Luna proposes to continue development on a high-speed fiber optic sensor and readout system for cryogenic temperature measurements in liquid oxygen (LOX) and liquid hydrogen (LH2). This work will be based on the solid proof of feasibility completed during the Phase I STTR project and will result in 1) extremely high-speed, minimally-intrusive fiber optic temperature sensors for cryogenic and high-temperature applications and 2) an industrially robust, turn-key fiber optic readout system capable of servicing numerous sensor types, addressing a broad range of needs within NASA. The sensors and system developed here will be specifically designed to meet NASA Stennis needs for facility and test article health-monitoring. Additionally, the basic readout system could be extended to include rotary and linear position for valve position feedback, which supports NASA's stated need for smart system components such as control valves, regulators, and relief valves that provide real-time, closed-loop control, component configuration, automated operation, and component health. Luna's research subcontractor, Virginia Tech, will develop new and improved methods to accurately model the transient interaction between cryogenic fluid flow and immersed sensors that predict the dynamic load on the sensors, frequency spectrum, heat transfer, and effect on the flow field as part of this effort.