Characterization of displacement sensing based on fiber optic microbend losses

Abstract

ABSTRACTThis article theoretically and experimentally characterizes single-mode fiber bending losses and associated sensing. As the bending radius decreased, the losses increased significantly, and shock phenomena were observed in the loss curve. Theoretical analysis shows that these processes were caused by coupling between fundamental models spreading in the optical fiber and whispering gallery mode spreading in the cladding and coating layers. Based on the principles of single-mode fiber bending losses, a loss modulator was designed to bend the single-mode fiber and produce losses due to external displacement. A displacement-loss model was constructed and the results were consistent with the theoretical analysis. The displacement resolving power of the loss modulator was 1 µm. The displacement measurement was from 0–350 µm, resulting in losses from 0–25 dB.