Fluorescent glass, optical amplification waveguide and optical amplification module

The present invention relates to a fluorescent glass capable of being doped with a high concentration of rare earth ions and suitable for optical communication application, and an optical component incorporating it. The fluorescent glass comprises Al2O3 of 15 to 50 mol %; SiO2 of 0 to 80 mol %; an oxide of 5 to 85 mol % in total comprising at least one of B2O3, Ga2O3, Y2O3, Ta2O5, Sb2O3, Nd2O5, La2O3, and Yb2O3; and a rare earth ion. Concentration quenching is more suppressed in this fluorescent glass than in conventional fluorescent glasses, and it is thus feasible for the fluorescent glass to be doped with a high concentration of rare earth ions and to highly efficiently generate fluorescence of wavelengths in the signal wavelength bands generally used in optical communication.