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QSFP+ 40G BASE Optical Transceivers

QSFP, QSFP+ and QSFP28. What’s the Difference?

There is a wide choice of abbreviations to try and understand when it comes to the many interface and data rate types of fibre optic transceivers that are available today. Over the next few weeks, the team at Complete Connect will try to help you get a better understanding of what these mean.

Today we are focusing on QSFP, QSFP+ and QSFP28. They look very similar in terms of their physical appearance but the data rates that they transmit at are quite different.

QSFP

This abbreviation stands for Quad Small Form Factor Pluggable.

This type of cable support Infiniband, Fibre Channel, Ethernet and Sonet/SDH standards as well as other types of proprietary interconnects.

They are available for use in either singlemode or multimode applications and is able to support 4 independent channels that can individually transmit at up to 1.25 Gbp/s per channel for an aggregate combined speed of 4.3Gbp/s. However, due to technology advancements these type of optics are seldom used.

QSFP+

This abbreviation stands for Quad Small Form Factor Pluggable Plus.

This interface type supports Ethernet, Fibre Channel and Infiniband at 10Gbps per channel up to a maximum of 4 channels (Quad) for a combined aggregate data rate of 40Gbps or 56Gbps

Like the QSFP interface, this QSFP+ version also supports transmission over both singlemode and multimode infrastructures to a maximum distance of 40km.

Line cards / ports that accept QSFP+ modules are typically used in one of two ways.

  1. Connecting two switches together with 40G or 56G connectivity
  2. Connecting one switch transmitting / receiving a 40G data rate to 4 devices each working at 10G

A common application is to use either an Active Optical Cables (AOC), Direct Attach Copper Cable (DAC) or passive MTP breakout cable to enable the 40G QSFP+ interface to be split out to 4 X independent data streams in different network devices.

AOC Breakout
DAC Breakout
OM3/OM4 SR4 Breakout
Singlemode PSM4 via PLR4 or LR4 PSM Breakout

QSFP28:

Whilst still quad based interface the QSFP28 ramps up the data speeds to (SFP28) 28Gbp’s per channel for a combined data rate of 100Gbp/s. Unlike the older CFP, CFP2 and CFP4 interface, the newer QSFP28 interface offer a much smaller form type and is becoming the standard interface choice for 100G transmission.

The QSFP28 interface is highly flexible and can be used in the following combinations.

  • 100Gbp/s
  • 2 X 50Gbp/s
  • 4 X 25Gbp/s (SFP28)

Like the QSFP+ interface above there are several breakout cable options that can be considered, depending on the application.

  1. AOC Breakout
  2. DAC Breakout
  3. OM3/OM4 SR4 Breakout
  4. Singlemode PLR4 Breakout

It is important to note that typically a QSFP28 module cannot be broken down in to 10G channels, however it is backwards compatible in that if used in a QSFP+ port, it would allow a breakdown into 4 X 10G SFP+ channels.

If you need a little more help and advice with any of our range of QSFP optics or fibre connectivity cables, then please do not hesitate to let us know.

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