1、 DOCUMENT FOTP-64 Procedure for Measuring Radiation- Induced Attenuation in Optical Fibers and Optical Cables TIA-455-64 Reaffirmed September 30,2002 March 1998 TELECOMMUNICATIONS INDUSTRY ASSOCIATION The Teleconmiunications Industry Association represents the conmiunications sector of NOTICETIA Eng
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6、d health practices and to determine the applicability of regulatory limitations before its use. (From Standards Proposal No. 3-2761, formulated under the cognizance of the TIA FO-4 Fiber Optics, FO-4.3 Subcommittee on Passive Optical Devices and Components.) Published by TELECOMMUNICATIONS INDUSTRY
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22、 DAMAGES. THE FOREGOING NEGATION OF DAMAGES IS A FUNDAMENTAL ELEMENT OF THE USE OF THE CONTENTS HEREOF, AND THESE CONTENTS WOULD NOT BE PUBLISHED BY TIA WITHOUT SUCH LIMITATIONS. STD-EIA TIA-455-bY-ENGL 1998 3234b00 Ob18846 42b TINElA-455-64 FOTP-64 Procedure for measuring radiation-induced attenuat
23、ion in optical fibers and optical cables Contents 1 Intent 5 2 Normative references . 7 3 Apparatus 9 4 Sampling and specimens . 15 5 Procedure 16 6 Calculations or interpretation of results 22 7 Documentation . 23 8 Specification information 25 Annex A- (normative) Hazard warnings 30 Annex B- (info
24、rmative) References . 33 Annex C . (informative) Comparison between this FOTP and FOTP-49 . 34 Annex D . (informative) Comparison between this FOTP and IEC and 35 ITUR test procedures Figure 1 a . Schematic instrumentation diagram . steady state . 26 Figure 1 b . Schematic instrumentation diagram .
25、transient . 27 Figure 1 c . Schematic instrumentation diagram . PM optical fibers 28 Figure 2 . Typical transient data traces . 29 1 STDoEIA TIA-455-64-ENGL 1998 m 3234b00 Ob38847 3b2 TINEIA-455-64 FOTP-64 Procedure for measuring radiation-induced attenuation in optical fibers and optical cables For
26、eword (This Foreword is informative only and is not part of this Standard.) This FOTP is from TIA Standards Proposal No. 2824 and No. 3425, formulated under the cognizance of TIA FO-6.6, Subcommittee on Optical Fibers and Materials. It has been developed by the NATO A/C 243, PANEL IV (RSG.12), Nucle
27、ar Effects Task Group. This FOTP is part of the series of test procedures included within Recommended Standard EIMIA-455. There are four annexes, one which is normative. Key words: radiation, gamma-ray, dose, pulse, neutrons, optical fibers. 3 Previous page is blank - - STD.EIA TIA-455-bq-ENGL 1998
28、3234b00 ObL8848 2T9 TINEIA-455-64 1 intent This test procedure outlines methods for measuring both the steady state response of optical fibers and cables exposed to continuous radiation and the transient response of optical fibers and cables exposed to a pulse of radiation. It can be used to determi
29、ne the level of radiation-induced attenuation produced in single-mode or multimode optical fibers, in either cabled or uncabled form. This test procedure is not intended to test the non-optical components of a fiber-optic cable. Other test methods may be required to evaluate the degradation of cable
30、 materials resulting from radiation exposure. rhe procedure specifically addresses steady state gamma-ray and neutron exposures, and transient gamma-ray, X ray, electron, and neutron exposures, but it would be applicable to other radiation sources (e.g., protons, heavy ions) as well, with appropriat
31、e changes in dosimetry and shielding considerations. 1 .I Background The attenuation of optical fibers generally increases when exposed to radiation. This is primarily due to the trapping of radiolytic electrons and holes at defect sites in the glass (Le., the formation of color centers). The depopu
32、lation of color centers by thermal or optical (photobleaching) processes causes recovery, usually resulting in a decrease of radiation-induced attenuation. Recovery occurs simultaneously with darkening during exposure and is evident immediately after irradiation. Recovery of the attenuation after an
33、 irradiation depends on many variables, including the temperature of the test sample, the configuration of the sample, the spectrum and type of radiation used, the total dose applied to the test sample, and the light level used to measure attenuation. Under some conditions, recovery is never complet
34、e. The attenuation of an optical fiber can vary as a function of time following pulsed exposure by four or more decades during the recovery process. This test procedure addresses both the steady state and pulsed radiation environment. Steady state measurements generally use radioactive isotope sourc
