Elimination of parasitic interference effect in fiber-optic external sinusoidal phase-modulating interferometer based on Kalman filter

The fiber-optic external sinusoidal phase-modulating interferometer (ESPMI) is sensitive, accurate, and robust. However, parasitic interference hinders further improvement of its precision, and reduces its adaptability to measurement targets with different characteristics. In this paper, we analyzed the mathematical model of parasitic interference, and proposed a Kalman filter-based method to eliminate the parasitic interference effect in the ESPMI. This method works by filtering out the time-varying offsets in quadrature signals brought by the parasitic interference. Simulations and experiments were conducted to verify the effectiveness of the proposal. The experimental results showed that our proposal had great parasitic interference effect elimination ability. Compared with existing schemes, our method is highly accurate and low-cost with no loss in interferometric range, thus having catalytic effect on the application of ESPMI in related fields.