Application of fiber Bragg grating sensors for the micro-strain measurement of optical components surface

摘要

Fiber Bragg Grating Sensors (FBGS) are gaining increasing attention in the fields of micro-stress analysis, showing high accuracy and sensitivity. In this paper, FBGS which wavelength variations can be converted to strains, are used to measure the microstrain variation of a plane mirror where the forces acting upon. Both the self-gravity and extrusion forces are applied to the surface of the optical elements, generating inevitable deformation and decreasing the test accuracy of the whole optical system. First, a micro-strain model is built using finite element analysis to obtain the qualitative value of the micro-strain variation. Next, a series experiments are performed to validate the model is effective. A detailed analysis of the micro-strain variation is acquired from the phase generated carrier homodyne demodulation and then the three-step phase-shifting algorithm based on an unbalanced MachZehnder interferometer system. The experimental results match well with the theory. Both the modeling and measurement results indicate that the sensitivity of this method in measuring the micro-strain can be reached as small as.