Analyte collection and testing systems and methods, and more particularly to testing systems and methods that achieve significant improvements in the detection of fluorescence signals in the reader by modulating the applied optical excitation. Also described herein are optical detection apparatuses and methods for removable photonic chips that do not require translation for calibration when coupling the photonics chip with the sensing system. Also described herein are methods and apparatuses for accurately calibrating a dilution factor when reading from a photonics chip.