| Thread Links | Date Links | ||||
|---|---|---|---|---|---|
| Thread Prev | Thread Next | Thread Index | Date Prev | Date Next | Date Index |
|
Jack, Thanks for your view points. While your assessment of the big systems
users may be accurate, I am not aware of any going on record in favor or
against any particular new proposal yet. They may be more like me. I still do
not have enough information to determine a solid preference. But as you have
expressed, at this point I too think it is likely that parallel singe-mode will
offer the lowest cost, especially when weighted by the channel length
distributions. We will see if that is true and whether that is sufficient to be
persuasive to the group to go in that direction. Also we must remember that while the big system users take center stage
in our views of the world because they participate in our discussions and are
potential early and substantial adopters, for every one of them there are hundreds
of other system users who are not represented. And it is very hard for them to
be heard, not just logistically, but with sufficient sincerity to affect the
standard. A case in point: using a survey, See http://www.ieee802.org/3/ba/public/AdHoc/MMF-Reach/swanson_xr_01_0608.pdf
Although we spent many meetings and teleconferences trying to address
their guidance, none was implemented. In some ways our current activity in search of a lower-cost alternative
to the existing standard to support data center channels longer than 150 m can
be viewed as the consequence of that inability. Because we have now moved up
to 25G lane rates we are focusing on SM solutions to fill that void. Yet the optimal
SM technologies to do this job are still potentially out on or beyond the
horizon. If we had implemented longer reach on MMF for both 40G and 100G as
those surveyed customers indicated, our current activities might have been
delayed until a more mature future because the implementation cost of their
directives would not have posed such a formidable market acceptance barrier, and
therefore I suspect one more tolerant to awaiting replacement alternatives. I’m hoping we can do it better this time. That’s why I am working to
provide the assessment tools we need, and to open the discussions around cost and
existing price. I also agree with Chris regarding the reach objective. The existing proposals
need to bake more, and we may hear even more varied proposals next meeting. Regards, Paul -----Original Message----- Jack, Thank you for continuing to lead the discussion. I am hoping it
encourages others to jump in with their perspectives, otherwise you will be
stuck architecting the new standard by yourself with the rest of us sitting
back and observing. Your email is also a good prompt to start discussing the specific reach
objective for 100GE-nR4. Since you mention 2000m reach multiple times in your
email, can you give a single example of a 2000m Ethernet IDC link? I am aware of many 150m to 600m links, with 800m mentioned as long term
future proofing, so rounding up to 1000m is already conservative. I understand
why several IDC operators have asked for 2km; it was the next closest existing
standard reach above their 500m/600m need; see for example page 10 of Donn
Lee's March 2007 presentation to the HSSG
(http://www.ieee802.org/3/hssg/public/mar07/lee_01_0307.pdf). It is very clear
what the need is, and why 2km is being brought up. Another example of IDC needs is in a 10x10G MSA white paper (http://www.10x10msa.org/documents/10X10%20White%20Paper%20final.pdf),
where Bikash Koley and Vijay Vusirikala of Google show that their largest data
center requirements are met by a <500m reach interface. In investigating the technology for 100GE-nR4, we may find as Pete
Anslow has pointed out in NG 100G SG, that the incremental cost for going from
1000m to 2000m is negligible. We may then chose to increase the standardized
reach. However to conclude today that this is in fact where the technology will
