1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T L.40 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (10/2000) SERIES L: CONSTRUCTION, INSTALLATION AND PROTECTION OF CABLES AND OTHER ELEMENTS OF OUTSIDE PLANT Optical fibre outside plant maintenance support, monitoring and testing system ITU-T Recommend
2、ation L.40 (Formerly CCITT Recommendation) ITU-T L.40 (10/2000) i ITU-T Recommendation L.40 Optical fibre outside plant maintenance support, monitoring and testing system Summary Outdoor optical fibre maintenance is important to create networks and to maintain their reliability. As traffic increases
3、, higher capacity fibre cables are installed. Recently, optical fibre cables with over 100 cores have become common, so many transmission systems use the same optical fibre cable. Minimal levels of maintenance and testing are required to provide high reliability and quick response. After a cable is
4、installed, functions like fibre monitoring and control have to be done without interfering with the data transmission signals. By monitoring dark fibres (that is, without signal traffic) an indication is given of the performance of the in-service fibres as the degradation and breaks that a cable und
5、ergoes affects all fibres in the same way. Nevertheless greater reliability is achieved by monitoring the fibres with traffic. Also fibre identification is important to control fibre networks because several fibres may have to be chosen from within a cable, even if the cable has many fibres in-servi
6、ce. Source ITU-T Recommendation L.40 was prepared by ITU-T Study Group 6 (1997-2000) and approved by the World Telecommunication Standardization Assembly (Montreal, 27 September 6 October 2000). This Recommendation includes Appendices I to V approved on 9 March 2001. ii ITU-T L.40 (10/2000) FOREWORD
7、 The International Telecommunication Union (ITU) 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
8、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 Recommendations on these topics.
9、 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 Recommendation, the expression “Ad
10、ministration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. 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 Pr
11、operty 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 development process. As of the date of approval of this Recommendation, ITU had not received notice
12、of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. ITU 2001 All rights reserved. No part of
13、 this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from ITU. ITU-T L.40 (10/2000) iii CONTENTS Page 1 Scope. 1 2 Fundamental requirements 1 2.1 Functions. 1 2.2 Interface 1 3 Testi
14、ng and maintaining principle 2 3.1 Methods 2 3.2 Wavelength . 2 4 Fundamental architecture 3 4.1 General system architecture 3 4.2 Optical testing module (OTM) . 5 Appendix I United States experience regarding remote fibre monitoring and testing . 6 I.1 Introduction. 6 I.2 Remote fibre testing and m
15、onitoring architectures. 6 I.2.1 Basic dark fibre remote test systems (RFTSs). 6 I.2.2 Remote fibre test systems with active fibre monitoring and testing 7 I.2.3 RFTS manager. 8 I.2.4 Alarms . 8 I.3 Conclusions. 9 I.4 References. 10 Appendix II Optical fibre outside plant maintenance support and tes
16、ting system . 10 II.1 Abstract. 10 II.1.1 Fundamental requirements 10 II.1.2 Testing and maintaining principle . 11 II.1.3 Fundamental architecture 12 II.2 Detail of the system 13 II.2.1 Purposes. 13 II.2.2 System functions 13 II.2.3 System configuration. 14 II.2.4 Control system overview . 15 II.2.
