Efficient phase regeneration of DPSK signal by sideband-assisted dual-pump phase-sensitive amplifier

A high phase sensitivity of 25 dB at the nonlinear phase shift of 0.8 rad in a sideband-assisted dual-pump phase-sensitive amplifier is achieved. Here the sidebands play an important role to evoke larger phase-sensitive attenuations for achieving higher phase sensitivity at such a lower nonlinear phase shift. This feature is utilised to improve the efficiency in the phase regeneration of 21.5 Gbit/s DPSK signals. The phase error of 22.6° was squeezed to 2.5° by operating such a sideband-assisted dual-pump phase-sensitive amplifier at 0.8 rad nonlinear phase shift. The operations at low nonlinear phase shift enable utilisation of the state-of-the-art silica-based highly nonlinear fibre with low noise and low dispersion slope by avoiding stimulated Brillouin scattering induced by higher pump power.