ASD-STAN PREN 3745-202-2016 Aerospace series Fibres and cables optical aircraft use Test methods Part 202 Fibre dimensions (Edition P 4).pdf

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1、ASD-STAN STANDARD NORME ASD-STAN ASD-STAN NORM prEN 3745-202 Edition P 4 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: 49.060 Supersedes edition P

2、3 of May 1999 and will supersede EN 3745-202:2005 Descriptors: ENGLISH VERSION Aerospace series Fibres and cables, optical, aircraft use Test methods Part 202: Fibre dimensions Srie arospatiale Fibres et cbles optiques usage aronautique Mthodes dessais Partie 202 : Dimensions de la fibre Luft- und R

3、aumfahrt Faseroptische Leitungen fr Luftfahrzeuge Prfverfahren Teil 202: Faserabmessungen 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 Eu

4、ropean Aerospace Industry. It has been technically approved 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, wi

5、thout re-identification of the standard. After examination 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 nationa

6、l 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 standards conflicting with the EN. ASD-STAN Technical Committee approves that: “This document is published by ASD-STAN for the needs of the European Aerospace

7、Industry. The use of this standard is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefrom, is the sole responsibility of the user.” ASD-STAN reviews each standard and technical report at least every five years at which

8、 time it may be revised, reaffirmed, stabilized or cancelled. ASD-STAN invites you to send your written comments or any suggestions that may arise. All rights reserved. No parts of this publication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electroni

9、c, mechanical, photocopying, recording, or otherwise, without prior written permission of ASD-STAN. Order details: E-mail: salesasd-stan.org Web address: http:/www.asd-stan.org/ Edition approved for publication 1st April 2016 Comments should be sent within six months after the date of publication to

10、 ASD-STAN Electrical Domain Copyright 2016 ASD-STAN prEN 3745-202:2016 (E) 2 Contents Page Foreword 2 1 Scope 3 2 Normative references 3 3 Preparation of specimens . 3 4 Apparatus . 3 5 Method 3 Foreword This standard was reviewed by the Domain Technical Coordinator of ASD-STANs Electrical Domain. A

11、fter 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 3745-202:2016 (E) 3 1 Scope This standard specifies several methods for measuring the diameter of an optical fibre or c

12、able, the non-circularity and the concentricity of the fibre core/cladding on an optical fibre. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest e

13、dition of the referenced document (including any amendments) applies. EN 2591-100, Aerospace series Elements of electrical and optical connection Test methods Part 100: General EN 3745-100, Aerospace series Fibres and cables, optical, aircraft use Test methods Part 100: General 3 Preparation of spec

14、imens 3.1 The specimen shall comprise a length of the optical fibre or cable to be measured. The fibre ends shall be prepared in accordance with EN 2591-100. The length of specimen shall be (3 0,5) m unless otherwise specified in the product standard. lf not yet at standard test conditions, the spec

15、imens shall be subjected to standard test conditions and stabilized at these conditions for 24 h as defined in EN 3745-100. 3.2 The following detail shall be specified if not already included in the product standard: type of fibre/cable from which the specimen was taken. 4 Apparatus For method B, th

16、e Light Launch System used shall be as specified in EN 2591-100 with an angular size 110 % of the fibre numerical aperture and a spot size 110 % of fibre core diameter. 5 Method 5.1 Method A: Refracted near field 5.1.1 Object The refracted near-field measurement is straightforward, accurate and meas

17、ures directly the refractive index variation the fibre (core and cladding). The measurement is capable of good resolution and can be calibrated to give absolute values of refractive indexes. It can be used to obtain profiles of both single-mode and multimode fibre. 5.1.2 Test apparatus A schematic d

18、iagram of the test apparatus is shown in Figures 1 and 2. 5.1.2.1 Source A stable laser giving a few milliwatts of power in the TEM00 mode is required. prEN 3745-202:2016 (E) 4 A HeNe laser, which has a wavelength of 633 nm, may be used, but a correction factor must be applied to the results for ext

