What is SFP?

The small form-factor pluggable (SFP) 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. 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.

SFP type:

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 MMF (SX), 1310 nm 10km SMF (LX), 1550 nm [40 km (XD), 80 km (ZX), 120 km (EX or EZX)], and DWDM. 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. 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. 10 Gbit/s transceivers are available in several form factors, such as XFP, and the newest variant "SFP+", in form factor virtually identical to the SFP type.

SFP Standardization

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 inch 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. 

Pinout

The SFP transceiver contains a PCB that mates with the SFP electrical connector

EEPROM information

The SFP MSA defines a 256-byte memory map in EEPROM describing the transceiver¡¯s capabilities, standard interface, manufacturer, and other information, which is accessible over I©÷C interface at the 8-bit address 10100000x(A0h.

Digital Diagnostics monitoring

Modern optical SFP transceivers support digital diagnostics monitoring(DDM functions according to the industry-standard SFF-8472. This feature is also known as digital optical monitoring(DOM. This feature gives the end user the ability to monitor real-time parameter of the SFP, such as optic output power, optic input power, temperature, laser bias current and transceiver supply voltage.