an electro - optical modulator has a monomode light waveguide modulator for which a pressure - sensitive signal generator is provided as a signal source for the purpose of modulating a light power signal supplied to the monomode light waveguide modulator over an input light waveguide , the electrical output of the signal generator being either directly or indirectly connected to an electrical input of the monomode light waveguide modulator . the arrangement serves for the transmission of signals representing pressure values , for example , acoustic pressure values , over an optical transmission system , and inasmuch as the electrical signals are generated by the pressure - sensitive signal generator , no external supply devices whatsoever are required at the modulator for the electrical energy .