Temperature-insensitive chemical sensor based on a fiber Bragg grating

Temperature-insensitive fiber Bragg grating sensors have been demonstrated by discriminating the peak wavelength difference caused by etching the cladding of half of the grating region. Thermal characteristics and chemical sensitivity of two fiber Bragg gratings are experimentally investigated. Experimental results indicate that the etched half and the rest of the grating region have almost the same thermal response, and concentration changes of the surrounding chemical solutions can be detected by measuring the peak wavelength difference. The two sensors have been used to measure the concentrations of propylene glycol solutions and sugar solutions, and one of them could detect 0.067% and 0.027% concentration change for two kinds of solutions with a low-cost wavelength interrogation module.