http://www.youtube.com/watch?v=A7HICe0MKB0&feature=player_embedded Shahriar Shahramian, one of the co creators of "The Signal Path", has created a wonderful tutorial on Waveform Shaping and Signal Constellation in an Optical Link.
Shahriar uses a few components to beyond what there were originally intended for in order to setup an optical link! By using a BlinkM RGB LED, a Color Sensor, and two PIC USB Boards from Sparkfun Electronics, a stand-alone optical link is established. Various theories of operation, including multilevel data transmission, signal constellation and detailed circuit diagrams are also presented. The final result is an 8-PAM, 3-Wavelength optical link with a colorful three-dimensional constellation graph.
To learn more and download the code for the transmitter IC, receiver IC and Matlab functions please visit the link below!