ASTM E1654-94(1999)
(Guide)Standard Guide for Measuring Ionizing Radiation-Induced Spectral Changes in Optical Fibers and Cables for Use in Remote Raman FiberOptic Spectroscopy
Standard Guide for Measuring Ionizing Radiation-Induced Spectral Changes in Optical Fibers and Cables for Use in Remote Raman FiberOptic Spectroscopy
SCOPE
1.1 This guide covers the method for measuring the real time, in situ radiation-induced alterations to the Raman spectral signal transmitted by a multimode, step index, silica optical fiber. This guide specifically addresses steady-state ionizing radiation (that is, alpha, beta, gamma, protons, etc.) with appropriate changes in dosimetry, and shielding considerations, depending upon the irradiation source.
1.2 The test procedure given in this guide is not intended to test the other optical and non-optical components of an optical fiber-based Raman sensor system, but may be modified to test other components in a continuous irradiation environment.
1.3 The values in SI units are to be regarded as standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: E 1654 – 94 (Reapproved 1999)
Standard Guide for
Measuring Ionizing Radiation-Induced Spectral Changes in
Optical Fibers and Cables for Use in Remote Raman
FiberOptic Spectroscopy
This standard is issued under the fixed designation E1654; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope MIL-STD-2196-(SH) Glossary of Fiber Optic Terms
1.1 This guide covers the method for measuring the real
3. Terminology
time,insituradiation-inducedalterationstotheRamanspectral
3.1 Definitions—Refer to the following documents for the
signal transmitted by a multimode, step index, silica optical
definition of terms used in this guide: MIL-STD-2196-(SH)
fiber. This guide specifically addresses steady-state ionizing
and E1614.
radiation (that is, alpha, beta, gamma, protons, etc.) with
appropriatechangesindosimetry,andshieldingconsiderations,
4. Significance and Use
depending upon the irradiation source.
4.1 Ionizing environments will affect the performance of
1.2 The test procedure given in this guide is not intended to
optical fibers/cables being used to transmit spectroscopic
test the other optical and non-optical components of an optical
information from a remote location. Determination of the type
fiber-based Raman sensor system, but may be modified to test
and magnitude of the spectral variations or interferences
other components in a continuous irradiation environment.
produced by the ionizing radiation in the fiber, or both, is
1.3 The values in SI units are to be regarded as standard.
necessary for evaluating the performance of an optical fiber
1.4 This standard does not purport to address all of the
sensor system.
safety concerns, if any, associated with its use. It is the
4.2 The results of the test can be utilized as a selection
responsibility of the user of this standard to establish appro-
criteria for optical fibers used in optical fiber Raman spectro-
priate safety and health practices and determine the applica-
scopic sensor systems.
bility of regulatory limitations prior to use.
NOTE 1—The attenuation of optical fibers generally increases when
2. Referenced Documents
theyareexposedtoionizingradiation.Thisisdueprimarilytothetrapping
ofradiolyticelectronsandholesatdefectsitesintheopticalmaterials,that
2.1 ASTM Standards:
is, the formation of color centers. The depopulation of these color centers
E 1614 Guide for Procedure for Measuring Ionizing
by thermal or optical (photobleaching) processes, or both, causes recov-
Radiation-InducedAttenuation in Silica-Based Optical Fi-
ery, usually resulting in a decrease in radiationinduced attenuation.
bers and Cables for Use in Remote Fiber-Optic Spectros-
Recovery of the attenuation after irradiation depends on many variables,
copy and Broadband Systems
including the temperature of the test sample, the composition of the
2.2 EIA Standards:
sample, the spectrum and type of radiation employed, the total dose
applied to the test sample, the light level used to measure the attenuation,
2.2.1 Test or inspection requirements include the following
and the operating spectrum. Under some continuous conditions, recovery
references:
is never complete.
EIA-455-57 Optical Fiber End Preparation and Examina-
tion
5. Apparatus
EIA-455-64 Procedure for Measuring Radiation-Induced
3 5.1 ThetestschematicisshowninFig.1.Thefollowinglist
Attenuation in Optical Fibers and Cables
identifies the equipment necessary to accomplish this test
2.3 Military Standard:
procedure.
5.2 Light Source—A laser source shall be used for the
Ramananalysis,andthewavelengthmustbechosensothatthe
This guide is under the jurisdiction of ASTM Committee E-13 on Molecular
Spectroscopy and is the direct responsibility of Subcommittee E13.09 on Fiber
fluorescentsignalsfromtheopticalcomponents(especiallythe
Optics in Molecular Spectroscopy.
spectralactivatorsampleandopticalfibers)areminimized,and
Current edition approved Dec. 15, 1994. Published February 1995.
Annual Book of ASTM Standards, Vol 03.06.
Available from Electronic Industry Association, Engineering Dept., 2001 4
AvailablefromStandardizationDocumentsOrderDesk,Bldg.4SectionD,700
Pennsylvania Ave., NW, Washington, DC 20006.
Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E 1654
FIG. 1 Test Configuration
sothatthewavelengthcorrespondstothespectralsensitivityof trograph, detector). The minimal requirement for these ele-
the detection scheme. Typically, the wavelength range ex- ments shall be that the numerical aperture of the components
ploited spans from 0.4 to 1.06 µm. The laser source must have are matched for efficient coupling. Optics may also be neces-
sufficient power to obtain the desired minimum signal-to-noise sary to enhance the interaction of the input light with the
ratio (S/N) (see 10.3). spectral activator.
