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 (ga mma) radiation exposure on the bit error rate (BER) of an optical fibe r data communication link While it is known that exposure to high radi ation dose rates will darken optical fiber permanently, comparatively little work has been done to evaluate moderate dose rates. The resulti ng increase in fiber attenuation over time represents an additional pe nalty in the link optical power budget, which can degrade the BER if i t is not accounted for in the link design. Modeling the link to predic t this penalty is difficult, and it requires detailed information abou t the fiber composition that may not be available to the link designer . We describe a laboratory method for evaluating the effects of modera te dose rates on both single-mode and multimode fiber. Once a sample o f fiber has been measured, the data can be fit to a simple model for p redicting (at least to first order) BER as a function of radiation dos e for fibers of similar composition.