Design & Implementation Of The Intellective Digital Optic-Fiber Transmitting System

Optic fiber communication technology plays an important role in the modern society. There are a lot of signals transmitted in the optic fiber communication system, such as: video, audio, data, telephone or other user-defined signals. If one fiber transmites one signal, it will take a lot of money. It is necessary to take multiplexing in order to make use of optic fiber effectively and reduce the cost. This project takes TDM(Time-Division Multiplexing) to transmit three signals(vedio, audio, data) in one fiber.There are random long successive "0" or "1" in the stream of signal, which are not fit for the transmition of the optical channel. If no measures are taken, the serious basic-line-shift as well as the loss of chip clock and the difficulty of the data recovery will be introduced in the optical receiver, which causes the communication to go along abnormally. The usual way to solve this problem is to transform the original signal into "0" , "1" equally-distributing circuitry code type which is fit for the optical channel, and then transmit. In the receiver, such code flows are divided into groups and then decoded. Thus the original data is received. But anciently, it always takes hardwares to code. Thus, it not only increases the cost, but also bring difficulties to the realization of circuit.In the project, coding and decoding are realized in software.In the TDM system, it is an important technology to realize frame synchronization for that the communication goes along normally. The project should reduce the probability of lose synchronization and false synchronization and protect synchronization when realize frame synchronization. In the usual system, these are accomplished in hardware;but, these are completed in software in this project.Because of DSP's very high speed, the above functions are all completed by DSP. At the same time, the system can also communicate by programming if the speed of three signals are changed. So it reduces the cost of project and expands the range of application.