Muni fiber: L1 or L2?

Fri Feb 1 21:16:45 UTC 2013

Actually, this is an issue… I should have seen it.

You have 3 loss components… Power out = (Power in - loss to splitter - splitter loss) / nOut - loss-to-customer

So, if the loss to the splitter is 3db and you have 20db (effective 320db on a 16x split) loss on each customer link, that's
a radically worse proposition than 20db loss to the splitter and 3db loss to each customer (which is effectively 48db
loss on a 16x split).

It's still do-able, but you either need amplifier(s) or very short distances between the customer and the MMR.

Given this consideration, I think the situation can still be addressed.

Put the splitters in the B-Box and allow for the possibility that each subscriber can be XC to either a splitter or
an upstream dedicated fiber. The provider side of each splitter would be connected to an upstream fiber
to the MMR.

So, each B-Box contains however many splitters are required and each splitter is connected upstream to a
single provider, but you can still have multiple competitive providers in the MMR.

This setup could support both PON and Ethernet as well as other future technologies.

Owen

On Feb 1, 2013, at 1:04 PM, Jason Baugher <jason at thebaughers.com> wrote:

> I should clarify: Distance x loss/km + splitter loss. = link loss.
> 
> 
> On Fri, Feb 1, 2013 at 3:03 PM, Jason Baugher <jason at thebaughers.com> wrote:
> I disagree. Loss is loss, regardless of where the splitter is placed in the equation. Distance x loss + splitter insertion loss = total loss for purposes of link budget calculation.
> 
> The reason to push splitters towards the customer end is financial, not technical.
> 
> 
> On Fri, Feb 1, 2013 at 2:29 PM, Scott Helms <khelms at zcorum.com> wrote:
> 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
> --------------------------------
> http://twitter.com/kscotthelms
> --------------------------------
> 
> 