1、INTERNATIONAL TELECOMMUNICATION UNION ITUWT TELECOM M U N I CATI ON STANDARDIZATION SECTOR OF ITU G.955 (I 1/96) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital transmission systems - Digital sections and digital line system - Digital line systems Digital line systems
2、based on the 1544 kbitls and the 2048 kbit/s hierarchy on optical fibre cables ITU-T Recommendation G.955 (Previously CCITT Recommendation) STD*ITU-T RECMN G-755-ENGL 1996 W LiAb257L Ob3705b 42b W ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATION
3、AL TELEPHONE CONNECTIONS AND CIRCUITS INTERNATIONAL ANALOGUE CARRIER SYSTEM TRANSMISSION SYSTEMS INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER- GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE
4、WITH METALLIC LINES SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY TRANSMISSION MEDIA CHARACTERISTICS DIGITAL TRANSMISSION SYSTEMS TERMINAL EQUIPMENTS General Coding of analogue signals by pulse code modulation Coding of analogue signa
5、ls by methods other than PCM Principal characteristics of primary multiplex equipment Principal characteristics of second order multiplex equipment Principal characteristics of higher order multiplex equipment Principal characteristics of transcoder and digital multiplication equipment Operations, a
6、dministration and maintenance features of transmission equipment Principal characteristics of multiplexing equipment for the synchronous digital hierarchy Other terminal equipment General aspects Design objectives for digital networks Quality and availability targets Network capabilities and functio
7、ns SDH network characteristics General Parameters for optical fibre cable systems Digital sections at hierarchical bit rates based on a bit rate of 2048 kbitls Digital line transmission systems on cable at non-hierarchical bit rates Digital line systems provided by FDM transmission bearers DIGITAL N
8、ETWORKS DIGITAL SECTIONS AND DIGITAL LINE SYSTEM Digital section and digital transmission systems for customer access to ISDN Optical fibre submarine cable systems Optical line systems for local and access networks G. 1 O-G. 199 G.200-G.299 G.300-G.399 G.400-G.449 G.450-G.499 G.600-G.699 G.700-G.799
9、 G.700-G.709 G.710-G.719 G.720-G. 729 G.730-G.739 G. 740-G . 749 G.750-G.759 G.760-G .769 G.770-G.779 G.780-G.789 G.790-G.799 G .800-G. 899 G.800-G.809 G.810-G.819 G.820-G.829 G .830-G. 839 G.840-G.899 G. 900-G .999 G.900-G.909 G.910-G.919 G.920-G.929 G.930-G.939 G ,940-G. 949 G. 960-G. 969 G.970-G.
10、979 G. 980-G. 999 For further details, please refer to ITU-T List of Recommendations. ITU-T RECOMMENDATION G.955 DIGITAL LINE SYSTEMS BASED ON THE 1544 kbit/s AND THE 2048 kbit/s HIERARCHY ON OPTICAL FIBRE CABLES Summary This Recommendation provides specifications for the transmission of optical sig
11、nals based on both the 1544 kbit/s and 2048 kbit/s hierarchies. Source ITU-T Recommendation G.955 was revised by ITU-T Study Group 15 (1993-1996) and was approved under the WTSC Resolution No. 1 procedure on the 8th of November 1996. STD-ITU-T RECMN G-755-ENGL L77b H q8b257L Ob37058 2T9 FOREWORD ITU
12、 (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical, operating and tariff questions and issuing
13、Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these
14、 topics. The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1. In some areas of information technology which fall within IT-Ts purview, the necessary standards are prepared on a collaborative basis with IS0 and IEC. NOTE In this R
15、ecommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. INTELLECTUAL PROPERTY RIGHTS The ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve
16、 the use of a claimed Intellectual Property Right. The 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 Rec
17、ommendation, the ITU hadhad not received notice of intellectual property, 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 da
18、tabase. O ITU 1997 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. Recommendation G.955 (11196) II STD-ITU-T RECMN G-755-ENGL 199b m
19、 Lib2571 0b37059 135 1 2 3 4 5 6 7 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 7.9 8 9 10 11 12 12.1 12.2 13 CONTENTS Scope References Terms and definitions . Abbreviations . Type of transmission medium System margin System specifications . Regenerator section lengths Error performance . Receiver dynamic range
