Polarization splitting and combining apparatus

An apparatus configured to split light into a plurality of polarizations, the apparatus comprising:

• an input waveguide configured to receive the light;
• a first interferometer configured to split the light into a first polarization and a second polarization;
• a second interferometer configured to split the light into a third polarization and a fourth polarization;
• and
• a wave plate disposed between an input terminal of the second interferometer and the input waveguide and configured to change a polarization state of the light input to the second interferometer, wherein
• the first interferometer comprises a first output waveguide configured to output the first polarization and a second output waveguide configured to output the second polarization, and
• the second interferometer comprises a third output waveguide configured to output the third polarization and a fourth output waveguide configured to output the fourth polarization.

An apparatus configured to combine a plurality of polarizations, the apparatus comprising:

• a first interferometer configured to output first light to which a first polarization and a second polarization are combined;
• a second interferometer configured to output second light to which a third polarization and a fourth polarization are combined;
• and
• an output waveguide configured to combine and output the first light and the second light, wherein
• the first interferometer and the second interferometer are connected in parallel,
• the first interferometer comprises a first input waveguide configured to receive the first polarization and a second input waveguide configured to receive the second polarization, and
• the second interferometer comprises a third input waveguide configured to receive the third polarization and a fourth input waveguide configured to receive the fourth polarization.