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Pete, The line of thinking expressed in your
second paragraph suggests that the MM reach objective would need to be
revisited, presumably to be shortened for lower cost, should the SM PMD cost be
projected to be low enough to cause it to be attractive for channel lengths
within that MM reach. If my interpretation is correct, and we do not have
confidence in SM optics achieving such an aggressive cost decline, then the
reach objective for MM should be at least as long as that established for
100GBASE-SR10, namely 150 m on OM4. Regards, Paul From: Chris, I don’t think that this really
helps. What you really need to know in order to determine if an SMF PMD
will affect what the reach should be for the MMF objective is the relative cost
of the new MMF and SMF modules. However, just knowing what the SMF reach
objective is won’t tell you that. Many of the decisions to be made
by the Task Force will affect this relative cost and there was some consensus
on the last SMF call that the only likely constraint on an SMF objective below
say 2 km is the cost of parallel fibre. It is not clear at this point
whether a PMD capable of 1km (say PAM-8) is more expensive or cheaper than one
that is only capable of 500m (say parallel fibre). I think that the Study Group should
decide on a MMF objective that stands on its own. If it turns out that
there is an SMF objective and the Task Force choices make the relative cost of
that PMD low enough to affect the MMF reach, then the Task Force can seek to
change the MMF objective. This is (in my opinion) the earliest point that
the group can rely on having a reasonable idea of the relative cost of the two
solutions. Regards, Pete
Anslow | Senior Standards Advisor From: Chris Cole [mailto:chris.cole@xxxxxxxxxxx] Steve I tend to agree with you, but Paul does
have a point that to some knowing what the SMF objective is important in
deciding what the MMF objective should be. My suggestion is that we keep the MMF
poll exactly as Jonathan crafted it. Anyone that feels the SMF objective has to
be decided first has the option to state so and then state their view of what
that is likely to be. This will allow us to not delay making progress towards
reaching consensus on a MMF objective So let’s call this question A. A) To make a decision on an MMF reach objective, I am assuming the SMF
reach objective will likely be: a.
No SMF objective b.
At least 500m c.
At least 1000m d.
At least 2000m Those like you and me who do not see
strong linkage simply do not answer question A. Jonathan can then record how many
responses he receives to question A and the choice. Both results will give us a
measure of the thinking of Ad Hoc participants. Chris From: Trowbridge, Stephen J (Steve)
[mailto:steve.trowbridge@xxxxxxxxxxxxxxxxxx] Hi Paul, I don’t think it is nearly so
clear that you should decide SM first. If there existed a SM solution that was
cost-competitive with a MM solution at some reach, it would be a game changer,
and those developing MM solutions would surely like to know if the game will
change before getting too far down the path. But most seem to believe that the
game will not change, and even if it did, it is hard to prove because it is
difficult to compare relative costs of dissimilar technologies. Most still seem to believe (in spite of
the interesting technology from Opnext) that there will be a significant step
function from MM to SM that will keep people from wanting to use it in data
centers. Furthermore, if you need a different cable type, for example, for a
70m link than you need for a 100m link, that creates its own kind of problem. So if the game does not change, then SR4
needs to try to address most, if not all, of the reach currently addressed by
SR10. If it turns out not to be technically or economically feasible to do that
(e.g., if you could only get 60 or 70m out of the beast within reasonable cost,
size and power), then if SM is to replace MM above that reach, it needs to get
down to a cost to compete with an SR10 with a reverse gearbox. Even if SM does
this, it isn’t clear they will get all of that market because of a likely
reluctance to mix cable types in the data center – maybe they are happier
to use SR10 with a reverse gearbox to reuse their existing cabling. Regards, Steve From: Jonathan, While I understand the
desire to find a launching point for the discussion, this poll is approaching
the problem in the wrong order because we need to know what the single-mode objective
is first. A purpose of the Study
Group is to set objectives that will allow us to establish cost-optimized
100GE. One cannot logically pick cost-optimized MM objectives without
first having framework around the SM optics that will be used to address
channels with lengths that exceed the MM reach. At this point, we have
not even established if we will have a SM objective. In other words, we
don’t know if the existing LR4 will remain the only one, or if there will
be another one added. Only when the SM situation is established can we
know the minimum capability that a new MM optic must fulfill to optimize cost. I suggest that we first
conduct such a poll for SM and use it to start the objective discussion in the
SM ad-hoc. If that produces solid results, then undertake the same
endeavor for MM. Regards, Paul From: Jonathan King
[mailto:jonathan.king@xxxxxxxxxxx] Dear all, On the Feb 14th MMF
ad hoc call , it seemed like we were beginning to converge on a possible
objective for MMF . In the next meeting
(Tuesday 28th Feb), I’d like to see if we can finalize a strawman
MMF objective. To that end I’ll prepare a presentation which
we can review during the call which will include a strawman objective for
review on the call, together with an overview of how it addresses the 5
criteria – to help get the best starting point for that discussion
I’d like to get your responses to the questions below questions: The strawman
objective will follow the wording in Anslow_01_0111 Define
a 4-lane 100 Gb/s PHY for operation over OMX MMF with lengths up
to at least Y m 1) A reasonable MMF reach objective (i.e. the value of Y)
would be a.
100m b.
Significantly less than 100m (what reach?) c.
Significantly more than 100m (what reach ?) d.
decided in the task force 2)
The MMF type should be a.
decided in the task force b.
OM3 c.
OM4 d.
at least as good as OM4 Please send your
responses to me directly at: jonathan.king@xxxxxxxxxxx I will collate and
report the results but will not reveal any individual’s responses. If you feel
uncomfortable expressing an opinion, say so and I’ll note that. To repeat, this
is not a formal poll or vote, just intended to give us the best starting point
for discussion on Tuesday. Please send your
responses as soon as possible, and at least by close of business on Monday 27th
Feb, 2012 Many thanks ! Jonathan King MMF ad hoc chair,
Next Gen 100G Optics From: Hi, Following
on from the meetings on 14 February, Jonathan and I are planning to hold an SMF
Ad Hoc meeting immediately followed by an MMF Ad Hoc meeting (1 hour each) starting
at 8:00 am Pacific on Tuesday 28 February. If you
would like to present a contribution at the SMF ad hoc, please send it to me
and for the MMF ad hoc, send it to Jonathan. Peter
Anslow from Ciena has invited you to join a meeting on the Web, using WebEx.
Please join the meeting 5-10 minutes early so we may begin on time. +44-203-4333547
( 4438636577 ( Conference
Code: 207 012 5535 France,
Paris : 0170375518 Hong Kong,
Regards, Pete Anslow | Senior Standards Advisor |