Receiving optical system control device and receiving optical system control method

A receiving optical system control method comprising:

• acquiring a reception signal by receiving, for each mode optical beam, a plurality of mode optical beams being incident optical beams coupled to a plurality of propagation modes of an optical transmission medium by an optical system including a variable mechanism;
• calculating light intensity of each of the mode optical beams from the reception signal;
• calculating an optical phase of each of the mode optical beams from the reception signal;
• calculating a relative phase between the plurality of mode optical beams from the optical phase;
• and
• calculating a control amount of the variable mechanism from the light intensity and the relative phase.

An optical receiving device comprising:

• a receiving optical system control device including
• a light intensity calculation unit configured to calculate light intensity of each mode optical beam from a reception signal acquired by receiving, for each mode optical beam, a plurality of mode optical beams being incident optical beams coupled to a plurality of propagation modes of an optical transmission medium by an optical system including a variable mechanism;
• an optical phase calculation unit configured to calculate an optical phase of each of the mode optical beams from the reception signal;
• a relative phase calculation unit configured to calculate a relative phase between the plurality of mode optical beams from the optical phase;
• and
• a control amount calculation unit configured to calculate a control amount of the variable mechanism from the light intensity and the relative phase;
• the optical system;
• the optical transmission medium;
• a coupling control unit configured to control the variable mechanism, based on the control amount, and couple the incident optical beams to the plurality of propagation modes;
• a mode demultiplexing unit configured to demultiplex the plurality of mode optical beams and outputting output each of the mode optical beams;
• and
• an optical receiving unit configured to receive each of the mode optical beams and generate the reception signal.