Fiber Bragg grating strain measurements in comparison with additional techniques for rock mechanical testing

Fiber Bragg gratings (FBGs) have been used as strain transducers for deformation measurements on two types of granite in uniaxial compression (UC) tests. A comparison of the strain results is given for mechanical extensometers based on cross-flexure strain gages, surface-mounted FBG sensors, and a noncontacting laser extensometer measuring system as additional optical reference.