The present invention provides a bidirectional communication optical
waveguide which can adopt a configuration in which light sources having
the same wavelengths are used and stray light is not inputted to either a
light emitting device or a light receiving device, and the bidirectional
communication optical waveguide realizes a bidirectional communication
module. The bidirectional communication optical waveguide includes a main
waveguide core and a sub-waveguide core. A main inclined plane is
provided in a midway of an optical path in the main waveguide core.