1、 International Telecommunication Union ITU-T G.697TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (02/2012) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Transmission media and optical systems characteristics Characteristics of optical systems Optical monitoring for dense wa
2、velength division multiplexing systems Recommendation ITU-T G.697 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-TRANSMISSION SYSTEMS G.200G
3、.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 RADIOTELEPHONY AND LINE TELE
4、PHONY 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.659 Characteristics of optical comp
5、onents and subsystems G.660G.679 Characteristics of optical systems G.680G.699DIGITAL 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 ASPECTS G.1000G.1999 TRANSMISSIO
6、N 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.697 (02/2012) i Recommendation ITU-T G.697 Optical monito
7、ring for dense wavelength division multiplexing systems Summary Recommendation ITU-T G.697 defines optical monitoring (OM) that can help in dense wavelength division multiplexing (DWDM) systems to perform the following activities: configuration management for system and channel activation, addition
8、of new channels, etc.; fault management to detect and to isolate faults; degradation management in order to keep the system running and to detect degradations before a fault occurs. DWDM technology is improving at a rapid pace, continuously stretching the channel count, channel speeds and reach limi
9、ts. Long-haul multi-span DWDM systems are capable of taking optical signals thousands of kilometres without electrical terminations or regeneration. This continuing trend is driving the increasing importance of optical monitoring, which is the subject of this Recommendation. This edition of this Rec
10、ommendation provides information on optical channel power changes due to gain variations, optical signal-to-noise ratio (OSNR) measurements, and introduces new appendices on possible positions for monitoring equipment and parameter encoding. History Edition Recommendation Approval Study Group 1.0 IT
11、U-T G.697 2004-06-13 15 2.0 ITU-T G.697 2009-11-13 15 2.1 ITU-T G.697 (2009) Cor. 1 2011-02-25 15 3.0 ITU-T G.697 2012-02-13 15 ii Rec. ITU-T G.697 (02/2012) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, informat
12、ion 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 telecommunications on a worldw
13、ide 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 laid down in WTS
14、A 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 telecommunication administ
15、ration 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 mandatory provisi
16、ons 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 attention to
17、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 others outside
18、 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 represent the lates
19、t 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 G.697 (02/2012) iii Table o
20、f Contents Page 1 Scope 1 2 References. 1 2.1 Normative references 1 3 Terms and definitions . 2 3.1 Terms defined elsewhere 2 3.2 Terms defined in this Recommendation . 2 4 Abbreviations and acronyms 2 5 Optical monitoring overview 3 6 Classification of monitoring methods . 5 6.1 Signal monitoring
21、. 5 6.2 Equipment monitoring (indirect methods) . 5 6.3 Embedded monitoring equipment 6 6.4 External monitoring equipment 6 7 Optical impairments . 6 8 Optical monitoring parameters . 8 9 Correlation between impairment effects and optical monitoring parameters degradation . 8 9.1 Variation of attenu
22、ation 8 9.2 Frequency (or wavelength) deviation from nominal 8 9.3 Optical channel power changes due to gain variations 9 10 Applications 9 11 Optical safety considerations 9 Appendix I Severity of optical impairments . 10 Appendix II Penalty severity value X . 12 Appendix III Optical monitoring per
23、formance . 13 III.1 OSNR measurement . 15 III.2 Q-factor measurement 19 Appendix IV Possible positions for suitable monitoring equipment and their relative functions in several optical network elements 22 IV.1 Introduction 22 IV.2 Embedded monitoring points . 23 IV.3 External monitoring points . 25
24、iv Rec. ITU-T G.697 (02/2012) Page Appendix V Parameter encoding 27 V.1 Wavelength ID (32 bits) . 27 V.2 Parameter ID source (8 bits) . 28 V.3 Parameter ID (8 bits) 28 V.4 Value of parameters (32 bits) . 28 Bibliography. 29 Rec. ITU-T G.697 (02/2012) v Introduction Fully regenerated optical networks
25、 traditionally had optical-to-electrical conversions at all network elements. Transmission performance is measured at the electrical layer with performance parameters such as errored seconds (ES) and severely errored seconds (SES). Since synchronous digital hierarchy (SDH) has built-in overhead in i
26、ts frame structure to measure error performance at section, line and path layers, it is relatively easy to measure network performance at all network elements within a fully regenerated SDH network. Current optical networks typically include many transparent optical network elements between electric
27、al regeneration points. This necessitates performance monitoring in the optical domain to assess the health of the optical channel (OCh). Moreover, DWDM technology is improving at a rapid pace, continuously stretching the channel count, channel speeds and reach limits. Long-haul multi-span DWDM syst
28、ems are capable of taking optical signals thousands of kilometres without electrical terminations or regeneration. This reduces the number of electrical monitoring points. Recommendation ITU-T G.697 is an initial step towards addressing these needs through optical monitoring. Rec. ITU-T G.697 (02/20
29、12) 1 Recommendation ITU-T G.697 Optical monitoring for dense wavelength division multiplexing systems 1 Scope The purpose of this Recommendation is to indicate a minimum, but not exhaustive, set of optical parameters that can be used to perform the optical monitoring (OM) functions in dense wavelen
