LEVELLER CALIBRATION DEVICE

A calibrating bar, for calibrating a multi-roll leveller for metal strips, the calibrating including a first groove on a first face wherein a first optical fibre is embedded by an adhesive, a second groove on a second face, being opposite to the first face, wherein a second optical fibre is embedded by means of an adhesive, the first optical fibre and the second optical fibre including a fibre Bragg grating and being essentially parallel, the first optical fibre and the second optical fibre being located at the same distance from the neutral plane N, the first embedded optical fibre and the second embedded optical fibre being configured such that they can be connected to an optical coupler and such that it has a sufficient length to extend over all the rolls of said multi-roll leveller.