ASTM E1614-94(2021)

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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Aug-2021
• ICS: 33.180.10 - Fibres and cables
• Technical Committee: E13 - Molecular Spectroscopy and Separation Science
• Drafting Committee: E13.09 - Fiber Optics, Waveguides, and Optical Sensors

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E1614 − 94 (Reapproved 2021)
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 2.2 Military Standard:
MIL-STD-2196-(SH)Glossary of Fiber Optic Terms
1.1 This guide covers a method for measuring the real time,
2.3 EIA Standards:
in situ radiation-induced spectral attenuation of multimode,
EIA-455-57Optical Fiber End Preparation and Examination
step index, silica optical fibers transmitting unpolarized light.
EIA-455-64ProcedureforMeasuringRadiation-InducedAt-
This procedure specifically addresses steady-state ionizing
tenuation in Optical Fibers and Cables
radiation (that is, alpha, beta, gamma, protons, etc.) with
EIA-455-78A-90Spectral Attenuation Cutback Measure-
appropriatechangesindosimetry,andshieldingconsiderations,
ment for Single-Mode Optical Fibers
depending upon the irradiation source.
3. Terminology
1.2 This test procedure is not intended to test the balance of
the optical and non-optical components of an optical fiber-
3.1 Definitions:
basedsystem,butmaybemodifiedtotestothercomponentsin 3.1.1 Refer to MIL-STD-2196 for the definition of terms
a continuous irradiation environment.
used in this guide.
1.3 The values stated in SI units are to be regarded as
4. Significance and Use
standard. No other units of measurement are included in this
4.1 Ionizing environments will affect the performance of
standard.
optical fibers/cables being used to transmit spectroscopic
1.4 This standard does not purport to address all of the
information from a remote location. Determination of the type
safety concerns, if any, associated with its use. It is the
and magnitude of the spectral attenuation or interferences, or
responsibility of the user of this standard to establish appro-
both, produced by the ionizing radiation in the fiber is
priate safety, health, and environmental practices and deter-
necessary for evaluating the performance of an optical fiber
mine the applicability of regulatory limitations prior to use.
sensor system.
1.5 This international standard was developed in accor-
4.2 The results of the test can be utilized as a selection
dance with internationally recognized principles on standard-
criteria for optical fibers used in optical fiber spectroscopic
ization established in the Decision on Principles for the
sensor systems.
Development of International Standards, Guides and Recom-
NOTE 1—The attenuation of optical fibers generally increases when
mendations issued by the World Trade Organization Technical
exposed to ionizing radiation. This is due primarily to the trapping of
Barriers to Trade (TBT) Committee.
radiolytic electrons and holes at defect sites in the optical materials, that
is, the formation of color centers. The depopulation of these color centers
2. Referenced Documents by thermal and/or optical (photobleaching) processes, or both, causes
recovery, usually resulting in a decrease in radiation-induced attenuation.
2.1 Test or inspection requirements include the following
Recovery of the attenuation after irradiation depends on many variables,
references: 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,
This guide is under the jurisdiction of ASTM Committee E13 on Molecular
Spectroscopy and Separation Science and is the direct responsibility of Subcom- Available from DLA Document Services, Building 4/D, 700 Robbins Ave.,
mittee E13.09 on Fiber Optics, Waveguides, and Optical Sensors. Philadelphia, PA 19111-5094, Philadelphia, PA 19111-5094, http://
Current edition approved Sept. 1, 2021. Published September 2021. Originally quicksearch.dla.mil.
approved in 1994. Last previous edition approved in 2013 as E1614 – 94 (2013). Available from Electronic Industries Alliance (EIA), 2500 Wilson Blvd.,
DOI: 10.1520/E1614-94R21. Arlington, VA 22201.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1614 − 94 (2021)
and the operating spectrum. Under some continuous conditions, recovery
or other luminescence phenomena), or due to wide spectral
is never complete.
power variances with the output of the broadband sources.
5.7 Optical Splitter—An optical splitter or fiber optic cou-
5. Apparatus
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 ≈350nm to ≈2100
nm,therefore,morethanonelightsourceormultipletesting,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
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 (2021)
scheme, then the detection system must be able to accept the the optical instrumentation outside the radiation chamber and
output from an optical fiber. If the detection scheme can the sample area, along with an irradiated test length of 50m 6
monitor the output of two optical fibers (for example, a CCD 5m.
detector with an imaging spectrometer), it may be advanta-
7.2 The test specimen may be an optical fiber cable
geous to package the reference fiber and sample fiber in the
assembly, as long as the cable contains the above specified
same termination so that a single detection system can simul-
fiber for analysis as in 7.1.
taneously monitor both outputs.This configuration is optional.
