Optical module, optical transmission system, and fabrication method for optical module

An optical transmission system, comprising:

• two optical modules, each of said optical modules comprising:
• a substrate;
• one or a plurality of planar optical devices mounted on said substrate;
• and
• a waveguide block including a flat surface and one or a plurality of curved waveguides formed on the flat surface;
• said waveguide block being mounted on said substrate such that the flat surface on which said curved waveguides are formed is perpendicular to said substrate and said curved waveguides and an incidence face or an emitting face of said planar optical device are opposed to each other on one end face of said waveguide block, and being configured so that an optical fiber can be connected to an other end face of said waveguide block which is orthogonal to the one end face;
• said two optical modules being optically connected to each other by an optical fiber array formed from a plurality of optical fibers;
• said optical fiber array being connected to said two optical modules while twisted by 180 degrees between said two optical modules such that the longest one of said curved waveguides of one of said optical modules and the shortest one of said curved waveguides of the other one of said optical modules are connected to each other.