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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
>> > Return-Path: <owner-stds-802-3-hssg@xxxxxxxx>
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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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>> > Aug 2000
>> > 	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
>> > 	>
>> > 	>
>> >
>> 
>