RE: [802.3ae_Serial] Jitter experiments
HI Jurgen
Thanks for the data.
Noticing that the total jitter/noise effects is causing BER of about 10e-10
in nearly all cases, it is highly likely that you have a noisy board. That
is,
since the sinusoidal jitter is also at 10e-10 you are getting cross coupling
from other sources. The usual suspects are power supply transients,
interference
from other busses and signals on board, and finally ground loops in your
measurement
setup that couple external noise in.
The sources may be found by using a spectrum analyzer with a small chip cap
in series
with the probe point. I usually just solder a chip cap of about 100 pf to
the center
conductor of a coax and probe the board with the capacitor itself. Once the
frequency of the dominanant interference sources are identified, analysis of
the possible interfering
sources including harmonics should reveal the problems.
Until you get the sinusoidal jitter(cross coupling) eliminated you will
never see the
effects of the other jitter components.
Gruss gut & good hunting.
Ron miller
-----Original Message-----
From: Rahn, Juergen (Juergen) [mailto:krahn@xxxxxxxxxx]
Sent: Tuesday, December 18, 2001 6:52 AM
To: 'piers_dawe@xxxxxxxxxxx'
Cc: stds-802-3-hssg-serialpmd@xxxxxxxx
Subject: AW: [802.3ae_Serial] Jitter experiments
Hi Piers ,
Unfortunately I may be miss the call today, at least it is likely I am late.
I do not have measurements about actual penalties yet, however we confirmed
the resulting SJ tolerance values for other transponders.
As soon as I have the penalties (sensitivities under different amount of
jitter I will communicate them)
Regards Juergen
----------
Von: piers_dawe@xxxxxxxxxxx [SMTP:piers_dawe@xxxxxxxxxxx]
Gesendet: Dienstag, 11. Dezember 2001 17:10
An: Rahn, Juergen (Juergen)
Cc: stds-802-3-hssg-serialpmd@xxxxxxxx
Betreff: RE: [802.3ae_Serial] Jitter experiments
Juergen,
Thank you, that's valuable information.
Was the optical power near to the receiver sensitivity (with the
sinusoidal
jitter turned off) or well above it?
Piers
> -----Original Message-----
> From: Rahn, Juergen (Juergen) [mailto:krahn@xxxxxxxxxx]
> Sent: 11 December 2001 15:47
> To: 802. 3ae Serial PMD (E-mail)
> Subject: 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.
>
> ----------
> 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@xxxxxxxxxxxxxxxxxxxx]
> 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
>