Co- and Counterphasing Tolerances for Dual-Pump Parametric $\lambda$ -Conversion of D(Q)PSK Signals

Recently, we have shown that a pump-phase modulation in single-pump parametric wavelength converters introduces severe signal degradations on differential (quadrature) phase-shift keying signals. In this letter, we extend our investigations to dual-pump parametric wavelength converters. It will be shown that even small deviations from ideal co- and counterphasing can lead to similar optical signal-to-noise ratio penalties as in the single-pump case. This nonideal behaviour can occur due to imperfections in the pump-phase modulation scheme as well as through walk-off between the pumps that is unavoidable for full tunable operation.