PURPOSE:To transfer plural pieces of information by several pieces of fibers, by executing the multiplexing by optical beams whose wavelengths are different. CONSTITUTION:Optical beams having wavelength lambda1 and wavelength lambda2 generated in a multi-wavelength light source group 5E in a device to be controlled (for instance, a room air conditioner) are transferred to a remote controller 3 through optical fibers 6B1 and 6B2, respectively. On the remote controller 3, an optical switch 3C for mixing the optical beams having wavelength lambda1 and wavelength lambda2 and outputting them to an optical fiber 6A is provided. The optical switch 3C mixes the light beams mechanically by a shield plate or a slit. Also, the mixing ratio of optical beams is formed to vary it in accordance with the mechanical extent of movement of the shield plate or the slit. The control variable is displayed on the remote controller 3 as the mechanical extent of movement, without assistance of other electric power supply, etc. The optical beam transferred by the optical fiber 6A is subjected to wavelength separation, and after that, is converted to a digital value and executes the control.