Research On Modeling And Noise Suppression Methods For Inter-Satellite Laser Channels

The improvement of inter-satellite laser communication network not only relies on the continuous advancement of laser communication node technology but also on a deep understanding of inter-satellite communication channels.The satellites in orbit are very vulnerable to the interference of complex environment,such as sun outage,Doppler frequency shift and platform random vibration,which severely impact the communication quality.In the thesis,a dynamic theoretical model of the laser inter-satellite link is established,based on this model,the effects of sun outage,Doppler frequency shift and vibration on the communication quality are further analyzed,and a corresponding experimental verification system is established.In response to the issue of degraded signals,the methods of using semiconductor optical amplifier(SOA)for all-optical regeneration and neural network(NN)algorithm are proposed to enhance signal quality,the feasibility of the two noise suppression approaches is demonstrated through of simulation and experiment,respectively.The research contents and innovation points of the thesis are summarized as follows:1.A simulation platform is established to construct an inter-satellite laser channel model,and the effects of sun outage,Doppler frequency shift and vibration communication quality of inter-satellite laser are discussed.Based on the simulation,a ground experimental verification system is established to quantify the degradation level of the coherent communication quality caused by sun outage,Doppler frequency shift,and vibration.2.An all-optical regeneration method is proposed to suppress the noise caused by sun outage in the optical domain,unlike the traditional methods that use physical devices such as shading masks and filter films.Both simulation and experimental platforms are established to investigate the impact of changes in pump-to-signal power ratio(PSR),regenerator current,and the elevation angle on the performance of noise suppression.The results confirm that the all-optical regeneration scheme can suppress the noise and improve the signal quality for all elevation angles.When the elevation angle is 0rad,that is when the sun outage intensity is maximum,the signal-to-noise ratio(SNR)can be improved by 3.5d B.3.An echo state network(ESN)based on recurrent neural network(RNN)is proposed to compensate for the inter-satellite signal damaged by the simultaneous effects of sun outage,Doppler frequency shift and vibration.By optimizing parameters such as the number of hidden layer neurons and the length of training data,the SNR after noise suppression can be increased by 5.6d B,which verifies the effectiveness of the NN compensation algorithm processing scheme in the inter-satellite communication system.