How Fast Can You Identify a QSFP-DD 400G Optical Transceiver Type?

With a wide variety of QSFP-DD 400G optical transceiver types it may be difficult to determine the specific type when its right in front of you. While some vendors make it easy by using module naming conventions that clearly indicate the type, this is far from universal practice. This article will describe how to quickly deduce the specific type of a QSFP-DD transceiver.

When the Vendor Does you a Solid

The best-case scenario for rapid identification is when the vendor labels their various transceiver types with human readable standardized naming. A great example of this is Cisco©. They have adopted a simple, very clear naming convention, as follows:

  • QDD-400G-DR4-S
  • QDD-400G-FR4-S
  • QDD-400G-LR4-S
  • QDD-400G-LR8-S
  • QDD-4X100G-FR-S
  • QDD-4X100G-LR-S

Once it’s understood that Cisco has chosen to abbreviate QSFP-DD to QDD, it is quite simple to sort out the rest. After QDD (the form-factor) next is the aggregate transmission speed. The first 4 types listed above are straightforward 400G aggregate modules. The last 2, while still supporting an aggregate of 400G, are broken out into four 100G pairs. Each of these pairs may be connected to a different QSFP28 100G module. This is very advantageous when connecting newer 400G capable network equipment with previous generation 100G devices.

OK, What if the Vendor Uses a More Cryptic Naming Convention?

For a variety of reasons, some vendors use module names that really do not have anything with the type of optical transceiver module. Dell© is a great example. Listed below are some of their QSFP-DD module names,

  • 407-BCHW
  • 407-BCIB
  • 407-BCIH

With just this information it is very difficult to determine what type of module you have. In such cases it is useful to take advantage of some other physical attributes of these parts for clues as to the parts’ type. The two most useful attributes are the pull-tab handle color and the optical connector type. The table below is maps these attributes to the specific QSFP-DD optical module type.

While these color schemes may not be universally applied, they are very commonplace. To identify a given QSFP-DD modules type, the first step is to note the color of pull tap. Referring to the table above, it the handle color is Orange or Beige, you may be fairly certain the module is a 400GBASE-DR4 or 400GBASE-SR8, respectively. If the module has either a Blue or Green pull-tab, refer to the second column to discriminate. If the module had a Green handle, take a look at the optical connector. If it’s a Duplex LC, the module is a 400GBASE-FR4. If the connector is MPO-12, then you have a 4X100GBASE-FR. Finally, if the handle is blue, the connector again clues you into the module type, Duplex LC indicates a 400GBASE-LR4 while an MPO-12 connectors means it’s a 4X100GBASE-LR.


If you are trying to identify a particular type of QSFP-DD optical transceiver module, there are usually enough clues given by just a few physical attributes. The first and easiest is the module name printed on the label. Many vendors explicitly label their parts with a clear designation of its types. However, if you are dealing with parts from a vendor with more cryptic naming conventions, all is not lost. By examining the pull-tab handle color and, in some cases, the type of optical connector, you can use the table in this article to quickly identify the module type. Please come visit Fluxlight and see our wide array of competitively priced, fully compatible 400G pluggable Optical Transceivers.

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