1、Designation: E1654 94 (Reapproved 2013)Standard Guide forMeasuring Ionizing Radiation-Induced Spectral Changes inOptical Fibers and Cables for Use in Remote RamanFiberOptic Spectroscopy1This standard is issued under the fixed designation E1654; the number immediately following the designation indica
2、tes 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 guide covers the method for measuring t
3、he realtime, in situ radiation-induced alterations to the Raman spectralsignal transmitted by a multimode, step index, silica opticalfiber. This guide specifically addresses steady-state ionizingradiation (that is, alpha, beta, gamma, protons, etc.) withappropriate changes in dosimetry, and shieldin
4、g considerations,depending upon the irradiation source.1.2 The test procedure given in this guide is not intended totest the other optical and non-optical components of an opticalfiber-based Raman sensor system, but may be modified to testother components in a continuous irradiation environment.1.3
5、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 establish appro-pr
6、iate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E1614 Guide for Procedure for Measuring IonizingRadiation-Induced Attenuation in Silica-Based OpticalFibers and Cables for Use in Remote Fiber-Optic Spe
7、c-troscopy andBroadband Systems2.2 EIA Standards:32.2.1 Test or inspection requirements include the followingreferences:EIA-455-57 Optical Fiber End Preparation and ExaminationEIA-455-64 Procedure for Measuring Radiation-InducedAttenuation in Optical Fibers and Cables2.3 Military Standards:4MIL-STD-
8、2196-(SH) Glossary of Fiber Optic Terms3. Terminology3.1 DefinitionsRefer to the following documents for thedefinition of terms used in this guide: MIL-STD-2196-(SH)and Guide E1614.4. Significance and Use4.1 Ionizing environments will affect the performance ofoptical fibers/cables being used to tran
9、smit spectroscopicinformation from a remote location. Determination of the typeand magnitude of the spectral variations or interferencesproduced by the ionizing radiation in the fiber, or both, isnecessary for evaluating the performance of an optical fibersensor system.4.2 The results of the test ca
10、n be utilized as a selectioncriteria for optical fibers used in optical fiber Raman spectro-scopic sensor systems.NOTE 1The attenuation of optical fibers generally increases whenthey are exposed to ionizing radiation.This is due primarily to the trappingof radiolytic electrons and holes at defect si
11、tes in the optical materials, thatis, the formation of color centers. The depopulation of these color centersby thermal or optical (photobleaching) processes, or both, causesrecovery, usually resulting in a decrease in radiationinduced attenuation.Recovery of the attenuation after irradiation depend
12、s on many variables,including the temperature of the test sample, the composition of thesample, the spectrum and type of radiation employed, the total doseapplied to the test sample, the light level used to measure the attenuation,and the operating spectrum. Under some continuous conditions, recover
13、yis never complete.5. Apparatus5.1 The test schematic is shown in Fig. 1. The following listidentifies the equipment necessary to accomplish this testprocedure.1This guide is under the jurisdiction of ASTM Committee E13 on MolecularSpectroscopy and Separation Science and is the direct responsibility
14、 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 version approved in 2004 as E1654 94 (2004).DOI: 10.1520/E1654-94R13.2For referenced ASTM standards, visit the ASTM websi
15、te, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from Electronic Industries Alliance (EIA), 2500 Wilson Blvd.,Arlington, VA 22201, http:/www.ecaus.org/
16、eia.4Available from Standardization Documents Order Desk, DODSSP, Bldg. 4,Section D, 700 Robbins Ave., Philadelphia, PA 19111-5098, http:/dodssp.daps.dla.mil.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15.2 Light SourceA laser sour
17、ce shall be used for theRaman analysis, and the wavelength must be chosen so that thefluorescent signals from the optical components (especially thespectral activator sample and optical fibers) are minimized, andso that the wavelength corresponds to the spectral sensitivity ofthe detection scheme. T
18、ypically, the wavelength range ex-ploited spans from 0.4 to 1.06 m. The laser source must havesufficient power to obtain the desired minimum signal-to-noiseratio (S/N) (see 10.3).5.3 Focusing/Collection OpticsA number of optical ele-ments are needed for the launch and collection of lightradiation in
