Optical signal transmitter

An optical transmitter which generates signal light including pilot light and phase conjugate light thereof, the optical transmitter comprising:

• a polarization separator which polarization-separates pilot light and polarization-multiplexed and modulated signal light into signal light of a first polarized component and signal light of a second polarized component that is orthogonal to the first polarized component and outputs the signal light of the polarized components to two output ports;
• a loop-type phase conjugate light generator having, on a path from one to another of the two output ports,
• the polarization separator,
• a polarization rotator which rotates by 90 degrees a polarized wave of the signal light of the first polarized component, and
• a first second-order non-linear optical element equipped with a first optical waveguide that generates phase conjugate light of the polarization-rotated signal light and phase conjugate light of the signal light of the second polarized component and performs degenerate parametric amplification in each of two directly opposite propagation directions with respect to the polarization-separated pilot light;
• an excitation light generator which supplies first excitation light that generates the phase conjugate light of the polarization-rotated signal light to one end of the first optical waveguide on a side where the polarization rotator is present and supplies second excitation light that generates the phase conjugate light of the second polarized component to the other end of the first optical waveguide;
• and
• a phase adjuster configured to change an optical path length of a path of the pilot light in accordance with a level of the pilot light subjected to degenerate parametric amplification in a first direction among the two propagation directions and to change an optical path length of a path of the pilot light in accordance with a level of the pilot light subjected to degenerate parametric amplification in a second direction among the two propagation directions.