Disclosed is an optical module comprising, an optical waveguide on the upper side of a substrate; a cutout with at least two slant surfaces, passing at least the core of the optical waveguide; and a film-filter above the cutout. Constructions of bi-directional multi-wavelength optical transmitter-receiver assembly using the optical module as a unit element are also provided in variety on a planar substrate. According to this invention, a bi-directional multi-wavelength transmitter-receiver, which is compact, reliable, excellent in the optical performance and simple in the alignments between the composing elements, can be produced.