Research On Channel Characteristics Of Uplink Blue-green Laser Communication

The influences of sea and air on blue-green uplink laser communication are analyzed emphatically, and the characteristics of laser transmission upward through the random undulate sea surface caused by wind waves are studied deeply. Based on the existing studies of sea wave spectrum and the mathematical models of random sea waves, the fluctuation in waves and feature parameters of the sea surface are simulated, and the sea wave model is used for analyzing effects of the random undulation of sea surface to uplink laser communication for the first time. According to the thought of beam division, the complex problem that beam propagation through stochastic fluctuant sea is simplified to a simple problem that ray with certain direction goes through an inclined surface with certain tilt angle. By the tank experiment, combining the model of random fluctuant surface with Snell's Law, specific parameters of the spot formed at the receiver plane after beam going through the stochastic fluctuant sea surface and a long distance of atmosphere are analyzed and calculated. By theoretical analysis and computer simulation, the author finds out that the influences of sea's random undulation lie on the relative scale of spot formed at the sea surface. Beam wanders in a limited area with the fluctuation of sea surface constantly, that behave as random scanning. Cooperated with effective scanning mechanism, quality of communication can be ensured. Also the random undulation of the sea surface aggravates the asymmetry of uplink and downlink. The refractive index of air distributes unevenly, so beam will be curved and deviate from the initial position during propagation through the atmosphere. According to the model of air index and analysis of beam offset, parameters of spot formed at the receiver plane can be amended in theory. In the paper theoretical analysis and computer simulation are discussed, combining with practical experiments, many important conclusions are educed, which have great significance in research on uplink laser communication and design of operational system.