Chris Baraniuk
Technological journalist
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Submarine cables are essential to the operation of the Internet
The diver had found the fiber optic cable located on the seabed of the North Sea. He swam closer, until he was close enough to touch.
He stretched his hand. But someone could say he was hiding there. Someone looked.
“It stops and touches the cable lightly lightly, you can clearly see the signal,” said Daniel Gerwig, a world sales director at AP Sensing, a German technology company. “The acoustic energy that moves through the fiber essentially disturbs our signal. We can measure this disturbance.”
Multiple reports of damaged telecommunications cables from the Baltic Sea have made the alarm in recent months.
These cables are so important, which carry huge volumes of Internet data between countries, that NATO launched a mission called “Sentry Baltic”, to patrol the Baltic Sea with planes, warships and drones.
The EU also intensifies measures to monitor and protect cables.
Despite these efforts, the authorities cannot be everywhere at the same time.
Thus, some companies are trying to monitor what is happening near any cable – using fiber optic signals to listen to collaborator underwater drones or hostile ships dragging their anchors along the seabed.
It is during tests of the AP Sensing system last year – it is not a real sabotage attempt – that the diver tapped his hand on the submarine cable monitored by the company.
The company also deployed ships, drones and divers with sea scooters to discover how its software could choose and identify the presence of these vehicles.
And, the team tested if their cable could “hear” a ship plunging its anchor into the water.
When light pulses move along a bit of fiber optics, tiny reflections sometimes bounce along this line. These reflections are affected by factors, including temperature, vibrations or physical disturbances of the cable itself.
Note a temperature change along a part of a buried cable could reveal that the game has become not buried, for example.
APS Sensing shows me a video of a man who crosses a lawn before lifting a rifle and pulling it during a test. A fiber optic cable burned in the ground a few meters away picked up the whole sequence.
“You see each step,” explains Clemens Pohl, managing director, when he points to a graph revealing disturbances in the fiber optic signal. The traces appear in the form of briefs or lines and the shot as a larger alsoel.
With this technology, it is even possible to determine the approximate size of a ship passing over a submarine cable, as well as its location and, in certain circumstances, its travel management. This could be correlated with satellite imaging, or even the recordings of the automatic identification system (AIS), which most ships diffuse at any time.
It is possible to add surveillance capacities to existing fiber optic cables if a unused “dark” fiber is available or an lit fiber with enough free channels, adds the company.
However, there are limits. David Webb at Aston University says that fiber optic detection technology cannot take disorders from far away, and you must install signal listening devices or interrogators every 100 km (62 miles) along a cable.
Ap Sensing says that it can pick up vibrations hundreds of meters but “generally not several kilometers”. The company confirms that its technology is currently deployed on certain cable installations in the North Sea, but refuses to comment more.
“People really need an early warning to determine what to do,” explains Paul Heiden, director general of Optics11, a Dutch company who also manufactures acoustic detection systems with fiber optic.
Mr. Heiden maintains that the cables installed only in order to monitor the marine activity could be particularly useful – one could place these listening cables, for example, 100 km from a vital port, or near a gas pipeline or a telecommunications cable, rather than in these assets themselves.
This could give operators an overview of ship traffic in the region, and potentially warn a ship heading for a critical asset.
Hexatronics
Cable installation ships connect continents
Optics11 fiber optic listening technology can be deployed on military submarines, adds HEIDEN, and he says that the company will soon start testing a surveillance cable installed somewhere on the soil of the Baltic Sea.
The demand for fiber optic detection technology is increasing, explains Douglas Clague at Viavi Solutions, a network for network tests and measures: “We see the number of requests increase.”
Some of the damaged cables in recent incidents have been manufactured by the Swedish Cablodistribution Company Hexatronic, explains Christian Priass, head of central Europe, the Middle East, Africa and the company’s submarine cable.
Acoustic detection is an emerging technology which, according to Mr. Priass, will become more common in the future. But there is relatively little that you can do to protect a cable from sabotage, in terms of physical strengthening.
Today’s optical fiber cables already have folded and welded metal envelopes closed around the fibers, he says. There is also a “armor wire”, thick metal cords, which turn along the outer parts of the cable and, in some cases, there are two layers of these cords. “On the British side of the chain where you have a lot of rocks and a lot of fishing, you want to have it double armor,” explains Mr. Priess.
OPTICS11
Although highly protected, cables are always vulnerable
But if a ship deliberately drags its heavy anchor on even a double armor cable, it will damage it almost certainly, says M. Priess – such is the strength of the collision or the traction action.
Although it is possible to bury cables in the seabed for additional protection, this could become prohibitive over long distances and at depths less than a few tens of meters.
“The cables break all the time,” explains Lane Burdette, research analyst at Telegeography, a telecommunications market research company. “The number of cable defects per year has really been stable in recent years,” she adds, explaining that 1-200 defects which generally occur annually have not increased despite the increasingly underwater cables during this period.
Ms. Burdette also notes that, even when a cable is cut, telecommunications networks generally have a significant redundancy which is integrated to them, which means that end users often do not notice much disruption of their service.
However, the military response visible to cables in the Baltic Sea is welcome, explains Thorsten Benner, co -founder and director of the Global Public Policy Institute, a reflection group: “It is good that NATO and the European Union woke up.”
And although cable detection technology can be useful, its effectiveness in terms of damage prevention is based on the speed with which coast guard or military patrols could receive alerts on potential sabotage and reaction. “The question is how speed you could make contact with a ship,” says Benner.
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