Potential of twist sensing based on multimodal interference in polymer optical fibers without core offset

This study explores the use of a commercially available polymer optical fiber within an axially aligned offset-free single-mode-multimode-single-mode (SMS) structure for twist sensing. We analyze the transmitted light spectral response to twist angles from -360° to 360°, identifying distinct behaviors for clockwise and counterclockwise twists. Focusing on two specific wavelengths, we demonstrate that this configuration can effectively measure both the magnitude and direction of twists.