We have characterized the FM response of frequency- tunable two-electrode DFB lasers operating at 1.35 µm. Under certain bias conditions, an FM response of ~ 1 GHz/mA is flat over a range of modulating frequencies from 10 kHz to several hundred megahertz. This region is followed by a shallow dip and a high-frequency relaxation resonance peak, allowing an overall 3 dB FM bandwidth of ~5 GHz. We believe this to be the widest FM bandwidth reported to date for such lasers; however, variations of the phase of the FM response could limit the useful bandwidth in an FSK system. The experimental response is a function of static tuning conditions, with significant differences between regions of red and blue frequency shift with increasing current. The observed behavior is well represented by theoretical curves derived from a small-signal analysis.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Atomic and Molecular Physics, and Optics
- Electrical and Electronic Engineering