Muni fiber: L1 or L2?

Fri Feb 8 08:36:31 UTC 2013

Jay Ashworth wrote:

>> As PON require considerably longer drop cable from a splitters
>> to 4 or 8 subscribers, it can not be cheaper than Ethernet,
>> unless subscriber density is very high.
> 
> Oh, ghod; we're not gonna go here, again, are we?

That PON is more expensive than SS is the reality of an example
contained in a document provided by regulatory body (soumu sho)
of Japanese government.

http://www.soumu.go.jp/main_sosiki/joho_tsusin/policyreports/chousa/bb_seibi/pdf/041209_2_14.pdf.

Assume you have 4000 subscribers and total trunk cable length
is 51.1Km, which is the PON case with example and trunk cable
length will be identical regardless of whether you use PON
or SS.

The problem of PON is that, to efficiently share a fiber and
a splitter, they must be shared by many subscribers, which
means drop cables are longer than those of SS.

For example, if drop cables of PON are 10m longer in average than
that of SS, it's total length is 40km, which is *SIGNIFICANT*.

Just as the last miles matter, the last yards do matter.

> Yes, a PON physical build can be somewhat cheaper, because it multiplexes
> your trunk cabling from 1pr per circuit to as many as 16-32pr per circuit
> on the trunk, allowing you to spec smaller cables.

That is a negligible part of the cost. Cable cost is not very
sensitive to the number of fibers in a cable.

						Masataka Ohta