Michelson interferometer based optical-fiber refraction index sensor and measuring method thereof

Abstract

The invention discloses a Michelson interferometer based optical-fiber refraction index sensor and a measuring method thereof. The sensor comprises a broadband light source (1), an optical fiber coupler (2), a measuring sensing head (3), a reference sensing head (4), a spectrometer (5) and a computer (6), wherein the broadband light source (1) is connected to a first input port of the optical fiber coupler (2), a first output port of the optical fiber coupler is connected to the measuring sensing head (3) by an optical fiber, a second output port of the optical fiber coupler is connected to the reference sensing head (4) by an optical fiber, and a second input port of the optical fiber coupler is connected with the spectrometer. In the measuring method disclosed by the invention, interference phenomenon happens when light reflected by the reference sensing head and the measuring sensing head passes through the optical fiber coupler, wherein the contrast of interference fringes is changed with the refraction index of a to-be-measured matter in which the measuring sensing head is located; the contrast of interference fringes is measured by the spectrometer and the computer; then, the refraction index of the to-be-measured matter is calculated by using the computer. The sensor and the method disclosed by the invention can realize high-precision and large-range refraction index measurement; and the sensor is simple in structure, and easy to operate.

Description

technical field [0001] The invention relates to a refractive index sensor, in particular to an optical fiber refractive index sensor based on a Michelson interferometer and a measuring method thereof. Background technique [0002] Refractive index is a very important parameter in the fields of physics, biology, chemistry and other disciplines, and its accurate measurement is of great significance and application in chemical industry, medicine, food and other related industrial sectors. Therefore, many methods for measuring the refractive index have emerged. Traditional measurement methods include grazing incidence, diffraction grating, laser irradiation and CCD measurement, as well as broadband absorption spectroscopy, titration and fluorescence quenching, but most of these methods are limited to the visible light range. Subsequently, some new technologies such as photoacoustics, SPR sensors, and Raman spectroscopy have emerged, but these methods are expensive and not easy ...

AI Technical Summary

Problems solved by technology

Traditional measurement methods include grazing incidence, diffraction grating, laser irradiation and CCD measurement, as well as broadband absorption spectroscopy, titration and fluorescence quenching, but most of these methods are limited to the visible range

Subsequently, some new technologies such as photoacoustics, SPR sensors and Raman spectroscopy have emerged, but these methods are expensive and not easy to operate

The refractometer based on long-period fiber grating has high sensitivity, but because the long-period fiber grating is greatly affected by its own bending, the reliability is greatly affected

Although the refractometer based on Fabry-Perot cavity has the advantage of small size, it is complicated to manufacture and expensive, and is easily affected by the stability of the light source

The refractive index sensing method based on fiber Bragg grating generally needs to remove the cladding of the fiber to increase the interaction between the evanescent field of the fiber and the material of the refractive index to be measured, causing the Bragg wavelength shift of the fiber Bragg grating to realize the change of the refractive index. Measurement, the disadvantage of this method is that because the cladding of the optical fiber is removed, the bearable strength is weakened, the stability is reduced, the application range is limited, and the cost is increased

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