通讯技术（Communication technology）.docVIP

通讯技术（Communication technology） (Communication Technology) is the technology of transferring and exchanging information between people. Modern communication technologies (optical fiber communication), (digital microwave communication), (satellite communication), (mobile communications) ) technology to narrow the distance between. Word communication is a communication mode that uses digital signals as carriers to transmit messages, or uses digital signals to modulate the carrier digitally and then to transmit them. It can transmit digital data cable, digital signal transmission, also can through voice and video analog signal digital processing. An optical fiber is a medium that transmits messages from one end to the other. It is a glass or plastic fiber that serves as a medium for passing messages. Usually fiber and cable two words would be confused. Most fiber must be covered by several layers of protection structure before use, the coated cable is called cable. To protect the structure fiber layer can prevent the environment of fiber damage, such as water, fire, electric cable and so on. For optical fiber, buffer layer and cladding. Similar to optical fiber and coaxial cable, but no mesh shielding layer. The center is the light transmitting glass core. In multimode fibers, the diameter of the core is 15mm~50mm, roughly the same as the thickness of the human hair. The diameter of the single-mode fiber core is 8mm~10mm. A glass envelope with a lower refractive index than the core is surrounded by the core to keep the fiber in the core. The outside is a thin plastic coat that protects the envelope. The fiber is usually bundled into a bundle and protected by a shell outside. The core is usually a double concentric cylinder made of quartz glass with a small cross section. It is brittle and easy to break, so it needs an additional protective layer. The characteristics of the optical fiber is a transmission medium, it can be like a general copper wire, transmission of tele