Fiber interferometric system for vehicle monitoring near railway level crossings

Abstract

The article describes the development of the vehicle monitoring system that is applicable in the vicinity of the railway level crossings. The proposed system is based on a Mach-Zehnder fiber interferometer sensor, which has a measurement arm embedded in the road surface. The sensor is passive and requires no electrical power at the installation site, immune electromagnetic interference, and is compatible with existing single-mode fiber infrastructure. Experimental measurements were focused on the response of sensors utilizing different mechanical structures of fiber loops, slow-moving vehicles, and sensor function in continuous snow cover. Installed optical fibers in the roadway are regularly monitored and evaluated for their durability. The results have shown that it is possible to detect individual vehicles but above all their axles, which opens the way for vehicle classification. The detection capability of the system is absolute even with continuous snow cover. For slow-moving vehicles, double axle detection occurred due to the longitudinal dimensions of the loop, which will be solved by the second generation of sensors. The resulting system will be installed on a selected railroad crossing as a complement to the existing camera system.