The application field of optical fiber communication is very wide, mainly used for local telephone trunks. The advantages of optical fiber communication can be fully exerted here, gradually replacing cables and being widely used. It is also used for long-distance trunk communication. In the past, it mainly relied on cable, microwave, and satellite communication. Now it is gradually using optical fiber communication and has formed a bit transmission method that dominates the world. It is also used for high-quality color TV transmission, industrial production site monitoring and dispatching, traffic monitoring and control command, urban cable television network, and shared antenna (CATV) system, with Used in fiber optic local area networks and other applications such as in aircraft, spaceships, ships, underground mines, power sector, military, and corrosion and radiation.