推动接入光纤化 促进社会信息化—中兴通讯FTTx光接入解决方案

随着光纤到户（FTTH）概念的兴起，至今已经历了窄带PON，APON，桌面型MSTP，EPON，GPON等光接入技术。当前最有发展前途的技术就是EPON和GPON。本文介绍了FTTx的发展、应用，以及中兴通讯“固网3G FTTx光接入整体解决方案”的应用模式。     

PON在宽带接入网中的应用方案

在业务．组网成本、技术．竞争等多方面驱动下，光纤直接接入商业用户并提供综合业务接入成为接入网发展的方向。PON作为一种新兴技术，具有高带宽．节省远端有源机房，便于维护．业务部署迅速等特点，将在宽带接入网中得到广泛应用。[编者按]     

自由空间光通信技术及发展

随着通信网建设的发展，局域网以及千兆以太网开始快速增长，将这些高速的局域网和千兆以太网连接到运营商的通信网络，必须依靠容量巨大的接入网络。当前有很多接入技术可供选择，比如光纤、微波、XDSL等，但光纤敷设时间长及高额投入限制了普及；微波技术日渐成熟，但这种接入方式需要高额的初始投资(频谱许可证)，对业务提供商而言，这种接入方式不很经济；尽管铜缆是一种易得的传输媒质，但XDSL带宽太低；而     

FTTH的黎明并非静悄悄

光纤到户(FTTH)是20年来人们不断追求的梦想和探索的技术方向,几乎没有人否认,FTTH将是未来宽带接入的最佳方式,相比ISDN、ADSL等接入方式,FTTH的带宽优势不言而喻,FTTH在国外呈现出良好的发展势头,然而由于成本、技术、需求等方面的障碍,至今还没有在中国真正起步,为何FTTH在通信大国“叫好不叫座”,迟迟发展不起来呢?究其原因到底是“技术推动市场,还是市场推动技术”?     

XDSL:应需而变

随着增值业务日益增多,用户对带宽的要求也越来越高,传统的接入技术已经无法满足业务开展的要求;另一方面,虽然光纤接入网络与铜线接入网络相比具有带宽高、接入距离长等优点,但是也受到成本、网络改建等诸多条件的限制,要完全取代目前广泛应用的铜缆接入仍然有待时日。如何能使业务得以顺利推广满足用户日益增长的需求?xDSL技术在这一问题上给出了答案。     

中国FTTH光缆解决方案

1.FTTH光纤实现技术 在接入网上,光纤替代各种铜质缆线是必然趋势,但在FTTH发展和推广初期,光纤与铜质缆线共存是必然的,光纤与铜质缆线的共存能使用户和电信运营商有效避免FTTH的技术风险.     

XDSL:应需而变

随着增值业务日益增多,用户对带宽的要求也越来越高,传统的接入技术已经无法满足业务开展的要求;另一方面,虽然光纤接入网络与铜线接入网络相比具有带宽高、接入距离长等优点,但是也受到成本、网络改建等诸多条件的限制,要完全取代目前广泛应用的铜缆接入仍然有待时日.如何能使业务得以顺利推广满足用户日益增长的需求?xDSL技术在这一问题上给出了答案.     

几种接入技术的比较

讨论了在铜线传输、光纤传输、光纤／铜线混合传输等不同方式下接入网的差别，分析了各类接入技术的组成和特点，并进行综合比较，以便在通信业务中更好发展和利用各类接入技术。     

PON在商业用户业务接入中的应用

在业务、组网成本、技术、竞争等多方面驱动下,光纤直接接入商业用户并提供综合业务接入成为接入网发展的方向.PON作为一种新兴技术,具有高带宽、节省远端有源机房、便于维护、业务部署迅速等特点,将在商业用户的接入方案中得到广泛应用.     

