All-optical parallel NRZ-DPSK to RZ-DPSK format conversion at 40 Gb/s based on XPM effect in a single SOA

We propose and demonstrate multi-channel parallel format conversions from the non return-to-zero differential phase shift keying (NRZ-DPSK) to the return-to-zero DPSK (RZ-DPSK) using a single semiconductor optical amplifier (SOA). The simultaneous conversions are based on the cross phase modulation (XPM) effect, which is induced by a synchronous optical clock signal with high input power. The XPM adds an identical phase shift onto every input bit, resulting in the phase difference unchanged. The input spectra are broadened and a subsequent filter is utilized to extract the specific part to form a RZ pulse. 6-channel NRZ-DPSK signals at 40 Gb/s can be converted to the corresponding RZ-DPSK signals with ~-0.8 to -1 dB power penalty for all the channels.