Optical multi/demultiplexer (4) device comprising a substrate, a plurality of wave guides (45, 46, 47, 48) on a surface of said substrate, a plurality of selective wavelength filters (452, 462, 472, 482). Each of said plurality of filter is able to transmit a first predetermined band of wavelengths (PB') and to reflect a second predetermined band (SB'). Each one of said plurality of filter comprising a plurality of transverse cuts (4521, 4522, 4523) provided on said waveguide disposed in predetermined positions. Said cuts forms a plurality of transmissive couple providing said first predetermined band and a plurality of reflective couple providing said second predetermined band. Said transmissive couples and said reflective couples are disposed in series. A wavelength selective filter is separately disclosed, an a method of making a filter.