Fiber optic weigh in motion: looking back and ahead

Abstract

This paper presents an analysis of the fiber optic weight- in-motion (WIM) smart sensor situation. Based on the interrelationship between technology and needs, the analysis is divided into three parts. The first part reflects WIM equipment development, such as piezo-electric sensors, and some of the pitfalls encountered in WIM measurements that led to fiber optic sensor utilization. With a chronological approach, the second part reviews the various optical principles that have been developed to measure dynamic weight. Since 1986, three techniques have been fully tested on actual highways. On the one hand, the simplest one based on light attenuation in multimode fibers as suitable for counting. On the other hand, speckle analysis at the end of a multimode fiber allowed a better strain and deformation determination. Finally, the sophisticated polarimetric configuration seemed to be more powerful and led to impressive findings such as dynamic phenomenon observation. The third and last part of this paper reviews some of the future needs for WIM systems, and the ongoing developments in the intelligent transportation system (ITS) field. Then, the factual report derived from this analysis shows that despite their tremendous potential, fiber optic sensors are almost nonexistent in current ITS worldwide developments.