ROADM全光交换网络关键技术发展与应用展望

介绍了可重构光分插复用器（reconfigurable optical add/drop multiplexer，ROADM）网络的发展历程、ROADM技术方案以及国内ROADM网络的部署情况。全面阐述了ROADM关键技术的发展方向，包括光交叉连接（optical cross-connect，OXC）设备、高维度波长选择开关（wavelength selected switch，WSS）、波长无关/方向无关/竞争无关ROADM （colorless/directionless/contentionless ROADM，CDC-ROADM）、400 Gbit/s FlexGrid ROADM、下一代波长交换光网络（next-generation wavelength switched optical network，WSON2.0）智能控制平面技术。分析了现有ROADM网络应用场景与技术发展趋势，展望了ROADM全光交换网络未来发展前景。     

Digital optical networks using photonic integrated circuits (PICs) address the challenges of reconfigurable optical networks

To reduce costs and simplify operations, carriers are deploying flexible optical networks that can be easily reconfigured and managed remotely. This article provides an overview of typical all-optical reconfigurable optical add/drop multiplexer (ROADM) systems and their associated network issues. We describe a novel digital optical network architecture based on digital ROADM systems, which use photonic integrated circuits (PICs) to overcome many of these issues. Digital ROADM systems use monolithic PICs to integrate over 60 discrete optical components, including lasers, modulators and detectors, into a single pair of optical components, allowing cost-effective optical-electrical-optical conversion at every node. This also allows key functions such as service reconfiguration, add/drop and protection to be implemented in the digital domain, and enables de-coupling of service provisioning from optical link engineering, termed bandwidth virtualization. Finally, key deployment, reliability and operational metrics for PIC-based digital ROADM systems are presented.     

Field Trial of 640-Gbit/s-Throughput, Granularity-Flexible Optical Network Using Packet-Selective ROADM Prototype

Reconfigurable optical add/drop multiplexers (ROADMs) are able to provide flexible wavelength path provisioning in wavelength division multiplexing (WDM) networks. However, the capability of conventional ROADMs is limited to handling wavelength paths, and it does not support fine granularity in add/drop multiplexing of packets. Recently, we have proposed and demonstrated a packet-selective ROADM that combines an acoustooptic wavelength-tunable filter (AOTF) and an optical packet ADM (PADM) using optical code label processing. It provides more efficient utilization of wavelengths than conventional ROADMs. However, the bit rate of the demonstration was limited up to 10 Gbit/s. In this paper, we newly develop a label-selectivity-enhanced optical en/decoder, which allows the optical label recognition with 40-Gbit/s nonreturn-to-zero (NRZ) data packets, and a wide pass-band AOTF for 40-Gbit/s signals. Furthermore, we develop 640-Gbit/s throughput, packet-selective ROADM prototype, and demonstrate a field trial of granularity-flexible 3-node optical network over 173 km. error-free packet ADMs (error rate of under 10^-12) for all 16-wavelength channels at all nodes are obtained.     

ROADM设备网管系统的实现

可重构的光分插复用(ROADM)设备是光传送网的重要节点,通过软件配置,可以灵活实现波长上下,使网络具备重构功能.建立基于SNMP协议的网元管理系统是保证ROADM设备稳定灵活工作的前提,文章简述了ROADM设备的功能结构,并讨论了设备网管系统的建立和配置功能的软件实现.     

ROADM技术及其实现的研究

随着ROADM技术的发展,运营商逐渐采用它作为传送网的重要光节点.文章分析了当前ROADM的三种主要技术(分别基于波长阻塞器、集成平面光波导和波长选择开关),讨论了实现ROADM的几个方案,提出一种称为Semi-ROADM的节点结构.它能在利用新技术的同时,降低成本、有效保护投资.     

Novel node upgradation strategy for migration to elastic optical networks

For migration from dense wavelength division multiplexing (DWDM) networks to elastic optical networks (EON),it is required to upgrade the traditional reconfigurable optical add-drop multiplexer (ROADM) to the new-generation ROADM that supports flexible grids.However,for a large-scale optical network,it is generally impossible to upgrade the ROADM nodes all in once; rather,they would be upgraded gradually.For this,it is critical to study different strategies for selecting the ROADM nodes to be upgraded.Also,for the interconnection between different generations of ROADM,the sub-band virtual concatenation (VCAT) technique was employed to enable an optical channel to be established via traversing different types of nodes.An integer liner programming (ILP) model and an efficient heuristic algorithm were developed to jointly select the ROADM nodes to upgraded and assign spectrum resources.Simulation studies show that the proposed strategy for the upgraded node selection is efficient to perform close to the ILP model in terms of the maximum number of FS used in the whole network.     

