Ethernet Passive Optical Network Based On Nios Onu Design

Ethernet Passive Optical Network (EPON) which combines the advantage of PON technology and Ethernet Network technology has become the best choice of optical access network for its advantages such as large bandwidth, low cost, easy to use and easy to upgrade. Recently the fact that the cost of single user is too high has become one main reason to the problem that the commercial extent of FTTH is not quite high. Optical Network Unite (ONU), one of the key components of EPON, is located beside the user and almost costs 80% of the whole expenses of FTTH. Thus, the research of low cost ONU is quite important to realize the FTTH.A novel scheme to realize the ONU is presented in this paper. This scheme is based on the embedded technology. In this scheme, a SOPC (system on programmable chip) can be constructed by integrating NIOS, custom logic, memory and I/O into a chip of low-cost FPGA to realize the function of the ONU in EPON. This scheme can decrease the time to integrate the components to system. Compared to the schemes using the PowerPC or ARM processor, this scheme can decrease the cost about 50%, has much lower consumption and is much steady for the high speed processing. Besides, in this scheme, the speciality and cost of ONU embedded system can be adjusted in accordance with the need, thus the product can be more quickly pushed into the market and the loss due to the renewal of the processor can be avoided. The main works are as follows:1) The principle of the system composing of EPON and the work principle of ONU in EPON is investigated. The whole scheme to realize the ONU based on the SOPC is proposed in detail.2) The core of the hardware system is realized using one FPGA and Verilog HDL is used as the hardware description language. The hardware system of ONU is composed of preliminary synchronization module, encrypt/decrypt module, FCS module and data transfer module. By SOPC builder, these components and NIOS can be hung to the Avalon switch bus to make a whole SOPC system. 3) The software system is developed in NIOSII IDE and the develop language is C. The software system is composed of three components: the development of the drivers of data transfer module, the development of OAM control frame application programs and the development of MPCP control frame application programs.4) The configuration files are downloaded into FPGA and then the application programs are downloaded into the extended flash by flash programmer. Thus a full ONU system is built and then tested by software/hardware cooperation simulation. The test results indicate that this ONU we designed can be used in the EPON.