A novel WDM passive optical network architecture supporting two independent multicast data streams

We propose a novel scheme to perform optical multicast overlay of two independent multicast data streams on a wavelength-division-multiplexed (WDM) passive optical network. By controlling a sinusoidal clock signal and shifting the wavelength at the optical line terminal (OLT), the delivery of the two multicast data, being carried by the generated optical tones, can be independently and flexibly controlled. Simultaneous transmission of 10-Gb/s unicast downstream and upstream data as well as two independent 10-Gb/s multicast data was successfully demonstrated.     

A bandwidth scalable OFDM passive optical network for future access network

In order to reduce the cost for delivering the ever increasing broadband services, network providers need to simplify their network architectures and have a better control of the bandwidth. In this article, we propose a simple and cost-effective bandwidth scalable passive optical network (PON) based on orthogonal frequency division multiplexing (BSOFDM-PON). We report performance analysis in terms of the signal-to-noise ratio (SNR), bit-error-rate (BER), and error vector magnitude (EVM) of a PON system accommodating 32 optical network units (ONUs). Our simulations have successfully demonstrated that throughputs of 35.5 and 53.2 Gbps can be achieved using 16 and 64 QAM, respectively, within a total distance ranging from 20 to 30 km. It gives throughputs of 1.10 and 1.66 Gbps per ONU.     

A novel medium access control protocol for passive optical network supporting local area networking capabilities

An alternate solution for Ethernet passive optical networks (EPON) providing local area networking (LAN) capabilities is proposed in this article. Our solution adopts a star coupler-based PON architecture and uses radio frequency subcarrier multiplexed transmission for the LAN traffic delivery. The proposed medium access control (MAC) protocol supports a fully distributed control plane among the optical network units (ONUs) for ONU–ONU communication as well as upstream access to the OLT. The simulation results indicate that the proposed MAC protocol outperforms the others in terms of the average packet end-to-end delay, especially for LAN traffic.     

A novel colorless WDM passive optical network delivering up/downstream signals and video broadcast signal simultaneously

A colorless wavelength division multiplexing passive optical network delivering up/downstream signals and video broadcast signal (VBS) simultaneously is presented in this paper. In this scheme, subcarrier modulation technique is adopted at the optical line terminal. Here un-modulated double-sideband subcarriers and optical carriers operating in different wavelength bands are used for downstream and video broadcast signal transmission, respectively. The use of differential-phase-shift-keying (DPSK) modulation for downstream transmission enables effective upstream transmission by direct re-modulation. The simulation results demonstrated with 2.5-Gb/s up/downstream signals and video broadcasting signal show this approach could work very well.     

High‐reliability grid architecture supporting discretionary and efficient communication between ONUs in metro‐access optical network

Direct communication of optical network units (ONUs) is an important function in metro‐access optical network. In this paper, a grid architecture supporting discretionary and efficient communication between ONUs is proposed. The grid architecture is built by using two interconnecting fibers to connect every two ONUs; this can give protection to every ONU by four ONUs. Additionally, the network reliability can be improved greatly. Grid topology of ONUs leads to their discretionary direct communication. In this topology, direct communication signal can be transmitted from one ONU to another ONU directly, rather than being returned to remote node central office. Also, the efficiency of direct communication can be improved remarkably with the proposed architecture. Finally, the performance analyses and the simulation results verify the feasibility of the proposed architecture. When the n reaches to 10, the reliability of downstream and direct communication signals is all larger than 99.993%.     

A high-reliability optical network architecture based on wavelength division multiplexing passive optical network

A highly reliable wavelength division multiplexing passive optical network architecture for the fifth generation (5G) applications is designed by combining a tree topology with a dual-fiber ring. While the tree topology ensures the transmission quality of the network, the dual-fiber ring topology allows one to achieve flexible switching between the nodes, which aims to provide fault protection and network reliability. The signal transmission under the normal and three types of protection modes are analyzed. The performance analysis verifies the feasibility of the proposed architecture.     

A next-generation optical regional access network

We describe an optical regional access network which combines electronic IP routing with intelligent networking functionality of the optical WDM layer. The optical WDM layer provides such networking functions as network logical topology reconfiguration, optical flow switching to offload traffic and bypass IP routers, wavelength routing of signals, protection switching and restoration in the optical domain, and flexible network service provisioning by reconfigurable wavelength connectivity. We discuss key enabling technologies for the WDM layer and describe their limitations. The symbiosis of electronic and optical WDM networking functions also allows support for heterogeneous format traffic and will enable efficient gigabit-per-second user access in next-generation Internet networks     

Flexible TDMA/WDMA passive optical network: Energy efficient next-generation optical access solution

Access networks must further advance to address the intensification of the requirements of growing speeds and the usage of Internet applications, and time and wavelength division multiple access (TDMA/WDMA) based passive optical networks (TWDM-PONs) have been widely considered as one of the evolutionary steps of next-generation optical access (NGOA) networks. TWDM-PON combines the flexibility of TDMA with an increased capacity offered by the use of a WDM layer. Moreover, it offers interesting and challenging avenues to minimize energy consumption: especially, with current access networks consuming about 80% of the energy consumed in the Internet. Along with other efforts, reducing energy consumption of central offices is conspicuous as it directly minimizes the operational expenditures of network providers. In this paper, we explore the new paradigms to conserve energy at the central offices in TWDM-PONs. By extensive simulations, we evaluate the possible energy savings in the various flavors of TWDM-PON. Based on the findings, we propose a new architectural flavor of TWDM-PON and benchmark the architecture for cost, power consumption and reach. We also propose a novel energy saving scheme for the proposed architecture and evaluate the impact of the proposed algorithm on energy savings by extensive simulations.     

