 This paper investigates the effects of tungsten doping on the thermal and optical properties of bismuth germinate glasses. It was found that the glass structure changed upon incorporating tungsten, resulting in a decrease in the glass transition temperature. Additionally, the presence of tungsten resulted in a red shift in the emission spectrum of erbium ions, which could potentially lead to higher gain signals in the L band. This article was authored by Hussein Kankamichi, Theo Guerrino, V.A.G. Rivera, and others.