1、 International Telecommunication Union ITU-T G.984.6TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Amendment 2(05/2012) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital sections and digital line system Optical line systems for local and access networks Gigabit-capable
2、passive optical networks (G-PON): Reach extension Amendment 2 Recommendation ITU-T G.984.6 (2008) Amendment 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
3、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 METALLIC LINES G.400G.449
4、COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY G.450G.499 TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS G.600G.699 DIGITAL TERMINAL EQUIPMENTS G.700G.799 DIGITAL NETWORKS G.800G.899 DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.900G.999 General G.900G.909 Parameters for optical fibre cable
5、systems G.910G.919 Digital sections at hierarchical bit rates based on a bit rate of 2048 kbit/s G.920G.929 Digital line transmission systems on cable at non-hierarchical bit rates G.930G.939 Digital line systems provided by FDM transmission bearers G.940G.949 Digital line systems G.950G.959 Digital
6、 section and digital transmission systems for customer access to ISDN G.960G.969 Optical fibre submarine cable systems G.970G.979 Optical line systems for local and access networks G.980G.989Access networks G.990G.999 MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE GENERIC AND USER-RELATED ASPECTS G.1
7、000G.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.984.6 (2008)/Amd.2 (05/2012) i Recom
8、mendation ITU-T G.984.6 Gigabit-capable passive optical networks (G-PON): Reach extension Amendment 2 Summary Amendment 2 to Recommendation ITU-T G.984.6 (2008) is aimed at defining additional features, specifications, and/or types of gigabit-capable passive optical networks (G-PONs) compatible reac
9、h extender units, especially using a distributed Raman amplified G-PON reach extender. It also includes miscellaneous corrections to the Recommendation. History Edition Recommendation Approval Study Group 1.0 ITU-T G.984.6 2008-03-29 15 1.1 ITU-T G.984.6 (2008) Amd. 1 2009-11-13 15 1.2 ITU-T G.984.6
10、 (2008) Amd. 2 2012-05-07 15 ii Rec. ITU-T G.984.6 (2008)/Amd.2 (05/2012) 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
11、 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), which meets
12、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 within ITU-Ts pur
13、view, 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 Recommendation is vol
14、untary. 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 as “must“ and
15、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 of this Recommendation may invol
16、ve 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 of this Recom
17、mendation, 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 patent database at
18、 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.984.6 (2008)/Amd.2 (05/2012) iii Table of Contents Page 1) Changes to ITU-T G.984.6 as amended by ITU-T G.984
19、.6 Amd.1 . 1 1.1) Changes to clause 1, “Scope“ . 1 1.2) Changes to clause 2, “References“ . 1 1.3) Changes to clause 3, “Definitions“ . 1 1.4) Changes to clause 4, “Abbreviations and acronyms“ . 2 1.5) New clause 6.6, “Raman amplified reach extenders“ . 2 1.6) Changes to clause 7.1, “Compatibility“
20、3 1.7) Changes to clause 7.2, “Management“ . 4 1.8) Modify clause 8.6.4, “Cyclic OTL wavelength allocation plan“ . 4 1.9) New clause 8.7, “Specifications for Raman amplified reach extender“ . 4 1.10) Add new Appendix IX, “General characteristics of reverse pumped distributed Raman amplifiers“ 5 1.11
21、) Add new Appendix X, “General considerations and guidelines of safety procedure“ 7 1.12) Bibliography . 8 Rec. ITU-T G.984.6 (2008)/Amd.2 (05/2012) 1 Recommendation ITU-T G.984.6 Gigabit-capable passive optical networks (G-PON): Reach extension Amendment 2 This amendment adds a Raman amplified reac
22、h extender to Recommendation ITU-T G.984.6 as amended. It defines the configuration, features, and specifications of the new type of G-PON reach extender using distributed Raman amplification in feeder fibre. It also includes miscellaneous corrections to the Recommendation. 1) Changes to ITU-T G.984
