1. Fibre and Polymer Technology, KTH, Teknikringen 56, 10044 Stockholm, Sweden, Institut Charles Sadron (CNRS-ULP), 6 rue Boussingault, 67083, Strassbourg Cedex, France, Department of Natural Sciences, Fibre Science and Communication Network, Mid Sweden University, 85170 Sundsvall, Sweden, and STFI Packforsk AB, Box 5604, 114 86 Stockholm, Sweden