Full quadrature regeneration of QPSK signals using sequential phase sensitive amplification and parametric saturation

We demonstrate all-optical regeneration of both the phase and the amplitude of a $10$\,GBaud quadrature phase shift keying (QPSK) signal using two nonlinear stages. First we regenerate the phase using a wavelength converting phase sensitive amplifier and then we regenerate the amplitude using a saturated single-pump parametric amplifier, returning the signal to its original wavelength at the same time. We exploit the conjugating nature of the two processing stages to eliminate the intrinsic SPM distortion of the system, further improving performance.