35、es for which the turn-on and turn-off times are typically comparable to 1 s. This corresponds to the times required to move the source itself, shields, or test samples in and out of the source. The instrumentation used for steady state measurements typically has a time response of -0.1 s. There are
36、two extremes of steady state exposure: the low dose rate regime for estimating the effect of environmental background radiation, and the high dose rate regime for estimating the effects of adverse nuclear environments (e.g., nuclear weapons detonation, specific areas of nuclear power plants, and acc
37、elerators). The effects of environmental background radiation are tested by a two-point atten- uation measurement approach similar to FOTP-46 or FOTP-78. Alternatively, an , optical time domain reflectometer (OTDR) may provide a more convenient measurement capability in some circumstances. The effec
38、ts of adverse nuclear environments are tested by measuring the attenuation of the optical power (by monitoring either the transmitted or reflected light; the latter are tested by OTDR) before, during, and after exposure of the test sample to gamma radiation. The Previous page 5 is blank STD-EIA TIA-
39、455-b4-ENGL 1998 3234b00 ObL8849 135 TINE IA-455-64 Detail Specification should specify the times at which measurements are to be made, based on the intended application. The response of fibers to the pulsed environment addresses the time-varying (transient) behavior of an optical fiber after exposu
40、re to a single pulsed dose of radiation. This pulsed dose, with durations of cl s, is typically generated by various types of accelerators or reactors. The transient protocol is applicable where the radiation is not only delivered in a short pulse, but where fiber performance is to be determined on
41、a time scale =I s. For measurements at times after irradiation that are long compared to 1 s or measurements of the average response (t I s) of fibers to a series of short pulses, the steady state protocol is applicable. The transient radiation-induced attenuation is tested by monitoring transmitted
42、 light power before, during, and after exposure of the test sample to the radiation pulse. The transient procedure can be used to document transient attenuation from gamma rays, X rays, electrons, and neutrons (Interaction of gamma and X rays involves processes that generate electrons or positrons h
43、aving energies comparable to the gamma ray energy.) Since few pulsed gamma/)(-ray laboratory sources exist that can deliver large (500 rad) radiation doses over significant volumes, most testing of such phenomena has involved pulsed electron sources. These irradiations yield the same results because
44、 the interaction of gamma rays and X rays with matter produces energetic electrons by the Compton process. Different applications of optical fibers may require drastically different recovery capabilities after a single pulse of radiation. For some applications near accelerators, for example, data ma
45、y be transmitted through the fibers in coincidence with the radiation pulse. For some military applications involving control systems or telecommunications, system “down times“ of milliseconds may be tolerable; other applications may be able to accommodate down times of minutes. For these reasons, t
46、his procedure does not specify times at which measurements are to be made. That information shall appear in the Detail Specification based on the intended application. Radiation exposures may result in luminescence phenomena that generate light in the fiber. Light will be generated during the pulsed
47、 radiation with gamma rays, X rays, or electrons through the Cerenkov process. Although the described procedure discusses only measurements of attenuation, the presence of transient Cerenkov or other luminescent light shall be anticipated by users. These sources of light could overload recording ins
48、trumentation and compromise system accuracy. In this procedure, output filters limit the fraction of the out-of-band luminescent or Cerenkov light reaching the detector. A short wavelength cutoff filter to eliminate all light just below the test wavelength of interest could be sufficient for Cerenko
49、v light because the spectral intensity is proportional to 1/3. The transient procedure primarily focuses on measurements conducted at short times, generally less than a few minutes. For time scales comparable to one minute or longer, the steady state procedure may be readily applied. Photobleaching (light-induced annealing) has not been observed at times IO0 keV unless confidence in dose profiles in the different materials comprising the fiber, buffer coating, jacket, and cable has been demonstrated. 3.2.1.3 Neutron Measurements The radiation sour
