光纤布拉格光栅型全光纤声光调制器的特性研究

摘要

将光纤光栅的傅里叶模式耦合理论应用于光纤布拉格光栅型全光纤声光调制器的理论分析中.与现有的分析方法相比，该模型算法简单、求解容易，能够快速有效地获得调制器的传输特性.基于该模型，理论分析了超声波频率及声致应变幅度对调制器特性的影响.仿真结果表明，该调制器反射谱的主反射峰与次反射峰的波长间隔与超声波频率成正比，反射峰的反射率随着声致应变幅度的改变而发生周期性的变化.另外，在同一声致应变幅度下，低频超声波调制的光栅反射中存在更多的次反射，光栅反射能量的周期性变化更加明显.实验中，使用频率为885.5 kHz的超声波对光纤布拉格光栅进行调制.实验结果与仿真结果相一致.%The Fourier mode coupling theory is applied to the analysis of the fiber Bragg grating based all-fiber acousto-optic modulator for the first time. Compared with the existing analysis methods, the algorithm of this model is simple and easy, and transmission characteristics of the modulator can be acquired effectively and efficiently. Based on the theory, the performances of the modulator, related to ultrasonic frequency and amplitude of acoustically induced strain, are investigated. Simulation results show that in reflection spectra of the modulator, the wavelength interval between the primary relection peak and the secondary relection peak is proportional to ultrasonic frequency, and the reflectivity of the reflection peak varies periodically with intensity change of the amplitude of acoustically induced strain. In addition, with the same amplitude of acoustically induced strain, more secondary reflections exist in the low-frequency ultrasonic modulated fiber Bragg grating, and the periodic variation of the energy reflected by fiber Bragg graing is more obvious. In the experiment, the fiber Bragg graing is modulated by an ultrasonic wave with a frequency of 885.5 KHz. The experimental results accord well with the simulation results.