I make a radio modem AFSK using Transceiver from **broken link removed**
and I make a modem AFSK from **broken link removed**
work 1200bps in full duplex, you can use others radio but this laipac Transceiver is too good because you can use full duples and not necessary controll PTT to tx
You could easily make a tranmitter/receiver with a generic 5 dollar laser pen and a red filter on a standard light sensative diode. Depends on the diode's responce rate to the bandwidth you'd get but if you found the right parts I imagine you could do some pretty large bandwidth. The difficulty with a laser system is the stability of the transmitter and the receiver and possible interference.