RE: A couple of questions on clause 52
> -----Original Message-----
> From: Jonathan Thatcher
> [mailto:Jonathan.Thatcher@xxxxxxxxxxxxxxxxxxxx]
> Sent: 17 April 2001 02:30
> To: serialpmd
> Subject: A couple of questions on clause 52
>
> Would someone please remind me:
>
> 1. Why is it that in the OMA tables that we spec the dBm
> range in OMA/2
> instead of just OMA? We specify the Rx in OMA (dBm). Are we
> just testing to
> see if the user knows to add 3dB when working on the link
> budgets? :-)
It's the difference between preferring to measure the "peak" value of a
time-varying ("AC")voltage/current/lightbeam or the "peak-to-peak". We
inherit the traditional measure of signal strength,
dBm(average) = dBm(peak)+ dB(extinction ratio penalty)
We also inherit OMA, defined on a peak-to-peak basis. So we are stuck with
an untidy situation. My preference is to use dB(OMA/2), daft as it looks,
because that provides better compatibility with traditional specifications
and actual power meters. I'd really like to redefine OMA, but I guess it's
too late for that.
> 2. What did we mean in Table 52-21 that the Minimum
> dispersion in ps/nm for
> ER/EW be the worst of i) 0.93... and ii) 0?
> If Lamda is within the specifications (1530 to 1565 nm)
> required for ER/EW,
> when would 0 (zero) be the worst case?
Facile answer:
We are just declaring a range of dispersions, from most positive to most
negative. We aren't taking a position on which end of the range is worst.
Perhaps you could suggest better wording in a comment.
Techie answer:
Negative dispersion penalties are possible, so there could be doubt about
which end is worst.
Hope I answered your questions,
Piers
>
> jonathan
>