AW: [802.3ae_Serial] Consistent treatment of sensitivities and margins
Hi,
Just for confirmation what will be specified now as normative visible values
in the tables. Are we now at:
TX power, Stressed sensitivity, Loss, Total sum out of remaining impairments
(penalty) and margin.
I read: Stressed Rx sensitivity = Tx power - Losses - impairments
not included by
> the shape of the stressful test eye - Margin
in your description. Is this now what will be indicated in the tables as the
requirements?
I would like to make the point ,that the informative and normative
parameters should be clearly separated. As the informative sensitivity is a
theoretical value that is not possible to be verified , I am severely
doubting of this is useful to be included. I at least have seen no receiver
model allowing such kind of calculation showing the required accuracy in
agreement with measurements . However there should be different receivers
possible providing the target sensitivity in real life but would all require
different modeling. So what does this bring for the specification.
Regards Juergen
> ----------
> Von: DAWE,PIERS (A-England,ex1)[SMTP:piers_dawe@xxxxxxxxxxx]
> Gesendet: Mittwoch, 10. Oktober 2001 20:10
> An: '802.3ae Serial'
> Cc: 'Tom Lindsay'
> Betreff: [802.3ae_Serial] Consistent treatment of sensitivities and
> margins
>
>
> I had an action with Tom Lindsay to document the proposed consistent
> treatment of sensitivities and margins which has gained consensus on the
> serial PMD conference calls. Here it is:
>
> First, a description of where we are
> ------------------------------------
> Apart from the errors, the position in draft 3.2 and link model 2.4.1 is:
>
> Budget = Tx power - Informative Rx sensitivity
>
> Budget = Impairments + Losses + Margin
>
> Where informative Rx sensitivity is also known as "nominal" or
> "unstressed" sensitivity, and here "Impairments" are penalties apart from
> (broadband) optical attenuation or loss.
>
> Also draft 3.2 and link model 2.4.1 have (slightly simplified):
>
> Stressed Rx sensitivity = Tx power - Losses
>
> The principle is that the impairments are recreated by creating the
> stressful test eye. However, we noticed that margin was treated
> differently
> in the stressed and nominal sensitivities. Also, impairments that are not
> recreated by the test eye are effectively being ignored in the stressed Rx
> sensitivity calculation.
>
> Second, a description of where we think we should be
> ----------------------------------------------------
>
> Stressed Rx sensitivity = Informative Rx sensitivity + impairments
> included
> by the shape of the stressful test eye
>
> and also
>
> Stressed Rx sensitivity = Tx power - Losses - impairments not included by
> the shape of the stressful test eye - Margin
>
> Subtracting the first equation from the second we get
>
> Informative Rx sensitivity = Tx power - Losses - all impairments - Margin
>
> as before.
>
> To simplify this description, questions of measurement at TP3 versus TP4,
> mean power versus OMA, and triple trade offs, are not mentioned. They are
> orthogonal questions to this one, which is what do we want stressed Rx
> sensitivity to mean?
>
> Now we had to split the impairments into two categories.
>
> Impairments which are included by the shape of the stressful test eye:
> Inter symbol interference penalty P_ISI
> Deterministic jitter penalty P_DJ
> The part of Rx baseline wander which is exacerbated by the shape of
> the stressful test eye
>
> This class are all pattern dependent penalties. The first two items
> combine
> to the "vertical eye closure penalty" in D3.2 52.9.13 Conformance test
> signal at TP3 for receiver testing.
>
> Impairments which are not included by the shape of the stressful test eye:
> Modal noise
> Reflection noise
> Mode partition noise
> Relative intensity noise
> Anticipated Tx baseline wander
>
> The second class are noise-like, mainly non-pattern dependent penalties.
>
> The proposed link model 10GEPBud3_1_14.xls implements nearly all of this.
> The fine detail of the baseline wander (in Pcross) is simplified and we
> have
> found an error in the Rx stressed OMA column: it should not contain Pmn.
> This error does not affect anything but the stressed sensitivities in
> cases
> with multimode fiber.
>
> In the draft standard there is no line item called "Margin" any more. In
> general we have spent most of it on penalties. But it was worth going
> through this exercise to account properly for all the noise-like terms in
> the stressed sensitivity test which is now our only normative receiver
> sensitivity criterion.
>
> Piers
>