Measurement of high pressure and high temperature using a dual-cavity Fabry–Perot interferometer created in cascade hollow-core fibers

A High Sensitivity Temperature Sensing Probe Based on Microfiber Fabry-Perot Interference

“…It has a more compact structure for developing high-performance temperature microprobes. Femtosecond laser [31] or ion beam etching technology [32], as well as high-precision fiber-splicing technology [36,37], can improve its temperature detection limit to as high as 1200 °C, making it suitable for extreme high temperature environments; furthermore, sol coating [35] or temperature-sensitive polymer encapsulation technology [39] can be used for enhance normal temperature microprobes, which will be a promising candidate for implantable microsensors for health or environmental monitoring under 200 °C.…”

“…In addition to the above complex optical fiber structures, single polymer optical fibers have been demonstrated with a temperature sensitivity of ~10 −3 °C [27], where the temperature performance were revealed by the transmission power and the effect of relative and twist have been experimentally obtained [28,29]. Furthermore, their packaging size is hard to reduce further depending on the bending loss of the optical fiber [30], which will seriously limit their application in a narrow space; the latter ones are carried out as reflective structures, where the temperature sensitive cavity was constructed at the end of the optical fiber by laser or ion beam processing, chemical etching or film forming and special fiber splicing technologies [31,32,33,34,35,36,37]. Among them, femtosecond laser processing can machine a refractive index turning point with good repeatability in the optical fiber, which was used as a Fabry-Perot cavity and can work at high temperatures up to 1000 °C [31]; focused ion beams can etch an air cavity at the tip of an optical fiber, based which a Fabry-Perot temperature sensor with a sensitivity of −654 pm/°C has been experimentally demonstrated [32].…”

“…The Fabry-Perot interferometer probe can be obtained conveniently and quickly by chemical etching or film forming technology [34], however, the fabrication repeatability is low, and the structural parameters are difficult to control accurately [35]. By using the special hollow-core photonic bandgap fiber (HC-PBF) or PCF, the temperature working range and sensitivity of cascaded splicing fiber based Fabry-Perot interferometer has been experimentally verified as high as 1200 °C and 17 nm/°C, respectively, but their structures are relatively fragile [36,37].…”

Comparison of Fiber-Based Gas Pressure Sensors Using Hollow-Core Photonic Crystal Fibers

“…For pressure sensing, the sensing element is required to be accessible to the external environment to sense the pressure change. Hollow-core PCF thus becomes a good candidate, which can be used to form the sensing cavity [3,6,7,[16][17][18] in a Fabry-Perot (FP) cavity configuration. Compared to FPI-based pressure sensors with solid PCFs, FPIs with air-cavity have additional advantage of low temperature cross-sensitivity [15].…”

Monolithic Structure-Optical Fiber Sensor with Temperature Compensation for Pressure Measurement

“…Optical fiber sensors are excellent candidates for constructing smart levees and dams because of many advantages of optical fiber sensing technology, such as their intrinsic safety, good insulation performance, strong immunity to electromagnetic interference, high sensitivity, high temperature resistance, and excellent distributed monitoring ability, and they are an effective way to address the seepage pressure monitoring problem of levees and dams. The Fabry–Perot interferometer (FPI) optical fiber pressure sensors have drawn great attention due to their high sensitivity and anti-polarization fading characteristic, and they have been extensively investigated in the fields of pressure [4,5,6] and strain [6,7,8,9] monitoring since 1988 [10]. The diaphragm-assisted FPI optical fiber sensors, which were first reported in 1991 [11], are the one of the important types of FPI sensor, and they have become the research focus in the field of acoustic wave [12,13], photo-acoustic spectroscopy [14,15], and for the improvement of performance parameters for dynamic and static pressure measurements [16,17,18,19,20].…”