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Re: [802.3BA] Discussion on 40G for => 10 km SMF

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.




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.




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.




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.




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.


(1) COST


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.

And most likely 6 times.

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.


(2) Time


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.


(3) Power consumption


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.


(4) Size


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.


(6) Another aspect


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



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   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 (, which is a survey of data centers that Alan Flatman did that shows 40G being deployed in access-to-distribution links in 2010.









From: Atsushi Takai [mailto:atsushi.takai@xxxxxxxxxx]
: Wednesday, July 30, 2008 2:26 AM
To: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3BA] Discussion on 40G for ="" 10 km SMF


Hi Mark


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




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.






From: John DAmbrosia [mailto:jdambrosia@xxxxxxxxxxxxxxx]
: 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 aa 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.




John D’Ambrosia

Chair, IEEE P802.3ba Task Force