Exposed-core microstructured optical fibers for real-time fluorescence sensing.

New methods for fabricating glass exposed-core microstructured optical fiber are demonstrated. The fiber designs consist of an optical fiber with a suspended micron-scale core that is partially exposed to the external environment, which is particularly useful for sensing. These fibers allow for strong evanescent field interactions with the surrounding media due to the small core size, while also providing the potential for real-time and distributed measurements. The experimental performance of an exposed-core fiber is compared to an equivalent microstructured fiber with an enclosed (protected) core in terms of their performance as evanescent field sensors. We demonstrate that the exposed-core fiber can provide a significantly improved measurement response time.