Bend- and Twist-Sensing Optical Fiber

A method was developed for concurrently measuring bending and twisting along an optical fiber using only the properties of light guided within the fiber. The method exploits polarization-dependent reflectivity from fiber Bragg gratings (FBGs) in a centrally located core (see figure). This polarization-based approach fundamentally separates the detection of fiber bending and fiber twist, and no twist bias must be applied during fiber draw.