RE: [802.3ae_Serial] Consistent treatment of sensitivities and margins
All,
I think this suggestion could provide a lot of value in the long term. If
implemented in multiple standards, it would allow people to possibly use on
hand equipment and common setups to make measurements, rather than having to
do a custom setup with some custom equipment for each different interface.
Gair
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-----Original Message-----
From: Vipul Bhatt [mailto:vipul.bhatt@finisar.com]
Sent: Friday, October 12, 2001 2:41 PM
To: '802.3ae Serial'
Subject: RE: [802.3ae_Serial] Consistent treatment of sensitivities and
margins
Peter,
You raise a good point. It seems to me that we have a lose-both-ways
situation:
- Nominal sensitivity is impossible to measure because it requires
the test signal input to be free of ISI and DJ. Yet, outside of a
small group of Serial PMD experts, that's the specification most
people are comfortable with.
- Stressed sensitivity is a pain in the neck to measure, even though
the idea behind it is worthy of keeping. The test setup is complex,
time consuming and unreliable.
I think one solution is to break out of this either-or deadlock. One
possibility may be to identify a means to calculate nominal
sensitivity from known measurements of input signal's
characteristics. (Yes, measurement imperfection will remain a
problem, but that's a separate issue.) We can provide some kind of a
formula or a table that provides the required sensitivity as a
function of test signal's rise time, jitter and inner eye height.
It lets the user make a pass/fail decision on a receiver under test,
but only after the test signal input is characterized. The crafting
of such a table will take some work, but it's a one time effort.
Regards,
Vipul
vipul.bhatt@finisar.com
408-542-4113
==============================
<snip>
> So, if people think that this is not a problem,
> especially for the 1300 and
> 1550 nm PMDs, we should consider eliminating the stressed
> rece9iver
> sensitivity and making the nominal receiver sensitivity
> normative. The
> 850nm case has to be considered more carefully.
>
> Peter
<snip>