ASTM E1614-94(2013)
(Guide)Standard Guide for Procedure for Measuring Ionizing Radiation-Induced Attenuation in Silica-Based Optical Fibers and Cables for Use in Remote Fiber-Optic Spectroscopy and Broadband Systems
Standard Guide for Procedure for Measuring Ionizing Radiation-Induced Attenuation in Silica-Based Optical Fibers and Cables for Use in Remote Fiber-Optic Spectroscopy and Broadband Systems
SIGNIFICANCE AND USE
4.1 Ionizing environments will affect the performance of optical fibers/cables being used to transmit spectroscopic information from a remote location. Determination of the type and magnitude of the spectral attenuation or interferences, or both, produced by the ionizing radiation in the fiber is necessary for evaluating the performance of an optical fiber sensor system.
4.2 The results of the test can be utilized as a selection criteria for optical fibers used in optical fiber spectroscopic sensor systems. Note 1—The attenuation of optical fibers generally increases when exposed to ionizing radiation. This is due primarily to the trapping of radiolytic electrons and holes at defect sites in the optical materials, that is, the formation of color centers. The depopulation of these color centers by thermal and/or optical (photobleaching) processes, or both, causes recovery, 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 the sample, the spectrum and type of radiation employed, the total dose applied to the test sample, the light level used to measure the attenuation, and the operating spectrum. Under some continuous conditions, recovery is never complete.
SCOPE
1.1 This guide 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 ionizing radiation (that is, alpha, beta, gamma, protons, etc.) with appropriate changes in dosimetry, and shielding considerations, depending upon the irradiation source.
1.2 This test procedure is not intended to test the balance of the optical and non-optical components of an optical fiber-based system, but may be modified to test other components in a continuous irradiation environment.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this 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: E1614 − 94 (Reapproved 2013)
Standard Guide for
Procedure for Measuring Ionizing Radiation-Induced
Attenuation in Silica-Based Optical Fibers and Cables for
Use in Remote Fiber-Optic Spectroscopy and
Broadband Systems
This standard is issued under the fixed designation E1614; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2.3 EIA Standards:
EIA-455-57Optical Fiber End Preparation and Examination
1.1 This guide covers a method for measuring the real time,
EIA-455-64ProcedureforMeasuringRadiation-InducedAt-
in situ radiation-induced spectral attenuation of multimode,
tenuation in Optical Fibers and Cables
step index, silica optical fibers transmitting unpolarized light.
EIA-455-78A-90Spectral Attenuation Cutback Measure-
This procedure specifically addresses steady-state ionizing
ment for Single-Mode Optical Fibers
radiation (that is, alpha, beta, gamma, protons, etc.) with
appropriatechangesindosimetry,andshieldingconsiderations,
3. Terminology
depending upon the irradiation source.
3.1 Definitions:
1.2 This test procedure is not intended to test the balance of
3.1.1 Refer to MIL-STD-2196 for the definition of terms
the optical and non-optical components of an optical fiber-
used in this guide.
basedsystem,butmaybemodifiedtotestothercomponentsin
a continuous irradiation environment.
4. Significance and Use
1.3 The values stated in SI units are to be regarded as
4.1 Ionizing environments will affect the performance of
standard. No other units of measurement are included in this
optical fibers/cables being used to transmit spectroscopic
standard.
information from a remote location. Determination of the type
and magnitude of the spectral attenuation or interferences, or
1.4 This standard does not purport to address all of the
both, produced by the ionizing radiation in the fiber is
safety concerns, if any, associated with its use. It is the
necessary for evaluating the performance of an optical fiber
responsibility of the user of this standard to establish appro-
sensor system.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
4.2 The results of the test can be utilized as a selection
criteria for optical fibers used in optical fiber spectroscopic
2. Referenced Documents
sensor systems.
2.1 Test or inspection requirements include the following
NOTE 1—The attenuation of optical fibers generally increases when
references:
exposed to ionizing radiation. This is due primarily to the trapping of
radiolytic electrons and holes at defect sites in the optical materials, that
2.2 Military Standard:
is, the formation of color centers. The depopulation of these color centers
MIL-STD-2196-(SH)Glossary of Fiber Optic Terms
by thermal and/or optical (photobleaching) processes, or both, causes
recovery, 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 the
This guide is under the jurisdiction of ASTM Committee E13 on Molecular
sample, the spectrum and type of radiation employed, the total dose
Spectroscopy and Separation Science and is the direct responsibility of Subcom-
applied to the test sample, the light level used to measure the attenuation,
mittee E13.09 on Fiber Optics, Waveguides, and Optical Sensors.
and the operating spectrum. Under some continuous conditions, recovery
Current edition approved Jan. 1, 2013. Published January 2013. Originally
is never complete.
approved in 1994. Last previous edition approved in 2004 as E1614 – 94 (2004).
