Research On Video Surveillance System Based On Transmission Of Optical Fiber

Due to its broad scope of application, video surveillance system has attracted attention for many years. Video surveillance has the characteristics of intuition, convenience and abundant information. Since the technology of digital communication and optical fiber communication is developing very fast, the quantity of transmitted information becomes more and more large and the video surveillance system also evolves from single channel to multi-channel. The techniques changes from analog to digital.By using the technology of digital optical fiber communication, the design is to make four channels of video signal to transmit at the same time. Meantime it can achieve audio and data transmission for multi-service data transmission. As the fiber has the broad bandwidth, we can realize the gigabits of data transmission in a single optical fiber. The system makes uses of the technologies of TDMA, CIMT-coding and PECL AC-coupled to realize the multi-service data transmission. The design adopts twice multiplexing method. At the transmitter, at first, the multi-channel of the video and audio signals is converted to digital signals from analogy signals, and RS-232/RS-485 signals are converted into TTL signals. Then these signals are all suitable for data transmission. After that, CPLD device completes the first multiplexing, and multiplexing signal is sent to TX chip. TX chip not only achieves the second multiplexing to convert the input 16bit parallel digital signal into PECL differential serial data, but also encode the data stream into CIMT code. The PECL electrical signal is then converted into optical signal by the optical transceiver. Finally the optical signal is sent into the optical fiber. At receiver, the optical transceiver transforms the received optical signal into electrical signal. Then the electrical signal gets to the RX chip. RX chip not only achieves the first demultiplexing, but also decodes the input serial data stream and recovers data clock. The demultiplexing signal and recovered clock is sent to CPLD device. The CPLD device achieves the second demultiplexing and separates the digital video, audio, data signal. Finally the digital video and audio signal is transformed into analogy signal by D/A device, the data signal is converted into RS-232/RS-485 signal.The first chapter of the thesis introduces the principles and virtues of the optical fiber communication and indicates the significance of the research. The second chapter first illuminates the whole frame of video surveillance system, and then introduces the basic theories of the video signal. The third chapter gives a detailed description of every part of the system. We use the high speed device AD9280 and AD9708 for video A/D or D/A conversion and MAX232/485 for electrical level conversion. CPLD chip is EPM570 of MaxⅡdevice the Altera company produces.TX and RX chip is a pair of transceiver chip which is produced by Agilent company. Because the transmission speed of the system is up to gigabits, we utilize the PECL AC-coupled technology to ensure the reliability of data transmission in the system. The fourth chapter indicates the results of the experiment and the designed circuit board works well. The last chapter gives a summary and expectation of the system.This video surveillance system adopts the optical fiber as transmission medium. With the fast development of the optical fiber communication, the digital optical terminal has a more and more broad application. The digital optical terminal we designed is applied in the high -speed road surveillance system. In other situation, we can expand the function on the basis of the digital optical terminal. As the Internet technology is developing very fast, the research and design of the video surveillance system based on Web technology has a significant of advantage. This is the next research direction.