Surface Plasmon Sensing of Gas Phase Contaminants Using a Single-Ended Multiregion Optical Fiber

Fiber-optic gas phase surface plasmon resonance (SPR) detection of several contaminant gases of interest to state-of-health monitoring in high-consequence sealed systems has been demonstrated. These contaminant gases include H₂, H₂S, and moisture using a single-ended optical fiber mode. Data demonstrate that results can be obtained and sensitivity is adequate in a dosimetric mode that allows periodic monitoring of system atmospheres. Modeling studies were performed to direct the design of the sensor probe for optimized dimensions and to allow simultaneous monitoring of several constituents with a single sensor fiber. Testing of the system demonstrates the ability to detect 9 Pa partial pressures of H₂ using this technique, <; 0.04 Pa partial pressures of H₂S, and increases in H₂O concentration from - 70°C frost point. In addition, a multiple sensor fiber has been demonstrated that allows a single fiber to measure H₂, H₂S, and H₂O without changing the fiber or the analytical system.