Optical waveguides and optical transmission/reception units are placed on
one principal plane of a semiconductor substrate. A light source is
placed on one end surface of the semiconductor substrate and guides
generated light to the optical waveguides. In the optical
transmission/reception units, each of optical resonant members optically
resonates with partial light of one of light beams propagating in the
optical waveguides and emits the partial light into an optical
transmission member if voltage is applied thereto. In the optical
transmission/reception units, each of another optical resonant members
optically resonates with light propagating in the optical transmission
member and emits the resonated light into a photodetector unit if voltage
is applied thereto.