FTTH Active vs Passive

Justin Shore justin at justinshore.com
Tue Dec 1 10:43:41 CST 2009


Luke Marrott wrote:
> I'm wondering what everyones thoughts are in regards to FTTH using Active
> Ethernet or Passive. I work for a FTTH Provider that has done Active
> Ethernet on a few networks so I'm always biased in discussions, but I don't
> know anyone with experience in PON.

Active is the way to go.  Passive is merely a stepping stone on the way 
to active.  Passive only makes sense (in some cases) if you are 1) fiber 
poor and 2) not doing a greenfield deployment.  If you have the fiber to 
work with or if you are building a FTTH plant from scratch go with 
active.  The only real proponents of PONs are the RBOCs who are 
exceedingly cheap, slow to react, and completely unable to think ahead 
(ie, putting in an abundance of fiber for future use instead of just 
enough to get by) and some MSOs who don't dread and loathe shared 
network mediums like CATV and PON (whereas those from a networking 
background would never ever pick such a technology).

> I've read before that almost all PON technology is proprietary, locking you
> into a specific hardware vendor. However I think this is changing or has
> already changed, opening PON up for interoperability. Can anyone confirm
> this?

There are several actual PON standards out there:

http://en.wikipedia.org/wiki/Passive_optical_network

Few vendors will ever admit that they interop with another vendor's gear 
though.  They don't want you to buy their optical switches (which have a 
small markup) and someone else's ONTs (which typically have a much 
greater markup).  In some cases even though that adhere to the standards 
to a point they diverge and go proprietary for things like integrating 
voice or video into the system.  That could cause management and/or 
support issues for you at some point in the life of the product. 
Personally I'd go with a vendor that offers the complete solution 
instead of piecing one together.

PON has some popularity in MDUs.  The splits are easy to manage because 
they're all in one location.  Bandwidth needs are typically on the low 
end in MDUs due to a lack of businesses (bandwidth being a severe 
future-proofing problem for PON).  PON's biggest limitations for us is 
the distance limitations.  We're deploying FTTH in the rural 
countryside, not in a dense residential neighborhood.  PON has very 
specific distance limitations for each split and cumulative across all 
splits that make rural deployments extremely difficult.  The price 
difference between Active and PON is negligible at this point and in 
many cases cheaper for active.  Go with active for FTTH.  You won't 
regret it.

Justin






More information about the NANOG mailing list