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.

中文翻译：

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基于光纤的相敏光放大器及其应用

光参量放大器依赖于非线性过程中的二阶磁化率（三波混频）或三阶磁化率（四波混频），其中入射光子的能量不发生变化（弹性散射）。在后一种情况下，两个泵浦光子被转换成一个信号和一个闲散光子。在某些条件下，与所涉及的波的相位演变有关，这种转换可能非常有效，从而导致输入信号的大幅放大。由于非线性过程可能非常快，因此除了纯放大之外的全光学应用也是可能的。如果放大器以光输入相位敏感的方式实现，则可以在没有过多噪声的情况下放大信号波，即噪声系数为 0 dB。在本文中，我们将提供此类放大器的基本概念和理论，重点介绍它们在依赖四波混频的高度非线性光纤中的实现。我们将讨论相位不敏感和相位敏感操作之间的区别，并包括几个实验结果来说明它们的能力。还讨论了参量放大器的不同应用，包括它们在光通信链路中的使用。