Re: [802.3BA] Discussion on 40G for => 10 km SMF
Hi Mori-san and others,
It goes without saying that the cost of a 40G 4x10G CWDM transceiver will not over the long term fall below 4x the cost of a 10G transceiver, but for a very trivial reason: Any cost reduction that results from development or volumes of 40 GbE will also reduce the cost of a quad 10G transceiver. So this is a meaningless comparison and not helpful for the decision. The decision needs to be made based on how the costs of 4x10G CWDM and serial 40G compare to each other, not how they compare to the cost of 10G. 40G serial technology has been in the market for ~6 years, and is still stubbornly expensive. Costs are finally decreasing somewhat, but the gap is not being closed vs. 10G because the cost of 10G is decreasing even faster than the cost of 40G.
From: Kazuyuki Mori [mailto:mori.kazuyuki-1@xxxxxxxxxxxxxx]
Sent: Sunday, August 03, 2008 10:21 PM
Subject: Re: [802.3BA] Discussion on 40G for => 10 km SMF
I'm Kazuyuki Mori, Fujitsu Labs. I support 40G Serial and I basically agree with Takai-san regarding below points.
My understanding is that, generally speaking, the final cost target for 40G optical transceiver should be 2 -3 times of 10G transceivers. In order to achieve this target , I again and again discussed the cost reduction approaches with TOSA/ROSA suppliers, IC suppliers, optical module suppliers and our laboratory experts. In case of CWDM, I haven't found any technical solution to achieve this target (<x4 cost of 10G transceiver), and there has been no presentations in IEEE to show this cost reduction approaches until now. On the other hand, 40G serial is feasible to achieve this target as shown in traverso_02_0708.
I wonder that 40G transceiver cost will remain more than 4 times of 10G in future if once CWDM solution is authorized.
I think the size reduction is another big challenging target in CWDM as
Chris already agreed in recent dialogues. Some people say that monolithic
DFB array enables high density package solution, but CWDM option is almost
impossible to be realized because the same active layer of LD cannot be
applied. Also the hybrid integration using PLC with an integrated AWG MUX is
sometimes picked up, but it is quite challenging due to high insertion loss
of AWG caused by intrinsic Gaussian profile, and also due to AWG temperature
dependence. In my perspective as a researcher, optical integration approach
in 40G CWDM has some intrinsic problems and leads the cost increase.
Please remember that this isn't the case of Vcsel array, but the case of
DFBs and also with optical mux.
Steve pointed out that '40G SerDes are very power hungry', but this is not
correct. Current SerDes is for 16:1 and 1:16, however 4:1 and 1:4 SerDes
should be asuumed in We need to compare using 4:1 and 1:4 SerDes. In our
estimation, 2W is possible by deleting unnecessary circuits from today's
SerDes even when SiGe was used.
----- Original Message -----
From: "Atsushi Takai" <atsushi.takai@xxxxxxxxxx>
Sent: Sunday, August 03, 2008 12:34 PM
Subject: Re: [802.3BA] Discussion on 40G for => 10 km SMF
> I do not know your background.
> However I found, in your comment below, you misunderstood the optical
> transmission technologies.
> I do not want to argue line by line.
> Just I would like to point one sentence:
> "The biggest downside of 40G serial, seems to be the physics problem of
> This is not true for 10km SMF.
> The 40Gbit/s PMD was a technical challenge in several years ago but now it
> is not downside.
> Even, we are discussing 1310-nm devices while current module includes
> 1550-nm devices.
> (We can neglect dispersion issue in case of 1310nm transmission)
> The biggest cost in current serial module is silicon chip that is much
> volume sensitive.
> I hope you know the accumulative shipment of 40Gbt/s client module is
> 10K peaces or such range.
> However IEEE confirmed market of 40GbE 10km serial enough for
> standardization, you can expect much lower cost with higher volume.
> Also investment for 40Gbit/s transmission networks started these years,
> industry started invest for 40Gbit/s technologies.
> You will find much activity in the industry.
> I am very concerning during the meeting and e-mail discussion,
> many of members may misunderstand the 40Gbit serial technology status and
> activity in the industry,
> and understand only the surface.
> We, who has technology especially optical device technology, should be
> responsible to let people understand the technology.
> I will think about it.
> Atsushi Takai
> ----- Original Message -----
> From: "Jeff Meyer" <jmeyer@xxxxxxxxx>
> To: <STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx>
> Sent: Sunday, August 03, 2008 2:33 AM
> Subject: Re: [802.3BA] Discussion on 40G for => 10 km SMF
> Chris has a excellent point about
> _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.
> The biggest downside of 40G serial, seems to be the physics problem of
> PMD. However there are an increasing number of long haul equipment
> providers who have solved this problem. There have been thousands of 40G
> serial long haul installations deployed to date.
> As far as the Cost, Power, Size & Reliability I think this favors
> serial. The cost saving of CWDM seems largely driven by the large number
> of vendors providing 10G IC's and components. But let us ponder, if the
> 10GE fathers chose 4x 2.5G WDM to reduce risk in the late 1990's would
> we be benefiting from the low costs and the large number of vendors? All
> we need is multiple vendors of 40G serial components and the prices will
> plummet. Lets face it the cost of SiGe is not that much higher than CMOS
> unless you get to volumes greater than 100,000 parts. By then, CMOS
> processes will catch up to SiGe in FT. I am a microwave guy and the 40G
> packaging is not difficult these days ( there are many vendors that can
> do LTCC fine line packages and they are "Open Tooled" so you can get a
> reference design for the 40G electrical packages for no NRE ). If we
> compare microwave packaging to flip chip mounting of lasers and optics,
> I would imagine optics costs more, but I have no "hard data" to support
> The biggest reason why I favor serial over CWDM is the leadership for
> the future. Lets take the risk like the 10G serial innovators did in the
> late 90's. Once we get several manufacturers of 40G parts this prices
> will plummet.
> Schedule Risk. Albeit the risk for serial is higher but how much?
> Let's keep technology moving forward for the future generations.
> Jeff Meyer
> Chris Cole wrote:
>> Takai-san痴 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 菟ower 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.