Fig. 1. Principle of distance measurement of multi wavelength heterodyne interference based on dual-optical frequency comb^[19]

Fig. 2. Schematic diagram of the spectrum of a heterodyne dual-optical frequency comb^[19]

Fig. 3. Variation curve of distance measurement uncertainty with m for different phase measurement uncertainty

Fig. 4. Variation curve of distance measurement uncertainty with m at different repetition frequencies

Fig. 5. Variation curve of uncertainty of distance measurement with uncertainty of repetition frequency of signal optical frequency comb under different distances to be measured

Fig. 6. Variation curve of the distance measurement uncertainty with the phase measurement uncertainty when different fine synthetic wavelengths

Fig. 7. Variation curve of distance measurement uncertainty with synthetic wavelength m for different methods

Fig. 8. Variation curve of distance measurement uncertainty with temperature for different methods

Fig. 9. Variation curve of distance measurement uncertainty with pressure for different methods

Fig. 10. Variation curve of measurement uncertainty with carbon dioxide volume fraction by different methods