1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T G.694.2TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (12/2003) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Transmission media characteristics Characteristics of optical components and subsystems Spectral grids for WDM applicat
2、ions: CWDM wavelength grid ITU-T Recommendation G.694.2 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.299 INDIV
3、IDUAL 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 TELEPHONY G.45
4、0G.499 TESTING EQUIPMENTS G.500G.599 TRANSMISSION MEDIA 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.649 Optical fibre cables G.650G.659 Characteristics of optical components and subsystems G.660G.699 DIGIT
5、AL TERMINAL EQUIPMENTS G.700G.799 DIGITAL NETWORKS G.800G.899 DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.900G.999 QUALITY OF SERVICE AND PERFORMANCE GENERIC AND USER-RELATED ASPECTS G.1000G.1999 TRANSMISSION MEDIA CHARACTERISTICS G.6000G.6999 DIGITAL TERMINAL EQUIPMENTS G.7000G.7999 DIGITAL NETWORKS
6、 G.8000G.8999 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. G.694.2 (12/2003) i ITU-T Recommendation G.694.2 Spectral grids for WDM applications: CWDM wavelength grid Summary This Recommendation provides the wavelength grid for coarse wavelength division multiple
7、xing (CWDM) applications. This wavelength grid supports a channel spacing of 20 nm. The wavelength grid in this version of this Recommendation has been moved by 1 nm to align it with current industry practice while maintaining symmetrical nominal central wavelength deviations.Source ITU-T Recommenda
8、tion G.694.2 was approved on 14 December 2003 by ITU-T Study Group 15 (2001-2004) under the ITU-T Recommendation A.8 procedure. ii ITU-T Rec. G.694.2 (12/2003) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The IT
9、U 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 worldwide basis. The World Telecommunication Standardiz
10、ation 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 WTSA Resolution 1. In some areas of information tech
11、nology 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 administration and a recognized operating agency. Complia
12、nce 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 provisions are met. The words “shall“ or some other obliga
13、tory 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 the possibility that the practice or implementation
14、 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 of the Recommendation development process. As of t
15、he 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, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to c
16、onsult the TSB patent database. ITU 2004 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. G.694.2 (12/2003) iii CONTENTS Page 1 Scope 1 2 References. 1 2.1 Normative references 1 2.2 Informative refer
17、ences 1 3 Definitions 1 3.1 Terms defined in this Recommendation. 1 3.2 Terms defined in other Recommendations. 1 4 Abbreviations and acronyms 2 5 Coarse WDM and its applications 2 6 Nominal central wavelengths for coarse WDM systems 2 Appendix I Central wavelength spacing and wavelength variation 3
18、 Appendix II Wavelength allocation 4 ITU-T Rec. G.694.2 (12/2003) 1 ITU-T Recommendation G.694.2 Spectral grids for WDM applications: CWDM wavelength grid 1 Scope The purpose of this Recommendation is to provide the definition of a wavelength grid to support coarse wavelength division multiplexing (
19、CWDM) applications. This grid is designed to allow simultaneous transmission of several wavelengths with sufficient separation to permit the use of uncooled sources. 2 References 2.1 Normative references The following ITU-T Recommendations and other references contain provisions which, through refer
20、ence 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 possibility of applying the most
21、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 Recommendation. 1 ITU-T Recommendat
22、ion G.671 (2002), Transmission characteristics of optical components and subsystems. 2.2 Informative references The following ITU-T Recommendations contain other relevant information. 2 ITU-T Recommendation G.983.3 (2001), A broadband optical access system with increased service capability by wavele
23、ngth allocation. 3 ITU-T Recommendation J.185 (2002), Transmission equipment for transferring multi-channel television signals over optical access networks by FM conversion. 4 ITU-T Recommendation J.186 (2002), Transmission equipment for multi-channel television signals over optical access networks
24、by sub-carrier multiplexing (SCM). 3 Definitions 3.1 Terms defined in this Recommendation This Recommendation defines the following term: 3.1.1 wavelength grid: A wavelength grid is a reference set of vacuum optical wavelengths used to denote allowed nominal central wavelengths that may be used in d
25、efining applications. 3.2 Terms defined in other Recommendations This Recommendation uses terms defined in ITU-T Rec. G.671: Coarse Wavelength Division Multiplexing (CWDM). Dense Wavelength Division Multiplexing (DWDM). 2 ITU-T Rec. G.694.2 (12/2003) 4 Abbreviations and acronyms This Recommendation
