The paper "Recent Progress in Distributed Fiber Optic Sensors" by Xiaoyi Bao and Liang Chen reviews the advancements in distributed fiber optic sensors, which use Rayleigh, Brillouin, and Raman scatterings to detect changes in temperature, strain, vibration, and birefringence over lengths ranging from meters to 100 kilometers. These sensors can be used for disaster prevention in civil structural monitoring, such as bridges, pipelines, dams, and railroads, as well as in aerospace smart structures, material processing, and optical device characterization. The authors discuss the motivation for distributed fiber sensors, highlighting their importance in monitoring the health of structures by detecting internal stresses and strains. They explain the working principles of these sensors, including the detection of changes in the amplitude, frequency, and phase of scattered light, and the use of coherent detection to observe changes in birefringence and beat length. The paper covers the definition and system limitations of distributed sensors, the theory and working principles of Rayleigh, Brillouin, and Raman scattering, and their applications. It also discusses the use of Stokes and anti-Stokes ratios in Raman scattering for distributed temperature sensing, and the performance of Rayleigh scattering-based optical time-domain reflectometry (OTDR) and optical frequency-domain reflectometry (OFDR). The authors further explore the development of Brillouin grating-based sensors and the limitations on sensing length and spatial resolution. They provide a performance chart of different sensing systems and discuss the applications of distributed sensors in monitoring structural conditions. Overall, the paper provides a comprehensive overview of the current state of distributed fiber optic sensors, their technological advancements, and their potential applications in various fields.The paper "Recent Progress in Distributed Fiber Optic Sensors" by Xiaoyi Bao and Liang Chen reviews the advancements in distributed fiber optic sensors, which use Rayleigh, Brillouin, and Raman scatterings to detect changes in temperature, strain, vibration, and birefringence over lengths ranging from meters to 100 kilometers. These sensors can be used for disaster prevention in civil structural monitoring, such as bridges, pipelines, dams, and railroads, as well as in aerospace smart structures, material processing, and optical device characterization. The authors discuss the motivation for distributed fiber sensors, highlighting their importance in monitoring the health of structures by detecting internal stresses and strains. They explain the working principles of these sensors, including the detection of changes in the amplitude, frequency, and phase of scattered light, and the use of coherent detection to observe changes in birefringence and beat length. The paper covers the definition and system limitations of distributed sensors, the theory and working principles of Rayleigh, Brillouin, and Raman scattering, and their applications. It also discusses the use of Stokes and anti-Stokes ratios in Raman scattering for distributed temperature sensing, and the performance of Rayleigh scattering-based optical time-domain reflectometry (OTDR) and optical frequency-domain reflectometry (OFDR). The authors further explore the development of Brillouin grating-based sensors and the limitations on sensing length and spatial resolution. They provide a performance chart of different sensing systems and discuss the applications of distributed sensors in monitoring structural conditions. Overall, the paper provides a comprehensive overview of the current state of distributed fiber optic sensors, their technological advancements, and their potential applications in various fields.