Abstract: A dispersive optical waveguide tap comprises a blazed and chirped refractive index grating in the core of the waveguide, coupling means and utilization means. The grating is selected such that guided mode light of predetermined wavelength will, in the absence of the coupling means, be directed into one or more cladding modes of the waveguide. The presence of the coupling means in optical co-operation with the waveguide, changes the guiding conditions such that the cladding modes are substantially eliminated from a portion of the waveguide that includes the cladding, whereby the grating directs the guided mode light into one or more radiation modes. The blaze angle typically is .ltoreq.15.degree.. The chirp serves to bring the radiation mode light substantially to a focus in at least one dimension, the focal point (or line) depending on the wavelength of the light.