四端口光纤声光器件的耦合模理论

Coupling Mode Theory of Acousto-Optic Fiber Devices with Four Ports

简述了光纤的声致折变机制,在复合光波导理论基础上讨论了光纤零耦合器与常规光纤耦合器的本质区别,指出零耦合器实质上是一段可以选择激励的双模光纤。从耦合模理论出发,求解了零耦合器中声致模耦合渐进方程组,给出了四端口光纤声光器件功率耦合的完整解析表达式,阐明了器件输出光的频移特性,解释了器件在声光谐振时具有的倍频声光调制、可调光移频、光滤波、光分束、光开关等功能。最后报道了器件作为可调光分束器或光开关的研究实例。

The acoustic-induced refraction index change in optic fiber is introduced simply. Based on the composite waveguide theory, the difference between the general fiber coupler and the null coupler is discussed, and the latter in essence acts like a section of two-mode fiber which can be exciting separately. From the coupling mode theory, the asymptotic acoustic-induced coupling-mode equations in null coupler is resolved, and a complete analytic expression for power conversion between the fibers is given out firstly. With that, the frequency shift characteristics and functions provided with this kind of device at resonance frequency are explained. In the end, an experimental study on an acousto-optic tunable splitter or a switch is reported.