Abstract
This paper presents the fabrication of a fiber Bragg grating (FBG)-based Fabry–Perot (FP) structure (7 mm total length) in an adiabatic fiber taper, investigates its strain and temperature characteristics, and compares the sensing characteristics with a standard polyimide coated FBG sensor. Firstly, a simulation of the said structure is presented, followed by the fabrication of an adiabatic fiber taper having the outer diameter reduced to 70 μ m (core diameter to 4.7 μ m). Next, the sensing structure, composed of two identical uniform FBG spaced apart by a small gap, is directly inscribed point-by-point using infrared femtosecond laser (fs-laser) micromachining. Lastly, the strain and temperature behavior for a range up to 3400 μ ε and 225 ° C, respectively, are investigated for the fabricated sensor and the FBG, and compared. The fabricated sensor attains a higher strain sensitivity (2.32 pm/ μ ε ) than the FBG (0.73 pm/ μ ε ), while both the sensors experience similar sensitivity to temperature (8.85 pm/ ° C). The potential applications of such sensors include continuous health monitoring where precise strain detection is required.
Highlights
Fiber sensors have been replacing conventional electronic sensors at a rapid rate because of their high sensitivity, compactness, robustness, immunity to electromagnetic interferences [1], etc
We present the detailed fabrication process of a Bragg grating-based FP sensor within the core of the biconical fiber taper using fs-laser
The sensing characteristics of the fabricated sensor were investigated for strain and temperature measurands, and compared with the response of an fiber Bragg grating (FBG), which is a widely used fiber sensor for continuous monitoring applications
Summary
Fiber sensors have been replacing conventional electronic sensors at a rapid rate because of their high sensitivity, compactness, robustness, immunity to electromagnetic interferences [1], etc. A standard way of sensor fabrication is by writing a sensing structure in an optical fiber using UV laser, which requires the optical fiber to be photosensitive. This article investigates the feasibility of point-by-point writing of the FP structure in a fiber taper using fs-laser micromachining because scalability is one of the foremost requirements in sensor fabrication and deployment for many industrial applications. This article investigates the strain and temperature characteristics of the sensor experimentally and will compare the response with a standard FBG sensor, which is the most commonly used fiber sensor for various structural health monitoring applications. The device was found to have a higher sensitivity to strain and has the potential to be used for structural health monitoring in harsh environments with long-term stability
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