Abstract
This study presents an extrinsic Fabry–Perot interferometric (EFPI) fiber-optic strain sensor with a very short cavity. The sensor consists of two vertically cut standard single-mode fibers (SMFs) and a glass capillary with a length of several centimeters. The two SMFs penetrate into the glass capillary and are fixed at its two ends with the use of ultraviolet (UV) curable adhesives. Based on the use of the lengthy glass capillary sensitive element, the strain sensitivity can be greatly enhanced. Experiments showed that the microcavity EPFI strain sensor with initial cavity lengths of 20 μm, 30 μm, and 40 μm, and a capillary length of 40 mm, can yield respective cavity length–strain sensitivities of 15.928 nm/με, 25.281 nm/με, and 40.178 nm/με, while its linearity was very close to unity for strain measurements spanning a range in excess of 3500 με. Furthermore, the strain–temperature cross-sensitivity was extremely low.
Highlights
Strain is one of the most important parameters that needs to be continually measured for monitoring buildings, bridges, railways, tunnels, and marine and aerospace engineering structures [1,2,3,4,5,6,7,8]
In the case of the long period fiber gratings (LPFGs) strain sensors, when a broadband light is illuminated on the sensor, some resonant peaks will appear in the transmission spectrum, which can be linearly shifted by the imposed strain
A fiber-optic strain sensor was proposed based on an EPPI microcavity structure
Summary
Strain is one of the most important parameters that needs to be continually measured for monitoring buildings, bridges, railways, tunnels, and marine and aerospace engineering structures [1,2,3,4,5,6,7,8]. Many different types of EFPI microcavity strain sensors have been proposed, limited by the wavelength range of the light source can be used, and the fabrication difficulties, the cavity length cannot be infinitely reduced. The main difficulty of this method is the optical lengths of the main sensing FP cavity and the matched FP cavity need to be precisely matched by carefully controlling the two cavity lengths Another effective way to increase the strain sensitivity is separate the strain active length from the FP cavity length. The proposed EFPI microcavity fiber-optic strain sensor has a centimeters-long glass capillary at its two ends. The proposed EFPI microcavity fiber-optic strain considerably enhanced sensitivity within a large measurement range, since sensitivity increasing effects sensor has a considerably enhanced sensitivity within a large measurement range, since sensitivity of the microcavity and the separation of the strain active length from the FP cavity length are combined.
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