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Dear Frank, Thank you for providing your newly proposed wavelength plans. I am Ken-Ichi Suzuki of NTT and I have comments as below. In option C, in order to receive signals in both narrow (1574-1580 nm) and wide (1580-1600 nm) band range, I think that the lower limits of an optical filter pass-band must be 1574 nm. If it is true, I think option C (called option D?) should be defined as 1574 ~ 1600 nm. Considering the coexistence with RF video and the use of common optical filter for each class, I think I can conclude option B and D are acceptable for me. These and the attached file are for my understanding. Option A: 1560 ~ 1580 nm Option A can receive signals in both narrow and wide wavelength ranges. The central wavelength for PX10/20 is 1570 nm near one of CWDM grids. Option A does not allow 10GEPON to coexist with RF video because of 0 guard band. Option B: 1574 ~ 1594 nm Option B can receive signals in both ranges. The central wavelength is 1584 nm (near the anti-CWDM grid). Option B allows 10GEPON to coexist with RF video with the guard band of 14 nm. Option C: 1580 ~ 1600 nm Option C can not receive signals in both ranges thus forcing us to develop dedicated optical filters for each class. The central wavelength is 1590 nm near one of CWDM grids. Option C allows 10GEPON to coexist with RF video with the relatively wider guard band of 20 nm. Option D: 1574 ~ 1600 nm Option D can receive signals in both ranges. The central wavelength for PX10/20 can be selected at 1590 nm near one of CWDM grids. Option C allows 10GEPON to coexist with RF video with the guard band of 14 nm. Best regards, Ken-Ichi At 2007/08/09 10:05 Frank Effenberger wrote: > Dear All, > > > > I agreed at the last meeting to facilitate the development of a more > inclusive wavelength plan for the downstream. > > > > The current situation is that the PX30 budget would seem to require cooled > transmitters, and so the 6nm wide transmitter window centered at 1577nm is > not an extra burden. > > > > However, for the PX10 and PX20 budgets, the OLT transmitter may be an > uncooled type, both because the output power is low, and because in the case > of PX10, the fiber distance is shorter and so dispersion control is less > needed. Therefore, there seems to be a justification for making the > wavelength band for the PX10 and PX20 types wider. > > > > So, the question then becomes: how to make the window wider? It was > discussed at the meeting that the wider window should contain the narrow > window inside of it. This has the possibility of defining a universal ONT > that can receive both the wide and narrow OLT signal. How that actually > works out in practice will have to be seen. > > > > One aspect to consider is the re-use of industry standard wavelength plans, > since then components are already available. From this perspective, the > CWDM wavelength at 1571 leaps out as a potential band. It is true that the > CWDM band is actually from 1563 to 1577 nm, but that is meant for 0~70 C > operation, and expansion to a 20nm width naturally occurs when the -40 to > +85 C operation is considered. So, proposal A would put the wider > wavelength band at 1560nm to 1580nm. > > > > Of course, this choice would make co-existence with the video overlay > impossible, with zero guard-band to the video band at 1550 to 1560nm. This > defeats the ¡®common ONT¡¯ idea, since it is impossible to make such an ONT. > > > > > Supposing we want to consider the coexistence with video for these classes, > then we must push the wavelength longer. Starting at 1574, we could expand > to a 1594nm. This is rather strange, having a center wavelength at 1584, > which is nearly the ¡®anti CWDM grid¡¯. We could call this proposal B. > > > > On this alternative, we have sacrificed the compatibility with those OTDR > filters we heard about. This raises an inescapable conclusion: to broaden > the band, we will sacrifice either the video overlay or the compatibility > with certainly legacy OTDR filters. It should be noted that there are even > fewer system deployments with this particular OTDR constraint than the video > overlay. > > > > Combining the two motivations above, we turn to the next longer CWDM > wavelength: 1590nm. This would define the band to be 1580 to 1600nm; called > proposal C. In most PONs, this wavelength has no difficulties of > transmission. It also provides a 20nm guard-band from the video, which is a > little better than the 14 nm with the narrow plan. It is disjoint with the > narrow plan; however, it is in a part of the spectrum where the narrow plan > seems not to care. So, we could build an ONU that responds from 1576 to > 1600, and that would receive both signals. This is probably not the most > practical solution, but at least it is possible. > > > > So, that¡¯s sort of what we have: > > Option A: 1560 ~ 1580nm > > Option B: 1574 ~ 1594nm > > Option C: 1580 ~ 1600nm > > > > I¡¯ll stop at this point, and leave the ¡®floor¡¯ open for comments. > > > > Sincerely, > > Dr. Frank J. Effenberger ¸¥À¼¿Ë °£·Ò²©¸ñ > > Huawei Technologies USA > > 1700 Alma Drive, Plano TX 75075 > > Office (732) 625 3002 > > Cell (908) 670 3889 > > > > -- Ken-Ichi Suzuki NTT Access Network Service Systems Labs. E-mail:kenyichi@ansl.ntt.co.jp Tel:+81-43-211-3189/Fax:+81-43-211-8250
Comparison_of_wavelength_plans.ppt