平行排列3×3单模光纤耦合器在光开关、光缓存器、光谐振腔、光滤波器等方面有很重要的应用,偏振态的演化和波长特性是耦合器应用中的关键问题.利用模耦合理论对平行排列3×3单模光纤耦合器的输出性能进行了详细分析,得出了光纤引线对耦合器的输出偏振态演化起主要作用,而耦合区的影响则比较小;通过理论推导模耦合系数,分析了耦合器的分光比随波长的变化关系,得出了输出分光比比较稳定的耦合器所需要的合适芯间距(对于我们研制的为12.5 μm).并采用可移动火焰实际研制出了具有长耦合区的平行排列3×3单模光纤耦合器,测试表明输入光波长在1.500～1.575 μm范围内变化时,耦合器的输出分光比变化不大,理论与实验结果基本相符.

Fused planar 3×3 single mode fiber coupler is very important in optic switch, optic buffer, optic resonator and optic filter etc, both the evolution of polarization and the performance of wavelength are the crux. Based on the coupled-mode equations, the theoretical analysis of a fused planar 3×3 fiber coupler was presented. It is not coupling field but optic fiber pigtail operating on the evolution of polarization. The appropriate distance of the cores of the fiber (it is 12.5 μm to us) is obtained via analyzing the relation between the spliting ratio and wavelength. And the fused planar 3×3 single mode fiber coupler is fabricated which has long coupling field by moving flame. The experiment results indicate that the splitting ratio of output of coupler has little change when the wavelength of the input optic range from 1.500 tp 1.575 μm, the experiment results are in good agreement with the theoretical analysis.