Ok – so thanks
for the laugh and pointing out how long I have been at this
J
The analogy and
point, however, is still valid. The impact and assessment
of cost is dependent on an individual’s target
implementation. This goes straight to the heart of Brad’s
point IMHO.
I think Mike
Dudek’s reply was a very good summary, so rather than ruin
his eloquence I’ll refer you to his e-mail
- thank you
Mike!
I should add
that the counterboring controversy was well before my time
– and I respect you all the more for ‘fessing up to the
memory John ….
Best wishes J
jonathan
Jonathan,
Can I ask what
perspective are you making your statement from regarding
sufficient cost, power, or size, to justify another PMD
spec. Would you consider it to be the sorts of deployments
you see associated with optics today or with high volume
manufacturing?
I ask this,
because I remember back in the early days of Backplane
Ethernet when people argued over the cost associated with
counterboring. I remember saying many times that a certain
company had imprinted the letters HVM into my forehead.
John
Hi Brad,
Thanks for
comments !
Ryan and I just
compared the proposals for MMF PMDs that have been
contributed to 802.3bm, with (for myself at least) a very
module-centric viewpoint, to see how our project goals of
significant reduction of cost, power, or size, would be
addressed by the un-retimed PMD proposal.
Slide 2 was
intended to provide a short summary of the context of the
comparison, it refers to the 100 m reach MMF PMD baseline
proposal, which makes it clear that CAUI-4 is an example
(not a required) 4 lane interface. I’m happy to add an
explicit reference to that baseline if that helps ?
Whether the
implementer uses CAUI-4 or not, for the PMD specs to be
viable, modeling shows that there are very tight jitter
requirements at the PMA/PMD interface; putting retiming
inside the module is one way of making that so (for the 100m
reach baseline).
I agree there
may be many proprietary methods for meeting the optical
specs for the 802.3bm 100m MMF PMD – but Ethernet doesn’t disallow
any of those by not standardizing an un-retimed
interface - it is a given that proprietary solutions
meeting the PMD specs are allowed and expected. But if
even they could allow use of a module without retiming, it’s
not going to save sufficient cost, power, or size, to
justify another PMD spec.
Best wishes
jonathan
Jonathan,
I want to touch
on your statement that the “PMA is expected to be inside the
module.” That is my primary concern. IEEE P802.3bm does not
specify modules, nor does it specify implementations.
CAUI-4 is an
OPTIONAL instantiation of the PMA service interface. The use
of CAUI-4 as the interface to an optical module or for any
other means is an implementation decision.
While the
presentation is correct relative to a very specific
implementation using CAUI-4 optical modules, there is a
potential market that is being ignored by assuming they will
use CAUI-4 and/or an optical module.
Would you (and
your supporters) be willing to add clarification to the
presentation that the material assumes the use of a CAUI-4
optical module and other implementations could result in
different cost, power and size estimates?
Thanks,
Brad
Hi Brad,
Thank for your
comments. You are right, the clock and data recovery are
part of the PMA; for the 100G 100m MMF baseline that part of
the PMA is expected to be inside the module.
You raise an
interesting point about having different power settings
controllable by management software – my initial thoughts
are that the difference between 20m and 100m reach link
budgets is about 1.4 dB, it’s probably not very significant
in terms VCSEL bias current savings for example. I don’t
think CDRs could be turned off without tighter jitter specs
being set at the electrical interface - as some of John
Petrilla’s work has shown in the MMF ad hoc meetings, the
chip to module CAUI-4 specs don’t support an un-retimed
optical link. John’s work showed that 20 m reach PMD
optical parameters would need to be as tight as the 100m
baseline in order to make the jitter specs achievable. Of
course, I’m happy to hear other opinions
Best wishes
jonathan
Jonathan,
Thanks for
forwarding the presentation.
There is one
aspect that does concern me as I reviewed the material and
that is it is only making a comparison of unretimed vs.
retimed implementations. As far as my understanding of a PMD
and its PMD service interface, there are no clock and data
recovery circuits (see Annex 86A). Therefore, I think the
presentation has not really focus on the differences that
could be specified relative to the PMDs.
I’m not an
optics expert, so please feel to correct my following
interpretation/thought-line. It would seem to me that the
Task Force could specify different optical power
requirements (one for 20m and another for 100m) that could
be controlled via the management interface. The 100m power
level would be the default, and the 20m power level could be
selected by either management software or the end user.
Would this scenario offer any potential power savings?
