RE: [EFM] Active Architectures
Hello Carlos, on your comment: "I see one immediate problem. I
assume that the 850 nm lasers are coupled to multimode fiber, and that the
downstream PON needs to use a singlemode fiber. If this is correct, then
every home would have to be served by two fibers of different construction.
I've heard news of fibers able to carry both single and multimode signals
but haven't seen any hard data on this."
Yes, that is why I made the below comment in my original message:
"There are a couple options on the fiber between the node and the ONU but
I'll leave that discussion for later."
I don't think I'd use the word "problem" to describe it since it is quite
solvable. It's more a question of which method is used. I would advocate the
use of microtubing or conduit between the node and each ONU. That way, the
fiber or fibers would only be installed (blown-in or pulled) when a
subscriber signs up for service. Likewise, the ONU would only be installed
at that time. It doesn't have to be done this way, but to do otherwise would
leave the network operator with stranded assets in the field. In some cases
these assets could sit idle for a very long time. Another option is the
customer could own both the fiber and the ONU and have them installed by a
third-party when they subscribe to a service. The second strand is still
quite a minimal cost compared to the transmitter cost savings that the
architecture provides. In a neighborhood of 1/4 acre lot sizes, the average
run for a cluster of 16 homes would be about 170 meters or so.
The extra fiber (if 2 are used) shouldn't be viewed as an additional cost
per-se. It is just a part of the architecture decision and the OVERALL costs
are what matter. It is easy to single out an architectural difference and
concentrate on what that costs, as an argument against something, but in
reality the big picture is what matters. Big-picture-wise, this apparent
extra cost disappears.
If a single fiber were used, I believe there are methods such that it could
be either singlemode or multimode. Anyone who can provide cost and
performance details of such an arrangement please do. I find very little
published on this, except to imply feasibility. In any case I tend to think
this would be more expensive overall than 2 separate fibers since mux and
demux components are needed. It may be straightforward off-the-shelf
components but I think those cost more than 170 meters of fiber.
-----Original Message-----
From: Carlos Ribeiro [mailto:cribeiro@xxxxxxxxxxxxxxxx]
Sent: Tuesday, August 21, 2001 4:16 AM
To: Frank Coluccio; david.m.horne@xxxxxxxxx
Cc: sganguly@xxxxxxxxx; ramu_raskan@xxxxxxxxxxxxx;
stds-802-3-efm@ieee.org
Subject: Re: [EFM] Active Architectures
(in the context of David Horne's "half-PON" idea)
At 20:22 20/08/01 +0000, Frank Coluccio wrote:
>For extremely long runs, have you considered the tradeoffs of an
>inexpensive cwdm
>solution in lieu of multiple strands coming back from the ONUs?
That was my first thought when reading David's proposal. In fact I already
discussed similar views not only with David, but with lots of people in
this list. That's the main reasoning to develop a wavelength alocation plan
that allows for the future use of C/DWDM. Gerry Pesavento is going to
discuss this issue.
As far as Mr. Horne proposal is concerned, I see one immediate problem. I
assume that the 850 nm lasers are coupled to multimode fiber, and that the
downstream PON needs to use a singlemode fiber. If this is correct, then
every home would have to be served by two fibers of different construction.
I've heard news of fibers able to carry both single and multimode signals
but haven't seen any hard data on this.
Carlos Ribeiro
CTBC Telecom