RE: Patch cord for 1300 WWDM
Eric,
I need to clarify a couple of points that you made which are somewhat
misleading:
1. "There is never a patch-cord required for 850 CWDM" You state this as
if it is an advantage with respect to 1300-nm WWDM!!
To meet the 802.3ae objectives as stated, there is no patch cord required
for 1300-nm WWDM either. This was the point of Dave's original e-mail. The
only time you need a patch cord is if you want to achieve 300-m on
DMD-challenged 62.5-micron fiber, something which is completely impossible
using 850 CWDM.
2. "... the 1300nm lasers and multiplexer have a higher cost than those
required for 850nm CWDM" Yes, the 1300-nm edge emitters are somewhat higher
cost than 850-nm VCSELs, but the multiplexer we use for 1300-nm WWDM is not
any more expensive than that used for 850-nm CWDM. In fact it is less
expensive.
I will be personally very surprised if the cost differential between 850-nm
CWDM and 1300-nm WWDM is anywhere close to some of the estimates that I have
seen presented by many 850-nm advocates on this reflector and at the
meetings. 1300-nm WWDM is a low-cost solution which will satisfy ALL the
multimode and single-mode objectives, from 100m up to 10km, including
support for 300m over the installed base of 62.5-micron fiber.
Brian Lemoff
***********************************************************************
Brian E. Lemoff, Ph.D.
Project Manager
LAN/MAN Optical Technologies
Agilent Laboratories
3500 Deer Creek Rd., MS 26M-9
Palo Alto, CA 94304-1392
phone: (650) 485-8957
FAX: (650) 485-3626
email: brian_lemoff@xxxxxxxxxxx
***********************************************************************
> -----Original Message-----
> From: Eric Grann [mailto:grann@xxxxxxxxxxx]
> Sent: Friday, August 04, 2000 2:20 PM
> To: stds-802-3-hssg@xxxxxxxx
> Subject: RE: Patch cord for 1300 WWDM
>
>
>
> Dave,
>
> I would like to make it clear that 850nm CWDM does not
> require any special
> launches to achieve the 100m (installed) and the 300m (MMF)
> objectives. Per
> Paul Kolesar's previous email, an overfilled launch on new
> multi-mode fiber
> results in a minimum bandwidth of 500MHz.km, which equates to
> 300m for 850nm
> CWDM. Installed 50 micron fiber also has a minimum bandwidth
> of 500MHz.km,
> which equates to 300m for 850nm CWDM.
>
> As you indicated, 850nm CWDM has a lower cost than the 1300nm
> WWDM. In
> addition to the tolerance differences you mentioned, the
> 1300nm lasers and
> multiplexer have a higher cost than those required for 850nm
> CWDM. Lastly,
> there is never a patch cord required for 850nm CWDM.
>
> In summary, 850nm CWDM is a multi-mode optimized solution for
> the 100m and
> 300m objectives.
>
> Eric Grann
> Blaze Network Products
>
>
> -----Original Message-----
> From: owner-stds-802-3-hssg@xxxxxxxx
> [mailto:owner-stds-802-3-hssg@xxxxxxxx]On Behalf Of Dave Dolfi 3764
> Sent: Friday, August 04, 2000 12:21 PM
> To: stds-802-3-hssg@xxxxxxxx; pkolesar@xxxxxxxxxx
> Cc: dave_dolfi@xxxxxxxxxxx
> Subject: RE: Patch cord for 1300 WWDM
>
>
>
> Dear Paul,
>
> I had a feeling I'd hear from you on this, and you didn't disappoint
> me! Thank you for your detailed response. You seem to be saying
> two things. First, you describe what is basically a doughnut shaped
> launch which will both satisfy the launch requirement for the
> new fiber
> to achieve greater than its OFL bandwidth, and at the same time,
> guarantee that the OFL bandwidth is achieved on the installed base
> of 62.5 um MMF. However, you also seem to be saying that it doesn't
> matter anyway, since ANY launch will achieve the OFL bandwidth on the
> 62.5 um installed base. (I assume that you are only referring to SX,
> since if it were true for LX as well we wouldn't need patch cords).
>
> With respect to your first statement, I would reply that the launch
> you describe can certainly be classified as a "conditioned" launch.
> I don't think it could easily be achieved with multiple sources,
> at least not with the kind of simple multiplexers which have been
> proposed by companies such as Blaze and Agilent. I also question
> whether the tolerances required by such a launch would allow the
> loose, multimode type tolerances which the 850 nm CWDM advocates have
> claimed for this PMD, and which form the basis of their claim of
> lower cost relative to 1300 nm WWDM. If this launch is really
> necessary for 850 nm CWDM to work, then these questions need to
> be addressed.
>
> With respect to your second statement, I would refer you to the work
> that was done by Agilent (HP at the time) during the DMD studies of
> 802.3z, particularly the presentation to 802.3z by Lewis Aronson at
> the March, 1998 meeting of 802.3z (available at the following URL:
> http://grouper.ieee.org/groups/802/3/z/public/presentations/).
> There are measurements presented there on both 62.5 um and 50 um
> MMF at short wavelength. I'm not in a position to challenge your
> assertion regarding the absence of launch restrictions at short
> wavelength (you're the expert here!) but I would appreciate it if
> you look over this paper and verify that the results presented are
> consistent with your statement.