5.3 Focusing/Collection Optics—A number of optical ele- 5.4 Interfacing Optical Fiber—The primary requirement of
ments are needed for the launch and collection of light the interfacing optical fiber is to provide the minimum power
radiation into and from the optical fibers (interfacing, sample to the activator sample at the proper wavelength(s). The fiber
and reference), and other instrumentation (light source, spec- lengthmaybeadjustedsothatthepowerrequirementsaremet.
E 1654
5.5 Light Radiation Filtering—Itisimportantthatallneigh- 5.11 Optical Detection—An optical detector with a known
boring laser lines are removed from the source beam prior to responseovertherangeofintensitiesthatareencounteredshall
interaction with the spectral activator. This can be accom-
be used. A typical system for Raman might include a single-
plished before or after the interfacing optical fiber. Placement point detector (that is, PMT) or a multichannel analyzer (that
of the filter before the interfacing fiber will eliminate the
is, CCD array). The spectrograph must exhibit fast scanning
neighboring laser lines, but any fluorescence and Raman
capabilities. As Fig. 1 indicates, it is recommended that a
scattering due to the fiber or associated optics will be allowed
single-imaging spectrometer be used with a 2D CCD detector
to interact with the sample. Placement of the laser pass filter
so that the output from the reference and sample fibers can be
aftertheinterfacingfiberispreferablebecauseitwilleliminate
evaluated simultaneously. Two spectrometers operating simul-
any signals created within the fiber. If it is necessary to place
taneously may also be used.
the filter before the interfacing fiber, then the fiber should be
5.11.1 The optical detection system must be capable of
−1
kept as short as possible (several metres).
obtainingtheRamanspectrumfrom500to3000cm fromthe
5.6 Spectral Activator Sample—The spectral activator used
excitation frequency.
must demonstrate a strong, well-characterized Raman spectral
5.12 Recorder System—Asuitable data recording, such as a
signal. The sample may be either liquid, gas, or solid, depend-
computer data acquisition system, is recommended.
ing on the requirements of the optical fiber arrangement. It is
5.13 Ambient Light Shielding—The irradiated fiber length
recommendedthataliquidbeused,sincetheRamanscattering
shall be shielded from ambient light to prevent photobleaching
in the proposed configuration will launch similarly into the
byanyexternallightsourcesandtoavoidbaselineshiftsinthe
sample and reference fibers. Standard recommended samples
zero light level. An absorbing fiber coating or jacket can be
are:acetonitrile,benzene,andcarbontetrachloride.Thesample
used as the light shield provided that it has been demonstrated
should be contained in a standard spectroscopic rectangular
to block ambient light and its influence on the dose within the
silica cuvette.
fiber core has been taken into consideration.
5.7 Optical Interconnections—Theinputandoutputendsof
the interfacing, reference, and sample optical fibers shall have
NOTE 2—The average total dose should be expressed in gray (Gy,
astabilizedopticalinterconnection,suchasaclamp,connector,
where 1 Gy 5100 rads) to a precision of 65%, traceable to national
splice, or weld. During an attenuation measurement, the
standards. For typical silica core fibers, dose should be expressed in gray
interconnection shall not be changed or adjusted. calculated for SiO , that is, Gy(SiO ).
2 2
5.8 Irradiation System—Theirradiationsystemshouldhave
6. Hazards
the following characteristics:
5.8.1 Dose Rate—ACo orotherirradiationsourceshallbe
6.1 Carefully trained and qualified personnel must be used
used to deliver radiation at dose rates ranging from 10 to 100
to perform this test procedure since radiation (both ionizing
Gy (SiO )/min. (See Note 2.)
and optical), as well as electrical, hazards will be present.
5.8.2 Radiation Energy—The energy of the gamma rays
emitted by the source should be greater than 500 KeVto avoid
7. Test Specimens
serious complications with the rapid variations in total dose as
7.1 Sample Optical Fiber—The sample fiber shall be a
a function of depth within the test sample.
previously unirradiated step-index, multimode fiber. The fiber
5.8.3 Radiation Dosimeter—Dosimetry traceable to Na-
shall be long enough to have an irradiated test length of 50 6
tionalStandardsshallbeused.Doseshouldbemeasuredinthe
5 m and to allow coupling between the optical instrumentation
same uniform geometry as the actual fiber core material to
outside the radiation chamber and the sample area.
ensure that dose-buildup effects are comparable to the fiber
7.2 The test specimen may be an optical-fiber cable assem-
core and the dosimeter. The dose should be expressed in gray
bly, as long as the cable contains at least one of the specified
calculated for the core material.
fibers for analysis.
5.9 Temperature-Controlled Container—Unless otherwise
7.3 Test Reel—The test reel shall not act as a shield for the
specified, the temperature-controlled container shall have the
radiation used in this test or, alternatively, the dose must be
capability of maintaining the specified temperature to 23 6
measured in a geometry duplicating the effects of reel attenu-
2°C. The temperature of the sample/container should be
ation. The diameter of the test reel and the winding tension of
monitored prior to and during the test.
the fiber can influence the observed radiation performance,
5.10 Collection Optics into Detection System—An appro-
therefore, the fiber should be loosely wound on a reel diameter
priatecol
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