1、 International Telecommunication Union ITU-T G.984.2TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Amendment 2(03/2008) 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): Physical Media Dependent (PMD) layer specification Amendment 2 ITU-T Recommendation G.984.2 (2003) Amendment 2 ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS G.100G.199 GEN
3、ERAL CHARACTERISTICS COMMON TO ALL 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 INTERCONNECT
4、ION WITH METALLIC LINES G.400G.449 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
5、Parameters for optical fibre cable 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 Digi
6、tal line systems G.950G.959 Digital 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.989 Access networks G.990G.999 QUALITY OF SERVICE AND PERFORMANCE GENERIC AND
7、 USER-RELATED ASPECTS G.1000G.1999 TRANSMISSION MEDIA CHARACTERISTICS G.6000G.6999 DATA OVER TRANSPORT GENERIC ASPECTS G.7000G.7999 PACKET OVER TRANSPORT ASPECTS G.8000G.8999ACCESS NETWORKS G.9000G.9999 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. G.984.2 (2003)
8、/Amd.2 (03/2008) i ITU-T Recommendation G.984.2 Gigabit-capable Passive Optical Networks (G-PON): Physical Media Dependent (PMD) layer specification Amendment 2 Summary This amendment provides an enhancement to ITU-T Recommendation G.984.2 to support optical layer supervision and a new optical line
9、termination (OLT) optical interface specification (C+) that can enable a loss budget extension of 4 dB. Also, a modification to the 2.488 Gbit/s downstream extinction ratio is made, to bring it in line with ITU-T Recommendation G.957, and to add some text regarding network timing. Source Amendment 2
10、 to ITU-T Recommendation G.984.2 (2003) was approved on 29 March 2008 by ITU-T Study Group 15 (2005-2008) under the ITU-T Recommendation A.8 procedure. ii ITU-T Rec. G.984.2 (2003)/Amd.2 (03/2008) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in th
11、e 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 view to stand
12、ardizing 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 Recommendations is co
13、vered 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 conciseness to ind
14、icate 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 Recommendation is achieve
15、d 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. INTELLECTUAL PR
16、OPERTY 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 Rights, whether asse
17、rted 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 are cautioned
18、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 2008 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. I
19、TU-T Rec. G.984.2 (2003)/Amd.2 (03/2008) iii CONTENTS Page 3 Definitions 1 3.1 Terms defined elsewhere 1 3.2 Terms defined in this Recommendation. 1 Appendix IV Description of physical layer measurements to support optical layer supervision 3 IV.1 Introduction 3 IV.2 Transceiver parameters monitorin
20、g 3 IV.3 Measurement table for transceiver parameters. 3 IV.4 OLS physical layer performance measurements requirements 4 Appendix V Industry best practice for Single-sided Extended 2.488 Gbit/s downstream, 1.244 Gbit/s upstream G-PON (class C+). 5 V.1 Introduction 5 Bibliography. 7 ITU-T Rec. G.984.
21、2 (2003)/Amd.2 (03/2008) 1 ITU-T Recommendation G.984.2 Gigabit-capable Passive Optical Networks (G-PON): Physical Media Dependent (PMD) layer specification Amendment 2 Abstract As a necessary part of OLS, transceiver parameter monitoring is important. A detailed description about transceiver parame
22、ter monitoring is added as Appendix IV to explain the purpose, requirements and recommended measurement parameters. Also, to address the possibility of a single-sided reach enhancement to G-PON systems, a new OLT optical interface specification is described, as Appendix V. Revise the title and conte
23、nts of clause 3 to read as shown below. 3 Definitions 3.1 Terms defined elsewhere This Recommendation makes frequent use of terms defined in b-ISO Guide 2, which are reproduced below for convenience. 3.1.1 accuracy of a measuring system (accuracy): This is the ability of a measuring system to provid
24、e an indication value that is close to the true value being measured. This is normally expressed as an error range around the true value. 3.1.2 range of indications (range): This term can be either called as “range of indications“ or “indication intervals“. It is the set of quantity values bounded b
25、y the extreme possible indications of a measuring system. 3.1.3 repeatability of a measuring system (repeatability): This is the property of a measuring system to provide closely similar indications for replicated measurements of the same quantity under repeatable conditions. This is normally expres
26、sed as a range of indications that result from repeated measurements of identical conditions. 3.1.4 resolution of a measuring system (resolution): This is the smallest change in the value of the quantity being measured by a measuring system that causes a perceptible change in the corresponding indic
27、ation. 3.2 Terms defined in this Recommendation This Recommendation uses the following terms related to the G-PON PMD layer: 3.2.1 optical access network (OAN): The set of access links sharing the same network-side interfaces and supported by optical access transmission systems. The OAN may include
28、a number of ODNs connected to the same OLT. 3.2.2 optical distribution network (ODN): In the PON context, a tree of optical fibres in the access network, supplemented with power or wavelength splitters, filters or other passive optical devices. 3.2.3 optical line supervision (OLS): A set of capabili
29、ties relating to the measurement and reporting of the state of the optical link. 2 ITU-T Rec. G.984.2 (2003)/Amd.2 (03/2008) 3.2.4 optical line termination (OLT): A device that terminates the common (root) endpoint of an ODN, implements a PON protocol, such as that defined by b-ITU-T G.984.3, and ad
