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What was being studied in ITU-T SG15 Q6 was whether the two impairments (3 and 4) are adequately covered by the EVMrms metric or alternatively whether they should be compensated for (i.e. removed from) EVMrms metric and controlled via a separate limit for each. The current agreement is not to remove them from EVMrms as there is insufficient evidence that this metric cannot adequately cover them. Obviously, the more impairments that can be covered via a single metric the better as this allows tradeoff between the various impairments.
Hope this helps,
Pete Anslow |
Senior Standards Advisor
Thanks for the clarification. There appear to be four parameters in play.
2. I-Q offset
3. I-Q imbalance
4. quadrature error
To help describe my confusion, I’ll paraphrase and parse the last sentence of the paragraph in question.
A study of parameters 3 and 4 showed sufficient lack of consistency to either:
a) justify their removal from the EVMrms metric, or
b) introduce them as additional metrics.
How can parameters 3 and 4 be included in the EVMrms metric yet not specified as additional metrics? Is this similar to TDECQ which includes a number of impairments, some that are not individually limited?
Thanks for your question for clarification.
First, I wrote this Liaison Statement from my role of Rapporteur (“chairman”) of ITU-T SG15 Q6.
Secondly there is no agreement/consensus in Q6 to use IQ-imbalance and Quadrature Error as additional metrics (beyond EVMrms and IQ offset) for the quality of 100G DP-QPSK transmitters.
At last week’s Q6 interim meeting in Hangzhou, China, the consensus on the provisional agreement from the June meeting was reconfirmed.
Even when it may still pop up again at a future meeting (ITU-T is contribution driven), I would expect the likelihood for adding IQ-imbalance and Quadrate Error as transmitter metrics as rather low, on the basis of the available test results and the discussions on those results.
Peter Stassar, 施笪安
Technical Director, 技术总监
Huawei Technologies Ltd, 华为技术有限公司
European Research Center, 欧洲研究所
Herikerbergweg 36, 1101 CM Amsterdam
Tel: +31 20 4300 832
Mob: +31 6 21146286
thanks for sharing this letter.
As the listed ITU-T contact, I’ll address my question to you. I am seeking clarification of the last sentence of this paragraph.
At the SG15 Plenary Meeting in Geneva, 19 – 30 June 2017, it was provisionally agreed to use EVMRMS (RMS of Error Vector Magnitude), corrected for the effects of I-Q offset, and a separate limit for corrected I-Q offset as metrics for the quality of the transmitter. There was also agreement that the results from testing of I-Q imbalance and Quadrature Error were not sufficiently consistent to justify their removal from the EVMRMS metric or the introduction of these parameters as additional metrics for the quality of the transmitter.
It seems to say that the inconsistency has caused the parameters to neither be accepted nor rejected. Does that mean they remain provisional?
Dear Study Group Participants,
In response to the liaison sent out of the July Plenary, the ITU-T has responded with the following - http://www.ieee802.org/3/minutes/nov17/incoming/ITU_SG15-LS-73_to_IEEE_802d3.pdf
I spoke with our WG Chair, Mr. Law, who has asked our Study Group to consider this liaison at the Nov Plenary.
Chair, IEEE 802.3 Beyond 10km Optical PHYs Study Group