Optical transmission system, optical transmission method, and relay amplifier

An optical transmission method in an optical transmission system, the system comprising:

• an optical transmitter;
• an optical receiver;
• and
• a relay amplification device for amplifying and relaying an optical signal, wherein the optical transmitter and the relay amplification device are connected by a first multi-core fiber, the optical receiver and the relay amplification device are connected by a second multi-core fiber, wherein the method comprising the steps of:
• branching optical signals transmitted by respective cores of the first multi-core fiber into a plurality of single-core fibers;
• performing optical parametric amplification on respective optical signals branched into respective single-core fibers with pump lights to output phase conjugate lights of optical signals generated by the optical parametric amplification;
• and
• multiplexing output phase conjugate lights of optical signals to output to the second multi-core fiber.

A relay amplification device for amplifying and relaying an optical signal in an optical transmission system, the system further comprising:

• an optical transmitter;
• and an optical receiver;
• wherein the relay amplification device comprising:
• a brancher configured to branch optical signals transmitted by respective cores of a first multi-core fiber connected with the optical transmitter into a plurality of single-core fibers;
• a spectrum inverter configured to perform optical parametric amplification on respective optical signals branched into respective single-core fibers with pump lights to output phase conjugate lights of respective optical signals generated by the optical parametric amplification;
• and
• a multiplexer configured to multiplex phase conjugate lights of respective optical signals output from the spectrum inverter to output to a first multi-core fiber connected with the optical receiver.