As data traffic rises in data centers and advanced networking applications, the optical module market is moving toward higher speeds, lower power consumption, and smaller form factors or sizes. what are the features and benefits of the QSFP-DD package? What are the differences between it and QSFP28/QSFP56 modules? In this issue's article, let's learn more about QSFP-DD package.

QSFP-DD Package Overview

QSFP-DD (Quad Small Form Factor Pluggable-Double Density) is a new modular connector system that uses a dual density four-channel small hot-swappable optical module package. The package has 8 channels of electrical interfaces with rates up to 25Gb/s (NRZ modulation) or 50Gb/s (PAM4 modulation) per channel, aggregating to provide solutions up to 200Gb/s or 400Gb/s for high performance computing data centers, cloud networks.

QSFP-DD package advantages

1、Adopts 8-channel electrical interface with backward compatibility, compatible with QSFP+/QSFP28/QSFP56 and other QSFP packages, reducing port cost and equipment deployment cost.

2、Using 2×1 stacked integrated cage and connector. Due to industry demand, most pluggable packages eventually develop a dual-height stacked cage connector system in addition to single-height cage connector systems. the QSFP-DD MSA team chose to develop both single-height and dual-height cage connector systems.

3. Using SMT (Surface-Mount Technology) connectors and 1xN cages, cage design optimization and module housing optimization can achieve a minimum of 12 watts of thermal capacity per module, and the higher thermal capacity reduces the module's requirement for heat dissipation features, thus avoiding unnecessary costs.

QSFP-DD Package vs. QSFP28/QSFP56

Compared to QSFP28/QSFP56 modules, QSFP-DD modules support double the number of high-speed electrical interfaces. The QSFP-DD supports a 50Gb/s PAM4 electrical modulation format, which provides a fourfold increase in port rate compared to the QSFP28 module.

The QSFP-DD and QSFP28/QSFP56 systems have the same port density. However, because each QSFP-DD port can accommodate eight channels instead of four, QSFP-DD doubles the number of ASIC ports it supports for existing interfaces such as the CAUI-4.

The mechanical interface of QSFP-DD on the motherboard is slightly deeper than QSFP28/QSFP56 to accommodate the extra row of contacts. QSFP-DD increases the bandwidth while maintaining the same port density with only a small increase in length compared to QSFP28/QSFP56, and has backward compatibility, reducing significant equipment costs in deployed networks.

QSFP-DD Package Related Products

QSFP-DD package can provide 200Gb/s or 400Gb/s solution, among which 200G QSFP-DD optical modules mainly have three kinds of 200G QSFP-DD SR8/PSM8/LR8, the difference is as follows:

The types of 400G QSFP-DD optical modules are 400G SR8/DR4/FR4/LR4/LR8, etc. The differences are as follows: