Things You Should Know about QSFP-DD

To further satisfy the market demands for high speed, high density networking solutions, QSFP-DD ( double density QSFP) come into sight of people, which is a new module developed by the QSFP-DD MSA as a key part of the industry’s effort to enable high-speed solutions. It’s known that there are still many people unfamiliar with it on account that its advent is for a short time. Then in this article, things you should know about QSFP-DD will be introduced by Gigalight.

What’s QSFP-DD?
QSFP-DD means Quad Small Form Factor Pluggable Double Density, in which the “Double Density” refers to the doubling of the number of high-speed electrical interfaces that the module supports compared with a common QSFP28 module. QSFP-DD is not only a new module but also cage/connector system similar to current QSFP, but with an additional row of contacts providing for an eight lane electrical interface, which can expand the standard QSFP four-lane interface. Furthermore, QSFP-DD is able to operate up to 25Gbps with Non-Return-to-Zero (NRZ) modulation or 50Gbps with Pulse Amplitude Modulation (PAM4). After that, QSFP-DD form factor is allowed to address solutions up to 400Gbps per QSFP-DD port, while providing backward compatibility with 40Gbps and 100Gbps.


An Introduction to QSFP-DD Specification
What characteristics QSFP DD has are defined by QSFP-DD specification with broad market support, which is released by the QSFP-DD MSA group and overcomes the technical challenges of specifying a QSFP28 compatible double-density interface. The QSFP-DD specification defines a new pluggable form factor that supports 8 high speed electrical interfaces connecting to the host. This will include a mechanical module, a single height 1×1 surface mount cage and connector and a press fit 2×1 cage with integrated connector, thermal, pinout and management specifications. The QSFP-DD can support both optical and copper interfaces, but those physical layer specifications will be defined outside of the MSA specification as is usual for form factor MSA specifications.
Simultaneously, the QSFP-DD specification also defines a module and both a stacked height integrated cage/connector system and a single height cage/connector system. These expand on the QSFP form factor, the industry’s leading multi-lane pluggable form factor used across Ethernet, Fibre Channel and InfiniBand for 40Gbps and 100Gbps network applications.

What’s the QSFP-DD Merits and Features?
QSFP-DD pluggable modules under the definition of QSFP-DD specification, can quadruple the bandwidth of networking equipment to keep pace with advances in ASIC technology. By quadrupling aggregate switch bandwidth while maintaining port density, QSFP-DD will support continuing growth in network bandwidth demand and datacenter traffic. Systems designed for QSFP-DD modules will be backward compatible with existing QSFP form factors and provide maximum flexibility for end users, network platform designers and integrators.
Except for these merits, QSFP-DD is also with those unique features:

• Expanding on the QSFP pluggable form factor, a widely adopted four-lane electrical interface
• 2×1 stacked integrated cage/connector
• SMT connector and 1xN cage
• Cage design optimizations and module case optimizations enable thermal support of at least 12w per module
• QSFP-DD electrical interfaces will employ eight lanes that operate up to 25Gbps NRZ modulation or 50Gbps PAM4 modulation, providing solutions up to 200Gbps or 400Gbps aggregate
• QSFP-DD can enable up to 14.4Tbps aggregate bandwidth in a single switch slot

Conclusion
QSFP-DD, available for 200G/400G Ethernet, is a good choice to meet the industry need for high-density, high-speed networking solutions from any perspective. It is predicted that QSFP-DD will become an useful family of modules for the industry with applications at 400GbE and beyond. Meanwhile,  there are no efforts underway to define these new speeds but it is expected that QSFP-DD will evolve to support higher data rates for future applications. In addition, to keep pace with the market development trend, Gigalight launches 200G QSFP-DD, providing reliable long life, high performance, consistent service and so on, based on advantages of QSFP-DD.