1、 International Telecommunication Union ITU-T L.87TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (07/2010) SERIES L: CONSTRUCTION, INSTALLATION AND PROTECTION OF CABLES AND OTHER ELEMENTS OF OUTSIDE PLANT Optical fibre cables for drop applications Recommendation ITU-T L.87 Rec. ITU-T L.87 (07/2010)
2、i Recommendation ITU-T L.87 Optical fibre cables for drop applications Summary Recommendation ITU-T L.87 describes the characteristics, construction and test methods of optical fibre cables for drop applications. Optical fibre drop cables are used to connect customer and optical access networks. Acc
3、ess points may be located both outdoors or indoors, depending on the access network configuration. When access points are located outdoors, optical drop cables are exposed to both outdoor and indoor environments. In this case the optical drop cable should be designed for both environments. This Reco
4、mmendation also describes the characteristics that a cable requires for an optical fibre to perform appropriately. Moreover, 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;
5、detailed test conditions must be agreed upon between the user and manufacturer as regards the environment in which the cable is to be used (in case of applying small bends during and after installation, especially). History Edition Recommendation Approval Study Group 1.0 ITU-T L.87 2010-07-29 15 ii
6、Rec. ITU-T L.87 (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 (ITU-T) is a permanent organ of ITU. ITU
7、-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 years, establishes the topics for stu
8、dy 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 necessary standards are prepared on a
9、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. However, the Recommendation may contain
10、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 negative equivalents are used to express req
11、uirements. 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 of a claimed Intellectual Property Ri
12、ght. 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, ITU had not received notice of intell
13、ectual 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.itu.int/ITU-T/ipr/. ITU 2010 All righ
14、ts reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T L.87 (07/2010) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 2 4 Abbreviations and acronyms 2 5 Conventions 2 6 Characteristics of the optical fibr
15、es and cables. 2 6.1 Optical fibres 2 6.2 Mechanical characteristics 3 6.3 Environmental conditions . 4 6.4 Fire safety . 4 7 Cable construction 5 7.1 Fibre protection 5 7.2 Cable element . 5 7.3 Sheath . 5 7.4 Armour . 6 7.5 Water-blocking materials . 6 7.6 Cable identification 6 8 Test methods . 6
16、 8.1 Test methods for cable elements 6 8.2 Test methods for mechanical characteristics of cable 7 8.3 Test methods for environmental characteristics . 8 8.4 Test methods for fire safety 8 Appendix I United States experience Cable installation conditions in multi-dwelling units (MDUs) when using bend
17、ing-loss insensitive fibre . 10 I.1 Mechanical reliability of optical fibre 10 I.2 Comments on mechanical reliability of optical cables used in MDUs 11 I.3 Reliability requirement for optical drop cables 12 Appendix II Drakas experience Reliability and handling concerns for cables using bending loss
18、 insensitive fibres 13 Appendix III Japanese experience Test conditions for optical fibre drop cables using bending loss insensitive fibres for indoor application 14 III.1 Repeated bending test . 14 III.2 Crush test 14 III.3 Torsion test . 14 III.4 Impact test 14 III.5 Folding test . 15 iv Rec. ITU-
19、T L.87 (07/2010) Page Appendix IV Chinese experience Optical fibre cables for drop applications 16 IV.1 Introduction 16 IV.2 Scope 16 IV.3 Requirements 16 Bibliography. 21 Rec. ITU-T L.87 (07/2010) v Introduction Optical fibre drop cables are used to connect the customer and optical access networks.
20、 For office users, conventional underground and aerial cables can be employed. However, household users usually require one or more fibre cables. Therefore, cables are often designed specifically for this purpose. Access points may be located both outdoors or indoors, depending on the access network
21、 configuration. When access points are located outdoors, optical drop cables are exposed to both outdoor and indoor environments. In this case, optical drop cables should be designed for both environments. The required characteristics may also differ from those of standard underground or aerial cabl
22、es. This Recommendation has been developed to deal with this situation. Rec. ITU-T L.87 (07/2010) 1 Recommendation ITU-T L.87 Optical fibre cables for drop applications 1 Scope This Recommendation: refers to optical fibre cables to be mainly used for connecting a household customer and an optical ac
23、cess network; deals with the mechanical and environmental characteristics of optical fibre cables for drop applications. The optical fibre dimensional and transmission characteristics, together with their test methods, should comply with ITU-T G.652 or ITU-T G.657, which deal with single-mode optica
24、l fibres. When using multi-mode or plastic fibres, IEC 60793-2-10 and IEC 60793-2-40 are suitable standards, respectively; deals with fundamental considerations related to optical fibre cables from mechanical and environmental standpoints; acknowledges that some optical fibre cables may contain meta
25、llic elements, for which reference should be made to other L-series Recommendations; recommends that an optical fibre cable should be provided with cable end-sealing and protection during cable delivery and storage, as used for metallic cables. If splicing components have been factory installed they
