Optical Fiber Fabry–Perot Interferometric CO2 Gas Sensor Using Guanidine Derivative Polymer Functionalized Layer

In this paper, a polymer polyhexamethylene biguanide (PHMB) based Fabry-Perot (FP) interferometric optical fiber sensor for carbon dioxide gas detection at atmospheric pressure is investigated and experimentally demonstrated. The absorption and release of CO₂ gas molecules lead to the refractive index change of the PHMB. The length of CO₂ sensitive FP cavity can be easily controlled by using the Czochralski method. The real-time measurement result shows that CO₂ gas concentration with a sensitivity of 12.2 pm/ppm in a 0-700 ppm range can be achieved.