end up is premature. We should state the reach objective to reflect the need,
not our speculation about the capabilities of yet to be defined technology. Thank you Chris -----Original Message----- From: Sent: Friday, November 18, 2011 9:38 AM To: Subject: Re: [802.3_100GNGOPTX] Emerging new reach space Hello All, Thanks for all the contributions to this discussion. Here's a synopsis
and my current take on where it's heading (all in the context of 150-2000m links). Starting Point: Need for significantly-lower cost/power links over 150-2000m reaches has been expressed for several years. Last week in parallel SMF media. Straw polls of "like to hear more about
___" received 41, 48, 55, and 48 votes, the 41 for one additionally involving new
fiber. The poll "to encourage more on…duplex SMF PMDs" received 35
votes. Another straw poll gave strong support for the most-aggressive low-cost target. Impressions from discussion and the largest ones) are strongly resistant to adopting parallel SMF. (not addressing reasons for that position, just stating an observation.) LR4 platform can be extended over duplex SMF via WDM by at least one more "factor-4" generation, and probably another (DWDM for
latter); PAM and line-rate increase may extend duplex-SMF's lifetime yet another generation. My Current Take: Given a 2-or-3-generation (factor-4; beyond
100GNGOPTX) longevity of duplex SMF, I'm finding it harder to make a compelling
case for systems vendors to adopt parallel SMF for 100GNGOPTX. My current expectation is that duplex SMF will be the interconnection medium. My ongoing efforts will have more duplex-SMF content. I still think
parallel SMF should deliver lowest cost/power for 100GNGOPTX, and provide an additional 1-2 generations of longevity; just don't see system vendors ready to adopt it now. BUT: What about the Starting Point (above), and the need for significantly-lower cost/power?? If a compelling case is to be made for
an alternative to duplex SMF, it will require a very crisp and convincing argument for significantly-lower cost/power than LR4 ("fair"
comparison such as mentioned earlier), or other duplex SMF approaches. Perhaps a modified version of LR4 can be developed with lower-cost/power lasers
that doesn't reach 10km. If, for whatever reasons, systems vendors insist on duplex SMF, but truly need significantly-lower cost/power, it may
require some compromise, e.g. "wavelength-shifted" SMF, or something
else. Would Si Photonics really satisfy the needs with no compromise? Without
saying they won't, it seems people aren't convinced, because we're having
these discussions. Cheers, Jack On 11/17/11 10:23 AM, "Arlon Martin"
<amartin@xxxxxxxxxx> wrote: >Hello Jack, >To your first question, yes, we are very comfortable with LAN WDM >spacing. That never was a challenge for the technology. We have
chosen to >perfect reflector gratings because of the combination of small size
and >great performance. I am not sure exactly what you are asking in
your >second question. There may be a slightly lower loss to AWGs than >reflector gratings. That difference has decreased as we have gained
more >experience with gratings. For many applications like LR and mR, the
much, >much smaller size (cost is related to size) of reflector gratings
makes >them the best choice. > >Thanks, Arlon > >-----Original Message----- >From: >Sent: Thursday, November 17, 2011 6:42 AM >To: >Subject: Re: [802.3_100GNGOPTX] Emerging new reach space > >Hi Arlon, >Thanks very much for this. You are right; I was referring to thin
film >filters. My gut still tells me that greater tolerances should
accompany >wider wavelength spacing. So I'm guessing that your manufacturing >tolerances are already "comfortable" at the LAN WDM
spacing, and thus the >difference is negligible to you. Is that a fair statement? Same
could be >true for thin film filters. At any rate, LAN WDM appears to have
one >factor-4 generation advantage over CWDM in this discussion, and
it's good >to hear of its cost effectiveness. Which brings up the next
