相干探测系统最佳本振光功率测量方法(特邀)

Approach for Measuring the Optimal Local Optical Power of Coherent Detection System(Invited)

相干探测系统受光电探测器非线性效应作用,难以达到散粒噪声极限下信噪比,存在最佳本振光功率使得系统信噪比最大。针对系统最佳本振光功率难以确定的问题,首先分析基于平衡探测器的最佳本振光功率理论,提出基于互相关法和频谱法直接测量外差信号并计算信噪比以确定最佳本振光功率,搭建实验完成了三型光电探测器对应的系统测试。结果表明,测量的信噪比随本振光功率的变化曲线与理论基本吻合,可以准确得到不同探测器对应的最佳本振光功率。本文方法可用于确定相干探测系统最佳本振光功率以及提高系统信噪比。

The Signal-to-Noise Ratio(SNR)of coherent detection system,which is affected by the nonlinear effect of the photodetector,can not achieve the SNR level under the shot noise limited operation.Hence,there is an optimal local optical power to maximize the SNR. Aiming at the problem that the optimal local optical power of the system is difficult to determine,the theory of optimal local optical power based on balance detector is analyzed firstly. A method for determining the optimal local optical power which measure the heterodyne signal directly and calculate the SNR based on cross-correlation method and spectrum method is proposed subsequently. The experiments are conducted by setting up the experimental system for testing three type photodetector. The results demonstrate that the curve of measured SNR versus the local oscillator optical power basically consistent with the theoretical value,the optimal local optical power can be accurately measured for different detectors. The proposed method in this paper can be used to determine the optimal local optical power of a coherent detection system and improve the system SNR.