Orthogonal time division modulation for nonlinear frequency-scanning interferometry and phase extraction

Abstract Frequency-scanning interferometry (FSI) is an absolute distance measurement method, and its measurement accuracy is affected by the nonlinearity of laser frequency scanning. To improve the accuracy of phase extraction of the nonlinear interference signal corresponding to nonlinear frequency scanning, this paper builds an FSI measurement system that performs orthogonal time division modulation on a reference optical path laser. By orthogonal time division modulation of the reference laser, a theoretical orthogonal interference signal is obtained through time-division multiplexing, and an instantaneous phase extraction method is proposed. However, due to the time division of the two signals, a orthogonal phase deviation is introduced. By theoretically analyzing the phase solution results when there is a orthogonal phase deviation, the error type can be determined and suppressed. Finally, the effectiveness of this method is verified by experiments.