20、. Optical source . Operating wavelength range . Optical path allowances for multimode fibre systems Equipment margin (Me) Optical path allowances for single-mode fibre systems . Wavelength division multiplexing . Power feeding . Systems for short haul applications Working conditions Overall design f
21、eatures . Maintenance strategy Fault conditions and consequent actions Type of supervision and fault location . Safety considerations Appendix I . Calculation of regenerator section length I . 1 Approaches . I . 1.1 Worst-case approach . 1.1.2 Statistical approach . I . 1.3 Semi-statistical approach
22、 . 1.2 Statistical data form 1.3 Examples 1.4 An example of a statistical optical power budget . Recommendation G.955 (1 1/96) Page 1 1 2 2 3 3 4 4 5 9 9 9 10 10 10 10 11 11 11 11 12 12 12 12 13 13 13 14 15 16 16 16 . 111 STD-ITU-T RECMN G-755-ENGL 177b 48b257L Ob37Db0 957 Recommendation 6.955 DIGIT
23、AL LINE SYSTEMS BASED ON THE 1544 kbit/s AND THE 2048 kbit/s HIERARCHY ON OPTICAL FIBRE CABLES (revised in I996) 1 Scope This Recommendation covers digital line systems for the transmission of signals based on both the 1544 kbit/s and the 2048 kbits hierarchy on optical fibre cables and includes sys
24、tems conveying the following bit rates: 2 048 kbits 8 448 kbits 34 368 kbits 139 264 kbits 4 x 139 264 kbits 1 544 kbits 3 152 kbits 6 3 12 kbits 32 064 kbits 44 736 kbils n x 44 736 kbits 97 728 kbits 4 x 97 728 kbits The requirements for overall performance and interfaces of the corresponding digi
25、tal sections are given in G.900-Series Recommendations. The aim of this Recommendation is to achieve longitudinal compatibility on elementary cable sections of different digital line systems, i.e. the possibility of installing digital line systems, produced by different manufacturers, on the same op
26、tical fibre cable. For the purpose of this Recommendation, optical fibre digital line systems can be represented as in Figure 1. The system may have no intermediate regenerators as in diagram a) of Figure 1, one intermediate regenerator as in diagram b) of Figure 1 or a larger number depending on th
27、e system design and route length. This Recommendation covers requirements for equipment intended to meet the relevant performance objectives of Recommendations G.82 1 and G.92 1 under all normally envisaged operating conditions. In any event, Recommendation G.821 remains the overriding performance o
28、bjective of the network. 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 referenc
29、es are subject to revision; all 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. - ITU-T Recom
30、mendation G.650 (1 997), DeJinition and test methods for the relevant parameters of single-mode jbres. Recommendation G.955 totally replaces Recommendations G.955 and G.956 as contained in the Blue Book. Recommendation 6.955 (11/96) 1 - ITU-T Recommendation G.65 1 (1 993), Characteristics of a 504 2
31、5 p multimode graded index optical fibre cable. ITU-T Recommendation G.652 (1 997), Characteristics of a single-mode opticalfibre cable. ITU-T Recommendation G.653 (1 997), Characteristics of a dispersion-shifted single-mode optical fibre cable. ITU-T Recommendation G.654 (1 997), Characteristics of
32、 a cut-off shifted single-mode optical$bre cable. CCITT Recommendation G.703 (1 99 i), Physical/electrical characteristics of hierarchical digital interfaces. ITU-T Recommendation G.82 1 (1 996), Error performance of an international digital connection operating at a bit rate below the primary rate
33、and formingpart of an integrated services digital network. CCITT Recommendation G.92 1 (1 988), Digital sections based on the 2048 kbit/s hierarchy. CCITT Recommendation G.950 (1 988), General considerations on digital line systems. ITU-T Recommendation G.957 (1 993, Optical interfaces for equipment
34、s and systems relating to the synchronous digital hierarchy. IEC 479, Effects of current on human beings and livestock, Part 1 (1994) - General aspects; Part 2 (1 987) - Special aspects. IEC 825 (1993), Safety of laser products, Part 1 - Equipment classijcation, requirements and users guide; Part 2
35、- Safety of optical fibre communication systems. - - - - - - - - - - 3 Terms and definitions This Recommendation defines the following terms: 3.1 different manufacturers on the same optical fibre cable. 3.2 cable margin: See 6.1. 3.3 equipment margin: See 6.2. longitudinal compatibility: The capabil
