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Dear Colleagues, I have received several comments that presented data tables make it difficult to understand the analysis, and suggestions were made to use graphs. As the saying goes, a picture is worth a thousand words. Therefore
I plotted the 400GBASE-ER8 RX Sens OMA (max) data and analysis from Tables 4, 5 and 6 (see previous email below), in the enclosed Data 2018 graph. (Please hold off looking at the Data 2018-19 graph until later in this email.) I ran out of time to do the same
for TX OMA (max). The 802.3cn Editor responses to the proposed Public Comment changes to increase Optical Margin and Yield of the Draft D3.0 Specifications have now been published on-line: http://www.ieee802.org/3/cn/comments/P802d3cn_D3p0_public_comments_prop_Cl.pdf All comments are suggested Reject and all use similar justification. Let’s look in detail at the Editor’s justification for rejecting one of the comments which proposed changing the critical RX Sens OMA (max) specification to improve the 400GBASE-ER8 receiver yield
from 2% to 100%. The data used in cole_3cn_01_190924.pdf on optical power levels comes from presentations to the IEEE 802.3 Beyond 10km Optical PHYs Study Group prior to the
adoption of the optical budget in the baseline for 400GBASE-ER8 in November 2018 (which is the same budget as in the latest P802.3cn draft) with vote Y:63, N:0, A:7. The devices reported in these presentations could not have been optimized for the 400GBASE-ER8
application that had yet to be defined. It is therefore not valid to try to assess manufacturing yield from these reported results. The source for the data used in the analysis supporting the change, is
all the data presented throughout 2018 in Beyond 10km Study Group, and then referenced in support of the Nov. 2018 400GBASE-ER8 baseline specification proposal chang_3cn_01b_1118.pdf.
The RX Sens OMA (max) spec in that proposal, -16.1dBm,
chang_3cn_01b_1118, is exactly the same value as it is today in the published Draft 3.0. The Editor response dismisses all of this data. This may be wise, since the data shows that the specification can not be met at a reasonable cost (2% yield). Since all 2018 data has now been invalidated, let’s look at what devices “optimized for the 400GBASE-ER8 application”
look like. The only additional data presented in 802.3cn was
chang_3cn_01a_0319, in Mar. 2019. Analysis of the data shows that the average of two devices RX Sens OMA (max) is worse by 0.5dB than the average of the 2018 data. The result of combining the 2019 data with the 2018 data is shown in the enclosed Data 2018-19
graph. The Optical Margin is degraded by 0.2dB and the yield is reduced by 10x, from 2% to 0.2%.
In a previously sent email, the major Network Operators (China Mobile, Chine Telecom,
Deutsche Telekom, Verizon, ATT and NTT) clearly stated that cost of Optical PMDs is critical. It is not a good reflection on our process that their requirements are ignored. Another change proposed in the submitted Public Comments was to use “R1” instead of “R” for single lane PMDs, specifically 50GBASE-ER1 (not 50GBASE-ER). The Editor suggests Reject, and justifies this by correctly
pointing out that IEEE 802.3 has not previously used “R1” for single lane optical PMDs. But that is exactly the reason all the major Cloud Data Center Operators (Alibaba, Amazon, Apple, Facebook, Google, Microsoft, and Tencent) requested of 802.3 that nomenclature
be changed from past practice of generic “R” to explicit “R1”;
cole_3cu_01a_0719. This pattern of disregarding End User requirements is troubling.
Chris From: Chris Cole Dear Colleagues, At ECOC 2019, I received several clarifications from contributors about their TF data sets. I have accordingly updated the Margin and Yield analysis Tables newly numbered 4, 5, 6, and 7, see below. The changes are only a few tenths of a
dB from previous analysis. Also added are new Tables 1, 2, and 3 for ER8, ER4, and ER1, respectively, comparing the Optical Margins between all the TF contributed data sets. Since Jan. 2018, every data set shows the same thing:
TF contributors recognized that to meet the 40km ER8 reach requirement with sufficient manufacturing margin requires technologies. For example,
Shuto Yamamoto identified stronger FEC and
Xinyuan Wang identified enhanced EML, enhanced APD, and enhanced FEC. There may be others. When applied to ER8, these will fundamentally alter the spec, in unknown combination of TX OMA (min), RX Sens (max), penalties, and other changes. It is very unlikely
that the new technologies will optimally match the 40km ER8 spec. baseline in Draft 3.0.
The TF choice is simple:
Adopting a 40km spec. not manufacturable with today’s technology does not serve anyone’s interests. Chris
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Attachment:
Data 2018.jpg
Description: Data 2018.jpg
Attachment:
Data 2018-19.jpg
Description: Data 2018-19.jpg
