1、 International Telecommunication Union ITU-T K.86TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (11/2011) SERIES K: PROTECTION AGAINST INTERFERENCE Method for measuring longitudinal conversion loss (9 kHz - 30 MHz) Recommendation ITU-T K.86 Rec. ITU-T K.86 (11/2011) i Recommendation ITU-T K.86 Meth
2、od for measuring longitudinal conversion loss (9 kHz - 30 MHz) Summary With the liberalization in telecommunications, unbundling becomes commonplace in telecommunication networks. The unbundling of the access network increases the number of operators that may provide services within a common access
3、network cable. In this context, unbalance is not only related to the transmission performance of the services, but also strongly related to electromagnetic compatibility (EMC) performance of the services. The longitudinal conversion loss (LCL) of telecommunication lines or telecommunication ports is
4、 a measure of the degree of unwanted transverse signal produced at the terminals of the network due to the presence of a longitudinal signal on the connecting leads. Considering the frequency range of broadband services such as integrated services digital network (ISDN), asymmetric digital subscribe
5、r line (ADSL), ADSL2, ADSL2plus, very high-speed digital subscriber line (VDSL) and VDSL2, Recommendation ITU-T K.86 presents the method for measuring longitudinal conversion loss for the frequency range from 9 kHz to 30 MHz and presents the suggestion of the admissible value for the unbundling cond
6、ition. History Edition Recommendation Approval Study Group 1.0 ITU-T K.86 2011-11-13 5 Keywords LCL, longitudinal conversion loss, unbalance. ii Rec. ITU-T K.86 (11/2011) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunicati
7、ons, 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 standardizing telecommunication
8、s 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 by the procedure lai
9、d 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 both a telecommunica
10、tion 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 when all of these mand
11、atory 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 PROPERTY RIGHTS ITU draws
12、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 by ITU members or o
13、thers 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 this may not repres
14、ent the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2012 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 K.86 (11/2011)
15、 iii Table of Contents Page 1 Scope 1 2 References. 1 3 Definitions 1 3.1 Terms defined elsewhere 1 3.2 Terms defined in this Recommendation . 2 4 Abbreviations and acronyms 3 5 Conventions 3 6 Test methods and measuring arrangement . 3 6.1 Test equipment . 3 6.2 Test methods and measuring arrangeme
16、nt for telecommunication ports . 4 6.3 Test methods and measuring arrangement for telecommunication cables . 5 7 Admissible longitudinal conversion loss value for the telecommunication port and cable 6 Appendix I Loss conversion ratio test of the shielded telecommunication cable . 7 I.1 Terms define
17、d in this appendix 7 I.2 Test configurations and calibration 7 I.3 LCR test result of the shielded telecommunication cable 9 Rec. ITU-T K.86 (11/2011) 1 Recommendation ITU-T K.86 Method for measuring longitudinal conversion loss (9 kHz - 30 MHz) 1 Scope This Recommendation specifies the method for m
18、easuring longitudinal conversion loss (9 kHz - 30 MHz) of the telecommunication cable and telecommunication port of the equipment used in analogue and digital communication systems by using the transmission measurement method; it also presents the suggestion of the admissible value for the unbundlin
19、g condition. This Recommendation is in agreement with the principles, the nomenclature and the definitions, addressed in ITU-T O.9 and in ITU-T G.117, which considers the transmission aspects of unbalance about earth. 2 References The following ITU-T Recommendations and other references contain prov
20、isions which, through reference in this text, constitute provisions of this Recommendation. At the time of 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 possib
21、ility of applying the most recent edition of the Recommendations and other references listed below. A list 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 Recommen
