From serial PMD call, 20 Feb. Next call at usual #
1. Jitter
Still mainly focussing on TP3. There's an issue of creating fixed? pattern
on WAN PHY. Expecting presentation on LAN? test patterns from John Ewen,
Bill Reysen, Jonathan Thatcher, probably at the March meeting. Jonathan
thinks the methodology is the high priority issue for a complete standard,
rather than the choice of pattern. Any early disclosure of this material
would help the standard proceed to schedule.
We didn't have time to discuss Juergen's slides.
From last week: "Is a transversal filter with two equal taps a suitable
worst case or does its symmetry null out an impairment? Piers to think
about this, other opinions welcome of course."
Having thought, I don't see why the equal taps wouldn't make a worst case.
2. Air gaps in connectors
Argument to ignore: Air gaps are out of standard. It is too involved to
standardise for out-of-standard conditions. We want to be clear what is
acceptable and what is not.
The counter-argument is that we could make more robust links if we take it
into account.
Consensus of the call is _not_ to take air gaps into account. This is a
change of policy: implies that we specify 1550 nm RIN at the rated back
reflection rather than -12 dB. Petar or Peter will present this at the
March meeting.
3. Interferometric Noise
Petar Pepeljugoski and Peter Ohlen presented their viewgraph pack sent out
today.
Action for Piers: include Interferometric Noise in power budget (may not get
this done by March meeting). Penalty thought to be <~0.5 dB at our "worst"
(longest links), but might be getting near a "cliff" or error floor (for the
shortest links, if the receiver is beginning to overload.
I was trying to think how to keep this issue within the receiver. I
suggested that the standard could be written so that a high reflection Rx
should ~0.5 dB better sensitivity than a low reflection one. That way the
receiver implementer gets to choose how to best cost-optimise.
No agreement. We should vote this in a larger body. If the stalemate
continues, we stay with the status quo.
Actions for Peter and Petar: write comments for their proposals, both the
agreed (air gaps, mention IN in the draft) and the not-agreed ones (change
Extinction ratio from 3 dB to 4 dB on one had, change Rx reflectivity from
-12 to -20 dB on the other).
Still interested in spending the last ~0.1? 0.3? dB of unallocated margin in
favour of the transmitter.
4. How to specify triple trade off curves for standard
Need unambiguous, black and white, precise definition of what is within and
without the standard. Options are tables or equations. David Kabal to see
how Fibre Channel handle this issue.
5. Launch conditions for new MMF
Need to include these in Draft 3.0 for completeness, or remove the new MMF
from the draft. Those working on the issue are requested to submit
comment(s) and bring a presentation.
6. Laser safety
In some geographies may need to classify the 850nm PMD as class 3B? (not
class 1) until CDRH align with IEC. Jonathan will write a comment to this
effect.
2 commenting days to go!! And after that,
Next meeting
------------
Will concentrate on jitter. Hope to hear from Tom Lindsay, John Ewen and
Bill Reysen.
Same time at the usual phone number:
4pm GMT = 8am PST Tuesday 27 February 2001 for an hour and a half -ish
+1(816)650-0631 Access code 39209
Piers