RE: Patch cord for 1300 WWDM
Paul, Dave, Brian (et. al.),
This has been an enlightening "discussion" (no pun intended).
Would someone be willing to compile the information into a matrix format so
that we can
1) agree to the assumptions and implications and
2) allow the group at large to have a simple reference chart to show the
combinations and relative distances
[WDM; Serial] X [850; 1310] X [62.5; 50; New 50] X [OFL; RML**] X [802.3z
Patch Cord; or Not]
**hopefully this means only one RML specification!
If you think this sounds tough, imagine what it is like for the majority of
the committee to keep this all straight.
jonathan
>-----Original Message-----
>From: Lemoff, Brian [mailto:brian_lemoff@xxxxxxxxxxx]
>Sent: Friday, August 04, 2000 5:52 PM
>To: stds-802-3-hssg@xxxxxxxx
>Subject: 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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>> cent.com>
>> > 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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>> > 13:43:06 -0400 (EDT)
>> > > 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
>> > >
>> > >
>> >
>>
>