Turning Telecommunication Fiber-Optic Cables into Distributed Acoustic Sensors for Vibration-Based Bridge Health Monitoring

We introduce a nondedicated bridge health monitoring (BHM) system that turns pre-existing telecommunication fiber-optic cables into distributed acoustic sensors to collect bridge dynamic strain responses. Due to extensively installed telecommunication fiber cables in the cities, our telecommunication cable-based system enables efficient and low-cost BHM without the requirement of on-site sensor installation and maintenance; however, it is challenging to extract bridge damage-sensitive information (e.g., natural frequencies and mode shapes) from this nondedicated strain data as it has large measurement noise and error propagation. To overcome the challenge, we develop a physics-guided system identification method that models strain mode shapes based on physics-guided parametric mode shape functions derived from bridge dynamics. We then estimate the displacement mode shape function by analytically double-integrating the modeled strain mode shape. Our method improves the accuracy of estimating bridge damage-sensitive features and reduces error propagation by constraining strain and displacement mode shapes with bridge dynamics. We evaluated our system on a concrete continuous three-span bridge in San Jose, California. Our system successfully identified the first three natural frequencies and reconstructed strain and displacement mode shapes in a meter-scale resolution.