In article , snipped-for-privacy@imec.be mentioned...
> How to create a data link of 115.2KBits/sec over 50-100Km (line of sight)
> > with total power consumption of less than 5W?
> > Is there any commercial unit for these type of an application?
>
> modulated laser + photodiode at the focal point of a telescope ?
> (I think there is an article about such an experiment in the ARRL
> Handbook IIRC).
>
> Hmmm actually the colimation will have to be excellent, because at 100
> km
> and a 4 mrad divergence of a laser diode (as the ones I've used
> previously)
> the laser would illuminate a 400 m-diameter area. I don't know what the
> divergence
> of a HeNe laser is (still less than 5 W, but takes more space).
I think the major problem would be atmospheric disturbances such as heat waves, making the link extremely unreliable, in fact nearly unusable. Also, at those distances, you will have to have the two sites at a higher elevation, because of the curvature of the earth.
You might check out the RONJA which uses LEDs to make a link over a half km. The original Loo Pipe version was for 115.2 kbps.
Jean-Michel