Fibre optic sensor system assessment in radiation environments

ABSTRACTAn optical fibre sensing system is assessed for radiation performance. The optical fibres are irradiated withgamma radiation from a cobalt 60 source. The sensing system consists of a white light source, silicon detectors and multimode optical fibres. The optical system measures the chromaticity of the light in dominant wavelength derived from either a distimulus or tristimulus measurement. Both measurement systems are generic and can operate with up to eightmodulating sensors simultaneously and are designed to form part of an existing monitoring or control system. Allcomponents are commercially available and the optical fibre system is undergoing trails in the nuclear, chemical and electrical power distribution industries. 1. INTRODUCTIONFibre optic cables have been used for communication purposes for 15 years. The bandwidth benefits offered bysuch systems has improved the speed and quality of information services. Optical sensors using fibres developed forcommunication purposes were also developed in parallel. The technology used for such sensing systems was, in thebeginning, much reliant upon the technology available in the communication sector and therefore these sensing systemshad inhereted limitations due to fibres, sources and detectors. The application of the communication technology formilitary purposes lead to much work in the development of not only radiation tolerant fibres but various optical sourcesand detectors. This advance coupled with the growth in optical sensing systems has lead to much interest in the potentialapplication of this new generation of optical fibre sensing systems to nuclear environments. The number of modulation