1、ASD-STAN STANDARD NORME ASD-STAN ASD-STAN NORM prEN 4533-002 Edition P 2 April 2016 PUBLISHED BY THE AEROSPACE AND DEFENCE INDUSTRIES ASSOCIATION OF EUROPE - STANDARDIZATION Rue Montoyer 10 - 1000 Brussels - Tel. 32 2 775 8126 - Fax. 32 2 775 8131 - www.asd-stan.org ICS: Supersedes edition P 1 of Ap
2、ril 2005 and will supersede EN 4533-002:2006 Descriptors: ENGLISH VERSION Aerospace 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 Handb
3、uch Teil 002: Tests und Messungen This “Aerospace Series“ Prestandard has been drawn up under the responsibility of ASD-STAN (The AeroSpace and Defence Industries Association of Europe - Standardization). It is published for the needs of the European Aerospace Industry. It has been technically appro
4、ved by the experts of the concerned Domain following member comments. Subsequent to the 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 examinati
5、on and review by users and formal agreement of ASD-STAN, it will be submitted as a draft 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 leve
6、l by giving the EN the status of a national standard and by withdrawing any national standards conflicting with the EN. Edition approved for publication 1st April 2016 Comments should be sent within six months after the date of publication to ASD-STAN Electrical Domain Copyright 2016 by ASD-STAN prE
7、N 4533-002:2016 (E) 2 Contents Page Foreword 2 Introduction .3 1 Scope 4 2 Normative references 4 3 Fibre types 4 4 Test and measurement: key parameters .5 5 Test and measurement in single-mode systems . 10 6 Test and measurement in multi-mode systems 10 7 Testing network paths: reflectometry and fo
8、otprinting 20 8 General considerations for test and measurement in fibre optic systems 26 9 Practical testing techniques 29 10 Reporting arrangements 37 11 Techniques for system design 38 12 Appendix: Matrices . 40 Foreword This standard was reviewed by the Domain Technical Coordinator of ASD-STANs
9、Electrical Domain. After inquiries and votes carried out in accordance with the rules of ASD-STAN defined in ASD-STANs General Process Manual, this standard has received approval for Publication. prEN 4533-002:2016 (E) 3 Introduction a) The Handbook This handbook aims to provide general guidance for
10、 experts and non-experts alike in the area of designing, installing, and supporting 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 aspects of an optical harness life cycle, namel
11、y: Part 001: Termination methods and tools Part 002: Test and measurement Part 003: Looming and installation practices Part 004: Repair, maintenance, cleaning and inspection b) Background It is widely accepted in the aerospace industry that photonic technology significant advantages over conventiona
12、l 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). Significant weight savings can also be realized in comparison to electrical harnesses which ma
13、y require heavy screening. To date, the EMI issue has been the critical 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
14、/s regime in some cases, i.e. beyond the limits of electrical interconnect 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 sys
15、tems, as well as in sensing many of the physical phenomena on-board aircraft. 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 application
16、s, an aircraft fibre-optic system needs to operate in a hostile environment (e.g. temperature extremes, humidity, vibration, and contamination) and accommodate additional physical restrictions imposed by the airframe (e.g. harness attachments, tight bend radii requirements, and bulkhead connections)
17、. Until recently, optical harnessing technology and associated practices 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 sp
18、ecific hardware and support. These factors collectively carried a significant cost penalty (procurement and through-life costs), that often made an optical harness less competitive than an electrical equivalent. This situation is changing with the adoption of more standardized (telecoms type) fibre
19、types in aerospace cables and the availability of more ruggedized COTS components. These improved developments have been possible due to significant research collaboration between component and equipment manufacturers as well as the end use airframers. prEN 4533-002:2016 (E) 4 1 Scope This handbook
20、examines the requirements to enable accurate measurement of fibre optic links from start of life and during the life cycle of the system from installation and through-service. Part 2 will explain the issues associated with optical link measurement and provide techniques to address these issues. This
21、 document discusses the measurement of key parameters associated with the passive layer (i.e. transmission of light through an optical harness). It does not discuss systems tests e.g. bit error rates. 2 Normative references The following documents, in whole or in part, are normatively referenced in
22、this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 2591-601, Aerospace series Elements of electrical and optical connection Test me
23、thods Part 601: Optical elements Insertion loss EN 4533-001, Aerospace series Fibre optic systems Handbook Part 001: Termination methods and tools EN 4533-003, Aerospace series Fibre optic systems Handbook Part 003: Looming and installation practices EN 4533-004, Aerospace series Fibre optic systems
24、 Handbook Part 004: Repair, maintenance, cleaning and inspection 3 Fibre types This section gives a brief summary of some of the different fibre types in use within the aerospace industry. Historically, large core, step index multimode fibres were the first to be used on aircraft. At the time of des
25、ign, these fibres enabled sufficient data bandwidth and the large core enabled ease of coupling (of light) into the fibre as well as ease of fibre alignment in connectors (also termed interconnects). Therefore in some current and legacy systems, fibre optic harnesses based on large core fibres can b
26、e found. Common larger core fibres include 200/280 m, 200/300 m and 100/140 m (where the notation indicates the core/cladding size). Improvements in bandwidth (mainly from reduced temporal dispersion), for multimode fibres is possible by using graded index fibres. In simple terms, the graded refract
27、ive index profile allows equalisation of different optical paths through a multimode fibre to reduce any pulse spreading in time (dispersion). These results in higher bandwidths compared to step index refractive index profiles. Early graded index fibres for aerospace included 100/140 m sized fibres.
