1、 International Telecommunication Union ITU-T G.987.4TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (06/2012) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital sections and digital line system Optical line systems for local and access networks 10 Gigabit-capable passive
2、optical networks (XG-PON): Reach extension Recommendation ITU-T G.987.4 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
3、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 RADIOTELEPHONY AND LIN
4、E 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 systems G.910G.919 Digital sections at
5、 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 section and digital transmission syst
6、ems 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.1000G.1999 TRANSMISSION MEDIA CHARACTER
7、ISTICS 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.987.4 (06/2012) i Recommendation ITU-T G.987.4 10 Gigabit-capable passive
8、optical networks (XG-PON): Reach extension Summary Recommendation ITU-T G.987.4 outlines the architecture and interface parameters for 10 Gigabit-capable passive optical network (XG-PON) systems with extended reach using a physical layer reach extension device, such as a regenerator or optical ampli
9、fier in the fibre link between the optical line termination (OLT) and optical network unit (ONU). Wavelength converting, continuous mode, 1:N and combination type reach extenders are also described. The maximum reach is up to 60 km with loss budgets of in excess of 28.5 dB being achievable in both s
10、pans. History Edition Recommendation Approval Study Group 1.0 ITU-T G.987.4 2012-06-06 15 ii Rec. ITU-T G.987.4 (06/2012) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (
11、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 worldwide basis. The World Telecommunicati
12、on 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 WTSA Resolution 1. In some areas of inf
13、ormation 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 administration and a recognized operating ag
14、ency. 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 provisions are met. The words “shall“ or so
15、me 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 the possibility that the practice or
16、 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 of the Recommendation development p
17、rocess. 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 latest information and are therefore stro
18、ngly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2013 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.987.4 (06/2012) iii Table of Contents Page 1 Scope 1 2 Refere
19、nces. 1 3 Definitions 2 4 Abbreviations and acronyms 2 5 Conventions 2 6 Optical extension schemes and architectures . 2 6.1 OA-based reach extenders 6 6.2 OEO-based reach extenders . 7 6.3 Hybrid architectures . 9 6.4 Wavelength conversion reach extenders 11 6.5 Wavelength re-conversion at OLT . 12
20、 6.6 Combination G-PON and XG-PON reach extenders . 14 6.7 Increased fanout reach extenders 16 7 General requirements on XG-PON reach extenders . 17 7.1 Compatibility 17 7.2 Management . 18 7.3 Power 18 7.4 Optional enhancements 18 8 Specifications for mid-span extenders 19 8.1 Optical trunk line 19
21、 8.2 Optical trunk line interface (R/S) and OLT interface (S/R) 19 8.3 Optical distribution network . 22 8.4 Extender interface to optical distribution network (S/R) and ONU interface (R/S) 22 8.5 TC layer impacts . 23 8.6 WDM wavelength allocation plan for OTL . 24 Appendix I Implications on OLT re
22、ceivers due to insertion of OA type extenders . 26 Appendix II Protection 28 II.1 Introduction 28 II.2 RE-independent type B protection . 28 II.3 OEO extender based Type B protection . 28 II.4 OA- Extender based Type B protection architecture . 29 Appendix III Optical time domain reflectometer 30 II
23、I.1 Introduction 30 III.2 Solution . 30 Appendix IV Transport of BM-to-CM converted signals over OTN . 31 iv Rec. ITU-T G.987.4 (06/2012) Page Appendix V Possible realization of OA and OEO-based extenders using wavelength conversion . 32 V.1 A transparent wavelength plan extender realization 32 V.2
24、A conventional wavelength plan extender realization 33 V.3 An OWC based extender realization 35 Bibliography. 37 Rec. ITU-T G.987.4 (06/2012) 1 Recommendation ITU-T G.987.4 10 Gigabit-capable passive optical networks (XG-PON): Reach extension 1 Scope This Recommendation concerns 10 Gigabit-capable p
25、assive optical network (XG-PON) systems with optical link budgets up to the logical limits of the transmission convergence (TC) layer. The increased optical capability, which includes both increased overall fibre length and increased overall splitting ratio, is referred to in this Recommendation as
26、“reach extension“. The primary concerns addressed are the increase of the loss budget and the management of optical impairments. This Recommendation considers mid-span extension, which uses an active extension node placed in the middle of the optical network. The recommended parameters for the optic
27、al distribution network(s) ODN(s) involved in this scheme are specified. Single-sided extension is considered as an improvement to the optical line terminal (OLT) interface. The systems considered here must remain compatible with existing optical network units (ONUs). Furthermore, the approaches sho
28、uld maintain compatibility with existing OLTs to the maximum extent possible. It is recognized that some modification of the OLT equipment may be necessary, but this should be minimized. Two system architectures are considered: optical amplification and opto-electronic regeneration. These can be vie
29、wed as providing reach extension at the physical layer. The key interfaces and functional blocks in each of these architectures are identified and specified. Optionally, optical-electronic-optical (OEO) type reach extender (RE) units may support a burst mode to continuous mode (BM to CM) conversion
