1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T L.54TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (02/2004) SERIES L: CONSTRUCTION, INSTALLATION AND PROTECTION OF CABLES AND OTHER ELEMENTS OF OUTSIDE PLANT Splice closure for marinized terrestrial cables (MTC) ITU-T Recommendation L.54 ITU-T Rec. L.54
2、 (02/2004) i ITU-T Recommendation L.54 Splice closure for marinized terrestrial cables (MTC) Summary This Recommendation refers to both the design and the main characteristics that an underwater splice closure for MTC should have in order to be suitable for this application, as well as to guarantee
3、the expected lifetime of the whole transmission link. This Recommendation provides the tests for characterization and evaluation of the underwater splice closures performance, including mechanical integrity and optical stability of the product simulating the effect of the environment (water), as wel
4、l as interventions related to installation and network maintenance. Source ITU-T Recommendation L.54 was approved on 6 February 2004 by ITU-T Study Group 6 (2001-2004) under the ITU-T Recommendation A.8 procedure. ii ITU-T Rec. L.54 (02/2004) FOREWORD The International Telecommunication Union (ITU)
5、is the United Nations 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 standardiz
6、ing 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 Recommendations on these topics. The approval of ITU-T Recommendations is covered
7、 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 Recommendation, the expression “Administration“ is used for conciseness to indicate
8、 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 or applicability) and compliance with the Recommendation is achieved wh
9、en 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 compliance with the Recommendation is required of any party. INTELLECTUAL PROPER
10、TY 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 Intellectual Property Rights, whether asserted
11、 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. However, implementors are cautioned that
12、 this may not represent 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.54 (02/2004) iii CONTENT
13、S Page 1 Introduction 1 2 Scope 1 3 References. 1 4 Abbreviations and definitions. 2 5 Main characteristics 2 6 Qualification tests . 3 7 Sample preparation . 4 8 Reference measurements 4 9 Tests 4 9.1 Temperature cycling. 5 9.2 Tensile with twist restrained. 5 9.3 Tensile with torque minimized. 6 9
14、.4 Bending under tension (sheave passage) 7 9.5 Repeated bending (optional). 7 9.6 Hydraulic pressure resistance. 8 9.7 Bumps. 8 9.8 Vibration. 9 9.9 Corrosion resistance (optional). 9 Appendix I Examples of different closure designs available on the market. 10 ITU-T Rec. L.54 (02/2004) 1 ITU-T Reco
15、mmendation L.54 Splice closure for marinized terrestrial cables (MTC) 1 Introduction An important part of any installed underwater optical cable system is the jointing between different cable spans. In fact, it is very important that a splice closure utilized for an underwater (i.e., MTC) optical ca
16、ble system is manufactured in order to guarantee not only a good quality of transmission during the expected lifetime, but also cost savings for maintenance purposes. A splice closure comprises a mechanical structure (closure housing) that is attached to the ends of two or more underwater cables, an
17、d a set of boxes (organizers) for containing and protecting the fibres and passive optical devices (if any). As a general rule, the closure housing and the armour terminations, generally designed for a whole MTC family, should be dimensioned for the strongest cable designed for that particular link
18、(maximum tensile strength and maximum pressure resistance). Splice closures for MTC applications may contain fibre splices, mass splices and passive devices. Moreover, since such closures are typically mounted on the cable before it is installed, it should also be designed to withstand all handling
19、and loads that occur during cable installation. 2 Scope This Recommendation details: the mechanical and environmental characteristics of splice closures for MTC applications; the main optical performances that such closures have to guarantee during their lifetimes. 3 References The following ITU-T R
20、ecommendations 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 Recommendation ar
21、e 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, as
22、a stand-alone document, the status of a Recommendation. ITU-T Recommendation G.972 (2000), Definition of terms relevant to optical fibre submarine cable systems. ITU-T Recommendation G.976 (2000), Test methods applicable to optical fibre submarine cable systems. ITU-T Recommendation L.12 (2000), Opt
23、ical fibre joints. ITU-T Recommendation L.13 (2003), Performance requirements for passive optical nodes: Sealed closures for outdoor environments. IEC 60068-2-6:1995, Environmental testing Part 2: Tests Vibration (sinusoidal). IEC 60794-1-2:2003, Optical fibre cables Part 1-2: Generic specification
24、Basic optical cable test procedures (Methods:E1, E6, E7, E18A, F1, F10). 2 ITU-T Rec. L.54 (02/2004) IEC 60794-3-30:2002, Optical fibre cables Part 3-30: Outdoor cables Family specification for optical telecommunication cables for lake and river crossings. IEC 61300-2-22:1995, Fibre optic interconne
25、cting devices and passive components Basic test and measurement procedures Part 2-22: Tests Change of temperature. IEC 61300-2-26:1995, Fibre optic interconnecting devices and passive components Basic test and measurement procedures Part 2-26: Tests Salt mist. IEC 61300-3-3:2003, Fibre optic interco
26、nnecting devices and passive components Basic test and measurement procedures Part 3-3: Examinations and measurements Active monitoring of changes in attenuation and return loss (multiple paths). 4 Abbreviations and definitions MTC Marinized Terrestrial Cable (see definition in ITU-T Rec. G.972). NO
27、TS Nominal Operating Tensile Strength (see definition in Appendix I/G.976). NOTS represents the maximum average operational tension during installation, recovery or repair. NTTS Nominal Transient Tensile Strength (see definition in Appendix I/G.976). NTTS represents the maximum transient or unexpect
28、ed load that may be applied to the cable, and is normally limited to a percentage of the CBL (Cable Breaking Load) from a mechanical safety point of view. NPTS Nominal Permanent Tensile Strength (see definition in Appendix I/G.976). NPTS represents the maximum residual load, which may be permanently
