An arrayed waveguide grating including a waveguide array extending between two free propagation regions is disclosed. One free propagation region is coupled to an input waveguide, and the other free propagation region is coupled to output waveguides. In an example, the input-side free propagation region has two sections that are moveable relative to one another. Movement is achieved by using, for example, a thermally responsive actuator that moves the input waveguide a desired distance to compensate for a temperature change. An arm formed of a low thermal expansion coefficient metal may be used as a thermally responsive actuator moving a substrate. In another example, both the input side and the output side free propagation regions have sections moveable relative to one another and, therefore, less movement is required to correct for thermal variations. An NN arrayed waveguide grating may also be formed.