[Laser] Atmosphere turbulence bubbles

[Karel Kulhavy]

> Chris Long spoke of light beams collimated by large fresnel lens having an  
> advantage over small, presumably laser, beams when dealing with what he termed  
> "turbulence bubbles".  
>  
> As I understand, the smaller the light beam, the smaller the bubble that is  
> likely to disrupt the communication path, and the more frequently the 
> disruption  will occur.    I think that puts a lower practical limit on the  beam size 
> and total beam power that can be used to establish a communications  channel 
> over a given distance with a minimum data rate.  Otherwise, for a  light 
> communication channel, you could use a large and powerful transmission  beam with a 
> small aperture receiver, or a moderate beam with less power to  a moderate 
> aperture receiver, or in theory a small transmit beam with low power  and a 
> large aperture receiver.  This disruption by the atmosphere will make  a small 
Or you can live with interrupted beam.

Let's say that 50% of the time the signal won't get through. You make an
error correction code like Le^H^HHamming, Reed-Solomon or Golay which
works still well at 50% loss rate. Then you interlace the data so that
when a block falls out, nothing happens.

What you get is a steady increased latency and a reliable transmission
with lower bandwidth.

CL<