1、 International Telecommunication Union ITU-T L.78TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (05/2008) SERIES L: CONSTRUCTION, INSTALLATION AND PROTECTION OF CABLES AND OTHER ELEMENTS OF OUTSIDE PLANT Optical fibre cable construction for sewer duct applications Recommendation ITU-T L.78 Rec. ITU
2、-T L.78 (05/2008) i Recommendation ITU-T L.78 Optical fibre cable construction for sewer duct applications Summary Recommendation ITU-T L.78 describes the characteristics, construction and test methods for optical fibre cables to be installed in sewer ducts and drainpipes. The characteristics that a
3、 cable should have for an optical fibre to perform appropriately are described. Also, a method is described for determining whether or not the cable has the required characteristics. The required conditions may differ according to the installation environment; detailed test conditions need to be agr
4、eed upon between the user and manufacturer for the environment in which the cable is to be used. Source Recommendation ITU-T L.78 was approved on 29 May 2008 by ITU-T Study Group 6 (2005-2008) under Recommendation ITU-T A.8 procedure. ii Rec. ITU-T L.78 (05/2008) FOREWORD The International Telecommu
5、nication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff
6、 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 years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommend
7、ations 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 necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendat
8、ion, the expression “Administration“ 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
9、 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 negative equivalents are used to express requirements. The use of such words does not suggest that complian
10、ce 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 of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or
11、 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, ITU had not received notice of intellectual property, protected by patents, which may be required to
12、 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.itu.int/ITU-T/ipr/. ITU 2009 All rights reserved. No part of this publication may be reproduced, by
13、any means whatsoever, without the prior written permission of ITU. Rec. ITU-T L.78 (05/2008) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 3 4 Abbreviations and acronyms 3 5 Characteristics of the optical fibres and cables. 3 5.1 Optical fibres 3 5.2 Mechanical characteristics 3 5.3 Envi
14、ronmental conditions. 4 5.4 Fire safety . 5 6 Cable construction 5 6.1 Fibre protection 5 6.2 Cable element . 5 6.3 Sheath . 6 6.4 Armour . 6 6.5 Water-blocking materials . 6 6.6 Cable identification 6 7 Test methods. 6 7.1 Test methods for cable elements 6 7.2 Test methods for mechanical characteri
15、stics of cable 7 7.3 Test methods for environmental characteristics. 8 7.4 Test methods for fire safety 9 Appendix I Chinese experience Construction of self-supporting optical fibre cables for sewer applications. 10 I.1 Cable design . 10 I.2 Fibre identification . 11 I.3 Mechanical performance of th
16、e cable. 11 I.4 Environmental characteristics of the cable. 12 Appendix II Italian experience Construction of optical fibre cables for sewer applications. 14 II.1 General design of the cable 14 II.2 Description of cable structure. 14 II.3 Main performance characteristics of the cable. 14 II.4 Other
17、characteristics of the cable . 15 iv Rec. ITU-T L.78 (05/2008) Introduction With the growth of fibre-to-the-home (FTTH) services, there is an increasing demand for ducts and tunnels in which to install optical fibre cables. However, in metropolitan areas it is difficult to increase the number of duc
18、ts and/or tunnels because of the cost and interference with traffic that it would involve. To install optical fibre cables in sewer ducts is one possible way to solve the duct shortage problem. However, the sewer pipe environment is different from that of ducts designed for telecommunication. Theref
19、ore, the required characteristics also differ from those for standard underground cables. This Recommendation is developed for this reason. Rec. ITU-T L.78 (05/2008) 1 Recommendation ITU-T L.78 Optical fibre cable construction for sewer duct applications 1 Scope This Recommendation: refers to optica
