FC stands for Fixed Connection. It is fixed by way of a threaded barrel housing. FC connectors are typical in test environments and for singlemode applications. FC connectors were designed for use in high-vibration environments, offer extremely precise positioning of the fiber optic cable with respect to the transmitter’s optical source emitter and the receiver’s optical detector. Once installed the position is maintained with absolute accuracy. They feature a position locatable notch and a threaded receptacle. FC connectors are generally constructed with a metal housing and are nickel-plated. They have ceramic ferrules and are rated for 500 mating cycles. The insertion loss for matched FC connectors is 0.25 dB. FC is the fiber optic connector standard for Nippon Telephone & Telegraph (NTT) installations, developed with Nippon Electric Co. (NEC). FC are being replaced by SC and LC connectors.
The 2.14 mm FC APC keyway format is typically called “wide key”, “NTT” or “type N”.The narrower 2 mm keyway format is called “Reduced” or “type R”. Some manufacturers mark type R keys with a single scribe mark on the key, and type N keys with a double scribe mark.