Co-Packaged Optics: Of Form Factors and Future Fights

Co-packaged optics (CPO) is flavor of the month right now; the question is, what kind of CPO?   There will surely be different form factors for data centers and telecommunications, and interconnects, sensors, and supercomputing. But there will also be different form factors proposed for CPO for within the data center.

Based on recent presentations by leading firms, we already have some idea what these formats will look like and they bear a close resemblance to each other but in the end there can be only one – or two maybe, as there were for COBO’s connector standards.

Facebook, Microsoft and the Collaboration

As things are institutionally arranged, we think that the key influencer on the data center CPO form factors will be the CPO Collaboration, which is an alliance of Facebook and Microsoft with other big cloud vendors likely to join in the near future. If there is to be a CPO MSA, the Collaboration is where it is going to come from.

Actually, Microsoft has not said much about such things.  But Facebook has.  It has already set out a structure for early and later generations of CPO which will presumably turn into the Collaboration’s offering for data center CPO at some point. In the Gen1 version of this platform, the switch die-to-optics connection is based on an XSR connection.  (XSR is comprehensive IP solution for high bandwidth connections between dies or chiplets in SiP devices, as well as between modules.)  This type of CPO device would be aimed at the 51.2T switching generation with 106G lane speed.

When the switching generation matures to the 102.4T level, Facebook envisions a somewhat different kind of connectivity.  In this Gen 2 connectivity, we probably have a 212G lane speed with analog direct-drive to optics.

OEMs Take a Stand:  Cisco and Juniper

It is possible that the equipment OEMs will take what they are offered by the CPO Collaboration.  Generally there have been squabbles over new standards, where one party pitches itself against another for dominance in the product format design stakes.  Making the likelihood of a standards war greater is the fact that OEMs are not being invited to the CPO Collaboration party.  The Collaboration membership is to be all cloud providers

Cisco: The current version of CPO that Cisco is a system using optical tiles and switch tiles at the core of the device with a remote light source.  Silicon photonics provides “tight/dense” integration with the switching chip.  The light source provides multiple lanes per laser.  The electrical specs embody 112G-XSR and the optical I/O is 400G-DR4/FR4, which allows interoperability with conventional optics.  Not so different from what Facebook is talking about but perhaps enough to start an argument.

Jupiter: Jupiter Networks, is distinctly different from most of the other form factors for Co-packaged optics being proposed.  Or it may be.  At one presentation it made, the CPO platform that it used to illustrate what CPO was all about was the Ranovus platform.  Whether this was just an illustration of CPO or if there is a closer relationship between Jupiter and Ranovus is hard to say, but Ranovus is distinctly heterodox technology by comparison with what we have discussed before.  The Ranovus platform uses integrated quantum dot lasers, while most others use external VCSELs.  It is hard to imagine any standards organization adopting Ranovus’s approach as a standard right now, but perhaps the standard will be written open enough to accept something like the Ranovus platform into its fold.

Facebook, Microsoft and Cisco have been standards setters before and it is likely they will be again the new business and technology environment emerging from Co-packaged optics. However, this environment has got some way to go before we see any real standards/MSAs emerge from it.

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