High-Accuracy Distributed Bend Sensor Eligible for High-Curvature Structures Based on Brillouin Optical Correlation Domain Analysis

Abstract

We present a high-accuracy distributed bend sensor suitable for high-curvature structures based on Brillouin frequency measurement using a multi-fiber probe. Brillouin optical correlation domain analysis (BOCDA) with differential measurement is adopted for distributed strain sensing with a cm-order spatial resolution (minimum 1 cm), and a specially designed sensing probe embedding three optical fibers is used to enhance the minimum measurable bending radius and accuracy of bend sensing. Analysis on the reconstruction accuracy is performed for various spatial resolutions (10, 20, 30, 40 mm) and steps (1, 5, 10, 15, 20 mm) of the BOCDA system. Our results show that the maximum measurable curvature of three-dimensional bending is 143 m(-1), which is the highest curvature so far measured by Brillouin sensors in three-dimensional space, with about 0.7% of tip position error. Additionally, both pseudo-discrete sensing and fully distributed sensing are performed together to analyze the relation between the methods of sensing (discrete or distributed) and the accuracy of probing multi-bend curvatures according to the measurement step.