Undersea cables and their historical significance

The existence of undersea cables reminds us that the Internet is not only virtual but also relies on material infrastructure, a reality that was well known to the general public in the 19th century. The laying of the first transatlantic cable for telecommunications was widely followed in newspapers, and when American adventurer Cyrus Field succeeded in laying a transatlantic cable for the first time, he was acclaimed by thousands of people, with parades in the streets of New York.

Modern use and forgotten importance

These cables have evolved and are now used for data exchanges for the Internet, but they are largely forgotten. They are considered taken for granted, even though we are totally dependent on them, which contributes to a certain vulnerability.

Cable construction and deployment

Undersea cables are made of an optical fiber, the thickness of a hair, which allows transmitting a considerable amount of data: up to a petabit per second for the recently announced PETAL cable. Around these fibers, several layers of protection constitute the size of a garden hose.

Deployment process and challenges

There are only about 600 in the world, and if we put them all one on top of the other, they would all fit in a room. These cables are laid by cable ships that have huge tanks, in which the cable is carefully wound around a reel. People walk around on them for thousands of kilometers, it takes days. The cable is then deployed at sea with a winch, placed on the seabed in the open sea. Near the coasts, the cable is buried in a trench. It connects to a landing station on land, which is often very discreet because it is a sensitive place. In Taiwan, in a context of tensions with China, they are guarded 24 hours a day.

France's role in cable infrastructure

France is leading in companies that lay and repair these cables. It is a small sector dominated by 4 or 5 actors in the world, including two French ones: Orange Marine and Alcatel Submarine Networks (ASN). The French state has bought 80 % of the shares of ASN, because it is considered a strategic company. France has a third of the global cable ship fleet.

Cable ownership and strategic importance

Undersea cables were previously the property of telecommunications operators who formed consortia, because the cost of cables is very high: 600 million dollars for a transatlantic cable. In recent years, Meta and Google have become owners themselves. Their development is huge: they went from 10 % of the bandwidth in 2010 to 90 % of the bandwidth. They are not owners of the majority of cables, but of the most important ones, those with a strong capacity, which they do not use entirely anyway. They certainly keep a place for the upcoming explosion of AI.

Geopolitical risks and cable sabotage

There is a risk that the United States could cut Europe off from these transatlantic cables in case of conflict. We know that the interests of Google and Meta are aligned with those of the USA, and we can clearly see Donald Trump's tendency to blackmail regarding technologies. He could ask Google and Meta to prohibit the use of American cables by Europeans. However, researchers explain that it is very difficult to know which path the data travels, making it impossible to predict who would be affected if a cable were cut.

Marseille as a key European hub

Europe has announced the financing of a project for a EU/Canada cable, which does not pass through the USA, as well as a EU/Greenland cable, which is quite symptomatic of the era we are currently living in. Marseille has become a major hub for undersea cables in Europe. Out of twenty-three undersea cables arriving in France, eighteen arrive in Marseille. This is due to its geographical position, which allows connecting Asia, Africa, the Middle East, and the Flap (Frankfurt, London, Amsterdam, Paris), strategic hubs in Europe.

Strategic importance in the context of war

Marseille is ideal for cables arriving in the Mediterranean because there is no obstacle of the Alps relief. This is the reason why so many data centers have been created on the same territory, to be geographically close to the cables. In the context of the war waged by Russia, undersea cables are a real strategic issue. Russia has mapped out the entire underwater infrastructure of Europe for a decade, whether it be Internet cables or electrical cables. This is a way for them to know our vulnerabilities to exploit them when needed.

Russian naval activities and sabotage risks

National navies, especially ours, are well aware of this. Russia launched the ship Yantar in 2015, supposedly dedicated to oceanographic research, but from the start it traveled around European strategic sites. It was designed to map these infrastructures and potentially sabotage them. It had hostile behavior with several ships, pursuing or spying on them. It recently entered British waters twice. The English responded by sending the Royal Air Force, and the ship aimed its lasers to blind the pilots.

Cable sabotage in the Baltic Sea

Specialists exclude no possibility regarding Russian attacks on these cables, such as a scenario of simultaneous sabotage of several important cables which would lead to a strong disruption of Internet access and certain services. In most cases, so far, when a cable fails, users do not notice. Especially since the French mainland is also connected to a terrestrial fiber network via the continent. The problem arises more for islands. Like Svalbard, which has only two cables connecting it to the Internet. If these fail, it is necessary to switch to satellites but they can only handle 5 % of the bandwidth of the cables. In case of sabotage, Ireland is one of Europe's Achilles' heels, because it is served by several major transatlantic cables.

Incidents and the difficulty of attribution

It is impossible to identify exactly what Russia could do, but in any case, she has identified this vulnerability. There have already been sabotage incidents, notably in the Baltic Sea, which are attributed to Russia. The highest concentration of unusual incidents on undersea cables in Europe is located in the Baltic Sea. On this sea, there are 4,000 ships permanently on the water, and the seabed is only 55 meters deep on average, so the cables are less protected. The Baltic Sea is surrounded by nine riparian states, eight of which are members of NATO, as well as Russia, making it a particularly strategic area.

Russia's interest in cable sabotage

In a short time, we have recorded one incident on a cable in October 2023, two in November 2024, and four severed at Christmas 2024, by the same ship. It is very difficult to formally establish who is the patron, which is the whole point of cable sabotage: one can deny that it was intentional. However, several think tanks and military commands attribute it to Russia. Even though these actions have no consequences on the Internet network, Russia finds an interest in it: it watches how we react, and these are actions that consume time and money to repair. Like cyberattacks, it is a kind of permanent harassment.