Fig. 1. Diagram of FSI ranging system

Fig. 2. Data processing process

Fig. 3. Diagram of equal optical frequency sampling. (a) Frequency-swept auxiliary interferometer signal; (b) rectified and frequency-doubled clock signal is used to resample the signal; (c) frequency-swept measuring interferometer signal; (d) final equal optical frequency interval sampling signal

Fig. 4. Diagram of extracting center frequency of the refined spectrum based on SFFT

Fig. 5. Process of refining spectrum of the resampled signal based on ZFFT

Fig. 6. Schematic diagram of the experimental device

Fig. 7. Experimental device. (a) Device for comparing the distance; (b) experimental optical beam path; (c) device for hardware resampling

Fig. 8. Effect of equal optical frequency sampling. (a) Spectrum of the signal without resampling; (b) software resampling and hardware resampling as well as their zoom-in spectra

Fig. 9. Comparison of spectra of FFT and SFFT with different sparsity degrees. (a) FFT spectrum; SFFT spectra with (b) k = 50, (c) k = 100, and (d) k = 200

Fig. 10. Computing time of FFT and SFFT with different sparsity degrees

Fig. 11. CZT spectrum and ZFFT spectrum as well as their zoom-in spectra

Fig. 12. Ranging residuals