Optical transmission module and optical communication system using the same

摘要

An optical transmission module includes a beam spot size expanding waveguide and a beam spot size reducing waveguide adjoining in the light propagating direction, or includes a beam spot size expanding waveguide, a beam spot size retaining waveguide and a beam spot size reducing waveguide aligning in the light propagating direction. Each waveguide has laminated core layers which are formed of materials of different refractive indexes.