1、AECMA STANDARD NORME AECMA AECMA NORM prEN 4533-002 Edition P 1 April 2005 PUBLISHED BY THE EUROPEAN ASSOCIATION OF AEROSPACE INDUSTRIES - STANDARDIZATION Gulledelle 94 - B-1200 Brussels - Tel. + 32 2 775 8110 - Fax. + 32 2 775 8111 - www.aecma-stan.orgICS: 49.060 Descriptors: ENGLISH VERSION Aerosp
2、ace series Fibre optic systems Handbook Part 002: Test and measurement Srie arospatiale Systmes des fibres optiques Manuel dutilisation Partie 002 : Essais et mesures Luft- und Raumfahrt Faseroptische Systemtechnik Handbuch Teil 002: Tests und Messungen This “Aerospace Series“ Prestandard has been d
3、rawn up under the responsibility of AECMA-STAN (The European Association of Aerospace Industries - Standardization). It is published for the needs of the European Aerospace Industry. It has been technically approved by the experts of the concerned Domain following member comments. Subsequent to the
4、publication of this Prestandard, the technical content shall not be changed to an extent that interchangeability is affected, physically or functionally, without re-identification of the standard. After examination and review by users and formal agreement of AECMA-STAN, it will be submitted as a dra
5、ft European Standard (prEN) to CEN (European Committee for Standardization) for formal vote and transformation to full European Standard (EN). The CEN national members have then to implement the EN at national level by giving the EN the status of a national standard and by withdrawing any national s
6、tandards conflicting with the EN. Edition approved for publication 30 April 2005 Comments should be sent within six months after the date of publication to AECMA-STAN Electrical Domain Copyright 2005 by AECMA-STAN Copyright Association Europeene des Constructeurs de Materiel Aerospatial Provided by
7、IHS under license with AECMANot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Page 2 prEN 4533-002:2005Foreword This standard was reviewed by the Domain Technical Coordinator of AECMA-STANs Electrical Domain. After inquiries and votes carried out in accordance with t
8、he rules of AECMA-STAN defined in AECMA-STANs General Process Manual, this standard has received approval for Publication. Contents Page Foreword 3 1 Scope 4 2 Normative references. 4 3 Problem areas and limitations. 4 3.1 The problem of testing avionic, multi-mode fibre installations . 4 3.2 Limita
9、tions of current insertion loss prediction and measurement techniques 5 3.3 The way forward. 6 4 Techniques for system design 7 4.1 General 7 4.2 Interpretation of component data sheets 7 4.3 Computer modelling 8 4.4 Matrices 9 5 Practical testing techniques. 12 5.1 General 12 5.2 Launch conditionin
10、g of test sources . 12 5.3 Test configurations. 19 5.4 Detector characteristics 24 5.5 Testing networks. 25 5.6 Network testing OTDRs 25 6 Reporting arrangements. 27 Bibliography. 28 Copyright Association Europeene des Constructeurs de Materiel Aerospatial Provided by IHS under license with AECMANot
11、 for ResaleNo reproduction or networking permitted without license from IHS-,-,-Page 3 prEN 4533-002:2005Foreword a) The handbook The handbook draws on the work of the Fibre-Optic Harness Study, part sponsored by the United Kingdoms Department of Trade and Industry, plus other relevant sources. It a
12、ims to provide general guidance for experts and non-experts alike in the area of designing, installing, and supporting multi-mode fibre-optic systems on aircraft. Where appropriate more detailed sources of information are referenced throughout the text. It is arranged in 4 parts, which reflect key a
13、spects of an optical harness life cycle, namely: Part 001: Termination methods and tools Part 002: Test and measurement Part 003: Looming and installation practices Part 004: Repair, maintenance and inspection b) Background It is widely accepted in the aerospace industry that photonic technology off
14、ers a number of significant advantages over conventional electrical hardware. These include massive signal bandwidth capacity, electrical safety, and immunity of passive fibre-optic components to the problems associated with electromagnetic interference (EMI). To date, the latter has been the critic
15、al driver for airborne fibre-optic communications systems because of the growing use of non-metallic aerostructures. However, future avionic requirements are driving bandwidth specifications from 10s of Mbits/s into the multi-Gbits/s regime in some cases, i.e. beyond the limits of electrical interco
16、nnect technology. The properties of photonic technology can potentially be exploited to advantage in many avionic applications, such as video/sensor multiplexing, flight control signalling, electronic warfare, and entertainment systems, as well as in sensing many of the physical phenomena on-board a
