I wont disagree with ronsimpson. Personally, I don't know if it is possible, but it does seem difficult. My gut feeling is that in order to have any chance of making this work you will need narrowband light source (laser edge emitting LED or superluminescent LED instead of standard LED), and then use the proper narrow band optical filter. Then, you may still need electrical modulation and electrical filtering to reject DC ambient light that gets through the filter, and perhaps even phase detection (PPL) to provide extra discrimination. Data rates will likely be limited too, even if you can get the concept to work.