1、 International Telecommunication Union ITU-T G.694.1TELECOMMUNICATION 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 Spectral grids for WDM applic
2、ations: DWDM frequency grid Recommendation ITU-T G.694.1 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 INDI
3、VIDUAL 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.4
4、50G.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 components an
5、d 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 TRANSMISSION MEDIA C
6、HARACTERISTICS 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.694.1 (02/2012) i Recommendation ITU-T G.694.1 Spectral grids for
7、WDM applications: DWDM frequency grid Summary Recommendation ITU-T G.694.1 provides a frequency grid for dense wavelength division multiplexing (DWDM) applications. The frequency grid, anchored to 193.1 THz, supports a variety of channel spacings ranging from 12.5 GHz to 100 GHz and wider. Edition 2
8、.0 of this Recommendation also includes a flexible DWDM grid. History Edition Recommendation Approval Study Group 1.0 ITU-T G.694.1 2002-06-13 15 2.0 ITU-T G.694.1 2012-02-13 15 ii Rec. ITU-T G.694.1 (02/2012) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized
9、 agency in the field of telecommunications, 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
10、view to standardizing telecommunications 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 Recommen
11、dations 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 on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conci
12、seness to indicate both a telecommunication 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 Recommenda
13、tion 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 express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party.
14、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 Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Right
15、s, 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 intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers
16、 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 2012 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permi
17、ssion of ITU. Rec. ITU-T G.694.1 (02/2012) 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 Recommendation . 1 4 Abbreviations and acronyms 1 5 Dense wavelength division multiplexing and its applications 2 6 Fixed grid nomin
18、al central frequencies for dense WDM systems 2 7 Flexible DWDM grid definition . 5 Appendix I Use of the flexible grid 6 I.1 Flexible grid examples . 6 I.2 Flexible grid compliance 7 Rec. ITU-T G.694.1 (02/2012) 1 Recommendation ITU-T G.694.1 Spectral grids for WDM applications: DWDM frequency grid
19、1 Scope The purpose of this Recommendation is to provide the definition of a frequency grid to support dense wavelength division multiplexing (DWDM) applications. 2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitut
20、e 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 recent edition of the Recomm
21、endations 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. ITU-T G.671 Recommendation ITU-T G.671 (2009),
22、Transmission characteristics of optical components and subsystems. 3 Definitions 3.1 Terms defined elsewhere This Recommendation uses the following terms defined in ITU-T G.671: Coarse Wavelength Division Multiplexing (CWDM). Dense Wavelength Division Multiplexing (DWDM). 3.2 Terms defined in this R
23、ecommendation This Recommendation defines the following terms: 3.2.1 frequency grid: A frequency grid is a reference set of frequencies used to denote allowed nominal central frequencies that may be used for defining applications. 3.2.2 frequency slot: The frequency range allocated to a slot and una
24、vailable to other slots within a flexible grid. A frequency slot is defined by its nominal central frequency and its slot width. 3.2.3 slot width: The full width of a frequency slot in a flexible grid. 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: CW
25、DM Coarse Wavelength Division Multiplexing DWDM Dense Wavelength Division Multiplexing WDM Wavelength Division Multiplexing 2 Rec. ITU-T G.694.1 (02/2012) 5 Dense wavelength division multiplexing and its applications Dense wavelength division multiplexing (DWDM), a wavelength division multiplexing (
26、WDM) technology, is characterized by narrower channel spacing than coarse WDM (CWDM), as defined in ITU-T G.671. In general, the transmitters employed in DWDM applications require a control mechanism to enable them to meet the applications frequency stability requirements, in contrast to CWDM transm
27、itters, which are generally uncontrolled in this respect. The frequency grid defined by this Recommendation supports a variety of fixed channel spacings ranging from 12.5 GHz to 100 GHz and wider (integer multiples of 100 GHz) as well as a flexible grid. Uneven channel spacings using the fixed grids
28、 are also allowed. The current steps in channel spacing for the fixed grids have historically evolved by sub-dividing the initial 100 GHz grid by successive factors of two. 6 Fixed grid nominal central frequencies for dense WDM systems For channel spacings of 12.5 GHz on a fibre, the allowed channel
29、 frequencies (in THz) are defined by: 193.1 + n 0.0125 where n is a positive or negative integer including 0 For channel spacings of 25 GHz on a fibre, the allowed channel frequencies (in THz) are defined by: 193.1 + n 0.025 where n is a positive or negative integer including 0 For channel spacings
30、of 50 GHz on a fibre, the allowed channel frequencies (in THz) are defined by: 193.1 + n 0.05 where n is a positive or negative integer including 0 For channel spacings of 100 GHz or more on a fibre, the allowed channel frequencies (in THz) are defined by: 193.1 + n 0.1 where n is a positive or nega
