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 (e.g. twisted pair or twinaxial copper cables, multi-mode or single-mode fiber cables). Transceivers are also designated by their transmission speed. SFP modules are commonly available in several different categories.
Name | Standard | Introduced | Status | Size (mm2) | Backward compatible | MAC block to a PHY chip | Media | Connector | Max channels | Notes |
---|---|---|---|---|---|---|---|---|---|---|
100 Mbit/s SFP | SFF INF-8074i | 2001-05-01 | current | 113.9 | none | MII | Fiber, Twisted Pair | LC, RJ45 | 1 | |
1 Gbit/s SFP | SFF INF-8074i | 2001-05-01 | current | 113.9 | 100 Mbit/s SFP* | SGMII | Fiber, Twisted Pair | LC, RJ45 | 1 | |
1 Gbit/s cSFP | current | 113.9 | Fiber | LC | 2 | |||||
10 Gbit/s SFP+ | SFF SFF-8431 4.1 | 2009-07-06 | current | 113.9 | 1 Gbit/s SFP | XGMII | Fiber, Twisted Pair, DAC | LC, RJ45 | 1 | |
25 Gbit/s SFP28 | SFF SFF-8402 | 2014-09-13 | current | 113.9 | 10 Gbit/s SFP+ | Fiber, DAC | LC | 1 | ||
50 Gbit/s SFP56 | current | 113.9 | Fiber, DAC | LC | 1 | |||||
4 Gbit/s QSFP | SFF INF-8438 | 2006-11-01 | current | 156 | none | GMII | 4 | |||
40 Gbit/s QSFP+ | SFF SFF-8683 | 2012-04-01 | current | 156 | none | XGMII | Fiber. DAC | LC, MTP/MPO | 4 | CWDM |
50 Gbit/s QSFP28 | SFF SFF-8665 | 2014-09-13 | current | 156 | QSFP+ | Fiber, DAC | LC | 2 | ||
100 Gbit/s QSFP28 | SFF SFF-8665 | 2014-09-13 | current | 156 | none | Fiber, DAC | LC, MTP/MPO-12 | 4 | CWDM | |
200 Gbit/s QSFP56 | SFF SFF-8665 | 2015-06-29 | current | 156 | none | Fiber, DAC | LC, MTP/MPO-12 | 4 | ||
400 Gbit/s QSFP-DD | SFF INF-8628 | 2016-06-27 | current | 156 | QSFP+, QSFP28 | Fiber, DAC | LC, MTP/MPO-16 | 8 | CWDM |
100 Mbit/s SFP
- Multi-mode fiber, LC connector, with black or Beige color coding
- SX – 850 nm, for a maximum of 550 m
- Multi-mode fiber, LC connector, with blue color coding
- FX – 1300 nm, for a distance up to 5 km.
- LFX (name dependent on manufacturer) – 1310 nm, for a distance up to 5 km.
- Single-mode fiber, LC connector, with blue color coding
- LX – 1310 nm, for distances up to 10 km
- EX – 1310 nm, for distances up to 40 km
- Single-mode fiber, LC connector, with green color coding
- ZX – 1550 nm, for distances up to 80 km, (depending on fiber path loss)
- EZX – 1550 nm, for distances up to 160 km (depending on fiber path loss)
- Single-mode fiber, LC connector, Bi-Directional, with blue and yellow color coding
- BX (officially BX10) – 1550 nm/1310 nm, Single Fiber Bi-Directional 100 Mbit SFP Transceivers, paired as BX-U (blue) and BX-D (yellow) 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 (RJ-45) connector
- 100BASE-TX – for distances up to 100m.
1 Gbit/s SFP
- 1 Gbit/s multi-mode fiber, LC connector, with black or beige extraction lever
- SX – 850 nm, for a maximum of 550 m at 1.25 Gbit/s (gigabit Ethernet). Other multi-mode SFP applications support even higher rates at shorter distances.
- 1.25 Gbit/s multi-mode fiber, LC connector, extraction lever colors not standardised
- SX+/MX/LSX (name dependent on manufacturer) – 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 2.5 Gbit/s single-mode fiber, LC connector, with blue extraction lever
- LX – 1310 nm, for distances up to 10 km (originally, LX just covered 5 km and LX10 for 10 km followed later)
- EX – 1310 nm, for distances up to 40 km
- ZX – 1550 nm, for distances up to 80 km (depending on fiber path loss), with a green extraction lever (see GLC-ZX-SM1)
- EZX – 1550 nm, for distances up to 160 km (depending on fiber path loss)
- BX (officially BX10) – 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 (XD), 80 km (ZX), 120 km (EX or EZX)
- SFSW – single-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 (CWDM) and dense wavelength-division multiplexing (DWDM) transceivers at various wavelengths achieve various maximum distances. CWDM and DWDM transceivers usually support link distances of 40 km, 80 km, and 120 km.
- 1 Gbit/s for copper twisted-pair cabling, 8P8C (RJ-45) connector
- 1000BASE-T – these 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 (or rather: do not have equivalents for) Fibre Channel or SONET. Unlike non-SFP, copper 1000BASE-T ports integrated into most routers and switches, 1000BASE-T SFPs usually cannot operate at 100BASE-TX speeds.