question. Your >data on slide 15 of Chris's presentation referenced in his message
shows >lower insertion loss for your array waveguide (AWG) DWDM filter than
for >the grating filters. Another factor-of-4 data throughput may be
gained in >the future via DWDM. >Cheers, Jack > >On 11/16/11 10:51 PM, "Arlon Martin"
<amartin@xxxxxxxxxx> wrote: > >>Hello Jack, >>As a maker of both LAN WDM and CWDM filters, I would like to
comment on >>the filter discussion. WDM filters can be thin film filters (to
which you >>may be referring) but more likely, they are PIC-based AWGs or
PIC-based >>reflector gratings. In our experience at Kotura with reflector
gratings >>made in silicon, both CWDM and LAN WDM filters work equally
well and are >>roughly the same size. It is practical to put 40 or more
wavelengths on a >>single chip. We have done so for other applications. There is
plenty of >>headroom for more channels when the need arises for 400 Gb/s or
1 Tbs. >>There may be other reasons to select CWDM over LAN WDM, but, in
our >>experience, filters do not favor one choice over the other. >> >>Arlon Martin, Kotura >> >>-----Original Message----- >>From: >>Sent: Wednesday, November 16, 2011 9:09 PM >>To: >>Subject: Re: [802.3_100GNGOPTX] Emerging new reach space >> >>Thanks Chris for your additions. >>1. "CWDM leads to simpler optical filters versus
"closer" WDM (LAN WDM)" >>- >>For a given throughput transmission and suppression of >>adjacent-wavelength >>signals (assuming use of same available optical filter
materials), use of >>a wider wavelength spacing can be accomplished with wider
thickness >>tolerance and usually with fewer layers. The wider thickness
tolerance is >>basic physics, with which I won't argue. In this context, I
consider >>"wider thickness tolerance" as "simpler." >>2. "CWDM leads to lower cost versus "closer" WDM
because cooling is >>eliminated" - I stated no such thing, though it's a common
perception. >>Ali >>Ghiasi suggested CWDM (implied by basing implementation on
40GBASE-LR4) >>might be lower cost, without citing the cooling issue. Cost is
a far more >>complex issue than filter simplicity. You made excellent points
regarding >>costs in your presentation cited for point 1, and I cited LAN
WDM >>(100GBASE-LR4) advantages as
"better-suited-for-integration, and >>"clipping >>off" the highest-temp performance requirement." We
must recognize that at >>1km vs 10km, chirp issues are considerably reduced. >>3. "CWDM is lower power than "closer" WDM
power" - I stated no such >>thing, >>though it's a common perception. I did say "More wavelengths
per fiber >>means more power per channel," which is an entirely
different statement, >>and it's darned hard to argue against the physics of it
(assuming same >>technological toolkit). >>All I stated in the previous message are the advantages of CWDM
(adopted >>by 40GBASE-LR4) and LAN WDM (adopted by 100GBASE-LR4), without
favoring >>one over the other for 100GbE (remember we're talking ~1km, not
10km). >>But >>my forward-looking (crude) analysis of 400GbE and 1.6TbE
clearly favors >>LAN WDM over CWDM - e.g. "CWDM does not look attractive on
duplex SMF >>beyond 100GbE," whereas the wavelength range for 400GbE
LAN 16WDM over >>duplex SMF "is realistic." Quasi-technically speaking
Chris, we're on the >>same wavelength (pun obviously intended) :-) >>Paul Kolesar stated the jist succinctly: "that parallel
fiber >>technologies >>appear inevitable at some point in the evolution of single-mode >>solutions. >> So the question becomes a matter of when it is best to embrace
them." [I >>would replace "inevitable" with
"desirable."] From a module standpoint, >>it's easier, cheaper, lower-power to produce a x-parallel
solution than a >>x-WDM one (x is number of channels), and it's no surprise that
last >>week's >>technical presentations (by 3 module vendors and 1 independent)
had a >>parallel-SMF commonality for 100GNGOPTX. There is a valid
