Research On Intersatellite Laser Communication System Based On Atomic Filtering Technology

Space laser communication is a communication method that uses laser as a carrier to transmit information in space.Compared with microwave communication,it has the characteristics of small size,light weight,low power consumption,high speed,and strong anti-interference ability.It is an inevitable trend in the development of current space data transmission technology.Due to the fact that China’s satellite ground stations can only be built domestically,it is necessary to carry out research on satellite laser network communication technology,especially high-speed laser communication from HEO satellites to GEO satellit,in order to ensure real-time and high-speed transmission of global satellite data in China.In order to achieve uplink laser communication from low orbit to high orbit,a new architecture of high orbit wide field of view "one receive multiple" space laser communication based on atomic filter technology is proposed in this paper.This architecture uses atomic filtering technology to achieve high background light suppression during Wide-Field-of-View reception,easing the contradiction in the design of laser beam divergence indicators in laser communication:high reception signal-to-noise ratio requires reducing the beam divergence angle,making the emitted laser energy as concentrated as possible;Reliable chain building requires increasing the beam divergence angle to achieve stable and fast search acquisition and tracking control during the communication chain building process.In this paper,a Wide-Field-of-View "one receive multiple" inter satellite laser communication channel model is established,and a stable frequency of atomic internal energy level transitions is proposed to achieve ultra narrow band filtering to achieve high background light suppression capability in a wide field of view staring state.At the same time,carry out the scheme design of the corresponding wavelength single frequency laser.The relative motion between high and low orbit satellites causes a Doppler frequency shift in the laser signal.When a ultra narrow band atomic filter is used at the receiving end,the Doppler frequency shift will cause the main frequency of the laser signal to shift out of the pass band range of the filter.In response to this problem,this paper proposes two working strategies:a pass band splice using a multi atomic filter at the receiving end and a direct communication using a single atomic filter at the receiving end,which can effectively solve the Doppler frequency shift and compensation problems in the communication process,and can simultaneously achieve laser communication from multiple low orbit satellites to a high orbit satellite,improving communication capabilities.The biggest feature of a Wide-Field-of-View ’one receive multiple’ laser communication system based on atomic filtering is that the Wide-Field-of-View receiver directly faces the strong background light of the Earth.In order to quantitatively calculate the background light intensity,this paper proposes a background light radiation brightness model under Wide-Field-of-View.The Borang body model and the wavelet surface model are used to model the land and ocean background light radiation brightness within the field of view,respectively.Through this model,the regularity of the spatial background light radiation brightness changing periodically with time is revealed.A study on the signal-to-noise ratio of the receiver has been carried out.The calculation results show that the signal-to-noise ratio of the "one receive multiple" receiver is superior to 22dB at a selected 766nm operating wavelength and a low orbit laser emission power of 10W.Potassium atom filter is a key component of a Wide-Field-of-View ’one receive multiple’ laser communication system.This paper focuses on the transition process of potassium atom 4²P_3/2→4²S_1/2.Based on the study of the basic theories of atomic filtering such as the ultra-fine energy level of alkali metal atoms,Zeeman effect,anomalous dispersion,and Faraday rotation effect,a theoretical calculation model for the transmission spectrum of potassium atomic filters was established,and the transmission characteristics of the filters,such as transmission frequency band and wide field of view reception,were analyzed.At the same time,a potassium atom filter has been developed,and the theoretical calculation model for the transmission spectrum of the potassium atom filter has been verified by measured data.The proposed ’one receive multiple’ space laser communication system architecture based on potassium atom filtering technology solves the core problem of strong background light interference in wide field of view angle receiving systems.It also has a simple and stable system,and has the ability to simultaneously communicate with multiple low orbit satellites to a high orbit satellite All optical data communication networks and other key technologies in high orbit laser communication systems have very important theoretical and practical significance.