Small form-factor pluggable transceiver
The small form-factor pluggable (SFP) or Mini-GBIC is a compact, hot-pluggable transceiver used for both telecommunication and data communications applications. It interfaces a network device mother board (for a switch, router, media converter or similar device) to a fiber optic or copper networking cable. It is a popular industry format supported by many network component vendors. SFP transceivers are designed to support SONET, Gigabit Ethernet, Fibre Channel, and other communications standards.
SFP transceivers are available with a variety of different transmitter and receiver types, allowing users to select the appropriate transceiver for each link to provide the required optical reach over the available optical fiber type (e.g. multi-mode fiber or single-mode fiber). Optical SFP modules are commonly available in several different categories:
850 nm 550m multi-mode fiber (SX)1310 nm 10 km single-mode fiber (LX)1490 nm 10 km single-mode fiber (BS-D)1550 nm 40 km (XD), 80 km (ZX), 120 km (EX or EZX)]1490 nm 1310 nm (BX), Single Fiber Bi-Directional Gigabit SFP Transceivers
SFP transceivers are also available with a copper cable interface, allowing a host device designed primarily for optical fiber communications to also communicate over unshielded twisted pair networking cable or transport SDI video signal over coaxial cable. There are also CWDM and single-fiber "bi-directional" (1310/1490 nm Upstream/Downstream) SFPs.
SFP transceivers are commercially available with capability for data rates up to 4.25 Gbit/s. An enhanced standard called SFP+ supports data rates up to 10.0 Gbit/s.
The SFP transceiver is specified by a multi-source agreement (MSA) between competing manufacturers. The SFP was designed after the GBIC interface, and allows greater port density (number of transceivers per cm along the edge of a mother board) than the GBIC, which is why SFP is also known as mini-GBIC. The related Small Form Factor transceiver is similar in size to the SFP, but is soldered to the host board as a pin through-hole device, rather than plugged into an edge-card socket.
However, as a practical matter, some networking equipment manufacturers engage in vendor lock-in practices whereby they deliberately break compatibility with "generic" SFPs by adding a check in the device's firmware that will only enable the vendor's own modules.