Re: Patch cord for 1300 WWDM
Dave,
My goal is NOT to reduce the number of PMDs. My goal is to reduce the cost
and time to market of a very large sector of the PMD deployment. If we are
allowed to get away from the traditional distances, I see P802.3ae as
having a very bi-polar distance deployment. A very large number of short
distance links and a large number of long haul links, with smaller
quantities in between.
Thank you,
Roy Bynum
At 09:06 AM 8/3/00 -0700, Dave Dolfi 3764 wrote:
>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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> > Date: Wed, 02 Aug 2000 23:08:14 -0500
> > 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
> >