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Re: [802.3_100GNGOPTX] Emerging new reach space



Hi Paul,


Good question. It is not yet in standards, but rather it is an example of an entry in the informative table that Matt proposed we add to future standards.


Specifically, the 100GE-LR4 link budget is 8.5dB, of which 6.3dB is loss budget which can be used in a variety of useful ways like going over SMF or through passive loss elements like path panels or cross-connects. There is also a 2.2dB allocation for penalties. That is one use scenario. The example I gave shows another use scenario. If an end user only needs a 2km reach, they have available in round numbers,~7dB of loss budget. Obviously if we were writing these numbers into the standard, we would be more precise.

 

Keep in mind that link budget itself is informative. The normative specs are TDP and SRS. So Matt’s proposal to add an informative link budget table is entire consistent with how we handle the single link budget entry today.

 

Chris

 

From: Kolesar, Paul [mailto:PKOLESAR@xxxxxxxxxxxxx]
Sent: Monday, November 21, 2011 5:29 AM
To: STDS-802-3-100GNGOPTX@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_100GNGOPTX] Emerging new reach space

 

Chris,

Can you cite the location of the 2km / 7dB information in the standard?  I only find information on 30 km vs 40 km engineered link for –ER4. 
Paul

 


From: Chris Cole [mailto:chris.cole@xxxxxxxxxxx]
Sent: Sunday, November 20, 2011 3:31 PM
To: STDS-802-3-100GNGOPTX@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_100GNGOPTX] Emerging new reach space

 

Matt,

Adding an informative table in future standards on reach vs. loss budget trade-off is an excellent idea. Many end users do this implicitly already, so they will benefit by having more exact numbers from those that write the standards.

For 100GE-LR4, this type of information is already informally provided, for example pointing out that for shorter reaches like ~2km, a ~7dB loss budget is available.

Chris

From: "Matt Traverso (mattrave)" <mattrave@xxxxxxxxx>
Date: November 20, 2011 12:36:21 PM EST
To: John D'Ambrosia <jdambrosia@xxxxxxxxxxxxxxx>, "STDS-802-3-100GNGOPTX@xxxxxxxxxxxxxxxxx" <STDS-802-3-100GNGOPTX@xxxxxxxxxxxxxxxxx>
Subject: RE: [802.3_100GNGOPTX] Emerging new reach space

Colleagues,

John wrote: "Also one lesson that we should learn from recent industry debates -forget the reach- what is the desired budget?"

As Chris Cole & others have pointed out, the reach is dependent upon the transmission penalties as well as the link budget -- see discussion on wavelength pitch.  It might be a useful approach to consider trading off a scenario where the amount of additional insertion loss (connectors, splices etc) versus distance.

For example, we could set an objective of 1km with 2dB of insertion loss (no significance -- I just pulled it out of the ether).  Then we could provide an informative table which could highlight at 500m reach the allowable insertion loss is 2dB + X.  Alternately, we could provide a scenario which shows that if the insertion loss is only 1dB then the reach is 1km + Y.

On the HSSG reference, I believe it was Ted Seely coming to the microphone to object to the presentation Chris, Eddie & I put together (http://www.ieee802.org/3/hssg/public/nov07/cole_01_1107.pdf) -- he was concerned that there were many scenarios where there were higher connectors/insertion loss such that he preferred 10km to accommodate the additional insertion loss.

cheers
--matt

-----Original Message-----
From: John D'Ambrosia [mailto:jdambrosia@xxxxxxxxxxxxxxx]
Sent: Saturday, November 19, 2011 12:27 PM
To: STDS-802-3-100GNGOPTX@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_100GNGOPTX] Emerging new reach space

Paul
I notice you used a city block but you did leave out the fact that it was a multifloor scenario.

However as I pointed out I remember this from hssg days which is 5 years ago.  I agree with the call for new data and am not sure what data that has been presented to the IEEE that details the industry 2km need.  How much of that is want and not need is unclear to me.

Also one lesson that we should learn from recent industry debates -forget the reach- what is the desired budget?

John

Sent from my iPhone

On Nov 19, 2011, at 2:16 PM, "Kolesar, Paul" <PKOLESAR@xxxxxxxxxxxxx> wrote:

Scott,

I agree with the thrust of your assessment.

