A system to optically measure a physiological parameter of tissue of a patient is provided. The system includes a tissue interface assembly configured to emit an optical signal into the tissue, receive a first measurement signal based on the optical signal propagating along a first path, receive a second measurement signal based on the optical signal propagating along a second path, and transfer the first measurement signal and the second measurement signal for delivery to a processing system. The processing system is coupled to the tissue interface assembly and configured to receive the first measurement signal and the second measurement signal, determine a phase delay between the first measurement signal and the second measurement signal based on a cross correlation analysis, and identify a value of the physiological parameter of the patient based on at least the phase delay between the first measurement signal and the second measurement signal.
