A multi-phase submarine power cable including: a plurality of power cores arranged in a stranded configuration, and a curvature sensor including: an elastic elongated member, and a plurality of Fibre Bragg Grating, FBG, fibres, each FBG fibre extending axially along the elongated member at a radial distance from the centre of the elongated member; wherein the elongated member extends between the stranded power cores along a central axis of the multi-phase submarine power cable.