RE: PMD discussion
Dear Seto,
Yes, we did spend several years working on 850-nm WWDM, and demonstrated
4x2.5 Gb/s about 2 years ago in our lab. As with the long wavelength WWDM
vs. Serial debate, I believe that 850nm-WWDM will be cheaper in the short
term than 850-nm serial. The VCSEL and electronics technology for 2.5-Gb/s
are already mature and very low-cost. Also, the 4-1 electronic MUX will not
be needed in the WWDM approach.
With the current FDA eye-safety requirements, it will be nearly impossible
to make an 850-nm WWDM module which meets Class I eye safety, without using
open fiber control. The expectation is that the FDA will soon raise the
limit quite substantially, opening up the possibility of Class I safe 850-nm
WWDM modules.
By the way, WWDM and CWDM are exactly the same thing. I know its convenient
to use WWDM for 1300 nm and CWDM for 850 nm, but this is completely
arbitrary. I personally always refer to the approach simply as WDM.
Best Regards,
Brian Lemoff
> -----Original Message-----
> From: Seto, Koichiro [mailto:seto@xxxxxxxxxxxxxxxxxxxx]
> Sent: Monday, May 29, 2000 11:43 PM
> To: stds-802-3-hssg@xxxxxxxx
> Subject: Re: PMD discussion
>
>
>
> [Date: 05/29/2000 From Seto]
>
> Dear Brian,
>
> Thanks for your clarification. I look forward to your
> evaluation result in
> July. I'm sure you are aware that I'm not at all against
> 1310nm-WWDM proposal.
>
> BTW, I assume your team has a lot of experience with
> 850nm-WWDM solution. I
> believe you once had a 850nm-WWDM lab prototype (per Mr.
> Dolfi's presentation
> in 3/1999). Would you provide your insight on the argument
> on 850nm-serial vs.
> 850nm-WWDM? Do you think there would be a potential laser
> eye safety issue
> in 850nm-WWDM proposal as suggested by Jonathan?
>
> Seto
>
> >
> > Dear Seto,
> >
> > No offense taken. There should be no problem going 10 km
> over single mode
> > fiber with the same module that is optimum for going 300 m
> over MMF. I
> > expect that a full set of link results will be presented in
> July, to provide
> > the physical evidence you are looking for. Until then,
> you'll have to trust
> > the link model.
> >
> >
> > As for relative cost, most people believe that WWDM will be
> cheaper than
> > serial in the short term and that in the long run, serial
> will be cheaper.
> > The debate seems to be over when the two will cross. Some
> believe it will be
> > as soon as 2 years from now, while others believe it will
> be 3 or 4 years
> > from now. The 1.8x and 3.0x numbers you are referring to
> have no basis,
> > other than an unscientific survey among a very small sample
> (I believe the
> > number of survey respondents was 4) of serial PMD advocates.
> >
> > Since companies that are actually developing serial and
> WWDM products for
> > sale usually choose to keep their cost models to
> themselves, it will be
> > difficult to establish relative cost until products hit the
> market. Even
> > then, selling price and cost are two different things!
> >
> > - Brian Lemoff
> >
> > -----Original Message-----
> > From: Seto, Koichiro [mailto:seto@xxxxxxxxxxxxxxxxxxxx]
> > Sent: Monday, May 29, 2000 7:25 AM
> > To: wthirion@xxxxxxxxxxxx; stds-802-3-hssg@xxxxxxxx
> > Subject: Re: PMD discussion
> >
> >
> >
> > [Date: 05/29/2000 From Seto]
> >
> > Walter,
> >
> > My understanding is that the following set is also one of
> the top favorites:
> >
> > ________________optimized for may be used for
> > 1310 nm WWDM MMF upto 300m SMF upto 10km
> > 1310 nm Serial SMF upto 10km MMF upto 86m
> > 1550 nm Serial SMF upto 40km
> > ________________
> >
> >
> > I understand there are some risks that 850nm-WWDM solution
> may not satisfy
> > laser eye safety as Jonathan pointed out in the discussion
> on Thursday.
> > Also, I learned that there are some risks that 1310nm-WWDM
> may not be able
> > to achieve 10km at SMF if not impossible. At least we have
> not seen any
> > data that would prove the feasibility of 1310nm-WWDM over
> 10km SMF. It is
> > not to say that this can not be done, but I have not been
> convinced that the
> > same 1310nm-WWDM optics at same cost factor will serve for
> both 300m MMF
> > and 10km SMF. Also, some people pointed out that
> 1310nm-Serial can be built
> > at cost factors of x1.8 to 850nm-Serial while 1310nm-WWDM
> is x3. If we can
> > achieve the same goal (SMF 10km), the cheaper is the better.
> >
> > I hope no one is offended by my not-so-educated opinion. I
> would appreciate
> > a healthy discussion.
> >
> > Seto
> >
> > >
> > > First of all, thanks to everybody that presented PMD
> proposals at the last
> > > meeting. I've sent my presentation to David Law, so it
> should be available
> > > on the web site in the next couple of days.
> > >
> > > In listening to the discussion after my presentation and
> then going around
> > > and talking to people, it feels to me like we're starting
> to converge. Not
> > > there, yet, but making progress.
> > >
> > > The equipment manufacturers made it pretty clear they
> would like to see no
> > > more than 3 PMDs in the standard. The PMD vendors have
> some concern that
> > > using only 3 PMDs may sub-optimize certain objectives,
> however, they could
> > > support the 3 PMD position if it is made clear which 3
> PMDs the equipment
> > > oems want.
> > >
> > > Based on an informal straw poll and anecdotal evidence,
> my opinion is the
> > > first choice would be the set:
> > > ________________
> > > 850 nm WWDM
> > > 1310 nm WWDM
> > > 1550 nm Serial
> > > ________________
> > >
> > > If that set isn't feasible, then the 2nd most popular choice is:
> > > ________________
> > > 850 nm WWDM
> > > 1310 nm Serial
> > > 1550 nm Serial
> > > ________________
> > >
> > > Thoughts, feedback?
> > >
> > > Walt
> > > ___________________
> > > Walter Thirion
> > > Chair, IEEE 802.3ae PMD Sub-Task Force
> > > 301 Congress Ave.
> > > Suite 2050
> > > Austin, Texas 78701
> > > Voice: 512-236-6951
> > > Fax: 512-236-6959
> > > wthirion@xxxxxxxxxxxx
> > > ___________________
> > >
> > >
> > >
>