Incorporating Optical Fiber Sensors into Fabrics

Optical fiber sensors have many attractive attributes including high sensitivity, environmental robustness, immunity to electromagnetic interference, and the ability to be remotely interrogated. Furthermore, by incorporating optical fibers into woven and nonwoven fabrics these sensors can be distributed across large areas. In woven optical fibers, microscopic bending is an issue due to the fibers going over and under the yarns. Microscopic and macroscopic bending losses are quantified by placing optical fibers on frames of different radii of curvature and measuring the loss of transmitted light. As an example of the non-woven process, electrospinning was used to overlay a net of sub-micron diameter fibers over the optical fibers. This protects the optical fiber, holds it in place, while still permitting flexibility. To form chemical sensors, standard telecommunications grade optical fibers were tapered such that the evanescent wave extended into the environment. Coating the fibers with a thin layer of gold then permits surface plasmon sensors to be formed. However, the resulting sensors were very fragile and hard to place into fabrics. As a result alternative processes were developed that form fiber structures that are robust enough to withstand textile manufacturing processes yet still allow interaction with the environment.