Muni fiber: L1 or L2?

Mon Feb 11 09:23:17 UTC 2013

Jason Baugher wrote:

>> No, as I said, I'm not trying to educate someone who don't want
>> to be educated.

> You're not trying to educate anyone at all. You're just stomping
> your foot and insisting that you're right rather than have a
> meaningful discussion.

So far, I have shown several figures derived from FTTH
deployment in the real world to show that PON is more
expensive than SS.

If you can't accept it, feel free to try to educate us. But,
do so with quantitative reasons.

> I did some research on what NTT has done on fiber deployment.
> From what I've seen, they split things up into feeder,
> distribution and drop cable, with the splitter between
> feeder and distribution.

So?

That is ordinary PON that you didn't have to do any research.

> We also do single-stage 32:1 splits.

NTT do not, well, with reasons.

> If we ran each drop cable from the
> splitter all the way to the house, we would have extremely long drop
> cables, and lots of them all bundled together going down the street. We
> don't do that, we use mainline distribution cable like I described above.

Then, you need to have on the trunk cable, for 32
subscriebrs, a huge closure with a splitter and 32
(or less, if some are shared) small closures, which
costs more than SS, because of extra material and
labor for the huge closure.

A political problem is that it becomes obvious that 32
(or less) closures required for SS is less expensive
than 32 long drop cables with conventional PON.

Worse, you have to have spare 31 fibers in the cable,
which denies the theory that PON were better than SS
because fibers were expensive.

If a trunk cable covers 196 subscribers, which is typical,
it is obviously a strange design to have only 6 trunk fibers,
because fibers are so expensive, but to have other 31 drop
fibers in the same cable.

You can reduce the number of spare fibers if you give
up 32:1 splitting at the first splitter and use the
fibers in more complex way to use them in both directions.
However, you need more spare fibers if the number of
subscribers increase and some splitter overflows and no
lengthy service interruption is allowed.

That is, reusing some fibers in a trunk cable as intermediate
drop is difficult to manage for future configuration changes.

It becomes even worse for NTT, which claims that it is
doing fair unbundling of its fibers, because NTT must
prepare 124 spare fibers, if they allow three other
competitors share its cable.

So, there is no reason to simply have SS just with small
closures, which can be trivially unbundled.

						Masataka Ohta