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[EFM] RE: Single wavelength, single fibre PMD for P2P


There is one additional consideration which you did not include in your
matrix. This has to do with compatibility with other transport.
Specifically, 1500nm to 1550nm overlays.

There will be applications in the future where a service provider will
desire to add other services, such as video, onto the same fiber. With a
1300nm system this will be relatively painless to do. The 1300nm and 1550nm
windows may be easily separated with widely available coarse WDM filters. 

On the other hand, a system using 1310nm and 1490nm to 1550nm in the other
direction is more complicated. The separation of the wavelengths will
require a more sophisticated filter and tighter wavelength control on the
longer wavelength laser. If this PMD also applies to 100M then this will be
the difference between an FP and a DFB laser. 

In this area I would give the single wavelength option a 1.



-----Original Message-----
From: Thomas.Murphy@xxxxxxxxxxxx [mailto:Thomas.Murphy@xxxxxxxxxxxx]
Sent: Thursday, February 14, 2002 11:25 AM
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Cc: Vipul_Bhatt@xxxxxxxx
Subject: Single wavelength, single fibre PMD for P2P

Hello All,

First off I apologise for a blanket bomb approach with sending out this
e-mail but
I have my reasons, as will become clear below.

As most of you will know, I am currently co-ordinating the development
of a single fibre, single wavelength PMD proposal for P2P links.
During a recent discussion of this work, it became clear that a number of
were unaware of what was happening or still unclear of some of the technical
issues involved. Several questions arose
which had already been answered in the course of dedicated telephone
conferences and
some new issues were also raised.

Of course this discussion is very good for the quality of the standard.
in the interest of progress and completion of a baseline proposal for March,
is essential that people allay any concerns they may have in the interim and
into the meeting feeling ready to make an informed decision. 

I would therefore ask people who have an opinion (or concern) in this
to speak up, raise the issues and avoid further surprises in St Louis.

Arising from the aforementioned discussions was the idea that a 2 wavelength
PMD may be an alternative approach. In order to facilitate comparison of the

two ideas, a matrix was proposed which I have included here in a somewhat
form. I divided the table into Today and Future, the former represent
current laser sources (FP and DFB)
and the later assuming the use of VCSELs, be that at 1310, 1490 or 1550 nm.
I dislike the 1-10
approach of comparing as this is too subjective, rather a binary 0 or 1
representing the better solution
for a particular criteria. In some cases there are no differences and both
receive 0. The 'points'
are added and a comparison may be made.  NOTE, this will not be the basis of
the decision, rather an aid
to objective comparison. I have included comments behind each issue cells
detailing my evaluation.

So, speak up, play with the table, add issues if necessary, send it back to
get on the telephone conferences.

Best regards and looking forward to further progress.

Tom and the P2P group

 <<Comparison matrix for 1 and 2 wavelength PMDs.xls>> 

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