More than 20 countries, including the United States, Japan, Britain and France, have announced that they will no longer build cable communication lines and are committed to the development of fiber-optic communications. China’s optical fiber communication has entered a practical stage. After entering the 21st century, due to the rapid development of Internet services and the growth of audio, video, data, and multimedia applications, there is a more pressing need for high-capacity (ultra-high-speed and ultra-long-haul) optical wave transmission systems and networks. Compared with the previous electrical communication, the main difference between optical fiber communication is that it has many advantages: transmission frequency bandwidth, large communication capacity, low transmission loss, long relay distance, thin wire diameter and light weight, and the raw material is quartz, which saves metal materials. Conducive to the rational use of resources; strong insulation and anti-electromagnetic interference; also has the advantages of strong anti-corrosion ability, strong anti-radiation ability, easy to enwind, no electric spark, small leakage and strong confidentiality.
The application fields of optical fiber communication are very wide, mainly used for local telephone trunk lines. The advantages of optical fiber communication can be fully utilized here, and the cable is gradually replaced, which is widely used. Also used for long-distance trunk communication in the past mainly relying on cable, microwave, satellite communication, and now gradually use fiber-optic communication and form a globally advantageous bit transmission method; for global communication networks, public telecommunications networks of various countries (such as China’s national first level trunk line, provincial secondary line and sub-sector branch line); it is also used for high-quality color TV transmission, industrial production site monitoring and dispatching, traffic monitoring and control command, town cable TV network, shared antenna (CATV) system, Used in fiber optic LANs and others such as in aircraft, in spacecraft, in ships, under mines, in the power sector, in military applications, and in corrosive and radiative applications.
The optical fiber transmission system mainly consists of an optical transmitter, an optical receiver, an optical cable transmission line, an optical repeater, and various passive optical components. To achieve communication, the baseband signal must also be processed by the electrical transceiver to the fiber transmission system to complete the communication process.
It is suitable to use in fiber optic analog communication systems, but also for fiber optic digital communication systems and data communication systems. In the optical fiber analog communication system, the electrical signal processing refers to the amplification and pre-modulation of the baseband signal, and the electrical signal inverse processing is the inverse process of the originating processing, that is, demodulation, amplification, and the like. In the optical fiber digital communication system, electrical signal processing refers to amplification, sampling, and quantization of the baseband signal, that is, pulse code modulation (PCM) and line code type encoding processing, and the electrical signal inverse processing is also the inverse process of the originating end. For data fiber communication, electrical signal processing mainly involves amplifying the signal. Unlike digital communication systems, it does not require pattern conversion.