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RE: PMD discussion

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]


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.


> 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
> ___________________