A cross section of the shore-end of a modern submarine communications cable.
1  Polyethylene
2  Mylar tape
3   – Stranded steel wires
4  Aluminium water barrier
5  Polycarbonate
6  Copper or aluminium tube
7  Petroleum jelly
8  Optical fibers
Submarine cables are laid using special cable layer ships, such as the modern René Descartes [fr], 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 continents (except Antarctica) when Java was connected to Darwin, Northern Territory, Australia, in 1871 in anticipation of the completion of the Australian Overland Telegraph Line in 1872 connecting to Adelaide, South Australia and thence to the rest of Australia.[1]

Subsequent generations of cables carried telephone traffic, then data communications traffic. These early cables used copper wires in their cores, but modern cables use optical fiber technology to carry digital data, which includes telephone, Internet and private data traffic. Modern cables are typically about 25 mm (1 in) in diameter and weigh around 1.4 tonnes per kilometre (2.5 short tons per mile; 2.2 long tons per mile) for the deep-sea sections which comprise the majority of the run, although larger and heavier cables are used for shallow-water sections near shore.[2][3]

Early history: telegraph and coaxial cables

First successful trials

After William Cooke and Charles Wheatstone had introduced their working telegraph in 1839, the idea of a submarine line across the Atlantic Ocean began to be thought of as a possible triumph of the future. Samuel Morse proclaimed his faith in it as early as 1840, and in 1842, he submerged a wire, insulated with tarred hemp and India rubber,[4][5] in the water of New York Harbor, and telegraphed through it. The following autumn, Wheatstone performed a similar experiment in Swansea Bay. A good insulator to cover the wire and prevent the electric current from leaking into the water was necessary for the success of a long submarine line. India rubber had been tried by Moritz von Jacobi, the Prussian electrical engineer, as far back as the early 19th century.

Another insulating gum which could be melted by heat and readily applied to wire made its appearance in 1842. Gutta-percha, the adhesive juice of the Palaquium gutta tree, was introduced to Europe by William Montgomerie, a Scottish surgeon in the service of the British East India Company.[6]: 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.[7] In 1847 William Siemens, then an officer in the army of Prussia, laid the first successful underwater cable using gutta percha insulation, across the Rhine between Deutz and Cologne.[8] In 1849, Charles Vincent Walker, electrician to the South Eastern Railway, submerged 3 km (2 mi) of wire coated with gutta-percha off the coast from Folkestone, which was tested successfully.[6]: 26–27 

First commercial cables

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.[6]: 192–193 [9] However, the experiment served to secure renewal of the concession, and in September 1851, a protected core, or true, cable was laid by the reconstituted Submarine Telegraph Company from a government hulk, Blazer, which was towed across the Channel.[6]: 192–193 [10][7]

In 1853, more successful cables were laid, linking Great Britain with Ireland, Belgium, and the Netherlands, and crossing The Belts in Denmark.[6]: 361  The British & Irish Magnetic Telegraph Company completed the first successful Irish link on May 23 between Portpatrick and Donaghadee using the collier William Hutt.[6]: 34–36  The same ship was used for the link from Dover to Ostend in Belgium, by the Submarine Telegraph Company.[6]: 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.[6]: 195 

In 1858, the steamship Elba was used to lay a telegraph cable from Jersey to Guernsey, on to Alderney and then to Weymouth, the cable being completed successfully in September of that year. Problems soon developed with eleven breaks occurring by 1860 due to storms, tidal and sand movements, and wear on rocks. A report to the Institution of Civil Engineers in 1860 set out the problems to assist in future cable-laying operations.[11]

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.[12]

Transatlantic telegraph cable

Main article: 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.[7] However, the technology of the day was not capable of supporting the project; it was plagued with problems from the outset, and was in operation for only a month. Subsequent attempts in 1865 and 1866 with the world's largest steamship, the SS Great Eastern, used a more advanced technology and produced the first successful transatlantic cable. Great Eastern later went on to lay the first cable reaching to India from Aden, Yemen, in 1870.

British dominance of early cable

Operators in the submarine telegraph cable room at the 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, 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.[13] Britain's very first action after declaring war on Germany in World War I was to have the cable ship Alert (not the CS Telconia as frequently reported)[14] cut the five cables linking Germany with France, Spain and the Azores, and through them, North America.[15] 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.[16] During World War I, Britain's telegraph communications were almost completely uninterrupted, while it was able to quickly cut Germany's cables worldwide.[13]

Cable to India, Singapore, East Asia and Australia

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.[17] 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 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.[18]

Submarine cables across the Pacific

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.[19] Canada, Australia, New Zealand and Fiji were also linked in 1902 with the trans-Pacific segment of the All Red Line.[20] Japan was connected into the system in 1906. Service beyond Midway Atoll was abandoned in 1941 due to World War II, but the remainder remained in operation until 1951 when the FCC gave permission to cease operations.[21]

