基于光参考的光纤激光传声器阵列相位噪声动态抑制方法

Dynamic Suppression Method of Phase Noise in Fiber Laser Microphone Array Based on Optical Reference

摘要:

在火箭发动机超高声压噪声测量领域，无振膜封装的光纤激光传声器耐压优势凸显。然而在工程应用中由非平衡干涉仪引入的相位噪声问题限制了其性能发挥。本文围绕光纤激光传声器阵列调制系统中非平衡干涉仪引入的相位噪声问题展开分析。首先，分析了调制系统的工作原理以及非平衡干涉仪相位噪声的来源，并将稳定的激光器光源入射至传声器系统共用的非平衡干涉仪，建立了具备光相位噪声抑制的光纤激光传声器阵列系统；之后，结合微分交叉相乘解调算法对抑制原理进行分析，利用光参考噪声去抵消干涉仪引入的噪声，进而达到动态抑制噪声的目的；最后，对传声器阵列系统进行了数值仿真和实验验证。实验结果表明：在外场实验条件下，非平衡干涉仪中测量的相位噪声与未引入光参考噪声的系统相比，传声器阵列7个基元的噪声由±0.34 rad左右减小到±0.15 rad以内，在噪声峰值处实现了7 dB以上的抑制效果，噪声功率谱密度由-25.02 dB/Hz降至-32.93 dB/Hz以下，相位噪声的抑制效果显著。

Abstract:

In the field of ultra-high sound pressure noise environment of rocket engines, fiber laser microphones without diaphragm packaging have prominent pressure-resistant advantages. However, the phase noise problem introduced by unbalanced interferometer in engineering applications limits their performance. This paper focuses on the phase noise of the fiber laser microphone array introduced by the unbalanced interferometer in the modulation system. Firstly, the working principle of the modulation system and the source of the phase noise of the unbalanced interferometer are discussed, and a stable laser light source is incident on the unbalanced interferometer shared by the microphone system, to construct fiber laser microphone array system with suppressed optical phase noise. Then, the suppression principle is theoretically analyzed using the differential cross multiplying (DCM) demodulation. The noise information of the optical reference is used to cancel out the system noise introduced by the interferometer, thereby achieving the dynamic noise suppression. Finally, numerical simulation and experimental verification are conducted on the microphone array system. As a result, the phase noise measured in the non-equilibrium interferometer is reduced from approximately ± 0.34 rad to within ± 0.15 rad compared with the system without optical reference under field experimental conditions. The noise peak is suppressed by more than 7 dB, and the noise power spectral density is reduced from -25.02 dB/Hz to below -32.93 dB/Hz. The suppression effect of phase noise is significant.