Strain Test Performance of Brillouin Optical Time Domain Analysis and Fiber Bragg Grating Based on Calibration Test.

Optical fiber sensing technology provides a new method for the deformation monitoring of engineering structures. To verify the reliability and accuracy of distributed optical fiber sensing technology based on Brillouin scattering, i.e., Brillouin optical time domain analysis (BOTDA) and fiber Bragg grating (FBG) technologies for deformation monitoring, the strain test performances of BOTDA and FBG technologies were investigated by carrying out calibration tests on a uniform-strength beam and uniaxial compression tests on standard rock specimens. The performances of a strain gauge, three-dimensional digital speckle measurement based on a digital image correlation (DIC) matching technique, and distributed optical fiber and FBG sensors were comparatively analyzed, and the strain measurement performance, monitoring stability, system error, and strain coefficients of distributed optical fibers with different diameters were obtained. Auxiliary verification was carried out by ANSYS numerical simulation. The measurement accuracy of the distributed optical fibers was found to be ±25 µe. When the frequency shift of an optical fiber was positive, the fiber was under tensile stress, and when the frequency shift was negative, the fiber was under compressive stress. The fluctuation of DIC measurement data was greater than that obtained with the FBG sensor, which indicates that FBG measurement is more stable. The maximum fluctuation rates of the strain gauge data and FBG data were 0.092 and 0.031, respectively. The stability of FBG technology for strain measurement is clearly better than that of traditional resistance strain gauges. A thicker packaging material increased the contact area between the optical fiber and the object under test, made the stress transfer more efficient, and improved the sensitivity of the optical fiber. The strain coefficients calculated by numerical simulation were larger than the calibration test results. By comprehensively considering the two sets of results, the strain coefficients of optical fibers with diameters of 0.1, 0.7, and 0.9 mm were found to be 0.0455, 0.0485, and 0.0520 MHz/µe, respectively. Research on the basic test performance of optical fiber sensing technology is of great significance for promoting its more effective application in engineering fields. [ABSTRACT FROM AUTHOR]