The first trans-Pacific telephone cable was laid from Hawaii to Japan in 1964, with an extension from Guam to The Philippines.[22] Also in 1964, the Commonwealth Pacific Cable System (COMPAC), with 80 telephone channel capacity, opened for traffic from Sydney to Vancouver, and in 1967, the South East Asia Commonwealth (SEACOM) system, with 160 telephone channel capacity, opened for traffic. This system used microwave radio from Sydney to Cairns (Queensland), cable running from Cairns to Madang (Papua New Guinea), Guam, Hong Kong, Kota Kinabalu (capital of Sabah, Malaysia), Singapore, then overland by microwave radio to Kuala Lumpur. In 1991, the North Pacific Cable system was the first regenerative system (i.e., with repeaters) to completely cross the Pacific from the US mainland to Japan. The US portion of NPC was manufactured in Portland, Oregon, from 1989 to 1991 at STC Submarine Systems, and later Alcatel Submarine Networks. The system was laid by Cable & Wireless Marine on the CS Cable Venture.

Construction

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.[23][24] The India Rubber, Gutta Percha and Telegraph Works Company, established by the Silver family and giving that name to a section of London, furnished cores to Henley's as well as eventually making and laying finished cable.[24] In 1870 William Hooper established Hooper's Telegraph Works to manufacture his patented 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.[24][25][26]

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.[27] 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.[28]

Many early cables suffered from attack by sea life. The insulation could be eaten, for instance, by species of Teredo (shipworm) and Xylophaga. Hemp laid between the 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 barnacles 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.[29]

Bandwidth problems

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 amplifiers in the cable. Large voltages 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, severely limiting the 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.[30][31] 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 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 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 electrician of the Atlantic Telegraph Company, he became involved in a public dispute with 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 circuited to the ocean when Whitehouse increased the voltage beyond the cable design limit.

Thomson designed a complex electric-field generator that minimized current by 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 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 lines to the higher frequencies required for high-speed data and voice.

Transatlantic telephony

Submarine communication cables crossing the Scottish shore at Scad Head on 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 pupinized telephone cable 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. It was inaugurated on September 25, 1956, initially carrying 36 telephone channels.

In the 1960s, transoceanic cables were coaxial cables that transmitted 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.[32] 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.[33]

Other uses

In 1942, Siemens Brothers of New Charlton, London, in conjunction with the United Kingdom 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.[34]

Modern history

Optical telecommunications cables

External image
image icon Map of sea cables (regularly updated)
World map showing submarine cables in 2015

In the 1980s, 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 erbium-doped fiber amplifier. 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.

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 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 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 kW.[35][36]

The optic fiber used in undersea cables is chosen for its exceptional clarity, permitting runs of more than 100 kilometres (62 mi) 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, although this has increased over the years; in 2014 unrepeated cables of up to 380 kilometres (240 mi) in length were in service; however these require unpowered repeaters to be positioned every 100 km.[37]

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?] 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 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 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.[38]

Originally, submarine cables were simple point-to-point connections. With the development of submarine branching units (SBUs), more than one destination could be served by a single cable system. Modern cable systems now usually have their fibers arranged in a self-healing ring to increase their redundancy, with the submarine sections following different paths on the ocean floor. One reason for this development was 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 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.

A further redundant-path development over and above the self-healing rings approach is the 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.

As of 2012, operators had "successfully demonstrated long-term, error-free transmission at 100 Gbps across Atlantic Ocean" routes of up to 6,000 km (3,700 mi),[39] meaning a typical cable can move tens of terabits per second overseas. Speeds improved rapidly in the previous few years, with 40 Gbit/s having been offered on that route only three years earlier in August 2009.[40]

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 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 5,600 km (3,500 mi),[41] this requires several land masses (Ireland, 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 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 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 0.172 dB per kilometer when carrying a 1550 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 (WDM), which allows for multiple optical carrier channels to be transmitted through a single fiber, each carrying its own information. 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 GHz (0.4 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.

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 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 nm laser leads to a noise of at most 3.5 dB, with a noise of 5 dB usually obtained with a 1480 nm laser. The noise has to be filtered using optical filters.

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 nm, and the other pumping them at 1450 nm. Launching a pump frequency (pump laser light) at a power of just one watt leads to an increase in reach of 45 km or a 6-fold increase in capacity.

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 nm laser light) to amplify the data signals carried on the rest of the fibers.[37]

WDM or wavelength division multiplexing was first implemented in submarine fiber optic cables from the 1990s to the 2000s,[42] followed by DWDM or 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.[43][44] The type of modulation employed in a submarine cable can have a major impact in its capacity.[45][46] SDM is combined with DWDM to improve capacity.[47] The open cable concept allows for the design of a submarine cable independently of the transponders or SLTE (Submarine Line Terminal Equipment) that will be used to transmit data through the cable.[48][49][50][51] C-OTDR (Coherent Optical Time Domain Reflectometry) is used in submarine cables to detect the location of cable faults.[52]

Importance of submarine cables

Currently 99% of the data traffic that is crossing oceans is carried by undersea cables.[53] The reliability of submarine cables is high, especially when (as noted above) multiple paths are available in the event of a cable break. Also, the total carrying capacity of submarine cables is in the terabits per second, while satellites typically offer only 1,000 megabits per second and display higher latency. However, a typical multi-terabit, transoceanic submarine cable system costs several hundred million dollars to construct.[54]

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.[55]

Submarine cables are important to the modern military as well as private enterprise. The US military, for example, uses the submarine cable network for data transfer from conflict zones to command staff in the United States. Interruption of the cable network during intense operations could have direct consequences for the military on the ground.[56]

Investment and finances

Modern fiber-optic cable around Africa's coast.
A map of active and anticipated submarine communications cables servicing the African continent in 2020.

