Abstract: Embodiments relate to a branching waveguide circuit where two or more waveguides branch from a main waveguide defining between them an intermediate region ranging from said main waveguide. The intermediate region comprises a plurality of holes of cladding material extending from the top of the core layer into intermediate material, said holes being arranged so that the depth of said holes increases away from said main waveguide with an average slope of the hole depth versus distance to main waveguide. This way, loss due to transition between the main and branching waveguides may be reduced.

Abstract: By a method for controlling the state of polarization (SOP) of an optical signal transmitted through an optical waveguide, the waveguide is buried in a planar structure and a plurality of stress-applying films, having variable stress, are placed on the top of the structure. Preferably the stress-applying films comprise materials that have thermal expansion coefficients different from that of the planar structure or comprise materials with piezoelectric properties. In this way it is possible to produce a cascaded series of optical elements with variable linear birefringence in a planar optical waveguide. Moreover according to the invention it is possible, by the method according to the invention, to manufacture optical components having an active polarisation controller.