Abstract
This investigation describes a detailed analysis of the fabrication and testing of optical fibre pressure and temperature sensors (OFPTS). The optical sensor of this research is based on an extrinsic Fabry–Perot interferometer (EFPI) with integrated fibre Bragg grating (FBG) for simultaneous pressure and temperature measurements. The sensor is fabricated exclusively in glass and with a small diameter of 0.2 mm, making it suitable for volume-restricted bio-medical applications. Diaphragm shrinking techniques based on polishing, hydrofluoric (HF) acid and femtosecond (FS) laser micro-machining are described and analysed. The presented sensors were examined carefully and demonstrated a pressure sensitivity in the range of = 2–10 and a resolution of better than = 10 Pa (0.1 cm HO). A static pressure test in 38 cmHO shows no drift of the sensor in a six-day period. Additionally, a dynamic pressure analysis demonstrated that the OFPTS never exceeded a drift of more than 130 Pa (1.3 cm HO) in a 12-h measurement, carried out in a cardiovascular simulator. The temperature sensitivity is given by , which results in a temperature resolution of better than = 0.1 K. Since the temperature sensing element is placed close to the pressure sensing element, the pressure sensor is insensitive to temperature changes.
Highlights
Sensors in research and industry demand measurements with great accuracy and high stability. in the medical field, a sensor has to be very accurate and should exhibit a high long-term stability with very little drift
The shift of the Fabry–Perot interferometer (FPI) spectrum is calculated by applying a pressure up to 100 kPa, in a pressure chamber designed for the optical fibre pressure and temperature sensors (OFPTS)
The OFPTS is mounted in the chamber to a ferrule connector (FC) and is in close proximity to an Arduino nano Board with a BMP085 pressure reference sensor
Summary
Sensors in research and industry demand measurements with great accuracy and high stability. Recent developments in optical fibre sensors (OFS) demonstrated an increasing growth in medical applications [1] to measure parameters, including pressure [2], force [3], temperature [4] or refractive index [5]. In the case of the medical field, OFS exhibit inherent advantages, such as their small size and the biocompatible glass structure These sensors are resistant to organic and chemical degradation, which makes them compatible for animal and human biology. Recent improvements in the fabrication of low-cost optical fibre pressure and temperature sensor (OFPTS) for medical applications are further discussed in this paper. The pressure measurement of an EFPI is affected by temperature, the simultaneous acquisition of both measurements can be used to compensate ambiguity due to cross-sensitivity [13,14,15]
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