Re: (SSIG) Taking the winning route
I'll try to explain, see my comments below:
> I don't understand the technical issue that you are raising by the
> following comment:
> "So far I didn't see any convincing proof that WWDM can support 300m of
> installed base MMF (as a matter of fact any distance of installed MMF). I
> also expect that such proof if it will come, will require a significant
> amount of work
> as was the case for Gb Ethernet. It is in fact necessary to field test the
> transceivers with a large sample of existing "fairly unknown" installed MMF.
> A long painful process that potentially could delay the standard
> ratification (sounds familiar?)."
> The WWDM proposal is based on the work of the Gigabit Ethernet committee. In
> common with all 10GbE proposals it has used the Gigabit Ethernet link model
> as the basis for its link budget. The GbE link model is known to be very
> conservative. This is evidenced by the obvious robustness of the large
> number of Gigabit Ethernet links in operation today.
> Also, the multimode fiber (MMF) environment of the installed base was
> extensively investigated as part of the work of the Gigabit Ethernet
> Standardization (see list of publications at end of e-mail). It is therefore
> wrong to say that it is "fairly unknown". The MMF issue that required
> significant work was Differential Modal Delay (DMD). For 1000BASE-LX the
> standardized offset launch patch cord was proven to remove this as an issue
> - that's why it became part of the standard.
I agree with you the Gigabit Ethernet model has been proven to be robust
and I congratulate with the work that has been done.
Based on a straightforward extension of that model, a 3.125 Gb/s link at 1.3um
can go approximately 280 m on installed MMF (62.5um 500MHz km).
This is below the objective of 300 m and does not consider additional
potential impairments introduced by the WDM process.
> So, given that the WWDM proposal is based on the work of Gigabit Ethernet
> including the offset launch patch cord, as far as the installed base is
> concerned, what new parameters need to be investigated?
The main difference is that WWDM claims that the distance can be
easily extended to 300 m with sufficient margin for the link to be robust.
It also assumes that penalties deriving from the optical muxing and demuxing
of four of such signals are not important.
These are the reasons why I personally would like to see more data
before claiming that WWDM can support the 300 m distance and meets the
> Since you brought the issue up I have to question the following statement:
> "So why eliminate a solution that is the only one proven (multi vendor
> testing) to work to embrace an unproved solution that is recognized (I
> believe you agree with this although we disagree on the amount) to be more
> I assume you are speaking on behalf of the serial MMF proposal that will use
> the newly developed MMF. I feel obliged to remind everyone of the following
> technical points:
> 1) The new high bandwidth MMF is not yet a standard,
Agreed, but the TIA FO 2.2 is working toward that goal and the timeline
for approval is consistent with the 802.3ab. Furthermore a
robust solution has been demonstrated from multiple vendors of fiber and
> 2) It's final standards-based performance is therefore undefined (only
> target specifications are known),
I agree the fiber specs are not defined yet but they seem to agree
that a 2000-2200 MHz km bandwidth number is reasonable (this is my personal
> 3) The laser launch requirements to guarantee its performance are not yet
I agree but there is a detailed proposal on the table at TIA FO 2.2 that is
> 4) The effect of link connectors on the performance of the standards-based
> version of the MMF fiber have yet to be specified.
The proposal at FO2.2 also includes the effects of connections.
Our results and results from multiple
transceiver manufacturers presented at 802.3ae
included several connections in the link. In my case I have shown that
up to four connections can be supported with a total connector loss > 1.5 dB.
> Also, to address the cost issue please remember that the installation of new
> fiber adds more cost to the user than can be saved by using lower cost short
> wavelength based transceivers.
We agree that the short wavelength serial proposal is of lower cost
than the 1300 4WDM solution.
However, the cost analysis presented by Lucent at the March 99 call
for interest meeting shows that the electronics savings
are far larger than the cost of upgrading the cabling plant.
Therefore the short wavelength system generates a net cost savings even when
cabling upgrades are included.
> Points 1 - 4 are evidenced by the call for transceivers companies to engage
> in a further round of testing with the new MMF that was recently broadcast
> over this reflector.
FO2.2 has the critical mass of participating companies to do the work in a
timely and thorough manner. The call for further participation by FO2.2 was
an invitation to participate by other interested companies, not a
declaration of insufficient capability within the group.
> Given all of this it could be argued that proposals
> based on the new MMF have the higher risk for 10GbE. Technically, until
> points 1 - 4 have been addressed, by the standardization of the new MMF, the
> worst case 10 GbE link performance with the new MMF cannot be finalized.
There are different types of risk. One type is the risk in moving from
concept to demonstration and another is meeting a schedule.
> Furthermore, projects to write supplements to the IEEE 802.3 standard can be
> proposed at almost any time. From an IEEE 802.3 Standards point of view it
> might therefore be wise wait until the new MMF has been standardized.