argument for >>initial parallel SMF implementation, to be later supplanted by
WDM, >>particularly LAN WDM. With no fiber re-installations. >>To very recent messages, we can choose which pain to feel
first, parallel >>fiber or PAM, but by 10TbE we're likely get both - in your face
or >>innuendo :-) >>Jack >> >> >> >>On 11/16/11 6:53 PM, "Chris Cole"
<chris.cole@xxxxxxxxxxx> wrote: >> >>>Hello Jack, >>> >>>You really are on a roll; lots of insightful perspectives. >>> >>>Let me clarify a few of items so that they don't detract
from your >>>broader ideas. >>> >>>1. CWDM leads to simpler optical filters versus
"closer" WDM (LAN WDM) >>> >>>This claim may have had some validity in the past, however
it has not >>>been the case for many years. This claim received a lot of
attention in >>>802.3ba TF during the 100GE-LR4 grid debate. An example
presentation is >>>http://www.ieee802.org/3/ba/public/mar08/cole_02_0308.pdf,
where on >>>pages >>>13, 14, 15, and 16 multiple companies showed there is no
practical >>>implementation difference between 20nm and 4.5nm spaced
filters. >>>Further, >>>this has now been confirmed in practice with 4.5nm spaced
LAN WDM >>>100GE-LR4 filters in TFF and Si technologies manufactured
with no >>>significant cost difference versus 20nm spaced CWDM
40GE-LR4 filters. >>> >>>If there is specific technical information to the contrary,
it would be >>>helpful to see it as a presentation in NG 100G SG. >>> >>>2. CWDM leads to lower cost versus "closer" WDM
because cooling is >>>eliminated >>> >>>This claim has some validity at lower rates like 1G or
2.5G, but is not >>>the case at 100G. This has been discussed at multiple 802.3
optical >>>track >>>meetings, including as recently as the last NG 100G SG
meeting. We again >>>agreed that the cost of cooling is a fraction of a percent
of the total >>>module cost. Even for a 40GE-LR4 module, the cost of
cooling, if it had >>>to be added for some reason, would be insignificant. Page 4
of the above >>>cole_02_0308 presentation discusses why that is. >>> >>>This claim to some extent defocuses from half a dozen other
cost >>>contributors which are far more significant. Those should
be at the top >>>of the list instead of cooling. Further, if cooling happens
to enable a >>>technology which reduces by a lot a significant cost
contributor, then >>>it >>>becomes a big plus instead of an insignificant minus. >>> >>>If there is specific technical information to the contrary,
a NG 100G SG >>>presentation would be a great way to introduce it. >>> >>>3. CWDM is lower power than "closer" WDM power. >>> >>>The real difference between CWDM and LAN DWDM is that
un-cooled is lower >>>power. However how much lower strongly depends on the
specific transmit >>>optics and operating conditions. In 100G module context it
can be 10% to >>>30%. However, for some situations it could be a lot more
savings, and >>>for >>>others even less. No general quantification of the total
power savings >>>can be made; it has to be done on a case by case basis. >>> >>>Chris >>> >>>-----Original Message----- >>>From: >>>Sent: Wednesday, November 16, 2011 3:20 PM >>>To: >>>Subject: Re: [802.3_100GNGOPTX] Emerging new reach space >>> >>>Great inputs! :-) >>>Yes, 40GBASE-LR4 is the first alternative to 100GBASE-LR4
that comes to >>>mind for duplex SMF. Which begs the question: why are they
different?? I >>>can see advantages to either: (40G CWDM vs 100G closerWDM)
- uncooled, >>>simple optical filters vs better-suited-for-integration,
and "clipping" >>>off" the highest-temp performance requirement. >>>It's constructive to look forward, and try to avoid
unpleasant surprises >>>of "future-proof" assumptions (think 802.3z and
FDDI fiber - glad I >>>wasn't >>>there!). No one likes "forklift upgrades" except
maybe forklift >>>operators, >>>who aren't well-represented here. Data centers are being
built, so >>>here's >>>a chance to avoid short-sighted mistakes. How do we want
100GbE, 400GbE >>>and 1.6TbE to look (rough guesses at the next generations)?
