Research And Analysis On Stray Light And Suppression Methods Of Satellite Terminal In Satellite-to-groud Laser Communications

Satellite optical communication (SOC) is a long distance and weak signal communication which can establish information communication between satellites or satellite and the ground by adopting laser as the information carrier, the stray light which enters the detector of the system will causes system performance degradation. To enhance the tracking and aiming stability, and improve the communication quality, it is necessary to analyze the generation mechanism of the stray light, and study methods to reduce it. Focusing on the satellite terminals in satellite-to-ground laser communication, stray light theory of the satellite terminal was studied, and models were simulated, the main contents are as follows:1. Stray light theoretical model establishment. The optical environment of the satellite terminal in satellite-to-ground laser communication was analyzed, and the corresponding stray light theoretical models including the spatial stray light theoretical model and the internal stray light theoretical model were established. Considering the special role of the detectors in satellite terminal, the establishment of the evaluation function which adapted to the satellite terminals was done.2. Research on methods for stray light suppression. Based on the optical energy transfer equation, the basic ideas of the stray light suppressing in satellite terminal were introduced. According to the characteristics of the satellite terminal, the stray light suppression methods which are often used in satellite terminal were introduced, and the design principles and methods of common baffles were summarized. For the terminal which has a secondary mirror, a new method was put out to eliminate the problem caused by the block of the secondary mirror, and the model was established.3. The spatial stray light simulation. The baffles were designed for the satellite terminal, and the influences of the stray light suppression ability which ware related to the baffle parameters were studied by simulation. Then, the impacts of the solar radiation and the earth background radiation in different conditions ware simulated.4. The internal stray light simulation. Based on the internal stray light theoretical model, detailed calculations of the receiving stray light power of the detector under different conditions were done. And the methods were discussed to reduce internal stray light by choosing the system parameters.Research work of this paper would provide a theoretical basis to analyze the stray light in satellite terminal, and simulation would provide a reference for the baffle design. Moreover, it has important reference value for the development of high-performance satellite optical communication terminals.