•Changes in Bi-doped fiber properties after irradiation by electron beam are studied.•Waveguide properties of Bi-doped fiber in pristine and irradiated states are modeled.•Ways to use Bi-doped fiber for dosimetry in harsh environments are proposed.•Stokes shift of cutoff wavelength vs. exposure dose is discovered for Bi-doped fiber. We report the changes in absorption and emission properties of Bismuth/Yttria codoped phosphosilicate fiber which arise after bombardment by a beam of high-energy (β) electrons. Despite dramatic rise of induced absorption in the fiber as the result of β-irradiation, reaching ~2000 dB/m in the visible, we reveal its remarkable resistance, at doses of exposure up to ~1014 cm−2, in terms of the emissive potential in the visible / near-IR and photo-bleaching contrast at pump wavelengths falling into the absorption bands of Bismuth active centers. Also, we uncover a novel effect of large spectral shift to the Stokes side (up to ~75 nm), experienced by the cutoff wavelength of the fiber in function of β-irradiation dose due to notable refractive index rise in its core region.