单芯光纤和双芯光纤的耦合问题是限制双芯光纤研究和应用深度的关键问题之一。利用突变光波导的分析方法, 在高斯近似的模场分布下, 推导了单芯单模光纤和双芯单模光纤对接和熔接的耦合能量、总体耦合效率和两纤芯耦合能量比的数学表达式。利用这组关系定量地详细分析了单芯光纤和双芯光纤耦合中的模场匹配、双芯光纤的纤芯距和纤芯位置对耦合效果的影响。利用其中一个纤芯位于光纤中心的双芯光纤, 通过保偏熔接机进行辅助定位, 实测了单芯单模光纤与双芯单模光纤对接耦合的输出能量与纤芯位置的关系, 测量结果能够很好地与理论结果相符合。

The coupling between singlecore fiber and dualcore fiber is one of the major obstacles to the further study and application of dualcore fibers. With Gaussian approximation for fundamental mode in fiber, the expressions of energy coupling into either of the two cores, overall coupling efficiency between the two fibers, and the ratio of energy coupling between the two cores are deduced. The quantitative characteristics of mode matching, the distance between the two cores in dualcore fibers, influence of core position on coupling effect, are discussed in detail. Experimental result shows a good agreement with calculated result.