----- Original
Message -----
Sent: Friday, February 24,
2012 3:54 PM
Subject: Re: [802.3_100GNGOPTX]
SMF and MMF Ad Hoc
meetings: MMF objective
Paul,
While I am not saying
that 150m over OM4
may not be the outcome of the Task
Force, it is my view that it is not
the
function of the Study Group to start
to make technical choices for the
Task
Force. I think the Study Group
should set an objective at which the
PMD
has broad market potential etc. and
try to make as few technical choices
as
possible. 150m over OM4 is quite a
challenging objective and setting it
would rule out some of the choices
that the Task Force might want to
make.
I am not of the view that if it
turns out to be 100m over OM4 that
this is not
worth doing, so I am more in favour
of setting the objective to be 100m
over MMF and leave the technical
choices as to whether this means
over OM3 or
OM4 etc. to the TF.
Regards,
Pete
Anslow | Senior Standards
Advisor
43-51 Worship
Street | London, EC2A 2DX,
UK
Direct +44 2070
125535 |
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
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
43-51 Worship
Street | London, EC2A 2DX,
UK
Direct +44 2070
125535 |
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
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
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
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
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.
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Topic: "SMF Ad Hoc followed by MMF
Ad Hoc"
Date & Time: Tuesday, 28
February 2012 at 16:00, GMT Time
(London, GMT)
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Regards,
Pete Anslow | Senior Standards
Advisor
43-51 Worship
Street | London, EC2A 2DX,
UK
Direct +44 2070
125535 |