简化的ROADM模块及其在传送网络升级改造中的应用

首先介绍了现在流行的实现动态可重新配置光上下路复用器(ROADM)模块的解决方案,然后提出了一种简化的ROADM模块和网络结构,接着探讨了它在传送网络升级改造中可能的应用。该方案可用于提高新老设备的利用率,解决峰值时间和各站点间通信堵塞问题。文章还提出了一种用简化的ROADM实现环间业务动态调度的方法。文章所建议的ROADM模块具有成本低、对网络中其它信号干扰小等优点。     

可调谐滤波器在DWDM系统中的应用

可调谐滤波器是实现未来全光网络的重要器件,在DWDM系统中有着广泛应用.文章介绍了几种常用的可调谐滤波器的原理、最新研究及其在可重构光分插复用和光传输性能监测中的应用.     

面向超100G系统的可变带宽ROADM及控制平面技术

研究了基于ROADM和灵活栅格技术的结合实现超100G光线路上的灵活封装和智能调度的解决方案。重点分析了如何通过控制平面的不同模块来实现更加高效支持灵活栅格的ROADM与整个超100G系统的协同统一工作,打造新一代智能弹性高速光网络的架构。     

Reconfigurable Optical Add‐Drop Multiplexer Using a Polymer Integrated Photonic Lightwave Circuit

We have developed a fully functional reconfigurable optical add‐drop multiplexer (ROADM) switch module using a polymer integrated photonic lightwave circuit technology. The polymer variable optical attenuator (VOA) array and digital optical switch array are integrated into one polymer PLC chip and packaged to form a 10‐channel VOA integrated optical switch module. Four of these optical switch modules are used in the ROADM switch module to execute 40‐channel switching and power equalization. As a wavelength division multiplexer (WDM) filter device, two C‐band 40‐channel athermal arrayed waveguide grating WDMs are used in the ROADM module. Optical power monitoring of each channel is carried out using a 5% tap PD. A controller and firmware having the functions of a 40‐channel switch and VOA control, optical power monitoring, as well as TEC temperature control, and data communication interfaces are also developed in this study.     

广播与选择型ROADM的设计与实现

文章对动态可重构光分插复用器（ROADM）进行了介绍;对实现ROADM的多种方案进行了归纳整理和简要分析;对其中解复用／开关矩阵／复用（DSM）、DSM波段、广播与选择（B＆S）3种典型的ROADM结构进行了较详细的说明。文章作者设计并实现了广播与选择型ROADM,井对实验系统的上／下路功能和信道功率均衡功能进行了验证。     

Spectrum-efficient optical drop-add-drop network with a centralized multi-carrier light source

Traditional ROADM networks strictly follow the coarse ITU-T standard wavelength grids and channel spacings, which would result in low optical spectrum utilizations under dynamic traffic requests of variable spectrum lightpaths. This paper presents a spectrum-efficient optical drop-add-drop network with a centralized multi-carrier light source (C-MCLS). The C-MCLS generates thousands of optical carriers with uniform and narrow channel spacings. The optical carriers are distributed to each network node as light sources on demand through ROADMs designed with the carrier-drop function. Spectrum-aware optical carrier allocation is studied first in the proposed network. This paper proposes a Minimum Fragmentation Request First (MinFragRF) optical carrier allocation algorithm compared with the Maximum Spectrum Request First (MaxSRF) and Minimum Spectrum Request First (MinSRF) allocation algorithms. This paper also studies how channel spacings of optical carriers impact on the network performance under variable traffic demands. We perform both network analysis and simulations to evaluate the network performance in terms of the lightpath blocking probability (LP_BP) and the effective spectrum efficiency. We analytically derive the formulas of LP_BP and average effective spectrum efficiency in the proposed network. Simulation results show that the proposed network with more narrow channel spacings greatly reduces the lightpath blocking probability compared with the traditional ROADM network. The average effective spectrum efficiency of the proposed network can be improved about 100 % compared with that of the traditional ROADM network by choosing appropriate network design parameters. The MinFragRF allocation algorithm has a better LP_BP performance than that of the MaxSRF and has a better spectrum utilization efficiency than that of the MinSRF. The optimal channel spacing evaluations show that narrow channel spacings such as 6.25 and 12.5 GHz greatly improve LP_BP performance when low bit-rate traffic requests dominate in the traffic model. However, as the high bit-rate traffic requests increase, the performance advantage of narrow channel spacings is gradually disappearing.     

