This paper presents a novel concept of simultaneously measuring pressure and temperature using a silica optical fibre extrinsic Fabry-Perot interferometric (EFPI) pressure sensor incorporating a fibre Bragg grating (FBG), which is constructed entirely from fused-silica. The novel device is used to simultaneously provide accurate pressure and temperature readings at the point of measurement. Furthermore, the FBG temperature measurement is used to eliminate the temperature cross-sensitivity of the EFPI pressure sensor. 1. Introduction Optical fibre extrinsic Fabry-Perot interferometric (EFPI) pressure sensors can be constructed entirely from fused-silica (i.e. entirely made of glass), e.g. using a glass capillary [1][2], a hollow core fibre [3] or standard telecommunication fibres [4][5]. Moreover, such all silica sensors have many advantages: present a cost-effective; have a simple fabrication process; are small in size; mechanically robust and are capable of operating at high temperatures [1]. In addition to their pressure sensitivity, all-fused silica optical fibre EFPI pressure sensors are also sensitive to temperature. This cross-sensitivity to temperature is due to the thermal expansion of the glass components and the air within the EFPI sensor cavity. Therefore, in practice the temperature cross-sensitivity of EFPI sensors can be a source of error in pressure measurements. In this paper a novel concept is presented, which can be used to simultaneous measure pressure and temperature. This hybrid sensor is based on a fibre Bragg grating (FBG) sensor for temperature measurement and an EFPI pressure sensor to measure pressure simultaneously. The all-fused silica optical fibre EFPI pressure and FBG sensor are both on the same fibre and co-located at the measurement point. In the embodiment presented, the FBG is used as a reference sensor to eliminate the temperature cross-sensitivity of the EFPI pressure sensor. The combination of an all-fused silica optical fibre EFPI pressure sensor and a FBG retains the advantages of an all-glass structure, is miniature size, exhibits a relatively high pressure sensitivity and facilitates the discrimination of pressure and temperature readings at the point of measurement. These properties make the novel FBG/EFPI hybrid sensor potentially suitable for many applications in both the biomedical and industrial domains.
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