1、INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU L.17 Appendix I (02/97) SERIES L: CONSTRUCTION, INSTALLATION AND PROTECTION OF CABLES AND OTHER ELEMENTS OF OUTSIDE PLANT Implementation of connecting customers into the public switched telephone network (PST
2、N) via optical fibres Appendix I: Examples of possible applications ITU-T Recommendation L.17 - Appendix I (Previously CCITT Recommendation) ITU-T L-SERIES RECOMMENDATIONS CONSTRUCTION, INSTALLATION AND PROTECTION OF CABLES AND OTHER ELEMENTS OF OUTSIDE PLANT For further details, please refer to ITU
3、TList of Recommendations. ITU-T RECOMMENDATION L.17 IMPLEMENTATION OF CONNECTING CUSTOMERS INTO THE PUBLIC SWITCHED TELEPHONE NETWORK (PSTN) VIA OPTICAL FIBRES APPENDIX I Examples of possible applications Source Appendix I to ITU-T Recommendation L.17 was prepared by IT-T Study Group 6 (1997-2000)
4、and was approved under the WTSC Resolution No. 1 procedure on the 7th of February 1997. Recommendation L.l7/Appendix I (02/97) 1 FOREWORD IT (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommuni- cations. The ITU Telecommunication Standardizatio
5、n Sector (ITU-T) is a permanent organ of the ITU. The 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 Conference (WTSC), w
6、hich meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1. In some areas of informat
7、ion technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with IS0 and IEC. NOTES 1. telecommunication administration and a recognized operating agency. In this Recommendation, the expression “Administration“ is used for conciseness to indicate bo
8、th a 2. follows: The status of annexes and appendices attached to the Series L Recommendations should be interpreted as - - an annex to a Recommendation forms an integral part of the Recommendation; an appendix to a Recommendation does not form part of the Recommendation and only provides some compl
9、ementary explanation or information specific to that Recommendation. INTELLECTUAL PROPERTY RIGHTS The ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The ITU takes no position concerning t
10、he 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, the ITLJ had not received notice of intellectual property, protected by pate
11、nts, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. O ITU 1998 All rights reserved. No part of this publication may be reproduced or ut
12、ilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. 11 Recommendation L.l7/Appendix I (02/97) CONTENTS Page . 1 . 3 Introduction References Recommendation L.l7/Appendix I (02/97) . 111 Recommendation L. 17 IM
13、PLEMENTATION OF CONNECTING CUSTOMERS INTO THE PUBLIC SWITCHED TELEPHONE NETWORK (PSTN) VIA OPTICAL FIBRES APPENDIX I Examples of possible applications (Geneva, 1997) Introduction Many countries are studying systems and network configurations to provide access for customers over optical fibres. These
14、 studies need to take into account not only the initial costs for providing services, but the ongoing costs of operation and the efficiency of maintenance. Also the future cost of shifting to broadband services must be considered. All studies show that economies can be achieved by the sharing of the
15、 OLT (Optical Line Termination) by the use of optical splitters. Beyond this, strategies vary widely for cost efficient solutions from the Japanese approach of locating the splitters in the exchange (central office) to the UK implementation of a modular plant system optimised for use in the access n
16、etwork. 1.1 Japanese culture i By a comparison of network configurations of point-to-point and point-to-multipoint, taking into account the total cost - the initial cost, the cost of shifting to broadband services in the future (cost of transferring to single star, that is, point-to-point) and the r
17、unning and maintenance costs, it is concluded that the most economic network is when the optical splitters are located in the exchange and the external cable configuration is point-to-point, see Figure I. 1. Point-to-multipoint Exchange OLT Point-to-point Exchange ONU ONU OLT ONU T0604240-98/d01 Fig
18、ure I.lL.17 - Network configurations Recommendation L.l7/Appendix I (02/97) 1 It is considered important not only to reduce the cost of optical fibre cables, especially high fibre count cables. by developing new technology but also to reduce the optical loss and make installation work more efficient
19、 in the networks (by minimising the number of jointing points through long length cabling). By the use of computer control at a central point: - - Maintenance operations can be made more efficient by the more speedy and accurate location of faults. A flexible assignment function can be implemented t
20、o redistribute the traffic in optical fibres in accordance with fluctuating demand. Efficient transference of fibres can be implemented to allow re-routing of the cables. - 1.2 With the introduction of optical fibre into the access network and the need to improve the quality of service offered to cu
21、stomers whilst minimising network costs, a new infrastructure philosophy has been developed within the UK resulting in a new architecture. This achieves: - - UK culture 2, 3, and 4 flexibility by adopting a modular approach to all components in the system; resilience by the ability to provide comple