有关家庭宽带光纤接入技术试论

文章首先对光纤接入进行了分析,对FTTX的优势进行了总结,然后对家庭宽带光纤接入技术进行了研究,最后结合实际案例对光纤接入技术进行了探讨,以期对家庭宽带光纤接入技术的推广起到一定的促进作用。     

低密度波分复用在城域网、接入网上的应用

近年来低密度波分复用（CWDM）系统开始应用在城域网和接入网中,这是因为其关键性零组件激光器、滤波器成本较低;长波长的CWDM可以用在旧的单模及多模光纤网上,电信运营商不需再铺设新的光纤;芯片高度整合,CWDM系统趋于成熟。CWDM技术结合10G以太网可以在短至300米的多模光纤到长过40公里的单模光纤上得到应用。     

永嘉县广电双向接入网改造方案选择

随着光纤技术的快速发展,光纤价格的大幅度下降,采用现有成熟的技术,广电运营商可以很方便地将户外光纤网络升级改造为双向网络,因此电缆分配网络的双向宽带接入网已经成为有线电视网络实现双向化的关键,探讨县级广电网络如何选择性价比最高的方案实现双向接入网改造,以成功实现战略转型。     

Broadbandloop: a full-service access network for residential andsmall business users

There is a worldwide effort to define a full-service access network. The Broadbandloop project was formed by a European consortium funded by the European Union with the objective of defining a strategy for evolution from a narrowband voice and data network to a broadband network. The project is defining a system concept based on new innovative PON technology, which enables fiber to cost effectively penetrate close to the customer, and VDSL technology for transmission over twisted copper pairs. The system concept is validated in field trials in Denmark, Portugal, and Poland. The article describes the different requirements for a full-service access network, the system concept, and technologies developed. Results from modeling of broadband traffic and the corresponding bandwidth are given. The cost effectiveness of using new optical fiber vs. reusing existing telephone copper plant has been evaluated, and results from these studies are presented     

Next generation hierarchical CWDM/TDM-PON network with scalable bandwidth deliverability to the premises

Long haul optical networks have been on focus for more than two decades. With the advent of dense wavelength division multiplexing technology, optical long haul fiber networks have been so successful in delivering an unprecedented amount of bandwidth that they outperformed the traffic deliverability from/to the access network by orders of magnitude. The reason was a cost-efficiency mismatch; long haul ultra-high bandwidth networks can take advantage of state of the art and costly technology, which cost-sensitive access networks cannot. The result was an unbalanced traffic flow from/to access points to the network if one compares the aggregate flow of the long haul network with that of the access. Nevertheless, over the last decade technology at the access advanced and new standards have been developed so that in the access layer of the overall communications network the focus has shifted onto fiber optic access again. Thus, in the optical regime, two proposals have prevailed. One uses a time division multiplexing (TDM) scheme over a single wavelength and a comprehensive timing protocol, and the other uses coarse wavelength division multiplexing (CWDM) technology. Each technology has advantages and disadvantages, and the one attempts to address the disadvantages of the other. In this paper we describe a hierarchical CWDM/TDM passive optical network (PON). Our access network architecture is scalable, it is flexible to accommodate one of several topologies simultaneously, and it delivers any type of payload, synchronous and asynchronous that spans from DS0 to Gbps. We discuss the bandwidth flexibility, versatility, resiliency and cost efficiency of the access network. We also demonstrate that our network can deliver payload to more than 16,000 end-users using simple and existing optical technology. Thus, if one considers cost per bandwidth or per user, the cost-efficiency outperforms any previous PON access network. Moreover, we provide simulation results to support the viability of our network architecture.     

Cost vs. reliability performance study of fiber access network architectures

Fiber to the home is the future-proof technology for broadband access networks. Several fiber access network architectures have been developed (e.g., point-to-point, active optical network, and passive optical network). PON is considered the most promising solution due to the relatively low deployment cost and high resource efficiency. Meanwhile, because of the growing demand for reliable service delivery, fault management is becoming more significant in all parts of communications networks. However, there is a trade-off between the cost of protection and the level of service reliability. Since economical aspects are most critical in the access part of networks, improving reliability performance by duplication of network resources (and capital expenditures) could be too expensive. Therefore, recent work has focused on PON protection schemes with reduced CAPEX. The future trend will probably migrate toward minimizing operational expenditures during the access network lifetime. The main contributions of this article include providing a general method for CAPEX and OPEX analysis that can be applied to any type of fiber access network with consideration of changed component cost in time and variable take rates, and comparing the total cost (i.e., sum of CAPEX and OPEX) for the selected representative architectures with and without protection for business and residential users in relation to reliability performance. The aim is to give a guideline for the design of the most cost-effective protection schemes, while maintaining acceptable service reliability.     