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.[57] 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 billion worth of investment between 1999 and 2001. This was followed by the bankruptcy and reorganization of cable operators such as Global Crossing, 360networks, FLAG, Worldcom, and Asia Global Crossing. Tata Communications' Global Network (TGN) is the only wholly owned fiber network circling the planet.[58]

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.[59]

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, which is 75% owned by East African and South African investors.[60] The project was delayed by a month due to increased piracy along the coast.[61]

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.[62][63][64][65]

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 −80 °C (−112 °F) as well as massive strain from ice flowing up to 10 metres (33 ft) 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.[66]

Arctic

Several projects are underway in the Arctic including 12,650 km "Polar Express" [67] and 14,500 km Far North Fiber[68].

Cable repair

An animation showing a method used to repair submarine communications cables.

Cables can be broken by fishing trawlers, anchors, earthquakes, turbidity currents, and even shark bites.[69][70] 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 1,000 km (620 mi) 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.[71] Still, cable breaks are by no means a thing of the past, with more than 50 repairs a year in the Atlantic alone,[72] and significant breaks in 2006, 2008, 2009 and 2011.

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 United States naval vessel, the 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 United States 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.[73]

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 reflectometry that can be used in live environments very quickly. Presently, SSTDR can collect a complete data set in 20 ms.[74] 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 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.[75] 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.[76] 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, Nova Scotia, was home to a half dozen such vessels for most of the 20th century including long-lived vessels such as the 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. The crews of these vessels developed many new techniques and devices to repair and improve cable laying, such as the "plough".

Intelligence gathering

Underwater cables, which cannot be kept under constant surveillance, have tempted intelligence-gathering organizations 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.[77] 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. In modern times, the widespread use of end-to-end encryption minimizes the threat of wire tapping.

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.[78] 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. Nevertheless, 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.[79] 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.[80]

Pollution

Submarine cables are made of copper or optical fibers, 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.[81]

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.[79]

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.[79]

Underwater noise and waves can modify the behavior of certain underwater species, such as migratory behavior, disrupting communication or reproduction.

Security implications

Submarine cables are problematic from a security perspective for several reasons: because maps of submarine cables are widely available; because many different threats jeopardise their safety; and because of the challenge that protecting them represents, given the difficulty and scale of the task.

Types of threats to submarine cables

As mentioned, submarine communication cables are exposed to numerous threats, some coming from natural disasters and human hand accidents, others from deliberate actions. An overview of those potential threats and security breaches to critical marine infrastructure such as cables would provide a four-category classification.[82]

Unintentional Harms

First of all, the Unintentional Harms, concerning natural disasters that could potentially damage the infrastructure, or the consequences of human activities, lack of maintenance leading to wear and breakage, and errors, such as collisions or fishing. For example, in 2022 the Islands of Tonga in the Pacific were cut from the internet after a volcanic eruption destroyed all the undersea cables in the area, notably severing an 827 km undersea cable.[83] About human error, it is estimated that commercial fishing and shipping account for approximatively 40% of the damage done to the undersea cable infrastructure.[84]

Deliberate Acts

Next, Deliberate Acts are identifiable, this term refers to physical attacks and sabotage targeting underwater cables,[85] including: wars and civil wars (during which cables become strategic targets like in Ukraine[86]), terrorism, blue crime, and inter-state attacks.

Cyber Threats

Thirdly, we can consider that the cyber threats have become a major concern due to the high connectivity of underwater infrastructures, and very particularly submarine communication cables. The large flow of data and information and their potential value are of great interest to hackers, so in order to protect against these new types of attack on the integrity of submarine cables, it is also advisable to take the measure of cyber risks and to develop security measures other than physical protection.

Hybrid Threats

Finally, a Hybrid Threats and grey zone warfare category could refer to situations where states use disruptive measures falling below the threshold of direct military actions, making attribution difficult; those activities are usually intentionally camouflaged as accidents or as actions of non-state actors in order to hide the real perpetrator.[82] The Nord Stream sabotage could be understood that way.

In essence, it's clear that the safety issues surrounding undersea cables are vast and complex. They combine nature and human activity, accidents and deliberate acts.

