An optical device for performing a light power transfer between two waveguides that includes a first waveguide, a second waveguide, a transfer rate control element for controlling a light power transfer rate between the first and second waveguides and an electric element for electrically controlling the transfer rate control element by imparting electric energy to the transfer rate control element. The transfer rate control element sets the light power transfer rate to zero when the transfer rate control element is in an inoperative state. The transfer rate control element falls into the inoperative state when the electric element imparts no electric energy to the transfer rate control element.