AW: [802.3ae_Serial] Jitter experiments
Hi,
we have continued the measurements measuring the tolerance for other error
rates. What we found under the conditions already used was that the limits
where nearly identical as for 10 to -10- This confirms the errors we
measured were related nearly complete to the SJ of a bit above 0.4 UI (there
was no significant random component visible) . This confirms for me that
looking purely on the horizontal component this determines the limits of
the CDR under nominal conditions.
It should be noted that this is a typical Lab environment test with few
different modules, BOL room temperature typical. I am sure some margin is
required to account for extreme temp drift, aging drift, and supply voltage
tolerance. This all is not specified by the third party modules we used in
this particular measurements.
We are now trying to measure what this would mean in terms of penalty to
estimate what would be possible under real conditions.
Regards Juergen.
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Von: Rahn, Juergen (Juergen)
Gesendet: Montag, 3. Dezember 2001 18:18
An: 802. 3ae Serial PMD (E-mail)
Betreff: AW: [802.3ae_Serial] Jitter experiments
Hi all,
Sorry for not being able to participate on the last call (I have a
conflict
tomorrow too). However I want to give some interim info about tests
on
jitter we did. We used a SDH test set for jitter based on the ITU
definitions. So we measured the broadband jitter generation and
tolerance
in the frequency domain between 4 and 80Mhz. However as concerning
the
tolerance it is not likely that a system is more tolerant to jitter
at
frequencies even higher above the PLL border the results may give
some
understanding of the underlying principles.
We used commercial transponders as available on the market. We
measured the
generation and tolerance w/o fiber to be free of influences of fiber
effects
(Which may be traded off in the future) (TP2=TP3). The Jitter
generation of
random jitter of the Transponder was at the measurement limit and
smaller
than the jitter comming out of the Test set. (Which gives me the
understanding that all this was clock jitter that will be further
reduced by
the PLL an the parallel stream. There was no visible DJ on the scope
of the
transmitted signal. Under these conditions we observed a tolerance
for a BER
of about 10 to -10 of a bit above 0.4 UI P-P sinus jitter, which was
nearly
equal to total jitter as stated before, nearly constant for
frequencies
above PLL border frequency. We will repeat those tests for other
error rates
to get an understanding how the theoretical bathtub may look like
(as we
used commercial modules we have no way to shift the sampling point
through
the eye) and get an understanding about the penalty induced by which
jitter
amplitude. It should be noted that the penalty in the measurement we
did was
real big, and so I do not believe at al that if we have at 0.4 UI
P-P (of
whatever waveform the jitter follows) a penalty that eats up a big
part of
the budget we see the nominal sensitivity at 0.35 UI. (So this
somewhat
confirms the measurements from Intel) I will come up with more
dedicated
results.
Regards Juergen
----------
Von: Lindsay, Tom [SMTP:tlindsay@stratoslightwave.com]
Gesendet: Samstag, 1. Dezember 2001 01:21
An: 802. 3ae Serial PMD (E-mail)
Betreff: [802.3ae_Serial] Jitter experiments
This email is in response to my committment on the 11/27/01
serial
PMD con-call. This is still very crude, and I apologize for lack of
appropriate thought, but hopefully it can stimulate more discussion.
****
A major concern for 10G serial is instrumentation error for
doing
jitter measurements. Steve's Buchheit's work clearly demonstrates
this.
Ideally, instrumentation will improve sufficiently to allay this
concern,
but none of us expect that to occur sufficiently in advance of
deployment.
So if we are to keep the basic definition and method for jitter
measurement,
then we require agreed upon means to compensate the instrumentation.
With this in mind, I simply brainstormed 5 categories of
test
settings and measurements, with the hopes (dreams?) that differences
in
their results can provide insight into how compensation can be
achieved.
1. Measuring instruments
Scope - eye patterns w/ crossing histograms
Error detector - jitter bathtub
2. Configurations (essentially the same used by Steve)
Pattern generator to measuring instrument
Pattern generator through E/O and O/E to measuring
instrument
Pattern generator through stress conditioning and E/O and
O/E to
measuring instrument
Pattern generator through DUT and O/E to measuring
instrument
3. Test patterns
Pattern 1
Pattern 2
PRBS31
00 00 00 00 00 00 00 03 FF FF FF FF FF FF FF FD (isolated
1,
isolated 0)
Repeating CC (square wave with 50% transition density,
same as
average PRBS)
4. Signal variations
rise/fall time (at least 2 levels of slow/fast)
amplitude (at least 2 levels of low/high)
5. Stress conditioning mechanisms
high frequency ISI/DDJ
low frequency BLW/DDJ
At this point, I do not know if there is a path through this
that
will lead anywhere (this is the apology again...). I hope someone
else can
determine if there is really any value in here. The 5-dimensional
matrix
results in a large number of test combinations - too many. A Design
of
Experiments may be required to reduce the set. Obviously more
directed
experiments can be defined with some risk of missing key
information.
Tom Lindsay
Stratos Lightwave, NW design center
425/672-8035 x105