small form-factor pluggable transceiver
DESCRIPTION
Small form-factor pluggable transceiverTRANSCRIPT
Small form-factor pluggable transceiver
Front view of SFP module (LC connector). The blue extractionlever indicates operation with single-mode fiber.
The small form-factor pluggable (SFP) is acompact, hot-pluggable transceiver used for bothtelecommunication and data communications appli-cations. The form factor and electrical interface arespecified by a multi-source agreement (MSA). It in-terfaces a network device motherboard (for a switch,router, media converter or similar device) to a fiber opticor copper networking cable. It is a popular industryformat jointly developed and supported by many networkcomponent vendors.[1] SFP transceivers are designed tosupport SONET, gigabit Ethernet, Fibre Channel, andother communications standards. Due to its smaller size,SFP obsolesces the formerly ubiquitous gigabit interfaceconverter (GBIC); the SFP is sometimes referred to as aMini-GBIC although no device with this name has everbeen defined in the MSAs.
1 Types
SFP transceivers are available with a variety of transmit-ter and receiver types, allowing users to select the appro-priate transceiver for each link to provide the required op-tical reach over the available optical fiber type (e.g. multi-mode fiber or single-mode fiber). Optical SFP modulesare commonly available in several different categories:
• for multi-mode fiber, with black or beige[1] extrac-tion lever
• SX - 850 nm, for a maximum of 550 m at1.25 Gbit/s (gigabit Ethernet) or 150m at 4.25Gbit/s (Fibre Channel)[2]
• for single-mode fiber, with blue[1] extraction lever
• LX - 1310 nm, for distances up to 10 km• EX - 1310 nm, for distances up to 40 km [3]
• ZX - 1550 nm, for distances up to 80 km,with green extraction lever (see GLC-ZX-SM1) [3][4]
• EZX - 1550 nm, for distances up to 160 km[3]
• BX - 1490 nm/1310 nm, Single Fiber Bi-Directional Gigabit SFP Transceivers, pairedas BS-U and BS-D for Uplink and Down-link respectively, also for distances up to 10km.[5][6] Variations of bidirectional SFPs arealso manufactured which use 1550 nm in onedirection.
• 1550 nm 40 km (XD), 80 km (ZX), 120 km(EX or EZX)
• SFSW – Single Fiber Single Wavelengthtransceivers, for bi-directional traffic on a sin-gle fiber. Coupled with CWDM, these doublethe traffic density of fiber links.[7][8]
• CWDM and DWDM transceivers at variouswavelengths achieving various maximum dis-tances
• for copper twisted pair cabling
• 1000BASE-T - thesemodules incorporate sig-nificant interface circuitry[9] and can only beused for gigabit Ethernet, as that is the inter-face they implement. They are not compatiblewith (or rather: do not have equivalents for)Fiber channel or SONET.
2 SFP+
The enhanced small form-factor pluggable (SFP+) isan enhanced version of the SFP that supports data ratesup to 16 Gbit/s. The SFP+ specification was first pub-lished on May 9, 2006, and version 4.1 published on July6, 2009.[10] SFP+ supports 8Gbit/s Fibre Channel, 10Gi-gabit Ethernet and Optical Transport Network standardOTU2. It is a popular industry format supported by manynetwork component vendors.Although the SFP+ standard does not include mention of16G Fibre Channel it can be used at this speed.[11] Be-sides the data rate, the big difference between 8G Fibre
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2 9 DIGITAL DIAGNOSTICS MONITORING
Channel and 16G Fibre Channel is the encoding method.64b/66b encoding used for 16G is a more efficient en-coding mechanism than 8b/10b used for 8G, and allowsfor the data rate to double without doubling the line rate.The result is the 14.025 Gbit/s line rate for 16G FibreChannel.In comparison to earlier XENPAK or XFP modules,SFP+ modules leave more circuitry to be implementedon the host board instead of inside the module.[12]
Consideration has to be given to whether the module islinear or limiting. Linear SFP+ modules are most appro-priate for 10GBASE-LRM; otherwise, limiting modulesare preferred.[13]
SFP+ also introduces Direct Attach for connecting twoSFP+ ports without dedicated transceivers.
3 Compatibility
It is possible to design an SFP+ slot that can accept a stan-dard SFP module.[14][15]
4 Applications
Ethernet switch with empty SFP slots (lower left)
SFP sockets are found in Ethernet switches, routers,firewalls and network interface cards. Storage inter-face cards, also called HBAs or Fibre Channel storageswitches, also make use of these modules, supporting dif-ferent speeds such as 2Gb, 4Gb, and 8Gb. Because oftheir low cost, low profile, and ability to provide a con-nection to different types of optical fiber, SFP providessuch equipment with enhanced flexibility.
