机械微弯长周期光纤光栅矢量模耦合特性研究

Properties of Vector Mode Coupling in Mechanically Induced Microbend Long-Period Fiber Gratings

针对机械微弯长周期光纤光栅的基模HE11到高阶纤芯矢量模式(TE01、TM01和HE21)的耦合特性,分析了阶跃型和反抛物线型两种少模光纤结构下机械微弯长周期光纤光栅的光栅周期、微弯幅度和耦合系数等参数对矢量模式耦合的影响。研究结果表明,耦合系数是模式耦合过程中的关键,通过施加压力改变光纤的微弯幅度可以有效调谐光栅矢量模式的耦合强度。基于反抛物线型光纤结构的机械微弯长周期光纤光栅可以特定波长激发特定的高阶矢量模式(TE01、TM01和HE21),并且由基模向高阶模式转换的谐振波长可调谐。该机械微弯长周期光纤光栅在矢量模式复用、轨道角动量的产生和复用领域有潜在的应用价值。

In this study,we intend to determine the coupling properties of the fundamental mode HE11 with respect to the high-order core vector modes(TE01,TM01,and HE21)in case of the mechanically induced microbend long-period fiber gratings(MLPGs).Therefore,the effects of various parameters,including the grating period,microbend amplitude,and coupling coefficient,on the coupling of the vector modes in the MLPGs were analyzed with respect to the step-index and inverse-parabolic-index fibers.The results denote that the coupling coefficient plays a critical role during the mode coupling process and that the strength of vector mode coupling can be effectively tuned by applying pressure to vary the microbend amplitude of the fibers.The MLPGs of the inverse-parabolic-index fiber can convert the high-order vector modes(TE01,TM01,and HE21)at specific wavelengths,and the resonant wavelength obtained using the high-order mode can be tuned.The MLPGs possess potential application value with respect to vector mode multiplexing,orbital angular momentum generation,and multiplexing.