Acoustic emission monitoring of infrastructure using distributed acoustic sensing (DAS) techniques - possibilities, limitations, and optimization

Abstract

Acoustic emission (AE) testing is an established method for structural health monitoring and damage detection in engineering structures. Conventional AE systems are based on piezoelectric sensors that are applied at discrete locations, requiring extensive cabling and offering limited spatial coverage. Distributed Acoustic Sensing (DAS) provides an alternative approach as a fiber-optic measurement technique, in which a single optical fiber cable serves as a continuous, spatially distributed sensor. In this work, both methods are systematically compared with respect to their detection capability, spatial resolution, sensitivity, and practical applicability. For this purpose, laboratory and field experiments were conducted using defined acoustic sources. The results demonstrate that DAS offers advantages over conventional AE in terms of large-area monitoring, resilience to harsh environmental conditions, and electromagnetic immunity. Furthermore, a novel coil-based fiber instrumentation was investigated to selectively enhance sensitivity. Conventional AE, on the other hand, exhibits advantages in local sensitivity and signal characterization. The comparison elucidates under which boundary conditions DAS can be employed as a complementary or alternative method to conventional acoustic emission testing – particularly for the monitoring of extensive offshore infrastructures or large-scale civil engineering structures.