Here are 3 >>>basic likely scenarios, assuming (hate to, but must) 25G
electrical >>>interface and no electrical mux/demux. Considering duplex
SMF, >>>4+4parallel >>>SMF, and 16+16parallel SMF: >>>Generation >>>100GbE duplex-SMF / 4WDM 4+4parallel / no WDM >>>16+16parallel / dark fibers >>>400GbE duplex-SMF / 16WDM 4+4parallel / 4WDM >>>16+16parallel / no WDM >>>1.6TbE duplex-SMF / 64WDM 4+4parallel / 16WDM >>>16+16parallel / 4WDM >>>The above is independent of distances in the 300+ meter
range we're >>>considering. Yes, there are possibilities of PAM encoding
and electrical >>>interface speed increases. Historically we've avoided the
former, and >>>the >>>latter is expected to bring a factor of 2, at most, for
these >>>generations. >>>Together, they might bring us forward 1 factor-of-4
generation further. >>>For 40GbE or 100GbE, 20nm-spaced CWDM is nice for 4WDM (4
wavelengths). >>>At >>>400GbE, 16WDM CWDM is a 1270-1590nm stretch, with 16 laser
products >>>(ouch!). 20nm spacing is out of the question for 64WDM
(1.6TbE). CWDM >>>does >>>not look attractive on duplex SMF beyond 100GbE. >>>OTOH, a 100GBASE-LR4 - based evolution on duplex SMF, with
~4.5nm >>>spacing, >>>is present at 100GbE. For 400GbE, it could include the same
4 >>>wavelengths, >>>plus 4-below and 12-above - a 1277.5-1349.5nm wavelength
span, which is >>>realistic. The number of "laser products" is
fuzzy, as the same >>>epitaxial >>>structure and process (except grating spacing) may be used
for maybe a >>>few, but nowhere near all, of the wavelengths. For 1.6TbE
64WDM, LR4's >>>4.5nm spacing implies a 288nm wavelength span and a
plethora of "laser >>>products." Unattractive. >>>On a "4X / generational speed increase,"
4+4parallel SMF gains one >>>generation over duplex SMF and 16+16parallel SMF gains 2
generations >>>over >>>duplex SMF. Other implementations, e.g. channel rate
increase and/or >>>encoding, may provide another generation or two of
"future >>>accommodation." >>>The larger the number of wavelengths that are multiplexed,
the higher >>>the >>>loss budget that must be applied to the laser-to-detector
(TPlaser to >>>TPdetector) link budget. More wavelengths per fiber means
more power per >>>channel, i.e. more power/Gbps and larger faceplate area.
While duplex >>>SMF >>>looks attractive to systems implementations, it entails
significant(!!) >>>cost implications to laser/transceiver vendors, who may not
be able to >>>bear "cost assumptions," and additional power
requirements, which may >>>not >>>be tolerable for systems vendors. >>>I don't claim to "have the answer," rather
attempt to frame the question >>>pointedly "How do we want to architect the next few
generations of >>>Structured >>>for >>>this-and-maybe-next-generation, then may hit a wall.
Installation of >>>parallel SMF provides a 1-or-2-generation-gap of
"proofing," with higher >>>initial cost, but with lower power throughout, and pushing
back the need >>>for those abominable "forklift upgrades." >>>Jack >>> >>> >>>On 11/16/11 1:00 PM, " >>> >>>>Brad, >>>>The fiber type mix in one of my contributions in
September is all based >>>>on cabling that is pre-terminated with MPO(MTP)array
connectors. >>>>Recall >>>>that single-mode fiber represents about 10 to 15% of
those channels. >>>>Such cabling infrastructure provides the ability to
support either >>>>multiple 2-fiber or parallel applications by applying
or removing >>>>fan-outs from the ends of the cables at the patch
panels. The fan-outs >>>>transition the MPO terminated cables to collections of
LC or SC >>>>connectors. If fan-outs are not present, the cabling
is ready to >>>>support >>>>parallel applications by using array equipment cords.
