Study On The Optical System Design And Its Polarization Characteristics Of Space Laser Communication

The technologies of space laser communication uses laser as the information transmission carrier,which has the advantages of good confidentiality,large capacity and high speed.Its detection methods include amplitude detection and coherent detection,and the latter has high detection sensitivity and large transmission capacity,which is the research hotspot of remote laser communication.Conventional laser communication systems are mostly single detection system,which is not flexible and cannot meet the needs of multi-band space communication.Using combinations of different detection systems can solve this problem,but it will greatly increase the volume and cost of the terminal system,which is difficult to apply.Therefore,an integrated design of the terminal is the best solution to this problem.As the core component of the integrated receiving system,the terminal optical system directly determines the transceiver performance of the communication system,which must have the characteristics of good image quality and compact structure.In the coherent communication optical system,due to the use of circularly polarized light as signal light,in addition to the requirement of small wave aberration,the optical system is also required to have good polarization maintaining ability,so as to ensure the communication performance of the system.In this paper,the optical system of laser communication based on multi band composite detection system is designed,and its polarization characteristics are analyzed,mainly includes the following contents:First of all,by investigating the domestic and foreign development status of laser communication terminal systems and consulting related materials,the laser communication optical system of the multi-band composite detection system is proposed in this paper.The current research status of the polarization characteristics of the coherent communication system is introduced,the deficiencies of the current research are pointed out,and the main problems to be analyzed in this paper are put forward.Secondly,according to the actual design requirements,the initial structure calculation of the laser emission structure was carried out,and the optical simulation software ZEMAX was used to further optimize the structure;the beacon light and signal light receiving systems are optimized respectively,and the integrated design of the three-way receiving system is completed by using the repeater splitter.The results show that the transmitting system has a good collimation effect;the receiving system has concentrated energy and good image quality,and the MTF is close to the diffraction limit,realizing the system's multi-band compound detection requirements.Then the optical system is tested and its performance is analyzed.The test and analysis results show that the terminal has excellent comprehensive performance,which can meet the demands of short and medium range communication of the system.Finally,based on the optical system of laser communication designed in this paper and the three-dimensional polarization ray tracing algorithm,the polarization characteristics of the orthogonal reflectors in the system are simulated and quantitatively analyzed,and the analytical expression of polarization transmission of the system is derived.In the case of incident circularly polarized light,the polarization state of the outgoing beam is calculated and simulated.The influence of the scanning motion of the galvanometer on the polarization characteristics of the orthogonal mirror is studied and analyzed,and the effective measures to reduce the polarization error of the system are proposed.The polarization compensation scheme during the practical application of the system is given.