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From: whit@milton.u.washington.edu (John Whitmore)
Newsgroups: comp.arch
Subject: Re: Optical Computers
Summary: Physical limitations on optics
Message-ID: <10789@milton.u.washington.edu>
Date: 8 Nov 90 07:09:20 GMT
References: <5506.9011011201@olympus.cs.hull.ac.uk>
Organization: University of Washington, Seattle
Lines: 27

In article <5506.9011011201@olympus.cs.hull.ac.uk> rst@cs.hull.ac.uk (Rob Turner) writes:
>
>
>I recently attended a series of lectures at Manchester University,
>England on optical computers given by Alan Huang of AT&T. 
...
>What are people's views on optical computers. Alan Huang was *enormously*
>enthusiastic (as you would expect him to be). 

	The patch-panel style of computers (like most old analog computers)
is a good model for the best of optical computing devices.  Lenses do
a kind of Fourier transform, gratings are a kind of resonant multipole
filter, and so forth.  You build the physical elements into the gizmo
you want, rather than programming it on the fly.

	Optical switching elements for digital computation are awkward,
need multiple light sources (like multicolor laser beams), and will
(IMHO) NEVER achieve current LSI device densities, because the wavelength
of light used is too long. 

	That said, there is real benefit to optical subsystems as
peripherals to electronic computers.  FDDI and Ethernet bridge fiber optic
data links are a good example, ROM and WORM optical disks are another,
and the future will no doubt reveal many more.

	John Whitmore
	whit@milton.u.washington.edu