Recent lightwave system work has underscored the importance of wavelength chirping in high-speed (>1-Gbit/sec) long-haul applications at the 1.5-μm fiber loss minimum. Theoretical discussions of chirp, or equivalently FM, usually focus on its relationship to drive current. A more direct and relevant measure is the relationship of chirp to the time-dependent optical power waveform since this is what must be specified in most lightwave applications.