全双工光载无线隧道通信系统

鉴于长距离隧道内复杂的无线传输环境,传统通信技术不能满足旅客高质量的通信需求,提出了一种基于波分复用无源光网络的光载无线（RoF）分布式隧道通信系统。采用波分复用技术实现不同业务在光域的物理隔离,协同分布式天线技术,在隧道内部提供高频无线接入,提升系统带宽的同时解决了隧道内部信号急剧衰减的问题。通过实验搭建了全双工的光载无线试验平台,实现了用光学的方法产生和传输载频为24 GHz的16/64QAM矢量信号,并且通过测量上下行链路的EVM值验证了方案的可行性。     

面向2G、3G、4G融合接入应用的光载无线分布式天线系统

近年来,信息技术以日新月异的速度飞快发展,对人们工作及生活产生了极大的影响,而2G、3G、4G等网络的变更,促使天线网络应用过程中功能提升.新时期,为了不断降低天线网络成本,相关机构提出了光载无线分布式天线系统,该系统当中需要将2G、3G、4G进行有效融合.本文首先分析了该系统当中的传输性能影响因素,并对SCM-CWDM这一分布式传输技术进行了充分地研究.     

基于光纤无线融合的射频无源光网络

文章认为为了实现更大的光接入网容量,并能更好地完成多业务的承载与融合,亟待发展下一代光接入网技术。文章提出了基于光纤无线融合的射频无源光网络(RPON),其不仅具有现有无源光网络系统低成本和易管控的特点,还具备光载射频系统灵活度高和移动性好的优势。该系统通过光生毫米波和波分复用的方式,实现了1Gb/s多媒体业务的单纤上下行传输,达到了10km光纤和5m无线的接入距离,能够满足低成本化推广应用要求。     

单模光纤受激布里渊散射阈值分析与计算

受激布里渊散射是光纤一种非常重要的非线性效应,不同光纤的受激布里渊散射阊值不同。在光纤通信系统和光纤分布式布里渊传感系统中,受激布里渊散射阈值的研究非常必要。设计并搭建受激布里渊散射阈值测量系统,实验测量了普通通信光纤（G．652）、大有效面积的非零色散位移光纤（G．655）在常温时的受激布里渊散射阈值。通过阈值测量可知,G．655光纤阈值明显大于G．652光纤,所以无论对于光纤通信系统,还是自发布里渊传感系统,都应优选G．655光纤。     

基于受激布里渊散射的30GHz毫米波单边带调制生成技术

本文提出了一种基于受激布里渊散射原理的单边带调制产生30GHz毫米波的新方法,可应用于光载射频系统。该方法利用一个双布里渊散射移频结构生成泵浦光,并将其反向注入到传输信号光的25 km单模光纤;通过受激布里渊散射,直接放大受调制信号光的正三阶边带,实现光载波的单边带调制,有效改善由色散效应引入的功率涨落问题,保证了毫米波功率稳定。此外,信号光和泵浦光由同一个激光器产生,有效消除两者间的相对频率漂移,从而大大提升了毫米波生成系统的频率稳定性。通过我们的方法,实验系统所生成的毫米波功率增益了21dB,其3dB线宽为10kHz。     

超宽带光载无线系统及其关键技术

基于微波光子技术的超宽带光载无线（RoF）系统是未来低成本、高性能超宽带无线接入网络的重要解决方案,前人已有许多研究成果。基于已有研究成果,文章设计了基于全光矢量调制技术的光载无线（RoF）系统,使信号的频谱效率进一步提高;基于毫米波相移键控调制的全双工光载无线系统,可以大大简化基站的结构和光纤的铺设;多业务混合传送的光载无线系统,可以同时承载有线和多个无线信号的业务。文章还展示了一种基于RoF的高清视频传输平台。     

基于受激布里渊散射的40 Gb/s时钟提取试验

对基于受激布里渊散射效应(SBS)的时钟恢复系统模型进行了试验验证,实现了40 Gb/s载波抑止归零码(CSRZ)的全光时钟提取.试验结果表明由于产生了强烈的受激布里渊散射的梳状放大特性,光信号的时钟分量得到显著增强.在不改变该模型结构的基础上,利用G.652普通单模光纤传输8 km而不经过色散补偿的40 Gb/s载波抑止归零码光信号恶化以后仍可进行良好地时钟恢复,时钟抖动小于6.5 ps.研究证明该方案可在一定程度上抵制传输信号恶化所造成的影响,并无明显的码型效应,适合高速长距离全光时钟提取.     

