Abstract

Wavelength chirping in directly-modulated distributed-feedback (DFB) laser diodes is a serious problem in high-bit-rate long-haul optical transmission systems. Longitudinal spatial hole burning (LSHB) is a major cause of chirping at modulation frequencies from a few megahertz (after thermal effect vanishes) to a few gigahertz (before relaxation oscillation takes over). In order to manage the LSHB, the DFB laser has often been segmented into two or three parts and driven by different current to each part.¹ In this case, however, external circuitry for driving becomes complicated and therefore is not compatible with high-speed modulation. In this paper, we propose a different approach to manage the LSHB and to control the wavelength chirping in DFB lasers, namely distributed electrode (DE) structure. With this structure incorporated, the chirping can be controlled without using more than one current source.

© 1994 Optical Society of America