Distributed Strain Sensing With Phase Unwrapping Error Suppression Based on Φ-OFDR

We propose a strain demodulation method with phase unwrapping error suppression based on phase-sensitive optical frequency domain reflectometer (Φ-OFDR), which can achieve wide measurement range, high spatial resolution and fast processing strain sensing. A phase unwrapping error suppression algorithm based on phase prediction is proposed, which detects and compensates the unexpected phase hopping through phase prediction, and replaces the outliers by interpolation. The algorithm is applicable for suppressing the phase unwrapping error with large strain, and does not degrade the spatial resolution. Position-deviation caused by strain accumulation and laser random tuning range is compensated, optimizing the demodulation performance under large strain and high spatial resolution. Experimental setup based on Φ-OFDR is established to validate the proposed scheme. All grating fiber (AGF) is utilized as fiber under test (FUT). When the strain measurement range is 0–2500 μϵ and the spatial resolution is 1 mm, the measurement error is approximately 17.32 μϵ. The processing time reaches approximately 0.063s with a demodulation length of 0.8 m.