Is Co-packaged Optics Just Around the Corner?
Optical engines co-packaged with switching ASIC are likely to offer an alternative to pluggable optical transceivers in mega datacenters. The pluggables were first introduced two decades ago for connections in enterprise networks and became the ubiquitous solution for optical connectivity across a variety of applications. Over 1 billion units of pluggable transceivers were shipped in the last 10 years, including more than 500 million for the fiber to the home or to the building (FTTx) market and more than 10 million for connections inside mega datacenters, operated by Amazon, Facebook, Google, Microsoft and other cloud companies. However, the industry is starting to look for an alternative to the pluggables with an objective to reduce power consumption of next generation Ethernet switches.
Facebook and Microsoft recently launched the Co-Packaged Optics (CPO) Collaboration. The goal of CPO is “the adoption of common design elements that will provide guidance for suppliers in the design and manufacturing of co-packaged optics.” Leading switch ASIC vendors, including Broadcom and Cisco, are also investing in development of these new solutions. There are a lot of technical challenges, but if everything goes well, consumption of pluggable transceivers by the Top 5 Cloud companies will start to decline in 2027-2028, as shown in the Figure.
Figure: Shipments of Ethernet transceivers and opto-chiplets to Top 5 Cloud companies (includes products with data rate of 100GbE and above with reach of 100m and 500m only).
This forecast was developed for a study commissioned by ARPA-E ENLITENED program, which funds development on next generation optical connectivity and switching technologies. The main goal of this program it to reduce power consumption of datacenter switches by a factor of ten.
IBM is among a few companies selected for Phase 2 ARPA-E funding this year. IBM was the first one to co-package optical engines with switching ASICs, as part of a DARPA funded supercomputer project in 2004-2008. It might have been a bit ahead of its time, like several other projects funded by DARPA, including computer networks that evolved into the Internet. It might be the right time now and IBM is developing very low power co-packeged optics based on VCSEL arrays for the ENLITENED project, including double wavelength VCSELs for Phase 2 of the program. Other teams funded by ARPA-E are planning to use silicon photonics technology.
The promise of co-packaged optics is to eliminate power to drive several inches of copper traces connecting a switching ASIC in the middle of a PCB board to optical transceivers plugged at the board edge or faceplate. Co-packaging involves simpler SerDes interfaces that not only consume less power but reduce latency.
Development of new technologies for opto-chiplets has to overcome many engineering challenges. Our forecast assumes that all these challenges can be resolved ahead of the early demand for these products in 2023-2024, but it is in the hands of engineers to make it happen.
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