A study of hygrometer based on the method of intracavity laser absorption

The article presents the results of experimental studies of a fiber-optic humidity sensor, the principle of operation of which is based on the method of intracavity laser absorption. A method of intracavity laser absorption is described, which makes it possible to dramatically increase the sensitivity of the fiber humidity sensor by switching to it. A schematic diagram of a fiber optical humidity sensor using a differential detection scheme and a design of an active ring laser fiber consisting of a diode pump laser, a fiber pump beam splitter, two directional couplers, a measuring ring laser, a ring comparison laser, two pump radiation filters and germanium photodetectors are developed. Graphical results of experimental studies of a fiber-optic sensor using a differential registration scheme are demonstrated. Measurements are shown in the range of 1800-1940 nm with a center of ~ 1872 nm, where the absorption of water vapor located in the cuvette is recorded, and from 1940 to 2090 nm - carbon dioxide located in the monochromator and having three absorption bands in this spectral region, according to which the frequency scale of the spectrophotometric hygrometer is calibrated. Comparison of the experimental data with the calculated values showed their satisfactory agreement.