Abstract
A high sensitivity optical fiber gas pressure sensor based on paralleled Fabry–Pérot interferometers (FPIs) was demonstrated. One micro-cavity FPI is used as a reference FPI (FPI-1) to generate a Vernier effect and the other FPI (FPI-2) is used as a sensing tip. Both FPIs are connected by a 3-dB coupler to form a paralleled structure. The FPI-1 was fabricated by fusion splicing a piece of hollow core fiber (HCF) between two sections of single-mode fibers (SMF), whereas FPI-2 was formed by fusion splicing a section of HCF between SMF and a piece of HCF with a slightly smaller inner diameter for sensing pressure. The gas pressure sensitivity was amplified from 4 nm/MPa of single FPI to 45.76 nm/MPa of paralleled FPIs with an amplification factor of 11.44 and a linearity of 99.9%. Compared with the traditional fiber gas pressure sensors, the proposed sensor showed great advantages in sensitivity, mechanical strength, cost, and temperature influence resistant, which has potential in adverse-circumstance gas pressure sensing.
Highlights
Optical fiber gas pressure sensors have been widely used in automatic production, aerospace, military, and medical diagnosis fields due to their advantages of compactness, anti-interference, and high-accuracy [1,2,3]
Various optical fiber sensors, such as long-period fiber gratings (LPFGs) [4,5], fiber Bragg gratings (FBGs) [6,7], Mach–Zehnder interferometers (MZIs) [8,9], and Fabry–Pérot interferometers (FPIs) [10,11] have been developed to measure gas pressure, and among them, FPI is very promising owing to its flexible manufacturing, easy operation, and convenient combination
In the open cavity structure, the femtosecond laser (Fs)–P cavity is directly in touch with the external environment, and the gas pressure can be detected by monitoring the shift of the reflection spectrum, which is induced by the change of the refractive index (RI) distribution [12,13]
Summary
Optical fiber gas pressure sensors have been widely used in automatic production, aerospace, military, and medical diagnosis fields due to their advantages of compactness, anti-interference, and high-accuracy [1,2,3]. The mechanism of FPI sensors for measuring gas pressure is to obtain the gas pressure variation tendency by observing the change of the fiber refractive index (RI) or the F–P cavity length. Reported an F–P gas pressure sensor based on a side-opened channel structure, which realized the gas pressure sensitivity of 4.24 nm/MPa [14]. The Vernier effect based on MZIs [30] and FPIs [31] have been proposed and exhibited an ultra-high sensitivity of. A high sensitivity gas pressure sensor using paralleled FPIs based on the Vernier effect is demonstrated. The proposed gas pressure sensor is expected to be used in broader areas for its high sensitivity, low cost, high mechanical strength, and temperature influence resistance
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