Orientation-dependent fiber-optic inclinometer based on core-offset michelson interferometer

An in-fiber Michelson interferometer (MI)-based inclinometer, which consists of misalignment-spliced fiber with end coating, is proposed and experimentally demonstrated. The incident light divided at the misalignment-spliced joint is reflected at the end coating, and then re-coupled into the fiber core. Due to the phase difference between the core mode and the m th cladding mode, a typical MI is formed. The fiber near the misalignment-spliced joint is inserted in two capillary quartz tubes. The tilt of the capillary quartz tube leads to a significant deformation and curvature of the misalignment-spliced joint, which causes the wavelength and intensity of the MI spectrum to change. The experimental results indicate a good response within the angle range of 0°–50°. Both the wavelength modulation and intensity modulation are realized, with sensitivities of 0.55 nm/deg and 0.17 dB/deg, respectively. Moreover, the sensor shows a strong orientation dependence due to the asymmetric structure in the misalignment-spliced joint.