The present invention relates to compositions comprising a polymeric substrate comprising at least one volume excluding polymer. The frame comprises a head tube on a front end thereof. During conveyance of the packaging material by the gripping elements, the distances between the gripping elements are reduced and the packaging material is made to buckle between the gripping elements to one side, forming a string of bags. A first free space optical channel couples to a first node through a receive path and through a transmit path.