5 Standardization
The SFP transceiver is not standardized by any officialstandards body, but rather is specified by a multi-sourceagreement (MSA) among competing manufacturers. TheSFP was designed after the GBIC interface, and allowsgreater port density (number of transceivers per cm alongthe edge of a mother board) than the GBIC, which is whySFP is also known asmini-GBIC. The related Small FormFactor transceiver is similar in size to the SFP, but is sol-dered to the host board as a through-hole device, ratherthan plugged into an edge-card socket.
However, as a practical matter, some networking equip-ment manufacturers engage in vendor lock-in prac-tices whereby they deliberately break compatibility with“generic” SFPs by adding a check in the device’s firmwarethat will enable only the vendor’s own modules.[16]
6 Signals
The SFP transceiver contains a PCB that mates with theSFP electrical connector in the host system.
7 Mechanical dimensions
Side view of SFP module (length is 6 cm).
The physical dimensions of the SFP transceiver areslightly smaller than the later XFP transceiver.
8 EEPROM information
The SFP MSA defines a 256-byte memory map into anEEPROM describing the transceiver’s capabilities, stan-dard interfaces, manufacturer, and other information,which is accessible over an I²C interface at the 8-bit ad-dress 1010000X (A0h).
9 Digital diagnostics monitoring
Modern optical SFP transceivers support digital diag-nostics monitoring (DDM) functions according to theindustry-standard SFF-8472. This feature is also knownas digital optical monitoring (DOM). Modules with thiscapability give the end user the ability to monitor pa-rameters of the SFP, such as optical output power, op-tical input power, temperature, laser bias current, andtransceiver supply voltage, in real time.The diagnostic monitoring controller is available as an I²Cdevice at address 1010001X (A2h).
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10 See also• Interconnect bottleneck
• Optical communication
• Optical fiber cable
• Optical interconnect
• Parallel optical interface
• Quad Small Form Factor Pluggable
• Serial digital interface
11 References[1] SFF Committee (2001-05-01), INF-8074i Specification
for SFP (Small Formfactor Pluggable) Transceiver (PDF),retrieved 2012-08-12
[2] Agilestar/Finisar FTLF8524P2BNV specification (PDF)
[3] 1000BASE Gigabit Ethernet SFP Transceiver, Optcore, re-trieved March 26, 2013
[4] https://www.google.com/search?q=GLC-ZX-SM1&rls=com.microsoft:en-za:IE-SearchBox&oe=&um=1&ie=UTF-8&hl=en&tbm=isch&source=og&sa=N&tab=wi&ei=-iADU9axCYfY7AaqkYCwDA
[5] Single Fiber Bidirectional SFP Transceiver (PDF), MRV,retrieved June 16, 2010
[6] Gigabit Bidirectional SFPs, Yamasaki Optical Technology,retrieved June 16, 2010
[7] “Single-fiber single-wavelength gigabit transceivers”.Lightwave. Retrieved September 5, 2002.
[8] “The principle of Single Wavelength BiDi Transceiver”.Gigalight. Retrieved 2011.
[9] VSC8211 media converter/physical layer specification
[10] “SFF-8431 Specifications for Enhanced Small Form Fac-tor Pluggable Module SFP+ Revision 4.1” (PDF). July 6,2009. Retrieved May 9, 2011.
[11] Tektronix (November 2013). “Characterizing an SFP+Transceiver at the 16G Fibre Channel Rate”.
[12] “10-Gigabit Ethernet camp eyes SFP+". LightWave.April 2006.
[13] Ryan Latchman and Bharat Tailor (January 22, 2008).“The road to SFP+: Examining module and system ar-chitectures”. Lightwave. Retrieved July 26, 2011.
[14] SFF-8432, Abstract, Page 1: “Themechanical dimension-ing allows backwards compatibility between IPF mod-ules plugged into most SFP cages which have been im-plemented to SFF-8074i. It is anticipated that when theapplication requires it, manufacturers will be able to sup-ply cages that accept SFP style modules. In both cases theEMI leakage is expected to be similar to that when SFPmodules and cages are mated.”
[15] SFF-8431, Chapter 2 Low Speed Electrical and PowerSpecifications, 2.1 Introduction, Page 4: “The SFP+ lowspeed electrical interface has several enhancements overthe classic SFP interface (INF-8074i), but the SFP+ hostcan be designed to also support most legacy SFP mod-ules.”
[16] John Gilmore. “Gigabit Ethernet fiber SFP slots and lock-in”. Retrieved December 21, 2010.
[17] INF-8074i Specification for SFP (Small Formfactor Plug-gable) Transceiver (PDF), SFF Committee, May 12,2001, p. 6
[18] “INF-8077i: 10 Gigabit Small Form Factor PluggableModule” (PDF). Small Form Factor Committee. August31, 2005. Retrieved June 16, 2011.
4 12 TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES
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