1、 International Telecommunication Union ITU-T G.672TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (10/2012) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Transmission media and optical systems characteristics Characteristics of optical components and subsystems Characteristi
2、cs of multi-degree reconfigurable optical add/drop multiplexers Recommendation ITU-T G.672 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-TR
3、ANSMISSION 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 RAD
4、IOTELEPHONY 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.659 Charac
5、teristics of optical components and subsystems G.660G.679Characteristics 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 ASPECTS
6、 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.672 (10/2012) i Recommendation I
7、TU-T G.672 Characteristics of multi-degree reconfigurable optical add/drop multiplexers Summary Recommendation ITU-T G.672 provides a description of the relevant characteristics of multi-degree reconfigurable optical add/drop multiplexer (MD-ROADM) network elements. The MD-ROADM is intended to be us
8、ed in optical networks based on dense wavelength division multiplexing (DWDM), to enhance network scalability and to support enhanced service provisioning and resilience features. This Recommendation also provides classification criteria and a list of optical transfer parameters (without values in t
9、he current version) for MD-ROADMs. In this version of this Recommendation, characteristics, classification criteria and optical transfer parameters are applied to MD-ROADMs appropriate for fixed DWDM grid applications. History Edition Recommendation Approval Study Group 1.0 ITU-T G.672 2012-10-29 15
10、 ii Rec. ITU-T G.672 (10/2012) 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 Standardization Sector (ITU-T) is a permanent organ of ITU
11、. 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), which meets every four years, establishes the topics fo
12、r 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 within ITU-Ts purview, the necessary standards are prepared
13、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 Recommendation is voluntary. However, the Recommendation may con
14、tain 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 as “must“ and the negative equivalents are used to expres
15、s 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 the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Proper
16、ty 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 of this Recommendation, ITU had not received notice of i
17、ntellectual 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 patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2013 All
18、 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.672 (10/2012) 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 Recommendatio
19、n . 2 4 Abbreviations and acronyms 4 5 Classification criteria 5 6 Main characteristics 6 7 MD-ROADM transfer parameters 7 7.1 Transfer parameters of MD-ROADMs without amplifiers 7 7.2 Transfer parameters of MD-ROADMs with amplifiers . 7 Appendix I MD-ROADM classification examples . 10 I.1 Example 1
20、 . 10 I.2 Example 2 . 11 Appendix II Configuration examples of MD-ROADM 13 II.1 Example of direction/degree expansion of MD-ROADM . 13 II.2 Example of an MD-ROADM with the directionless and colourless feature 13 Rec. ITU-T G.672 (10/2012) 1 Recommendation ITU-T G.672 Characteristics of multi-degree
21、reconfigurable optical add/drop multiplexers 1 Scope This Recommendation deals with the classification and the characteristics of multi-degree reconfigurable optical add/drop multiplexers (MD-ROADMs), including two-degree ROADMs. Some examples of MD-ROADM configurations and applications are given in
22、 the appendices. Photonic cross connects (PXC), which are a special category of MD-ROADM characterized by a unique switching matrix (see Figures 7-4, 7-5, 7-6, 7-7, 9-2, I.4 of ITU-T G.680) are outside the scope of this Recommendation. 2 References The following ITU-T Recommendations and other refer
23、ences 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; users of this Recommendation are therefore encouraged to inve
24、stigate 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 Recommendation does not give it, as a stand-alone document, the st
25、atus of a Recommendation. ITU-T G.661 Recommendation ITU-T G.661 (2007), Definitions and test methods for the relevant generic parameters of optical amplifier devices and subsystems. ITU-T G.671 Recommendation ITU-T G.671 (2012), Transmission characteristics of optical components and subsystems. ITU
26、-T G.680 Recommendation ITU-T G.680 (2007), Physical transfer functions of optical network elements. ITU-T G.806 Recommendation ITU-T G.806 (2012), Characteristics of transport equipment Description methodology and generic functionality. ITU-T G.870 Recommendation ITU-T G.870 (2010), Terms and defin
27、itions for Optical Transport Networks (OTN). 3 Definitions 3.1 Terms defined elsewhere This Recommendation uses the following terms defined elsewhere: 3.1.1 adjacent channel isolation ITU-T G.671 3.1.2 channel addition/removal (steady-state) gain response ITU-T G.661 3.1.3 channel differential group
28、 delay (see “polarization mode dispersion (PMD)“) ITU-T G.671 3.1.4 channel extinction ITU-T G.671 3.1.5 channel frequency range ITU-T G.671 3.1.6 channel gain ITU-T G.661 3.1.7 channel input power range ITU-T G.661 2 Rec. ITU-T G.672 (10/2012) 3.1.8 channel insertion loss ITU-T G.671 3.1.9 channel
29、insertion loss deviation ITU-T G.671 3.1.10 channel output power range ITU-T G.661 3.1.11 channel polarization dependent loss (PDL) ITU-T G.671 3.1.12 channel signal-spontaneous noise figure ITU-T G.661 3.1.13 channel spacing ITU-T G.671 3.1.14 defect ITU-T G.806 3.1.15 input reflectance ITU-T G.661
30、 3.1.16 maximum reflectance tolerable at input ITU-T G.661 3.1.17 maximum reflectance tolerable at output ITU-T G.661 3.1.18 maximum total output power ITU-T G.661 3.1.19 multichannel gain-change difference (inter-channel gain change difference) ITU-T G.661 3.1.20 multichannel gain tilt (inter-chann
