1、 I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n ITU-T G.650.2 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (08/2015) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Transmission media and optical systems characteristics Optical fibre cables Definition
2、s and test methods for statistical and non-linear related attributes of single-mode fibre and cable Recommendation ITU-T G.650.2 ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS G.100G.199 GENERAL CHARACTERIS
3、TICS 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 METALLI
4、C LINES 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
5、Optical fibre cables G.650G.659 Characteristics 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 PERFO
6、RMANCE 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. I
7、TU-T G.650.2 (08/2015) i Recommendation ITU-T G.650.2 Definitions and test methods for statistical and non-linear related attributes of single-mode fibre and cable Summary Recommendation ITU-T G.650.2 contains definitions of the statistical and non-linear parameters of single-mode fibre and cable. I
8、t also contains both reference test methods and alternative test methods for characterizing these parameters. This edition of the Recommendation has removed the state of polarization (SOP) method (first alternative test method). History Edition Recommendation Approval Study Group Unique ID* 1.0 ITU-
9、T G.650 1993-03-12 XV 11.1002/1000/879 2.0 ITU-T G.650 1997-04-08 15 11.1002/1000/4017 3.0 ITU-T G.650 2000-10-06 15 11.1002/1000/5182 4.0 ITU-T G.650.1 2002-06-29 15 11.1002/1000/6072 4.0 ITU-T G.650.2 2002-06-29 15 11.1002/1000/6073 4.1 ITU-T G.650.1 (2002) Amd. 1 2003-03-16 15 11.1002/1000/6259 4
10、.1 ITU-T G.650.2 (2002) Amd. 1 2003-03-16 15 11.1002/1000/6260 5.0 ITU-T G.650.1 2004-06-13 15 11.1002/1000/7319 5.0 ITU-T G.650.2 2005-01-13 15 11.1002/1000/7468 6.0 ITU-T G.650.2 2007-07-29 15 11.1002/1000/9152 6.0 ITU-T G.650.1 2010-07-29 15 11.1002/1000/10868 6.1 ITU-T G.650.1 (2010) Amd. 1 2012
11、-10-29 15 11.1002/1000/11767 6.2 ITU-T G.650.1 (2010) Cor. 1 2013-08-29 15 11.1002/1000/11981 7.0 ITU-T G.650.2 2015-08-13 15 11.1002/1000/12528 _ * To access the Recommendation, type the URL http:/handle.itu.int/ in the address field of your web browser, followed by the Recommendations unique ID. F
12、or example, http:/handle.itu.int/11.1002/1000/11830-en. ii Rec. ITU-T G.650-2 (08/2015) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication S
13、tandardization 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 basis. The World Telecommunication Standardization Assembly (WTSA)
14、, 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 Resolution 1. In some areas of information technology which fall wit
15、hin 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 and a recognized operating agency. Compliance with this Recomme
16、ndation 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 met. The words “shall“ or some other obligatory language such
17、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 RIGHTSITU draws attention to the possibility that the practice or implementation of this Recommendat
18、ion 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 Recommendation development process. As of the date of approval
19、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 information and are therefore strongly urged to consult the TSB paten
20、t database at http:/www.itu.int/ITU-T/ipr/. ITU 2015 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 G.650.2 (08/2015) iii Table of Contents Page 1 Scope . 1 2 References . 1 3 Terms and definitions
21、. 1 3.1 Polarization mode dispersion (PMD) . 1 3.2 Types of test methods . 7 4 Abbreviations and acronyms 7 5 Conventions 8 6 Test methods . 8 6.1 Test methods for polarization mode dispersion 9 6.2 Test methods for non-linear attributes 35 Appendix I Determination of PMD delay from an interferogram
22、 36 I.1 RMS calculation for TINTY 36 I.2 RMS calculation for GINTY 38 Appendix II Non-linear attributes . 39 II.1 Background . 39 II.2 Effective area (Aeff) . 39 II.3 Correction factor k 40 II.4 Non-linear coefficient (n2/Aeff) . 42 II.5 Stimulated Brillouin scattering . 43 II.6 Other effects . 52 A
