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The objectives for P802.3bs (Provide physical layer specification which support 400 Gb/s operation over: At least 100 m of MMF) and P802.3cd (Define 200 Gb/s PHYs for operation over MMF with lengths up to at least 100 m) could be generic because there weren’t any pre-existing PHYs at these rates of operation over MMF, it was believed to be technically and economically feasible for the project to pick an appropriate lane count, lane rate and number of fibers for each of these PHYs.
Since we now have the existing PHYs, this new effort cannot be this generic: the objectives need to be specific enough to clarify what is different (and better) about the 400 Gb/s MMF PHY to be developed by this project than the one developed by P802.3bs, and what is different (and better) about the 200 Gb/s MMF PHY to be developed by this project than the one developed by P802.3cd.
The easy way out is to do what Paul suggested (400 Gb/s over fewer than 16 MMF pairs and 200 Gb/s over fewer than four MMF pairs), but if there is enough evidence by the time the PAR is submitted to know what the right number of pairs is for each, it seems fine to me to be specific.
I agree that was the form in 802.3cd. But here we would like some latitude regarding whether we will need to define a PHY or just a PMD. If we specify a PHY in the objectives, I think it does not preclude reuse of the PCS and PMA (and FEC) defined already in other clauses, nor does it preclude us from defining something new in these upper layers. If that is true, then this form is acceptable because it provides the desired latitude.
If it is not true, then I’d prefer the third option.
Here the PHY terminology is replaced by something more generic that I think could be fulfilled with either a PHY or a PMD project.
I believe the goal in both cases is the same. So to make the optimal selection, a ruling from the leadership of 802.3 on the any differences (between PHY and physical layer) would be helpful.
I think option 1, “Define a 400Gb/s PHY for operation over fewer than 16 pairs of MMF with channel lengths up to at least 100 m” is how we have specified objectives in the past, e.g., see 802.3cd:
“Define 200 Gb/s PHYs for operation over MMF with lengths up to at least 100m”
Steven E. Swanson
Senior Standards Manager
Global Technology & Industry Standards
Corning Optical Communications
800 17th Street NW
Hickory, NC 28603-0489
Standards are a bridge between markets and technologies; whoever controls the bridge controls the future…
Happy New Year!
Please consider several options for the form of objectives that will be produced by the Study Group for “Next-Gen 200 & 400 Gb/s PHYs over fewer MMF pairs than Existing Ethernet Projects & Standards.” These differences arise from 1) different forms of objectives in recent projects plus 2) whether we should choose the number of fiber pairs for a speed in Study Group vs. Task Force. (I only included single-pair and even numbers of fiber pairs, since those are the practical choices.) Historically we have not specified that a specific grade of MMF was required to meet the objective. I show a 400 Gb/s example below, but the options would apply to a 200Gb/s objective as well.
Q. What are the pro’s and con’s of these options? Which do you prefer?
Let us have a healthy discussion in advance of the 1/11 telecon, so we can begin to write down draft objectives.
Robert Lingle, Jr., Ph.D.
Director, OFS Systems & Technology Strategy
2000 Northeast Expy | Norcross, GA 30071