Despite all the satellites and antennas that travel and orbit the planet, practically 97% of humansAccording to data from the European Cybersecurity Agency, we depend on underwater cables for your daily dose of the internet. But from now on, these same cables could have another purpose: submarine detection.
Underwater fiber optic cables, which They extend over more than 1.2 million kilometers along the seabedare being used in an innovative way in anti-submarine warfare thanks to a technology called Distributed Acoustic Detection (DAS).
Originally designed for communications, these cables are now adapted to act as giant passive sonar arrays capable of detecting, classifying and tracking submarines, surface vessels and other underwater activities through sea routes.
The concept, which was initially theoretical, is rapidly evolving into real-world defense applications. The DAS technique works by using standard fiber optic cables as long chains of acoustic sensors. When a pulsed laser is sent through the cable, tiny backscattered signals vary based on vibrations or stress caused by nearby sound waves. Simply put, they bounce off these structures and indicate their presence, their direction and even their size.
By analyzing these patterns, advanced algorithms They can detect and locate underwater sounds, such as submarine engines, ship propellers, or seismic activity.
The technology effectively converts existing telecommunications cables into a continuous monitoring system, distributed and in real time, capable of listening to the ocean thousands of kilometers awayat a fraction of the cost of traditional sonar systems or hydrophone networks.
In recent years, different studies have confirmed that DAS can detect and track ships and submarines in deep and shallow water environments, matching acoustic readings with ships’ GPS or AIS data using artificial intelligence.
This has caused the United States, the United Kingdom, Australia and several European countrieshave launched programs to integrate DAS into their maritime domain knowledge frameworks.
Obviously, they are not the only countries interested: China and Russia are also exploring DAS capabilities. With one of the densest regional cable networks, China is likely testing DAS for surveillance and anti-manipulation missions.
But how exactly does DAS technology work? The Fiber optic cables use a sensor called an interrogator that sends pulses of laser light through the cable. The light interacts with microscopic imperfections in the fiber, causing it to scatter toward the interrogator.
When acoustic energy from a nearby submarine exerts pressure on the cable, it alters, in a very subtle but measurable way, the intensity of the backscattered light. This is when the sensor (the aforementioned interrogator) receives backscattered light and analyzes changes in its properties.
Using algorithms and artificial intelligence, these patterns can be interpreted and the source of the sound located. The technology is profitable, since it Leverages an existing network, provides a constant flow of data in real timeallowing even the most subtle underwater activity to be detected.
Beyond military use, the technology also It is used to detect other threats, such as cable tampering, and to monitor natural phenomena such as earthquakes.. It stands to reason that the system generates huge volumes of data, requiring advanced AI processing to filter out useful signals and discard uninteresting ones.
But the biggest problem is who will use it. 99% of cables belong to large companies (Google, Microsoft) and the rest have investments from some governments. Therefore, deciding who uses the sensors and on which cables is even more complex than the development of the technology itself.