A novel practical 1.66-micron pulse light source with adjustable pulse duration is proposed. A 2.5-km Raman fiber is placed into a ring type Q-switched erbium-doped fiber laser (Q-EDFL), serving as both delay line fiber and Raman gain medium so that in addition to the wavelength shifted to 1.6 microns, the pulse duration and the buildup time can be relatively extended. By properly controlling the fall edge of the acousto-optic switch (AOS), the pulse duration of 30-345 ns for ~770-Hz repetition
