Optical voice transceiver over the air...

Is there any links to tutorials, projects, schematics, kits... that you know of for a LED based voice intercom/transceiver over the air ? (not laser, not fiber optics)

Obviously you can alter led brightness directly according to the audio amplitude. (Level-shift your signal into the positive region.) However this does not give linear response.

Instead a better way is PWM or PFM. A 555 IC can create PWM output, by applying your audio signal to its 'ctl' pin.

Also try an internet search on "555 pwm led".

If you are wondering about carrier free communication system, please be advised that you may encounter severe noise and interference problem from all other sources. You may consider the setup commonly used by the remote controls used by many electronic instruments. You can also use AM or FM modulation (how do you plan to take care of unwanted reflections from other objects in the room).

Thanks.
OK. Pulse frequency modulation, pulse width modulation, amplitude modulation, frequency modulation...

-No expected reflections nor interference-

What about the receivers for them ? Any links where to learn ?

Here is a complete system. Falstad's simulator does not support an optosensor, therefore I put in a resistor as a middleman between the transmitter and receiver.

The capacitor low-pass filter lets through the audio.

The carrier needs to be a higher frequency than my simulation has. Therefore reduce capacitor values to suit.