Multi-mode fiber is a type of optical fiber designed to carry multiple light rays or modes simultaneously, each at a marginally different reflection angle inside the optical fiber core.
Multi-mode fiber is mainly used to transmit across comparatively shorter distances, as the modes are more likely to disperse over longer extents. This phenomenon is known as modal dispersion. Another common type of optical fiber is the single-mode fiber, which is used mainly for longer distances.
Multi-mode fiber is also known as multi-mode optical fiber.
Techopedia explains Multi-Mode Fiber
Multi-mode cable consists of glass fibers with a common diameter in the range of 50 to 100 microns for the light-carrying element. The most prevalent size is 62.5 microns. Plastic optical fiber (POF) is a modern plastic-based cable that ensures performance much like glass cable for brief runs, but economically.
On the contrary, single-mode fibers include a small glass core, usually close to 9 microns. With single-mode fibers, data can be transmitted at high speed over longer distances. Multi-mode fibers are more vulnerable to attenuation compared with single-mode fibers.
Multi-mode fiber provides users with high bandwidth at high speeds across moderate distances. Light waves are spread into various modes, or paths, as they travel via the core of the cable, usually at 850 or 1300 nm.
On the other hand, in long cable runs (e.g., more than 3000 feet), various paths of light may lead to signal distortion on the receiving end. This ultimately results in an ambiguous and incomplete transmission of data.
Multi-mode fibers may not be suitable for high-speed data transmission. It is not advisable to mix and match fibers either. Attempting to connect a single-mode fiber with a multi-mode fiber may result in a 20-dB loss, which is 99% of the total power.