Observing this "backscatter" phenomenon through a technique called Distributed Acoustic Sensing (DAS), the 20 km long cable was turned into a bed of 10,000 motion sensors that could detect seismic activity with picometer precision.
AP Sensing...recently received funding from the Department for Transport as part of Network Rail’s R&D program....sensors will tap into Network Rail’s existing fiber optic cable network using AP Sensing’s Distributed Acoustic/Vibration Sensing
A recent proof-of-concept field trial from Verizon and NEC demonstrated the ability “to use network infrastructure with existing fiber-optic cables already laid in the ground as distributed optical sensors to collect information on city traffic patterns
For remote borders with little or no infrastructure, there are various techniques that can keep an eye, or rather an ear, out. QinetiQ, a British firm, has a system called OptaSense, which uses a fiber-optic cable laid in the ground. Sound from above creates vibrations in this cable.
The Toro Company announced Feb. 15 that it has entered into a definitive agreement to acquire privately-held The Charles Machine Works, Inc., an Oklahoma corporation and the parent company of Ditch Witch