Submarine Cables as Sensors: Finland Transforms Cables into Anti-Sabotage 'Sentinels'

Elisa, a Finnish telecommunications operator, has completed a series of field tests on an underwater infrastructure monitoring system based on Distributed Acoustic Sensing (DAS), a technology that transforms fiber optic cables into distributed sensors capable of detecting vibrations and anomalies along the seabed.
The principle behind the system consists of analyzing variations in the reflections of light passing through the fiber optic: anomalous disturbances, such as those generated by a ship passing with a dragged anchor, can be identified and localized along the stretch of the cable. The tests, conducted in the Gulf of Finland, simulated various operational scenarios, including attempts to damage the infrastructure.
The project now aims to evolve towards an automated alert service, capable of notifying both the relevant authorities and operators of critical infrastructures in real-time in case of anomalous events. The system will be integrated into the information flows of the Coast Guard and the Finnish Navy, with the goal of improving preventive response capabilities.
According to Elisa, protecting underwater infrastructures represents a national strategic priority. The company highlighted how recent episodes of damage have prompted the development of early warning solutions, including collaboration with maritime authorities. The system is designed to intervene before physical damage to the cables occurs.
About 99% of global internet traffic passes through submarine cables, making these infrastructures extremely critical yet difficult to protect. In recent years, there have been increases in incidents of suspected damage, often associated with sensitive geopolitical scenarios such as the Baltic Sea, the Red Sea, and the area around Taiwan.
Among the observed phenomena are also activities attributable to so-called “shadow fleets,” with ships suspected of deliberately dragging anchors to damage the cables.
At the same time, various international initiatives are accelerating the development of dedicated defense systems: the trilateral AUKUS program between Australia, the United Kingdom, and the United States is working on underwater drones for infrastructure protection, while the Pentagon has initiated requests for the development of economical, quickly producible autonomous submarines. Startups in the sector are also introducing autonomous underwater vehicles capable of operating at great depths.