Real time active aiming?( was Re: [Laser] Laser comm stuff)

[Derek Weston]

"J. Forster" wrote:
> 
> If a retro was co-located with each receiver, tracking would be possible without
> tracking data transfers.

True, but even with a 100% effective retro relector, range with
autoalign would be half the link's potential range.

Then again, perhaps the bandwidth of the modulation of the alignment
signal could be much lower than that of the modulation for the data, so
lower received levels during alignment than during data transfer could
be OK in some cases. 

It'd be interesting to experiment using one of the precision retro
reflectors used by surveyors.  Does anyone have an idea of the % of
incident light these return and the typical angular difference between
incident and returned beams?