可重构型光分插复用器浅析

随着可重构型光分插复用器(ROADM)在过去几年的发展,完全的光交换成为可能,使得动态光网络逐渐取代了传统的静态光网络,在通信和网络领域占据了重要的地位。这里首先介绍了ROADM架构,然后阐述了目前ROADM中最为关键的波长选择交换器的实现原理以及4种不同的可用的解决方案,并对他们的优点和缺点进行了分析。最后对未来可能的应用和发展方向进行了讨论。     

可重构光分插复用器(ROADM)的技术实现与性能评估

从光网络节点的功能要求出发,详细讨论了开关型和调谐型两大类ROADM的技术实现方案,并对各种ROADM技术的性能进行了比较分析。     

Cost efficient traffic grooming and regenerator placement in impairment-aware optical WDM networks

In this paper, we address the problem of traffic grooming and regenerator placement in a WDM optical network in which lightpaths are hop-constrained by physical impairments. The efficient placement of regenerators and electronic grooming equipment at ROADM nodes for a given network topology is required such that all traffic demands can be supported with minimum cost. We present a detailed ROADM node architecture together with an associated cost model. We model the problem by Integer Linear Programming (ILPs) and propose an auxiliary-graph-based heuristic for jointly placing regenerators and electronic grooming equipment in the network. To evaluate the performance of the proposed heuristic, we also derive a lower bound on the network cost. The numerical results show that combining the grooming problem with the placement of regenerators reduces the network cost significantly compared to the cases in which traffic grooming and regenerator placement are handled separately. The performance of the proposed polynomial-time heuristic is very close to the lower bound and approaches the bound as the network load increases.     

光开关矩阵技术及其应用研究

光开关矩阵是智能光交叉连接设备和可重构光分插复用器核心技术,是构建自动交换光网络的基础.文章介绍了大规模商用的光开关矩阵的关键技术及其进展,详细分析了光开关矩阵在自动交换光网络中的应用.     

Parallel-stage-based reconfigurable optical add-drop multiplexer for WDM optical transport networks

This letter proposes a simple and flexible reconfigurable optical add-drop multiplexer (ROADM) based on parallel-stage configuration using Mach-Zehnder-based fiber gratings, 1/spl times/2 optical switches, and Y-model combiners. The proposed ROADM with four-stage parallel configuration is designed and experimentally investigated to show its performance in full wavelength selection and advantages in reducing the discrepancy of the insertion loss between channels and upgrading.     

GMPLS控制ROADM的光传送网结构和路由协议扩展

ROADM提供了光网络的灵活性和重配置能力,GMPLs是多层次交换网络统一的控制平面.在介绍ROADM技术和CMPLS协议的基础上,描述了由GMPLS控制ROADM构成的光网络结构,并完成扩展GMPLS路由协议以支持在ROADM端口约束条件下的路由.     

High Spectral Efficiency 400G i＇ransmission

This paper gives an overview of the generation and transmission of 450 Gb/s wavelength-division multiplexed (WDM) channels over the standard 50 GHz ITU-T grid at a net spectral efficiency (SE) of 8.4 b/s/Hz. The use of nearly ideal Nyquist pulse shaping, spectrally-efficient high-order modulation format, distributed Raman amplification, distributed compensation of ROADM filtering effects, coherent equalization, and high-coding gain forward error correction (FEC) code may enable future 400G systems to operate over the standard 50 GHz grid optical network.     

Terabit Transmission at 42.7-Gb/s on 50-GHz Grid Using Hybrid RZ-DQPSK and NRZ-DBPSK Formats Over 16 × 80 km SSMF Spans and 4 Bandwidth-Managed ROADMs

We demonstrate for the first time the use of asymmetric-bandwidth interleaver-based reconfigurable optical add-drop multiplexer (ROADM) to transmit 42.7-Gb/s channels on a 50-GHz grid. Differential binary phase shift keyed (DBPSK) format was used on the wide passband side and differential quadrature phase shift keyed (DQPSK) format was used on the narrow passband side of the ROADM. 25 channels with an aggregate capacity of 1-Tb/s were transported over 1280-km of standard single-mode fiber (SSMF) including 4 ROADMs.