Experimental Measurement And Spaceborne Environmental Simulation Analysis Of All-fiber Spectrophotometric Temperature Lidar

As an important parameter describing the state of the atmosphere,atmospheric temperature reflects the degree of cold and warm air,which plays a key role in climate change,air pollution research and early warning of extreme weather.As an active remote sensing method,lidar is widely used in atmospheric temperature measurement because of its high spatial an d temporal resolution and long-term observation.The traditional rotational Raman temperature-measuring lidar system is large in size and difficult to adjust.It is difficult to be applied to spaceborne lidar.Fiber Bragg grating(FBG)makes up for the above shortcomings.Therefore,the research of all-fiber spectrophotometric rotational Raman temperature measurement lidar is carried out,which provides a way for the spaceborne lidar to effectively detect the atmospheric temperature profile.Based on the detection principle of rotational Raman temperature lidar,a 532.2nm pulsed laser is used as the light source to cdesign an all-fiber spectrophotometric lidar.The system uses fiber Bragg grating as the core spectrophotometric device,and uses the two-stage spectrophotometric structure to extract high and low quantum channel signals with center wavelength of 529.16nm(rotation quantum number J=14)and 530.96nm(rotation quantum number J=6).The inhibition rate of the Rayleigh scattering signal 10-7.The night experiment results show that the system can detect atmospheric temperature below 800m,and the system is effective and feasible.In the experiment,the echo signal received by the telescope is coupled to the spectrophotometric system through a multimode fiber.The spectrophotometric device of the spectrophotometric system is a fiber Bragg grating,which is fabricated on the basis of a single mode fiber.Since the diameter of the multimode fiber and the single mode fiber are greatly different,there is a problem of low coupling efficiency,and it is proposed to use a photonic lantern to improve the coupling efficiency.The photon lantern is a low-loss device connecting a single multimode waveguide and multiple single-mode waveguides.Three different photonic lanterns are simulated by optical design software.The results show that the photonic lantern can effectively improve the coupling efficiency,among which three single-mode fiber equilateral triangles The total coupling efficiency of the arranged photon lanterns is 2.27%,The use of photonic lanterns as a spectroscopic system for coupling devices can effectively improve the system signal-to-noise.As a spaceborne instrument,the all-fiber spectroscopic system will experience the random vibration environment during transportation,the acceleration environment during launch,the sinusoidal vibration environment during on-orbit operation,and the impact environment during landing.The stability of the all-fiber spectroscopic system is verified by finite element analysis from frequency,acceleration,shock,random vibration and sinusoidal vibration.The results show that the natural frequency of the all-fiber spectroscopic system is much larger than the normal operating frequency of the satellite and will not resonate with the spectroscopic system,after the acceleration,impact,random vibration and sinusoidal vibration excitation are applied,the stress and displacement will not be generated.The structure of the spectroscopic system is damaged,and the cantilever beam is not permanently deformed,and the normal operation of the spectroscopic system is not affected,and the spectroscopic system has good stability.