ETCHED FIBERS AS STRAIN-GAUGES

Presented in this work is a new class of optical fiber intensity sensors that do not require the use of external structures to impose perturbations on fibers. Instead, the topological structures are formed directly onto the fiber cladding. The geometry of the features is defined photolithographically and the structures are formed by chemical etching. The etched fiber sensing elements have been fabricated and tested as strain sensors. Depending on the amount of the cladding material removed and the symmetry of the etched structure, the measured gauge factor of the etched fiber strain sensors may be larger than 100. The responses of the optical fiber strain gauges are linear, repeatable, have a high cyclic endurance and no measurable hysteresis. These sensors can be used to monitor a strain as large as 0.4%.