Directional optical waveguide coupler and power tap arrangement

Abstract

A directional optical waveguide coupler and power tap is disclosed for use with optical fibers or planar-form optical waveguides. Abutted to the end of a cladded optical transmission waveguide is a section of a second optical waveguide comprising a core surrounded by a cladding layer, the core having a smaller cross-sectional area than the core of the transmission waveguide. In the present arrangement, light energy propagating in the core of the second waveguide towards the transmission waveguide is coupled into the core of the transmission waveguide at the point of abuttment, whereas light energy propagating in the core of the transmission waveguide towards the second waveguide is coupled into both the core and cladding layer of the second waveguide at the point of abuttment. Means disposed along the second waveguide adjacent the point of abuttment couples out of the cladding layer the cladding modes transferred from the core-guided modes of the transmission waveguide for subsequent conversion into a representative electrical signal. A stripper-absorber means is also disposed along the second waveguide for removing spurious cladding modes propagating therebeneath towards both the coupling out means and the point of abuttment between the two waveguides.