The FC connector is a fiber optic connector with a threaded body which was designed for use in high-vibration environments. It is widely used with both single-mode and multi-mode fiber.
The fiber’s ending point is implanted in a 2.5 mm ferrule (metal cap or band placed on a wooden pole to avoid splitting) made of Zirconium Oxide ceramic or stainless steel. The tip is then furnished to create a rounded surface, called "physical contact". This surface profile means that when the fibers are connected they come in contact only at their cores, permitting conduction with little loss. The fibers are spring-loaded to manage the power as the plug is fastened into the holder. A key stops the fiber from rotating while the connectors are being connected.
FC connectors' floating ferrule offers good mechanical isolation. FC connectors need to be connected with utmost care than push-pull type connectors due to the requirement of aligning the key, and due to the risk of scratching the fiber surface while inserting the ferrule into the jack. FC connectors have been replaced in many applications by SC and LC connectors.
The FC connector has been standardized in a FOCIS 4 (Fiber Optic Connector Intermateability Standards) in EIA/TIA-604-04.