长周期光纤光栅和双锥形光纤间的倏逝波耦合作用

对长周期光纤光栅和双锥形光纤之间的倏逝波耦合作用进行了研究。理论分析和实验研究表明,由于锥形光纤和长周期光纤光栅物理边界外倏逝波之间的交叠,长周期光纤光栅产生的包层模,可以耦合到锥形光纤的包层模并从锥形光纤的纤芯输出。要获得高的耦合效率,应满足模式匹配的条件,同时要尽量减小两光纤之间的距离。耦合特性还与长周期光栅和双锥形光纤的相对位置有关,为获得高的耦合效率,耦合区应位于长周期光栅区的后面。这种倏逝波耦合作用,为监测实际应用系统中长周期光纤光栅的特性提供了一种新方法;为利用锥形光纤和长周期光纤光栅开发新型光纤器件,提供了一种可能的方案。

Evanescent-Field Coupling Based on Long-Period Grating and Tapered Fiber

Evanescent-field coupling based on long-period fiber grating (LPG) and bi-conical tapered fiber is proposed and investigated both theoretically and experimentally. The light coupled to the cladding modes by LPG can be transferred to a bi-conical fiber. In order to obtain high coupling efficiency, the phase-matched condition should be satisfied and the two fibers should be close enough. The characteristics of the coupling also depend on the position of the coupling region. To get higher coupling efficiency, the coupling region should locate after LPG. This kind of evanescent-field coupling can be used to monitor the characteristics of the LPG which is used in the devices or systems on line.