On-line dualbeam interference-type fiber refractive index sensor and refractive index detection system

Abstract

The invention belongs to the technical field of sensing, and provides an on-line dualbeam interference-type fiber refractive index sensor. The dualbeam interference-type fiber refractive index sensor comprises first single-mode fiber, light splitting fiber, offset-welded sensing single-mode fiber and reference single-mode fiber, light composition fiber and second single-mode fiber; while measuring, the sensing single-mode fiber is positioned in a to-be-checked substance; the wide spectrum light is input from the first single-mode fiber, then is coupled to the sensing single-mode fiber, and is subjected to propagation by a fiber core mode and a cladding mode and then mode transition, the fiber core mode is coupled to a cladding layer for continuous propagation, the partial energy of the cladding mode is coupled in the fiber core for continuous propagation, the light output by the reference single-mode fiber is subjected to light composition interference in the light composition fiber and is output through the second single-mode fiber, wavelength demodulation is carried out, and the refractive index change is obtained. Due to the light path compensation of the reference single-mode fiber, interference fringe drift distance is large, sensitivity is higher; the cooperation of the sensing single-mode fiber and the reference single-mode fiber have temperature compensating effect, so that the interference immunity and detection precision of the sensor are increased.

Description

technical field [0001] The invention belongs to the technical field of optical sensing, and in particular relates to an online double-beam interference optical fiber refractive index sensor and a refractive index detection system. Background technique [0002] The online dual-beam interferometric optical fiber sensor is an interferometric sensor that detects through the interference between the core mode and the cladding mode. Due to its simple process, low cost, and compact structure, this sensing structure has attracted the attention of researchers and is used in In the study of refractive index sensing, it is of great significance to optical detection in the fields of biology and medicine. Such as figure 1 , the core components of the existing on-line dual-beam interference optical fiber refractive index sensor include an input single-mode fiber 101, a light-splitting structure 102, a sensing single-mode fiber 103, a light-combining structure 104, and an output single-mo...

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Problems solved by technology

[0003] However, this existing refractive index sensor has some disadvantages. Because the refractive index of the cladding mode has low sensitivity to external refractive index changes, and the free spectral range of the interference fringes is relatively small, the drift of the interference fringes is too small, so the refractive index Sensitive sensitivity is low

In addition, the thermo-optic coefficients of the core and cladding of the optical fiber are quite different, which increases the temperature drift, increases the error of the measurement results, and lowers the accuracy.

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