The planar waveguide of 12Na(2)O-35WO(3)(.)53TeO(2)lEr(2)O(3) glass (in mol%) was prepared by Ag+-Na+ ion-exchange at 330 degrees C for 5 h. The effective mode indices and propagation losses of the waveguide at the wavelengths of 473, 632.8, 983.1 and 1548 nin for TE and TM modes were measured by means of a prism coupler technique. The results were compared with those of a planar waveguide of the tungsten tellurite glass without Er3+ ions. Especially, the propagation losses of ion-exchanged tellurite glass waveguides were estimated for the first time to the best of our knowledge. (c) 2006 Elsevier B.V. All rights reserved.