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Re: [10GMMF] Connector offsets in Worst case model



Joerg,

I think something went wrong in your probability calculation: Let's try to reverse it. If the probability of one connector is having a offset larger than 7 um is 5% then the probability of this connector having less than 7 um offset is 95%. So the probability of 4 connectors all having an offset of 7um or below will be (95%)^4=81%. That is the probability that one or more of the 4 connectors has an offset larger than 7 um is 19%! So there is no reason for reducing the offset in the link calculation when you have more than 1 connector.

If you want the overall probability to be p=5% then for n connectors the probability Px of one or more connectors having an offset larger than x um is
Px=1-(1-p)^1/n giving:

n       Px      x (approx)
----------------------
1       5%      7 um
2       2.5%    7.8 um
3       1.7%    8.1 um
4       1.3%    8.2 um

Off cause this depends on what you consider to be the worst case scenario: one connector with a large offset and the others with less offset or all connectors having approximately the same offset. Perhaps both cases should be included in the calculations!

Best regards,

Jesper Hanberg

Senior Systems Engineer, M. Sc. Physics, Ph.D.
Intel Copenhagen ApS

Mileparken 22
DK2740  Skovlunde

Business:       +45 44 54 61 30
Business 2:     +45 70 10 10 62
Business Fax:   +45 70 10 10 63

E-mail: jesper.hanberg@intel.com

Web Page:       http://www.intel.com


-----Original Message-----
From: owner-stds-802-3-10gmmf@listserv.ieee.org [mailto:owner-stds-802-3-10gmmf@listserv.ieee.org] On Behalf Of <Joerg-R.> <Kropp>
Sent: 9. august 2004 11:38
To: STDS-802-3-10GMMF@listserv.ieee.org
Subject: [10GMMF] Connector offsets in Worst case model

Jonathan and all,
in the conference call I stated that I will give a detailed explaination why we proposed this special set of offsets.
We took the same Rayleigh distribution as it was done for the 10GbE -50Ám multimode simulation (mean value about 3,6Ám and 7Ám offset with a probability of 5%).
For the second offset we used the value which we get for two connectors (with the same offset) with a combined probability of 5%.
For the third offset we used the value which we get for three connectors (with the same offset) with a combined probability of 5%.
And similar for the fourth connector.
See the short presentation encl.
The resulting set of offsets is 7Ám, 5Ám, 4Ám (not 4,5Ám!) and 3,5Ám (not 3,0Ám!) and the overall probability (for exceeding this set of 4 offsets) is p=0,04%, which seems to us as a resonable value for a worst case scenario.
Regards,
Joerg
 <<Connector Scenario for Worst Case proposal 2.ppt>>


Infineon Technologies Fiber Optics GmbH
MOD CE
Dr. Joerg-R. Kropp
Senior Staff Expert
Wernerwerkdamm 16
D-13629 Berlin / Germany
Phone -49-30-85400-4918
Fax     -49-30-85400-4900
Mail     joerg.kropp@infineon.com