23、ppendix III Test methods for effective area (Aeff) 53 III.1 The far-field scan (FFS) technique . 53 III.2 The variable aperture (VA) technique 55 III.3 The near-field scan (NFS) technique 59 Appendix IV Information on polarization mode dispersion statistics 62 IV.1 Introduction 62 IV.2 Data collecti
24、on 63 IV.3 Calculation of PMDQ (Monte Carlo) 63 IV.4 Calculation for DGDmax (Monte Carlo) 63 Bibliography. 65 Rec. ITU-T G.650.2 (08/2015) 1 Recommendation ITU-T G.650.2 Definitions and test methods for statistical and non-linear related attributes of single-mode fibre and cable 1 Scope This Recomme
25、ndation contains definitions and test methods suitable mainly for factory measurements of the statistical and non-linear attributes of the single-mode optical fibres and cables described in b-ITU-T G.652, b-ITU-T G.653, b-ITU-T G.654, b-ITU-T G.655, b-ITU-T G.656, and b-ITU-T G.657. These definition
26、s and test methods are generally not appropriate for multimode fibre, such as that described in b-ITU-T G.651.1. Some of the test methods, when so indicated, may also be used to characterize discrete optical components, such as those described in b-ITU-T G.671. b-ITU-T G.650.1 contains definitions a
27、nd test methods for linear deterministic attributes. Methods to compensate for impairments caused by polarization mode dispersion (PMD) can be found in b-ITU-T G.666. 2 References None. 3 Terms and definitions This Recommendation defines the following terms (for more background information see b-IEC
28、/TR 61282-9): 3.1 Polarization mode dispersion (PMD) 3.1.1 phenomenon of PMD: The differential group delay (DGD) time between two orthogonal polarized modes, which causes pulse spreading in digital systems and distortions in analogue systems. NOTE 1 In ideal circular symmetric fibres, the two polari
29、zation modes propagate with the same velocity. However, real fibres cannot be perfectly circular and can undergo local stresses; consequently, the propagating light is split into two local polarization modes travelling at different velocities. These asymmetry characteristics vary randomly along the
30、fibre and in time, leading to a statistical behaviour of PMD. A “maximum“ value of DGD can be inferred from the statistics. NOTE 2 For a given arbitrarily deployed fibre at a given time and optical frequency, there always exist two polarization states, called principal states of polarization (PSPs;
31、see clause 3.1.2) such that the pulse spreading due to PMD vanishes if only one PSP is excited. Conversely, the maximum pulse spread due to PMD occurs when both PSPs are equally excited, and is related to the difference in the group delays associated with the two PSPs. 3.1.2 principal states of pola
32、rization (PSPs): When operating an optical fibre at a wavelength longer than the cut-off wavelength in a quasi-monochromatic regime, the output PSPs are the two orthogonal output states of polarization for which the output polarizations do not vary when the optical frequency is varied slightly. The
33、corresponding orthogonal input polarization states are the input PSPs. NOTE 1 The local birefringence changes along the fibre, and the PSP depends on the fibre length (contrary to high-birefringence). NOTE 2 The PSPs are random complex vectors depending on time and optical frequency. However, accord
34、ing to the definition, there exists a small frequency range, the PSP bandwidth, over which they can be considered practically constant. 2 Rec. ITU-T G.650-2 (08/2015) NOTE 3 If a signal has a bandwidth broader than the PSP bandwidth, second order PMD effects come into play. They may imply a depolari
35、zation of the output field, together with an additional chromatic dispersion effect. 3.1.3 differential group delay (DGD; () in ps): The time difference in the group delays of the PSPs. The DGD between two PSPs is wavelength-dependent and can vary randomly in time due to random mode coupling and ran
36、domized stresses along the optical propagation path due, among other causes, to environmental conditions. Variations in the order of a factor of two are typical for normal transmission fibres. As the PMD increases, the variance of the DGD values increases and the characteristic periodicity also decr
