Bus movement along Unter den Eichen captured via dark fiber, with identifiable stops at bus stations and a red traffic light.
Source: BAM
Traffic monitoring is essential for sustainable smart cities. While traditionally used to manage traffic flow and safety, its applications now extend to assessing the health of infrastructure like roads and bridges. By analyzing vehicle movement and vibrations, engineers can detect early signs of structural issues. This dual-purpose use of traffic data supports both efficient transportation systems and proactive infrastructure maintenance.
The Division "Fibre Optic Sensors" at BAM has long been developing innovative techniques using distributed fiber optic sensing. These methods repurpose existing "dark fiber" (unused telecommunication cables running alongside roads) transforming them into thousands of virtual sensors that detect vibrations from passing vehicles. This approach eliminates the need for installing additional cameras or sensors and offers a seamless way to monitor both traffic patterns and infrastructure health.
The newly published paper presents a significant advancement in a BAM-patented sensing technique. Through hardware improvements and smarter signal processing, two fundamental properties of light are detected and processed independently, leading to more reliable results. Therefore, the system achieves substantially higher accuracy by minimizing previously large measurement errors. The improved method has been successfully validated in laboratory settings and applied in the field along Unter den Eichen, where it delivered clearer and more reliable results. This development marks a key step toward real-time, cost-effective monitoring of road and bridge integrity—critical for safer, smarter cities.
Error suppression in wavelength scanning coherent optical time domain reflectometry by polarization diversity detection
Xin Lu and Konstantin Hicke
Measurement, vol. 253, part C, page 117733, 2025