Raman amplification has been commercially utilized in optical transmission systems for more than a decade. The drive towards higher spectral density has increased the interest in Raman to improve system performance. This tutorial reviews the benefits of Raman amplification, defines methods to analyze system performance, and describes the issues involved with system deployment and operation.Index Terms-Distributed amplifiers, optical fiber amplifiers, Raman scattering, optical fiber communications, optical fiber networks, coherent communications. 0733-8724 (c)