AW: Test patterns ?
Hi
When discussing test patterns another minor point comes to my mind.
The Jitter test and Consecutive Identical Digit (CID) immunity measurement
is moved from G.958 to G.957 of ITU. This due to the fact that G.958 will
soon become obsolete. Technical there is no change. We should use G.957
instead of G.958.
Regards Juergen Rahn
----------
Von: DAWE,PIERS (A-England,ex1) [SMTP:piers_dawe@xxxxxxxxxxx]
Gesendet: Dienstag, 2. Januar 2001 16:35
An: 'Serial PMD Ad Hoc Reflector'
Betreff: RE: Test patterns ?
The pattern for extinction ratio and OMA measurements should have
the
following characteristics:
Convenient to generate, e.g.:
Real traffic
Idling
Something synchronous to the ICs:
66 bit word oriented?
Byte oriented?
Convenient to measure
Static pattern?
Gives sufficient accuracy
Depends what we want to measure...
Acceptable measurement time
There are at least three competing philosophies on what we want to
measure:
1. We are trying to find the "1" and "0" levels well away from
the
transients (as in GigE)
2. We may as well measure the average "1" and "0" levels. Then
we can
measure in or near service. This is ITU-T's approach.
3. It is of little interest to the customer that some bits are
better
than others. Just measure the eye opening, including the isolated
bits.
While the GigE is 10 bit word oriented, 5x"1" + 5x"0" makes sense in
that
scenario; criterion easy to generate. Not for either 10GE serial
line code.
The amplitude measurements under philosophy 1 are not intended to
stress
anything to do with long run lengths. 3,4,8,or even 66 x"1" then
x"0" would
probably work for this test, even though the transition densities
are far or
very far from normal. I doubt if there is need for a hard "shall"
to define
the pattern.
Piers
> -----Original Message-----
> From: Rich Taborek [mailto:rtaborek@xxxxxxxxxxxxx]
> Sent: 27 December 2000 08:55
> To: 'Serial PMD Ad Hoc Reflector'
> Subject: Re: Test patterns ?
>
> Peter,
>
> Just some "food for thought comments":
>
> Öhlén Peter wrote:
> >
> > We need a few test patterns for serial PMDs, and I think it
> would be good to
> > start listing the different measurements which need
> specific patterns, and
> > what kind of patterns that would be good to use. In 1GbE 5
> different test
> > patterns seem to be defined, and a few of them are based on
> 8b/10b code
> > groups which I don't think is a good idea for 10G serial PMDs.
>
> > 1. For extinction ratio and OMA measurements I think a
> repeating "11110000"
> > pattern (4x"1" + 4x"0") would be a good idea. (Better than
> 5x"1" + 5x"0" as
> > in 1G.)
>
> For 8B/10B, the extreme maximum run length is 5 and the
> typical maximum
> run length is 4. For 64B/66B, the extreme maximum run length is 66
and
> the typical maximum run length is >>4. Since 64B/66B is
> employed for all
> 10G serial PMDs, why would a repeating "11110000" pattern,
> equivalent to
> a 1.25 GHz square wave, be "a good idea" for extinction ratio and
OMA
> measurements? Why would it be any better than a "1111100000"
> pattern? Is
> it representative in any way of the very wide dynamic range of
64B/66B
> signaling (relative to the narrow dynamic range of 8B/10B)?
>