| 摘要 |
PURPOSE:To improve crosstalk by providing a radiation mode means for radiating light with wavelength longer than that separated from a directional coupler to the outside of a waveguide between the directional coupler on the final stage and an output terminal. CONSTITUTION:In structure constituted of connecting plural directional couplers 12-1, 12-2 so as to form a multi-stage, the radiation mode means 31 for radiating wavelength longer than the wavelength lambda2 separated from the coupler 12-2 on the final stage is connected between the coupler 12-2 and the output terminal 14. After passing the coupler 12-2, an optical signal is turned to a state shown by a code 5a. The means 31 radiates an optical signal component 5a-1 belonging to the long wavelength side longer than the wavelength lambda2 to the outside of the optical wave 5a to improve crosstalk to be generated on the long wavelength side longer than the wavelength lambda2. Consequently an optical signal 5b whose crosstalk is improved even on the long wavelength side longer than the wavelength lambda2 is outputted from the output terminal 14. |
