Measuring radiation induced changes in the error rate of fiber optic data links

The purpose of this work is to investigate the effects of ionizing (gamma) radiation exposure on the bit error rate (BER) of an optical fiber data communication link. While it is known that exposure to high radiation dose rates will darken optical fiber permanently, comparatively little work has been done to evaluate moderate dose rates. The resulting increase in fiber attenuation over time represents an additional penalty in the link optical power budget, which can degrade the BER if it is not accounted for in the link design. Modeling the link to predict this penalty is difficult, and it requires detailed information about the fiber composition that may not be available to the link designer. We describe a laboratory method for evaluating the effects of moderate dose rates on both single-mode and multimode fiber. Once a sample of fiber has been measured, the data can be fit to a simple model for predicting (at least to first order) BER as a function of radiation dose for fibers of similar composition.