A Fiber-Optic Angular Displacement Sensor Based on Optical Microfibers and Its Calibration Method

A fiber-optic angular-displacement sensor with a pendulum sensing element based on an optical microfiber with end and side directional radiation outputs, which serve, respectively, for measuring angular displacements and creating a transverse component of the light pressure force that leads to a deflection of the pendulum from the local vertical direction. A method of remote calibration and an algorithm for the sensor operation are proposed, which provide the possibility of calibration without violating the measurement mode. The method is based on the laser excitation of forced resonant oscillations of a pendulum–optical microfiber under the action of a transverse light-pressure force and the comparison of the resulting maximum values of the sensor output signals with the reference amplitude values of the angular deflections of the optical microfiber, which were calculated within the framework of the model of an elastic thin cantilever rod with a load at its end located in the Earth’s gravity field. The results obtained in this study and the approaches outlined in it may serve as the basis for creating new types of fiber-optic sensors characterized by a long service life and highly stable metrological indicators, which can be used, e.g., in systems for monitoring the technical conditions of construction structures and antenna mast systems, in systems of angular orientation and stabilization of platforms, etc.