarization–based seismic and water wave sensing on transoceanic cables |journal=[[Science (journal)|Science]] |date=26 February 2021 |volume=371 |issue=6532 |pages=931–936 |doi=10.1126/science.abe6648 |pmid=33632843 |bibcode=2021Sci...371..931Z |s2cid=232050549 |url=https://www.science.org/doi/10.1126/science.abe6648}}</ref>

==Modern history==
===Optical telecommunications cables===
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[[File:Submarine cable map umap.png|thumb|upright=1.35|World map showing submarine cables in 2015]]

In the 1980s, [[optical fiber|fiber-optic cables]] were developed. The first transatlantic telephone cable to use optical fiber was [[TAT-8]], which went into operation in 1988. A fiber-optic cable comprises multiple pairs of fibers. Each pair has one fiber in each direction. TAT-8 had two operational pairs and one backup pair. Except for very short lines, fiber-optic submarine cables include repeaters at regular intervals.

Modern optical fiber repeaters use a solid-state [[optical amplifier]], usually an [[Optical amplifier#Doped fiber amplifiers|erbium-doped fiber amplifier]] (EDFA). Each repeater contains separate equipment for each fiber. These comprise signal reforming, error measurement and controls. A solid-state laser dispatches the signal into the next length of fiber. The solid-state laser excites a short length of doped fiber that itself acts as a laser amplifier. As the light passes through the fiber, it is amplified. This system also permits [[wavelength-division multiplexing]], which dramatically increases the capacity of the fiber. EDFA amplifiers were first used in submarine cables in 1995.<ref>{{cite book | url=https://books.google.com/books?id=rutYPgFCwaUC&dq=submarine+wet+plant&pg=PA163 | title=Core Networks and Network Management | isbn=978-90-5199-497-1 | last1=Faulkner | first1=D. W. | last2=Harmer | first2=Alan | date=May 10, 1999 | publisher=IOS Press }}</ref>

Repeaters are powered by a constant direct current passed down the conductor near the centre of the cable, so all repeaters in a cable are in series. Power feed equipment (PFE) is installed at the terminal stations. Typically both ends share the current generation with one end providing a positive voltage and the other a negative voltage. A [[virtual ground|virtual earth]] point exists roughly halfway along the cable under normal operation. The amplifiers or repeaters derive their power from the potential difference across them. The voltage passed down the cable is often anywhere from 3000 to 15,000VDC at a current of up to 1,100mA, with the current increasing with decreasing voltage; the current at 10,000VDC is up to 1,650mA. Hence the total amount of power sent into the cable is often up to 16.5&nbsp;kW.<ref>{{cite web|url=https://www.networkworld.com/article/2235353/the-incredible-international-submarine-cable-systems.html|title=The Incredible International Submarine Cable Systems|first=Michael|last=Morris|date=April 19, 2009|website=Network World}}</ref><ref>{{cite conference|url= https://www.suboptic.org/wp-content/uploads/2014/10/255_Poster_EC_04.pdf|title= Very Compact and High Voltage Power Feeding Equipment (PFE) for Advanced Submarine Cable Network|conference= SubOptic|date= 2010|first1= Tomoyuki|last1= Kaneko|first2= Yoshinori|last2= Chiba|first3= Kaneaki|last3= Kunimi|first4= Tomotaka|last4= Nakamura|access-date= 2020-08-08|archive-date= 2020-08-08|archive-url= https://web.archive.org/web/20200808071549/https://www.suboptic.org/wp-content/uploads/2014/10/255_Poster_EC_04.pdf|url-status= dead}}</ref>

The optic fiber used in undersea cables is chosen for its exceptional clarity, permitting runs of more than {{Convert|100|km|}} between repeaters to minimize the number of amplifiers and the distortion they cause. Unrepeated cables are cheaper than repeated cables, and their maximum transmission distance is limited. This transmission distance has increased over the years; in 2014 unrepeated cables of up to {{Convert|380|km|}} in length were in service; however these require unpowered repeaters to be positioned every 100&nbsp;km.<ref name = art>{{cite conference|url= https://www.suboptic.org/wp-content/uploads/2014/10/We2.19.pdf|title= Unrepeatered Systems: State of the Art Capability|first1= Nicolas|last1= Tranvouez|first2= Eric|last2= Brandon|first3= Marc|last3= Fullenbaum|first4= Philippe|last4= Bousselet|first5= Isabelle|last5= Brylski|conference= |access-date= 2020-08-08|archive-date= 2020-08-08|archive-url= https://web.archive.org/web/20200808070142/https://www.suboptic.org/wp-content/uploads/2014/10/We2.19.pdf|url-status= dead}}</ref>

[[File:Submarine cable repeater SVG.svg|thumb|upright=1.35|left|Diagram of an optical submarine cable repeater]]

The rising demand for these fiber-optic cables outpaced the capacity of providers such as AT&T.{{when|date=June 2014}} Having to shift traffic to satellites resulted in lower-quality signals. To address this issue, AT&T had to improve its cable-laying abilities. It invested $100&nbsp;million in producing two specialized fiber-optic cable laying vessels. These included laboratories in the ships for splicing cable and testing its electrical properties. Such field monitoring is important because the glass of fiber-optic cable is less malleable than the copper cable that had been formerly used. The ships are equipped with [[Bow thruster|thrusters]] that increase maneuverability. This capability is important because fiber-optic cable must be laid straight from the stern, which was another factor that copper-cable-laying ships did not have to contend with.<ref name="keith">{{cite news |last1=Bradsher |first1=Keith |date=15 August 1990 |title=New Fiber-Optic Cable Will Expand Calls Abroad, and Defy Sharks |work=[[The New York Times]] |url=https://www.nytimes.com/1990/08/15/business/business-technology-new-fiber-optic-cable-will-expand-calls-abroad-defy-sharks.html |access-date=14 January 2020}}</ref>

Originally, submarine cables were simple point-to-point connections. With the development of [[submarine branching unit]]s (SBUs), more than one destination could be served by a single cable system. Modern cable systems now{{when|date=June 2014}} usually have their fibers arranged in a [[self-healing ring]] to increase their redundancy, with the submarine sections following different paths on the [[seabed|ocean floor]]. One reason for this development was{{when|date=June 2014}} that the capacity of cable systems had become so large that it was not possible to completely back up a cable system with satellite capacity, so it became necessary to provide sufficient terrestrial backup capability. Not all telecommunications organizations wish to take advantage of this capability, so modern cable systems may have dual [[Cable landing point|landing points]] in some countries (where back-up capability is required) and only single landing points in other countries where back-up capability is either not required, the capacity to the country is small enough to be backed up by other means, or having backup is regarded as too expensive.{{citation needed|date=December 2024}}

A further redundant-path development over and above the self-healing rings approach is the [[Mesh networking|mesh network]] whereby fast switching equipment is used to transfer services between network paths with little to no effect on higher-level protocols if a path becomes inoperable. As more paths become available to use between two points, it is less likely that one or two simultaneous failures will prevent end-to-end service.{{citation needed|date=December 2024}}

As of 2012, operators had "successfully demonstrated long-term, error-free transmission at 100&nbsp;Gbps across Atlantic Ocean" routes of up to {{convert|6000|km|-2|abbr=on}},<ref>{{cite web |url=http://www.submarinenetworks.com/systems/trans-atlantic/hibernia-atlantic/hibernia-atlantic-trials-100g-transatlantic |title=Submarine Cable Networks&nbsp;– Hibernia Atlantic Trials the First 100G Transatlantic |publisher=Submarinenetworks.com |access-date=2012-08-15 |url-status=dead |archive-url=https://web.archive.org/web/20120622130600/http://submarinenetworks.com/systems/trans-atlantic/hibernia-atlantic/hibernia-atlantic-trials-100g-transatlantic |archive-date=2012-06-22 }}</ref> meaning a typical cable can move tens of [[terabits]] per second overseas. Speeds improved rapidly in the previous few years, with 40&nbsp;Gbit/s having been offered on that route only three years earlier in August 2009.<ref>{{cite web |url= http://www.lightreading.com/document.asp?doc_id=180473 |title=Light Reading Europe&nbsp;– Optical Networking&nbsp;– Hibernia Offers Cross-Atlantic 40G&nbsp;– Telecom News Wire |publisher=Lightreading.com |access-date=2012-08-15 |url-status=live |archive-url= https://web.archive.org/web/20120729194852/http://www.lightreading.com/document.asp?doc_id=180473 |archive-date=2012-07-29 }}</ref>

Switching and all-by-sea routing commonly increases the distance and thus the round trip latency by more than 50%. For example, the round trip delay (RTD) or latency of the fastest transatlantic connections is under 60&nbsp;ms, close to the theoretical optimum for an all-sea route. While in theory, a [[great circle route]] (GCP) between London and New York City is only {{convert|5600|km|-2|abbr=on}},<ref>{{cite web |url=http://www.gcmap.com/mapui?P=NYC-LCY&DU=km |title=Great Circle Mapper |publisher=Gcmap.com |access-date=2012-08-15 |url-status=dead |archive-url=https://web.archive.org/web/20120725194235/http://www.gcmap.com/mapui?P=NYC-LCY&DU=km |archive-date=2012-07-25 }}</ref> this requires several land masses (Ireland, [[Newfoundland (island)|Newfoundland]], Prince Edward Island and the isthmus connecting [[New Brunswick]] to [[Nova Scotia]]) to be traversed, as well as the extremely tidal [[Bay of Fundy]] and a land route along [[Massachusetts]]' north shore from [[Gloucester, Massachusetts|Gloucester]] to [[Boston]] and through fairly built up areas to [[Manhattan]] itself. In theory, using this partial land route could result in round trip times below 40&nbsp;ms (which is the speed of light minimum time), and not counting switching. Along routes with less land in the way, round trip times can approach [[speed of light]] minimums in the long term.

