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详细分析了光子晶体光纤包层气孔塌缩对光纤传输特性的影响,建立了包层气孔塌缩结构模型,利用有限元法和局域耦合模理论对环形结构改变下形变区域的有效折射率分布和模式耦合系数进行了计算,得到了调制区域各模式的有效折射率和耦合系数分布。研究了基模和包层模的耦合规律,得到了纤芯基模(LP01)和包层模(LP11,LP02)耦合下的传输谱,探讨了此种结构性改变成栅方法的可能性。在此基础上进一步分析了结构性参数如周期长度、周期个数和塌缩深度对传输特性的影响,得到了谐振峰随这些参数变化的规律。研究结果表明,光子晶体光纤包层空气孔塌缩可以形成光栅,调整塌缩参数可以改变所成光栅传输特性。研究结论为结构性改变光子晶体光纤光栅的刻写和应用提供了理论依据。
The effect of the collapse of photonic crystal fiber cladding on optical fiber transmission was analyzed in detail. A model of the collapse of the cladding was established. The effective refractive index distribution of the deformed area under the change of the ring structure was analyzed by the finite element method and the local coupled mode theory And modal coupling coefficients are calculated, and the effective refractive index and the coupling coefficient distribution of each mode in the modulated region are obtained. The coupling law between the fundamental mode and the cladding mode was studied, and the transmission spectrum under the coupling between the core mode (LP01) and the cladding mode (LP11, LP02) was obtained. The possibility of this structural change to the gate mode was also discussed. On this basis, the influence of structural parameters such as cycle length, number of cycles and collapse depth on the transmission characteristics is further analyzed, and the law of resonance peak with these parameters is obtained. The results show that the grating can be formed by the collapse of photonic crystal fiber cladding air holes, and adjusting the collapse parameters can change the transmission characteristics of the resulting grating. The research conclusion provides a theoretical basis for the writing and application of structurally changing photonic crystal fiber gratings.