I built one of these years ago, didn't use that that much though. Totally supersed by radio these days. One interesting use of free space optics is working aro

I built one of these years ago, didn't use that that much though. Totally supersed by radio these days. One interesting use of free space optics is working around legal issues. At least in Australia the Telco act (via reference to the Radiocommunications Act) only goes up to 420THz which is red colour, so free space optics can be unregulated.