| Today's era, has entered a high-speed development of the information era. People are getting bigger and bigger to each kind of information's demand,the image,the audio information,and relative,transmission signal's medium applies the transmission mode and the transmission facility also become the key research the object. Looking from the market development, the simulation means of communication has been gradually being replaced by digital, which is the development of modern communications technology trend. At present, most of the domestic digital fiber optic transmission equipment selects the advanced digital fiber optic transmission.Therefore, this design take highway's transportation monitoring as the application background, to has conducted the research to the multi-channel data transmission of the digital optical termination which take the optical fiber as transmission medium.As the background of this research projects and the current technological trends, this topic selects non-compressed digital fiber optic transmission equipment principle, and takes optical fiber as a transmission medium. In the transmission process of information uses the TDM multiplex mode, single-mode optical fiber transmission. In a variety of video, audio, data transmission process, by multi-channel two-way data transmission research primarily.The data design request completes the control of the two-way data transmission in a multi-channel fiber-optic. By the control room through the computer sends data and control signal, to control the various camera. At the same time, the computer may also communicate between the long-distance two points. The data transmission RS232/485 signal, the both sides can be used as the signal source, the data signal is two-way , a R +,T + input of the other side have the same signal output. Indicating lamp request: When RS232/485 data transmission, a lamp show.The data transmission is mainly through the computer issuing control command, including the photograph scope choice, the rotation and adjustment of the video camera hereunder supports ,and so on, these orders transmit from the computer to the transmitter of digital fiber optic transmission equipment , firstly, the level conversion of the multi-channel data signals carries on by transmitter's data processing module, the data is converted into integrated circuit interior available level, afterward compiles the multi-channel data, and then directly sends the date in the first multiplex unit and take the reorganization by the TDM multiplex technology, after finishing into the second multiplex module to carry on multiplexing, the low-speed signal is multiplexed into high-speed signal, the multiplexed high-speed serial code transforms after the electro-optical transformation module, electrical signal transforms into the light signal, afterward the signal is sent in the optical fiber to carry on the transmission.In the receiver, integrated optical transceiver module receives the light signal from the optical fiber transmission, and transforms the light signal into the serial electrical signal. Then sent the signal to first demultiplex module, the serial high speed data stream is changed into the low speed the data stream, and then sends it in the second demultiplex module to carry on the demultiplexing. Through the programmable logical component's procedure control, the demultiplexing unit isolates the each group data control signals from the serial signals, the programmable logic device will receive the multi-channel data signals , afterward sends in each road's data processing module again, we can obtains the control data after the level conversion and return to original data message which transmits. The data control information is mainly aims at the rotation and position of hereunder. The first chapter of this paper first introduces the optical fiber communication system development and the principle, introduces optical fiber transmission system's classification as well as this article topic background simply, and the research significance. The second chapter mainly introduces optical transmitter and optical receiver's principle framework of digital fiber optic transmission equipment, and describes the multi-channel data two-way transmission part principle of design with emphasis. The third chapter introduces the multi-channel two-way data transmission system each module specific transmission mode and circuit design in detail. Including the control terminal of transmission part and receiving unit's, the data processing module, the first multiplex module used of a programmable logic device, and the second multiplex module to complete the string conversion function ,the correspondence to demultiplex module, the electro-optical transformation module , the optical fiber which the transmission uses, and also describes the entire system power circuit's design. The fourth chapter key to carry on the detailed narration by the data processing module design which completes the level conversion, put forward two RS232/485 serial communication standard (optional). This part has mainly completes the serial data communications and the level conversion function, and proposes separately level conversion of several specific design of the RS-232 and RS-485 serial communication standard ,finally, according to the design request, the electric circuit cost and the practical application, has designated suited this system's preferred plan. The fifth chapter mainly describes the programming design of the programmable logical component (CPLD) in the first multiplex, a system clock control circuit and clock frequency design, the reasons for the vibration in the data transmission process , the design to eliminate the data vibration as well as the multiplex data simulation. Programs uses the VHDL language, the simulation software chooses Altera to provide the free Quartus II foundation version software, which bases on the procedures to debug, modify. The sixth chapter carry on the summary and the forecast of the work.This design's multi-channel data transmission signal's sampling frequency is 13.5MHz, the sampling encoding is 8bit, the transmission uses two types of data formats: RS-232/RS-485 (optional), through the built-in adjustment to meet the different projects at different of the demand, at the same time, supports video, audio and Ethernet signal's transmission expansion.This procedure of the design can be edit and changed by Quartus II , only modify the program online, then download it again to the CPLD chip which can be rewritten . Through the different modification of the procedure and the expansion of the circuit design ,this kind of design may also apply to other areas of fiber optic transmission.In addition, in the monitoring system, besides the essential requirements of large capacity and high speed, from practical application angle to develop the function of digital fiber optic transmission equipment configuration, and more humane, intelligent design becomes advantageous competitive condition. This is also the key point of the development direction of digital fiber optic transmission equipment and the focus of future research. |
PDF Full Text Request