Optical transmission system, optical transmission apparatus and optical transmission method

An optical transmission apparatus comprising:

• a mode group permutation unit configured to receive a mode-multiplexed signal obtained by multiplexing a plurality of optical signals of different types of modes from a transmission line on an input side, changes, on a mode-group-by-mode-group basis, an optical signal of a mode belonging to a mode group to an optical signal of another mode belonging to a mode group after permutation corresponding to the mode group in such a manner that the modes are interchanged between at least some of the plurality of optical signals multiplexed into the received mode-multiplexed signal, and outputs the mode-multiplexed signal after mode interchange to a transmission line on an output side,
• wherein the mode group permutation unit includes:
• a mode demultiplexer configured to separate the optical signals of a plurality of types of modes multiplexed into the mode-multiplexed signal input from the transmission line on the input side,
• mode group permutation devices corresponding to a plurality of mode groups, and
• a mode multiplexer configured to output a mode-multiplexed signal obtained by multiplexing the optical signals of a single mode output from the mode group permutation devices corresponding to the plurality of mode groups to the transmission line on the output side, and
• each of the mode group permutation devices receives, from the mode demultiplexer, the optical signals of modes belonging to the mode group before permutation corresponding to the mode group permutation device, changes a mode of at least some of the received optical signals to another mode belonging to a mode group after permutation corresponding to the mode group permutation device, and outputs the optical signals after mode change to the mode multiplexer.

An optical transmission method in an optical transmission system including a plurality of transmission lines through which a mode-multiplexed signal obtained by multiplexing a plurality of optical signals of different types of modes is transmitted, and one or more mode group permutation units provided between the plurality of transmission lines, the optical transmission method comprising:

• by each of the one or more mode group permutation units, changing, on a mode-group-by-mode-group basis, an optical signal of a mode belonging to a mode group to an optical signal of another mode belonging to a mode group after permutation corresponding to the mode group in such a manner that the modes are interchanged between at least some of the plurality of optical signals multiplexed into the mode-multiplexed signal input from one of the plurality of transmission lines on an input side, and outputting the mode-multiplexed signal after mode interchange to one of the plurality of transmission lines on an output side including:
• separating the optical signals of the plurality of types of modes multiplexed into the mode-multiplexed signal input from the transmission line on the input side, and
• outputting a mode-multiplexed signal obtained by multiplexing the optical signals of a single mode output from mode group permutation devices corresponding to a plurality of mode groups to the transmission line on the output side, and
• receiving the optical signals of modes belonging to the mode group before permutation corresponding to the mode group permutation device and changing a mode of at least some of the received optical signals to another mode belonging to a mode group after permutation corresponding to the mode group permutation device, and outputting the optical signals after mode change.