[gtsteve]

Perhaps they like the fiber cable because it's tougher than other cables. I think many animals have an instinct to do stuff like this to sharpen their teeth perhaps or to clean them.

Perhaps do some research, find something they'd like more, like something they'd find in their natural habitat and put it near the cable so they use that instead. Like a sacrificial anode on a ship.

You could also just try buying a spool of fiber cable (not sure of the cost) and constantly put a length somewhere easier to get to. Make sure you replace it as it gets damaged.