The invention relates to medium-
infrared gain sulfide optical fibers and a preparation method thereof, and belongs to
laser gain optical fibers and a preparation method thereof. According to the present invention, the
optical fiber core material is a
rare earth ion doped Ga-Sb-As-S glass, the
optical fiber cladding material is a Ga-Sb-As-S glass, the
refractive index of the
optical fiber core glass is greater than the
refractive index of the cladding glad, the
chemical formula of the Ga-Sb-As-S glass is Ga(1-x-y-z)SbxAsySz, x is 0.26-0.32, y is 0.02-0.06, z is 0.55-0.65, the
rare earth ion is one selected from Dy<3+>, Er<3+> and Tm<3+>, and the
molar concentration of the doped
rare earth ions is 0.05-1%; the optical fibers are prepared through a rod tube method, wherein the
fiber core glass and the cladding glass are respectively prepared into the thin rod and the
bushing, the
fiber core glass thin rod is inserted into the cladding glass
bushing, and drawing is performed to obtain the optical fibers having the final size; and the
gain sulfide optical fibers have strong
luminescence at a
wavelength of 2.5-5 [mu]m, the
luminescence quantum efficiency is greater than 70%, and the gain
sulfide optical fibers can be adopted as the core gain medium of the low-cost and compact medium-
infrared optical
fiber laser.