A type of fiber-optic cabling that allows multiple signals to be transmitted simultaneously. Line drivers for multimode fiber-optic cabling use light-emitting diodes (LEDs) to generate the light signals that carry the data down the fiber.
Multimode fiber, which has a glass core whose index of refraction varies with the distance from the core axis, is implemented in two main forms:
Multimode fiber is available with different core diameters, typically 50, 62.5, and 100 microns. Multimode fiber can carry more bandwidth than single-mode fiber, but single-mode fiber can carry signals up to 50 times farther than multimode.
Multimode fiber is not recommended for long cable runs and should generally be restricted to runs of 914 meters. If this limit is exceeded, the light traveling along different paths through the fiber can produce a condition called modal dispersion, which results in parts of the signal arriving at unexpected times at the end station. This can degrade the quality of the signal or cause it to be unrecognizable.
Graphic M-20. Multimode fiber-optic cabling.
Step-index fiber is cheaper than graded-index fiber and should be used only for shorter cable runs or where less bandwidth is required.