Optical communication device, optical transmission system, wavelength converter, and optical communication method
An optical communication device includes an excitation light source that outputs excitation light, a multiplexer that multiplexes signal light and the excitation light outputted from the excitation light source, a first nonlinear optical medium into which the multiplexed excitation light and the signal light are inputted, and a second nonlinear optical medium that is coupled to the first nonlinear optical medium in series and has an optical property different from that of the first nonlinear optical medium.
1. An optical communication device comprising:
an excitation light source that outputs excitation light;
a multiplexer that multiplexes signal light and the excitation light outputted from the excitation light source;
a first nonlinear optical medium into which the multiplexed excitation light and the signal light are inputted; and
a second nonlinear optical medium that is coupled to the first nonlinear optical medium in series and has an optical property different from that of the first nonlinear optical medium, wherein
the first nonlinear optical medium generates polarization rotation in a first direction, depending on a frequency of a light wave propagating in the first nonlinear optical medium, and
the second nonlinear optical medium generates polarization rotation in a second direction opposite to the first direction, depending on the frequency.
2. The optical communication device according to claim 1 , wherein
in the first nonlinear optical medium, a fourth derivative relating to a frequency of a propagation constant has a first sign, and
in the second nonlinear optical medium, the fourth derivative has a second sign different from the first sign.
3. The optical communication device according to claim 1 , wherein
in the first nonlinear optical medium, a third derivative relating to a frequency of a propagation constant has a first sign, and
in the second nonlinear optical medium, the third derivative has a second sign different from the first sign.
4. The optical communication device according to claim 1 , wherein
a length of the first nonlinear optical medium in an optical axis direction and a length of the second nonlinear optical medium in the optical axis direction are designed such that at least one of relative differential group delay of the converted signal light relative to the input signal light and a relative polarization angle between excitation light inputted to the first nonlinear optical medium and the input signal light is minimized at an exit plane of the second nonlinear optical medium.
5. An optical communication method comprising:
making input signal light having a first wavelength and excitation light having a second wavelength different from the first wavelength incident on a wavelength converter in which a first nonlinear optical medium and a second nonlinear optical medium having an optical property different from that of the first nonlinear optical medium are coupled in series, to generate converted signal light having a third wavelength different from the first wavelength and the second wavelength; and
outputting, to an optical transmission path, the converted signal light outputted from the second nonlinear optical medium, wherein
the first nonlinear optical medium generates polarization rotation in a first direction, depending on a frequency of a light wave propagating in the first nonlinear optical medium, and
the second nonlinear optical medium generates polarization rotation in a second direction opposite to the first direction, depending on the frequency.