Thanks,
Brad
From:
Jonathan King [mailto:jonathan.king@xxxxxxxxxxx]
Sent: Friday, April 26, 2013 6:32 PM
To: STDS-802-3-100GNGOPTX@xxxxxxxxxxxxxxxxx;
a_flatman@xxxxxxxxxxxxx;
Abbott, John S Dr; Amezcua, A. (Adrian); Andy Moorwood;
Anslow, Peter; Anthony Torza; Bernstein, Gary; Booth,
Brad; Daniel Dove; Ephrem Wu; Gary Nicholl (gnicholl);
Harry Fu; Jack Jewell; Jeffery Maki; John Petrilla;
Keith Nellis; Kolesar, Paul; Lian Zhao; Martin
Gilpatric; Phil.McClay@xxxxxx;
Mike Peng Li; mike.dudek@xxxxxxxxxx;
mnowell@xxxxxxxxx;
Oren Sela; Piers Dawe; Rabinovich, Rick (Rick); Rick.Pimpinella@xxxxxxxxxxx;
Robert Coenen; ryan.latchman@xxxxxxxxxxxxx;
Scott Kipp; Shmuel Levy; Swanson, Steven E; Tracy,
Nathan L; Vipul Bhatt
Subject: 802.3_100GNGOPTX : 'Cost power and size
differences of proposed MMF PMDs' - seeking
supporters/detractors
Dear
all,
Following
a couple of comments, I’ve revised the slides slightly to be
more clear that those listed as supporters (or detractors)
are supporting the conclusions, rather than necessarily 100%
agreeing with the specific details in the presentation .
Obviously power estimates vary somewhat between companies.
I’ve moved the supporters and detractors lists to the end
of the presentation and labeled them as ‘supporting the
conclusions’ and ‘not supporting the conclusions’ .
Best
wishes
jonathan
From: Jonathan King <jonathan.king@xxxxxxxxxxx>
Date: Thursday, April 25, 2013 1:44 PM
To: <STDS-802-3-100GNGOPTX@xxxxxxxxxxxxxxxxx>,
Jonathan King <jonathan.king@xxxxxxxxxxx>,
<a_flatman@xxxxxxxxxxxxx>,
"Abbott, John S Dr" <AbbottJS@xxxxxxxxxxx>,
"Amezcua, A. (Adrian)" <adrian.amezcua@xxxxxxxxx>,
Andy Moorwood <amoorwood@xxxxxxxxxxx>,
"Anslow, Peter" <panslow@xxxxxxxxx>,
Anthony Torza <anthony.torza@xxxxxxxxxx>,
"Bernstein, Gary" <GBernstein@xxxxxxxxxxx>,
Brad Booth <Brad_Booth@xxxxxxxx>,
Daniel Dove <ddove@xxxxxxx>,
Ephrem Wu <ephremw@xxxxxxxxxx>,
"Gary Nicholl (gnicholl)" <gnicholl@xxxxxxxxx>,
Harry Fu <harryf@xxxxxxxxxx>,
Jack Jewell <jack@xxxxxxxxxxxxxx>,
Jeffery Maki <jmaki@xxxxxxxxxxx>,
John Petrilla <john.petrilla@xxxxxxxxxxxxx>,
Keith Nellis <knellis@xxxxxxxxx>,
"Kolesar, Paul" <PKOLESAR@xxxxxxxxxxxxx>,
Lian Zhao <lzhao@xxxxxxxxx>,
Martin Gilpatric <marting@xxxxxxxxxx>,
<Phil.McClay@xxxxxx>,
Mike Peng Li <mpli@xxxxxxxxxx>,
<mike.dudek@xxxxxxxxxx>,
<mnowell@xxxxxxxxx>,
Oren Sela <orens@xxxxxxxxxxxx>,
Piers Dawe <piers.dawe@xxxxxxxxxxxxx>,
"Rabinovich, Rick (Rick)" <rick.rabinovich@xxxxxxxxxxxxxxxxxx>,
<Rick.Pimpinella@xxxxxxxxxxx>,
Robert Coenen <rcoenen@xxxxxxxxxxxxxxxxxxx>,
<ryan.latchman@xxxxxxxxxxxxx>,
Scott Kipp <skipp@xxxxxxxxxxx>,
Shmuel Levy <shmuel@xxxxxxxxxxxx>,
"Swanson, Steven E" <SwansonSE@xxxxxxxxxxx>,
"Tracy, Nathan L" <ntracy@xxxxxx>, Vipul
Bhatt <Vipul_Bhatt@xxxxxxxx>
Subject: 802.3_100GNGOPTX : 'Cost power and size
differences of proposed MMF PMDs' - seeking
supporters/detractors
Dear all ,
Ryan and I
are seeking supporters and detractors for the attached
joint presentation:
“Cost, power,
size differences of proposed MMF PMDs: 20 m reach
un-retimed vs 100 m reach retimed baseline”, which will
be submitted for to the May meeting of 802.3bm in
Victoria, BC.
The slides
conclude that
“• By about
the same time 802.3bm is technically stable (H2 2014)
there will be no significant power, cost, or size,
advantage to be gained from an un-retimed short reach
PMD.
– A 20 m reach un-retimed PMD would
not meet the criteria for distinct identity.
• The 20 m
reach objective is met by the 100 m reach PMD, a
separate 20 m PMD is not required”
If you agree
(or disagree) with the presentation and wish to be
listed as a supporter (or detractor) of the
presentation, please let me know by e-mailing me.
Thanks !
Best wishes
jonathan
jonathan.king@xxxxxxxxxxx