The type of optical fiber used in unrepeated and very long cables is often PCSF (pure silica core) due to its low loss of 0.172dB per kilometer when carrying a 1550&nbsp;nm wavelength laser light. The large chromatic dispersion of PCSF means that its use requires transmission and receiving equipment designed with this in mind; this property can also be used to reduce interference when transmitting multiple channels through a single fiber using [[Wavelength-division multiplexing|wavelength division multiplexing]] (WDM), which allows for multiple optical carrier channels to be transmitted through a single fiber, each carrying its own information.<ref>{{Cite web|url=https://www.fujitsu.com/global/documents/about/resources/publications/fstj/archives/vol42-4/paper07.pdf|title=High-Performance Submarine Line Terminal Equipment for Next-Generation Optical Submarine Cable System: FLASHWAVE S650}}</ref> WDM is limited by the optical bandwidth of the amplifiers used to transmit data through the cable and by the spacing between the frequencies of the optical carriers; however this minimum spacing is also limited, with the minimum spacing often being 50&nbsp;GHz (0.4&nbsp;nm). The use of WDM can reduce the maximum length of the cable although this can be overcome by designing equipment with this in mind.<ref name = art/>

Optical post amplifiers, used to increase the strength of the signal generated by the optical transmitter often use a diode-pumped erbium-doped fiber laser. The diode is often a high power 980 or 1480&nbsp;nm laser diode. This setup allows for an amplification of up to +24dBm in an affordable manner. Using an erbium-ytterbium doped fiber instead allows for a gain of +33dBm, however again the amount of power that can be fed into the fiber is limited. In single carrier configurations the dominating limitation is self phase modulation induced by the [[Kerr effect]] which limits the amplification to +18 dBm per fiber. In WDM configurations the limitation due to crossphase modulation becomes predominant instead. Optical pre-amplifiers are often used to negate the thermal noise of the receiver. Pumping the pre-amplifier with a 980&nbsp;nm laser leads to a noise of at most 3.5&nbsp;dB, with a noise of 5&nbsp;dB usually obtained with a 1480&nbsp;nm laser. The noise has to be filtered using optical filters.<ref name = art/>

[[Raman amplification]] can be used to extend the reach or the capacity of an unrepeatered cable, by launching 2 frequencies into a single fiber; one carrying data signals at 1550&nbsp;nm, and the other pumping them at 1450&nbsp;nm. Launching a pump frequency (pump laser light) at a power of just one watt leads to an increase in reach of 45&nbsp;km or a 6-fold increase in capacity.<ref name = art/>

Another way to increase the reach of a cable is by using unpowered repeaters called remote optical pre-amplifiers (ROPAs); these still make a cable count as unrepeatered since the repeaters do not require electrical power but they do require a pump laser light to be transmitted alongside the data carried by the cable; the pump light and the data are often transmitted in physically separate fibers. The ROPA contains a doped fiber that uses the pump light (often a 1480&nbsp;nm laser light) to amplify the data signals carried on the rest of the fibers.<ref name = art/>

WDM or wavelength division multiplexing was first implemented in submarine fiber optic cables from the 1990s to the 2000s,<ref>{{Cite web|url=https://www.itu.int/dms_pub/itu-t/opb/tut/T-TUT-HOME-2022-1-PDF-E.pdf|title=GSTR-SDM}}</ref> followed by DWDM or [[wavelength division multiplexing#Dense WDM|dense wavelength division mulltiplexing]] around 2007. Each fiber can carry 30 wavelengths at a time. SDM or [[spatial division multiplexing]] submarine cables have at least 12 fiber pairs which is an increase from the maximum of 8 pairs found in conventional submarine cables, and submarine cables with up to 24 fiber pairs have been deployed.<ref>{{Cite web|url=https://www.datacenterdynamics.com/en/news/nec-to-build-worlds-highest-capacity-submarine-cable-for-facebook-shuttling-500tbps-from-us-to-europe/|title=NEC to build world's highest capacity submarine cable for Facebook, shuttling 500Tbps from US to Europe|first=Sebastian Moss|last=Comment|date=October 12, 2021|website=www.datacenterdynamics.com}}</ref><ref>{{Cite web|url=https://sumitomoelectric.com/sites/default/files/2023-04/download_documents/E96-07.pdf|title=Optical Fibers for High Fiber Count Submarine Cable Systems}}</ref><ref>{{Cite web|url=https://subtelforum.com/stf-mag-feature-next-generation-transponder-technology-to-align-with-subsea-sdm-cables/|title=STF Mag Feature: Next Generation Transponder Technology to Align with Subsea SDM Cables|date=September 27, 2022}}</ref> The type of modulation employed in a submarine cable can have a major impact in its capacity.<ref>{{Cite web|url=https://topconference.com/wp-content/uploads/1Towards-Maximizing-Data-Throughput-on-Subsea-Fiber-Optic-Cables-Geoff-Bennett-Infinera.pdf|title=Maximizing Performance on All Types of Submarine Cable}}</ref><ref>{{Cite web|url=https://2023.apricot.net/assets/files/APPS314/sdm-a-new-subsea-par_1677480490.pdf|title=Spatial Division Multiplexing A New (Subsea) Cable Paradigm}}</ref> SDM is combined with DWDM to improve capacity.<ref>{{Cite web|url=https://www.lightwaveonline.com/optical-tech/transmission/article/16667943/google-subcom-to-deploy-space-division-multiplexing-on-dunant-submarine-cable|title=Google, SubCom, to deploy space-division multiplexing on Dunant submarine cable|first=Stephen|last=Hardy|date=April 10, 2019|website=Lightwave}}</ref>

Transponders are used to send data through the cable. The open cable concept allows for the design of a submarine cable independently of the transponders that will be used to transmit data through the cable.<ref>{{Cite journal|title=Design, Acceptance and Capacity of Subsea Open Cables|journal=Journal of Lightwave Technology|date=February 2021 |volume=39 |issue=3 |pages=742–756 |doi=10.1109/JLT.2020.3045389 |last1=Rivera Hartling |first1=Elizabeth |last2=Pilipetskii |first2=Alexei |last3=Evans |first3=Darwin |last4=Mateo |first4=Eduardo |last5=Salsi |first5=Massimiliano |last6=Pecci |first6=Pascal |last7=Mehta |first7=Priyanth |bibcode=2021JLwT...39..742R |doi-access=free }}</ref><ref>{{Cite journal|title=Design, Acceptance and Capacity of Subsea Open Cables|first1=Elizabeth|last1=Rivera Hartling|first2=Alexei|last2=Pilipetskii|first3=Darwin|last3=Evans|first4=Eduardo|last4=Mateo|first5=Massimiliano|last5=Salsi|first6=Pascal|last6=Pecci|first7=Priyanth|last7=Mehta|date=February 14, 2021|journal=Journal of Lightwave Technology|volume=39|issue=3|pages=742–756|doi=10.1109/JLT.2020.3045389|bibcode=2021JLwT...39..742R |doi-access=free}}</ref><ref>{{Cite web|url=https://web.asn.com/media/data/files_user/72/SDM1/How_to_Open_Cable_The_Guidelines_and_the_Gotchas_-_04-07-2019_R1.pdf|archive-url=https://web.archive.org/web/20220413060821/https://web.asn.com/media/data/files_user/72/SDM1/How_to_Open_Cable_The_Guidelines_and_the_Gotchas_-_04-07-2019_R1.pdf|url-status=dead|title=Subsea Open Cables: A Practical Perspective on the Guidelines and Gotchas|archive-date=2022-04-13}}</ref><ref>{{Cite web|url=https://comfutures2020.ieee-comfutures.org/wp-content/uploads/sites/101/2020/02/ComFutures2020-Ses1-SubseaCom-Kovsh.pdf|title=Subsea Communications}}</ref> SLTE (Submarine Line Terminal Equipment) has transponders and a ROADM ([[Reconfigurable optical add-drop multiplexer]]) used for handling the signals in the cable<ref name="auto">{{Cite web|url=https://www.itu.int/en/ITU-D/Regional-Presence/AsiaPacific/SiteAssets/Pages/Events/2017/Submarine%20Cable/submarine-cables-for-Pacific-Islands-Countries/Ciena%20Subsea%20PITA%20Aug2017%20v2.pdf|title=International High Capacity Connectivity through Submarine Cables}}</ref><ref>{{cite web | url=https://subtelforum.com/the-open-road-to-submarine-capacity/ | title=The Open Road to Submarine Capacity | date=January 26, 2021 }}</ref> via software control. The ROADM is used to improve the reliability of the cable by allowing it to operate even if it has faults.<ref>{{cite book | url=https://books.google.com/books?id=KvMQCgAAQBAJ&dq=SLTE+ROADM&pg=PA354 | isbn=978-0-12-804395-0 | title=Undersea Fiber Communication Systems | date=November 26, 2015 | publisher=Academic Press }}</ref> This equipment is located inside a cable landing station (CLS). C-OTDR (Coherent Optical Time Domain Reflectometry) is used in submarine cables to detect the location of cable faults.<ref name="auto"/> The wet plant of a submarine cable comprises the cable itself, branching units, repeaters and possibly OADMs ([[Optical add-drop multiplexer]]s).<ref>{{Cite web|url=https://www.fujitsu.com/global/documents/about/resources/publications/fstj/archives/vol35-1/paper05.pdf|title=WDM Optical Submarine Network Systems}}</ref><ref>{{cite book | url=https://books.google.com/books?id=2KDSDwAAQBAJ&dq=submarine+wet+plant&pg=PA399 | isbn=978-3-030-39445-5 | title=Advances in Information and Communication: Proceedings of the 2020 Future of Information and Communication Conference (FICC), Volume 1 | date=February 24, 2020 | publisher=Springer }}</ref> The SLTE is usually installed in a [[data center]] and it may be possible to purchase capacity in a cable for connecting to other points of the cable, connecting the internet,<ref>{{cite web | url=https://arstechnica.com/information-technology/2016/05/how-the-internet-works-submarine-cables-data-centres-last-mile/#page-4 | title=How the Internet works: Submarine fiber, brains in jars, and coaxial cables | date=May 26, 2016 }}</ref> for example at the [[NAP of the Americas]] which connects many Latin American ISPs with networks in the US.<ref>{{cite web | url=https://www.datacenterknowledge.com/networking/equinix-expands-miami-data-center-that-s-key-to-latin-american-connectivity | title=Equinix Expands Miami Data Center Key to Latin American Connectivity }}</ref>

===Investment and finances===
[[File:African_undersea_cables_v44.jpg|thumb|alt=Modern fiber-optic cable around Africa's coast.|A map of active and anticipated submarine communications cables servicing the African continent in 2020.]]

