All-optical data format conversion between RZ and NRZ based on a Mach-Zehnder interferometric wavelength converter

We demonstrate all-optical conversion between two different data formats: return-to-zero (RZ) and nonreturn-to-zero (NRZ) using a Mach-Zehnder interferometric wavelength converter. For RZ-to-NRZ conversion, a duplication scheme is demonstrated to reduce the ripples caused by the carrier recovery of the semiconductor optical amplifier. The relationship between the ripple-to-signal ratio and the number of pulse duplications is numerically analyzed. For the NRZ-to-RZ conversion, the wavelength converter also shows high performance. The converted RZ signal has a negative power penalty to the NRZ signal due to the change of the data format.