Study On Temporal Propagation Characteristics Of Ultrashort Space-time Gaussian Pulses In A Laser Satellite Communication System

Simple analytic expressions are derived for the temporal broadening and scintillations of a narrowband, space-time Gaussian pulse propagating through clear-air weak atmospheric turbulence in a laser satellite communication system. The temporal broadening is deduced from the 1 e 2 point of the temporal mean intensity and calculation of the temporal scintillations involves the second moment of intensity. Integral representations for the first and second moment of intensity are obtained by means of the two-frequency mutual coherence function and four-frequency cross-coherence function, respectively. The integrals, which are present with the modified Von Karman spectrum model for the refractive-index fluctuations and the Hufnagel-Valley turbulence profile mode are analyzed. Numerical implementations are given for both upper atmosphere UAV-UAV cross-links (near field) and uplink/downlink communication propagation paths (far field). The temporal pulse broadening and temporal scintillation of propagation in the far-field horizontal and slant path are discussed when the height is constant or variable. The impact of the strength of turbulence, the outer scale, the initial pulsewidth, the beam radius of the transmitted beam, the zenith angle, the inner scale and the optical wave length on temporal broadening and temporal scintillation index is investigated in detail. The comparison and validation of the numerical results are presented, which show that the critical parameters affecting the broadening and scintillations are the strength of atmospheric turbulence, the outer scale and the pulsewidth of the transmitted pulse.