模式耦合理论在圆周对称长周期光纤光栅建模中的应用

长周期光纤光栅是不同于光纤Bragg光栅的一种光纤光栅器件 ,根据模式耦合理论 ,长周期光纤光栅表现为前向传播的纤芯导模和同向的各阶次包层模式之间的耦合。分析研究了长周期光纤光栅轴向的模场变化。忽略轴向的模式耦合以及包层模式之间的相互耦合作用 ,并认为折射率指数的调制只存在于纤芯中 ,建立了简化的长周期光纤光栅数学模型。对圆周对称轴向均匀型长周期光纤光栅谱特性进行了仿真 ,其结果与实验结果基本吻合 ,表明了简化的数学模型的合理性

Application of coupled mode theory on modeling for circularly symmetric LPFG

Long period fiber grating (LPFG) is a fiber component different from the fiber Bragg grating. According to coupled mode theory, the forward propagating guided core mode is coupled to a number of co propagating cladding modes in an LPFG. The axial distribution for mode fields of the LPFG is analyzed and researched. Then the simplified model for the LPFG is deduced with ignoring longitudinal coupling of modes and coupling of cladding modes themselves, and also assuming the modulation of refractive index exists only in fiber core. Spectral characteristics of the circularly symmetric axial uniform LPFG is simulated. The accordant results between experiment and simulation show the simplified model deduced rational and appropriate.