Optical Antenna Design And Stray Light Research Based On Inter-Satellites Laser Communication Terminal

Inter-satellites laser communication is a crucial part of space laser communication network.The hundreds or even thousands of kilometers’ information transmission between satellites makes the energy of communication light finally reaching the receiving terminals extremely weak.On the other hand,the space environment of laser communication terminals on satellites is quite complicated,so when the stray light enters the communication terminals,it will significantly affect the tracking,acquisition and communication process.In order to achieve high quality laser communication between satellites,it is necessary to study optical antenna design and stray light suppression.The transceiver-style inter--satellites laser communication terminal has to consider not only the external stray light from the space environment,but also the internal stray light caused by optical antennas’ back-reflection of the transmitted beam which is different from other space optical systems.Therefore,this essay studies the following aspects on this premise:1)Compare and analyze a variety of typical optical antenna systems and finally decide to study the improved Cassegrain optical antenna and off-axis two-mirror optical antenna according to certain designing indicators.Then complete the optical design and image quality analysis of both two antennas through the Zemax software.2)Compare and analyze the characteristics of different external stray light sources according to the space environment in which the inter-satellites laser communication terminal is located.Then summarize the analysis model,the common suppression method and the evaluation function of the external stray light of space optical systems.A series of de-stray light structures are designed and the effect of eliminating stray light is analyzed through simulation experiment based on the improved Cassegrain antenna.3)In this essay,an optimized method to increase the isolation level of the optical antenna of inter-satellites laser communication system has been brought out.This method helps to reduce the back-reflection energy of each optical element surface of the system by increasing the YNI value.The result of the simulation experiment in Light Tools software verifies the effectiveness of this method.The calculation of the overall isolation level of a typical laser communication terminal also proves that it is the isolation level of the antenna which determines the isolation level of the terminal as a whole.The methods to calculate the signal-to-noise ratio of the communication unit’ detector in the IM/DD communication system and the coherent communication system are studied respectively.The variation trend of the signal-to-noise ratio under different isolation levels of the system is also analyzed which clarifies the important impact of isolation level on laser communication terminals.In this paper,the design of the optical antenna and the stray light suppression of the inter-satellites laser communication terminal are studied,which provide a valuable reference for practical engineering.