No. By that logic, PVC pipes wouldn't be safe from thieves, because thieves wouldn't be able to understand the difference from copper pipes. Anyone who's ever touched a fiber cable before immediately understands the difference from a copper cable, and if thieves can't get paid, they're not going to waste their time stealing it.

The question is if they can tell it's fiber _before_ cutting through it and damaging it. This seems way easier with PVC pipes than with fiber cables.