1、 International Telecommunication Union ITU-T L.86TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (07/2010) SERIES L: CONSTRUCTION, INSTALLATION AND PROTECTION OF CABLES AND OTHER ELEMENTS OF OUTSIDE PLANT Considerations on the installation site of branching components in passive optical networks for
2、 fibre to the home Recommendation ITU-T L.86 Rec. ITU-T L.86 (07/2010) i Recommendation ITU-T L.86 Considerations on the installation site of branching components in passive optical networks for fibre to the home Summary Recommendation ITU-T L.86 describes considerations for determining the installa
3、tion site of a (fibre optic) branching component for a passive optical network (PON) designed to provide fibre to the home (FTTH). History Edition Recommendation Approval Study Group 1.0 ITU-T L.86 2010-07-29 15 Keywords Branching component, capital expenditures (CAPEX), operating expenditures (OPEX
4、), passive optical network (PON). ii Rec. ITU-T L.86 (07/2010) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (IT
5、U-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four
6、years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. The approval 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 n
7、ecessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. How
8、ever, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance 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 negativ
9、e equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use
10、of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation,
11、ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. 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.
12、itu.int/ITU-T/ipr/. ITU 2011 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T L.86 (07/2010) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 1 3.1 Terms defined elsewhere 1 3.2 Terms defined
13、 in this Recommendation . 2 4 Abbreviations and acronyms 2 5 Conventions 2 6 Configuration of optical access network and installation site of fibre optic branching component for PON . 2 7 Considerations when determining installation site of branching component for PON 3 7.1 Minimization of CAPEX and
14、 OPEX 3 7.2 Quick response to demand 4 7.3 Maintenance . 5 7.4 Subscriber density 5 Appendix I OFSs experience Examples of FTTx networks in United States . 7 I.1 Introduction 7 I.2 Overall network configurations 7 Appendix II Japanese experience Examples of PON architectures in Japan . 9 II.1 Introd
15、uction 9 II.2 Passive optical network architectures in Japan 9 II.3 Consideration for more effective optical access network architectures . 11 Bibliography. 13 iv Rec. ITU-T L.86 (07/2010) Introduction PONs are used to provide an FTTH service to subscribers in many regions and countries. The primary
16、 feature of a PON is that it realizes FTTH economically by sharing fibre access infrastructures, namely an optical line termination (OLT), fibre cable and branching component, between multiple subscribers. The branching component is one of the most important elements in a PON because its installatio
17、n site has a powerful effect on both capital expenditures (CAPEX) and operating expenditures (OPEX). Therefore, the branching component installation site is an important consideration in designing this network. Recommendation ITU-T L.86 recommends considerations for selecting the location of the bra
18、nching component in the network as a function of the scale of the subscriber density and geographical extent. Rec. ITU-T L.86 (07/2010) 1 Recommendation ITU-T L.86 Considerations on the installation site of branching components in passive optical networks for fibre to the home 1 Scope This Recommend
19、ation deals mainly with considerations concerning the installation site of the (fibre optic) branching component for a PON providing FTTH. This Recommendation also deals with consideration for useful PON configuration in urban and rural areas. 2 References The following ITU-T Recommendations and oth
20、er references contain provisions which, through reference 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
21、 to investigate the possibility of applying the most recent 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
22、 the status of a Recommendation. ITU-T G.983.1 Recommendation ITU-T G.983.1 (2005), Broadband optical access systems based on Passive Optical Networks (PON). ITU-T G.987 Recommendation ITU-T G.987 (2010), 10-Gigabit-capable passive optical network (XG-PON) systems: Definitions, abbreviations, and a
23、cronyms. ITU-T L.40 Recommendation ITU-T L.40 (2000), Optical fibre outside plant maintenance support, monitoring and testing system. ITU-T L.42 Recommendation ITU-T L.42 (2003), Extending optical fibre solutions into the access network. ITU-T L.50 Recommendation ITU-T L.50 (2003), Requirements for
24、passive optical nodes: Optical distribution frames for central office environments. ITU-T L.52 Recommendation ITU-T L.52 (2003), Deployment of Passive Optical Networks (PON). ITU-T L.53 Recommendation ITU-T L.53 (2003), Optical fibre maintenance criteria for access networks. ITU-T L.65 Recommendatio
25、n ITU-T L.65 (2006), Optical fibre distribution of access networks. ITU-T L.72 Recommendation ITU-T L.72 (2008), Databases for optical access network infrastructure. 3 Definitions 3.1 Terms defined elsewhere This Recommendation uses the following terms defined elsewhere: 3.1.1 optical distribution f
26、rame ITU-T L.50 3.1.2 optical line termination ITU-T G.983.1 3.1.3 optical network unit ITU-T G.987 2 Rec. ITU-T L.86 (07/2010) 3.2 Terms defined in this Recommendation This Recommendation does not define any terms. 4 Abbreviations and acronyms This Recommendation uses the following abbreviations an
27、d acronyms: CAPEX Capital Expenditure FTTH Fibre to the Home ODF Optical Distribution Frame OLT Optical Line Termination ONU Optical Network Unit OPEX Operating Expenditure PON Passive Optical Network 5 Conventions None. 6 Configuration of optical access network and installation site of fibre optic
28、branching component for PON An optical access network consists of four areas, as described in ITU-T L.65 (Figure 1). The feeder area is from optical distribution frames (ODFs) in the central office area to a distribution point. The distribution area extends from the distribution point to the access
