Distributed fiber optic sensors (DFOS) are advanced tools for monitoring tunnel infrastructure, offering long-distance strain and temperature sensing. This review discusses DFOS applications in monitoring various tunnel types, including bored, immersed, conventional (NATM), and cut-and-cover tunnels. DFOS systems use Brillouin and Rayleigh scattering principles to measure distributed strain and temperature. The fiber optic cable can be installed along transverse and longitudinal directions to measure distributed strain or point displacements. Key aspects of DFOS monitoring include selecting the appropriate sensing fiber, choosing the measurement principle, designing an effective sensor layout, and establishing robust field instrumentation. The review highlights the advantages of DFOS over traditional methods, such as their ability to provide continuous, high-resolution data over long distances. DFOS systems are particularly useful for monitoring structural health, detecting deformations, and assessing the integrity of tunnel linings. The review also discusses the practical implementation of DFOS in both new and existing tunnels, emphasizing the importance of proper calibration and sensor placement. DFOS have shown significant potential in practical monitoring applications, but challenges remain in ensuring reliable and robust monitoring schemes for diverse tunnel environments. The review provides a comprehensive overview of DFOS applications, focusing on their use in monitoring tunnel deformation and structural health.Distributed fiber optic sensors (DFOS) are advanced tools for monitoring tunnel infrastructure, offering long-distance strain and temperature sensing. This review discusses DFOS applications in monitoring various tunnel types, including bored, immersed, conventional (NATM), and cut-and-cover tunnels. DFOS systems use Brillouin and Rayleigh scattering principles to measure distributed strain and temperature. The fiber optic cable can be installed along transverse and longitudinal directions to measure distributed strain or point displacements. Key aspects of DFOS monitoring include selecting the appropriate sensing fiber, choosing the measurement principle, designing an effective sensor layout, and establishing robust field instrumentation. The review highlights the advantages of DFOS over traditional methods, such as their ability to provide continuous, high-resolution data over long distances. DFOS systems are particularly useful for monitoring structural health, detecting deformations, and assessing the integrity of tunnel linings. The review also discusses the practical implementation of DFOS in both new and existing tunnels, emphasizing the importance of proper calibration and sensor placement. DFOS have shown significant potential in practical monitoring applications, but challenges remain in ensuring reliable and robust monitoring schemes for diverse tunnel environments. The review provides a comprehensive overview of DFOS applications, focusing on their use in monitoring tunnel deformation and structural health.