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 optical fiber communication and form a global transmission of bit transmission methods; for global communication networks, national public telecommunications networks (such as China's national one) 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.