Re: Muni fiber: L1 or L2?

[Jay Ashworth <jra () baylink com>]

----- Original Message -----
> From: "Jean-Francois Mezei" <jfmezei_nanog () vaxination ca>

> On 13-02-01 22:52, Owen DeLong wrote:
> > Since the discussion here is about muni fiber capabilities and ideal
> > greenfield
> > plant designs, existing fiber is irrelevant to the discussion at
> > hand.
>
> Not so irrelevant. If the municipality wishes to attract as many
> competitive ISPs as possible, it wants to build a "standard" last mile
> that ISPs can easily interface to. One which is compatible with other
> FTTH systems.
>
> Currently, the standard is GPON (even though there are many variations
> to the theme).

There is a certain amount of utility to the "we should provide something
which incoming providers who are already revved up in a specific direction 
can work with easily" argument, yes.

Assuming there really are no loss or dispersal problems with 'splitter
at the MDF', this will serve; an incoming L3 provider would have to put 
the boxes in slightly different places than usual, but at least they'd be 
the same boxes.

> Sone may say that having L1 service with each ISP having their OLT
> with
> splitters at the CO is an advantage. It also means that each ISP has
> to
> have its own ONTs in homes and they can all choose different configs
> for
> OLTs and the light in the fibre. Greater flexibility to differentiate
> between ISPs. (one may choose RFoG for TV with DOCSIS for data while
> the
> other is an all data link with IPTV.)

Correct; we say that.

> But for an end user, switching ISPs would mean switching the CPE
> equipment too since the ONT installed by ISP-1 may not be compatible
> with OLT used by ISP-2.

Sure, but that's already true, and that's not a problem I'm trying to
optimize out, frankly.  

> Requiring an ISP to have its own OLT at the CO with its own splitter
> also raises startup costs and reduces the chances of having
> competitive ISP environment.

See below.

> Providing L2 service means that ISPs connect to a municipal OLT, so they
> do not have to purchase OLTs and bother with splitters. At that point,
> it si simpler and cheaper to deploy splitters in neighbouhoods. It
> also reduces number of splices.

Yes, and no, in that order.

If you'd been following along all week, you would have seen that the OP
(me :-) wants to do *both*; supply L1 service to providers or subscribers
that want that, and L2 service for other providers who are willing to pay
more per sub per month, but have less capital investment up front.

> When you do 1:1, you may have a big cable with lots of strands leaving
> the CO, but you'll have a JWI in neighbouhood where you cross connect
> the strands from CO to the strand that uses the pre-fab cable to the
> backyards of homes served.

Sure.

Just no splitter.
 
> So in all the calculations made on dB loss, the number of splices was
> not factored in. You're not going to get a continuous cable from the CO
> to the telephone pole behind a home. If you put the splitter at the CO
> you get the losses from the splitter, and then losses from a splice at
> the neighbouhood where trunk from CO connects to cables that runs
> through backyards.

True.  Why I'll be subbing the plant design to a company that does that
every day of the year, instead of trying to do it myself.

> When you put the splitter in the neighbouhood, it performs both the
> splitting and the connection of the cable from CO to the backyards. So
> you eliminate one splice.

Yes, but everyone on a splitter must be backhauled to the same L1 provider,
and putting splitters *in the outside plant* precludes any other type
of L1 service, *ever*.  So that's a non-starter.

Cheers,
-- jra
-- 
Jay R. Ashworth                  Baylink                       jra () baylink com
Designer                     The Things I Think                       RFC 2100
Ashworth & Associates     http://baylink.pitas.com         2000 Land Rover DII
St Petersburg FL USA               #natog                      +1 727 647 1274