As shown in Fig. 7, the fiber that received the plasmatreatment has a very smooth and homogeneous coating. On the other hand, the picture on the left hand side shows amore irregular surface. The raised vertical line in the center is probably due to a previous fiber defect; however it was noticed that this kind of defect was detected especially in samples without plasma treatment; a plasma cleaning effect has perhaps attenuated some of the original fiber surface unevenness.