Reliability Evaluation of Fiber Coating Anomalies

Dual-coated optical fibers provide easier stripping and less sensitivity to micro-bending. Despite a record of success in the field, dual-coated fibers can still pose a challenge within the manufacturing environment since they are susceptible to developing physical anomalies during processing and fiber-handling. Although these anomalies are believed to be benign, there are very few published reports on reliability assessments. We have investigated the effect that the presence of two types of anomalies has on the long-term reliability of fiber under a variety of conditions. The results are consistent with the favorable field experience to date, but also highlight the need for meticulous fiber-handling and diligent inspection techniques. 1. BACKGROUND The earliest undersea optical fiber systems used fiber with a robust single coating for glass fiber protection. Shortcomings in the use of these coatings in the terrestrial marketplace led fiber manufacturers to develop a dual-coated protection layer. The dual coating design is optimized for fiber stripping and micro-bending. The inner primary coating is soft and rubbery with a low glass transition temperature (Tg). The outer coating is much harder and its main function is to protect fibers from external environmental and mechanical aggression. Tyco Telecommunications has used dual-coated (UV Acrylate) fibers since the late 1990s. Compared to single-coated fibers, dual-coated fibers are easier to strip and less sensitive to micro-bending. Despite the successful field record of dual-coated fibers in terrestrial applications, the presence of coating anomalies raises concern for the use of dual-coated fibers in submarine applications. The most prevalent anomaly is delamination between the inner primary coating and the glass fiber. Others such as compression artifacts and surface contaminations are also observed under certain circumstances. 2. FIBER COATING ANOMALIES During submarine fiber subsystem manufacturing, the following anomalies in the fiber coating are most often encountered: