Optical fibres are also pretty good sensors so it's not unlikely that some fibres are added just for sensing purposes (they are eput into lots of bridges and ot

Optical fibres are also pretty good sensors so it's not unlikely that some fibres are added just for sensing purposes (they are eput into lots of bridges and other things for example). That said it highly depends on the length of your electrical cables if putting in fibre for communications makes sense. Typically (grossly simplified) you need optical amplifiers when you go significantly over transmission distances of 100km so they need power supplies, take up quite a bit of space etc..