Browsing by Author "Webb, D. J."
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Item Open Access General expression of poly(methyl methacrylate) optical fiber Bragg grating sensing response(IEEE, 2018-12-25) Zhang, Wei; Webb, D. J.Poly(methyl methacrylate) (PMMA) optical fiber inherently responds to the changes of temperature and relative humidity. PMMA optical fiber Bragg grating (POFBG) has been reported with diverse temperature and relative humidity sensitivities. These results cannot present the full performance of a POFBG sensor, as they are measured at limited environmental conditions. In this letter, we systematically investigated the POFBG temperature and relative humidity sensing responses. We found that POFBG temperature/relative humidity sensitivity is the function of both temperature and relative humidity. In the experiments, POFBG sensing responses vary linearly with temperature/relative humidity at fixed relative humidity/temperature. Based on this linearity, a general expression of POFBG sensing response to temperature and relative humidity has been obtained and verified for the first time to describe the POFBG performance in the desired operation range. The anisotropy in POF induced by drawing history could induce uncertainty in POFBG response but pre-straining POFBG overcomes this problem.Item Open Access Ground-water monitoring using polymer optical fibre Bragg gratings(SPIE, 2019-08-28) Mehravar, M.; Yang, H.; Zhang, Wei; Webb, D. J.Optical fibre Bragg grating sensors inscribed in polymer optical fibre have been shown to be sensitive to the water content of the medium surrounding the fibre and this property has been applied, for example, to the monitoring of humidity and the water content of aviation fuel. In this work we assess the feasibility of using such sensors for monitoring the saturation of soils, which is important for civil engineering applications. We find a very non-linear response, with a rapid increase in Bragg wavelength as the water content increases from 0 to 0.5%, with a much more gradual, but still monotonic, increase thereafter. We speculate on the causes of this response.