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给出了平衡式相干探测系统的一般信噪比数学模型,对该数学模型和普通单源相干探测系统的信噪比模型进行了数值仿真对比研究。仿真结果表明,当平衡式相干探测系统中的光电探测器理想匹配时,其系统的信噪比以分束比系数等于0.5呈对称分布;而当光电探测器失配时,系统的最大信噪比所对应的最佳光束分束比发生偏离。最后搭建了2μm平衡式相干探测实验系统,实验结果表明,在相同的输入光功率下,平衡式相干探测系统的最大信噪比比普通单源相干探测系统的信噪比高19dB;平衡式相干探测系统的信噪比趋于饱和的范围比普通相干探测系统趋于饱和的范围宽大约0.2。
The general signal-to-noise ratio mathematical model of the balanced coherent detection system is given, and the numerical simulation comparison between the mathematical model and the signal-to-noise ratio model of the common single-source coherent detection system is carried out. The simulation results show that when the photodetectors in the balanced coherent detection system are perfectly matched, the signal-to-noise ratio of the system is symmetrically distributed with the splitting ratio coefficient equal to 0.5. When the photodetectors are mismatched, the maximum signal-to-noise Deviates from the corresponding optimum beam splitting ratio. Finally, a 2μm balanced coherent detection system is set up. The experimental results show that the maximum SNR of balanced coherent detection system is 19dB higher than that of common single-source coherent detection system under the same input optical power. The range over which the signal-to-noise ratio of the detection system tends to saturate is about 0.2 wider than that of the conventional coherent detection system.