How to Find an Underground Cable by the Noise of Traffic express
Beneath city streets lies a web of fiber optics — hundreds of kilometers of glass threads carrying the internet. But accurate maps of this web are often lost or outdated. Finding a cable underground is like feeling for a wire inside a wall without knowing where it runs.
This new method turns the cable itself into an ear. Fiber optics already buried in the ground pick up the slightest ground vibrations. When a car drives down the street, the earth under its wheels compresses slightly, and the cable feels that deflection. Scientists take data from one end of the fiber and watch how the strain changes at each point. At the same time, they track the cars using cameras or GPS sensors on the vehicles themselves. Then an algorithm takes over: it finds the cable shape that makes the predicted vibrations best match the real ones.
The method has already been tested in simulations and on real sites. It doesn't require tearing up asphalt or digging trenches, just ordinary traffic and access to one end of the fiber. This approach could become a standard tool for inventorying underground utilities and even for monitoring the urban environment: vibrations can reveal road congestion or soil conditions.
Original abstract
as written by the authors arXiv:2604.10331
We present a scalable method for geolocalizing buried fiber-optic cables using Distributed Acoustic Sensing (DAS) and traffic-induced quasi-static seismic signals. Assuming access to one end of the fiber, the method fuses DAS measurements with vehicle trajectories obtained from either video tracking or vehicle-mounted GPS. The fiber geometry is estimated by minimizing the mismatch between the measured and physics-based synthetic strain-rate maps. The framework combines a matched-filter initialization with neural-network-based trajectory optimization, enabling robust convergence under realistic noise and trajectory-uncertainty conditions. Simulation and field experiments demonstrate sub-meter localization accuracy, often on the order of tens of centimeters, and strong agreement with manual calibration by tap-testing. This approach provides a practical tool for mapping poorly documented underground fiber infrastructure and for supporting urban sensing applications.
Fiber optics, which usually transmit data, here act as a giant microphone: they pick up vibrations from every passing car, even if the car is tens of meters away from the cable.