QSFP-DD Wiki and Comparison of QSFP-DD vs OSFP and QSFP
What is QSFP-DD?
QSFP-DD, or QSFP56-DD, stands for Quad Small Form Factor Pluggable Double Density. Based on the design of QSFP, the form factor of QSFP-DD is identical to the previous QSFP+ and QSFP28. Yet it doubles the number of electrical interface lanes to 8 against 4 and provides the highest bandwidth in the QSFP cage system module. A standard QSFP-DD delivers a maximum 400G data rate by 8 x 50G or 4 x 100G PAM4. It supports up to 36 400GbE ports in a standard 1U space and is backward compatible with QSFP+ and QSFP28.
QSFP-DD MSA
QSFP-DD MSA (multi-source agreement) is the de facto standard that defines and develops the QSFP-DD form factor. MSA working members include dozens of brand companies such as Cisco, Juniper and etc. They contribute to drafting or refining the QSFP-DD specifications. These 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” (Excerpted from qsfp-dd.com).The career of the QSFP-DD MSA group is to address the requirement for high-speed, high-bandwidth, and high-density applications in a backward compatibility form factor. In fact, QSFP-DD MSA mentions that the QSFP-DD module supports a max bandwidth of 14Tb/s with 36 ports of 400GbE in a 1RU.
QSFP-DD Types
Based on QSFP-DD Data Rates
Published QSFP-DD transceiver comes with QSFP-DD 200G and QSFP-DD 400G. The maximum speed capacity is due to different modulation technology. QSFP-DD200 supports a total of 200G by each of the 8 channels carrying a 25G data rate with NEZ modulation. With PAM4 modulation, QSFP-DD400 each channel will run at a maximum of 50G to offer a total of 400G data rate.
QSFP-DD800 is the enhanced version of QSFP-DD, with backward compatibility with all QSFP form factors. However, the QSFP-DD thermal whitepaper clearly points out its differences from the standard QSFP-DD. QSFP-DD800 is the industry's smallest form factor of the 800G module that provides a data rate of 800G. It has further developed the QSFP-DD spec with optimized features, such as signal integrity performance supporting 100Gb/s electrical IO in 8 lanes, and a type 2B mechanical design for adding connector port separation by increasing the height of the nose heatsink.
Type 1: QSFP28 mechanicals
Type 2: longer back cage to make room for internal design
Type 2A: QSFP-DD adds a heatsink to allow better cooling
Type 2B: QSFP-DD800 heatsink is higher to make room for the internal connector port separation
Based on QSFP-DD Specifications
Take 400G QSFP-DD as an example, there are 400G SR8, 400G DR4, 400G DR4+, 400G FR4, and 400G LR4, 400G LR8, and 400G ER8. These QSFP-DD transceivers, designed with different physical characteristics and performances are to address multiple deployment applications. The selection covers optical connectors, working wavelength, media, maximum transmission distance, transmitter and etc. The QSFP-DD specs are shown in the table below.
OSFP vs QSFP-DD
Both OSFP and QSFP-DD support 400G and even 800G data rates, which makes the two become the best options for spine/leaf and core networks. OSFP connectors and QSFP-DD connectors are made in 200G/400G/800G optical modules, and 400G DAC and AOC cables.
QSFP-DD vs QSFP28/QSFP+
The major differences between QSFP-DD vs QSFP system modules that are compliant with QSFP112 MSA are:
Physical characteristics
Longer extension beyond the faceplate
adds a QSFP-DD heatsink to facilitate cooling
eight electrical interface lanes against four
A total Data Rate of 400G and even 800G against 100G and 40G
A Single channel Data Rate of 25G/50Gand even 100G against 25G and 10G
Summary
This post introduces the QSFP-DD form factor and popular QSFP-DD types in the market from data rate and specifications. QSFP-DD is developed by QSFP-DD MSA to address the high-speed and high-density networking applications. Compared to OSFP, QSFP-DD is based on the QSFP cage, delivering a max data rate of 200G, 400G, or 800G while with backward compatibility with the QSFP connector (QSFP+/QSFP28/QSFP56). This feature grants QSFP-DD flexibility to fit the legacy equipment and devices, therefore saving upgrading costs and extending the whole system's lifespan.QSFPTEK provides 400G QSFP-DD modules with wide vendor compatibility. Get a quote via one of the contact methods below.
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