Failure analysis of connector-terminated optical fibers: two case studies

Two of the most common fiber-optic connector failures involve fiber breaks caused by thermal changes. Type I failures involve fiber buckling during cooling from the epoxy cure temperature and are related to the free length of fiber inside the ferrule/backbone assembly. Type II failures occur during the heating phase of thermal cycling and are caused by expansion of epoxy in the ferrule entry under certain conditions. These conditions lead to otherwise unexpected tension at the ferrule capillary entry. In both cases the failure probability is increased by fiber damage during the termination process. Examples of the two types of failure are presented together with a discussion of the mechanisms and the reliability implications