Ameliorated PGC demodulation scheme using Taubin least squares fitting of ellipse in fiber optic interferometric sensors.

• An ameliorated PGC demodulation scheme using Taubin least squares (LS) fitting of ellipse is proposed. • A combined internal modulation is used and optimized to guarantee the effectiveness of the ellipse fitting algorithm. • Compare with LS, Taubin LS has a high fitting accuracy, thereby reducing the extra low frequency modulation amplitude. • Quadrature signals are extracted from 0th and 1st harmonics of the interference signal, reducing the system complexity. • The scheme has a phase resolution of 3.16 μrad/√Hz, a dynamic range of 120 dB @ 1 KHz and a linearity of 99.996%. In this paper, we propose an ameliorated phase generated carrier (PGC) demodulation scheme using Taubin least squares (LS) fitting of ellipse to eliminate the nonlinear errors. Taubin LS has carefully chosen a normalization matrix and the ellipse fitting parameters are directly obtained by solving the generalized eigenvector problem, leading to a high accuracy result. Quadrature signals are extracted from the signal fundamental and the sidebands of the fundamental of the carrier, and then corrected by the ellipse fitting algorithm (EFA) based on Taubin LS. A combined internal modulation is used to ensure the proper operation of the EFA under small signals. And the desired phase signal is extracted from the corrected quadrature signals by the differential-cross-multiplying method and evaluated by the total harmonic distortion. Experimental results show that the proposed scheme is superior and highly stable, it has a phase resolution of 3.16 μrad/√Hz, a large dynamic range of 120 dB @ 1 KHz and a good linearity of better than 99.99%. [ABSTRACT FROM AUTHOR]