1、 International Telecommunication Union ITU-T L.37TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (02/2007) SERIES L: CONSTRUCTION, INSTALLATION AND PROTECTION OF CABLES AND OTHER ELEMENTS OF OUTSIDE PLANT Optical branching components (non-wavelength selective) ITU-T Recommendation L.37 ITU-T Rec. L.
2、37 (02/2007) i ITU-T Recommendation L.37 Optical branching components (non-wavelength selective) Summary ITU-T Recommendation L.37 describes the main features of fibre-optic branching devices in terms of types, fields of application, configurations and technical aspects. Furthermore, ITU-T Recommend
3、ation L.37 describes the requirements of the mechanical, environmental and physical performance and reliability for optical branching components, which are stipulated in ITU-T Recommendation G.671 with regard to the optical performance of PONs, advising on general requirements and test methods. Sour
4、ce ITU-T Recommendation L.37 was approved on 22 February 2007 by ITU-T Study Group 6 (2005-2008) under the ITU-T Recommendation A.8 procedure. ii ITU-T Rec. L.37 (02/2007) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunicat
5、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
6、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
7、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
8、ncy. 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 achieved when all of these mandatory provisions are met. The words “shall“ or some
9、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 PROPERTY RIGHTS ITU draws attention to the possibility that the practice or im
10、plementation 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 asserted by ITU members or others outside of the Recommendation development proc
11、ess. 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 that this may not represent the latest information and are therefore strongl
12、y urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2007 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. L.37 (02/2007) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Defin
13、itions 2 4 Abbreviations and acronyms 2 5 Conventions 2 6 General information 2 7 Types and configurations 2 8 Technological aspects. 3 9 Optical parameters and performance 3 10 Application environments and test methods for optical branching components 3 10.1 Application environments 4 10.2 Performa
14、nce and reliability test methods . 4 Appendix I Optional performance requirement 9 I.1 Low temperature storage 9 Appendix II Additional criteria for performance and reliability tests for optical branching components for PONs 10 II.1 Introduction 10 II.2 Criteria for performance and reliability tests
15、 for optical branching components for PONs. 10 ITU-T Rec. L.37 (02/2007) 1 ITU-T Recommendation L.37 Optical branching components (non-wavelength selective) 1 Scope This Recommendation applies to optical branching components (non-wavelength selective) to be used for passive optical networks (PONs).
16、This Recommendation: gives general information on fundamental types of optical branching components, and their field of application; classifies optical branching components into types and configurations; provides a general description of the basic operating principle and the fabrication technologies
17、; describes the application environments of optical branching components for PONs; reports the performance and outlines reliability test methods for optical branching components for PONs. NOTE Performance and reliability requirements in this Recommendation relate only to the properties of the optica
18、l branching component. This does not include the behaviour of optical connectors that may be used to terminate input and/or output fibres. 2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Rec
19、ommendation. At the time of publication, the editions indicated 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 refe
20、rences 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 it, as a stand-alone document, the status of a Recommendation. ITU-T G.671 ITU-T Recommendation G.671 (2005), Transmission characteris
21、tics of optical components and subsystems, plus Amendment 1 (2006). ITU-T G.983.1 ITU-T Recommendation G.983.1 (2005), Broadband optical access systems based on Passive Optical Networks (PON). ITU-T G.983.3 ITU-T Recommendation G.983.3 (2001), A broadband optical access system with increased service
22、 capability by wavelength allocation. ITU-T G.984.2 ITU-T Recommendation G.984.2 (2003), Gigabit-capable Passive Optical Networks (G-PON): Physical Media Dependent (PMD) layer specification. IEC 60695-11-10 IEC 60695-11-10 (2003), Fire hazard testing Part 11-10: Test flames 50 W horizontal and verti
23、cal flame test methods. IEC 61300 IEC 61300-series, Fibre optic interconnecting devices and passive components Basic test and measurement procedures. IEC 62005-2 IEC 62005-2 (2001), Reliability of fibre optic interconnecting devices and passive components Part 2: Quantitative assessment of reliabili
24、ty based on accelerated ageing test Temperature and humidity; steady state. 2 ITU-T Rec. L.37 (02/2007) 3 Definitions This Recommendation defines the following term: 3.1 optical branching component: A passive optical component with three or more ports that shares optical power among its ports in a p
25、redetermined fashion, without any amplification, switching or other active modulation. 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: CVD Chemical Vapour Deposition FBT Fused Biconic Taper FHD Flame Hydrolysis Deposition FIT Failures In Time (number o
26、f device failures in 109device hours) OLT Optical Line Termination ONU Optical Network Unit PON Passive Optical Network 5 Conventions None. 6 General information Optical branching components provide a method for splitting optical signals between M input and N output ports (see Figure 6-1); optical b
27、ranching components are required when an optical signal has to be split into two or more fibre lines or when several signals coming from different fibre lines have to be mixed in a single fibre line; in general, optical branching components are dividers/combiners of transit signals. Figure 6-1 MxN b
28、ranching component (schematic) In a point-to-multipoint distribution architecture, optical branching components are used to connect an OLT located at a central office to several ONUs located in outside plant or on subscriber premises. 7 Types and configurations Optical branching components can be cl
