Theoretical and Experimental Investigations into Crack Detection with BOTDR-Distributed Fiber Optic Sensors

Development of a model for the analysis of strain transfer mechanism in Brillouin-based sensors with strain singularities is provided in this study. The main objective of the research pertained to the development of a method for accurate detection of cracks and their locations in sensing with Brillouin-based fiber optic distributed sensors. The work involved formulation of a shear lag–based model considering the elastic as well as elastoplastic stages of the fiber optic coating strains. Feasibility of the proposed approach is evaluated through an experimental program. The experimental program involved use of a Brillouin optical time domain reflectometer (BOTDR) for distributed measurement of strain and detection of simulated cracks in a 15-m-long beam. The results indicate that the discontinuities in the strain distribution based on the theoretical analysis provide the means to accurately pinpoint the location of simulated cracks. On the other hand, the distortion effect of the BOTDR system due to...