面向数据中心光互连的高速光传输技术

数据中心光互连场景可分为数据中心内部和数据中心之间2大类。对于数据中心内部光互连,利用新型调制方案、高性能光器件和高速数字信号补偿算法是提升单通道速率的主要方式;对于数据中心之间光互连,结合单边带调制和非线性补偿算法克服色散功率衰落是重要研究方向。未来数据中心的升级依赖于光电器件和数字信号处理的共同进步。     

自由空间光互连系统的结构和设计分析

光互连技术是光通信网络的基础。文章结合现代微电子系统中所采用的自由空间光互连技术,进行较全面的光互连结构和设计分析     

光互连与面发射激光二极管

为克服光通信、电子计算技术等的速度限制,采用光互连是一种有效途径。光互连也是光计算机的基本技术。文中对光互连技术进行了分析,并介绍了一种有利于光互连的最理想光源——面发射激光二极管。     

面发光激光器和超并行光电技术

为建立多媒体信息网络等未来的信息通信社会基础,光电技术的重要性在增加,特别是光通信网络、用光连接计算机的光互连,在下一代光系统中其信息传输的容量越发增大,开拓新的光技术变得很重要。以往的光通信系统是以点和点之间的传输为主,但今后利用网络及并联光传输大量信息将越来越重要。     

光信号测控系统远程控制技术

光通信系统的远程测控技术是实现光互连的基础.建立了光谱测试仪远程测控系统模型.基于GPIB总线通信,在Windows2000操作系统下,以NI的虚拟仪器编程语言LabWindows/CVI 7.0为系统软件开发平台,成功实现对光通信系统的远程控制.从而为远程光子实验室的建立、光互连的实现做技术上的准备.     

光电子集成器件

以光通信应用为中心,研制了激光器,发光二极管,光探测器等半导体光电器件,并且已经用于很多实用化系统。要使这些发光,和探测器件工作,必须要有驱动电路和放大电路。由于半导体光电器件和电子电路之间的互连会直接影响到响应速度和噪声特性,所以这是在系统结构方面必须注意的问题之一。在力求解决这种光一电互连问题的同时,考虑并提出了一种性能更高,功能更多的新一代器件,这就是光电子集成电路。     

数据中心的高速光互连技术

介绍了数据中心的高速光互连技术的最新进展,重点关注新型调制和解调技术。为了降低成本,需要采用低带宽光电器件,高级QAM调制和直接检测将可能用于高速光互连技术中。同时介绍了中兴通讯近年来在这方面的研究进展,包括最先采用直接检测实现了4x128 Gbit/s信号传输距离超过300 km的实验。     

面发光激光器

一、概述 为了构筑将来多媒体信息网络等的通信社会的基础设施,光电子技术的重要性日益增长。特别是下一代的光通信网络和计算机用光连接的光互连等的下一代光系统中,其信息传输容量的增大和新型光技术的开拓越来越显得重要。过去的光通信系统主要是从点到点的传输,但今后特别指望网络化和用光传输巨大信息量的并列光传输。     

HDMI光缆的研制及自动化测试

给出了一种HDMI光缆连接器制作方式。利用并行光互连技术实现HDMI中4通道高速信号的传输,同时通过编码技术及控制器模拟热插拔过程实现低速互连。通过实际测试,其单通道在3.25 Gbit/s可以传输300 m,可以实现HDMI的长距离传输。HDMI光缆同普通HDMI铜缆一样可热插拔。并且提供了一种自动化测试系统,用于测试并行光互连模块的各个通道,测试系统可以应用到其他的多通道高速光通信产品的测试中,大大降低HDMI光缆的测试成本。     

云计算数据中心光互联技术及应用趋势

云计算不断发展将使数据中心聚集大量的数据,这不仅要求数据中心内部的服务器之间需要更加高效的互联,同时要求数据中心之间也要新的互联技术。本文从云数据中心对网络的需求出发,分析了云计算数据中心之间和数据中心内部的光互联技术方案,探讨了数据中心光互联技术的应用趋势。     