17、ircraft. The basic optical interconnect fabric or optical harness is the key enabler for the successful introduction of optical technology onto commercial and military aircraft. Compared to the mature telecommunications applications, an aircraft fibre-optic system needs to operate in a hostile envir
18、onment (e.g. temperature extremes, humidity, vibrations, and contamination) and accommodate additional physical restrictions imposed by the airframe (e.g. harness attachments, tight bend radii requirements, and bulkhead connections). Until recently, optical harnessing technology and associated pract
19、ices were insufficiently developed to be applied without large safety margins. In addition, the international standards did not adequately cover many aspects of the life cycle. The lack of accepted standards thus lead to airframe specific hardware and support. These factors collectively carried a si
20、gnificant cost penalty (procurement and through-life costs), that often made an optical harness less competitive than an electrical equivalent. c) The fibre-optic harness study The Fibre-Optic Harness Study concentrated on developing techniques, guidelines, and standards associated with the through-
21、life support of current generation fibre-optic harnesses applied in civil and military airframes (fixed and rotary wing). Some aspects of optical system design were also investigated. This programme has been largely successful. Guidelines and standards based primarily on harness study work are begin
22、ning to emerge through a number of standards bodies. Because of the aspects covered in the handbook, European prime contractors are in a much better position to utilise and support available fibre optic technology. Copyright Association Europeene des Constructeurs de Materiel Aerospatial Provided by
23、 IHS under license with AECMANot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Page 4 prEN 4533-002:20051 Scope Insertion loss is the most frequent measurement performed on a fibre optic link. The avionic system designer will want to know or predict the insertion los
24、s of a link to determine its performance. Aircraft manufacturers will want to measure the insertion loss of harness components during assembly and before it is delivered to the customer to highlight faults and to provide a record of the performance of the harness at the beginning of its lifetime (fo
25、otprinting). The insertion loss will be measured at intervals during the lifetime of the aircraft to discover or identify faults and any gradual degradation in performance of the harness. There is, however, one problem. It is difficult to collect reliable and consistent measurements of the insertion
26、 loss on any multi-mode fibre optic harness where the distance between components is relatively small (less than 100 metres). The reason is that the insertion loss of a component or a harness depends on the power distribution of the light injected into it. This leads to very large differences in the
27、 measured value of the insertion loss 1 depending on the power distribution of the source used to make the measurement. This Part of EN 4533 will explain the measurement problem and the techniques used to overcome them in greater detail. 2 Normative references The following referenced documents are
28、indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 4533-004, Aerospace series Fibre optic systems Handbook Part 004: Repair, maintenance
29、 and inspection. 1)ARP5061, Guidelines for Testing and Support of Aerospace, Fiber Optic, Inter-Connect Systems. 2)3 Problem areas and limitations 3.1 The problem of testing avionic, multi-mode fibre installations The insertion loss of a fibre optic harness can be divided into two contributions. The
30、 first is the intrinsic loss of the harness caused by the properties of the materials such as the absorption of the silica of the fibre core. In the case of multi-mode fibres, this would include the variation in the loss of the component caused by changes in the power distribution. When discussing i
31、nsertion loss, the term power distribution will be used to describe the spatial and angular variation of the power across the fibres core rather than the temporal variation of the power along the length of the fibre. The second contribution is the additional loss that is introduced into the harness
32、from extrinsic losses such as misalignment errors in connectors and contamination. The insertion loss of components used in any fibre optic link depends on the power distribution of the light that passes through them. However, in some types of fibre harness, the shape of the power distribution does
33、not change as the light propagates through it and the component insertion loss is independent of its position within the harness. For example, the power distribution in single-mode fibre harnesses is fixed by the fibre parameters and the sources wavelength. Long-haul (a few kilometres between compon
