The millions of kilometers of fiber optic cable lying on the ocean floor have traditionally been invisible assets—laid once and forgotten until something breaks. But Distributed Acoustic Sensing (DAS) technology is transforming this dark infrastructure into a vast network of intelligent sensors capable of detecting everything from anchor drags to earthquakes.
In this episode of the TeleGeography Explains the Internet podcast, Mark Englund, CEO of Fibersense, discusses how DAS brings sonar capabilities to telecommunications cables. "Every meter of that infrastructure can be converted into an optical fiber sensor," he explains.
Here are some key takeaways from the conversation.
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Using DAS and Machine Learning to Protect Submarine Cables
Distributed Acoustic Sensing (DAS) technology works by analyzing light traveling through fiber to detect acoustic vibrations, essentially allowing cables to "hear" their surroundings with remarkable precision—down to five-meter resolution across thousands of kilometers.
The challenge isn't just detecting sounds—it's interpreting them. Ocean environments create what Englund calls a "cacophony" of noise: surface waves, biological activity from whales and other marine life, ship traffic, and micro-seismic background pressure. Distinguishing a threatening anchor drag from this chaos requires sophisticated machine learning.
This is where Fibersense's service model becomes critical. Rather than selling equipment boxes, they maintain continuous monitoring and build what Englund calls a "data lake"—years of acoustic signatures that train AI classifiers to recognize specific threats. This technology not only recognizes what is making a sound, but also what that thing is doing. The result? False positive rates of just 1-3%, accurate enough that cable operators can confidently dispatch expensive repair vessels or contact ships in real-time when threats are detected.
The system has proven its forensic capabilities. In one case involving a pedestrian fatality, Fibersense's terrestrial system reconstructed the entire incident: the pedestrian's walking speed, the vehicle's velocity six kilometers before impact, post-impact movements, and even identified eyewitness vehicles—all from acoustic data alone.
Preventing Cable Faults and Providing Accountability
Over 80% of cable faults occur near shore, within the first repeater section where fishing activity, anchors, and excavation pose constant threats. DAS monitors submarine cables in these vulnerable areas, not only detecting active threats but also alerting before events occur. Precursor events like cable "strumming," when a suspended cable vibrates like a guitar string, is one example of a known indicator of impending failure.
DAS creates accountability when cable faults occur, helping ease geopolitical tensions among governments that have vested interests in understanding what happened when cables break. DAS can pinpoint which ships are involved in cable faults. While ships can disable their Automatic Identification Systems to operate invisibly, they cannot silence their acoustic signatures. Fibersense can fingerprint specific vessels and identify them even when AIS is turned off, providing critical evidence for specific causes of cable breaks.
Acoustic Sensing Beyond the Ocean Floor
The same technology monitoring submarine cables is revolutionizing terrestrial infrastructure. Fibersense can detect excavators approaching buried fiber, preventing costly cable cuts. Their water leak detection algorithms identify failing pipes before sinkholes form, a capability that will become its own business division by 2027.
Most ambitiously, the technology is enabling a new vision for traffic safety. By passively detecting individual vehicles through existing fiber networks—no transponders required—Fibersense can provide bird's-eye views of traffic patterns, identify dangerous driving behaviors, and feed data to autonomous vehicle systems. The goal is moving road safety from the stochastic realm of random accidents to the predictable domain of measured, actionable data.
With less than 1% of submarine cables currently equipped with sensing capabilities, and 2,000 cable landings worldwide, the industry is just beginning to tap this technology's potential. As Englund notes, adding intelligence to previously dark assets always proves valuable—just as radar transformed aviation despite initial skepticism, DAS is making the invisible infrastructure that powers our digital world finally visible.
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