Deliberate threats and attacks

As explained, the deliberate threats hovering over the cables refers to physical attacks and sabotage targeting undersea cables. Here again, it is possible to determine the different modes of referenced attack to which cables may fall victim.[87]

Physical Destruction

The most common mode is physical destruction, involving damaging equipment with weapons, explosives, or submersible technologies. Another form of physical destruction diverts from the cables but targets them indirectly: by attacking cable landing stations or maintenance infrastructure, assailants ensure that any functioning or repair becomes impossible. Therefore, concerns about securing undersea cables must also consider what happens on land.

Data theft and Intelligence

Another mode of attack is data theft and intelligence. In this scenario, rather than destroying, perpetrators aim to exploit. It involves information theft, spying, and intelligence operations targeting cables at sea. Ground-based cable management and data stations are also prime targets for data thieves and spies.

Digital means

Lastly, a third mode of attack, digital means, refers to the previously mentioned cyber-attacks. By hacking into network management systems, attackers can manipulate various cable systems, observe networks and data traffics, acknowledge physical cable vulnerabilities, and potentially have the power to monitor, disrupt and redirect traffic. Concerns about security in the area of cyber threats have increased over the years, and have now become one of the most important sensitive points in terms of submarine cable security issues.

Threatening international actors

Another major aspect of the security implications around the submarine communication cables are the mains involved actors in this global threatening marine and undersea environment. Here, a distinction can be drawn between state-sponsored threats and those emanating from non-state actors.[87]

State-sponsored threats

The first category includes direct threats arising from state actions, providing concrete examples of potentially threatening activities. For these cases, certain countries emerge more frequently than others in research and in the specialist press,[87] such as Russia, China,[88] North Korea,[89] Iran,[90] Israel,[90] and Turkey.[91]  These states can be, therefore, considered as threatening for submarine cables activities, insofar as they are regularly described as such.

Russia

Observations of Russian submarine movements in territorial waters and in proximity to the cables[92] continue to generate concerns that the cables could be manipulated or cut as part of the Russian navy's hybrid warfare strategy.[87] The conflict in Ukraine has also heightened the apprehensions of the international community and NATO members, who now fear that they may be faced with subversive actions designed to inflame the conflict, export it and further destabilise it.[87]

China

China seems to be adopting a different strategy.[87] Through corporations and mega-companies affiliated or at least close to the central state, China is massively stepping up its involvement in submarine cable and infrastructure construction, repair and maintenance; and is thereby strengthening its control over communications flows. The Chinese company HMN Technologies has, for example, built or repaired almost 100 of the world's 400 submarine cables.[93] This situation also worries the West, which fears that China will take advantage of the situation to intercept data and create a technological dependence of certain regions of the world on China. Furthermore, China has the military ability to cause substantial damage to the submarine cable network by sabotaging or destroying one or more cables. For the time being, such actions do not appear to be in line with their current strategy, remaining more of a potential threat than an immediate reality.

Western countries

On the other hand, it is also important not to focus exclusively on those state actors who are known to use grey zone tactics for political ends. A brief review of research and thematic publications also highlights the lack of diversity in the origin of these papers. The vast majority of accessible publications dealing with potential state dangers to underwater cables and infrastructures come from Western countries and researchers. This points to a potential lack of retrospective look at the activities of the leaders of the Western world at sea, and in the same way, a hyperfocus on the Chinese and Russian threats induced by a strictly Western viewpoint. To date, there are no authenticated and publicly available reports documenting with certitude deliberate attacks against the cable network, whether attributed to Russia, China, or any other actor.[87]

Non-states actors threats

In addressing non-state threats, in the past, terrorist organisations have shown that they are keen and able to target critical infrastructure. So, the threat still exists, and governments need to guard against potential attacks on the submarine cable network with a view to destabilising markets and communications. For the time being, however, if no terrorist organisation seems to have turned its attention to the cables, and if these threats are still in the domain of scenarios and anticipation, they still need to be considered.

International responses

While the security of undersea cables involves many threats to their long-term survival and many potentially dangerous parties, we also need to take a close look at the responses being developed to protect these critical marine infrastructures. Late in coming, but gradually emerging, international organisations and states are organising themselves to ensure the defense of these technologies. Committees, texts, and policies are being set up with the aim of legislating and standardising the relationships and interconnections that surround submarine cables and their security.

International Organisations

UNCLOS

The role of UNCLOS (and its criticism) in managing affairs related to undersea cables is almost systematically addressed by publications discussing security and cable management. UNCLOS is frequently cited as a common basis for developing security policies and an international foundation (as a United Nations product) for managing undersea infrastructure. However, its inadequacy in coordinating and effectively protecting is consistently pointed out. Thus, although the United Nations Convention on the Law of the Sea includes specific clauses designed to guarantee the safety and protection of submarine cables, it cannot be said that this is of major importance or has a significant deterrent effect, not least because of the non-coercive nature of the text. Nevertheless, the safety-related provisions of the Convention dealing with submarine cable safety issues are mainly set out in Part XII, entitled "Peaceful uses of the oceans", and are explicitly detailed in Articles 113 to 115.[94] It is therefore clear that these provisions constitute a negligible proportion of the Convention as a whole, and therefore that this text is obsolete when it comes to ensuring the protection of submarine cables.

