以耦合模理论导出的超模为基础,推导出适用于双芯光纤矩形折射率分布长周期光栅(LPG)计算的理论方法,给出了输出的一般解析表达式。针对两纤芯完全相同的双芯光纤上写入两同步均匀且完全相同光栅的特殊模型,给出了单芯输出可用于直接计算的一般解析表达式,这种模型中光栅的影响表现为各波长上的附加相位和谐振波长的偏移,可以用于双芯光纤谐振波长的调整和可控的相位变化。对于两光栅仅有折射率变化幅度差异的模型,给出了数值模拟结果,讨论了这一因素对输出的影响。 Based on the supermodular derived from coupled-mode theory, a theoretical method for calculating the long-period grating (LPG) with rectangular refractive index distribution is deduced, and the general analytical expression of the output is given. The special analytical model of single-core output for direct calculation is given for the two special models of uniform and exactly the same grating on the same two-core fiber with two cores. The influence of grating in this model is The additional phase at the wavelength and the shift of the resonant wavelength can be used to adjust the resonant wavelength of the dual-core fiber and to control the phase change. For the model with only the difference of the refractive index of the two gratings, the numerical simulation results are given and the influence of this factor on the output is discussed.