This projects has a transmitter and an optical receptor for sending analog signals using a 2W LED and fresnel lens.
The system has been tested with success reaching about 8Km in distance (from São Brás de Alportel to the Cerro de São Miguel in Tavira, where you can find the RTP towers) where it transmitted a music signal with almost no noise during the night.
The project involves designing electronic circuits and digital fabrication. The transmitter and receptor boxes were milled in homemade CNC built by the project author.
The author is Emídio Martins, a member of the eLab Hackerspace, also an ham radio enthusiast and a true analog electronics dinosaur.