Simultaneous measurement of linear and angular displacement sensor using POF based on macro-bend loss

This paper presents a plastic optical fiber-based sensor for simultaneous linear and angular displacement measurement through intensity modulation of macro-bend loss. The sensing mechanism relies on generating bend-induced losses in twisted fiber probes and coupling the attenuated light into receiving fibers. Two independent probes are integrated along a single illuminating fiber: the first measures linear displacement, while the second detects angular displacement. Each probe is actuated by a dedicated stepper motor, which varies the bend radius through controlled dragging, converting mechanical displacement into measurable optical power variations. The system is characterized for both individual and synchronized operation, demonstrating a wide dynamic range (0–150 mm linear, 0°–360° angular) with high repeatability and consistent performance across rotational speeds of 5–20°/s. The sensor exhibited limit of detection values of approximately 0.98° for angular measurement and 0.27 mm for linear displacement measurement, with corresponding hysteresis errors of 0.47% and 0.42% of full-scale deflection, respectively. Environmental robustness is ensured by a protective black tube that eliminates humidity effects and external light interference. The sensor’s compact design, dual-parameter measurement capability, and reliable performance make it ideal for many applications.