1、 I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n ITU-T L.315 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (03/2018) SERIES L: ENVIRONMENT AND ICTS, CLIMATE CHANGE, E-WASTE, ENERGY EFFICIENCY; CONSTRUCTION, INSTALLATION AND PROTECTION OF CABLES AND OTHER ELEMENTS OF OUTSIDE P
2、LANT Maintenance and operation Optical fibre cable maintenance Water detection in underground closures for the maintenance of optical fibre cable networks with optical monitoring system Recommendation ITU-T L.315 ITU-T L-SERIES RECOMMENDATIONS ENVIRONMENT AND ICTS, CLIMATE CHANGE, E-WASTE, ENERGY EF
3、FICIENCY; CONSTRUCTION, INSTALLATION AND PROTECTION OF CABLES AND OTHER ELEMENTS OF OUTSIDE PLANT OPTICAL FIBRE CABLES Cable structure and characteristics L.100L.124 Cable evaluation L.125L.149 Guidance and installation technique L.150L.199 OPTICAL INFRASTRUCTURES Infrastructure including node eleme
4、nts (except cables) L.200L.249 General aspects and network design L.250L.299 MAINTENANCE AND OPERATION Optical fibre cable maintenance L.300L.329 Infrastructure maintenance L.330L.349 Operation support and infrastructure management L.350L.379 Disaster management L.380L.399 PASSIVE OPTICAL DEVICES L.
5、400L.429 MARINIZED TERRESTRIAL CABLES L.430L.449 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T L.315 (03/2018) i Recommendation ITU-T L.315 Water detection in underground closures for the maintenance of optical fibre cable networks with optical monitoring system
6、Summary Widely used underground optical fibre cables employ water-blocking materials and are maintenance free in regard to water penetration. However, water penetrated into closures/cabinets would increase the risk of significant degradation to the optical fibres and/or connectors. Recommendation IT
7、U-T L.315 describes the methodology for water detection in splice closures/cabinets, the fundamental requirements for water sensors and technical considerations concerning the optical time domain reflectometry (OTDR)-based water ingress monitoring and location system design. History Edition Recommen
8、dation Approval Study Group Unique ID* 1.0 ITU-T L.315 2018-03-16 15 11.1002/1000/13568 Keywords Cabinet, closure, optical fibre cable, OTDR testing, underground, water detection, water sensor. * To access the Recommendation, type the URL http:/handle.itu.int/ in the address field of your web browse
9、r, followed by the Recommendations unique ID. For example, http:/handle.itu.int/11.1002/1000/11830-en. ii Rec. ITU-T L.315 (03/2018) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication tec
10、hnologies (ICTs). 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 Tele
11、communication 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 a
12、reas 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 both a telecommunication administration and a recognized o
13、perating 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 when all of these mandatory provisions are met. The words “s
14、hall“ 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 PROPERTY RIGHTSITU draws attention to the possibility that the p
15、ractice 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 by ITU members or others outside of the Recommendation dev
16、elopment 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, implementers are cautioned that this may not represent the latest information and are ther
17、efore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2018 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T L.315 (03/2018) iii Table of Contents Page 1 Scope .
