Re: [10GMMF] Loss of worst case test configuration

[Paul Kolesar <PKOLESAR@xxxxxxxxxxxx>]

Joerg,
thanks for filling in the missing piece
on 70/70 launch.  I note that the 70/70 launch always produces higher
loss than David's steady state launch for a given transverse offset.  
My steady state loss data agrees most closely with David's calculation,
and is empirically collected using the mode power distribution at the end
of a long fiber of a vintage of at least 10 years ago.   

The differences between the 70/70 and
the other steady state launch conditions lead me to ask you about what
appears to be an inconsistency within fiber measurement standards regarding
launch prescriptions.  The standards where such prescriptions can
be found include TIA 455-50 (FOTP-50) and IEC-60793-1-40 appendix A.  
FOTP-50 defines two launch methods. One is the 70/70 beam optics approach.
 The other is the overfilled launch followed by mandrel wrap.  
These are both described as creating steady state conditions that are roughly
equivalent.  My question to you is whether there exist any means of
analytically determining the mode power distribution caused by a particular
mandrel wrap.    For example, the 62.5 um fiber prescription
is 5 turns around a 20 mm diameter mandrel.  The 50 um prescription
is 5 turns around a 25 mm mandrel.  In other words, is there a way
to calculate the loss of high order mode energy due to a bend in the fiber
and deduce the remaining guided mode power distribution so that one could
plot the loss of a connection as a function of transverse offset?  There
are discussions in IEC 86 that would benefit from this type of information.
 Perhaps some of your colleagues are involved in them.

Regards,
Paul Kolesar
SYSTIMAX® SOLUTIONS
1300 East Lookout Drive 
Richardson, TX 75082 
Phone:  972.792.3155
Fax:      972.792.3111
eMail:   pkolesar@systimax.com

"Joerg-R. Kropp" <Joerg.Kropp@INFINEON.COM> Sent by: owner-stds-802-3-10gmmf@listserv.ieee.org 08/31/2004 02:02 PM Please respond to "IEEE 802.3aq 10GBASE-LRM"

To:        STDS-802-3-10GMMF@listserv.ieee.org         cc:        (bcc: Paul F Kolesar/CommScope)         Subject:        [10GMMF] Loss of worst case test configuration

Hi everyone,
In the discussion for the worst case test configuration there was some
discussion about the loss of connector transverse offsets if the 70/70%
launch condition (which should represent the so called steady state power
distribution) is applied.
I calculated the connector loss vers transverse offset for various launch
conditions including the 70/70% launch.
It turns out that the loss with the 70/70% launch is somewhat larger than
the 23µm offset launch. Therefore the total loss of our worst case test
configuration would be larger than 1,5dB if such 70/70% launch would be
applied.

It is common agreement today to use the defined offset patchcord and I
do not want to change that but I want to share the results for the sake
of completeness because it shows the sensitivity of our selection on the
launch conditions.

Joerg 



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