A singlemode lightwaveguide-coupling element is positioned between an initial waveguide section which there has a basic final width (W0f) and a final waveguide section which there has a basic initial width (Wn+1i) which is bigger than the basic final width (W0f). The lightwave directions of both waveguide sections are inclined at a predetermined total angle (&Dgr;&agr;) towards each other. Starting from the initial waveguide section, the lightwaveguide element comprises intermediate waveguide sections each of which at its end has a lightwave direction which is inclined towards the lightwave direction at its opposite end at an inclination angle (&Dgr;&agr;v), such that the sum of all inclination angles equals the predetermined total angle (&Dgr;&agr;).