- 100 Mbit/s copper and optical – some vendors have shipped 100 Mbit/s 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 100 Mbit/s SFPs.
- Although it is not mentioned in any official specification document the maximum data rate of the original SFP standard is 5 Gbit/s. 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 2.5 Gbit/s and 5 Gbit/s Ethernet speeds with SFPs with 2.5GBASE-T and 5GBASE-T.
10 Gbit/s SFP+
The SFP+ (enhanced small form-factor pluggable) 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 8 Gbit/s 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 16 Gbit/s Fibre Channel, it can be used at this speed.
SFP+ also introduces direct attach for connecting two SFP+ ports without dedicated transceivers. Direct attach cables (DAC) exist in passive (up to 7 m), active (up to 15 m), and active optical (AOC, up to 100 m) variants.
10 Gbit/s 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 (degraded) received signal whereas linear ones do not. Linear modules are mainly used with low bandwidth standards such as 10GBASE-LRM; otherwise, limiting modules are preferred.
25 Gbit/s SFP28
SFP28 is a 25 Gbit/s interface that evolved from the 100 Gigabit Ethernet interface which is typically implemented with 4 by 25 Gbit/s data lanes. Identical in mechanical dimensions to SFP and SFP+, SFP28 implements one 28 Gbit/s lane accommodating 25 Gbit/s 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 (cSFP) 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 (SFP-DD) 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 supported:
- SFP-DD: 100Gbit/s using PAM4 and 50Gbit/s using NRZ
- SFP-DD112: 200Gbit/s using PAM4
- QSFP-DD: 400 Gbit/s/200 Gbit/s (8 × 50 Gbit/s and 8 × 25 Gbit/s)
- QSFP-DD112: 800 Gbit/s (8 × 112 Gbit/s)
QSFP types
Quad Small Form-factor Pluggable (QSFP) 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 multi-mode or single-mode fiber.
4 Gbit/s QSFP
- The original QSFP document specified four channels carrying Gigabit Ethernet, 4GFC (FiberChannel), or DDR InfiniBand.
40 Gbit/s QSFP+
- QSFP+ is an evolution of QSFP to support four 10 Gbit/s channels carrying 10 Gigabit Ethernet, 10GFC FiberChannel, or QDR InfiniBand. The 4 channels can also be combined into a single 40 Gigabit Ethernet link.
50 Gbit/s QSFP14
- The QSFP14 standard is designed to carry FDR InfiniBand, SAS-3. or 16G Fibre Channel
100 Gbit/s QSFP28
- The QSFP28 standard is designed to carry 100 Gigabit Ethernet, EDR InfiniBand, or 32G Fibre Channel. Sometimes this transceiver type is also referred to as “QSFP100” or “100G QSFP” for sake of simplicity.
200 Gbit/s QSFP56
- QSFP56 is designed to carry 200 Gigabit Ethernet, HDR InfiniBand, or 64G Fibre Channel. The biggest enhancement is that QSFP56 uses four-level pulse-amplitude modulation (PAM-4) instead of non-return-to-zero (NRZ). It uses the same physical specifications as QSFP28 (SFF-8665), with electrical specifications from SFF-8024 and revision 2.10a of SFF-8636. Sometimes this transceiver type is referred to as “200G QSFP” for sake of simplicity.
Fanout or breakout
Switch and router manufacturers implementing QSFP+ ports in their products frequently allow for the use of a single QSFP+ port as four independent 10-gigabit ethernet connections, greatly increasing port density. For example, a typical 24-port QSFP+ 1U switch would be able to service 96x10GbE connections. There also exist fanout cables to adapt a single QSFP28 port to four independent 25 gigabit ethernet SFP28 ports (QSFP28-to-4×SFP28) as well as cables to adapt a single QSFP56 port to four independent 50 gigabit ethernet SFP56 ports (QSFP56-to-4×SFP56).
Standardization
The SFP transceiver is not standardized by any official standards body, but rather is specified by a multi-source agreement(MSA) among competing manufacturers. The SFP was designed after the GBIC interface and allows greater port density (number of transceivers per given area) than the GBIC, which is why SFP is also known as mini-GBIC.
However, as a practical matter, some networking equipment manufacturers engage in vendor lock-in practices whereby they deliberately break compatibility with “generic” SFPs by adding a check in the device’s firmware that will enable only the vendor’s own modules. Third-party SFP manufacturers have introduced SFPs with EEPROMs which may be programmed to match any vendor ID.
