An optical device for optically
multiplexing or demultiplexing light of different predetermined wavelengths is provided, the optical device comprising at least one first
waveguide (11) and at least one second
waveguide (12) formed on a substrate (10), wherein the at least one first
waveguide and the at least one second waveguide intersect at an intersection, comprising a
diffraction grating structure (13) formed at the intersection. There exists a first
wavelength or
wavelength band travelling within the first waveguide (11) exciting the
grating structure and being diffracted an angle corresponding to an outcoupling direction and there exists a second
wavelength or
wavelength band, different from the first wavelength or
wavelength band, travelling within the second waveguide (12) exciting the
grating structure and being diffracted at an angle corresponding to the same outcoupling direction. The two
radiation beams comprising
radiation of two different wavelengths or wavelength bands are spatially separated into the optical waveguides (11 and 12) or combined into single outcoupling direction, e.g. into a single optical element, e.g. a single
optical fiber (21). An optical device may be used in local access communications such as
fiber to the home, office or curb applications.