A method for manufacturing a polychromatic optical measuring device capable of operating under ionising radiation, the method comprising the following steps: - selecting at least one first crown optical glass from a group of crown optical glasses each having a cerium-free composition, said selected crown optical glass being called crown glass, - selecting at least one first flint optical glass from a group of flint optical glasses each having a cerium-free composition, said selected flint optical glass being called flint glass, - providing a detection system capable of operating under ionising radiation, - forming at least one first optical component made of crown glass and at least one second optical component made of flint glass, - combining the first optical component and the second optical component to form an optical system of the optical measuring device, - combining the detection system and the optical system to form the optical measuring device, wherein the step of selecting the flint glass comprises the following substeps: - measuring at least one first magnitude representative of an optical transmission in at least one first range of wavelengths of interest for a sample of each glass from the group of flint optical glasses, said first magnitude representative of an optical transmission being called pre-irradiation transmission magnitude, - irradiating each sample with ionising radiation with a dose greater than or equal to 100 kGy, - measuring at least one second magnitude representative of an optical transmission in the first range of wavelengths of interest for each sample, said second magnitude representative of an optical transmission being called the post-irradiation transmission magnitude, - selecting the flint glass from the glasses of the group of flint optical glasses for which a mean value of the radiation-induced attenuation, RIA, in the first length range is less than 0.25 dB/mm, said mean value of the radiation-induced attenuation being determined from the first magnitude representative of a corresponding optical transmission and the second magnitude representative of a corresponding optical transmission. - selecting at least one first crown optical glass from a group of crown optical glasses each having a cerium-free composition, said selected crown optical glass being called crown glass, - selecting at least one first flint optical glass from a group of flint optical glasses each having a cerium-free composition, said selected flint optical glass being called flint glass, - providing a detection system capable of operating under ionising radiation, - forming at least one first optical component made of crown glass and at least one second optical component made of flint glass, - combining the first optical component and the second optical component to form an optical system of the optical measuring device, - combining the detection system and the optical system to form the optical measuring device, - measuring at least one first magnitude representative of an optical transmission in at least one first range of wavelengths of interest for a sample of each glass from the group of flint optical glasses, said first magnitude representative of an optical transmission being called pre-irradiation transmission magnitude, - irradiating each sample with ionising radiation with a dose greater than or equal to 100 kGy, - measuring at least one second magnitude representative of an optical transmission in the first range of wavelengths of interest for each sample, said second magnitude representative of an optical transmission being called the post-irradiation transmission magnitude, - selecting the flint glass from the glasses of the group of flint optical glasses for which a mean value of the radiation-induced attenuation, RIA, in the first length range is less than 0.25 dB/mm, said mean value of the radiation-induced attenuation being determined from the first magnitude representative of a corresponding optical transmission and the second magnitude representative of a corresponding optical transmission.