Application of Semiconductor Optical Amplifiers in High-Speed All-Optical NRZ to RZ Format Conversion

We present two types of 42.6 Gbit/s all-optical non-return-zero (NRZ) to return-zero (RZ) format converters using semiconductor optical amplifiers (SOAs). The converters are based on cross-phase modulation (XPM) and cross-polarisation modulation (XPolM) in SOAs. Both format converters produce a correctly-coded, polarity- preserved RZ signal at the output and have the flexibility of variable NRZ input data wavelength. Error-free operation was achieved for both converters with switching energy below 50 f J/pulse. The format converter based on XPM has the additional advantage of variable duty-cycle of the RZ signal and exhibited negative power penalties.