Optical phase conjugator, optical transmission system using the same, and optical phase conjugation method

An optical phase conjugator comprising:

• an optical nonlinear medium for receiving first light having a first light frequency and second light having a second light frequency, and outputting a third light having a third light frequency generated by a nonlinear optical effect based on the first light and the second light, said optical nonlinear medium containing an element to be activated upon irradiation of fourth light having a fourth light frequency and having an amplification function with respect to at least the second light in an active state;
• a first optical coupler having a first terminal to which the first light is input, a second terminal to which the second light is input, and a third terminal from which coupled light of the first light and the second light is output, the third terminal being optically connected to an input end of said optical nonlinear medium;
• and
• a second optical coupler, optically connected to at least one end selected from the group consisting of the input end and an output end of said optical nonlinear medium, for inputting the fourth light into said medium, said second optical coupler having a first terminal to which the fourth light is input, a second terminal to which light output from said first optical coupler is input, and a third terminal from which coupled light of light input from the second terminal and the fourth light is output, the second terminal being optically connected to the third terminal of said first optical coupler, and the third terminal being optically connected to the input end of said optical nonlinear medium.

An optical phase conjugator comprising:

• an optical nonlinear medium for receiving first light having a first light frequency and second light having a second light frequency, and outputting a third light having a third light frequency generated by a nonlinear optical effect based on the first light and the second light, said optical nonlinear medium containing an element to be activated upon irradiation of fourth light having a fourth light frequency and having an amplification function with respect to at least the second light in an active state;
• a first optical coupler having a first terminal to which the first light is input, a second terminal to which the second light is input, and a third terminal from which coupled light of the first light and the second light is output, the third terminal being optically connected to an input end of said optical nonlinear medium;
• a second optical coupler, optically connected to at least one end selected from the group consisting of the input end and an output end of said optical nonlinear medium, for inputting the fourth light into said medium, said second optical coupler having a first terminal to which the fourth light is input, a second terminal to which light output from said first optical coupler is input, and a third terminal from which coupled light of light input from the second terminal and the fourth light is output, the second terminal being optically connected to the third terminal of said first optical coupler, and the third terminal being optically connected to the input end of said optical nonlinear medium;
• and
• a third optical coupler having a first terminal to which the fourth light is input, a second terminal to which light output from said optical nonlinear medium is input and from which the fourth light is output, and a third terminal from which light input from the second terminal is output, the second terminal being optically connected to the output end of said optical nonlinear medium.

An optical transmission system comprising:

• a) an optical phase conjugator including an optical nonlinear medium for receiving first light having a first light frequency and second light having a second light frequency, and outputting a third light having a third light frequency generated by a nonlinear optical effect based on the first light and the second light, said optical nonlinear medium containing an element to be activated upon irradiation of fourth light having a fourth light frequency and having an amplification function with respect to at least the second light in an active state,
• a first optical coupler having a first terminal to which the first light is input, a second terminal to which the second light is input, and a third terminal from which coupled light of the first light and the second light is output, the third terminal being optically connected to an input end of said optical nonlinear medium, and
• a second optical coupler, optically connected to at least one end selected from the group consisting of the input end and an output end of said optical nonlinear medium, for inputting the fourth light into said medium;
• b) an optical fiber, having an input end optically connected to the output end of said optical nonlinear medium of said optical phase conjugator, for transmitting light output from said optical phase conjugator;
• c) an optical amplifier, having input and output ends optically connected to the output end of said optical nonlinear medium of said optical phase conjugator, and the input end of said optical fiber, respectively, for amplifying light output from said optical phase conjugator;
• d) a local light source for generating fifth light having substantially the same light frequency as the third light frequency;
• and
• e) a fourth optical coupler having a first terminal optically connected to said local light source, a second terminal optically connected to the output end of said optical fiber, and a third terminal from which coupled light of light transmitted along said optical fiber and the fifth light is output.