摘 要

随着互联网信息流量的快速增长，光交换技术的优势使得国内外学者深入对其的研究。光交换技术可以消除物理设备的局限性。与此同时，光交换技术研究将改变人们的试件空间的限制，光交换技术的研究也会给经济，政治，文化，社会等等带来改进。毫无疑问，光交换技术的研究是一场革命性的飞跃。它完全反映了最新的数字技术，计算机技术。而且，光交换技术研究的进一步发展也将为电信部门，医疗部门，政治部门等提供服务，使快速通信成为可能。本文针对这一问题，主要工作和结论有：

第一部分，对相关光交换技术的国内外研究内容进行概述和分析，对光交换技术进行定义，分析讨论本文研究的目的和意义，介绍其国内外研究现状。

第二部分，了解学习光交换技术的基本原理，主要以MEMS，OTDM，WDM，GMPLS等方式为主。

第三部分，该部分重点关注OBS光交换的研究，认为其是光网络中最新最合适的光交换方式。但由于其核心节点的处理有限，倾向于支持高优先级流量类的资源池及容纳机制，从而使其服务出现差异化。

第四部分，讲述了以OPS，OCS，OBS为主的新光交换技术中出现的问题，寻找其，在光切换技术中常见的缺点缺陷， 以便基于此寻找合适的解决方法。

第五部分，介绍了新光交换技术中发生的问题的分析和解决方案，通过比较光电路切换，脉冲串和数据包之间的关系；光域中切换和电子域中的比较优势；科学客观的认识到光器件的当前局限性，可以通过优化分组处理和编码技术来解决当前的主要问题。

关键词：新型光交换技术；互联网；OBS

Abstract

With the rapid growth of Internet information flow, the advantages of optical switching technology research make domestic and foreign scholars in-depth study of it. Optical switching technology can eliminate the limitations of physical equipment. At the same time, optical switching technology research will change the limits of people's test space, optical switching technology exchange technology research will also bring great improvements to the economy, culture, society and so on. There is no doubt that the study of optical technology is a revolutionary leap. It fully reflects the latest digital technology, computer technology. Moreover, the further development of optical switching technology research will also serve the telecommunications sector, the medical sector, the political sector, etc., which makes fast communication. In this paper, the main work and conclusions are:

In the first part, the paper summarizes and analyzes the research contents of the related optical exchange technology at home and abroad, defines the optical switching technology, analyzes and discusses the purpose and significance of this paper, and introduces the research status at home and abroad.

In the second part, this paper shows the basic principles of optical switching technology, mainly in MEMS, OTDM, WDM, GMPLS and other ways.

In the third part, this part focuses on the study of Bursts optical exchange, which is the latest and most suitable optical switching method in optical network. In the fourth part, this paper analyzes the problems and shortcoming mainly in new optical switching technology of the OPS, OCS, OBS, in order to find suitable solutions.

In the fifth part, the analysis and solution of the problems in the new optical switching technology are introduced. By comparing the relationship between the optical circuit switching, the relationship between the pulse train and the data packet; the comparative advantages between the optical domain and the electronic domain; recognizing the current limitations of optical devices, we can solve the current major problems by optimizing packet processing and coding techniques.

