Radiation and cladding modes as independent measurements of Bragg grating sensor integrity

摘要

This article presents the use of Bragg reflection and cladding mode measurements to independently measure axial strain and the integrity of a Bragg grating sensor. While the Bragg reflection is known to be sensitive to applied strain, the cladding modes are shown to be sensitive to expected damage within the sensor such as microcracking and debonding from the host structure. This phenomenon allows the intelligent self-testing of the Bragg grating sensor without additional instrumentation and permits the separate identification of sensor failure from the failure of the host structure. The growth of cladding modes during degradation of a Bragg grating is experimentally demonstrated in controlled tension tests with different fiber-host interface conditions.