Fig. 1. (a) Set-up schematic of typical OFDR distributed strain sensing system; Time and frequency representations of the corresponding beat signals at an arbitrary position along the fiber (b) when the light source is tuned ideally and (c) when the light source is tuned non-ideally

Fig. 2. Strain demodulation results when the light source is tuned ideally. (a) Distribution of wavelength offset along the fiber axis; (b) Variation curve of wavelength with strain

Fig. 3. Partial enlargement of the measured instantaneous frequency-time curve of the tunable laser source. Insert: the overall curve

Fig. 4. (a) The polynomial fitting effect of linear fitting error (R²) and root mean square error (RMSE) increasing with the degree of higher-order terms; (b) Fitting curve of phase noises

Fig. 5. (a) The influence of polynomial coefficient on the measurement error of strain; (b) The impact of increasing polynomial coefficients on position error and strain calculation error, respectively; (c) The variation of distributed strain measurement error with phase noises

Fig. 6. (a) The influence of random phase noises on the optical frequency measured by auxiliary interferometer; (b) b in Fig.(a); (c) c in Fig.(a)

Fig. 7. (a) The influence of random phase noises on strain measurement error; (b) The effect of increasing random phase noises on distributed strain measurement error

Fig. 8. The results of interpolation and secondary compensation in deep learning on the strain measurement

Fig. 9. The Unet model architecture