Design Of A Digital Optical Terminal Based

Monitoring system with digital optical terminal as the main part is essential to the forest fire prevention system. This research is part of a forest fire monitor project from Little-Jingling corporation, and is also applicable to such safety protection as expressway electromechanical project, urban traffic and security monitor, urban rail transport, power plant, water conservancy, oilfield, mine, and so on.The characteristics of field forest fire prevention system are the great temperature and humidity variation and heavy fog and the hard enviroment and restricting supply. According to images, sound, control data and network of general forest fire prevention system, a digital optical terminal system is designed using FPGA as the control centre, using Verilog HDL as the program language, using Quartusâ…¡as the compile environment, using ModelSim as the simulation interface, and present a basis for intelligent monitor. The system adopts Cyclone series,the high cost-performmance of FPGA as the controller. Hardware of the digital optical terminal is mainly composed of optical relay, optical transmitter, optical receiver. In the optical transmitter, LD or LED is used as the light source, video and audeo signals from the ADC is modulated by direct ditection communication system. PLL theory,TDM technique of uncompressed multichannel digital video and audio signals transmission and electric to optical conversion is realized upon HDMP-1022(Tx). Control data from optical receiver is received by the signal reduction in the optical transmitter. Optical receiver uses APD as optical detector, mainly receiving signals and datas from optical transmitter, and demultiplexing technique and optical to electic conversion is realised by HDMP-1024(Rx), and the analog signal is reduced and transferred, and control signals are converted to optical signals and sent to optical fiber network.The actual debugging verifies that signal distortion is small, and the transmission is stable, and the error detecting ability is strong, and it is a good real-time transmission effect and high performance-price ratio. All these proves the system is safe and reliable, can meet the need of forest fire prevention system.