Differential phase tracking applied to Bragg gratings in multicore fiber for high accuracy curvature measurement

We report interferometric interrogation of fiber Bragg gratings in separate cores of a multicore fiber for high resolution quasi-static and dynamic bend measurements. Two axis curvature measurements are made by measuring the differential strain between three FBG sensors formed in a singlemode four-core fiber using a common interrogating interferometer. Therefore a measurement of the differential phase from each FBG yields the differential strain and compensates for the common-mode random drift of the interrogating interferometer. A DC curvature accuracy of 3.4 x 10(-3) m(-1), and an AC curvature resolution of 1.2 x 10(-4) m(-1)/Hz(1/2) are reported