In this paper, fundamental problems connected with optical amplifiers and multichannel transmission are considered. A type-based division of optical amplifiers and their possible applications in optical transmission lines are presented. The physical phenomena occurring in optical amplifiers, particularly in EDFAs (Erbium Doped Fiber Amplifiers), are discussed. A method of optimizing the basic parameters (gain, noise, etc.) of EDFAs is given. The properties of EDFAs and the latter's applicability to optical transparent networks are considered. How to increase the capacity of telecommunications lines is a topical issue. In this paper, ways of achieving a wide waveband for an optical transparent network through the use of a set-up of hybrid (Raman and EDFA) optical fiber amplifiers are presented.