31、tive integer including 0 Table 1 illustrates some nominal central frequencies within the C and L bands based on the 12.5 GHz minimum channel spacing anchored to the 193.1 THz reference. Table 1 also illustrates the 25, 50 and 100 GHz grid frequencies within the same region. The endpoints shown are i
32、llustrative, not normative. Note that the value of “c“ (speed of light in vacuum) that should be used for converting between frequency and wavelength is 2.99792458 108m/s. Table 1 Example nominal central frequencies of the DWDM grid Nominal central frequencies (THz) for spacings of: Approximate nomi
33、nal central wavelengths (nm)(Note) 12.5 GHz 25 GHz 50 GHz 100 GHz and above 195.9375 1530.0413 195.9250 195.925 1530.1389 195.9125 1530.2365195.9000 195.900 195.90 195.9 1530.3341 Rec. ITU-T G.694.1 (02/2012) 3 Table 1 Example nominal central frequencies of the DWDM grid Nominal central frequencies
34、(THz) for spacings of: Approximate nominal central wavelengths (nm)(Note) 12.5 GHz 25 GHz 50 GHz 100 GHz and above 195.8875 1530.4318 195.8750 195.875 1530.5295 195.8625 1530.6271195.8500 195.850 195.85 1530.7248 195.8375 1530.8225195.8250 195.825 1530.9203 195.8125 1531.0180195.8000 195.800 195.80
35、195.8 1531.1157 195.7875 1531.2135195.7750 195.775 1531.3112 195.7625 1531.4090195.7500 195.750 195.75 1531.5068 195.7375 1531.6046195.7250 195.725 1531.7024 195.7125 1531.8003195.7000 195.700 195.70 195.7 1531.8981 195.6875 1531.9960195.6750 195.675 1532.0938 195.6625 1532.1917 193.2375 1551.4197 1
36、93.2250 193.225 1551.5200 193.2125 1551.6204193.2000 193.200 193.20 193.2 1551.7208 193.1875 1551.8212193.1750 193.175 1551.9216 193.1625 1552.0220193.1500 193.150 193.15 1552.1225 193.1375 1552.2229193.1250 193.125 1552.3234 193.1125 1552.42394 Rec. ITU-T G.694.1 (02/2012) Table 1 Example nominal c
37、entral frequencies of the DWDM grid Nominal central frequencies (THz) for spacings of: Approximate nominal central wavelengths (nm)(Note) 12.5 GHz 25 GHz 50 GHz 100 GHz and above 193.1000 193.100 193.10 193.1 1552.5244 193.0875 1552.6249193.0750 193.075 1552.7254 193.0625 1552.8259193.0500 193.050 1
38、93.05 1552.9265 193.0375 1553.0270193.0250 193.025 1553.1276 193.0125 1553.2282193.0000 193.000 193.00 193.0 1553.3288 192.9875 1553.4294192.9750 192.975 1553.5300 192.9625 1553.6307 184.7750 184.775 1622.4731 184.7625 1622.5828184.7500 184.750 184.75 1622.6926 184.7375 1622.8024184.7250 184.725 162
39、2.9122 184.7125 1623.0220184.7000 184.700 184.70 184.7 1623.1319 184.6875 1623.2417184.6750 184.675 1623.3516 184.6625 1623.4615184.6500 184.650 184.65 1623.5714 184.6375 1623.6813184.6250 184.625 1623.7912 184.6125 1623.9012184.6000 184.600 184.60 184.6 1624.0111 184.5875 1624.1211184.5750 184.575
40、1624.2311 184.5625 1624.3411184.5500 184.550 184.55 1624.4511 Rec. ITU-T G.694.1 (02/2012) 5 Table 1 Example nominal central frequencies of the DWDM grid Nominal central frequencies (THz) for spacings of: Approximate nominal central wavelengths (nm)(Note) 12.5 GHz 25 GHz 50 GHz 100 GHz and above 184
41、.5375 1624.5612 184.5250 184.525 1624.6712 184.5125 1624.7813184.5000 184.500 184.50 184.5 1624.8914 NOTE The wavelengths given in this table are approximations only. The specifications applied to DWDM applications are defined with respect to the nominal central frequencies and not the approximate w
42、avelengths. 7 Flexible DWDM grid definition For the flexible DWDM grid, the allowed frequency slots have a nominal central frequency (in THz) defined by: 193.1 + n 0.00625 where n is a positive or negative integer including 0 and 0.00625 is the nominal central frequency granularity in THz and a slot
43、 width defined by: 12.5 m where m is a positive integer and 12.5 is the slot width granularity in GHz. Any combination of frequency slots is allowed as long as no two frequency slots overlap. Further information on the use of the flexible grid can be found in Appendix I. 6 Rec. ITU-T G.694.1 (02/201
44、2) Appendix I Use of the flexible grid (This appendix does not form an integral part of this Recommendation.) I.1 Flexible grid examples In addition to the fixed spacing dense wavelength division multiplexing (DWDM) grids defined in clause 6, a newer flexible DWDM grid has been introduced in clause
45、7. One of the motivations for the flexible grid is to allow a mixed bit rate or mixed modulation format transmission system to allocate frequency slots with different widths so that they can be optimized for the bandwidth requirements of the particular bit rate and modulation scheme of the individua
46、l channels. Because of the complexity of defining multi-vendor interoperable transmission systems containing mixed bit rates or modulation formats, there are currently no DWDM optical interface Recommendations that make use of this grid. An example use of the flexible DWDM grid is shown in Figure I.
47、1, where two 50 GHz slots are shown together with two 75 GHz slots. For each slot in the figure, the values of n and m in the formulae defining the slot parameters in clause 7 are also given. The frequency range between 193.125 THz and 193.18125 THz is shown unallocated. This range could be left as
48、a “guard band“ between the two sets of channels or it could subsequently be allocated to an additional slot with a width of 50 GHz (n=8, m=4), leaving 6.25 GHz unallocated, or other alternatives (e.g., two 25 GHz slots n=6, m=2 and n=10, m=2). 75 GHz50 GHz 50 GHz 75 GHz 193.1193.125 193.05193.075 193.18125193.25625193.33125193.025 193.21875193.29375n = -8, m = 4 n = 0, m = 4 n = 19, m =
