Re: Building a Light Clock

From: Randy M. Dumse (rmd_at_newmicros.com)
Date: 12/01/04 

Date: Wed, 1 Dec 2004 08:29:18 -0600

"Pmb" <someone@somewhere.com> wrote in message
news:ZcmdnU1-_v9FVjDcRVn-1Q@comcast.com...
> Anyone know of some specs on light emitters and light detectors
> that can operate at 1 MHz - 150 MHz? What complications arise
> when constructing circuitry that operates at 1MHz? Is that
> something "easily" done at home?

I think today it probably is reasonable. In 1995 I made a barrel racing
timer with a Quarton laser. I modulated the beam by digital switching
the applied power, and checked the output. I found it rolled off rather
quickly above 500 kHz, and it was still operational at 600 kHz, but with
half the power output. I also found, with some difficulty, a detector
that worked well in those frequency ranges.

Things have progressed quite a bit in optoelectronics with the push to
fiber communications.

For instance if you go to www.digikey.com and search on Optoisolators
you will find there are a few with less than 100nS on/off specs, which
would mean there's an opto pair (emitter - detector) there which
approach 10MHz capacity.

A quick check of fiber optic transceivers shows some around 125
Megabits/sec, and lots in the 8 and 13 MBPS range.

So, I think it is possible to construct a 1MHz transmitter/receiver in
one's (electronics lab equipped) basement today. 

-- 
Randy M. Dumse
Caution: Objects in mirror are more confused than they appear.