An ultrahigh-sensitivity fiber-optic humidity sensor based on a full-agar f-p cavity

Abstract

The invention provides an optical fiber humidity sensor with ultrahigh sensitivity and based on an all-agar F-P cavity and a manufacturing method of the optical fiber humidity sensor. The sensor comprises a leading-in optical fiber and the humidity-sensitive agar F-P cavity composed of an agar colloid. The leading-in optical fiber and the agar F-P cavity are directly connected through an end face dipping method, the leading-in optical fiber is used for leading in a light source signal and transmitting reflected light, and the agar F-P cavity is used for sensing humidity changes in the environment. The agar colloid has hygroscopicity because the surface of the agar colloid contains a large number of hydrophilic groups, the agar colloid can expand when absorbing water and shrink when losing water, and the refractive index and size change at the same time. Changes of the refractive index and thickness of an agar film are fully utilized for manufacturing the sensor, the ultra-short agar F-P cavity can be used as a sensing unit, and therefore ultrahigh sensitivity is obtained. Besides, agar powder is cheap, easy to obtain and easy to dissolve in hot water, the cooled colloid is stable in optical property, the coating process is quite simple, a complicated operation process and expensive equipment are not needed, and the manufacturing cost of the sensor can be lowered.

Description

technical field [0001] The invention relates to the technical field of optical fiber sensing, in particular to an ultrahigh-sensitivity optical fiber humidity sensor. Background technique [0002] Humidity sensors are widely used in air-conditioning, food processing, chemical processing and building safety monitoring. Optical fiber humidity sensors have a series of advantages such as small size and light weight, and are more and more popular in the market. In order to detect changes in environmental humidity, there are basically two principles when making an optical fiber humidity sensor. One is based on the change of the refractive index, as described in Patent Document 1 (Chinese Patent Publication No. CN 101776493A), using a fence to surround the sensing sensitive liquid around the periphery of the optical fiber, the length of the sensing area is 0.1-6cm, and the operation is relatively complicated; The other is based on volume change, as described in Patent Document 2 (...

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