1、 International Telecommunication Union ITU-T L.68TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (10/2007) SERIES L: CONSTRUCTION, INSTALLATION AND PROTECTION OF CABLES AND OTHER ELEMENTS OF OUTSIDE PLANT Optical fibre cable maintenance support, monitoring and testing system for optical fibre cable
2、networks carrying high total optical powerITU-T Recommendation L.68 ITU-T Rec. L.68 (10/2007) i ITU-T Recommendation L.68 Optical fibre cable maintenance support, monitoring and testing system for optical fibre cable networks carrying high total optical power Summary ITU-T Recommendation L.68 descri
3、bes the functional requirements for optical fibre cable maintenance systems for optical fibre cable carrying a high total optical power. It also considers safety procedures and guidelines for the maintenance of outside optical fibre plant carrying a high total optical power. Source ITU-T Recommendat
4、ion L.68 was approved on 22 October 2007 by ITU-T Study Group 6 (2005-2008) under the ITU-T Recommendation A.8 procedure. ii ITU-T Rec. L.68 (10/2007) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and
5、 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 questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide bas
6、is. 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 by the procedure laid down in WTSA Resol
7、ution 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 both a telecommunication administration
8、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 when all of these mandatory provisions are m
9、et. 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 PROPERTY RIGHTS ITU draws attention to the possi
10、bility 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 by ITU members or others outside of the R
11、ecommendation 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, implementers are cautioned that this may not represent the latest informa
12、tion and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2008 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.68 (10/2007) iii CONTENTS Page 1 S
13、cope 1 2 References. 1 3 Definitions 2 4 Abbreviations 2 5 Fundamental requirements for optical fibre cable maintenance systems for optical fibre cable carrying high total optical power 2 6 System requirements for optical fibre cable maintenance systems for optical fibre cable carrying high total op
14、tical power 2 6.1 Connection for optical fibre cable carrying high total optical power. 3 6.2 Termination for optical fibre cable carrying high total optical power . 3 6.3 Testing access modules for optical fibre carrying high total optical power. 4 6.4 Optical switch for optical fibre cable carryin
15、g high total optical power 4 7 Testing and maintenance procedure . 4 Appendix I Japanese experience: Catastrophic damage and destructive process induced in optical fibre cord by high power pump light 5 I.1 Introduction 5 I.2 Experiments exposing optical fibre cords to high power . 5 I.3 Destructive
16、process. 7 I.4 Conclusion 7 Appendix II Japanese experience: Ignition induced by a high power light input at a butt-joint splice with refractive index matching material 8 II.1 Introduction 8 II.2 Experiments on high power light at a butt-joint splice. 8 II.3 Observation of ignition caused by high po
17、wer light input . 9 II.4 Conclusion 10 Bibliography. 11 iv ITU-T Rec. L.68 (10/2007) Introduction Broadband optical access services are now commercially available. The number of FTTx subscribers is increasing rapidly. Trunk line communication traffic is also growing quickly due to the expansion of F
18、TTx services. To meet the demand for increased transmission capacity, wavelength division multiplexing (WDM) and distributed Raman amplifier (DRA) technologies have been employed in trunk line transmission systems, and consequently high power communication signals and high pump powers have been intr
19、oduced into optical fibre cables. If we are to maintain the optical cable networks reliably, we must study optical fibre cable maintenance systems that can be applied to optical fibre cable carrying a high total optical power. Recently, the optical power in optical communication systems has been inc
20、reasing rapidly through the use of WDM or distributed Raman amplification technologies. When DRA technology is applied to WDM systems, a high power light is launched into optical fibres and fibre-optic components. The intensity of that optical power reaches several watts, and such a high power light
21、 may induce damage in optical fibres or fibre-optic components. During maintenance work, network operators must handle optical fibres or fibre-optic components carefully in central offices that employ high power systems with a view to preventing accidental eye or fire hazards. Since the light with t
22、he highest optical power is launched into the optical fibre distribution systems and the maintenance systems in a central office, we must clarify the effect that it has on the fibre-optic components in these systems. ITU-T Rec. L.68 (10/2007) 1 ITU-T Recommendation L.68 Optical fibre cable maintenan
23、ce support, monitoring and testing system for optical fibre cable networks carrying high total optical power 1 Scope This Recommendation describes the functional requirements of optical fibre cable maintenance systems for optical fibre cable carrying a high total optical power. It applies to test eq
24、uipment, optical switches for selecting a test fibre, test access modules for connecting test equipment to the communication line, testing optical fibre cords and optical connecting devices that are contained in the maintenance system. It also considers safety procedures and guidelines for the maint
25、enance of outside optical fibre plant carrying a high total optical power. 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
26、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 of the currently valid ITU-T Recomme
27、ndations 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 ITU-T Recommendation G.652 (2005), Characteristics of a single-mode optical fibre and cable. ITU-T G.664 ITU-T Recommendati
28、on G.664 (2006), Optical safety procedures and requirements for optical transport systems. ITU-T L.25 ITU-T Recommendation L.25 (1996), Optical fibre cable network maintenance. ITU-T L.40 ITU-T Recommendation L.40 (2000), Optical fibre outside plant maintenance support, monitoring and testing system