Class-limited algorithm for supporting QoS and fairness in Ethernet passive optical network

Ethernet passive optical network (EPON) becomes a key technology for the next generation broadband access networks due to its cost-effectiveness and high data rate. One of the research issues in EPON is to support service differentiation and fairness. For service differentiation, the conventional limited algorithm is extended with strict priority queuing (SPQ). However, due to ONU-bounded bandwidth allocation, those extensions from the limited algorithm have difficulties in supporting QoS and fairness when the uplink is instantaneously overloaded. To overcome the disadvantages of ONU-bounded bandwidth allocation, instead of allocating the bandwidth on per ONU basis, the proposed class-limited algorithm allocates the bandwidth on per service class basis. Our simulations show that the class-limited algorithm is more efficient to differentiate services and to fairly share residual bandwidth than other limited schemes combined with SPQ, particularly for instantaneous overload condition.     

SUCCESS: a next-generation hybrid WDM/TDM optical access network architecture

In this paper, the authors propose a next-generation hybrid WDM/TDM optical access network architecture called Stanford University aCCESS or SUCCESS. This architecture provides practical migration steps from current-generation time-division multiplexing (TDM)-passive optical network (PONs) to future WDM optical access networks. The architecture is backward compatible for users on existing TDM-PONs, while simultaneously capable of providing upgraded high-bandwidth services to new users on DWDM-PONs through advanced WDM techniques. The SUCCESS architecture is based on a collector ring and several distribution stars connecting the CO and the users. A semipassive configuration of the Remote Nodes (RNs) enables protection and restoration, making the network resilient to power failures. A novel design of the OLT and DWDM-PON ONUs minimizes the system cost considerably: 1) tunable lasers and receivers at the OLT are shared by all ONUs on the network to reduce the transceiver count and 2) the fast tunable lasers not only generate downstream data traffic but also provide DWDM-PON ONUs with optical CW bursts for their upstream data transmission. Results from an experimental system testbed support the feasibility of the proposed SUCCESS architecture. Also, simulation results of the first SUCCESS DWDM-PON MAC protocol verify that it can efficiently provide bidirectional transmission between the OLT and ONUs over multiple wavelengths with a small number of tunable transmitters and receivers.     

Low-cost and scalable passive optical network architecture using remote repeater

We report a new passive optical network (PON) architecture to reduce customer transmitter cost using an upstream repeater at the remote node. The system can further provide both downstream and upstream regeneration by utilising standard bidirectional transceivers. Our architecture can extend a conventional PON's feeder fibre reach to 50 km and split ratio to 1:256. The system demonstration shows insignificant penalty to the existing network performance and meets the IEEE 802.3ah standard requirements.     

Research of novel complex optical network routing architecture

This article puts forward a novel routing architecture for complex optical network,which core component is path calculation element(PCE).As is well known,the PCE-based distributed path computation structure is making the routing control and computation loosely coupled from traditional control plane.In the study,the resource allocation and routing algorithm are the critical part of PCE hierarchy.To compare the performance of new architecture and the traditional one,the user uses the flooding suppression,routing delay,resource utilization and traffic blocking probability as performance simulation parameters and taking the verification simulation on objective modular network testbed(OMNeT)platform against to source-node routing architecture.The numerical analysis,computer simulation and experiment work indicate that the operation of PCE-based routing architecture can reduce the flooding information of path calculation request as well as the routing hops significantly and improve the quality of service(QoS)by decreasing the blocking probability when failure happened.     

Dual-fiber optical burst switching network: A novel architecture for metropolitan area networks

Fiber optic rings are widely deployed in metropolitan area networks (MAN). These rings currently employ architectures and protocols that are neither optimized for nor scalable to the network demand. Therefore, emerging technologies are being pushed to replace the traditional architectures. Among these technologies, optical burst switching (OBS) is an effective and promising technology. In this study, a novel architecture, dual-fiber OBS (DOBS), is proposed. This architecture has similar functions to those of fiber delay lines, partial wavelength conversion and deflection routing. A theoretical model is developed to evaluate the performance of DOBS, which is compared with single-fiber and simple two-fiber schemes by introducing them into ring and mesh MAN in simulations. The results reveal that DOBS can exponentially reduce the burst dropping probability. Moreover, since DOBS can be implement using commercially available devices and dark fibers, it is commercially viable in metro networks.     

一种新型三层卫星光网络结构

依据空间卫星网络分层化设计的思想,提出了新型GEO/MEO/LEO三层卫星激光通信网络结构.阐述了上层负责资源调度、路由表发布和下层负责承载业务的基本原理、网络吞吐量大、鲁棒性强等特点.     

