Optical amplification apparatus, and mode division multiplexing system including optical amplification apparatus

A mode division multiplexing system comprising:

• a single-mode transmitter module;
• a single-mode receiver module;
• a mode multiplexer;
• a mode demultiplexer;
• at least one few-mode fiber;
• and at least one optical amplification apparatus;
• wherein the single-mode transmitter module is connected to an input port of the mode multiplexer, an output port of the mode multiplexer is connected to an input port of the mode demultiplexer through the few-mode fiber, an output port of the mode demultiplexer is connected to the single-mode receiver module, and the optical amplification apparatus is connected between few-mode fibers;
• the single-mode transmitter module is configured to:
• generate a plurality of paths of wavelength division multiplexing signals, and transmit the plurality of paths of wavelength division multiplexing signals to the mode multiplexer;
• the mode multiplexer is configured to:
• process the plurality of paths of wavelength division multiplexing signals, and generate one path of signals based on the plurality of paths of wavelength division multiplexing signals, wherein the path of signals comprises a plurality of optical signals carried in a plurality of transmission modes, C1, C2, . . . , CM, and gain values corresponding to the plurality of transmission modes of the few-mode fiber are respectively G1(C1)>G2(C2)> . . . >GM(CM);
• the optical amplification apparatus comprises a first optical amplifier, a second optical amplifier, and a mode exchanger;
• the first optical amplifier is connected to an input port of the mode exchanger, and the second optical amplifier is connected to an output port of the mode exchanger;
• the first optical amplifier is configured to amplify the plurality of optical signals carried in the plurality of transmission modes of the few-mode fiber, the plurality of transmission modes of the few-mode fiber are grouped into N groups, each group comprises two transmission modes:
• (Ci, CM+1−i), and N is a positive integer greater than 1;
• the mode exchanger is configured to exchange the two transmission modes carrying the optical signals in each group, and an exchange policy of the mode exchanger is to centrosymmetrically exchange a mode Ci in gain Gi and a mode C(M+1−i) in gain G(M+1−i);
• the second optical amplifier is configured to amplify the optical signals that are carried in the two transmission modes in each group and whose modes are exchanged;
• the mode demultiplexer is configured to demultiplex a plurality of transmission modes corresponding to one path of signals on the few-mode fiber, to obtain a plurality of paths of to-be-received signals;
• and
• the single-mode receiver module is configured to:
• receive the plurality of paths of to-be-received signals, and demodulate the plurality of paths of to-be-received signals.