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QSFP-DD vs QSFP112: What’s the Difference?

February 13, 2026 , , , ,

QSFP-DD vs QSFP112: What’s the Difference?

The rapid evolution of data center networks has pushed optical transceiver technology to new heights. As the demand for higher bandwidth continues to grow, newer form factors like QSFP-DD and QSFP112 have emerged to support 400G and 800G Ethernet applications. While both modules serve high-speed networking needs, they differ significantly in design, performance, and use cases.

What Are QSFP-DD and QSFP112?

QSFP-DD stands for Quad Small Form-factor Pluggable Double Density. Its “double density” design means it adds a second row of electrical contacts, enabling eight high-speed lanes instead of the traditional four. This expanded interface allows QSFP-DD modules to support aggregate speeds from 200G to 800G per module by using modulation technologies like NRZ and PAM4.

What Are QSFP-DD and QSFP112?

In contrast, QSFP112 uses a four-lane electrical interface but takes advantage of PAM4 signaling at 100G per lane, enabling 400G throughput within the same QSFP footprint. It represents the peak performance level for a four-lane pluggable system.

Side-by-Side: Key Specifications

Side-by-Side: Key Specifications

Why QSFP-DD is Considered More Flexible ?

One of the biggest advantages of QSFP-DD is backward compatibility. A QSFP-DD port can accept legacy QSFP modules like QSFP28, QSFP56 and even QSFP112 devices — allowing smooth migration from older speeds to newer ones without replacing existing hardware. However, when using QSFP112 in a QSFP-DD port, it operates in a 4-lane mode and requires the host ASIC to support 4×100G PAM4.

QSFP-DD also maintains the same physical width as older QSFP modules, giving network designers more port density on rack switches while enabling higher overall throughput.

Use Case Differences

  • QSFP-DD is ideal for high-density, high-bandwidth environments such as hyperscale data centers and HPC clusters where 800G links are becoming more common.
  • QSFP112 is optimized for 400G deployments, offering excellent performance and efficiency in cloud infrastructure and mid-to-upper networking layers.