37、eases. For normal random-mode-coupled fibre, the DGD distribution is ergodic, which means that the distribution remains the same over time and wavelength, for a sufficiently long period or wide range. This allows an assumption that measurements over a finite wavelength range are representative of ot
38、her wavelength ranges or the same wavelength range at different times over a long period of time. For mode-coupled fibres, the distribution is usually Maxwellian. Instantaneous DGD values limit the transmission capacity of digital systems. The derivative of the DGD with respect to the wavelength lim
39、its the signal-to-noise ratio (SNR) in analogue systems. Therefore, the statistical distribution of the DGDs (vs time or vs wavelength) plays an important role in predicting real system performance. Negligible mode coupling is found on some specialty fibre, such as polarization-maintaining fibre (PM
40、F), and some components. For these devices, there is very little DGD variation with wavelength. The DGD is measured in picoseconds. 3.1.4 PMD value: PMDAVG is defined as the linear average of the DGD values () over a given optical frequency range 1 to 2, 12AVG21P M Dvvdvvvv (3-1) PMDRMS is defined a
41、s the root mean square (RMS) 21/2 of the DGD values () over a given optical frequency range 1 to 2, 2/11222/12R M S21)(P M Dvvdvvvv(3-2) NOTE 1 For Equations 3-1 and 3-2 to be valid, the range 1 to 2 should be sufficiently wide, e.g., of the order of 100 nm in the corresponding wavelength range. If
42、the distribution of these DGD values over the given optical frequency range may be approximated by a Maxwell distribution with sufficient amount of confidence and fidelity, PMDAVG can be mathematically related to PMDRMS. 2/122/138 (3-3) For fibre and cable, the PMD reference test method (RTM) report
43、s the linear average. Rec. ITU-T G.650.2 (08/2015) 3 NOTE 2 Averaging over temperature, time or mechanical perturbations is generally an acceptable alternative to averaging over frequency. In this case, the expected value operator is over all conditions. The expected value of a set of finite wavelen
44、gths at a given time is equal to the long-term expected value over any frequency range. Both Equations 3-1 and 3-2 are considered as an averaging in this context. NOTE 3 Equation 3-3 applies only when the distribution of DGDs is Maxwellian, for instance, when the fibre is randomly mode coupled. The
45、generalized use of Equation 3-3 can be verified by statistical analysis. A Maxwell distribution may not be the case if there are point sources of elevated birefringence (relative to the rest of the fibre), such as a tight bend, or other phenomena that reduce the mode coupling, such as a continual re
46、duced bend radius with fibre in tension. In these cases, the distribution of the DGDs will begin to resemble the square root of a non-central Chi-square distribution with three degrees of freedom. For these cases, the PMDRMS value will generally be larger relative to the PMDAVG that is indicated in
47、Equation 3-3. 3.1.5 PMD coefficient: The PMD value normalized to the measurement length. There are two normalization formulas, one for random mode coupling, associated with normal transmission fibres, and one for negligible mode coupling, associated with specialty fibres such as polarization maintai
48、ning fibres. 3.1.5.1 random mode coupling: For random mode coupling, the PMD coefficient is the PMD value (PMDAVG or PMDRMS) divided by the square root of the length (L1/2) and is usually reported in picoseconds per root kilometre. 3.1.5.2 negligible mode coupling: For negligible mode coupling, the
49、PMD coefficient is the PMD value (PMDAVG or PMDRMS) divided by the length (L) and may be reported in picoseconds per kilometre or femtoseconds per metre. 3.1.6 mathematical definitions: PMD can be described in terms of Stokes or Jones vectors. The evolution of the output Jones vector with angular optical frequency, /22 c, is the source of system impairment. All parameters, vectors and matrices in
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