Intrusion detection system for the protection of railway assets by using Fiber Bragg Grating sensors: a Case Study

In this work, we demonstrate the capability of Fiber Bragg Gratings (FBGs) sensors to protect large areas from unauthorized activities in railway scenarios such as stations, depots or tunnels. In particular, here we report on the technological strategy we adopted in order to protect a “specific” railway depot, but representative of a quite common scenario in railway environment for outdoor security applications. One of the concerns associated with to the protection of a railway area, indeed, relies on the unavoidable presence of the railroad tracks that cannot be practically obstructed with physical barriers. We propose an integrated optical fiber sensing system, composed by FBGs strain sensors, deployed in a network, to detect human intrusion through the perimeter to be protected, combined with FBG accelerometers sensors to protect the rail track access. Several trials have been carried out in indoor and even outdoor environment. Experimental results reveal that FBGs strain sensors, bonded under a ribbed rubber mat, enable the detection of intruder´s break-in and FBG accelerometer sensors, installed under rails, enable the detection of walking intruder on the railroad tracks through the acoustic surface waves generated by the footsteps. The integrated system, based on a single enabling technology, represents a valuable intrusion detection system for railway security and could be further integrated with other sensing functionalities in the railway field using the fiber optic technology.