Remote structural health monitoring employing OFDR via optical fiber communication networks

In the field of structural health monitoring with optical fiber sensing, installing instrumentation close to the structure is often challenging. By connecting the structure to the measuring device with a transmission optical fiber (this section not subject to measurement), advantages such as indoor installation of the measuring device and shared monitoring of multiple structures can be achieved. However, in such cases, part of the measurement range is consumed by the length of the transmission fiber, significantly limiting the effective measurement range. In this paper, we propose a novel optical frequency domain reflectometry (OFDR) configuration that bypasses the transmission fiber. We demonstrate remote strain measurements on a 1-km section of the fiber under test, located 25 km away from the OFDR system. Strain measurements of up to 1000 με with a spatial resolution of 10 cm were successfully achieved.