| Wavelength conversion is a key issue for wavelength division multiplexed (WDM) networks. Wavelength converters based on semiconductor optical amplifiers (SOA) are promising candidates for implementing wavelength conversion. Cross-gain modulation (XGM), cross-phase modulation (XPM) and four-wave mixing (FWM) are three methods to implement wavelength conversion using SOAs. Cross-phase modulation in SOAs is currently the most practical approach. This thesis presents a thorough investigation of wavelength converters based on semiconductor optical amplifiers with an emphasis on using XPM in SOAs in the arms of a Mach-Zehnder interferometer (MZI). The major contributions of this thesis include a comprehensive experimental characterization of an SOA-MZI wavelength converter, a novel experimentally based model of SOA-MZI wavelength converters for system simulations, and a detailed time-domain theoretical model for both SOAs and SOA-based wavelength converters. The research consists of both experimental and theoretical investigations, which are almost equally divided. In the experimental part, the modulated amplified spontaneous emission noise, small-signal α-parameter, large-signal time-resolved chirp, and optical frequency responses have been, for the first time, characterized in detail. Based on these characterizations, a novel experimentally based model for SOA-MZI wavelength converters has been developed. This experimental model is efficient and particularly suitable for system simulations where computational efficiency is a key issue. In the theoretical part, a novel model for SOAs used in XPM wave-length converters has been derived. Based on this model, a time-domain computer simulator of SOAs for both the counter- and co-propagation schemes has been developed. Using this simulator, static and dynamic operation for XGM and SOA-MZI wavelength converters has been simulated. The simulation results have been compared with the experimental data. Good agreement between experiment and theory has been obtained. |
