The optical signal just like an electrical signal suffers from attenuation (signal loss). It has to be amplified so many km. In the past, optical signals were converted back to an electrical signal, pulses reshaped, by stripping off noise and amplified, then converted back to an optical siganl (called OEO optical-electical-optical). As an electrical signal it was vulnerable to electromagnetic induction or picking up the signal.
Yes, but I think we were putting a pick-up mat under copper cables before fiber optics even existed.
The relly cool part was the opponent could raise the cable, inspect it, find no evidence of a bugging device, and lay it right back on the mat!