Simultaneous vibration and soil moisture sensing using a single mode fiber for structural health monitoring applications

A dual-purpose single mode optical fiber sensor was developed for simultaneous soil moisture and structural health monitoring. Unmodified G655 SMF with polarization coupled phase components was used to detect environmental changes due to ground movement and moisture content variations. Spectral distribution profiles of the baseband frequencies below 10 Hz were analyzed for structural health monitoring, while resonant peak frequencies higher than 110 Hz had notable dependence on the damping effect of moisture on the spectral peak intensity of the detected acoustic waves. Using these peaks, moisture content was measured within a root mean square error value of +/-0.04. The sensor demonstrates a critical resource optimization tool for distributed sensing applications and monitoring in PON systems.