分布式EDFA中受激布里渊散射效应的研究

利用含有受激布里渊散射效应（ＳＢＳ）的传输方程，研究了透明传输和最佳掺杂浓度下，受激布里渊散射效应对分布式掺铒光纤放大器（ｄ－ＥＤＦＡ）的各种特性的影响。结果表明：受激布里渊散射消耗了ｄ－ＥＤＦＡ的泵功率，恶化了系统的噪声特性，使传输系统的最佳泵浦周期减小，所需的总泵浦功率增大     

受激布里渊散射的空间光限幅效应的数值研究

采用布里渊噪声起源模型求解受激布里渊散射瞬态耦合波方程,数值模拟了截面光强为高斯分布的光束通过布里渊介质后的光强分布。结果表明,透射光束截面光强呈现出近似平顶的超高斯分布,光强峰值被限制,显示出受激布里渊散射的空间光限幅效应。当改变相互作用长度或者介质增益系数,即可以改变受激布里渊散射的产生阈值,进而改变输出脉冲空间限幅的幅值。     

光纤的非线性效应——受激布里渊散射

石英单模光纤在一般情况下为一条线性的光传输线，但在输入光纤的光功率超过某个阈值后，光纤中将出现非线性效应。当光纤中出现非线性效应时，光纤已不是一条线性的传输线，光信号在光纤中传输时，将产生失真，从而限制了光信号在光纤中的传输。光纤中的非线性效应分为受激喇曼散射、受激布里渊散射（SBS）、自相位调制和四波混频等物理现象。其中，对于模拟信号长距离传输影响最大的非线性效应是受激布里渊散射，本文着重对SBS的产生、物理现象、对光通信的影响和如何减小SBS效应对光通信带来的危害进行讨论。     

Broadband access using subcarrier multiplexing and asymmetric digital subscriber lines

A broadband access system using subcarrier multiplexing on optical fibre and asymmetric digital subscriber lines (ADSL) or very high‐speed digital subscriber lines (VDSL) on unshielded twisted‐pair is proposed to provide broadband access. In this hybrid‐fibre/twisted‐pair (HFTP) system, the digital multiplexing/demultiplexing process is moved back to the central office by using subcarrier multiplexing for fibre transmission. Instead of installing in remote node, ADSL/VDSL transceivers are installed at the central office to greatly reduce the remote node complexity. The local node simply down‐converts the subcarrier multiplexed ADSL/VDSL signal to the baseband, suitable to send directly into the twisted‐pair. The reduction of complexity could result in a lower initial installation cost, especially for a low service penetration rate. Copyright © 2000 John Wiley & Sons, Ltd.     

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.     

Bandwidth allocation for multiservice access on EPONs

Ethernet passive optical networks are a low-cost high-speed solution to the bottleneck problem of the broadband access network. A major characteristic of EPONs is the shared upstream channel among end users, mandating efficient medium access control to facilitate statistical multiplexing and provision multiple services for different types of traffic. This article addresses and provides an overview of the upstream bandwidth allocation issue for multiservice access provisioning over EPONs, and proposes an algorithm for dynamic bandwidth allocation with service differentiation. Based on the multipoint control protocol (MPCP) and bursty traffic prediction, our algorithm enhances QoS metrics such as average frame delay, average queue length, and frame loss probability over other existing protocols     

1.25-Gb/s Transmission Over an Access Network Link With Tunable OADM and a Reflective SOA

The emerging broadband services and the avalanche-like growth of the broadband subscribers result in the intensification of data traffic in access networks. This drives the development of last-mile technologies to support multiservice provision on high bit-rate-capable reconfigurable networks. In this letter, we present the first transmission experiments carried out on the testbed of a hybrid wavelength-division-multiplexing/time- division-multiplexing access network based on cost-efficient elements like an integrated optical add–drop multiplexer and a reflective semiconductor optical amplifier. We successfully transmit two 1.25-Gb/s wavelength channels over 26-km standard single-mode fiber carrying data to and from the user.      