7.3 Test Reel—The test reel shall not act as a shield for the
5.11 Recorder System—A suitable data recording system,
radiation used in this test or, alternatively, the dose must be
such as a computer data acquisition system, is recommended
measured in a geometry duplicating the effects of reel attenu-
due to the large spectral data sets necessary.
ation. The diameter of the test reel and the winding tension of
5.12 Ambient Light Shielding—The irradiated fiber length
the fiber can influence the observed radiation performance,
shall be shielded from ambient light to prevent photobleaching
therefore, the fiber should be loosely wound on a reel diameter
byanyexternallightsourcesandtoavoidbaselineshiftsinthe
exceeding 10 cm.
zero light level. An absorbing fiber coating or jacket can be
7.4 Fiber End Preparation—The test sample shall be pre-
used as the light shield, provided that it has been demonstrated
pared such that its end faces are smooth and perpendicular to
to block ambient light and that its influence on the dose within
the fiber axis, in accordance with EIA-455-57.
the fiber core has been taken into consideration.
5.13 Irradiation System—The irradiation system should
8. Radiation Calibration and Stability
have the following characteristics:
60 8.1 Calibration of Radiation Source—Calibration of the
5.13.1 Dose Rate—ACo or other irradiation source shall
radiation source for dose uniformity and dose level shall be
be used to deliver radiation at dose rates ranging from
made at the location of the device under test (DUT) and at a
10Gy(SiO )/min to 100 Gy(SiO )/min (see Note 3).
2 2
minimum of four locations, prior to introduction of fiber test
5.13.2 Radiation Energy—The energy of the gamma rays
samples. The variation in dose across the fiber reel volume
emitted by the source should be greater than 500 KeVto avoid
shall not exceed 610%. If thermoluminescent detectors
serious complications with the rapid variations in total dose as
(TLDs) are used for the measurements, four TLDs shall be
a function of depth within the test sample.
used to sample dose distribution at each location.The readings
5.13.3 Radiation Dosimeter—Dosimetry traceable to na-
from the multiple TLDs at each location shall be averaged to
tional standards shall be used. Dose should be measured in the
minimize dose uncertainties. To maintain the highest possible
same uniform geometry as the actual fiber core material to
accuracy in dose measurements, the TLDs shall not be used
ensure that dose-build-up effects are comparable to the fiber
more than once. TLDs should be used only in the dose region
core and the dosimeter. The dose should be expressed in gray
where they maintain a linear response.
calculated for the core material.
8.2 Thetotaldoseshallbemeasuredwithanirradiationtime
5.14 Temperature-Controlled Container—Unless otherwise
equaltosubsequentfibermeasurements.Alternatively,thedose
specified, the temperature-controlled container shall have the
rate may be measured and the total dose calculated from the
capability of maintaining the specified temperature to 23°C 6
product of the dose rate and irradiation time. Source transit
2°C. The temperature of the sample/container should be
time (from off-to-on and on-to-off positions) shall be less than
monitored prior to and during the test.
5% of the irradiation time.
NOTE2—Thewavelengthrangeindicatedin5.2isthelargestrangethat
8.3 Stability of Radiation Source—The dose rate must be
should be tested if the equipment (that is, sources, detectors) is available.
Silicaglasswilltransmitfrom≈190nmto≈3300nm,butthisrangeisnot
constant for at least 95% of the shortest irradiation time of
practical for optical fiber applications due to the high attenuations in the
interest. The dose variation provided across the fiber sample
ultraviolet (UV) and near-infrared (NIR). The widest wavelength range
shall not exceed 610%.
that can be tested that satisfies the requirements of the test procedure
should be evaluated if the equipment is available.
9. Procedure
NOTE 3—The average total dose should be expressed in Gray (Gy,
where 1 Gy=100 rads) to a precision of 65%, traceable to national
9.1 Place the reel of fiber or cable in the attenuation test
standards. For typical silica core fibers, dose should be expressed in Gy
setup as shown in Fig. 1. Couple the light source into the end
calculated for SiO , that is, Gy(SiO ).
2 2
of the test fiber, and position the light exiting the fiber for
collection by the spectrograph or other appropriate detection
6. Hazards
system.
6.1 Carefully trained and qualified personnel must be used
9.2 Temperature Stability—Stabilize the test sample in the
to perform this test procedure since radiation (both ionizing
and optical), as well as electrical, hazards will be present. temperature chamber at 23°C 6 2°C prior to proceeding.
9.3 System Stability—Verify the stability of the total system
7. Test Specimens
under illumination conditions prior to any measurement for a
7.1 Sample Optical Fiber—The sample fiber shall be a time exceeding that required for determination of P (λ) and
b
previously unirradiated, silica-based, step-index, multimode P(t,λ ) (see 10.1) during the duration of the attenuation
fiber.Thefibershallbelongenoughtoallowcouplingbetween measurement.
E1614 − 94 (2021)
9.4 Forstabilitymeasurements,thesystemoutputneedonly levels of the reference signal before, during, and after the
be evaluated in 50nm increments over the useful range of the irradiation. The induced
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