Abstract: A system and method use an optical strain gage to measure engine bearing thrust. Reflecting surfaces, or mirrors, encapsulated in a housing, are separated by an initial gap. An incoming fiber receives light from an interferometer and transmits the light to the reflecting surfaces, which then reflect the light back to the interferometer. An engine load is introduced to a bearing element bonded to the housing, and the rotor thrust into the bearing element causes a change in the initial gap. An increase in the initial gap indicates tension and a decrease in the initial gap indicates compression.