Low-chirp, 2.5 Gbit/s directly modulated fiber grating laser for WDM networks

Densely spaced wavelength-routed optical transport and access networks will require low-cost, stable, low-chirp narrow linewidth lasers operating on precisely specified wavelengths. Directly modulated semiconductor lasers with short external fiber gratings (FGL) can optimally satisfy these requirements. Although 10-Gbit/s externally modulated soliton transmission using a mode-locked FGL over 27,000 km was reported, wavelength chirp and transmission performance of directly modulated FGLs have not been investigated at bit rates higher than 155 Mbit/s for NRZ transmission. In this paper, we report on the very low chirp performance of a directly modulated FGL at 2.5 Gbit/s. Transmission over distances of >300 km in standard fiber and >10,000 km in dispersion-shifted fiber was demonstrated