1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T L.42TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (05/2003) SERIES L: CONSTRUCTION, INSTALLATION AND PROTECTION OF CABLES AND OTHER ELEMENTS OF OUTSIDE PLANT Extending optical fibre solutions into the access network ITU-T Recommendation L.42 ITU-T Rec.
2、L.42 (05/2003) i ITU-T Recommendation L.42 Extending optical fibre solutions into the access network Summary This Recommendation describes the optical access network to be used in the design and construction of fibre to the home (FTTH). It deals mainly with access network architectures, and the upgr
3、ading of optical networks to optical access networks. Source ITU-T Recommendation L.42 was approved on 14 May 2003 by ITU-T Study Group 6 (2001-2004) under the ITU-T Recommendation A.8 procedure. ii ITU-T Rec. L.42 (05/2003) FOREWORD The International Telecommunication Union (ITU) is the United Nati
4、ons 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 Recommendations on them with a view to standardizing telecommunicat
5、ions 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 approval of ITU-T Recommendations is covered by the procedure
6、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 “Administration“ is used for conciseness to indicate both a telecommun
7、ication 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 compliance with the Recommendation is achieved when all of these man
8、datory 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 required of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws
9、 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 Intellectual Property Rights, whether asserted by ITU members or
10、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. However, implementors are cautioned that this may not repre
11、sent the latest information and are therefore strongly urged to consult the TSB patent database. ITU 2004 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. L.42 (05/2003) iii CONTENTS Page 1 Introducti
12、on 1 2 Scope 1 3 References. 1 4 Terms and definitions . 3 5 Abbreviations 3 6 Features of access network architecture . 3 6.1 Point-to-point network 3 6.2 Ring network 4 6.3 Point-to-multipoint network . 6 7 Optical fibre distribution method in outside plant 7 8 Upgrading the optical network . 7 9
13、Optical transmission performance for optical access network . 7 10 Optical components 7 10.1 Optical fibre cable 8 10.2 Optical fibre joint . 8 10.3 Other optical components. 8 11 Optical network maintenance support, monitoring and testing system 9 12 Electrical power supply 9 13 Safety 9 13.1 Elect
14、rical safety 9 13.2 Optical safety 9 Appendix I Brazil experience Example of architecture of optical access network . 10 I.1 Introduction 10 I.2 Scope 10 I.3 Proposed model 10 I.4 Further discussion and results 11 I.5 Conclusions 11 Appendix II Japanese experience Outline of optical access network s
15、tructural design technologies 12 II.1 Loop scale optimization (Feeder area) . 13 II.2 Customer drop area size optimization (Distribution area) . 13 Appendix III Korea experience Distribution methods for the design of optical networks in access areas. 15 III.1 Number and size of loops in the feeder n
16、etwork 17 iv ITU-T Rec. L.42 (05/2003) Page Appendix IV Netherlands experience. 19 IV.1 Introduction 19 IV.2 Mini-tube system configurations 20 IV.3 Access networks using mini-tube system. 21 ITU-T Rec. L.42 (05/2003) 1 ITU-T Recommendation L.42 Extending optical fibre solutions into the access netw
17、ork 1 Introduction Progress on multimedia technologies has led to the active development of many kinds of broadband services such as data and video communication using access networks. It is important that high-speed broadband networks be developed to provide such services economically. In order to
