An optical channel waveguide having a reflection grating and a related method for its fabrication. The grating is apodized to provide a desired reflection or transmission spectral characteristic, by varying the grating width along the length of the grating in the direction of light propagation. The grating has multiple parallel elements extending across the waveguide channel width, and apodization is effected by appropriate selection of the width of each element relative to the width of the channel, without varying the grating duty cycle or other parameters.