Authored by Shajan George Technical Director, R&M India
The strong demand for solutions specifically optimized to serve the hyperscale data center market has led to a series of developments in the industry. There is a general push towards interoperability, open systems, and faster unification of the solutions.
One manifestation of this is the proliferation of MSAs (Multi-Source Agreements) as opposed to the traditional path for the generation of standards which is usually a slower process. The MSAs created to standardize fiber-optic solutions for 400 Gigabit Ethernet (400G) have recently released their specifications. Several companies have already deployed pluggable and on-board optics modules that support 400G.
QSFP-DD (high-speed double-density quad small form factor pluggables) which supports 400G in an 8-channel configuration had a strong presence across the vendors exhibiting at OFC and ECOC meetings in 2019. COBO (Consortium for On-Board Optics) modules were showcased by several vendors.
Radical shift
The shift towards on-board optics that can be observed today is a more radical one and thus requires adaptation from the industry. It must rethink the installation process in data centers and the time required for monetization. However, the promoters of the COBO approach fully support this development.
New MSAs for the 800G generation were announced fast on the heels of all the 400G releases. The most notable of these are the QSFP-DD800 and 800G Pluggable. QSFP-DD800 is a natural step from the original 400G specification. The change will be achieved by increasing line speeds to 112Gb/s while retaining the physical form factor. Backwards compatibility is an important issue for this consortium and an important factor of their success in attaining industry support for the 400G generation. Now they will be able to continue this backwards compatibility. Modules will be able to function correctly when connected to legacy equipment.
Currently, the promoters of QSFP-DD800 are limited to a small group of large American companies. Further companies will be allowed to join once the key design elements have been incorporated in the specification. The companies joining at a later point will be invited to work on refining the specification.
New competition
Meanwhile, the 800G Pluggable MSA group was formed in late 2019 and is comprised mostly of companies based in China with a few exceptions. The approach of this MSA towards 800G is based on both 8x100G and 4x200G routes. The key work is meant to be in the definition of the modulation and multiplexing of signals.
The MSA has two different use cases, one is data center connectivity up to 100 m where they focus on cost and power minimizing. The other is the 2 km scenario for Tier 1-2 and Tier 2-3 connections. When it comes to form factor, 800G pluggable aims to adopt the available QSFP-DD or OSFP cage and connector specifications.
Companies are invited to join this consortium although only as contributors with voting rights reserved to those companies listed as promoters.
Third in the league
The Consortium for On-Board Optics (COBO) specification, which currently already includes an 800G solution (although based on a 16-channel configuration), is also prepared for doubling the transmission rates to obtain 1.6Tb. COBO’s 800G solution can be compared in certain circumstances to the future QSFP-DD800 and 800G Pluggable modules. Regardless of the double number of channels, the density in the front panel is much higher and thermal management greatly improved.
The COBO topic of moving towards co-packaging with a fully optical front panel and away from pluggables also gained momentum. Several parts of the industry would prefer to delay the shift as long as possible. But everyone agrees that this may be the last speed generation where this delay is feasible. To this effect, Microsoft and Facebook have jointly launched the Co-Packaged Optics Collaboration intending to unify development efforts across the industry.
Short deadline
It is expected that cloud companies will need these 800G modules by 2023-2024 to keep up with the bandwidth growth inside their data centers.
