Design Of EPON Optical Network Unit Based On PAS6201

With the rapid development of Internet services,higher and higher requirements of network bandwidth are needed.Since the backbone has already the adequate ability to sustain the broadband,access network bandwidth becomes the bottleneck of the whole network.Based on the Ethemet,EPON will an important technical means for the accomplishment of high bandwidth and multi-service integrated access.The protocal of EPON is simple,its specification is low for optical transceiver.So it can reduce the cost of system.Otherwise,EPON inherits the scalability of Ethernet,with the features of high efficiency for the IP data operation,supporting high-speed Internet access,voice,IPTV,TDM,CATV and so on,the guarantee of QoS,the support of multicast.EPON is the best solution for access network.An EPON network includes an optical line terminal(OLT) and an optical network unit(ONU).In the middle,Passive optical distribution network device completes optical power distribution of the downlink and optical coupling of the uplink.The OLT resides in the central office side,The OLT system is the mangement controle center of the whole system and the exchange of the engine.The ONU resides in the user side.Through the user network interface(UNI),it provides voice,data and video interface for the client and almost costs 80%of the whole expenses of FTTH,Thus,the research of low cost ONU is quite important to realize the FTTH.First of all,this paper introduces the current study situation of EPON at home and abroad,and the EPON application prospect briefly.And it introduces EPON operating principle,system structure,multi-point control protocol(MPCP),the technical advantages and difficulties.On this basis,it raises the design scheme of the EPON ONU based on PON chip PAS6201.In this paper,it describes EPON ONU system from the hardware circuit design and software design.The hardware circuit design mainly includes:PON interface circuit,UNI interface circuit,ARM memory circuit,Watchdog reset circuit,the Power circuit,the clock circuit design as well as the debugging circuit design.The software design mainly includes:Bootloader and transplantation,Linux kernel and transplantation,create a file system,design the ONU embedded software system architecture and the core part of ONU embedded software in detail.And three primary parts of the ONU embedded software system architecture,which are information exchange and processing task,hardware management task,the exchange module mangement task.This paper describes the design of hardware and software in detail,gives the schematic diagram design.This paper is a valuable reference for EPON system development in the future and especially in the realization of ONU system.