30、function, as specified in clause 6.2. In this case, it is also necessary to introduce a CM to BM conversion function before the S/R interface at the OLT. Optionally, both optical amplifier (OA) and OEO type RE units may support the wavelength conversion (WC) function, as specified in clause 6.4. In
31、case of WC-enabled RE units, it is also necessary to introduce a WC-function block before the S/R interface. Optionally, combination RE units may support all the functions described here in ITU-T G.987.4, and the G-PON RE functions described in ITU-T G.984.6. The optional support of a type-B type pr
32、otection in RE units is described. 2 References 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 othe
33、r references are subject to revision; 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 ref
34、erence to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T G.984.5 Recommendation ITU-T G.984.5 (2007), Gigabit-capable Passive Optical Networks (G-PON): Enhancement band. ITU-T G.984.6 Recommendation ITU-T G.984.6 (2008), Gigab
35、it-capable passive optical networks (GPON): Reach extension. ITU-T G.987 Recommendation ITU-T G.987 (2010), 10-Gigabit-capable passive optical network (XG-PON) systems: Definitions, abbreviations, and acronyms. 2 Rec. ITU-T G.987.4 (06/2012) ITU-T G.987.1 Recommendation ITU-T G.987.1 (2010), 10-Giga
36、bit-capable passive optical networks (XG-PON): General requirements. ITU-T G.987.2 Recommendation ITU-T G.987.2 (2010), 10 Gigabit-capable passive optical networks (XG-PON): Physical media dependent (PMD) layer specification. ITU-T G.987.3 Recommendation ITU-T G.987.3 (2010), 10 Gigabit-capable pass
37、ive optical networks (XG-PON): Transmission convergence (TC) layer specification. ITU-T G.988 Recommendation ITU-T G.988 (2010), ONU management and control interface (OMCI) specification. ITU-T L.66 Recommendation ITU-T L.66 (2007), Optical fibre cable maintenance criteria for in-service fibre testi
38、ng in access networks. 3 Definitions See clause 3 of ITU-T G.987. 4 Abbreviations and acronyms See clause 4 of ITU-T G.987. 5 Conventions See clause 5 of ITU-T G.987. 6 Optical extension schemes and architectures The basic PON architecture is shown in Figure 1. The OLT interfaces with multiple ONUs
39、via the ODN. The OLT also provides interfaces to one or more service node interfaces (SNIs), as well as the management system. The ONU interfaces with various UNIs. The only interfaces of interest to this Recommendation are those that face the ODN. The XG-PON physical medium dependent (PMD) specific
40、ation ITU-T G.987.2 specifies the loss profile for the ODN to be 14 29 dB, 16 31 dB, 18 33 dB, or 20 35 dB. The OLT-ODN and ONU-ODN interfaces for XG-PON are specified in ITU-T G.987.2. Indeed, most ITU-compliant PONs deployed today adhere to these Recommendations. Figure 1 Basic PON architecture Th
41、e architecture considered in this Recommendation is illustrated in Figure 2. A mid-span extender device is inserted between the ODN (compliant with existing PON Recommendations) and an optical trunk line (OTL), which is connected to the OLT. This architecture extends the reach of the PON by the leng
42、th of the OTL, and may also increase the split ratio of the PON. However, it does require electrical power for the mid-span extender. ONUONUODN OLTUNIUNISNIR/SR/SS/RRec. ITU-T G.987.4 (06/2012) 3 Figure 2 Mid-span reach extension An extended architecture considered in this Recommendation is presente
43、d in Figure 3. A WC-enabled RE-unit is inserted between the ODN (compliant with existing PON recommendations) and an optical trunk line (OTL), which is connected to the OLT. This architecture extends the reach of the PON by the length of the OTL, and may also increase the split ratio of the PON. Add
44、itionally, the WC-RE unit may aggregate several XG-PON-class ODNs, enabled by the WDM multiplexing over OTL to achieve more cost-efficient use of existing fibre infrastructure. The WC function block inserted before the S/R interface at the OLT performs adaptation between the WDM optical signals tran
45、smitted over the OTL and the ITU-T G.987 series-Recommendations compliant OLT interfaces. Figure 3 Wavelength conversion reach extender architecture An additional extended architecture considered in this architecture is shown in Figure 4. “BM-to-CM“ means burst mode to continuous mode converter, and
46、 vice versa. A BM to CM converter is used at the remote PON reach extender to convert the bursty upstream signal into a conventional continuous mode signal. A CM to BM converter is theoretically present at the OLT location, although it will most likely be integrated with the OLT itself. ONUONUODN OL
47、TUNIUNISNIR/SR/SS/RMid-SpanExtenderOTLS/R R/SOLTOTLWC+REODNONUONUSNIS/RR/SS/RR/SR/SUNIUNIWCS/RODNONUONUS/RR/SR/SUNIUNIOLTSNIS/R4 Rec. ITU-T G.987.4 (06/2012) Figure 4 BM-to-CM conversion reach extender architecture An additional aspect of XG-PON systems is their coexistence with the ITU-T G.984 G-PO
48、N systems. The reach extender function can be combined to support both systems simultaneously, as shown in Figure 5. The “combo“ reach extender fulfils the roles of both an ITU-T G.984.6 RE and an ITU-T G.987.4 RE. Figure 5 Combination G-PON/XG-PON reach extender Reach extenders can also incorporate
49、 additional fanout within the RE, as shown in Figure 6. In this case, the RE has multiple S/R interfaces that are combined with the usual PON logical connectivity (downstream broadcast, upstream combining) to a single R/S interface. However, it is not the same as placing a splitter next to the RE, as the loss budget constraints would prevent this. A couple of physical methods to achieve this are described in clause 6.7. The motivation for such a scheme is to in