19、rapolation at different wavelengths. It shall be noted that measurement at 633 nm may not give complete information at longer wavelengths; in particular non-uniform fibre doping can affect the correction. A quarter-wave plate is introduced to change the beam from linear to circular polarization beca

20、use the reflectivity of light at an air-glass interface is strongly angle and polarization dependent. A pinhole placed at the focus of lens 1 acts as a spatial filter. 5.1.2.2 Launch optics The launch optics, which are arranged to overfill the NA of the fibre, brings a beam of light to a focus on th

21、e flat end of the fibre. The optical axis of the beam of light should be within 1 of the axis of the fibre. The resolution of the equipment is determined by the size of the focused spot, which should be as small as possible in order to maximize the resolution, for example less than 1,5 m. The equipm

22、ent enables to focused spot to be scanned across the fibre diameter. 5.1.2.3 Liquid cell The liquid in the liquid cell shall have a refractive index slightly higher than that of the fibre cladding. 5.1.2.4 Sensing The refracted light is collected and brought to the detector in any convenient manner

23、provided that all the refracted light is collected. By calculation, the required size of disc and its position along the central axis can be determined. 5.1.3 Sample preparation A length of fibre of about 1 m is required. All fibre coating shall be removed from the section of fibre immersed in the l

24、iquid cell. The fibre ends shall be clean, smooth and perpendicular to the fibre axis. 5.1.4 Procedure Refer to the schematic diagram of the test apparatus (Figure 2). 5.1.4.1 Fibre index profile plot The launch end of the fibre to be measured is immersed in a liquid cell hose refractive index is sl

25、ightly higher than that of the fibre cladding. The fibre is back illuminated by light from a tungsten lamp. Lenses 2 and 3 produce a focused image of the fibre. The position of lens 3 is adjusted to centre and focus the fibre image, and the laser beam is simultaneously centred and focused on the fib

26、re. The disc is centred on the output cone. For multimode fibre, the disc is positioned on the optical axis to just block the leaky mode. For single-mode fibre, the disc is positioned to give optimum resolution. Refracted modes passing the disc are collected and focused onto a photodiode. The focuse

27、d laser spot is traversed across the fibre end and a plot of fibre refractive index variation is directly obtained. prEN 3745-202:2016 (E) 5 5.1.4.2 Equipment calibration The equipment is calibrated with the fibre removed from the liquid cell. During the measurement the angle of the cone of light va

28、ries according to the refractive index seen at the entry point to the fibre (hence the change of power passing the disc). With the fibre removed and the liquid index and cell thickness known, this change in angle can be simulated by translating the disc along the optic axis. By moving the disc to a

29、number of predetermined positions the profile can be scaled is terms of relative index. Absolute indices, i.e. n1 and n2, can only be found in the cladding index or the liquid index, at the measurement wavelength and temperature is known accurately. 5.1.4.3 Results The following details shall be pre

30、sented: test arrangement and wavelength correction procedure; relative humidity and ambient temperature; fibre identification. Depending on specification requirement: profile through core and cladding centres calibrated for a given wavelength; profile along the core major and minor axes calibrated f

31、or a given wavelength; profiles along the cladding major and minor axes calibrated for a given wavelength. By the raster scan of the cross-section of the profile, the following quantities may be calculated: diameter of core; diameter of cladding; concentricity error core/cladding; non-circularity of

32、 core; non-circularity of cladding; maximum theoretical numerical aperture; index difference; relative index difference; indication of accuracy and reproducibility. 5.2 Method B: Near field light distribution 5.2.1 Object The following test is for incoming and/or outgoing inspection. Imaging is made

33、 on a cross section at the end of the fibre under test. The image is magnified by an output optics, for example microscope and various kinds of sensors can be used (direct examination, photographic camera, digital video analyzer, scanning detector, etc.). prEN 3745-202:2016 (E) 6 5.2.2 Sample prepar

34、ation The sample shall be a short length of the optical fibre to be measured. This length shall be noted. The fibre ends shall be clean, smooth and perpendicular to the fibre axis. 5.2.3 Apparatus 5.2.3.1 Light source The core illumination source shall be incoherent, adjustable in intensity and the

