Re: AW: 3PMD Proposal
Bernd,
The primary reason that the 1300 4 channel WDM solution works over 300
300 meters of multimode fiber is that each channel is running at only
one fourth of the aggragate baud rate (2.5 Gbd, or 3.125 Gbd if 8B/10B
coding is used). The offset patch cord simply guarantees that, at minimum,
the overfilled launch bandwidth of the fiber (160 Mhz-km or 500 MHz-km on
62.5 or 50 um fiber, respectively) can be obtained for the great majority
of the installed fiber. If you use a 1300 nm serial solution on MMF with
a patch cord you are now running ~ 10 Gbd over fiber whose bandwidth can
only be guaranteed to be 500 MHz-km or less, and you're not going to go
very far (~100 meters or less) before the ISI overwhelms you. The link
model will confirm this. The fact that you found some MMF which happens
to work with 10 Gb serial only illustrates the wide variety of performance
that exists in the MM installed base.
David Dolfi
Agilent Technologies
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> Subject: AW: 3PMD Proposal
> Date: Thu, 15 Jun 2000 12:31:14 +0200
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>
> David,
> "min. overfilled launch" as in the Ottawa presentation from Del may imply the use of a patch cord. At least myself (and maybe others) missed it.
> Anyway, a patch cord is a solution that guarentees greater distance over old fiber and that's good.
> For our 5 distance objectives this could mean that a serial 1300nm solution fulfills them all probably long term at lower cost then a CWDM just by adding a patch cord were necessary.
> In this matter I agree with Ed Cornejo that most (90%+) of the LX GBE applications today work without patch cord. We tested serial 10 Gig on random fiber over 500m without any problem!
>
> Best wishes
>
> Bernd
>
> -----Ursprüngliche Nachricht-----
> Von: david_cunningham@xxxxxxxxxxx [mailto:david_cunningham@xxxxxxxxxxx]
> Gesendet am: Dienstag, 13. Juni 2000 23:45
> An: stds-802-3-hssg@xxxxxxxx
> Betreff: FW: 3PMD Proposal
>
>
>
> -----Original Message-----
> From: CUNNINGHAM,DAVID (A-SanJose,ex1)
> Sent: Tuesday, June 13, 2000 10:27 AM
> To: 'Larry Miller'
> Cc: 'Stds-802-3-Hssg@xxxxxxxx'
> Subject: RE: 3PMD Proposal
>
>
> Larry,
> 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
> there.
>
> 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
> LX links."
>
> 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.
>
> Best wishes,
> David.
>
> -----Original Message-----
> From: Larry Miller [ mailto:ldmiller@xxxxxxxxxxxxxxxxxx
> <mailto:ldmiller@xxxxxxxxxxxxxxxxxx> ]
> Sent: Tuesday, June 13, 2000 6:59 AM
> To: david_cunningham@xxxxxxxxxxx <mailto:david_cunningham@xxxxxxxxxxx> ;
> Bernd.Prediger@xxxxxxxxxxxx; piers_dawe@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
> that.....
>
> Larry Miller
>
> -----Original Message-----
> From: david_cunningham@xxxxxxxxxxx [SMTP:david_cunningham@xxxxxxxxxxx]
> Sent: Monday, June 12, 2000 9:04 PM
> To: Bernd.Prediger@xxxxxxxxxxxx; piers_dawe@xxxxxxxxxxx
> Cc: Stds-802-3-Hssg@xxxxxxxx
> Subject: RE: 3PMD Proposal
>
>
> Bernd,
> 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
> nm WWDM
> proposal 500 MHz.km is the correct modal bandwidth to use for the multimode
> links.
>
> Best wishes,
>
> David.
>
> -----Original Message-----
> From: Bernd.Prediger@xxxxxxxxxxxx [ mailto:Bernd.Prediger@xxxxxxxxxxxx
> <mailto:Bernd.Prediger@xxxxxxxxxxxx> ]
> Sent: Wednesday, June 07, 2000 9:49 AM
> To: piers_dawe@xxxxxxxxxxx
> Cc: Stds-802-3-Hssg@xxxxxxxx
> Subject: 3PMD Proposal
>
>
>
> Hello Piers,
> 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
> (Slide 4).
> 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!)
> Best wishes
> Bernd
>