Development Of Multi-Service Laser Communication Machine In Atmosphere

In recent years, the requirement of broadband multimedia service promotes the development of the communication network; light wave is considered as the best carrier, which has been proved by the development of optical communication. Compare with optical communication, the atmospheric laser communication is more suitable for broadband wireless attachment. In this paper, Video coding technique, telephone line transmission system and point-to-point communication are combined together to build a multi-service atmospheric laser communication system.State of development and basis principle of multi-service atmospheric laser communication are presented, and its features and applications are also illustrated in this thesis. We develop atmospheric laser communication equipment which has 20Mbps transmission rate and 1000m transmission distance in full-duplex mode. The system could achieve the bidirectional transiting of phone, data and image. The key technique, system architecture and basis principle of the equipment are demonstrated from the semiconductor laser modulation, the photo detection and communication terminal device. This thesis carried through the following aspects of study:1. Design and implement of laser transmitting subsystem. Laser's modulation principle and character are analyzed in detail, and the hardware circuit is designed. Then the optical mission antenna and Golay code are simply declared.2. Design and implement of photo electricity receiving subsystem. The choice of photo detector, optical signal detection and processing are firstly introduced. Then, the optical receiver antenna and decode operation are asserted respectively.3. Design of multi-service communication subsystem. The system consists of three parts: power module, synchronism module of different signal and encoding and transmitting of multi-service information module. Connecting to the telephone line transmission system, the compound interface between digital signal and voice was implemented in FPGA, and then 10 channels telephone switching are realized. Image compression technique employs MPEG-2. The system is rich in peripheral interface, including parallel port and serial port. Transmission of one channel data and binary channel MPEG-2 image are achieved.And the experiment results show that the system can implement the communication with stability. So its developing will play an important role in practical equipment's popularizing. At last, the theory and actual working are generalized, and furthermore, some problems should be studied and analyzed in-depth in future.