This Recommendation describes the classification, the type code and the reference models of various Raman amplifiers. Raman amplification / ˈrɑːmən / is a way of increasing the signal strength in an optical fiber. Technically, it works by stimulating Raman scattering, in which a lower frequency 'signal' photon. General Symmetric cable pairs Land coaxial cable pairs Submarine cables Free space optical systems Optical fibre cables G. 659 Characteristics of optical components and subsystems G. 679 Characteristics of optical systems. A Raman amplifier is an optical amplifier based on Raman gain, which results from the effect of stimulated Raman scattering in some Raman gain medium.