Abstract: A gas sensor system and its method of fabrication is disclosed. The sensor system comprises an optrode, light source, and a light detector. In a sensor for hydrogen gas, the optrode is comprised of a porous substrate into which an intimate mixture of reagent and catalyst is incorporated. The mixture reacts with the hydrogen to produce a color/intensity change in relation to the concentration of gas. The optrode further includes a reversing agent, boron, to restore the benchmark conditions of the sensor system in real-time. The method of fabricating the optrode includes the steps of cleaning; etching to achieve the proper porosity; incorporating the reagent, catalyst, and reversing agent using capillary action; and removing excess reagent and catalyst.