Self-referencing optical intensity sensor based on radio-frequency spectrum interrogation

•Non-interfering superposition through Mach-Zehnder structure doubles the input RF frequency.•Power imbalance induced by the sensing measurand influences the peak values of RF spectrum.•Correlated peak values of RF spectrum provides immunity to input optical intensity variation.•The sensor system uses uncomplicated data processing and has capability of multiplexing. This paper proposes an optical sensor system that is based on non-interfering optical power superposition in Mach-Zehnder configuration. The sensor generates radio-frequency (RF) spectrum that responds to the imbalance of optical power between the branches of the Mach-Zehnder structure induced by the sensing measurand. The sensing signal provides self-referencing intensity-based interrogation without requiring typical expensive optical frequency apparatus and complicated signal processing technique. Its reliability is demonstrated in a load sensing application.