1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T G.985TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (03/2003) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital sections and digital line system Optical line systems for local and access networks 100 Mbit/s point-to-point Eth
2、ernet based optical access system ITU-T Recommendation G.985 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
3、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 LINE TELEPHONY
4、 G.450G.499 TESTING EQUIPMENTS G.500G.599 TRANSMISSION MEDIA 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 syste
6、ms 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 G.1000G.1999 TRANSMISSION MEDIA CHARACTERISTICS G.6000G.6999 DIGITAL TERMINAL EQUIPME
7、NTS G.7000G.7999 DIGITAL NETWORKS G.8000G.8999 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. G.985 (03/2003) i ITU-T Recommendation G.985 100 Mbit/s point-to-point Ethernet based optical access system Summary This Recommendation describes the 100 Mbit/s point-to-
8、point Ethernet based optical access system, including ODN (optical distribution network) specification, physical layer specification and the requirements for the OAM (operation, administration and maintenance). This Recommendation is based on 1-fiber WDM bidirectional transmission system. Source ITU
9、-T Recommendation G.985 was prepared by ITU-T Study Group 15 (2001-2004) and approved under the WTSA Resolution 1 procedure on 16 March 2003. ii ITU-T Rec. G.985 (03/2003) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunicat
10、ions. 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 Telecommunicatio
11、n 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 info
12、rmation 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 age
13、ncy. 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
14、Rights, 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, impleme
15、ntors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. ITU 2003 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.
16、985 (03/2003) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 1 4 Abbreviations 2 5 Configuration of an OAN . 2 5.1 System configuration 2 5.2 Fibre type 3 5.3 Transmission methodology 3 5.4 Wavelength allocation 3 5.5 ODN model 3 5.6 Class for optical path loss. 4 5.7 Reflectance in ODN .
17、 4 6 Physical layer specification 4 6.1 Transmit wavelength/Receive wavelength. 6 6.2 Bit rate and line coding. 6 6.3 Spectral characteristics . 6 6.4 Mean launched power. 6 6.5 Receiver characteristics 7 6.6 Extinction ratio . 7 6.7 Pulse mask 7 6.8 S/X 7 6.9 Optical return loss of the interface .
18、7 6.10 Test pattern . 8 6.11 Jitter 8 6.12 Signal detect . 8 6.13 Optical connector 8 7 Requirements for the OAM 8 7.1 General requirements 8 7.2 Requirements for the OAM functions 9 7.3 Managed entities. 10 7.4 Requirements for the OAM signals and sequences 11 7.5 Requirements for the performance m
19、onitor function . 11 ITU-T Rec. G.985 (03/2003) 1 ITU-T Recommendation G.985 100 Mbit/s point-to-point Ethernet based optical access system 1 Scope This Recommendation describes 100 Mbit/s point-to-point Ethernet based optical access system for the optical access services including ODN (optical dist
20、ribution network) specification, physical layer specification and the requirements for the OAM (operation, administration and maintenance). For an effective use of optical fibres, this Recommendation specifies only a single fibre bi-directional transmission system, dual-fibre systems being out of th
21、e scope of this Recommendation. 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 other r
22、eferences 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 refere
23、nce to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation 1 ITU-T Recommendation G.957 (1999), Optical interfaces for equipments and systems relating to the synchronous digital hierarchy. 2 ITU-T Recommendation G.982 (1996), Optical acce
24、ss networks to support services up to the ISDN primary rate or equivalent bit rates. 3 ITU-T Recommendation G.983.1 (1998), Broadband optical access systems based on Passive Optical Networks (PON). 4 ITU-T Recommendation G.652 (2003), Characteristics of a single-mode optical fibre cable. 5 IEEE Stan
25、dard 802.3-2000, Information technology LAN/MAN Part 3: Carrier Sense Multiple Access with Collision Detection (CSMA/CD) Access Method and Physical Layer Specifications. 3 Definitions This Recommendation defines the following terms: 3.1 Optical Access Network (OAN): The set of access links sharing t
26、he same network-side interfaces and supported by optical access transmission systems. 3.2 Optical Distribution Network (ODN): An ODN provides the optical transmission means from the OLT towards the users, and vice versa. It utilizes passive optical components. 3.3 Optical Line Termination (OLT): An
27、OLT provides the network-side interface of the OAN, and is connected to the ODN. 3.4 Optical Network Termination (ONT): An ONT provides the user-side interface of the OAN, and is connected to the ODN. 3.5 Wavelength Division Multiplexing (WDM): Bidirectional multiplexing using different optical wave
28、length for up and downstream signals. 2 ITU-T Rec. G.985 (03/2003) 4 Abbreviations This Recommendation uses the following abbreviations: CRC Cyclic Redundancy Check FEFI Far End Fault Indication MII Media Independent Interface MLM Multi-Longitudinal Mode NRZI Non Return to Zero Inverted OAM Operatio
29、n, Administration and Maintenance OAN Optical Access Network ODN Optical Distribution Network OLT Optical Line Termination ONT Optical Network Termination PCS Physical Coding Sub-layer PMA Physical Medium Attachment PMD Physical Medium Dependent RMS Root Mean Square RS Reconciliation Sub-layer SLM S
30、ingle Longitudinal Mode SMF Single Mode Fibre SNI Service Network Interface UNI User Network Interface UTP Unshielded Twisted Pair cable WDM Wavelength Division Multiplexing 5 Configuration of an OAN 5.1 System configuration Figure 1 shows the system configuration of the point-to-point Ethernet base
