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Re: [8023-10GEPON] Downstream wavelength for 10G EPON




Dear Frank,
 
just a few quick comments:
 
in terms of option C, the PX30 remains centered at 1577 with 6 nm window ? If so, the window we need to cover in this option needs to be larger i.e. span from (1577 - 6/2)nm to 1600 nm.
 
what is the reason of not using 1580 - 1600 nm window for all PX10/PX20/PX30 budgets and specifying the lasers for 1590 nm central wavelength ? is there a lack of high power output lasers for PX30 budget ?  Perhaps it is a lame question - if so, please ignore it.
 
Best wishes
 

Marek Hajduczenia (141238)
NOKIA SIEMENS Networks S.A., Portugal - R
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* Marek.Hajduczenia@siemens.com
http://www.marekhajduczenia.info/index.php
(+351.21.416.7472  4+351.21.424.2082

"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

 


From: Frank Effenberger [mailto:feffenberger@HUAWEI.COM]
Sent: quinta-feira, 9 de Agosto de 2007 2:05
To: STDS-802-3-10GEPON@listserv.ieee.org
Subject: [8023-10GEPON] Downstream wavelength for 10G EPON

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      弗兰克 埃芬博格

Huawei Technologies USA

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