NATO

Given the UN's lack of success in taking effective action to protect cables, NATO seems determined to act on its own, by raising awareness among its members and organising a unified defence. NATO is therefore at once a place for exchanging expertise and research in this field, an arena for discussion in which Western policy in this domain is both debated and decided upon, and a driving force for the improvement of specialised legislation.[95] At the beginning of 2023, NATO defence ministers unveiled a plan to strengthen undersea infrastructure and prevent incidents such as that involving the Nord Stream 1 and 2 pipelines (Their explosion, confirmed as an act of sabotage representing an example of critical undersea infrastructure remaining vulnerable to hostile intentions while being easily disrupted - exactly such as submarine cables). Secretary General Jens Stoltenberg has announced the creation of a Critical Underwater Infrastructure Coordination Cell within NATO, which will be responsible, among other duties, for taking the utmost care to properly protect and survey the condition of the cables.[85] It can therefore be stated that NATO is currently the leading contributor to the improvement of cable safety - producing numerous articles, reports and notes on these issues. On the other hand, it can be noted that the control and leadership of the United States within this institution leads to a Western centrality in the policy-making process - which could, in tandem, lead to a desire on the part of Europeans for self-administration and to develop their own policies in this area.

European Union

EU's increasing activity in securing its cables are sufficiently well on track that it is worth highlighting.[96] While it seems that the EU has long been slow to take concrete initiatives in this area, it now seems keen to close the gap, in particular by attempting to coordinate the actions of its Member States, and above all by sponsoring research into safety and security through the production of massive reports dealing specifically with the security issues surrounding submarine cables[87] (in a kind of NATO manner). Thus, it is crucial to recognize that the literature not only assesses existing situations but is also directed by the actors themselves to better understand their subject.

States responses

It can also happen that certain States, even though they are involved in the institutions mentioned above, decide to take a unilateral interest in the security issues surrounding submarine cables in order to defend themselves directly.

France

After being targeted, in October 2022, by an attack[97] near the port of Marseille (the main hub for submarine cables in the Mediterranean), France, on the initiative of its President Emmanuel Macron and through a plan included in the agenda of the Ministry of the Army, has decided to considerably strengthen its defensive capabilities to protect its cables and infrastructures from possible new attacks.[85] With the second-largest maritime zone globally, France is particularly concerned about its current lack of defense capabilities, despite having a powerful army and navy. A new equipment plan, named Seabed Warfare Strategy, aims to equip the French navy with more advanced robots, drones, and submarines, by 2025 and allocate additional resources to defend the no fewer than 30 cables crossing French territory.[85]

United States

Another notable example of current unilateral initiatives to strengthen cable protection is the US Cable Ship Security Program (CSSP). Under this programme, the US government pays an annual allocation to a number of vessels flying its flag, guaranteeing their permanent availability for rapid response and defensive action in the case of any damage inflicted to one submarine infrastructure directly affecting the United States. This proactive approach guarantees rapid access and defence, response and repair capabilities in the event of potential attacks or incidents, somewhat in the same vein as France approach.[85]

Private sector

Finally, after acknowledging some plurilateral and unilateral attempts to strengthen defense potential response to security implications around cables, it is necessary to consider the role of the private sector in defending submarine cables. Given that most cables are owned, operated, and maintained by private multinational actors, close cooperation is deemed necessary and must be organized. Some countries share infrastructures and hold a particularly important position in the international cable system, requiring cooperation that extends beyond conventional bilateral or regional forms as mentioned previously. Thus, it is necessary to observe the interactions between the public and private sectors — a somewhat opaque sphere, but crucial for a comprehensive understanding of cable dynamics and means of securing them. The International Cable Protection Committee (ICPC) is another area of discussions and decisions among nation-states members, companies, and corporations.[98] By facilitating exchanges among states, companies, and experts, the ICPC embodies another one of those international institutions working towards the collective advancement in securing cables. Reports and recommendations are generated there, all under the banner of extensive collaboration.

In all cases, the main idea across these arguments is that global regulation is still relatively weak and needs improvement. The treatment of these subjects also reveals a lack of knowledge and a need to push research further to better understand the political challenges surrounding cable management and security implications.

Legal Provisions and Issues

Despite being a fundamental facilitator of modern life, submarine communications cables face a plurality of legal issues. In the wake of rising maritime security threats and awareness about protecting this critical maritime infrastructure, the debates around these legal issues are becoming increasingly important.[99] The importance of submarine communications cables arose as a particular issue following the 2022 Nord Stream pipeline sabotage in the Baltic Sea. The security and political response was clear; however, the legal is less so.[100][101] With this, awareness has risen of the necessity to re-evaluate and modify the existing legislation. Overall, the legal landscape regarding submarine cables is complex and multifaceted which can cause issues when assigning liability, and, critically, ensuring their protection. Without submarine communication cables, contemporary societies and the interconnected would be almost unable to function.[102] As such, these cables must be protected to a greater extent with legal provisions.

