Date: Mon, 5 Oct 1992 17:13:11 GMT
From: deej@cbnewsf.cb.att.com (david.g.lewis)
Newsgroups: comp.dcom.telecom
Subject: Re: Comments on the Multimedia Article
Organization: AT&T
X-Submissions-To: telecom@eecs.nwu.edu
X-Administrivia-To: telecom-request@eecs.nwu.edu
X-Telecom-Digest: Volume 12, Issue 763, Message 1 of 6

In article <telecom12.756.2@eecs.nwu.edu> TDARCOS@MCIMAIL.COM writes:

> We will buy the capacity as we want it.  Just have the capacity
> there and have it low enough cost to allow anyone who can afford a
> phone now to get in on this stuff.

> Note to anyone working for a telephone company: Do us all a favor and
> oversupply capacity!  You should build for a factor of one hundred
> times current capacity, the equivalent of running a small PBX into
> each house.

Unfortunately, as you touch on in the previous paragraph, there is a
cost issue involved.  You can not put in a factor of 100 overbuild in
capacity without an increase of cost.  Even if economies of scale can
somehow provide a factor of 10 improvement, you're still talking a
cost ten times current cost.  Are you willing to pay $100/month for a
POTS line just so the capacity can be there sometime in the future?

> I believe that 10 fiber optic (FO) cables are the size of one
> twisted pair, and one FO cable is the equivalent of something like
> 5,000 phone lines or 20 tv channels.

Size of the cables is the least concern; the biggest cost element in a
fiber optic system is the cost of the electronics hanging on either
end.  A 12-fiber cable (the smallest I've seen used in my, albeit
limited, experience) is probably no bigger than a piece of CATV coax
(remember, you've got to have the physical support built into the
cable -- it's not just ten fibers in a sheath).  Those six pairs of
fiber can get you anywhere from one DS1 (1.544 kb/s) (using a single
pair) to 72 DS3s (over 20Gb/s), at a cost ranging from about $5000 to,
oh, somewhere in the neighborhood of $2 million.  When you're dealing
with these numbers, cable size gets kind of lost in the noise.

Don't get me wrong; fiber's great, and one of the things that makes it
great is the fact that you can yank out the existing electronics and
upgrade the capacity of the link by orders of magnitude without having
to change out the cable plant.  But when you're talking about running
to the home, the electronics cost is *the* significant cost factor.

> Figure sending 1/2 of the capacity of a FO cable per house, and you
> can expect to cover the bandwidth demands of the future and several
> years from now.

Using your 5000 phone lines per (I'm guessing you mean) fiber pair, at
64kb/s for a phone line, you're talking sending 160Mb/s to each house.
Let's use 155Mb/s, since that's an STS-3 SONET/SDH rate.  Anyone know
what an STS-3 FOT is going for these days?  I don't have any
up-to-date information (and if I did, I probably wouldn't be allowed
to post it), but I'd guess that $30k/link (both ends) is correct
within an order of magnitude.  Even if using ring architectures and
ADMs can drop your costs by a factor of two (unlikely to impossible),
you're talking $15k electronics costs per house.

Even if the cost of overlaying the fiber itself goes to zero, you've
just incurred a $15k per subscriber incremental cost.  At a 50,000
line CO, that's an investment of $750 million dollars.  For capacity
which will, basically, sit there until people figure out how to use
it.

Try selling that to your local PSC.

> You can't go wrong overestimating capacity; if one party doesn't use
> it, someone else will.

But who pays for it??

> We did not, when steel was invented, build metal copies of wooden
> bridges; we have new technology, we need new ideas.

Actually, when iron and steel were first used as structural members in
bridges, we built metal copies of stone and wooden bridges.  It took
some years before the engineers designing bridges got sufficiently
creative to understand the paradigm shift.

(Then they went too far the other way and got too radically different;
witness Tacoma Narrows and the hideous side beams on the
Bronx-Whitestone Bridge -- but that's another story ...)

Agreed, we need new ideas.  And I would agree, up to a point, that one
element of these new ideas is to overlay fiber in sufficient quantity
that one or two fiber pairs can be dropped at each home, on spec.  But
I'd find it hard to justify pulling a fiber pair into each home and
terminating it with the electronics to support any amount of
bandwidth, unless I could charge at least ten times the going rate for
a POTS line -- and even that might not cut it.

Disclaimer: my opinions; AT&T has nothing to do with them.  In fact,
my colleagues over in Network Systems have this great Fiber To The
Curb product, the SLC(R)-DT ...