Gas detection method and gas detection system based on hollow-core optical fiber photothermal effect

Abstract

The invention provides a gas detection method based on a hollow-core optical fiber photothermal effect. The method comprises the following steps: filling a fiber core of the hollow-core optical fiber with to-be-detected gas; inputting detection laser and periodically-modulated pumping laser into the hollow-core optical fiber; generating the photothermal excitation effect by the to-be-detected gas after the pumping laser is absorbed, and periodically modulating the laser phase; demodulating the phase modulation information of the detection laser to obtain the concentration of the to-be-detected gas, wherein the periodic modulation is the modulation of wavelength and / or density of the pumping laser. The pumping laser and the detection laser are used for detection, the method is simple and practical, an extremely-small spot area can be realized, the optical power density is greatly improved, and the photothermal signal strength is enhanced; the selective ppb-magnitude gas concentration measurement can be realized, and the method and the system are universally suitable for the gas capable of absorbing the light of near-infrared band.

Description

technical field [0001] The invention belongs to the technical field of gas measurement, and in particular relates to a gas concentration detection method and system based on the photothermal effect of a hollow-core optical fiber. Background technique [0002] Among the existing gas concentration detection methods, the most important one is the spectral detection technology based on light absorption. The simplest method is to use direct absorption spectroscopy (DAS). According to Lambert-Beer's law, when light of a specific wavelength passes through the gas to be measured, part of the light energy is absorbed by the gas to be measured, so that the transmitted light power is reduced to analyze the measured gas. Measure the gas concentration. Although this method is simple and effective, it is interfered by the light absorption length (gas cell length) and various noises in the actual detection process, which often causes inaccurate results due to interference factors in the d...

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Problems solved by technology

However, the measurement using this method needs to be combined with an electrical detector, and can only achieve single-point measurement, which cannot meet the needs of various multi-point and remote measurements during the measurement process

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