34、ents), multi-mode fibre harnesses also effectively have a fixed power distribution because the distance between components is sufficient for the power distribution to reach an equilibrium state that depends only on the fibre parameters. The insertion loss of a long-haul multi-mode harness component
35、is defined by this equilibrium power distribution. 1) Published as AECMA Prestandard at the date of publication of this standard. 2) Published by: Society of Automotive Engineers (SAE), 400 Commonwealth Drive, Warrendale, PA 15096-0001. Copyright Association Europeene des Constructeurs de Materiel A
36、erospatial Provided by IHS under license with AECMANot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Page 5 prEN 4533-002:2005In contrast, short-haul multi-mode fibre harnesses (less than 200 metres), like those found in avionic systems, do not have sufficient distan
37、ce between components to allow the equilibrium power distribution to be attained. The power distribution entering a component within such a harness will now depend on the original power distribution from the source and changes to this distribution caused by the preceding components of the harness. T
38、here are two consequences of this power distribution dependent insertion loss: a) The insertion loss will depend on the source used to make the measurement. b) The insertion loss of a particular component will depend on its position within the harness. A way of reducing the variation in the measured
39、 insertion loss is to use modal filters on the source and power meter that alter the sources power distribution to a known or standard distribution. If all measurements are made with the same power distribution, the insertion loss value will be much more repeatable. Clause 5 will describe some of th
40、ese standard distributions and the various techniques that can be used to measure the insertion loss of harnesses and their components. 3.2 Limitations of current insertion loss prediction and measurement techniques 3.2.1 General This section outlines some of the limitations of the current design an
41、d measurement techniques that are used to determine the insertion loss of multi-mode fibre optic harnesses. (See Figure 1) 3.2.2 Harness design It is difficult for fibre optic harness designers to predict with accuracy the harness performance. It is unlikely that insertion loss values of commerciall
42、y available components will have been measured with a specific power distribution based on the parameters of any avionic fibre. The designer will therefore usually apply a pessimistic estimate for the insertion loss and obtain a much poorer prediction of the harness performance than may necessarily
43、be the case. This may not be important in simple point-to-point communication links between transmitter and receiver where there can be a very large power budget. However, it will be significant in more complex networks, where there are many connector breaks, or in networks that contain components s
44、uch as passive star-couplers where the power budget is likely to be much tighter. 3.2.3 Insertion loss measurements Many measurements that are made on short-haul fibre optic harnesses use no form of filtering on the output of the source to modify its power distribution. This may not be very importan
45、t if the measurements are for comparison with measurements made with exactly the same source. However, they cannot give reliable measurements of insertion loss that can be reproduced by another manufacturers set of test equipment. These measurements cannot be used to guarantee the performance of the
46、 harness to a customer because it is unlikely that the customer will be able to check the loss measurements without using the suppliers test equipment. The filtering used to modify the power distribution could also be inappropriate for an avionic application. For example, a power distribution more a
47、ppropriate for telecommunication links may be used which will underestimate the loss of components in an avionic harness. Additionally, the power distribution used to make the measurement should be changed for each fibre type that is used because the fibre parameters will be different. Copyright Ass
48、ociation Europeene des Constructeurs de Materiel Aerospatial Provided by IHS under license with AECMANot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Page 6 prEN 4533-002:2005a) A large area detector collects light from the fibre that is outside of the defined limit
49、s for the source b) The removal of an interface by not using a test lead between the lead under test and the power meter Figure 1 Causes of unrepresentative power measurements 3.2.4 Optical time domain reflectometry Optical time domain reflectometry (OTDR) is a single ended diagnostic/measurement technique that relies on the backscatter of light from imperfections and discontinuities in a fibre-optical system. It is used extensively in
