Differential phase tracking applied to Bragg gratings in multi-core fibre for high accuracy curvature measurement

High resolution quasi-static and dynamic curvature measurements are made by differential interferometric phase measurement of fibre Bragg gratings in separate cores of a multi-core fibre. A DC curvature stability of 1 X 10(-3) m(-1) and an AC curvature resolution of 1 X 10(-4) m(-1)/Hz(1/2) are reported.