Optical transmission system

An optical transmission system comprising:

• a first optical transmitter configured to generate a plurality of first optical signals encoded and modulated with the same first client data being carriers with the same wavelength, and having different carrier phases, and output the plurality of generated first optical signals using a plurality of first optical transmitter output ports, each of the first optical transmitter output ports corresponding to one of the plurality of first optical signals;
• a second optical transmitter configured to generate a plurality of second optical signals encoded and modulated with the same second client data different from the first client data and being carriers with the same wavelength, and having different carrier phases, and output the plurality of generated second optical signals using a plurality of second optical transmitter output ports, each of the second optical transmitter output ports corresponding to one of the plurality of second optical signals;
• a first directional coupler including a plurality of first input ports, each of the first input ports connected to a corresponding one of at least two of the plurality of first optical transmitter output ports, and a plurality of first output ports;
• a second directional coupler including a plurality of second input ports, each of the second input ports connected to a corresponding one of at least two of the plurality of second optical transmitter output ports, and a plurality of second output ports;
• a third directional coupler including a plurality of third input ports, each of the third input ports connected to a corresponding one of a first first output port being one of the plurality of first output ports, a first second output port being one of the plurality of second output ports;
• and
• a fourth directional coupler including a plurality of fourth input ports, each of the fourth input ports connected to a corresponding one of at least one second first output port being the first output port different from the first first output port and being one of the plurality of first output ports, and at least one second second output port being the second output port different from the first second output port and being one of the second output ports.

An optical transmission system comprising:

• an optical transmitter configured to generate four or more optical signals encoded and modulated with the same client data being carriers with the same wavelength, and having different carrier phases, and output the four or more generated optical signals using a plurality of optical transmitter output ports, each of the optical transmitter output ports corresponding to one of the four or more optical signals;
• one or a plurality of first directional couplers including a plurality of first input ports, each of the first input ports connected to a corresponding one of the plurality of first optical transmitter output ports being two or more optical transmitter output ports among the plurality of optical transmitter output ports, and a plurality of first output ports;
• one or a plurality of second directional couplers including a plurality of second input ports, each of the second input ports connected to a corresponding one of a plurality of second optical transmitter output ports being optical transmitter output ports different from the first optical transmitter output ports and being two or more optical transmitter output ports among the plurality of optical transmitter output ports, and a plurality of second output ports;
• a third directional coupler including a third input port connected to one of the plurality of first output ports, and a third output port;
• a fourth directional coupler including a fourth input port connected to one of the plurality of second output ports, and a fourth output port;
• and
• a fifth directional coupler including a plurality of fifth input ports, each of the fifth input ports connected to a corresponding one of the third output port and the fourth output port.