RE: [802.3ae_Serial] From serial PMD call 2 Apr: measurement, preview of a few comments
(See below under "Tom") - actually, I preferred to sample the reference
transmitter only at the eye center, but Stretch suggested the method
allow the same routine to be used for both reference and DUT
measurements. I have structured my comment in a way that I hope allows
both.
I agree with your capture of the rest of that topic.
I originally thought (still do) that muddling signal_detect and
Rx_local_fault was eliminating diagnostic information, but the Logic
track folks didn't seem to care. Good luck.
At the bottom, you mention the need to still sort out the stressed Rx
test. I agree. But equally high should be sorting out the TDP penalty
values and test method.
Thanks, Tom
-----Original Message-----
From: piers_dawe@agilent.com [mailto:piers_dawe@agilent.com]
Sent: Thursday, April 04, 2002 12:11 PM
To: stds-802-3-hssg-serialpmd@ieee.org
Subject: [802.3ae_Serial] From serial PMD call 2 Apr: measurement,
preview of a few comments
Collecting test results; measurement
------------------------------------
Not very surprisingly, Stretch had not received any test results yet but
was
hoping for them very soon: please provide by Thursday 4 April if
possible,
format not critical. A couple of groups had not done as much
experimental
stressed eye generation as they had hoped.
I explained that I believe the effective OMA with a sinusoidal
interferer
present is the total excursion of the waveform; if everything were
linear,
this would be OMA with interferer off, plus pk-pk amplitude of
interferer.
In other words, the interferer raises the OMA and also raises the VECP
by
more than D4.1 says, giving the same inner eye opening as is really
there.
There was a discussion of the effect of the interferer. Petar has found
that ISI from interferer and ISI from filter can be substituted for each
other in the range 50-90% from filter. Meanwhile my colleague has found
unexpectedly large effects from the interferer. I thought that this
would
apply with typical receiver bandwidths.
Stretch found that a filter which generated 1.3 dB VECP with scope
filter
on, measured 0.6 dB with it off - with PRBS7. Others thought low
frequency
effects with longer patterns could affect these figures.
Tom would like 52.9.11.3 to specify measurement of the reference
sensitivity
S in the same way as the DUT sensitivity e.g. +/- 0.05 UI. He also
would
like the definition of "eye center" there clarified - it does not mean
"optimum" or "wherever suits you". I think he was going to propose a
time
midway between the 10^-3 points, which is current good practice.
Specs and other comments
-----------------------
Mike thought the TDP for 10GBASE-S should be 4.3 dB. I wondered if it
had
to be 3.6 dB because that is our limit for ISI and the TDP measurement
doesn't define the cause of the penalty. We went away to think about
it.
I pointed out that in our RIN test (and in our definition of reflection
for
TDP) we had forgotten about reflection noise (10GBASE-L only - we sorted
this out maybe a year ago). Petar mentioned a recent paper on the
subject
in January Photonics Technology Letters.
I would be making some other comments as follows:
Muddling signal detect and receive fault is unhelpful for diagnostics;
Need to have minimum average power limits;
Can now have minimum OMA for 10GBASE-E as we have for 10GBASE-L;
Very wide variability of sinusoidal jitter in Rx test is bad.
With a TDP measurement do we need and SMSR spec?
There was a short discussion of the practical difficulties of
implementing
the transversal filter.
In summary: no significant bad news, some old issues remain, in
particular,
still need to sort out the stressed receiver conformance test. It's
still
worth trying to wrap this up next week in Vancouver.
Present
-------
Piers Dawe Agilent SPG
Petar Pepeljugoski IBM
Stretch Camnitz Agilent T&M
Mike Dudek Cielo
Tom Lindsay Stratos
David Kabal Picolight
Adam Healey Agere
Mike Stout Network Elements
Piers