How to tell if an optical module interface is LC or FC

LC connectors are small form-factor with a latch mechanism, while FC connectors are round with a threaded screw coupling.Visual and Mechanical DifferencesLC Connector: LC connectors are small, compact, and use a push-pull latch mechanism similar to an RJ-style clip. They are designed for high-density applications such as SFP/SFP+ modules in modern data centers. The ferrule diameter is typically 1.25 mm, and the connector body is usually plastic with a rectangular shape . LC connectors are often found in duplex pairs, side by side, for single-mode or multimode fiber.FC Connector: FC connectors have a round metal body with a threaded screw coupling. They are designed for high-precision or high-vibration environments, such as telecom systems or measurement equipment. The ferrule diameter is 2.5 mm, and the connector is screwed into the port to secure it, which makes it more rugged but slower to install compared to LC .Practical Identification TipsCheck the Shape: LC connectors are rectangular and small, while FC connectors are round and metallic.Check the Locking Mechanism: LC uses a push-pull latch, FC uses a screw thread.Port Density: LC ports are often closely spaced for high-density modules; FC ports are usually larger and spaced further apart.Module Type: Modern SFP/SFP+ optical modules almost always use LC connectors, whereas FC connectors are more common in older or specialized telecom equipment . By observing the connector shape, ferrule size, and locking mechanism, you can reliably determine whether an optical module interface is LC or FC.