Research And Hardware Design Of GPON ONU System

With the development of communication technology, backbone network and local area network have made enormous development. However, the access network which connects the subscribers and backbone network has become the bottleneck of the information highway. In the field of wired solutions, passive optical network (PON) has good market prospects because of its bandwith capacity. As a broadband access network with the purpose of achieving full service access, GPON has greater advantage in bandwith capacity, security and manageability compared to other PON technologies. GPON has been considered as one of the best solution to the broadband access network.As the core module of GPON system oriented users, the implementation technology and cost of ONU affect the affordability of users directly, and also affect the development and application prospects of GPON technology, so it is meaningful to study ONU system.First of all, this paper summarizes the status quo and development trends of broadband access network, introduces the development history of PON, then compares of three PON technologies and points out technical advantages and development prospects of GPON. Secondly, this paper introduces the GPON optical access system specified by ITU-T G.984, analyses the network structure and layerd model of GPON system, then discusses each layer's function, working principle and key technologies of GPON system. The most important port of this paper is hardware design and implementation of ONU system. Combined with the network layered structure and each layer's functions of ONU, the hardware design scheme of ONU based on FPGA and MPU is proposed. The ONU system constitutes of four parts: Physical Media Dependent (PMD) layer, GTC layer, User Interface and Management Control plane. According to market research, selects the most appropriate device, elaborates the function of each module and the application circuit, then analyses the design principle of high-speed differentical interface interconnection, completes schematic and PCB design of ONU system with OrCAD and Allegro. Combined the practial experience gained from this project, a few notes of PCB design are summarized, and the key signals of ONU system are simulated by signal integrity simulation tool-SpecctraQuest. At the last of this paper, the debugging process of ONU system is analysed.