Application of novel distributed fibre-optic sensing for slope deformation monitoring: a comprehensive review

Distributed fibre-optic sensing (DFOS) has developed expeditiously over recent decades in multiple technical fields, including slope engineering, as it furnishes several advantages over conventional landslide monitoring approaches. Fibre-optic (FO) cables can be embedded in a shallow trench or buried in a borehole to detect precursory signs of failure well before collapse. By measuring sent and backscattered light, FO systems detect mass movement from changes on the cable so that early warning measurements can be made. This review paper briefly discusses the fundamentals of optical fibres, followed by a compendious explanation of the sensing principle of various DFOS techniques (Rayleigh, Brillouin, and Raman backscattering). The significant considerations for installing an FO cable in a borehole/shallow trench for deformation sensing and the ground-anchor-cable coupling mechanism are emphasised. The most recent advancements of DFOS applications on slope deformation monitoring from the laboratory model size to the field scale are discussed in great detail, emphasising the progress made within the last ten years. Ultimately, some challenges associated with DFOS sensing and future development prospects are discussed. Engineering geologists and slope hazard mitigation planners are anticipated to benefit from the wide-ranging, in-depth information gathered here.