RE: 3PMD Proposal
as far as I know it has always been stated that the offset launch
patchcord was part of the WWDM proposal, so there should be no surprises
Regarding: "The offset patchcord has been terribly unpopular with us"
For 1 Gigabit Ethernet this may be your and your companies position.
However, it must be remembered that from a technical point of view
1000BASE-LX with the offset launch patchcord is the ONLY way to robustly (in
a worst case sense) go beyond 300 m on installed 160/500 and 200/500
multimode fiber (not the new multimode fiber types with RML specifications).
It is true that 1000BASE-SX links typically go further than 300 m - but this
is by no means guaranteed.
Regarding: "adding so much cost that it nearly doubles the cost of 1 Gb MM
If customers want to use installed links with lengths of up to at least 550m
whilst avoiding the much larger cost of installing new multimode fiber -
then the offset launch patchcord makes very good economic sense. I know
that some equipment suppliers suggest their customers use 1000BASE-LX with
the patchcords for such cases.
Regarding: "Is the Agilent 4X WWDM going to work with SMF? I will be wanting
to know that...."
The WWDM proposal to the IEEE 802.3ae is for a PMD that is capable of
operating on either SMF or MMF - just like 1000BASE-LX does. That it is will
be mandatory that is the WWDM PMD is dual use for SMF and MMF.
From: Larry Miller [ mailto:ldmiller@xxxxxxxxxxxxxxxxxx
Sent: Tuesday, June 13, 2000 6:59 AM
To: david_cunningham@xxxxxxxxxxx <mailto:david_cunningham@xxxxxxxxxxx> ;
Cc: Stds-802-3-Hssg@xxxxxxxx <mailto:Stds-802-3-Hssg@xxxxxxxx>
Subject: RE: 3PMD Proposal
Arghhhh!!! Are we really back to that, David? The offset patchcord has been
terribly unpopular with us, adding so much cost that it nearly doubles the
cost of 1 Gb MM LX links.
Is the Agilent 4X WWDM going to work with SMF? I will be wanting to know
From: david_cunningham@xxxxxxxxxxx [SMTP:david_cunningham@xxxxxxxxxxx]
Sent: Monday, June 12, 2000 9:04 PM
To: Bernd.Prediger@xxxxxxxxxxxx; piers_dawe@xxxxxxxxxxx
Subject: RE: 3PMD Proposal
the offset launch patchcord is assumed for the 1300 nm WWDM case for
10 Gigabit Ethernet. As was documented in IEEE 802.3z 1000BASE-LX the
offset launch patchcord ensures a worst-case minimum bandwidth of 500
MHz.km. For 1300 nm links the inclusion of the offset launch patchcord
obsoleted the 385 Mhz.km modal bandwidth value that was present in some
older drafts of the 1000BASE-LX clause.
In conclusion, since the offset launch patchcord is part of the 1300
proposal 500 MHz.km is the correct modal bandwidth to use for the multimode
From: Bernd.Prediger@xxxxxxxxxxxx [ mailto:Bernd.Prediger@xxxxxxxxxxxx
Sent: Wednesday, June 07, 2000 9:49 AM
Subject: 3PMD Proposal
I just got through Del's presentation from Ottawa again and stumpled over
your calculation for the "Minimum Range" of CWDM over installed MM-Fiber
You calculated 2-300m for all 500MHz*km fiber but I understood that since
Gigabit Ethernet the worst case effective bandwidth everbody agreed on is
375MHz*km. Our calculation with the latter value let to about 180m.
What am I missing here? (Of course we used your spreadsheet!)