Radiation-induced attenuation in polarization maintaining fibers: low dose rate response, stress, and materials effects.

The loss induced in polarization-maintaining (PM) fibers by low dose rate [<0.01 Gy/h, where 1 Gy = 100 rads(Si)] radiation exposure has been found to vary from <0.4 to approximately 6 dB/km-10 Gy, depending on the wavelength of measurement and the fiber. Correlations have been established between low dose rate response and the "permanent" induced loss determined by fitting the recovery of the induced loss following high dose rate exposure to nth-order kinetics. Using this technique, both 0.85- and 1.3-microm PM fibers have been found which show virtually no permanent incremental loss and would therefore appear to be resistant to low dose rate radiation environments. The asymmetric stress inherent in PM fibers has been shown to reduce the permanent induced loss, while the recovery of the radiation-induced attenuation was found to be enhanced in fibers with Ge-F-doped silica clads.