The master thesis deals with Optical Fiber Sensing and aims to improve geological vibrations detections of dangerous events in a mountain landscape. In the system, the sensors are represented by the optical fibers and their polarization state is continuously monitored by a polarimeter. The intensity of a vibration detected on a mountain side is monitored looking at the variation of the angular speed of the state of polarization . Higher will be the speed and bigger will be the event degree of strength. One of the main goals of the work is to sense multiple fibers at the same time and, as the title of the work quotes, to maintain the low cost condition in the system.