While listening to the “This Week In Amateur Radio” podcast this morning, I heard reference to a new record setting non-line-of-sight one way contact that took place over optical wavelengths. A sucessful transmission over a distance of 288 kilometers was achieved by using an LED based transmitter. The report (PDF) provides many interesting details, such as their use of a GPS locked sound card to permit received signals to be resolved to just a milliHertz or so. Nice!
Here is some video of the transmitter in action. The floodlight that you see is generated by an array of 60 Luxeon LEDs, collimated by Fresnel lenses. Each LED is about 3.3 watts. Pretty cool.