Ultrahigh-speed all-optical wavelength conversion and format conversion for polarisation-shift-keying signal based on four-wave mixing in light-holding semiconductor optical amplifier

An ultrahigh-speed all-optical module, which can realise both the wavelength conversion of polarisation-shift-keying (PolSK) signal and the format conversion from non-return-to-zero (NRZ)-PolSK to return-to-zero (RZ)-PolSK, is proposed based on four-wave mixing (FWM) in light-holding semiconductor optical amplifier (SOA). This scheme is simple and free of pattern effect. The conversion efficiencies are improved by utilising a holding light. Using the polarisation-dependent broadband model, wavelength conversion and format conversion for PolSK signal are theoretically realised at 40 Gbit/s. Moreover, the effects of holding light, polarisation dependence of SOA and polarisation angle between input pump light and PolSK signal on the output performance of wavelength conversion and format conversion for PolSK signal are theoretically investigated in detail.