[Laser] References to effect of atmospheric turbulence on laser comms.

[Chris L]

Dear group,

These refs, though a little old, were assembled from practical research 
undertaken in the days when atmospheric optical comms were promising far 
more than they ever delivered - late 60s/early 70s. They stimulated 
organisations like Bell labs to start work on optical fibres which (of 
course) grew to be the major part of practical optical comms. However they 
do elucidate and quantify the problems of transmitting coherent beams 
through the atmosphere...

D L Fried: "Atmospheric modulation noise in an optical heterodyne receiver". 
IEEE Journal of Quantum Electronics, vol QE-3, pps 213 - 221, June 1967.

"Optical heterodyne detection of an atmospherically distorted wave front". 
Proceedings of IEEE, vol 55, pps 55 - 67, January 1967.

These references are also useful:

F E Goodwin: "A Review of Operational Laser Communication Systems", Proc 
IEEE, vol 58, pps 1746 - 1752, October 1970. (Note that some of these 
systems used polarisation modulation, a system relevant to a recent posting 
on this website).

D L Begley: "Free Space Laser Communications" - SPIE Optical Engineering 
Press, Bellingham, Washington USA, circa 1990.

Let me also quote from the classic early text "Laser Receivers" by Monte 
Ross, one of the first textbooks in this field (John Wiley and Sons, New 
York, 1966, page 125):

"...One of the practical problems of photomixing (heterodyne detection) is 
that it requires a stable light source for the local oscillator and the 
carrier. Except for the HeNe type and possibly the ruby laser, the present 
laser or quasi-laser devices have too broad a spectrum to qualify... The 
spectrum generated by a coherent GaAs diode which is not specially cooled is 
about ... 3 by 10 to the 11th power Hz. Any modulation frequency less than 
(this) number will be lost in the self beats and cross beats of the local 
oscillator spectrum components and the carrier spectrum".

As I'm on a freemail service I'll provide the rest of this in a second 
posting to follow,

With thanks,

Chris Long