Abstract: Optical sensor measurement methods that convert a wavelength change in an optical sensor to a measurable optical intensity change, which can be calibrated and used to measure optical wavelength change and environmental changes such as temperature or strain which affect sensor wavelength. The current invention makes use of tunable fiber Fabry-Perot filters as the wavelength selective elements for the wavelength to optical intensity conversion. The invention provides high measurement sensitivities to small amplitude, high frequency modulations to the fiber sensor center wavelength, accommodates for system drift from thermal or other perturbations, and enables either frequency mode or time varying resolution of sensor modulation events. Selection of proper Fabry-Perot optics allow for measurement optimization of either high sensitivity or high strain measurement range.