1、 International Telecommunication Union ITU-T L.65TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (12/2006) SERIES L: CONSTRUCTION, INSTALLATION AND PROTECTION OF CABLES AND OTHER ELEMENTS OF OUTSIDE PLANT Optical fibre distribution of access networks ITU-T Recommendation L.65 ITU-T Rec. L.65 (12/200
2、6) i ITU-T Recommendation L.65 Optical fibre distribution of access networks Summary This Recommendation deals with four stages of optical fibre distribution based on the increasing number of customers, namely the initial stage, the growth stage, the mature stage and the final stage, to enable desig
3、n, construction and maintenance of optical fibre access networks immediately, effectively and economically. Source ITU-T Recommendation L.65 was approved on 22 December 2006 by ITU-T Study Group 6 (2005-2008) under the ITU-T Recommendation A.8 procedure. ii ITU-T Rec. L.65 (12/2006) FOREWORD The Int
4、ernational Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommen
5、dations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. The app
6、roval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “Administra
7、tion“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g. interoperability or applicability) and complianc
8、e with the Recommendation is achieved when all of these mandatory provisions are met. The words “shall“ or some other obligatory language such as “must“ and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is re
9、quired of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intell
10、ectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation.
11、However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2007 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without th
12、e prior written permission of ITU. ITU-T Rec. L.65 (12/2006) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 1 4 Abbreviations and acronyms 2 5 Conventions 2 6 Optical fibre distribution. 2 6.1 Initial stage . 3 6.2 Growth stage. 4 6.3 Mature stage . 4 6.4 Final stage. 4 Appendix I Japanes
13、e experience. 5 I.1 Introduction 5 I.2 Design of optimum margin for demand fluctuation for feeder area. 5 I.3 Balanced use of distributed fibre to each drop area in aerial distribution areas 6 I.4 Reference 7 iv ITU-T Rec. L.65 (12/2006) Introduction Progress on communication technologies has led to
14、 the active development of many kinds of broadband services such as data and video communication using access networks. It is important to realize high-speed broadband networks to provide such services economically. In order to provide these services in a timely way, we must construct optical access
15、 networks immediately, effectively and economically for “fibre-to-anything“ (FTTx). The development of optical fibre access networks for FTTx can largely be divided into four stages based on the increasing number of customers, namely the initial stage, the growth stage, the mature stage and the fina
16、l stage. To achieve the above goals, the network design must take construction, maintenance and operation into account. ITU-T Rec. L.65 (12/2006) 1 ITU-T Recommendation L.65 Optical fibre distribution of access networks 1 Scope This Recommendation deals mainly with important considerations concernin
17、g optical fibre distribution of each stage in terms of designing, constructing, maintaining and operating optical fibre access networks immediately, effectively and economically for FTTx. 2 References The following ITU-T Recommendations and other references contain provisions which, through referenc
18、e in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most rec
19、ent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T G.982 ITU-T Reco
20、mmendation G.982 (1996), Optical access networks to support services up to the ISDN primary rate or equivalent bit rates. ITU-T G.983.1 ITU-T Recommendation G.983.1 (2005), Broadband optical access systems based on Passive Optical Networks (PON). ITU-T G.983.2 ITU-T Recommendation G.983.2 (2005), ON
21、T management and control interface specification for B-PON. ITU-T G.983.3 ITU-T Recommendation G.983.3 (2001), A broadband optical access system with increased service capability by wavelength allocation. ITU-T G.983.4 ITU-T Recommendation G.983.4 (2001), A broadband optical access system with incre
22、ased service capability using dynamic bandwidth assignment. ITU-T G.983.5 ITU-T Recommendation G.983.5 (2002), A broadband optical access system with enhanced survivability. ITU-T G.984.1 ITU-T Recommendation G.984.1 (2003), Gigabit-capable Passive Optical Networks (G-PON): General characteristics.
