Control Over the Pressure Sensitivity of Bragg Grating-Based Sensors in Highly Birefringent Microstructured Optical Fibers

We present fiber Bragg grating (FBG)-based hydrostatic pressure sensing with highly birefringent microstructured optical fibers. Since small deformations of the microstructure can have a large influence on the material birefringence and pressure sensitivity of the fiber, we have evaluated two microstructured fibers that were made from comparable fiber preforms, but fabricated using different temperature and pressure conditions. The magnitude and sign of the pressure sensitivity are found to be different for both fibers. We have simulated the corresponding change of the Bragg peak separation with finite-element models and experimentally verified our results. We achieve very high experimental sensitivities of -15 and 33 pm/MPa for both sensors. To our knowledge, these are the highest sensitivities ever reported for birefringent FBG-based hydrostatic pressure sensing.