A typical multi-terabit, transoceanic submarine cable system costs several hundred million dollars to construct.<ref>{{cite news |author=Gardiner, Bryan |date=2008-02-25 |title=Google's Submarine Cable Plans Get Official |url=https://www.wired.com/epicenter/2008/02/googles-submari |url-status=live |archive-url=https://web.archive.org/web/20120428222444/http://www.wired.com/epicenter/2008/02/googles-submari |archive-date=2012-04-28 |magazine=Wired |format=PDF}}</ref> Almost all fiber-optic cables from TAT-8 in 1988 until approximately 1997 were constructed by consortia of operators. For example, TAT-8 counted 35 participants including most major international carriers at the time such as [[AT&T Corporation]].<ref>{{citation |author=Dunn, John |title=Talking the Light Fantastic |date=March 1987 |journal=The Rotarian}}</ref> Two privately financed, non-consortium cables were constructed in the late 1990s, which preceded a massive, speculative rush to construct privately financed cables that peaked in more than $22&nbsp;billion worth of investment between 1999 and 2001. This was followed by the bankruptcy and reorganization of cable operators such as [[Global Crossing]], [[360networks]], [[Fiber-Optic Link Around the Globe|FLAG]], [[Worldcom]], and Asia Global Crossing. [[Tata Communications]]' Global Network (TGN) is the only wholly owned fiber network circling the planet.<ref>{{cite web |last1=Dormon |first1=Bob |date=26 May 2016 |title=How the Internet works: Submarine fiber, brains in jars, and coaxial cables |url=https://arstechnica.com/information-technology/2016/05/how-the-internet-works-submarine-cables-data-centres-last-mile/ |access-date=November 28, 2020 |website=Ars Technica |publisher=Condé Nast}}</ref>

Some governments have invested in cables. For example, [[Tonga Cable System|Tonga-Fiji Submarine Cable System]] is owned and operated by Tonga Cable Limited, which developed and manages the cable with financing support from the [[Asian Development Bank]] and [[World Bank]]. Tonga Cable Limited is a public enterprise 80% owned by the government. In China, three state-owned companies in China—[[China Mobile]], [[China Telecom]], and [[China Unicom]]—invested in undersea cables. In the United States, the [[United States Navy|U.S. Navy]] owns over 40,000 nautical miles of various subsea cables.<ref>{{Cite web |title=Protection of Undersea Telecommunication Cables: Issues for Congress |url=https://sgp.fas.org/crs/misc/R47648.pdf |access-date=2025-05-05 |website=www.congress.gov}}{{source-attribution}}</ref>

Most cables in the 20th century crossed the Atlantic Ocean, to connect the United States and Europe.  However, capacity in the Pacific Ocean was much expanded starting in the 1990s.  For example, between 1998 and 2003, approximately 70% of undersea fiber-optic cable was laid in the Pacific.  This is in part a response to the emerging significance of Asian markets in the global economy.<ref>Lindstrom, A. (1999, January 1). Taming the terrors of the deep. America's Network, 103(1), 5–16.</ref>

After decades of heavy investment in already developed markets such as the transatlantic and transpacific routes, efforts increased in the 21st century to expand the submarine cable network to serve the [[Developing World]].  For instance, in July 2009, an underwater fiber-optic cable line plugged East Africa into the broader Internet.  The company that provided this new cable was [[SEACOM (African cable system)|SEACOM]], which is 75% owned by East African and South African investors.<ref>{{cite web |title=SEACOM – South Africa – East Africa – South Asia – Fiber Optic Cable |url=http://www.seacom.mu/index2.asp |url-status=dead |archive-url=https://web.archive.org/web/20100208221700/http://www.seacom.mu/index2.asp |archive-date=2010-02-08 |access-date=2010-04-25}} SEACOM (2010)</ref>  The project was delayed by a month due to increased [[piracy]] along the coast.<ref>{{cite news |author=McCarthy, Diane |date=2009-07-27 |title=Cable makes big promises for African Internet |url=http://www.cnn.com/2009/TECH/07/22/seacom.on/index.html |url-status=live |archive-url=https://web.archive.org/web/20091125042844/http://www.cnn.com/2009/TECH/07/22/seacom.on/index.html |archive-date=2009-11-25 |work=CNN}}</ref>

Investments in cables present a commercial risk because cables cover 6,200 km of ocean floor, cross submarine mountain ranges and rifts. Because of this most companies only purchase capacity after the cable is finished.<ref name=":2">{{cite web |title='Visionary' fund for early stage European infrastructure backed by nations and EU |url=https://www.eib.org/en/stories/pan-european-infrastructure-fund |access-date=2021-04-16 |website=European Investment Bank |language=en}}</ref><ref>{{cite web |date=15 May 2013 |title=Background {{!}} Marguerite |url=https://www.marguerite.com/about-us/background/ |url-status=dead |archive-url=https://web.archive.org/web/20200813021312/http://www.marguerite.com/about-us/background/ |archive-date=2020-08-13 |access-date=2021-04-16 |language=en}}</ref><ref>{{cite news |author=James Griffiths |date=26 July 2019 |title=The global internet is powered by vast undersea cables. But they're vulnerable. |url=https://www.cnn.com/2019/07/25/asia/internet-undersea-cables-intl-hnk/index.html |access-date=2021-04-16 |website=CNN}}</ref><ref>{{cite web |date=2017-10-18 |title=Harnessing submarine cables to save lives |url=https://en.unesco.org/courier/2017-october-december/harnessing-submarine-cables-save-lives |access-date=2021-04-16 |website=UNESCO |language=en}}</ref>

===Antarctica===
[[Antarctica]] is the only continent not yet reached by a submarine telecommunications cable.  Phone, video, and e-mail traffic must be relayed to the rest of the world via [[satellite]] links that have limited availability and capacity. Bases on the continent itself are able to communicate with one another via radio, but this is only a local network. To be a viable alternative, a fiber-optic cable would have to be able to withstand temperatures of {{Convert|-80|C|}} as well as massive strain from ice flowing up to {{Convert|10|m|}} per year. Thus, plugging into the larger Internet backbone with the high bandwidth afforded by fiber-optic cable is still an as-yet infeasible economic and technical challenge in the Antarctic.<ref>{{Citation |last=Conti |first=Juan Pablo |title=Frozen out of broadband |date=2009-12-05 |journal=Engineering & Technology |volume=4 |number=21 |pages=34–36 |url=http://eandt.theiet.org/magazine/2009/21/frozen-out-of-broadband.cfm |archive-url=https://web.archive.org/web/20120316161253/http://eandt.theiet.org/magazine/2009/21/frozen-out-of-broadband.cfm |archive-date=2012-03-16 |url-status=dead |doi=10.1049/et.2009.2106 |issn=1750-9645}}</ref>

=== Arctic ===
The [[climate change]] induced melting of [[Arctic]] ice has provided the opportunity to lay new cable networks, linking continents and remote regions.<ref name=":4" /><ref name=":7" /><ref name=":18">{{Cite journal |last=Shvets |first=D. |date=2018 |title=Law of the Sea and environmental law acting together: Experience of laying submarine cable in the Arctic |journal=Revista Catalana de Dret Ambiental |volume=9 |issue=2 |doi=10.17345/rcda2128}}</ref> Several projects are underway in the [[Arctic]] including 12,650 km "[[Polar Express (cable system)|Polar Express]]"<ref>{{Cite web |title=Characteristics of the project |url=https://xn--e1ahdckegffejda6k5a1a.xn--p1ai/en/ |url-status=live |archive-url=https://web.archive.org/web/20231208174804/https://xn--e1ahdckegffejda6k5a1a.xn--p1ai/en/ |archive-date=2023-12-08 |access-date=2024-03-21 |website=Polar Express}}</ref> and 14,500 km [[Far North Fiber]].<ref>{{Cite web |title=Project description |url=https://www.farnorthfiber.com/ |url-status=live |archive-url=https://web.archive.org/web/20240307231425/https://www.farnorthfiber.com/ |archive-date=2024-03-07 |access-date=2024-03-21 |website=Far North Fiber}}</ref> However, scholars have raised environmental concerns about the laying of submarine cables in the region and the general lack of a nuanced regulatory framework.<ref name=":18" /><ref name=":23">Shvets, D. (2020). The Legal Regime Governing Submarine Telecommunications Cables in the Arctic: Present State and Challenges. In Salminen, M., Zojer, G., Hossain, K. (eds) ''Digitalisation and Human Security. New Security Challenges.'' Palgrave Macmillan, Cham. https://doi.org/10.1007/978-3-030-48070-7_7

