On Fri, 23 Feb 2007 22:55:09 -0600, Tom Ring
wrote:


Someone, I think it may have been Richard, once mentioned a form of
distortion that was due, I think, to the modulation itself.

Hi Tom,

There are several, some that are way out in the decimals but separable
(Raman scattering). Others like Solitons (a rather old observation)
are used to increase bandwidth in commercial links.

I hesitate to ask what the question is, because all of these effects
require some strain to achieve with very high power densities, often
in the megawatts to gigawatts. If you can find a suitably fast pulse
source, you might do it on a kitchen table. The hardest part of
getting a lot of optical power into a small fiber is overcoming
Numerical Aperture mismatch (sound familiar once you discard the NA?).
Some sources take this in stride (notably semiconductor lasers), while
others (like the sun) are stunningly inefficient.

I had a buddy who built a CO2 UV laser from a Scientific American
Amateur Scientist column. It packed quite a punch for all of five to
ten nanoseconds (capacitor arc discharge from a cap of several hundred
picofarads charged to twenty thousand volts using a very low
inductance lead design). He chose to be careful by aiming it out the
window into the sky. He fired the laser and cracked the window. The
thermal expansion of the glass was sufficiently slow enough to
accumulate enough stress (due to the attenuation) to create a
fracture. Classic thermal runaway.

The design comes from the June, 1974 issue (available from Wes'
introduction of Dr. Shawn here some months ago). The lead paragraph
says it all:
"A RECENTLY DEVELOPED LASER that operates on a six-volt dry
battery emits 10 pulses of ultraviolet radiation per minute, each
pulse about the size and shape of a broomstick. The pulses range
in power from 50 to 100 kilowatts."
....
"The ultraviolet laser can readily be scaled to higher powers. A
discharge path one meter long can develop an output pulse of
almost a million watts, although there is a trick to it."

I will leave the details of that trick to subscribers of Dr. Shawn to
investigate further - if push comes to shove, email me for a copy of
the details.

One thought occurred, this device (augmented to one meter length)
could suitably test the illusion of the anti-glare coating hypothesis.
Free suntan lotion will be supplied to those who rely on faith and
half baked mathematics to prove all reflections are canceled. :-O

Hi Wes,

Thanx again for introducing Dr. Shawn here. I had been looking for a
complete collection of Scientific American construction articles for a
very long time.

73's
Richard Clark, KB7QHC