Systems and methods for customizing messages are described. To this end, a transmitter has a first coding stage, a transmission-demultiplexer stage, a second coding stage, a modulator stage, a transmission-multiplexer stage and a multi-carrier modulator, whereby said transmission-demultiplexer stage and the transmission-multiplexer stage are controlled by a bit loading device. A light source provides light to the fiber for illuminating the wall and a detector coupled to the fiber receives light from within the wall.