Modal analysis of an aluminum rectangular plate by use of the balanced-detection DPP-BOTDA method

In this work we report an experimental modal analysis of an aluminum rectangular plate, carried out by use of the balanced-detection DPP-BOTDA method based on double-pulse pump waveform, combined with the Slope-Assisted BOTDA technique. Compared to standard DPP-BOTDA, the balanced-detection DPP-BOTDA method allows to retrieve the differential Brillouin gain in real time, i.e. without the need of post-processing differentiation, therefore allowing its combination with the Slope-Assisted BOTDA technique. The experimental mode shape of the first resonance of the aluminum plate is compared to numerical results based on a finite-element analysis (FEA), demonstrating that the proposed technique is well suited to perform the modal analysis of a vibrating structure.