Muni fiber: L1 or L2?

Fri Feb 1 20:29:32 UTC 2013

Owen,

You're basing your math off of some incorrect assumptions about PON.  I'm
actually sympathetic to your goal, but it simply can't work the way you're
describing it in a PON network.  Also, please don't base logic for open
access on meet me rooms, this works in colo spaces and carrier hotels but
doesn't in broadband deployments because of economics.  If you want to
champion this worthy goal you've got to accept that economics is a huge
reason why this hasn't happened in the US and is disappearing where it has
happened globally.

> Bottom line, you've got OLT -> FIBER(of length n) -> splitter ->
> fiber-drops to each house -> ONT.
>

So far you're correct.

>
> All I'm proposing is making n really short and making "fiber-drops to each
> house" really long.
> I'm not proposing changing the fundamental architecture. Yes, I recognize
> this changes the economics and may well make PON less attractive than other
> alternatives. I don't care. That's not a primary concern. The question is
> "can PON be made to work in this environment?" It appears to me that it can.
>

Here is where you're problems start.  The issue is that the signal *prior
to being split* can go 20km if you're splitting it 32 ways (or less) or
10km if you're doing a 64 way split. AFTER the splitter you have a MAX
radius of about 1 mile from the splitter.

Here is a good document that describes the problem in some detail:

http://www.ofsoptics.com/press_room/media-pdfs/FTTH-Prism-0909.pdf

Also, here is a proposed spec that would allow for longer runs post
splitter with some background on why it can't work in today's GPON
deployments.

http://www.ericsson.com/il/res/thecompany/docs/publications/ericsson_review/2008/3_PON.pdf

-- 
Scott Helms
Vice President of Technology
ZCorum
(678) 507-5000
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