Integrated Optical Device

An integrated optical device having a first and a second integrated waveguide arranged so as to be in optical coupling relationship in a first and a second spaced-apart coupling region and having respective optically uncoupled waveguide sections in between the first and second coupling regions. A first and a second modulated refractive index structures are provided, each one formed along a respective uncoupled waveguide section; the modulated refractive index structures each having at least one pair of regions of mutually different refractive index adjacent to each other along the respective uncoupled waveguide section. The regions of mutually different refractive index have a portion of the respective uncoupled waveguide section and a gap formed in the uncoupled waveguide section, the refractive indexes of the regions differing from each other by at least approximately 1.5%. The device can be exploited to form optical multiplexers/demultiplexers, particularly adapted to the use in wavelength division multiplexing optical communications.