36、ity of installing digital line systems, produced by 4 Abbreviations This Recommendation uses the following abbreviations: BER Bit Error Ratio C Connector FWHM Full-Width Half-Maximum IS1 Inter-Symbol Interference LED Light-Emitting Diode Mc Cable Margin Me Equipment Margin MLM Multi-Longitudinal Mod
37、e N/A Not Applicable OFA Optical Fibre Amplifier 2 Recommendation G.955 (11/96) PDF Probability Distribution Function REG Regenerator Rx Receiver SLM Single Longitudinal Mode Tx Transmitter 5 Type of transmission medium Multimode optical fibres conforming to Recommendation G.65 1 or single-mode opti
38、cal fibres conforming to Recommendations G.652, G.653 and G.654 are considered suitable for these systems. Operation may be in the region of either 850 nm, 1310 nm or 1550 nm or some other wavelength depending on the fibre and system type employed. The attenuation considered the most appropriate for
39、 operation at the various bit rates and wavelengths will be chosen by the Administrations in relation to the characteristics of the link to be realized and in accordance with this Recommendation. Similarly, splice losses, connector losses and the cable margin must be chosen together with the attenua
40、tion of the optical fibre in order to achieve the overall attenuation specified in clause 7. 6 System margin For the purpose of this Recommendation, the total system margin see diagram a) of Figure i, or regenerator section margin see diagram b) of Figure i, is subdivided into two main contributions
41、. The disposition of these margins is shown in Figure 2. T , .cs R c-c s R C. . T. T1507390-92 b) T, T S R Equipment interface in accordance with Recommendation G.703. Point on the optical fibre just after the Transmitter (TX) or the Regenerator (REG) optical Connector C). Point on the optical fibre
42、 just before the Receiver (RX) or the Regenerator (REG) optical Connector ( L ). NOTE -Additional connectors at a distribution frame (if used) are considered to be part of fibre link and to be located between points S and R. Figure UG.955 Recommendation G.955 (11196) 3 r? Tl5074W-92 i/ /I n u Rx Me
43、- Mc NOTE -Me represents the total combined equipment impairments from both transmitter and receiver. Figure 2/G.955 6.1 cable margin (MC): The cable margin, M, covers allowances for: 0 future modifications to the cable configuration (additional splices, increased cable lengths, etc.); ii) fibre cab
44、le performance variations due to environment factors; and iii) degradation of any connector between points S and R when provided. 6.2 equipment margin (Me): The equipment margin, (Me), covers allowances for the effect of time and environmental factors on equipment performance (e.g. transmitter launc
45、hed power, receiver sensitivity, equipment connector degradations). NOTE 1 - The design margin, which covers the allowance for the tolerances on the characteristics of the various components of the system, is not considered because worst-case values for such characteristics are reflected in the spec
46、ifications of clause 7. NOTE 2 - The system margin is in relation to a BER threshold of 1 x lo- even though for practical reasons the measurements of receiver sensitivity may be carried out at other thresholds. NOTE 3 - The approaches adopted in this Recommendation leave some additional margin in op
47、erating systems which can be considered as an unallocated margin. 7 System specifications The optical link of a regenerator section can be represented as in Figure 2 from the point of the system specifications. As a minimum requirement for maximum section length of typical commercially available sys
48、tems, the transmitter and the receiver shall be designed so that the error performance requirements of 7.2 are obtained with an optical path as defined in 7.6 or 7.7. 7.1 Regenerator section lengths The regenerator section length achievable with the systems specified in this Recommendation is relate
49、d to the fibre characteristics and the specific capabilities of the transmitterheceiver equipment. Examples are given in Appendix I. For multimode systems, the description of the baseband response with a single value (the -3 dB optical bandwidth) may not be sufficient to determine the suitability of the fibre for the specified system. In some cases, a more detailed description of this characteristic or the description of the impulse response may be necessary. Additionally, the overall -3 dB optical bandwidth is assumed to include modal and chromatic co