A survey on high-precision time synchronization techniques for optical datacenter networks and a zero-overhead microsecond-accuracy solution

A datacenter, which is a highly distributed multiprocessing system, needs to keep accurate track of time across a large number of machines. Precise time synchronization has become a critical component due to stringent requirements of several time critical applications such as real-time big data analytics, high-performance computing, and financial trading. Our study starts with a survey on the most relevant time synchronization techniques for datacenter networks. Then, we propose a zero-overhead microsecond-accuracy solution to synchronize a packet-switched optical network for datacenters. To achieve the desired time accuracy, we consider precision time protocol to synchronize the server clocks with a central controller clock. Zero-overhead is maintained by using data traffic to carry the time messages instead of a separate control channel. Through simulation, we show that microsecond level of time accuracy can be achieved. We also discuss the dependency of the accuracy on different traffic loads, traffic distributions, and packet lengths.     

A high-throughput energy-efficient passive optical datacenter network

Datacenter applications impose heavy demands on bandwidth and also generate a variety of communication patterns (unicast, multicast, incast, and broadcast). Supporting such traffic demands leads to networks built with exorbitant facility costs and formidable power consumption if conventional design is followed. In this paper, we propose a novel high-throughput datacenter network that leverages passive optical technologies to efficiently support communications with mixed traffic patterns. Our network enables a dynamic traffic allocation that caters to diverse communication patterns at low power consumption. Specifically, our proposed network consists of two optical planes, each optimized for specific traffic patterns. We compare the proposed network with its optical and electronic counterparts and highlight its potential benefits in terms of facility costs and power consumption reductions. To avoid frame collisions, a high-efficiency distributed protocol is designed to dynamically distribute traffic between the two optical planes. Moreover, we formulate the scheduling process as a mixed integer programming problem and design three greedy heuristic algorithms. Finally, simulation results show that our proposed scheme outperforms the previous POXN architecture in terms of throughput and mean packet delay.     

Experimental demonstration of time-aware software defined networking for OpenFlow-based intra-datacenter optical interconnection networks

Nowadays, most service providers offer their services and support their applications through federated sets of data centers which need to be interconnected using high-capacity optical networks in intra-datacenter networks. Many datacenter applications in the environment require lower delay and higher availability with the end-to-end guaranteed quality of service. In this paper, we propose a novel time-aware software defined networking (TaSDN) architecture for OpenFlow-based intra-datacenter optical interconnection networks. Based on the proposed architecture, a time-aware service scheduling (TaSS) strategy is introduced to allocate the network and datacenter resources optimally, which considers the datacenter service scheduling with flexible service time and service bandwidth according to the various time sensitivity requirements. The TaSDN can arrange and accommodate the applications with required QoS considering the time factor, and enhance the data center responsiveness to quickly provide for intra-datacenter service demands. The overall feasibility of the proposed architecture is experimentally verified on our testbed with real OpenFlow-enabled tunable optical modules. The performance of TaSS strategy under heavy traffic load scenario is also evaluated based on TaSDN architecture in terms of blocking probability and resource occupation rate.     

Efficient algorithms for scheduling multiple bulk data transfers in inter‐datacenter networks

Bulk data transfers, such as backups and propagation of bulky updates, account for a large portion of the inter‐datacenter traffic. These bulk transfers consume massive bandwidth and further increase the operational cost of datacenters. The advent of store‐and‐forward transfer mode offers the opportunity for cloud provider companies to transfer bulk data by utilizing dynamic leftover bandwidth resources. In this paper, we study the multiple bulk data transfers scheduling problem in inter‐datacenter networks with dynamic link capacities. To improve the network utilization while guaranteeing fairness among requests, we employ the max–min fairness and aim at computing the lexicographically maximized solution. Leveraging the time‐expanded technique, the problem in dynamic networks is formulated as a static multi‐flow model. Then, we devise an optimal algorithm to solve it simultaneously from routing assignments and bandwidth allocation. To further reduce the computational cost, we propose to select an appropriate number of disjoint paths for each request. Extensive simulations are conducted on a real datacenter topology and prove that (i) benefiting from max–min fairness, the network utilization is significantly improved while honoring each individual performance; (ii) a small number of disjoint paths per request are sufficient to obtain the near optimal allocation within practical execution time. Copyright © 2013 John Wiley & Sons, Ltd.     

