光无源接入网复用技术比较

当今接入网的业务模式已从基于音频和文本转向基于图像和视频.该变化要求接入网具备高速率(大于100 Mb/s),对称的和足够带宽的新特性适应未来发展的需要.采用点到多点的无源光网络(PON)结构是最经济有效的方案.主要讨论时分复用无源光网络(TDM-PON)和波分复用无源光网络(WDM-PON)两种复用技术的原理与应用前景.     

三种宽带无源光接入网技术比较

无源光网络(PON)是一种新兴的覆盖最后一公里的宽带光纤接入技术.随着PON的发展,应用于PON的技术也层出不穷,基于ATM的无源光网络(APON)/宽带无源光网络(BPON)、以太网无源光网络(EPON)以及最近出现的千兆以太网无源光网络(GPON)技术都进一步推动了宽带光接入网的发展.文章回顾了宽带PON技术的发展,介绍了3种宽带PON技术,并对它们进行了比较和分析.     

光接入网用光无源器件

为了平稳地过渡到“光纤到家”（ＦＴＴＨ），已经引入了好几种光接入网。除了技术上的考虑外，经济上的可行性在这些网络中也是非常重要的。我们正在研制一些组成这些网络基本部分的廉价、小型、高密度的无源光器件。在本文中，我们叙述了开发这些器件中所采用的先进应用技术。诸如分光器、光分路模块、滤光器、机械式光开关，以及它们的光学和机械性能在文中也作了叙述。     

宽带无源光接入网技术GPON

随着光通信技术的高速发展,国内的骨干网已经基本实现光纤化、数字化、宽带化,传送的业务除了传统的电话、传真等低速业务外。还有基于高速数据传送的视频点播、可视电话等宽带业务。而位于网络边缘的接入网发展一直比较缓慢,难以满足用户日益增长的带宽需求。因此运营商迫切需要建立一个数字化、宽带化、智能化、综合化及个人化的用户接入网,最理想的方式是建立一个以光纤为主的用户接入网。无源光网     

我国无源光接入网技术体制要点

就我国无源光接入网技术体制中关于接入网的定义、特点、接口、应用、网络性能、供电、可靠性等主要问题作一简要介绍。     

波分多路的无源光接入网

一、前言 随着计算机和通信技术的发展,多媒体通信终将成为21世纪的基本通信方式。多媒体通信系统的通信网可以分为两大部分,即主干网和用户接入网。主干网又称为核心网或局间网;用户接入网,简称用户网或接入网,是中心局和用户之间的连接网络,或者说是核心网到用户设备的接入通道,它包括接入复用安排和网络终端。 用户接入可采用铜钱、光纤、同轴电缆和无线等几种方式,因而接入网有非对称数字用户环路     

基于Ethernet无源光接入网关键技术的研究

以Ethernet为基础的无源光网络（Ethernet－PON）是未来实现宽带，多业务综合接入的重要技术手段，本文分析了EPON系统的基础结构和个组成部分，所支持的业务，实现系统所需要解决的关键技术及实现方法，同时对系统设计时所需考虑的一些重要问题进行了探讨。     

无源光接入网中反射式ONU的研究

对光纤到户(FTTH)网络来说,一个低成本高效的灵活接入方案是非常重要的.在波分复用-无源光网络(WDM-PON)中,用户端的收发器件以及波长分配方案是系统的关键.单纤双向单波长方案可以大大简化网络结构,降低用户的接入成本,但这种结构存在很严重的瑞利反向散射的串扰.文章分析了各种不同ONU端光源的实现方式,并分析了若干种抑制瑞利反向散射串扰影响的技术.     

PON的演进

PON（无源光网络）技术是一种点对多点的光纤传输和接入技术，下行采用广播方式、上行采用时分多址方式，可以灵活地组成树型、星型、总线型等拓扑结构，在光分支点不需要节点设备，只需要安装一个简单的无源光分路器，光信号在传输过程中不再经过放大和再生，网络的分路由光分路器来实现。PON的优点是：宽带化、业务综合化、灵活的组网能力、低成本。无源光网络技术在90年代中期由FSAN发起，在一个通用、快捷的宽带接入系统上同时提供宽带和窄带服务，如IP数据，视频，10/100以太网、话音以及TDM业务，通过光纤在世界范围内传送。无…     

Optical Maintenance in PONs

The maintenance of the ODN (optical distribution network) in PONs (Passive Optical Networks) to be used for the future telecommunication access networks is discussed. A review of the techniques used to perform this function, aimed to guarantee the performances of optical cables, splices, connectors, and other passive components of the network, is provided. Post-fault maintenance (to detect, locate, and restore the faults) and preventive maintenance (to reduce the fault events) are both considered. The use of measuring and monitoring systems based on OTDRs (optical time domain reflectometers) is examined in detail, considering the different proposed schemes. These are based on reference reflectors set at the end of the branches, fiber selectors, wavelength division routing, chained branches, and use of dedicated fibers. An overview of the key components for the considered measuring and monitoring systems is given, considering the present status and the foreseeable evolution for the different devices: optical selectors, filters, reflectors, couplers, selective wavelength routers, and OTDRs.     

Design and dimensioning of hybrid PONs

We investigate the greenfield deployment of hybrid time division multiplexing/wavelength division multiplexing passive optical networks, i.e., the optimized covering of a given geographical area by a set of cost-effective and properly dimensioned hybrid PONs. We first propose a three-phase optimization scheme. In the first phase, a p-center model is proposed to determine the best ONU clusterings and the lower-level passive distribution node equipment locations. The second phase takes care of the placement of the upper-level passive distribution node equipment and the third one, using the traffic demands, a mix of unicast and multicast requests, selects the most appropriate passive distribution node equipment, i.e., either an arrayed waveguide gratings or a splitter. We next merge the first two phases, leading then to a two-phase scheme. Computational experiments are conducted on two sets of ONUs, one with 128 and one with 512 ONUs. We compare the two- and three-phase schemes in terms of PON design costs. We observe that the two-phase scheme provides more cost-effective solutions. We also provide a sensitivity analysis with respect to several parameters in order to identify the number of ONU clusters that minimizes the deployment cost.     

