| In this thesis, we are interested in the RF/Fiber optical interface for microcellular wireless transceivers as an essential part of the whole communications link. The key element in this research is the telecommunication semiconductor laser diode. However, the inhibiting factor for analog applications is the natural nonlinearity exhibited by semiconductor lasers, which degrades the overall system performance and capabilities.; Performance evaluation and analysis of the communications link before implementation is extremely desirable; however, the device fabrication is excessively, costly and too time consuming for this purpose. Rather, robust, fast and accurate semiconductor laser simulation capability will give a way for more complex and diverse laser design, characterization and performance evaluation. This requires comprehensive laser modeling.; In this thesis, semiconductor laser gain modification, and the effects of device heating, leakage and noise were studied and added simultaneously to conventional laser models. Suitable model implementations for device and systems simulations in both frequency and time domains are also presented. Laser's nonlinearity was analyzed in detail as a prelude to choosing the pre-distorter most appropriate linearization technique. Model verification and validation were then performed by comparing the simulation results with the measurement results.; Analytical expressions for the pre-distorter model in time and frequency domains are also derived. The performance of the pre-distorter was evaluated by a software implementation of the frequency domain models of both the pre-distorter and the proposed laser model in cascade.; Simulation results show that the proposed pre-distorter improves the laser diode's nonlinear performance as measured by harmonic and intermodulation distortion. Comparison between the conventional gain-based pre-distorter and the proposed modified gain-based pre-distorter shows that the performance of the laser and pre-distortion circuit combination, in which the pre-distortion circuit is designed based upon the modified gain formulation, provides remarkable improvement over implementation based on previous laser models. Typically, an improvement of 10 dB in intermodulation distortion can be realized based on the work presented in this thesis, using the pre-distortion circuit designed based upon the modified gain formulation. |