19、to and from the optical fibers (interfacing, sampleand reference), and other instrumentation (light source,spectrograph, detector). The minimal requirement for theseelements shall be that the numerical aperture of the compo-nents are matched for efficient coupling. Optics may also benecessary to enh
20、ance the interaction of the input light with thespectral activator.FIG. 1 Test ConfigurationE1654 94 (2013)25.4 Interfacing Optical FiberThe primary requirement ofthe interfacing optical fiber is to provide the minimum powerto the activator sample at the proper wavelength(s). The fiberlength may be
21、adjusted so that the power requirements are met.5.5 Light Radiation FilteringIt is important that all neigh-boring laser lines are removed from the source beam prior tointeraction with the spectral activator. This can be accom-plished before or after the interfacing optical fiber. Placementof the fi
22、lter before the interfacing fiber will eliminate theneighboring laser lines, but any fluorescence and Ramanscattering due to the fiber or associated optics will be allowedto interact with the sample. Placement of the laser pass filterafter the interfacing fiber is preferable because it will eliminat
23、eany signals created within the fiber. If it is necessary to placethe filter before the interfacing fiber, then the fiber should bekept as short as possible (several metres).5.6 Spectral Activator SampleThe spectral activator usedmust demonstrate a strong, well-characterized Raman spectralsignal. Th
24、e sample may be either liquid, gas, or solid, depend-ing on the requirements of the optical fiber arrangement. It isrecommended that a liquid be used, since the Raman scatteringin the proposed configuration will launch similarly into thesample and reference fibers. Standard recommended samplesare: a
25、cetonitrile, benzene, and carbon tetrachloride.The sampleshould be contained in a standard spectroscopic rectangularsilica cuvette.5.7 Optical InterconnectionsThe input and output ends ofthe interfacing, reference, and sample optical fibers shall havea stabilized optical interconnection, such as a c
26、lamp, connector,splice, or weld. During an attenuation measurement, theinterconnection shall not be changed or adjusted.5.8 Irradiation SystemThe irradiation system should havethe following characteristics:5.8.1 Dose RateACo60or other irradiation source shall beused to deliver radiation at dose rate
27、s ranging from 10 to 100Gy (SiO2)/min. (See Note 2.)5.8.2 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.5.8.3 Radiation DosimeterDosim
28、etry traceable to Na-tional Standards shall be used. Dose should be measured in thesame uniform geometry as the actual fiber core material toensure that dose-buildup effects are comparable to the fibercore and the dosimeter. The dose should be expressed in graycalculated for the core material.5.9 Te
29、mperature-Controlled ContainerUnless otherwisespecified, 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.5.10 Collection Optics into Detection Sys
30、temAn appropri-ate collection configuration shall be used at the distal end of thesample and reference optical fibers. It is recommended that thecollection and focusing optic(s) is f/number matched to thenumerical aperture of the fibers and detection system.5.10.1 Raman analysis requires that the la
31、ser line be elimi-nated prior to detection.Alaser reject (or long pass filter) mustbe used at the entrance to the detection system. The filtershould pass all energy at 500 cm1below the laser excitationline. The filter should be placed between the optical elementsprior to the spectrometer.5.11 Optica
32、l DetectionAn optical detector with a knownresponse over the range of intensities that are encountered shallbe used. A typical system for Raman might include a single-point detector (that is, PMT) or a multichannel analyzer (thatis, CCD array). The spectrograph must exhibit fast scanningcapabilities
33、. As Fig. 1 indicates, it is recommended that asingle-imaging spectrometer be used with a 2D CCD detectorso that the output from the reference and sample fibers can beevaluated simultaneously. Two spectrometers operating simul-taneously may also be used.5.11.1 The optical detection system must be ca
