Subsea internet cables can now ‘listen’ for sabotage using irregular pulses of light

• Subsea cables can detect disturbances in the light pulses they carry
• These can be used to locate potential sources of sabotage or damage
• Acoustic sabotage detection will become more common for subsea cables

Following several recent incidents of sabotage against undersea internet cables, many European countries, the European Union, and NATO, are looking for ways to detect attacks as and when they happen.

AP Sensing has now developed a way to ‘listen’ for irregular light pulses travelling through undersea fiber optic cables caused by acoustic energy, such as a diver touching a cable, or a ship dragging its anchor towards one.

Over 95% of the world's internet traffic travels using undersea cables, with damage to these cables being the leading cause of internet disruptions in early 2024.

Detecting sabotage

During a diver detection demonstration shown to the BBC, Daniel Gerwig, global sales manager at AP Sensing, said, “He stops and just touches the cable lightly, you clearly see the signal. The acoustic energy which travels through the fiber is basically disturbing our signal. We can measure this disturbance.”

In addition to the disturbances created by the acoustic energy of a diver touching the cable or a ship passing by, the light signals travelling through fiber optic cables can also be disturbed by changes in temperature, potentially indicating that a section has become unburied.

The technology developed by AP Sensing can also provide some approximate insight into a vessel’s size, location, and even direction of travel. The technology does not require brand new cables to be installed, as the system can use ‘dark’ or unused fibers, or live fibers with free channels.

The system is not perfect however, and requires listening stations to be installed on the cables around every 100km or so, with Gerwig noting that its systems can pick up vibrations up to hundreds of meters away, but “usually not several kilometers away.” The detection distance also varies on how much acoustic energy is transmitted into the cables.

Many other telecommunications and subsea cable companies are developing novel ways of detecting potential damage or sabotage of undersea cables following damage to a number of cables in the Baltic Sea that evidence suggests was deliberately caused by Russia’s ‘shadow fleet’.

Russia’s shadow fleet is made up of incognito commercial shipping vessels that appear to be engaged in maritime trade, but in reality often conduct reconnaissance, espionage, and, in this case, subsea cable sabotage. The vessels often have complex ownership structures and obscured or unknown insurance.

In 2024, the International Advisory Body for Submarine Cable Resilience was launched by the International Telecommunication Union (ITU) and the International Cable Protection Committee (ICPC) in response to increasing geopolitical tensions and the targeting of subsea cables by groups in the Red Sea area.

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