Wired and single sideband wireless service based on a single optical modulator

In order to provide more flexible and convenient service for users in the hybrid transmission network,a novel system using a single optical modulator to provide wired and single side band (SSB) wireless signal was proposed.By combining the application of dual-polarization binary phase shift keying modulator (DP-BPSK),phase shifter and other devices,wired and SSB wireless signals were directly generated to suppress the walk-off effect caused by dispersion,and the effective transmission of 5 Gbit/s SSB wireless signal carried on 40 GHz millimeter wave and 10 Gbit/s wired signal over 65 km single-mode fiber (SMF) were successfully achieved.The experiments show that the application of polarization multiplexing technology and optical subcarrier multiplexing technology can make the signal have a greater improvement in transmission rate and performance,and play an important role in the future broadband communication network.     

以太网无源光网络中的时间标签法测距

基于千兆以太网的无源光网络将千兆以太网与无源光纤接入的优势相结合,实现低成本的高速、远距离接入。针对EPON系统上行链路多个ONU共享带宽的树型拓扑结构,为实现EPON系统上行TDMA接入,提出了时间标签法测距方案,论述了方案的可行性并指出其优点。     

正交频分复用无源光网络

认为当采用低频段的射频资源时,色散导致的双边带功率衰落对正交频分复用无源光网络(OFDM-PON)的影响很小。基于时分复用(TDM)架构的OFDMPON,充分利用正交频分复用(OFDM)技术的优势与TDM架构的无色性,与现有的以太网无源光网络(EPON)、千兆比无源光网络(GPON)兼容性高,是解决上行无色性传输的最优方案。基于OFDM的时波分复用无源光网络(TWDM-PON)充分利用了OFDM调制优势,用来提升单载波容量,在不改变TWDM-PON系统结构情况下,实现100 Gbit/s的高速接入,是未来无源光网络的重要候选方案。     

RACE Project R1030, ACCESS-a system study of the broad-bandsubscriber loop

The ACCESS project, which is a project within the RACE (Research in Advanced Communication in Europe) program, is described. The scope of the project is to study the entire customer access connection, including the transmission, the multiplexing, and the passive optical network. The goal of the project is to perform an overall cost optimization, leading to one or more preferred implementations. Because the project is oriented toward the early phases of the integrated broadband network, the majority of the effort is spent on optimization and supplementation of present near-commercial technologies. The project involves 13 partners who share the work organized in three major areas, namely, the 622 Mb/s transmitter/receiver unit for bidirectional transmission on one single-mode (SM) fiber at 1330 and 1550 nm; the passive optical components, including mass splicing techniques, low-cost connectors, wavelength division multiplexing (WDM) devices, optical distribution frames, and optical cables; and system aspects of the frame structure and the interfaces to the customer premises network and to the exchange, with the associated functional units being the multiplexers and the broadband channel selector     

100G光传送技术渐入佳境

高速Internet和视频业务的迅速发展,IP网络流量持续强劲增长,对运营商的骨干传送网络提出了更高的要求,100G光传技术因此应运而生。该技术在码型、复用方式、相干接收和前向纠错(FEC)等关键技术方面都有创新。对于100G传输商用设备,业界一般看好的长距传输码型是采用相干接收的偏振复用正交相移键控(PDM-QPSK),但由于目前模数转换器(ADC)和DSP芯片等处理技术水平的限制,几乎所有高速电信号处理芯片都没有商用解决方案,这是目前的技术攻关重点。近年来实验室和现网实验方兴未艾,预计基于100G的长距传送系统在1～2年后开始部署。