MATLAB Simulation of a Distributed Feedback (DFB) Laser with Chirp Effects

摘要

A model of a distributed feedback (DFB) laser was implemented in MATLAB andSIMULINK. Using the laser rate equation, the model was simulated to obtain general characteristics of the chirp of the lasers frequency. The simulations were controlled by using different drive current waveforms, based on various bit patterns, data rates, and drive current values (threshold current and the extinction ratio). Once created, the laser drive current was passed to the SIMULINK DFB laser model. The output of a simulation provided frequency chirp, laser power emitted, photon density, and carrier density data. Two sets of simulations were conducted. The first set of simulations focused on the data rates and bit patterns. From these simulations it was determined that the transition from a ZERO bit to a ONE bit caused the greatest frequency excursions. Also, as the data rate increases the maximum frequency excursion increases. Finally, the first set of simulations revealed that the predictability of the chirp decreases as the data rate increases and as the complexity of the bit pattern increases. The second set of simulations examnined the effect of the extinction ratio on frequency chirp. By plotting the maximum frequency excursion against its respective extinction ratio, it was determined that in some cases the maximum frequency excursions in a system could be minimized.