The U.S. Military seems to have been aware of fiber's potential for surveillance since at least 1999.  Activist Post has reported before about this before too.

More from Wired:

How Underground Fiber Optics Spy on Humans Moving Above

Vibrations from cars and pedestrians create unique signals in cables. Now scientists have used the trick to show how Covid-19 brought life to a halt.

When last spring's lockdown quieted the Penn State campus and surrounding town of State College, a jury-rigged instrument was "listening." A team of researchers from the university had tapped into an underground telecom fiber optic cable, which runs two and half miles across campus, and turned it into a kind of scientific surveillance device.