RE: [802.3ae_Serial] Issue with 1500 Power
Here is a short power budget the way I see it. For simplicity, let the
ISI & dispersion penalty be 0. All powers in OMA [dB].
The transmitter output power is -1.39 dBm. At the receiver you have
-14.39 dBm. I think the confusing part is the stressed sensitivity.
The stressed sensitivity is measured with an eye having 3 dB eye
closure. In addition to that, there will be a small additional vertical
eye closure due to sinusoidal jitter, which I don't account for here.
With the stressed eye the sensitivity in OMA (measured between the
nominal 1 and 0 levels) is -11.8. If we instead of the stressed eye have
an eye without the 3 dB eye closure, the sensitivity would be
-11.8-3=-14.8 dBm. This would give you roughly 0.4 dB margin.
To make this more accurate, you would have to take the sinusoidal jitter
in the stressed eye into account (--> more margin), as well as some
penalties that could occur in the real link (e.g. interferometric noise
and other known and unknown penalties --> less margin).
Hope this helps,
/Peter
> -----Original Message-----
> From: Rahn, Juergen (Juergen) [mailto:krahn@lucent.com]
> Sent: den 27 juni 2001 12:30
> To: stds-802-3-hssg-serialpmd@ieee.org
> Subject: AW: [802.3ae_Serial] Issue with 1500 Power
>
>
>
> Hi,
> as discussed in the PMD call I understand there is a mismatch
> in the values
> defined for the 1550 case. The minimum transmitter OMA is -1.39dBm +
> penalties. Link attenuation is set to 13 dB , so this would give a
> sensitivity requirement of -14,39 dBm OMA ,. however the stressed
> sensitivity (In OMA) is defined to be -11.4 dBm. so there are 10 dB
> difference between those two values. The trade off that has
> been introduced
> (that I do not like, but this is a different discussion) will
> shift this
> complete link power level. When comparing this with powers
> and sensitivities
> as defined in ITU the following appears: ITU defines 2 dB
> path penalty with
> this OMA we would end at a minimum transmitter power average
> of about - 1
> dBm which is in line to ITU. with 109 dB attenuation there is
> margin in the
> ITU numbers, with 11 dB and ITU sensitivity (Which has been
> confirmed by
> measurements) we add up to 0. ( -14 dBm average power
> sensitivity and 2 dB
> penalty gives us the G.691 application). When simply taking
> this transmitter
> power and 13 dB attenuation we end up with 2 dB better sensitivity
> requirement as currently experienced by measurements (worst case EOL).
> This may start this conversation.
> Regards Juergen
>
>
>