18、1 2 References . 1 3 Definitions 2 3.1 Terms defined elsewhere 2 3.2 Terms defined in this Recommendation . 2 4 Abbreviations and acronyms 2 5 Conventions 2 6 Fundamental requirement of water detection in underground splice closures/cabinets . 2 6.1 Overview of monitoring system . 2 6.2 Water sensor
19、 . 3 6.3 Test procedure 4 Appendix I Information on insertion-loss type water sensor 6 I.1 Introduction 6 I.2 Structure of the sensor 6 I.3 Principles of water detection 6 I.4 Characteristics of the sensor . 7 Appendix II Consideration of periodic test cycle for detecting water penetration . 8 II.1
20、Introduction 8 II.2 Example of periodic test cycle consideration . 8 II.3 Conclusion 9 Bibliography. 10 Rec. ITU-T L.315 (03/2018) 1 Recommendation ITU-T L.315 Water detection in underground closures for the maintenance of optical fibre cable networks with optical monitoring system 1 Scope This Reco
21、mmendation covers: water detection systems in splice closures/cabinets to ensure the reliability of underground optical fibre cable networks; fundamental requirements for water sensors attached to non-active optical fibre dedicated for maintenance use; technical considerations for the design of an o
22、ptical fibre cable maintenance support, monitoring and testing system to monitor and locate water penetration. 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
23、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 Recommendations and other references listed below. A list
24、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.652 Recommendation ITU-T G.652 (2016), Characteristics of a single-mode optical fibre and c
25、able. ITU-T G.653 Recommendation ITU-T G.653 (2010), Characteristics of a dispersion-shifted, single-mode optical fibre and cable. ITU-T G.654 Recommendation ITU-T G.654 (2016), Characteristics of a cut-off shifted single-mode optical fibre and cable. ITU-T G.655 Recommendation ITU-T G.655 (2009), C
26、haracteristics of a non-zero dispersion-shifted single-mode optical fibre and cable. ITU-T G.656 Recommendation ITU-T G.656 (2010), Characteristics of a single-mode optical fibre and cable with non-zero dispersion for wideband optical transport. ITU-T G.657 Recommendation ITU-T G.657 (2016), Charact
27、eristics of a bending-loss insensitive single-mode optical fibre and cable. ITU-T L.300 Recommendation ITU-T L.300/L.25 (2015), Optical fibre cable network maintenance. ITU-T L.302 Recommendation ITU-T L.302/L.40 (2000), Optical fibre outside plant maintenance support, monitoring and testing system.
28、 IEC 60793-2-50 IEC 60793-2-50 (2015), Optical fibres Part 2-50: Product specifications Sectional specification for class B single-mode fibres. IEC 60794-1-31 IEC 60794-1-31 (2018), Optical fibre cables Part 1-31: Generic specification Optical cable elements Optical fibre ribbon. 2 Rec. ITU-T L.315
29、(03/2018) 3 Definitions 3.1 Terms defined elsewhere This Recommendation uses the following terms defined elsewhere: 3.1.1 maintenance support, monitoring and testing system ITU-T L.300. 3.1.2 preventative maintenance ITU-T L.300. 3.1.3 surveillance ITU-T L.300. 3.2 Terms defined in this Recommendati
30、on None. 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: CRT Cathode Ray Tube CPU Central Processing Unit GP-IB General Purpose Interface Bus IL Insertion Loss OTDR Optical Time Domain Reflectometry RL Return Loss 5 Conventions None. 6 Fundamental requ
31、irement of water detection in underground splice closures/cabinets 6.1 Overview of monitoring system With the goal of ensuring the sustainability of optical fibre cable networks, it is very important to keep optical fibres and splices away from water penetrating into closures/cabinets. The lifetimes
32、 of optical fibres with residual stress at splice points are significantly affected by environmental conditions such as water and contaminants associated with water immersion. Although underground closures/cabinets are normally designed to be sealed for protection, as specified in b-ITU-T L.201 and
33、b-IEC 61753-111-8, water penetration may occur in actual cable networks because it depends on the level of protection afforded to the products, the immersion period, pressure and the quality with which they are assembled in the field. Water detection is defined as a function of surveillance and test
34、ing maintenance activity that is categorized in preventative maintenance ITU-T L.300. An overview of the entire monitoring system is shown in Figure 1. The fundamental requirements are as follows: it should be conducted in conjunction with the optical time domain reflectometry (OTDR) testing using a
