1、 International Telecommunication Union ITU-T G.650.1TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Amendment 1(10/2012) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Transmission media and optical systems characteristics Optical fibre cables Definitions and test methods for
2、 linear, deterministic attributes of single-mode fibre and cable Amendment 1 Recommendation ITU-T G.650.1 (2010) 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
3、 COMMON TO ALL ANALOGUE CARRIER-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 LI
4、NES G.400G.449 COORDINATION OF RADIOTELEPHONY 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 Opti
5、cal fibre cables G.650G.659Characteristics 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 PERFORMANC
6、E GENERIC AND USER-RELATED ASPECTS 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
7、G.650.1 (2010)/Amd.1 (10/2012) i Recommendation ITU-T G.650.1 Definitions and test methods for linear, deterministic attributes of single-mode fibre and cable Amendment 1 Summary Amendment 1 to Recommendation ITU-T G.650.1 (2010) is aimed to provide measurement procedures for coherent multi-path int
8、erference (MPI) in short optical fibre cables (jumpers). An improvement in bending-loss in a single-mode fibre affects not only the fundamental mode but may also influence the higher order modes. This may change the cut-off wavelength mechanism. In this case, the single-mode operability of an optica
9、l fibre can be investigated by evaluating the MPI characteristics. Appendix IV introduces three kinds of test methods: ECL/PM (External cavity laser/Power meter) method, LED/OSA (Light emitting diode/Optical spectrum analyser) method, FS (Fibre stretching) method. A new note is added at the bottom o
10、f clause 3.6.1 which gives reference to MPI and the addition of Appendix IV. History Edition Recommendation Approval Study Group 1.0 ITU-T G.650 1993-03-12 XV 2.0 ITU-T G.650 1997-04-08 15 3.0 ITU-T G.650 2000-10-06 15 4.0 ITU-T G.650.1 2002-06-29 15 4.0 ITU-T G.650.2 2002-06-29 15 4.1 ITU-T G.650.1
11、 (2002) Amd. 1 2003-03-16 15 4.1 ITU-T G.650.2 (2002) Amd. 1 2003-03-16 15 5.0 ITU-T G.650.1 2004-06-13 15 5.0 ITU-T G.650.2 2005-01-13 15 6.0 ITU-T G.650.2 2007-07-29 15 6.0 ITU-T G.650.1 2010-07-29 15 6.1 ITU-T G.650.1 (2010) Amd. 1 2012-10-29 15 ii Rec. ITU-T G.650.1 (2010)/Amd.1 (10/2012) FOREWO
12、RD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field 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 t
13、echnical, operating and tariff questions and issuing 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 whi
14、ch, 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 areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and
15、 IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to
16、 ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when 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
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18、rning 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 of intellectual property, protected by pa
19、tents, which may be required to implement this Recommendation. However, implementers are cautioned that 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 2013 All rights reserved. No part of this pub
20、lication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T G.650.1 (2010)/Amd.1 (10/2012) 1 Recommendation ITU-T G.650.1 Definitions and test methods for linear, deterministic attributes of single-mode fibre and cable Amendment 1 1) Abbreviations and
21、 acronyms Add the following abbreviations to clause 4. EELED Edge Emitting Light Emitting Diode FS Fibre Stretching FSR Free Spectral Range MPI Multi-Path Interference OSA Optical Spectrum Analyser PM Power Meter SSMF Standard Single Mode Fibre 2) Note to clause 3.6.1 Add the following at the end of
22、 clause 3.6.1. NOTE The single-mode operability of a short (typically less than 10 m) optical fibre can be additionally investigated by evaluating the MPI. General information on MPI is provided in clause 6.1 of b-ITU-T G.Sup.47 and coherent MPI test methods are described in Appendix IV of this Reco
23、mmendation. 3) Appendix IV Add Appendix IV as shown below. Appendix IV Test methods for measuring coherent MPI in short optical fibre cables (jumpers) (This appendix does not form an integral part of this Recommendation.) The measurement of coherent MPI is performed to ensure low noise contribution
24、from a short (typically 4 dBm at the shortest wavelengths of interest (usually 1260 nm) and wide tuning range (100 nm). The stability of the power should be 100 measured power values have been captured. The photodetector/oscilloscope combination allows very high scrambling rates to be used (thereby
25、shortening the testing time). Operate at high optical power to minimize receiver noise (but verify linearity of the detector at these power levels). Use a vertical offset on the oscilloscope trace and expand the vertical scale to maximize signal capture. Do not average. Set the acquisition sample ra
26、te according to a polarization scrambling speed and maximize the number of samples (record length). Set the time base to either capture all data in a single trigger and identify maximum and minimum voltages or run multiple triggers with a fast time base and collect voltage extrema over a sequence of
27、 triggers. The oscilloscope data acquisition should be triggered in synchronism with the ECL wavelength steps. IV.1.3 Measurements procedure IV.1.3.1 Preparation of the fibre under test If the short cable (fibre) to be tested has connectors, make sure proper cleaning procedures are followed. Choose
28、a cable length to be tested and connectorize the ends or prepare the ends for fusion splice. IV.1.3.2 Baseline measurement This step identifies the lowest MPI the test set-up is capable of measuring. In addition, the average transmitted power obtained here is useful in removing the light source powe
29、r variation with wavelength as prescribed in clause IV.1.3.5. 4 Rec. ITU-T G.650.1 (2010)/Amd.1 (10/2012) Before including the test cable in the measurement set-up, measure a baseline response by connecting the polarization scrambler and RX in Figure IV.1 with either a 10 m long SSMF or two connecto