Key words：New optical Switching Technology；Internet；OBS

目 录

摘 要 I

Abstract II

Chapter1 INTRODUCTION 1

1.1 Significance and Purpose of the study 2

1.2 Domestic and foreign research 3

1.3 Content of the study 6

1.4 Summary of the chapter 6

Chapter2 THE BASIC PRINCIPLES OF OPTICAL SWITCHING TECHNOLOGY 7

2.1 MEMS 8

2.2 OTDM 9

2.3 WDM 9

2.4 GMPLS and Others 10

2.5 The Optical Domain 14

2.5.1 The Transmission Medium: 14

2.5.2 Granularity 16

Chapter3 OPTICAL SWITCHING BY BURST (OBS) 18

3.1. Principles of Optical Switching for Bursts 18

3.2 Node Architecture 21

3.3 Signaling Protocols 22

3.3.1. Tell and Wait (TAW) 22

3.3.2. Tell and Go (TAG) 23

3.3.3 Just in Time (JIT) 23

3.3.4 Just Enough Time (JET) 24

3.4 Quality of service 24

Chapter4 PROBLEMS OCCUR IN THE NEW OPTICAL SWITCHING 26

4.1 Problems with OBS 27

4.2 Problems with OCS 27

4.3 Problems with OPS 28

Chapter5 ANALYSIS AND HOW WE CAN SOLVE THE PROBLEMS OCCUR IN THE NEW OPTICAL SWITCHING 29

5.1. Comparison between optical circuit switching, bursts and packet 30

5.2 Switching in the optical domain against switching in the electronic domain 34

5.3. Current Limitations of Optical Devices 35

5.4. Solutions for all problems occur in the new optical switching 37

5.4.1 Techniques of Packet Processing and Coding 37

Chapter6 CONCLUSION 40

Acknowledgments 41

Reference 42

Chapter1 INTRODUCTION

Optical switching technologies can be classified in different ways. Two generic types are usually recognized, namely, the type based on guided lightwave (fiber and/or waveguides) and the type based on free-space optics. Optical switching technologies may also be classified, more specifically, based on the underlying physical effect that is responsible for the switching process. In this case, we see several technological categories. Each of these categories comprises a number of technology types depending on the manner in which the physical effect is exploited, device design, material used, and on other considerations: 1) Electro-Optic (EO) Switching: this category utilizes electro-optic effects. The most well-known switching technology in this category is based on optical waveguides and directional couplers which are implemented on Lithium Niobate substrates. Other technologies which can be considered electro-optic in nature include liquid-crystal optical switches utilizing polarization control and electro-holographic optical switches. 2) Acousto-Optic (AO) Switching: this guided-wave category exploits the acousto-optic effect and can also be implemented on Lithium Niobate. 3) Thermo-Optic (TO) Switching: this category utilizes the thermo-optic effect in optical waveguides. Two main types of materials are deployed to implement these switches, namely, silica and polymers. 4) Opto-Mechanical (OM) Switching: this category is mostly based on free-space optics. It comprises classical technologies based on moving fiber, and/or moving macroscopic optical components as well as modern technologies such as those based on optical Micro Electro Mechanical Systems (MEMS) or on planar waveguide crosspoints which are controlled by movable air bubbles. 5) Optical-Amplifier based Switching: both semiconductor and fiber amplifiers have been proposed as switching devices. However, Semiconductor Optical Amplifiers (SOA) are more common in optical switching applications. SOAs are also used for wavelength conversion and for multiplexing/switching in the time domain In the early 70s, the optical fiber was discovered and its first applications were given in the field of medicine. At that time, optical fiber could be used for a few meters and then with the discovery of the internet. Several researchers discovered that it could only be applied in medicine and also in other fields if its wavelength is extended. Since fiber optics is the technology par excellence not only in medical applications but also in telecommunication among others, but with the passage of time until the discovery of internet, the optical fiber has been affected to a great extent by the lack of technologies that face the great demand that implied the great discovery of Internet that through it was born new services of (voice, data and video , Digital television, high definition audio online game), which have required an evolution not only at the access level but also the network that supports this information. It is precisely at the level of transport where it is necessary to supply the greater capacity of bandwidth so the optical medium has presented itself to be the answer to those needs but still with the great Information capacity that can carry a fiber wire and the inclusion of Wavelength Division Multiplex (WDM) systems. There is still a limitation that this prevents you from fully leveraging the unlimited virtual bandwidth you provide the optical medium: electronic processors, whose speed is significantly less than the speed transmission of data by a fiber optic cable. But as the networks evolved there should also be evolution of suitable technologies to these networks, it is here when the optical switches appear with the purpose of adapting and avoiding the limitations that had the old technologies enter these technologies are OBS, OPS and OCS, as the main technologies for optical switching, thus disappears the old technology that was used to connect two points in a network (WDM).