30、apts PON PDUs for uplink communications over the provider service interface. The OLT provides management and maintenance functions for the subtended ODN and ONUs. 3.2.5 optical network termination (ONT): A single subscriber device that terminates any one of the distributed (leaf) endpoints of an ODN
31、, implements a PON protocol, and adapts PON PDUs to subscriber service interfaces. An ONT is a special case of an ONU. 3.2.6 optical network unit (ONU): A generic term denoting a device that terminates any one of the distributed (leaf) endpoints of an ODN, implements a PON protocol, and adapts PON P
32、DUs to subscriber service interfaces. In some contexts, an ONU implies a multiple subscriber device. 3.2.7 response time (RT): The response time explains the real-time requirement for OLS reasons. It refers to the response time for a measurement circuit, from the time the test is initiated to the ti
33、me the valid measurement is available. It does not include the delays associated with the transmission of the result to higher layers. 3.2.8 time division multiple access (TDMA): Transmission technique involving the multiplexing of many time slots onto the same time payload. 3.2.9 wavelength divisio
34、n multiplexing (WDM): Bidirectional multiplexing using different optical wavelength for upstream and downstream signals. Add the following note to the end of clause 8.2.3.1 (downstream): NOTE The OLT may source its timing from either a dedicated timing signal source or from a synchronous data interf
35、ace (line timing). A packet-based timing source may also be used. Modify row 13 of Table 2c as follows: Extinction ratio (Note 5) dB more than 8.2 more than 8.2 Add the following note at the end of Table 2c: NOTE 5 The extinction ratio of 8.2 dB was a relaxation of the former value of 10 dB. The new
36、 value does imply an improvement of the ONU receiver of 0.5 dB optical modulation amplitude. Add the following new Appendices IV and V: ITU-T Rec. G.984.2 (2003)/Amd.2 (03/2008) 3 Appendix IV Description of physical layer measurements to support optical layer supervision (This appendix does not form
37、 an integral part of this Recommendation) IV.1 Introduction This appendix describes physical layer parameter measurements that are required to provide the G-PON system with a basic optical layer supervision capability. The quantities to be measured are enumerated, along with the desired range, accur
38、acy and resolution. These measurements can be obtained by different practical and cost-effective monitoring methods, and the method of measurement is left to implementation choice. IV.2 Transceiver parameters monitoring In PON systems, physical monitoring for OLS may be used for: 1) Normal status mo
39、nitoring: Get and buffer historic data as a reference in a normally working system. 2) Degradation detection: Find the potential faults before they become service-affecting, and identify the source of the problem (e.g., ODN, OLT or ONT). 3) Fault management: Detect, localize and diagnose faults. In
40、order to achieve these objectives, the following performance items should be monitored in a PON system. Transceiver temperature (OLT and ONT); Transceiver voltage (OLT and ONT); Laser bias current (OLT and ONT); OLT transmit power; OLT receive power (per ONT); ONT transmit power; ONT receive power.
41、Clause IV.3 specifies recommended measurement performance parameters for each of these transceiver performance measurements. NOTE These are obtainable using currently available detecting and monitoring technology. IV.3 Measurement table for transceiver parameters Table IV.1 gives information on the
42、standard measurement performance that should be obtainable with measurement equipment embedded in the OLT and/or ONTs. NOTE The values specified in this table pertain to the measurement, and not the reporting, of data. Therefore, the resolution mainly refers to the intrinsic quantization size of the
43、 measurement circuit, and not the message field format of the report. The typical response time refers to the timeliness of the measurement circuit in the optical module, and not to the actual reporting of data over the PON or to the EMS. 4 ITU-T Rec. G.984.2 (2003)/Amd.2 (03/2008) Table IV.1/G.984.
44、2 Optical line supervision-related measurement specifications Typical range Note 1 Resolution Accuracy Repeatability Typical response time Temperature OLT and ONT 45 to +90 C 0.25 C 3 C 1 C 1 s Voltage OLT and ONT Note 4 0 to 6.55 V 0.5% of nominal 3% of nominal 1% of nominal 1 s Bias current OLT an
45、d ONT Note 4 0 to 131 mA 1% of nominal 10% of nominal 5% of nominal 1 s ONT transmit power 10 to +8 dBm 0.1 dB 3 dB 0.5 dB Note 2 300 ns ONT receive power 34 to 8 dBm 0.1 dB 3 dB 0.5 dB Note 2 300 ns OLT transmit power 10 to +9 dBm 0.1 dB 2 dB 0.5 dB Note 2 300 ns OLT receive power Note 3 34 to 8 dB
46、m 0.1 dB 2 dB 0.5 dB Note 2 300 ns NOTE 1 The typical range attempts to capture the most common range of parameters of an operational optical module. If a module has a different operational range, then the measurement range should follow that range, augmented by the measurement inaccuracy on either
47、end. NOTE 2 ONT and OLT optical repeatability refers to multiple measurements taken when the true values of the ONT or OLT temperature and voltage are the same at the time of measurement. However, the normal range of those parameters should be exercised in between tests as a means to gauge their agi
48、ng effects. NOTE 3 The OLTs measurement should reflect the average power received during a burst. This requires the OLT to perform the measurement at the proper time with respect to the incoming burst, and that said burst is long enough to support the response time of the detector. The deviation due
49、 to non-50% duty cycle in the upstream data pattern is not to be charged against the measurement accuracy or repeatability specifications. NOTE 4 Nominal refers to the design value of the quantity being measured (i.e., voltage or bias current) for the particular device implementation. IV.4 OLS physical layer performance measurements requirements All the above parameters should be monitored continuously in real time in order to reflect the actual quality of physical links an
