Low-coherence interferometric demodulation method based on spectrum nonlinear effect dispersion compensation

Abstract

The invention discloses a low-coherence interferometric demodulation method based on spectrum nonlinear effect dispersion compensation. The method comprises the following steps: step 1, achieving discrete Fourier transform of interference fringe signals to obtain the magnitude spectrum and the phase spectrum under the discrete frequency domain; step 2, setting a threshold H, taking a region of which the amplitude is larger than H, except for the low-frequency part, as the selected discrete frequency band, calculating wave numbers corresponding to all points in the frequency band, and transforming the phase spectrum from the discrete frequency domain to the wave number domain; step 3, selecting the wave number corresponding to the maximum amplitude in the magnitude spectrum, within the wave number band in which the optical spectrum of a light source is distributed, as the specific wave number, carrying out phase unwrapping in the wave number band, calculating the interference level of the specific wave number, reconstructing the absolute phase of the specific wave number, which directly reflects the range information, according to the relative phase value and the interference level of the specific wave number. The low-coherence interferometric demodulation method realizes high-precision distance demodulation and is suitable for light sources with any wideband.

Description

technical field [0001] The invention relates to the field of optical fiber sensing, in particular to a low-coherence interference demodulation method based on spectral nonlinear effect dispersion compensation. Background technique [0002] Low-coherence interference technology is an effective distance measurement method. The specific method is to demodulate low-coherence interference signals through appropriate demodulation methods, and good measurement results can be obtained. Among them, the peak determination method based on intensity information directly demodulates by determining the displacement of the interference fringe pattern. The demodulation method based on phase information is to demodulate according to the phase displacement information. On the premise of accurately determining the interference order, the demodulation method based on phase information can obtain high demodulation accuracy. Demodulation methods based on phase information mainly include phase sh...

AI Technical Summary

Problems solved by technology

However, when there are optical components with depth-dependent dispersion factors (for example, birefringent wedges) in the system, due to the influence of dispersion, spectral nonlinear effects will occur, which will cause serious errors in the demodulation results of the spatial frequency method

Therefore, for a low-coherence interferometric system that includes depth-related dispersion factors, the spatial frequency method is affected by depth-related dispersion. If the spectral nonlinear effect caused by depth-related dispersion cannot be compensated, when a certain measurement range is exceeded, the demodulation result would produce a step error that limits the measurement range of the method

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