US, EU navies to use 750,000-mile cable network to track submarines

The US, EU, UK, Australia, and several European nations are repurposing over 750,000 miles (1.2 million kilometers) of undersea fiber-optic communication cables into vast passive sonar arrays using Distributed Acoustic Sensing (DAS) technology. DAS works by sending laser pulses through fiber-optic cables and analyzing backscattered signals caused by vibrations from nearby underwater sounds, such as submarine engines or ship propellers. This approach effectively transforms existing telecommunications infrastructure into a continuous, real-time ocean monitoring system capable of detecting, classifying, and tracking submarines and surface vessels at a fraction of the cost of traditional sonar systems. Beyond military applications, DAS also offers benefits for detecting cable tampering, natural disasters, and illegal underwater activities. Several countries have moved from experimental trials to operational integration of DAS data within their maritime domain awareness frameworks. The US is combining DAS with data from maritime patrol aircraft and undersea drones, using AI to enhance detection across the Pacific. The UK has publicly