Parallel Eight Channels All-Optical NRZ-to-RZ Format Conversions at 40 Gb/s Using a Single SOA

We experimentally demonstrate simultaneous nonreturn-to-zero to return-to-zero (RZ) conversion for eight channels at 40 Gb/s with a single semiconductor optical amplifier (SOA) and a subsequent delay interferometer (DI), which is designed to have a specific free spectral range to accommodate the multiple dense wavelength-division-multiplexing channel spacing. The proposed conversions are based on the cross-phase modulation effect in a single SOA, which is operated in deep saturation to mitigate the undesired cross-gain modulation. Good quality RZ signals can be achieved by optimizing the detuning between the peaks in the DI spectrum and each corresponding carrier. The bit-error ratio results show that the conversions can be achieved with negative power penalty.