Re: AW: Patch cord for 1300 WWDM
Daer Carsten,
I don't believe I've mixed up anything. The 300 link lengths achievable
by 1300 nm WWDM on the installed base are based on the assumption of
a 500 MHz-km OFL fiber modal bandwidth. The work in Gb Ethernet verified
that, for edge emitting lasers such as FP or DFB's, this bandwidth
could be achieved at 1300 nm on both 62.5 and 50 um MMF, including
fiber with poor DMD, provided an offset patch cord was used. If you
therefore assume this modal bandwidth and use the spreadsheet, you
can convince yourself that 300 meters is achievable at 3.125 Gbd. Del
Hanson and David Cunningham have shown tables for 1300 WWDM based on
these calculations at several of the meetings. These same results
included numbers indicating the single mode 10 km link length, where
modal bandwidth is no longer an issue, attenuation being the primary
mechanism limiting the link length.
As regards the new enhanced BW fiber, Paul Kolesar's presentation
at the July 99 meeting in Montreal described the new fiber as having
a 500 MHz/km bandwidth at 1300 nm with either an OFL or restricted
("laser") launch. As far as I know, that's still the spec of the new
fiber at 1300 nm.
Dave Dolfi
Agilent Technologies
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> Subject: AW: Patch cord for 1300 WWDM
> Date: Thu, 3 Aug 2000 19:13:13 +0200
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>
> Nice but just temporary success.....
> The discussion just gets very unprecise.
> Dave, can you explain in more detail your calculations ?
> I believe you mixed up launch conditions and bandwith assumptions, maybe even
single mode and multimode, standard MMF and new MMF. I´m concerned about your
bandwith assumption for new MMF at 1300nm. Can somebody else confirm the
500MHzkm OFL bandwith for new MMF at 1300nm ?
> A matrix would be helpfull.
>
> Carsten Schwantes
> Infineon Technologies
>
> -----Ursprüngliche Nachricht-----
> Von: Dave Dolfi 3764 [mailto:dolfi@xxxxxxxxxxxxxxxxxxxxxxxx]
> Gesendet am: Donnerstag, 3. August 2000 18:06
> An: stds-802-3-hssg@xxxxxxxx; rabynum@xxxxxxxxxxxxxx
> Cc: dave_dolfi@xxxxxxxxxxx
> Betreff: Re: Patch cord for 1300 WWDM
>
>
> Roy,
>
> I could just as easily argue that, since 1300 nm WWDM satisfies
> 300 meters on both 62.5 and 50 um installed MMF (which NONE of the
> other PMDs can do), 300 meters on the enhanced BW MMF, and in
> addition satisfies 10 km on SMF, why not drop all the 850 PMDs
> and drop 1300 nm serial as well? If your goal is to minimize
> PMD choices, this would be more efficient than what you suggest.
>
> Dave Dolfi
> Agilent Technologies
>
>
>
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> > To: David W Dolfi <dolfi@xxxxxxxxxxxxxxxxxxxxxx>, stds-802-3-hssg@xxxxxxxx
> > From: Roy Bynum <rabynum@xxxxxxxxxxxxxx>
> > Subject: Re: Patch cord for 1300 WWDM
> > Cc: dave_dolfi@xxxxxxxxxxx
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> >
> >
> > David,
> >
> > From your last paragraph, am I to understand that 850nm CWDM will meet the
> > objective of 100m over installed 62.5u MMF and the 300m objective over
> > (implied) new MMF. With 850nm VCSEL technology is already available for
> > the 850nm CWDM, why do we need the 1300nm WWDM? The SMF objectives are
> > already addressed by the 1300nm 10km and 1500nm 40km PMDs. If the TF wants
> > to trim PMDs, drop the 1300 WWDM PMD.
> >
> > Thank you,
> > Roy Bynum
> >
> > At 02:11 PM 8/2/00 -0700, David W Dolfi wrote:
> >
> >
> > >Everyone,
> > >
> > >
> > >There seems to have been some confusion at the La Jolla
> > >meeting over the necessity for an offset patch cord for
> > >1300 nm WWDM. Because of this, and additional comments
> > >made on the reflector since the meeting, I am writing
> > >this email to clarify the situation.
> > >
> > >Fact 1. An offset patch cord is NOT required for 1300 nm
> > >WWDM in order to meet the current MMF objectives of 802.3ae.
> > >That is to say, it is NOT required in order to achieve a 100
> > >meter link length on the installed base (this includes both
> > >62.5 and 50 um standard MMF, which both have a 500 MHz-km OFL
> > >bandwidth length product at 1300 nm), NOR is it requred to
> > >achieve a 300 meter link length on the new enhanced BW
> > >MMF, which also has a 500 MHz-km OFL bandwidth at 1300 nm.
> > >
> > >Needless to say (but I will for the sake of completeness)
> > >1300 nm WWDM also supports single mode fiber up to 10 km,
> > >again without a patch cord.
> > >
> > >
> > >Fact 2. The ONLY time you need to use a patch cord with
> > >1300 nm WWDM is if:
> > >
> > >1. You want to extend the link length of the MMF installed base
> > >to 300 meters
> > >
> > >AND IN ADDITION TO THIS
> > >
> > >2. The fiber in question is "DMD challenged".
> > >
> > >
> > >Please note that if you are in this particular situation, none
> > >of the 850 nm based PMDs will satisfy your need, patch cord or
> > >not (but see Note below). Your only alternative in this situation,
> > >with an 850 nm PMD, is to install new fiber, either the enhanced BW
> > >multimode fiber or single mode fiber. Therefore, the notion that
> > >the patch cord is some sort of "penalty" you pay for using 1300 nm
> > >WWDM is really the wrong way to think about it. Rather than a
> > >shortcoming, it is actually a benefit, since it gives you the (rel-
> > >atively speaking) low cost option of using a patch cord in a sit-
> > >uation where your only other alternative is to pull new fiber.
> > >
> > >Note: The 850 nm 4 channel CWDM PMD will allow you a 300 meter link
> > >length, without a patch cord, on the installed base of 50 um fiber
> > >ONLY. However, this is a small benefit, since the great majority
> > >of the MMF installed base is 62.5 um fiber, on which 850 nm CWDM
> > >will only support a 100 meter link length (due to the fact that
> > >62.5 um fiber has an OFL bandwidth length product of only 160
> > >MHz-km at 850 nm).
> > >
> > >
> > >David Dolfi
> > >Agilent Technologies
> >