Abstract

Long-wavelength ultrafast laser with high-repetitive frequency and ultrashort pulsewidth has played an important role in ultrahigh-bit rate optical communication, high-speed optical time division multiplexed transmission, optical-controlled phase-array antennas, and electro-optical sampling systems. The actively mode-locked erbium-doped fiber laser (AML-EDFL) which provides stable, nearly transform-limited, and pi-cosecond optical pulses with low timing jitter has been developed to meet these demands. However, the mode-locked condition of conventional AML-EDFL system usually evolutes as function of time owing to the temperature- or pressure-dependent change in the length of the fiber ring cavity. This essentially degrades or even destroys the mode-locking mechanism of the EDF laser. To improve the stability of mode-locked EDF laser, versatile skills that real-time compensate the variation in length of the EDFL ring cavity were introduced.^6–14 Particularly, the regeneratively mode-locking regimes that employ phase-locked loops to feedback control either a PZT ring for compensating the cavity length or a voltage-controlled oscillator for tuning the mode-locked frequency have recently emerged to be the most promising candidates. In this work, we demonstrate for the first time the implementation of pulse-delay tunable, regeneratively mode-locked EDFL by replacing the feedback controlling circuit of such laser with a voltage-controlled optoelectronic delay-locked loop phase shifter (DLL-PS). Perfect mode-locking with very low phase noise density and accurate delay-time tuning can be achieved.

© 2002 Optical Society of America