</ref><ref name=":3" /> Environmental concerns pertain both to ice-related hazards damaging the cables, and cable installation disturbing the [[seabed]] or [[electromagnetic field]]s and [[thermal radiation]] of the cables impacting sensitive organisms.<ref name=":18" /><ref name=":23" /><ref>{{Cite journal |last=OSPAR Commission |date=2009 |title=Assessment of the environmental impacts of cables. |url=https://qsr2010.ospar.org/media/assessments/p00437_Cables.pdf |journal=Biodiversity |series=Series 1}}</ref>

== Importance of submarine cables ==
Submarine cables, while often perceived as ‘insignificant’ parts of communication infrastructure as they lay "hidden" in the seabed,<ref>{{Cite journal |last=Abildgaard |first=M. S. |date=2022 |title=The question of icebergs: A cryo-history of Arctic submarine cables |url=https://doi.org/10.1017/s0032247422000262 |journal=Polar Record |volume=58|doi=10.1017/s0032247422000262 |bibcode=2022PoRec..58E..41A }}</ref><ref name=":0">{{Cite journal |last1=Bueger |first1=C. |last2=Liebetrau |first2=T. |date=2021 |title=Protecting hidden infrastructure: The security politics of the global submarine data cable network |url=https://doi.org/10.1080/13523260.2021.1907129 |journal=Contemporary Security Policy |volume=42 |issue=3|pages=391–413 |doi=10.1080/13523260.2021.1907129 }}</ref> are an essential infrastructure in the [[digital era]], carrying 99% of the data traffic across the oceans.<ref>{{Cite news |title=Undersea Cables Transport 99 Percent of International Data |url=http://europe.newsweek.com/undersea-cables-transport-99-percent-international-communications-319072?rm=eu |access-date=2016-11-16 |newspaper=Newsweek}}</ref> This data includes all [[internet traffic]], military transmissions, and [[financial transaction]]s.<ref name=":0" /><ref name=":1">{{Cite journal |last1=Bueger |first1=C. |last2=Liebetrau |first2=T. |last3=Franken |first3=J. |date=2022 |title=Security threats to undersea communications cables and infrastructure –consequences for the EU |url=https://www.europarl.europa.eu/RegData/etudes/IDAN/2022/702557/EXPO_IDA(2022)702557_EN.pdf |journal=European Parliament |volume=PE 702.557}}</ref><ref name=":3">Saunavaara, J. (2020). Connecting the Arctic While Installing Submarine Data Cables Between East Asia, North America and Europe 205. In M. Salminen, G. Zojer, & K. Hossain (Eds.), ''Digitalisation and human security: A multi-disciplinary approach to cybersecurity in the European high north'' (pp. 205–230). Palgrave Macmillan. https://doi.org/10.1007/978-3-030-48070-7</ref>

The total carrying capacity of a submarine cable is in the [[terabits]] per second, while a [[satellite]] typically offers only 1 [[gigabit]] per second, a ratio of more than 1000 to 1. Satellites handle less than 5%<ref name=":4">Carter, L., & Burnett, D. R. (2015). Subsea Telecommunications. In H. D. Smith, J. L. Vivero, & T. S. Agardy (Eds.), ''Routledge Handbook of Ocean Resources and Management'' (1st ed.). Routledge.</ref> – to an estimate of even 0.5% – of global data transmission,<ref name=":3" /> and are less efficient, slower, and more expensive.<ref name=":5">Frascà, D., & Galantini, L. (2023). The Issue of Submarine Cable Security. In F. Cappelletti (Ed.), ''Towards a New European Security Architecture''. ELF Study 6. https://doi.org/10.53121/ELFS6</ref> Therefore, satellites are often exclusively considered for remote areas with challenging conditions for laying submarine cables.<ref name=":6">Wasiuta, O. (2023). Russian threats to the submarine internet cable infrastructure. ''Zeszyty Naukowe SGSP'', ''87.''https://doi.org/10.5604/01.3001.0053.9127</ref> Submarine cables are thus the essential technical infrastructure for all internet communication.

=== National security ===
As a result of these cables' cost and usefulness, they are highly valued not only by the corporations building and operating them for profit, but also by national governments. For instance, the Australian government considers its submarine cable systems to be "vital to the national economy". Accordingly, the [[Australian Communications and Media Authority]] (ACMA) has created protection zones that restrict activities that could potentially damage cables linking Australia to the rest of the world. The ACMA also regulates all projects to install new submarine cables.<ref name=":19">{{cite web |url=http://archive.acma.gov.au/WEB/STANDARD/1001/pc=PC_100223 |publisher=Australian Communications and Media Authority |date=February 5, 2010 |title=Submarine telecommunications cables}} {{Dead link|date=December 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>

Due to their critical role, disruptions to these cables can lead to [[Communications blackout|communication blackouts]] and, thus, extensive economic losses.<ref name=":4" /> The impact of such disruptions is often exemplified by the [[2022 Hunga Tonga–Hunga Haʻapai eruption and tsunami|2022 Tonga volcanic eruption]] that severed the island's only submarine cable and thus connectivity to the rest of the world for several days.<ref name=":0" /><ref name=":7">{{Cite journal |last1=Clare |first1=M. A. |last2=Yeo |first2=I. A. |last3=Bricheno |first3=L. |last4=Aksenov |first4=Y. |last5=Brown |first5=J. |last6=Haigh |first6=I. D. |last7=Wahl |first7=T. |last8=Hunt |first8=J. |last9=Sams |first9=C. |last10=Chaytor |first10=J. |last11=Bett |first11=B. J. |last12=Carter |first12=L. |date=2023-02-01 |title=Climate change hotspots and implications for the global subsea telecommunications network |journal=Earth-Science Reviews |volume=237 |pages=104296 |doi=10.1016/j.earscirev.2022.104296 |bibcode=2023ESRv..23704296C |issn=0012-8252|doi-access=free }}</ref><ref name=":5" /><ref name=":8">Guilfoyle, D., Paige, T. P., & McLaughlin, R. (2022). The final frontier of cyberspace: The seabed beyond national jurisdiction and the protection of submarine cables. ''International and Comparative Law Quarterly'', ''71''(3). https://doi.org/10.1017/s0020589322000227</ref><ref name=":9">McGeachy, H. (2022). The changing strategic significance of submarine cables: Old technology, new concerns. ''Australian Journal of International Affairs'', ''76''(2), 161–177. https://doi.org/10.1080/10357718.2022.2051427</ref> The cable break was declared a “national crisis,” and repairs took several weeks, leaving Tonga largely isolated during a crucial period for disaster response.<ref name=":0" /><ref name=":7" /><ref name=":5" /><ref name=":8" />

Submarine cable infrastructure may even have additional technical advantages, such as carrying SMART environmental sensors supporting national disaster [[early warning system]]s.<ref>International Telecommunication Union. (2023). ''Innovative approaches to natural disaster management: Leveraging AI for data related processes'' (1–134). https://www.itu.int/dms_pub/itu-t/opb/fg/T-FG-AI4NDM-2023-3-PDF-E.pdf</ref> Furthermore, the cables are predicted to become even more critical with growing demands from [[5G network slicing|5G networks]], the ‘[[Internet of things]]’ (IoT), and [[artificial intelligence]] on large data transfers.<ref name=":0" />

=== International security ===
Submarine communication cables are a critical infrastructure within the context of [[international security]].<ref name=":0" /> Transmitting massive amounts of sensitive data every day, they are essential for both state operations and private enterprises.<ref name=":0" /> One of the catalysts for the amount and sensitivity of data flowing through these cables has been the global rise of [[cloud computing]].<ref name=":15">{{Cite web |last=Sherman |first=Justin |date=2021-09-13 |title=Cyber defense across the ocean floor: The geopolitics of submarine cable security |url=https://www.atlanticcouncil.org/in-depth-research-reports/report/cyber-defense-across-the-ocean-floor-the-geopolitics-of-submarine-cable-security/ |access-date=2024-12-05 |website=Atlantic Council |language=en-US}}</ref>

The [[United States Armed Forces|U.S military]], for example, uses the submarine cable network for data transfer from conflict zones to command staff in the United States (U.S.). Interruption of the cable network during intense operations could have direct consequences for the military on the ground.<ref name=":11">{{cite journal |last1=Clark |first1=Bryan |date=2016 |title=Undersea cables and the future of submarine competition |journal=Bulletin of the Atomic Scientists |volume=72 |issue=4 |pages=234–237 |bibcode=2016BuAtS..72d.234C |doi=10.1080/00963402.2016.1195636 |doi-access=free}}</ref>

The criticality of cable services makes their geopolitical influence profound. Scholars argue that state dominance in cable networks can exert political pressure,<ref name=":9" /><ref name=":6" /> or shape global internet governance.<ref name=":0" />

An example of such state dominance in the global cable infrastructure is China's ‘Digital Silk Road’ strategy funding the expansion of Chinese cable networks, with the Chinese company [[Huawei|HMN Technologies]] often criticised for providing networks for other states, holding up to 10% of the [[Market share|global market share]].<ref name=":1" /><ref>{{Cite web |date=2023 |title=CHINA'S SUBSEA CABLE POWER PLAY IN THE MIDDLE EAST AND NORTH AFRICA |url=https://www.atlanticcouncil.org/wp-content/uploads/2023/05/ChinasGrowingInfluence_052423-1.pdf |access-date=2024-12-05 |website=Atlantic Council}}</ref> Some critiques argue that Chinese investments in critical cable infrastructure, being involvement in approximately 25% of global submarine cables,<ref name=":9" /> such as the [[PEACE Cable]] linking Eastafrica and Europe, may enable China to reroute data traffic through its own networks, and thus apply political pressure.<ref>{{Cite web |last=Caro |first=Carlo J. V. |date=2024-11-26 |title=Underwater Geopolitics {{!}} RealClearDefense |url=https://www.realcleardefense.com/articles/2024/11/26/underwater_geopolitics_1074698.html |access-date=2024-12-05 |website=www.realcleardefense.com |language=en}}</ref> The strategy is countered by the U.S., supporting alternative projects.<ref name=":1" /><ref name=":9" /><ref name=":20">{{Cite web |last1=Guarascio |first1=Francesco |last2=Nguyen |first2=Phuong |last3=Brock |first3=Joe |date=2024-09-18 |title=Exclusive: Inside the US push to steer Vietnam's subsea cable plans away from China |url=https://www.reuters.com/business/media-telecom/inside-us-push-steer-vietnams-subsea-cable-plans-away-china-2024-09-17/ |website=Reuters}}</ref>

