Highly sensitive pressure sensor based on long-period gratings written in a boron co-doped optical fiber

The paper presents a novel pressure sensor based on long-period gratings (LPGs) written with an arc-induced method in a boron co-doped photosensitive fiber. The achieved pressure sensitivity for these gratings is at least four to eight times higher than for gratings written in other fibers which have been presented to date. The sensitivity is strongly dependent on the investigated order of modes, and for the 7th cladding mode can reach δλ/δp = 78 pm bar−1. It was found that the incorporation of B2O3 in the core of the fiber is responsible for the higher pressure sensitivity of these LPGs. This conclusion is based on consideration of variations in the elastic properties of the glass versus its composition. According to our simulations, the pressure-optic coefficient of the B/Ge-doped core of the fiber is 2.03 RIU bar−1. The sensitivity of the structure to temperature and to external refractive index is discussed from the point of view of the possible indirect influence of these conditions on the pressure response. It is proven that the experiment was conducted in such a way that the measured pressure sensitivity was not significantly affected by variations in either the temperature or the external refractive index.

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