ARRAYED WAVEGUIDE GRATING

An arrayed waveguide grating (AWG) device is described in which there are a plurality of output waveguides ( 10 ) coupled at one end to the output side of an second optical interaction region ( 4 ) of the AWG, and wherein the output waveguides are substantially identically curved in at least a portion of the fan-out region of the AWG. This improves the channel (frequency) spacing accuracy of the AWG. In one embodiment input waveguides ( 2 ) of the AWG are also substantially identically curved in at least a portion of the fan-in region of the AWG, these being inversely curved to the substantially identically curved portions of the output waveguides, with respect to the direction of travel of light along the waveguides. This has been found to reduce asymmetry in the channel output response.