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All-optical wavelength conversion of differential phase-shift keyed (DPSK) signals based on semiconductor optical amplifier Mach-Zehnder interferometer (SOA-MZI) is simulated and analyzed. The results show that, to obtain both good quality of the converted signal and high conversion efficiency, phase difference between the upper and lower arms of MZI should be near ??, which suggests strong cross-phase-modulation (XPM) and cross-gain-modulation (XGM) for optimized operation of this wavelength converter, while weak XPM and XGM will lead to sacrifice of conversion efficiency. The results also show larger wavelength up-conversion range, and suggest non-return-to-zero (NRZ) format for 10 Gb/s operation while return-to-zero (RZ) format for 40 Gb/s operation. Besides, short carrier lifetime is preferred for high-speed applications and appropriate linewidth enhancement factor can be utilized to mitigate amplitude fluctuation of the converted signal if the carrier lifetime is not short enough.
Date of Publication: Dec.15, 2009