These devices utilize the principle of stimulated Raman scattering to amplify optical signals. Typically, the Raman gain medium comprises optical fibers, bulk crystals, waveguides in photonic integrated circuits, or cells filled with gas or liquid. It is often used in a fiber that carries a signal for a long distance (such as in an undersea cable). The basic principles for SRS are as follows: If weak signal light and strong pump light are transmitted along a. The document summarizes Raman fibre amplifiers. Raman amplifiers function by using a pump beam.