Steady state radiation responses of graded-index germanosilicate multimode optical fibers

• Dose rate strongly impacts RIA in OM1–OM5 at room temperature. • OM1 shows higher RIA; OM2–OM5 exhibit similar, lower radiation responses. • RIA spectral decomposition identifies dominant bands at telecom wavelengths. • 850 nm: GeX/GeY; 1310 nm: GeY + unknown; 1550 nm: Ge-STH + unknown. • GeX and GeY are the most dose-rate-sensitive defects (∼2 × at 6 Gy/s). This study investigates the radiation response of commercially available germanosilicate graded-index multimode optical fibers (conforming to the OM1 through OM5 standards) at room temperature. The main objective is to monitor the radiation induced attenuation (RIA) and to identify the point defects at its origin, their generation and recombination mechanisms. The samples were irradiated under continuous X-ray exposure at two dose rates, 0.6 Gy/s and 6 Gy(SiO 2 )/s, up to total ionization doses of 52 kGy and 109 kGy, respectively. The RIA kinetics at 850 nm, 1310 nm, and 1550 nm exhibited rapid initial growth followed by either a slower increase or a plateau, reflecting the interplay of defect generation, recombination, and conversion. OM2 through OM5 optical fibers showed a similar response with lower RIA compared to OM1 optical fiber, which justifies restricting the deeper analysis to OM1 and OM5 samples. Spectral decomposition of the RIA spectra shows that the dominant contributors are GeX and GeY at 850 nm; GeY and an unidentified band at 1310 nm; and Ge-STH together with the same unidentified band at 1550 nm. Moreover, GeX and GeY defects are the most dose rate sensitive defects, with their amplitudes nearly doubling at 6 Gy/s. The results obtained can be exploited to determine the potential of these Telecom-grade fibers for harsh environments with limited radiation constraints.