This paper shows the way to turn a defect inherent to single-mode fiber, namely birefringence, into a prime quality for a powerful and reliable sensor. The latter is entirely devoted to Weigh-In-Motion (WIM) applications extended to complete active traffic management systems. After a brief description of the sensor and its principle of operation, the theoretical model is developed. Then, a full characterization made in both static and dynamic conditions is presented. The results obtained illustrate how it is difficult to interpret a weight measured in dynamic conditions and correlate the value with the static weight.

This paper presents an analysis of the fiber optic weigh-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 was 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 systems (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.

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The coronavirus and its associated economic dislocations have complicated the technology’s 2020 rollout. But the changes wrought by the pandemic may boost the case for 5G in the long run.