Abstract: An arrayed wavelength grating device has a series of waveguiding channels (3) interconnecting two free space regions (2,4) across which light inputting and outputting the device passes. There are differences in optical path length between any two of said channels (3) lying adjacent to one other in said series, which differences are defined by respective optical path length increments. The optical path length progression across said channels (3) is non-linear, not being defined by any one value of the path length increments, nor by a plural number of values of the path length increments each defining a linear optical path length progression of a subset of at least three of said channels (3).

Abstract: An arrayed wavelength grating device has a series of waveguiding channels (3) interconnecting two free space regions (2,4) across which light inputting and outputting the device passes. There are differences in optical path length between any two of said channels (3) lying adjacent to one other in said series, which differences are defined by respective optical path length increments. The optical path length progression across said channels (3) is non-linear, not being defined by any one value of the path length increments, nor by a plural number of values of the path length increments each defining a linear optical path length progression of a subset of at least three of said channels (3).