30、gth division multiplexing (DWDM) systems and optical network elements (e.g., reconfigurable optical add-drop multiplexers (ROADMs), particularly relevant to those network elements without optical-electrical-optical conversions. In order to achieve this objective, this Recommendation: 1) indicates th
31、e methods for measuring the optical signal degradation; 2) classifies those methods by type; 3) defines the suitable optical parameters to detect optical signal degradation; and 4) describes the applications or conditions where these optical parameters can be relevant. This Recommendation refers to
32、DWDM systems and optical network elements with optical channels with bit rates up to approximately 10 Gbit/s using non-return to zero (NRZ) or return to zero (RZ) line coding. Bit rates above 10 Gbit/s and systems employing other modulation formats are for further study. 2 References 2.1 Normative r
33、eferences The following ITU-T Recommendations and other references contain provisions 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;
34、users of this Recommendation are therefore encouraged to investigate the possibility 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 Recom
35、mendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T G.650.2 Recommendation ITU-T G.650.2 (2007), Definitions and test methods for statistical and non-linear related attributes of single-mode fibre and cable. ITU-T G.652 Recommendation ITU-T G.652 (2005), Char
36、acteristics of a single-mode optical fibre and cable. ITU-T G.653 Recommendation ITU-T G.653 (2006), Characteristics of a dispersion-shifted single-mode optical fibre and cable. ITU-T G.655 Recommendation ITU-T G.655 (2006), Characteristics of a non-zero dispersion-shifted single-mode optical fibre
37、and cable. ITU-T G.663 Recommendation ITU-T G.663 (2000), Application-related aspects of optical amplifier devices and subsystems. ITU-T G.664 Recommendation ITU-T G.664 (2006), Optical safety procedures and requirements for optical transport systems. ITU-T G.692 Recommendation ITU-T G.692 (1998), O
38、ptical interfaces for multichannel systems with optical amplifiers. ITU-T O.201 Recommendation ITU-T O.201 (2003), Q-factor test equipment to estimate the transmission performance of optical channels. 2 Rec. ITU-T G.697 (02/2012) 3 Terms and definitions 3.1 Terms defined elsewhere This Recommendatio
39、n uses the following term defined in ITU-T G.650.2: Stimulated Brillouin scattering (SBS) This Recommendation uses the following terms defined in ITU-T G.663: Polarization mode dispersion (PMD) (1st and higher orders) Four-wave mixing (FWM) Amplified spontaneous emission (ASE) Noise in OA Chromatic
40、dispersion Reflections (see reflectance) Cross Phase Modulation (XPM) Self Phase Modulation (SPM) Stimulated Raman Scattering (SRS) This Recommendation uses the following term defined in ITU-T G.692: Frequency (or wavelength) deviation from nominal (see central frequency deviation) This Recommendati
41、on uses the following term defined in ITU-T. O.201: Q-factor This Recommendation uses the following terms defined in b-ITU-T G.Sup39: Optical Signal-to-Noise Ratio (OSNR) Inter-channel crosstalk Interferometric crosstalk 3.2 Terms defined in this Recommendation This Recommendation defines the follow
42、ing terms: 3.2.1 chromatic dispersion slope: The slope of the curve of chromatic dispersion coefficient versus wavelength. 3.2.2 fully regenerated optical networks: Optical networks where optical-electrical-optical conversion is performed in each network element using re-amplification, reshaping and
43、 retiming (3R) regeneration. 3.2.3 transparent optical network element: An optical network element where there is no optical-electrical-optical conversion of the optical signal. 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: 3R Re-amplification, Resha
44、ping and Retiming ASE Amplified Spontaneous Emission BER Bit Error Ratio DCM Dispersion Compensation Module Demux Demultiplexer DWDM Dense Wavelength Division Multiplexing Rec. ITU-T G.697 (02/2012) 3 EME Embedded Monitoring Equipment EMP External Monitoring Point ES Errored Second ESR Errored Secon
45、d Ratio FWM Four-Wave Mixing Mux Multiplexer NOC Network Operations Centre NRZ Non-Return to Zero OA Optical Amplification OADM Optical Add-Drop Multiplexer OD Optical Demultiplexing OLA Optical Line Amplifier OM Optical Monitoring OM Optical Multiplexing ONE Optical Network Element OSA Optical Spec
46、trum Analyser OSNR Optical Signal-to-Noise Ratio OTN Optical Transport Network PDL Polarization-Dependent Loss PMD Polarization Mode Dispersion ROADM Reconfigurable Optical Add-Drop Multiplexer RZ Return to Zero SBS Stimulated Brillouin Scattering SDH Synchronous Digital Hierarchy SES Severely Error
47、ed Second SESR Severely Errored Second Ratio SLA Service Level Agreement SPM Self Phase Modulation SRS Stimulated Raman Scattering XPM Cross Phase Modulation 5 Optical monitoring overview The management of existing SDH networks relies on monitoring digital parameters such as bit error ratio (BER), e
48、rrored second ratio (ESR) and severely errored second ratio (SESR), which are measured at the electrical layer (at 3R regenerators), as described in b-ITU-T G.826. A similar approach is used in the OTN (using ITU-T G.709 framing) for monitoring the end-to-end connections and the optical connections
49、at the electrical level. 4 Rec. ITU-T G.697 (02/2012) While these methods give a reliable measure of the end-to-end performance of an optical channel, they cannot be applied inside a transparent optical domain where no 3R regenerators are available to terminate the frame overhead. Therefore, they may not provide sufficient information to isolate the root cause of problems in complex DWDM networks. Moreover, the rapid progress in optical technology is leading to ever-increas
