An optical transmission system includes light supply devices, light receiving devices, an optical fiber cable, an electric power combiner and a data processing unit. MIMO communication is performed by the light receiving devices receiving signal beams having signals different from one another, output from the light supply devices and transmitted through a single core or cladding of the optical fiber cable. The signal beams are feed beams. The light supply devices output the feed beams with signals different from one another superimposed thereon by modulation. The light receiving devices convert the feed beams transmitted thereto into electric powers. The electric power combiner combines the electric powers obtained by the conversion. The data processing unit obtains signals superimposed on the feed beams received by the light receiving devices, and based on the obtained signals, obtains the signals superimposed by the light supply devices on the feed beams.