Reduction of transient laser chirp in 1.5 ¿¿m dfb lasers by shaping the modulation pulse

It is shown that the dynamic linewidth of 1.5¿¿m ridge-waveguide distributed-feedback lasers can be reduced by appropriate shaping of the modulating current waveform. A theoretical model is used to predict the result of two different shaping techniques, both in terms of the optical pulse and spectral outputs, with the optimum conditions being derived for each shaping method. Experimental results confirm the theoretical predictions and demonstrate between 40% and 60% dynamic linewidth reduction with optimum shaped modulating pulses.