Experimental and numerical studies in the evaluation of epoxy-cured fiber optic connectors

The fiber optic connector (FOC) is a passive optical component that is used in many applications and whose function is to physically and optically link two fiber joints. It is important for the reliability of fiber optic infrastructure to identify the mechanisms of degradation and failure of these components. This paper reviews work at the University of Maryland CALCE Center to accomplish this, including experimental strain analysis utilizing fiber sensors and calculations and models to predict the stresses in FOCs and their effect on the response of the sensors used. In-fiber Bragg grating sensors have been used to study the mechanical strain state in optical fibers that have been terminated in ST connectors. Our findings indicate that terminated sensors experience a compressive strain whose magnitude depends on the cure profile of the epoxy encapsulant used in these connectors. Specifically, we have found that room temperature cures result in lower strain as compared to thermally cured samples. The measured strain magnitude is also believed to be sensitive to the position of the sensor along the axis of the connector. It is believed that to adequately account for such phenomena to occur and predict failure and degradation of the connector, the behavior and response of the epoxy encapsulant is a key consideration.