In recent years, natural and anthropogenic geohazards have occured frequently all over the world, and field monitoring is becoming an increasingly important task to mitigate these risks. However, conventional geotechnical instrumentations for monitoring geohazards have a number of weaknesses, such as low accuracy, poor durability, and high sensitivity to environmental interferences. In this aspect, fiber Bragg grating (FBG), as a popular fiber optic sensing technology, has gained an explosive amount of attention. Based on this technology, quasi-distributed sensing systems have been established to perform real-time monitoring and early warning of landslides, debris flows, land subsidence, earth fissures and so on. In this paper, the recent research and development activities of applying FBG systems to monitor different types of geohazards, especially those triggered by human activities, are critically reviewed. The working principles of newly developed FBG sensors are briefly introduced, and their features are summarized. This is followed by a discussion of recent case studies and lessons learned, and some critical problems associated with field implementation of FBG-based monitoring systems. Finally the challenges and future trends in this research area are presented.

Vertical deformation can be revealed by various techniques such as precise leveling, satellite imagery, and extensometry. Despite considerable effort, recording detailed subsurface deformation using traditional extensometers remains challenging when attempting to detect localized deformation. Here we introduce distributed fiber optic sensing based on Brillouin scattering as a geophysical exploration method for imaging distributed profiles of vertical deformation. By examining fiber optic cable‐soil interaction we found a threshold in confining pressure to achieve a strong cable‐soil coupling, thus validating data collected from a borehole‐embedded fiber optic cable deployed in Shengze, southern Yangtze Delta, China. Clear‐cut strain profiles acquired from November 2014 to December 2016 allowed us to pinpoint where compaction or rebound was actively occurring and examine strain responses at various locations along the entire cable length. We suggest that distributed fiber optic sensing can complement with extensometry and remote sensing techniques for improved monitoring of vertical deformation.