31、el gain-change ratio) ITU-T G.661 3.1.21 non-adjacent channel isolation ITU-T G.671 3.1.22 reconfigure time ITU-T G.680 3.1.23 reflectance ITU-T G.671 3.1.24 ripple ITU-T G.671 3.1.25 optical transport module (OTM nr.m) ITU-T G.870 3.1.26 output reflectance ITU-T G.661 3.1.27 transient duration ITU-
32、T G.661 3.1.28 transient gain increase ITU-T G.661 3.1.29 transient gain reduction ITU-T G.661 3.2 Terms defined in this Recommendation This Recommendation defines the following terms: 3.2.1 degree of an MD-ROADM: The degree of an MD-ROADM is the number of bidirectional optical lines which can be co
33、nnected between the MD-ROADM and other optical network elements. It is also the number of R-WADDs which are installed in the MD-ROADM. 3.2.2 hitless operation: An operation performed on an optical network element embedded in an optical network is hitless when, considering the full time period from t
34、he start of the operation to its end, the following two conditions are both satisfied: no defects are detected on any of the unswitched optical channels managed by that optical network element, or their related client signals; the bit error ratio measured at the receiver interfaces of those client s
35、ignals is less than or equal to the maximum bit error ratio allowed for them. Rec. ITU-T G.672 (10/2012) 3 G.672(12)_F01MaximumBER1Client signalsBER0TimeTStart operation1Hitless operationin this regionTEnd operation2DefectsNodefectsHitless operationin this regionTEnd operation2TStart operation1TimeF
36、igure 1 Illustration of hitless operation conditions 3.2.3 multi-degree reconfigurable optical add/drop multiplexer (MD-ROADM): An element of an optical transport network capable of transferring any wavelength from one optical line to any other optical line, by means of reconfigurable wavelength add
37、/drop devices (R-WADD), and also to transfer local add/drop wavelengths to/from optical lines, by means of reconfigurable local add/drop devices (R-LADD). Moreover, for an MD-ROADM it should be possible to increase or decrease the optical node degree (i.e., to add or remove optical lines) up to the
38、maximum supported, without any impact on live traffic. G.672(12)_F02Optical line #2R-WADDInter-portcross-connectionOptical line #NTo/from local transpondersOptical line #1R-LADDR-WADDR-WADDFigure 2 MD-ROADM reference diagram 3.2.4 reconfigurable local add drop/devices (R-LADD) NxM: A wavelength sele
39、ctive branching device which has a reconfigurable “drop“ function in which wavelengths coming from any of N optical input ports can be transferred to any of M optical drop ports, and also it has a reconfigurable “add“ function in which wavelengths presented to any of M optical add ports can be trans
40、ferred to any of N optical output ports. 4 Rec. ITU-T G.672 (10/2012) .G.672(12)_F03.Optical input port #1Optical input port #2Optical input port #NOptical output port #1Optical output port #2Optical output port #NOptical drop port #1Optical drop port #2Optical drop port #MOptical add port #1Optical
41、 add port #2Optical add port #MN to MdropM to NaddR-LADD NxMFigure 3 R-LADD NxM reference diagram 3.2.5 reconfigurable wavelength add/drop device (R-WADD) 1xN: A reconfigurable wavelength selective branching device capable of transferring wavelengths from one optical line input port to any of N opti
42、cal output ports, and also capable of transferring wavelengths coming from any of N optical input ports to the optical line output port while avoiding transferring the same wavelength from more than one input to the optical line output. .G.672(12)_F04Optical line inputOptical line outputOptical outp
43、ut port #1Optical output port #2Optical output port #NOptical input port #1Optical input port #2Optical input port #N1 to NtransferN to 1selectR-WADD 1xNFigure 4 R-WADD 1xN reference diagram 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: BER Bit Error
44、 Ratio DWDM Dense Wavelength Division Multiplexing MD-ROADM Multi-Degree Reconfigurable Optical Add/Drop Multiplexer OTF Optical Transfer Function OTM Optical Transport Module PDL Polarization Dependent Loss PMD Polarization Mode Dispersion R-LADD Reconfigurable Local Add/Drop Device R-WADD Reconfig
45、urable Wavelength Add/Drop Device WSS Wavelength Selective Switch Rec. ITU-T G.672 (10/2012) 5 5 Classification criteria In an MD-ROADM it should be possible to increase or decrease the optical node degree (i.e., to add or remove optical lines) up to the maximum supported. Consequently, the total nu
46、mber of wavelengths which can be managed both for node pass-through and also for local add/drop, can change dynamically. The following criteria are defined: Maximum node degree: the maximum number of bidirectional optical lines supported by an MD-ROADM. Maximum node channel count: the total number o
47、f channels which can be managed on all of the bidirectional optical lines. It is the maximum number of incoming wavelengths per line multiplied by the maximum node degree. Minimum channel spacing: the minimum value of the channel spacing as defined in ITU-T G.671. Maximum add/drop ports: the number
48、of add/drop ports provided by the MD-ROADM at its maximum add/drop capability. Maximum add/drop ratio: the maximum add/drop ports divided by the maximum node channel count (expressed as a percentage). In an MD-ROADM, the R-LADD feature should provide both the “wavelength-dependent“ add/drop of optic
49、al channels, as well as the “wavelength-independent“ add/drop. Therefore, the following criteria are defined: Coloured local add/drop: an MD-ROADM with a coloured local add/drop feature is able to add/drop an optical channel with a specific wavelength. Colourless local add/drop: an MD-ROADM with a colourless local add/drop feature is able to add/drop an optical channel with any supported wavelength. In an MD-ROADM, the R