== Vulnerabilities of submarine cables ==
Submarine cables are exposed to a variety of potential threats. Many of these threats are accidental, such as by [[Trawling|fishing trawlers]], [[Anchor|ship anchors]], earthquakes, [[turbidity current]]s, and even shark bites.<ref name=":1" /><ref name=":4" /><ref name=":7" /><ref name=":6" /><ref name="dangerstocables">{{cite news |last=Tanner |first=John C. |date=1 June 2001 |title=2,000 Meters Under the Sea |url=http://findarticles.com/p/articles/mi_m0DUJ/is_9_105/ai_n27568414/ |url-status=dead |archive-url=https://archive.today/20120708035409/http://findarticles.com/p/articles/mi_m0DUJ/is_9_105/ai_n27568414/ |archive-date=8 July 2012 |access-date=9 August 2009 |work=America's Network |publisher=bnet.com}}</ref><ref>{{Cite magazine |last=McMillan |first=Robert |title=Sharks Want to Bite Google's Undersea Cables |url=https://www.wired.com/2014/08/shark-cable/ |magazine=Wired |via=www.wired.com}}</ref>

Based on surveying breaks in the Atlantic Ocean and the [[Caribbean Sea]], it was found that between 1959 and 1996, fewer than 9% were due to natural events. In response to this threat to the communications network, the practice of cable burial has developed. The average incidence of cable faults was 3.7 per {{convert|1000|km|-1|abbr=on}} per year from 1959 to 1979. That rate was reduced to 0.44 faults per 1,000 km per year after 1985, due to widespread burial of cable starting in 1980.<ref name=":12">{{cite web |author=Shapiro, S. |author2=Murray, J.G. |author3=Gleason, R.F. |author4=Barnes, S.R. |author5=Eales, B.A. |author6=Woodward, P.R. |date=1987 |title=Threats to Submarine Cables |url=http://www.scig.net/Section07b.pdf |archive-url=https://web.archive.org/web/20041015081858/http://www.scig.net/Section07b.pdf |archive-date=2004-10-15 |access-date=2010-04-25}}</ref>

Still, cable breaks are by no means a thing of the past, with more than 50 repairs a year in the Atlantic Ocean alone,<ref name=":13">{{cite news |author=John Borland |date=February 5, 2008 |title=Analyzing the Internet Collapse: Multiple fiber cuts to undersea cables show the fragility of the Internet at its choke points. |url=http://www.technologyreview.com/Infotech/20152/?a=f |work=Technology Review}}</ref> and significant breaks in [[2006 Hengchun earthquake#Disruption in communications|2006]], [[2008 submarine cable disruption|2008]], 2009 and [[2011 submarine cable disruption|2011]].

Several vulnerabilities of submarine communication cables make them attractive targets for [[organized crime]]. The following section explores these vulnerabilities and currently proposed counter measures to organized crime from different perspectives.

=== Technical perspective ===

==== Technical vulnerabilities ====
The remoteness of these cables in international waters, poses significant challenges for continuous monitoring and increases their attractiveness as targets of physical tampering, [[data theft]], and service disruptions.<ref name=":4" />

The cables' vulnerability is further compounded by technological advancements, such as the development of [[unmanned underwater vehicle]]s (UUVs), which enable covert cable damage while avoiding detection.<ref name=":16">Wrathall, L. R. (2010). The vulnerability of subsea infrastructure to underwater attack: Legal shortcomings and the way forward. ''San Diego International Law Journal'', ''12''(1), 223–262. <nowiki>https://digital.sandiego.edu/ilj/vol12/iss1/8</nowiki></ref> However, even [[Low technology|low-tech]] attacks can impact the cable's security significantly, as demonstrated in 2013, when three divers were arrested for severing the main cable linking [[Egypt]] with Europe, drastically lowering Egypt's [[Bandwidth (computing)|internet speed]].<ref name=":11" /><ref>{{Cite web |date=2013-03-27 |title=Egypt catches divers cutting Internet cable amid disruptions |url=https://www.reuters.com/article/technology/egypt-catches-divers-cutting-internet-cable-amid-disruptions-idUSBRE92Q1AQ/ |website=Reuters}}</ref> 

Even in shallow waters, cables remain exposed to risks, as illustrated in the context of the [[Korea Strait]].<ref name=":14">O’Malley, S. (2019). Assessing threats to South Korea's undersea communications cable infrastructure. ''The Korean Journal of International Studies'', ''17''(3), 385–414. https://doi.org/10.14731/kjis.2019.12.17.3.385</ref> Such sea passages are often marked as ‘maritime choke points’ where several nations have conflicting interests, increasing the risk of harm from shipping activities and disputes.<ref name=":5" />

Further, most cable locations are publicly available,<ref name=":5" /> making them an easy target for criminal acts such as disrupting services or stealing cable materials, which potentially lead to substantial [[Communications blackout|communication blackouts]].<ref name=":14" /><ref name=":17">Raha, U. K., & D., R. K. (2021). ''Submarine cables protection and regulations: A comparative analysis and model framework'' (pp. 1–177). Springer Nature. https://doi.org/10.1007/978-981-16-3436-9_1</ref> The stealing of submarine cable has been reported in [[Vietnam]], where more than 11 km of cables went missing in 2007 and were later presumed to be found on fishing boats, attributed to their incentives to sell them, according to media reports.<ref>Bdnews24.com. (2007, June 1). ''Vietnam's submarine cable lost and found''. Vietnam's submarine cable lost and found. https://bdnews24.com/bangladesh/vietnam-s-submarine-cable-lost-and-fou nd</ref><ref>Khan, A. S. (2007, June 2). ''Vietnam's submarine cable 'lost' and 'found' — LIRNEasia''. LIRNEasia. https://lirneasia.net/2007/06/vietnams-submarine-cable-lost-and-found/</ref>

==== Technical countermeasures ====
Typically, cables are buried in waters with a depth of less than 2,000 meters, but increasingly, they are buried in deeper seabed as a means of protection against high seas fishing and [[bottom trawling]].<ref name=":4" /><ref name=":7" /> However, this may also be advantageous against physical attacks from organized crime.

Further technical solutions are advanced protective casings,<ref name=":4" /> and monitoring them with, e.g., UUVs.<ref name=":11" /> Such technical solutions, however, can be challenging to implement and are limited in the remote areas of the high sea.<ref name=":4" /> Other proposed solutions include spatial modelling through protective or safety zones and penalties,<ref name=":19" /><ref name=":17" /><ref name=":16" /> increasing resources for surveillance,<ref name=":14" /> and a more collaborative approach between states and the private sector.<ref name=":1" /><ref name=":21">Hansen, S. T., & Antonsen, S. (2024). Taking connectedness seriously. A research agenda for holistic safety and security risk governance. ''Safety Science'', ''173'', 106436. https://doi.org/10.1016/j.ssci.2024.106436</ref><ref name=":3" /><ref name=":16" /> However, how to implement and enforce these solutions remains to be determined.<ref name=":17" /> The cables' remoteness thus complicates both physical attacks and their protection.

===== Cable repair =====
[[File:Submarine cable repair animation.gif|thumb|right|An animation showing a method used to repair submarine communications cables.]]

Shore stations can locate a break in a cable by electrical measurements, such as through [[spread-spectrum time-domain reflectometry]] (SSTDR), a type of [[Time-domain reflectometer|time-domain reflectometry]] that can be used in live environments very quickly. Presently, SSTDR can collect a complete data set in 20ms.<ref>Smith, Paul, [[Cynthia Furse|Furse, Cynthia]], Safavi, Mehdi, and Lo, Chet. "Feasibility of [http://livewiretest.com/analysis-of-spread-spectrum-time-domain-reflectometry-for-wire-fault-location/ Spread Spectrum Sensors for Location of Arcs on Live Wires] Spread Spectrum Sensors for Location of Arcs on Live Wires." ''IEEE Sensors Journal''. December, 2005. {{webarchive |url= https://web.archive.org/web/20101231231446/http://livewiretest.com/analysis-of-spread-spectrum-time-domain-reflectometry-for-wire-fault-location |date= December 31, 2010 }}</ref> Spread spectrum signals are sent down the wire and then the reflected signal is observed. It is then correlated with the copy of the sent signal and algorithms are applied to the shape and timing of the signals to locate the break.

