基于千兆以太网的无源光网络系统及其实现技术

以太网无源光网络EPON是目前光纤到户宽带接入的主流方式．时延补偿、动态带宽分配以及局端桥接等是构建EPON系统的关键技术．为了避免多个ONU发送冲突，实现用户端设备的时延补偿和自动加入，本文采用绝对时标来补偿不同光网络单元(ONU)往返时间的差异，完成其往返时间的计算和动态测距．上行链路动态带宽分配则采用基于逻辑链路标识(LLID)的流量统计算法，结合其服务水平协议(SLA)，获得了较低的延时特性和很高的带宽利用率．在EPON光线路终端(OLT)中借助动态过滤数据库技术实现了一个OLT和多个ONU的逻辑链路MAC仿真，解决了EPON和常规以太网IAN的兼容性问题．这些技术方案在武汉邮电科学研究院(WRI)完成的863科技攻关项目中均进行了严格的测试，结果符合预期要求．提供的现场测试数据表明研制的样机系统能很好支持多种业务的综合接入．     

光时分多址技术及其在APON中的应用

在光纤通信系统中，OLT至ONU（光网络单元）的下行信号传输较简单，一般是在OLT中采用时分复用方式（或副载波复用方式，或光波波分复用方式）将需要送至各ONU的信息汇合起来送至馈线光纤，经光分路器进行功率分路，以广播方式送至每一个ONU。而ONU到OLT的上行信号的传输采用先进的多址技术。光多址接入技术比较多，如光时分多址TDMA、副载波多址SCMA、波分多址WDMA等。而光时分多址以其独特的优点成为光多址接入技术的热点之一。 一、光时分多址的基本原理及其优点 光时分多址是在同一光载波波长上，把时间分割成周期性的帧…     

无源光网络技术及其应用

无源光网络（PON）是依赖光功率分路器达到网络资源共享的一种网络结构，是目前光接入网（OAN）的一种传输体制。与有源光网络系统（SDH、PDH）相比，重要的实现了无源光分支，设备投资少，安装简单，运行维护费用低。其特有的测距技术，增减ONU站点方便，特别适应复杂地形的需要。PON系统根据接入链路要求由一个局端（OLT）和多个远端（ONU）以及无源光分配网（ODN）构成。 一、双向传输技术 在PON系统中，OLT与ONU的信号交换采用上行信号和下行信号予以解决的，OLT至ONU的下行信号的传输进程一般来说较为简单，通常采用…     

支持高性能多业务的EPON技术

1 EPON DBA EPON技术可提供双向1 Gbit/s的连接,下行链路采用1 490 nm波长,上行链路采用1 310 nm波长,另外保留1 550 nm用于模拟视频下行广播.下行数据流是连续的,可传输至所有ONU,在前导码搭载逻辑链路标识以区分PON内部特定帧的目标地址,而在上行链路,DBA负责为已注册的ONU分配带宽.     

传统ODN遇瓶颈智能ODN系统提升光纤管理水平

ODN作为基于PON设备的FTTH光缆网络,是FTTH光缆网络中非常重要的组成部分,其份额约占整个FTTH工程投资的一半,它是光纤接入网中设置在光线路终端(OLT)和光网络单元(ONU)之间线路及设备的总称,用来分配光信号功率.ODN在PON工程中为OLT和ONU之间提供光信号传输的物理通道,主要由OLT设备和ONU设备之间的光纤光缆、光连接器、光分路器,以及配线箱、接头盒等所有无源光纤、无源设备组成的网络.目前,ODN正在走向智能化.     