Significance and Purpose of the study

At present, control automation technology of China's industrial, is to the intelligent, network and integrated direction. Using the information, network to driven industrialization and to promote the further development of industrial automation technology is the main trend. In the future network, the all-optical network takes full advantage of the huge bandwidth resources of the fiber to meet the explosive growth of various communication services. In order to overcome the "electronic bottleneck" in the optical network, the all-optical network with high survivability becomes the future development goal of the broadband communication network. Optical switching technology, as an important support technology in all-optical network system, plays an important role in all-optical communication system. It can be said that the development of optical switching technology to a certain extent also determines the development of all-optical communication.

With the development of all-optical networks, network optimization, routing, protection and self-healing function in the field of optical communications is increasingly important. Optical switching technology not only guarantees the reliability of the network but also provides a flexible signal routing platform. The difference with the current communication network is that the future all-optical network needs pure optical switching technology to complete the signal routing function to achieve high network speed and protocol transparency.

The all-optical network with optical switching as the core technology makes the data from the source node to the destination node, transfer, exchange and route in the way of light. This avoids the mutual conversion between multiple optoelectronic devices on each network node, saves the cost of expensive conversion equipment and greatly improves the bandwidth and capacity of the communication network. While, the optical signal is not sensitive to electromagnetic interference characteristics also improve the survival of the network. The biggest advantage of the all-optical network is its openness and transparency, as well as the flexibility of the structure, which makes it the focus and hotspot of future development. Optical switching technology is one of the most important technical supports of all-optical network, and its development also determines the development of all-optical network, to a certain extent. Therefore, it is of great significance to study optical switching technology deeply.

Domestic and foreign research

At the national level we have a large list of engineers who, thanks to their advanced studies in technologies and to want to improve the situation of optical switching .At the national level research has been carried out and experiments have been carried out in search of an improvement for optical switching technologies, including research in 2008 by Changjun Min, Pei Wang, Cheng Chen, Yan Deng, Yonghua Lu, Hai Ming, Ning Tingyin, Yueliang Zhou, and Guozhen Yang on (All-optical switching in subwavelength metallic grating structure containing nonlinear optical materials).

China has emerged a number of products with independent intellectual property rights, and gradually competes in the international market with foreign products. Chinese Academy of Sciences, institutions of higher learning and scientific research institutes to carry out the national 863 major project "China High-speed Information Network CAINONET" and so on. Wuhan Institute of Posts and Telecommunications and Huazhong University of Science and Technology, developed a key device in the optical network - semiconductor optical amplifier. And soon they realized the product, as the bulk supply of domestic optical switch semiconductor light amplifier suppliers after ALCATEL Company. This marks the development of China's self-developed quantum devices have taken a commercialization of the key step. Li Xiaoqiang, Li Wei believes that due to the current level of development of optical technology, mainly to take photoelectric hybrid electronic control optical switching structure, that is, all-optical signal exchange, and optical device control is still completed by the electronic circuit, the current test system are mostly used it. With the development of optical technology, and ultimately to achieve light control, optical switching, that is, the system logic, control and exchange by the photon to complete, the technology to ensure that the signal transmission between users and exchange all use of light technology, according to experts estimate it will take about 10 years’ time.

As the core technology of all-optical network optical switching technology and its system more and more attention, in recent years, major communications companies have introduced a new generation of optical switching system. Nortel Networks Introduces OPTera Connect HDX's New Generation of Multi-Bit-Level Optical Transport Node Equipment Optical Switches. It can connect thousands of routers, ATM and SONET / SDH, and achieve 3.84T large-capacity switching connection, through the open optical interface to provide line rate from 2.5 G to 40G or even higher wavelength channel. Lucent has also introduced a new generation of intelligent multi-service optical switching system Lambda Unite Multi Service Switch (MSS) and enhanced Metropolis series of optical metropolitan area network solutions. It can be based on different network needs to provide 160G, 320G, 1.28T and other cross-connect matrix. With Lucent Technologies Lamb da Transport, more than 1,000 km of photoelectric relay can be achieved. Lambda Unite MSS can provide traditional SDU / S O NET optical interfaces from 155Mb / S to 10Gb / S and 40Gb / S. SDH / SONET transparent optical interface for large customer, enterprise and carrier applications.