1、 International Telecommunication Union ITU-T G.650.3TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Amendment 1(02/2011) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Transmission media and optical systems characteristics Optical fibre cables Test methods for installed singl
2、e-mode optical fibre cable links Amendment 1 Recommendation ITU-T G.650.3 (2008) Amendment 1 ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS G.100G.199 GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-
3、TRANSMISSION SYSTEMS G.200G.299 INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES G.300G.399 GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES G.400G.449 COORDINATION OF R
4、ADIOTELEPHONY AND LINE TELEPHONY G.450G.499 TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS G.600G.699 General G.600G.609 Symmetric cable pairs G.610G.619 Land coaxial cable pairs G.620G.629 Submarine cables G.630G.639 Free space optical systems G.640G.649 Optical fibre cables G.650G.659Chara
5、cteristics of optical components and subsystems G.660G.679 Characteristics of optical systems G.680G.699 DIGITAL TERMINAL EQUIPMENTS G.700G.799 DIGITAL NETWORKS G.800G.899 DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.900G.999 MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE GENERIC AND USER-RELATED ASPEC
6、TS G.1000G.1999 TRANSMISSION MEDIA CHARACTERISTICS G.6000G.6999 DATA OVER TRANSPORT GENERIC ASPECTS G.7000G.7999 PACKET OVER TRANSPORT ASPECTS G.8000G.8999 ACCESS NETWORKS G.9000G.9999 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T G.650.3 (2008)/Amd.1 (02/2011) i
7、 Recommendation ITU-T G.650.3 Test methods for installed single-mode optical fibre cable links Amendment 1 Summary Amendment 1 to Recommendation ITU-T G.650.3 (2008) adds a new Appendix III, which describes a method for differentiating splice loss and macrobending loss in installed links. The method
8、 is based on OTDR measurement at two wavelengths, and it is recommended to use a bidirectional OTDR method which is able to determine the exact loss at the splice point. This optional method can be used to identify the main loss factor when large loss is observed in an OTDR trace. History Edition Re
9、commendation Approval Study Group 1.0 ITU-T G.650.3 2007-07-29 15 2.0 ITU-T G.650.3 2008-03-29 15 2.1 ITU-T G.650.3 (2008) Amend. 1 2011-02-25 15 ii Rec. ITU-T G.650.3 (2008)/Amd.1 (02/2011) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the fiel
10、d of telecommunications, information and 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 standardizi
11、ng 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
12、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
13、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
14、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
15、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
16、 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, implementers are cautioned that
17、 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 2011 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec.
18、ITU-T G.650.3 (2008)/Amd.1 (02/2011) iii Table of Contents Page 1) Appendix III . 1 2) Bibliography . 7 Rec. ITU-T G.650.3 (2008)/Amd.1 (02/2011) 1 Recommendation ITU-T G.650.3 Test methods for installed single-mode optical fibre cable links Amendment 1 1) Appendix III Add the following Appendix III
19、: Appendix III Method for differentiating splice loss and macrobending loss in installed links (This appendix does not form an integral part of this Recommendation.) III.1 General When large loss is observed at a fusion splice point after cable installation by OTDR measurement, it is usually inferre
20、d that the loss is due to low quality fusion splice or other causes such as fibre macrobending in a closure. Fibre macrobending in a closure is caused by rough fibre handling following fusion splice in cable installation or by other causes, e.g., fibre axial strain. Optical system performance might
21、be degraded at longer wavelengths for an optical fibre cable link with fibre macrobending. Hence, it is quite important to identify the location of fibre macrobending for a cable link. This appendix describes a simple method for differentiating splice loss and macrobending loss in installed links. T
22、he method is based on OTDR measurement at two wavelengths, and it is recommended to use a bidirectional OTDR method which is able to determine the exact loss at the splice point. This optional method can be used to identify the main loss factor when large loss is observed in an OTDR trace in the vic
23、inity of a splice. The application of the method is limited to ITU-T G.652 fibres. A general application of the method to ITU-T G.657 fibres is difficult to implement, because of low bending loss, and is not recommended. Moreover, if the users do not know the exact fibre types in the link, it is dif
24、ficult to apply this method since the method is only effective for ITU-T G.652 fibres. III.2 Theory III.2.1 Definition of macrobending indicator Measurement of the macrobending indicator is based on an OTDR measurement at two different wavelengths. The macrobending indicator k is defined as follows
25、b-Ryu: )/()(2121= AAk (dB/nm) (III-1) 2 Rec. ITU-T G.650.3 (2008)/Amd.1 (02/2011) In Equation III-1, it is assumed that OTDR measurement is performed at wavelengths of 1and 2(nm) and that the measured loss at a fibre splice point at each wavelength is A1and A2(dB), respectively. The 1and 2should be
26、set at values longer than the cable cutoff wavelength. Figure III.1 shows examples of the calculation results of the macrobending indicator using the theory b-Marcuse-JOSA, and b-Sharma when a fibre is wound one turn with a radius of R (mm). In the calculation, 1was fixed at 1310 nm and 2was changed
27、 and shown in the horizontal axis. Figure III.1 Macrobending indicator vs wavelength (2) for various bending radii (1 = 1310 nm) From Figure III.1, it is clear that as 2increases, the macrobending indicator becomes larger, which means that the detection sensitivity of macrobending has improved. III.