22、dation. ITU-T G.117 Recommendation ITU-T G.117 (1996), Transmission aspects of unbalance about earth. ITU-T G.961 Recommendation ITU-T G.961 (1993), Digital transmission system on metallic local lines for ISDN basic rate access. ITU-T G.992.1 Recommendation ITU-T G.992.1 (1999), Asymmetric digital s
23、ubscriber line (ADSL) transceivers. ITU-T G.992.5 Recommendation ITU-T G.992.5 (2009), Asymmetric digital subscriber line 2 (ADSL2) transceivers Extended bandwidth ADSL2 (ADSL2plus). ITU-T G.993.2 Recommendation ITU-T G.993.2 (2011), Very high speed digital subscriber line transceivers 2 (VDSL2). IT
24、U-T O.9 Recommendation ITU-T O.9 (1999), Measuring arrangement to assess the degree of unbalance about earth. 3 Definitions 3.1 Terms defined elsewhere This Recommendation uses the following term defined elsewhere: 2 Rec. ITU-T K.86 (11/2011) 3.1.1 longitudinal conversion loss (LCL) ITU-T O.9: The L
25、CL of a one- or two-port network is a measure (a ratio expressed in dB) of the degree of unwanted transverse signal produced at the terminals of the network due to the presence of a longitudinal signal on the connecting leads. It is calculated as Longitudinal conversion loss (LCL) = 20 lg 11TLVVdB a
26、nd measured as shown in Figure 1 and Figure 2. This technique is applicable to either the input or output terminals, e.g., transpose terminals a and b with d and e, respectively. (See clause 4.1.3 of ITU-T G.117.) K.86(11)_F01ZL1abZ1deZ2VT1ItemundertestGcVL1G: Signal generator. Figure 1 Measurement
27、of longitudinal conversion loss for a two-port network K.86(11)_F02ZL1abZ1VT1ItemundertestGcVL1G: Signal generator. Figure 2 Measurement of longitudinal conversion loss for a one-port network Z1and Z2are the impedances connected in parallel to the input and/or output port, respectively, of the item
28、under test. Z1and Z2are generally within 25% of the nominal impedance of the port to which they are connected. If measurements are made via high-impedance input ports, an additional impedance Z1should be connected between points a and b. The longitudinal impedance ZL1is nominally equal to Z1/4. Diff
29、erent values, however, may be used. This may be necessary to more properly simulate operating conditions of the item under test. 3.2 Terms defined in this Recommendation None. Rec. ITU-T K.86 (11/2011) 3 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms:
30、ADSL Asymmetric Digital Subscriber Line EUT Equipment Under Test ISDN Integrated Services Digital Network LCL Longitudinal Conversion Loss LCR Longitudinal Conversion Ratio ONU Optical Network Unit RFI Radio Frequency Interference VDSL Very high-speed Digital Subscriber Line VTU VDSL2 Transceiver Un
31、it VTU-O VTU at the ONU (or central office, exchange, etc., that is, operator end of the loop) VTU-R VTU at the remote site (i.e., subscriber end of the loop) 5 Conventions None. 6 Test methods and measuring arrangement Longitudinal conversion loss (LCL) is measured using a network analyser by injec
32、ting a “common mode“ signal between the pair and earth, and measuring the resulting “differential mode“ signal between the wires in a pair. 6.1 Test equipment For the measurement of LCL as shown in Figures 1 and 2, the test circuits shall be the combination of the following elements: a common mode s
33、ignal injection circuit a common mode signal measurement transverse signal measurement balanced line termination. The network analyser is the source for injecting a “common mode“ signal between the pair and earth, and measuring the resulting “differential mode“ signal between the wires in a pair. A
34、balun transformer as shown in Figure 3 combines the required elements listed above in a single package to interface directly with a network analyser. The inherent longitudinal conversion loss of the balun transformer within the frequency range from 9 kHz to 30 MHz should be 20 dB greater than the li
35、mit set for the item under test. Port 3 of the balun interfaces directly to the network analyser with matched impedance for measuring the transverse signal. Port 1 of the balun interfaces to the network analyser with matched impedance for injecting a longitudinal signal. Port 2 of the balun interfac
