Optical signal processor

A method comprising:

• forming an input/output comprising an optical waveguide into which multiplex light with multiple wavelengths enters, wherein forming the input/output comprises:
• forming a slab optical waveguide into which the multiplex light enters;
• forming an array optical waveguide optically connected to the slab optical waveguide, the array optical waveguide comprising a plurality of optical waveguides that are equal in optical path length;
• forming a polarization processor configured to separate the multiplex light into TE polarization and TM polarization;
• and
• forming a half-wave plate configured to give a phase difference of 180° to the TE polarization or the TM polarization separated by the polarization processor;
• forming a wavelength multiplexer/demultiplexer configured to perform demultiplexing for forming a plurality of signal lights by spatially demultiplexing the multiplex light emitted from the input/output, by one diffraction, into light of each wavelength, and to perform multiplexing for multiplexing the spatially demultiplexed plurality of signal lights that are different in wavelength;
• forming a spatial light modulator configured to reflect each of the plurality of signal lights demultiplexed by the wavelength multiplexer/demultiplexer in a set direction;
• forming a mirror configured to change optical paths of the plurality of signal lights forming a plurality of changed signal lights;
• forming a second optical system configured to collect the plurality of changed signal lights to the spatial light modulator;
• and
• forming a second spacer arranged between the wavelength multiplexer/demultiplexer and the second optical system, to transmit light.