There is provided a method for determining an in-band noise parameter, such as the Optical Signal-to-Noise Ratio, on an optical signal-under-test propagating along an optical communication link and comprising a data-carrying signal contribution of any arbitrary degree of polarization and a noise contribution. The inter-cell contacts of the attached battery pack are connected to nodes between cells of the attached battery pack. The lifting unit is composed of a joint portion and a plurality of cantilevers. The input end and the output end are separately connected to first ends of the second transmission line and the third transmission line.