Development of a fiber-optic sensor for enhancing functional security of perimeter protection

This paper presents the design, implementation, and experimental evaluation of a compact macrobend-based fiber-optic sensor intended for perimeter intrusion detection with an additional capability for estimating the mass of an intruding object. The sensing principle relies on controlled macrobending of a single-mode optical fiber, which induces radiative power loss that is collected by a secondary fiber and converted into an electrical signal for analysis. Three standard commercial telecom fibers (G.652, G.655, and G.657) were experimentally characterized at four wavelengths (1310, 1490, 1550, and 1625 nm) in order to quantify macrobend sensitivity as a function of bend radius and arc length. The results demonstrate that G.655 exhibits the highest macrobend sensitivity, reaching up to 0.21 dB·mm −1 at 1625 nm, and provides a measurable and approximately linear response suitable for mass estimation. Within the identified linear operating range, the sensor achieves a mass sensitivity of approximately 1.4 dB·kg −1 . A compact mechanical macrobend shaper, the complete optical and electronic measurement chain, and an analytical calibration framework linking applied load, induced displacement, bend geometry, and optical attenuation are presented. Repeatability experiments conducted over more than fifty measurement cycles show a coefficient of variation below 5% in the linear regime. The proposed approach offers a low-cost and mechanically simple solution for enhanced perimeter monitoring while highlighting practical trade-offs related to sensitivity, operating range, and calibration stability.