As far as I am >>>>aware this pre-terminated cabling approach is the
primary way data >>>>centers are built today, and has been in practice for
many years. So >>>>array terminations are commonly used on single-mode
cabling >>>>infrastructures. While that last statement is true, it
could leave a >>>>distorted impression if I also did not say that
virtually the entire >>>>existing infrastructure e! >>>> mploys fan-outs today simply because parallel
applications have not >>>>been >>>>deployed in significant numbers. But migration to
parallel optic >>>>interfaces is a matter of removing the existing
fan-outs. This is what >>>>I >>>>tried to describe at the microphone during November's
meeting. >>>> >>>>Regards, >>>>Paul >>>> >>>>-----Original Message----- >>>>From: Brad Booth [mailto:Brad_Booth@xxxxxxxx] >>>>Sent: Wednesday, November 16, 2011 11:34 AM >>>>To: >>>>Subject: Re: [802.3_100GNGOPTX] Emerging new reach
space >>>> >>>>Anyone have any data on distribution of parallel vs
duplex volume for >>>>OM3/4 and OS1? >>>> >>>>Is most SMF is duplex (or simplex) given the alignment
requirements? >>>> >>>>It would be nice to have a MMF version of 100G that
doesn't require >>>>parallel fibers, but we'd need to understand relative
cost differences. >>>> >>>>Thanks, >>>>Brad >>>> >>>> >>>> >>>>-----Original Message----- >>>>From: Ali Ghiasi
[aghiasi@xxxxxxxxxxxx<mailto:aghiasi@xxxxxxxxxxxx>] >>>>Sent: Wednesday, November 16, 2011 11:04 AM Central
Standard Time >>>>To: >>>>Subject: Re: [802.3_100GNGOPTX] Emerging new reach
space >>>> >>>>Jack >>>> >>>>If there is another LR4 PMD out there the best starting
point would be >>>>40Gbase-LR4, look at its cost structure, and build a
40G/100G >>>>compatible >>>>PMD. >>>> >>>>We also need to understand the cost difference between
parallel MR4 vs >>>>40Gbase-LR4 (CWDM). The 40Gbase-LR4 cost with time
could be assumed >>>>identical to the new 100G MR4 PMD. Having this
baseline cost then we >>>>can >>>>compare its cost with 100GBase-LR4 and parallel MR4.
The next step is >>>>to >>>>take >>>>into account higher cable and connector cost associated
with parallel >>>>implementation then identify at what reach it gets to
parity with 100G >>>>(CWDM) or >>>>100G (LAN-WDM). >>>> >>>>In the mean time we need to get more direct feedback
from end users if >>>>the parallel SMF is even an acceptable solution for
reaches of 500-1000 >>>>m. >>>> >>>>Thanks, >>>>Ali >>>> >>>> >>>> >>>>On Nov 15, 2011, at 8:41 PM, >>>> >>>>Thanks for this input Chris. >>>> I'm not "proposing" anything here, rather
trying to frame the >>>>challenge, >>>>so that we become better aligned in how cost-aggressive
we should be, >>>>which guides the technical approach. As for names,
"whatever works" :-) >>>>It would be nice to have a (whatever)R4, be it nR4 or
something else, >>>>and >>>>an english name to go with it. The Structured Data
Center (SDC) links >>>>you >>>>describe in your Nov2011 presentation are what I am
referencing, except >>>>for the restriction to "duplex SMF." My input
is based on use of any >>>>interconnection medium that provides the overall
lowest-cost, >>>>lowest-power solution, including e.g. parallel SMF. >>>>Cost comparisons are necessary, but I agree tend to be
dicey. Present >>>>10GbE costs are much better defined than projected
100GbE NextGen >>>>costs, >>>>but there's no getting around having to estimate
NextGen costs, and >>>>specifying the comparison. Before the straw poll, I got
explicit >>>>clarification that "LR4" did NOT include
mux/demux IC's, and therefore >>>>did not refer to what is built today. My assumption was
a "fair" cost >>>>comparison between LR4 and (let's call it)nR4 - at
similar stage of >>>>development and market maturity. A relevant stage is
during delivery of >>>>high volumes (prototype costs are of low relevance).
