The small form-factor pluggable (SFP) is a compact, hot-pluggable network interface module used for both telecommunication and data communications applications. An SFP interface on networking hardware is a modular slot for a media-specific transceiver in order to connect a fiber-optic cable or sometimes a copper cable. The advantage of using SFPs compared to fixed interfaces (e.g. modular connectors in Ethernet switches) is that individual ports can be equipped with any suitable type of transceiver as needed.
The form factor and electrical interface are specified by a multi-source agreement (MSA) under the auspices of the Small Form Factor Committee. The SFP replaced the larger gigabit interface converter (GBIC) in most applications, and has been referred to as a Mini-GBIC by some vendors.
SFP transceivers exist supporting synchronous optical networking (SONET), Gigabit Ethernet, Fibre Channel, PON, and other communications standards. At introduction, typical speeds were 1 Gbit/s for Ethernet SFPs and up to 4 Gbit/s for Fibre Channel SFP modules. In 2006, SFP+ specification brought speeds up to 10 Gbit/s and the SFP28 iteration is designed for speeds of 25 Gbit/s.
A slightly larger sibling is the four-lane Quad Small Form-factor Pluggable (QSFP). The additional lanes allow for speeds 4 times their corresponding SFP. In 2014, the QSFP28 variant was published allowing speeds up to 100 Gbit/s. In 2019, the closely related QSFP56 was standardized doubling the top speeds to 200 Gbit/s with products already selling from major vendors. There are inexpensive adapters allowing SFP transceivers to be placed in a QSFP port.
Both a SFP-DD, which allows for 100 Gbit/s over two lanes, as well as a QSFP-DD specifications, which allows for 400 Gbit/s over eight lanes, have been published. These use a form factor which is backward compatible to their respective predecessors. An alternative competing solution, the OSFP (Octal Small Format Pluggable) transceiver is also intended for 400 Gbit/s fiber optic links between network equipment via 8 × 50 Gbit/s electrical data lanes. It is slightly larger version than the QSFP formfactor which is capable of handling larger power outputs. The OSFP standard was initially announced on November 15, 2016. Its proponents say a low cost adapter will allow for QSFP module compatibility.
SFP transceivers are available with a variety of transmitter and receiver specifications, allowing users to select the appropriate transceiver for each link to provide the required optical or electrical reach over the available media type (e.g. twisted pair copper cables, multi-mode or single-mode fiber cables). Transceivers are also designated by their transmission speed. SFP modules are commonly available in several different categories.