Abstract

Frequency chirping in semiconductor lasers under high-speed direct modulation due to carrier density and refractive-index change can lead to significant dynamic line broadening. It has been pointed out^1,2 that such dynamic line broadening in single-longitudinal-mode (SLM) semiconductor lasers may become the limiting factor in high-bit-rate long-distance single-mode fiber transmission even with dynamic SLM lasers. The obvious solution is to avoid frequency chirping completely by using an external modulator with the laser in cw operation. Alternatively one may want to design a system which uses controlled frequency chirping for pulse compression and improved pulse transmission in dispersion-shifted fibers.³

© 1985 Optical Society of America