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1310 nm vs. 1550 nm for 40 km links

I would like to respond to a couple of comments made on this
reflector about the possibility of using 1310 nm wavelength for 40
km Serial links. I think we should stay with 1550 nm.

Following a presentation I gave at the 10GEA Santa Clara meeting,
and also during Serial SIG discussions, the feedback I have received
from many members is that for Metro Area Networks, it is desirable
to be able to extend the link distance beyond the stated 40 km goal.
Metro Area links capable of supporting distances beyond 40 kms will
be a significant potential application of 10G Ethernet. This does
not mean that we need to include optical amplifiers or dispersion
compensation blocks in the standard, only that our link should be
compatible with them. Compatibility with long distance
infrastructure tilts the balance in favor of 1550 nm. Limiting the
operation of this link to 40 kms will be like clipping the wings of
10G Ethernet.

If you ask the question - "Do we want a link that is the lowest cost
solution for 40 kms, or do we want a link that is more expensive but
capable of plugging into the long distance infrastructure?" - my
recommendation is to choose the latter.