利用偏振控制器连续调节光纤环镜的反射率

Continuously adjusting the reflectivity of fiber loop mirror using a polarization controller

研究了一种新型光纤环镜(FLM)的原理与特性,这种FLM由在普通光纤环镜中插入光纤型偏振控制器(PC)构成.通过等效光路分析建立了该FLM的理论模型,并对其反射特性进行了数值模拟.研究表明,通过改变PC的状态,即改变其双折射效应的快轴取向或强度,可连续调节FLM的反射率,反射率谱具有宽带特性,主要受光纤耦合器工作带宽的影响.此外,对FLM的反射特性还进行了实验研究.实验结果也证实,通过调节PC状态,FLM反射率可在其最大和最小值之间连续调节,实验测得FLM最大和最小反射率分别可达93%和2%.根据PC双折射效应的快轴取向和强度与其三个圆盘倾斜角度之间的对应关系,比较实验与模拟结果后发现,两者符合很好.

Reflection characteristics of a novel fiber loop mirror （ FLM）, which is formed by inserting a fiber polarization controller （PC） into the loop, are investigated. Based on the equivalent optical-path analysis, a theoretical model for the FLM is presented. The reflection characteristics of the FLM are then simulated in detail with the model. Our simulation results show that, by varying the PC working conditions, i.e. the fast axis orientation or the intensity of the birefringence induced by the PC, the refrectivity of the FLM may be continuously tuned between 0 and 1. The spectral characteristic of reflectivity of the FLM is wide and flattened, limited only by the operating bandwidth of the optical fiber coupler used. Moreover, the reflection characteristics of the FLM are further investigated experimentally. The experimental results also show that by varying the working conditions of the PC, the reflectivity of the FLM may actually be continuously adjusted between its maximum and minimum values,which were measured to be 93% and 2%, respectively. The experimentally determined dependence of the fast axis orientation and intensity of the birefringence induced by the PC on the inclination angle of the three rigid discs with respect to the level of the PC verified the results of theoretical simulations.