17、5 Testing and measurement principles . 16 II.3 Mandatory conditions . 18 II.3.1 Network topologies 18 II.3.2 Capacities. 18 II.3.3 Test wavelength. 18 iv ITU-T L.40 (10/2000) Page II.3.4 System data management 18 II.3.5 Interface . 19 Appendix III Optical fibre outside plant maintenance support and
18、testing system 19 III.1 Introduction. 19 III.2 Scenario 20 III.3 Benefits of attenuation continuous monitoring. 20 III.4 Basic principles of the optical cable supervisory system . 22 III.5 Requirements of the optical cable supervisory system. 22 III.6 Conclusions. 26 Appendix IV The Indonesian exper
19、ience on optical fibre cable operation and maintenance support system . 26 IV.1 Introduction. 26 IV.2 Fundamental requirements 27 IV.3 Systems basic configuration. 27 IV.4 Functions of main units. 28 IV.5 Systems hardware configuration 29 IV.6 General specification of optical fibre cable O 2) propri
20、etary on-line interface; 3) an external storage medium such as magnetic optical disc or floppy disc. 3 Testing and maintaining principle 3.1 Methods There are several ways to implement these functions. OTDR testing, loss testing, monitoring a proportion of the signal power (power monitoring) and ide
21、ntification light detection are commonly used. Table 2 shows the most common methods. Table 2/L.40 Suitable test methods Category Activity Functions Methods Surveillance Detection of fibre loss increase Detection of signal power loss increase Detection of water penetration OTDR/loss testing Power mo
22、nitoring OTDR/loss testing Testing Measurement of fibre fault location Measurement of fibre strain distribution Measurement of water location OTDR testing B-OTDR testing OTDR testing Preventative maintenance Control Fibre identification Fibre transfer ID light detectinga)Switchingb)Surveillance Inte
23、rface with path operation system Interface with customer service operation system On-line/external medium On-line/external medium Testing Confirmation of fibre condition Fault distinction between transmission equipment and fibre network Measurement of fibre fault location OTDR/loss testing OTDR/loss
24、 testing OTDR testing After installation before service or post-fault maintenance Control Fibre identification Fibre transfer Interface with outside plant database Interface with mapping system ID light detecting Switchingb)On-line/external medium On-line/external medium a)ID light means identificat
25、ion light such as 270 Hz, 1 kHz, 2 kHz modulated light. b)Switching includes mechanical and manual switching. 3.2 Wavelength It is important to choose the correct wavelength. Specifically, maintenance functions have to be performed without interfering with data transmission signals. Table 3 shows ap
26、propriate wavelengths for given functions. ITU-T L.40 (10/2000) 3 Table 3/L.40 Wavelength selection Category Activity Functions Wavelength Surveillance Detection of fibre loss increase Detection of signal power loss increase Detection of water penetration Maintenance wavelengtha)Signal wavelength An
27、y wavelength on fibres not carrying signals Testing Measurement of fibre fault location Measurement of fibre strain distribution Measurement of water location Any wavelength on fibres not carrying signals Any wavelength on fibres not carrying signals Any wavelength on fibres not carrying signals Pre
28、ventative maintenance Control Fibre identification Fibre transfer Maintenance wavelengtha) None Surveillance Interface with path operation system Interface with customer service operation system None None Testing Confirmation of fibre condition Fault distinction between transmission equipment and fi
29、bre network Measurement of fibre fault location Any wavelength Any wavelength Any wavelength After installation before service or post-fault maintenance Control Fibre identification Fibre transfer Interface with outside plant database Interface with mapping system Any wavelength None None None a)Ref
30、er to “Recommendation of Maintenance wavelength on fibres carrying signals (ITU-T L.41)“. 4 Fundamental architecture 4.1 General system architecture Systems (see Figure 1) must have at least an operation terminal and optical testing module (OTM). The minimum system consists of only these two items.
