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From: mwg@petrus.UUCP (Mark Garrett)
Newsgroups: net.research
Subject: Re: Photonics - replacing eletronics?
Message-ID: <753@petrus.UUCP>
Date: Thu, 12-Dec-85 10:38:22 EST
Article-I.D.: petrus.753
Posted: Thu Dec 12 10:38:22 1985
Date-Received: Sat, 14-Dec-85 07:53:47 EST
References: <57100003@hpcnof.UUCP>
Organization: Bell Communications Research, Inc
Lines: 24

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> 	The most recent issue of "Science News (Nov 30th) has a very
> fascinating article about a new technology dubbed 'Photonics', hailed 
> as the replacement for current electronics.

'Photonics', as a word, has been around long enough for it to be incorporated
into the names of a couple of research districts here at Bellcore.
The main motivation for it is that photons can be made to switch on and
off faster than electrons, and you can get more bandwidth-distance product
from fiber than from coax.  There are two disadvantages that I can think of.
First, it is fundamentally impossible to get as many circuits into a small
chip with light (assuming the order of magnitude of visible light) because
the size of 'wires' must be larger than the wavelength.  This is about one
half micron for light and some tens of Angstroms for electrons (correct me
if I'm wrong).  Already we see VLSI chips made with one micron line spacing
in electonics.  Second, if you have a signal that needs to be distributed
to a number of points (eg, fanout in a circuit or taps in a multi-access
network), you need a large fraction of the total signal energy to detect
it accurately in the optical case, and very little in the electrical case.

For more on Photonics, one place to start might be the Proceedings of the
IEEE July 1984 special issue on optical computing.

-Mark Garrett