Jurisdiction and Regulation through UNCLOS

The issue of protection of submarine cables involves a high degree of legal complexity, with the primary legal provision being the United Nations Convention on the Law of the Sea, 1982 (UNCLOS).[103] UNCLOS, concerning submarine cables, lays out distinct geographical categories where different legal provisions apply, and with this, it aims to ensure the protection and functioning of submarine communication cables.

Territorial Waters

UNCLOS Section 2 sets out the list of rights states have in their own territorial waters. In this, Article 3 states that every state has sovereignty over waters up to 12 nautical miles from their coast. Within this, they have complete jurisdiction. In these territorial waters, seabed cables are protected and are the legal responsibility of that nation. As such, it is down to the respective state to manage the cables' laying, operation and protection. One example is New Zealand, which implemented the ‘Submarine Cables and Pipelines Protection Act 1996'.[104] Within this, a legal framework for protecting and regulating submarine cables is pursued, including setting penalties for damage, facilitating repair and minimising environmental damage.[104]

Exclusive Economic Zones (EEZs) and Continental Shelves

The Exclusive Economic Zones are outside territorial waters, which extend up to 200nm from a country's coast. In effect, countries have limited legal protection over these areas, but legal provisions must be met by any actors in these areas.[103] Article 58 of UNCLOS guarantees that all states, whether landlocked or coastal, have a right to lay and operate submarine cables across the seabed.[103] However, this right is subject to three conditions. Firstly, using the sea, and therefore the cable, must suffice all other legal provisions in UNCLOS. Secondly, the freedoms guaranteed must not interfere with other countries' lawful use of the sea. Thirdly, where the coastal state has legal authority, the actions involved with the submarine cable cannot impede the coastal state's rights guaranteed in UNCLOS: to exploit resources and protect the environment (this extends to the continental shelf). In practice, this means that coastal states can regulate cable laying by requiring permits or assigning specific areas to ensure environmental protection and prevent potential conflicts arising over resource exploitation, as outlined in Article 211.[105] For example, in 1993, Brazil enacted a law that requires its consent to lay submarine cables, which is also permitted in UNCLOS Article 79.[106] This law was observed in practice in August 2023, as Google was awarded an environmental permit by the Brazilian government for landing points for its new ‘Firmina’ cable, partly as a result of the minimisation of environmental damage they guaranteed through employing Nova Ambient (an industrial waste treatment company).[107]

‘whether coastal or land-locked, enjoy, subject to the relevant provisions of this Convention, the freedoms referred to in article 87 of navigation and overflight and of the laying of submarine cables and pipelines, and other internationally lawful uses of the sea related to these freedoms, such as those associated with the operation of ships, aircraft and submarine cables and pipelines, and compatible with the other provisions of this Convention.’.[103]

High Seas

UNCLOS is the primary framework for the laying, operation, and protection of submarine cables. This is guaranteed in UNCLOS and enables coastal and land-locked states to lay and operate cables in the high seas, regardless of their geographical location.[103] Here, UNCLOS sets the rules for the construction and maintenance of submarine cables and limits activities such as fishing or vessel anchoring, which could potentially damage the cables in Article 114.[103] These provisions aim to protect the operation and security of the cables. However, crucially, UNCLOS faces challenges between the freedom to lay cables, and environmental protection of the cables.[108]

Other important legislation

1884 Convention for the Protection of Submarine Cables

The 1884 Convention for the Protection of Submarine Cables, despite being superseded in scope by UNCLOS, retains legal and historical importance in safeguarding the essential infrastructure of global communication. Prior to its adoption, submarine cables lacked comprehensive legal protection and were vulnerable to both intentional and accidental damage, which could disrupt international communication flows. The Convention addressed this gap by establishing a framework of international cooperation and individual accountability.

Key provisions of the Convention include the criminalization of willful damage to submarine cables (Article 2)[109][110] and fostering international responsibility for protecting these critical cables. This provision aimed to deter malicious actors seeking to disrupt communication flows, mitigating potential economic and societal consequences. Additionally, the Convention mandated minimum distances for vessels to maintain from cable-laying operations (Article 5),[109] minimising the risk of accidental damage causing disruption. This approach emphasised the shared responsibility of all sea users to protect the cables which had begun to underpin global connectivity.

While UNCLOS offers a broader regulatory framework encompassing various ocean uses and legal regimes, the 1884 Convention's historical significance lies in its pioneering role.[111] It stands as a testament to early efforts towards international cooperation in protecting critical maritime infrastructure beyond national jurisdictions, foreshadowing the development of a global legal framework. Whilst the Convention does have limitations, its legacy remains to this day and still has a role in influencing agreements and shaping the foundation for the interconnected world. Furthermore, whilst UNCLOS does contain many of the legal provisions made in the 1884 convention, some are missed out and some scholars say that these should be consolidated in revised legal protections of cables.[111] In addition, only a limited number of countries (especially in Asia) signed the 1884 convention, and thus, questions remain as to whether this applies to them.

