Re: [8023-10GEPON] PR-20 Performance comparison between 1550nm and 1590 nm
Dear Otaka-san,
I believe it does not. We DO NOT need to specify the bending radius for the cable plant - it is completely out of the scope of the TF as You also pointed out. We see only power budget as a whole and if some vendor deploys fibre plant with 10 mm bend radius, they will have to suffer the incurred loss. We cannot simply afford to get into such details in our group - otherwise we will end up doing the specifications which are useless and do not find practical application.
As for the attenuation difference between 1550 and 1590 nm as included in the presentation, according to fibre measurement data collected and compiled by Pete Anslow > http://www.ieee802.org/3/hssg/email/msg00869.html, the fibre has attenuation of 0.277 dB/km and 0.276 dB/km for 1550 and 1590 nm windows, respectively. I fail to see how that is compliant with the measurements You present. Pete's data is a relatively large sample of various cable plants and even if the values are expected to be higher in PON plants (worse splices??, more splices ??, connectors ??), definitely it is hard to expect 2-3 dB power budget difference which is stated in the presentation. That would require at least 0.1 dB/km difference between 1550 and 1590 nm in favour of 1550 nm window at the material properties level, assuming both plants are prepared in the very same way. The data I have and which is quoted as reliable by various people (Pete and Piers are not afraid to put their names under that)!
suggests otherwise. I would say such an argument will not hold. I agree with the worse bend loss parameters as quoted, though again the indicated difference is slightly exaggerated - the ODNs I had a chance to see had fibre bent with at least 30 mm radius to avoid excessive loss. I do not see a valid reason to go below that value, unless really tight ducts are available, which is quite uncommon.
Since the upstream channel loss is dominant in the system we design, You're right - we have to assure upstream channel works (0.466 dB/km according to Pete's data). That is significantly lower than the 1550/1590 nm windows.
Best wishes and thank You for keeping the topic rolling
Marek Hajduczenia (141238)
NOKIA SIEMENS Networks S.A., Portugal - R
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"C makes it easy to shoot yourself in the foot; C++ makes it harder, but when you do, it blows away your whole leg." - Bjarne Stroustrup
-----Original Message-----
From: ext Akihiro Otaka [mailto:ootaka@ANSL.NTT.CO.JP]
Sent: quinta-feira, 8 de Novembro de 2007 10:26
To: STDS-802-3-10GEPON@LISTSERV.IEEE.ORG
Subject: Re: [8023-10GEPON] PR-20 Performance comparison between 1550nm and 1590 nm
Dear Bong Kyu Kim,
This is Akihiro Otaka.
Thank you for the slide.
I have just one comment about fiber loss.
I understand that the IEC standard say nothing about macrobending
loss of r=10mm. Therefore, the value of r=10mm should be a
vender specific value. These values may be different from venders.
And I think that some venders may not guarantee such values,
and that some venders may guarantee the smaller value.
I don't think the discussion based on such kind of value is usefull.
And if we use the value of r=30mm shown in the standard,
there is no difference between 1550 nm and 1590 nm.
Of course, in the real installation, you can allocate 20dB CHIL for
any kinds of loss in ODN. I think it is out of scope of the task
force.
And the transmission loss of 1590 nm and 1260 nm is nearly
the same. So, in my understanding, I have to design the ODN loss using
1260 nm, whether 1550 nm or 1590 nm.
Best regards,
Akihiro Otaka
NTT
At 23:08 07/11/07, ア霄タアヤ wrote:
>
>Dear All,
>
>Sorry! Once more for clear title.
>
>In our knowledge, 1550 nm wavelength has better performance than 1590 nm
>wavelength.
>The attached file is our proposal for wavelength plan for PR-20.
>Please let me know if you have any comment on the proposal.
>
>Sincerely yours,
>
>Bong Kyu Kim, Ph.D.
>Senior Research Staff
>Optical Access Tech. Team
>BcN Research Lab.
>Electronics and Telecommunications Research Institute
>Tel: +82-42-860-1344, Fax: +82-42-860-5213
>E-mail: <mailto:bongkim@etri.re.kr>bongkim@etri.re.kr