# Re: [10GMMF] 62MMF connector loss and draft test link config

```This thread  brings up an interesting question. In the past, we have never
written into the standard any requirements, or even guidance regarding a mix
of 50 and 62.5 micron fiber. Need we now?

jonathan

-----Original Message-----
From: owner-stds-802-3-10gmmf@listserv.ieee.org
[mailto:owner-stds-802-3-10gmmf@listserv.ieee.org]On Behalf Of David
Cunningham
Sent: Friday, August 20, 2004 4:45 AM
To: STDS-802-3-10GMMF@listserv.ieee.org
Subject: Re: [10GMMF] 62MMF connector loss and draft test link config

Paul,

RE: 70/70 launch

In the literature there are many versions of the so called steady state
launch mode power distribution (MPD) or the equilibrium mode power
distribution.  As far as I can ascertain the 70/70 launch method is a simple
method to approximate the steady state mode power distribution condition.
So on that basis I believe the calculations are consistent with the 70/70
launch condition.  But I did not specifically model 70/70 launch.

For your information, from the various forms of steady state MPD equations,
I used the one that was simplest for me to add to my calculation. It is the
(1 - N/Nmax) version of Olshanksy:

Olshanky, R (1975). Applied. Opt. 14: 935-45.

As I said there are others I could have used but with little real difference
in the results.

RE: 7 or 9 um

The range of MPD distributions that could have be used to measure the
installed connectors span the range from OFL to the Steady State.  I agree
that if Steady State is assumed then the offset could be as high as 9 um for
0.5 dB loss.  However, the discussion concluded that 9 um did not appear to
be a believable value to use - it's an awfully big offset even for MMF
connectors.  So, as I recorded we decided to use the value of 7 um.  We also
placed two connectors at the 7 um offset.

The good news is that we done enough work to narrow the range  of offset to
(7 to 9) um.  This is quite a small range of values and hopefully we can
formally adopt a value in that range at the next meeting.

I would suggest that those that have started testing or simulations might be
wise to include both 7 um and 9 um as the maximum offset value.

Regards,
David

-----Original Message-----
From: owner-stds-802-3-10gmmf@listserv.ieee.org
[mailto:owner-stds-802-3-10gmmf@listserv.ieee.org]On Behalf Of Paul Kolesar
Sent: 20 August 2004 04:30
To: STDS-802-3-10GMMF@listserv.ieee.org
Subject: Re: [10GMMF] 62MMF connector loss and draft test link config

David,
thanks for this work.  The model I have for 62.5 agrees with your analysis
the steady state condition represents a 70/70 launch (i.e. 70% of maximum
core diameter and 70% of maximum NA).

I have a comment regarding the 7 um limit. The 7 um value was chosen for the
OM3 work because it represented 0.5 dB for 50 um fiber under steady state
conditions.  The remaining 0.25 dB needed to reach the 0.75 dB limit was
allotted to mechanisms other than lateral offset.  The equivalent offset for
62 um fiber is 9 um from your graph.  Thus connectors need to be of tighter
tolerance for 50 um fiber than for 62 um fiber.  As product lines of cabling
vendors in North America and other parts of the world have shifted to
include a larger mix of 50 um fiber, the tolerance for connectors needed to
be tightened to maintain good performance.  Fortunately progress in
connector technology permitted this.  The result is that over time
connectors have gotten better.  This leads to an interesting issue when
dealing with legacy plant. The older plant likely has poorer connectors due
to both tolerance and wear.  I think this leads to a need for considering
different values for legacy 50 and 62 um plants.  To address these
considerations, I would suggest that the limit for 62 um fiber be set at 9
um and that for 50 set at 7 um.

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

David Cunningham <david_cunningham@AGILENT.COM>
Sent by: owner-stds-802-3-10gmmf@listserv.ieee.org

08/18/2004 02:24 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] 62MMF connector loss and draft test link
config

Dear All,

As promised on todays Fiber Channel Ad Hoc I attach a PDF file containing
the following information:

* My calculated graphs of connector loss versus offset for overfilled
launch, steady state launch and 23 um offset single mode launch.

* The agreed draft of the worst-case test configuration for channel time
variation measurements with comments from our call to document our reasoning
behind the chosen configuration.

Regards,
David

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