Chirp-managed directly modulated laser (CML)

We demonstrate a new highly dispersion tolerant modulation format using a chirp-managed directly modulated laser (CML) for uncompensated 10-Gb/s transmission over >200 km at 1.55 μm. The CML consists of a distributed feedback (DFB) laser followed by an optical filter. We show that the combination of adiabatic chirp from the DFB and filter edge response produces high extinction ratio pulses with nearly uniform phase, abrupt phase shifts at bit transitions, and a correlation between the 1 bits; 1 bits separated by odd number of 0 bits are /spl pi/ out of phase. This results in carrier suppression, 1/2 the bandwidth of standard nonreturn-to-zero, and high tolerance to positive and negative dispersion.