Submarine cables
This has always surprised me, but relatively few people are actually familiar with the field of submarine cables. I am not only referring to the technology itself, but it is quite surprising to realize that some people are not even aware of their existence. It must be said that, lying deep on the ocean floor, it is tempting to forget about them. Yet they handle 98% of intercontinental telephone communications and data transfers every day. Without them, our daily lives and our economy would be profoundly disrupted.
A (brief) history
I will not address submarine cables used primarily for transporting electrical power, and will instead focus on those dedicated to telecommunications. Cables are not a recent invention: the first experiments with telegraphic transmission through submarine cables date back to the mid-19th century, followed by the first commercial use for transmitting stock market orders (already!) between France and England. At the time, however, cables were fragile equipment: sensitive to earthquakes, strong pressures, tides, and sometimes rough seabeds, they had a limited lifespan.
It was not until the end of the 19th century, particularly with the creation of the French Telegraph Cable Company, that the first long-distance cable (nicknamed the “Direct”!) enabled communications without relay between France (the Brest Déolen station) and the United States. Cable development then continued rapidly in the early 20th century, with deployments between Europe and Africa, as well as across the Pacific Ocean. Cables, mainly used for telegraphy at the time, gradually moved toward more efficient and suitable coding systems such as the Baudot code.
Improvements in technology, such as the use of coaxial cables and repeaters, then made it possible to consider telecommunications over much greater distances, as well as the transmission of telephone communications. In the 1990s, optical fiber became the reference technology: offering very advantageous multiplexing possibilities, it dramatically increased the number of telephone circuits available on cables. The symbolic milestone of 1 Gbit/s was reached.
The Sea-Me-We 3 cable (South-East Asia – Middle East – Western Europe) was commissioned on August 23, 1999. Using optical technology, it connects Europe to the Indian Ocean, Japan, and Australia. With a length of 40,000 km, it remains today the longest submarine cable in service, while still remaining competitive (130 Gbit/s per pair of optical fibers).
But what exactly is a cable?
A modern submarine cable is above all a physical medium (remember the famous layer 1 of the OSI model). In this case, it enables the transmission of light (more precisely, wavelengths—different colors) over long distances. Wavelength division multiplexing techniques (WDM, Wavelength Division Multiplexing) or more recently SDM are used to improve capacity in terms of throughput.
Looking only at the cables themselves is not sufficient: the whole system must be considered, namely:
- the designer of the physical cable (in France, for example, Nexans)
- the cable owners (in France, Orange Marine)
- the cable installers (in France, Alcatel Submarine Networks, Orange Marine)
- the cable-laying ships, very recognizable (for Orange Marine: Pierre de Fermat, René Descartes, Léon Thévenin, Raymond Croze; and for Alcatel Submarine Networks: Île d’Aix, Île de Batz, Île de Sein, Île de Bréhat)
- the landing sites: in France, examples include Lille (France-UK5), Dieppe (France-UK3), Cayeux (Circe South), Saint-Valéry-en-Caux (TAT 14, Cross Channel), Surville (Ingrid), Plérin (Flag Atlantic 1), Lannion (Apollo, HUGO), Penmarch (ACE, Sea-Me-We3), St Hilaire de Riez (Dunant), Le Porge (AMITIE, project), Marseille (2Africa, AAE-A, Ariane 2, Atlas Offshore, Hawk, IMEWE, Med Cable Network, PEACE Cable, SeaMeWe-4, TE North/TGN-Eurasia/SEACOM/Alexandro/Medex), La Seyne (CC5), Toulon (Sea-Me-We5), Cannes (CC4), Île Rousse (CC4), Ajaccio (CC5), Saint Pierre and Miquelon (St Pierre and Miquelon cable), Sainte-Marie (La Réunion, Lower Indian Ocean Network), Saint-Paul (La Réunion, SAFE), Le Port (La Réunion, Meltingpot Indianoceanic Submarine System), Cayenne (French Guiana, Americas II), Kourou (Kanawa, Ellalink), French Polynesia (Honotua, Natitua, Manatua), New Caledonia (Picot-1 and 2, Gondwana 1 and 2)
- the control and monitoring stations responsible for supervising proper cable operation, SDN links, and routing.
Cables: a political and strategic issue
In 2019, the oceans contained 448 submarine cables, with an average cost of about €700 million per cable. Representing 50% of the investments made by the GAFAM companies, the “cable race” is far from trivial: whoever owns the cables in some sense “owns” the data flowing through them and holds significant geopolitical power. Indeed, cable cuts can have considerable effects on affected countries (as has been the case for Algeria and Somalia, among others).
Among the other risks associated with cables, interception must of course be mentioned (some landing stations are “known” to have duplication devices whose purpose is easy to imagine; some countries are believed to possess submarines capable of physically interacting with cables). There are also risks of physical destruction (cutting a cable whose position is known is, ultimately, relatively simple). Finally, landing stations are critical facilities that must be protected.
Some references on the subject: