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[802.3_B10GAUTO] Desired comparisons to understand proposed link segment IL limit

All –

Based on the discussions the other day, I put together a short example of what would be useful for PHY engineers to evaluate the proposed link segment IL baseline.

It is common for cabling manufacturers to ensure that the IL will not exceed a limit line at all frequencies by providing margin to that limit line at all frequencies.  It is also common to exclude points where the measured IL is low (say < 1dB). 

Rather than just present a limit line and say ‘it is good and we can build to it’, it is useful for the group to understand how close (or not) that limit line might be to reality.  That way we can avoid burdening our phys with margin on top of margin added in the cabling, and we can also avoid perhaps not adding enough margin in the phy design.

I understand that several factors, such as ageing, are estimated, but it would be good to know the accuracy of those estimates.  For example, if the 1.15 factor could be as high as 1.17 and as low as 1.13, that would be good to know.

Hopefully this will lead us all to being able to support the proposal and be comfortable to move on with specification work on the phy. 

The attached presentation shows an example of the metrics desired for cable measurements presented.

 

PLEASE DO NOT SPEND TIME ANALYZING THE NUMBERS THEMSELVES – THEY ARE JUST AN EXAMPLE OF THE KIND OF MEASUREMENTS WANTED.  I didn’t spend a lot of time adjusting the cable data – it is just scaled on a per-meter basis.  (yes, I am aware that it is 23C data and needs to be temperature adjusted, which is one reason the average margin is so high)

 

What is desired are:

  • With measured numbers < 1 dB excluded:
    • Minimum over frequency of [Proposed IL Limit (dB) – Measured IL (dB) ]
    • Average over frequency of the same.

 

This will help confidence and help thinking on achievable reach and phy complexity.

 

-george

 

 

George Zimmerman, Ph.D.

President & Principal

CME Consulting, Inc.

Experts in Advanced PHYsical Communications

george@xxxxxxxxxxxxxxxxxxxx

310-920-3860

 

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