Optical fiber is a kind of tool that uses light to transmit information by light in the small optical fiber which is drawn by high purity glass or plastic, and has the phenomenon of total reflection to realize photoelectric conversion. It can not only be used to transmit analog signal and digital signal, but also make the transmission of video signal possible. Its appearance has changed the traditional information transmission tool with copper and other materials as the main transmission medium mode, and effectively promoted the development of communication.
In 1977, the world's first commercial optical fiber communication system was opened between two telephone offices 7 km apart in Chicago, USA. This optical fiber communication system adopts multimode fiber transmission mode. In the system, two glass wires with a diameter of only 0.1 mm can open 8000 telephone lines. The commercial optical fiber communication system has been put into use, which has made great changes in the field of human communication.