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1、Optical fiber access network technology 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 c
2、onnection between the parts, usually 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)
3、 refers to a node interface (SNI) 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 configura
4、tions percentile management 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 acc
5、ess network is integrated service 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 connot
6、ation and forms has changed 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 ac
7、cess network recommendations 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
8、 can be summarized as the 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 i
9、n business node. 1.2.3 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 mana
10、gement system, this system 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 net
11、work structure. Its characteristic 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 a
12、ll share a fiber optic 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.
13、Defect is hanged by the 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 functi
14、ons of the astral couplers 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
15、 reliability requirements 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 i
16、s suitable for broadcasting business. Defect is power loss is bigger, two-way communication difficulty bigger. 3The status of optical access network in the modern communicationOptical fiber in realizing national information modernization access plays a more and more important role, is an indispensable part of modern communications network. Modern communications network basic realized based on fiber backbone transmission and exchange, and access section is
