McKinstrie C J, Karlsson M, Tong Z
Bell Laboratories, Alcatel–Lucent, Holmdel, New Jersey 07733, USA.
Opt Express. 2010 Sep 13;18(19):19792-823. doi: 10.1364/OE.18.019792.
In a previous paper [Opt. Express 13, 4986 (2005)], formulas were derived for the field-quadrature and photon-number variances produced by multiple-mode parametric processes. In this paper, formulas are derived for the quadrature and number correlations. The number formulas are used to analyze the properties of basic devices, such as two-mode amplifiers, attenuators and frequency convertors, and composite systems made from these devices, such as cascaded parametric amplifiers and communication links. Amplifiers generate idlers that are correlated with the amplified signals, or correlate pre-existing pairs of modes, whereas attenuators decorrelate pre-existing modes. Both types of device modify the signal-to-noise ratios (SNRs) of the modes on which they act. Amplifiers decrease or increase the mode SNRs, depending on whether they are operated in phase-insensitive (PI) or phase-sensitive (PS) manners, respectively, whereas attenuators always decrease these SNRs. Two-mode PS links are sequences of transmission fibers (attenuators) followed by two-mode PS amplifiers. Not only do these PS links have noise figures that are 6-dB lower than those of the corresponding PI links, they also produce idlers that are (almost) completely correlated with the signals. By detecting the signals and idlers, one can eliminate the effects of electronic noise in the detectors.
在之前的一篇论文[《光学快报》13, 4986 (2005)]中，推导了多模参量过程产生的场正交分量和光子数方差的公式。在本文中，推导了正交分量和数关联的公式。这些数公式用于分析基本器件的特性，如双模放大器、衰减器和频率转换器，以及由这些器件组成的复合系统，如级联参量放大器和通信链路。放大器产生与放大信号相关的闲频，或使预先存在的模式对相关联，而衰减器则使预先存在的模式去相关。这两种类型的器件都会改变它们所作用模式的信噪比(SNR)。放大器根据其工作方式是相位不敏感(PI)还是相位敏感(PS)，分别降低或增加模式的信噪比，而衰减器总是降低这些信噪比。双模PS链路是由传输光纤(衰减器)后跟双模PS放大器组成的序列。这些PS链路不仅具有比相应PI链路低6 dB的噪声系数，而且还产生与信号(几乎)完全相关的闲频。通过检测信号和闲频，可以消除探测器中电子噪声的影响。
