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Re: [802.3_MAINT] Follow up on proposed Comment to add distance specification for 10GBASE-S over OM4 media

Steve,
 
The scenario you listed is not an apples-to-apples comparison, but rather an apples-to-oranges comparison.
 
I'm sure I don't need to remind you that the compliance point in an Ethernet network is at the medium dependent interface (MDI).
 
A customer that purchases a switch or server that has a port type 10GBASE-SR or 10GBASE-ER assumes that the device is compliant with the specifications at the MDI. In the case of the ER channel, if the channel is compliant with the specification - whether it is 30 km or an engineered 40 km link - then the system will be interoperable.
 
As for your concern, if the 500 m OM4 link was compliant to the channel specifications at the MDI, then there would be no issue. From what has been presented, the specification at the MDI looking into the PHY and into the channel needs to be changed to permit a 500 m OM4 link. This is radically different than what 10GBASE-ER requires, hence the inability to do an apples-to-apples comparison.
 
To try to require a tighter specification at the MDI while still calling the port type 10GBASE-SR is misleading. As an industry, we would be unable to guarantee interoperability to an end user that has purchase 10GBASE-SR optics for their devices and expect them to operate over 500 m of OM4, because the only requirement for 10GBASE-SR is to be "minimally" compliant with the specification at the MDI. Therefore, a new port type is required for your proposal.
 
To create an apple-to-apple comparison, don't touch the spectral width of the 10GBASE-S PMD. If you can "engineer" the 500 m OM4 channel to have the same performance specifications as a 400 m OM4 channel, then you would be creating a system similar to what 10GBASE-ER does.
 
This is just my take on it.
 
Cheers,
Brad

On Tue, Aug 16, 2011 at 8:49 AM, Swanson, Steven E <SwansonSE@xxxxxxxxxxx> wrote:
Dan,
 
Thanks for the comment; I think this subject will be discussed further in a future call but I would like to understand the concern here.
 
If someone releases a product tomorrow that is 100% compliant, but minimally meets the laser specs for SR, then he can support a minimum of 400m per the standard.
 
If someone releases a product tomorrow that is 100% compliant, but exceeds the minimum laser specs, fiber specs and connector specs for SR by a defined amount, then he can support a minimum of 500m per the standard (by definition, an engineered link).
 
Contrast this with:
 
If someone releases a product tomorrow that is 100% compliant, but minimally meets the single-mode fiber specs for ER, then he can support a minimum of 30km per the standard.
 
If someone releases a product tomorrow that is 100% compliant, but exceeds the minimum single-mode fiber specs for ER by a defined amount, then he can support a minimum of 40km per the standard (by definition, an engineered link).
 
But it is still 10GBASE-ER, right?
 
Steve

Steven E. Swanson
Corning Incorporated
800 17th Street NW, HI/ES
Hickory, NC 28603-0489

t       828-901-5328
f       828-901-5533
c       607-725-1129

swansonse@xxxxxxxxxxx

 

From: Dove, Daniel [mailto:dan.dove@xxxxxx]
Sent: Monday, August 15, 2011 5:42 PM
To: STDS-802-3-MAINT@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_MAINT] Follow up on proposed Comment to add distance specification for 10GBASE-S over OM4 media

Hi Steve,

 

I tend to agree with Brad. We cannot specify the reach based upon empirical laser data. We must consider the specifications and assume that somebody is going to release a product tomorrow that is 100% compliant, but minimally meets the laser specs for SR.

 

The goal of this maintenance effort should stick to confirmation that existing SR optics (per spec) will support the reaches defined and I think we have done that. We can debate about how much margin should be necessary as this might allow a slight increase in reach, but 400m is a nice round number and retaining some margin will increase confidence in passing the spec readily.


Dan

 

From: Brad Booth [mailto:bjbooth@xxxxxxxxx]
Sent: Monday, August 15, 2011 12:35 PM
To: STDS-802-3-MAINT@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_MAINT] Follow up on proposed Comment to add distance specification for 10GBASE-S over OM4 media

 

Thanks Steve.

 

BTW, you make reference to last week's presentation. I remember reviewing it on the conference call but was it ever uploaded? I'd like to be able to reference back to it.

 

As mentioned on the call, the concern is lack of 100% coverage with available 10GBASE-S PMDs. If only a subset of PMDs would satisfy the spectral width requirements for achieving 500m reach, then that subset would require a new PMD name to distinguish them as exceeding the 10GBASE-S requirements. I believe some felt that we don't add a new PMD specification to 802.3 without a PAR that permits use to do so. A new PMD is probably considered by many to be outside the scope of the revision PAR.

