Low-noise optical amplification and signal processing in parametric devices

Recent progress in low-noise optical amplification and signal processing has raised prospects of practical devices operating below the conventional quantum limit. We review the basic principles, practical implementation, and performance of such devices. In particular, we focus on the operation and limitations of χ(3)-based nonlinear platforms, such as silica high-confinement fiber. Classified by the parametric process application, we discuss the use of low-noise parametric mixers as optical amplifiers, phase regenerators, wavelength converters, and signal multicasters.