BRAGG GRATINGS WRITTEN IN HIGH BIREFRINGENCE OPTICAL FIBERS FOR TRANSVERSAL STRAIN SENSORS

Fiber Bragg gratings are written in high birefringence PANDA optical fiber, aimed to transversal stress measurements. Optical characterization, without and with transversal load applied, is presented together with numerical simulations of the optical spectra. Fiber Optic Bragg Grating (FOBG) sensors usually have one or more Bragg grating written in a single (standard) fiber. The shift in the spectral position of the reflection band of each grating permits to determine physical measurand acting on it like, e.g., longitudinal strain or temperature. However, there are several FOBG applications (material science, composites, aircraft, biomechanics...) where the strain along all principal axis of the material are required [1], involving the experimental measurement of both the longitudinal and the transversal components of the strain. Such measurement can be done using several FOBG aligned along three perpendicular axis but the dimensions of this assembly, its influence in the material where is embedded and the associated complexity in the optical access restricts its widespread use. A single FOBG able to detect all three components of strain would be required to fulfill the experimental needs in that areas [2]. In this work we present the characterization of FOBG written in polarization preserving optical fibers. The results show that it is possible to optimize the grating parameters in order to use that grating to measur