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Pulse-prepump Brillouin optical time domain analysis (PPP-BOTDA) is a novel technique for distributed strain measurements, in which a pre-pump pulse is inputted in front of the measuring pump pulse to stimulate the phonon, so that higher spatial resolution and measurement precision can be obtained. Principle, methodologies and technical parameters of the PPP-BOTDA are presented and the influence of temperature on measurements is discussed. Applications are made in the bond test of steel rebars and the bending test of concrete girders. Test results show that the PPP-BOTDA can provide a precise description on the strain distribution of steel rebar and concrete, exhibiting the ability for crack detection. Moreover, structural deformation can be obtained indirectly by accumulating the distributed strains along the optical fiber, thus the deflection curves of the concrete girder during the loading process are obtained. Suggestions with regards to the application of the PPP-BOTDA in strain measurements and crack monitoring for civil infrastructures are given.
Pulse-prepump Brillouin optical time domain analysis (PPP-BOTDA) is a novel technique for distributed strain measurements, in which a pre-pump pulse is input in front of the measuring pump pulse to stimulate the phonon, so that higher spatial resolution and measurement Principle, methodologies and technical parameters of the PPP-BOTDA are presented and the influence of temperature on measurements is discussed. Applications are made in the bond test of steel rebars and the bending test of concrete girders. Test results show that the PPP-BOTDA can provide a precise description on the strain distribution of steel rebar and concrete, exhibiting the ability for crack detection. Moreover, structural deformation can be obtained indirectly by accumulating the distributed strain along the optical fiber, thus the deflection curves of the Suggestions with regards to the application of the PPP-BOTDA in strain m easurements and crack monitoring for civil infrastructures are given.