Small Form-factor Pluggable


Small Form-factor Pluggable is a compact, hot-pluggable network interface module format used for both telecommunication and data communications applications. An SFP interface on networking hardware is a modular slot for a media-specific transceiver, such as for a fiber-optic cable or a copper cable. The advantage of using SFPs compared to fixed interfaces is that individual ports can be equipped with different types of transceivers as required, with the majority of devices including optical line terminals, network cards, switches and routers.
The form factor and electrical interface are specified by a multi-source agreement under the auspices of the Small Form Factor Committee. The SFP replaced the larger gigabit interface converter in most applications, and has been referred to as a Mini-GBIC by some vendors.
SFP transceivers exist supporting synchronous optical networking, Gigabit Ethernet, Fibre Channel, PON, and other communications standards. At introduction, typical speeds were for Ethernet SFPs and up to for Fibre Channel SFP modules. In 2006, SFP+ specification brought speeds up to and the later SFP28 iteration, introduced in 2014, is designed for speeds of.
A slightly larger sibling is the four-lane Quad Small Form-factor Pluggable. The additional lanes allow for speeds 4 times their corresponding SFP. In 2014, the QSFP28 variant was published allowing speeds up to. In 2019, the closely related QSFP56 was standardized doubling the top speeds to with products already selling from major vendors. There are inexpensive adapters allowing SFP transceivers to be placed in a QSFP port.
Both a SFP-DD, which allows for over two lanes, as well as a QSFP-DD specifications, which allows for over eight lanes, have been published. These use a form factor which is directly backward compatible to their respective predecessors.
An even larger sibling, the Octal Small Format Pluggable, had products released in 2022 capable of links between network equipment. It is a slightly larger version than the QSFP form factor allowing for larger power outputs. The OSFP standard was initially announced in 2016 with the 4.0 version released in 2021 allowing for via 8× electrical data lanes. Its proponents say a low-cost adapter will allow for backwards compatibility with QSFP modules.

SFP types

SFP transceivers are available with a variety of transmitter and receiver specifications, allowing users to select the appropriate transceiver for each link to provide the required optical or electrical reach over the available media type. Transceivers are also designated by their transmission speed. SFP modules are commonly available in several different categories.
Note that the QSFP/QSFP+/QSFP28/QSFP56 are designed to be electrically backward compatible with SFP/SFP+/SFP28 or SFP56 respectively. Using a simple adapter or a special direct attached cable it is possible to connect those interfaces together using just one lane instead of four provided by the QSFP/QSFP+/QSFP28/QSFP56 form factor. The same applies to the QSFP-DD form factor with 8 lanes which can work downgraded to 4/2/1 lanes.

SFP

  • Multi-mode fiber, LC connector, with ' or ' color coding
  • * SX850 nm, for a maximum of 550 m
  • Multi-mode fiber, LC connector, with ' color coding
  • * FX 1300 nm, for a distance up to 5 km.
  • * LFX 1310 nm, for a distance up to 5 km.
  • Single-mode fiber, LC connector, with ' color coding
  • * LX1310 nm, for distances up to 10 km
  • * EX1310 nm, for distances up to 40 km
  • Single-mode fiber, LC connector, with ' color coding
  • * ZX1550 nm, for distances up to 80 km,
  • * EZX1550 nm, for distances up to 160 km
  • Single-mode fiber, LC connector, Bi-Directional, with ' and color coding
  • * BX 1550 nm/1310 nm, Single Fiber Bi-Directional 100 Mbit SFP Transceivers, paired as BX-U and BX-D for uplink and downlink respectively, also for distances up to 10 km. Variations of bidirectional SFPs are also manufactured which higher transmit power versions with link length capabilities up to 40 km.
  • Copper twisted-pair cabling, 8P8C connector
  • * 100BASE-TX for distances up to 100m.

