system
Given the following post, respond as if you're commenting on Reddit:
human
Why doesn't the glass inside optic fibers break?
gpt
The individual optical glass fibers used in cables are very strong and very flexible because they have a large tensile strength and small diameter. This is the same material used fiberglass boats, ladders, etc. 

When bundled together inside a coating, along with strengthening components such as Kevlar, and then wrapped in extra material (the cabling) to protect against dirt, bending, crushing, etc. you have a very tough fiber optic cable.

Having said that, breaks and faults in fiber optic cables are not unheard of.