29、 applied to the cable on the seabed after installation. OTDR Optical Time Domain Reflectometer. 5 Main characteristics Hereinafter, a list of the main characteristics (optical, mechanical and environmental) for a splice closure for MTC applications is given. Even though such a list cannot be conside
30、red exhaustive due to particular environments and applications, it is intended to give the basic and essential guidance for a suitable characterization of the splice closure. Additional requirements can be agreed upon between Customer(s) and Manufacturer(s) to reflect local or special conditions. Mo
31、reover, test methods already standardized are also given where applicable. A splice closure for MTC applications is designed: To restore the integrity of sheath, including mechanical continuity of strength members of MTC; To protect the fibres, fibre splices and optical devices, from the external en
32、vironment (water) and unwanted handling; To provide proper storage of fibre splices, passive devices (if any) and excess of fibres; To resist corrosion; To prevent hydrogen effects; To allow re-intervention on cables and splices; To provide for electrical continuity, if required. ITU-T Rec. L.54 (02
33、/2004) 3 Basic components of the splice closure are: Jointing box with cable core holder and optical organizer; Corrosion-resistant jointing box housing (e.g., stainless steel); Suitable jointing box covering with high grade protection and insulation; Appropriate bend restrictor; Metallic sacrificia
34、l elements (optional). The splice closure shall be watertight in order to avoid fibres being exposed to water both during the operating lifetime, and during and after maintenance operations. Moreover, it shall be equipped to avoid the effect on fibres from hydrogen released by cable armouring. In ca
35、se metallic sacrificial elements are present, much care should be taken in order to prevent induced loss on optical fibres from hydrogen evolution. The problem of hydrogen evolution is one that can lead to attenuation increases. It is normally solved by different engineering approaches, that shall b
36、e documented by the manufacturer. The splice/storage trays shall meet minimum bending diameter of fibres. NOTE Information about the design of the closure housing and the organizer system, as well as the splicing of fibres can be found in ITU-T Recs L.13 and L.12, respectively. Splices should have a
37、n average loss less than 0.5 dB. The optical attenuation due to ageing should be less than 0.2 dB. The optical attenuation due to fibre coiling should be not more than 0.2 dB over the entire joint. Fibre bend radius should be greater than 25 mm and, where possible, greater than 30 mm. Other informat
38、ion on fibre handling and fibre identification for splicing at cable joints can be found in ITU-T Manual “Construction, installation, jointing and protection of optical fibre cables“. Finally, examples of closures available on the market, patented by the most important world constructors can be foun
39、d in Appendix I. 6 Qualification tests The purpose of qualification tests is to verify the integrity of the splice closure during storage, transport, installation and service. The splice closure for MTC shall be qualified for use up to the maximum water depth of the link. Qualification tests are car
40、ried out as part of the development program so as to choose proper design and technology, to demonstrate that they adequately satisfy the performances, reliability and lifetime expectation of the system. Tests carried out by the manufacturer can be considered adequate and therefore taken into consid
41、eration. An evaluation test program shall be agreed between Manufacturer and Customer. Depending on a particular application and upon agreement between Customer and Manufacturer, the test qualification program may be limited to some of the tests hereunder listed. For each test description, where app
42、licable, the reference to the corresponding international standard is also reported. NOTE 1 The tests described in this Recommendation shall assess functionalities and performances of the splice closures. Moreover, in order to guarantee the operating lifetime of splice closures, long-term ageing tes
43、ts and failure effects, on materials and accessories of closures, could be necessary. NOTE 2 The parameters specified in this Recommendation may be affected by measurement uncertainty arising either from measurement errors, or calibration errors due to a lack of suitable standards. Acceptance criter
44、ia shall be interpreted with respect to this consideration. The total uncertainty of measurement for this Recommendation shall be less than or equal to 0.05 dB for attenuation. The expression of “no change in attenuation“ means that any change in measurement value, either positive or negative, withi
45、n the uncertainty of measurement shall be ignored. 4 ITU-T Rec. L.54 (02/2004) 7 Sample preparation The splice closure shall be connected between two specimen cables used in the link in accordance with assembly and disassembly procedures given by the manufacturer. Depending on specific tests, differ
46、ent cable lengths (specimen) may be connected to the splice closure. Moreover, depending on the topology and criticality of the link, a different number of samples can be accordingly defined between the Customer(s) and the Manufacturer(s). 8 Reference measurements Prior to the tests, optical attenua
47、tion, electrical continuity of the metallic sheath and the insulation resistance between metallic tube and steel armour wires shall be measured for reference. The optical fibres may be spliced in loop(s) in order to achieve the desired accuracy in attenuation measurement. Optical attenuation measure
48、ments shall be performed at the wavelength of 1550 nm. Evaluation at 1625 nm is under consideration. The evaluation of optical attenuation of fibres and splices shall be performed either with the transmitter power technique or with the backscattering technique as described in IEC 61300-3-3, Part 3-3
49、. The electrical insulation resistance shall be performed at 500 V DC. The detected value should be approximately equal to the insulation resistance of the cable as stated in its type-approval certificate. Moreover, the electrical continuity measurement of the metallic sheath should give a resistance value across the closure of around 0.2 Ohm. 9 Tests The tests should be done in the following sequences, unless otherwise agreed between the Customer and the Manufacturer. The expression of “no signi