29、point. In this area, a distribution cable is connected to a feeder and a drop cable at the distribution point and the access point, respectively. In the user area, the drop cable is connected to an optical network unit (ONU) on a subscribers premises. There are three main installation sites for the
30、branching component, namely in a central office, an outside plant and on a subscribers premises, as described in ITU-T L.52. In fact, the installation site in the outside plant is separated into two locations, namely a distribution point and an access point. Therefore, telecommunication companies sh
31、ould select one or more of the following four locations for the branching component, as shown in Figure 2. 1) central office; 2) distribution point (outside plant); 3) access point (outside plant); 4) final location on the subscriber side (e.g., subscribers building, apartment or residential premise
32、s). Rec. ITU-T L.86 (07/2010) 3 L.86(10)_F01Distribution point(feeder point) Access point(drop point)Feeder areaCentral office areacentral officeODFOLTUser areaapartment houseUser arearesidential houseONUUser areabuildingDistribution areaFigure 1 Basic configuration of optical access network L.86(10
33、)_F02Access pointCentral officeDistribution pointOLTAccess pointResidentialhouseONUONUFibre optic branchingcomponent Access pointCentral officeDistribution pointOLTAccess pointONUONUa) b)Fibre optic branchingcomponentResidentialhouseAccess pointCentral officeDistribution pointOLTAccess pointApartmen
34、t houseand buildingONUONUFibre optic branchingcomponentAccess pointCentral officeDistribution pointOLTAccess pointONUsONUsFibre optic branchingcomponentResidentialhousec) d)Figure 2 Installation site of fibre optic branching component for PON: a) in central office, b) at distribution point (in outsi
35、de plant), c) at access point (in outside plant) and d) in final location on subscribers side 7 Considerations when determining installation site of branching component for PON 7.1 Minimization of CAPEX and OPEX Telecommunication companies should determine the installation site for the branching com
36、ponent with a view to minimizing the total cost, which consists of the CAPEX and the OPEX, based on increases in demand. The location of one or more fibre branching components and each split ratio may also depend on the engineering plan and the mapping distribution of the premises. Both the CAPEX an
37、d the OPEX are influenced by the installation site of the branching component, the demand and economies-of-scale. Progress with respect to demand, as shown in Figure 3 a), is divided into four stages, as described in ITU-T L.65. The ratios of the CAPEX and the OPEX to the total cost for each stage a
38、re shown in Figure 3 b). In the initial stage when the demand is small, a reduction in the CAPEX reduces the total cost, excluding any consideration of economy-of-scale. After the mature stage when demand is saturated, the total cost is reduced by reducing the OPEX, excluding any consideration for i
39、nstallation and short-term maintenance. As just described, the dominant factor (i.e., the CAPEX or the OPEX) of the total cost for each stage changes. This may 4 Rec. ITU-T L.86 (07/2010) make it difficult to maintain the minimization of the total cost solely by the individual installation site over
40、 all the stages. Therefore, it is also necessary to consider combining some installation sites in an access network to respond to the changes of the dominant factor and in demand. L.86(10)_F03MaturestageGrowthstageInitialstageFinal(decline)stage NumberofsubscribersTime Timea) b)Ratiotototal costInit
41、ialstageGrowthstageMaturestageFinal(decline)stage CAPEXOPEXFigure 3 a) Increase in number of FTTH subscribers and b) ratio of CAPEX and OPEX to total cost for each stage 7.2 Quick response to demand The demand will increase rapidly and will occur over a wide area in the growth stage, as shown in Fig
42、ure 3 a). Therefore, telecommunication companies should determine the installation sites for branching components taking the need for a quick response to demand into consideration. To achieve such a prompt response, ease of deployment over the last mile is important. The installation sites described
43、 in Figure 2 b), c) and d) may be effective as regards increasing ease of deployment of the last mile. However, in the initial stage where the demand is small and dispersed over a wide area, the location described in Figure 2 a) may be more effective in terms of the CAPEX than the other locations. T
44、herefore, telecommunication companies should also consider combining some branching component installation sites, as shown in Figure 4. L.86(10)_F04. .Central officeDistribution pointOLTApartment houseand buildingFibre optic branchingcomponentsONUsONUsb)a)Central officeDistribution pointOLTResidenti
45、alhouseFibre optic branchingcomponentsONUDistribution pointFigure 4 Examples of PON configuration with combined branching component installation sites which are a) in distribution point and the final location on the subscriber side and b) in central office and distribution point Rec. ITU-T L.86 (07/
46、2010) 5 7.3 Maintenance It is important to consider ease of maintenance if we are to reduce the OPEX. In particular, a reduction in the OPEX strongly affects the total cost because it is the dominant factor in the total cost after the mature stage when demand is saturated and there are a large numbe
47、r of facilities. The optical network maintenance support, monitoring and testing system described in ITU-T L.40 and ITU-T L.53 is useful for reducing the OPEX. However, when using a branching component in an outside plant or the final location on the subscriber side, functions in addition to those i
48、ndicated in ITU-T L.40 and ITU-T L.53, are required when an individual optical fibre from a branching component to an ONU is monitored and tested. Moreover, the database for an optical access network infrastructure described in ITU-T L.72 and fibre identification technology are also needed for the m
49、aintenance of a large number of facilities. Therefore, when telecommunication companies decide the installation site, they should give sufficient consideration to increases in the OPEX imposed by the additional functions. 7.4 Subscriber density In order to providing effective PON configuration, it is important to consider subscriber density in order to maintain a higher branching component utilization ratio with low cable costs absorbed by a single subscriber for both an urban and a rural area. To meet the
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