Dynamic reconfiguration policies for reconfigurable coded-WDM PONs

This article studies the issues arising when reconfiguring coded-WDM networks to provide protection against eavesdropping. Although the ability to reconfigure coded-WDM PONs dynamically has been recognized as an effective means of improving the security of OCDMA networks, this article provides the first in-depth study of the tradeoffs involved in carrying out this reconfiguration process. The article commences by showing that the degree of confidentiality and the traffic loss are two important, but conflicting, objectives in the design of reconfiguration policies. The reconfiguration problem is then formulated as a Markovian decision process (MDP). The results obtained from MDP theory are applied to establish optimal reconfiguration policies for coded-WDM networks with various system parameters. Finally, the advantages of the optimal reconfiguration policies over a class of threshold-based policies are illustrated through simulation results.     

Connection anonymity analysis in coded-WDM PONs

A coded wavelength division multiplexing passive optical network (WDM PON) is presented for fiber to the home (FTTH) systems to protect against eavesdropping. The proposed scheme applies spectral amplitude coding (SAC) with a unipolar maximal-length sequence (M-sequence) code matrix to generate a specific signature address (coding) and to retrieve its matching address codeword (decoding) by exploiting the cyclic properties inherent in array waveguide grating (AWG) routers. In addition to ensuring the confidentiality of user data, the proposed coded-WDM scheme is also a suitable candidate for the physical layer with connection anonymity. Under the assumption that the eavesdropper applies a photo-detection strategy, it is shown that the coded WDM PON outperforms the conventional TDM PON and WDM PON schemes in terms of a higher degree of connection anonymity. Additionally, the proposed scheme allows the system operator to partition the optical network units (ONUs) into appropriate groups so as to achieve a better degree of anonymity.     

Dynamic bandwidth allocation for quality-of-service over Ethernet PONs

Ethernet-based passive optical network (EPON) technology is being considered as a promising solution for next-generation broadband access networks due to the convergence of low-cost Ethernet equipment and low-cost fiber infrastructures. A major feature for this new architecture is the use of a shared transmission media between all users; hence, medium access control arbitration mechanisms are essential for the successful implementation of EPON: i.e., to ensure a contention-free transmission and provide end users with equal access to the shared media. We propose to use the multipoint control protocol defined by the IEEE 802.3ah task force to arbitrate the transmission of different users, and we present different dynamic bandwidth allocation (DBA) algorithms to allocate bandwidths effectively and fairly between end users. These DBA algorithms are also augmented to support differentiated services, a crucial requirement for a converged broadband access network with heterogeneous traffic. We show that queueing delays under strict bandwidth allocation algorithms result in an unexpected behavior for certain traffic classes, and we suggest the use of DBA with appropriate local queue management to alleviate this inappropriate behavior. We conduct detailed simulation experiments to study the performance and validate the effectiveness of the proposed protocols.     

Routing and fast protection in networks of long-reach PONs

This paper reports on proposed solutions to the recovery from faults in a generic class of networks, where customer access is achieved via long-reach passive optical networks (LR-PONs), with the majority of customers enjoying protection in the backhaul regime to two separate metro nodes. Initial modelling studies suggest that in the event of a cable failure or single equipment element failure, redirected data will almost always leave the transmitting node in under 50 ms. For more catastrophic failures (such as router failure or loss of a metro node), recovery might take between 100–200 ms. Reachability information for each LR-PON is discovered over each area of the network, and used to inform the redirection of traffic via tunnels. The scheme uses IP signalling to enable traffic re-routing, although the underlying services may be of any type (e.g. private line) — making the scheme separate from the service, customer or provider.     

Effects of Upstream Incoherent Crosstalk Caused by ASE Noise from Tx‐Disabled ONUs in XG‐PONs and TWDM‐PONs

A large incoherent crosstalk (IC) caused by amplified spontaneous emission (ASE) noise power from Tx‐disabled optical network units and a differential path loss has been shown to degrade upstream transmission performance in time‐division multiplexing passive optical networks. This paper considers the IC‐induced power penalty of an upstream signal both in an XG‐PON and in a TWDM‐PON. We investigate the degradation of the extinction ratio and relative intensity noise through a simulation and experiments. For the XG‐PON case, we observe a 9.6 dB difference in the level of ASE noise power from Tx‐disabled ONUs (hereafter known simply as ASE noise) between our result and the ITU‐T XG‐PON PMD recommendation. We propose an optical filtering method to mitigate an IC‐induced power penalty. In the TWDM‐PON case, the IC‐induced power penalty is naturally negligible because the ASE noise is filtered by a wavelength multiplexer at the optical line terminal. The results provide design guidelines for the level of ASE noise in both XG‐PONs and TWDM‐PONs.     

Dynamic Bandwidth Allocation Algorithm for Multimedia Services over Ethernet PONs

Ethernet passive optical networks (PONs) are an emerging access network technology that provides a low‐cost method of deploying optical access lines between a carrier's central office and a customer site. In this paper, we propose a new algorithm of dynamic bandwidth allocation for multimedia services over Ethernet PONs. To implement the suggested dynamic bandwidth allocation algorithm, we present control message formats that handle classified bandwidths in a multi‐point control protocol of Ethernet PONs.