<title>Mechanical behavior of coated fused silica optical fibers aged at elevated temperature in air and filling compound</title>

Abstract

In this report, we present an experimental analysis of the mechanical behavior of fused silica standard telecommunication fibers aged in hot air and hot filling compound. Our measurements at standard room temperature conditions after the aging treatments indicated tensile strength increases of up to 5 % at 85°C and 1 5 % in filling compound after one-to six-month aging. The dynamic fatigue for the fibers aged in the filling compound also improved (n-values from 17 -20 to 25 -30) in parallel with the fiber strength while the fiber static fatigue tests gave large n-value increases from 30 to 140. In order to examine the effects of the aging treatments on the fiber coatings, we used dynamic mechanical analysis to measure the coating mechanical properties, storage modulus E' and loss tangent tan ö. In general, we have found that aging in hot air and in the filling compound results in a significant decrease in E' and increase in tan ö, thereby suggesting an aging-related increase in the capacity ofthe coating to absorb substantial amounts of mechanical energy. A qualitative theoretical analysis ofthe coating contribution to the fiber crack growth and mechanical behavior in conjunction with our experimental results suggests that the coatings' ability to absorb more mechanical energy during aging contributes to increased fiber strength and improved fatigue behavior. Thus, our results to date provide the first experimental evidence for that a fiber coating can stabilize cracks on fused silica surfaces and contribute in a significant way to fiber mechanical behavior.