Assessment of Scattered-Bend Loss in Polymer Optical Fiber (POF) Displacement Sensor

Abstract

This work investigated the coupling behavior of the scattered-bend loss in displacement sensor during the bending of the fiber by using a multimode polymer optical fiber (POF). To utilize the scattered-bend effect for displacement measurement, a side coupling technique can be used by twisting a pair of POF fibers and bent the structure into a loop. The working principle of the sensor is quite simple. The bent radius grows smaller as the fiber draughts which simulate a change of displacement. The scattered-bend loss increases as the illuminating fiber is bent in decreasing angle and the light being coupled to the receiving fiber. The fabricated sensor is tested based on static measurement analysis and the sensor is characterized by its sensitivity, resolution, linearity, and repeatability error. From the experiment, the fabricated sensor has a range of roughly 160 mm with a sensitivity of 0.817 nW/mm, a resolution of 1.228 mm, and a repeatability error of 1.856 %. The sensor exhibits high linearity from 0 mm to 80 mm. The sensor's design structure and analysis are simple, comprehensive, and cost-effective, with potential benefits in industrial applications.