1、INTERNATIONAL TELECOMMUNICATION UNION ITU-T TE LEC0 MM UN I CATI0 N STANDARDIZATION SECTOR OF ITU L.47 (1 0/2000) SERIES L: CONSTRUCTION, INSTALLATION AND PROTECTION OF CABLES AND OTHER ELEMENTS OF OUTSIDE PLANT Access facilities using hybrid fibrelcopper networks ITU-T Recommendation L.47 (Formerly
2、 CCITT Recommendation) ITU-T Recommendation L.47 Access facilities using hybrid fibrekopper networks Summary This Recommendation gives information and guidelines about access facilities using HFC (“Hybrid Fibre/Copper“) networks. HFC networks are necessary for the future introduction of multimedia s
3、ervices with several broadband applications. HFC networks offer more chances of use as only pure networks for telecommunication or for CATV (Cable Television) distribution. Additional services as Pay-TV, Pay-per-View, Video-on Demand, home-banking, -working, -shopping and Internet access can be offe
4、red by means of these networks. HFC networks represent also a step in the evolution process to GI1 (Global Information Infrastructure), that means a connection between CATV, telecommunications, data and mobile networks. Appendix II provides examples of HFC networks. Source ITU-T Recommendation L.47
5、was prepared by ITU-T Study Group 6 (1997-2000) and approved by the World Telecommunication Standardization Assembly (Montreal, 27 September - 6 October 2000). ITU-T L.47 (10/2000) i FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of tel
6、ecommunications. 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 telecommunications on a worldwide basis. The World Telec
7、ommunication 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 laid down in WTSA Resolution 1. In some ar
8、eas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with IS0 and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized op
9、erating agency. 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 Intellectua
10、l 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. Howev
11、er, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. O ITU 2001 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, incl
12、uding photocopying and microfilm, without permission in writing from ITU. CONTENTS 1 2 3 3.1 3.2 4 4.1 4.2 Scope Fundamental types of hybrid fibre/copper networks Optical elements . Physical elements of hybrid fibre/copper networks . 3.1.1 Optical cables 3.1.2 Optical connectors . 3.1.3 Optical ampl
13、ifiers 3.1.4 Optical splitters . Electrical and copper elements . 3.2.1 HFC-S networks 3.2.2 HFC-C networks . Installation HFC-S networks . HFC-C networks . 4.2.1 Coaxial cables . 4.2.2 Cabinets . 4.2.3 Indoor installation . Appendix I . Questionnaire on Question 13/6 Access facilities using hybrid
14、fibre/copper networks . I . 1 Introduction 1.2 Topology . 1.3 Cable construction 1.4 Components for CATV networks . 1.5 Cable installation 1.6 Cabinet installation . Appendix II - Italian experience on HFC-C networks II . 1 Introduction 11.2 The HFC-C project . 11.3 Network infrastructure for Italy
15、11.4 Coaxial network design 11.5 Appendix III - Indonesias experience on HFC-C networks Access facilities using hybrid fibre/copper networks . III . 1 Introduction Evolution towards all optical networks 111.2 Background . ITU-T L.47 (10/2000) Page 1 1 2 2 2 2 3 4 8 8 8 10 13 14 15 15 15 . 111 111.3
16、111.4 111.5 111.6 111.7 III . 8 111.9 III . 1 o III . 1 1 III . 12 Network topology . 111.3.1 Transport networktopology 111.3.2 Access network topology 111.3.3 Coaxial network topology . Cable construction 111.4.1 Optical cabling 111.4.2 Coaxial cabling Bandwidth allocation System configuration 111.
