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            Light is everywhere. In the early days of human development, light has been used to transmit information. But at that time, the information capacity was very small and the limitations were very large.
            With the development of society, the amount of information transmission and exchange is increasing day by day. The traditional way of telecommunication can not meet people's needs. In order to expand the communication capacity, the communication mode has developed from medium wave and short wave to microwave and millimeter wave, which in fact expands the communication capacity by increasing the carrier frequency of the communication. In this way, the present optical communication technology is optical fiber communication.
            Optical fiber communication is a communication mode which modulates the image, data and other signals to be transmitted to the optical carrier and uses optical fiber as the transmission medium.
            Compared with traditional telecommunications, optical fiber communication uses high frequency light wave as carrier and optical fiber as transmission medium. Because of the advantages of low loss, wide transmission bandwidth, large capacity, small size, light weight, anti-electromagnetic interference, and not easy to cross talk, optical fiber communication has been favored by the industry since its emergence and developed very rapidly. The transmission capacity of optical fiber communication system has increased nearly 10,000 times since 1980, and the transmission speed has increased about 100 times in the past 10 years.
            Development and Application of Optical Fiber
            In order to develop optical communication technology, people have considered and tried various transmission media, but their losses are very high. Until 1966, Chinese-American Dr. Gao Rong and Dr. Hockham published papers predicting that low-loss optical fibers could be used in communications, opening the door to optical communications.