Parametric amplification and processing of optical signals

Parametric devices based on four-wave mixing in fibers provide many functions that are required by optical communication systems. When operated in the linear regime, parametric devices provide amplification, frequency conversion and phase conjugation, all with high gain levels and broad bandwidths. They can also be used to monitor and switch signals. When operated in the nonlinear regime, parametric devices regenerate optical signals. In this paper the current status of research on parametric devices is reviewed briefly, and some promising directions for future research are indicated.