Gas/liquid detection system based on intra-cavity absorption spectroscopy and tilted fiber Bragg grating

Abstract

Abstract A gas/liquid detection system is developed based on the intra-cavity absorption spectroscopy (ICAS) and a tilted fiber Bragg grating (TFBG). Multiple gases such as acetylene, carbon monoxide and ammonia gas with absorption lines within C-band can be detected using the proposed scheme. The wavelength sweeping range can be controlled to obtain a specific number of absorption lines to meet the requirements on different measurement accuracy. In this work, a TFBG structure is introduced into the ICAS technique to realize the sensing of liquid refractive index. The TFBG works around the wavelength of 1550 nm, which allows a long-distance signal transmission and a flexible system adjustment. The proposed system has been applied to detect the concentration of acetylene with an absolute error of less than 46 ppm. In addition, a set of glycerol-water solutions with refractive indices from 1.3959 to 1.4430 have been measured using the proposed scheme with a sensitivity of 528.2 nm/RIU.