Abstract. Results of numerical investigation of phase nonreciprocity (phase drift) induced by external nonstationary mechanical forces on sensitive element of the fiber-optic gyroscope (FOG) are presented. The basis of the approach is the numerical modeling technique developed by the authors in a previous work. The specific feature of this method is that computational domain is constructed using a CAD–model of sensitive device of the FOG. Along with the fiber coil of the fiber-optic path, the model also includes the elements of the gyroscope structure. The fiber-optic path is considered as a nonhomogeneous medium with unaveraged properties with the account for its inherent periodic microstructure. The problem of non-stationary stress-strain state is solved for the entire computational domain. Then, the time of counter-propagating beam travel along the optical path and the resulting drift are calculated, using the constitutive relations of piezooptics.  The approach allows to model the nonreciprocity of phases under the action of both thermal and mechanical loads. Results of calculation of the shape of drift function for varying duration of the shock pulse, as well as for a series of pulses are demonstrated. The calculated drift shape is shown to correlate with the first derivative of the force function with respect to time. The calculated drift amplitude values are demonstrated to agree well with data of angular rate sensor tests.  

Keywords: fiber-optic gyro, drift, nonreciprocity of phases, dilatation waves, shock, impulse of force, photo-elasticity, numerical modelling, fiber-optic path, microstructure of fiber

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