23、.6 as amended by ITU-T G.984.6 Amd.1 1.1) Changes to clause 1, “Scope“ Add the following text after the last paragraph: “Optionally, Raman amplified type RE units are described in clause 6.6.“ 1.2) Changes to clause 2, “References“ Add the following references to the list: ITU-T G.664 Recommendation
24、 ITU-T G.664 (2006), Optical safety procedures and requirements for optical transport systems. ITU-T G.665 Recommendation ITU-T G.665 (2005), Generic characteristics of Raman amplifiers and Raman amplified subsystems. ITU-T G.698.3 Recommendation ITU-T G.698.3 (2012), Multichannel seeded DWDM applic
25、ations with single-channel optical interfaces. IEC 60825-1 International Standard IEC 60825-1 (2007), Safety of laser products Part 1: Equipment classification and requirements. IEC 60825-2 International Standard IEC 60825-2 (2000), Safety of laser products Part 2: Safety of optical fibre communicat
26、ion systems. 1.3) Changes to clause 3, “Definitions“ Add the following to clause 3: 3.2 maximum pump power (based on ITU-T G.665): The highest pump power(s) available at RPi(as defined in Appendix I) for reverse pumping. 3.3 minimum pump power (based on ITU-T G.665): The lowest pump power(s) availab
27、le at RPi(as defined in Appendix I) for reverse pumping for which the operation of the Raman amplifier is usable. 3.4 net gain (based on ITU-T G.665): Net gain is defined as the Raman On-Off gain with the loss between the input and output reference points of the amplifier subtracted from it. 3.5 Ram
28、an on-off gain (based on ITU-T G.665): The increase in signal optical power at the gain measurement point (GMP) defined in Appendix I when the Raman pump is activated compared to the signal optical power at the GMP when the Raman pump is de-activated. This Recommendation uses the following terms def
29、ined elsewhere: automatic power reduction (APR) ITU-T G.664: A technique (procedure) to automatically reduce the output power of laser and optical amplifiers to avoid exposure to hazardous levels. 2 Rec. ITU-T G.984.6 (2008)/Amd.2 (05/2012) DOP of pump laser ITU-T G.665: The degree of polarization o
30、f the pump laser. loss of continuity (of an optical link) ITU-T G.664: Any event which may cause hazardous optical power levels to be emitted from some point along the path of an optical transmission system. Common causes of loss of continuity of an optical link are a fibre cable break, equipment fa
31、ilure, connector unplugging, etc. reverse pumped Raman amplifier ITU-T G.665: The pump energy and signal propagate in opposite directions in the transmission fibre. RIN of pump laser ITU-T G.665: Relative Intensity Noise of pump energy. 1.4) Changes to clause 4, “Abbreviations and acronyms“ Add the
32、following items to the list: AEL Accessible Emission Limit APR Automatic Power Reduction GMP Gain Measurement Point R/S Optical trunk line interface to ODN RPiReverse-Pumped signal input reference point RPoReverse-Pumped signal output reference point S/R Optical line termination interface to Raman r
33、each extender 1.5) New clause 6.6, “Raman amplified reach extenders“ Add the following clause 6.6: 6.6 Schemes and architectures on Raman amplified reach extenders The general architecture of a Raman RE is shown in Figure 7c. The Raman RE device is inserted between the OLT and the optical trunk line
34、 (OTL), which is optical fibre. The OLT and ONU are compliant with existing G-PON Recommendations, i.e., ITU-T G.984-series. This approach extends the reach of the PON by increasing the allowable length of the OTL, and may also increase the split ratio of the PON. Note the Raman-RE device can be co-
35、located with the OLT at the central office (CO) and therefore it keeps the ODN passive (no electrical power required in R/S to R/S section). G.984.6(08)-Amd.2(12)_F7cUNIUNIONUONUR/SR/SODN OTLR/S R/SRaman reachextenderCOOLTSNIS/RFigure 7c Raman G-PON reach extension Rec. ITU-T G.984.6 (2008)/Amd.2 (0
36、5/2012) 3 The generic configuration of a Raman-RE is shown in Figure 7d by way of example. The Raman pumps at appropriate wavelengths are coupled into the OTL to provide reverse pumped distributed Raman gain for the G-PON upstream (US) signals. An optional optical amplifier (OA) may be used to boost