31、This type of system is convenient for initial installation. A server can improve performance by keeping outside plant, test results, and interfaces with other systems. The server can also control OTMs. There are several choices for Data Communication Network (DCN), including POTS, ISDN and X.25. Tra
32、ffic analysis is important for an economical high-performance system. 4 ITU-T L.40 (10/2000) T0604740-00OTMDBDBOTMOperation Terminal Operation TerminalServerStand-alone Type Client-Server TypeDB DatabaseDCN DCNFigure 1/L.40 System architectures Figure 2 shows these system interfaces. There are sever
33、al kinds of interface between an operating system (OS), which runs on an operation terminal or server, and OTM. A proprietary interface is convenient for closed systems. Standard interfaces are useful for open systems. A hybrid type is also possible. The system has to have interfaces with other syst
34、ems. This may be done in a variety of ways, for example: 1) standard on-line interface; 2) proprietary on-line interface; 3) an external storage medium such as magnetic optical disc or floppy disc. ITU-T L.40 (10/2000) 5 T0604750-00OTMOSOTMOTMOS OSMDStandard IFStandard IFHybrid TypeStandard IFStanda
35、rd IFStandard TypeOther OSProprietary IFProprietary IFProprietary TypeOther OSProprietary IFProprietary IFOther OSOther OSMD Mediation DeviceDCNDCNDCNDCNFigure 2/L.40 System interfaces 4.2 Optical testing module (OTM) The optical testing module (OTM) consists of a controller, an optical testing unit
36、 (OTU), fibre selectors (FS), optical couplers, filters, water sensors and by path units. 1) The controller controls the OTU, communicates with the server or the operation terminal, and analyses test results, along with performing several other functions. 2) The OTU is used for the actual testing. I
37、t comprises an Optical Time Domain Reflection meter (OTDR) and other instruments, light sources, power meters and a controller for these devices. 3) Fibre selectors (FS) are installed within a fibre termination frame and/or an OTU frame. Their function is to select the fibre to be tested under instr
38、uction from the OTU. 4) An optical coupler is installed within a fibre termination frame. Its function is to inject and detect a test light in the optical fibre or to detect a proportion of the signal for monitoring proposes. 5) A filter is installed to protect transmission equipment from being affe
39、cted by the test light. 6) A water sensor is installed at the optical fibre cable joints to detect the water penetration. 7) A bypath unit is used to make a roundabout route to avoid a transmission device. 6 ITU-T L.40 (10/2000) APPENDIX I United States experience regarding remote fibre monitoring a
40、nd testing I.1 Introduction Based on our experience with customers in the United States, many of the larger network providers that predominantly provide local telephony services do not use Remote Fibre Test Systems (RFTSs). These companies rely on transmission system equipment alarms, ring topology
41、and protection switching. In response to an alarm, traffic is switched to an alternate fibre, and after applying proprietary maintenance analyses an OTDR is used to determine the location of a cable break. These companies have historical and landmark data available for fault location. Network provid
42、ers that are predominantly long-distance providers do use some level of remote fibre testing systems in their networks. The RFTSs range from the basic dark fibre systems to identify and roughly locate fibre breaks to more sophisticated systems that can monitor working systems, detect degradation of
43、the network before it fails and accurately locates fibre faults. RFTSs may be controlled locally, regionally or at a central maintenance centre of a network provider. In the case of the dark fibre system, the main purpose is to reduce the time to locate faults and thus reduce the time of circuit out
44、ages. The sophisticated systems are integrated into the network surveillance operational system that monitors the transmission, switching equipment and the RFTS. These systems can also determine degradation of the fibre network and sound alarms before the network is out of service. I.2 Remote fibre
45、testing and monitoring architectures I.2.1 Basic dark fibre remote test systems (RFTSs) The basic dark fibre Remote Fibre Test System (RFTS), shown in Figure I.1, consists of three elements. The first is an Optical Test Access Unit (OTAU), which is essentially a remotely controlled optical switch. T
46、he size of the switch depends on the number of fibres under test, a common size is 72 fibres, but larger switches are used. The switch connects the test fibres to the second element, the Remote Test Unit (RTU), which is a remotely controlled OTDR that provides the test signal and makes the OTDR meas
47、urements. The third element is the Test System Controller (TSC), which selects the test fibre and operates the RTU. This architecture is typical of the dark fibre monitoring in use today in the United States. The test operating system may be integrated into a surveillance operational system using pr
48、oprietary software. In a stand-alone system the TSC contains a database for the fibres under test that includes prior OTDR trace data and related geographic data of the fibre routes. In these systems only dark fibres are tested. The RFTS is capable of fault detection based on a process where the TSC
49、 cycles through each fibre connected to it. One TSC can control multiple RTUs. This means that a TSC may not discover a cable break for some time if the number of fibres connected to it is very large and if the fibres of that cable were tested shortly before the break occurred. The TSC may be connected to a Test Operating System (Test OS), which is located in a maintenance centre where other alarms from the network terminate. Operators there analyse the alarms coming from the TSC and other sources, suc
