Liquid refractive index sensing method and liquid refractive index sensing device

Abstract

The invention relates to a liquid refractive index sensing method and a liquid refractive index sensing device. The method comprises the following steps: enabling broadband probe light to pass through a hollow Bragg fiber filled with a liquid, wherein the hollow Bragg fiber comprises a hollow fiber core, a cladding and a protective layer, the cladding is of a plurality of periodic structures, the periodic structures contain a plurality of normal periodic structures formed by a first dielectric layer and a second dielectric layer and a defected periodic structure formed by a first dielectric layer and a defect layer, the refractive index of the defect layer is greater than or equal to that of the first dielectric layer, and the refractive index of the first dielectric layer is greater than that of the second dielectric layer; obtaining the transmission spectrum of the broadband probe light passing through the hollow Bragg fiber, and then obtaining a resonant wavelength generated by mutual coupling of a defect mode and a fiber mode in the hollow Bragg fiber; using the resonant wavelength as a characteristic wavelength, and realizing the refractive index sensing of liquid to be detected based on a linear relation of the characteristic wavelength and the refractive index of the liquid to be detected. High sensitivity can be maintained, and meanwhile a relatively large liquid refractive index dynamic measurement range is obtained.

Description

technical field [0001] The invention relates to the technical field of optical fiber sensing, in particular to a liquid refractive index sensing method and a liquid refractive index sensing device. Background technique [0002] Liquid refractive index measurement has important application value in many aspects closely related to the national economy and people's livelihood, such as environmental water quality monitoring, industrial process control, marine scientific research, food safety testing, and biomedical diagnosis. focus on. In recent years, fiber optic sensor technology has made great progress, and has gradually emerged in many application fields due to its advantages of anti-electromagnetic interference, high sensitivity, compact structure, and easy construction of long-distance and distributed sensor networks. People began to use optical fiber sensing technology to realize remote, real-time and online measurement of liquid refractive index. [0003] A variety of ...

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Problems solved by technology

Although both use the sensing mechanism that the central wavelength of PBG as the characteristic wavelength drifts with the change of the refractive index of the core filling liquid, the output characteristics of the refractive index sensors based on the combination of these two types of materials are quite different.

Although the Bragg optical fiber sensor based on the high refractive index difference cladding material has a large dynamic measurement range (1.402-1.578), its sensitivity is only 330nm / RIU (K.J.Rowland, S.Afshar V., A. Stolyarov, Y.Fink, and T.M.Monro, "Bragg waveguides with low-index liquid cores," Opt. Express, vol.20, no.1, pp.48-62, Jan.2011.); while Bragg waveguides based on low-index-difference cladding materials Although the optical fiber sensor has a sensitivity as high as 1400nm / RIU (theoretical value is about 2100nm / RIU), its dynamic measurement range is small (1.333-1.378), which is mainly due to the linear relationship between the characteristic wavelength and the refractive index of the fiber core. The range will be worse (Qu H, SkorobogatiyM. "Liquid-core low-refrative-index-contrast Bragg fiber sensor", Appl. Phys. Lett., 2011, 98:201114; H.Qu and M.Skorobogatiy, "Resonant bio-andchemical sensors using low-refractive-index-contrast liquid-core Braggfibers,"Sens.Actuators B,161(1),2012,261-268.)

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