22、te redundant or back-up paths to those who require 24-hour operation by using a feeder ring structure; reliability by understanding which are the critical parameters of the system and specifying components with the most dependable performance; upgradeability by ensuring the components capable of wor
23、king at both 1300 nm and 1550 nm windows; low maintenance by the modular approach and the reliability criteria. - - - The basis of the modular system consists of a linear array or stack of splice trays which are of two types: - a single circuit tray which fulfils the functions of identification, sto
24、rage, connection, inspection and re-connection on a single fibre or pair of fibres. The single circuit tray allows network configuration and reconfiguration without disturbance to other circuits which may be carrying traffic. Provision is also made for non-intrusive optical circuit diagnosis when an
25、 individual tray is opened by only exposing limited fibre for testing. Splitter tray u T060425-%/d02 Figure I.2L.17 -Stack principle - a single element tray which fulfils the functions of identification, storage, connection and re-connection of a multiplicity of fibres, for example, splicing togethe
26、r two units each of eight fibres commonly encountered in a loose-tube type cable. The linear array may be used with point-to-point configurations or with PON systems. In the latter case 1 x N or 2 x N way optical splitters or Wavelength Division Multiplexing (WDM) devices can be incorporated. 2 Reco
27、mmendation L.17IAppendix i (02/97) The use of trays and arrays provides the craft person with a familiar system at all points in the network and allows for considerable factory preconfiguration, thereby minimising field configuration, testing and reconfiguration time. The overall system provides for
28、 dense fibrekable management whilst preserving defined minimum bend radii for the fibres. In the exchange, arrays are (pre-)assembled into telecommunication standard rack frames. They can also be installed in the cable chamber joint units. In the external network, arrays are (pre-)assembled into enc
29、losures which can be hermetically sealed and installed in manholes. The cable configuration in the external network for a feeder ring or spine is typically a 96-fibre cable with eight fibres per loose tube plus a copper quad for field telephony or order wiring. Typically one tube is used per primary
30、 node allowing up to twelve nodes in a feeder. Blown fibre may be used between the primary nodes and the customers premises allowing rapid just-in-time installation. T0604260-98/603 Figure I.3L.17 - Manhole enclosure At the customers premises, arrays are (pre-)assembled into appropriately styled enc
31、losures and outlets suitable for installation within domestic and commercial buildings of all types. The overall system allows for the appropriate procedures necessary for transition between external and internal plant, for example gas blocking. For maintenance purposes, an out-of-band test signal c
32、an be injected via the exchange equipment with the power level being interrogated at any single circuit tray. Apertures are provided in the trays that allow interrogation at both sides of the splice. By this means the relative attenuation may be assessed at any reconfigurable point in the network an
33、d a footprint obtained for maintenance purposes. References i NTT, Japan: The configuration of optical access network. COM 6-44, January 1995. 2 Pirelli Cables, UK: Plant for connection of customers to the Public Switched Telecommunication Network (PSTN) via optical fibres, COM 6-37, January 1995. 3
34、 BICC, UK: Modular optical plant items implementing proposals in draft Recommendation L.imp, COM 6-42, January 1995. 4 HALE (P. G.), BREWER (D. A.), Pirelli Cables UK, PEACOCK (J.), BELL (P.), BT, UK: Modular optical plant for the access network: a practical solution, Proc. EFOC & N (Technology and
35、infrastructure), pp.158-161, 1995. Recommendation L.l7/Appendix I (02/97) 3 Series A Series B Series C Series D Series E Series F Series G Series H Series I Series J Series K Series L Series M Series N Series O Series P Series Q Series R Series S Series T Series U Series V Series X Series Z ITU-T RE
36、COMMENDATIONS SERIES Organization of the work of the ITU-T Means of expression: definitions, symbols, classification General telecommunication statistics General tariff principles Overall network operation, telephone service, service operation and human factors Non-telephone telecommunication servic
37、es Transmission systems and media, digital systems and networks Audiovisual and multimedia systems Integrated services digital network Transmission of television, sound programme and other multimedia signals Protection against interference Construction, installation and protection of cables and othe
38、r elements of outside plant TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits Maintenance: international sound programme and television transmission circuits Specifications of measuring equipment Telephone transmission qual
39、ity, telephone installations, local line networks Switching and signalling Telegraph transmission Telegraph services terminal equipment Terminals for telematic services Telegraph switching Data communication over the telephone network Data networks and open system communication Programming languages