 

A minor correction.  I did include the entire link distribution in my analysis.  The only truncated input in my analysis is the patch cord distribution above 70 ft.  The percentage of channels within (or above) any length is the result of convolution of the length distributions of constituent links and cords, which carries the probabilities with it.  For example, if 10% of links lie above 100 m, the probability of two concatenated links being longer than 200 m is 0.10 x 0.10 = 1%.  This is over simplified because it does not include the equipment cords and the patch cord that create full channels.

 

I note that your cut-off at 400,000 square feet allows for a square footprint that is 632 feet on a side, substantially bigger than a square block which, at one tenth of a mile on a side, is 279,000 square feet.

 

Paul

 

-----Original Message-----

From: Scott Kipp [mailto:skipp@xxxxxxxxxxx]

Sent: Saturday, November 19, 2011 11:59 AM

To: STDS-802-3-100GNGOPTX@xxxxxxxxxxxxxxxxx

Subject: Re: [802.3_100GNGOPTX] Emerging new reach space

 

Jeff,

 

I agree with your point about distributions.

 

No, it was not arbitrary that I stopped at 400,000 sq ft.  I stopped at 400,000 sq ft because I wanted to cut off the tail of the distribution of the size of the data centers.  I propose that there are only a few % (probably les than 1%) of data centers that are over 400,000 sq ft.  The larger ones are the mega data center or massive data centers (MDC in either case) that Google and others are deploying.

 

Google is a very interesting case study since they deliver over 6% of all Internet traffic.  I just got a response from Bikash and he says they do have 2 km links and he is getting frustrated with the IEEE second guessing this reality.  What I think we need to do is understand that the MDC market has atypical needs and we do have solutions for this with LR4, 10X10-2km and 10X10-10km.

 

I suggest that we have a bifurcation in the market where we have what most people do and we have what the MDCs do.  One piece of data on this is in Paul Kolesar's data where he shows over 5% of permanent links between patch panels in 2010 are over 119 meters long (see slide 8 of http://www.ieee802.org/3/100GNGOPTX/public/sept11/kolesar_02_0911_NG100GOPTX.pdf).  Paul did not include these outliers in his analysis that shows only 1% of links are over 256 meters long (cell R31 of the Kolesar Kalculator).  We need to understand what assumptions and limits we're putting on the data since this affects our conclusions.

 

I will present on this more in Newport Beach.  I have gone to some large data centers, but not MDCs because they won't let people like me in!  We need to make the distinction between the white space (the raised floor where equipment resides) and the building size of the data center.  The white space is a significant subset of the building size.  The white space can be separated by significant distances and this can lead to long permanent links between the white space.

 

I'm proposing that the nR4 solution would meet the needs of many links that are longer than SR4.  From the Kolesar Kalculator, 19% of links are longer than 100 meters and less than 256 meters (cells R14-R31).  19% of links would need nR4 or LR4 if SR4 only supports 100 meters.

 

If SR4 matches the 150 meters of SR10 which will be very challenging with 25G lanes, then the nR4 market would shrink to about 8% of links (cells R19 to R31).  Paul told me that the 2:1 mix is the most likely deployment scenario in the industry and corresponds to column R in the spreadsheet. Only 1% of links are longer than 256 meters according to Paul's work.

 

I hope that helps,

Scott

 

 

 

 

-----Original Message-----

From: Jeffery Maki [mailto:jmaki@xxxxxxxxxxx]

Sent: Friday, November 18, 2011 5:05 PM

To: Scott Kipp; STDS-802-3-100GNGOPTX@xxxxxxxxxxxxxxxxx

Subject: RE: [802.3_100GNGOPTX] Emerging new reach space

 

Scott,

 

Was the choice to end your table at 400,000 sq. ft. arbitrary?

 

All,

 

I believe we need to know if the potential square footage may or may not grow larger over the coming years for what is known as a mega datacenter.  How big is a mega datacenter to be?  At some point, 100GBASE-LR4 will be the right choice just based on loss budget.  We need to know the distribution of reaches to understand where to draw the line in selecting a break in the PMD definitions.

 

Jeff

 

 

-----Original Message-----

From: Scott Kipp [mailto:skipp@xxxxxxxxxxx]

Sent: Friday, November 18, 2011 1:38 PM

To: STDS-802-3-100GNGOPTX@xxxxxxxxxxxxxxxxx

Subject: Re: [802.3_100GNGOPTX] Emerging new reach space

 

Chris and all,

 

I have been wanting to discuss the reach objective for 100GBASE-nR4, so thanks for kicking off this discussion.

