A data signal to be transmitted is supplied to a modulator of a transmitter, and the modulator modulates the output of a blue light-excited white LED and outputs blue LED light and phosphor light. The modulated blue light enters to a photo-electric converter through an LED light transmission color filter. The modulated phosphor light on the other hand enters to another photo-electric converter through a phosphor light transmission color filter. The photo-electric converters convert incident light to electric signals. The converted signals are amplified by amplifiers. Then, equalizers emphasize the harmonic component therein according to the response characteristic of the blue light and the response characteristic of the phosphor light for reduction of the dullness of waveforms.