Single-to-dual channel NRZ-to-RZ format conversion by four-wave mixing in single semiconductor optical amplifier

All-optical single-to-dual channel format conversion from non-return- to-zero (NRZ) to return-to-zero (RZ) using four-wave mixing (FWM) in a single semiconductor optical amplifier (SOA) is demonstrated. The original NRZ format is converted to RZ format by injecting a synchronised clock signal into the SOA. The FWM effect generates two sideband components, which contain the same data stream as the original NRZ signal with RZ format. The format conversion is successfully implemented both at 20 and at 40 Gbit/s, and all converted RZ signals have a Q-factor larger than 6.