Vibration measurement technology of optical fiber SS-OCT based on All-phase Fast Fourier Transform

Abstract

This study utilizes the All-phase Fast Fourier Transform (FFT) spectral analysis phase difference technique combined with a Kaiser-Hanning hybrid convolution window to enhance the displacement resolution of Swept Source Optical Coherence Tomography (SS-OCT), enabling sub-nanometer level micro-vibration measurements. By employing a designed ultra-small Gradient Index (GRIN) fiber probe, the signal-to-noise ratio (SNR) is increased to 40 dB, and the frequency estimation error of the All-phase FFT phase difference method is reduced to 10^-4. An SS-OCT system incorporating the ultra-small GRIN probe is developed and applied to micro-vibration detection experiments. The system successfully captures vibration signals from a 0.8 mm diameter micro-motor shaft, showing an increase in vibration amplitude from 2 μm to 6 μm after damage. Experimental results demonstrate a displacement resolution of 1 nm under optimal conditions. These findings highlight the potential of the ultra-small GRIN fiber probe-based SS-OCT system for detecting micro-mechanical damage and the effectiveness of the All-phase FFT spectral analysis phase difference method in improving the system's displacement resolution, enabling the fiber-optic SS-OCT system to maintain sub-nanometer-level measurement precision.