23、ITU-T L.40 ITU-T Recommendation L.40 (2000), Optical fibre outside plant maintenance support, monitoring and testing system. ITU-T L.42 ITU-T Recommendation L.42 (2003), Extending optical fibre solutions into the access network. ITU-T L.53 ITU-T Recommendation L.53 (2003), Optical fibre maintenance
24、criteria for access networks. ITU-T L.58 ITU-T Recommendation L.58 (2004), Optical fibre cables: Special needs for access network. 3 Definitions For the purpose of this Recommendation, the definitions given in ITU-T G.982, ITU-T G.983.1, ITU-T G.983.2, ITU-T G.983.3, ITU-T G.983.4, ITU-T G.983.5, IT
25、U-T G.984.1 and ITU-T L.42 apply. 2 ITU-T Rec. L.65 (12/2006) 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: FTTB Fibre to the Building FTTC Fibre to the Curb FTTH Fibre to the Home FTTx “Fibre to the x“, where “x“ indicates the final location on the
26、user side of any one of a variety of optical fibre architectures, e.g., FTTH, FTTB, FTTC. ODF Optical Distribution Frame OLT Optical Line Terminal ONU Optical Network Unit PON Passive Optical Network 5 Conventions None. 6 Optical fibre distribution An optical access network comprises four areas, nam
27、ely a central office area, a feeder area, a distribution area and a user area from a central office to residential premises as shown in Figure 1. The feeder area extends from optical distribution frames (ODFs) in the central office to a distribution point. In the distribution area, a distribution ca
28、ble is connected with a feeder cable at the distribution point and led to an access point. In the user area, a drop cable is connected with a distribution cable at the access point and led to an optical network unit (ONU) in an individual home, apartment or business building, etc. It is most importa
29、nt that the optical fibres are distributed in such a way that efficient design, construction, maintenance and operation for FTTx is achieved. L.65(06)_F01Central officeDistribution point(feeder point) Access point(drop point)Telecommunication poleFeeder areaDistributionarea Central officeareaDistrib
30、utioncableFeeder cableODF OLTUser area ResidentialhouseDrop cableONUUser areabuildingUser area apartment houseFigure 1 Configuration of an optical access network Therefore, in order to determine the network architecture, design, construction, maintenance and operation approach for the optical access
31、 network, and to select optical components for FTTx, telecommunication companies should mainly consider the following: ITU-T Rec. L.65 (12/2006) 3 Scalability (number of terminated fibres, number of fibre jointing points (joint closures), total fibre length of network, etc.). Survivability (security
32、, supervisory system, etc.). Functionality (bit rate, transmission distance, etc.). Construction and maintenance costs (cost, quality and reliability of components to position in the network, etc.). Network upgradeability (increased transmission capacity, transmission length, number of customers (in
33、cluding future demand) and potential evolution or migration of architecture). Operability and suitability over designed network lifetime. Telecommunication companies should develop appropriate designs based on the optical access network requirements for each country. In addition, the development of
34、optical fibre access networks can largely be divided into four stages based on the increasing number of subscribers as shown in Figure 2, namely the initial stage, the growth stage, the mature stage and the final stage. Telecommunication companies should focus particularly on the following items in
35、each stage. L.65(06)_F02TimeInitialstageGrowthstageMaturestage Finalstage Number of subscribersFigure 2 Progressive increase in number of FTTx subscribers 6.1 Initial stage 6.1.1 Effective and economical optical fibre distribution for demand dispersed over a wide area In the initial stage, the deman
36、d for optical fibre will be dispersed over a wide area. Therefore, telecommunication companies should respond by designing effective and economical approaches to optical fibre distribution. For example, it is important to determine the distribution point and access point allocation, which is closely
37、 related to construction cost and construction workability. Moreover, to flexibly respond to demand, ease of branching and dropping after the initial cable installation should be considered as described in ITU-T L.58 when selecting the optical fibre cables. 6.1.2 Optical fibre distribution taking ac
38、count of future demand In addition to the above, it is important that the optical fibre distribution scheme should take account of the potential demand during the growth and mature stages. For example, the number of fibres in the cables and the number of branches for the branching devices in a passi
39、ve optical network (PON) are important optical fibre distribution parameters as regards future demand. Technologies that support deferred cost for subsequent up-scaling of fibre capacity could be considered. 4 ITU-T Rec. L.65 (12/2006) 6.2 Growth stage 6.2.1 Optical fibre distribution for quick resp
40、onse to demand In the growth stage, the demand for optical fibre will occur randomly over a wide area. It is therefore very important for the optical fibre distribution scheme to be able to quickly respond to this demand. In particular, it is necessary to design the optical access network with a vie
41、w to achieving easy optical fibre distribution over the last mile between an access point and individual homes, apartments, business building, etc., because the distribution over the last mile is large scale and the demand is random. However, in the growth stage, the demand for optical fibre will be
42、 widely dispersed in rural areas. Therefore, an effective and economical optical fibre distribution scheme that responds to this demand will be needed for rural areas. 6.2.2 Optical fibre distribution for easy maintenance and operation In addition to the above, at this stage there will be a rapid ex
43、pansion of the optical access network infrastructure, including optical fibre and optical fibre cable. Therefore, it is important to be able to easily maintain and operate the optical access network infrastructure. For example, there will be a need to use the optical fibre network maintenance suppor
44、t, monitoring and testing system described in ITU-T L.40 and ITU-T L.53. In addition, an optical access network infrastructure database will need to be constructed and used to operate and administer the huge expansion of the infrastructure, taking into account other future Recommendations on databas
45、es for optical access network infrastructure and system architecture for data transmission, database access and interoperability. Moreover, it is anticipated that overlay of fibre networks into areas of legacy metallic networks will eventually occur, presenting challenges for both aerial and undergr
46、ound deployment. In addition, it will be important to use existing facilities such as cable ducts for the effective and economical installation of optical fibre cables. For example, several optical fibre cables could be installed in a cable duct. This is because the optical access network infrastruc
47、ture will increase and the available facilities may become scarce. Consideration could be given to active cable duct management solutions to ensure their future economical usability. 6.3 Mature stage 6.3.1 Optical fibre distribution for easy maintenance and operation In the mature stage, the demand
48、for new optical fibre will be slow and a huge optical access network infrastructure will be in place. Therefore, it is of utmost importance that the optical fibre distribution scheme be easy to maintain and operate. This will require an optical fibre network maintenance support, monitoring and testi
49、ng system, and a corresponding database. In addition, customers who require very high reliability should be provided with two or more fibres using a ring network in each stage, as described in ITU-T L.42. Telecommunication companies should select appropriate architectures and optical components (e.g., optical fibre cable and passive optical components), and design and construct optical access networks taking account of the above factors in each stage. 6.4 Final stage In the final stage, demographic considerations may determine
