Re: [10GMMF] Loss of worst case test configuration
past (1985-1997) we applied the 70/70 launch for the specification and test of
all passive multimode products like ESCON connectors. The reason was
that we think the mandrel wrap definition is not good enough in order get
reproducable results: i) it depends on the tensile force when you are
wrapping the fiber, ii) the amount of mode selection depends on the
characteristics of the fiber coating of the individual
think that because of the reason ii) it is very difficult to calculate the modal
power distribution for such a setup, therefore we never tried to do
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.
Richardson, TX 75082
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08/31/2004 02:02 PM
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[10GMMF] Loss of worst case test
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.
out that the loss with the 70/70% launch is somewhat larger than the 23Ám
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.
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
Infineon Technologies Fiber Optics
Dr. Joerg-R. Kropp
Senior Staff Expert
D-13629 Berlin / Germany