All-optical RZ-to-NRZ format converters based on nonlinearity and walk-off in optical fibers

Two methods of RZ-to-NRZ modulation format conversion are experimentally studied and compared. The first method is based on the cross-phase modulation with walk-off in a nonlinear optical loop mirror. The second method is based on nonlinear polarization rotation with walk-off in a segment of dispersion-shifted optical fiber. Both methods are shown to give very good results and their performance is almost independent on the exact shape of input RZ pulses. The converter based on nonlinear polarization rotation is more stable and simpler for adjustment, and it has no power dependent bias. The performance of converters is evaluated at 10 Gb/s but the converters can be easily operated at higher transmission rates.