FOCL: types of optical fibers

The optical fibers used to construct the fiber optic link differ in the material of manufacture and in the mode structure of light. As for the material, there are distinguished all-glass fibers (with a glass core and a glass optical sheath), all-plastic fibers (with a plastic core and a sheath) and combined models (with a glass core and a plastic sheath). Glass fibers provide the best throughput; a cheaper plastic option is used if the requirements for attenuation and throughput are not critical.

By the type of paths that light travels in the fiber core, single and multimode fibers are distinguished (in the first case, one beam of light propagates, in the second - several: tens, hundreds and even thousands).

• Single-mode fibers (SM) are characterized by a small core diameter through which only one beam of light can pass.
• Multimode fibers (MM) are distinguished by a large core diameter and can be with a stepped or gradient profile. In the first case, the light beams (modes) diverge along different paths and therefore come to the end of the fiber at different times. With a gradient profile, the time delays of various rays almost completely disappear, and the modes go smoothly due to a change in the speed of light propagation along wave-like spirals.

All modern works (both single and multi-mode), with which data lines are created, have the same outer diameter - 125 microns. The thickness of the primary protective buffer coating is 250 μm. The thickness of the secondary buffer coating is 900 microns (used to protect connecting cords and internal cables). The sheath of multi-fiber cables is painted in various colors (for each fiber) for convenience.

Also check: fiber optic certifications