Simultaneous Measurement of Gas Pressure and Temperature Using a Microbubble Resonator Combined With an FBG

We propose and demonstrate a microbubble resonator combined with a fiber Bragg grating (FBG) for simultaneous measurement of gas pressure and temperature. The approach used allows for very close proximity (<200 μm) between the FBG and the microbubble resonator. The microbubble resonator is fabricated in a section of hollow-core fiber (HCF), spliced to a single-mode fiber (SMF) with a pre-inscribed FBG to form a single-ended open structure. Fresnel reflection from the HCF cleaved end means that broadband light is reflected backwards in the same direction as the Bragg wavelength from the FBG. A tapered fiber couples the reflected broadband light to the microbubble, and both the Bragg peak and whispering gallery modes (WGM) are distinguishable in the signal available for interrogation. The experimental results show that this sensor structure consisting of a microbubble resonator combined with an FBG has the ability to simultaneously measure gas pressure and temperature, while also eliminating temperature crosstalk in gas pressure measurement and providing a useful platform for high accuracy gas pressure detection.