can point this out before Ryan. It seems to me that many pcb layouts
will present sufficient challenges such that a direct connection
between the host IC and pluggable module will not be supported and a
signal conditioner will be needed between the host IC and module. This
means that for reasons other than extending the optical link reach, the
means to extend the optical link reach are in place at least for these
situations. All that is needed then is a way to permit the installer
to take advantage of the optical link extension that an external signal
conditioner, adjacent to but not included in the module, provides. It
will be frustrating to have all the pieces paid for and in place and
not be able to take advantage of the extended link reach that they
By the way,
a similar situation exists with respect to using FEC.
that’s what has been happening in the 10G world, people are forced to
amortize the cost of 300m reach (LRM), while in reality the number of
people who need 300m is close to 0.
That’s why I
am strongly in support of your approach of keeping the 100m objective
as primary goal.
can add as much cost as it wants to, the beauty is the added cost goes
directly where it’s needed, which is the longer links. Alternatives
force higher cost/higher power consumption on all ports regardless of
whether it’s needed there or not.
If I interpret correctly,
you are saying that all users should amortize the cost of very few who
need extended reach.
We need to be careful how
we proceed here - we should not repeat the mistakes of the past if we
want successful standard.
1101 Kitchawan Road,
Rte. 134 (shipping)
your comment. You missed one critical point that there is cost increase
from OM3 to OM4. If you take ribbon cable cost in perspective, OM4
option is possibly the largest of the 4 options.
use of OM4 requires to tighten TX specs which impact TX yield, so you
are actually compromising the primary goal.
From: Jeff Maki [mailto:jmaki@xxxxxxxxxxx] 1194 North
Sent: Wednesday, July 09, 2008 7:02 PM
Subject: Re: [802.3BA] XR ad hoc Phone Conference Notice
Dear MMF XR Ad Hoc
I believe our current
objective of “at least 100 meters on OM3 MMF” should remain as a
primary goal, the baseline. Support for any form of extended reach
should be considered only if it does not compromise this primary goal.
A single PMD for all reach objectives is indeed a good starting
premise; however, it should not be paramount. In the following lists
are factors, enhancements, or approaches I would like to put forward as
acceptable and not acceptable for obtaining extended reach.
1. Cost increase for the
baseline PMD (optic) in order to obtain greater than 100-meter reach
2. EDC on the system/host
board in any case
3. CDR on the system/host
board as part of the baseline solution
4. EDC in the baseline
5. CDR in the baseline
1. Use of OM4 fiber
2. Process maturity that
yields longer reach with no cost increase
In summary, we should not
burden the baseline solution with cost increases to meet the needs of
an extended-reach solution.
Jeffery J. Maki, Ph.D.
Principal Optical Engineer
Juniper Networks, Inc.