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Chris
says:
Other
Aspects
It is no longer
possible to simply increase Baud to match data rate, because of fundamental
electrical and optical propagation limits. This was recognized during the 100G
SMF PMD discussion, with Serial never a viable alternative for the 10km or 40km
reach. In the future, all data rates beyond 100G will use some form of
multi-lane technology. 40G is the inflection point where cost and difficulty of
Serial rises dramatically compared to multi-lane alternatives. Optical
communication has reached the point that all other forms of communication (wired
or wireless) reached many years ago, where simple modulation format serial
solutions are not practical.
This
is a valid point. But if we believed that 10G lanes were the best we can
do for now, we would have voted for 10 x 10 WDM for 100G SMF, rather than 4 x
25G. If we think we have it right with 25G wavelengths for 100G SMF, then
20G wavelengths for 40G SMF are right too.
I
believe that 40GBASE-LR2 with two, 20G wavelengths will be lower power, smaller
size and lower cost than either four, 10G wavelengths or one, 40G wavelength in
the timescales that a standards project like this must
consider.
Piers
Takai-san's 7/31/08
email discusses a number of points. Our arguments concerning his first two
points (Cost and Time to Market) are unchanged from cole_04_0708, so are not
repeated here. The remaining points are addressed below.
Power
The long term power
consumption of 40GE CWDM and 40GE Serial is similar. Four 10G un-cooled DFBs
and associated Laser Drivers use about the same power as one cooled 40G EML
and associated Modulator Driver. The remaining ICs are also about the same if
advanced process nodes and new designs are assumed. As was pointed out by Joel
Goergen during the Q&A session in Denver, a 40GE Serial block
diagram has comparable circuitry to 40GE CWDM block diagram when drawn fairly
to permit apples to apples comparison.
There is no basis for
a claim at this late stage in the debate that Serial has a power advantage
over CWDM, and that CWDM "power reduction plans are invisible." In
jewell_03_0508, p.9 and again in traverso_02_0708 p. 12, ratios of
power between an aggressive Serial implementation and CWDM implementation are
0.96 and 0.97, i.e. clear statements in pro-serial presentations that
there is no advantage.
Size
For future generation
products, CWDM has an advantage over Serial for fitting into a smaller form
factor like QSFP because similar to a 10GE-LR SFP+, the re-timing CDRs can be
moved outside of the module. Serial always has to have the 4:1 SerDes function
in the module. Even with aggressive projections about future component size
and power, Serial has a packaging and thermal management design challenge to
fit into QSFP.
What is required to
fit 40GE CWDM into QSFP is optics integration. This type of technology
has been described in numerous presentations to the HSSG and involves
flip-chipping lasers onto a PLC with an integrated AWG Mux. The CWDM grid
prevents use of a monolithic DFB array and requires flip-chipping discrete
DFBs, but that is a yield and cost issue not a feasibility or size issue. The
time line for such an advanced development program is lengthy, but is similar
to realistic PCB RF-interconnect 40GE Serial development schedules. The
investment required to bring this advanced technology to market is high, again
similar to one required for low cost 40GE Serial.
In contrast, no
advanced technology development is required to quickly bring to market first
generation low cost CWDM products based on discrete optics packaged in a
larger form factor.
Reliability
There is no current
1310nm 10G DFB failure data that justifies bringing up concerns about the
reliability of a 4x10G CWDM PMD. 10G 1310nm PMDs ship in volume today with
very high reliability. If there is actual field failure data behind this
concern, it would add credibility to have it presented.
Other
Aspects
It is no longer
possible to simply increase Baud to match data rate, because of
fundamental electrical and optical propagation limits. This was recognized
during the 100G SMF PMD discussion, with Serial never a viable alternative for
the 10km or 40km reach. In the future, all data rates beyond 100G
will use some form of multi-lane technology. 40G is the inflection point where
cost and difficulty of Serial rises dramatically compared to multi-lane
alternatives. Optical communication has reached the point that all other forms
of communication (wired or wireless) reached many years ago, where simple
modulation format serial solutions are not practical.