31、d optical access system. In this Recommendation, both UNI and SNI are Ethernet interfaces. The two directions for optical transmission in the ODN are identified as follows: downstream direction for signals travelling from the OLT to the ONT; upstream direction for signals travelling from the ONT to
32、the OLT. G.985_F01UNIONT OLTR/S S/RSNIODN(point-to-point)ServicenetworkR/S Reference pointsFigure 1/G.985 System configuration ITU-T Rec. G.985 (03/2003) 3 5.2 Fibre type Single-mode fibre should be used in accordance with ITU-T Rec. G.652. 5.3 Transmission methodology Bidirectional transmission is
33、accomplished by use of Wavelength Division Multiplexing (WDM) technique of 1310 nm region and 1550 nm region wavelengths on a single fibre, allowing the connection to be a point-to-point type ODN. 5.4 Wavelength allocation For downstream, the operating wavelength range should be 1260-1360 nm. For up
34、stream, the operating wavelength range should be 1480-1580 nm. These wavelength ranges are compatible with ITU-T Rec. G.982 though it specifies point-to-multipoint configuration. 5.5 ODN model The ODN provides the optical transmission medium for the physical connection between ONT and OLT. The ODN f
35、or the point-to-point configuration consists of passive optical elements as follows: single-mode optical fibres and cables; optical fibre ribbons and ribbon cables; optical connectors; passive optical attenuators; splices. The ODN is defined between the reference points S and R. In analogy with the
36、definitions provided in ITU-T Rec. G.957, S and R are defined as follows: S: Point on the optical fibre just after the OLT/ONT optical connection point (i.e., optical connector or optical splice). R: Point on the optical fibre just before the OLT/ONT optical connection point (i.e., optical connector
37、 or optical splice). Because of the 1-fibre bidirectional transmission, the point S and R at each end of the ODN are located on the same fibre. The optical properties of the ODN shall enable the provision of any presently foreseeable service without the need of extensive modifications to the ODN its
38、elf. A set of essential items, which have a direct influence on the optical properties of the ODN, are identified as follows: Optical wavelength transparency: Devices, which are not intended to perform any wavelength-selective function, shall be able to support transmission of signals at any wavelen
39、gth in the 1310 nm and 1550 nm regions. Reciprocity: Reversal of input and output ports shall not cause significant change of the optical loss through the device. Fibre compatibility: All optical components shall be compatible with single-mode fibre as specified in ITU-T Rec. G.652. If additional co
40、nnectors or other passive devices are needed for ODN rearrangement, they shall be located between the reference points S and R and their losses shall be taken into account in any optical loss calculation. 4 ITU-T Rec. G.985 (03/2003) 5.6 Class for optical path loss Recommended classes for optical pa
41、th loss are shown in Table 1. Table 1/G.985 Classes for optical path loss Class S Class A Class B Minimum loss 0 dB For further study For further study Maximum loss 15 dB For further study For further study Class A and B are for further study. Class A is for the transmission within 20 km of distance
42、 and Class B is for the transmission within 30 km of distance. 5.7 Reflectance in ODN The reflectance of an ODN depends on the return loss characteristics of the individual components along the optical path and on any reflection points existing in the ODN. A reflection model is described in 6.8. 6 P
43、hysical layer specification The optical interface of ONT and OLT should follow the transmission and coding specification in conformance with PMA, PCS, MII, RS of 100 BASE-FX (IEEE Standard 802.3), except for the physical layer specification defined in this Recommendation. Physical layer specificatio
44、n is also specified for each of the following applicable areas. Class S: optical path loss 15 dB, Power penalty 1 dB. Class A: For further study. The transmission distance is assumed to be within 20 km. Class B: For further study. The transmission distance is assumed to be within 30 km. NOTE The dis
45、tance described above is not a standard, but for classification. This physical layer specification describes PMD sub-layer on the layer structure in Figure 2. G.985_F02Repeater or higher layer functionPMAPCSMIIPMDPMAPCSMedium (SMF) Medium (UTP)OLT/ONTMIIRS RSPMDMIIOAM sub-layerSpecified in this clau
46、seFigure 2/G.985 Index of clause 6 in the layer structure ITU-T Rec. G.985 (03/2003) 5 All parameters are specified as follows, and should be in accordance with Table 2 for an ONT, and Table 3 for an OLT. Table 2/G.985 Physical layer specification for ONT Items Unit Specification ODN class Class S C
47、lass A Class B Nominal bit rate Mbit/s 125 Transmit wavelength nm 1260-1360 Receive wavelength nm 1480-1580 Line code NRZI and 4B5B block coding Spectral characteristic If MLM laser Maximum RMS width nm 7.7 For further study For further studyIf SLM laser Maximum 20 dB width nm For further study If S
48、LM laser Minimum side mode suppression ratio dB For further study Mean launch power MAX dBm 8 Mean launch power MIN dBm 14 Minimum overload dBm 8 Minimum sensitivity dBm 30 Power penalty dB 1 Extinction ratio dB More than 8.2 Pulse mask Conformance with ITU-T Rec. G.957, STM-1 S/X Optical return los
49、s condition dB More than 14 For further study For further studyBit error ratio Less than 1010Optical return loss of the interface dB More than 14 6 ITU-T Rec. G.985 (03/2003) Table 3/G.985 Physical layer specification for OLT Items Unit Specification ODN class Class S Class A Class B Nominal bit rate Mbit/s 125 Transmit wavelength nm 1480-1580 Receive wavelength nm 1260-1360 Line code NRZI and 4B5B block coding Spectral characteristic If MLM laser Maximum RMS width nm 6 For furth
