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From: gnu@hoptoad.UUCP.UUCP
Newsgroups: comp.society.futures
Subject: Re: 500MB/sec is only local, I think...
Message-ID: <8711201132.AA03014@hop.toad.com>
Date: Fri, 20-Nov-87 06:32:58 EST
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Posted: Fri Nov 20 06:32:58 1987
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>                                                      ...Bell today has
> the capability to deliver optical fiber to every house in America, with
> a bandwidth of 500 gigabits per second.  I was wrong.  The figure is
> actually half a gigabit per second.  (500 megabits/sec)  I was only off
> by a factor of 1000.  This figure is given on page 68 of Brand's book.

I doubt that Bell intends to provide switched 500MB/sec cross-country
bandwidth; you and everybody else can probably get 500MB/sec through
your local central office, perhaps 50MB/sec through your local city,
and maybe 5MB/sec cross-country.  (Though you could carry on more than
one conversation at the lower rates.)  If it takes a whole fiber to
carry 500MB/sec, and ten thousand people want to talk at that rate from
California to New York, they'd have to run 10,000 fibers each 3000
miles long.  More likely they run 100 fibers and give you a fraction of
the bandwidth.

Also note that equipment that runs at 500MHz will not be cheap enough
to put into every home, or every phone, "today".  Even the lowly 100MHz
video in Sun-3's gets its final shifting done in ECL chips, because the
TTL/MOS technologies that are easy to build gate arrays & VLSI with don't run
quickly enough.  (This could've changed somewhat in the last 2 years.)

Has anybody designed a "modular telephone jack" for optical fiber?  Note
that it has to provide a "T" connection, not just an end.  Probably it
would be more like a contention based bus for around-the-house use,
with a full speed gateway at the telco service point.  But today's
fastest existing and contemplated LANs (FDDI, Hyperchannel, etc) run
~100MBit/sec, and get nowhere near that thruput, due to processing bottlenecks
in host interfaces and gateways.  Most main memory subsystems can't handle
100MBits/sec -- Ethernet at 10MBits/sec gives them trouble!

	John