Wavelength division multiplexer and silicon photonic integrated chip

A wavelength division multiplexer, comprising:

• at least two polarization control structures and at least one polarization-independent Mach-Zehnder interferometer that are disposed on a silicon substrate;
• wherein each of the at least two polarization control structures includes two input ports and one output port, the at least one Mach-Zehnder interferometer includes two input ports and one optical signal output port, the optical signal output port is used for outputting a multiplexed optical signal, and the output ports of the at least two polarization control structures are connected to the input ports of the at least one Mach-Zehnder interferometer;
• wherein each of the at least two polarization control structures receives two linearly-polarized light beams of linearly-polarized incident light beams, all the linearly-polarized incident light beams have different wavelengths, the two linearly-polarized light beams are combined and outputted as a sub-multiplexed optical signal in which linear polarization states of the two linearly-polarized light beams are rotated to be perpendicular to each other, and the sub-multiplexed optical signal is inputted through one of the input ports of the at least one Mach-Zehnder interferometer;
• wherein the at least one polarization-independent Mach-Zehnder interferometer receives the sub-multiplexed optical signals outputted by the at least two polarization control structures, and the sub-multiplexed optical signals are combined and outputted as the multiplexed optical signal which includes two linear polarization states that are perpendicular to each other.