35、type shall be noted. A second light source can be used to illuminate the fibre for cladding measurement purposes. The light source selected shall be stable for the required period of measurement. 5.2.3.2 Detection systems Different detection systems can be used depending on the type of measurement t

36、o be done (visual inspection, photography, calculation on the complete pattern). 5.2.3.2.1 Microscope An inverted metallurgical microscope or a biological microscope with a resolution near the diffraction limit shall be used (for example it should have a calibrated magnification of up to 600 x and b

37、e equipped with the filar micrometre). 5.2.3.2.2 Microscope with a photographic camera The microscope described in 5.2.3.2.1 may be equipped with a camera for micro photography. A suitable scale shall be used to calibrate the dimensions in the photograph. 5.2.3.2.3 Video analyzer The microscope desc

38、ribed in 5.2.3.2.1 may be equipped with a TV camera. The output signal of the camera can be sent to a TV monitor for visual inspection or to a video analyzer in order to record the complete output near of the fibre. 5.2.3.2.4 Scanning detector The TV camera described in 5.2.3.2.3 can be replaced by

39、a pinhole photodetector, to make one or several scans of the fibre output near field. The signal of the detector is sent to a XY recorder. 5.2.4 Procedure a) The end of the sample from which the image will be produced shall be prepared and so set as to make the end face perpendicular to the axis of

40、the sample. b) The numerical aperture and hence the resolving power of the objective lens shall be compatible with the measuring accuracy required. The magnification shall be selected to be compatible with the fibre size and the field of view. c) The light source shall be attached to the other end o

41、f the sample, which may be prepared in the same way as the first end, and adjusted so that the fibre end image will be substantially free of any missing or unclear part. If necessary, index matching fluid shall be used couple the optical power between source and sample. prEN 3745-202:2016 (E) 7 5.2.

42、4.1 Microscope technique with visual inspection a) The microscope shall be calibrated by measuring the length of an object of already known dimensions. b) The parameters of the sample to be measured may be determined by means of the filar micrometre and the known calibration. The minimum and maximum

43、 diameter shall be measured by rotating the image or the scale. 5.2.4.2 Microscope technique with photography a) The intensity of the front and back illumination, the shutter speed, f” stop and a film shall be selected to obtain a clear photograph, for example clearly showing the boundary between co

44、re and cladding. b) The overall image magnification shall be determined by photographing a scale of known calibration such as a stage micrometre. c) The size of the photographic image shall be more than 30 mm xx30 mm the parameter to be measured shall be determined from the size of the image and the

45、 magnification. d) When using a scale as described in 5.2.3.2.2, a transparent scale be placed upon the photographs and judged. 5.2.4.3 Microscope technique with a video analyzer a) The output filed of the microscope is processed with a digital video analyzer controlled by a computer, such as a scan

46、ning vidicon, charge coupled device (CCD) or other pattern intensity recognition device. b) The complete image is monitored and the line being processed is indicated, for example by a cursor. c) The boundaries are found by contrast level and referenced to a standard grating to give the geometrical p

47、arameters to be measured. 5.2.4.4 Microscope technique with a pinhole scanning detector a) Focus a magnified image of the sample core onto a plane. b) Determine the intensity of the magnified near filed patterns. As examples, any of the following techniques may be used: 1) scanning detector with pin

48、hole; 2) scanning mirror with fixed pinhole aperture detector. c) Record the intensity as a function of detector position. d) Use a phase-locked amplifier system (or equivalent apparatus) to amplify the low level signal. e) Scan fibre core image or pinhole detector by mean of a stepping motor transl

49、ation stage or a scanning mirror. f) Record intensity (signal) a signal a function of position of the core diameter. g) The microscope shall be calibrated by measuring the length of an object of already known dimensions. prEN 3745-202:2016 (E) 8 5.2.5 Documentation The following data shall be presented: fibre identification; number of samples; relative humidity and ambient temperature; description of apparatus; magnification; parameter