Research On Key Technologies Of Relay And Switching For Hybrid Satellite Network Of Laser And Microwave

With the development of high-speed data communication,navigation and positioning,high-resolution image acquisition and deep space exploration,the demand for large-capacity information transmission of inter-satellite and satellite-to-ground is increasing,and the demand for various types of inter-satellite and satellite-to-ground data relay services is growing.On the basis of the original satellite microwave communication system,the laser communication technology is further used to establish a high-speed laser link between the data relay satellites,thus forming a hybrid laser/microwave satellite network,which has become an inevitable trend of the development of space information network in the future.As the key payload of data relay satellites,satellite transponders need to support the functions such as relaying and switching of multiple channels and different types of signals.Traditional satellite transponders are getting closer to the limit of electronic rate,which limits the further improvement of signal switching and processing rate.However,microwave photonics can effectively reduce the size,weight and power consumption of satellite transponders,and achieve large bandwidth and ultra-high speed switching and signal processing.Meanwhile,the microwave signal processing capability of satellite transponder can be improved by using its parallel processing characteristics,such as multi-frequency local oscillator distribution,low-damage frequency conversion of multi-channel signals and interconnections between beams.Therefore,the application of microwave photonics in the data relay system of the future laser/microwave hybrid networks has become an inevitable trend in the development of high-frequency,multi-beam and large-capacity satellite communication systems,which has important scientific significance and practical value.This dissertation is based on the national and international research status of the satellite laser/microwave hybrid networks.The key issues of switching system architecture,flexible bandwidth switching and on-board wavelength conversion,multi-channel frequency conversion,parallel transmission of high-speed links are investigated by the theoretical analyses,numerical simulations and experimental validations.The detailed contributions of this dissertation are listed as follows.(1)The system structure of satellite laser/microwave hybrid switching is designed,and the optimized strategy of flexible bandwidth allocation based on service distribution is proposed.Based on the simulation,the experimental system of on-board flexible bandwidth switching based on wavelength selective switch(WSS)is built.The experiment verifies the abilities of flexible spectrum allocation and bandwidth switching.The scheme can effectively improve the spectrum utilization of the network,and is suitable for flexible and efficient switching of different granularity services in future satellite laser/microwave hybrid network.(2)The scheme of all-optical wavelength conversion based on optical frequency comb is proposed,and the principle and technology of wavelength conversion are analyzed.The experimental system is established.The experimental results show that the system can realize the "point-to-multipoint" wavelength conversion and the wavelength allocation of the frequency slot level through the coordination of optical frequency comb and WSS,and the bit error rate of the baseband data transmitted by each channel is lower than 10-9.The proposed scheme can reduce the traffic congestion caused by the wavelength conflicts between nodes,thereby improving the transmission capacity of the inter-satellite optical links.(3)The parallel multi-band frequency conversion schemes based on the DSB-SC and the reconfigurable single optical frequency comb(OFC)are proposed.The principle of on-board frequency conversion is analyzed,and the structure of satellite transponder system suitable for future multi-band broadband satellites is designed.An on-board multi-band frequency conversion experiment system based on microwave photonics is established.The Ka-band signal is converted to other satellite bands as an example to verify the feasibility of the system.The output of the frequency conversion scheme is not limited by the wavelength division multiplexing(WDM)channels,and the parallel frequency conversion method reduces the power consumption and system complexity of the payload onboard.(4)The parallel data transmission technique for satellite-ground high-speed links is proposed.The synchronization control of four microwave signals is realized by adding synchronization information to parallel channels.The scheme is experimentally verified based on the FPGA hardware platform of the Virtex-6 series we developed.The original 5Gbps baseband data could be recovered at the receiving end,which verifies the synchronization of the four parallel data.Meanwhile,the high-speed optical transceiver array for space optical communication based on RocketIO is designed and developed,and the 6.25Gbps high-speed serial communication is realized,which has the characteristics of high integration,flexible debugging and good scalability.