Strain monitoring and fatigue life of Bragg grating fiber optic sensors

The number of advanced sensors such as optical fiber sensors has exhibited tremendous growth in recent years. Optical fiber sensors, which are dielectric and chemically inert, possess characteristics that are attractive for aerospace applications. These characteristics include small size, immunity to Electromagnetic (EM) and radio frequency (RF) interference, solid state electronics reliability, geometric versatility and flexibility, and multi-parametric sensitivity. In this paper in-fiber Bragg grating fiber optic sensors are employed as strain sensors. The output of the fiber optic sensor is evaluated against currently employed sensors, resistance strain gauges and a photoelastic coating, for sensitivity, accuracy, reliability, and fatigue durability. This experimental study, which employs a tensile specimen with bonded sensors and sensors embedded between the host material and a photoelastic coating, also illustrates the reduced intrusiveness of embedded optical fiber sensors as compared to resistance strain gauges.