The Study And Design On Wireless Laser Communication System With USB Interface

With the development of technologies on wireless laser communication, the application of laser becomes more and more popular. Meanwhile the laser has been the reliant carrier, accepted as a method of access in wireless Broad Band, and the magisterial technology in resolving "last mile" problem as a new method. Conventional method of microwave is licensed by the frequency of broadcasting station. Fiber network is so expensive and complexity, and it is not suitable for temp network. The paper put forward a method of wireless laser communication system based on the interface of USB with the semiconductor LD.The paper combines the advantages of laser communication and the interface of USB. First introduce the protocol and communication standard of interface of USB, put forward a new method of wireless communication, which use the interface to settle the task of remote wireless laser communication. The circuit is easy to fix and speeding in transferring with little resource in host, special to the situation of temporarily network in war, shopping mart and office block using lots of connection without much money and time, or the instance limited by nature condition. The design is including circuit of interface, compiling the program of AN2131Q, compiling USB device driver and Windows application program.Then the paper puts forward a driver and modulator for circuit of LD, which can work steady in wireless communication. The circuit chooses the cosmically integration chip to make the design simple, practicality and low cost with high capability. Then give the characteristic of atmosphere channel, This paper mainly discuss the influence on the laser transmission for its stochastic behavior, analyze the scatter , absorption and turbulence of atmosphere channel, and calculate the atmosphere attenuation ratio by visible, with theorem of channel coding, we discuss the style of code in transmission, especially RS coding, inducing the way and gist to choose the length and ratio of code suitable for atmosphere channel, and discuss the shape of burble laser beam in lots of experiments. Bringing up a new opinion in judging the facular center of interferential stripes in experiment. We provide some reference for later coding and decoding and PAT system. At last we give some data and images and we give some advice for the future work.