The
small form-factor pluggable (
SFP) or
Mini-GBIC is a compact, hot-pluggable
transceiverA transceiver is a device comprising both a transmitter and a receiver which are combined and share common circuitry or a single housing. When no circuitry is common between transmit and receive functions, the device is a transmitter-receiver. The term originated in the early 1920s...
used for both
telecommunicationTelecommunication is the transmission of information over significant distances to communicate. In earlier times, telecommunications involved the use of visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded...
and data communications applications. It interfaces a network device mother board (for a
switchA network switch or switching hub is a computer networking device that connects network segments.The term commonly refers to a multi-port network bridge that processes and routes data at the data link layer of the OSI model...
, router,
media converterFiber media converters are simple networking devices that make it possible to connect two dissimilar media types such as twisted pair with fiber optic cabling. They were introduced to the industry nearly two decades ago, and are important in interconnecting fiber optic cabling-based systems with...
or similar device) to a fiber optic or copper networking cable. It is a popular industry format jointly developed and supported by many network component vendors. SFP transceivers are designed to support
SONETSonet may refer to:* Sonet Records, European record label* Synchronous optical networking * Saab Sonett...
,
Gigabit EthernetGigabit Ethernet is a term describing various technologies for transmitting Ethernet frames at a rate of a gigabit per second , as defined by the IEEE 802.3-2008 standard. It came into use beginning in 1999, gradually supplanting Fast Ethernet in wired local networks where it performed...
,
Fibre ChannelFibre Channel, or FC, is a gigabit-speed network technology primarily used for storage networking. Fibre Channel is standardized in the T11 Technical Committee of the InterNational Committee for Information Technology Standards , an American National Standards Institute –accredited standards...
, and other communications standards.
Types
SFP transceivers are available with a variety of 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:
- for multi-mode fiber, with black or beige extraction lever
- SX - 850 nm, for a maximum of 550 m at 1.25 Gb/s (Gigabit Ethernet) or 150m at 4.25 Gb/s (Fibre Channel)
- for single-mode fiber, with blue extraction lever
- LX - 1310 nm, for distances up to 10 km
- BX - 1490 nm/1310 nm, Single Fiber Bi-Directional Gigabit SFP Transceivers, paired as BS-U and BS-D for Uplink and Downlink respectively, also for distances up to 10 km
- 1550 nm 40 km (XD), 80 km (ZX), 120 km (EX or EZX)
- CWDM and DWDM transceivers at various wavelengths achieving various maximum distances
- for copper twisted pair cabling
- 1000base-T - these modules incorporate significant interface circuitry and can only be used for Gigabit Ethernet
Gigabit Ethernet is a term describing various technologies for transmitting Ethernet frames at a rate of a gigabit per second , as defined by the IEEE 802.3-2008 standard. It came into use beginning in 1999, gradually supplanting Fast Ethernet in wired local networks where it performed...
, as that is the interface they implement. They are not compatible with (or rather: do not have equivalents for) Fibre channel or SONET.
SFP transceivers are commercially available with capability for data rates up to 4.25 Gbit/s. An enhanced standard called SFP+ supports data rates up to 10.0 Gbit/s.
SFP+
The
enhanced small form-factor pluggable (
SFP+) is an enhanced version of the SFP. It supports data rates up to 10
Gbit/sIn telecommunications, bit rate or data transfer rate is the average number of bits, characters, or blocks per unit time passing between equipment in a data transmission system. This is typically measured in multiples of the unit bit per second or byte per second.- Avoiding confusion :To be as...
. The SFP+ was first published on May 9, 2006, and version 4.1 published on July 6, 2009.
SFP+ supports 8 Gbit/s
Fibre ChannelFibre Channel, or FC, is a gigabit-speed network technology primarily used for storage networking. Fibre Channel is standardized in the T11 Technical Committee of the InterNational Committee for Information Technology Standards , an American National Standards Institute –accredited standards...
,
10 Gigabit EthernetThe 10 gigabit Ethernet computer networking standard was first published in 2002. It defines a version of Ethernet with a nominal data rate of 10 Gbit/s , ten times faster than gigabit Ethernet.10 gigabit Ethernet defines only full duplex point to point links which are generally connected by...
and
Optical Transport NetworkITU-T defines an Optical Transport Network as a set of Optical Network Elements connected by optical fibre links, able to provide functionality of transport, multiplexing, switching, management, supervision and survivability of optical channels carrying client signals...
standard OTU2. It is a popular industry format supported by many network component vendors.
