Modeling of the Magneto-Optical Channel of a Fiber-Optic Displacement Sensor

According to earlier studies conducted by the authors it was found that contactless fiber-optic sensors based on the magneto-optical Faraday effect (FOSF) in epitaxial films of iron garnet can be used for contactless monitoring of the status of control plate valves that regulate the flow of fire and explosion hazardous substances and operate over a wide temperature range. FOSF makes it possible to control the displacement and tilt angle of the valve regulating element (valve plate). However, at the moment there are no sufficiently accurate mathematical models for such FOSF. Studies have shown that the discrepancy between simulation results and experiments can reach 105%. The discrepancy between the results increases significantly when the FOSF is operated in a wide temperature range (from minus 196 to +80 °C). The low accuracy of the FOSF models does not make it possible to develop efficient means of compensating its intrinsic and complementary errors. The existing FOSF models are not sufficiently accurate, since they do not take into account: the distribution of the normal component of the magnetic field strength along the magneto-optical element (MOE) cross-section; the distribution of the optical radiation intensity along the MOE cross-section; optical absorption of the FOSF optical elements. According to the results of research carried out by the authors a set of mathematical models that takes into account the nonuniform distribution of the optical radiation intensity along the MOE cross-section, the nonuniform distribution of normal component of the magnetic field strength along the MOE cross-section, the optical absorption in FOSF optical elements and their temperature dependences was developed. This allowed us to significantly reduce the modelling error. The discrepancy between the results of mathematical modeling and experimental studies of FOSF prototypes does not exceed 7.2%.