A cable repair ship will be sent to the location to drop a marker buoy near the break. Several types of [[grapple (tool)|grapples]] are used depending on the situation. If the sea bed in question is sandy, a grapple with rigid prongs is used to plough under the surface and catch the cable. If the cable is on a rocky sea surface, the grapple is more flexible, with hooks along its length so that it can adjust to the changing surface.<ref>[https://books.google.com/books?id=TuQDAAAAMBAJ&pg=PA621 "When the ocean floor quakes"] ''Popular Mechanics'', '''vol.53''', no.4, pp.618–622, April 1930, {{ISSN|0032-4558}}, pg 621: various drawing and cutaways of cable repair ship equipment and operations</ref> In especially deep water, the cable may not be strong enough to lift as a single unit, so a special grapple that cuts the cable soon after it has been hooked is used and only one length of cable is brought to the surface at a time, whereupon a new section is spliced in.<ref>Clarke, A. C. (1959). ''Voice Across the Sea''. New York, N.Y.: Harper & Row, Publishers, Inc.. p. 113</ref> The repaired cable is longer than the original, so the excess is deliberately laid in a "U" shape on the [[seabed]]. A [[submersible]] can be used to repair cables that lie in shallower waters.

A number of ports near important cable routes became homes to specialized cable repair ships. [[Halifax Regional Municipality|Halifax]], Nova Scotia, was home to a half dozen such vessels for most of the 20th century including long-lived vessels such as the [[Cable Ship|CS]] ''Cyrus West Field'', CS ''Minia'' and ''[[CS Mackay-Bennett]]''. The latter two were contracted to recover victims from the [[sinking of the RMS Titanic|sinking of the RMS ''Titanic'']]. The crews of these vessels developed many new techniques and devices to repair and improve cable laying, such as the "[[Pipe-and-cable-laying plough|plough]]".

=== Cybersecurity perspective ===

==== Cyber vulnerabilities ====
Increasingly, sophisticated [[Cyberattack|cyber-attacks]] threaten the data traffic on the cables, with incentives ranging from financial gain, espionage, or [[extortion]] by either state actors or non-state actors.<ref name=":1" /><ref name=":11" /><ref name=":8" /> Further, [[hybrid warfare]] tactics can interfere with or even weaponize the data transferred by the cables.<ref name=":8" /> For example, low-intensity cyber-attacks can be employed for [[ransomware]], data manipulation and theft,<ref>Grabosky, P. (2007). The internet, technology, and organized crime. ''Asian Journal of Criminology'', ''2''(2), 145–161. https://doi.org/10.1007/s11417-007-9034-z</ref><ref name=":8" /> opening up new a new opportunity for the use of [[cybercrime]] and [[Grey-zone (international relations)|grey-zone tactics]] in interstate disputes.<ref>Bueger, C., & Edmunds, T. (2024). ''Understanding maritime security''. Oxford University Press. https://10.1093/oso/9780197767146.001.0001{{Dead link|date=March 2025 |bot=InternetArchiveBot |fix-attempted=yes }}</ref><ref>Heller, K. J. (2022). ''Low-Intensity Cyber Operation and State Sovereignty in Cyberspace'' (1st ed.). Djøf Publishing and The Centre for Military Studies.</ref>

The lack of binding international [[Information security standards|cybersecurity standards]] may create a gap in dealing with cyber-enabled sabotage, that can be used by organized crime.<ref name=":8" /> However, attributing an incident to a specific actor or motivation of such actor can be challenging, specifically in cyberspace.<ref>Jaggard, A. D., Johnson, A., Cortes, S., Syverson, P., & Feigenbaum, J. (2015). 20,000 in league under the sea: Anonymous communication, trust, MLATs, and undersea cables. ''Proceedings on Privacy Enhancing Technologies'', ''2015''(1), 4–24. https://doi.org/10.1515/popets-2015-0002</ref>

==== Cyber espionage and Intelligence-gathering ====
The rising sophistication of cyberattacks underscores the vulnerability of submarine cables to [[cyberespionage]], ultimately complicating their security. Techniques like [[Wiretapping|cable tapping]], hacking into network management systems, and targeting [[Cable landing point|cable landing stations]] enable covert data access by intelligence agencies, with Russia, the U.S., and the United Kingdom (U.K.) noted as primary players.<ref name=":5" /><ref name=":14" />

These activities are driven by both strategic and economic motives, with advancements in technology making interception and data manipulation more effective and difficult to detect.<ref name=":1" /> Recent technological advancements increasing the vulnerability include the use of remote access portals and remote network management systems centralizing control over components, enabling attackers to monitor traffic and potentially disrupt data flows.<ref name=":1" /><ref name=":15" />

[[List of intelligence gathering disciplines|Intelligence-gathering]] techniques have been deployed since the late 19th century. Frequently at the beginning of wars, nations have cut the cables of the other sides to redirect the information flow into cables that were being monitored. The most ambitious efforts occurred in [[World War I]], when British and German forces systematically attempted to destroy the others' worldwide communications systems by cutting their cables with surface ships or submarines.<ref>Jonathan Reed Winkler, ''Nexus: Strategic Communications and American Security in World War I'' (Cambridge, MA: [[Harvard University Press]], 2008)</ref>

During the [[Cold War]], the [[United States Navy]] and [[National Security Agency]] (NSA) succeeded in placing wire taps on Soviet underwater communication lines in [[Operation Ivy Bells]].

These historical intelligence-gathering techniques were eventually countered with technological advancements like the widespread use of [[end-to-end encryption]] minimizing the threat of [[Wiretapping|wire tapping]].

==== Cybersecurity countermeasures ====
Cybersecurity strategies for submarine cables, such as [[encryption]], access controls, and continuous monitoring, primarily focus on preventing unauthorized data access but do not adequately address the physical protection of cables in vulnerable, remote, high-sea areas as stated above.<ref name=":11" /> 

As a result, while cybersecurity protocols are effective near coastal landing points, their enforcement across vast stretches of the open ocean becomes a challenge.<ref name=":11" /> To address these limitations, experts suggest a broader, multi-layered approach that integrates physical security measures with international cooperation and legal frameworks, especially given the jurisdictional ambiguities in international waters.<ref name=":8" /><ref name=":17" /> 

Multilateral agreements to establish cybersecurity standards specific to submarine cables are highlighted as critical. These agreements can help bridge the jurisdictional ambiguities and often resulting enforcement gaps in international waters, which ultimately hinder effective protection and are frequently exploited by organized crime.<ref name=":8" />

Some scholars advocate for heightened European Union (E.U.) coordination, recommending improvements in surveillance and response capabilities across various agencies, such as the [[Coast guard]] and specific telecommunication regulators.<ref name=":1" /> Given the central role of private companies in cable ownership, some experts also underscore the need for stronger collaboration between governments and tech firms to pool resources and develop more innovative security measures tailored to this critical infrastructure.<ref name=":11" />

=== Geopolitical perspective ===

==== Geopolitical vulnerabilities ====
[[Fishing vessel]]s are the leading cause of accidental damage to submarine communication cables.<ref name=":1" /><ref name=":4" /> However, some of the academic discussions and recent incidents point to geopolitical tactics influencing the cable's security more than previously expected.<ref name=":0" /> These tactics include the ease and potential with which fishing vessels can blend into regular maritime traffic and implement their attacks.<ref name=":14" />

The propensity for [[fishing trawler]] nets to cause cable faults may well have been exploited during the [[Cold War]]. For example, in February 1959, a series of 12 breaks occurred in five American trans-Atlantic communications cables. In response, a U.S. naval vessel, the [[USS Roy O. Hale (DE-336)|USS ''Roy O. Hale'']], detained and investigated the Soviet trawler ''Novorosiysk''. A review of the ship's log indicated it had been in the region of each of the cables when they broke. Broken sections of cable were also found on the deck of the ''Novorosiysk''. It appeared that the cables had been dragged along by the ship's nets, and then cut once they were pulled up onto the deck to release the nets. The Soviet Union's stance on the investigation was that it was unjustified, but the U.S. cited the [[Convention for the Protection of Submarine Telegraph Cables]] of 1884 to which Russia had signed (prior to the formation of the Soviet Union) as evidence of violation of international protocol.<ref>The Embassy of the United States of America. (1959, March 24). U.S. note to Soviet Union on breaks in trans-Atlantic cables. The New York Times, 10.</ref>

Several media outlets and organizations indicate that Russian fishing vessels, particularly in 2022, passed over a damaged submarine cable up to 20 times, suggesting potential political motives and the possibility of hybrid warfare tactics used from Russia's side.<ref>{{Cite news |last=Humpert |first=M |date=24 October 2022 |title=Fiber-optic submarine cable near Faroe and Shetland Islands damaged; Mediterranean cables also cut. |url=https://www.highnorthnews.com/en/fiber-optic-submarine-cable-near-faroe-and-shetland-islands-damaged-mediterranean-cables-also-cut |work=High North News.}}</ref><ref>{{Cite news |last=EUobserver |date=October 26, 2022 |title=Mysterious Atlantic cable cuts linked to Russian fishing vessels. |url=https://euobserver.com/nordics/156342 |work=}}</ref> Russian naval activities near submarine cables are often linked to increased hybrid warfare strategies targeting submarine cables, where sabotage is argued to serve as a tool to disrupt communication networks during conflict and destabilise adversaries.<ref name=":1" /><ref name=":6" /> 

These tactics elevate cable security to a significant geopolitical issue.<ref name=":6" /> Criminal actors may further target cables as a means of economic warfare, aiming to destabilize economies or convey political messages.<ref name=":11" /><ref name=":5" /><ref name=":8" /> The disruption of submarine communication cables in highly politicised maritime areas thus has a significant political component that is receiving increased attention.

