Investigation on chirping characteristics of a 1.55-µm directly modulated distributed feedback laser
We investigate the laser chirp characteristics of a 1.55-µm directly modulated DFB laser by simulation. The chirp is characterized by two important parameters: gain compression and α-factor. Measurements of the chirp parameters using transfer function and the chirp-to-modulated power ratio are presented here. We have identified that the characteristic frequency (fc) represents the boundary between the adiabatic and transient chirp, i.e., the adiabatic chirp dominates for f < fc and the transient chirp dominates for f > fc. Frequency excursion for both chirp terms is well characterized by the phase rate equation model that describes the chirping behavior, switching transients and the power overshoots. Finally, proper adiabatic chirp is generated by adjusting: the laser device parameters and the operating conditions to achieve dispersion-tolerant system.
KeywordsDistributed feedback laser (DFB) Chirping (adiabatic and transient) Chirp-to-modulated power ratio (CPR) Gain compression α-Factor
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