A variety of constructions are used for fiber cables:

A variety of constructions are used for fiber cables:

There are simple coated fibers (called bare fibers despite the coating), where a single glass fiber is surrounded with a polymer coating with a diameter which is often 250 μm, i.e., twice the fiber diameter.

This low level of protection is often sufficient for cables within some optical setup.
Alternatively, one may use tight buffered cables, where a thicker polymer buffer (often with an outer diameter of 900 μm) protects the fiber. The buffer can protect the fiber against excessive bending, but not much against stretching.
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One may package one or several tight buffered cables, for example, into a larger cable structure providing additional protection, e.g. with an aramid yarn, a ripcord and an outer jacket (sheath, often made of PVC). There may be a central strength member around which the fibers are placed. (When pulling such a fiber, one should pull it on the strength member, not at the jacket.)

Some fibers of this type are used as distribution cables within buildings. Others, called breakout cables or fanout cables, contain multiple smaller cables which are stronger than the single fibers in distribution cables; they are usually larger and more expensive than distribution cables. Some fiber cables even contain hundreds of glass fibers.