 

Cheers,

Brad

On Mon, Aug 15, 2011 at 12:56 PM, Swanson, Steven E <SwansonSE@xxxxxxxxxxx> wrote:

Brad,

 

I didn't do it for spectral width because I attached a plot of all of the VCSEL spectral widths but here is the raw data:

 

0.2

1

1.43%

0.25

3

5.71%

0.3

25

41.43%

0.35

26

78.57%

0.4

11

94.29%

0.45

3

98.57%

More

1

100.00%

So in the proposal we made last week, ~40% of the lasers would support 500m with 1.1 dB margin; with a little less margin, I think .35nm will work suggesting that ~78% of the lasers would support the proposal.

Steven E. Swanson
Corning Incorporated
800 17th Street NW, HI/ES
Hickory, NC 28603-0489

t       828-901-5328
f       828-901-5533
c       607-725-1129

swansonse@xxxxxxxxxxx

 

 

From: Brad Booth [mailto:bjbooth@xxxxxxxxx]
Sent: Monday, August 15, 2011 12:23 PM
To: STDS-802-3-MAINT@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_MAINT] Follow up on proposed Comment to add distance specification for 10GBASE-S over OM4 media

Steve,

 

In bullet points #2 and 3, you list the worst case wavelength and OMA power. Can you also do the same for bullet point #1 for spectral width?

 

Thanks,
Brad

On Mon, Aug 15, 2011 at 10:23 AM, Swanson, Steven E <SwansonSE@xxxxxxxxxxx> wrote:

Matt,

 

I had an error in my calculation:

 

1. The average spectral width is 0.317

2. The average wavelength is 850.6; worst case 845.7

3. The average OMA power is -1.41; worst case -2.42

Using these numbers in the IEEE model yields 4.9 dB of margin at 400m.

Using these numbers in the IEEE model yields 2.6 dB of margin at 550m.

 

Steven E. Swanson
Corning Incorporated
800 17th Street NW, HI/ES
Hickory, NC 28603-0489

t       828-901-5328
f       828-901-5533
c       607-725-1129

swansonse@xxxxxxxxxxx

 

 

From: Swanson, Steven E [mailto:SwansonSE@xxxxxxxxxxx]
Sent: Monday, August 15, 2011 10:50 AM
To: STDS-802-3-MAINT@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_MAINT] Follow up on proposed Comment to add distance specification for 10GBASE-S over OM4 media

Matt etal,

 

I had our guys look at the VCSELs we have purchased on the open market used in our test facilities; there are 70 transceivers from 6 different manufacturers. 78% of the spectral widths are less than 0.35. The triple trade-off numbers are as follows:

 

1. The average spectral width is 0.286

2. The average wavelength is 849.4; worst case 845.7

3. The average OMA power is -1.24; worst case -2.42

Using these numbers in the IEEE model yields 5.2 dB of margin at 400m.

Using these numbers in the IEEE model yields 3.3 dB of margin at 550m.

The more I look at this, I think we are being REALLY, REALLY conservative in IEEE, maybe too much so; here is the distribution of spectral width:

 

Steven E. Swanson
Corning Incorporated
800 17th Street NW, HI/ES
Hickory, NC 28603-0489

t       828-901-5328
f       828-901-5533
c       607-725-1129

swansonse@xxxxxxxxxxx

 

 

From: Matt Traverso (mattrave) [mailto:mattrave@xxxxxxxxx]
Sent: Thursday, July 28, 2011 9:05 PM
To: STDS-802-3-MAINT@xxxxxxxxxxxxxxxxx
Subject: [802.3_MAINT] Follow up on proposed Comment to add distance specification for 10GBASE-S over OM4 media

Hello to the now very active IEEE Maintenance reflector!

 

As I mentioned during my presentation at the IEEE plenary in July I would like to schedule a few calls to follow up on the questions/comments raised during the meeting. (see http://www.ieee802.org/3/maint/public/traverso_1_0711.pdf)

 

My goal for these calls per the discussion on the floor is to try to build more confidence in the proposed reach value.  I believe that there was broad consensus at the meeting that (a) goal of specifying value is worthwhile,(b) theoretical analysis was sound.  I hope to confirm my perception at the first call & discuss further justification for 400m reach.

 

My intention is to submit a comment by the comment deadline of Aug 26th.

 

Call timing:

Wednesday Aug 10th, 10 – 11:30 am PT

Wednesday Aug 17th , 10 – 11:30 am PT

 

Meeting login details below

 

best regards

--matt traverso

 

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