Fiber-based phase-sensitive optical amplifiers and their applications

Reviewartikel, 2020

Optical parametric amplifiers rely on second-order susceptibility (three-wave mixing)
or third-order susceptibility (four-wave mixing) in a nonlinear process where the energy
of incoming photons is not changed (elastic scattering). In the latter case, two pump
photons are converted to a signal and to an idler photon. Under certain conditions,
related to the phase evolution of the waves involved, this conversion can be very efficient,
resulting in large amplification of an input signal. As the nonlinear process can
be very fast, all-optical applications aside from pure amplification are also possible. If
the amplifier is implemented in an optical input-phase-sensitive manner, it is possible
to amplify a signal wave without excess noise, i.e., with a noise figure of 0 dB. In this
paper, we will provide the fundamental concepts and theory of such amplifiers, with a
focus on their implementation in highly nonlinear optical fibers relying on four-wave
mixing. We will discuss the distinctions between phase-insensitive and phase-sensitive
operation and include several experimental results to illustrate their capability. Different
applications of parametric amplifiers are also discussed, including their use in optical
communication links.