When I said
“many…”, I did
not mean all or even most. I continue to believe there are many
applications where direct connections between the host IC and pluggable
viable. Much of my effort has been in support of that. I am pleased
to hear that you also believe these direct connections are reasonable
I do not agree with, John statement below, broad assessment that PMD
interface can not be supported directly from the ASIC.
to me that many pcb layouts
will present sufficient challenges such that a direct connection
IC and pluggable module will not be supported and a signal conditioner
needed between the host IC and module."
Definitely in the controller application direct PMD interface can be
supported. In the switch applications it evolve
trade offs which should be left to the System/ASIC OEM to determine, I
supporting PMD interface directly
from a large switch will be challenging.
In IEEE we should not force an implementation or draw line in sand
limit implementation and future
cost reduction, we should provide set of building blocks which can be
The current optional XLAUI/CAUI definition and PMD service interface
the flexibility to not use any CDR/EQ,
put CDR in the module, or put CDR on the host board.
Gary Nicholl (gnicholl) wrote:
If it turns
out that a signal conditioner
will always be needed and a direct attach between the host IC and the
module cannot be supported (at least for the many situations you
below), then I think the signal conditioner should be integrated into
pluggable optical module (and ideally into the existing Tx and Rx ICs
module as Ryan as suggested in the past).
provide the lowest overall
system power (and especially if the SC is integrated into existing ICs
module). It also means that we would have one less electrical interface
with, as the PMD service interface would now be an internal module
completely under the control of the individual module vendors and there
be no need to specify it within 802.3ba (which would save us all alot
Sent: Wednesday, July
Subject: Re: [802.3BA]
XR ad hoc
Phone Conference Notice
can point this out before Ryan.
It seems to me that many pcb layouts will present sufficient
such that a direct connection between the host IC and pluggable module
be supported and a signal conditioner will be needed between the host
module. This means that for reasons other than extending the optical
reach, the means to extend the optical link reach are in place at least
these situations. All that is needed then is a way to permit the
installer to take advantage of the optical link extension that an
signal conditioner, adjacent to but not included in the module,
It will be frustrating to have all the pieces paid for and in place and
able to take advantage of the extended link reach that they offer.
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
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
interpret correctly, you are saying that all users should amortize the
very few who need extended reach.
need to be careful how we proceed here - we should not repeat the
the past if we want successful standard.
1101 Kitchawan Road,
Rte. 134 (shipping)
Yorktown Heights, NY 10598
your comment. You missed one critical point that
there is cost increase from OM3 to OM4. If you take ribbon cable cost
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 Mathilda Avenue
Sent: Wednesday, July 09, 2008 7:02 PM
Subject: Re: [802.3BA] XR ad hoc Phone Conference Notice
MMF XR Ad Hoc Committee Members,
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
goal. A single PMD for all reach objectives is indeed a good starting
premise; however, it should not be paramount. In the following lists
factors, enhancements, or approaches I would like to put forward as
and not acceptable for obtaining extended reach.
Cost increase for the baseline PMD (optic) in order to obtain greater
on the system/host board in any case
on the system/host board as part of the baseline solution
in the baseline PMD (optic)
in the baseline PMD (optic)
of OM4 fiber
Process maturity that yields longer reach with no cost increase
summary, we should not burden the baseline solution with cost increases
the needs of an extended-reach solution.
J. Maki, Ph.D.
Sunnyvale, CA 94089-1206