Tolerance of Ge-doped multi-mode fibers in total ionizing dose Article Swipe

Purpose: The fiber optical links in 850 nm band with Ge-doped multi-mode (MM) fibers are well developed for data transmission at 10 Gbps and higher. The applications in nuclear environments require radiation resistance. The characteristics of Ge-doped MM fibers are investigated for radiation-induced attenuation (RIA) in total ionizing dose (TID). Methods: Commercial samples of Ge-doped MM fibers were irradiated in Go-60 gamma rays at dose rates of 5 to 1.4k Gy(SiO $$_2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mn>2</mml:mn> <mml:mrow/> </mml:mmultiscripts> </mml:math> )/hr. The fiber samples were packaged in water tanks maintained at constant temperatures in the range of $$\text{-15 }$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mtext>-15</mml:mtext> <mml:mspace/> </mml:mrow> </mml:math> to 45 $$^\circ $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mo>∘</mml:mo> </mml:mmultiscripts> </mml:math> C. The optical powers transmitted through the fibers were recorded in irradiation, and in annealing when the source was shielded. The measurements of RIA in time are analyzed for dose rate and temperature dependencies. Results: Ge-doped fiber samples of OM2 to OM4 grades were investigated for attenuation of optical power in radiation ionizing dose. Depending on the fabrication technology, two of the fiber types show radiation resistance with the RIAs of 0.2 dB/m and 0.05 dB/m, respectively, for the TID of 300 kGy(SiO $$_2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mn>2</mml:mn> <mml:mrow/> </mml:mmultiscripts> </mml:math> ). At low dose rate of 5 Gy/hr, the RIA increases steadily and the annealing of ionizing defects is effective in two hours. At very high dose rate of 1.4 kGy/hr, the abundant defects are generated causing pileup to twice higher RIA during irradiation. The cold temperature (below $$\sim $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mo>∼</mml:mo> </mml:math> 0 $$^\circ $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mo>∘</mml:mo> </mml:mmultiscripts> </mml:math> C) can slow down the recovery, with a factor three higher RIA observed at 30 Gy/hr. However, once the source is shielded, the recovery is effective in a few hours and the RIA depends only on the TID received. Conclusion: The telecom products of 850 nm Ge-doped MM fibers provide high speed communication in distances of a few hundred meters. The industrial fabrication methods can deliver fibers that endure radiation ionizing dose for applications in nuclear instrumentation.