The invention relates to wavelength couplers (11) with high isolation and in particular it is directed and describes devices that include a fused taper wavelength division multiplexer (DWM) which incorporates wavelength selective optical reflection elements such as fibre Bragg gratings. The incorporation of wavelength filtering means (12, 13) located on at least one of the output ports (7, 8) on the coupler allow the filtering of light of particular wavelengths through the output ports (7, 8).
