Question about SAS3_EYEOPENING

Mathieu Gagnon Mathieu.Gagnon at
Tue Feb 26 10:02:03 PST 2013

* From the T10 Reflector (t10 at, posted by:
* Mathieu Gagnon <Mathieu.Gagnon at>
Dear Justin,
The previous version of the script (up to 1.2) was computing only
worst-case eye closure.
This means eye closure that could happen only if thousands of bits had
the exact worst-case condition - i.e., at a very low BER, much below the
target of 1E-15.
These results were usually pessimistic.
The latest version computes an estimation of the closure at a BER 1E-15.
However, it still reports the worst-case closure earlier in the output.
This is why the final Opening - Xtalk is not equal to the above
"Worst-case opening" - "worst-case Xtalk".
I will add a mention of the target BER in the final report to reduce
While verifying the code, I noticed that sometimes the worst-case
computed in v1.2 was however optimistic. I updated the code to compute
this, so in some cases the worst-case is lower. You seem to have a
pretty extreme case, going from 80.7% to 54.1%. Noise correction has
also been improved, and some type of responses could give different
results. In v1.2, noise correction was sometimes too aggressive.
You can look at the cumulative closure plots - any long tail not
flattening out is an indication that the noise correction was not strong
enough, while a curve that flattens out very quickly, together with the
pulse response (also plotted) showing some significant cursors, is an
indication that noise correction was too strong.
I've devoted significant efforts lately to improve these computations,
so hopefully the results will be more consistent.
The closure at a BER of 1E-15 is also less sensitive to these kind of
errors, as the effect of any remaining error does not influence so much
the result when their amplitude is not significant - whereas worst-case
closures integrate these errors without limit.
-----Original Message-----
From: owner-t10 at [mailto:owner-t10 at] On Behalf Of justin
Sent: February-26-13 4:06 AM
To: t10 at
Subject: Question about SAS3_EYEOPENING
* From the T10 Reflector (t10 at, posted by:
* justin <power at>
Dear sir,
I have a question about the simulated result.
For example in case 0;
The previous script got result as below:
Noiseless Eye Opening from fixed CDR = 80.7 %
Crosstalk Eye Closure = 19.3 % (unconstrained pattern)
Min Eye Opening = 61.4 %
Opening-Xtalk = 61.4 %
The newest script got results as below:
Noiseless Eye Opening from fixed CDR = 54.1 %
Crosstalk Eye Closure = 16.4 % (unconstrained pattern)
Worst-Case Eye Opening = 37.7 %
Opening-Xtalk = 48.9 %
How the 48.9 % be calculated?
Thank you~
Uniconn Corp.
127, Jing An Road, Chung Ho City,
Taipei County, Taiwan, R.O.C.
Tel: (02)2948-1518 #26
Fax: (02)2940-5688
Email: power at
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