Wideband interferometer type polarization light beam combiner and splitter

A wideband interferometer type polarization beam combiner and splitter, comprising:

• an optical splitting unit;
• an optical coupling unit;
• an optical path length difference imparting unit comprising a plurality of optical waveguides arranged between the optical splitting unit and the optical coupling unit;
• one or two first input/output ports connected to the optical splitting unit;
• and
• two second input/output ports connected to the optical coupling unit;
• wherein:
• the optical path length difference imparting unit includes, along the optical waveguides, means for generating differential birefringence and means for generating a difference in refractive index dispersion;
• and
• wherein:
• polarization combining is performed by inputting light in a first polarization state and light entering in a second polarization state at the two second input/output ports connected to the optical coupling unit, and by outputting the light through the one or two first input/output ports connected to the optical splitting unit, or
• polarization splitting is performed by inputting light at the one or two first input/output ports connected to the optical splitting unit, and by outputting light in the first polarization state and light in the second polarization state, respectively, through the two second input/output ports connected to the optical coupling unit, and
• wherein:
• a half-integer of a wavelength of λc is set as a normalized phase difference, for the optical path length difference imparting unit, between the first polarization state and the second polarization state;
• and
• wavelength fluctuation of the normalized phase difference is suppressed by a difference in refractive index dispersion that is provided by the means for generating a difference in refractive index dispersion, the wavelength fluctuation having opposite plus and minus signs for the first polarization state and the second polarization state.