Sensitivity comparison of acoustic vibration detection methods in underground optical networks

Optical fibers, commonly used in communication networks, can also serve as highly sensitive vibration sensors. This property raises security concerns, as vibrations induced by environmental factors or human activity can be detected and analyzed, potentially enabling unauthorized monitoring. Various sensing techniques leverage different physical principles to interpret these disturbances. In this study, we evaluate and compare the performance of three distinct methods: phase-sensitive OTDR, state of polarization detection, and Michelson interferometry. Presented measurements were conducted on optical fibers deployed along a roadside within a university campus, where we examined how external conditions influence signal behavior. The results provide insights into the feasibility and limitations of these sensing methods in practical scenarios. Our findings contribute to the ongoing development of fiber-based vibration monitoring systems, with potential applications in infrastructure security and environmental sensing.