1、中文 1866 字 附 录 一、英文原文 Optical fiber access network technology During the early 1980s, analog cellular telephone systems were experiencing rapid growth in Europe, particularly in Scandinavia and the United Kingdom, but also in France and Germany. Each country developed its own system, which was incomp
2、atible. The entire telecommunication network according to network function is divided into three sections: switching, transmission,and access. Access to telecommunications business transparent to users, transmit specific, access to local switch and the user that the connection between the parts, usu
3、ally include subscriber line transmission system, reuse equipment, crossing connection device or user/network terminal equipment. And actually pick for business entity is business nodes. 1. Access network development process 1.1 Access Network （ AN: Access by business） refers to a node interface （ S
4、NI） and related users Network interface （ UNI） between a series of transmit entity （ such as line facilities and transmission facilities） for transmission consisting of telecommunication business provide the required transmit load capacity, implementation system configurations percentile management
5、interface via and management. Access can be seen as with business and application irrelevant transmission network, mainly finish crossing connection, reuse and transmission function, it is transparent to users of signaling. Based on modern of telecommunication network access network is integrated se
6、rvice access, simple local voice access will be increasingly cannot meet the requirements, the voice, data and image comprehensive access is becoming access network development trend. After years of development, access network define though does not change, but its connotation and forms has changed
7、significantly. Superior traditional access network integrated optical fiber access network will be users access the future developing trend. Optical fiber access from SNI to UNI refers to all or part of the access network by using optical fiber as medium. ITU - T about access network recommendations
8、 indicate that fiber, user access system is composed of three parts: optical line terminal（ OLT） , optical distribution network （ ODN） and optical network unit （ ONU） . 1.2According to the requirement of system access framework and the important characteristics, access network can be summarized as t
9、he following: 1.2.1 Access to access business provides bearing capacity, achieve business transparent transfer. 1.2.2. The access is transparent to users signaling, except for some users signaling format conversion outside, signaling and business processing function is still in business node. 1.2.3
10、The introduction of should not be restricted access all kinds of existing access types and business, access network should through the limited standardization interface and business node connected. 1.2.4Access network have independent from the business node in the network management system, this sys
11、tem through the standardized interfaces connected TMN, access network operation for implementation TMN, maintenance and management. 2 .fiber structure 2.1general linear structure. Refer to the public bus, fiber as each user terminals through direct connect with bus coupler network structure. Its cha
12、racteristic is sharing backbone fiber, save lines to remove node investment, the demand is higher, dynamic range, interfere with each other effect is small. Defect is loss of accumulation, the backbone fiber user acceptance dependence is strong. 2.2 ring structure. Refers to all share a fiber optic
13、link node, fiber optic link its end to end the closed loop network structure. Characteristic is self-healing, namely can be realized without intervention, the network can be in a relatively short period of time to recover from failure have preached business, high reliability. Defect is hanged by the
14、 number of users of monocylic limited, polycyclic interchange is relatively complex, not suitable for CATV, etc FenPeiXing business. 2.3star structure. This structure is actually point-to-point way, each user terminals in the central node through with control and switch functions of the astral coupl
15、ers exchange information. Characteristics of simple structure, maintenance is convenient and easy to upgrade and expansion between, each user relatively independent, good secrecy, business adaptability. Defect is higher, networking required fiber cost of poor flexibility, high reliability requiremen
16、ts of central node. 2.4 tree structure. Similar to the branches, a hierarchical structure, shape in transfer boxes and FenXianHe place adopts multiple optical distributor, will signal filtering down top end innings allocation, have strong control coordination. Characteristic is suitable for broadcas
17、ting business. Defect is power loss is bigger, two-way communication difficulty bigger. 3 The status of optical access network in the modern communication Optical fiber in realizing national information modernization access plays a more and more important role, is an indispensable part of modern com
18、munications network. Modern communications network basic realized based on fiber backbone transmission and exchange, and access section is still restricted modern telecommunications further development and improvement of the bottleneck, therefore, to construction of national information infrastructu
19、re （ NII） , access network is the key. Access network technology development, will result in great changes of telecommunications and information network, namely, voice, data, video, etc. Various kinds of information transmission, comprehensive business together for implementing the resources sharing
20、, and gradually optimized communication network, greatly improving network benefits. Two optical fiber optical transmission technology access with the combination of the access technology 3.1 Light transmission technology development and evolution Since 1979, the human use of optical fiber as commun
21、ication mode, optical transmission technology experience since from analog to digital, from PDH to sdh-based WDM, from passive and active to a series of MSTP from SDH to the development and evolution process, transmission capacity and reliability, the transmission distance such indicators have reach
22、ed a very high level. The current mainstream of optical transmission technology is still SDH, STM - 1/4/16/64/256 series synchronous transfer module has been achieved, including STM - 256 frame rate as high as 40Gbps. Based on SDH, fusion broadband data business multi-task transmitting platform （ th
23、e MSTP） has also become the best choice for todays construction intracity networks, moreover elastic grouping ring （ RPR） technology is also gradually become the direction of the development of a light transmission. The future will be optical transmission network to optical transmission network （ ot
24、ns） in the direction of development, many exchange, network otns choose road and other intelligent function will be implemented on light layer. Otns the intelligent network development degree can realize ASON intelligent optical network. 3.2 Light transmission technology and access technology consti
25、tute fiber access network The needs of the user, the diversification and broadband access technology from initial made of pure narrowband access to broadband access, size, and with integrated access to transmission platform requirement light more and more is also high. Optical transmission technolog
26、y and access technology together constitute fiber access network system. Optical fiber access network in different stages of development of need to resort to the corresponding optical transmission means to achieve the operational load and transfer. With the light network will be dispersed access devices （ OLT ONU） together with organic whole, form a unified fiber access network system.