34、pable ofobtaining the Raman spectrum from 500 to 3000 cm1from theexcitation frequency.5.12 Recorder SystemA suitable data recording, such as acomputer data acquisition system, is recommended.5.13 Ambient Light ShieldingThe irradiated fiber lengthshall be shielded from ambient light to prevent photob
35、leachingby 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 its influence on the dose within thefiber core has been taken into considera
36、tion.NOTE 2The average total dose should be expressed in gray (Gy, where1 Gy = 100 rads) to a precision of 65 %, traceable to national standards.For typical silica core fibers, dose should be expressed in gray calculatedfor SiO2, that is, Gy(SiO2).6. Hazards6.1 Carefully trained and qualified person
37、nel 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 unirradiated step-index, multimode fiber. The fibershall be long enough to have an
38、irradiated test length of 50 65 m and to allow coupling between the optical instrumentationoutside the radiation chamber and the sample area.7.2 The test specimen may be an optical-fiber cableassembly, as long as the cable contains at least one of thespecified fibers for analysis.7.3 Test ReelThe te
39、st 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 the winding tension ofthe fiber can influence the observed radiation performance,therefore, t
40、he fiber should be loosely wound on a reel diameterexceeding 10 cm.7.4 Fiber End PreparationPrepare the test sample suchthat its end faces are smooth and perpendicular to the fiber axis,in accordance with EIA-455-57.E1654 94 (2013)37.5 Reference FiberThe reference fiber shall have thesame requiremen
41、ts as the sample fiber. It should have similarcharacteristics, be packaged in the same configuration, andshould be used in an identical fashion as the sample fiberexcept for the radiation exposure.8. Radiation, Calibration, and Stability8.1 Calibration of Radiation SourceMake calibration ofthe radia
42、tion source for dose uniformity and dose level at thelocation of the device under test (DUT) and at a minimum offour other locations, prior to introduction of fiber test samples.The variation in dose across the fiber reel volume shall notexceed 610 %. If thermoluminescent detectors (TLDs) areused fo
43、r the measurements, use four TLDs to sample dosedistribution at each location. Average the readings from themultiple TLDs at each location to minimize dose uncertainties.To maintain the highest possible accuracy in dosemeasurements, do not use the TLDs more than once. TLDsshould be used only in the
44、dose region where they maintain alinear response.8.2 Measure the total dose with an irradiation time equal tosubsequent fiber measurements. Alternatively, the dose ratemay be measured and the total dose calculated from theproduct of the dose rate and irradiation time. Source transittime (from off-to
45、-on and on-to-off positions) shall be less than5 % of the irradiation time.8.3 Stability of Radiation SourceThe dose rate must beconstant for at least 95 % of the shortest irradiation time ofinterest. The dose variation provided across the fiber sampleshall not exceed 610 %.9. System Stability and C
46、alibration9.1 System StabilityThe stability of the total system underillumination conditions, including the light source, light injec-tion conditions into the interfacing fiber, variation in fibermicrobend conditions, light coupling from the spectral activa-tor to the sample and reference fibers, li
47、ght coupling to adetector/spectrometer, the detector, the recording device, andthe sample temperature must be verified prior to any measure-ment.9.1.1 The intensity (counts per second) detected from thesample and reference fibers prior to irradiation shall be within10 %.9.2 Baseline StabilityVerify
48、the baseline stability for atime comparable to the attenuation measurement with the lightsource turned off. Record the maximum fluctuation in outputpower and reject any subsequent measurement if the transmit-ted power out of the irradiated fiber is not greater than ten timesthe recorded baseline.10.
49、 Procedure10.1 Place the reel of fiber or cable in the attenuation testsetup as shown in Fig. 1. Couple the light source into the endof the interfacing fiber.10.2 Position the output end of the interfacing fiber suchthat all the light exiting the fiber impinges the spectral activatorsample. Position the sample and reference fibers to collect thespectral energy scattered (see Note 3).10.3 Position the light exiting the fibers for collection by thedetection scheme. The spectra obtained through the sample andreference fibers must exhibit a minimum sign
