This paper details measurements of 1.0 μm 3H 4 → 1G 4 absorption and site selective studies of the 1.3 μm 1G 4 → 3H 5 fluorescence of Pr 3+-doped gallium lanthanum sulphide (GLS) glasses containing oxide impurities. This oxide produces a second, preferentially-occupied site for the Pr 3+ within the GLS, which increases the inhomogeneity of the spectral lines, and decreases the lifetime and the quantum efficiency of the 1G 4 level.