A passive protected self-healing mesh network architecture andapplications

The self-healing mesh network architecture using digital cross-connect systems (DCSs) is a crucial part of an integrated network restoration system. The conventional DCS self-healing networks using logical channel protection may require a large amount of spare capacity for network components (such as DCSs) and may not restore services fast enough (e.g., within 2 s). The authors propose a passive protected DCS self-healing network (PPDSHN) architecture using a passive protection cross-connect network for network protection. For the PPDSHN architecture, network restoration is performed in the optical domain and is controlled by electronic working DCS systems. Some case studies have suggested that the proposed PPDSHN architecture may restore services within a two-second objective with less equipment cost than the conventional DCS self-healing network architecture in high-demand metropolitan areas for local exchange carrier networks. The proposed PPDSHN architecture may apply to not only the centralized and distributed control DCS network architectures, but also asynchronous, SONET and ATM DCS networks. Transparency of line rates and transmission formats makes the PPDSHN network even more attractive when network evolution is a key concern of network planning     

A passive network termination for BISDN optical subscriber lines

Considerable cost saving and overall simplification can be achieved if the protocol for the access digital section is made identical to the one at the T interface. The network termination (NT1) may then be realized as a passive device, such as a simple connector. All active functions associated with the NT1 can then be performed on a time-shared basis from the premises of the network provider. This scheme obviates the need for remote power feeding and activation mechanisms of the NT1. The time sharing of active functions, such as optical time domain reflectometry (OTDR) for supervision of the physical conditions of the lines, allows a substantial cost reduction of the subscriber access. It is shown that this technique yields a more efficient maintenance scheme than that afforded by an active NT1, resulting in a cost saving also in the long term. Ways of implementing the passive NT1 are discussed, and also its position in the evolution of passive optical networks (PON) towards BISDN.     

A high-throughput energy-efficient passive optical datacenter network

Datacenter applications impose heavy demands on bandwidth and also generate a variety of communication patterns (unicast, multicast, incast, and broadcast). Supporting such traffic demands leads to networks built with exorbitant facility costs and formidable power consumption if conventional design is followed. In this paper, we propose a novel high-throughput datacenter network that leverages passive optical technologies to efficiently support communications with mixed traffic patterns. Our network enables a dynamic traffic allocation that caters to diverse communication patterns at low power consumption. Specifically, our proposed network consists of two optical planes, each optimized for specific traffic patterns. We compare the proposed network with its optical and electronic counterparts and highlight its potential benefits in terms of facility costs and power consumption reductions. To avoid frame collisions, a high-efficiency distributed protocol is designed to dynamically distribute traffic between the two optical planes. Moreover, we formulate the scheduling process as a mixed integer programming problem and design three greedy heuristic algorithms. Finally, simulation results show that our proposed scheme outperforms the previous POXN architecture in terms of throughput and mean packet delay.     

一种PON系统光缆监测新方案

无源光网络(PON)是一种点到多点的光接入技术,采用传统的光时域反射仪(OTDR)技术对PON的各分支光路进行监测出现了技术瓶颈.针对这一问题,文章分析了现有几种解决方案的不足之处,在此基础上,提出了一种以光供能方式驱动光开关测试的新方案,并详细描述了该方案的实现过程.     

A novel FPGA architecture supporting wide, shallow memories

This paper investigates an architecture designed to implement wide, shallow memories on a field programmable gate array (FPGA). In the proposed architecture, existing configuration memory normally used to control the connectivity pattern of the FPGA is made user accessible. Typically, not all the switch blocks in an FPGA are used to transport signals. By adding only a modest amount of circuitry, the configuration memory in these unused switch blocks (or unused paths within used switch blocks) can be used to implement wide, shallow buffers and other similar memory structures. The size of FPGA required to implement a benchmark circuit that makes use of the wide, shallow memories, is 20% smaller than a standard memory architecture. In addition, the benchmark circuit is on average 40% faster using the proposed architecture.     

SUCCESS-HPON: A next-generation optical access architecture for smooth migration from TDM-PON to WDM-PON

Optical access networks are considered to be a definite solution to the problem of upgrading current congested access networks to ones capable of delivering future broadband integrated services. However, the high deployment and maintenance cost of traditional point-to-point architectures is a major economic barrier. Current TDM-PON architectures are economically feasible, but bandwidth-limited. In this article we first discuss the possible role of WDM in access networks and investigate the associated issues. We then present the Stanford University Access Hybrid WDM/TDM Passive Optical Network (SUCCESS-HPON), a next-generation hybrid WDM/TDM optical access architecture that focuses on providing a smooth migration path from current TDM-PONs to future WDM-PONs. The first testbed for this architecture is described, along with the experimental results obtained, including feasibility of bidirectional transmission on the same wavelength on the same fiber for access networks and ONU modulation of upstream data on continuous waves provided by the OLT, eliminating the need for tunable components at the ONUs. The development of a second testbed and the issues it will address, including the implementability of the SUCCESS-HPON MAC protocol and scheduling algorithms, are also described.