Beyond the International Legal Framework

Outside the legislation already mentioned, individual countries and regional bodies often implement additional regulations regarding submarine communications for various reasons, usually security or competition related. Below are some examples of respective countries legislation:

Key Legal Issues and Challenges

Damage and Repair

The 1884 Convention for the Protection of Submarine Cables[117] broadly covers most issues regarding damage and repair of submarine cables; however, some of its content is also covered in Article 114 of UNCLOS. Specifically, it establishes criminal liability for wilful or negligent damage to submarine communication cables. Most frequently, these damages are suspected to be caused by fishing vessels,[118] and here, the responsibility rests with the vessel's Skipper. Not contained in UNCLOS, but in the 1884 convention is that the mariner must provide proof of the sacrifice in a written statement supported by testimony of the crew, and this proof must be lodged with the consular authorities of the cable owner within 24 hours of the vessel's arrival in the first port after the event.[111] Some scholars, such as Raha and Raju, raise the idea that ships should have a formal legal requirement to maintain a certain distance from cable ships to avoid damage to submarine communication cables, which may increase their protection.[119] Outside of this, assigning liability for damage to submarine communication cables can be difficult, as damage is often done in remote sea locations where finding evidence can be particularly challenging. As such, damage to submarine communication cables is often an area where liability is rarely concluded.

Environmental Protection

Whilst UNCLOS does, to a certain extent, cover environmental protection, the enforcement is largely left to states (only is it universally agreed in the territorial waters). Submarine communication cables generally have very little impact on marine biodiversity once laid.[108] However, the installation of cables may potentially disturb the benthic environment which may require greater consideration legally. The International Maritime Organization, OSPAR Commission, and the International Cable Protection Committee do provide guidelines for best environmental practices in cable laying and operation, but these are not legally binding.[120][121][122] One current key legal area that, scholars such as Davenport say, may require further legal attention is whether states have the right to impose environmental restrictions related to cable laying in EEZs and on the continental shelf as this does remain an area contested in international law.[105] Furthermore, as the impacts of climate change such as storm surges, waves, cyclones, earthquakes, floods, and volcanic eruptions become a serious reality, the need for legal considerations on the protection of cables may also become a new area of concern.[123]

Protection and Vulnerability

The vulnerability of critical maritime infrastructure was shown through the Nord Stream pipeline attack, and with this, the vulnerability and legal protection of submarine communications may need more development. Kurbalija says that, outside of any other measures, to protect these cables, there must be “more robust … international legal protection”.[124] However, to ensure this, the issue of many different actors involvement in the operation of cables must be considered to a greater extent in the existing legal framework. In addition to this, the International Cable Protection Committee, an industry group which represents 97% of the world's cable operators, continues to emphasise the importance of peacetime instruments and the need for new agreements to increase the rules that apply during armed conflict.[125]

Actors

Part of the issue around legal provisions for submarine cables is the multiple actors involved in the operation and protection of cables. International law, primarily UNCLOS, was signed by and is concerned with the interactions and responsibilities of nation-states. As this page earlier explores, submarine cables are owned and operated by a varying combination of private companies, government-owned entities, or by consortia of companies, with costs, operation/maintenance of the cable, and each respective actor's roles and responsibilities sometimes unclear.[126] With this, deciding the liability for damage and repairs can be challenging in the current legal framework.[127] Thus, while the existing conventions attempt to comprehensively govern state interactions in the ocean, its provisions often struggle to cover the intricacies of public-private partnerships driving cable infrastructure.[111] This disconnect can cause issues regarding liability, which can potentially leading to disputes, delayed repairs, and ultimately, disruptions to cables which ensure global connectivity. Further legal work may seek to address this multi-actor situation. A collaborative approach, combining existing legal frameworks at the private level with (new) international agreements which assign and enforcing liability across range of actors involved may greater protect cables.

Influence of cable networks on modern history

Submarine communication cables have had a wide variety of influences over society. As well as allowing effective intercontinental trading and supporting stock exchanges, they greatly influenced international diplomatic conduct.[128] Before the existence of submarine communication connection, diplomats had much more power in their hands since their direct supervisors (governments of the countries which they represented) could not immediately check on them. Getting instructions to the diplomats in a foreign country often took weeks or even months. Diplomats had to use their own initiative in negotiations with foreign countries with only an occasional check from their government. This slow connection resulted in diplomats engaging in leisure activities while they waited for orders. The expansion of telegraph cables greatly reduced the response time needed to instruct diplomats. Over time, this led to a general decrease in prestige and power of individual diplomats within international politics and signalled a professionalization of the diplomatic corps who had to abandon their leisure activities.[129]

Incidents

20th century

In 1914, Germany raided the Fanning Island cable station in the Pacific.[130]

The Newfoundland earthquake of 1929 broke a series of transatlantic cables by triggering a massive undersea mudslide. The sequence of breaks helped scientists chart the progress of the mudslide.[131]