17、6.1 Headend . 111.6.2 Distribution hub . 111.6.3 Fibre node 111.6.4 Amplifier (active component) . 111.6.5 Passive component Powering system . Outside plant (OSP) 111.7.1 Powering system in coaxial cable . 111.8.1 Pole III . 8.2 Cabinet Standardization . Coaxial network planning tool . Component for
18、 coaxial HFC-C networks . Legend Page 15 15 16 16 17 17 17 18 18 19 19 20 20 20 21 21 21 21 22 22 22 23 23 iv ITU-T L.47 (10/2000) ITU-T Recommendation L.47 Access facilities using hybrid fibrekopper networks 1 Scope This Recommendation: e gives general information on the fundamental types of hybrid
19、 fibre/copper networks; describes the most important physical elements of HFC networks apart from transmission gives general information and guidelines for the installation of HFC networks. e equipment; e 2 Very different HFC network topologies can be considered, according to different Administratio
20、ns and private operators requirements, different country or regional situations, different provided multimedia services. Moreover, HFC networks can be based on already existing telephone networks, both for the fibre and for the copper part of the network. However, the following general consideration
21、s can be applied to all the HFC network types. An HFC network can be thought as composed of two main sections: Fundamental types of hybrid fibrekopper networks e First section: the “Transport Network“ where the services are generated and delivered (at a national, regional or local level) up to main
22、distribution points. The extension of the Transport Network can be huge. The physical transmission medium is the optical fibre. to the main distribution points. The extension of the Access Network is typically limited to a few kms in length. The bearer used in the first part of the Access Network is
23、 the optical fibre. The physical transmission medium of the last portion of the Access Network up to the users can be the symmetrical copper pair (“HFC-S“ networks) or the coaxial copper/aluminium pair (“HFC-C“ networks). Typically, HFC-S networks are directly derived from traditional telephone copp
24、er access networks. The evolution towards new services can be achieved by means of particular data compression (JPEG, MPEG for instance) and transmission (HDSL, ADSL, VDSL for instance) techniques on the existing symmetrical pair cables. It is worth noticing that HFC-S type identifies a wide set of
25、very different network solutions, according to the level of the optical fibre penetration into the Access Network and to the network topology. So, for instance, HFC-S type ranges from a simple point-to- point ADSL copper link up to FTTB (“Fibre To The Building“) point-to-multipoint PON architectures
26、. The term HFC-C identifies a more restricted set of network solutions. HFC-C networks typically entail the installation of new active and passive coaxial components in the last portion of the Access Network, even if a simple update of an already existing HFC-C unidirectional network towards interac
27、tive services is considered. New HFC-C networks can offer up to 1 GHz bandwidth for CATV broadcast transmission and other broadband multimedia services. It should be taken into account that: e Second section: the “Access Network“ where the final users are connected (at a local level) e a study of ec
28、onomic factors, of already existing telecommunication networks, of present and future service requirements, of rules and regulations in each region should be carried out in order to decide between a HFC-S and a HFC-C type network; 1 ITU-T LA7 (10/2OOO) e already existing infrastructures and ad hoc t
29、echnical solutions should be used wherever possible in order to limit the environmental impact of the new HFC network, especially for the HFC-C network type. 3 Physical elements of hybrid fibrekopper networks 3.1 Optical elements 3.1.1 Optical cables Both HFC-S and HFC-C networks make use of single-
30、mode optical fibre cables in the Transport and in the Access Network. It should be taken into account that: e ITU-T G.652, G.653, G.654 or G.655 single-mode optical fibre should be used in the Transport Network. ITU-T G.652 or G.655 single-mode optical fibre are used in the Access Network; optical c
31、able capacity: from 100 up to 1000 optical fibre cable capacities have been reported. e suitable studies have to be carried out in order to dimension the proper Access Network 3.1.2 Optical connectors Any standard (IEC) connector can be used in the Transport and in the Access Network. In the case of
32、 analogue CATV transmission, the return loss of optical connectors needs to be carefully considered in order to meet the system requirements. 3.1.3 Optical amplifiers Optical amplifiers are used both in the Transport and in the Access Network. The use of optical amplifiers as boosters can be associa
33、ted with tree-type optical network topologies and with the use of optical splitters. 3.1.4 Optical splitters In HFC networks, optical splitters are typically used in tree-type optical network topologies together with optical amplifiers in order to expand the distribution area of a single optical tra
