Design, sensing principle and testing of a novel fiber optic displacement sensor based on linear macro-bending loss

Abstract This paper presents a linear fiber optic displacement sensor for the use over a large range based on the macro-bending loss. The sensor incorporates an extremely simple design, light source and detector. A concentric gear shaft is used to bend the fiber and transfer the displacement. The linear relationship between the measured displacement and the bending loss of optical fiber was proved theoretically and its expression was derived. A series of calibration experiments and performance tests were conducted. The experimental results show that the sensor was characterized by a wide measurement range, a high sensitivity and a minimum displacement resolution of 0–200 mm, 0.1668 dB/mm and 0.06 mm, respectively. The stability and repeatability of the sensor was verified by repetitive testes with a maximum measurement deviation of 0.162 mm. The predicted displacements of the sensor were similar to the actual values, and the difference errors of all samples are basically within 10%. These characteristics demonstrate that the sensor can be used for displacement monitoring for large-scale civil structures and has a promising prospect.