级联倾斜长周期光纤光栅传输谱特性研究

Spectral Characteristics of Cascaded Tilted Long Period Fiber Gratings

通过理论模拟和实验研究了级联倾斜长周期长纤光栅(CTLPFG)的传输谱特性。基于耦合模理论和传输矩阵法,分析了级联长度、级联位置、级联个数和光栅倾角对级联倾斜长周期光纤光栅传输谱的影响:级联长度和级联位置对CTLPFG和级联长周期光纤光栅(CLPFG)传输谱的影响是一致的;随着光栅倾角的增大,CTLPFG的二阶包层模对应的损耗峰增强,三阶包层模对应的损耗峰变化不明显,且二阶包层模显著强于三阶包层模,二阶模的传输谱对60°以上的光栅倾角的变化很敏感;级联段数的增加可以明显增加通带的宽度,且通带宽度与级联段数呈很好的线性关系(回归系数为0.9988),表明CTLPFG在双峰滤波器中有良好的应用价值。实验上,利用逐点写入法刻制了CTLPFG,通过实验结果和理论模拟结果的比较分析,发现实验和理论结果表现出较好的一致性。

The transmission spectral characteristics of the cascaded tilted long period fiber grating（CTLPFG） are studied theoretically and experimentally. Based on the coupled-mode theory and transfer matrix method, the effects of cascading lengths, cascading location, the number of cascades and tilt angle on CTLPFG transmission spectrum are simulated. The transmission spectrum of the CTLPFG is consistent with the transmission spectrum of the cascaded long period fiber grating（CLPFG） in cascading length and cascading location. The loss peaks of the second and 3rd-order cladding modes increase as the tilt angle is enhanced, and the second-order cladding mode is stronger than the 3rd-order mode. The second-order transmission spectra are sensitive to changes in the inclination for the angle above 60°. The width of the pass-bands increases along with the increase of the cascaded segments number, and they are in linear relationship. The results show that CTLPFG has a good value in a bimodal filter.CTLPFGs are made in experiments through point by point. Experimental results and theoretical simulations are comparatively analyzed, which demonstrates that they are in favorable consistency.