The following links are good reference material for experimenters in the field of optical sound and field recording of modulated light.
A Brief History of Optical Synthesis. A detailed historical timeline of optical sound technology with focus on its use in experimental music. Published by Derek Holzer.
Photophones Revisited. A very nice review article on the use of modulated light for free-space voice communications over long distances, with in-depth technical details. Published by Mike Groth.
Build Your Own UFO Bino-Scope Unit. An article that describes how to make a long-range modulated light receiver with a pair of binoculars and a photodiode amplifier.
QSD2030 Datasheet. Technical data sheet for a typical PIN photodiode. Published by Fairchild Semiconductor / ON Semiconductor.