In comparison to earlier
XENPAKXENPAK is a Multisource Agreement , instigated by Agilent Technologies and Agere Systems, that defines a fiber-optic or wired transceiver module which conforms to the 10 Gigabit Ethernet standard of the Institute of Electrical and Electronics Engineers 802.3 working group...
or XFP modules, SFP+ modules leave more circuitry to be implemented on the host board instead of inside the module.
Consideration has to be given to whether the module is linear or limiting. Linear SFP+ modules are appropriate for 10GBASE-LRM otherwise limiting modules are preferred.
Applications
SFP sockets are found in Ethernet switches and network interface cards. Storage interface cards, also called HBA's and Fibre Channel storage switches is another use of these type of modules, supporting different speeds like 2Gb, 4Gb and 10Gb. Because of their ability to provide a connection to different types of optical fiber, SFP provides such equipment with enhanced flexibility.
Standardization
The SFP transceiver is specified by a multi-source agreement (MSA) between competing manufacturers. The SFP was designed after the
GBICA gigabit interface converter is a standard for transceivers, commonly used with Gigabit Ethernet and fibre channel in the 1990s...
interface, and allows greater
port density (number of transceivers per cm 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.
However, as a practical matter, some networking equipment manufacturers engage in
vendor lock-inIn economics, vendor lock-in, also known as proprietary lock-in or customer lock-in, makes a customer dependent on a vendor for products and services, unable to use another vendor without substantial switching costs...
practices whereby they deliberately break compatibility with "generic" SFPs by adding a check in the device's
firmwareIn electronic systems and computing, firmware is a term often used to denote the fixed, usually rather small, programs and/or data structures that internally control various electronic devices...
that will only enable the vendor's own modules.
Signals
The SFP transceiver contains a
PCBA printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring board or etched wiring...
that mates with the SFP electrical connector in the host system.
SFP pin-out
| 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
I²C is a multi-master serial single-ended computer bus invented by Philips that is used to attach low-speed peripherals to a motherboard, embedded system, cellphone, or other electronic device. Since the mid 1990s, several competitors I²C ("i-squared cee" or "i-two cee"; Inter-Integrated Circuit;...
identification EEPROMEEPROM stands for Electrically Erasable Programmable Read-Only Memory and is a type of non-volatile memory used in computers and other electronic devices to store small amounts of data that must be saved when power is removed, e.g., calibration...
- MOD-DEF 2 is a data SDA line for the I²C identification EEPROM
Mechanical dimensions
SFP dimensions are:
- Height: 8.5 mm (0.33 inches)
- Width: 13.4 mm (0.53 inches)
- Depth: 56.5 mm (2.22 inches)
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 1010000X (A0h).
Digital diagnostics monitoring
Modern optical SFP transceivers support digital diagnostics monitoring (DDM) functions according to the industry-standard [ftp://ftp.seagate.com/sff/SFF-8472.PDF SFF-8472]. This feature is also known as digital optical monitoring (DOM). 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.
The diagnostic monitoring controller is available as I²C device at address 1010001X (A2h).
See also
- Optical interconnect
Optical interconnect is a way of communication by optical cables. Compared to traditional cables, optical wires are capable of a much higher bandwidth, from 10 Gb/s up to 100 Gb/s....
- Interconnect bottleneck
The interconnect bottleneck, the point at which integrated circuits reach their capacity, is expected sometime around 2010.Improved performance of computer systems has been achieved, in large part, by downscaling the IC minimum feature size. This allows the basic IC building block, the transistor,...
- Optical fiber cable
An optical fiber cable is a cable containing one or more optical fibers. The optical fiber elements are typically individually coated with plastic layers and contained in a protective tube suitable for the environment where the cable will be deployed....
- Optical communication
Optical communication is any form of telecommunication that uses light as the transmission medium.An optical communication system consists of a transmitter, which encodes a message into an optical signal, a channel, which carries the signal to its destination, and a receiver, which reproduces the...
- Parallel optical interface
A parallel optical interface is a form of fiber optic technology aimed primarily at communications and networking over relatively short distances , and at high bandwidths....
- Serial digital interface
Serial digital interface is a family of video interfaces standardized by SMPTE. For example, ITU-R BT.656 and SMPTE 259M define digital video interfaces used for broadcast-grade video...