给出了一种新的数值计算W-型单模单偏振光纤截止基模能量损耗的方法--区域模场边界条件匹配法.用这种方法分析了截止基模能量损耗与光纤结构参数的关系,得出了截止基模能量损耗随椭圆内包层长半轴、短半轴或内包层折射率深度的增加而迅速减小,以及高椭圆度内包层情形下截止基模能量损耗仅由内包层短半轴、内包层折射率深度和纤芯外包层相对折射率差确定的结论;同时得出了截止基模能量损耗与纤芯外包层相对折射率差的平方根成正比的解析结果.最后将数值计算和实验进行了比较,两者较为一致.

A new numerical method based on point-matching is presented to calculate leakage loss of cutoff fundamental mode in W-tunneling optical fibers. Relationship between leakage loss and optical fiber parameter is analysed. It is found that leakage loss is proportional to square root of relative index difference between core and outer cladding and decreases quickly with increasing of elliptical inner cladding semimajor axis, semiminor axis or inner cladding index depth. When inner cladding is highly elliptical, leakage loss is determined only by inner cladding semiminor axis, inner cladding index depth and relative index difference between core and outer cladding. Numerical results are compared with experiment and they agree well with each other.