Effects of fluid immersion on splice index-matching gel and splice performance

Although optical splices are protected from fluid immersion during their service life, unanticipated exposures have occurred. For this reason, Bellcore generic requirements include a water immersion test to determine whether splices can tolerate a short-term water exposure and still perform adequately. Mechanical splice failures have been observed in the field and in laboratory experiments. Almost all mechanical splices use index-matching gel, and failures were believed to result from fluid migration along the fiber/gel interface, or fluid diffusion through the gel. We used a photographic analysis to provide direct evidence for these failure modes. We immersed simulated splices in a variety of contaminated fluids and observed that the most rapid mechanism, and the one we consider most likely to result in splice failure, was fluid migration. In addition, we measured loss and reflectance performance for actual splices immersed in contaminated fluids, correlating performance to the results of our photographic analysis. We show that immersion in contaminated water representative of the outdoor plant environment accelerates splice failures.