-----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 1000Base PX10 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
. T he 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_Penalt y makes
reasonable sense.
The inequality (Dispersion_Penalty+TDP)
<= ITU_Optical_Path_Penalt y makes no sense at all as it is roughly
equivalent to saying:
DP + (EP +
DP) < = DP
I agree
that Dispersion_Penalty
<= ITU_Optical_Path_Penalt
y 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 a n 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 d ecide 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 qu
ite 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
-----------------------------------------