An oxygen sensing system comprises a substrate structured to communicate optical signals. An oxygen sensing layer is disposed on the substrate and comprises an oxygen sensing molecule in a matrix in a first unexcited state and formulated to: (a) be excited by a first optical signal to move to a second state; (b) be quenched in the second state by oxygen; and (c) emit a second optical signal corresponding to an amount of oxygen. A protective layer, disposed on the oxygen sensing layer, includes at least one of i) an oleophobic layer and ii) an anti-fouling layer. A controller is optically coupled to the substrate and structured to generate the first optical signal, receive the second optical signal and determine oxygen concentration from the second optical signal.