Fig. 1. Spectral intensity and coverage band comparison of different sources

Fig. 2. Photosignal and frequency of LDLS

Fig. 3. Optical path of near-infrared Fourier transform spectrometer

Fig. 4. Near-infrared Fourier transform spectrometer system
(a): Light source high-frequency modulated by using chopper; (b): LDLS system

Fig. 5. Detector background noise without light signal input

Fig. 6. The spectral comparison results with different integration times of the lock-in amplifier
(a): Integration time=20 ms; (b): Integration time=10 ms; (c): Integration time=5 ms;(d): Integration time=1 ms; (e): Integration time=0.5 ms; (f): SNR_I vs integration time

Fig. 7. Fourier transform interference spectral results with LDLS
(a): Without demodulation; (b): With demodulation

Fig. 8. Spectral SNR_I before and after replacing the light source

Fig. 9. The near-infrared standard sample absorption spectra measured with LDLS Fourier transform spectral system
(a): Fourier transformation spectra with and without standard sample; (b): near-infrared Fourier transformation spectra with background removed