Abstract: Parallel-aligned core layers are formed by patterning a core sheet laminated on a base plate, and a clad/core bonded body is formed by laminating a cladding sheet. The base plate is peeled from one surface of the clad/core bonded body and a dicing tape is pasted on the other surface of the clad/core bonded body. An inclined surface is formed by bevel-cutting both end portions of the core layers. Clad/core bonded pieces are formed by straight-cutting the cladding sheet between core layers and on an outside of outermost core layers. A mask is disposed on the clad/core bonded pieces, and then a metal film is formed on the inclined surface. The clad/core bonded pieces are separated individually by peeling the pieces from the dicing tape after the mask is removed. The clad/core bonded piece is brought into contact with the liquid adhesive coated on a circuit substrate and aligned thereon. Then, the liquid adhesive is cured.

Abstract: An optical waveguide includes an optical waveguide main body and mirrors. The optical waveguide main body includes a first cladding layer, a second cladding layer and a core portion provided between the first cladding layer and the second cladding layer. The optical waveguide main body has a first region in which the core portion and the mirrors are arranged and the light signal is transmitted, and a second region arranged on both sides of the first region and not contributing to a transmission of a light signal. Through vias that pass through the optical waveguide main body is provided in the second region. The first region on a side that faces the light emitting element or the light receiving element is protruded larger than the second region on a side that faces the light emitting element or the light receiving element.