Comparison of Bragg and Polarimetric Optical Fiber Sensors for Stress Monitoring in Composite Materials

Composite structures are made of two or more components with significantly different physical or chemical properties and they remain separate and distinct in a macroscopic level within the finished structure. This feature allows for introducing optical fiber sensors into the composite material. These sensors can demonstrate stress distribution inside tested material influenced by external tensions. Two types of the optical fiber sensors are used as the 3D structure. One of them is based on application of fiber Bragg grating inside the core of the fiber. Longitudinal stress changes parameters of the Bragg grating and simultaneously, spectral characteristics of the light transmitted through the fiber. The second one is based on application of highly birefringent fibers which, under external stress, introduce polarization changes of the output light.