Radiation Damage In Optical Fibers

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Abstract
Damage sustained by optical fibers from exposure to ionizing radiation has generally been determined by transmission measurements with the data reduced to induced absorption of signal as dB/km. Thermoluminescence (TL) has been used in conjunction with transmission measurements to determine the depth of the traps responsible for the absorption increase in aluminum jacketed waveguide. In Si02-Ge02-P205 fibers, two TL peaks have been found. One is transient at 403°K and the other is permanent at 653°K. These peaks have been found after 30K rads (Si) dose of gamma rays from a 60Co source. Following the paper by van Gorkum, the kinetics for the TL emission from the "permanent" peak has been determined as 2nd order. The "attempt to escape" frequency, S, has been calculated to be 7 x 109 sec-1. This would seem to imply that there is a non-radiative emptying of traps, and repopulation of emptied traps at the elevated temperatures. Spectral evidence indicates that most of the emitted light is in the 0.450-0.480 μ region. Transmission tests at 0.82 μ taken in situ during the irradiation show that the induced absorption is linear with dose. The induced absorption losses are lower than previously reported for low phosphorus content fibers. The transmission measurements indicate that a peak in radiation sensitivity occurs at around 1-2% (mol) P205. Fibers with 10-15 mol % P205 show markedly lower radiation damage, as evidenced by relatively low induced loss, and lower TL peak height. This research is partially supported by the U.S. Army Research Office under Contract DAAG-29-80-C-0139.© (1982) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

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