The Study And Implementation Of The Function Of OAM Sublayer In EPON

EPON is one of the best technologies to realize broadband access and multi-service access in future. In this article, OAM, the sub-layer of EPON, is deeply analyzed in the terms of functions, hardware realizing and applications.As the beginning of this article, the present situation of access network and its development trend in future are analyzed and concluded, and separately, the structure, working principle of EPON and its advantages are introduced. Specially, the hierarchical structure of EPON is explained and analyzed deeply.Taken IEEE 802.3ah protocol as the reference, which is the standard protocol of EPON, the OAM sub-layer protocol and its main functions are introduced in detail, which including remote trouble indicating, link detecting and full circle testing. Specially, the OAM Discovery procedure and the data unit format of OAM protocol is explained in detail.According to the three function modules divided in the general function-realizing frame in the protocol, which are Parser, Control, Multiplexer, the working flow chart of each function module is designed. And based on this, the external circuit interface of each module is coding in VHDL language and designed by ISE5.1 tools of Xilinx company. Seen from the simulating charts of these function modules, the aim of the design is reached very well. Interrupt request level is adopted in Multiplexer function module, that is processing and inputting the OAMPDU data, MAC Client data and Loopback data sending from Control module in three different interrupt request level. The research on EPON OAM sub-layer's functions ensures further development of EPON MAC chipset with our own property right, and is of reference value for the researches on EPON devices.In the end of the article, the application of EPON OAM sub-layer protocol in EPON management base in SNMP is discussed. A Proxy Agent is set in EPON OLT to translate communications between SNMP management system and ONU. As a result, SNMP management system can get all the information of network devices. The function realizing flow chart of Proxy Agent is designed as follows. Using Proxy Agent as the agent of ONU management can realize a SNMP management to each EPON unit.on the other hand, The application of OAM in EPON multicast is discussed. A scheme of realizing multicast in EPON is designed, including multicast filtering scheme and using extension defined OAMPDU to realizing multicast management of OLT. Introducing multicast can make EPON more capable of supporting multimedia services.This article is of reference value for further development of EPON chipset, EPON devices or network management system and as well as the new functions of EPON.