400G Pluggable Modems Enter The Market
1046 2021-10-13
The 400GBASE Quad Small Form-Factor Pluggable Double Density (QSFP-DD) portfolio offers customers a wide variety of super high-density transceiver modules and the flexibility of 400 Gigabit Ethernet connectivity options for data center, high- performance computing networks, enterprise core and distribution layers, and service provider applications. The QSFP-DD modules are our new generation of 400G transceiver modules based on a QSFP-DD form factor.
QSFP-DD (Quad Small Form Factor Pluggable-Double Density) double-density four-channel small pluggable package is a high-speed pluggable module package defined by the QSFP-DD MSA group. It is the first choice for 400G optical module package. The center can effectively grow and expand cloud capacity as needed. 

Features
It is forward and backward compatible to QSFP, compatible with existing QSFP28 optical modules and AOC/DAC, etc.
Using 8-channel electrical interfaces, each channel rate is up to 25Gb/s (NRZ modulation) or 50Gb/s (PAM4 modulation), providing up to 200Gb/s or 400Gb/s aggregation solutions. QSFP-DD can achieve up to 14.4Tb/s aggregate bandwidth in a single switch slot. 
Using SMT (Surface-Mount Technology) connectors and 1xN cages, cage design optimization and module housing optimization can achieve a heat capacity of at least 12 watts per module.
Transmission media include passive copper cables (DAC), multi-mode fiber (MMF) and single-mode fiber (SMF). 

Bandwidth
The bandwidth of QSFP-DD is up to ten times that of QSFP+ or four times that of QSFP28.
QSFP has four electrical channels, each with a rate of 10Gb/s (QSFP+) or 25Gb/s (QSFP28), and aggregation provides 40Gb/s or 100Gb/s solutions.
The electrical interface of the QSFP-DD pluggable package adopts 8 channels, and each channel has a rate of up to 25Gb/s (NRZ modulation) or 50Gb/s (PAM4 modulation). The aggregation provides solutions up to 200Gb/s or 400Gb/s.

Compatibility
QSFP-DD is backward compatible with QSFP+/QSFP28.
Systems designed with QSFP-DD modules are backward compatible and support existing QSFP+/QSFP28 modules, providing flexibility for end users and system designers.

Port density
The port density of QSFP-DD and QSFP+/QSFP28 systems are the same.
But because each QSFP-DD port can accommodate 8 channels instead of 4 channels, QSFP-DD doubles the number of ASIC ports for existing interfaces (such as CAUI-4) it supports.
The mechanical interface of QSFP-DD on the motherboard is slightly deeper than QSFP+/QSFP28 to accommodate an extra row of contacts.
Compared with QSFP+/QSFP28, QSFP-DD only increases the length by a small amount, and increases the bandwidth to 10 times/4 times of the latter while ensuring the same port density. It is also backward compatible, which means that customers skip QSFP directly. It does not matter if the QSFP-DD system is deployed, which reduces a lot of equipment costs.

Comparison of QSFP-DD and OSFP
OSFP (Octal Small From Factor Pluggable) is a new pluggable package with 8 high-speed electrical channels and will initially support 400Gb/s (8x50G). 

Size
The volume of OSFP (Octal Small From Factor Pluggable) is more than twice that of QSFP-DD. 

Compatibility
OSFP and QSFP-DD are backward compatible with QSFP+/QSFP28, but an additional OSFP to QSFP adapter is required to achieve this.

Bandwidth
QSFP-DD can only support up to 400Gb/s at present, but OSFP can support up to 800Gb/s.
QSFP-DD is mainly used for the 400G network that is about to be deployed on a large scale (and the overused 200G from 100G to 400G), while OSFP is more likely to be prepared for the future 800G network. Therefore, combined with the current situation, QSFP-DD is more suitable as a 400G optical module package. 

400G Pluggable Modems Will Enter The Market
https://www.htfwdm.com/news/400g-pluggable-modems-will-enter-the-market-36578202.html