30、rized 5 m SSMF fibres. Angled connectors should be used for both ends of the SSMF. Sweep the wavelength (over a range of roughly 3 nm) in steps small enough to resolve the interference fringes expected in the test cable (iteration might be required, or use a small step such as 0.02 nm). At each wave
31、length capture the minimum, maximum and average power for 100 randomized polarization values. Use a wide enough wavelength scan to capture the free spectral range (FSR) of the jumper interference pattern. Since the FSR is not known before the jumper is measured, the baseline measurement might need t
32、o be repeated after a jumper measurement has been performed. IV.1.3.3 Insert short-cabled fibre Either disconnect the two 5 m SSMF fibres or cut the SSMF at its centre and insert the test cable into the set-up (between points A and B in Figure IV.1), and characterize splice/connector losses at each
33、end. Intentional offset fusion splices are a convenient way to obtain a desired connection loss. An alternative is to use offset connectors. When the MFD values of SSMF and test fibre are 9.00.5 m at 1310 nm, an offset of 1-2 m corresponds to a connection loss of 0.5-1 dB (this loss should be direct
34、ly measured). The coupling ratio of LP01power in the 5 m SSMF lead to LP01power in the test cable is desired for both connection points. It may be necessary to use mode filters and trial and error to eliminate the higher order modes (see the following note for more details). The geometrical layout o
35、f the test cable may be substantially straight, as this is the configuration which will generally give worst case MPI results. Other, more preferable, configurations can be tested as well, which involve multiple small radius cable bends. NOTE The meaning of the MPI value obtained from this measureme
36、nt is unclear without accurate knowledge of the LP01loss through each of the connection points. Stripping of the high order mode is required to determine this loss. Some additional comments are made here on mode stripping in ITU-T G.657 fibres. Some ITU-T G.657.A fibres may be mode stripped by using
37、 a suitably small fibre loop (the loop should not be so small that it attenuates the LP01mode). If this is the case for the fibre under test, the first connection is made while monitoring the power through the jumper with a mode stripping loop present. When the first connection is satisfactory, the
38、second connection is made, again with mode stripping loops present and power through the 5 m SSMF jumper is monitored until the total loss (through both splices) is satisfactory. Some ITU-T G.657.A fibres and all ITU-T G.657.B fibres cannot be mode stripped with fibre loops. However, these fibres ge
39、nerally do have a substantial HOM loss with fibre length (even when straight). Lengths required to strip out the HOM may be several hundred metres for some fibre types. In this case the first offset connection is made between the 5 m SSMF and a spool of the desired jumper fibre. Accounting for the L
40、P01loss through the spool (this may be measured separately using an aligned splice to the SSMF launch fibre) the offset connection is adjusted until the desired LP01loss is obtained. The spooled test fibre is now cut back to the desired jumper length and connectorized or fusion spliced to the output
41、 5 m SSMF. Loss through this second connection point is found by monitoring power at the RX and comparing with LP01input power minus the first connection LP01loss. In either case, LP01loss data should be taken over the FSR ( 3 nm) of the jumper interference pattern. The average over this wavelength
42、range is the connection loss. For consistency, it is important to equalize the splice loss at each end of the test cable. This is because, for a fixed total loss in the splices, maximum MPI is found when the individual splice losses are equal. IV.1.3.4 Short-cabled fibre measurement The measurement
43、procedure of clause IV.1.3.2 is followed. With the jumper under test included, ensure that the wavelength scan range is sufficient to encompass several cycles of the roughly sinusoidal variation in transmitted power (FSR). In addition, ensure that the wavelength step is sufficiently small to resolve
44、 the spectral intensity pattern. Rec. ITU-T G.650.1 (2010)/Amd.1 (10/2012) 5 IV.1.3.5 Calculations Though not mandatory, it is informative to first subtract the baseline average power from the maximum and minimum power measured through the test cable. This corrects for the power variation with wavel
45、ength of the light source. To compute the MPI, the data (corrected maximum and minimum transmitted power versus wavelength) is processed through a moving window of width FSR. For each position of the window (denoted by its central wavelength), the maximum and minimum power are found and used in equa
46、tion (IV-1) to find the MPI. +=110110log20)(20/20/PRPRdBMPI (IV-1) where PR is the difference between the maximum and minimum power levels detected (in dB). Note that if the photodetector/oscilloscope method is used, the output data is an electrical voltage, not an optical power. Due to the linearit
47、y of the photodetector, equation (IV-1) can still be used with a voltage difference when voltages have been converted to dB (10 log V). Dark current corrections should be made prior to this conversion. Verify that the MPI, computed directly from the baseline data, is suitably low. IV.1.3.6 Presentat
48、ion of the results a) Test set-up arrangement. b) Optical source characteristics. c) Polarization scrambling rate. d) Fibre identification (cabled or uncabled), length, insertion loss and splice loss. e) Methodology for measuring insertion/splice loss. f) Geometrical layout of test cable. g) Receive
49、r characteristics (including signal acquisition time). h) Table of MPI versus wavelength. i) After data is taken for a number of fibres of a given design, a mapping between the cut-off wavelength and MPI noise may be compiled. IV.2 Second test method: The wideband LED/OSA technique IV.2.1 General The wideband LED/OSA technique monitors transmitted optical power through the jumper under test as a function of wavelength. The interference phenomenon between the fundamental, LP01, and HOM is measured by capturing the maximum and minim
