The invention relates to an aluminium phosphate glass product containing rare-earth ions, intended to be used as optical sensors, and to a process for preparing the same. According to the invention, the glass contains 60…80% PO, 2…10% LiO, 5…15% AlOand 1…10% either SmO, or EuO, the percentage being expressed by weight, at a density of 2.17…2.90 g/cm, with a linear thermal dilation coefficient αof 90…100 x 10/K, with a refraction index n, measured in the wavelength of 589.29 mm, in the range of 1.54…1.59, n- 546 mm – of 1.54…1.58, n- 656 mm – of 1.54…1.59, n- 486 mm – of 1.52…1.57, n- nof 0.04…0.03 and an Abbe number υof 61…68. The process, as claimed by the invention, consists in processing the mixtures of starting materials, such as acids, oxides and salts which introduce the phosphor oxide as a lattice shaper, and, as lattice modifiers, lithium, aluminium, barium and lanthanum oxides, along with samarium, europium and terbium oxides as doping agents, while adding a supplementary amount of reagents, lithium oxide and phosphor oxide precursors, preferably 15% and 25%, respectively, the chemical reactions between the solid reagents and the phosphoric acid solution, precursor of phosphor oxide, being conducted with the starting materials so dosed that metaphosphate-type chemical compounds are formed in the final product, the oxygen atoms which do not form bridges being linked to the vitreous lattice modifying ions consisting of lithium, aluminium, barium and rare earths.