Chris
From: Atsushi
Takai [mailto:atsushi.takai@xxxxxxxxxx]
Sent: Thursday, July 31, 2008 12:18
AM
To:
STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3BA] Discussion on 40G
for ="" 10 km SMF
TF
members
I am supporting 40G
serial.
My view on 40G
Serial and CWDM is as below.
We can achieve less than
4x10G cost using 40G serial
while we need
some breakthrough technology using 40G CWDM
I agree 40G
CWDM will be 4-8 times of 10G as written in "cole_04_0708" page
8.
Using current technology,
it is difficult to achieve less than 4 because we have to pay for wavelength
control.
In case of 40G
serial, module structure is the same as X2.
I believe we can achieve
less than 4 times cost for each part in the 40G module comparing 10G
serial.
We are waiting 3rd
generation SERDES and 2nd generation of driver and TIA IC to achieve low cost
40GbE serial.
I am sure that industry
is working on these devices.
There exists plural 40G serial module vendors today using 1550-nm
EA-DFB.
1310-nm EA-DFB is
easier because we can neglect dispersion problem.
Thus 40GbE serial is
possible.
And cost reduction plan
is visible.
I also sure 40G CWDM
will be available if market will accept larger than 4 times
cost.
Cost reduction plan will
follow the same as 10G and plan for less than 4 times is invisible
today.
We need also breakthrough
to achieve less than 4 time power consumption using
CWDM.
Power consumption
reduction plan is invisible
We are sure we can
achieve less than 4 time power consumption using serial in
future.
I am not sure it is too
early to talk 40G electrical interface.
But 40GbE serial has
possibility for XFP or SFP+ size.
I did not hear LX4 XFPor SFP+ due to pin constraint and power
consumption.
(5) Risk for wavelength
failure
WDM technology has always
the risk for wavelength failure, while serial does not
have.
We may resolve some way
for 40G CWDM because of high reliability of long wavelength optical
devices.
We made speed
breakthrough every 4 or 5 years in the past.
We started to deliver 10G
modules in 1997.
The 300-pin MSA started
in 2000.
10GbE was issued in
2002.
40G is the next milestone
for technology evolution and now is a little bit behind the past
trend.
(We had unhappy period
that every progress seemed to stop.)
Today 40G is
the technology to challenge and overcome for both optical and electrical
technology.
I
think IEEE should not avoid such technology
evolution.
I believe IEEE should
take 40GbE serial.
=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=
Atsushi
Takai
Marketing Division, Opnext Japan, Inc
=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=
----- Original Message
-----
Sent: Wednesday, July 30,
2008 8:30 PM
Subject: RE: [802.3BA]
Discussion on 40G for ="" 10 km SMF
Atsushi,
First, let me say
that the email below is intended to make sure that this group does not stray
in a direction that would ultimately lead to the violation of IEEE-SA
Antitrust and Competition Policy. As chair, I am remaining neutral on
the TF's technical decisions.
Regardless of the
decision that this body makes, the market may demand that both solutions are
developed anyway.
Please note in the
following document from the IEEE, "Promoting Competition and
Innovation:
What
You Need to Know about the IEEE Standards Association's Antitrust and
Competition Policy," which
may be found at http://standards.ieee.org/resources/antitrust-guidelines.pdf.
Please note the following statement:
"For
example, selecting one technology for inclusion in a standard is lawful, but
an agreement to prohibit standards
participants (or
implementers) from implementing a competing standard or rival technology
would be unlawful - although as a practical matter, a successful standard
may lawfully achieve this result through the workings of the
market."
As I have phrased it to the Task
Force, the Task Force makes decisions about what it is going to do, it does not make decisions about what it is not going
to do.