DOI: 10.1520/E1614-94R13.
AvailablefromStandardizationDocumentsOrderDesk,Bldg.4SectionD,700
Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS.Available from Stan-
dardization Documents Order Desk, DODSSP, Bldg. 4, Section D, 700 Robbins Available from Electronic Industries Alliance (EIA), 2500 Wilson Blvd.,
Ave., Philadelphia, PA 19111-5098, http://dodssp.daps.dla.mil. Arlington, VA 22201, http://www.ecaus.org/eia.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1614 − 94 (2013)
5. Apparatus 5.7 Optical Splitter—An optical splitter or fiber optic cou-
pler shall divert some portion of the input light to a reference
5.1 ThetestschematicisshowninFig.1.Thefollowinglist
detector for monitoring the stability of the light source.
identifies the equipment necessary to accomplish this test
procedure. 5.8 Optical Interconnections—The input and output ends of
the optical fiber shall have a stabilized optical interconnection,
5.2 Light Source—Thelightsourceshouldbechosensothat
such as a clamp, connector, splice, or weld. During an
thespectralregionofinterestisprovided.Lampsorglobars,or
attenuation measurement, the interconnection shall not be
both, may be used for analysis as long as they satisfy the
changed or adjusted. If possible, the optical interconnections
power, stability, and system requirements defined. In general,
should not be within the irradiation region.
the silica fibers should be evaluated from ≈350 to ≈2100 nm,
therefore, more than one light source or multiple testing, or 5.9 Wavelength Demultiplexor—A means of separating the
both, may be necessary. spectral information must be used at the detector end of the
system so that multiple wavelengths can be simultaneously
5.3 Shutter—In order to determine the background stability,
evaluated (that is, grating, prism, Acousto-optic tunable filter,
thelightwillhavetobeblockedfromenteringtheopticalfiber
etc.).
by a shutter.
5.10 Optical Detection—The optical detection system shall
5.4 Focusing/Collection Optics—A number of optical ele-
be wavelength calibrated in accordance with the manufactur-
ments may be needed for the launch and collection of light
er’s recommended procedure utilizing standard spectral line
radiation into/from the test optical fiber and other instrumen-
sources. The calibration and spectral response of the detection
tation (light source, spectrometer, detector). The minimal
systems should be documented.
requirement for these elements shall be that the numerical
5.10.1 Sample Detector—An optical detector that is linear
aperture of the adjacent components are matched for efficient
and stable over the range of intensities that are encountered
coupling.
shall be used. The method employed must be able to evaluate
5.5 Mode Stripper—High-order cladding modes must be
a wide spectral range rapidly (that is, 500 ms). The primary
attenuatedbymodestripping,andmodestrippingshouldoccur
requirement of the detector is that the spectral detectivity
prior to and after the radiation chamber, especially if the fiber
corresponds to the spectral transmission of the light source/
length is shorter than that specified in this guide. If it is found
fiber system and that a spectral resolution of 610 nm is
that the coating material effectively strips the cladding modes
attainable.
from the optical fiber, then a mode stripper is not necessary.
5.10.2 Reference Detector—The reference detector is used
5.6 Light Radiation Filtering—Filters may be necessary to for light source stability measurements for the wavelength
restrict unwanted regions of the light spectrum. They may be rangeofinterest.Thereferencedetectionsystemshouldhavea
needed to avoid saturation or nonlinearities of the detector and similar response to the sample detection system. If an optical
recording instrumentation by transient light sources (Cerenkov fiber splitter is used for the reference arm of the detection
or other luminescence phenomena), or due to wide spectral scheme, then the detection system must be able to accept the
power variances with the output of the broadband sources. output from an optical fiber. If the detection scheme can
NOTE 1—If a shuttered source is not used, the test engineer must account for the placement and extraction of the test sample in the irradiator.
FIG. 1 Schematic Instrumentation Diagram
E1614 − 94 (2013)
monitor the output of two optical fibers (for example, a CCD 7.2 The test specimen may be an optical fiber cable
detector with an imaging spectrometer), it may be advanta- assembly, as long as the cable contains the above specified
geous to package the reference fiber and sample fiber in the fiber for analysis as in 7.1.
same termination so that a single detection system can simul-
7.3 Test Reel—The test reel shall not act as a shield for the
taneously monitor both outputs. This configuration is optional.
radiation used in this test or, alternatively, the dose must be
5.11 Recorder System—A suitable data recording system, measured in a geometry duplicating the effects of reel attenu-
such as a computer data acquisition system, is recommended ation. The diameter of the test reel and the winding tension of
due to the large spectral data sets necessary. the fiber can influence the observed radiation performance,
therefore, the fiber should be loosely wound on a reel diameter
5.12 Ambient Light Shielding—The irradiated fiber length
exceeding 10 cm.
shall be shielded from ambient light to prevent photobleaching
byanyexternallightsourcesandtoavoidbaselineshiftsinthe 7.4 Fiber End Preparation—The test sample shall be pre-
zero light level. An absorbing fiber coating or jacket can be pared such that its end faces are smooth and perpendicular to
used as the light shield, provided that it has been demonstrated the fiber axis, in accordance with EIA-455-57.
to block ambient light and that its influence on the dose within
8. Radiation Calibration and Stability
the fiber core has been taken into consideration.
