Abstract: An optical device for the contactless measurement of a liquid level contained in a storage device by an optical signal, the optical device including an optical unit fixedly positioned above the storage device and an electronic control unit capable of emitting an optical signal, dissociated from the optical unit and positioned at a distance from the optical unit. The optical unit includes a single channel for the emission and the reception of the optical signal. The optical unit is connected to the electronic control unit through an optical fibre capable of transmitting the optical signal emitted by the electronic control unit and an optical signal reflected by the liquid. The optical fibre has first and second optical cores that juxtapose each other such that at least a part of the optical signal emitted in the first optical core of the optical fibre is backscattered in the second optical core.