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Thanks to both of you for the draft standard; it appears that the draft is in really good shape for D0.1. I reviewed both Clauses and just have a couple comments for consideration on the call tomorrow.
My rationale is as follows: Clause 138.1 states “The
PMD sublayers provide point-to-point 50, 100, and 200, and 400 Gigabit Ethernet links over one, two, or four, or eight pairs of multimode fiber, with a reach of up to at least 100 m.”
Clause 200.1 states “The PMD sublayers provide point-to-point 400 Gigabit Ethernet links over
four pairs of multimode fiber, with a reach of up to at least 150 m.” This leads the reader to believe that 400GBASE-SR4.2 is “more capable” than 400GBASE-SR8 (because it can support a longer link length) but it is not clear why this is the case and some clarification
may be helpful. When we developed 40GBASE-SR4, Clause 86.1 stated The 40GBASE-SR4 and 100GBASE-SR10 PMD sublayers
provide point-to-point 40 Gb/s and 100 Gb/s Ethernet links over four or ten pairs of multimode fiber, up to at least 100 m.” even though OM4 was specified to support 150m. Both Clauses note that “A PMD that exceeds the operating range requirement while meeting all other optical specifications is considered compliant” so my
preferred remedy is just to change 200.1 to read “The PMD sublayers provide point-to-point 400 Gigabit Ethernet links over four pairs of multimode fiber, with a reach of up to at least 100 m.” This supports the objective that we defined for the 4-pair 400G
solution: “ Define a physical layer specification that supports 400 Gb/s operation over 4 pairs of MMF with lengths up to at least 100m.” A review of the transmit specifications in Tables 138-8 and 200-7 shows identical transmit specifications with the exception of the wavelength range but
this alone does not explain the difference. A review of Table 200-9 provides some explanation to readers skilled in the understanding of the fiber differences in that OM5 has higher effective modal
bandwidth at 918nm than OM4 and therefore should be capable of supporting longer link lengths at 918nm. However, Table 200-9 also shows that the effective modal bandwidth at 850nm is identical for both OM4 and OM5. So it is understood how 400GSR4.2 can support
longer link lengths at 918nm but it is not clear why 400GBASE-SR4.2 can support longer link lengths at 850nm than 400GBASE-SR8 on OM4 and OM5. Stated differently, if we can support 400GBASE-SR4.2 to 150m at 850nm on OM5, why can we not support 400GBASE-SR8
to 150m at 850nm on OM4 and OM5? I am open to any suggestions from the task force on how to make this clearer to the reader of the standard but I think we should make it clearer than it
is currently.
Thanks in advance for consideration of these two comments, Steve Steven E. Swanson Senior Standards Manager Distinguished Associate Global Technology & Industry Standards MT&E Corning Optical Communications 800 17th Street NW Hickory, NC 28603-0489 t
828-901-5328 t
607-974-5757 m 607-725-1129 swansonse@xxxxxxxxxxx Standards are a bridge between markets and technologies; whoever controls the bridge controls the future… From: Jonathan King [mailto:jonathan.king@xxxxxxxxxxx]
Dear all, The initial version of 802.3cm D0.1 has been posted on the 802.3cm private area, for your review. http://www.ieee802.org/3/cm/private/8023cm_D0p1.pdf Not much attention has been paid to PICS so far, and changes to clause 1 and 45 are untouched. I’d ask that comments focus primarily on the changes described in clause 138 and the new clause 200. You could mark up the pdf directly, or e-mail comments are OK too, whichever suits you best. My rough plan is that Jonathan and I will implement any non-controversial editorial comments against D0.1, and any comments which are not obviously uncontroversial can be part of the review and resolution discussion at the next ad hoc
on August 30th. We will post a revised draft, D0.2, soon after the August 30th ad hoc, and ask for further review and comments for Task Force discussion at the Spokane meeting. If you can’t remember the username and password for the 802.3cm private area, e-mail Mabud. If you’re unable to download the pdf, let me know and I’ll send a copy by e-mail. Best wishes Jonathan
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