Re: [8023-10GEPON] Define TDP values

[Frank Chang <ychang@xxxxxxxxxxx>]

Title: RE: [8023-10GEPON] Define TDP values

Hi Pete;

 

I am very happy you chime in to clarify the confusion which exists for a while in the email thread and also associated mtg discussions so far. I also feel the term "TDP" or even "stress RX sens" was misinterpreted in link budget formalism, which is quite inconsistent with what is defined in IEEE 802.3 for the TP2 and TP3 methodology.  

 

FYI- In line with what you said, actually I provided a tutorial to elaborate this during July mtg as follows:

http://www.ieee802.org/3/av/public/2007_07/3av_0707_chang_1.pdf

 

Best Regards

Frank C.

-----Original Message-----
From: Pete Anslow [mailto:pja@nortel.com]
Sent: Thursday, November 29, 2007 3:13 AM
To: STDS-802-3-10GEPON@listserv.ieee.org
Subject: Re: [8023-10GEPON] Define TDP values

Hi,

The way the term “TDP” is being discussed in this thread seems to me to be inconsistent with the way it is defined in IEEE 802.3.

TDP stands for Transmitter and Dispersion Penalty.  It is the penalty due to the combination of the eye closure of the transmitter and the further eye closure caused by the link dispersion.

The TDP measurement procedure for 1000BasePX10 and PX20 is defined in subclause 58.7.9.  The sensitivity of the reference receiver is measured with as near an ideal test transmitter as possible and then this is corrected for any residual transmitter eye closure to give the sensitivity with an ideal transmitter S.  Then the receiver sensitivity is measured again using the transmitter under test through the worst case dispersion.  The TDP value is then the difference between the second measurement and S.

If we label the two penalty components as EP for the transmitter Eye Penalty (penalty due to non-ideal eye shape at the transmitter) and DP for the transmitter Dispersion Penalty (further eye closure caused by the link dispersion) then we can say:

TDP = EP + DP

Now, for most ITU-T power budgets Path Penalty is approximately equal to DP (and the specified receiver sensitivity has to be met using a transmitter with a worst case EP).

Consequently, Dispersion_Penalty <= ITU_Optical_Path_Penalty makes reasonable sense.

The inequality (Dispersion_Penalty+TDP) <= ITU_Optical_Path_Penalty makes no sense at all as it is roughly equivalent to saying:

DP + (EP + DP) < = DP

I agree that Dispersion_Penalty <= ITU_Optical_Path_Penalty is not sufficient to establish that the power budget is feasible with available optics.  As I understand the current spreadsheet, it calculates the receiver sensitivity that would be required given the various input parameters.  In order to test for the feasibility of this sensitivity value an additional input cell containing the achievable receiver sensitivity with an ideal transmitter would be required.

Regards,

Pete Anslow

Nortel Networks UK Limited, London Rd, Harlow, Essex CM17 9NA, UK

External +44 1279 402540 ESN 742 2540

Fax +44 1279 402543

_____________________________________________
From: Hiroshi Hamano [mailto:hamano.hiroshi@JP.FUJITSU.COM]
Sent: 29 November 2007 02:55
To: STDS-802-3-10GEPON@LISTSERV.IEEE.ORG
Subject: Re: [8023-10GEPON] Define TDP values

Dear Dr. Maricondo,

Thank you very much for your explanations, and I apologize for my late reply.

Now, I understand that, in your E-mail, (Dispersion_Penalty+TDP) means the dispersion penalty value using a realistic transmitter with worst case TDP, in contrast to that using an ideal or perfect transmitter with small or no TDP.

I am not sure, whether (Dispersion_Penalty), in the Spreadsheet, is figured out based on such an ideal transmitter or not, but I agree that the result should indicate the worst case value in order to decide the fail/pass condition.

But I am not sure either, how TDP should be counted into such transmitter parameters for calculating (Dispersion_Penalty+TDP), in the Spreadsheet, and how big its impact will be.  If you have any suggestions, that will be quite helpful.

If TDP value should be derived from the measurement results, not from Spreadsheet calculations, some penalty value may remain only assumed and uncalculated, unless the relationship between the measured TDP and Dispersion_Penalty is justified.

Any comments or discussions will be highly appreciated.

Best regards,

Hiroshi Hamano

%% "Ken Maricondo" <kmaricondo@ieee.org> %% Re: [8023-10GEPON] Define TDP values %% Fri, 23 Nov 2007 17:07:53 -0500

>

> Dear Hamano-san and Hajduczenia,

>

> I agree (from all that I have read) that the ITU_optical_path_penalty

> basically includes no transmitter penalty and that receiver

> sensitivity value in ITU formalism should share the TDP within the

> margin. The rationale as to why I suggested adding the TDP to

> *Dispersion_Penalty <=

> ITU_Optical_Path_Penalty* is as follows:

>

> 1.    Any penalty such as chirp, extinction ratio, MPN, etc., will require

> that the photodiode receiver to receive an increased proportional

> optical receive level in order to maintain the same BER verse a system

> without the same penalties. The *Dispersion_Penalty <=

> ITU_Optical_Path_Penalty* from what I can tell assumes an ideal

> transmitter and receiver over a given optical path and that only if

> the dispersion penalty exceeds the optical path penalty then the link

> fails.  If I use only dispersion penalty in a network calculation

> without the TDP, then I am not truly taking into account worse

> case/end of life network performance.  In my point of view, a network

> designed with a TDP of 3dB for example will have a shorter operational

> lifetime or be performance limited then an identical network with an

> ideal transmitter with no TDP or lower value of TDP.  So to compensate for the TDP a more robust FEC scheme or higher quality receiver might be in order.

