This book describes the electromagnetic theory for the propagating modes of dielectric guides with the objective of understanding the applications of these guides to a telecommunication system. The dispersionless "solitonic" solution is introduced to inform the reader on this new optical pulse shape which may soon ensure transoceanic communications. The study of the minimization of the waveguide dispersion leads us, by means of several calculated frames, to the weakly-guiding condition. This essential condition for a large bandwidth fibre leads us to the introduction of the practical LP...