26、 should be adequately protected. 2 References The following ITU-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
27、references are subject to revision; users of this Recommendation 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 refer
28、ence 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 (2010), Definitions and test methods for linear, deterministic attributes of single-mode fibre and cable. ITU-T G.652 Recommendation I
29、TU-T G.652 (2009), Characteristics of a single-mode optical fibre cable. ITU-T G.657 Recommendation ITU-T G.657 (2009), 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
30、protection of telecommunication cables in public networks. ITU-T L.46 Recommendation ITU-T L.46 (2000), Protection of telecommunication cables and plant from biological attack. IEC 60189-1 IEC 60189-1 (2007), Low-frequency telecommunication cables and wires with PVC insulation and PVC sheath Part 1:
31、 General test and measuring methods. IEC 60332-1 IEC 60332-1 (1979), Tests on electric cables under fire conditions Part 1: Test for vertical insulated wire or cable. 2 Rec. ITU-T L.87 (07/2010) IEC 60332-3-24 IEC 60332-3-24 (2000), Test on electric cables under fire conditions Part 3-24: Test for v
32、ertical flame spread of vertically-mounted bunched wires or cables Category C. IEC 60754-1 IEC 60754-1 (1994), Test on gases evolved during 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 combus
33、tion of electric cables Part 2: Determination of degree of acidity of gases evolved during the combustion of materials taken from electric cables by measuring pH and conductivity. IEC 60793-1 IEC 60793-1 (2001), Optical fibres Part 1: Generic specification. IEC 60793-1-32 IEC 60793-1-32 (2001), Opti
34、cal 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 A1 multimode fibres. IEC 60793-2-40 IEC 60793-2-40 (2009), Optical fibres Part 2-40: Produc
35、t specifications Sectional specification for category A4 multimode fibres. IEC 60794-1-1 IEC 60794-1-1 (2003), Optical fibre cables Part 1-1: Generic specification General. IEC 60794-1-2 IEC 60794-1-2 (2005), Optical fibre cables Part 1-2: Generic specification Basic optical cable test procedures. I
36、EC 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 conditions Part 1: Test procedure and requirements. IEC/TR 62048 IEC/TR 62048 (2
37、002), Optical fibres Realibility Power law theory. 3 Definitions For the purpose of this Recommendation, the definitions given in ITU-T G.650.1 apply. 4 Abbreviations and acronyms None. 5 Conventions None. 6 Characteristics of the optical fibres and cables 6.1 Optical fibres 6.1.1 Single-mode fibres
38、 ITU-T G.652 or ITU-T G.657 should be used. 6.1.2 Multimode fibres IEC 60793-2-10 should be used. Rec. ITU-T L.87 (07/2010) 3 6.1.3 Plastic fibres IEC 60793-2-40 should be used. 6.2 Mechanical characteristics If mechanical forces (e.g., longitudinal strain, buckling, bending, torsion, crush and kink
39、) are applied, they may affect the performance of a fibre and a cable. This clause describes the relationship between typical mechanical forces and cable performance. 6.2.1 Bending Cable bending during installation and operation may impose strain on fibres, and this may affect fibre reliability. Ben
40、ding also causes a loss increase. Therefore, the cable bending radius must be kept large enough to avoid any loss increase or fibre lifetime degradation when designing a tensile member or limiting the installation conditions. In case of using bending loss insensitive fibres, fibre lifetime calculati
41、on should be done carefully based on actual installation conditions. Therefore, it is important for manufacturers and users to agree upon typical, general or harsh (worst case) installation conditions. IEC/TR 62048 describes two regions of mechanical reliability. One is the low strength tail of the
42、distribution or extrinsic region which covers large flaws in the glass optical fibre. The other region is the intrinsic strength portion which describes the high strength bulk of the fibre. When the fibre bending radius is small, there are two considerations to avoid risks of fibre degradation. One
43、is to increase the fibre proof stress level to limit extrinsic flaws on the fibre. The second is to limit the small bend portions along the route where the cable is installed. The random flaws that limit the extrinsic strength have a very low probability distribution in glass optical fibres manufact
44、ured with modern materials using well controlled processes. Therefore, it is negligible that a small bend will occur at the exact location of a random flaw. The cable structure is also an important issue when fibre lifetime calculation and fibre loss estimation are done, because fibre bending radius
45、 is strongly dependent on the cable structure. Generally, the cable bending radius is determined by its inner radius. Therefore, when the fibre is located in the centre of the cable, with cable diameter D and cable bending radius r, the fibre bending radius is r + D/2. In case of a small cable bendi
46、ng radius, such as when r is nearly equal to D, the above calculation cannot be neglected. 6.2.2 Tensile strength The 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
47、.g., temperature variation). 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 incr
48、eases the optical loss 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
49、 permanent loading during its operational life, the fibre should preferably not experience additional strain. 6.2.3 Bending with tension (axial strain) It may happen that small bending and residual strain are applied to the fibres simultaneously. In this case, precise analyses for fibre degradation will be described in IEC/TR 62048 edition 2. However, in order to estimate fibre lifetime, a calculation model which is agreed between man
