[160173] in North American Network Operators' Group
Re: Muni fiber: L1 or L2?
daemon@ATHENA.MIT.EDU (Owen DeLong)
Fri Feb 1 16:19:11 2013
From: Owen DeLong <owen@delong.com>
In-Reply-To: <CAGbD49rpL2CTM-CEA=wVqMnTGo=txwf=XbNAXt6hcLSbMzX_SQ@mail.gmail.com>
Date: Fri, 1 Feb 2013 13:16:45 -0800
To: Jason Baugher <jason@thebaughers.com>
Cc: NANOG <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
Actually, this is an issue=85 I should have seen it.
You have 3 loss components=85 Power out =3D (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@thebaughers.com> wrote:
> I should clarify: Distance x loss/km + splitter loss. =3D link loss.
>=20
>=20
> On Fri, Feb 1, 2013 at 3:03 PM, Jason Baugher <jason@thebaughers.com> =
wrote:
> I disagree. Loss is loss, regardless of where the splitter is placed =
in the equation. Distance x loss + splitter insertion loss =3D total =
loss for purposes of link budget calculation.
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> The reason to push splitters towards the customer end is financial, =
not technical.
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> On Fri, Feb 1, 2013 at 2:29 PM, Scott Helms <khelms@zcorum.com> wrote:
> Owen,
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> 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.
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> > Bottom line, you've got OLT -> FIBER(of length n) -> splitter ->
> > fiber-drops to each house -> ONT.
> >
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> So far you're correct.
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> >
> > 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.
> >
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> 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.
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> Here is a good document that describes the problem in some detail:
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> http://www.ofsoptics.com/press_room/media-pdfs/FTTH-Prism-0909.pdf
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> 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.
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> =
http://www.ericsson.com/il/res/thecompany/docs/publications/ericsson_revie=
w/2008/3_PON.pdf
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> --
> Scott Helms
> Vice President of Technology
> ZCorum
> (678) 507-5000
> --------------------------------
> http://twitter.com/kscotthelms
> --------------------------------
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>=20
