1、Designation: E1614 94 (Reapproved 2013)Standard Guide forProcedure for Measuring Ionizing Radiation-InducedAttenuation in Silica-Based Optical Fibers and Cables forUse in Remote Fiber-Optic Spectroscopy andBroadband Systems1This standard is issued under the fixed designation E1614; the number immedi
2、ately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This g
3、uide covers a method for measuring the real time,in situ radiation-induced spectral attenuation of multimode,step index, silica optical fibers transmitting unpolarized light.This procedure specifically addresses steady-state ionizingradiation (that is, alpha, beta, gamma, protons, etc.) withappropri
4、ate changes in dosimetry, and shielding considerations,depending upon the irradiation source.1.2 This test procedure is not intended to test the balance ofthe optical and non-optical components of an optical fiber-based system, but may be modified to test other components ina continuous irradiation
5、environment.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to es
6、tablish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 Test or inspection requirements include the followingreferences:2.2 Military Standard:2MIL-STD-2196-(SH) Glossary of Fiber Optic Terms2.3 EIA Standards:
7、3EIA-455-57 Optical Fiber End Preparation and ExaminationEIA-455-64 Procedure for Measuring Radiation-InducedAt-tenuation in Optical Fibers and CablesEIA-455-78A-90 Spectral Attenuation Cutback Measure-ment for Single-Mode Optical Fibers3. Terminology3.1 Definitions:3.1.1 Refer to MIL-STD-2196 for t
8、he definition of termsused in this guide.4. Significance and Use4.1 Ionizing environments will affect the performance ofoptical fibers/cables being used to transmit spectroscopicinformation from a remote location. Determination of the typeand magnitude of the spectral attenuation or interferences, o
9、rboth, produced by the ionizing radiation in the fiber isnecessary for evaluating the performance of an optical fibersensor system.4.2 The results of the test can be utilized as a selectioncriteria for optical fibers used in optical fiber spectroscopicsensor systems.NOTE 1The attenuation of optical
10、fibers generally increases whenexposed to ionizing radiation. This is due primarily to the trapping ofradiolytic electrons and holes at defect sites in the optical materials, thatis, the formation of color centers. The depopulation of these color centersby thermal and/or optical (photobleaching) pro
11、cesses, or both, causesrecovery, usually resulting in a decrease in radiation-induced attenuation.Recovery of the attenuation after irradiation depends on many variables,including the temperature of the test sample, the composition of thesample, the spectrum and type of radiation employed, the total
12、 doseapplied to the test sample, the light level used to measure the attenuation,and the operating spectrum. Under some continuous conditions, recoveryis never complete.1This guide is under the jurisdiction of ASTM Committee E13 on MolecularSpectroscopy and Separation Science and is the direct respo
13、nsibility of Subcom-mittee E13.09 on Fiber Optics, Waveguides, and Optical Sensors.Current edition approved Jan. 1, 2013. Published January 2013. Originallyapproved in 1994. Last previous edition approved in 2004 as E1614 94 (2004).DOI: 10.1520/E1614-94R13.2Available from Standardization Documents O
14、rder Desk, Bldg. 4 Section D, 700Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS.Available from Stan-dardization Documents Order Desk, DODSSP, Bldg. 4, Section D, 700 RobbinsAve., Philadelphia, PA 19111-5098, http:/dodssp.daps.dla.mil.3Available from Electronic Industries Alliance (EIA), 2500
15、 Wilson Blvd.,Arlington, VA 22201, http:/www.ecaus.org/eia.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15. Apparatus5.1 The test schematic is shown in Fig. 1. The following listidentifies the equipment necessary to accomplish this
16、testprocedure.5.2 Light SourceThe light source should be chosen so thatthe spectral region of interest is provided. Lamps or globars, orboth, may be used for analysis as long as they satisfy thepower, stability, and system requirements defined. In general,the silica fibers should be evaluated from 3
17、50 to 2100 nm,therefore, more than one light source or multiple testing, orboth, may be necessary.5.3 ShutterIn order to determine the background stability,the light will have to be blocked from entering the optical fiberby a shutter.5.4 Focusing/Collection OpticsA number of optical ele-ments may be
18、 needed for the launch and collection of lightradiation into/from the test optical fiber and other instrumen-tation (light source, spectrometer, detector). The minimalrequirement for these elements shall be that the numericalaperture of the adjacent components are matched for efficientcoupling.5.5 M
19、ode StripperHigh-order cladding modes must beattenuated by mode stripping, and mode stripping should occurprior to and after the radiation chamber, especially if the fiberlength is shorter than that specified in this guide. If it is foundthat the coating material effectively strips the cladding mode
20、sfrom the optical fiber, then a mode stripper is not necessary.5.6 Light Radiation FilteringFilters may be necessary torestrict unwanted regions of the light spectrum. They may beneeded to avoid saturation or nonlinearities of the detector andrecording instrumentation by transient light sources (Cer
21、enkovor other luminescence phenomena), or due to wide spectralpower variances with the output of the broadband sources.5.7 Optical SplitterAn optical splitter or fiber optic cou-pler shall divert some portion of the input light to a referencedetector for monitoring the stability of the light source.