After two cable breaks in the [[Baltic Sea]] in November 2024, one between [[Lithuania]] and Sweden and the other between [[Finland]] and Germany, Defence Minister [[Boris Pistorius]] argued: 

''“No one believes that these cables were cut accidentally. I also don't want to believe in versions that these were ship anchors that accidentally caused the damage. Therefore, we have to state, without knowing specifically who it came from, that it is a 'hybrid' action. And we also have to assume, without knowing it yet, that it is sabotage."'' <ref>{{Cite web |last1=Cook |first1=Ellie |last2=Feng |first2=John |date=2024-11-19 |title="NATO lake" sabotage feared as two undersea cables damaged in 24 hours |url=https://www.newsweek.com/nato-baltic-sea-undersea-cables-sabotage-finland-germany-sweden-lithuania-1988002 |access-date=2024-12-06 |website=Newsweek |language=en}}</ref><ref>{{Cite web |date=2024-11-19 |title=Sweden opens "sabotage" investigation into severed Baltic Sea fibre-optic cables |url=https://www.france24.com/en/europe/20241119-germany-believes-telecom-cables-cut-in-baltic-sea-was-act-of-sabotage |access-date=2024-12-06 |website=France 24 |language=en}}</ref> 

This statement underlines the current discourse to recognize cable disruptions as threats to national security, which ultimately leads to their [[Securitization (international relations)|securitization]] in the international context.<ref>{{Cite web |last=Katzman |first=Jonathan |title=Securitization of Physical Cyberspace Infrastructure as a Nexus in U.S.-Russia Relations: The Case of Submarine Communications Cables |url=https://russiancouncil.ru/en/analytics-and-comments/columns/cybercolumn/securitization-of-physical-cyberspace-infrastructure-as-a-nexus-in-u-s-russia-relations-the-case-of/ |access-date=2024-12-06 |website=russiancouncil.ru |language=en}}</ref>

==== Geopolitical risks and countermeasures ====
Submarine cables are inherently vulnerable to transnational threats like organized crime.<ref name=":1" />  International collaboration to address these threats tends to fall to existing organizations with a cable specific focus – such as the [[International Cable Protection Committee|International Cable Protection Committee (ICPC)]] – which represent key submarine stakeholders, and play a vital role in promoting cooperation and information sharing among stakeholders.<ref name=":1" /><ref name=":5" /> Such organizations are argued to be crucial to develop and implement a comprehensive and coordinated global strategy for cable security.<ref name=":17" />

As of 2025, a tense U.S.-China relationship complicates this task especially in the [[South China Sea]] where there are territorial disputes.  China has increasing control and influence over global cables networks, while both it and the USA financially supports allied-owned cable projects and exerts diplomatic pressure and regulatory action, e.g. against [[Vietnam]].<ref>{{Cite news |last1=Guarascio |first1=Francesco |last2=Nguyen |first2=Phuong |last3=Brock |first3=Joe |date=18 September 2024 |title=Exclusive: Inside the US push to steer Vietnam's subsea cable plans away from China |url=https://www.reuters.com/business/media-telecom/inside-us-push-steer-vietnams-subsea-cable-plans-away-china-2024-09-17/ |access-date=7 December 2024 |work=Reuters}}</ref><ref name=":1" /><ref name=":9" /><ref name=":20" /> 

In light of [[Nord Stream pipelines sabotage]] in the [[Baltic Sea]], where subsea infrastructure vital to Germany and Russia was physically destroyed, and other incidents there, [[NATO]] has increased patrols and monitoring operations.<ref name=":6" /><ref>{{Cite web |date=2023-06-16 |title=NATO moves to protect undersea pipelines, cables as concern mounts over Russian sabotage threat |url=https://apnews.com/article/nato-russia-sabotage-pipelines-cables-infrastructure-507929033b05b5651475c8738179ba5c |access-date=2024-12-07 |website=AP News |language=en}}</ref>

=== Legal perspective ===

==== Legal vulnerabilities ====
Submarine cables are internationally regulated within the framework of the [[United Nations Convention on the Law of the Sea]] (UNCLOS), in particular through the provisions of Articles 112 and 97, 112 and 115, which mandate operational freedom to lay cables in international waters and beyond the continental shelf and reward measures to protect against shipping accidents.<ref name=":22">Davenport, T. (2018). The high seas freedom to lay submarine cables and the protection of the marine environment: Challenges in high seas governance. ''AJIL Unbound'', ''112'', 139–143. https://doi.org/10.1017/aju.2018.48</ref>

However, submarine cables face significant legal challenges and lack specific legal protection in UNCLOS and enforcement mechanisms against emerging threats, particular in international waters.<ref name=":0" /><ref name=":22" /><ref name=":17" /><ref name=":8" /> This is further complicated by the non-ratification of the treaty by key states such as the U.S. and [[Turkey]].<ref name=":5" /> Many countries lack explicit legal provisions to criminalize the destruction or theft of undersea cables, creating jurisdictional ambiguities that organized crime can exploit.<ref name=":1" /><ref name=":8" /><ref name=":17" /> Other legal frameworks, such as the 1884 [[Convention for the Protection of Submarine Telegraph Cables]] are outdated and fail to address modern threats like cyberattacks and hybrid warfare tactics.<ref name=":8" /> The unclear jurisdiction and weak enforcement mechanisms, demonstrate the difficulty to protect submarine cables from organized crime.

The Arctic Ocean in particular exemplifies the challenges associated with surveillance and enforcement in vast and remote areas, leaving a legal vacuum that criminals may exploit. In the [[Arctic]], the absence of a central international authority to oversee submarine cable protection and the reliance on military organizations like NATO hinders general coordinated global responses.<ref name=":18" />

Organizations such as the [[International Cable Protection Committee|ICPC]] thus highlight the need for updated and more comprehensive legal frameworks to ensure the security of submarine cables.<ref>{{Cite news |date=July 13, 2021 |title=International Cable Protection Committee Launches 'Best Practices for Cable Protection and Resilience as Resource for Governments' |url=https://www.businesswire.com/news/home/20210713006068/en/International-Cable-Protection-Committee-Launches-%E2%80%98Best-Practices-for-Cable-Protection-and-Resilience-as-Resource-for-Governments%E2%80%99 |work=Businesswire}}</ref>

==== Legal countermeasures ====
The legal challenges of protecting submarine cables from organized crime have resulted in recommendations ranging from treaty amendments to domestic law reforms and [[multi-level governance]] models.

Some scholars argue that UNCLOS should be updated to protect cables extensively, including cooperative monitoring and enforcement protocols.<ref name=":22" /> Additionally, principles from the [[law of the sea]], state responsibility, and the laws on the use of force could be creatively applied to strengthen protections for cables.<ref name=":8" /> Enforcement issues could be tackled by aligning domestic laws with UNCLOS, implementing national response protocols, and creating streamlined points of contact for cable incidents.<ref name=":8" /> Given the increased involvement of organizations like NATO, others recommend to clarify the roles of military and non-military actors in cable security and enhanced multi-level governance models.<ref name=":18" /><ref name=":21" />

While these proposed legal solutions seem promising, their practical implementation still remains a challenge due to the complexity of international treaties, the need for international cooperation, the lack of domestic criminalization of cable damage, and the evolving nature of technological threats.<ref name=":0" /><ref name=":1" /><ref name=":8" /><ref name=":17" />  Additionally, while UNCLOS's ambiguous jurisdiction in international waters hinders effective enforcement, limited political interests seems to hamper treaty development.<ref name=":0" /><ref name=":1" /><ref name=":6" />

==Environmental impact ==

The presence of cables in the oceans can be a danger to marine life. With the proliferation of cable installations and the increasing demand for inter-connectivity that today's society demands, the environmental impact is increasing.

Submarine cables can impact [[marine life]] in a number of ways.

=== Alteration of the seabed ===
Seabed ecosystems can be disturbed by the installation and maintenance of cables. The effects of cable installation are generally limited to specific areas. The intensity of disturbance depends on the installation method.

Cables are often laid in the so-called [[benthic zone]] of the seabed. The [[benthic zone]] is the ecological region at the bottom of the sea where benthos, clams and crabs live, and where the surface sediments, which are deposits of matter and particles in the water that provide a habitat for marine species, are located.

Sediment can be damaged by cable installation by trenching with water jets or ploughing. This can lead to reworking of the sediments, altering the substrate of which they are composed.

According to several studies, the biota of the benthic zone is only slightly affected by the presence of cables. However, the presence of cables can trigger behavioral disturbances in living organisms.<ref>Carter, L. Brunett,D. Drew, S. Marie, G. Hagadorn, L. Barlett-McNeil, D. Irvine, N. (2009). ‘Submarines Cables ond the Oceans- Connecting the World. UNEP_WCMC Biodiversity Series No. 31. ICPC/UNEP/UNEP-WCMC. http://www.unep-wcmc.org/resources/publications/UNEP_WCMC_bio_series/31.aspx{{Dead link|date=January 2024 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> The main observation is that the presence of cables provides a hard substrate for anemones attachment. These organisms are found in large number around cables that run through soft sediments, which are not normally suitable for these organisms. This is also the case for [[flatfish]]. Although little observed, the presence of cables can also change the water temperature and therefore disturb the surrounding natural habitat.

However, these disturbances are not very persistent over time, and can stabilize within a few days. Cable operators are trying to implement measures to route cables in such a way as to avoid areas with sensitive and vulnerable ecosystems.

=== Entanglement ===
Entanglement of marine animals in cables is one of the main causes of cable damage. Whales and sperm whales are the main animals that entangle themselves in cables and damage them. The encounter between these animals and cables can cause injury and sometimes death. Studies carried out between 1877 and 1955 reported 16 cable ruptures caused by whale entanglement, 13 of them by sperm whales. Between 1907 and 2006, 39 such events were recorded.<ref name=":10">{{Cite journal |last1=Taormina |first1=Bastien |last2=Bald |first2=Juan |last3=Want |first3=Andrew |last4=Thouzeau |first4=Gérard |last5=Lejart |first5=Morgane |last6=Desroy |first6=Nicolas |last7=Carlier |first7=Antoine |date= 2018|title=A review of potential impacts of submarine power cables on the marine environment: Knowledge gaps, recommendations and future directions |url=https://doi.org/10.1016/j.rser.2018.07.026 |journal=Renewable and Sustainable Energy Reviews |volume=96 |pages=380–391 |doi=10.1016/j.rser.2018.07.026 |bibcode=2018RSERv..96..380T |issn=1364-0321}}</ref> Cable burial techniques are gradually being introduced to prevent such incidents.