>

> 2.    I do not discount or object to the TDP value from being subtracted

> from the *IEEE_Rx_Stressed_Sensitivity_OMA* to get *IEEE_Rx_Sen_OMA*,

> but I think that TDP should show up in the system margin as worse

> case/end of life calculation within the spreadsheet.  The fact that

> the receiver sensitivity has to go lower to compensate for the TDP

> only points out that I have to have a higher quality ideal receiver at first glance.

>

> I am acutely aware of the fact that 10GEPON standard will allow for

> degree of flexibility in the network design to compensate for network

> design short comings.  My suggestion for *(Dispersion_Penalty+TDP) <=

> ITU_Optical_Path_Penalty* to be changed is to make sure that there is

> no ambiguity in the standard (spreadsheet) and to point out to the

> adopter of the 10GEPON standard that *all* penalties have been

> accounted for, analyzed and documented.  At the end of the day it is

> up to task force as whole to adopt what they feel is appropriate for the standard.

>

> Best regards,

>

> Ken Maricondo

>

>

>

>

> On Nov 22, 2007 5:27 AM, Hiroshi Hamano

> <hamano.hiroshi@jp.fujitsu.com>

> wrote:

>

> > Dear Dr. Maricondo and Dr. Hajduczenia,

> >

> > Thank you for your quick response and discussion.

> > I am not sure how TDP values have been defined in the previous

> > specifications such as IEEE 802.3ae and 802.3ah.  If they have also

> > reflected the vendor data based on the transmitter measurement

> > results, vendor feedbacks may be quite important similarly for

> > 10GE-PON.

> >

> > > but should read *(Dispersion_Penalty+TDP) <=

> > > ITU_Optical_Path_Penalty* to insure all possible noise and

> > > penalties

> > are

> > > accounted for.

> >

> > Perhaps, I misunderstand the last sentence of Dr. Maricondo's E-mail.

> > But my understanding is that ITU_optical_path_penalty basically

> > includes no transmitter penalty.  Receiver sensitivity value in ITU

> > formalism should share the margin, instead, for possible transmitter

> > penalty compared to the ideal one.

> > Would you please explain again your intension about the sentence??

> >

> > Best regards,

> > Hiroshi Hamano

> > Fujitsu Labs. Ltd.

> >

> > %% "Ken Maricondo" <kmaricondo@ieee.org> %% Re: [8023-10GEPON]

> > Define TDP values %% Wed, 21 Nov 2007 19:15:31 -0500

> >

> > >

> > > Dear Hamano-san,

> > >

> > > Although the TDP is a controversial value to be added to the

> > > 10GEPON standard, I have to agree with the previous committee (

> > > 802.3ah) for assigning a TDP value; albeit not an apparent

> > > benefit, the TDP does set

> > a

> > > reference value/point for determining transmitter quality which

> > > does

> > impacts

> > > system performance.  I agree with your assessment that the lack of

> > > high power reference transmitter to make a TDP measurement at this

> > > time is a problem.  In the absence of such a reference

> > > transmitter/s, I think that

> > the

> > > TDP values you have chosen are a good reference point to start

> > > with and

> > I

> > > support you on this issue.

> > >

> > > I also think that the spreadsheet should reflect the impact of TDP

> > > on

> > the

> > > systems' overall performance.   From what I have been able to determine,

> > the

> > > TDP value is subtracted from the

> > > *IEEE_Rx_Stressed_Sensitivity_OMA* to

> > get *

> > > IEEE_Rx_Sen_OMA*, which does not readily translate into a system

> > performance

> > > impact/limitation.  The system pass/fail calculation is based on

> > > *Dispersion_Penalty <= ITU_Optical_Path_Penalty* only, but should

> > > read

> > *(Dispersion_Penalty+TDP)

> > > <= ITU_Optical_Path_Penalty* to insure all possible noise and

> > > penalties

> > are

> > > accounted for.

> > >

> > > Best regards,

> > >

> > > Ken Maricondo

---

-----------------------------------------

Hiroshi Hamano

Network Systems Labs., Fujitsu Labs. Ltd.

Phone:+81-44-754-2641 Fax.+81-44-754-2640 E-mail:hamano.hiroshi@jp.fujitsu.com

-----------------------------------------