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Dear Task Force Participants, During the 3/29/22 meeting, we started debating IMDD and Coherent alternatives for campus reach PMD.
In Transport, the debate was settled long ago as soon as feasibility of Coherent was established. It’s obvious that eliminating DCFs and reducing the number of EDFAs is a good idea. In Datacom, the CD, PMD and Sensitivity advantages of Coherent are not clear benefits, and Coherent is not an automatic choice. We have to do the hard work of analyzing technical and market trade-offs. Unfortunately, the 3/29/22 discussion
was not a good start, so a reset is in order. We know that when there is an FR interface, LR is not going to ship in the millions; it will ship in the tens of thousands. Similarly, we know that ZR interfaces don’t ship in the millions. Using LightCounting Vendor Survey Results through
Q4 2021, 100G/200G Coherent volume was ~½ million over the last five years, which is less than 2% of the 100G IMDD Datacenter volume over the same time period.
This means neither an IMDD nor Coherent LR solution will have a dedicated DSP ASIC. IMDD 800G LR4 will use the same DSP ASIC as FR4 and DR4, because these will ship in the many millions. Coherent 800G LR1 will use the same DSP ASIC as ZR
or ZR+ because those will ship in the tens and possibly hundreds of thousands. The IMDD DSP ASIC will be much lower cost than the ZR DSP ASIC because it’s volume will approach two orders of magnitude higher volume, like at a 100G. We don’t have to speculate
about the cost ratio of DSP ASICs at 800G; we have the answer at lower rates. The specs on IMDD LR4 optics are more stringent than FR4, which raises cost. The Coherent LR TX source doesn’t have to be tunable, which lowers cost. However this fixed laser is nothing like an IMDD source, it has to be cooled and held
to a precise wavelength otherwise it won’t match the RX LO. The most interesting argument in favor of Coherent is that if nothing is done, the standard ZR solution works for LR, without the need for another code. This has both R&D and OpEx advantages. Since the debate between IMDD and Coherent is likely to be replayed many times, let’s set a good example for the future by how we conduct it in .3df.
Chris From: John D'Ambrosia <jdambrosia@xxxxxxxxx> All, Presentation material for our Task Force meeting on 29 March has been posted -
https://www.ieee802.org/3/df/public/22_03/index.html [ieee802.org]. Please note that Mr. Williams presentation has undergone legal review by IEEE legal. Mr. Law and I will provide guidance
regarding this presentation prior to Tom presenting, and ask that all comments are held to that time. As a reminder,
All interim teleconference meeting participants should review the following documents prior to participation in an interim meeting teleconference: ·
IEEE SA patent policy ·
IEEE SA Copyright Policy ·
IEEE SA Participation Policy All of these policies may be found at http://ieee802.org/3/policies.html
[ieee802.org]. Regards, John D’Ambrosia Chair, IEEE P802.3df Task Force To unsubscribe from the STDS-802-3-B400G list, click the following link:
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