Nonlinear Distortion Analysis of Directly Modulated ... - 연세대학교

nonlinear phenomena simulation should be executed and the comparisonbetween the simulation and experiment is needed.C. Injection Wavelength and Power Dependence of NonlinearDistortion SuppressionFrom the previous section, III-A, it is investigated numerically andanalytically that the nonlinear distortion can be suppressed by means ofinjection locking. However, the distortion suppression does not equally appearaccording to the optical injection frequency and power. In this section, opticalinjection wavelength and power dependence for the nonlinear distortionsuppression will be observed.First, by using the rate equation simulation model, eqn. 3-1, the relaxationoscillation frequency and damping factor change are investigated according tothe optical injection wavelength. As can be seen in section III-A, the laserfrequency response is calculated by the small signal analysis of the laser rateequations. The injection power ratio is set at –8 dB, and by referring the stablelocking range of fig. 3-1, the stable frequency detuning at this injection ratio isdetermined from –5.5 GHz to –37 GHz. Then, within this range, the frequencyresponse changes are observed. Fig. 3-9(a) and (b) show the results. Fig 3-9(a)is the frequency responses when the detuning frequency is near upperboundary of stable locking region and fig. 3-9(b) is the frequency responseswhen the detuning frequency is near lower boundary of stable locking region.When the detuning frequency is near upper boundary, the relaxation oscillationfrequency increases very much. This indicates that the nonlinear distortion34