A capnography system for measuring oxygen in liquid and gaseous environments comprising: an optical fiber including a proximal end and distal end; an optical sensor positioned adjacent to the distal end of the optical fiber for measuring oxygen gas level in a medium, the optical sensor comprising: a substrate having a first surface and a second surface opposite the first surface; a first coating layer including an oxygen permeable matrix applied on the first surface of the substrate, the first coating layer including a first fluorophore having a fluorescence characteristic that is dependent upon temperature; a second coating layer including an oxygen permeable matrix and a second fluorophore having a fluorescence characteristic that is dependent upon temperature and oxygen concentration in liquid and gaseous environments that contact the second coating layer; and an oxygen barrier layer between the first coating layer and the second coating layer; an optical luer adapter configured to allow the optical fiber to be affixed to another device enabling measurement of oxygen in gaseous and liquid environments located in or around an organism; an excitation source configured to transmit light from the proximal end of the optical fiber to the distal end of the optical fiber to excite the first and second fluorophores of the optical sensor; and a fluorescence emission sensor configured to receive one or more fluorescence characteristics from each of the first and second fluorophores travelling from the distal end of the optical fiber to the proximal end of the optical fiber. an optical fiber including a proximal end and distal end; an optical sensor positioned adjacent to the distal end of the optical fiber for measuring oxygen gas level in a medium, the optical sensor comprising: a substrate having a first surface and a second surface opposite the first surface; a first coating layer including an oxygen permeable matrix applied on the first surface of the substrate, the first coating layer including a first fluorophore having a fluorescence characteristic that is dependent upon temperature; a second coating layer including an oxygen permeable matrix and a second fluorophore having a fluorescence characteristic that is dependent upon temperature and oxygen concentration in liquid and gaseous environments that contact the second coating layer; and an oxygen barrier layer between the first coating layer and the second coating layer; a substrate having a first surface and a second surface opposite the first surface; a first coating layer including an oxygen permeable matrix applied on the first surface of the substrate, the first coating layer including a first fluorophore having a fluorescence characteristic that is dependent upon temperature; a second coating layer including an oxygen permeable matrix and a second fluorophore having a fluorescence characteristic that is dependent upon temperature and oxygen concentration in liquid and gaseous environments that contact the second coating layer; and an oxygen barrier layer between the first coating layer and the second coating layer; an optical luer adapter configured to allow the optical fiber to be affixed to another device enabling measurement of oxygen in gaseous and liquid environments located in or around an organism; an excitation source configured to transmit light from the proximal end of the optical fiber to the distal end of the optical fiber to excite the first and second fluorophores of the optical sensor; and a fluorescence emission sensor configured to receive one or more fluorescence characteristics from each of the first and second fluorophores travelling from the distal end of the optical fiber to the proximal end of the optical fiber.