INTEGRATED OPTICAL CHIP

PURPOSE: To prevent the occurrence of error due to polarized light cross coupling by propagating an optical signal, which is inputted to an integrated optical chip by a first optical waveguide, to a Y coupler and branching it to first and second optical waveguides and comining optical signals, which are inputted to the integrated optical chip by second and third optical waveguides, in the Y coupler and making them interfere with each other. CONSTITUTION: Waveguides 12, 14, and 16 join at a junction point 18. Light made incident on the waveguide 12 is branched to waveguides 14 and 16 at the junction point 18. Light made incident on waveguides 14 and 16 are coupled at the junction point 18 and are made incient on the waveguide 12. Waveguides 14 and 16 are brought into contact with slots 26 and 28 formed on the end part face 20 of an integrated optical chip 10 respectively. The slot 26 is shorter than the slot 28. The difference in length between waveguides 14 and 16 is made longer than the coherence distance, and asymmetry occurs in polarized light cross coupling because of this difference. Thus, error due to cross coupling is eliminated by this asymmetry in polarized light cross coupling.