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RE: [EFM] Split ratios

At 06:33 19/07/01 -0700, Horne, David M wrote:
>Carlos, yes, I understand all these considerations. That was not my
>question. The apparent consensus with splits of 16 and 32 seems to have been
>arrived at devoid of any engineering considerations. Those engineering
>considerations are exactly what I was suggesting are needed. The final
>comment you made of "just don't ask me why" is what I WAS asking.

Sorry if my answer appeared to be too superficial or condescending. I 
understood your point, as I was trying to analyze some of the factors that 
lead to the apparent 1:16 or 1:32 consensus. The 'just don't ask me' was a 
joke, to point out exactly what you are saying; we don't know what is the 
best split ratio, technically and economically speaking.

>Use of 16 or 32 for interim discussion purposes is fine; I am just
>suggesting we not get too attached to those numbers since other ratios may
>prove to be more beneficial for Ethernet PON based on more detailed
>considerations. 16 and 32 have not been cast in concrete, correct?

There are some issues on the FTTH market that make such determination even 
harder. On one hand, we know that the number of people using the service 
simultaneously is not as high in the residential market as it is in the 
business market. So (bandwidth wise) you can actually oversubscribe the IP 
service by a much larger ratio in the residential market. On the other 
hand, there are some practical concerns in the residential market. I 
believe that we will end up needing to develop more practical ways to build 
the fiber drop to the user's home, in order to make maintenance easier and 
faster. For instance, instead of fusing fiber, we may use more connectors 
and patch cords, allowing the field crew to make changes immediately. If 
you have enough density, it may end up being much cheaper to replace the 
entire fiber drop on the field than to fuse it when you have a failure. The 
problem is that, in general, the connectors that are easier to handle in 
the field are the same ones that have higher optical losses. This is going 
to limit the split ratio to a smaller number.

In the end, all of this makes for an interesting discussion that will only 
be settled with more practical experience. Solutions for the professional 
market - corporations, and even medium-sized businesses - don't apply for 
the small business and residential markets. The scale is much bigger, and 
the market is so cost sensitive that many compromises will have different 

Carlos Ribeiro
CTBC Telecom