The fiber is the abbreviation of the optical fiber. Optical fiber communication is to light as an information carrier, as a communication transmission medium. From a principle point of view, the basic material elements constituting the optical fiber communication is an optical fiber, the light source and the photo detector. Addition to the classification by the manufacturing process, materials, composition and optical properties of the optical fiber applications, the optical fiber often by use classification, can be divided into communication with the fiber and a sensor optical fiber. Transmission medium fiber is divided into both general and specialized, functional devices fiber for the completion of the light wave amplification, shaping, divider, multiplier, modulation, as well as light oscillation function of the optical fiber, and often some kind of functional devices form. The reason why the rapid development of optical fiber communications, mainly because it has the following characteristics:

(1) Large communication capacity, long transmission distance;

(2) Small signal crosstalk, good performance of confidentiality;
(3) anti-electromagnetic interference, the transmission quality is good;
(4) fiber optic small size, light weight, ease of laying and transport;
(5) a rich source of material, good environmental protection;

 (6) no radiation, it is difficult to eavesdrop;
 (7) fiber optic cable is high adaptable, long life.