Four wave mixing (FWM) is a technique used to amplify optical signals
. In this process, three light signals interact with each other: one signal beam and two pump beams.
Wave Mixing Four wave mixing is implemented in Optical Parametric Amplifiers (OPA) and is based on four optical waves interacting with each other in the nonlinearities of a crystal or a light guide. Two beams, a signal beam and a pump beam, create a virtual image that is read out by a second pump beam. The energy of the second pump beam is reflected as a fourth wave in the direction of the signal beam. The method, which uses a nonlinear Kerr effect
, is used in optical networks in Dense Wavelength Division Multiplexing (DWDM).