1、 International Telecommunication Union ITU-T L.50TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (07/2010) SERIES L: CONSTRUCTION, INSTALLATION AND PROTECTION OF CABLES AND OTHER ELEMENTS OF OUTSIDE PLANT Requirements for passive optical nodes: Optical distribution frames for central office environm
2、ents Recommendation ITU-T L.50 Rec. ITU-T L.50 (07/2010) i Recommendation ITU-T L.50 Requirements for passive optical nodes: Optical distribution frames for central office environments Summary Recommendation ITU-T L.50 deals with general requirements for individual optical distribution frames (ODF),
3、 as well as combined frames (ODCF), in a central office environment, including cable ducting systems between multiple ODFs. History Edition Recommendation Approval Study Group 1.0 ITU-T L.50 2003-11-28 6 2.0 ITU-T L.50 2010-07-29 15 ii Rec. ITU-T L.50 (07/2010) FOREWORD The International Telecommuni
4、cation Union (ITU) is the United Nations specialized agency in the 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 q
5、uestions 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 the ITU-T study groups which, in turn, produce Recommendat
6、ions 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 collaborative basis with ISO and IEC. NOTE In this Recommendatio
7、n, 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 mandatory provisions (to ensure, e.g., interoperability
8、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. The use of such words does not suggest that complianc
9、e 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 takes no position concerning the evidence, validity or
10、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 not received notice of intellectual property, protected by patents, which may be required to
11、implement this Recommendation. However, implementers are cautioned 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 2010 All rights reserved. No part of this publication may be reproduced, by a
12、ny means whatsoever, without the prior written permission of ITU. Rec. ITU-T L.50 (07/2010) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 1 3.1 Terms defined elsewhere 1 3.2 Terms defined in this Recommendation . 1 4 Abbreviations and acronyms 3 5 Conventions 3 6 Functional requirements
13、of ODFs and ODCFs 3 6.1 General requirements 3 6.2 Access and maintenance . 3 6.3 Termination of cables . 3 6.4 Storage and protection of splices and optical devices 4 6.5 Connectors and cross-connection of circuits 4 6.6 Pigtail storage and routing 4 6.7 Optical fibre duct 4 7 Performance evaluatio
14、n test programme 4 Appendix I Performance evaluation criteria (example) 5 I.1 Mechanical evaluation 5 I.2 Optical evaluation . 5 Appendix II Performance test programme for ODF (example) 7 II.1 Mechanical and optical evaluation . 7 Appendix III Product characterization checklist . 9 Appendix IV Examp
15、le of the performance evaluation method for optical duct components . 11 IV.1 Performance test of optical fibre duct 11 Bibliography. 12 Rec. ITU-T L.50 (07/2010) 1 Recommendation ITU-T L.50 Requirements for passive optical nodes: Optical distribution frames for central office environments 1 Scope T
16、his Recommendation describes the functional requirements of optical distribution frames (ODF) in central office environments. It does not apply to: active network elements such as optical line terminals (OLTs); outdoor cabinets; termination boxes at the customer premises. 2 References The following
17、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 references are subject to revision; users of this Recommenda
18、tion 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 reference to a document within this Recommendation does not give
19、it, as a stand-alone document, the status of a Recommendation. ITU-T K.25 Recommendation ITU-T K.25 (2000), Protection of optical fibre cables. ITU-T L.51 Recommendation ITU-T L.51 (2003), Passive node elements for fibre optic networks General principles and definitions for characterization and perf
20、ormance evaluation. 3 Definitions 3.1 Terms defined elsewhere None. 3.2 Terms defined in this Recommendation This Recommendation defines the following terms: 3.2.1 central office environment: The term “central office environment“ refers to any room or space inside a building that is only accessible
21、to qualified staff. Examples: Traditional central offices and local exchanges, co-location rooms, other leased rooms inside building. 3.2.2 frame: Frame refers to the mechanical structure to which cables are attached and that holds all other elements of the optical distribution frame (ODF). It may b
22、e a rack and shelve-type structure, similar to what is used to contain the electronics, as well as any other type of structure. Its main functions are mechanical support and a basic level of protection of its content. 3.2.3 fibre organizer: In a node, the optical fibres are to be properly managed an
23、d guided from where a cable or pigtail enters the node, until it leaves again. The fibre organizer comprises the whole of the means and features that are intended to guide and store fibres, pigtails, splices, connectors and passive devices inside a node, at any location where they are not protected
24、by the cable sheath. 2 Rec. ITU-T L.50 (07/2010) 3.2.4 optical distribution combined frame (ODCF): ODCF refers to a combination of several individual ODFs into a superstructure in order to provide more capacity than can be held by a single ODF. Another reason for creating an ODCF may be the need for
25、 multiple service providers to connect to the optical access network. An ODCF includes the necessary means and features to route cables between the individual ODFs. An example of an ODCF, in which different functionalities are spread over the different individual frames, is shown in Figure 1. If the
26、re is no optical fibre duct between individual ODFs, it is necessary to do the connection between the ODFs by using optical cables for the protection of the fibre. Pigtail from splice frameEntering optical cablePatchcords to equipmentPatchcords for crossconnectionOptical fibre ductSpliceframeLineter
27、minalframeLineterminalframeEquipmentterminalframeEquipmentterminalframeL.50(10)_F01Figure 1 Construction of ODCF (example) 3.2.5 optical distribution frame (ODF): The term “ODF“ refers to a frame, including the fibre organizer and the means to store and guide pigtails and cables inside the frame. In
28、 the industry the term “ODF“ is often used as the general term including both individual frames, as well as combinations of multiple frames, or optical distribution combined frame (ODCF). 3.2.6 optical fibre duct: Optical fibre ducts are dedicated ducts or suspendable gutter systems that hold and gu
