A nonlinearity correction using ellipse fitting technique based on orthogonal polarized laser interferometer is
proposed in this paper. In this paper, characteristics of four-channel output signals based on polarized Michelson laser
interferometer are studied. The orthogonal signal's non-orthogonal error which is caused by temperature disturbance and
low frequency vibration noise is compensated. Besides, a new algorithm of demodulating small phase signal is proposed.
Low frequency vibration signal demodulation system based on DSP technique is constructed. It proposed an ellipse
fitting algorithm based on Least-squares theory. This algorithm can achieve correction error of less than ±0.3%.
System's real-time measurement capability and its resolution can be improved.