Fiber-optic cable has a construction surprisingly similar to some multi-conductor wire. One or more buffer-coated optical fibers are enclosed in a protective outer jacket with a fibrous strength member in between.

This construction is shown in above Figure. The buffer is rather like the insulation that surrounds a copper wire in a conventional cable. The strength fibers are added to prevent stretching of the cable, which would fracture the optical fiber.

construction of optical fiber is made of extruded glass (silica) or plastic, specially formulated to pass light of specific wavelengths with very little loss. Most fiber-optic LAN wiring is used for backbone wiring and uses glass fiber. Plastic step-index fiber is available from a few sources, but has traditionally suffered from high attenuation and limited bandwidth, factors that are critical to the deployment of fiber technology.

Recent developments in graded-index plastic construction of optical fiber (GIPOF) may offer increased bandwidths in the future, perhaps with lower cost and suitable attenuation when compared to glass fiber. Plastic fiber construction is not yet blessed by the standards for LAN wiring.

Optical fiber can carry very large bandwidths of information at low attenuation. Multimode fiber can be used at distances exceeding 3000 m, although other constraints, such as transmitted bandwidth, may limit operation to less distance.