Re: [10GMMF] AW: [10GMMF] Connector offsets in Worst case model
Jens,
No, I mean that as links become increasingly difficult to make work, it is
essential to understand the characteristics of the components of those links
in greater detail. This is the natural time progression of optical science,
no?
One of the places where there is little to no data in on the actual
distributions of offset. From a distance, I cannot tell the degree of
sensitivity of the model to this parameter and make any kind of reasonable
engineering judgment about risk. In the past, I decided to let it rest,
knowing that we had sufficient fat in the model to make the risk minimal. As
best as I can tell, this decision has been justified (but, I may well not be
aware of the data that would indicate otherwise).
The committee is going to have to decide if this remains the case.
I would think that it would be fairly simple to set up a bench and grab a
random sample of cables and make 20 to 40 measurements. If a couple of
companies/labs did this with a couple of different suppliers, you would have
in a couple of days sufficient information to know if a more extensive
survey is required and also be able to bound the impact of the problem, if
there is one. It would be important to include samples from known, low-tech
"chop shops."
Consistent with statements made earlier, I believe that a large percentage
of cable infrastructures have more than two connectors.
One thing that everyone needs to be clear on is which connectors are being
counted. At times, discussions have presumed to exclude the connectors on
the PMDs. At times, these are included. This is ultimately a discussion of
what the model is intended to include and how does this relate to the
specifications at TP2 and TP3 (which usually includes a discussion about
what TP2 and TP3 really mean/are). I don't know if you have had these
discussions yet with regard to this specific issue.
jonathan
> -----Original Message-----
> From: owner-stds-802-3-10gmmf@listserv.ieee.org
> [mailto:owner-stds-802-3-10gmmf@listserv.ieee.org]On Behalf Of
> Jens.Fiedler@INFINEON.COM
> Sent: Wednesday, August 11, 2004 6:33 AM
> To: STDS-802-3-10GMMF@listserv.ieee.org
> Subject: [10GMMF] AW: [10GMMF] Connector offsets in Worst case model
>
>
> Jonathan,
> Do you mean we should therefore use 2 connectors with each 6µ
> offset as the worst case model?
> Jens Fiedler
>
> -----Ursprüngliche Nachricht-----
> Von: owner-stds-802-3-10gmmf@listserv.ieee.org
> [mailto:owner-stds-802-3-10gmmf@listserv.ieee.org] Im Auftrag
> von Jonathan King
> Gesendet: Mittwoch, 11. August 2004 05:58
> An: STDS-802-3-10GMMF@listserv.ieee.org
> Betreff: Re: [10GMMF] Connector offsets in Worst case model
>
>
> Following the e-mail threads on connector I think I conclude that
> - Jonathan Thatchers observations: imply that connector
> offset is truncated beyond spec (i.e. Raleigh stats won't be
> realistic, so they shouldn't drive a standard link model ?)
> - David Cunningham: Gigabit Ethernet specs a max 0.75dB OFL
> loss per connector, and 0.75dB OFL loss = 6 micron offset.
> Together, these would suggest that we should not consider
> more than 6 micron offset for any individual connector -
> since it would be much less likely to occur in real life and
> also be out of spec.
>
>
> jonathan king
>
> tel: 1 408 524 5110
> e-mail: jking@bigbearnetworks.com
>
>
>
>
>
> -----Original Message-----
> From: Jonathan Thatcher [mailto:jonathan.thatcher@IEEE.ORG]
> Sent: Monday, August 09, 2004 10:16 AM
> To: STDS-802-3-10GMMF@listserv.ieee.org
> Subject: Re: [10GMMF] Connector offsets in Worst case model
>
> It will be important for you to decide on the importance of
> the precision of this data. During 10 Gig, we had a
> discussion about the relative error implicit in this model.
> It was deemed to be sufficiently close as to not require
> additional work.
>
> More specifically, during 10G, I did an informal survey of
> two cable manufacturers to see what their process was for
> "connectorizing" cables. The basic process was that an
> operator "dialed in" the offset until it met specification. A
> variant of the process was that the operator only corrected
> when the offset was out of specification.
>
> Both cases yield manufactured offsets which were not standard
> distributions, the distributions where strongly skewed
> towards the specified limit. If you think about it, in the
> second case, the distribution would have been close to a
> standard distribution if the number of corrections was small.
> In fact, the number of corrections approached 40%, meaning
> that without correction only 60% met specification. You get the idea.
>
> In these informal surveys, I did not take data, as I promised
> to not interfere with the manufacturing flow; I simply
> watched the method.
>
> If this is critical to the modeling you are doing, it is
> probably the case that you need a more rigorous survey and statistics.
>
> jonathan
>
> > -----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: Monday, August 09, 2004 2:38 AM
> > 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 -50µm
> > multimode simulation (mean value about 3,6µm and 7µm 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 7µm, 5µm, 4µm (not 4,5µm!)
> > and 3,5µm (not 3,0µm!) 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
> >
> >
> >
> >
>