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When light propagates in the atmosphere, it will be absorbed and scattered by the atmospheric molecules and aerosols. Using a detector to collect the scattered light, a nonlineofsight (NLOS) optical information transmission system can be constructed. Its basic structure consists of an optical transmitting system and a receiving system. The light emitter emits modulated laser pulses into the atmosphere, and the light receiver collects the scattered light signal and converts it into electrical signal. In this transmission model, the optical impulse response of the receiver is a key parameter that affects the communication rate. Ultraviolet (UV) light has a short transmission distance in the atmosphere, so in the existing research, ultraviolet light source is usually used to realize shortrange NLOS communication system. Due to the short transmission distance, the impulse response performance of the receiver is usually analyzed under the assumption of uniform atmosphere distribution. But when the transmitting and receiving pitch angle are large, the signal scattering domain may be in a relatively large region, as a result the influence of nonuniform atmospheric distribution on signal transmission needs to be considered. In this paper, a MonteCarlo (MC) simulation program based on nonuniform transmission model is developed to simulate this NLOS transmission model, and the relationship between impulse response and pitch angle is studied. The results show that when the pitch angle is large the atmospheric molecular density and aerosol density will decrease with the increase of altitude, resulting in the decrease of absorption coefficient and scattering coefficient. By comparison, it is found that the uniform model overestimates the pulse response width and the pulse energy. Therefore, in the design of NLOS communication system, the nonuniform transmission model can provide more accurate analysis.
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