🚀 go-pugleaf

Quite a few years ago, Bell Labs put together a "fiber optic telephone", in
which a single fiber was used for *both* bi-directional signal *and* power
supply, over (as I recall) a several kilometer fiebr-optic cable. The phone
looked like an ordinary "desk set" (you know, type 2500), except it had this
piece of fiber coming out going to a spool of the stuff.

The article said that they were using a form of TDM on the fiber -- somewhat
like the "ping-pong" versions of ISDN -- wherein more than 90% of the time
was outgoing "power", and the rest of the time was input signal pulse
(with guard "dead time" around it).  The outgoing "signal" was carried
by position-modulation of one edge of the "power" signal. They spent a
lot of time talking about the trouble they went to building a ringer with
enough efficiency to make an acceptably loud sound with the small amount
of power that was available. (The power for the signal electronics was much
less of a problem!)

Cute...

(Of course, there's no way to plug in an "extension" phone without a
locally-powered repeater.)


Rob Warnock
Systems Architecture Consultant

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