Fig. 1. Schematic diagram of Raman scattering principle

Fig. 2. Structure schematic of laser radar system

Fig. 3. Schematic diagram of multiple-beam interference principle

Fig. 4. Schematic diagram of polychromator. OF, optical fiber; L1–L5 ,lenses; IF1a–IF4,interference filters; ND, neutral density attenuator; PMT1–PMT4, photomultiplier tubes for detection of the elastic, low- and high-quantum-number rotational Raman and N₂ vibrational–rotational Raman signals, respectively^[24]

Fig. 5. Splitting and filtering optical path of rotating Raman lidar. OF, optical fiber; L, Lens; IF1a-IF2, interference filter; Nd, neutral density attenuator; PMT photomultiplier^[29]

Fig. 6. Schematic diagram of Fabry-Perot interferometer. S1, light source; L1-L2, lens; G1-G2, parallel glass plate; S2, light screen

Fig. 7. Optical layout of single-line-extracted PRR lidar proposed by Wuhan University for measuring atmospheric temperature and aerosol optical properties. BS, beam splitter; L, lens; IF, interference filter; FPI, Fabry-Perot interferometer; PMT, photo-multiplier tube^[35]

Fig. 8. Schematic diagram of grating structure. i， are incident and reflection angles, respectively. d is the grating constant 光栅结构原理示意图。i， 分别是入射角和反射角，d为光栅常数

Fig. 9. Double diffraction grating monochromator structure. PMT, photomultiplier tube^[39]

Fig. 10. Schematic diagram of the double grating monochromator independently designed by the Beijing Institute of Technology. Two luminous gratings on the left working in the band of 532 nm under the Elitro incident condition^[44]

Fig. 11. All-fiber splitter system. FC01, fiber coupler; FBG, Bragg grating; signal output S_R12, S_R21 to photoelectric detector^[50]

Fig. 12. Schematic diagram of the Raman spectroscopic optical path of the all-fiber with a high suppression rate composed of SFBG and FBG cascades^[52]