For the NASA SBIR Phase 2 project, Broadband Photonics will develop a distributed fiber optic sensor for in-space hydrogen leak detection. Reliable and fast detection of hydrogen leaks is critical to both operational safety and maintenance of propellant quantities for in-space hydrogen systems. Characteristics of the plume formed by a hydrogen leak are unpredictable in low gravity due to lack of buoyancy effects. The proposed hydrogen fiber sensor can detect any flow direction of a hydrogen leak, determine the leak location, and measure hydrogen concentration. The fiber sensor can also detect hydrogen leaks from unexpected locations in space vehicles caused by stress-induced tiny cracks or other various damages. The proposed sensor will have the same fast response speed and high sensitivity in cryogenic environments as in room temperature. Furthermore, the proposed fiber sensor offers several significant advantages, including reconfigurable, lightweight, one feed-through, easy installation, easy maintenance, and capability of working in radiation harsh environments. Upon Phase 2 completion, the proposed hydrogen fiber sensor prototype will be produced for field trial.