High-Performance Bending Sensor Based on Fiber Microspheres Array Michelson Interferometer

A compact, high-performance bending sensor based on fiber microspheres array (FMA) Michelson interferometer (MI) was experimentally proved. The sensor consists of a refractive index modulation region (RIMR) fused by three microspheres, interference arm and end face protection. The RIMR acts as a modal coupling device between core and cladding modes. Due to the different stress for the RIMR in the middle (lowest point) of the stepper motor or the side (high point) during the bending process, the mode field distribution excited to the cladding is inconsistent which shows a discrepancy in sensitivity. The results show that the bending sensitivity at the lowest point is lower than the high point, which is consistent with the theory. Meanwhile, the variable range method is used to realize the repeatability verification of the sensor. Besides, the relative sensitivity (the ratio of wavelength sensitivity to intensity sensitivity) is defined to realize the resolution of strain and bending.