At 10:38 AM 2/14/96 -0500, you wrote:
This idea of sending data via laser beams across open spaces has some very useful potential. ...
Eavesdropping and channel-blocking and physical-location-discovery are related threats to which most traditional data channels are susceptible. Any link which depends on a physical conduit (phone line, fiber, coax) is relatively easy to interrupt and to trace to its end points. RF links, even with frequency hopping, are subject to triangulation and jamming. All these kinds of links can be eavesdropped.
Point-to-point conduitless laser signalling, as envisioned by "Bill" and Tim in their quotes below, eliminates or reduces these threats
Dust will cause diffraction of the beam (at a reduced intensity, of course). Near the source, a detector tuned narrowly to the wavelength of interest would probably succeed quickly. If you have a line of sight channel, there are many other ways to signal that will preserve some deniability. Rick F. Hoselton (who doesn't claim to present opinions for others)