28、2.2 Features of macrobending indicator As is described in Appendix I, in the OTDR measurement, accurate loss values can be derived by averaging bidirectional measurement results. The necessity for bidirectional measurement is due to different Rayleigh backscattering coefficients of the spliced fibre
29、s. Figure III.2 shows an OTDR set-up for measuring the macrobending indicator. In the set-up, Fibre A and Fibre B are spliced. Macrobending exists at the Fibre B side. G.650.3-Amd.1(11)_FIII.2AiOTDRMacrobendingFibre A Fibre BSplicepointABPAiPBiAiBiFigure III.2 Measurement set-up of macrobending indi
30、cator Here it is assumed that the OTDR measurement is carried out from side A and that PAiis optical power immediately before the splice point at a wavelength i(i = 1, 2), and PBiis power right after the point with macrobending. It is also assumed that the splice loss for this case is negligibly sma
31、ll. Rayleigh backscattering coefficients for Fibre A and Fibre B at a wavelength iare assumed to be 0.0000.0050.0100.0150.0201300 1400 1500 1600 1700Wavelength (nm)Macrobendingindicator(dB/nm)R=5(mm) R=7.5(mm) R=10(mm)R=12.5(mm) R=15(mm)Rec. ITU-T G.650.3 (2008)/Amd.1 (02/2011) 3 Aiand Bi, respectiv
32、ely. It is well known that Aiand Biare inversely proportional to 4i , so that they can be expressed as: 4/iAAi= (III-2) 4/iBBi= (III-3) The loss Aiat a wavelength ican be derived as: ()()()()BiBAiABiBiAiAiiPPPPA = /log10 /log101010(III-4) From Equations III-1 and III-4, the macrobending indicator be
33、comes: ()2122101110)/(log10)/(log10 =BABAPPPPk (III-5) In Equation III-5, the influence of Rayleigh backscattering coefficient has been cancelled due to the differential operation in the definition of k. Equation III-5 shows that k is only dependent on the exact power before and after the fibre macr
34、obending point at each wavelength. The results above show that bidirectional measurement is not necessary for the determination of k. This feature is quite important since it is not always easy to perform OTDR measurement from both sides of the cable because both end points are at different location
35、s geographically. Then a case with the splice loss is taken into account. Regarding the splice loss, if the fibres with a different mode field diameter (MFD) are spliced, the loss due to MFD mismatch is observed. The influence of the loss-increase due to MFD mismatch is discussed in clause III.4.2.
36、Figure III.3 shows a measurement configuration for such a case. G.650.3-Amd.1(11)_FIII.3AMiASiOTDRMacrobendingFibre A Fibre BSplice pointABPAiPBiAiBiFigure III.3 Macrobending indicator measurement set-up with both macrobending and splice loss The optical power PAiand PBiare assumed as in Figure III.