In 1986[132] during prototype and pre-production testing of the TAT-8 fiber-optic cable and its lay down procedures conducted by AT&T in the Canary Islands area, shark bite damage to the cable occurred. This revealed that sharks will dive to depths of 1 kilometre (0.62 mi), a depth which surprised marine biologists who until then thought that sharks were not active at such depths. The TAT-8 submarine cable connection was opened in 1988.[133]

2000s

In July 2005, a portion of the SEA-ME-WE 3 submarine cable located 35 kilometres (22 mi) south of Karachi that provided Pakistan's major outer communications became defective, disrupting almost all of Pakistan's communications with the rest of the world, and affecting approximately 10 million Internet users.[134][135][136]

On 26 December 2006, the 2006 Hengchun earthquakes rendered numerous cables between Taiwan and Philippines inoperable.[137]

In March 2007, pirates stole an 11-kilometre (7 mi) section of the T-V-H submarine cable that connected Thailand, Vietnam, and Hong Kong, afflicting Vietnam's Internet users with far slower speeds. The thieves attempted to sell the 100 tons of cable as scrap.[138]

The 2008 submarine cable disruption was a series of cable outages, two of the three Suez Canal cables, two disruptions in the Persian Gulf, and one in Malaysia. It caused massive communications disruptions to India and the Middle East.[139][140]

2010s

In April 2010, the undersea cable SEA-ME-WE 4 was under an outage. The Southeast Asia – Middle East – Western Europe 4 (SEA-ME-WE 4) submarine communications cable system, which connects Southeast Asia and Europe, was reportedly cut in three places, off Palermo, Italy.[141]

The 2011 Tōhoku earthquake and tsunami damaged a number of undersea cables that make landings in Japan, including:[142]

In February 2012, breaks in the EASSy and TEAMS cables disconnected about half of the networks in Kenya and Uganda from the global Internet.[143]

In March 2013, the SEA-ME-WE-4 connection from France to Singapore was cut by divers near Egypt.[144]

In November 2014, the SEA-ME-WE 3 stopped all traffic from Perth, Australia, to Singapore due to an unknown cable fault.[145]

In August 2017, a fault in IMEWE (India – Middle East – Western Europe) undersea cable near Jeddah, Saudi Arabia, disrupted the internet in Pakistan. The IMEWE submarine cable is an ultra-high capacity fiber-optic undersea cable system which links India and Europe via the Middle East. The 12,091-kilometre-long (7,513 mi) cable has nine terminal stations, operated by leading telecom carriers from eight countries.[146]

AAE-1, spanning over 25,000 kilometres (16,000 mi), connects Southeast Asia to Europe via Egypt. Construction was finished in 2017.[147]

2020s

In June 2021, Google announced it was building the longest undersea cable in existence that would run from the east coast of the United States to Las Toninas, Argentina, with additional connections in Praia Grande, Brazil, and Punta del Este, Uruguay. The cable would ensure users fast, low-latency access to Google products, such as Search, Gmail and YouTube, as well as Google Cloud services.[148]

In August 2021, Google and Facebook announced that they would develop a subsea cable system, dubbed "Apricot", for 2024 in order to improve internet connectivity, and serve growing demand for broadband access and 5G wireless connectivity across the Asia-Pacific region, including Japan, Singapore, Taiwan, Guam, the Philippines and Indonesia.[149]

On 15 January 2022 the undersea eruption of the Hunga Tonga Hunga Ha'apai volcano broke the single international cable to Tonga, and at least one of Tonga's inter-island cables, severely disrupting communications to the rest of the world and leaving only limited satellite communications. The cable was repaired in July 2023, 18 months after the original damage took place. The estimation of damage took 5 months to confirm, with another 7 months for ACN to manufacture the cable.[150][151][152]

On 20 October 2022 the under sea cable (SHEFA-2) between Banff UK mainland and the Shetland Islands was damaged.[153] A full telecom and broadband outage was reported on the Shetland Islands, effectively rendering all emergency telecommunications inoperable. The undersea cable between the Shetland Islands and the Faroe Islands was also rendered damaged which contributed to the lack of redundancy and full telecommunications outage. It was reported that fishing activity contributed to the damage.

At the beginning of March 2024, several submarine cables were damaged in the Red Sea. Hong Kong internet service provider HGC Global Communications (HGC), owned by CK Hutchison Holdings, reported that a quarter of data traffic between Asia, Europe and the Middle East at AAE-1 was affected. SEACOM also reported a disruption. HGC and SEACOM began redirecting traffic.

According to the German operator of Internet nodes DE-CIX, the cables were damaged after a cargo ship that was shot at in February 2024 drifted uncontrollably and sank with its anchor extended at the turn of the month. At the beginning of February 2024, Yemen's government-in-exile warned that the Houthis terrorist group was planning an attack on submarine cables. The Houthis had previously attacked civilian ships in the Red Sea, but denied being responsible for the damage.[154][155]

See also

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