Winter 2018 Optical Connections Magazine


The speed with which optical communications technology is progressing means existing transceiver form factors and capabilities could soon be obsolete. The Consortium for On-Board Optics (COBO) is leading the charge to develop future-proof solutions, so Peter Dykes spoke with Brad Booth , chair of COBO and principal network architect for Azure hardware at Microsoft, about the organisation’s work in progress. COBO takes on the challenge of high- speed optical communications TRANSFORMING TRANSCEIVER DESIGN

What issues has COBO identified with current transceiver design?

fastest we could go to at the time and 25G was pretty difficult, although it is commonplace now. With 50G PAM4, people are already discovering the pain points and when we get to 100G PAM4, there are going to be even more pain points. Looking at that, the question is, why do we keep putting the optics out on the face plane and having this chip drive so much power? That’s really not making good sense when you look at these switched silicon [chips]. They’re 200 Watts or 300 Watts, and now we’re looking at up to 700-Watt cards. That’s more power than I’m putting into my CPU’s! This is not an equation that is going to continue to work.

savings by going to COBO, but now the organisation exists, people can actually design specifically to optimise some of that power. We’ve heard numbers from anywhere between 10% and 15% power savings. That doesn’t sound like a lot, but if you figure it’s 500 Watts of power and you save 50 Watts on tens of thousands of switches, that’s a lot of power saved. My problem as a person that’s providing a service to end users, whether it be Office 365 or Azure, is that those customers don’t pay me for the network, they pay me for the application. The network is there to support what they want to do and by burning power, and by burning power in my network means I’m not using power to sell them more applications, VM’s or services, so it’s actually a detriment. With the network, we’ve got to be very careful as we continue to progress and be more cognisant of the power we are using because it becomes a very large part of the CapEx. If you’ve got a server


For years now in optics, everything has been embedded, as in for example 200 and 300-


pin Multi-Service Agreements (MSAs). A lot of this was done with embedded optics, but when we started looking at it from the point of view of deployment models, one of the things we realised at Microsoft, was one of our biggest failure rates was from human contact with those modules. So, we started looking at if we could figure out how to get them mounted and pluggable at the factory and shipped to us. We figured that would work, but all those MSA’s are not designed for shock and vibration requirements and we realised we need to do something a little better there. Then we started looking at the speeds that we’re going to on these electrical interfaces, like 25G NRZ. 10G was the

Why is power consumption such a critical issue?


I know with the existing generation of switched silicon no-one is going to see power



| ISSUE 15 | Q4 2018

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