This does NOT >>>>imply >>>>same volumes. It wouldn't be fair to project ER costs
based on SR or >>>>copper volumes. I'm guessing these assumptions are
mainstream in this >>>>group. That would make the 25% cost target very
aggressive, and a 50% >>>>cost target probably sufficient to justify an optimized
solution. Power >>>>requirements are a part of the total cost of ownership,
and should be >>>>consider! >>>> ed, but perhaps weren't. >>>>The kernel of this discussion is whether to pursue
"optimized >>>>solutions" >>>>vs "restricted solutions." LR4 was specified
through great scrutiny and >>>>is expected to be a very successful solution for 10km
reach over duplex >>>>SMF. Interoperability with LR4 is obviously desirable,
but would a >>>>1km-spec'd-down version of LR4 provide sufficient
cost/power savings >>>>over >>>>LR4 to justify a new PMD and product development? Is
there another >>>>duplex >>>>SMF solution that would provide sufficient cost/power
savings over LR4 >>>>to >>>>justify a new PMD and product development? If so, why
wouldn't it be >>>>essentially a 1km-spec'd-down version of LR4? There is
wide perception >>>>that SDC's will require costs/powers much lower than
are expected from >>>>LR4, so much lower that it's solution is a major topic
in HSSG. So far, >>>>it looks to me like an optimized solution is probably
warranted. But >>>>I'm >>>>not yet convinced of that, and don't see consensus on
the issue in the >>>>group, hence the discussion. >>>>Cheers, Jack >>>> >>>>From: Chris Cole >>>><chris.cole@xxxxxxxxxxx<mailto:chris.cole@xxxxxxxxxxx>> >>>>Reply-To: Chris Cole >>>><chris.cole@xxxxxxxxxxx<mailto:chris.cole@xxxxxxxxxxx>> >>>>Date: Tue, 15 Nov 2011 17:33:17 -0800 >>>>To: >>>>< >>>>I >>>>S >>>>T >>>>SERV.IEEE.ORG>> >>>>Subject: Re: [802.3_100GNGOPTX] Emerging new reach
space >>>> >>>>Hello Jack, >>>> >>>>Nice historical perspective on the new reach space. >>>> >>>>Do I interpret your email as proposing to call the new
150m to 1000m >>>>standard 100GE-MR4? ☺ >>>> >>>>One of the problems in using today’s 100GE-LR4 cost as
a comparison >>>>metric for new optics is that there is at least an
order of magnitude >>>>variation in the perception of what that cost is. Given
such a wide >>>>disparity in perception, 25% can either be impressive
or inadequate. >>>> >>>>What I had proposed as reference baselines for making
comparisons is >>>>10GE-SR (VCSEL based TX), 10GE-LR (DFB laser based TX)
and 10GE-ER (EML >>>>based TX) bit/sec cost. This not only allows us to make
objective >>>>relative comparisons but also to decide if the
technology is suitable >>>>for >>>>wide spread adoption by using rules of thumb like 10x
the bandwidth >>>>(i.e. 100G) at 4x the cost (i.e. 40% of 10GE-nR cost)
at similar high >>>>volumes. >>>> >>>>Using these reference baselines, in order for the new
reach space >>>>optics >>>>to be compelling, they must have a cost structure that
is referenced to >>>>a >>>>fraction of 10GE-SR (VCSEL based) cost, NOT referenced
to a fraction of >>>>10GE-LR (DFB laser based) cost. Otherwise, the argument
can be made >>>>that >>>>100GE-LR4 will get to a fraction of 10GE-LR cost, at
similar volumes, >>>>so >>>>why propose something new. >>>> >>>>Chris >>>> >>>>From: >>>>Sent: Tuesday, November 15, 2011 3:06 PM >>>>To: >>>> >>>>S >>>>T >>>>S >>>>ERV.IEEE.ORG> >>>>Subject: [802.3_100GNGOPTX] Emerging new reach space >>>> >>>>Following last week's meetings, I think the following
is relevant to >>>>frame our discussions of satisfying data center needs
