An optical waveguide directional coupler includes a base and a Y-shaped optical waveguide formed in the base. The base includes a planar member and a ridge member extending from a side of the planar member. The planar member includes a top surface. The ridge member includes a recessed planar portion and a raised portion raised relative to the recessed planar portion and perpendicularly extending from the planar member. The raised portion has an upper surface coplanar with the top surface. The Y-shaped optical waveguide is exposed to the upper surface and the top surface. One end of the Y-shaped optical waveguide is exposed to an end of the ridge member, and the other two ends are exposed to an end of the planar member.