An experimental design for broadband audio signal transmissions using electrooptical modulation is described. A birefringent quartz sheet induces a constant step difference in the signal, which proceeds through an electrooptical transverse modulator cut at a 45 deg angle. The modulator changes the step pattern into the form of the data code as a function of voltage. The signal is generated by a white light source whose phase is modulated. Two wave trains leave the emitter, one a reference beam and the other the out-of-step coded beam differentiated by its phase delay. The signal is received through another quartz aperture where decoding is performed as a function of changes in the luminous intensity over the width of the passband. The technique allows simultaneous transmission of multiple signals using one luminous source. An experimental set-up which successfully transmitted two television video signals simultaneously over several meters of optic fiber is described.