Re: [8023-10GEPON] [CHANNEL_LINK] New Excel spreadhseet available ...
Dear Saeki-san,
Your understanding is correct. In my idea, TDP (Transmitter and dispersion
penalty) is not necessary. The receiver sensitivity would already contain
the "T" part of the TDP, and the OPP would contain the "D" part. So, all is
accounted for.
If it so happens that somebody down the line wants to calculate the "T" part
as an informative number, then I wouldn't mind it at all. However, it would
only be a guide to certain testing folks. That is to say, if you want to
test your detectors with a 'perfect' transmitter waveform, then you would
derate the measured value by the "T" part to get to the nominal value.
But, I would not recommend such an approach, because the actual degradation
due to transmitter imperfections is not so easy to calculate. It would be
better to use a nominal transmitter, and then derate by a certain amount
based on statistical observations over a large set of detectors AND
transmitters. In practice, this is how it is done.
Sincerely,
Frank E.
-----Original Message-----
From: NAOTO SAEKI [mailto:n-saeki@bl.jp.nec.com]
Sent: Tuesday, July 03, 2007 3:15 AM
To: STDS-802-3-10GEPON@listserv.ieee.org
Subject: Re: [8023-10GEPON] [CHANNEL_LINK] New Excel spreadhseet available
...
Dear Dr. Effenberger,
Thank you for your quick comment.
I understood how to use spread sheet and TDP will not be calculated by
spread sheet.
To describe optical link model, OPP and LOSS_max will be
necessary.
Let me confirm again,
There are no necessity to define TDP in standard.
Is it right understanding?
Regards.
Naoto Saeki
> -----Original Message-----
> From: Frank Effenberger [mailto:feffenberger@HUAWEI.COM]
> Sent: Wednesday, June 27, 2007 11:02 PM
> To: STDS-802-3-10GEPON@listserv.ieee.org
> Subject: Re: [8023-10GEPON] [CHANNEL_LINK] New Excel spreadhseet
> available ...
>
> Dear Saeki-san and All,
>
> I was also tasked with working on the spreadsheet with Marek, and I owe
> him
> some suggestions on the equation style, and how it will be used. So, I'll
> take your Email as the trigger to force me to discuss it, here:
>
> Basic ideas: ITU Style is what we would like to use; however, we'd also
> like
> to capture the OMA method, since this allows for cheaper optics. That
said,
> we also want to allow users to enter in average power values, because this
> is the basis in which most researchers 'think in'.
>
> So, I propose the following:
>
> Preliminaries: The group decides on two extinction ratios that will be
used.
> The first is the 'nominal ER', and is a pretty good value (e.g., 9dB).
This
> is used to convert the nominal average power into OMA.
>
> The second is the 'worst case ER', and is a pretty bad value (e.g., 6 dB).
> This is a hard limit on the optics, just to prevent shot noise overload.
>
> For each direction, we have a budget:
> User enters in the nominal minimum average power and the maximum average
> power at the nominal extinction ratio (9 dB.)
>
> Spreadsheet calculates the OMA that this corresponds to. The OMA is the
> real requirement on the optics. Call it OMA_tx
>
> User enters in the fiber length, the split ratio, and excess loss.
>
> Spreadsheet calculates the maximum link loss to include: Fiber (calculated
> from formula), splitter (calculated from formula), and excess loss (user
> entry). Call it LOSS_max
>
> User enters in the desired dynamic loss range.
>
> Spreadsheet calculates the minimum link loss to be the maximum loss -
> dynamic range. Call it LOSS_min
>
> User enters an optical path penalty (e.g, 1 dB). This path penalty is
> defined in the ITU style, which is the penalty that is caused by the
optical
> path interacting with a worst-case signal. Call it OPP
>
> User enters the nominal receiver sensitivity and overload at the nominal
> extinction ratio (9 dB.) Note that this sensitivity is the worst case
> sensitivity of a back-to-back Tx-attenuator-Rx test set-up.
>
> Spreadsheet calculates the OMA that the sensitivity corresponds to. Call
> it
> OMA_rx
>
> Spreadsheet now can perform two tests to confirm if link works:
> OMA_rx < OMA_tx - LOSS_max - OPP
> Overload > Max_tx_power - LOSS_min
>
> That's it!
>
> This method has very little in the way of equations or other flim-flam.
> However, we like equations, because they give us a way to gauge if our
> assumptions are way off. For example, we calculate what we think the link
> loss should be (based on splitters and fiber), but we also reserve the
> 'excess loss' category to fix up the number to make the total loss what
> we
> want.
>
> In the case of optical path penalty, this value is user entered. However,
> the spreadsheet should have a side calculation that estimates the OPP
based
> on the optical values we have available. I believe that at 10G, the
> predominant factor is chromatic dispersion, and we saw the equation for
> that
> in the presentation in May. So, the spreadsheet can calculate the OPP
based
> on those equations, and perhaps print the value right next to where the
> user
> plugs in his manual value. I would expect that the user-entry should be
> close to the theoretical value, but it doesn't need to match it.
>
> (Needless to say, the flaw in that theory is that we need a chirp
parameter,
> but the chirp parameter is measured only by finding out the OPP. So, the
> theory is really circular in its methodology. The theory is only a guide,
> and the real spec is the OPP. In other words, the Tx must be required to
> produce an OPP that is less than the value entered by the user. That may
> sound upside down (that the OPP is a requirement on the Tx), but it is the
> truth.)
>
> I hope that is clear enough.
>
> Regards,
> Frank E.
>
>
>
>
> -----Original Message-----
> From: NAOTO SAEKI [mailto:n-saeki@bl.jp.nec.com]
> Sent: Wednesday, June 27, 2007 5:04 AM
> To: STDS-802-3-10GEPON@listserv.ieee.org
> Subject: Re: [8023-10GEPON] [CHANNEL_LINK] New Excel spreadhseet available
> ...
>
> Dear Marek,
>
> This is Saeki of NEC Corporation.
>
> Thank you for your great effort to define Optical link model for 10GE-PON.
> I would like to know how to handle the TDP in draft text.
> As we discussed in Geneva meeting, power budget will be discussed ITU-T
> like
> model.
> Path penalty is important parameter for link model.
> With this scheme, I think that TDP will be no longer define in standard.
> Is this correct understanding?
> If you will put TDP value in standard, how can we define a appropriate
> value?
>
> I would like to hear your opinion.
>
> Best Regards.
>
> --
>