A fiberoptic deflectometer is under development to diagnose bearing degradation of the turbine end bearings of the Space Shuttle Main Engine (SSME) high pressure oxidizer turbopump (HPOTP). The deflectometer, which measures bearing outer race deformations, provides better diagnostic sensitivity than traditional diagnostic sensors (such as accelerometers). The sensor construction, materials, and method of bringing the optical signal out of the HPOTP are described. Accuracy and repeatability results obtained in a static liquid nitrogen test rig are presented. Finally a potentially viable solution to the difficult problem of calibration in cryogen is discussed.