You normally think of fiber optic as something used in network cables. However, scientists employ dedicated fibers to detect earthquakes. In simple terms, they fire a laser down the fiber and watch reflections caused by imperfections. When vibrations hit the cable, it changes the defects, which show up in the return pattern. However, with the right techniques, those vibrations could just as easily be from people speaking near the cable.
If you are alarmed, there’s good news and bad news. The good news is that the technique seems to be limited to coils of fiber that are not buried, and you have to be within about 5 meters of the fiber. The bad news is that there is plenty of dark cable all over the place. Besides, if researchers can do this successfully, you would imagine three-letter agencies around the world could do it even better.
There have been several recent papers about the same topic. Of course, you can also read laser bounces from windows. Noisy keyboards can also give you away.
Title image from [Compare Fibre] via Unsplash.