引入衔套调制结构形成相移长周期光纤光栅的特性研究

Study on characteristics of phase-shifted long period grating with an embedded-modulation structure

通过在长周期光纤光栅(LPG)上某个位置引入一段衔套调制结构,设计并研制出了一种新型相移长周期光纤光栅(PSLPG),并采用传输矩阵法模拟了其光谱特性。模拟结果表明:在LPG某点引入衔套调制结构,当衔套调制结构都为均匀短光栅,且与被调制光栅的折射率调制深度相同但周期不同时,所形成的光栅仍旧可等效为一个单PSLPG,而引入相移量的大小相当于两个调制结构的分别引入相移量之和。最后采用CO2激光单侧曝光法写制技术对引入衔套调制结构形成的PSLPG进行了写制,实验结果与理论分析相符。

We propose a new method to design a phase-shifted long period grating （PSLPG） by adding an embedded-modulation structure in a long period grating at some position. The spectral characteristics are obtained by the transfer matrix simulated approach. The studies show that when a uniform short grating embedded-modulation structure, which has the same modulated depth but different period with the origi- nal one,is added in a long period grating;the grating also could be seen as a single phase-shifted long period gating,and the magnitude of phase-shifting is the sum of the two modulation structures in the em bedded-modulation structure. Furthermore, we fabricated the embedded-modulation PSLPG by CO2 laser exposure, and the experiment agrees well with the theory.