Distributed fiber optic sensing technologies and applications - An overview

Needs for structural health monitoring in the last decades were rapidly increasing, and these needs stimulated developments of various sensing technologies. Distributed optical fiber sensing technologies have reached market maturity and opened new possibilities in structural health monitoring. Distributed strain sensor (sensing cable) is sensitive at each point of its length to strain changes and cracks. Such a sensor practically monitors one-dimensional strain field and can be installed over the entire length of the monitored structural members, and therefore provides for integrity monitoring, i.e. for direct detection and characterization of local strain changes generated by damage (including recognition, localization, and quantification or rating). The aim of this paper is to help researchers and practitioners to get familiar with distributed sensing technologies, to understand the meaning of the distributed measurement, and to learn on best performances and limitations of these technologies. Hence, this paper briefly presents light scattering as the main physical principle behind technologies, explains the spatial resolution as the important feature for interpretation of measurements, compares performances of various distributed technologies found in the market, and introduces the concept of integrity monitoring applicable to various concrete structures. Two illustrative examples are presented, including applications to pipeline and bridge.