光纤超声传感系统3×3耦合器输出信号的影响因素研究
Research on the factors affecting the output signal of 3×3 coupler in optical fiber ultrasonic sensing system

光纤超声传感单位通常使用3×3耦合器作为核心干涉部件，其输出信号往往变化范围大、稳定性差，为了分析3×3耦合器输出信号产生不同现象的原因，开展了3×3耦合器输出信号的影响因素研究。应用干涉理论，分析了声信号和环境噪声对3×3耦合器输出信号稳定性的影响。数值计算结果与实验结果表明：声信号与环境噪声共同调制了干涉仪的相位，环境噪声使得3×3耦合器输出信号稳定性差；通过增大声信号幅值，使其引起的干涉仪相位幅值大于π rad，此时3×3耦合器输出信号的稳定性增强。
Optical fiber ultrasonic sensors usually use 3×3 coupler as their core interferometer. The output signals of 3×3 coupler often vary in a wide range and have poor stability. In order to understand why different phenomena happen in the output signals, the factors affecting the output signal of 3×3 coupler are studied. By using interference theory, the effects of acoustic signal and ambient noise on the stability of output signal of the 3×3 coupler are analyzed. Both simulation and experimental results show that a stable output signal can be obtained when the amplitude of acoustic signal is relatively large.