Study on phase measurement uncertainty according to the number of phase shifting steps in a multiwavelength interferometer directly using optical comb modes

An electro-optic comb has a wide frequency mode spacing of more than several tens of GHz, making it possible to resolve each comb mode by using commercial spectrometers. The individual frequency modes of the electro-optic comb can be employed as the multiple stabilized lasers required for a multi-wavelength interferometer in absolute distance measurements. For absolute distance measurements, the phase information for each frequency mode, i.e., wavelength, is necessary for determining the absolute distance using the excess fraction method, and this requires a phase shifting process. Typically, the phase shifting is implemented through the sequential translation of a reference mirror by an equal distance. However, since the wavelength values corresponding to every frequency mode are different, even the same amount of shifting of the reference mirror generates different phase change for each wavelength. In such a situation, to accurately measure the phase for each wavelength, a model-based analysis method for phase shifting intensity signals itself was adopted. In the model-based analysis of phase shifting intensity signals, the phase determination uncertainty can vary depending on the number of the phase shifting step. Therefore, in this study, we aim to estimate the phase determination uncertainty according to the number of the phase shifting step through numerical simulations.