Fiber Optics is made of 2 main components or structures.
They are :-
Both structures are made of glass.
Another layer of coating is applied over fiber optic cladding to protect against abrasion and damage. Normally coating is made of plastic or other compound.
I have been in the field of fiber optics since early 1990s. I gained fiber optics skills and knowledge via my working experience as end-user, main contractor and sub-contractor and finally as an optical fiber enterpreneur.