28、 More recently, fibre sizes commonly used in the telecoms and datacomms fields have been utilised for aerospace. Multimode fibres of size 62,5/125 m and 50/125 m and with graded index profile are now being deployed for data transmission on both civil and military aircraft, fixed wind and rotary craf
29、t. Fibres are available with different bandwidths. Multimode fibres are designated by the OM identification (meaning optical multimode). OM1 describes 62,5/125 m fibre, OM2, OM3 and OM4 describe 50/125 m fibres of increasing bandwidth. Using these sizes of fibre (particularly with a 125 m outer diam
30、eter enables the use of volume production parts (e.g. ceramic alignment ferrules) from the telecoms industry. As will be discussed in this document, the issue of test and measurement in multimode systems is complicated by the light distribution in the fibre and also the relatively short length of in
31、stalled fibre which typically has several connector breaks in the harness path (e.g. connectors located at airframe production breaks). The light distribution launched into the fibre to make measurements is critically important for making consistent measurements in multimode systems. prEN 4533-002:2
32、016 (E) 5 Whilst most of the deployed fibre in aerospace is currently multimode, there is increasing interest in using singlemode fibre. Single-mode (sometimes called monomode fibres) are optical fibres designed to support only a single propagation mode per polarization direction for a given wavelen
33、gth. They usually have a relatively small core (with a diameter of only a few ms) and a small refractive index difference between core and cladding. The mode radius is typically a few microns. Singlemode fibres are often termed OS1 (for optical singlemode). There are also other types of singlemode f
34、ibre as OS2 and A2. The small core enables many benefits to be realised (e.g. higher bandwidth (minimal dispersion), wavelength multiplexing, novel sensor applications). However the smaller core makes the coupling and alignment more difficult at the source and at connectors (particularly in the hars
35、h aerospace environment with potential extremes of temperature and vibration). The issue of test and measurement in singlemode fibres is not as complicated as for multimode systems. This is principally because the light travels down the fibre in a predominant single mode or path. It should be rememb
36、ered that the optical fibres discussed above will be packaged in rugged cable form suitable for installation and performance on an airframe. More detail of cable constructions can be found in Part 001 of the EN 4533 standard. It is further noted that modern fibre optical cable designs are now utilis
37、ing bend tolerant optical fibres and a number of aerospace designs exist. These exhibit lower losses when bent to a small radius (A2 fibre). Test and measurement in glass fibre multimode systems will generally use LEDs or multimode VSCSELs as the test light source. Test and measurement in singlemode
38、 glass fibre systems will generally use semiconductor lasers or newer singlemode VCSEL light sources. The common transmission wavelengths used for glass multimode fibres are 850 nm (sometimes 1 300 nm). Glass singlemode systems generally use 1 550 or 1 300 nm transmission wavelength. For completenes
39、s it is noted that plastic optical fibre (POF) is being considered for some applications in aerospace. However at the present time, the TRL of this technology is much lower than for glass fibre (at least in an aerospace environment). POF is generally much larger than glass fibre e.g. with size 980/1
40、 000 m. This large core makes coupling and connector alignment much easier. However POF is much more lossy (higher attenuation) than glass fibre and works best with visible transmission wavelengths (typically in the 520 nm to 650 nm region). 4 Test and measurement: key parameters 4.1 Insertion Loss
41、Insertion loss is probably the most frequent measurement performed on a fibre optic component or link / harness during its life cycle. When an optical device, component or fibre section is inserted into an optical link, some of the optical power will be lost in the device (e.g. a splitter) or at opt
42、ical interfaces (e.g. at a connector or splice). Fibre sections will also introduce a loss albeit small (the attenuation at the common transmission wavelength for glass fibre is very low). Some of the optical power will be lost due to non-perfect interfaces e.g. reflective surfaces or scattering. An
43、other factor is misalignment in connectors. Such misalignment can be lateral, axial or angular. Contamination will also impact on the insertion loss (dirty connectors will have higher loss than clean connectors). The insertion loss (or attenuation) is usually specified in decibels, calculated as 10
44、times the logarithm of base 10 of the ratio of output and input powers. For fibre connectors, for example, it is often of the order of 0,2 dB. High-quality fusion splices may reach values like 0,02 dB. I.L = 10log10 (Pin/Pout) e.g. for a transmission of 90 % (0,9), the insertion loss would be 0,46 d
45、B. prEN 4533-002:2016 (E) 6 4.1.1 Importance of low insertion loss Clearly for efficient light transmission, a low insertion loss is desired. This means that only a small amount of light will be lost at the component or link under test. The system power budget will generally dictate how much power n
46、eeds to be transmitted through the link from source to receiver. The difference between the source power and the minimum required receiver power will give a power budget figure. The total insertion loss of the components must not exceed this value. It is also useful to have a safety margin to allow
47、for system degradation and ageing. A 3 dB ageing margin is typical for aircraft links. 4.1.2 Measurement techniques Various methods exist for measuring insertion loss depending on the type of component and whether it is connectorised. These are detailed in the EN standard EN 2591-601. In terms of eq
48、uipment, insertion loss can be measured with a fibre optic light source and power meter arrangement or more sophisticated equipment such as an OTDR or OFBR (discussed later in 6.1 and 6.2) can also be used. An important point to emphasise particularly for multimode systems is that the insertion loss
49、 measured for a component, fibre section or complete link will depend on the light distribution in the component (and the launch light distribution from the source). This means that if two different light sources (e.g. from different manufacturers) are used to test the insertion loss it is possible that different insertion loss values will be obtained. This makes it difficult to design systems using test data on components alone especially where the metho