for low-cost >>>>low-power interconnections over reaches in the roughly
150-1000m range. >>>>This is a "30,000ft view,"without getting
overly specific. >>>>Throughout GbE, 10GbE, 100GbE and into our discussions
of 100GbE >>>>NextGenOptics, there have been 3 distinct spaces, with
solutions >>>>optimized for each: Copper, MMF, and SMF. With
increasing data rates, >>>>both copper and MMF specs focused on maintaining
minimal cost, and >>>>their >>>>reach lengths decreased. E.g. MMF reach was up to 550m
in GbE, then >>>>300m >>>>in 10GbE (even shorter reach defined outside of IEEE),
then 100-150m in >>>>100GbE. MMF reach for 100GbE NextGenOptics will be even
shorter unless >>>>electronics like EQ or FEC are included. Concurrently,
MMF solutions >>>>have >>>>become attractive over copper at shorter and shorter
distances. Both >>>>copper and MMF spaces have "literally"
shrunk. In contrast, SMF >>>>solutions >>>>have maintained a 10km reach (not worrying about the
initial 5km spec >>>>in >>>>GbE, or 40km solutions). To maintain the 10km reach,
SMF solutions >>>>evolved from FP lasers, to DFB lasers, to WDM with
cooled DFB lasers. >>>>The >>>>10km solutions increasingly resemble longer-haul
telecom solutions. T! >>>> here is an increasing cost disparity between MMF and
SMF solutions. >>>>This >>>>is an observation, not a questioning of the reasons
behind these >>>>trends. >>>>The increasing cost disparity between MMF and SMF
solutions is >>>>accompanied by rapidly-growing data center needs for
links longer than >>>>MMF can accommodate, at costs less than 10km SMF can
accommodate. This >>>>has the appearance of the emergence of a new
"reach space," which >>>>warrants its own optimized solution. The emergence of
the new reach >>>>space >>>>is the crux of this discussion. >>>>Last week, a straw poll showed heavy support for
"a PMD supporting a >>>>500m >>>>reach at 25% the cost of 100GBASE-LR4" (heavily
favored over targets of >>>>75% or 50% the cost of 100GBASE-LR4). By heavily
favoring the most >>>>aggressive low-cost target, this vote further supports
the need for an >>>>"optimized solution" for this reach space. By
"optimized solution" I >>>>mean >>>>one which is free from constraints, e.g.
interoperability with other >>>>solutions. Though interoperability is desirable, an
interoperable >>>>solution is unlikely to achieve the cost target. In the
3 reach spaces >>>>discussed so far, there is NO interoperability between
copper/MMF, >>>>MMF/SMF, or copper/SMF. Copper, MMF and SMF are
optimized solutions. It >>>>will likely take an optimized solution to satisfy this
"mid-reach" >>>>space >>>>at the desired costs. To repeat: This has the
appearance of the >>>>emergence >>>>of a new "reach space," which warrants its
own optimized solution. >>>>Since >>>>the reach target lies between "short reach"
and "long reach," "mid! >>>> reach" is a reasonable term >>>>Without discussing specific technical solutions, it is
noteworthy that >>>>all 4 technical presentations last week for this
"mid-reach" space >>>>involved parallel SMF, which would not interoperate
with either >>>>100GBASE-LR4, MMF, or copper. They would be optimized
solutions, and >>>>interest in their further work received the highest
support in straw >>>>polls. Given the high-density environment of
datacenters, a solution >>>>for >>>>the mid-reach space would have most impact if its
operating power was >>>>sufficiently low to be implemented in a form factor
compatible with MMF >>>>and copper sockets. >>>>Cheers, Jack |