SFP (Small Form Factor Pluggable)

The small form-factor pluggable (SFP) is a compact, hot-pluggable optical module transceiver used for both telecommunication and data communications applications. The form factor and electrical interface are specified by a multi-source agreement (MSA) under the auspices of the Small Form Factor Committee. It is a popular industry format jointly developed and supported by many network component vendors.

An SFP interface on networking hardware is a modular (plug-and-play) slot for a variable, media-specific transceiver in order to connect a fiber optic cable or sometimes a copper cable. SFP transceivers exist supporting SONET, Gigabit Ethernet, Fibre Channel, and other communications standards. At introduction, speeds were limited to 1 Gbit/s.

The enhanced small form-factor pluggable transceiver (SFP+) brought speeds up to 10 Gbit/s and the SFP28 iteration is designed for speeds of 25 Gbit/s. The SFP replaced the larger GBIC in most applications, and has been referred to as a Mini-GBIC by some vendors.

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. The latest published variant is QSFP28 variant allowing speeds up to 100 Gbit/s. 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 formfactor which is backwardly compatible to their respective predecessors.

An alternative competing solution, the OSFP (Octal Small Format Pluggable) transceiver is also intended for 400Gbps fiber optic links between network equipment via 8 x 50 Gbps 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.

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