Regardless of the decision that
this Task Force makes, it is very easy to envision both implementations
getting developed in the industry. Given the need stated by CWDM
supporters for a near term solution, it is easy to envision an industry
effort happening if the TF goes serial. It is just as easy to envision
a new CFI happening for a serial solution if the TF chooses to go CWDM.
Also, as a point of
clarification, as I am currently looking at the presentation for another
discussion, you may wish to refer to Flatman_01_0108 (http://grouper.ieee.org/groups/802/3/ba/public/jan08/flatman_01_0108.pdf),
which is a survey of data centers that Alan Flatman did that shows 40G being
deployed in access-to-distribution links in 2010.
Regards,
John
From:
Atsushi Takai [mailto:atsushi.takai@xxxxxxxxxx]
Sent: Wednesday, July 30, 2008 2:26
AM
To:
STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3BA] Discussion on
40G for ="" 10 km SMF
I agree that DC
application is cost sensitive.
As many people agreed
in some presentations at meeting, CWDM will be cheaper at near term and
serial will became cheaper in maybe 2011 or beyond.
That means transceiver
supplier have to develop CWDM in 2009 timeframe and serial in 2010 or
11.
This development will
cost much. And I do not think CWDM cost in 2009 or 2010 will be cheaper than
4x10G.
Even more DC
application users can choose 8x10G CWDM that has more
bandwidth.
I do not think CWDM has
superior merit for DC application.
Also I think there was
a presentation that said that DC will start install
40G in 2015 or beyond.
=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=
Atsushi
Takai
Marketing Division, Opnext Japan, Inc
=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=
----- Original
Message -----
Sent: Wednesday, July 30,
2008 4:08 AM
Subject: Re: [802.3BA]
Discussion on 40G for ="" 10 km SMF
John,
I agree some reflector
discussion would be helpful on this topic.
I characterize the discussion
I heard around the choice of PMD as really boiling down to a debate on the
primary applications and the drivers for those
applications.
The original justification for
adding the 40G SMF objective was primarily based on the application of
Data Center inter-switch links. There was also other applications such as for use in interconnecting to
OTN equipment which is good for BMP. In both cases lower cost
solutions are preferential. The debate appears to revolve around
what other assumptions there are around market timing, technology risks,
cost projections and operational issues etc.
To me the simple view is that
to achieve low cost, you need higher volume. Higher volume is
achieved by the having a solution that addresses the largest primary
application and as many others as possible. I am assuming that the
primary application is still the DC.
Since DC applications are
inherently much more sensitive to cost, a near term low cost solution is
needed or else the application will likely not be adopted. In this
case, if 40G SMF PMD is uneconomical in the near term then the DC users
will likely stay with nx10G as long as possible and then presumably assess
the 40G/100G economics at some later date.
The argument for adopting
serial technology now is that the potential higher volume of the DC
application will trigger the necessary development investments now and
drive the cost of that technology down so we will ultimately get it to the
low cost solutions needed. My concern is that the timing and cost
windows needed for the DC application do no fit with that model and we
would end up with little adoption in that market and end up with a lower
volume, higher cost PMD which is what we would all like to
avoid.
Mark
From:
John DAmbrosia [mailto:jdambrosia@xxxxxxxxxxxxxxx]
Sent: Monday, July 28, 2008 6:53
PM
To:
STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: [802.3BA] Discussion on
40G for ="" 10 km SMF
Dear Task Force
Members,
Per Motion #9 from July, the
editorial team is working on creating a "a draft based on adopted baseline
proposals for circulation prior to the September 2008 interim
meeting
."
Unfortunately, at the July meeting the Task
Force did not reach consensus on a baseline proposal to satisfy the 40G
over => 10km SMF objective. Therefore, in September we need to
reach closure on this issue.
With that
said, I would like to strongly recommend that the TF make use of the
reflector to discuss the various issues of debate that have been going
on, both during the meetings and during offline discussions.
Let's use the
next several weeks to have meaningful debate so we can reach consensus
at the September meeting.
Regards,
John D'Ambrosia
Chair, IEEE
P802.3ba Task
Force
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