On-chip integrated wavelength division multiplexer and chip

An on-chip integrated wavelength division multiplexer, comprising a bus waveguide and at least three cascaded wavelength division multiplexing units disposed on the bus waveguide, the at least three cascaded wavelength division multiplexing units comprising a first-level wavelength division multiplexing unit and at least two non-first-level wavelength division multiplexing units;

• wherein each of the wavelength division multiplexing units comprises two input ports and one output port, and is used for combining two optical signals received by the two input ports and outputting the combined optical signal from the output port;
• wherein the two input ports of the first-level wavelength division multiplexing unit are used for receiving incident optical signals having different polarization states, respectively, or, one of the two input ports of the first-level wavelength division multiplexing unit is used for receiving one beam of incident optical signal having a polarization state, and the other is not used for receiving any optical signal;
• one of the two input ports of each of the non-first-level wavelength division multiplexing units is used for receiving an incident optical signal and the other is used for receiving a combined optical signal outputted from a previous-level wavelength division multiplexing unit, and incident optical signals received by two of the non-first-level wavelength division multiplexing units corresponding to adjacent input center wavelengths have different polarization states;
• and
• wherein each of the incident optical signals has a different wavelength.