1、 International Telecommunication Union ITU-T G.957TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (03/2006) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital sections and digital line system Digital line systems Optical interfaces for equipments and systems relating to t
2、he synchronous digital hierarchy ITU-T Recommendation G.957 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 I
3、NDIVIDUAL 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 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 hierarchical bit rates based on
5、 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 systems for customer access to ISDN
6、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 USER-RELATED ASPECTS G.1000G.1999 TRANSMISSION MEDIA CHARACTERISTICS G.6000G.6999 DATA OVER TRANSPORT GE
7、NERIC ASPECTS G.7000G.7999 ETHERNET OVER TRANSPORT ASPECTS G.8000G.8999 ACCESS NETWORKS G.9000G.9999 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. G.957 (03/2006) i ITU-T Recommendation G.957 Optical interfaces for equipments and systems relating to the synchrono
8、us digital hierarchy Summary This Recommendation specifies optical interface parameters for equipments and systems based on the Synchronous Digital Hierarchy to enable transverse compatibility. Source ITU-T Recommendation G.957 was approved on 29 March 2006 by ITU-T Study Group 15 (2005-2008) under
9、the ITU-T Recommendation A.8 procedure. ii ITU-T Rec. G.957 (03/2006) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is r
10、esponsible 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 every four years, establishes the topics for study by t
11、he 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 purview, the necessary standards are prepared on a collabo
12、rative 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 voluntary. However, the Recommendation may contain certain
13、 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 the negative equivalents are used to express requirements
14、. 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 involve the use of a claimed Intellectual Property Right. ITU
15、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 Recommendation, ITU had received notice of intellectual proper
16、ty, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. ITU 2006 All rights reserved. No part of this publication may
17、be reproduced, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. G.957 (03/2006) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Terms and definitions . 2 3.1 Definitions 2 3.2 Terms defined in other Recommendations. 2 4 Abbreviations 2 5 Classification of optical interf
18、aces 3 6 Parameter definitions 8 6.1 System operating wavelength range. 8 6.2 Transmitter . 9 6.3 Optical path 11 6.4 Receiver 13 7 Optical parameter values for SDH applications . 13 8 Optical engineering approach. 14 8.1 Design assumptions 14 8.2 Worst-case design approach. 14 8.3 Statistical desig
19、n approach . 15 8.4 Upgradeability considerations 16 8.5 Joint engineering 16 Annex A System operating wavelength considerations 17 A.1 Operating wavelength ranges determined by fibre attenuation 17 A.2 Operating wavelength ranges determined by fibre dispersion . 18 Annex B Measurement of the mask o
20、f the eye diagram of the optical transmit signal 20 B.1 Measurement set-up 20 B.2 Transfer function of the optical reference receiver 20 Appendix I Methods for measuring reflections 22 I.1 Optical continuous-wave reflectometer 22 I.2 Optical time-domain reflectometer. 22 Appendix II Implementation o
21、f the Consecutive Identical Digit (CID) immunity measurement. 24 II.1 Introduction 24 II.2 Method 25 Appendix III Possible method for evaluating aging margin contribution in receiver sensitivity specifications. 26 III.1 Receiver sensitivity and eye opening . 26 III.2 S/X test method. 27 iv ITU-T Rec
22、. G.957 (03/2006) Page Appendix IV Upgradeability examples. 29 IV.1 Example 1. 29 IV.2 Example 2. 29 ITU-T Rec. G.957 (03/2006) 1 ITU-T Recommendation G.957 Optical interfaces for equipments and systems relating to the synchronous digital hierarchy 1 Scope This Recommendation covers optical interfac
23、e parameter specifications for equipments and systems supporting the Synchronous Digital Hierarchy (SDH) defined in ITU-T Rec. G.707/Y.1322 and operating on single-mode optical fibres conforming to ITU-T Recs G.652, G.653 and G.654. The purpose of this Recommendation is to provide specifications for
24、 the optical interfaces of SDH equipment, described in ITU-T Rec. G.783, to achieve the possibility of transverse (multivendor) compatibility on elementary cable sections, i.e., the possibility of mixing various manufacturers equipments within a single optical section. However, the specifications in
25、 this Recommendation are also intended to be in accordance with ITU-T Rec. G.955 which provides the possibility to achieve longitudinal compatibility for equipment of comparable hierarchical level and application. This Recommendation is based on the use of one fibre per direction. Any other optical
26、arrangements may require different specifications and are for further study. 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 indicate
27、d 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 Recommendations and other references listed below. A list of the currently valid ITU-T Recom
28、mendations 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 Recommendation G.652 (2005), Characteristics of a single-mode optical fibre and cable. ITU-T Recommendation G.653 (2003), Chara
29、cteristics of a dispersion-shifted single-mode optical fibre and cable. ITU-T Recommendation G.654 (2004), Characteristics of a cut-off shifted single-mode optical fibre and cable. ITU-T Recommendation G.655 (2006), Characteristics of a non-zero dispersion-shifted single-mode optical fibre and cable
30、. ITU-T Recommendation G.707/Y.1322 (2003), Network node interface for the synchronous digital hierarchy. ITU-T Recommendation G.783 (2006), Characteristics of synchronous digital hierarchy (SDH) equipment functional blocks. ITU-T Recommendation G.826 (2002), End-to-end error performance parameters
