Fig. 1. Schematic of strain demodulation of OFDR system based on image processing

Fig. 2. Positional mismatch in OFDR distributed strain sensing system. (a) Positional mismatch phenomenon; (b) small strain demodulation result; (c) medium strain demodulation result; (d) large strain demodulation result

Fig. 3. Flowchart of position self-correction algorithm

Fig. 4. Gaussian image filtering with non-uniform convolution kernel

Fig. 5. Experimental setup based on OFDR for distributed strain sensing

Fig. 6. Demodulation results when the strain is 2000‒8000 με. (a) Cross-correlation algorithm demodulation result; (b) position self-correction algorithm demodulation result

Fig. 7. 2D demodulation results at 8000με. (a) Cross-correlation algorithm demodulation result; (b) position self-correction algorithm demodulation result

Fig. 8. Different Gaussian filter kernels and their denoising results at 8000με. (a)(b)(c) Weight distribution of different Gaussian filter kernels; (d) transverse Gaussian filter kernel denoising result; (e) uniform Gaussian filter kernel denoising result; (f) longitudinal Gaussian filter kernel denoising result

Fig. 9. Non-uniform Gaussian image filtering denoising results. (a) 2000‒8000 με demodulation results; (b) linear relationship between wavelength shift and strain from 2000 με to 8000 με