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Comparing QSFP28 and QSFP-DD

The QSFP-DD is the newest member of the QSFP family of optical transceivers and it is the smallest form factor for 400G transceivers on the market today. In this article, we will consider how it differs from the common QSFP28 transceiver used for 100G data rates.

Understanding the QSFP-DD

QSFP-DD stands for Quad Small Form factor Pluggable Double Density. The double density is the main distinction between the QSFP-DD and the QSFP28 and signifies the doubling of the number of high speed electrical interfaces from 4 to 8 that the module supports when compared to a standard QSFP28 module.

Commonly referred to as QSFP-DD, a more precise name would be QSFP56-DD where the 56 refers to the bandwidth that each electrical interface supports which is 56Gb/s. This is also the second major difference when compared to the standard QSFP28 which, as the name implies, support 28Gb/s per electrical interface.

When you combine the doubling of the transmission rate per electrical interface from 28Gb/s to 56Gb/s with the doubling of the number of electrical interfaces, this is how the QSFP56-DD transceivers achieves 400G data transmission compared to 100G for the QSFP28.

As a side note, also available on the market is the QSFP28-DD for 200G data transmission. This transceiver is also double density, meaning it has 8 electrical interfaces, but has the same bandwidth per electrical interface as the standard QSFP28.

Advantages of QSFP-DD form factor

The first one is backward compatibility. The QSFP-DD is backward compatible with all other QSFP transceivers therefore providing flexibility for both users and also systems planners and designers.

The second advantage is in the actual design of the QSFP-DD which can enable thermal support for up to 12W per module. This reduces the requirement for heat dissipation capabilities within the transceiver thus reducing unnecessary costs.

GigOptics QSFP-DD transceivers

GigOptics has recently added a full range of 200G and 400G optical transceivers; all tested to ensure quality and reliability. For more information, contact us at

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