29、assified as one or more of the following: a) star branching devices: A branching device typically balanced; possessing more than four ports; ITU-T Rec. L.37 (02/2007) 3 b) tree branching devices: A branching device with a single optical input distributed among several outputs, or vice versa. Optical
30、 branching components can be designed to operate at a single wavelength (e.g., 1310 or 1550 nm), to be wavelength flat (e.g., insensitive to wavelength variations within a single window) or to be wavelength independent (e.g., insensitive to wavelength variations within both the second and third wind
31、ows, 1260-1360 nm and 1450-1600 nm, or 1260-1360 nm and 1450-1660 nm). 8 Technological aspects There are several methods used to manufacture optical branching components, and they can be grouped into the following classes: a) fusion technology: This technology has proved to be simple, versatile and
32、effective, allowing the industrial implementation of several kinds of branching devices for a variety of applications. With the fused biconic taper (FBT) method, bare or etched fibres are brought into contact, stretched, possibly twisted, and fused so that evanescent mode coupling occurs along the i
33、nteraction length; b) planar optics technology: Planar waveguide branching devices are made by photolithographic technology, using parallel processing techniques. To produce the refractive index profile, ions are diffused into a substrate such as glass, semiconductor (silicon), LiNbO3or polymer. Alt
34、ernatively, doped silica glass is fabricated by chemical vapour deposition (CVD) or by flame hydrolysis deposition (FHD) and consolidation. The optical profile and the geometrical properties of the guiding structure are defined by photolithographic masking techniques followed by etching; c) polishin
35、g technology: In order to position fibre cores close enough to allow the overlap of the evanescent fields (coupling conditions), the fibre cladding is removed to within a few microns of the core. This controlled removal of the cladding is achieved by mechanical abrasion (polishing). 9 Optical parame
36、ters and performance Optical branching components for PONs are characterized by several parameters, the most important of which are the following: insertion loss; reflectance; optical wavelength range; polarization-dependent loss. directivity; uniformity. These parameters are defined in Amendment 1
37、to ITU-T G.671. 10 Application environments and test methods for optical branching components The following describes application environments, and performance and reliability test methods for optical branching components for PONs. During or after each test, the device should still meet loss criteri
38、a according to Amendment 1 to ITU-T G.671. Insertion loss measurements should be executed at least at 1310 and 1550 nm, but also at 1625 nm if agreed between user and supplier. 4 ITU-T Rec. L.37 (02/2007) 10.1 Application environments The recommended temperature range in which the performance should
39、 be guaranteed is from 40 C up to at least +75 C (for applications in passive nodes). The recommended humidity range in which the performance should be guaranteed is from 5% to 95% RH. 10.2 Performance and reliability test methods 10.2.1 Basic performance requirements These requirements apply to all
40、 splitters to assess their performance. 10.2.1.1 Vibration The test procedure should be in accordance with IEC 61300, part 2-1, and insertion loss measurements are performed before and after this test. The test parameter values are as follows: Frequency range: 10-55 Hz. Sweep rate: to vary uniformly
41、 between 10 and 55 Hz and to return to 10 Hz in approximately 4 min. Endurance duration per axis: at least 20 minutes in each of three mutually perpendicular planes. Number of axes: 3. Vibration amplitude: 1.52 mm. 10.2.1.2 Impact The test procedure should be in accordance with IEC 61300, part 2-9,
42、and the insertion loss measurements are performed before and after this test. The test parameter values are as follows: Peak acceleration and duration: 500 g; 1 ms pulse duration. Number of impacts per direction: 5. Number of axes: 3 (two directions per axis). 10.2.1.3 Fibre retention The test proce
43、dure should be in accordance with IEC 61300, part 2-4, and the insertion loss measurements are performed before and after this test. The test parameter values are as follows: Magnitude of the load: 5 N for coated fibres (primary and secondary), 10 N for 4-fibre ribbon. Load rate: 400 m/s for coated
44、fibres until attaining the maximum load. Point of application of the tensile load: minimum 0.1 m from the end of the fibre. Duration of the test: 1 min while maintaining the load. 10.2.1.4 Fibre side pull The test procedure should be in accordance with IEC 61300, part 2-42, and the insertion loss me
45、asurements are performed before and after this test. The test parameter values are as follows: Magnitude of the load: 2.5 N for single fibre/5 N for ribbon fibre or loose tube. Angle of application to interface: 90. Duration of the load application: 5 s. Number of mutually perpendicular directions o
46、f load application: 2. Point of application of the load: 22 to 28 cm from the component housing. ITU-T Rec. L.37 (02/2007) 5 10.2.1.5 Temperature humidity cycle The test procedure should be in accordance with IEC 61300, part 2-48, and the insertion loss measurements are performed before, during and
47、after this test. The test parameter values are as follows (see Figure 10-1): Temperature range: 40 to +75 C. Humidity range: 10 to 80% RH. Thermal profile: from 2 to 32 C, maintain a constant relative humidity of 80 2%; from 32 to 75 C, maintain a constant humidity ratio from 80% RH at 32 C to 10% R
48、H at 75 C; below 2 C, humidity is uncontrolled. Minimum duration at extreme temperature: 1 hour. Temperature rate of change: 1 C/min. Number of cycles: 42 (8 h/cycle). Figure 10-1 Thermal profile of temperature humidity cycle test 10.2.1.6 Temperature humidity ageing The test procedure should be in
49、accordance with IEC 61300, part 2-19, and the insertion loss measurements are performed before and after this test. The test parameter values are as follows: Temperature: +75 C (or +85 C as an alternate condition). Relative humidity: 85%. Duration of exposure: 336 hours. 10.2.1.7 Water immersion The test procedure should be in accordance with IEC 61300, part 2-45, and the insertion loss measurements are performed before, during and after this
