APPARATUS AND METHOD FOR COUPLING LIGHT

An optical coupler (40; 50) comprises a substrate (41). A first waveguide element (45) is provided in a first layer with respect to the substrate, wherein the first waveguide element (45) comprises a first end (45a) and a second end (45b), and wherein the first end (45a) of the first waveguide element (45) is coupled to input/output light to/from a first end of the optical coupler. A second waveguide element (43) is provided in a second layer, the second layer arranged adjacent to the first layer, wherein the second waveguide element (43) comprises a first end (43a) and a second end (43b), and wherein the first end (43a) of the second waveguide element (43) is coupled to input/output light to/from a second end of the optical coupler. The first waveguide element (45) is configured to extend from the first end of the optical coupler towards the second end of the optical coupler, and the second waveguide element (43) is configured to extend from the second end of the optical coupler towards the first end of the optical coupler, such that the first waveguide element (45) partly overlaps with the second waveguide element (43) to adapt light passing between the first end (45a) of the first waveguide element (45) and first end (43a) of the second waveguide element (43).