8.1 Calibration of Radiation Source—Calibration of the
5.13 Irradiation System—The irradiation system should
radiation source for dose uniformity and dose level shall be
have the following characteristics:
made at the location of the device under test (DUT) and at a
5.13.1 Dose Rate—ACo or other irradiation source shall
minimum of four locations, prior to introduction of fiber test
be used to deliver radiation at dose rates ranging from 10 to
samples. The variation in dose across the fiber reel volume
100 Gy(SiO )/min (see Note 3).
shall not exceed 610%. If thermoluminescent detectors
5.13.2 Radiation Energy—The energy of the gamma rays
(TLDs) are used for the measurements, four TLDs shall be
emitted by the source should be greater than 500 KeVto avoid
used to sample dose distribution at each location.The readings
serious complications with the rapid variations in total dose as
from the multiple TLDs at each location shall be averaged to
a function of depth within the test sample.
minimize dose uncertainties. To maintain the highest possible
5.13.3 Radiation Dosimeter—Dosimetry traceable to na-
accuracy in dose measurements, the TLDs shall not be used
tional standards shall be used. Dose should be measured in the
more than once. TLDs should be used only in the dose region
same uniform geometry as the actual fiber core material to
where they maintain a linear response.
ensure that dose-build-up effects are comparable to the fiber
core and the dosimeter. The dose should be expressed in gray
8.2 Thetotaldoseshallbemeasuredwithanirradiationtime
calculated for the core material.
equaltosubsequentfibermeasurements.Alternatively,thedose
rate may be measured and the total dose calculated from the
5.14 Temperature-Controlled Container—Unless otherwise
product of the dose rate and irradiation time. Source transit
specified, the temperature-controlled container shall have the
time (from off-to-on and on-to-off positions) shall be less than
capability of maintaining the specified temperature to 23 6
5% of the irradiation time.
2°C. The temperature of the sample/container should be
monitored prior to and during the test.
8.3 Stability of Radiation Source—The dose rate must be
constant for at least 95% of the shortest irradiation time of
NOTE2—Thewavelengthrangeindicatedin5.2isthelargestrangethat
should be tested if the equipment (that is, sources, detectors) is available. interest. The dose variation provided across the fiber sample
Silica glass will transmit from ≈190 to ≈3300 nm, but this range is not
shall not exceed 610%.
practical for optical fiber applications due to the high attenuations in the
ultraviolet (UV) and near-infrared (NIR). The widest wavelength range
9. Procedure
that can be tested that satisfies the requirements of the test procedure
should be evaluated if the equipment is available. 9.1 Place the reel of fiber or cable in the attenuation test
NOTE 3—The average total dose should be expressed in Gray (Gy,
setup as shown in Fig. 1. Couple the light source into the end
where 1 Gy=100 rads) to a precision of 65%, traceable to national
of the test fiber, and position the light exiting the fiber for
standards. For typical silica core fibers, dose should be expressed in Gy
collection by the spectrograph or other appropriate detection
calculated for SiO , that is, Gy(SiO ).
2 2
system.
6. Hazards
9.2 Temperature Stability—Stabilize the test sample in the
6.1 Carefully trained and qualified personnel must be used
temperature chamber at 23 6 2°C prior to proceeding.
to perform this test procedure since radiation (both ionizing
9.3 System Stability—Verify the stability of the total system
and optical), as well as electrical, hazards will be present.
under illumination conditions prior to any measurement for a
7. Test Specimens time exceeding that required for determination of P (λ) and
b
P(t,λ ) (see 10.1) during the duration of the attenuation
7.1 Sample Optical Fiber—The sample fiber shall be a
measurement.
previously unirradiated, silica-based, step-index, multimode
fiber.Thefibershallbelongenoughtoallowcouplingbetween 9.4 Forstabilitymeasurements,thesystemoutputneedonly
the optical instrumentation outside the radiation chamber and be evaluated in 50-nm increments over the useful range of the
the sample area, along with an irradiated test length of 50 6 5 detection system. At each wavelength, convert the maximum
m. fluctuationintheobservedsystemoutputduringthattime,into
E1614 − 94 (2013)
an apparent change in optical attenuation due to system noise, achieved. This can be relaxed, however, if the induced attenu-
∆α (t, λ), using Eq 1. Any subsequent measurement must be ation is increasing at such a rapid rate that this is unattainable.
n
rejected if the observed ∆A(t, λ) (defined in 10.1) does not In general,
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