=== The risk of fishing ===

Although submarine cables are located on the [[seabed]], fishing activity can damage the cables. Fishermen using fishing techniques that involve scraping the seabed, or dragging equipment such as trawls or cages, can damage the cables, resulting in the loss of liquids and the chemical and toxic materials that make up the cables.

Areas with a high density of submarine cables have the advantage of being safer from fishing. At the expense of benthic and sedimentary zones, marine fauna is better protected in these maritime regions, thanks to limitations and bans. Studies have shown a positive effect on the fauna surrounding cable installation zones.<ref>{{Cite journal |last1=Bueger |first1=Christian |last2=Edmunds |first2=Timothy |date=2017-11-01 |title=Beyond seablindness: a new agenda for maritime security studies |url=http://academic.oup.com/ia/article/93/6/1293/4111108 |journal=International Affairs |language=en |volume=93 |issue=6 |pages=1293–1311 |doi=10.1093/ia/iix174 |issn=0020-5850|hdl=1983/a9bb7d69-6274-4515-8db4-886079ca3668 |hdl-access=free }}</ref>

=== Pollution ===

Submarine cables are made of copper or [[optical fiber]]s, surrounded by several protective layers of plastic, wire or synthetic materials. Cables can also be composed of dielectric fluids or [[hydrocarbon]] fluids, which act as electrical insulators. These substances can be harmful to marine life.<ref>{{Cite book |last=Worzyk |first=Thomas |url=https://books.google.com/books?id=X8QfRT_SYDgC&dq=environmental+impact+of+submarines+cables&pg=PR6 |title=Submarine Power Cables: Design, Installation, Repair, Environmental Aspects |date=2009-08-11 |publisher=Springer Science & Business Media |isbn=978-3-642-01270-9 |language=en}}</ref>

Fishing, aging cables and marine species that collide with or become entangled in cables can damage cables and spread toxic and harmful substances into the sea. However, the impact of submarine cables is limited compared with other sources of ocean pollution.

There is also a risk of releasing pollutants buried in sediments. When sediments are re-suspended due to the installation of cables, toxic substances such as hydrocarbons may be released.

Preliminary analyses can assess the level of sediment toxicity and select a cable route that avoids the remobilization and dispersion of sediment pollutants. And new, more modern techniques will make it possible to use less polluting materials for cable construction.<ref name=":10" />

=== Sound waves and electromagnetic waves ===
The installation and maintenance of cables requires the use of machinery and equipment that can trigger sound waves or electromagnetic waves that can disturb animals that use waves to find their bearings in space or to communicate. Underwater sound waves depend on the equipment used, the characteristics of the seabed area where the cables are located, and the relief of the area.<ref name=":10" />

Underwater noise and waves can modify the behavior of certain underwater species, such as migratory behavior, disrupting communication or reproduction. Available information is that underwater noise generated by submarine cable engineering operations has limited acoustic footprint and limited duration.<ref>{{cite web |last1=Hale |first1=Richard |title=Dr. |url=https://www.un.org/depts/los/consultative_process/icp19_presentations/2.Richard%20Hale.pdf |website=www.un.org |publisher=United Nations |access-date=22 August 2024}}</ref>

==See also==
* [[Bathometer]]
* [[Cable layer]]
*[[Cable landing point]]
* [[List of domestic submarine communications cables]]
* [[List of international submarine communications cables]]
* [[Loading coil#Loaded submarine cable|Loaded submarine cable]]
* [[Submarine power cable]]
* [[Transatlantic communications cable]]
* [[SMART cables]]

==Notes==
{{reflist|group=note}}

==References==
{{reflist}}

==Further reading==
* {{cite book |title=Submarine Telegraphs: Their History, Construction, and Working |url=https://archive.org/details/submarinetelegr00briggoog |author=Charles Bright |year=1898 |publisher=Crosby Lockward and Son |isbn=9780665008672 }} 
* {{cite book |title=A Retrospective Technology Assessment: The Transatlantic Cable of 1866 |author=Vary T. Coates and Bernard Finn |year=1979 |publisher=San Francisco Press}}
* {{cite book |title=The Atlantic Cable |author=Bern Dibner |year=1959 |publisher=Burndy Library}}
* {{Cite news |last=Dzieza |first=Josh |date=2024-04-16 |title=The cloud under the sea: The invisible seafaring industry that keeps the internet afloat |url=https://www.theverge.com/c/24070570/internet-cables-undersea-deep-repair-ships |access-date=2024-04-16 |website=The Verge}}
* {{cite book |title=Communications Under the Seas:The Evolving Cable Network and Its Implications |editor=Bernard Finn |editor2=Daqing Yang |year=2009 |publisher=MIT Press}}
* {{cite book |title=Cableships and Submarine Cables | author=K.R. Haigh |year=1968 |publisher=United States Underseas Cable Corporation}}
* {{cite book |title=Cableships | author=Norman L. Middlemiss |year=2000 |publisher=Shield Publications}}
* {{cite book |title=The Undersea Network (Sign, Storage, Transmission) |author=Nicole Starosielski |year=2015 |isbn=978-0822357551 |publisher=Duke University Press}}
* {{cite book |title=A thread under the Ocean |author= John Steele Gordon|year = 2000 | isbn= 978-0743231275 |publisher = World of Books}}

==External links==
{{Commons category|Submarine communications cables }}
* [http://www.iscpc.org/ The International Cable Protection Committee]&nbsp;– includes a register of submarine cables worldwide (though not always updated as often as one might hope)
* [http://www.atlantic-cable.com/Cables/CableTimeLine/index.htm Timeline of Submarine Communications Cables, 1850–2010]
* [http://www.kisca.org.uk/ Kingfisher Information Service&nbsp;– Cable Awareness; UK Fisherman's Submarine Cable Awareness site]
* [http://www.sigcables.com Orange's Fishermen's/Submarine Cable Information]
* [http://www.ofcc.com/ Oregon Fisherman's Cable Committee] {{Webarchive|url=https://web.archive.org/web/20060203123501/http://www.ofcc.com/ |date=2006-02-03}}

===Articles===
* [http://www.atlantic-cable.com/Article/WireRope/wirerope.htm History of the Atlantic Cable & Submarine Telegraphy]&nbsp;– Wire Rope and the Submarine Cable Industry
* [https://www.wired.com/wired/archive/4.12/ffglass.html Mother Earth Mother Board]&nbsp;– Wired article by [[Neal Stephenson]] about submarine cables
* {{cite journal | last1=Medford | first1=L. V. | last2=Meloni | first2=A. | last3=Lanzerotti | first3=L. J. | last4=Gregori | first4=G. P. | title=Geomagnetic induction on a transatlantic communications cable | journal=Nature | volume=290 | issue=5805 | date=1981-04-02 | issn=1476-4687 | doi=10.1038/290392a0 | pages=392–393 | bibcode=1981Natur.290..392M | s2cid=4330089 | url=https://www.nature.com/articles/290392a0 | access-date=2022-07-21}}
* {{cite journal|author=Hunt, Bruce J. |title=Lord Cable|journal=Europhysics News|year=2004|volume=35|issue=6|page=186 |doi=10.1051/epn:2004602 |bibcode=2004ENews..35..186H |doi-access=free}}
* [http://www.hup.harvard.edu/catalog/WINNEX.html Winkler, Jonathan Reed. Nexus: Strategic Communications and American Security in World War I. (Cambridge, MA: Harvard University Press, 2008)] {{Webarchive|url=https://web.archive.org/web/20080510085718/http://www.hup.harvard.edu/catalog/WINNEX.html |date=2008-05-10}} Account of how U.S. government discovered strategic significance of communications lines, including submarine cables, during World War I.
* [https://web.archive.org/web/20080129082716/http://www1.alcatel-lucent.com/submarine/how/index.htm Animations from Alcatel showing how submarine cables are installed and repaired]
* [http://news.bbc.co.uk/2/hi/technology/7228315.stm Work begins to repair severed net]
*[https://www.oceannews.com/feature-story/2015/01/05/december-editorial-focus Flexibility in Undersea Networks] – Ocean News & Technology magazine Dec. 2014

===Maps===
{{Commons category|Maps of submarine communication cables}}
 
* [https://www.submarinecablemap.com Submarine Cable Map by TeleGeography]
* [https://web.archive.org/web/20140308180835/http://www.telegeography.com/telecom-resources/map-gallery/index.html Map gallery of submarine cable maps by TeleGeography], showing evolution since 2000. [http://image.guardian.co.uk/sys-images/Technology/Pix/pictures/2008/02/01/SeaCableHi.jpg 2008 map in the ''Guardian'']; [https://edition.cnn.com/2014/03/04/tech/gallery/internet-undersea-cables/index.html 2014 map on CNN].
* [http://eyeball-series.org/cable-eyeball.htm Map and Satellite views of US landing sites for transatlantic cables]
* [http://eyeball-series.org/cablew-eyeball.htm Map and Satellite views of US landing sites for transpacific cables]
* [https://web.archive.org/web/20081222010717/http://www.kisca.org.uk/charts.htm Positions and Route information of Submarine Cables in the Seas Around the UK]

{{Telephony}}
{{Telecommunications}}

{{Authority control}}

{{DEFAULTSORT:Submarine Communications Cable}}
[[Category:Coastal construction]]
[[Category:Submarine communications cables|*]]
[[Category:Telecommunications equipment]]
[[Category:History of telecommunications]]

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