 

You referenced the 10X10 MSA white paper that calls out a maximum distance of <500 meters.  You reference the authors of Vijay and Bikash, but I was the co-author that wrote this section of the paper and did the mathematical analysis which they agreed to. The actual distance of 414 meters is a simple calculation based on a 400,000 sq ft data center.  Even if the data center is 550,000 sq ft, the link distance is less than 500 meters long.  So I propose that 500 meters is long enough for the largest data centers that we should target.

 

The problem with a 500 meter distance is in the way that the IEEE defines the maximum link length.  The IEEE defines the reach objective for SM fibers and gives an insertion loss based on the 2.0dB of connector and splice loss and the fiber attenuation loss.  Specifically, 802.3ba states this below table 87.9:

 

The channel insertion loss is calculated using the maximum distance specified in Table 87–6 and cabled optical fiber

attenuation of 0.47 dB/km at 1264.5 nm plus an allocation for connection and splice loss given in 87.11.2.1.

 

For the 10km link of 100GBASE-LR4, the attenuation is 6.7dB = 10km * 0.47dB/km + 2.0dB of connector and splice loss.

 

If this project follows this example for a 500 meter nR4 link, then the insertion loss would only be 2.2dB = 0.5km * 0.47dB/km + 2.0dB for connector and splice loss. Many attendees know that this could limit the applicability of the nR4 link because it won't support structured cabling environments.  With many MPO ribbon connectors in a link, it could be difficult to support a typical link in the structured cabling environments that will be required in large data centers.

 

To make nR4 a success, we need to take these structured cabling environments into account and increase the connector loss.  I would like to hear from some cabling vendors and especially end users as to range of insertion losses that they have seen and what they expect to see if ribbon fibers are used instead of the usual duplex SM fibers.

 

Jonathan King did a great statistical analysis of 4 duplex MM connection loss in king_01_0508.  We should do a similar analysis for 6 SM ribbon connectors to determine the loss of a long link.

 

If we determine the loss to be 3.5dB, then the insertion loss for the nR4 link could be 3.7dB = 0.5km * 0.47dB/km + 3.5dB for connector and splice loss.  With these parallel solutions, this loss might even be larger since they don't have the WDM losses in the link.

 

That's my 42 cents,

Scott

 

 

-----Original Message-----

From: Chris Cole [mailto:chris.cole@xxxxxxxxxxx]

Sent: Friday, November 18, 2011 11:12 AM

To: STDS-802-3-100GNGOPTX@xxxxxxxxxxxxxxxxx

Subject: Re: [802.3_100GNGOPTX] Emerging new reach space

 

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: Jack Jewell [mailto:jack@xxxxxxxxxxxxxx]

Sent: Friday, November 18, 2011 9:38 AM

To: STDS-802-3-100GNGOPTX@xxxxxxxxxxxxxxxxx

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

Atlanta, four technical presentations on the subject all dealt with

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 Atlanta meeting: Systems users (especially

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: Jack Jewell [mailto:jack@xxxxxxxxxxxxxx]

Sent: Thursday, November 17, 2011 6:42 AM

To: STDS-802-3-100GNGOPTX@xxxxxxxxxxxxxxxxx

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: Jack Jewell [mailto:jack@xxxxxxxxxxxxxx]

Sent: Wednesday, November 16, 2011 9:09 PM

To: STDS-802-3-100GNGOPTX@xxxxxxxxxxxxxxxxx

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: Jack Jewell [mailto:jack@xxxxxxxxxxxxxx]

Sent: Wednesday, November 16, 2011 3:20 PM

To: STDS-802-3-100GNGOPTX@xxxxxxxxxxxxxxxxx

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 Data Center interconnects?" Insistence on duplex SMF works

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, "Kolesar, Paul" <PKOLESAR@xxxxxxxxxxxxx> wrote:

 

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: STDS-802-3-100GNGOPTX@xxxxxxxxxxxxxxxxx

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: STDS-802-3-100GNGOPTX@xxxxxxxxxxxxxxxxx

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, Jack Jewell wrote:

 

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:

<STDS-802-3-100GNGOPTX@xxxxxxxxxxxxxxxxx<mailto:STDS-802-3-100GNGOPTX@L

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: Jack Jewell [mailto:jack@xxxxxxxxxxxxxx]

Sent: Tuesday, November 15, 2011 3:06 PM

To:

STDS-802-3-100GNGOPTX@xxxxxxxxxxxxxxxxx<mailto:STDS-802-3-100GNGOPTX@LI

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