36、es to the telecommunication cable or telecommunication port of the equipment under test (EUT) with transverse terminating impedance. 4 Rec. ITU-T K.86 (11/2011) K.86(11)_F03DM PORT3 (J1)BalunPORT2abcCM PORT1 (J2)Parallel or seriesresistor hereFigure 3 Internal structure of the balun A metal drum is
37、necessary for the measurement of unscreened cable; it should be big enough to hold the length of unscreened cable in one layer for measurement. 6.2 Test methods and measuring arrangement for telecommunication ports Generally the LCL of telecommunication ports such as the VDSL2 transceiver unit at th
38、e optical network unit (VTU-O) or VTU at the remote site (VTU-R) should be measured as a one-port network. Figure 4 shows the test methods and measuring arrangement for telecommunication ports with the equipment listed in clause 6.1. K.86(11)_F04Network analyserOut InCoaxial lead Coaxial leadBalun t
39、ransformerPORT1 PORT3abcEUTFigure 4 Measuring arrangement for telecommunication ports The transverse terminating impedance between terminals a and b should be referenced to the relevant ITU-T Recommendations as given in Table 1. Table 1 Impedance of telecommunication ports Services Frequency (Hz) Im
40、pedance (ohms) Reference ISDN 80 8-800 150, 110 ITU-T G.961 ADSL 25-1104 100 ITU-T G.992.1 VDSL2 12 000 Up to 30 000 100 ITU-T G.993.2Rec. ITU-T K.86 (11/2011) 5 6.3 Test methods and measuring arrangement for telecommunication cables The LCL of the telecommunication cable should be measured as a two
41、-port network. Figures 5 and 6 show the test methods and measuring arrangement for telecommunication cables with the equipment listed in clause 6.1. The ends of the cable under test shall be prepared such that when connected to the terminals of the test equipment the twisting of the pairs/quads is m
42、aintained. The length of cable under test depends on the service for which the cable will be used. The length of cable for the Ethernet service should be 100 m 1 m. Appendix I provides a detailed description of the LCL test of shielded cables. K.86(11)_F05Network analyserOut InCoaxial lead Coaxial l
43、eadBalun transformerPORT1 PORT3abcCableFar-end resistorFar-end resistorFigure 5 Measuring arrangement for shielded telecommunication cables Terminal C of the balun transformer in Figure 5 is connected to the outer shield of the test lead. The cable pair under test should be connected to the differen
44、tial mode balun output terminals a and b. The far-end resistor network should be bonded together and connected to earth. K.86(11)_F06Network analyserOut InCoaxial lead Coaxial leadBalun transformerPORT1 PORT3abcCableFar-end resistorFar-end resistorFigure 6 Measuring arrangement for unshielded teleco
45、mmunication cables The cable in Figure 6 for the measuring arrangement shall be wound tightly around the metal drum in one layer. The distance between the windings should be at least the diameter of the cable. The metal drum shall be earthed by fixing the balun to the drum. Far-end resistors are the
46、 impedances connected in parallel to the far ends of the telecommunication cable, respectively, of the item under test. Far-end resistors with precision better than 0.1% are generally within 25% of the nominal impedance of the port to which they are connected. 6 Rec. ITU-T K.86 (11/2011) 7 Admissibl
47、e longitudinal conversion loss value for the telecommunication port and cable Cables for telecommunication purposes sometimes have to pass areas that have strong disturbing electromagnetic fields which may cause significant longitudinal signals along the cables. The disturbing effect may be caused b
48、y conversion from longitudinal mode to differential mode due to unbalance in the lines, the terminal, the switching equipment and any other equipment inserted in the longitudinal path. Unbalance to earth is described in terms of longitudinal conversion loss (LCL). Admissible minimum LCL value for th
49、e telecommunication port measured in accordance with the above test method should be referenced to the relevant ITU-T Recommendations as given in Table 2. Table 2 Admissible minimum LCL values for the telecommunication port Services Frequency (Hz) LCL Reference ISDN 80 8-800 44 dB 5 dB/decade decrease ITU-T G.961 ADSL ADSL2(plus) 25-1104 25-2208 40 dB ITU-T G.992.1 ITU-T G.992.5 (Note 1) VDSL2 12 000 38 dB ITU-T G.993.2 (Note 2) NOTE 1 This value is defined in clause A.4.3.1 of ITU-T G.992.1 as LCL at the U-C
