All-Optical Wavelength Conversion Based On Semiconductor Optical Amplifiers

All-optical wavelength conversion (AOWC) has emerged as apromising technique for wavelength division multiplexing (WDM) inoptical fiber communication systems. AOWC provides the functions ofwavelength routing and wavelength reuse, which can save networkresources like optical fiber and wavelengths, efficiently solve the datablocking problems in the optical fiber networks, simplify the managementof networks and reduce the complexity of the network interconnection.Compared to traditional optical-electrical-optical (O-E-O) wavelengthconversion, AOWC operates purely in the optical domain, and thus itoffers the benefits of higher data rate operation, and lowers the systemcomplexity and energy consumption. In recent years, AOWC incorporatingsemiconductor optical amplifiers (SOAs) has been one of the hot researchtopics since it could be particularly attractive due to the facts of its smallsize, lower power consumption, ease of integration, and highnonlinearities.In the thesis, both of the theoretical and experimental researches ofthe AOWC based on SOAs will be given. The research results will bepresented as follows:1) A time-domain model of SOA is studied, and we deeply analyse theAOWC based on SOA-based Mach-Zehnder interferometers (SOA-MZIs)using this model. We propose an all-optical AND/XOR gates fornon-return-to-zero (NRZ) data using SOA-MZI. For AND/XOR gates, thecomplementary data is applied as the additional input to SOA-MZIs, inorder to mitigate the pattern effect of SOAs, while increase the operationdata rate for NRZ signal up to40Gb/s. Numerical simulations have shownthat, the proposed novel scheme can effectively mitigate the patterningeffect in SOAs via shortening the rising/falling transition times of theoptical signals. The high quality of the output signal (Q>6) are numericallyevaluated for both AND/XOR gates.2) A frequency-domain model is established for SOAs, which is used to analyse all-optical turbo-switch incorporating two cascading SOAs infrequency-domain. This model exploits the small-signal analysis theoryand Fourier transform to transform the rate equations and travelling-waveequations into frequency equations for optical power and phase shift inSOA. And we get the the the small-signal frequency response (SSFR)which represents the transfer function of SOA. On the basis of the model,we simulate the SSFR curves and analyze the influence of SOA gain andthe phase-shift of delayed interferemeter (DI) on the SSFR curves. In termsof the three different structures of turbo-switches, we deduce the SSFRs.The results are in good agreement with the reported experiment results.After optimizing the device parameter and turbo-switch structure, wesuggest the optimum structure which outputs the best performance. Inaddition, we analyse the influence of the number of the cascaded SOAs onswitching bandwidth.3) The AOWC experiments are performed to study the AOWC basedon a SOA-MZI, which including the research of cross gain modulation(XGM) and the cross phase modulation (XPM) inside SOA-MZI. Inaddition, the differential XPM scheme is evaluated by the experiment ofpush-pull approach based on a SOA-MZI. In the experiments, the gainrecovery time of a single SOA, and the performance of AOWC are givenin terms of high-speed data pattern and the eye diagrams. It isdemonstrated that, the AOWC base on a SOA-MZI can be operated at thedata rate up to40-80Gb/s.