We designed, manufactured and characterized two birefringent microstructured fibers that feature a 5-fold increase in polarimetric sensitivity to hydrostatic pressure compared to the earlier reported values for microstructured fibers. We demonstrate a good agreement between the finite element simulations and the experimental values for the polarimetric sensitivity to pressure and to temperature. The sensitivity to hydrostatic pressure has a negative sign and exceeds -43 rad/MPa x m at 1.55 microm for both fibers. In combination with the very low sensitivity to temperature, this makes our fibers the candidates of choice for the development of microstructured fiber based hydrostatic pressure measurement systems.

Fiber Bragg gratings written in highly birefringent microstructured optical fiber with a dedicated design are embedded in a composite fiber-reinforced polymer. The Bragg peak wavelength shifts are measured under controlled axial and transversal strain and during thermal cycling of the composite sample. We obtain a sensitivity to transversal strain that exceeds values reported earlier in literature by one order of magnitude. Our results evidence the relevance of using microstructured optical fibers for structural integrity monitoring of composite material structures.

In this article, we study the possibility to use a pair of specifically designed microstructured optical fiber Bragg gratings (MOFBGs) as a multi-component strain sensor when embedded within composite materials. The dependence on the orientation of the transverse sensitivity of the MOFBGs is exploited to build a sensing device able to measure the strain field along the three principal mechanical directions of a laminate composite. We developed an analytical and numerical model of such a sensor and benchmarked it with experiments performed on laminated composite coupons equipped with this sensor. We report on a theoretical strain resolution of about 5 με in the transverse directions of the composite material, which is a six-fold improvement over results reported in literature.