عنوان مقاله [English]
Monitoring the safety of huge structures and buildings such as bridges, dams, subways railways and airports as well as energy transmission pipelines and also monitoring places such as borders, security centers etcetera to reduce damages due to natural and non-natural disasters are subjects of particular interest in passive defense. In order to reduce the detriment of the events, various methods are applied such as: the use of accelerometers, radars, and vibration detection systems that operate with GPS to monitor the safety of bridges, tunnels and dams; the use of radars to monitor runways; the use of various wireless communication methods in rail lines, as well as methods to detect leakage of energy pipelines and etc. The safest and most innovative way to achieve this goal is the use of phase-sensitive distributed optical fiber sensor based on Rayleigh scattering. In these sensors, the Erbium amplifier and stimulated Raman and Brillouin scatterings are used to increase the sensing range. In the initial configurations of the sensor, the sensing range was about 6 km by utilizing Erbium amplifier. Maximum sensing range belongs to combination of Erbium and Brillouin amplifiers, which is about 300 kilometers. Along with the high sensing range, the accuracy and sensitivity of this category of sensors attract the attention of researchers and officials of various communities, especially for the purpose of passive defense measures.