Lightning is unable to travel through fiber optic cable itself because fiber optic cable is made of glass fibers.
Only light can travel through the fiber optic cable and it's how data is sent through the fiber optic cable.
When the fiber optic cable is not lit up it's called dark fiber and when the fiber optic cable is not lit up there's no way for signals and data to travel through it.
However once the fiber optic cable is lit up then data and information can be sent through it and it travels at a really fast speed.
But fiber optic cable cannot carry lightning through it because it's not a conductor of electricity.
Fiber optic cable does not conduct any electricity because it's made of glass and not metal wire.
However fiber optic cable can have some metal wires inside it for strength and as a locator and a ground for it.
So if the lightning does strike the fiber optic cable the lightning can travel down that wire.