Optical analog computing?

R. A. Hettinga rah at shipwright.com
Tue Oct 1 23:25:07 EDT 2002

--- begin forwarded text

Status: RO
Subject: Optical analog computing?
From: Rohit Khare <khare at alumni.caltech.edu>
To: fork at xent.com
Sender: fork-admin at xent.com
Date: Tue, 1 Oct 2002 10:54:02 -0700

I'm at a speech by Terry Essex, CTO of Essex Corp. He worked on optical
computing at the NSA for a long time.

"the first computer to crack enigma was optical"
"the first synthetic-aperture-radar processor was optical"
"but all these early successes were classified -- 100 to 200 projects,
and I probably know of less than half."

--> Do these claims compute?! is this really a secret history, or does
this mean holography, of am I just completely out of the loop?1

Optical info is a complex-valued wave (spatial frequency, amplitude and

lenses, refractions, and interference are the computational operators.
(add, copy, multiply, fft, correlation, convolution) of 1D and 2D arrays

and, of course, massively parallel by default.

and, of course, allows free-space interconnects.

Here's a commercialized effort from israel: a "space integrating
vector-matric multiplier"  [ A ] B = [ C ]
laser-> 512-gate modulator -> spread over 2D
"256 Teraflop equivalent" for one multiply per nanosecond.

Unclassified example: acousto-optic spectrometer, 500 Gflops equivalent
(for 12 watts!) doing continuous FFTs.  Launched in 1998 on a 2-year
mission. Submillimeter wave observatory.

Of course, the rest of the talk is about the promise of moving from
optoelectronic to all-optical processors (on all-optical nets & with
optical encryption, & so on).

very compact supercomputing, made much cheaper by telecom industry's
investment in opto components.

Key is to follow the wideband signal processing applications, not
"balancing your checkbook" applications.

displaying MRIs in 3-D in realtime (you can collect, but not yet display
in r/t).

[ps: there was a great piece on developing portable (handheld!) passive
MRI devices in a recent Caltech alumni magazine report.  article
attached in next email]

1.6 Tflop imager for mine-detection for ground-penetrating radar in 3D
SAR is a new commercial application

--- end forwarded text

R. A. Hettinga <mailto: rah at ibuc.com>
The Internet Bearer Underwriting Corporation <http://www.ibuc.com/>
44 Farquhar Street, Boston, MA 02131 USA
"... however it may deserve respect for its usefulness and antiquity,
[predicting the end of the world] has not been found agreeable to
experience." -- Edward Gibbon, 'Decline and Fall of the Roman Empire'

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