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从耦合模理论出发,对由两相同的长周期光纤光栅构成的级联光栅的光谱特性进行了较为详细的研究。研究发现,级联的距离不但影响边频分量的数目而且影响边频分量的强弱,距离越大,级联光栅产生的边频分量越多。而相移则只影响着边频分量强弱的位置,如果相移较小,则在单光栅谐振点位置左边的边频分量对应的损耗峰较浅,右边的边频分量对应的损耗峰较深,否则反之。
Based on the coupled mode theory, the spectral characteristics of cascaded gratings composed of two identical long-period fiber gratings are studied in detail. The research shows that the distance of cascades not only affects the number of side frequency components but also affects the strength of side frequency components. The larger the distance, the more the side frequency components generated by the cascaded grating. However, the phase shift affects only the position of the side frequency component. If the phase shift is small, the loss peak corresponding to the left side frequency component at the single grating resonance point is shallower and the loss peak corresponding to the right side frequency component Deep, otherwise the opposite.