Color coding of SFP
Color coding of SFP
Color | Standard | Media | wavelength | Notes |
---|---|---|---|---|
black | INF-8074 | Multimode | 850 nm | |
Beige | INF-8074 | Multimode | 850 nm | |
black | INF-8074 | Multimode | 1300 nm | |
Blue | INF-8074 | Singlemode | 1310 nm | |
Red | proprietary (non SFF) |
Singlemode | 1310 nm | Used on 25GBASE-ER |
Green | proprietary (non SFF) |
Singlemode | 1550 nm | Used on 100BASE-ZE |
Red | proprietary (non SFF) |
Singlemode | 1550 nm | Used on 10GBASE-ER |
White | proprietary (non SFF) |
Singlemode | 1550 nm | Used on 10GBASE-ZR |
Color coding of CWDM SFP
Color | Standard | wavelength | Notes |
---|---|---|---|
Grey | 1270 nm | ||
Grey | 1290 nm | ||
Grey | 1310 nm | ||
Violet | 1330 nm | ||
Blue | 1350 nm | ||
Green | 1370 nm | ||
Yellow | 1390 nm | ||
Orange | 1410 nm | ||
Red | 1430 nm | ||
Brown | 1450 nm | ||
Grey | 1470 nm | ||
Violet | 1490 nm | ||
Blue | 1510 nm | ||
Green | 1530 nm | ||
Yellow | 1550 nm | ||
Orange | 1570 nm | ||
Red | 1590 nm | ||
Brown | 1610 nm |
Color coding of BiDi SFP
Name | Standard | Side A Color TX | Side A wavelength TX | Side B Color TX | Side B wavelength TX | Notes |
---|---|---|---|---|---|---|
1000BASE-BX | Blue | 1310 nm | Purple | 1490 nm | ||
1000BASE-BX | Blue | 1310 nm | Yellow | 1550 nm | ||
10GBASE-BX 25GBASE-BX |
Blue | 1270 nm | Red | 1330 nm | ||
10GBASE-BX | White | 1490 nm | White | 1550 nm |
Color coding of QSFP
Color | Standard | wavelength | Multiplexing | Notes |
---|---|---|---|---|
Beige | INF-8438 | 850 nm | No | |
Blue | INF-8438 | 1310 nm | No | |
White | INF-8438 | 1550 nm | No |
Signals
SFP transceivers are ‘right-handed’: From their perspective, they transmit on the right and receive on the left. When looking into the optical connectors, the transmission comes from the left and reception is on the right.
The SFP transceiver contains a printed circuit board with an edge connector with 20 pads that mate on the rear with the SFP electrical connector in the host system. The QSFP has 38 pads including 4 high-speed transmit data pairs and 4 high-speed receive data pairs.
Pad | Name | Function |
---|---|---|
1 | VeeT | Transmitter ground |
2 | Tx_Fault | Transmitter fault indication |
3 | Tx_Disable | Optical output disabled when high |
4 | SDA | 2-wire serial interface data line (using the CMOS EEPROM protocol defined for the ATMEL AT24C01A/02/04 family) |
5 | SCL | 2-wire serial interface clock |
6 | Mod_ABS | Module absent, connection to VeeT or VeeR in the module indicates module presence to host |
7 | RS0 | Rate select 0 |
8 | Rx_LOS | Receiver loss of signal indication |
9 | RS1 | Rate select 1 |
10 | VeeR | Receiver ground |
11 | VeeR | Receiver ground |
12 | RD- | Inverted received data |
13 | RD+ | Received data |
14 | VeeR | Receiver ground |
15 | VccR | Receiver power (3.3 V, max. 300 mA) |
16 | VccT | Transmitter power (3.3 V, max. 300 mA) |
17 | VeeT | Transmitter ground |
18 | TD+ | Transmit data |
19 | TD- | Inverted transmit data |
20 | VeeT | Transmitter ground |
Pad | Name | Function |
---|---|---|
1 | GND | Ground |
2 | Tx2n | Transmitter inverted data input |
3 | Tx2p | Transmitter non-inverted data input |
4 | GND | Ground |
5 | Tx4n | Transmitter inverted data input |
6 | Tx4p | Transmitter non-inverted data input |
7 | GND | Ground |
8 | ModSelL | Module select |
9 | ResetL | Module reset |
10 | Vcc-Rx | +3.3 V receiver power supply |
11 | SCL | Two-wire serial interface clock |
12 | SDA | Two-wire serial interface data |
13 | GND | Ground |
14 | Rx3p | Receiver non-inverted data output |
15 | Rx3n | Receiver inverted data output |
16 | GND | Ground |
17 | Rx1p | Receiver non-inverted data output |
18 | Rx1n | Receiver inverted data output |
19 | GND | Ground |
20 | GND | Ground |
21 | Rx2n | Receiver inverted data output |
22 | Rx2p | Receiver non-inverted data output |
23 | GND | Ground |
24 | Rx4n | Receiver inverted data output |
25 | Rx4p | Receiver non-inverted data output |
26 | GND | Ground |
27 | ModPrsL | Module present |
28 | IntL | Interrupt |
29 | Vcc-Tx | +3.3 V transmitter power supply |
30 | Vcc1 | +3.3 V power supply |
31 | LPMode | Low power mode |
32 | GND | Ground |
33 | Tx3p | Transmitter non-inverted data input |
34 | Tx3n | Transmitter inverted data input |
35 | GND | Ground |
36 | Tx1p | Transmitter non-inverted data input |
37 | Tx1n | Transmitter inverted data input |
38 | GND | Ground |