Re: [8023-10GEPON] [CHANNEL_LINK] New Excel spreadhseet available ...
Dear Tatsuta-san,
First of all, sorry for a delayed answer but I was stuck with the examination and backtracking the history of this now-famous Excel spreadsheet.
As for Your question: You did understand that right. Form what I can say, the LD Pen value was not included in the power budget figure which You can see in neither original file which was submitted for revision and adaptation for 10GEPON 802.3av Task Force (i.e. EFM0_0_2.7for10GEPON.xls, please find it attached) nor the file which was produced (e.g. 10GEPON-D.0.4_with_examples.xls, which we already exchanged several times). The value of the penalties is calculated in the column which You referred to in one of Your previous emails, but the final link between the column name and the power budget is missing.
Regarding how we can estimate the penalty value for our power budget.
You identified the two possible ways: I would say we are probably going to be better of with the first approach. Why ? First of all, we cannot accommodate any type of penalty since we do not know the fibre plant, so trying to do so is a logical suicide. We know that our Rx and Tx devices can give us X dB at most, out which Y dB will be lost due to fibre attenuation, PSC and splices. The X-Y dB value is what we can allow to be consumed by all types of transmission penalties. This is also the value we need to included in the specs. We DO NOT need to say that our system allows for k dBs of ISI or l dBs of RIN related penalty. The system designer should decide whether the link which is defined by the Rx and Tx devices can provide a sufficiently low overall penalty to handle transmission over the given PON plant.
From a practical standpoint: we really do not want to go into wars trying to decide e.g. which ISI penalty model is precise and models well the observed phenomena. We are supposed to engineer a link and provide the border conditions under which the system works. Anything better will work for sure. At the same time, we cannot exclude the possibility that the link will be worse but then, can we cover all 100% of cases?
All in all, I would opt for the first option. We define the CHIL, acceptable transmission penalty value and build on top of that.
If we cannot find Rx/Tx to provide the target budget in the first place, we will have to opt for option 2 but that is a distant alternative if I understand the message relayed by equipment vendors.
Hope that answers Your question
Marek Hajduczenia (141238)
NOKIA SIEMENS Networks S.A., Portugal - R
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* Marek.Hajduczenia@siemens.com
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I rechecked a relationship between IEEE802.3ah spec and the spread sheet,
and I understood your answers. If my understanding is right, there is not
so strict relationship between a value of the penalty in IEEE802.3ah spec
and the spread sheet.
So, there is still remaining one question in my head.
How can we calculate a penalty value for estimating a power budget?
I think there are two ways to estimate the power budget.
1. We decide the power budget and CHIL at first, and then we calculate the
allocation for penalty by subtracting the CHIL from the power budget.
2. We decide CHIL and the penalty at first, and then we calculate the
power budget by adding the CHIL and the penalty.
Do you have any opinions?
Sincerely yours,
Tsutomu TATSUTA
EFM0_0_2.7for10GEPON.zip