Conception and preliminary evaluation of an optical fibre sensor for simultaneous measurement of pressure and temperature

Abstract

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.

Fiber-optic combined FPI/FBG sensors for monitoring of radiofrequency thermal ablation of liver tumors: ex vivo experiments

“…Several EFPI-based configurations have been recently presented [21][22][23][24][25][26][27][28]; in addition, EFPI-based medical devices are commercially available [29]. It is possible to combine an EFPI probe with a fiber Bragg grating (FBG) [30,31], acting as temperature sensor in proximity of the EFPI sensor, to provide a dual sensing with cross compensation; such configuration has been proposed in [26][27][28]. In [26,27], a dual EFPI/FBG sensor is proposed, achieving 1.68 nm∕kPa pressure sensitivity, and 1.7 nm∕°C cross sensitivity; [28] proposes a novel manufacturing technique based on UV mold, with limited biocompatibility, and 1.53 nm∕kPa and 15.8 nm∕°C sensitivity coefficients.…”

“…It is possible to combine an EFPI probe with a fiber Bragg grating (FBG) [30,31], acting as temperature sensor in proximity of the EFPI sensor, to provide a dual sensing with cross compensation; such configuration has been proposed in [26][27][28]. In [26,27], a dual EFPI/FBG sensor is proposed, achieving 1.68 nm∕kPa pressure sensitivity, and 1.7 nm∕°C cross sensitivity; [28] proposes a novel manufacturing technique based on UV mold, with limited biocompatibility, and 1.53 nm∕kPa and 15.8 nm∕°C sensitivity coefficients. Commercial devices [29], on the other side, do not offer dual sensing option, and are not compatible with >60°C temperature operation.…”

Polyimide-Coated Fiber Bragg Grating Sensors for Humidity Measurements

“…Figure 13 is the output spectrum of the fiber laser sensor, measured at port "A" of a 3-dB optical coupler, OC 1 . From this result, it is clear that this sensor system actually worked in a dual-wavelength lasing mode with two oscillating wavelengths at 1537,28 nm and 1541,64 nm, respectively.…”

“…FBG 1 was taken as a vibration or temperature sensor and FBG 4 as a wavelength reference of FBG 1 .A n o t h e rp a i ro fF B G s ,F B G 2 and FBG 3 also had same Bragg wavelength at λ = 1541,64 nm. FBG 2 was coated with a ten-layer polyimide film as a humidity sensor, while FBG 3 coated with single polyimide layer as FBG 4 's wavelength reference.…”

“…One important topic in sensor applications is how to extend the sensor system ability to achieve the simultaneous detections of multiple physical parameters within a single measurement process [1,23,26,27,29,37]. In many applications, for example, in the pump system, the vibration and temperature are two important parameters that often are used for evaluating working states of the pump system, especially of bearings, shafts and gear box subsystems.…”