Fiber Bragg grating sensor for accurate and sensitive detection of carbon dioxide concentration

To accurately, sensitively, and rapidly detect carbon dioxide (CO2) concentration, a novel fiber Bragg grating (FBG) CO2 sensor was fabricated based on a polysulfone (PSF)/polyimide (PI) material, surfactant polyethylene glycol (PEG), and temperature-compensated FBG unit. The results indicate that the response sensitivity of the sensor is affected by the PI doping ratio, and the surfactant PEG can effectively shorten the response time of CO2 sensing. The sensitivity and response time of the sensor are positively correlated with the thickness of the PSF/PI/PEG CO2-selective coating. The hydrophobic coating can prevent water molecules from moving into the CO2-sensitive film, and the FBG temperature-compensation unit can effectively eliminate the interference of temperature on CO2 detection. When the PI doping ratio was 10 wt%, the surfactant doping ratio was 0.1 wt%, the thickness of the CO2-sensitive membrane was 49 mu m, and the number of superhydrophobic membrane coatings was 15. In addition, the sensor could accurately measure the CO2 concentration in the temperature range of 25-50 degrees C and relative humidity of 35-80%RH. The sensitivity of the proposed sensor was 3.39 pm/mM, response time was 310 s, limit of detection was 0.087 mM, maximum relative error was less than 7.28%, and the sensor exhibited high selectivity and long service life.