AW: [802.3ae_Serial] Jitter experiments
Hi
I think here you did not correctly understand what has been done. We used a
variety of commercial transponders and measured the jitter tolerance with
sinus jitter at high input power levels. In this case there will be never a
big tail of random errors (if you have random errors under such conditions
something is wrong in contrast to your statement). The sinusoidal
distribution is bounded with the highest probabilities at the edges. So with
error measurements at low error rates counting only view errors the variance
of this process will hide any other small effects, therefore the resulting
values are virtually similar (the sinus distribution will give a very steep
slope).
There of course may be improper designed transponders that may have problems
with internal X-talk also but the modules we used are fulfilling the current
specs for carrier interfaces (we have already selected out the stuff that
does not fulfill the other requirements). The sensitivity of those
transponders in Lab BOL conditions is in range of what is expected, so for
1550 nm better than -16dBm (average power). So this is no failed equipment.
In addition I an a bit surprised a bout your statement as a tolerance of a
receiver of better than 0.4 UI under the said conditions is not bad (in
light of experience from the past) and I personally would question
correctness of the result if they would be much better.
Regards Juergen
----------
Von: Ron Miller [SMTP:rmiller@brocade.com]
Gesendet: Dienstag, 18. Dezember 2001 18:21
An: Rahn, Juergen (Juergen)
Cc: stds-802-3-hssg-serialpmd@ieee.org
Betreff: 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@lucent.com]
Sent: Tuesday, December 18, 2001 6:52 AM
To: 'piers_dawe@agilent.com'
Cc: stds-802-3-hssg-serialpmd@ieee.org
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@agilent.com [SMTP:piers_dawe@agilent.com]
Gesendet: Dienstag, 11. Dezember 2001 17:10
An: Rahn, Juergen (Juergen)
Cc: stds-802-3-hssg-serialpmd@ieee.org
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@lucent.com]
> 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@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
>