Fig. 1. Experimental setup of off-axis integrated cavity output spectrum

Fig. 2. Transmission light intensity through off-axis integrated cavity. (a) Positive axis incidence; (b) off-axis incidence; (c) signal after 100 times average

Fig. 3. (a) Absorption spectra of water vapor at different partial pressures; (b) relationship between water vapor partial pressure and integrated absorption

Fig. 4. Fitting diagrams of absorption coefficient of water vapor. (a) Experimental data and fitting line; (b) fitting residual error

Fig. 5. Comparison of measured concentration and known concentration

Fig. 6. Variation of water vapor concentration with the injection of nitrogen with different flows

Fig. 7. Variation of water vapor concentration