Disclosed in an embodiment of the present invention is an array waveguide grating (AWG), comprising: W input waveguides, M array waveguides, a first free propagation region (FPR), a second FPR, one output waveguide, and W monitoring waveguide sets, the length of the X-th array waveguide being greater than the length of the (X-1)-th array waveguide by [delta]L; neighboring array waveguides from the first array waveguide to the Nth array waveguide in the M array waveguides form a second array waveguide set, and the remaining M-N neighboring array waveguides form a first array waveguide set; the first array waveguide set is connected to the output waveguide through the second FPR; the second array waveguide set is connected to the W monitoring waveguide sets through the second FPR; and the grating periods of the first array waveguide set and the second array waveguide set are different. One AWG can be used to realize wavelength multiplexing and monitoring, while dispersing part of the energy into different monitoring waveguides for monitoring, thus avoiding using complicated pilot technology.