37、 the G-PON downstream (DS) signal power before launching into the OTL. The OA could be a semiconductor optical amplifier (SOA), discrete Raman amplifier, and EDFA, or any other suitable optical amplifier providing gain over the 1480-1500 nm wavelength range. The OA may be omitted if the G-PON DS pow
38、er is high enough to accommodate the high loss for long reach or higher split ratio. Furthermore, the OA may also be replaced by an opto-electronic repeater providing improved launch power to overcome increased losses in the OTL and ODN. A Raman pump at the appropriate wavelength may also optionally
39、 be used to couple into the OTL to provide forward pumped distributed Raman gain for the G-PON DS signal. A WDM combiner is used to combine the G-PON DS signals with the Raman pump and separate the G-PON US signals. The pass bands of the WDM combiner are designed to ensure compatibility with the wav
40、elength band specifications for G-PON signals as defined in ITU-T G.984.5. The WDM combiner may optionally act as an optical bandpass filter (OBF) to remove amplified spontaneous emission (ASE) noise outside of the signal bands in order to improve transmission performance. G.984.6(08)-Amd.2(12)_F7dO
41、LTS/RRaman reach extenderOTL:feeder fiberR/SR/SWDMcombinerOAUSDSRaman pumps for DSRaman pumps for USDiplexerSNIFigure 7d Example configuration for Raman RE; OA and Raman pumps for DS are optional Due to the nature of the Raman RE system, the equipment should be specified for a defined application ra
42、nge taking into account applicable penalties due to ASE and any non-linear penalties. The equipment should also be specified with the key parameters for Raman pumps, such as the Raman pump wavelength, maximum power, and the expected Raman on-off gain for the specified OTL fibre type. Other parameter
43、s for reverse pumped distributed Raman amplifiers defined in ITU-T G.665 may also be included in the equipment specifications. It is recommended to refer to ITU-T G.665 on “Generic characteristics of Raman amplifiers and Raman amplified subsystems“. The key performance parameters and test methods us
44、ed for Raman RE, as defined in ITU-T G.665, are summarized in Appendix I. In addition, the equipment may be specified with the key parameters for the OA including, for example, the saturated output power, linear gain and noise figure. 1.6) Changes to clause 7.1, “Compatibility“ Add the following tex
45、t at the end of clause 7.1: The Raman-RE will be compatible with both narrow wavelength band option (US: 1300-1320 nm) and the reduced wavelength band option (US: 1290-1330 nm) as defined in ITU-T G.984.5. Due to the limited Raman gain bandwidth and laser safety considerations, support is not intend
46、ed for the regular wavelength band option (US: 1260-1360 nm) as defined in ITU-T G.984.5. The Raman-RE must be compatible with existing G-PON 2.4/1.2 Gbit/s class B+ rated ONT equipment and class B+ ODN ITU-T G.984.2 Amd.1. It is also possible for the extender to support a more capable ODN, such as
47、the class C+ defined in Amendment 2 to ITU-T G.984.2. 4 Rec. ITU-T G.984.6 (2008)/Amd.2 (05/2012) As the Raman-RE uses the OTL fibre to provide gain, the system gain is dependent on the length of the OTL. A typical OTL length greater than 20 km will be employed before optical splitting (see “specifi
48、cation for Raman amplified reach extender“). OTL lengths shorter than 20 km are possible but will result in a reduction of the Raman on-off gain and thus the supported loss budget. 1.7) Changes to clause 7.2, “Management“ Add the following text at the end of clause 7.2: The Raman-RE shall support fu
49、ll management functions for configuration, performance monitoring, and fault reporting. This will include the configuration and provision of the output power level of Raman pumps. Considering that the Raman-RE will most likely operate at optical power levels well in excess of the Hazard Level 1 limit, as specified by IEC 60825-2, it should provide optical safety features for automatic power reduction (APR) of the Raman pump lasers when a loss of continuity occurs in the
