IEC 60793-1-54-2018 pdf download.Optical fibres – Part 1-54: Measurement methods and test procedures – Gamma irradiation.
This document outlines a method for measuring the steady state response of optical fibres and optical cables exposed to gamma radiation. It can be employed to determine the level of radiation-induced attenuation produced in Class B single-mode or Class A, category A1 and A2 multimode optical fibres, in either cabled or uncabled form, due to exposure to gamma radiation. The attenuation of cabled and uncabled optical fibres generally increases when exposed to gamma radiation. This is primarily due to the trapping of radiolytic electrons and holes at defect sites in the glass (i.e. the formation of “colour centres”). This test procedure focuses on two regimes of interest: the low dose rate regime suitable for estimating the effect of environmental background radiation, and the high dose rate regime suitable for estimating the effect of adverse nuclear environments. The testing of the effects of environmental background radiation is achieved with an attenuation measurement approach similar to IEC 60793-1 -40 method A, cut-back. The effects of adverse nuclear environments are tested by monitoring the power before, during and after exposure of the test sample to gamma radiation. The depopulation of colour centres by light (photo bleaching) or by heat causes recovery (lessening of radiation induced attenuation). Recovery can occur over a wide range of time which depends on the irradiation time and annealing temperature. This complicates the characterization of radiation induced attenuation since the attenuation depends on many variables including the temperature of the test environment, the configuration of the sample, the total dose and the dose rate applied to the sample and the light level used to measure it. This test is not a material test for the non-optical material components of a fibre optic cable. If degradation of cable materials exposed to irradiation is studied, other test methods will be used. This test method is written to contain a clear, concise listing of instructions. The background knowledge that is necessary to perform correct, relevant and expressive irradiation tests as well as to limit measurement uncertainty is presented separately in IEC TR 62283.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
IEC 60793-1 -40, Optical Fibres – Part 1-40: Measurement methods and test procedures – Attenuation
IEC 60793-1 -44, Optical fibres – Part 1-44: Measurement methods and test procedures – Cut-off wavelength
IEC 60793-1 -46, Optical fibres – Part 1-46: Measurement methods and test procedures – Monitoring of changes in optical transmittance
IEC 61 280-4-1 , Fibre-optic communication subsystem test procedures – Part 4-1: Installed cable plant – Multimode attenuation measurement
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
4 Apparatus
4.1 General
Attention is drawn to the fact that strict regulations and suitable protective facilities are to be adopted in the laboratory for this test. Carefully selected trained personnel shall be used to perform this test. It can be extremely hazardous to test personnel if it is improperly performed or without qualified conditions.
4.2 Radiation source
4.2.1 Testing of environmental background radiation
A 60 Co or equivalent ionising source shall be used to deliver gamma radiation. This environment is characterised by relatively low total dose and dose rate.
4.2.2 Testing of adverse nuclear environments
A 60 Co or equivalent ionizing source(s) shall be used to deliver gamma radiation. This environment is characterised by higher total dose and dose rate.IEC 60793-1-54 pdf download.