Multimode Vs. Single-Mode Fiber
By Andrea Stein
An optical fiber refers to a flexible, thin fiber through which light can be transmitted via internal reflections. Optical fibers can take the form of single-mode or multimode fibers.
A single-mode fiber refers to an optical fiber designed to carry only one mode, or a single ray of light. A multimode fiber is optical fiber able to transmit multiple modes or light rays simultaneously, each at a different reflection angle within the optical fiber core.
Multimode fiber and single-mode fibers have significant core differences. Multimode fibers contain light-carrying cores that are 62.5 microns or more in diameter. Single-mode fiber contains a light-carrying core that has a diameter between 8 and 10 microns. A micron is one-millionth of a meter.
A multimode fiber provide bandwidth transmissions of a few hundred megahertz (MHz) per kilometer (km) of length. Multimode fibers permit transmission distances of up to approximately 10 miles and can be used with receivers and optic transmitters that are relatively inexpensive. Single-mode fibers transmit over distances greater than 10 miles, but must be used with solid-state laser diodes or other single-mode transmitters. A diode refers to a device composed of two terminals that conduct currents in one direction. Single-mode transmitters can be up to four times as expensive as multimode fiber equipment.