29、ide indoor (pigtail) cables as they are routed from and to optical distribution frames (ODFs) or within an optical distribution combined frame (ODCF). Optical fibre ducts are sometimes also referred to as “raceway“ systems. Rec. ITU-T L.50 (07/2010) 3 4 Abbreviations and acronyms This Recommendation
30、 uses the following abbreviations: ODCF Optical Distribution Combined Frame ODF Optical Distribution Frame OLT Optical Line Terminal 5 Conventions No special conventions are used within this Recommendation. 6 Functional requirements of ODFs and ODCFs Since OD(C)Fs are optical nodes, the general prin
31、ciples of ITU-T L.51 are applicable. The specific requirements for OD(C)Fs are listed below, sorted by their typical functions. Not all of these functions are necessarily present simultaneously in each individual OD(C)F. 6.1 General requirements Each OD(C)F must comply to the general requirements li
32、sted in clause 8 of ITU-T L.51. Dimensional compatibility to existing local or international frame standards should be considered. In general, a minimum fibre bend radius of 30 mm must be ensured throughout the entire OD(C)F. For special applications or fibre types, a smaller bend radius may be agre
33、ed between customer and supplier. A modular design, which can accommodate combinations of different functions, is preferable. The OD(C)F must allow easy identification of all connections. For the cases that it is likely that an ODF would be in the future expanded to an ODCF, the individual ODF shoul
34、d have the necessary provisions to combine them into an ODCF, in any required orientation (e.g., side by side, back-to-back, etc.). Provisions for guiding (pigtail) cables between individual ODFs should be provided (e.g., through the sides, back, top, bottom or front plane, or via a separate ducting
35、 system as appropriate). 6.2 Access and maintenance An OD(C)F should be re-accessible without interruptions to the live circuits, other than the ones that are subject to reconfiguration. This implies that it shall be possible to separate fibre circuits up to the desired separation level as defined i
36、n ITU-T L.51. These separation levels are not applicable for pigtail bundles. 6.3 Termination of cables An OD(C)F must allow: the termination of one or more cable-ends of various cable constructions and diameters, including: attachment of the cable sheath; termination of strength members; storage of
37、 uncut fibre loops; electrical connection of metallic cable elements in accordance with ITU-T K.25; the addition or removal of a cable without disturbing the cables that are already present; 4 Rec. ITU-T L.50 (07/2010) the possibility of entering cables and pigtails through any plane of the ODF (top
38、, bottom, sides or back) is preferable. 6.4 Storage and protection of splices and optical devices The OD(C)F should be able to properly store: fibre splices; different types of passive devices (including coupler and filter devices, used for network testing purposes) and the related bare fibre or rib
39、bon overlengths. 6.5 Connectors and cross-connection of circuits Within a single ODF, it should be possible to connect and reroute any incoming circuit to any outgoing circuit, with a fixed length of patchcords or a pigtail end. Within an ODCF, it may be an advantage to be able to connect any circui
40、t to any other circuit; however, in reality, only a certain percentage requires this level of flexibility throughout the entire ODCF. Cross-connect schemes and capacity, as well as the required patchcord lengths, are to be agreed between supplier and customer. Each individual connector must be acces
41、sible, without the need to disconnect other (adjacent) connectors. 6.6 Pigtail storage and routing An OD(C)F must contain the necessary means to guide and store pigtail overlengths in an orderly manner. Provision to properly store unused connectors or cable ends should be present if necessary for th
42、e application. Provisions to group and identify pigtails and jumpers for easy retrieval are recommended. 6.7 Optical fibre duct Optical fibre ducts shall be able to protect and lead optical (pigtail) cables. It should not be harmful to optical fibres and cables and should not cause a change in atten
43、uation. The duct should fit in horizontal and vertical fibre pathways. 7 Performance evaluation test programme The performance evaluation programme for an OD(C)F should take into account: both mechanical integrity and optical stability; the effects of: the environmental conditions in which it will b
44、e installed; all typical manipulations, related to an intervention at the ODF; all available functionalities of the product; the general principles for optical nodes as per ITU-T L.51. An example of evaluation criteria and a performance test programme can be found in Appendices I and II. An example
45、of a product characterization checklist can be found in Appendix III. An example of evaluation criteria for optical fibre duct systems can be found in Appendix IV. Rec. ITU-T L.50 (07/2010) 5 Appendix I Performance evaluation criteria (example) (This appendix does not form an integral part of this R
46、ecommendation) This appendix contains an example of performance criteria values. Exact performance criteria are to be determined between customer and supplier. The performance evaluation criteria shall be assessed during or after the tests in Appendix II. I.1 Mechanical evaluation I.1.1 Visual appea
47、rance International standard: b-IEC 61300-3-1. Conditions: Examination of product with the unaided naked eye. Requirement: No defects which would affect product performance. I.2 Optical evaluation NOTE 1 All optical losses indicated are referenced to the initial optical signal at the start of the te
48、st. NOTE 2 An “incoming fibre“ is defined as a part of an optical circuit containing the fibre entering the product, connected to a fibre leaving the product. One optical circuit can contain many “incoming fibres“. Light will sequentially flow through all the “incoming fibres“. NOTE 3 Fibre type use
49、d for single mode: b-ITU-T G.652 matched cladding. I.2.1 Change in insertion loss (static optical stability) International standard: b-IEC 61300-3-3, Method 1. Conditions: Source wavelength: 1310, 1550 or 1625 nm (select the highest applicable wavelength). Requirements: IL 0.2 dB (1310/1550 nm) per incoming fibre during the test (excursion loss). IL 0.5 dB (1625 nm) per incoming fibre during the test (excursion loss). IL 0.1 dB (1310/1550/1625 nm) per incoming fibr