There is no need to wait since FO2.2 has established a schedule for its work
on next generation MMF coincident with the IEEE 802.3ae timeline.
To conclude I just want to point out that personally at this stage
I am in favor of keeping both solutions (10 G serial over new MMF and WWDM)
in the standard since this maximizes the chances of success (timely
introduction of the most cost effective solution for 10G Ethernet)
and minimizes the risks of delays.
I prefer to leave the choice to the end customer.
Dave and others, please note that my name is GIORGIO not GEORGIO.
> List of relevant publications
> "Evaluation of Gb/s laser based fibre LAN links: Review of the Gigabit
> Ethernet model", Mark C. Nowell, David G. Cunningham, Delon C. (Del) Hanson
> and Leonid Kazovsky, Opitical and Quantum Electronic, vol.32, pages 169-192,
> "A statistical analysis of conditioned launch for gigabit ethernet links
> using multimode fiber", Webster, M.,Raddatz, L.,White, I.H.,Cunningham,
> D.G., Journal of Lightwave Technology, vol.17, no.9, pages 1532-41,Sept.
> "Influence of restricted mode excitation on bandwidth of multimode fiber
> Raddatz, L.,White, I.H.,Cunningham, D.G.,Nowell, C., IEEE Photonics
> Technology Letters, vol.10, no.4, pages 534-6, April 1998.
> "An experimental and theoretical study of the offset launch technique for
> the enhancement of the bandwidth of multimode fiber links", Raddatz,
> L.,White, I.H.,Cunningham, D.G.,Nowell, M.C. Journal of Lightwave Technology
> vol.16, no.3, pages 324-31 March 1998
> "The Gigabit Ethernet Modal Bandwidth Investigation", Chapter 10, Gigabit
> Ethernet Networking, Macmillan Technical Publishing, 1999. ISBN:
> MBI group field test data can be found at:
> -----Original Message-----
> From: Giorgio Giaretta [mailto:giorgio@xxxxxxxxxx]
> Sent: Monday, April 10, 2000 11:32 AM
> To: rtaborek@xxxxxxxxxxx; HSSG
> Subject: Re: (SSIG) Taking the winning route
> even if we don't consider cost I would change your statement
> "WWDM meets all HSSG MMF objectives as well as SMF objectives to 10km."
> to WWDM POTENTIALLY meets (or WE HOPE WILL MEET) all HSSG MMF objectives as
> as SMF objectives to 10 km.
> So far I didn't see any convincing proof that WWDM can support 300m of
> base MMF (as a matter of fact
> any distance of installed MMF). I also expect that such proof if it will
> come, will
> require a significant ammount of work
> as was the case for Gb Ethernet. It is in fact necessary to field test the
> transceivers with a large sample of existing
> "fairly unknown" installed MMF. A long painful process that potentially
> could delay
> the standard ratification (sounds familiar?).
> So why eliminate a solution that is the only one proven (multi vendor
> testing) to
> work to embrace an unproved solution that
> is recognized (I believe you agree with this although we disagree on the
> amount) to
> be more expensive?
> I believe this point has been raised from other members before but so far no
> has answered.
> Are you aware of any data that I didn't see?
> Giorgio Giaretta
> Rich Taborek wrote:
> > Vipul, Rob,
> > It should be pointed out that a Serial 850nm solution only partially meets
> > HSSG distance/cable plant objective: 300m on MMF. However, this MMF must
> be the
> > new, enhanced MMF. The Serial 850nmsolution addresses no SMF objectives
> > WWDM meets all HSSG MMF objectives as well as SMF objectives to 10km.
> > I agree with Vipul's choice of 3 PMDs as the best possible PMD set to
> > HSSG HSSG distance/cable plant objectives.
> > Best Regards,
> > Rich
> > --
> > Vipul Bhatt wrote:
> > >
> > > Rob,
> > >
> > > Rob Marsland wrote:
> > > >
> > > > Finally, I hate to be annoying, but this is the SERIAL sig. Since
> when is
> > > > WWDM a serial solution?
> > > >
> > >
> > > There is nothing annoying about your question. I should answer. I
> believe it
> > > is in our (the Serial SIG's) best interest to rise above our Serial
> focus and
> > > recognize that an "all Serial" set of solutions that meets all the
> > > objectives is not something our customers are willing to sign up for. By
> > > proposing a set of three solutions - two of which are Serial - I am
> > > a set that has the highest chance of being accepted by our customers and
> > > majority of 802.3ae members. I understand you disagree, and I respect
> > > opinion.
> > >
> > > Vipul
> > -------------------------------------------------------
> > Richard Taborek Sr. Phone: 408-845-6102
> > Chief Technology Officer Cell: 408-832-3957
> > nSerial Corporation Fax: 408-845-6114
> > 2500-5 Augustine Dr. mailto:rtaborek@xxxxxxxxxxx
> > Santa Clara, CA 95054 http://www.nSerial.com
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