Optical communications terminal station, optical signal transmission method, and optical signal increasing method in wavelength multiplexing system

A method of transmitting an optical signal for use in a wavelength multiplexing optical transmission communications system, comprising:

• (a) generating and transmitting at least one main signal containing information, such that when a plurality of main signal is generated and transmitted, the main signals have different wavelengths;
• (b) generating a light having a power large enough to generate a nonlinear effect in an optical transmission line when fewer than a predetermined number of main signals is transmitted, and having a power small enough to avoid the nonlinear effect when the predetermined number of main signals is transmitted;
• (c) optically coupling the at least one main signal and the light generated in step (b);
• and
• (d) generating a light by four-wave mixing the main signal and the light generated in step (b) when less than the predetermined number of main signals is transmitted.

An optical communications device, comprising:

• an optical signal generator to output less than or equal to a predetermined number of wavelength separated optical channels;
• a light generator to output a compensating light having a power large enough to generate a nonlinear effect in an optical transmission line when fewer than the predetermined number of wavelength separated optical channels is output and having a power small enough to avoid the nonlinear effect when the predetermined number of wavelength separated optical channels is output;
• and
• a coupler to wavelength-multiplex the outputs of the optical signal generator and the light generator such that when the optical signal generator outputs less than the predetermined number of wavelength separated optical channels, four-wave mixing is caused in the optical transmission line.

A method of transmitting an optical signal for use in a wavelength multiplexing optical transmission communications system, comprising:

• generating and transmitting at least one main signal containing information, such that when a plurality of main signal is generated and transmitted, the main signals have different wavelengths;
• generating a supplemental light having a power large enough to generate a nonlinear effect in an optical transmission line when fewer than a predetermined number of main signals is transmitted, and having a power small enough to avoid the nonlinear effect when the predetermined number of main signals is transmitted;
• optically coupling the at least one main signal and the supplemental light;
• generating a light by four-wave mixing the main signal and the supplemental light when less than the predetermined number of main signals is transmitted;
• and
• reducing the power of the supplemental light when the predetermined number of main signals is transmitted.