18、provide these services in a timely way, it is necessary to construct fibre to the home (FTTH) optical access networks immediately, efficiently and cost-effectively. To achieve this, the network design must take construction, maintenance and operation into account. Here, an optical access network is
19、defined as a network of optical fibres that extend from a carriers central office into individual homes, apartment houses and business offices for FTTH. 2 Scope This Recommendation deals mainly with access network architectures and the ability to upgrade optical networks, which are the most importan
20、t items in terms of designing and constructing optical access networks. Moreover, this Recommendation describes the optical transmission performance, the maintenance system and power supply required for the design and construction of an optical access network for FTTH. 3 References The following ITU
21、-T Recommendations and other 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 Recommendatio
22、n are therefore encouraged 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,
23、 as a stand-alone document, the status of a Recommendation. 1 ITU-T Recommendation G.652 (2003), Characteristics of a single-mode optical fibre cable. 2 ITU-T Recommendation G.662 (1998), Generic characteristics of optical amplifier devices and subsystems. 3 ITU-T Recommendation G.664 (2003), Optica
24、l safety procedures and requirements for optical transport systems. 4 ITU-T Recommendation G.671 (2002), Transmission characteristics of optical components and subsystems. 5 ITU-T Recommendation G.694.1 (2002), Spectral grids for WDM applications: DWDM frequency grid. 6 ITU-T Recommendation G.694.2
25、(2003), Spectral grids for WDM applications: CWDM wavelength grid. 7 ITU-T Recommendation G.982 (1996), Optical access networks to support services up to the ISDN primary rate or equivalent bit rates. 8 ITU-T Recommendation G.983.1 (1998), Broadband optical access systems based on passive optical ne
26、tworks (PON). 2 ITU-T Rec. L.42 (05/2003) 9 ITU-T Recommendation G.983.2 (2002), ONT management and control interface specification for B-PON. 10 ITU-T Recommendation G.983.3 (2001), A broadband optical access system with increased service capability by wavelength allocation. 11 ITU-T Recommendation
27、 G.983.4 (2001), A broadband optical access system with increased service capability using dynamic bandwidth assignment (DBA). 12 ITU-T Recommendation G.983.5 (2002), A broadband optical access system with enhanced survivability. 13 ITU-T Recommendation G.983.6 (2002), ONT management and control int
28、erface specifications for B-PON system with protection features. 14 ITU-T Recommendation G.983.7 (2001), ONT management and control interface specification for dynamic bandwidth assignment (DBA) B-PON system. 15 ITU-T Recommendation G.983.8 (2003), B-PON-OMCI support for IP, ISDN, video, VLAN taggin
29、g, VC cross-connections and other select functions. 16 ITU-T Recommendation G.984.1 (2003), Gigabit-capable Passive Optical Networks (GPON): General characteristics. 17 ITU-T Recommendation K.51 (2000), Safety criteria for telecommunication equipment. 18 ITU-T Recommendation L.10 (2002), Optical fib
30、re cables for duct and tunnel application. 19 ITU-T Recommendation L.12 (2000), Optical fibre joints. 20 ITU-T Recommendation L.13 (2003), Performance requirements for passive optical nodes: Sealed closures for outdoor environments. 21 ITU-T Recommendation L.15 (1993), Optical local distribution net
31、works Factors to be considered for their construction. 22 ITU-T Recommendation L.26 (2002), Optical fibre cables for aerial application. 23 ITU-T Recommendation L.31 (1996), Optical fibre attenuators. 24 ITU-T Recommendation L.36 (1998), Single mode fibre optic connectors. 25 ITU-T Recommendation L.
32、37 (1998), Fibre optic (non-wavelength selective) branching devices. 26 ITU-T Recommendation L.40 (2000), Optical fibre outside plant maintenance support, monitoring and testing system. 27 ITU-T Recommendation L.41 (2000), Maintenance wavelength on fibres carrying signals. 28 ITU-T Recommendation L.
