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Small form-factor pluggable(SFP) transceiver--From wikipedia

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Small form-factor pluggable transceiver

From Wikipedia, the free encyclopedia

Front view of SFP module (LC connector).

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.^[1])

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SFP types

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 four different categories: 850 nm (SX), 1310 nm (LX), 1550 nm (ZX), 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-optic (1310/1490 nm upstream/downstream) SFPs.

SFP transceivers are commercially available with capability for datarates up to 4.25 Gbit/s. A variant standard, XFP, is capable of 10 Gbit/s.

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 (SFF) 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.

Digital Optical Monitoring

Modern optical SFP transceivers support digital optical monitoring (DOM) functions according to the industry-standard SFF-8472 Multi Source Agreement (MSA). This feature gives the end user the ability to monitor real-time parameters of the SFP, such as optical output power, optical input power, temperature, laser bias current, and transceiver supply voltage.

Pinout

Side view of SFP module (length is 6 cm).

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

Pin	Function	Pin	Function
20	VeeT	1	VeeT
19	TD-	2	TxFault
18	TD+	3	TxDisable
17	VeeT	4	MOD-DEF(2)
16	VccT	5	MOD-DEF(1)
15	VccR	6	MOD-DEF(0)
14	VeeR	7	RateSelect
13	RD+	8	LOS
12	RD-	9	VeeR
11	VeeR	10	VeeR

MOD-DEF 0,1,2 are the mode definition pins.

MOD-DEF 0 is grounded by the module to indicate that the module is present
MOD-DEF 1 is a clock SCL line for the I²C identification EEPROM
MOD-DEF 2 is a data SDA line for the I²C identification EEPROM

EEPROM information

The SFP MSA defines a 256-byte memory map in EEPROM describing the transceiver's capabilities, standard interfaces, manufacturer, and other information, which is accessible over I²C interface at the 8-bit address 10100000X (A0h).