Its purpose is to protect the fiber from physical and environmental damage. Single-mode fiber has a smaller diameter core, generally uses laser as a light source, and can transmit data in excess of 25 miles without having to regenerate the signal. LANs and campus networks usually make use of multimode fiber. Both categories of fiber are generally much more expensive than twisted pair wire. Because of this, fiber is usually limited to situations where long distance runs or very high speeds are needed.
Coaxial cable is probably the most well-known type of cable.
The term coaxial denotes a class of cable that has several layers of material surrounding a common axis. A center conductor, either solid or stranded, is surrounded by a nonconductive material, covered by a shielding material, then covered by an abrasion-resistant jacket. At one time, coaxial cable was the only media available for use in data networking. Today, the most common use of coaxial cable is for video distribution, while UTP and fiber are commonly used in data networking. Several new technologies allow for the use of radio or microwave transmission for data networks.