Protection cost evaluation of WDM-based next generation optical access networks

New technologies and advanced network devices make it possible to move towards high capacity access networks able to satisfy the growing traffic demand. Wavelength division multiplexing (WDM) is considered as one of the promising technologies for the next generation access networks since it offers higher bandwidth and longer reach compared to the current technologies (such as time division multiplexing (TDM) based networks). However, the migration to a new technology is typically based on an overall techno-economic study which should assure the network operator that the new implementation is cost effective and profitable while able to provide the required services to the users. Another important aspect in the access network design is the network reliability performance, which can be improved by providing a certain level of protection for equipment and/or infrastructure with high failure impact ratio in order to prevent a big number of the users being affected by a single failure. The cost of protection should be carefully evaluated since providing the backup resources may be too expensive for a network operator.In this paper, we investigate the capital and operational expenditures for two next generation optical access (NGOA) networks based on the WDM technology in dense urban areas. Three scenarios with different splitting ratios are studied for each technology, with and without protection. The aim of this work is to investigate the impact of providing protection on the total cost of NGOA networks. The results show that in the dense urban areas the fibers and digging costs are highly shared among the end users but still vary according to the splitting ratios for different scenarios and the fiber layout. It also can be seen that with a proper fiber layout design, minor extra investment for protection of NGOA networks can make a significant saving on failure related operational cost and that operational expenditures depend significantly on the fiber layout.     

光载无线电(RoF)网络技术

光载无线电(RoF,Radio-over-Fiber)技术是无线宽带接入的发展趋势,这项技术是把射频(RF,Radio Frequency)副载波调制到光载波上,从而在光纤网络中传输。它结合光纤通信和无线通信两大技术,可以实现超过Gb/s的无线业务传输,在未来高速宽带无线通信系统中具有重要的应用。在RoF系统中使用光纤传输的优点是高带宽、低损耗,不受电磁干扰、串扰小,重量轻、投资小、灵活性高等。主要介绍RoF系统的结构,优势、限制以及关键技术等。     

城域网和接入网发展需要的低水峰单模光纤

密集波分复用(DWDM)的出现扩大了长途传输网的容量,但是DWDM技术的复杂性和使用了昂贵的器件,限制了DWDM在城域网的应用.最新研制的光纤,其在整个宽工作带,包括在(1 380±3) nm上都具有低水峰.低水峰光纤与粗波分复用(CWDM)系统比用标准单模光纤(SMF)的同一系统所用的信道间隔宽33%.经过恶劣的环境试验证明,低水峰光纤具有稳定的抗氢气引起的衰减性能,可确保现场安装的低水峰光纤光缆长期可靠地工作.由于低水峰光纤具有优异的弯曲敏感性,使其与最近研制的宽带接入技术,即所谓的光纤到驻地(FTTP)完全相适应.     

Analysis and Simulation of a Plastic Optical Fiber Access Network Based on OCDMA Technology

In this paper a plastic optical fiber (POF) access network based on optical code-division multiple access (OCDMA) technology is proposed. Recently, optical transmission using POF has received much attention due to its low weight, large core diameter, flexibility, and easy installation. Specially, its high bandwidth makes POF a very attractive candidate for a transmission media in an access network based on OCDMA technology. A conventional OCDMA system only allows a finite number of units to transmit and access simultaneously according to the number of channels which is restricted by BER. To resolve this problem a novel protocol is also proposed in this paper. The protocol can efficiently support variable-sized messages, and any new unit can join the network at any time without requiring network initialization. To implement the demonstration, each optical network unit is equipped with a fixed and a tunable optical encoder/decoder. The optical encoder/decoder employing planar holographic optical processors (HOPs) in this system may be of low fabrication cost. The network throughput and average delay using various system parameters has been investigated by numerical analysis and simulation experiments. It is shown that the dynamic control protocol in this POF access network based on OCDMA technology is valid and efficient.     

Multimode Fiber Bragg Grating Wavelength Filter in a 10-Gb/s System

A 10-Gb/s transmission experiment has been performed on multishell multimode fiber Bragg gratings. The device can simultaneously serve as wavelength filter and mode selector and is compatible with conventional graded refractive index multimode fiber (MMF) components. This could be a promising technology for wavelength-division multiplexing and mode diversity in practical MMF-based optical access networks.