Chirp characteristics of 40-Gb/s directly modulated distributed-feedback laser diodes

For short-reach applications, 40-Gb/s directly modulated semiconductor lasers enable high-capacity transmission with a simple and low-cost configuration. We investigated the chirp characteristics of 40-Gb/s directly modulated 1.55-mu m distributed-feedback laser diodes (DFB-LDs) and measured the linewidth enhancement factor and dynamic chirp. We then evaluated the fiber-dispersion dependence of the bit error rates (BERs) and dispersion tolerance for 40-Gb/s transmissions.