33、43 (2002), Optical fibre cables for buried application. 29 ITU-T Recommendation L.44 (2000), Electric power supply for equipment installed as outside plant. 30 ITU-T Recommendation L.50 (Draft), Requirements for passive optical nodes: Optical distribution frames for central office environments. 31 I
34、TU-T Recommendation L.51 (2003), Passive node elements for fibre optic networks General principles and definitions for characterization and performance evaluation. 32 ITU-T Recommendation L.53 (2003), Optical fibre maintenance criteria for access networks. ITU-T Rec. L.42 (05/2003) 3 33 IEC 60825 (2
35、001), Safety of laser products. 34 IEC 60950 (2001), Information technology equipment Safety. 4 Terms and definitions For the purpose of this Recommendation, the definitions given in ITU-T Recs G.652, G.662, G.664, G.671, G.694.1, G.694.2, G.982, G.983.1 to G.983.8, G.984.1, K.51, L.13, L.26 and L.5
36、1 apply. 5 Abbreviations This Recommendation uses the following abbreviations: CATV Cable Television CWDM Coarse Wavelength Division Multiplexing DWDM Dense Wavelength Division Multiplexing FTTH Fibre to the Home OLT Optical Line Terminal ONU Optical Network Unit WDM Wavelength Division Multiplexing
37、 6 Features of access network architecture In order to select or design an optical access network for FTTH, telecommunication companies should mainly consider: 1) scalability (number of terminated fibres, total fibre length of network, etc.); 2) survivability (security, supervisory system, etc.); 3)
38、 functionality (bit rate, transmission distance, etc.); 4) construction and maintenance costs; 5) upgrading the optical network (increase transmission capacity, increase transmission length, increase number of customers including future demand). When designing or constructing an optical access netwo
39、rk, telecommunication companies should select and use one or more of the following architectures, based on the optical access network requirements in each region. 6.1 Point-to-point network The basic configuration for a point-to-point network is shown in Figure 1. This distributes one or more fibres
40、 individually from an OLT in a central office to an ONU in buildings, apartment houses or residential premises. Therefore, a large number of fibres are installed and distributed from a central office to customers. This configuration has low optical loss and provides the maximum distance between cent
41、ral offices and customers. Moreover, this may be suitable for customers requiring large bandwidth and/or high security. 4 ITU-T Rec. L.42 (05/2003) L.042_F01Central officeOLTONUOptical fibreOLTOLTONUONUBuilding, apartment house or residential premisesOLTONUOptical Line TerminalOptical Network UnitFi
42、gure 1/L.42 Point-to-point network 6.2 Ring network The basic configuration of a ring network is shown in Figure 2. This starts and ends at the same central office and distributes two or more fibres to ONUs in buildings, apartment houses or residential premises. Therefore, for point-to-point ring ne
43、tworks as shown in Figure 2a, a very large number of fibres are installed and distributed from central offices to customers. By contrast, for multiple-type ring networks as shown in Figure 2b, the number of distributed fibres can be reduced compared to a point-to-point ring network. The advantages o
44、f the ring network are very high reliability and ease of maintenance for alternative routing. ITU-T Rec. L.42 (05/2003) 5 L.042_F02 (A)OLTONUOptical fibre OLTOLTONUONUBuilding, apartment house or residential premisesCentral officeOLTONUOptical Line TerminalOptical Network UnitFigure 2a/L.42 Ring net
45、work (Point-to-point type) L.042_F02 (B)Central officeONUOptical fibre OLT ONUONUBuilding, apartment house or residential premisesOLTONUOptical Line TerminalOptical Network UnitFigure 2b/L.42 Ring network (Multiple type) 6 ITU-T Rec. L.42 (05/2003) 6.3 Point-to-multipoint network The basic configura
46、tion of a point-to-multipoint network is shown in Figure 3. The feature of the point-to-multipoint network is that a (fibre optic) branching component or an active node is placed between an OLT and several ONUs. The location which is installed for use with (fibre optic) branching components or activ
47、e nodes is the most important item in terms of this network design and construction. Moreover, two types of (fibre optic) branching component can be used in this network. One type has a wavelength multiplexer and demultiplexer, the other does not. A (fibre optic) branching component without a wavele
48、ngth multiplexer and demultiplexer increases the insertion loss and reduces the transmission distance as the number of branches is increased. By contrast, a (fibre optic) branching component with a wavelength multiplexer and demultiplexer is mainly used in WDM systems. The insertion loss does not in
49、crease greatly but it is difficult to control and manage the wavelength when the number of branches is increased. When a (fibre optic) branching component is installed in a central office, at least one fibre is connected between the central office and a customers building, apartment house or residential premises. Therefore, a large number of fibres are installed and distributed from the central office. Moreover, the environmental conditions for the (fibre optic) branching component are benign because i
