Over 95% of the world’s internet traffic is carried by underwater cables, and damage to these cables has become a major cause of internet outages in recent years. AP Sensing has proposed a way to “listen” and detect irregular light pulses that occur in underwater fibre optic cables, caused by acoustic interference when a diver touches the cable or when it comes into contact with a ship’s anchor.
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During a demonstration of the technology, AP Sensing Global Sales Manager Daniel Gerwig explained, “[An object] just lightly touches the cable, you can clearly see the signal. The acoustic energy that’s traveling through the fiber is essentially disrupting our signal. We can measure that disruption.” In addition to the interference created by acoustic energy from contact with the cable, the light pulses traveling through fiber optic cables can also be distorted by temperature changes, potentially indicating that a section of the cable has been subjected to unwanted disturbance.
The technology developed by AP Sensing can provide an approximate idea of a vessel’s size, location and even direction of travel. This data can then be cross-referenced with satellite images or automatic identification system (AIS) recordings that most ships broadcast continuously.
The method does not require replacing cables, as the system can use “dark” or unused fibers or active fibers with free channels. However, the system is not perfect and requires listening stations to be installed on the cables approximately every 100 km. AP Sensing said its technology has already been deployed on some cable installations in the North Sea, but declined to comment further.
Many telecommunications and submarine cable companies are developing new ways to detect potential damage or sabotage to submarine cables following damage to a number of cables in the Baltic Sea. In 2024, the International Telecommunication Union (ITU) and the International Cable Protection Committee (ICPC) created the International Advisory Body on Submarine Cable Resilience in response to growing geopolitical tensions and damage to submarine cables in the Red Sea.
Paul Heiden, CEO of Dutch firm Optics11, which makes fibre-optic acoustic sensor systems, said his company’s cable integrity monitoring technology could even be deployed on submarines. Optics11 will soon begin testing its method on a monitoring cable laid on the bottom of the Baltic Sea.
Image source: Optics11
Demand for fiber optic cable monitoring technology is growing, says Douglas Clague of Viavi Solutions, a network testing and measurement company: “We’re seeing more requests.”
Christian Priess, head of the department at Swedish cable company Hexatronic, is confident in the prospects of acoustic monitoring and probing technologies for fiber optic cables. He noted that this will help to respond more quickly to damage, but it is almost impossible to protect the cable from serious physical impact, although modern fiber optic cables are enclosed in a metal sheath with additional reinforcement.