OPTICAL WAVEGUIDE AND ITS MANUFACTURING METHOD

PROBLEM TO BE SOLVED: To provide an optical waveguide easy in manufacturing and high in a yield. SOLUTION: In the optical waveguide having structure wherein a core 3 consisting of resin is held between a pair of clads 21, 22 consisting of resin having a refractive index lower than that of the core 3, the core 3 exists within a groove formed in one side of clad 21, the width of the groove is not increased as the depth from the surface of one side of clad 21 is increased in the cross section orthogonal to the propagating direction of light, and moreover at least a part of the contour of the groove is composed of a curved line.