Cryogenic leak detection is critical to space missions, particularly for avoiding launch delays. The real-time, multi-location, early leak detection of oxygen and hydrogen down to ppm levels is extremely important for safety, reliability, and economic reasons. One of the significant challenges in meeting these requirements has been the drift effect that is caused by the exposure to extreme temperatures. This paper discusses the effect of the development of a sensor supporting matrix to improve the overall behavior of oxygen and hydrogen optical sensors at cryogenic temperatures. These achievements offer great advances in the fiber optic leak detection of cryogenic oxygen and hydrogen, specifically for space applications. Emphasis on operational conditions such as -150 K and vacuum environments, in addition to performance characteristics such as sensitivity (10 ppm) and response time (similar to 3 sec), are addressed in this paper.