Scientists Turn Undersea Fiber Optic Cables Into Seismographs
November 28th, 2019Via: TechCrunch:
These cables carry data over long distances, sometimes as part of the internet’s backbones, and sometimes as part of private networks. But one thing they all have in common is that they use light to do so — light that gets scattered and distorted if the cable shifts or changes orientation.
By carefully monitoring this “backscatter” phenomenon it can be seen exactly where the cable bends and to what extent — sometimes to within a few nanometers. That means that researchers can observe a cable to find out the source of seismic activity with an extraordinary level of precision.
The technique is called Distributed Acoustic Sensing, and it essentially treats the cable as if it were a series of thousands of individual motion sensors. The cable the team tested on is 20 kilometers worth of of Monterey Bay Aquarium Research Institute’s underwater data infrastructure — which divided up into some ten thousand segments that can detect the slightest movement of the surface to which they’re attached.
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Of course most major undersea cables don’t just have a big exposed end for random researchers to connect to. And the signals that the technology uses to measure backscatter could conceivably interfere with others, though of course there is work underway to test that and prevent it if possible.
