三包层级联长周期光栅的传输谱特性

Spectral Characteristics of Triple-Clad Cascaded Long-Period Fiber Gratings

运用传输矩阵法对三包层级联长周期光纤光栅(LPFG)的传输谱特性进行分析,讨论了级联处光纤的长度、位置以及薄膜参数等对级联光栅传输谱的影响,并对级联长周期光栅和相移长周期光栅的传输谱进行了比较。结果表明两者传输谱在级联光纤长度较小或级联位置靠近光栅两端时具有较强的一致性;而在级联处光纤较长并且级联位置在中间时,两者表现出截然不同的特性,这一点和两包层级联光栅一致。另外,薄膜参数可以更灵活地调节传输谱衰减峰位置和峰值损耗的大小。

Spectral characteristics of three-layered cascaded long-period fiber gratings （LPFGs） were analyzed by the coupled-mode theory together with the transfer matrix method. The effects of the length, position of the fiber that connects the LPFGs on the transmission spectrum of the cascaded LPFG were discussed, and the transmission spectra between the cascaded LPFG and the phase-shifted LPFG were compared. The results show that their spectra have great consistency when the length of the cascading fiber is small or the cascading position is near the end of the cascaded LPFG. But when the cascading fiber is large or the cascading position is in the middle of the cascaded LPFG, the spectra of the cascaded LPFG and the phas-shifted LPFG are different. These results agree well with the two-layered cascaded LPFG. The changes of the film parameters can adjust flexibly the attenuation peak shifts of the spectra and the peak values of the spectra.