Patent ID: 8818142

Claim:
An optical semiconductor device comprising: an optical demultiplexer having a first and a second input ports and a first and a second output ports wherein intensity of an optical signal that is output from the first output port and an optical signal that is output from the second output port are equal to each other when an optical signal is introduced into the first input port whereas intensity of an optical signal that is output from the first output port is larger than intensity of an optical signal that is output from the second output port when an optical signal is introduced into the second input port; an optical multiplexer having a third and a fourth input ports and a third and a fourth output ports; a first optical waveguide of semiconductor to connect the first output port to the third input port; a second optical waveguide of semiconductor to connect the second output port to the fourth input port; a first modulation electrode to apply an electric field to the first optical waveguide so as to cause changes in the optical path length of the first optical waveguide; and a second modulation electrode to apply an electric field to the second optical waveguide so as to cause changes in the optical path length of the second optical waveguide.