Abstract

40-Gbit/s based wavelength division multiplexing (WDM) system is becoming a key issue for long haul high-capacity optical communication, and the optical clock pulse source is the one of the devices most important in this technology. Mode-locked semiconductor lasers (MLLDs) are excellent sources because they can directly generate pulses with a high signal-to-noise ratio (SNR). From the viewpoint of practical optical communication use, the MLLD should be a monolithically integrated one because of its cost performance in fabricating a number of devices. Many efforts have been made toward developing a monolithic MLLD, in which a distributed Bragg reflector (DBR), a saturable absorber (SA) section, a gain section, and a passive waveguide section are integrated.^1,2 In contrast, external-cavity MLLDs (EC-MLLDs), offering wavelength tun-ability and mode-locking frequency flexibility, as well as the optical pulse width controllability, are ideal devices for evaluating system performance.

© 2002 Optical Society of America