31、and objectives for international, constant bit-rate digital paths and connections. ITU-T Recommendation G.955 (1996), Digital line systems based on the 1544 kbit/s and the 2048 kbit/s hierarchy on optical fibre cables. ITU-T Recommendation I.432.2 (1999), B-ISDN user-network interface Physical layer
32、 specification: 155 520 kbit/s and 622 080 kbit/s operation. 2 ITU-T Rec. G.957 (03/2006) IEC 60825-1 (2001), Safety of laser products Part 1: Equipment classification, requirements and users guide. IEC 60825-2 (2005), Safety of laser products Part 2: Safety of optical fibre communication systems (O
33、FCS). 3 Terms and definitions 3.1 Definitions This Recommendation defines the following terms: 3.1.1 transverse compatibility: The capability to mix various manufacturers equipments within a single optical section. 3.1.2 joint engineering: The process by which Administrations/operators agree on a se
34、t of interface characteristics of an optical link that meet agreed performance characteristics of the link when the available interface specifications in ITU-T Recommendations are insufficient to ensure the performance level. 3.2 Terms defined in other Recommendations This Recommendation uses the fo
35、llowing terms defined in other ITU-T Recommendations as indicated: S/R reference points: see ITU-T Rec. G.955. Synchronous Digital Hierarchy (SDH): see ITU-T Rec. G.707/Y.1322. Synchronous Transport Module (STM): see ITU-T Rec. G.707/Y.1322. Longitudinal compatibility: see ITU-T Rec. G.955. 4 Abbrev
36、iations This Recommendation uses the following abbreviations: BER Bit Error Ratio EX Extinction ratio LED Light-Emitting Diode MLM Multi-Longitudinal Mode NA Not Applicable NRZ Non-Return to Zero ORL Optical Return Loss RMS Root-Mean-Square SDH Synchronous Digital Hierarchy SLM Single-Longitudinal M
37、ode STM Synchronous Transport Module UI Unit Interval WDM Wavelength-Division Multiplexing ITU-T Rec. G.957 (03/2006) 3 5 Classification of optical interfaces It is expected that optical fibres will be used in SDH-based systems for both inter-office transport between stations and in intra-office app
38、lications for connecting equipment within a single station. By appropriate combinations of transmitters and receivers, power budgets for optical fibre line systems can be achieved which are optimized in terms of attenuation/dispersion and cost with respect to the various applications. However, to si
39、mplify the development of transverse compatible systems, it is desirable to limit the number of application categories and corresponding sets of optical interface specifications for standardization. As shown in Table 1, this Recommendation recognizes three broad application categories: intra-office
40、corresponding to interconnect distances less than approximately 2 km; short-haul inter-office corresponding to interconnect distances of approximately 15 km; long-haul inter-office corresponding to interconnect distances of approximately 40 km in the 1310 nm window and approximately 80 km in the 155
41、0 nm window. Table 1/G.957 Classification of optical interfaces based on application and showing application codes Inter-office Application Intra-office Short-haul Long-haul Source nominal wavelength (nm) 1310 1310 1550 1310 1550 Type of fibre G.652 G.652 G.652 G.652 G.652 G.654 G.653 Distance (km)a
42、) 2 15 40 80 STM-1 I-1 S-1.1 S-1.2 L-1.1 L-1.2 L-1.3 STM-4 I-4 S-4.1 S-4.2 L-4.1 L-4.2 L-4.3 STM level STM-16 I-16 S-16.1 S-16.2 L-16.1 L-16.2 L-16.3 a)These are target distances to be used for classification and not for specification. The possibility of applying the set of optical parameters in thi
43、s Recommendation to single-channel systems on G.655 fibre is not to be precluded by the designation of the fibre types in the application codes. Within each category, it is possible to consider use of either nominal 1310 nm sources on optical fibre complying with ITU-T Rec. G.652 or nominal 1550 nm
44、sources on optical fibre complying with ITU-T Recs G.652, G.653 or G.654. This Recommendation covers both possibilities for the two inter-office applications and considers only nominal 1310 nm sources on G.652 fibre for the intra-office application. Since the overall system characteristics and speci
45、fic values for the optical parameters generally depend on system bit rate, it is convenient to classify the SDH optical interfaces based on applications considered in this Recommendation using the set of application codes shown in Table 1. This application code is constructed in the following way: A
46、pplication-STM level. Suffix number with the application designations being I (Intra-office), S (Short-haul), or L (Long-haul), and the suffix number being one of the following: (blank) or 1 indicating nominal 1310 nm wavelength sources on G.652 fibre; 2 indicating nominal 1550 nm wavelength sources
47、 on G.652 fibre for short-haul applications and either G.652 or G.654 fibre for long-haul applications; 3 indicating nominal 1550 nm wavelength sources on G.653 fibre. 4 ITU-T Rec. G.957 (03/2006) NOTE The use of the term intra-office is not meant to exclude any other applications consistent with th
48、e set of optical parameters specified (e.g., B-ISDN user network interfaces physical layer specifications defined in ITU-T Rec. I.432.2). The distances chosen for the application codes in Table 1 are based on parameter values that are achievable with present technology and which are thought to suit
49、network requirements. The intra-office and short-haul inter-office application codes have been proposed as low-cost equipment implementations. The long-haul application codes have been proposed to provide maximum length repeater spans consistent with limits set by present technology and the objective of transverse compatibility. The distances proposed may allow for the upgrading of present systems by exploiting the 1550 nm region. The distances in Table 1 represent approximate maximum r
