ronpin
Imagine Reality
join:2002-12-06
Nirvana
 ·AT&T Southwest
| reply to wtffiber
Re: FiOS's one mistake?
Great article -- but it's not aware of any cost savings with distributed splitter/smaller conduit -- which alter his "equation" (math is a dangerous thing  )
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When Clinton lied -- no one died. |
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ronpin
Imagine Reality
join:2002-12-06
Nirvana
·AT&T Southwest
| 
Ooops -- Forgot to include the credits! ("fair-use") |
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PONman
join:2005-06-09
Fairfax, VA
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Fig 4 |
or this: There is a 1x2 splitter before the 1x32 splitters, and due to there only being 32 users, the system will work correctly (assuming the optical loss isn't too much)
So whats the real deal here? Could someone explain to me what this Fig 4 looks like from a physical level but more importantly from an optical level, end to end. Also, what is Verizon doing today? |
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ronpin
Imagine Reality
join:2002-12-06
Nirvana
·AT&T Southwest
2 edits | 
Cascaded Splitter Option |
said by PONman  : or this: There is a 1x2 splitter before the 1x32 splitters, and due to there only being 32 users, the system will work correctly (assuming the optical loss isn't too much) Your right-on for the current "Sub-Division Centralized Splitters".
It's the "or this:" (above) is actually the "other" diagram in the PDF link above -- the "cascaded splitter design". It uses an initial 1x8 splitter resulting in 1x4 distribution splits.
"All Things Being Equal" -- centralized splitters win hands-down. It's the "equal" part that screws-up the equation. A "tiny-tiny" subsurface copper "air-blow" conduit that serves 320 users in a static cascaded-splitter design (see diagram) is "much much" cheaper than a 2" horizontally bored conduit (minimal space to accommodate the hundreds of homeruns required in a centralized splitter design)
Horizontal boring is expensive -- about $10 foot -- cheaper if your Verizon.
Alternately, Labor + 1/4" coated copper-conduit is ~about $3 foot -- a whopping 70% cost reduction -- $35,000 per mile -- all because you opted for a cascaded-splitter design (above).
Now, we just have to get over accepting that effectively pre-subscribing 320 passings inside of 10 1x32 feeder fibers (terminated in 18-strand air blown fiber cables near a RT,CO or local cross connect) is a bad-thing - not if it's actually cheaper.
It is the last item above that also requires a clever marketing model -- which is beyond our scope here
The savings is so great that you can now afford to split every home to a final 1x4 fiber/FTTP drop fanout -- and still save money over the current generation of buried conduit.
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High ideals breed lowly hypocrites |
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tschmidt
Premium,MVM
join:2000-11-12
Milford, NH
 ·Hollis Hosting
·Verizon Online DSL
·Fairpoint Communic..
| I believe Verizon is using a lot of preterminated fiber. If so that means conduit/innerduct must be relatively large to pass the connector regardless of how many fibers are used.
I assume Verizon looked at the tradeoff between Capex and Opex and decided a centralized splitter cabinet optimized OLT loading and reduced Opex as user and speed mix changes over time.
It is a lot easier to go to one location and change splitter allocation as needs change. When the time comes to upgrade to next generation PON conversion will be a lot easier if all that is needed is to add a few nexgen PON OLT line cards, upgrade a few customers to new spec and modify splitter cabinet crossconnect.
This is also much the same outside plant arrangement used with copper so the OSS system that manages copper is easily adaptable to fiber.
I'm just guessing, I have no knowledge of why Verizon is doing what they are doing, other then I have to assume a lot of smart people modeled various alternatives and decided on balance this was the best.
/Tom |
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ronpin
Imagine Reality
join:2002-12-06
Nirvana
·AT&T Southwest
2 edits | I appreciate why a fiber architect would have selected the centralized splitter option -- before now
To date, nobody has offered a cascade-specific vastly cheaper conduit option. That changes everything yes?
How many 1x32 OLT ports will $35,000 of savings per-mile buy? (really, how many?) related savings from static outside plant infrastructure? (no on-demand splitter changes, smaller maint. staff) Premise work only (outsourced). Let's ignore the miles of extra fiber -- saved here as well.
I'm saying that the massive savings enabled by 1/4" surface-groove/curb-line tiny coated copper tubes for air-blowing is well-worth pre-installing a 1x32 OLT port -- as required in the cascaded-splitter architecture.
As long as a 1x32 OLT port is substantially less than $35,000 ea. -- we have a substantial savings in the cascaded option.
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High ideals breed lowly hypocrites |
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