Spiral Optical Fiber Sensor for Precision Vibration and Structural Strain Detection

This study presents the design and theoretical analysis of a distributed fiber-optic sensing system for localization of mechanical vibrations and micro-strain in structural materials. The proposed architecture combines multimode and spiral single-mode optical fibers with different effective optical path lengths, enabling detection and spatial reconstruction of localized perturbations through differential signal propagation and timing analysis. The sensing principle is based on strain-induced variations in optical propagation conditions, scattering losses, and signal delay between coupled optical channels. The spiral geometry increases the effective optical path length and enhances sensitivity to local deformations, while the use of multiple sensing lines improves robustness in the presence of simultaneous perturbations. The proposed configuration represents a compact and scalable sensing approach that may be integrated into aerospace structures, industrial systems, seismic monitoring networks, and laboratory-scale experimental platforms. Analytical estimates indicate that the system is capable of resolving localized structural perturbations with high spatial sensitivity under realistic assumptions regarding timing resolution and optical losses.