Cascaded all-optical wavelength conversion for RZ-DPSK signal based on four-wave mixing in semiconductor optical amplifier

We have demonstrated ten-stage cascaded wavelength conversion together with 800-km transmission for 10-Gb/s return-to-zero differential phase-shift keying (RZ-DPSK) format using four-wave mixing (FWM) in semiconductor optical amplifiers. To the best of our knowledge, this is the first experiment reported on cascade wavelength conversion for RZ-DPSK format, which cannot be realized by methods based on cross-gain modulation and cross-phase modulation using a semiconductor optical amlifier. Compared with wavelength conversion using FWM for conventional ON-OFF keying format, the signal-to-pump ratio for RZ-DPSK format can be increased to higher level to achieve better performance.