A simple configuration to generate tunable single-mode pulses by self-injection seeding of a gain-switched semiconductor laser is demonstrated. The key part of the setup consists of a highly dispersive fiber and a fiber mirror. The configuration shows improved stability and promise to operate at both 1.3 and 1.55 /spl mu/m. The lasers at the respective wavelengths have been successively tuned over 13.43 and 12.81 nm with a side-mode suppression ratio >15 dB. Continuous access of wavelength with an enhanced tuning range is also achieved by combining both electrical and thermal control on the laser.