采用多LLID技术的EPON综合接入系统

采用远端光网络单元（ONU）设备和多逻辑链路标识（LLID）的技术,将以太网无源光网络（EPON）系统的多业务管理和远端设备管理融入新的框架,并通过将服务等级协议（SLA）与链路相联系,将业务在链路上分流,使得系统的带宽保证和严格的时延抖动控制成为可能,从而克服了以太网传送体制只能“尽力转发”的不足,较好地解决了多种业务综合接入能力的问题。     

华为OLT下“流氓ONU”的故障处理

众所周知,EPON系统光传输机制是:下行广播方式,上行TDMA方式。所谓TDMA方式就是将上行总带宽分成若干个时隙,各个ONU通过占用不同的时隙来传送业务。上行时隙的分配由OLT来完成,并由OLT通知各个ONU,各ONU只能在分配的时隙内发光。若某个ONU持续长时间发光,它就会占用OLT分配给其他ONU的发光时间,从而与其它ONU的发光信号发生冲突,造成了其它ONU的离线。这种不按照分配的时间戳向上发送光信号的ONU,即是我们通常说的"流氓ONU"。     

ODN中光纤的宏弯损耗对ONU弱光的影响

通过对ONU弱光的ODN链路衰耗进行分析,发现ODN链路的下行衰耗严重超标的现象,在用OTDR进行故障定位、并测试光纤在相应波长的宏弯损耗后,得出光纤的宏弯损耗是导致ODN链路下行衰耗超标的原因;进一步对ODN链路的入户段光缆进行衰耗测试,从而验证了宏弯损耗是引起ONU弱光的主要原因。     

基于MAX3656芯片的EPON系统中新型ONU的设计

论述了EPON系统的光模块工作模式,对ONU端光模块的设计从理论上进行了分析,包括对ONU光端模块中的芯片选择、与激光器间的耦合设计、连续接收模块等各个方面.在此基础上,讨论了一种EPON系统ONU端用的模块的设计和实现.     

双模ONU模式切换方案的设计与实现北大核心

针对双模ONU(光网络单元)注册前如何正确识别当前系统的问题,提出了两种双模ONU的切换方法,结合双模ONU可能出现的切换情况,选择适合当前切换场景的切换方法,设计并实现了双模ONU自动识别当前GPON(吉比特无源光网络)/EPON(以太无源光网络)系统的方案,从而解决了运营商采用混合方式部署接入系统的问题,同时也为实现两种技术的融合提供了参考。     

A self-seeded reflective SOA-based optical network unit for optical beat interference robust WDM/SCM-PON link

We have proposed and experimentally demonstrated a novel optical source configuration that uses a self-seeded reflective semiconductor optical amplifier (RSOA) as an optical network unit (ONU) in a wavelength division multiplexed/subcarrier multiplexing (SCM)-passive optical network (PON). A fiber Bragg grating (FBG) was used to obtain a single longitudinal mode of the RSOA. The proposed ONU configuration is simple, cost-effective, and effective regardless of wavelength allocation. Additionally, it would be robust for optical beat interference (OBI) noise. As the ONU is composed only of an RSOA and FBG, the self-seeded RSOA, due to the strong self-injection caused by the reflection of the FBG, has a broad optical spectrum. A self-homodyne apparatus method was performed in order to demonstrate the robustness of the self-seeded RSOA in OBI. To confirm the validity of the proposed scheme, a 16-quadrature amplitude modulation transmission experiment was performed in a 10-, 20-km optical access link with an SCM frequency of 1 GHz. An error vector magnitude of less than 4% for 2 Msps was successfully obtained through the transmission experiment.     

Two‐Stage Resource Allocation to Improve Utilization of Synchronous OFDM‐PON Supporting Service Differentiation

We propose a two‐stage resource allocation algorithm for the high link utilization of an orthogonal frequency‐division multiplexing passive optical network (OFDM‐PON). An OFDM‐PON is assumed to use a synchronous frame structure in supporting service differentiation. In distributing resources, the proposed algorithm first allocates a time window for each optical network unit (ONU), and then it arranges a subchannel, which is a group of subcarriers. This algorithm needs to satisfy two constraints. First, computations for the resource allocation should be done using a frame unit. Second, an ONU has to use a single subchannel to send upstream data for multiple services within a frame duration. We show through a computer simulation that the proposed algorithm improves the link utilization.     

