Optical EngineeringAnalytical expressions, modeling, and simulations of intensity and frequency fluctuations in directly modulated semiconductor lasers
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Analytical expressions for the intensity and frequency/phase noise of single-mode semiconductor lasers based on quantum-mechanical rate equations are derived. Correlated photons, electrons, and phase Langevin noise sources and their auto and cross-correlation relations are presented, along with a novel self-consistent normalized laser model that includes the laser's correlated noise sources. A symbolically defined device (SDD) is constructed using the proposed normalized model and implemented in Agilent's advanced design system (ADS) CAD tool. Dynamic laser characteristics are predicted using the SDD implementation for 1300-nm InGaAsP/InP lasers. The results of time domain dynamic simulations of photons, carriers, optical output power, and phase—with and without the effects of noise—are presented. Simulation results are used to show the effects of random noise on both the phase and optical power output of semiconductor lasers. Simulation results are analyzed to demonstrate the resonance frequency shift dependence on the bias current levels, the relation between the frequency response and the bias current, and the dependence of the laser line width broadening on the frequency fluctuations. Comparison between the presented results and other published results (simulations and measurements) show good agreement while achieving simulation time enhancement. The suitability of the proposed models for the study and characterization of the performance of complete systems in both circuit and system simulations is examined.