High Spatial Resolution Φ-OFDR Strain Sensing With Robust Phase Unwrapping Utilizing Adaptive Unscented Kalman Filter

This paper proposes a distributed strain sensing method based on phase-sensitive optical frequency domain reflectometry (Φ-OFDR), featuring high spatial resolution and measurement accuracy. A robust phase unwrapping method based on adaptive unscented Kalman filter (AUKF) and an all grating fiber (AGF) is proposed. High signal-to-noise ratio (SNR) wrapped phase is obtained through the AGF, and a mapping relationship is established between the covariance matrix of the Kalman filter and the corresponding signal intensity of the AGF, effectively suppressing the non-Gaussian phase noise in optical fibers. Additionally, Gaussian phase noise is further suppressed using wavelet packet denoising while preserving both spatial resolution and valid strain information. To validate the proposed scheme, a Φ-OFDR experimental setup is constructed. Experimental results demonstrate that, with a strain measurement range of 0-3000μϵ and a demodulation length of 0.8m, the spatial resolution reaches 602.97μm, and the measurement error is approximately 6.27μϵ.