Five types of pigtails are commonly used in SFP systems for transmission

FC-SC type, i.e. circular to square pigtail. FC is connected to the ODF box, and SC is connected to the optical port of the device. This type of fiber optic connector was widely used in SBS and Optix equipment in the early days.

FC-FC type, commonly referred to as circular to circular tail fiber. It is typically used as a jumper fiber between ODF racks.

SC-SC type, commonly referred to as square to square tail fibers, is commonly used for optical plate connections between devices.

SC-lC type, commonly known as small square end tail fiber, belongs to the buckle type connector. At present, Huawei OSN series equipment, ZTE S series equipment, including early Lucent's wavelength division equipment, all use this fiber optic connector.

The LC-LC type is generally used for internal fiber optic connections between wavelength division devices and is rarely used.