20、l fibre cables to be used for telecommunications networks in sewer ducts and/or drainpipes; deals with the mechanical and environmental characteristics of optical fibre cables for sewer applications. The optical fibre dimensional and transmission characteristics, together with their test methods, sh
21、ould comply with IEC 60793-2-10, ITU-T G.652, ITU-T G.653, ITU-T G.654, ITU-T G.655, ITU-T G.656 and ITU-T G.657, which deal with a multi-mode graded index optical fibre and single-mode optical fibres, respectively; deals with fundamental considerations related to optical fibre cable from mechanical
22、 and environmental standpoints; acknowledges that some optical fibre cables may contain metallic elements, for which reference should be made to b-ITU-T Plant (see ITU-T L.1), and other L-Series Recommendations; recommends that an optical fibre cable should be provided with cable end-sealing and pro
23、tection during cable delivery and storage, as used for metallic cables. If splicing components have been factory installed they should be adequately protected. 2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute p
24、rovisions 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 recent edition of the Recommend
25、ations 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.650.1 Recommendation ITU-T G.650.1 (2002),
26、 Definitions and test methods for linear, deterministic attributes of single-mode fibre and cable. ITU-T G.651.1 Recommendation ITU-T G.651.1 (2007), Characteristics of a 50/125 m multimode graded index optical fibre cable for the optical access network. ITU-T G.652 Recommendation ITU-T G.652 (2005)
27、, Characteristics of a single-mode optical fibre cable. ITU-T G.653 Recommendation ITU-T G.653 (2003), Characteristics of a dispersion-shifted single-mode optical fibre and cable. ITU-T G.654 Recommendation ITU-T G.654 (2004), Characteristics of a cut-off shifted single-mode optical fibre and cable.
28、 ITU-T G.655 Recommendation ITU-T G.655 (2006), Characteristics of a non-zero dispersion-shifted single-mode optical fibre and cable. ITU-T G.656 Recommendation ITU-T G.656 (2004), Characteristics of a fibre and cable with non-zero dispersion for wideband optical transport. 2 Rec. ITU-T L.78 (05/200
29、8) ITU-T G.657 Recommendation ITU-T G.657 (2006), Characteristics of a bending loss insensitive single mode optical fibre and cable for the access network. ITU-T L.1 Recommendation ITU-T L.1 (1988), Construction, installation and protection of telecommunication cables in public networks. ITU-T L.46
30、Recommendation ITU-T L.46 (2000), Protection of telecommunication cables and plant from biological attack. IEC 60189-1 IEC 60189-1 (2007), Low-frequency cables and wires with PVC insulation and PVC sheath Part 1: General test and measuring methods. IEC 60793-1 IEC 60793-1 (in force), Optical fibres
31、Part 1: Measurement methods and test procedures. IEC 60793-1-32 IEC 60793-1-32 (2001), Optical fibres Part 1-32: Measurement methods and test procedures Coating strippability. IEC 60793-2-10 IEC 60793-2-10 (2007), Optical fibres Part 2-10: Product specifications Sectional specification for category
32、A1 multimode fibres. IEC 60794-1-1 IEC 60794-1-1 (2001), Optical fibre cables Part 1-1: Generic specification General. IEC 60794-1-2 IEC 60794-1-2 (2003), Optical fibre cables Part 1-2: Generic specification Basic optical cable test procedures. IEC 60794-2 IEC 60794-2 (2002), Optical fibre cables Pa
33、rt 2: Indoor cables Sectional specification. IEC 60794-2-10 IEC 60794-2-10 (2003), Optical fibre cables Part 2-10: Indoor cables Family specification for simplex and duplex cables. IEC 60332-1 IEC 60332-1 (1979), Tests on electric and optical fibre cables under fire conditions Part 1: Test for verti
34、cal flame propagation for a single insulated wire or cable. IEC 60332-3-24 IEC 60332-3-24 (2000), Tests on electric cables under fire conditions Part 3-24: Test for vertical flame spread of vertically-mounted bunched wires or cables Category C. IEC 60754-1 IEC 60754-1 (1994), Test on gases evolved d
35、uring combustion of materials from cables Part 1: Determination of the amount of halogen acid gas. IEC 60754-2 IEC 60754-2 (1991), Test on gases evolved during combustion of electric cables Part 2: Determination of degree of acidity of gases evolved during the combustion of materials taken from elec
