Fig. 1. Experimental setup for calibration tests

Fig. 2. Diagram of 2D spectra acquired by HRS. (a) ThAr; (b) FPE

Fig. 3. Flow chart describing the principle of wavelength calibration by FPE

Fig. 4. Refractive index of HPFS 7980 fused silica varying with the wavelength

Fig. 5. Optical path compensation function fitting, which is derived from the measured 2D spectra of FPE and ThAr shown in Fig. 2. (a) Data and the fitted curve. The arrow and the big point show an example of the wavelength of an FPE transmission peak is corrected; (b) residuals in fitting

Fig. 6. Residuals between the wavelength of spectral lines and the wavelength calculated by wavelength solutions, which are derived from the measured 2D spectra of FPE and ThAr shown in Fig. 2. (a) Residuals for spectral lines with different wavelength; (b) histogram showing the distribution of residuals

Fig. 7. Residuals between the locked wavelength of LFC spectral lines and the wavelength calculated by wavelength solutions, which are derived from the measured 2D spectra of FPE and ThAr shown in Fig. 2

Fig. 8. Optical path compensation functions for different (m₀,d₀) degenerate solutions

Fig. 9. FPE wavelength solution for S_-2 minus that for S₀ and FPE wavelength solution for S₊₂ minus that for S₀