An arrayed waveguide grating includes an input/output waveguide 1, an input/output waveguide 2, a slab waveguide, an arrayed waveguide 1, a reflection zone 1, an arrayed waveguide 2, and a reflection zone 2. The input/output waveguide 1 and the input/output waveguide 2 are located on a same side of the slab waveguide, and are coupled to the slab waveguide. The reflection zone 1 is configured to reflect a light wave in a first band, and to transmit a light wave in a second band. The reflection zone 2 is configured to reflect the light wave in the second band. It is implemented that a single arrayed waveguide grating outputs light waves with different adjacent channel wavelength spacings, and a quantity of devices used in a system in which an uplink adjacent channel wavelength spacing and a downlink adjacent channel wavelength spacing are asymmetrical is further reduced.