22、5.8 Optical InterconnectionsThe input and output ends ofthe optical fiber shall have a stabilized optical interconnection,such as a clamp, connector, splice, or weld. During anattenuation measurement, the interconnection shall not bechanged or adjusted. If possible, the optical interconnectionsshoul
23、d not be within the irradiation region.5.9 Wavelength DemultiplexorA means of separating thespectral information must be used at the detector end of thesystem so that multiple wavelengths can be simultaneouslyevaluated (that is, grating, prism, Acousto-optic tunable filter,etc.).5.10 Optical Detecti
24、onThe optical detection system shallbe wavelength calibrated in accordance with the manufactur-ers recommended procedure utilizing standard spectral linesources. The calibration and spectral response of the detectionsystems should be documented.5.10.1 Sample DetectorAn optical detector that is linea
25、rand stable over the range of intensities that are encounteredshall be used. The method employed must be able to evaluatea wide spectral range rapidly (that is, 500 ms). The primaryrequirement of the detector is that the spectral detectivitycorresponds to the spectral transmission of the light sourc
26、e/fiber system and that a spectral resolution of 610 nm isattainable.5.10.2 Reference DetectorThe reference detector is usedfor light source stability measurements for the wavelengthrange of interest. The reference detection system should have asimilar response to the sample detection system. If an
27、opticalfiber splitter is used for the reference arm of the detectionscheme, then the detection system must be able to accept theoutput from an optical fiber. If the detection scheme canNOTE 1If a shuttered source is not used, the test engineer must account for the placement and extraction of the tes
28、t sample in the irradiator.FIG. 1 Schematic Instrumentation DiagramE1614 94 (2013)2monitor the output of two optical fibers (for example, a CCDdetector with an imaging spectrometer), it may be advanta-geous to package the reference fiber and sample fiber in thesame termination so that a single detec
29、tion system can simul-taneously monitor both outputs. This configuration is optional.5.11 Recorder SystemA suitable data recording system,such as a computer data acquisition system, is recommendeddue to the large spectral data sets necessary.5.12 Ambient Light ShieldingThe irradiated fiber lengthsha
30、ll be shielded from ambient light to prevent photobleachingby any external light sources and to avoid baseline shifts in thezero light level. An absorbing fiber coating or jacket can beused as the light shield, provided that it has been demonstratedto block ambient light and that its influence on th
31、e dose withinthe fiber core has been taken into consideration.5.13 Irradiation SystemThe irradiation system shouldhave the following characteristics:5.13.1 Dose RateACo60or other irradiation source shallbe used to deliver radiation at dose rates ranging from 10 to100 Gy(SiO2)/min (see Note 3).5.13.2
32、 Radiation EnergyThe energy of the gamma raysemitted by the source should be greater than 500 KeV to avoidserious complications with the rapid variations in total dose asa function of depth within the test sample.5.13.3 Radiation DosimeterDosimetry traceable to na-tional standards shall be used. Dos
33、e should be measured in thesame uniform geometry as the actual fiber core material toensure that dose-build-up effects are comparable to the fibercore and the dosimeter. The dose should be expressed in graycalculated for the core material.5.14 Temperature-Controlled ContainerUnless otherwisespecifie
34、d, the temperature-controlled container shall have thecapability of maintaining the specified temperature to 23 62C. The temperature of the sample/container should bemonitored prior to and during the test.NOTE 2The wavelength range indicated in 5.2 is the largest range thatshould be tested if the eq
35、uipment (that is, sources, detectors) is available.Silica glass will transmit from 190 to 3300 nm, but this range is notpractical for optical fiber applications due to the high attenuations in theultraviolet (UV) and near-infrared (NIR). The widest wavelength rangethat can be tested that satisfies t
