<title>Experimental results of the influence of ionic strength in liquid environment on fiber life</title>

Stress free corrosion such as chemical dissolution of silica optical fibers is normally assumed to be a pure pH dependent reaction. In our investigation we have found that it is not only the pH values that influence the lifetime of the fiber in water, but also the ionic strength of the water in contact with the fiber. We have seen that the lifetime of the normal dual coated fibers is severely reduced in seawater compared to the lifetime in deionized water. Carbon coated fibers show better results in these harsh conditions; but the experiments also demonstrate that the carbon coated fibers begin to fail before they have had a sufficient lifetime. A chemical explanation of the results, based on dissolution of glass in water and influence from the ions in question, is given. In this paper, experimental results from long term static fatigue tests on fibers in different liquid environments is shown. In the laboratory we have samples still living after almost four years in different environments. We have buffered water at pH values from 3 to 11, artificial seawater and deionized water. The fibers in the tests are both commercially available dual coated and carbon coated fibers and carbon coated test fibers.