We propose and experimentally investigate a highly reliable WDM-PON system. The proposed system adopts the
colorless solution. It can detect the failure of the feeder fiber by the polling and restoring mechanism of the system
management module, and then trigger the OSW switching to the preplanned path for restoring the disrupted traffic, and
produce a broken fiber alarm if needed. The system management module can send polling frames to ONUs periodically
and judge whether it is necessary to send trigger signals to the OSW according to the number of ONUs registered in line
cards. The preplanned path is the feeder fiber of the neighboring line card. This system can automatically protect against
the feeder fiber failures without duplicating the feeder fiber link. The OTDR or optical power meter can be saved which
is used for on-line monitoring. Its restoration time is less than 16ms in experiments.
As EPON system becomes attractive integrated broadband access solution in worldwide Fiber To The Home(FTTH) and Fiber To The Building (FTTB) deployment, the QoS guarantee and the management of multiple services is inevitably a urgent issue in EPON system implementation. Instead of only using priority method as defined in IEEE802.1p, this paper proposes a native model for multi-service access platform with SLA enforcement, which specifying Service Level Agreements (SLAs) on logical links in EPON transmission segment and strictly enforcing SLAs by EPON MPCP protocol and DBA algorithm in both upstream and downstream. SLA normally uses multiple parameters to describe requirements of service bandwidth, delay and jitter. In EPON, the specification of SLA for service may use 4 parameters: the minimal Guarantee bandwidth, maximum allow bandwidth, sensitivity of delay and maximum burst size. As EPON schedules traffic on logical link basis, the right QoS demand of each service will be the same as its logical link. To guarantee different services' different SLAs, it was supposed to use multiple logical link IDentifies (LLIDs) in each remote ONU, each service is mapped to its own LLID. By classifying services packet into different links, combining with powerful Hierarchical WRR schedule algorithm it is possible to guarantee the bandwidth and control transmission delay and jitter for each service bidirectional. The proposed scheme has overcome the best-effect forwarding deficiency of the Ethernet, brought the management of multiple services and the management of remote ONUs into a new framework, given cost efficient and effective solution for EPON multiple services access.
Proc. SPIE. 5626, Network Architectures, Management, and Applications II
KEYWORDS: Lithium, Light emitting diodes, Fiber to the x, Remote sensing, Networks, Passive optical networks, Telecommunications, Local area networks, Broadband telecommunications, Standards development
Ethernet Passive Optical Network (EPON), which represents the convergence of low-cost Ethernet equipment and reliable fiber infrastructure, appears to be the best candidate for the next-generation broadband access network. A coin has two sides. Although EPON inherits the benefits of Ethernet, it also suffers some disadvantages. With its origin as a LAN technology, where “best effort” delivery and 99.96% uptime were acceptable, Ethernet was never considered to be a candidate for achieving “carrier-class” status, mainly because lack of powerful OAM capabilities. That’s to say OAM function is essential to carrier-class EPON. In this study, the principals of EPON and OAM, together with the necessity of OAM, are presented firstly. Besides, different ways to provide OAM in ITU-T APON, GPON are analyzed respectively. Three means to obtain EPON OAM, using MAC Control Frame, Physical Link Service Overhead Coding Sublayer (PLSOCS) and Reconciliation Sublayer (RS) Preamble are proposed in detail. Moreover, the main functions, such as remote failure indication, remote loop-back, link monitoring and variable retrieval are studied subsequently. After that, the concrete implementation of OAM in EPON is addressed, combining with hardware and software. As a result, an effective way to carry out EPON OAM can be easily drawn.
Recent years, data traffic is increasing at an unprecedented rate. Digital Subscriber Line (DSL) and cable modem (CM) networks will not afford the huge bandwidth consuming in the near future. Ethernet Passive Optical Network (EPON) is an inexpensive, simple, scalable, and capable of delivering bundled voice, data and video services to an end-user over a single network. EPON, which is a typical point to multi point topology, has become an attractive technology to both vendors and carriers. To ensure compatibility with the IEEE 802 architecture, Logical Link Identifier (LLID) tag is introduced in EPON to achieve point to point emulation. Usually one LLID tag associates with one stream or one ONU (Optical Network Unit) which is remote device of EPON. In order to simplify operations, LLID tag is added as part of preamble in Optical Line Terminal (OLT) Reconciliation Sublayer (RS) and is checked at ONU side. It’s urgent to have a powerful mechanism to achieve dynamic LLID filtering. Just in the downstream, each packet must have its own LLID according to the Destination Address field before being sent; in the upstream, LLID is learned based on the Source Address Field of the packet. Although address filtering is very popular in the L2 switch chips, it can’t be applied to EPON LLID filtering directly, owing to EPON is neither a point to point network nor a broadcast network. In this paper, the main principles and features of Logical Link Identifier (LLID) tagging system are firstly explained, and then the process of LLID both in OLT and in ONU side is described. What’s more, a novel method to realize dynamic LLID filtering is discussed in detail, involving in LLID scanning, LLID learning, LLID aging, and so on. An erasable Content Addressable Memory (CAM) structure is used to meet this demand. Not only the architecture of the concrete circuits, but the related timing sequences, operation process, service arbitration and aging state transition diagram are presented. Note that this mechanism has been verified in the actual EPON system and worked very well. At last, some conclusion remarks about using LLID filtering to enhance the performance of EPON is given.
Ethernet Passive Optical Network (EPON) aims at providing full services to end users over a single platform, which combines the low cost Ethernet equipment and economic fiber infrastructure, appears to be the best candidate for the future broad access network. Due to Ethernet has a seamless connection with modern IP network, EPON has shown excellent performance when transmitting data service. However, a key technical challenge for EPON vendors lies in enhancing Ethernet’s capabilities to support real-time services, such as VoIP, live video and other TDM services, e .g. POTS and T1/E1. In order to guarantee the required QoS, many new technologies are introduced, either common to all IP based network or dedicated to EPON network. Firstly, a short overview of EPON technology is given. Then, two prevailing QoS architectures, Intserv and Diffserv, are presented in detail. Both their advantages and disadvantages are also discussed. Subsequently, the light is turned to a certain DBA algorithm, which is more efficient in EPON. Both the features of the algorithm and the main ideas are described in particular. At last, reserving bandwidth for TDM service, which is simple but not very efficient, is also proposed.