Optical coupler and producing method thereof

A optical coupler comprising:

• a first conversion element that converts an electric signal into an optical signal mounted on a surface of a first terminal plate;
• and
• a second conversion element that converts the optical signal into the electric signal mounted on a surface of a second terminal plate,
• wherein the surface of the first terminal plate and the surface of the second terminal plate are oriented toward an identical direction,
• wherein the first conversion element and the second conversion element are covered with a translucent primary mold resin,
• wherein a surface of the primary mold resin is covered with a secondary mold resin having a refractive index lower than that of the primary mold resin,
• wherein the first conversion element and the second conversion element are optically coupled by totally reflecting the optical signal emitted from the first conversion element at an interface between the primary mold resin and the secondary mold resin,
• wherein the surface of the primary mold resin is formed into an elliptical surface,
• wherein an emission center of the first conversion element is located on a side farther away from a center of the elliptical surface than a plane perpendicular to a plane that passes through one of focal points on an axis on which the elliptical surface exists, is perpendicular to a surface in which the first conversion element is mounted on the first terminal plate and a plane including the axis, and the surface in which the first conversion element is mounted on the first terminal plate, and
• wherein a center of a light receiving region of the second conversion element is located on a side farther away from the center of the elliptical surface than a plane perpendicular to a plane that passes through the other focal points on the axis, is perpendicular to a surface in which the first conversion element is mounted on the first terminal plate and the plane including the axis, and the surface in which the first conversion element is mounted on the first terminal plate.