36、tric cables by measuring pH and conductivity. Rec. ITU-T L.78 (05/2008) 3 IEC 61034-1 IEC 61034-1 (2005), Measurement of smoke density of cables burning under defined conditions Part 1: Test apparatus. IEC 61034-2 IEC 61034-2 (2005), Measurement of smoke density of cables burning under defined condi
37、tions Part 2: Test procedure and requirements. EIA/TIA-598 EIA/TIA-598 (2000), Color Coding of Fiber Optic Cables. 3 Definitions For the purpose of this Recommendation, the definitions given in ITU-T G.650.1 and ITU-T G.651.1 apply. 4 Abbreviations and acronyms This Recommendation uses the following
38、 abbreviations and acronyms: APL Aluminium Polyethylene Laminate CSM Central Strength Member PBT Polyethylene Terephthalate 5 Characteristics of the optical fibres and cables 5.1 Optical fibres The optical fibres described in IEC 60793-2-10 and ITU-T G.652, ITU-T G.653, ITU-T G.654, ITU-T G.655, ITU
39、-T G.656 and ITU-T G.657 should be used. 5.2 Mechanical characteristics If mechanical forces (e.g., expanding, buckling, bending, torsion, crush and kink) are applied, they may affect the performance of a fibre and a cable. This clause describes the relationship between typical mechanical forces and
40、 cable performance. 5.2.1 Bending Cable bending during installation and operation may impose strain on fibres, and this may affect fibre strength. Bending also causes a loss increase. Therefore, the cable bending radius must be kept large enough to avoid any loss increase or fibre lifetime degradati
41、on when designing a tensile member or limiting the installation conditions. 5.2.2 Tensile strength Optical fibre cable is subjected to short-term loading during manufacture and installation, and may be affected by continuous static loading and/or cyclic loading during operation (e.g., temperature va
42、riation). Changes to the tension of the cable as a result of the various factors encountered by a cable during its service life can cause the differential movement of the cable components. This effect needs to be considered in the cable design. Excessive cable tensile loading increases the optical l
43、oss and may cause increased residual strain in the fibre if the cable cannot relax. To avoid this, the maximum tensile strength determined by the cable construction, especially as regards the design of the strength member, should not be exceeded. NOTE Where a cable is subjected to permanent loading
44、during its operational life, the fibre should preferably not experience additional strain. 4 Rec. ITU-T L.78 (05/2008) 5.2.3 Crushing and impact The cable may be subjected to crushing and impact both during its installation and operational life. This crushing and impact may increase the optical loss
45、 (permanently or during the time the stress is applied) and excessive stress may lead to fibre fracture. 5.2.4 Torsion Under the dynamic conditions encountered during installation and operation, the cable may be subjected to torsion, resulting in residual strain on the fibres and/or sheath damage. I
46、f this is the case, the cable design should allow a specified number of cable twists per unit length without any increase in fibre loss and/or sheath damage. 5.3 Environmental conditions The environmental conditions in a sewer pipe may be harsh compared with those experienced by conventional undergr
47、ound cables. This clause describes expected environmental conditions that require consideration when designing optical fibre cables for sewer applications. 5.3.1 Temperature variation Temperature variation strongly depends on climatic conditions and the temperature of liquid passing through a sewer
48、pipe. Therefore, it is important to examine the expected temperature range during a cables operational lifetime. It is recommended that the optical fibre cable structure be designed so that no increase in fibre attenuation exceeds the specified limits under those conditions. 5.3.2 Rodent attack Rode
49、nts may be found in sewer pipes. Where those rodents cannot be excluded, a suitable and effective protection should be provided. Further information is described in ITU-T L.46. Effective protection can be provided by metallic (steel tape or wire armouring) or non-metallic (e.g., fibreglass rods, glass yarns/tapes) barriers. 5.3.3 Chemical attack Although it is undesirable, there is a possibility that certain kinds of chemical agent will flow th
