Fiber-Optic Sensor for Directional Bending Monitoring Based on a Pattern Recognition Algorithm

A fiber sensor for directional bending monitoring is presented. The sensor is made of a single piece of a multimode elliptical-core fiber (ECF) and works in a reflection regime. The interference spectrum generated by the proposed system has a nonuniform amplitude and nonperiodic shape that makes the sensing signal adequate for a pattern recognition algorithm to be implemented. The ECF is fixed to a flexible rod, and each bending position of the rod generates a specific optical spectrum, which is then identified by a pattern recognition algorithm. Using algorithm identification, the trajectory of the flexible rod can be calculated. Experimental results demonstrating directional bending monitoring, based on pattern recognition and estimation of the flexible rod trajectory, are presented.