一种改进的PON保护组解决方案

无源光网络(PON)无疑是下一代接入网的一种主流方案。由于该技术一般采用点到多点(P2MP)的树形拓扑结构,因此从局端设备OLT的PON MAC到ONU的PON MAC之间的链路可靠性就显得极为重要。文章提供了一种快速、稳定、成本低、易扩展且与PON系统其他软件模块兼容的光纤保护倒换的整体方案。     

Impact of backreflection on upstream transmission in WDM single-fiber loopback access networks

This paper investigates the impact of backreflection lights on upstream transmission in wavelength division multiplexing (WDM) single-fiber loopback access networks, where a WDM light source is located at the central office (CO) and each optical network unit (ONU) includes an optical modulator with optical amplifiers. This study considers backreflection lights from two sources, the continuous wave (CW) light at the CO (Reflection-I) and the modulated signal at the ONU (Reflection-II). It is confirmed, for the first time, that the impact of Reflection-II increases strongly with ONU gain. To estimate the impact of these backreflection lights, a simple intensity noise estimation scheme is presented. This scheme clarifies that the acceptable transmission line losses is 10 dB for 1.25 Gb/s under the optical return loss (ORL) of -32 dB.     

Efficient Power‐Saving 10‐Gb/s ONU Using Uplink Usage‐Dependent Sleep Mode Control Algorithm in WDM‐PON

We propose and demonstrate an efficient power‐saving optical network unit (ONU) based on upstream traffic monitoring for 10‐Gb/s wavelength division multiplexed passive optical networks (WDM‐PONs). The power‐saving mode controller uses a μ‐processor and traffic monitoring modules followed by the proposed power‐saving processes to operate the sleep mode ONU. The power consumption of the ONU is effectively reduced from 19.3 W to 6.4 W when no traffic from the users is detected. In addition, we design a power‐saving mechanism based on a cyclic sleep mode operation to allow a connectivity check between the optical line terminal and ONU. Our calculation results show that the WDM‐PON ONU reduces the power consumption by around 60% using the proposed mechanism.     

Adaptive Optical Network Unit for Point-to-Point and PON Systems Based on Gigabit Ethernet

This paper proposes an optical network unit (ONU) that works in point-to-point (P2P) optical access systems as well as passive optical network (PON) systems and so reduces the operational expenditure of optical access networks in the full FTTH era. First, we discuss its design and implementation; after clarifying the requirements for the adaptive ONU, we describe how it should work while focusing on Gigabit-Ethernet-based P2P and PON systems. Next, we study its feasibility through experiments on a prototype. Also, we provide some additional considerations regarding the implementation and future application of the adaptive ONU.     

Optimization of Rayleigh-Limited WDM-PONs With Reflective ONU by MUX Positioning and Optimal ONU Gain

In this work, the influence of the distribution element position and the reflective optical network unit (ONU) gain in wavelength-division-multiplexing passive optical networks are reported. After the theoretical and experimental analysis, it is determined that the best crosstalk-to-signal ratio is achieved if the multiplexer is placed either in the ONU or optical light termination vicinity, and the ONU gain has a new optimum value depending on the position. Also, it is demonstrated that Rayleigh backscattering is generally irrelevant in downstream transmission.      

A Wavelength-Division-Multiplexed Passive Optical Network With Flexible Optical Network Unit Internetworking Capability

We propose and experimentally demonstrate a novel flexible optical network unit (ONU) internetworking architecture over a wavelength-division multiplexed passive optical network (WDM-PON). By employing our designated wavelength assignment and remodulating the downstream differential phase-shift keying signal as the ONU internetworking carrier, one ONU can broadcast its own message to all other ONUs, with negligible signal interference. Moreover, the inter-ONU communication can further be partitioned into arbitrary virtual private groups of ONUs by employing designated RF tones for identification and control. It was experimentally demonstrated that the performance degradation due to the introduction of RF tones is negligible compared with the full broadcast case. Our proposed scheme can provide high flexibility and practical implementation for WDM-PONs.     

海口市光纤接入网主干光缆网络的规划与建设

概述了海口市光纤接入网规划的必要性和步骤，阐述光网络单元（ＯＮＵ）规划的主要考虑；重点简介了主干光缆网络规划的思路、考虑因素及主要结论；提出在建设时应注意的几点问题。