    SFP

  • 1 to 1. multi-mode fiber, LC connector, with black or beige extraction lever
  • * SX850 nm, for a maximum of 550 m at 1.. Other multi-mode SFP applications support even higher rates at shorter distances.
  • 1 to 1. multi-mode fiber, LC connector, extraction lever colors not standardized
  • * SX+/MX/LSX/LX 1310 nm, for a distance up to 2 km. Not compatible with SX or 100BASE-FX. Based on LX but engineered to work with a multi-mode fiber using a standard multi-mode patch cable rather than a mode-conditioning cable commonly used to adapt LX to multi-mode.
  • 1 to 2. single-mode fiber, LC connector, with blue extraction lever
  • * LX1310 nm, for distances up to 10 km
  • * EX1310 nm, for distances up to 40 km
  • * ZX1550 nm, for distances up to 80 km, with green extraction lever
  • * EZX1550 nm, for distances up to 160 km
  • * BX 1490 nm/1310 nm, Single Fiber Bi-Directional Gigabit SFP Transceivers, paired as BX-U and BX-D for uplink and downlink respectively, also for distances up to 10 km. Variations of bidirectional SFPs are also manufactured which use 1550 nm in one direction, and higher transmit power versions with link length capabilities up to 80 km.
  • * 1550 nm 40 km, 80 km, 120 km
  • * SFSWsingle-fiber single-wavelength transceivers, for bi-directional traffic on a single fiber. Coupled with CWDM, these double the traffic density of fiber links.
  • * Coarse wavelength-division multiplexing and dense wavelength-division multiplexing transceivers at various wavelengths achieve various maximum distances. CWDM and DWDM transceivers usually support link distances of 40, 80 and 120 km.
  • for copper twisted-pair cabling, 8P8C connector
  • * 1000BASE-Tthese modules incorporate significant interface circuitry for Physical Coding Sublayer recoding and can be used only for gigabit Ethernet because of the specific line code. They are not compatible with Fibre Channel or SONET. Unlike most non-SFP, copper 1000BASE-T ports integrated into most routers and switches, 1000BASE-T SFPs usually cannot operate at 100BASE-TX speeds.
  • copper and opticalsome vendors have shipped limited SFPs for fiber-to-the-home applications and drop-in replacement of legacy 100BASE-FX circuits. These are relatively uncommon and can be easily confused with SFPs.
  • Although it is not mentioned in any official specification document the maximum data rate of the original SFP standard is. This was eventually used by both 4GFC Fibre Channel and the DDR Infiniband especially in its four-lane QSFP form.
  • In recent years, SFP transceivers have been created that will allow 2. and Ethernet speeds with SFPs with 2.5GBASE-T and 5GBASE-T.

    SFP+

The SFP+ is an enhanced version of the SFP that supports data rates up to 16 Gbit/s. The SFP+ specification was first published on May 9, 2006, and version 4.1 was published on July 6, 2009. SFP+ supports Fibre Channel, 10 Gigabit Ethernet and Optical Transport Network standard OTU2. It is a popular industry format supported by many network component vendors. Although the SFP+ standard does not include mention of Fibre Channel, it can be used at this speed. Besides the data rate, the major difference between 8 and Fibre Channel is the encoding method. The 64b/66b encoding used for is a more efficient encoding mechanism than 8b/10b used for, and allows for the data rate to double without doubling the line rate. 16GFC doesn't really use signaling anywhere. It uses a 14. line rate to achieve twice the throughput of 8GFC.
SFP+ also introduces direct attach for connecting two SFP+ ports without dedicated transceivers. Direct attach cables exist in passive, active, and active optical variants.
SFP+ modules are exactly the same dimensions as regular SFPs, allowing the equipment manufacturer to re-use existing physical designs for 24 and 48-port switches and modular line cards. In comparison to earlier XENPAK or XFP modules, SFP+ modules leave more circuitry to be implemented on the host board instead of inside the module. Through the use of an active electronic adapter, SFP+ modules may be used in older equipment with XENPAK ports and X2 ports.
SFP+ modules can be described as limiting or linear types; this describes the functionality of the inbuilt electronics. Limiting SFP+ modules include a signal amplifier to re-shape the received signal whereas linear ones do not. Linear modules are mainly used with the low bandwidth standards such as 10GBASE-LRM; otherwise, limiting modules are preferred.

SFP28

SFP28 is a interface which evolved from the 100 Gigabit Ethernet interface which is typically implemented with 4 by data lanes. Identical in mechanical dimensions to SFP and SFP+, SFP28 implements one lane accommodating of data with encoding overhead.
SFP28 modules exist supporting single- or multi-mode fiber connections, active optical cable and direct attach copper.

cSFP

The compact small form-factor pluggable is a version of SFP with the same mechanical form factor allowing two independent bidirectional channels per port. It is used primarily to increase port density and decrease fiber usage per port.

SFP-DD

The small form-factor pluggable double density multi-source agreement is a standard published in 2019 for doubling port density. According to the SFD-DD MSA website: "Network equipment based on the SFP-DD will support legacy SFP modules and cables, and new double density products."
SFP-DD uses two lanes to transmit.
Currently, the following speeds are defined:
  • SFP112: using PAM4 on a single pair
  • SFP-DD: using PAM4 and using NRZ
  • SFP-DD112: using PAM4
  • QSFP112:
  • QSFP-DD: /
  • QSFP-DD800 :
  • QSFP-DD1600