35、 maintenance support, monitoring and testing system ITU-T L.302; it should use an inactive optical fibre (not carrying a communication signal) dedicated for maintenance use as a monitor line; it should be capable of monitoring multiple sensors in the longitudinal direction of an optical fibre link w
36、ithin the dynamic range of OTDR testing, and; Rec. ITU-T L.315 (03/2018) 3 it should be capable of locating splice closures/cabinets where water penetration has occurred. The locating resolution should be higher than the minimum installation distance of the water sensors in an optical fibre link. Fi
37、gure 1 Overview of monitoring system 6.2 Water sensor 6.2.1 Configuration 6.2.1.1 Sensing principle insertion loss (IL) type: This type of water sensor changes insertion loss to a monitor line when water surrounds the sensor; return loss (RL) type: This type of water sensor changes return loss to a
38、monitor line when water surrounds the sensor. 6.2.1.2 Installation method According to installation methods used for dedicated optical fibres, the water sensor can be classified as follows: external type: This type of water sensor is externally attached to a dedicated optical fibre, such as a bender
39、 mechanism; pigtail type: The pigtails of this type of water sensor are spliced to a dedicated optical fibre. 6.2.1.3 Size The water sensor should be small enough to be accommodated in fibre organizing trays in closures/cabinets. 6.2.1.4 Material The water sensor should not contain conductive materi
40、als. The constituent materials should have sufficient durability in underground environmental conditions. 6.2.2 Applicable fibre and cable The characteristics of the optical fibre in this Recommendation should comply with ITU-T G.652, ITU-T G.653, ITU-T G.654, ITU-T G.655, ITU-T G.656 and ITU-T G.65
41、7. The water sensor can be applied to primary coated fibre IEC 60793-2-50 and/or optical fibre ribbon IEC 60794-1-31. 4 Rec. ITU-T L.315 (03/2018) One sensor product does not necessarily cover all fibre/cable types. For example, several different products may be required depending on the fibre type.
42、 6.2.3 Functional requirements The functional requirements of the water sensor are summarized in Table 1. The IL/RL change should not reach the threshold value before water gets in contact with the sensor. After sufficient amount of water surrounds the sensor, the IL/RL change should exceed their th
43、resholds within the response time and maintain their states (latching). The IL/RL threshold should be designed to be clearly distinguishable from normal events on an OTDR trace such as splices and/or connectors. Table 1 Functional requirements of water sensor Type IL RL Operational temperature (Note
44、 1) 0C to 60C Threshold (Note 2) 2 dB 25 dB Response time (Note 3) 24 hours Hold after detection (Note 4) Latching NOTE 1 Water with contamination may not freeze exactly at 0C. Lower operational temperature is possible. NOTE 2 For wavelengths of 1550 nm 20 nm. NOTE 3 Time taken to reach the threshol
45、d value after sufficient amount of water surrounds the sensor. NOTE 4 Function that maintains the state over thresholds after detection. The hold time should be determined by operators maintenance policy. The mechanical characteristics of the sensor module itself should be comparable to those of pas
46、sive optical components. The details should be agreed upon between the operator and the supplier. 6.3 Test procedure 6.3.1 Test wavelength A wavelength of 1550 nm 20 nm or longer is used. 6.3.2 Periodic test cycle The periodic test cycle should be less than the sensor hold time. The cycle is also de
47、fined by considering the risk to the mechanical reliability of optical fibre caused by the time of exposure to the water and the mean time to repair after water penetration has been detected in accordance with the maintenance policy of the operators (see Appendix II). Rec. ITU-T L.315 (03/2018) 5 Fi
48、gure 2 Timeline for performing periodic test 6.3.3 Action after water detection If an event exceeding the threshold is detected, the maintenance system should send an alarm, or report the problem to the appropriate division. After restoration, the sensor should be treated in accordance with the manu
49、facturers instructions. 6 Rec. ITU-T L.315 (03/2018) Appendix I Information on insertion-loss type water sensor (This appendix does not form an integral part of this Recommendation.) This appendix introduces an example of the IL-type water sensor with a bender mechanism for detecting water penetration. This appendix does not contain the RL-type water sensor, which can be found in, for example, b-Hsu. I.1 Introduction The fibre optic bending-typ
