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1、Optical fiber access network technologyThe 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 co

2、nnection 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 configurat

4、ions 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 acce

5、ss 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 connota

6、tion 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 acc

7、ess 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 in

9、 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 manag

10、ement 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 netw

11、ork 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 al

12、l 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. D

13、efect 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 functio

14、ns 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 is

16、 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 indispensabl

17、e part of modern communications 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 info

18、rmation infrastructure (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

19、 resources sharing, 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 optic

20、al fiber as communication 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 ind

21、icators have reached 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 transmit

22、ting platform (the 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 transmiss

23、ion network (otns) 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 te

24、chnology constitute 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 transmi

25、ssion technology 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 dispe

26、rsed access devices (OLT ONU) together with organic whole, form a unified fiber access network system.4. The current development of fiber-optic access hotspot Currently, fiber-optic access network continue presented the vigorous development momentum and various new access technology arises at the hi

27、storic moment. The development of better have xDSL, FTTX, dual bus size take comprehensive access technologies. In addition, HFC APON EPON, such technology is also in constant developing and perfecting. 4.1 The development and application of XDSL XDSL technology refers to the ADSL (asymmetric digita

28、l subscriber loop) as a representative of digital subscriber loop (DSL) the floorboard of a series of technology. By using of ground wire although more than 2Mbps broadband data transmission, but the transmission distance is very limited. XDSL and optical fiber integrated access network structure, w

29、ith the UNI bounded user-oriented provide narrowband normal telephone, 2Mbps line, 10Base_T and ATM broadband interface. Using fibre solve access network transmission of feeder section, XDSL solve finally hundreds meters to 3.5 kilometers (in this range, can guarantee a high rate), it is quite broad

30、band access broadband technology effectively. The current market most successful is ADSL technologies, including China telecom, China netcom, China unicom, China tietong, each big telecom operators are spending heavily construction ADSL network. In the user is relatively scattered, twisted-pair cabl

31、e resources under the condition of comparative energetic, ADSL can low cost to solve users network bandwidth needs. SHDSL, HDSL can provide users with broadband data line, these two kinds of digital subscriber loop in special circumstances, the technical solution to the problem of providing data lin

32、e. VDSL technology is with ADSL) the development and popularization of and gradually moving towards the commercial, but because it can support distance is short, at present its popularity still far less ADSL. 4.2 FTTX technology In all sorts of broadband access network technology, optical SDH techno

33、logy adopted the access network system is applied the most common. SDH technology application in access network has already widespread, but still just FTTC (optical fiber to the side of the road), FTTB (fiber to the floor), the huge bandwidth optical fiber level still no to household. Therefore, to

34、really provide broadband business ability, just using SDH technology solve feeder, wiring, paragraph of the broadband is not enough, still need to introduce line in part by broadband access technology combined. Can FTTB/C + used respectively FTTB/C + xDSL, Cable Modem, FTTB/C + local-area network (L

35、AN) access methods such as resident and company respectively, enterprise users to provide business. Among them the way FTTX + LAN FTTLAN is called again, in this way our Shanghai, Beijing and other developed city new district has been widely used. The final is FTTH access development goals, but beca

36、use the cost, the user needs and market and other reasons, FTTH is still a long-term task. Access the latest development direction with SDH support for IP business is, is to develop a business network platform for MSTP/RPR) (. FTTX MSTP/RPR and combining with business realized width comprehensive tr

37、ansfer. 4.3Double (more) bus size take integrated business access network Optical fiber access from the preliminary narrowband integrated service access to comprehensive business access with width of the development process, had two ideas: a view by unified IP business platform realize voice and dat

38、a services integrated access; Another argument is because Everything over IP technology in be used actually are still exist many problems, when in to realize comprehensive access or let narrowband service (circuit switching methods) and broadband business (packet switching mode) respectively take di

39、fferent channels. The former realization ways can the soft exchange to do help, then a realization way by current is most mainstream solutions - double (more) bus integrated service access network. In 1999, he launched a double before and after the comprehensive access network equipment bus model. S

40、ome manufacturers provide bus types according to the backboard, and puts forward four buses parlance, including: management bus, TDM business bus, group business bus, general bus. General bus is to expand business ability, or to support now still unforeseeable some business and reserved. Due to its

41、specific also unable to estimate the design parameters usually be categorized as one of the first three bus. Management bus is to realize the management of the whole system is designed for the Lord, because the bus ability to support business types is more and more abundant, need management informat

42、ion more and more, now also many USES high-speed management bus bus. This so-called dual bus, is providing the equipment backplane of the two businesses bus, namely TDM bus and packet bus. Most of the developed countries access equipment is dual bus structure. International technical development dir

43、ection, adopt the most advanced system structure, launched with IP for the kernel, built-in MSTP double bus type comprehensive access network equipment. Can foresee dual bus integrated access network is the development direction of access in the coming years, each big access network equipment manufa

44、cturers will strive for in this huge market competitive advantage, to re-establish throughout the status of optical fiber access product market. 5. Access network support business 5.1 Voice class business: SPC telephone new business, magnetic card phone business, etc 5.2Data class business: DDN busi

45、ness, packet switching, etc 5.3 Image communication class business: meeting TV business, videophone business, etc 5.4 Multimedia business: home office, shopping, VOD, remote medical treatment, etc 6.the development direction of future optical fiber access 6.1 Broadband is changed and comprehensivize

46、d Broadband access is market development trends, fiber in-home will be broadband access inevitable. XDSL, dual bus integrated access as the transition complete fibre optic access technology, will play in the next few years broadband market protagonist. Future access to achieve a single platform with

47、 various business width of comprehensive access, achieve business and network of separation, i.e. to further to be changed to the broadband and integrated direction. Meanwhile fiber access network also must be able to support and other access flexible joint networking. 6.2 To next generation network

48、 (NGN) of evolution Judging from the technical development, the traditional telephone network, data communications network and the technology of industry of cable television network three is gradually disappear, technology difference of fusion will further trigger network fusing, business fusion and

49、 industrial integration. Next generation network (NGN) are available including voice, data and multimedia and other business integrated, open network. The trend of its development can be summarized as: network equipment of components, network communication gateway change, access technology diversification, network management integration, terminal intelligent, business exchange control functions of separation and core network group. In the future of communications-net NGN dominant, opti