29、. ITU-T L.41 ITU-T Recommendation L.41 (2000), Maintenance wavelength on fibres carrying signals. ITU-T L.42 ITU-T Recommendation L.42 (2003), Extending optical fibre solutions into the access network. ITU-T L.50 ITU-T Recommendation L.50 (2003), Requirements for passive optical nodes: Optical distr
30、ibution frames for central office environments. ITU-T L.53 ITU-T Recommendation L.53 (2003), Optical fibre maintenance criteria for access networks. IEC 60825-1 IEC 60825-1 (2007), Safety of laser products Part 1: Equipment classification and requirements. IEC 60825-2 IEC 60825-2 (2007), Safety of l
31、aser products Part 2: Safety of optical fibre communication systems (OFCS). IEC 61292-4 IEC/TR 61292-4 (2004), Optical amplifiers Part 4: Maximum permissible optical power for the damage-free and safe use of optical amplifiers, including Raman amplifiers. 2 ITU-T Rec. L.68 (10/2007) 3 Definitions Fo
32、r the purpose of this Recommendation, the definitions given in ITU-T G.652, ITU-T G.664, ITU-T L.25, ITU-T L.40, ITU-T L.41, ITU-T L.42, ITU-T L.50 and ITU-T L.53 apply. 4 Abbreviations This Recommendation uses the following abbreviations: DRA Distributed Raman Amplification FTTx Fibre to the x (whe
33、re “x“ indicates the final location on the user side of any one of a variety of optical fibre architectures, e.g., FTTH, FTTB, FTTC) ODF Optical Distribution Frame OPM Optical Power Meter OTDR Optical Time Domain Reflectometer WDM Wavelength Division Multiplexing 5 Fundamental requirements for optic
34、al fibre cable maintenance systems for optical fibre cable carrying high total optical power “High power light“ for optical fibre cable maintenance systems is defined as follows. When high power light is launched into maintenance systems, the fibre-optic components in the systems may be damaged in s
35、uch a way that they do not meet their specifications (e.g., optical loss). Generally, the term high power light is used to refer to light that has an optical power of several hundred milliwatts. The fundamental requirements for optical fibre cable maintenance systems for optical fibre cable carrying
36、 a high total optical power are as follows: It must be safe for network operators to handle the optical fibre cables, cords and fibre-optic components when they are carrying a high total optical power light. Network operator safety must be in accordance with ITU-T G.664, IEC 60825-1 and IEC 60825-2.
37、 An optical fibre cable maintenance system should provide the functions of surveillance, testing and control listed in ITU-T L.40 to meet the specifications for optical fibres or fibre-optic components even if they are carrying a high power light. 6 System requirements for optical fibre cable mainte
38、nance systems for optical fibre cable carrying high total optical power There are two kinds of safety issue as regards optical fibre cable carrying a high total optical power. One is human safety, and this problem relates to the exposure of eyes or skin to high power light. The other is component sa
39、fety when there is a high power light input. There are several fibre-optic components in optical fibre cable maintenance systems for optical fibre cable carrying a high total optical power. When the components have a larger optical loss than usual, this may pose a fire-hazard in the worst case. It i
40、s important for optical fibre cable maintenance systems to be able to detect faults in optical fibre cable networks, because this makes it possible for network operators or physical plant to avoid dangerous situations. There are several ways to implement maintenance functions: OTDR testing for optic
41、al fibre cable, optical loss testing and the optical power monitoring of optical signal or pump power using OPM. Therefore, optical fibre cable maintenance systems must have optical branching devices for test light insertion (e.g., an optical coupler). ITU-T Rec. L.68 (10/2007) 3 Table 6-1 shows the
42、 functions in optical fibre cable maintenance systems for optical fibre cable carrying high optical power. The list below includes the system requirements for high power light input and the methods employed to achieve them. Table 6-1 Functions in optical fibre cable maintenance systems Functions Sys
43、tem requirements for high power light input Methods Connection No fibre fuse or intense temperature increase Use of fusion splices. No need for optical connectors or polishing and cleaning of connector endfaces. Termination No tight bending of optical fibre Minimum bending radius R 30 mm for testing
44、 optical fibre cords in ODF, but fibres with improved bending capability will allow more severe conditions. Testing access for optical fibre line No fibre fuse or intense temperature increase Use of fusion splices. Optical branching component with high tolerance to high power light exposure. Optical
45、 switch with butt-joint splice connection mechanism (e.g., fibre selector) No intense temperature increase or optical loss increase Attenuation of high power light or gap between fibres at butt-joint splice d 10 m. 6.1 Connection for optical fibre cable carrying high total optical power In terms of
46、preventing a “fibre fuse“, connectors should not be used for optical fibre connection especially near the output of a high power optical source. Instead, fusion splices should be employed for the optical connection of an optical fibre line that carries a high total optical power. Materials that do n
47、ot easily induce a temperature increase should be recommended as the sleeves for fusion splices with a view to avoiding fire hazards. If connectors must be used for the optical connection of optical fibre cable carrying a high total optical power, the connector endfaces must be carefully cleaned and
48、 polished. 6.2 Termination for optical fibre cable carrying high total optical power 6.2.1 Optical fibre cord for testing The minimum bending radius of testing optical fibre cords in an ODF in a central office should be 30 mm in accordance with ITU-T L.50. If a minimum bending radius of at least 30
49、mm is maintained for general single mode fibres (e.g., that defined in ITU-T G.652), there will be no damage to the optical fibre cord of the maintenance system for optical fibre carrying a high total optical power. The susceptibility to damage depends on the coating and jacket material, the macro-bending loss, the energy conversion to local heating, the input power levels and the wavelengths. However, fibres with improved bending capability will allow the use of more severe conditions. 6.2.2 Optical fibre handling Becau
