Spatial multiplexing optical receiver, spatial multiplexing optical transmission system, and spatial multiplexing optical reception method

A spatial multiplexing optical transmission system comprising:

• a transmitter configured to transmit signals of plurality of modes to a receiver via a transmission path;
• and
• a receiver comprising a spatial multiplexing optical receiver comprising:
• a plurality of coherent receivers configured to coherently receive each of signals of a plurality of modes spatially multiplexed and transmitted, by using independent continuous-wave light for each mode as local oscillator light;
• a plurality of frequency offset compensators configured to perform, independently for each mode, frequency offset compensation based on a correlation between a known training signal and a signal of each mode for each of the signals of the plurality of modes being coherently received;
• and
• a multi-input multi-output (MIMO) signal processing circuit configured to perform MIMO signal processing on the signals of the plurality of modes subjected to the frequency offset compensation in the frequency offset compensator.

A spatially multiplexed optical reception method comprising:

• coherently receiving each of signals of a plurality of modes spatially multiplexed and transmitted by using independent continuous-wave light for each mode as local oscillator light;
• performing, independently for each mode, frequency offset compensation based on a correlation between a known training signal and a signal of each mode for each of the coherently received signals of the plurality of modes;
• and
• performing multi-input multi-output (MIMO) signal processing on the signals of the plurality of modes subjected to the frequency offset compensation.