>
>
> Dave Dolfi
> Agilent Technologies
>
>
> > From owner-stds-802-3-hssg@xxxxxxxx Fri Aug 4 09:14:56 PDT 2000
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> > From: "Kolesar, Paul F (Paul)" <pkolesar@xxxxxxxxxx>
> > To: stds-802-3-hssg@xxxxxxxx
> > Subject: RE: Patch cord for 1300 WWDM
> > Date: Fri, 4 Aug 2000 11:42:30 -0400
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> >
> >
> > Dave Dolfi,
> >
> > I would like to address your concerns over launch conditions.
> >
> > The launch requirement for the new 50 um fiber is presently
> specified as
> >=
> > 85% encircled flux within a 16 um radius of the center of
> the fiber. This
> is
> > not much different than the launch requirement determined
> to be optimal
> for
> > enhanced 62.5 um fiber which is <= 25% encircled flux
> within 4.5 um radius
> > and >= 75% within 15 um radius of the center of the fiber. The main
> > difference is that the 62.5 um spec limits the amount of
> power allowed in
> > the very center of the fiber (within 4.5 um radius) while
> the 50 um spec
> has
> > no such limitation. But, the similarity of the outer radii
> specification
> > (85% within 16 um vs 75% within 15 um) permits solutions
> that meet both
> > requirements simultaneously. In short, the overall power
> concentration in
> > the center of the 50 um fiber is not required to be much
> different than
> that
> > for enhanced 62.5 fiber.
> >
> > Further, the TIA FO2.2 data indicates launches that meet the above
> > requirements for enhanced 62.5 um fibers do not cause
> degradation of the
> > bandwidth below the OFL specification on installed-base
> 62.5 um fibers. In
> > fact, such launches usually cause bandwidth enhancement. By
> combining
> these
> > launches with 62.5 um fibers tested and determined to produce higher
> > restricted launch bandwidth, we can guarantee enhanced performance.
> Perhaps
> > even more to the point, the data collected by both the TIA
> and IEEE on
> this
> > subject has not shown any launch condition that caused the
> bandwidth to
> > collapse below the 160 MHz-km OFL spec for 62.5 um fiber.
> This includes
> > launches produced by single-transverse mode "CD" lasers as well as
> > multi-transverse mode VCSELs with various spot sizes and numerical
> > apertures. It also includes Radial Overfilled Launches that
> were developed
> > as a possible test launch condition by the IEEE MBI study
> group, which are
> > said to extract the "worst case" modal bandwidth for any
> laser launch. In
> > summary, there is no evidence of any launch condition that
> causes less
> than
> > 160 MHz-km bandwidth from the installed base of 62.5 um
> fiber. The 100 m
> > capability of the 850 CWDM PMD is based on 160 MHz-km bandwidths.
> >
> >
> > Regards,
> > Paul Kolesar
> >
> > ----------
> > From: Dave Dolfi 3764 [SMTP:dolfi@xxxxxxxxxxxxxxxxxxxxxxxx]
> > Sent: Thursday, August 03, 2000 6:17 PM
> > To: stds-802-3-hssg@xxxxxxxx; billw@xxxxxxxxxxx
> > Cc: dave_dolfi@xxxxxxxxxxx
> > Subject: RE: Patch cord for 1300 WWDM
> >
> >
> > Dear Bill,
> >
> > I'm happy that you agree with my summary of the patch cord
> > situation.
> > Unfortulately, I'm not sure that I agree with
> everything you seem
> > to be saying about 850 nm CWDM. Specifically, while I
> agree that
> > you could specify a VCSEL and a mux design which would
> achieve 100
> > meters on the installed 62.5 um MMF OR > 550 meters on the new
> > enhanced
> > bandwidth 50 um MMF, I'm not sure that a single design
> could achieve
> >
> > both at the same time.
> >
> > The 62.5 um conventional fiber requires a large spot at
> its input to
> > mitigate potential DMD problems if too much of the
> excitation is in
> > the central portion of the fiber, while the new fiber requires a
> > small spot centered at its input in order to satisfy
> the encircled
> > flux
> > requirement necessary to achieve the higher bandwidth. Can you
> > really
> > achieve both of these at the same time?
> >
> > I think you need to prove that this is true before you
> can claim to
> > simultaneously achieve the bandwidths you are claiming over both
> > fiber
> > types.
> >
> >
> > Dave Dolfi
> > Agilent Technologies
> >
> >
> > > From owner-stds-802-3-hssg@xxxxxxxx Thu Aug 3
> 11:18:07 PDT 2000
> > > Return-Path: <owner-stds-802-3-hssg@xxxxxxxx>
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> > > Reply-To: <billw@xxxxxxxxxxx>
> > > From: "Bill Wiedemann" <billw@xxxxxxxxxxx>
> > > To: <stds-802-3-hssg@xxxxxxxx>
> > > Subject: RE: Patch cord for 1300 WWDM
> > > Date: Thu, 3 Aug 2000 10:38:21 -0700
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> > >
> > >
> > > Thank You.
> > > Everything you say is correct. 850CWDM has been designed to
> > directly meet
> > > the 100 meter objective over installed (DMD
> challenged) 62.5u MMF
> > and the
> > > 300m objective over MMF. In addition we can meet 300
> meters over
> > existing
> > > 50 micron fiber and greater than 550 meters with the new high
> > bandwidth MMF.
> > >
> > > Finally experimental evidence has shown greater than 300 meter
> > performance
> > > over installed 62.5 micron fiber that is not DMD challenged.
> > >
> > > Bill Wiedemann
> > > Blaze
> > > 925-560-1610 x169
> > >
> > > 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
> > >
> > >
> >
>