Muni network ownership and the Fourth

Tue Feb 5 12:51:47 UTC 2013

Jay Ashworth <jra at baylink.com> writes:

>> Still, the power budget improvements by not going with a single strand
>> active ethernet solution (which were another suggested technology and
>> has actually been deployed by some muni PON folks like Clarkesville,
>> TN) are huge. Imagine a 24 port switch that draws 100 watts. OK,
>> that's 4w per customer. 30k customers from a served location, that's
>> 120kw ($13k power bill if you had 100% efficient UPSes and 0 cost
>> cooling, neither of which is true) just for the edge, not counting any
>> aggregation devices or northbound switch gear.
>
> Hmm.  the optics don't have auto power control?

Auto power control would apply to launch levels for the light;
assuming a launch level of -3 dBm and lasers that were only 1 percent
efficient (combination of spec max launch power for LX optics and
unrealistically crummy efficiency lasers) your total power budget for
the laser is only 50 milliwatts out of that 4 watts - wrong place to
look for power savings.  The rest is taken up by stuff like the
ethernet chip and supporting logic in the switch, inefficiencies in
the power supply, etc. etc.

>> Back at NN, we discounted this as a technology almost immediately
>> based on energy efficiency alone.
>> 
>> Anyway, in summary, for PON deployments the part that matters *is* a
>> greenfield deployment and if the fiber plant is planned and scaled
>> accordingly the cost differential is noise.
>
> I assume you mean "the cost diff between GPON plant and home-run plant";
> that's the answer I was hoping for.

Close; I meant "the cost difference between a home run fiber
architecture with centralized splitters for *PON and distributed
splitters in the field is minimal, and one gains it back in
future-proofing and avoiding forklift upgrades down the road".

The question of where one puts the splitters (if any) is coupled to
the PON vs. active ethernet question only insofar as AE doesn't need
splitters - but assuming:

          * $10k/month cost differential for power in the scenario above
          * unity cost for head end equipment (almost certainly wrong)
          * a 16 way split ratio (worst case; you might get 24 or 32)
          * $100 apiece splitters (24 or 32 would be marginally more)
          * today's stupid-low cost of capital

break-even point on the decision to go with a PON type of technology
is still less than two years.

If you have a customer who needs the whole pipe to himself (or next
generation optics for 10g or 100g to the couch), with centralized
splitters the solution is easy.  You re-patch him with an attenuator
instead of a splitter (or hook him to the new kit), re-range, and go
to town.  Of course you lose the power advantages of a PON
architecture but those customers are the exception not the rule.

-r