The Design Of Atmospheric Laser Video Transmission System And Research Of Polarization Modulation

Atmospheric laser communication is a new communication technology developed quickly in recent30years, which uses a laser beam as a carrier to transmit information in space. The communication technology is the combination of microwave communication technology and optical fiber communication technology, which features larger transmission capacity, construction flexible,better secrecy, without the authorization license and smaller device size, so that it has broad prospects in the ground station communication.By taking advantage of laser communication, such as high-speed and linear directional propagation characteristics, we design and implement a suit of atmospheric laser video transmission system based on OOK modulation/direct detection.In the existing optical system and tracking&pointing system basis, the system can realize long-distance and high-bandwidth digital video real-time transmission. The hardware circuit of the system mainly realizes the level conversion, serial/parallel conversion, the FPGA configuration and reset, the laser transceiver control and signal processing and we achieve data synchronization, video data cache and median filtering in FPGA chip through the Verilog hardware description language.In view of laser polarization characteristic having stability in the space transmission, the paper also discusses the polarization modulation mode. We introduce principle of the polarization modulation and four kind of commonly used intensity modulation, meanwhile, show the polarization modulation has superiority in bandwidth utilization rate and bit error ratio through the performance comparison. The use of OptiSystem simulation software to build the line polarization modulation system model, the communication performance and sensitivity are analyzed and simulated.