36、he requirements of the test procedureshould be evaluated if the equipment is available.NOTE 3The average total dose should be expressed in Gray (Gy,where 1 Gy = 100 rads) to a precision of 65 %, traceable to nationalstandards. For typical silica core fibers, dose should be expressed in Gycalculated
37、for SiO2, that is, Gy(SiO2).6. Hazards6.1 Carefully trained and qualified personnel must be usedto perform this test procedure since radiation (both ionizingand optical), as well as electrical, hazards will be present.7. Test Specimens7.1 Sample Optical FiberThe sample fiber shall be apreviously uni
38、rradiated, silica-based, step-index, multimodefiber. The fiber shall be long enough to allow coupling betweenthe optical instrumentation outside the radiation chamber andthe sample area, along with an irradiated test length of 50 6 5m.7.2 The test specimen may be an optical fiber cableassembly, as l
39、ong as the cable contains the above specifiedfiber for analysis as in 7.1.7.3 Test ReelThe test reel shall not act as a shield for theradiation used in this test or, alternatively, the dose must bemeasured in a geometry duplicating the effects of reel attenu-ation. The diameter of the test reel and
40、the winding tension ofthe fiber can influence the observed radiation performance,therefore, the fiber should be loosely wound on a reel diameterexceeding 10 cm.7.4 Fiber End PreparationThe test sample shall be pre-pared such that its end faces are smooth and perpendicular tothe fiber axis, in accord
41、ance with EIA-455-57.8. Radiation Calibration and Stability8.1 Calibration of Radiation SourceCalibration of theradiation source for dose uniformity and dose level shall bemade at the location of the device under test (DUT) and at aminimum of four locations, prior to introduction of fiber testsample
42、s. The variation in dose across the fiber reel volumeshall not exceed 610 %. If thermoluminescent detectors(TLDs) are used for the measurements, four TLDs shall beused to sample dose distribution at each location. The readingsfrom the multiple TLDs at each location shall be averaged tominimize dose
43、uncertainties. To maintain the highest possibleaccuracy in dose measurements, the TLDs shall not be usedmore than once. TLDs should be used only in the dose regionwhere they maintain a linear response.8.2 The total dose shall be measured with an irradiation timeequal to subsequent fiber measurements
44、.Alternatively, the doserate may be measured and the total dose calculated from theproduct of the dose rate and irradiation time. Source transittime (from off-to-on and on-to-off positions) shall be less than5 % of the irradiation time.8.3 Stability of Radiation SourceThe dose rate must beconstant f
45、or at least 95 % of the shortest irradiation time ofinterest. The dose variation provided across the fiber sampleshall not exceed 610 %.9. Procedure9.1 Place the reel of fiber or cable in the attenuation testsetup as shown in Fig. 1. Couple the light source into the endof the test fiber, and positio
46、n the light exiting the fiber forcollection by the spectrograph or other appropriate detectionsystem.9.2 Temperature StabilityStabilize the test sample in thetemperature chamber at 23 6 2C prior to proceeding.9.3 System StabilityVerify the stability of the total systemunder illumination conditions p
47、rior to any measurement for atime exceeding that required for determination of Pb() andP(t, ) (see 10.1) during the duration of the attenuationmeasurement.9.4 For stability measurements, the system output need onlybe evaluated in 50-nm increments over the useful range of thedetection system. At each
48、 wavelength, convert the maximumfluctuation in the observed system output during that time, intoE1614 94 (2013)3an apparent change in optical attenuation due to system noise,n(t, ), using Eq 1. Any subsequent measurement must berejected if the observed A(t, ) (defined in 10.1) does notexceed 10 n(t,
49、 ).9.5 Baseline StabilityAlso verify the baseline stability fora time comparable to the attenuation measurement with thelight source blocked off. Record the baseline output power, Pn,for the same wavelengths monitored for system stability. Anysubsequent measurement must be rejected if the transmittedpower out of the irradiated fiber is not greater than 10 Pn.9.6 Fig. 2 depicts the values described in 9.3-9.5.9.7 If the initial attenuation spectrum of the fiber is known,either from the fiber manufacturer or from prior testing, then
