Twist Angle Compensation for Three Dimensional Real-Time Shape Sensing Method Based on Multi-Core Optical Fiber

Multi-core fiber is attractive for shape sensing because of its spatial symmetrical distribution of the different cores. A real-time shape sensing approach to enhance the precision of the three dimensional reconstruction shape based on multi-core optical fiber gratings is proposed and demonstrated. The precision of reshaping curve is improved by correcting fiber twisting angle error resulted from twisting loads which are inevitable when fiber bends. By modeling the bending state of optical fiber under twisting load, the twist angles between neighboring fiber gratings are derived from measured strain signal. To be compared with standard deviation of 49.9°bending angle error, the experimental results show that the error of bending angle is less than 8.9°when twist angle measurements are taken into the shape solution and thus the error of curve points position are less than 2.3% in comparison with actual curve points position and absolute cumulative position error is less than 5 cm for 1-meter-long fiber test.