A system comprising: an arrayed waveguide grating, AWG, comprising a plurality of waveguides (103, 207) connected between a first input free propagation region, FPR, and a first output FPR; and a beam sweeper for tuning a wavelength response of the AWG, the beam sweeper comprising a second input FPR, a second output FPR adjoining and optically coupled to the first input FPR of the AWG, at least three waveguides connected between the second input FPR and the second output FPR, the at least three waveguides and the second output FPR being configured to focus light propagating in the at least three waveguides from the second input FPR to the second output FPR at a focus at an interface between the second output FPR and the first input FPR, and at least one pair (400, 402) of forward (404, 406) and backward heaters (405, 407) laterally overlapping with the at least three waveguides, each of the heaters configured to impart an incremental phase shift between the light propagating in the at least three waveguides to thereby shift a lateral position of the focus, the phase shift imparted by the forward heater being of an opposite sign than the phase shift imparted by the backward heater, whereby the forward heater and the backward heater shift the lateral position of the focus in mutually opposite directions. an arrayed waveguide grating, AWG, comprising a plurality of waveguides (103, 207) connected between a first input free propagation region, FPR, and a first output FPR; and a beam sweeper for tuning a wavelength response of the AWG, the beam sweeper comprising a second input FPR, a second output FPR adjoining and optically coupled to the first input FPR of the AWG, at least three waveguides connected between the second input FPR and the second output FPR, the at least three waveguides and the second output FPR being configured to focus light propagating in the at least three waveguides from the second input FPR to the second output FPR at a focus at an interface between the second output FPR and the first input FPR, and at least one pair (400, 402) of forward (404, 406) and backward heaters (405, 407) laterally overlapping with the at least three waveguides, each of the heaters configured to impart an incremental phase shift between the light propagating in the at least three waveguides to thereby shift a lateral position of the focus, the phase shift imparted by the forward heater being of an opposite sign than the phase shift imparted by the backward heater, whereby the forward heater and the backward heater shift the lateral position of the focus in mutually opposite directions. a second input FPR, a second output FPR adjoining and optically coupled to the first input FPR of the AWG, at least three waveguides connected between the second input FPR and the second output FPR, the at least three waveguides and the second output FPR being configured to focus light propagating in the at least three waveguides from the second input FPR to the second output FPR at a focus at an interface between the second output FPR and the first input FPR, and at least one pair (400, 402) of forward (404, 406) and backward heaters (405, 407) laterally overlapping with the at least three waveguides, each of the heaters configured to impart an incremental phase shift between the light propagating in the at least three waveguides to thereby shift a lateral position of the focus, the phase shift imparted by the forward heater being of an opposite sign than the phase shift imparted by the backward heater, whereby the forward heater and the backward heater shift the lateral position of the focus in mutually opposite directions.