Disaster-aware service provisioning with manycasting in cloud networks

Cloud services delivered by high-capacity optical datacenter networks are subject to disasters which may cause large-area failures, leading to huge data loss. Survivable service provisioning is crucial to minimize the effects of network/datacenter failures and maintain critical services in case of a disaster. We propose a novel disaster-aware service-provisioning scheme that multiplexes service over multiple paths destined to multiple servers/datacenters with manycasting. Our scheme maintains some bandwidth (i.e., degraded service) after a disaster failure vs. no service at all. We formulate this problem into a mathematical model which turns out to be an Integer Linear Program (ILP), and we provide heuristic optimization approaches as ILP is intractable for large problem instances. Numerical examples show that exploiting manycasting by intelligently selecting destinations in a risk-aware manner for service provisioning offers high level of survivability against link and node failures that may be caused by disasters and post-disaster failures at no extra cost compared to the other survivable schemes.     

组建光数据网的新设想

首先简述国际上对发展未来通信网的普通想法,认为应该重点看待近年数据通信业务的迅速增长趋势,因而有必要提出通信网应当优先考虑建设光传送网和光数据网。于是,文中对光传送网近年发展趋向作一综合概述。     

Cross-stratum resource reservation (CSRR) algorithm for deadline-driven applications in datacenter networks

Nowadays, datacenters interconnected with optical networks have become the fundamental infrastructure to accommodate high-performance datacenter applications. Lacking of layer interaction between datacenters and networks during service provisioning, many end user applications cannot efficiently utilize the network capabilities, nor can they achieve the desired quality of service objectives. In response to these challenges, cross-stratum optimization has been studied to optimize the computing and network resources utilization from a united view. Meanwhile, the type of network applications becomes diverse. Compared to traditional immediate reservation (IR) request, a new type of request called advance reservation (AR) has recently been gaining attention for optical networks. IR’s start time of data transmission is assumed to be immediate, while AR request typically specifies the earliest time or the deadline of data transmission. According to the time features of AR request, AR applications should be scheduled in time dimension. Thus, it is both important and challenging to reserve computing and network resources in efficient manners. In this study, a cross-stratum resource model considering time dimension is set up, and a cross-stratum resource reservation (CSRR) algorithm is proposed to schedule AR applications and to reserve cross-stratum resource. Simulation results show that CSRR can reduce the failure rates of AR applications and improve the resource consumption ratio significantly.     

光因特网中的关键光器件技术研究

对光因特网中的关键光器件技术进行了探讨与研究。下一代光通信网络的发展,关键在于其光器件技术的突破上,要克服光网络节点处理的速率瓶颈、实现全光联网、高效传送和交换IP业务,就必须积极研究开发新的光器件。在光开关技术、光纤放大器技术、波长变换器技术以及其它关键光器件技术上有所突破,是建设光因特网的关键所在。     

我国光通信技术发展的回顾和展望

光通信技术具有许多其他传输技术所不可比拟的优点,因此自问世以来就得到人们的充分关注,如今已经成为通信网络中最主要的传输技术之一。我国光通信技术的发展起步较早,发展非常迅速,并仍在继续快速发展。笔者作为我国光通信技术发展的参与者,目睹和经历了我国光通信技术发展的全过程。文中从光纤光缆技术、光电子器件技术、光传输设备和系统等方面简要回顾我国光通信发展的主要历程,介绍目前技术的状况,并展望光通信进一步发展的前景。