ST-FC fiber coupler, also known as ST-FC fiber adapter and ST-FC fiber flange, is an important component used to connect two different types of fiber connectors, ST interface and FC interface. It can realize the conversion between different interfaces, make the optical path unblocked, and allow the light energy output by the transmitting optical fiber to be coupled to the receiving optical fiber to the maximum extent. Its ST interface is a keyed snap-on locking structure with a round buckle to ensure accurate alignment during connection; the FC interface adopts a metal sleeve for external reinforcement and a screw buckle for fastening. The coupler has the advantages of simple operation, stability and reliability, long life, easy maintenance and low price. It is widely used in optical fiber distribution frames (ODF), optical fiber communication equipment, instruments, telecommunication long-distance optical transmission networks, optical fiber access networks, data communication networks, local area networks (LANs), optical fiber CATV and other fields.