26、uses the following abbreviations: CWDM Coarse Wavelength Division Multiplexing DWDM Dense Wavelength Division Multiplexing WDM Wavelength Division Multiplexing 5 Coarse WDM and its applications Coarse Wavelength Division Multiplexing (CWDM), a WDM technology, is characterized by wider channel spacin
27、g than Dense WDM (DWDM) as defined in ITU-T Rec. G.671. CWDM systems can realize cost-effective applications, through a combination of uncooled lasers, relaxed laser wavelength selection tolerances and wide passband filters. CWDM systems can be used in transport networks in metropolitan areas for a
28、variety of clients, services and protocols. Appendix I provides an explanation of the rationale for choosing the central wavelength spacing and the determining factors of the wavelength variation. 6 Nominal central wavelengths for coarse WDM systems The nominal central wavelengths for coarse WDM sys
29、tems are used as a reference to define, for each channel used, an upper wavelength bound and a lower wavelength bound. These bounds define limits for the wavelength of the transmitter under all conditions and at the same time the wavelength limits over which the specifications of the optical multipl
30、exers and demultiplexers must be met. The upper wavelength bound is the central wavelength of the channel plus the central wavelength deviation found in the Recommendation defining the application. The lower wavelength bound is the central wavelength of the channel minus the central wavelength devia
31、tion found in the Recommendation defining the application. The CWDM grid wavelengths within the range 1271 nm to 1611 nm are shown in Table 1. The value of “c“ (speed of light in vacuum) that should be used for converting between wavelength and frequency is 2.99792458 108m/s. ITU-T Rec. G.694.2 (12/
32、2003) 3 Table 1/G.694.2 Nominal central wavelengths Nominal central wavelengths (nm) for spacing of 20 nm 1271 1291 1311 1331 1351 1371 1391 1411 1431 1451 1471 1491 1511 1531 1551 1571 1591 1611 NOTE The endpoints of this table are illustrative only. Appendix I Central wavelength spacing and wavele
33、ngth variation Effective CWDM realizations with uncooled lasers and wide passband filters require a nominal central wavelength spacing of not less than 20 nm. Total source wavelength variation of the order of 6-7 nm is expected to be compatible with current filter technologies. As for the guardband,
34、 one third of the minimum channel spacing is sufficient. Therefore, in order to maximize the number of channels, 20 nm has been chosen. Specific values and allocations of this variation will be defined in individual applications. The wavelength variation is determined by mainly two factors. First, t
35、he laser manufacturer is allowed a wavelength variation around the nominal wavelength in order to achieve a higher yield and/or relax fabrication tolerances. Second, the use of uncooled lasers will cause the wavelength to change with temperature within the specified temperature range of the laser. 4
36、 ITU-T Rec. G.694.2 (12/2003) Appendix II Wavelength allocation ITU-T Rec. G.983.3 (March 2001) defines the wavelength allocation for video distribution signals multiplexed with B-PON. ITU-T Recs J.185 and J.186 (February 2002) define the wavelength allocation for transferring multi-channel televisi
37、on signals. Geneva, 2004 SERIES OF ITU-T RECOMMENDATIONS Series A Organization of the work of ITU-T Series B Means of expression: definitions, symbols, classification Series C General telecommunication statistics Series D General tariff principles Series E Overall network operation, telephone servic
38、e, service operation and human factors Series F Non-telephone telecommunication services Series G Transmission systems and media, digital systems and networks Series H Audiovisual and multimedia systems Series I Integrated services digital network Series J Cable networks and transmission of televisi
39、on, sound programme and other multimedia signals Series K Protection against interference Series L Construction, installation and protection of cables and other elements of outside plant Series M TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimi
40、le and leased circuits Series N Maintenance: international sound programme and television transmission circuits Series O Specifications of measuring equipment Series P Telephone transmission quality, telephone installations, local line networks Series Q Switching and signalling Series R Telegraph tr
41、ansmission Series S Telegraph services terminal equipment Series T Terminals for telematic services Series U Telegraph switching Series V Data communication over the telephone network Series X Data networks and open system communications Series Y Global information infrastructure, Internet protocol aspects and Next Generation Networks Series Z Languages and general software aspects for telecommunication systems
