Optical fiber sensors are sensors that monitor variations of the physical parameters through an optical fiber that is the sensor itself, in particular Distributed Optical Fiber Sensors (DOFSs) provide spatial continuity along the whole length of the optical fiber. Sensing systems of this kind gain all the properties and all the advantages of optical fibers and are specifically indicated for monitoring of big structures and natural environments. The measurement of the backscattered light and the analysis of the evolution of changes in polarization over time are the concepts studied in this thesis, with the purpose of designing an optical fiber sensor that is able to send out an alarm signal with the occurrence of debris flows and snow avalanches in mountain environments.