Research On Application Of OTDM In Railway Section Optical Fiber Communication System

Optical fiber communication system used in railway section can increase the system bandwidth greatly and the advantage of optical fiber can prevent electromagnetic interference causing higher quality communication. With the price of copper rising quickly, optical fiber instead of copper has become a trend. Therefore, under the premise of meeting the demand, it has practical significance to research a railway section optical fiber communication system.According to the requirement of section telephone in the railway section communication specification, a new communication system is proposed in this paper, which is based on optical time division multiplexing technology and passive optical network structure. Several key problems in the hardware design have been researched and resolved, the main work is as follows:1. According to the structure of passive optical interface, considering the influences of various factors in the actual fiber transmission fully, a power equalization design is made for optical fiber link. In accordance with the requirements for optical power equalization, the best splitter configuration scheme of each node is given via optimizing the design. It can make the least types of splitter and help to reduce the cost.2. Some circuits, including the synchronous clock recovery circuit, the multiplexing circuit, the demultiplexing circuit and the protocol processing circuit, are designed. Synchronous clock recovery circuit can get the reference clock information from the received signal and generate the synchronous clock to solve the optical synchronization among several passive optical interfaces. Multiplex circuit can send signal to the corresponding time slot in the optical domain via timing control. Demultiplexing circuit can demultiplex the required data from the received signal. Protocol processing circuit can make CPLD chip to communicate with external MCU, so that the system has an automatic control mechanism.3. The core circuits of the main console, the deputy console and the terminal are designed based on the four functional circuits, in which the main console and the deputy console are the station equipments, terminal is the equipment between stations. A section communication system is built based on these and a series of experiments were did in accordance with the specifications, then the experimental results were given. Finally the field test was did between Jinmacun station and Yangtianchong station on the Shanghai-Kunming line, the results demonstrate the feasibility of the program.