Fiber optic sensor coatings with enhanced sensitivity and longevity

ABSTRACT Fiber optic sensors that utilize evanescent field interactions as a detection mechanism have proven to be quite sensitive. We recently reported on the development of this type of distributed sensor for toxic chemicals such as HCN, H 2 S, and Cl 2 . The optical fibers are multimode and consist of a fused silica core and an agent-specific chemically-sensitive cladding. Upon exposure to the corresponding challenge gas, the cladding changes color, resulting in an attenuation of the light throughput of the fiber. These fibers were produced in long lengths using conventional fiber optic draw towers. However, failure mechanisms, such as indicator migration, crystallization, and oxidation, decrease the lifetime of the sensors. We report on recent progress we have made in the effort to optimize the sensor longevity with respect to these degradation mechanisms. The optimizations include covalent attachment of the indicators with the polymer cladding during fiber processing, and the use of antioxidants to minimize degradation. Keywords: chemical sensors, fiber optic chemical sensors, distributed sensors, sensor lifetime