34、nsmitter. In HFC-S PON (Passive Optical Networks) architectures optical splitters are used as branching devices both in central offices and in the field. From 1:2 up to 1:32 splitting ratios have been reported. 3.2 Electrical and copper elements 3.2.1 HFC-S networks 3.2.1.1 Symmetrical pairs cables
35、From 0.4 mm to 0.64 mm wire diameter symmetrical pairs copper cables are typically used in the Access Network for 100 up to 1500 metres typical distances. From 10 up to 3000 symmetrical pairs cable capacities are used, according to different Access Network requirements. Studies and characterizations
36、 should be carried out on the already existing symmetrical pair copper cables in order to verify that they can support the chosen xDSL transmission technique. Refer also to the G.990-series Recommendations. 3.2.2 HFC-C networks 3.2.2.1 Coaxial cables e Coax-trunk cable 1 GHz bandwidth, 12.7 mm (U2 i
37、nch) or 19.05 mm (3/4 inch) outer conductor diameter, 75 ohm impedance coax-trunk cables are used in HFC-C Access Networks from 100 up to 500 metres typical link length between the launch and the last amplifier. 1 GHz bandwidth, RG-11 and RG-6 standard types, 75 ohm impedance coax-drop cables are us
38、ed in HFC-C Access Networks from 50 up to 150 metres typical link length between the last amplifier and the coaxial network termination. Wherever possible, cables should be chosen in order to limit the number of coaxial amplifiers. In spite of their low mechanical flexibility (which can constitute a
39、 problem during installation), 19.05 mm (3/4 inch) outer conductor diameter coax-trunk cables offer very good attenuation performance. e Coax-drop cable 3.2.2.2 Coaxial connectors The 15.825 mm (5/8 inch) and F type coaxial connectors are typically used for cable terminations. However, many differen
40、t connector versions can be used according to the different coaxial cables versions, dimensions and applications. Careful choice of connectors should be made in order to prevent in-field problems due to environmental causes (such as temperature, humidity, vibrations, etc.). In most of the cases, coa
41、xial connectors should be protected by means of a shrinkable plastic sheath. 3.2.2.3 Coaxial splitters Coaxial splitters are typically used on the output ports of coaxial amplifiers (especially in front of launch amplifier) in order to subdivide the electrical signal on the different coax-trunk cabl
42、es of the HFC-C network. 1:2, 1:3 and 1:4 splitting ratios are common. 3.2.2.4 Coaxial taps Coaxial taps are typically used on the output ports of the last amplifiers or for in-building coaxial distribution networks. Many types and versions are available on the market; 2, 4, 8 and 16 output ports co
43、axial taps are common. 3.2.2.5 Electro/optical converters, launch amplifiers, line extenders and last amplifiers are used in HFC-C network respectively in order to transform the optical signal into an electrical one, to launch the electrical signal on the coaxial network, to amplify the electrical s
44、ignal in the case of very long coaxial links (typically more than 500 metres), to amplify and to distribute the electrical signal to the final users area. The active tree-type coaxial network originated by a single electro/optical converter is usually designed in order to serve from 100 up to 500 us
45、ers, by means of from 3 to 9 last amplifiers. The use of line extenders should be limited to those cases of actual necessity. Electro/optical converter and coaxial amplifiers 3.2.2.6 Power supply The coaxial portion of an HFC-C network is remotely powered from the electro/optical-launch amplifier ca
46、binet by means of a properly dimensioned power supply (45-60 Vac, 10-1 5 A are typical values). 3 ITU-T LA7 (10/2OOO) The power supply should be designed in order to limit the environmental impact (noise) in urban installation. 4 Installation This clause gives general information and guidelines on s
47、ome particular aspects of the installation of metallic cables forming a part of HFC-S and HFC-C networks. See L-series Recommendations for optical fibre cable installation practices. 4.1 HFC-S networks HFC-S type identifies a wide set of very different network solutions, according to the level of th
48、e optical fibre penetration into the Access Network and to the network topology. So, installation procedures can involve a simple ADSL modem installation up to the in-field layering of new optical cables and ONU (Optical Network Unit) cabinets in the Access Network, with a huge variety of situations
49、 and potential problems. It should be taken into account that: - - existing infrastructures should be used wherever possible (ducts, manholes, etc.); proper technical solutions should be studied in order to limit the environmental impact of new cabinets and new cable installation in terms of civil works, urban soil occupation, visual effect; proper technical solutions should be studied in order to ensure the reliability and the maintenance of the HFC-S network from the viewpoint of hardware and software; existing infrastructures should be studied as to how they could be reused in HFC-S net
