The small form-factor pluggable (SFP) is a compact optical transceiver used in optical communications for both telecommunication and data communications applications. It interfaces a network device mother board (for a switch, router or similar device) to a fiber optic or unshielded twisted pair networking cable. It is a popular industry format supported by several fiber optic component vendors.
SFP transceivers are designed to support SONET, Gigabit Ethernet, Fibre Channel, and other communications standards. The standard is expanding to SFP+ which will be able to support data rates up to 10.0 Gbit/s (that will include the data rates for 8 gigabit Fibre Channel, and 10GbE. SFP+ module versions for optics as well as copper are being introduced. In comparison to Xenpak, X2 or XFP type of modules, SFP+ modules leave some of the circuitry to be implemented on the host board instead of inside the module.)
Reference:
http://en.wikipedia.org/wiki/SFP_transceiver
