Fiber Backbone:

Either of these fibers is an excellent way to connect computer rooms, whether the other computer rooms are inside the same building or even in another city. This provides one company to have one network (Ethernet).

Multi-Mode Fiber:

Multi-mode fiber allows many modes of light to generate down the fiber-optic path. Multimode fibers are generally used for short-distance data links, as they provide limited bandwidth due to modal dispersion. The relatively large core or a multimode fiber allows good coupling from inexpensive LEDs, and the use of inexpensive couplers and connectors. Multi-mode fiber typically has a core diameter of 25 to 200 microns. The core is much larger than single-mode fiber and allows several modes of light to be passed through it. Multimode fiber was the original medium specified for FDDI.

Single Mode Fiber:

Single-mode fiber is a fiber that allows only a single-mode of light to generate. This eliminates the main limitation to bandwidth, modal dispersion. However, the small core of a single-mode fiber makes coupling light into the fiber more difficult, and thus lasers must be used. The main limitation to the bandwidth of a single-mode fiber is chromatic dispersion. Laser sources must also be used to attain high bandwidth, because LEDs emit a large range of frequencies, and thus chromatic dispersion becomes significant. The current bandwidth of the fastest commercial systems (as of 1995) is approximately 5 gigabits/second, which can be transmitted for approximately 100-200 kilometers before a repeater or fiber-optic amplifier is required.