37、2. ASiand AMidenote the loss due to the splice and macrobending, respectively. The macrobending indicator k becomes: () ()21212121/)(/)( +=MMSSAAAAk (III-6) The macrobending indicator due to the splice loss is defined as: ()2121/)( =SSSAAk (III-7) and that due to the macrobending is: ()2121/)( =MMMA
38、Ak (III-8) From Equations III-6, III-7, and III-8: MSkkk +=(III-9) From Equation III-9, it can be said that the total macrobending indicator is the summation of both contributions. 4 Rec. ITU-T G.650.3 (2008)/Amd.1 (02/2011) III.3 Considerations on practical applicability This clause discusses a pra
39、ctical detection limit of the macrobending indicator. Regarding conventional OTDR systems, the detection limit of optical loss is (dB) considering the accuracy of the OTDR equipment. The detection limit of the macrobending indicator kmincan be expressed as: ()12min=k (dB/nm) (III-10) Figure III.4 sh
40、ows applicable measurement conditions of the macrobending indicator with one turn for various bending radii when is assumed to be 0.1 (dB), considering the accuracy of the conventional OTDR measurement. Figure III.4 Applicable measurement conditions It can be made clear from Figure III.4 that as 2be
41、comes longer, the macrobending with a larger radius can be detected. In other words, the detection sensitivity becomes improved for longer 2. From Figure III.4, an approximate detection limit of the maximum bending radius can be summarized as in Table III.1. Table III.1 Detection limit of maximum be
42、nding radius Wavelength 2(nm) 1550 1625 Maximum detection limit of bending radius (mm) 11 13III.4 Measurement examples and influence of various conditions on measurement results In this clause, some measurement examples are shown in terms of the influence of various conditions on the measurements re
43、sults. III.4.1 High splice loss Table III.2 shows splice loss of two ITU-T G.652 fibres when they are spliced with the fibre core axis misalignment to emulate a large splice loss condition. It is known from Table III.2 that splice loss decreases as the wavelength becomes longer. This is because at l
44、onger wavelength the MFD becomes larger, thus the loss increase due to the core axis misalignment is alleviated. Figure III.5 Applicable regionDetection limit1550 nm 1625 nm0.0000.0050.0100.0150.0201300 1400 1500 1600 1700Wavelength (nm)Macrobendingindicator(dB/nm)R=5(mm) R=6(mm) R=7(mm)R=8(mm) R=9(
45、mm) R=10(mm)R=11(mm) R=12(mm) R=13(mm)R=14(mm) R=15(mm) Detection limitMacrobendingindicator(dB/nm)Rec. ITU-T G.650.3 (2008)/Amd.1 (02/2011) 5 shows the macrobending indicator calculated from Table III.2. It can be seen from Figure III.5 that the macrobending indicator becomes a negative value due t
46、o the reasons above. In this case, applicable measurement conditions in Figure III.4 may be degraded since the macrobending indicator is the summation of both splice and macrobending losses as shown in Equation III-9. Table III.2 Splice loss in case of fibre core axis misalignment Wavelength (nm) Lo
47、ss (from side A) (dB) Loss (from side B) (dB) Average (dB) 1310 0.89 1.29 1.09 1450 0.79 1.18 0.991550 0.74 1.13 0.93 1625 0.69 1.10 0.90Figure III.5 Macrobending indicator with large splice loss III.4.2 Mode field diameter mismatch This clause discusses the influence of the MFD mismatch on the macr
48、obending indicator since the MFD of the commercial ITU-T G.652 fibres is different from one fibre to another as far as the MFD is within the specified values in ITU-T G.652. According to ITU-T G.652, the MFD at 1310 nm is specified as follows: Range of nominal values: 8.6-9.5 m; Tolerance: 0.6 m. So
49、, for the consideration of the influence of the MFD mismatch, it is sufficient to consider the MFD range 8.0-10.1 m. Figure III.6 shows the calculation results of the macrobending indicator considering the splice loss theory b-Marcuse-BSTJ when fibres with MFD of 8.0 m and 10.1 m are spliced. -0.0050.0000.0051450 1500 1550 1600 1650Wavelength (nm)Macrobendingindicator(dB/nm)From side A From side B6 Rec. ITU-T G.650.3 (2008)/Amd.1 (02/2011) Figure III.6
