Stress sensor based on periodically inserted color-changing tactile films to detect mishandling of fiber optic cables

摘要

The present invention is a fiber optic cable which uses pressure sensitive films or tactile films in order to detect areas on a fiber optic cable where excessive loads have been applied or experienced. In the present invention, a plurality of strips of tactile film or pressure sensitive film are inserted, at regular intervals, throughout the fiber optic cable structure in a fashion similar to that of swellable tape. The tactile film or pressure sensitive film used can be any color-changing stress sensor which is formed in the shape of a flat strip. The present invention uses strips of tactile or pressure sensitive film of different widths which are inserted periodically throughout the cable, both circumferentially and along the length of the cable. The films are located between the buffer tube(s) and the outer jacket of the cable or between the fibers and the outer jacket of the cable. This intermittent use decreases the overall cost and weight of the cable, over using a continuous length of tactile film. It is also desirable, in the present invention, to have the tactile or pressure sensitive film with corrugated folds along the width of the film. This corrugation provides a much higher sensitivity to loads experienced by the cables due to more “aggressive” deformation of the film during buckling.